the lzr2000® and laser

the lzr2000® and laser
THE LZR2000® AND LASER
FEEDBACK SYSTEM
OPERATION & TECHNICAL MANUAL
P/N: EDU169 (V1.0)
AEROTECH, Inc. • 101 Zeta Drive • Pittsburgh, PA. 15238-2897 • USA
Phone (412) 963-7470 • Fax (412) 963-7459
Product Service: (412) 967-6440; (412) 967-6870 (Fax)
www.aerotechinc.com
If you should have any questions about the LZR2000 and/or comments regarding the documentation, please refer to
Aerotech online at:
http://www.aerotechinc.com.
For your convenience, a product registration form is available at our web site.
Our web site is continually updated with new product information, free downloadable software, and special pricing
on selected products.
The LZR2000 and Laser Feedback System
Operations and Technical Manual Revision History:
Rev 1.0
October 13, 2000
LZR2000
Table of Contents
TABLE OF CONTENTS
CHAPTER 1:
1.1.
1.2.
1.3.
1.4.
1.5.
1.6.
INTRODUCTION ............................................................................ 1-1
Overview of the LZR2000 Laser Feedback System ........................... 1-1
1.1.1. General Description ............................................................. 1-2
1.1.2. The LZR2000 Laser Head.................................................... 1-2
1.1.3. Cables................................................................................... 1-5
1.1.4. The Optics Package.............................................................. 1-5
Theory of Operation ........................................................................... 1-6
Options and Accessories..................................................................... 1-7
Applications and Configurations ........................................................ 1-8
1.4.1. Sample Configuration 1: Motor Control Based on
Interferometer Position Feedback Using a Signal
Multiplier and an External Motion Controller...................... 1-9
1.4.2. Sample Configuration 2: Temperature, Pressure and
Humidity Compensation for Enhanced Accuracy .............. 1-10
1.4.3. Sample Configuration 3: Motor Control Using an
External Motion Controller with Interferometer
Position Feedback .............................................................. 1-11
Proper Handling and Storage Techniques ........................................ 1-12
Laser Safety and Precautions............................................................ 1-13
CHAPTER 2:
2.1.
2.2.
2.3.
2.4.
UNPACKING AND INSPECTING THE LZR2000 SYSTEM..... 2-1
Introduction ........................................................................................ 2-1
Unpacking the Components................................................................ 2-1
Inspecting the LZR2000 Laser Head .................................................. 2-2
Inspecting the Optical Packages ......................................................... 2-2
CHAPTER 3:
3.1.
3.2.
GETTING STARTED, A FIRST LOOK ....................................... 3-1
Introduction ........................................................................................ 3-1
Physical Setup of the Laser Head ....................................................... 3-2
3.2.1. Mounting the Laser Head ..................................................... 3-2
3.2.2. Setup of the Laser on the Tripod .......................................... 3-3
3.2.3. Leveling the Laser Head....................................................... 3-4
Optical Components and Alignment Aides......................................... 3-5
Layouts and Configurations................................................................ 3-6
Aligning the System............................................................................ 3-7
3.3.
3.4.
3.5.
CHAPTER 4:
4.1.
4.2.
4.3.
4.4.
4.5.
4.6.
4.7.
Version 1.0
PHYSICAL SETUP OF THE LASER HEAD AND TRIPOD ..... 4-1
Introduction ........................................................................................ 4-1
The LZR2000 Laser Head .................................................................. 4-1
Mounting the Laser Head ................................................................... 4-3
4.3.1. Setup of the Laser on the Tripod .......................................... 4-4
4.3.2. Tripod and Laser Head Positioning Controls ....................... 4-6
4.3.3. Leveling the Laser Head....................................................... 4-7
Defining the System Layout ............................................................... 4-8
4.4.1. Positioning the Laser Head and Tripod ................................ 4-8
Supplying Power and Signal Connections to the Laser Head ........... 4-11
4.5.1. Environmental Compensator Connections ......................... 4-12
Customized Laser Head Cables ........................................................ 4-13
LZR2000 System Measurements ...................................................... 4-13
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Table of Contents
LZR2000
CHAPTER 5:
5.1.
5.2.
5.3.
5.4.
5.5.
5.6.
5.7.
CHAPTER 6:
6.1.
6.2.
6.3.
6.4.
6.5.
6.6.
PLANE/FLAT MIRROR MEASUREMENTS .............................. 6-1
Introduction ........................................................................................ 6-1
Measurement Specifications and Optical Hardware ........................... 6-1
Layouts and Configurations ................................................................ 6-3
Aligning the System............................................................................ 6-5
6.4.1. Coarse Alignment Process.................................................... 6-5
6.4.2. Fine Tuning the Alignment................................................. 6-11
Perpendicular Axis Measurements.................................................... 6-11
Effects on Accuracy.......................................................................... 6-11
CHAPTER 7:
7.1.
7.2.
7.3.
7.4.
7.5.
SYSTEM MAINTENANCE ............................................................ 7-1
Introduction ........................................................................................ 7-1
Storing the Components of the LZR2000 System............................... 7-1
Cleaning the Laser Head..................................................................... 7-1
Cleaning the Optics............................................................................. 7-1
Calibration .......................................................................................... 7-2
CHAPTER 8:
8.1.
8.2.
TECHNICAL DETAILS.................................................................. 8-1
Introduction ........................................................................................ 8-1
The LZR2000 Laser Head .................................................................. 8-1
8.2.1. Electrical Connections of the Laser Head ............................ 8-1
8.2.2. General Specifications of the Laser Head ............................ 8-2
8.2.3. Dimensions of the Laser Head.............................................. 8-2
Optics and Optical Accessories .......................................................... 8-4
8.3.
iv
LINEAR DISPLACEMENT AND VELOCITY
MEASUREMENTS .......................................................................... 5-1
Introduction ........................................................................................ 5-1
Measurement Specifications and Optical Hardware ........................... 5-1
5.2.1. The Retroreflector ................................................................ 5-3
5.2.2. The PBS Cube ...................................................................... 5-3
Optical Alignment Aides .................................................................... 5-5
Layouts and Configurations ................................................................ 5-6
Aligning the System............................................................................ 5-8
5.5.1. Coarse Alignment................................................................. 5-9
5.5.2. Fine Tuning the Alignment................................................. 5-15
5.5.2.1. Target Method...................................................... 5-17
5.5.2.2. The Overlapping Dots Method............................. 5-18
5.5.3. Alignment Example............................................................ 5-22
Perpendicular Axis Measurements.................................................... 5-24
Accuracy and Potential Sources of Error.......................................... 5-25
5.7.1. Environmental Conditions over the Measurement
Span.................................................................................... 5-25
5.7.2. Environmental Conditions over the Length of the
Dead Path ........................................................................... 5-26
5.7.3. Material Temperature Compensation Due to Thermal
Expansion of Mounting Surfaces........................................ 5-29
5.7.4. Measurement Axis and Travel Axis Alignment
(Cosine Error)..................................................................... 5-30
5.7.5. Abbé Error.......................................................................... 5-31
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Version 1.0
LZR2000
8.4.
8.5.
CHAPTER 9:
9.1.
9.2.
Table of Contents
Environmental and Material Expansion Compensation...................... 8-8
Miscellaneous Specifications............................................................ 8-11
8.5.1. Resolution and Velocity for Linear Displacement.............. 8-11
8.5.2. Plane/Flat Mirror Measurement Specifications .................. 8-11
TROUBLESHOOTING................................................................... 9-1
Introduction ........................................................................................ 9-1
Setup and Alignment .......................................................................... 9-1
APPENDIX A: GLOSSARY OF TERMS ............................................................... A-1
APPENDIX B: WARRANTY AND FIELD SERVICE...........................................B-1
INDEX
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Version 1.0
LZR2000
List of Figures
LIST OF FIGURES
Figure 1-1.
Figure 1-11.
The LZR2000 System with Optional Environmental
Compensator....................................................................................... 1-1
Sample Single-axis LZR2000 Configuration...................................... 1-2
Front View of the Laser Head (LZR2000) ......................................... 1-3
Rear View of the Standard LZR2000 Laser Head .............................. 1-4
Operation Diagram of the Laser Head and Optics.............................. 1-4
LZR2000 System Showing the Role of Optics ................................... 1-5
Closed-loop Systems .......................................................................... 1-8
Closed-loop Position Feedback Application Using a Multiplier ........ 1-9
Sample Environmental Compensation Configuration....................... 1-10
Sample Motion Control Configuration with Interferometer
Feedback........................................................................................... 1-11
Standard Caution and Shipping Labels............................................. 1-14
Figure 2-1.
The Linear Interferometer and Reflector Optics................................. 2-2
Figure 3-1.
Mounting the Laser Head on a Tripod and on a Stationary
Table................................................................................................... 3-2
Setup of Tripod and Installation of the Laser Head............................ 3-3
Laser Head Motions with Position Controls....................................... 3-4
Interferometer Mounting .................................................................... 3-5
Alternate Methods of Mounting the Reflector .................................... 3-5
Laser Head, Interferometer, and Reflector Setup ............................... 3-6
Front View of Laser Head .................................................................. 3-7
Front View of a Retroreflector ........................................................... 3-8
Different Degrees of Beam Alignment (View from Front of
Laser Head) ........................................................................................ 3-9
Figure 1-2.
Figure 1-3.
Figure 1-4.
Figure 1-5.
Figure 1-6.
Figure 1-7.
Figure 1-8.
Figure 1-9.
Figure 1-10.
Figure 3-2.
Figure 3-3.
Figure 3-4.
Figure 3-5.
Figure 3-6.
Figure 3-7.
Figure 3-8.
Figure 3-9.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 4-4.
Figure 4-5.
Figure 4-6.
Figure 4-7.
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 5-4.
Figure 5-5.
Figure 5-6.
Figure 5-7.
Figure 5-8.
Figure 5-9.
Figure 5-10.
Figure 5-11.
Version 1.0
Front View of the Laser Head (LZR2000) ......................................... 4-2
Rear View of the Standard LZR2000 Laser Head . ............................. 4-3
Mounting the Laser Head on a Tripod and on a Stationary
Table................................................................................................... 4-4
Setup of Tripod and Installation of the Laser Head............................ 4-5
Laser Head Motions with Position Controls....................................... 4-6
Machine Tool Positioning of Tripod and Laser.................................. 4-9
Electrical and Signal Connections .................................................... 4-12
Front View of a Retroreflector ........................................................... 5-3
Reference and Measurement Beams................................................... 5-4
Mounting of the Interferometer .......................................................... 5-5
Interferometer and Retroreflector Layout........................................... 5-6
Four Basic Optical Configurations ..................................................... 5-7
Position of Optics (Table moves) ..................................................... 5-10
Position of Optics (Spindle moves) .................................................. 5-10
Interferometer Mounting .................................................................. 5-11
Retroreflector Mounting ................................................................... 5-12
Different Degrees of Beam Alignment (View from Front of
Laser Head) ...................................................................................... 5-13
Interferometer and Retroreflector with Targets ................................ 5-14
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List of Figures
LZR2000
Figure 5-12.
Figure 5-13.
Figure 5-14.
Figure 5-15.
Figure 5-16.
Figure 5-17.
Figure 5-18.
Figure 5-19.
Figure 5-20.
Figure 5-21.
Figure 5-22.
Figure 5-23.
Figure 5-24.
Figure 5-25.
Figure 5-26.
Different Degrees of Beam Alignment (Side View) ......................... 5-16
Target Alignment Process................................................................. 5-18
Displaced Reflector Beam ................................................................ 5-19
Overlapping Dots Alignment Procedure........................................... 5-20
When to Rotate Laser ....................................................................... 5-21
When to Translate the Laser ............................................................. 5-21
Front View of a Retroreflector.......................................................... 5-22
Laser Head, Interferometer, and Reflector Setup.............................. 5-22
Positioning of Optics for Perpendicular Measurements.................... 5-24
Measurement Distance of the Interferometer System ....................... 5-25
Location of the Dead Path in the LZR2000 System.......................... 5-27
Mechanical Dead Path Compensation (System Side View).............. 5-28
Mechanical Dead Path Compensation Close-up of Linear
Interferometer Optic and Mounting Hardware (Front View)............ 5-29
Illustration of Cosine Error............................................................... 5-30
Illustration of Abbé Error ................................................................. 5-32
Figure 6-1.
Figure 6-2.
Figure 6-3.
Figure 6-4.
Figure 6-5.
Figure 6-6.
Figure 6-7.
Plane/Flat Mirror Layout .................................................................... 6-3
Position of Plane/Flat Optics (Spindle Moves)................................... 6-6
Plane/Flat Mirror Measurement.......................................................... 6-7
Perpendicular Plane/Flat Mirror Measurement................................... 6-8
Front View of a Retroreflector............................................................ 6-8
Plane/Flat Mirror Optics Mounting .................................................... 6-9
Attachment of Target to Interferometer (Plane/Flat
Measurement) ................................................................................... 6-10
Figure 8-1.
Figure 8-2.
Figure 8-3.
Figure 8-4.
Figure 8-5.
Figure 8-6.
Figure 8-7.
Figure 8-8.
Figure 8-9.
Figure 8-10.
Rear View of the LZR2000 Laser Head ............................................. 8-1
Dimensions of the LZR2000 Laser Head............................................ 8-3
Dimensions of the LZR2400 Optical Retroreflector........................... 8-4
Dimensions of the LZR2300 PBS/Retro Combination ....................... 8-4
Dimensions of the Post-Mount Height Adjuster and Posts ................. 8-5
Dimensions of the LZR1002 Base ...................................................... 8-6
Dimensions of the LZR2710 Quarter Wave Plate .............................. 8-6
Dimensions of the Turning Mirror (Cube) LZR1003 ......................... 8-7
Dimensions of the Mirror (LZR1004, LZR1005 & LZR2720)........... 8-7
LZR1100 Air Sensor, LZR1010 Material Temperature Sensor
and LZR1020 Remote Ambient Temperature Sensor......................... 8-9
Dimensions of the LZR1010 Material Temperature Sensor ............. 8-10
Dimensions of the LZR1100 Environmental Compensator ............. 8-10
Dimensions of the LZR1020 Remote Ambient Temperature
Sensor ............................................................................................... 8-10
Figure 8-11.
Figure 8-12.
Figure 8-13.
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Version 1.0
LZR2000
List of Tables
LIST OF TABLES
Table 1-1.
Options and Accessories Available for the LZR2000 System.................. 1-7
Table 2-1.
Minimal System Components................................................................... 2-1
Table 4-1.
Table 4-2.
Measurement versus Setup Axis............................................................. 4-10
Hardware versus Measurement .............................................................. 4-14
Table 5-1.
Table 5-2.
Table 5-3.
Table 5-4.
Linear and Velocity Measurement Hardware List.................................... 5-2
Linear and Velocity Operating Specifications.......................................... 5-2
Optical Mounting Accessories ................................................................. 5-6
Environmental Conditions Affecting Accuracy...................................... 5-26
Table 6-1.
Table 6-2.
Plane/Flat Mirror Measurement Hardware List........................................ 6-2
Plane/Flat Mirror Operating Specifications.............................................. 6-2
Table 8-1.
Table 8-2.
Table 8-3.
Table 8-4.
Table 8-5.
Table 8-6.
Table 8-7.
Table 8-8.
Pinouts for the 8-pin DIN Output Connector of the Laser Head .............. 8-2
Pinouts for the 9-pin D-type Output Connector of the Laser Head .......... 8-2
General Specifications for the LZR2000 Laser Head............................... 8-3
Environmental Compensation Specifics of the LZR1100 ........................ 8-8
Specifics of the Material Temperature Sensors (LZR1010) ..................... 8-8
Specifics of the Remote Ambient Temperature Sensor (LZR1020) ......... 8-9
Resolution and Velocity Details............................................................. 8-11
Plane/Flat Mirror Operating Specifications............................................ 8-11
Table 9-1.
Setup and Alignment Problems ................................................................ 9-1
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List of Tables
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LZR2000
Aerotech, Inc.
Version 1.0
LZR2000
Preface
PREFACE
This section gives you an overview of topics covered in each of the sections of this
manual as well as conventions used in this manual. The LZR2000 Operation & Technical
Manual contains information on the following topics:
CHAPTER 1: INTRODUCTION
This chapter contains an overview of the LZR2000 Laser Feedback System. Included is a
general description of the components of the system, options and accessories, a typical
system diagram, an application overview, proper handling and storage techniques, and
laser safety and precautionary statements. This chapter also contains information to
familiarize the operator with the terminology associated with interferometry, the laser
head and optics. In addition, Chapter 1 introduces special temperature, humidity and
pressure considerations for maintaining accurate measurements.
CHAPTER 2: UNPACKING AND INSPECTING THE SYSTEM
This chapter explains the proper procedures for unpacking and inspecting the components
of the LZR2000 system prior to their installation.
CHAPTER 3: GETTING STARTED, A FIRST LOOK
This chapter provides the user with a first look at the LZR2000 Laser Feedback System. It
is designed to briefly walk the user through the setup and use of a simple measurement
application.
CHAPTER 4: PHYSICAL SETUP OF THE LASER HEAD AND
TRIPOD
This chapter explains how to install the laser including choosing a location, mounting,
positioning, making electrical connections, aligning the optics, accuracy and possible
error sources.
CHAPTER 5: LINEAR DISPLACEMENT AND VELOCITY
MEASUREMENTS
This chapter explains how to position and setup the required optical components of the
interferometer system for linear distance and velocity measurements. The information
contained in this chapter covers an overview of the optics to the process of aligning the
system.
CHAPTER 6: PLANE/FLAT MIRROR MEASUREMENTS
This chapter contains information on how to setup and use optics for plane/flat mirror
measurements where movement perpendicular to the laser axis is limited in traditional
linear measurement optics. It steps the user through choosing a layout and mounting
surface and the process of aligning the system.
Version 1.0
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xi
Preface
LZR2000
CHAPTER 7: SYSTEM MAINTENANCE
This chapter explains the proper procedures for storing, cleaning and calibrating the
components of the LZR2000 system.
CHAPTER 8: TECHNICAL DETAILS
This chapter supplies a variety of technical specifications for the LZR2000 system.
General specifications, dimensions, signals and pinouts (as appropriate) are included for
the laser head, the optics, and cables.
CHAPTER 9: TROUBLESHOOTING
This chapter provides a reference tool if problems arise with the LZR2000.
APPENDIX A: GLOSSARY
Appendix A contains a list of terminology and abbreviations used in this manual.
APPENDIX B: WARRANTY AND FIELD SERVICE
Appendix B contains the warranty and field service policy for Aerotech products.
INDEX
Throughout this manual the following conventions are used:
é
é
DANGER
WARNING
é
é
é
é
é
é
Danger and/or Warning symbols (see left) appear in the outer margins next to
important precautions. Failure to observe these precautions could result in
serious injury and/or damage to the equipment.
The terms UNIDEX 500 and U500, UNIDEX 600 and U600 are used
interchangeably throughout this manual.
Keys such as Shift, Ctrl, Alt and Enter are enclosed in brackets (e.g., <Shift>,
<Ctrl>, <Alt> and <Enter>) to distinguish them from individual keystrokes.
Hexadecimal numbers are listed using a preceding "0x" (for example, 0x300,
0x12F, 0x01EA, etc.) to distinguish them from decimal numbers.
The terms <Enter> and <Return> are used interchangeably throughout this
document when referring to the keyboard.
The terms retroreflector and retro are used interchangeably throughout this
document.
Graphic icons or keywords may appear in outer margins to provide visual
references of key features, components, operations or notes.
This manual uses the symbol "∇ ∇ ∇" to indicate the end of a chapter.
Although every effort has been made to ensure consistency, subtle differences may exist
between the illustrations in this manual and the components that they represent.
∇ ∇ ∇
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Version 1.0
LZR2000
Introduction
CHAPTER 1: INTRODUCTION
In This Section:
• Overview of the LZR2000 Laser Feedback System ........ 1-1
• Theory of Operation ........................................................ 1-6
• Options and Accessories.................................................. 1-7
• Applications and Configurations ..................................... 1-8
• Proper Handling and Storage Techniques ..................... 1-12
• Laser Safety and Precautions......................................... 1-13
1.1.
Overview of the LZR2000 Laser Feedback System
This chapter provides an introduction to the LZR2000 - a Laser Feedback System used
for precision measurement applications such as machine tools, semiconductor
lithography, optics fabrication, IC and LCD inspection, precision machining and others.
The LZR2000 system is used to provide highly accurate position data in closed-loop
motion control systems. Refer to Figure 1-1.
Figure 1-1.
Version 1.0
The LZR2000 System with Optional Environmental Compensator
Aerotech, Inc.
1-1
Introduction
LZR2000
1.1.1. General Description
The basic LZR2000 system is a highly accurate Laser Feedback System that consists of
the following components:
• a single-frequency, helium-neon laser head
• one linear reflector
• one linear interferometer (polarized beam splitter and retroreflector
combination)
• two alignment targets
• cables.
The laser head can also be purchased separately to complement existing optical
components/systems or additional optical accessory kits can be purchased separately to
complement other measurement requirements. Refer to Aerotech’s Motion Product
Guide for more information. A sample single-axis system is illustrated in Figure 1-2.
Laser Head
Linear
Interferometer
Linear
Reflector
Environmental Compensator with
Air Temperature and Pressure Sensors
Distance
Axis of Motion
Material
Temperature
Sensor
MX
Multiplier
Stage
M
Motor
123,456,789,000
U500 or U600
PC
Aerotech UNIDEX 500
or UNIDEX 600 Motion Controller
(OPTIONAL)
Figure 1-2.
DR 500
Aerotech
DR500 Drive Rack
with Amplifiers
Sample Single-axis LZR2000 Configuration
This system provides resolution to 0.6 nm (0.024 µin) for enhanced positioning
performance, as well as velocities up to 500 mm/sec at sub-micron resolution for
increased productivity. Environmental compensation provides 0.15 µm/100 mm
(6.0 µin/4.0 in) accuracy.
1.1.2. The LZR2000 Laser Head
The laser head of the LZR2000 system (shown in Figure 1-2 as part of a typical
configuration) is the component responsible for generating the single-frequency laser
beam and detecting/interpreting the interference patterns of the return beam. The head
contains the circuitry needed to convert the interference patterns into standard A-quad-B
line drive and A-quad-B sinusoidal (SIN/COS) signals. Laser head features include a
single-frequency, helium-neon laser, internal DC power supply circuitry for the laser
(converted from the external 100-240 volt AC switching power supply) and detector
optics enclosed in a sturdy metal housing. External features include diagnostic LEDs
(Laser On, Laser Ready), the laser beam exit and return apertures, a laser output control
1-2
Aerotech, Inc.
Version 1.0
LZR2000
Introduction
shutter (with Target, On and Off settings), output signal connectors and an AC power
connector. A front view of the laser head is illustrated in Figure 1-3.
Laser On LED
On Position
Target Position
Laser Ready LED
Warning Label
Off Position
Shutter
Aperture
(Laser Return)
Aperture
(Laser Exit)
Laser Head
Hole for Leveling
Screw
Hole for Leveling
Screw
Figure 1-3. Front View of the Laser Head (LZR2000)
The laser head of the LZR2000 system emits laser radiation from the top aperture.
Never stare directly into the laser beam or its reflections.
DANGER
The “Laser On” LED (shown in Figure 1-3) is a red LED that is lit when power is
supplied to the laser head. The “Laser Ready” LED is a green LED that is lit when the
laser frequency has been stabilized (usually about 15 minutes after power is supplied to
the laser head). Never attempt to use the laser head if the “Laser Ready” LED is not lit,
otherwise inaccurate readings may result.
The “Laser on” LED will flash on and off during the 15 minute warm up of the laser
head.
The laser head provides a standard λ/2 (316 nm) output signal in A-quad-B differential
line driver and SIN/COS (analog) formats. The A-quad-B line driver output can interface
directly to a motion controller that supports such inputs (e.g., an Aerotech UNIDEX 500,
UNIDEX 600, etc.). However, the typical user will utilize the SIN/COS (analog) outputs
connected to an Aerotech MXH multiplier box. The multiplier box multiplies the
resolution and converts the signal to the standard differential (square wave) signal. Refer
to Figure 1-2 on page 1-2. A rear view of the standard LZR2000 laser head shows the
three connectors (for AC power connector, differential analog output signals and
differential TTL output signals). A rear view of the LZR2000 laser head is shown in
Figure 1-4.
Version 1.0
Aerotech, Inc.
1-3
Introduction
LZR2000
The laser head of the LZR2000 contains no user-serviceable components and
should not be opened.
Standard
8-Pin Differential Analog
Output Signal Connector
(A-quad-B SIN/COS Output)
External AC
Power
Connector
Leveling Screw
9-Pin D-type Differential
TTL Output Signal Connector
(A-quad-B TTL Line Driver Output)
Figure 1-4. Rear View of the Standard LZR2000 Laser Head
An operation diagram of the laser head and optics is illustrated in Figure 1-5.
AC Input
Laser Head
Linear Interferometer
Fixed
Retroreflector
Linear
Reflector
Power Supply
Measurement
Retroreflector
Beam Splitter
Single-Frequency
Laser
Detector
Fixed
Polarized
Beam Splitter
Single-frequency
Controller
LZR1100
Laser On,
Laser Ready
λ/2
A-quad-B
Sinusoidal
Output Signals
To Controller
MXH
Figure 1-5.
1-4
λ/2
A-quad-B
Line Driver
Output Signals
Operation Diagram of the Laser Head and Optics
Aerotech, Inc.
Version 1.0
LZR2000
Introduction
1.1.3. Cables
The standard LZR2000 system includes a 6-foot AC power cord for the laser head. Other
cables may need to be customized depending on the requirements and configuration of the
system.
1.1.4. The Optics Package
The LZR2000 system includes an optics package needed for linear measurements. This
standard optics package includes two retroreflectors and a single polarized beam splitter
(PBS).
For interferometer configurations, the PBS is connected to one of the retroreflectors
(retro). The linear interferometer (PBS/retro combination [LZR2300]) is either mounted
along an axis that is parallel to the laser beam or perpendicular to it. The linear
interferometer is positioned between the laser head and the second retroreflector
(LZR2400). With the laser head and the linear interferometer mounted in fixed positions,
the second retroreflector is mounted to a moveable base to form a path for the
measurement beam. The PBS and the retroreflector of the linear interferometer form the
path for the fixed reference beam. Figure 1-6 shows a complete LZR2000 system
highlighting the roles of the linear interferometer and retroreflector optics. It is also
possible to mount the linear reflector to a fixed surface and then mount the linear
interferometer to the moveable surface. The laser head should never be the moveable
component of the system.
Reference Beam
Single-frequency Beam
Splits at Point "A" to form a
Reference Beam and a
Measurement Beam
Linear Interferometer
Measurement Beam
Fixed Linear Interferometer
Retro
Moveable Retro
A
B
A
B
PBS
Beams Join and Interfere
at Point "B"
Distance
Laser Head
Linear Interferometer
Linear
Reflector
Axis of Motion
Stage
Motor
Figure 1-6. LZR2000 System Showing the Role of Optics
The linear interferometer and the linear reflector should be positioned as close as
possible to one another. This minimizes the effects of dead path error. Refer to
Chapter 5: Linear Displacement and Velocity Measurements.
Version 1.0
Aerotech, Inc.
1-5
Introduction
LZR2000
1.2.
Theory of Operation
The LZR2000 interferometer uses laser and optical techniques to perform very accurate
distance measurements. Linear, incremental displacement is determined using the relative
shift in the laser beam’s frequency between measurement and reference beams. This shift
in frequency is introduced by the motion of either the measurement or reference object
with respect to the other from a known starting (zero) point along the axis of motion.
Refer to Figure 1-6. As a result of this motion (from some starting reference point to the
destination point), an interference fringe is generated. This interference fringe is a dark
and bright pattern that is detected and measured by the detector optics and circuitry in the
laser head itself. The intensity of the interference fringe that is seen by the detector is a
sinusoidal signal where the signal peaks correspond to bright lines of the interference
fringe, and the valleys correspond to the dark lines.
1-6
Aerotech, Inc.
Version 1.0
LZR2000
1.3.
Introduction
Options and Accessories
A variety of options and accessories may be purchased with the LZR2000 system to
enhance its standard operation. Refer to Table 1-1 for part numbers and descriptions.
Table 1-1. Options and Accessories Available for the LZR2000 System
Part #
Description
LZR2250
Angular/Linear Combination Optical Kit
LZR2700
Plane Mirror Optical Kit
LZR2900
Linear Optical Kit
LZR1001
Post-mounted height adjusters
LZR1002
Base Plate
LZR1003
90 degree turning mirror cube
LZR1004
Mirror (0 degree incidence)
LZR1005
Mirror (45 degree incidence)
LZR1010
Material temperature sensor with cable (requires LZR1100)
LZR1020
Remote Ambient Temperature Sensor
LZR1100
Environmental compensation electronics, air and pressure sensor, and
10-foot cable
AR-4
AR-4M
AR-6
4 in (100 mm) length post with standard threads
4 in (100 mm) length post with metric threads
6 in (150 mm) length post with standard threads
AR-6M
6 in (150 mm) length post with metric threads
LZRTRIPOD
Heavy duty tripod with precision 3-axis alignment head/mounting plate
CASE1
Storage/Travel case for laser head and optics
CASE2
Storage/travel case for tripod
Version 1.0
Aerotech, Inc.
1-7
Introduction
LZR2000
1.4.
Applications and Configurations
The laser interferometer is an accurate and versatile scientific tool. The standard
LZR2000 system contains the laser and optical components necessary to perform linear
measurement.
The sample configurations provided in the following sections are configurable with
any motion control system (e.g., UNIDEX 500, UNIDEX 600, etc.) and not just
specifically for the system illustrated in the examples.
B. Motion of Measurement Optics
Closed-loop System
A. Motion Control
D. Feedback Signal
U500/U600
Feedback
Figure 1-7.
1-8
Closed-loop Systems
Aerotech, Inc.
Version 1.0
LZR2000
Introduction
1.4.1. Sample Configuration 1: Motor Control Based on
Interferometer Position Feedback Using a Signal Multiplier
and an External Motion Controller
This sample configuration is similar to the other examples, only a signal multiplier is
used. The A-quad-B sinusoidal signal from the laser head (9 pin D-type connector) is
sent to the signal multiplier using a customized cable. (Refer to Chapter 8: Technical
Details for laser head pinouts. Refer to documentation supplied with the MXH signal
multiplier for input/output pinouts and technical information). The output of the signal
multiplier is sent to the motion controller.
Range
Linear Interferometer
Laser Head
Linear
Reflector
Motor
A-quad-B
Sinusoidal
Signal
Axis of Motion
Stage
Customized Cables
λ /2
M
MXH Signal
Multiplier
x 100
A-quad-B
Line Driver
Signal
Position Commands
λ /200
DR 500
U500/U600
DR Series
(DR300, DR500, DR600, DR800)
Motion Controller
Figure 1-8.
Closed-loop Position Feedback Application Using a Multiplier
Consider a motion controller (e.g., a UNIDEX 500, UNIDEX 600, etc.) that requires very
accurate positioning. In this application, a motion controller commands the axis to a
desired position while the laser interferometer provides the highly accurate position
feedback. The A-quad-B sinusoidal position signal (with a resolution of λ/2) is sent from
the laser head to the MXH multiplier. The signal multiplier then provides an A-quad-B
line driver signal output (with a λ/200 resolution, for example). This multiplied signal is
sent back to the motion controller. A signal multiplier configuration is illustrated in
Figure 1-8.
Version 1.0
Aerotech, Inc.
1-9
Introduction
LZR2000
1.4.2. Sample Configuration 2: Temperature, Pressure and Humidity
Compensation for Enhanced Accuracy
Measurement accuracy is dependent on the wavelength of light. The wavelength of light,
in turn, is affected by air temperature, pressure, and humidity. The optional
environmental compensator (LZR1100) and remote material temperature sensor
(LZR1010) packages measure any temperature and pressure changes and compensates the
wavelength to provide a system accuracy of 0.15 µm per 100 mm.
Linear
Interferometer
Laser Head
Distance
Linear
Reflector
Potential
Heat
Source
123,456,789,000
Axis of Motion
A-Quad-B
Sinusoidal
Signal
λ /2
PC
MXH Signal
Multiplier
x 100
Air
Sensor
λ /200
Servo
Stage
Material
Temperature
Sensor
DR500
DR 500
U500/U600
λ /32 or λ /1,024
Position Commands to Amplifier
Figure 1-9. Sample Environmental Compensation Configuration
A sample configuration showing the use of the temperature and pressure compensation
option is illustrated in Figure 1-9. Humidity compensation is entered manually.
To help minimize the effects of ambient temperature fluctuations, always plan the
system layout so that potential heat sources (e.g., stage motors, air conditioning/
heating ducts, etc.) do not directly radiate into the path of the laser beam.
See the controllers online help file documentation for more information on using the
LZR1100.
1-10
Aerotech, Inc.
Version 1.0
LZR2000
Introduction
1.4.3. Sample Configuration 3: Motor Control Using an External
Motion Controller with Interferometer Position Feedback
This sample configuration illustrates an application that uses a generic motion controller
for positioning and an LZR2000 laser head (with optics) for highly accurate position
feedback information. This configuration requires an LZR2000 laser head, optics, cables
and a motion controller.
In this example, an LZR2000 laser head is connected to the motion controller using a
customized cable. Precise position information in the form of A-quad-B line driver
signals is sent from the laser head to the motion controller. A linear stage with a motor
defines the axis of motion on which the measurement reflector is mounted.
After the motion controller commands the stage to move, position feedback signals from
the laser head are sent back to the motion controller. Figure 1-10 illustrates a sample
closed-loop motion control configuration that uses interferometer position feedback from
the laser head.
Range
Laser Head
Linear Interferometer
Linear
Reflector
Motor
Axis of Motion
A-quad-B
Line Driver
Signal
M
Stage
Customized Cable
Position Commands
DR 500
U500/U600
DR Series
(DR300, DR500, DR600, DR800)
UNIDEX 500/600
Motion Controller
Figure 1-10. Sample Motion Control Configuration with Interferometer Feedback
Version 1.0
Aerotech, Inc.
1-11
Introduction
LZR2000
1.5.
40 C
15 C
Proper Handling and Storage Techniques
The LZR2000 system contains precision measurement equipment. All components
should be handled carefully to ensure proper operation. Exposure to harsh elements such
as excessive temperatures (exceeding 15-40° C), humidity extremes (above 90%, noncondensing), and shocks/vibrations (in excess of 30 g for 11 ms) should be avoided.
When not used for extended periods of time, the LZR2000 system components should be
stored in their original packaging. Electronic hardware and optics should be kept where
they are not subject to physical abuse, excessive dirt, temperature, moisture, or vibration.
Although the laser head of the LZR2000 system consists of a rugged metal enclosure, it
houses sensitive components such as a laser and precision optics. Never drop or bump
the laser head. In addition, the laser head contains no user-serviceable parts and should
not be opened. Opening the laser head can cause serious electrical injuries and will void
the warranty.
Never remove the protective cover from the laser head. There are no userserviceable components inside. Removal may cause severe electrical shock,
irreparable component damage, excessive radio frequency (RF) interference,
and will void the Aerotech warranty.
DANGER
Like the laser head, the optics used in the LZR2000 system are precision devices that
should be handled carefully. Never touch the glass or mirrored surfaces of any optical
device in the LZR2000 system (i.e., the linear reflector and the linear interferometer).
Touching these surfaces can leave residue that may interfere with the accuracy of the
system.
Never touch the glass or mirrored surfaces of the optical components in the
LZR2000 system.
WARNING
LZR2000 system cables should be installed so that they do not interfere with the
operation of the system. Never kink or severely bend any cable in the LZR2000 system.
Never disconnect a cable by pulling on the cable. Instead, hold the cable by its connector
and gently remove it. Never connect or disconnect cables to a system that already has
power supplied to it.
Be sure that system power (i.e., power to the PC, the optional motion controller,
etc.) is turned off before connecting or disconnecting any system cables.
DANGER
1-12
Aerotech, Inc.
Version 1.0
LZR2000
1.6.
Introduction
Laser Safety and Precautions
This product is a Class II laser product conforming to the Federal Bureau of radiological
health regulations 21 CFR 1040.10 and 1040.11 and to the laser international laser safety
regulations. The output beam of the LZR2000 laser head is limited to less than 1.0 mW
output power with a maximum intensity of 0.1 mW/mm2. At these low power levels, eye
protection is not required for normal scatter or indirect reflections. However, no one
should ever look directly into the beam of the laser. The pulse specification is continuous
wave, the laser medium is helium-neon, and the wavelength is 632.9907 nanometers.
Never look directly into the beam of the LZR2000 laser head.
The laser head has appropriate grounding connections for the HeNe laser. Under no
circumstances should the ground be defeated or circumvented.
DANGER
Never attempt to defeat or circumvent the ground connection on the LZR2000.
The input voltage to the laser head can exceed 10,000 volts during startup. Even though
the available output current is limited to a relatively safe limit, exercise extreme caution
when using the LZR2000 system.
DANGER
Two labels (a caution label and a shipping label) are attached to the standard laser head to
warn operators of potential hazards. These labels are illustrated in Figure 1-11.
Version 1.0
Aerotech, Inc.
1-13
Introduction
LZR2000
ELECTRO OPTICAL DIV.
AEROTECH
CAUTION
AEROTECH, INC.
101 Zeta Drive
Pittsburgh, PA 15238
(412) 963-7470
MODEL NUMBER:
LASER RADIATION
DO NOT STARE
INTO BEAM
Helium-Neon Laser
1.0 Milliwatt
Maximum Output
Class II Laser Product
SERIAL NUMBER:
RUN NUMBER:
MANUFACTURED:
This laser product conforms to the
provisions of 21CFR 1040.10 and 1040.11.
CAUTION - Laser
radiation when open.
DO NOT STARE
INTO BEAM.
CAUTION - High
voltage present
when cover removed.
CLASS II
Figure 1-11. Standard Caution and Shipping Labels
Use of controls, adjustments, or performance of procedures, other than those
specified herein, may result in hazardous radiation exposure.
DANGER
1-14
∇ ∇ ∇
Aerotech, Inc.
Version 1.0
LZR2000
Unpacking and Inspecting the LZR2000 System
CHAPTER 2:
UNPACKING AND INSPECTING THE
LZR2000 SYSTEM
In This Section:
• Introduction .............................................................................. 2-1
• Unpacking the Components...................................................... 2-1
• Inspecting the LZR2000 Laser Head ........................................ 2-2
• Inspecting the Optical Packages ............................................... 2-2
2.1.
Introduction
Chapter 2 sets the groundwork for the actual installation and setup of the individual
system components. This chapter steps the operator through the logical sequence of
unpacking the LZR2000 system components and then inspecting them for damage or
looseness that may have occurred during shipment.
2.2.
Unpacking the Components
Before unpacking any components, visually inspect the containers of the LZR2000 system
for any evidence of shipping damage. If any such damage exists, notify the shipping
carrier immediately.
All electronic equipment is wrapped in antistatic material and packaged with
desiccant (a drying agent used to reduce moisture). Make certain that the antistatic
material is not damaged during unpacking.
WARNING
Remove the packing list from the LZR2000 container(s). Make sure that the items
specified on the packing list are contained within the package(s). The items listed in
Table 2-1 may be included with the LZR2000 system. Visually inspect all items that are
received. Key details in the inspection process are listed in the sections that follow.
Table 2-1.
Part #
LZR2000
LZR2300
LZR2410
-EDU169
Version 1.0
Minimal System Components
Description
1 Single-frequency HeNe Laser Head
1 LZR2300 Linear Interferometer
2 LZR2410 Alignment Targets
1 Signal Cable
1 Operations and Technical Manual.
Aerotech, Inc.
2-1
Unpacking and Inspecting the LZR2000 System
2.3.
LZR2000
Inspecting the LZR2000 Laser Head
All products undergo a total quality inspection before they are shipped from Aerotech.
Even with a stringent quality assurance program, however, it is still possible that a
product may arrive in less than perfect condition due to improper handling during
shipment. After unpacking the LZR2000 laser head, check to ensure that the laser head
has no visible signs of damage. Also, ensure that the shutter rotates without excessive
resistance into its three positions (Off, On, and Target).
2.4.
Inspecting the Optical Packages
After unpacking the optics package, inspect the components for visible signs of damage
or breakage. Be careful not to touch any glass or reflective surfaces of the optical
devices. Contact with these surfaces can leave oil and dirt residue from the fingerprints.
This residue can be detrimental to the proper operation of the optical components of the
Laser Feedback System. The linear reflector and interferometer are illustrated in
Figure 2-1.
Figure 2-1.
WARNING
The Linear Interferometer and Reflector Optics
Never touch the glass and reflective surfaces of the optical components. Residue
from fingerprints can interfere with the proper operation of the Laser Feedback
System.
∇ ∇ ∇
2-2
Aerotech, Inc.
Version 1.0
LZR2000
Getting Started, A First Look
CHAPTER 3: GETTING STARTED, A FIRST LOOK
In This Section:
• Introduction ..............................................................................3-1
• Physical Setup of the Laser Head .............................................3-2
• Optical Components and Alignment Aides ..............................3-5
• Layouts and Configurations......................................................3-6
• Aligning the System .................................................................3-7
3.1.
Introduction
The information in this chapter provides the user with a first look at the LZR2000 Laser
Feedback System. This chapter is designed to briefly walk the user through setting up the
laser head and connecting the signal cables.
Individuals that need detailed explanations about other features, techniques, and
procedures should review Chapter 4 through Chapter 9.
Also, the information in this chapter is just one example to help the user become
familiar with the LZR2000 Feedback System. It should not be regarded as the only
configuration or use of the system.
Version 1.0
Aerotech, Inc.
IMPORTANT
3-1
Getting Started, A First Look
3.2.
LZR2000
Physical Setup of the Laser Head
This section explains how to install and setup the laser head and tripod (if used) in the
LZR2000 system. This includes choosing suitable locations for the laser head and
positioning the laser head.
3.2.1. Mounting the Laser Head
Typically, the laser head can be mounted on either a tripod or directly to a flat, fixed
(non-moving) rigid table.
Before beginning, decide on the desired/required position for the laser head.
The mounting surface for the LZR2000 System should be a fixed, vibration-free
surface. Vibrations can cause erroneous readings and possible damage to the
equipment.
IMPORTANT
For standard table mounting, the laser head is secured to the table (or optical breadboard)
using the supplied leveling screws. For tripod configurations, the laser head is mounted
to the tripod’s mounting plate using three supplied leveling screws. Figure 3-1 illustrates
tripod and stationary table mounting diagrams of the laser head.
Leveling Screws
Laser
Head
Leveling Screws
Laser
Head
Base Plate
Stationary Table
Mounting Tripod
Figure 3-1.
3-2
Mounting the Laser Head on a Tripod and on a Stationary Table
Aerotech, Inc.
Version 1.0
LZR2000
Getting Started, A First Look
3.2.2. Setup of the Laser on the Tripod
If the desired installation of the laser head is with the tripod, decide on the required
position for the laser head. Also, refer to Figure 3-2 and Figure 3-3 for setup of the tripod
and use of the positioning controls. For more detailed instructions, turn to Chapter 4:
Physical Setup of the Laser Head.
Leveling Foot and Nut (3)
Gear Head Assembly
0RXQWLQg Plate
Translational Lock
Translational Adjustmert
1 Cap screw (1/4 * 20)
Vertical Lock
Horizontal Rotation Lock
Horizontal Rotation Adjustmert
Vertiacal Rotation Adjustmert
Captive Set Screw
Vertical Lock
Access Hole in Tripod Collar
Vertical Lift Adjustment
Tripod
Figure 3-2.
Version 1.0
Setup of Tripod and Installation of the Laser Head
Aerotech, Inc.
3-3
Getting Started, A First Look
LZR2000
Translational Adjustment
Translational Lock
Vertical Rotation Lock
Horizontal Rotation
Adjustment
Horizontal Rotation Lock
Vertical Rotation
Adjustment
Vertical Lock
Figure 3-3.
3.2.3.
Vertical Lift
Adjustment
Laser Head Motions with Position Controls
Leveling the Laser Head
Positioning one leg of the tripod in line with the laser beam in most cases will make it
easier to level the baseplate.
Observing the bubble level on top of the tripod, adjust the leg lengths until the baseplate
is level. This is done by loosing the black knobs on each leg of the tripod. Ensure the
knobs are securely tightened when the leveling operation is complete.
3-4
Aerotech, Inc.
Version 1.0
LZR2000
3.3.
Getting Started, A First Look
Optical Components and Alignment Aides
The optics portion of the LZR2000 System consists of a linear reflector (LZR2400) and a
linear interferometer (LZR2300). These optical components are used in linear
displacement and velocity measurement applications.
Mounting hardware is also available for the reflector and linear interferometer that allows
attachment to most machine surfaces and tool spindles. Post-mount height adjusters
connect to the optical devices using a pair of knurled screws, refer to Figure 3-4. Then the
height adjusters attach to a variety of optical posts available with threaded ends in either
standard or metric threads. Figure 3-5 provides examples of alternative ways to mount the
retroreflector.
Table Mounting
Retroreflector
Height Adjuster
(LZR1001)
Post
Linear
Interferometer
(LZR2300)
Side View
Front View
Base (LZR1002)
Figure 3-4.
Interferometer Mounting
Linear Reflector
LZR2400
Stage
Figure 3-5.
Version 1.0
Stage
Servo
Servo
Alternate Methods of Mounting the Reflector
Aerotech, Inc.
3-5
Getting Started, A First Look
3.4.
LZR2000
Layouts and Configurations
There are several optical configurations that are available for linear measurement
applications. We will use a configuration that best suits the particular application. The
interferometer is always placed in between the laser head and two retroreflectors, refer to
Figure 3-6. Normally, one of the retroreflectors will be physically attached to the
interferometer and the other will be allowed to move with respect to the interferometer.
Linear
Interferometer
Retroreflector
Distance
Linear Reflector
Stage
Axis of Motion
Figure 3-6.
3-6
Servo
Laser Head, Interferometer, and Reflector Setup
Aerotech, Inc.
Version 1.0
LZR2000
3.5.
Getting Started, A First Look
Aligning the System
The alignment of optical components in the system is performed visually using the laser
beam from the laser head.
The laser head of the LZR2000 System emits laser radiation from the top aperture.
Never stare directly into the laser beam or its reflection.
It is recommended that the “Ready” LED be illuminated before beginning the alignment
process. The “Ready” LED indicates that the laser has been stabilized and is ready for
taking measurements. It takes approximately 15 minutes for the “Ready” LED to come on
after power is supplied to the laser head.
DANGER
The following outlines the process of getting acquainted with coarsely aligning and
setting up the system. For more detailed alignment instructions, turn to
Chapter 5: Linear Displacement and Velocity Measurements.
1.
Turn on the laser and allow it to stabilize while positioning the optics. Set the shutter
to the target (+) position. Refer to Figure 3-7.
Figure 3-7.
Front View of Laser Head
2.
Mount the linear reflector (retroreflector) so that its opening is facing the exit
aperture of the laser head. Be sure to orient the retroreflector and/or laser head so that
the laser beam will hit the center of a “triangle” and be reflected to the opposite
“triangle.” Refer to Figure 3-8.
3.
Position the moveable table/stage so that the retroreflector is at the travel limit closest
to the laser head.
4.
When the laser is stabilized, adjust the laser head so that the return beam hits the
center of the target on the laser head.
5.
Now move the table/stage so that the retroreflector moves to the travel limit that is
furthest from the laser head. During this movement, align the head so that the return
beam is always centered on the target. Refer back to Figure 3-6.
Version 1.0
Aerotech, Inc.
3-7
Getting Started, A First Look
LZR2000
Beam from Laser Head
Beam from Laser Head
1
6
2
5
3
4
Beam Reflected to Laser Head
Six "Triangles" in
a Retroreflector
Figure 3-8.
Beam Reflected to Laser Head
Proper Orientation of
a Retroreflector
Improper Orientation of
a Retroreflector
Front View of a Retroreflector
6.
Mount and position the linear interferometer on a non-moving surface between the
laser head and the measurement retroreflector so that the beam hits the upper half of
the PBS opening. The retroreflector of the linear interferometer should be oriented
so that the portion of the laser beam reflected by the PBS will (1) hit the center of a
“triangle”, (2) be reflected to the opposite “triangle”, (3) return to the PBS, and (4)
be reflected back to the laser head. Refer to Figure 3-8.
7.
The linear interferometer should be mounted as closely as possible to the
measurement reflector. This distance should be minimized so that the measurement
beam is minimally effected by air temperature, pressure and humidity differences.
8.
Verify that the measurement reflector does not interfere with the linear interferometer
at any point in the travel range.
9.
Block the transmitted beam between the interferometer and the reflector (using a
piece of paper, for example) and adjust the linear interferometer assembly so that the
reference portion of the return beam hits the center of the target on the laser head.
Refer to Figure 3-9.
10. Remove the piece of paper and perform the same adjustment to the reflector until its
return beam is also centered on the crosshair of the lower aperture on the laser head.
Refer to Figure 3-9.
11. Repeat the previous steps to fine tune the system further.
There should be only one dot visible on the lower aperture, since both beams overlap
each other completely. Refer to Figure 3-9.
12. Rotate the shutter of the laser head to the ON position.
3-8
Aerotech, Inc.
Version 1.0
LZR2000
Getting Started, A First Look
A - Beams Not Visible
B - One Beam Is Visible
C - Beams Not Aligned or on Target
D - One Beam Is on Target
E - Both Beams Nearly Aligned
F - Beams Aligned and on Target
Figure 3-9.
Different Degrees of Beam Alignment (View from Front of Laser Head)
∇ ∇ ∇
Version 1.0
Aerotech, Inc.
3-9
Getting Started, A First Look
3-10
Aerotech, Inc.
LZR2000
Version 1.0
LZR2000
CHAPTER 4:
Physical Setup of the Laser Head and Tripod
PHYSICAL SETUP OF THE LASER
HEAD AND TRIPOD
In This Section:
• Introduction ....................................................................................... 4-1
• The LZR2000 Laser Head ................................................................. 4-1
• Defining the System Layout .............................................................. 4-8
• Mounting the Laser Head .................................................................. 4-3
• Supplying Power and Signal Connections to the Laser Head .......... 4-11
• Customized Laser Head Cables ....................................................... 4-13
• LZR2000 System Measurements ..................................................... 4-13
4.1.
Introduction
This chapter explains how to install and setup the laser head and tripod used in the
LZR2000 System. This includes choosing suitable locations for the laser head, supplying
power and signal cables to the laser head, and positioning the laser head.
4.2.
The LZR2000 Laser Head
The LZR2000 laser head (shown at right and in Figure 4-1) is the component responsible
for generating the single-frequency laser beam and detecting/interpreting the interference
patterns of the return beam. The head contains the circuitry needed to convert the
interference patterns into standard A-quad-B line driver and A-quad-B sinusoidal
(SIN/COS) signals. Laser head features include a single-frequency, helium-neon laser,
internal DC power supply circuitry for the laser (converted from the external 100-240 volt
AC switching power supply) and detector optics enclosed in a sturdy metal housing.
External features include diagnostic LEDs (Laser On, Laser Ready), the laser beam exit
and return apertures, a laser output control shutter (with Target, On and Off settings),
output signal connectors and an AC power connector. A front view of the laser head is
illustrated in Figure 4-1.
Version 1.0
Aerotech, Inc.
4-1
Physical Setup of the Laser Head and Tripod
LZR2000
On Position
Laser On LED
Laser Ready LED
Target Position
Warning Label
Off Position
Shutter
Aperture
(Laser Return)
Aperture
(Laser Exit)
Laser Head
Hole for Leveling
Screw
Hole for Leveling
Screw
Figure 4-1. Front View of the Laser Head (LZR2000)
The laser head of the LZR2000 system emits laser radiation from the front top
aperture. Never stare directly into the laser beam or its reflections.
DANGER
The “Laser On” LED (shown in Figure 4-1) is a red LED that is lit when power is
supplied to the laser head. The “Laser Ready” LED is a green LED that is lit when the
laser frequency has been stabilized (usually about 15 minutes after power is supplied to
the laser head). Never attempt to use the laser head if the “Laser Ready” LED is not lit,
otherwise inaccurate readings may result.
The “Laser on” LED will flash on and off during the 15 minute warm up of the laser
head.
A rear view of the standard LZR2000 laser head shows the three connectors (for AC
power connector, differential analog output signals and differential TTL output signals).
A rear view of the LZR2000 laser head is shown in Figure 4-2.
The laser head of the LZR2000 contains no user-serviceable components and
should not be opened.
4-2
Aerotech, Inc.
Version 1.0
LZR2000
Physical Setup of the Laser Head and Tripod
Standard
8-Pin Differential Analog
Output Signal Connector
(A-quad-B SIN/COS Output)
External AC
Power
Connector
Leveling Screw
9-Pin D-type Differential
TTL Output Signal Connector
(A-quad-B TTL Line Driver Output)
Figure 4-2.
4.3.
Rear View of the Standard LZR2000 Laser Head
Mounting the Laser Head
Typically, the laser head can be mounted on either a tripod or directly to a flat, fixed
(non-moving) rigid table. The placement, orientation and alignment of the laser head,
regardless of the method of mounting, depend on the desired configuration as well as
other factors such as the size of the work area and the amount of clearance between
system components. These factors may ultimately dictate how the laser head must be
mounted and/or oriented.
The mounting surface for the LZR2000 System should be a fixed, vibration-free
surface. Vibrations can cause erroneous readings and possible damage to the
equipment.
IMPORTANT
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4-3
Physical Setup of the Laser Head and Tripod
LZR2000
For standard table mounting, the laser head is secured to the table (or optical breadboard)
using the supplied leveling screws. For tripod configurations, the laser head is mounted
to the tripod’s mounting plate using three supplied leveling screws. Figure 4-3 illustrates
tripod and stationary table mounting diagrams of the laser head.
Leveling Screws
Laser
Head
Leveling Screws
Laser
Head
Base Plate
Stationary Table
Mounting Tripod
Figure 4-3.
Mounting the Laser Head on a Tripod and on a Stationary Table
4.3.1. Setup of the Laser on the Tripod
If the desired installation of the laser head is with the tripod, decide on the required
position for the laser head. Also, follow the steps listed next when setting up the tripod for
installation of the laser head. Refer to Figure 4-4.
1.
Insert the geared head assembly into the tripod collar.
a)
b)
c)
d)
e)
f)
g)
h)
4-4
Ensure that the captive set screw is in place inside the geared head
assembly and is not protruding out.
Position the geared head assembly so the captive set screw lines up
with the access hole in the tripod’s collar.
Using the supplied 3/17-inch Allen wrench, tighten the set screw in
the geared head assembly. This prevents the geared head assembly
from moving in relation to the tripod’s collar.
Adjust the height of the geared head by using the vertical lift
adjustment on the tripod.
Tighten the vertical lock on the tripod. This prevents the geared
head from moving up or down from within the tripod.
Lock the horizontal rotation lock on the geared head. This prevents
the geared head from rotating left or right.
Using the vertical rotation adjustment, adjust the geared head until
it appears to be level.
Lock the vertical lock on the geared head. This prevents the geared
head from moving up or down.
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Physical Setup of the Laser Head and Tripod
2.
Line up the mounting plate with the cap screw on the geared head and
secure the mounting plate to the geared head by tightening the cap screw.
The cap screw is accessible through an opening in the geared head. Ensure
that the front of the base plate is positioned so that vertical rotation
adjustments cause the front of the base plate to rotate vertically and not
cause the plate to roll.
3.
Place the laser head on the mounting plate so the two front feet and rear foot
line up with the corresponding holes in the mounting plate and drop into the
mounting plate’s miniature cross-slide assembly.
4.
Secure the laser head to the mounting plate using the three leveling feet and
lock nuts.
Leveling Foot and Nut (3)
Gear Head Assembly
0RXQWLQg Plate
Translational Lock
Translational Adjustmert
1 Cap screw (1/4 * 20)
Vertical Lock
Horizontal Rotation Adjustmert
Horizontal Rotation Lock
Vertiacal Rotation Adjustmert
Captive Set Screw
Vertical Lock
Access Hole in Tripod Collar
Vertical Lift Adjustment
Tripod
Figure 4-4.
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Setup of Tripod and Installation of the Laser Head
Aerotech, Inc.
4-5
Physical Setup of the Laser Head and Tripod
LZR2000
4.3.2. Tripod and Laser Head Positioning Controls
When using the tripod, every measurement made requires translational and rotational
movements of the laser head. These adjustments are made often, so now is the time to
become familiar with them. Laser head motion resulting from operating these controls is
shown in Figure 4-5.
Translational Adjustment
Translational Lock
Vertical Rotation Lock
Horizontal Rotation Lock
Horizontal Rotation
Adjustment
Vertical Rotation
Adjustment
Vertical Lock
Vertical Lift
Adjustment
Figure 4-5.
Laser Head Motions with Position Controls
For vertical translation (linear up and down movement) of the laser head, perform the
following procedures.
4-6
1.
Unlock vertical lock located on the tripod assembly.
2.
Turn the vertical lift adjustment to raise or lower the laser head to the
desired height.
3.
Lock the vertical lock.
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Physical Setup of the Laser Head and Tripod
For vertical rotation (tilting) of the laser head, perform the following procedures.
1.
Unlock the vertical rotation lock.
2.
Turn the vertical rotation adjustment to raise or lower the laser head up or
down to the desired position.
3.
Lock the vertical rotation lock at the desired setting.
For horizontal translation (linear side to side movement) of the laser head, perform the
following.
1.
Unlock the translational lock on the mounting plate.
2.
Turn the translational adjustment to slide the laser left or right to the desired
position.
3.
Lock the translational lock.
For horizontal rotation (turning) of the laser head, perform the following procedures.
1.
Unlock the horizontal rotation lock.
2.
Rotate the laser head so it points in the desired direction.
3.
Lock the horizontal rotation lock after reaching the desired setting.
4.3.3. Leveling the Laser Head
Positioning one leg of the tripod in line with the laser beam in most cases will make it
easier to level and align the baseplate.
Watching the bubble level on top of the tripod, adjust the leg lengths until the baseplate is
level. Make these adjustments by loosing the black knobs on each leg of the tripod.
Ensure the knobs are securely tightened when the leveling operation is complete.
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4-7
Physical Setup of the Laser Head and Tripod
4.4.
LZR2000
Defining the System Layout
Before beginning the installation process, it is helpful to plan the system configuration.
Understanding the precise needs of the application is vital in this endeavor. Consider the
following topics to help in planning the system configuration.
•
•
•
•
•
•
•
•
What is the purpose/goal of the application (in other words, does the application
involve a measurement/control process)?
What type of motion control system is going to be used and what types of
input/output signals does it require?
How many axes of motion are involved with the application?
What degree of accuracy is needed?
Does the application require the use of an external signal multiplier for higher
resolution?
Does the application require environmental compensation (i.e., temperature,
pressure and humidity) for increased accuracy?
Which components of the system will be in motion (i.e., what will be the motion
axis)?
Will the reference path and measurement path of the Laser Feedback System
need to be parallel or perpendicular to each other?
Consider the desired application needs and define the required configuration accordingly.
When choosing a location for the LZR2000 System, be sure to consider such factors as
the temperature and humidity extremes. The laser head (and the entire LZR2000 System)
has an operating temperature range of 15-40° C and a humidity range of 0-90%
(noncondensing). Also, the environment should be free of anything that could interfere
with the operation of the system (such as excessive moisture, dust, or smoke). The
mounting surface for the LZR2000 System should be a stable, vibration-free surface. The
location should provide an electrically “clean” and stable power source for proper
operation of the head (and other electrical components). In addition, the location should
provide sufficient clearance for all moving parts and should allow all cables to be routed
so they do not interfere with operators or moving parts.
4.4.1. Positioning the Laser Head and Tripod
Where the position of the laser will be depends on the reason for making the
measurements and where the optics will be mounted. Consider the following.
•
The user may want to make measurements as close as possible to the area
where the tool meets the workpiece.
•
The user may want to make measurements as close as possible to the system,
since any offsets between the user’s measurement axis and the distance
measuring system’s axis may introduce error (types of errors are discussed
later in this manual).
Laser system measurements for three different axes can be made from only two setups of
the laser head. Refer to Figure 4-6.
4-8
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Physical Setup of the Laser Head and Tripod
1. Set up along the
bed of the machine
Z Axis
Y
X
2. Set up into the machine
Z
Y
X
Y Axis
Figure 4-6.
Machine Tool Positioning of Tripod and Laser
Table 4-1 illustrates what measurements can be made with the laser head set up as shown
in Figure 4-6. The measurements are easily made from these two positions since:
1.
All the optics have been designed around a common centerline that allows
complete interchangeability for all measurements along an axis.
For distance and angular measurements, the user can use the same
mounting hardware with no adjustments between measurements.
2.
Measurements on the “Z” axis can be made from either the “X” or “Y” axis
by turning the distance and angular interferometers on their sides or by using
a turning mirror for straightness measurements (refer to the individual
measurement chapters in this manual for additional information on this
procedure).
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Physical Setup of the Laser Head and Tripod
Table 4-1.
LZR2000
Measurement versus Setup Axis
Measurement
Setup Axis
Distance
X axis
Yaxis
Z axis
4-10
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X axis or Y axis
X axis or Y axis
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4.5.
Physical Setup of the Laser Head and Tripod
Supplying Power and Signal Connections to the Laser Head
This section discusses the steps necessary to provide power to the laser head and making
the signal connections between the laser head and the controller with the appropriate
cable(s).
The laser head of the LZR2000 System emits laser radiation from the upper front
aperture. Never stare directly into the laser beam or its reflections.
DANGER
Connecting an external power source to the standard laser head is done using a standard 6
foot (2 m) power cord that is supplied with the LZR2000 System. This keyed cable is
inserted into the power connector located on the back panel of the LZR2000 laser head
and connected to a 100-240 VAC source. The standard laser head uses a maximum of
50 watts of power at 100-240 VAC. To make the signal connection between the laser
head and the controller, use the signal cable (typically) provided. Additional wiring
information can be found in Chapter 8: Technical Details.
Standard Laser Head
AC Power Connector
Firmly grip any cable connector at the end (not the cord) before trying to separate a
cable from its mating connector. Failure to do this may cause undo strain on the
cable, damaging it internally.
WARNING
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Physical Setup of the Laser Head and Tripod
Standard
8-pin Differential Analog
Output Signal Connector
(A-quad-B SIN/COS Output)
LZR2000
External AC Power
Connector
9-pin D-type Differential TTL
Output Signal Connector
(A-quad-B TTL Line Driver Output)
(cable typically provided)
DR 500
DR Series
(DR300, DR500, DR600, DR800)
Environmental Compensator
Material
Temperature
Sensor
Figure 4-7.
Electrical and Signal Connections
4.5.1. Environmental Compensator Connections
If an environmental compensator (LZR1100) is used, be sure to connect the supplied
cable to the Misc. I/O connector of the DR300/DR500/DR600/DR800 (refer to
Figure 4-7). The connectors on this cable and the mating connectors are keyed.
When attaching a remote ambient temperature sensor (LZR1020), connect the cable to the
connector labeled “Temperature 1” on the LZR1100. Also, remote material temperature
sensor(s) (LZR1010) can be attached in any order to the LZR1100 connector(s) labeled
“Material 1”, “Material 2”, “Material 3”, or “Material 4”.
Unlock any cable connectors before trying to separate a cable from its mating
connector. Failure to do this may cause undo strain on the cable, damaging it
internally.
WARNING
4-12
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4.6.
Physical Setup of the Laser Head and Tripod
Customized Laser Head Cables
Before positioning and aligning the system, create (if necessary) and attach all the
required cables to the laser head. Standard cables are attached as described earlier. To
create cables for custom applications, refer to Chapter 8: Technical Details for connector
types and pinout information.
4.7.
LZR2000 System Measurements
The LZR2000 Laser Feedback System is designed specifically to make a variety of very
accurate measurements in a machine tool environment. The types of accurate
measurement the Laser Feedback System can make are:
•
•
Distance
Velocity
The hardware, other than the optics, needed to make any measurement with the LZR2000
Laser Feedback System are a LZR2000 laser head and a feedback signal cable. This is
used for all measurements made with the laser measurement system. A tripod may be
needed depending on the user’s application. If a tripod is not used, an alternative type of
rigid support must be provided for the laser head. In addition, optical kits and other
accessories are required to manipulate the laser beam for the desired measurement.
Table 4-2 lists the hardware required for each measurement.
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Physical Setup of the Laser Head and Tripod
Table 4-2.
LZR2000
Hardware versus Measurement
Measurements
Aerotech Part & Part
Linear Displacement
Number
(distance/velocity)
á
Laser Head (LZR2000)
Linear Interferometer
á
(LZR2000)
á
Linear Reflector (LZR2400)
Plane Mirror Optical Kit
(LZR2700)
á
Alignment Target (LZR2410)
Recommended Optional Accessories
á
LZR-TRIPOD
Environmental Compensator
á
(LZR1100)
Material Temperature Sensor
á
(LZR1010)
á
Height adjusters (LZR1001)
Base Plate (LZR1002)
Turning Mirror (LZR1003)
á
Posts (AR-)
Storage/ Travel Case for laser
á
head (CASE1)
Storage /Travel Case for
á
Tripod (CASE2)
Mirror (0 degree incidence)
(LZR1004)
Mirror (45 degree
incidence) (LZR1005)
Remote Ambient
Temperature Sensor
(LZR1020)
Laser Interferometer
Computer System
(LZR1500)
Plane Mirror
á
á
á
á
á
á
á
á
á
∇ ∇ ∇
4-14
Aerotech, Inc.
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LZR2000
CHAPTER 5:
Linear Displacement and Velocity Measurements
LINEAR DISPLACEMENT AND
VELOCITY MEASUREMENTS
In This Section:
• Introduction ....................................................................................... 5-1
• Measurement Specifications and Optical Hardware .......................... 5-1
• Optical Alignment Aides ................................................................... 5-5
• Layouts and Configurations............................................................... 5-6
• Aligning the System........................................................................... 5-8
• Accuracy and Potential Sources of Error......................................... 5-25
• Environmental Conditions over the Measurement Span.................. 5-25
• Environmental Conditions over the Length of the Dead Path.......... 5-26
• Material Temperature Compensation .............................................. 5-29
• Cosine Error .................................................................................... 5-30
• Abbé Error....................................................................................... 5-31
5.1.
Introduction
This chapter explains how to position and setup the required optical components of the
interferometer system for linear distance and velocity measurements. The positioning
process discussed in this chapter is divided into several steps. The first provides an
overview of the optics, their components and their functions. The second section
provides an introduction to optical accessories/aides such as height adjusters and
mounting posts and their roles in positioning the optics. The third section covers the
process of choosing a layout and mounting surface for the application, then mounting and
positioning the optical components appropriately. The fourth section covers the process
of aligning the system, from coarse alignment to the two most common methods of
alignment. Each of these steps is discussed individually in the sections that follow.
5.2.
Measurement Specifications and Optical Hardware
The LZR2000 Laser Feedback System is a basic system capable of measuring both
velocity and linear displacement. A distance (or linear) measurement is made by
measuring the change in position of one of the optics while the other is held stationary.
The LZR2000 is a stand-alone product, (i.e., the product includes the necessary hardware
[laser head, PC-board, software, cables, and optics]) for linear measurements. These
optical components are used in linear distance and velocity measurement applications.
Table 5-1 lists the required components needed for linear and velocity measurements.
Besides what is listed in Table 5-1, the user may need a tripod (LZR-TRIPOD). If a
tripod is not used, an alternative type of rigid support must be provided for the laser head.
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5-1
Linear Displacement and Velocity Measurements
Table 5-1.
LZR2000
Linear and Velocity Measurement Hardware List
Part Number
Description
LZR2000
Laser Head
LZR2300
Linear Interferometer
LZR2400
Linear Reflector
LZR2410 (2 each)
Alignment Target
EDU169
Manual
Table 5-2 contains the operating specifications for linear and velocity measurements. The
accuracy of distance measurements are accurate within the following tolerances
depending on the velocity of light compensation method and operating temperature.
Values shown in Table 5-2 apply at a known material temperature with a known
coefficient of thermal expansion.
Table 5-2.
Linear and Velocity Operating Specifications
Accuracy
Temp. Range
Uncompensated
Compensated
Vacuum
20°±1°C
±10 ppm
±1.5 ppm
±0.1 ppm
20°±5°C
±14 ppm
±1.7 ppm
±0.1 ppm
Measurement Range (Axial Separation)
10m (33 feet)
5-2
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Linear Displacement and Velocity Measurements
5.2.1. The Retroreflector
A retroreflector is an optical component that contains a single opening and has
specialized internal mirrors that allow incoming laser beams to be reflected in a path that
is parallel to the incident beam. One retroreflector is used by itself to reflect the
measurement beam and the other retroreflector is connected to the polarized beam splitter
(PBS) to reflect the reference beam. Each retroreflector has predrilled holes and knurled
screws for mounting to the PBS or a height adjuster (LZR1001).
With the laser turned off, look inside the retroreflector. Notice the pattern of six
connected triangles. The orientation of these triangles with respect to the incident laser
beam is very important. For proper operation of the LZR2000 system, the orientation of
the retroreflector is just as critical as its placement. The retroreflector must be oriented so
that the incident beam strikes one of the six triangles and is reflected back from the
opposite triangle. This is illustrated in Figure 5-1. If the retroreflector is not oriented
properly, simply rotate the retroreflector 90 degrees.
Beam from Laser Head
Beam from Laser Head
1
6
2
5
3
4
Beam Reflected to Laser Head
Six "Triangles" in
a Retroreflector
Figure 5-1.
Proper Orientation of
a Retroreflector
Beam Reflected to Laser Head
Improper Orientation of
a Retroreflector
Front View of a Retroreflector
5.2.2. The PBS Cube
The PBS is a cube with four openings. Internally the PBS contains a mirrored surface at a
45° angle to the incident laser beam. This allows one component of the incident beam to
be transmitted directly through the PBS and another component of the incident beam to
be reflected at a 90° so that the resulting beam is perpendicular to the incident beam. One
side of the PBS cube has a label that shows the direction of the incident and output
beams. The PBS has predrilled holes for mounting it to a retroreflector or a height
adjuster (LZR1001).
The PBS and one retroreflector are connected to form the linear interferometer
(LZR2300). With the laser turned off, look inside the linear interferometer in the
direction of the laser beam. Notice the pattern of six connected triangles from the
retroreflector. (It may be necessary to block the exit path of the PBS with white paper in
order to see the “triangles” of the retroreflector. The orientation of these triangles with
respect to the PBS and incident laser beam is very important. For proper operation of the
interferometer system, the orientation of the retroreflector portion of the linear
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5-3
Linear Displacement and Velocity Measurements
LZR2000
interferometer is just as critical as its placement. The retroreflector must be oriented so
that a portion of the incident beam is reflected by the PBS, then strikes one of the six
triangles of the connected retroreflector and is then reflected back to the PBS from the
opposite triangle (refer to Figure 5-1). If the retroreflector is not oriented properly,
simply disconnect it from the PBS using the knurled screws and then rotate the
retroreflector 90 degrees. Be sure to securely reattach the retroreflector to the PBS.
The laser beam from the LZR2000 laser head enters one aperture of the linear
interferometer and hits the internal mirrored surface of the beam splitter. A polarized
beam splitter (PBS) is a special optical component used to split the incident laser beam
into two separate beams that are perpendicular to each other: a reference beam and a
measurement beam. Refer to Figure 5-2 which shows an application where the linear
interferometer is fixed and the linear retroreflector is the moving optic. This is one of
several possible applications that can be seen in Section 5.4.
Single-frequency Beam Splits at Point "A" to form
a Reference Beam and a Measurement Beam
Measurement Beam
Reference Beam
Fixed Linear Interferometer
Fixed Linear Interferometer
Retro
Moveable Retro
A
B
A
B
PBS
Beams Join and Interfere at Point "B"
Figure 5-2.
Reference and Measurement Beams
The reference beam is reflected to the retroreflector portion of the linear interferometer
and is reflected back to the mirrored surface of the polarized beam splitter. Unlike the
reference beam that is reflected from the polarized beam splitter, the measurement beam
is transmitted through the mirrored surface of the PBS. The measurement beam travels to
a moveable retroreflector and is reflected back to the PBS. At this point, the reference
beam and measurement are joined and sent back to the detector portion of the laser head.
5-4
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5.3.
Linear Displacement and Velocity Measurements
Optical Alignment Aides
Mounting hardware is available for the linear reflector and linear interferometer that
allows attachment to most machine surfaces and tool spindles. This permits orientation of
the optics as required. The LZR1001 (post-mount height adjuster) connects to the optical
devices using a pair of knurled screws. A single larger knurled tightening knob is located
on the side of the height adjuster. The knob is used to secure the height adjuster (with the
connected optical component) to vertical posts that can be purchased separately.
Numerous optical posts are available with threaded ends in either standard or metric
threads. These mounting posts have 8-32 threads on one end and 1/4-20 threads on the
other end. Mounting post sizes, thread types, and other optical accessories are
summarized in Table 5-3.
Each optic in a system requires at least one post and height adjuster. Attach the height
adjuster to the side of the interferometer as shown in Figure 5-3. Then slide the height
adjuster over a post supported by a base.
Retroreflector
Height Adjuster
LZR1001
Post
Base LZR1002
Linear
Interferometer
LZR2300
Side View
Figure 5-3.
Version 1.0
Front View
Mounting of the Interferometer
Aerotech, Inc.
5-5
Linear Displacement and Velocity Measurements
Table 5-3.
Optical Mounting Accessories
Part Number
AR-2
Description
2 in (50mm)
AR-2M
2 in (50mm) (metric threads)
AR-3
3 in (75mm)
AR-3M
3 in (75mm) (metric threads)
AR-4/
4 in (100mm)
AR-4M
4 in (100mm) (metric threads)
AR-6/
6 in (150mm)
AR-6M
6 in (150mm) (metric threads)
AR-8
8 in (200mm)
AR-8M
5.4.
LZR2000
8 in (200mm) (metric threads)
LZR1001
Post Mount Height Adjuster
LZR1002
Base Plate
LZR1003
Turning Mirror Cube (90° rotation)
LZR1004
Mirror (0 degree incidence)
LZR1005
Mirror (45 degree incidence)
Layouts and Configurations
There are several optical configurations that are available for linear measurement
applications. Choose a configuration that best suits the particular application. To
summarize these optical configurations, we will focus on the three fundamental
components (the laser head, the linear interferometer and reflector), their orientation to
the incident laser beam (i.e., parallel or perpendicular) and their relationship to the axis of
motion (i.e., which component will move and what is the direction of the movement).
The interferometer is always placed in between the laser head and the two retroreflectors,
refer to Figure 5-4. Normally, one of the retroreflectors will be physically attached to the
interferometer and the other will be allowed to move with respect to the interferometer.
Retroreflector
Laser Head
Interferometer
Side View
Figure 5-4.
5-6
Interferometer and Retroreflector Layout
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Linear Displacement and Velocity Measurements
When planning the setup, it is important that the tail end of one of the arrows on the
interferometer’s label points toward the laser head. Also, the head of each arrow must
point toward a retroreflector, whether attached or moving.
The four basic optical configurations are: (1) moveable retroreflector along an axis
parallel to (i.e., in line with) the incident beam, (2) moveable linear interferometer along
an axis parallel to (i.e., in line with) the incident beam, (3) moveable retroreflector along
an axis perpendicular to the incident beam (horizontal plane), and (4) moveable
retroreflector along an axis perpendicular to the incident beam (vertical plane). These
configurations are illustrated in Figure 5-5.
The optical components of the system can be mounted in a variety of ways depending on
the particular application and configuration. Stationary optical components may be
attached to post mount height adjusters and then secured onto mounting posts that are
screwed into predrilled optical tables. Likewise, stationary optical components may be
vacuum mounted to precision granite tables. Regardless of the type of mounting used, it
is important to (1) begin with a surface that is flat and (2) ensure that the stationary
optical component is securely mounted to that surface.
A
Top View
B
Head
Linear Interferometer
Retro
A
Top View
B
Head
Retro
Linear Interferometer
Retro
"A" distance is the range
of motion. "B" distance
should be as small as
possible to minimize the
effects of temperature,
pressure and humidity
variations in the air
(dead path error).
Retro
A
A
Top View
Side View
B
Head
B
Head
Linear Interferometer
Figure 5-5.
Version 1.0
Linear Interferometer
Four Basic Optical Configurations
Aerotech, Inc.
5-7
Linear Displacement and Velocity Measurements
LZR2000
When mounting the moveable optical component, be sure that it is securely fastened to
the motion device (e.g., the stage, table or spindle). The axis of motion should be either
parallel or perpendicular (as appropriate) to the incident beam.
When aligning the optical components of the system, consider using a straight edge
to aid in the coarse alignment process. This can reduce the amount of time needed to
fine tune the alignment later.
There are some important considerations that must be addressed during the installation
and alignment of the optics.
1.
The interferometer assembly must be located between the laser head and the
reflector.
2.
The beam from the laser head must enter the interferometer at the tail end of
one of the arrows on its label.
3.
Vibrations and loose connections must be minimized by proper mounting.
Avoid long extensions and make sure that all supports are completely
stationary. A spindle, for example, must be secured by a brake so it won’t
rotate. If a brake isn’t available try using a hose clamp or a wedge.
4.
The laser beam must be returned to the bottom port on the laser head.
5.
The optics must be aligned to the laser beam well enough to keep the cosine
error at an acceptable level (see Section 5.7. Accuracy and Potential Sources
of Error).
6.
The optics must be aligned to the laser beam well enough to keep the beam
on target at the detector.
7.
If the angular optics have previously been installed, the distance optics can
be installed simply by changing the optics without changing the mounting
hardware.
After coarsely aligning the optical components of the system, the fine tuning process can
begin. This is discussed in the next section.
5.5.
Aligning the System
The alignment of the optical components of the system is accomplished visually using the
laser beam of the laser head. With the optical components already coarsely aligned,
supply power to the laser head using the cables discussed earlier in the previous chapter.
The laser head of the LZR2000 System emits laser radiation from the front top
aperture. Never stare directly into the laser beam or its reflections.
DANGER
5-8
It is recommended that the “Ready” LED be illuminated before beginning the alignment
process. The “Ready” LED indicates that the laser has been stabilized and is ready for
taking measurements. It takes approximately 15 minutes for the “Ready” LED to come
on after power is supplied to the laser head.
Aerotech, Inc.
Version 1.0
LZR2000
Linear Displacement and Velocity Measurements
5.5.1. Coarse Alignment
The best way to become familiar with the LZR2000 system is to use it. The following
pages will lead the user through the process of getting acquainted with the system by
coarsely aligning and setting up the system. The goal of this alignment process is to adjust
the positions of the optical components (laser head, linear interferometer and/or reflector)
such that the measurement and reference beams returning from the linear interferometer
are superimposed to form a single spot that is centered on the return port of the laser
head.
To set up the coarse alignment, perform the following:
1.
Move the moveable part of the machine as close to the laser head as possible. This
will keep the machine from hitting the laser head during a measurement and help
establish the near-end-of-travel.
The moveable part of the machine may depend on the axis being measured. Meaning,
the “X” axis moveable part may not necessarily be the “Y” axis or the “Z” axis
moveable part.
2.
Visually align the laser head parallel to the direction of travel as well as possible and
position it at an appropriate height. Some things to consider are:
•
3.
4.
Position for an axis appropriate for the type of measurement being made
Decide where to position the optics so that:
•
The interferometer is between the reflector and the laser head
•
One optic is where the tool mounts and the other is where the workpiece
mounts
•
The optics are at the near-end-of-travel. This means that any subsequent
motion of the machine will separate the optics further instead of bringing
them closer together, refer to Figure 5-6 and Figure 5-7.
•
If measuring a perpendicular axis from the same laser head position,
position the interferometer on part of the machine that remains stationary
and can serve as a beginning point to measure this axis.
Attach the interferometer and the reflector to a height adjuster and post to
accommodate the positions chosen in the previous step. Refer to Figure 5-8 and
Figure 5-9.
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Aerotech, Inc.
5-9
Linear Displacement and Velocity Measurements
Interferometer
Assembly
LZR2000
Distance
Linear Reflector
Stage
Axis of Motion
Figure 5-6.
Servo
Position of Optics (Table moves)
Linear
Reflector
Interferometer
Figure 5-7.
5-10
Position of Optics (Spindle moves)
Aerotech, Inc.
Version 1.0
LZR2000
Linear Displacement and Velocity Measurements
Table Mounting
Retroreflector
Height Adjuster
(LZR1001)
Side View
Linear
Interferometer
(LZR2300)
Post
Front View
Base
(LZR1002)
Spindle Mounting
Post and
Height Adjuster (LZR1001)
Linear Interferometer (LZR2300)
Side View
Figure 5-8.
Front View
Interferometer Mounting
•
If the optic is mounted in a spindle, do one of two things. Either attach the
height adjuster to a post like the method for table mounting or screw the
post into the height adjuster after removing the large knurled knob.
•
For longer distances, it is important to reduce beam scattering, by ensuring
the beam does not strike the corners of the glass in the retroreflector. This is
done by mounting the retro so that its opening is facing the exit aperture of
the laser head. Be sure to orient the reflector and/or the laser head so that
the laser beam will hit the center of a “triangle” and be reflected to the
opposite “triangle”.
5.
Select the small opening of the laser head’s exit port by rotating the crosshairs
(target) into place over the laser head’s bottom (return) port.
6.
Move the interferometer into the path of the laser beam while observing the front of
the laser head. Adjust the position of the interferometer or the laser head so the return
beam is centered on the laser head’s return port target (bottom aperture).
Version 1.0
Aerotech, Inc.
5-11
Linear Displacement and Velocity Measurements
7.
LZR2000
Secure the entire assembly to the machine so that the interferometer is as square as
possible relative to the incoming beam (pitch limitations are ±2 degrees; yaw and roll
limitations are ±5 degrees). Using the post and height adjuster automatically takes
care of the pitch requirement.
Table Mounting
Linear Reflector
(LZR2400)
Height Adjuster
(LZR1001)
Laser Beam
Base (LZR1002)
Spindle Mounting
Linear Reflector
(LZR2400)
Post
Height Adjuster
(LZR1001)
Horizontal Measurements
Laser Beam
Vertical Measurements
Figure 5-9.
8.
Retroreflector Mounting
Take the reflector and position it as close as possible to the interferometer. Observing
the front of the laser head, adjust the reflector until its return beam hits the laser
head’s return port target. Block the laser beam path between the interferometer and
reflector with a piece of paper to distinguish between the two returning beams.
The dot that remains on the front of the laser head is the return beam from the
interferometer. It may be helpful to start by lining up the edges of the reflector with those
of the interferometer.
9.
Secure the reflector assembly to the machine.
Figure 5-10 shows the front view of the laser head when the optics are in different states
of alignment. In illustration A, neither beam is visible on the laser head. This can be
caused by an insufficient coarse alignment or something blocking the path of the laser
beam. To correct this, try adjusting the coarse positions of the individual optical
components slightly.
5-12
Aerotech, Inc.
Version 1.0
LZR2000
Linear Displacement and Velocity Measurements
A – Beams Not Visible
B – One Beam Is Visible
C – Beams Not Aligned or on Target
D – One Beam Is on Target
E – Both Beams Nearly Aligned
F – Both Beams Aligned
Figure 5-10.
Different Degrees of Beam Alignment (View from Front of Laser
Head)
To determine which optical component(s) may be out of alignment, use the supplied
targets (LZR2410) to check the alignment of the optics.
1.
Attach one target to the interferometer so the hole in the interferometer’s target is
above the target’s crosshair, see Figure 5-11. Ensure that the target is positioned
squarely on the interferometer, covering the opening facing the reflector (the user can
use their fingers to line up the edges of the target with the bottom and side edges of
the interferometer).
2.
Attach the other target to the reflector so its crosshair is above the hole. Again,
ensure that the target is positioned squarely on the reflector, covering the opening
facing the interferometer, refer to Figure 5-11.
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5-13
Linear Displacement and Velocity Measurements
LZR2000
Target
Linear Reflector
Linear Interferometer
Laser Head
Figure 5-11.
Interferometer and Retroreflector with Targets
3.
Move the interferometer up or down (after loosening the height adjuster’s large
knob), or move the base back and forth until the laser beam passes through the hole
in the interferometer’s target.
4.
Adjust the reflector in the same manner until the laser beam is centered on the
crosshair of the reflector’s target.
5.
Remove the target from the reflector. Make sure the laser beam is centered on the
crosshair of the interferometer’s target. If necessary, adjust the reflector until it (the
laser beam) is centered on the crosshair.
6.
Remove the target from the interferometer, there should be two dots seen on the front
of the laser head.
Checking the coarse adjustment of components in this way will typically result in at least
two return beams being visible on the laser head (as in illustration C of Figure 5-10).
7.
Place a piece of paper between the interferometer and the reflector in order to block
the beam.
Looking at the front of the laser head, one dot should disappear. The dot that does
disappear is the reflector’s return beam. The dot that remains is the interferometer’s return
beam.
8.
Adjust the interferometer’s position, vertically and horizontally, until its return beam
is centered on the crosshair of the lower aperture on the laser head.
9.
Perform the same adjustment to the reflector until its return beam is also centered on
the crosshair of the lower aperture on the laser head.
There should be only one dot visible on the lower aperture, since both beams overlap
each other completely.
10. Move the reflector slightly to one side and verify that the beam remains on target.
5-14
Aerotech, Inc.
Version 1.0
LZR2000
Linear Displacement and Velocity Measurements
Figure 5-12 illustrates side views of several sample optical configurations in varying
degrees of alignment. Once the beams are aligned and on target, verify that the alignment
remains intact for the entire range of motion of the system. Once the alignment process is
complete, be careful not to bump or jar any system components, otherwise the system
may need to be re-aligned.
After both beams are visible, it is usually only a matter of making fine adjustments to the
components to get one beam (illustration D of Figure 5-10) aligned and on target.
Making careful adjustments to the tripod (if used) and leveling screws is usually sufficient
to accomplish this. The beams may be aligned such that neither beam is exactly on target
as shown in illustration E of Figure 5-10. Continued adjustment of the optical components
should eventually result in both beams being properly aligned and on target as shown in
illustration F of Figure 5-10.
5.5.2. Fine Tuning the Alignment
The above adjustment aligned the optic’s path to the laser beam. However, the normal
practice is aligning the laser beam (by adjusting the laser head) to match the optics path.
In any measurement made with the laser measurement system, the laser head must be
aligned to the optic’s or the machine’s travel path. This section provides the information
needed to adjust the laser head to the travel path of the optics.
Version 1.0
Aerotech, Inc.
5-15
Linear Displacement and Velocity Measurements
LZR2000
Laser Head Is Not Level (Beam is Blocked)
PBS/Retro Is Not Level
Retroreflector is Too High (Beam is Blocked)
Retroreflector is Too Low (Beam is Blocked)
Beams are Properly Aligned and On Target
Figure 5-12.
Different Degrees of Beam Alignment (Side View)
The most commonly used alignment methods are “target” and “overlapping dots.” The
target method can be used for all measurement types and overlapping dots is used for only
distance and velocity measurements.
Each alignment method requires translational and turning movements of the laser head. It
is much easier to separate these motions into vertical and horizontal components where
these adjustments will be used over and over again.
5-16
Aerotech, Inc.
Version 1.0
LZR2000
5.5.2.1.
Linear Displacement and Velocity Measurements
Target Method
The following alignment procedure is the target method and can be used for any
measurement.
1.
Attach targets to the optics as instructed in the previous coarse adjustment.
Both optics must be at the near-end-of-travel and already adjusted around the laser
beam. The near-end-of-travel means that any subsequent motion of the machine will
separate the optics further rather than bring them closer together.
2.
3.
Move the reflector away from the laser. Stop the movement when the laser beam
begins to move off the reflector’s target, or when the optic reaches the end of travel.
Make a series of adjustments to the laser head until the beam returns to the crosshair
on the reflector, Refer to Figure 5-13.
a. Rotate (turn) the laser head to move the beam back toward the crosshair on
the reflector. See step 2 in Figure 5-13.
As soon as the laser head is rotated, the laser beam will be partially or fully blocked
by the interferometer.
b.
Translate the laser head vertically and horizontally until the beam travels
through the hole of the interferometer’s target, Refer to step 3 in
Figure 5-13.
If the laser beam is not hitting the crosshair on the reflector, repeat the process of
turning and translating the laser head.
4.
Continue the process of moving the reflector away from the laser and adjusting the
laser head as many times as necessary until the end of travel is reached. At this point
the laser will be aligned to the table and the optics.
To summarize the target method, translate the laser head or move the optics in order to
initially position the optics around the laser beam. After movement of one optic, rotate
(tilt or turn) the laser head any time the beam does not hit the target on the reflector.
Translate the laser head linearly (up/down or left/right) any time the beam does not travel
through the interferometer’s target hole.
Version 1.0
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5-17
Linear Displacement and Velocity Measurements
LZR2000
Laser Head
Laser Head
€
Original Setup
Move Retroreflector
=
Laser Beam Does Not Hit
Crosshair On Reflector Target.
Laser Head
Laser Head
Laser Head
ó
New Situation From No. 1.
Laser Beam Is In Line With The
Retroreflector Crosshair, But Doesn’t Go
Through Interferometer Target Hole
Turn Laser Head =
Laser Head
Laser Head
ì
Laser Head
New Situation From No. 2.
=
ALIGNMENT!
Beam Travels Through The Interferometer
Target Hole & Hits Reflector Target.
Translate Laser Head
Figure 5-13.
5.5.2.2.
Target Alignment Process
The Overlapping Dots Method
The next method of alignment is the overlapping dots method. This process is only for
distance and velocity measurements. It is identical to the target method, except that the
interferometer and reflector targets are removed and the laser head return port becomes
the target.
The following alignment procedure is the overlapping dot method.
1.
Install the optics as instructed in the coarse adjustment.
The return beams from both optics (the linear interferometer and the reflector) should
completely overlap the laser heads lower (return) port. Set the optics at the near-endof-travel.
2.
5-18
Move the reflector away from the laser or separate the optics. If the laser beam is not
aligned to the travel axis, the reflector dot will begin to move away from the return
port. The dot will move until the beam is cut off by the edge of the interferometer’s
window.
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Version 1.0
LZR2000
3.
Linear Displacement and Velocity Measurements
Stop the movement before the beam is blocked or disappears from the front of the
laser head. This step is identical to the target alignment, step 2. The exception is the
laser head’s return port must be viewed instead of the targets on the optics.
Figure 5-14 shows a two-dot pattern of a displaced reflector beam as the optics are moved
away from the laser.
Figure 5-14.
4.
Displaced Reflector Beam
Make a series of adjustments to the laser head until both return beams are centered on
the laser head’s return port. Use the following steps to accomplish this.
Vertical Axis
a.
Tilt the laser head up or down until both return dots are in line with each
other. Refer to step 1 in Figure 5-15. This matches the reflector’s position
with this adjustment.
b. Translate the laser head up or down until the interferometer’s return dot is
centered on the laser head’s return port. Refer to step 2 in Figure 5-15.
Performing this process maintains the interferometer’s position with this adjustment.
If the dots are not in line with each other at this point, continue to repeat steps “a”
and “b” until the dots are in line with each other, refer to step 2 in Figure 5-15.
Horizontal Axis
c.
Turn the laser head left or right until both dots overlap. Refer to step 3 in
Figure 5-15. This matches the reflector’s position with this adjustment.
d. Translate the laser head left or right until both dots move to the center of the
return port. Refer to step 4 in Figure 5-15. This maintains the
interferometer’s position with this adjustment.
If the dots separate, repeat steps “c” and “d”. At the end of this procedure both dots
should overlap completely at the laser head’s return port. Refer to step 4 in
Figure 5-15.
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5-19
Linear Displacement and Velocity Measurements
LZR2000
Vertical Axis
Existing position of return dots
+
Laser head movement
=
New position of return dots
1.
Turn Head
+
Reflector Dot
=
Interferometer Dot
2.
Translate
Head
+
=
Horizontal Axis
3.
+
=
Turn Head
4.
+
Figure 5-15.
5-20
Translate
Head
=
Overlapping Dots Alignment Procedure
Aerotech, Inc.
Version 1.0
LZR2000
5.
Linear Displacement and Velocity Measurements
After aligning, continue to move the reflector toward the end of travel. Stop and
repeat the previous steps each time the reflector’s return beam starts to get clipped by
the interferometer, or when the end of travel is reached.
To summarize rotation and translation of the laser head, review the following:
Rotate (tilt or turn) the laser head any time the laser’s beam does not hit the head’s return
port. Turn until both dots are in line with each other. Refer to Figure 5-16.
Interferometer dot
Reflector dot
Turn in the
direction of
retroreflector
dot
Turn in the
direction of
retroreflector
dot
Figure 5-16.
When to Rotate Laser
Translate the laser head up and down or left and right any time the interferometer return
dot is not centered on the laser’s return port. Refer to Figure 5-17.
Translate in
the direction
of the dots
Translate in
the direction
of the dots
Figure 5-17.
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When to Translate the Laser
Aerotech, Inc.
5-21
Linear Displacement and Velocity Measurements
LZR2000
5.5.3. Alignment Example
The following is an alignment procedure that summarizes a linear configuration that uses
a moveable measurement reflector and a stationary linear interferometer. The procedure
used is “overlapping dot” method.
1.
Turn on the laser and allow it to stabilize while positioning the optics. Set the shutter
to the target (+) position.
2.
Mount the reflector so that its opening is facing the exit aperture of the laser head.
Be sure to orient the reflector and/or laser head so that the laser beam will hit the
center of a “triangle” and be reflected to the opposite “triangle”.
Beam from Laser Head
Retroreflector
Beam from Laser Head
1
6
2
5
3
4
PBS
Linear Interferometer
Beam Reflected to Laser Head
Six "Triangles" in
a Retroreflector
Proper Orientation of
a Retroreflector
Figure 5-18.
Beam Reflected to Laser Head
Improper Orientation of
a Retroreflector
Front View of a Retroreflector
3.
Position the moveable table/stage so that the reflector is at the travel limit closest to
the laser head.
4.
When the laser is stabilized, adjust the laser head so that the return beam hits the
center of the target on the laser head.
5.
Now move the table/stage so that the reflector moves to the travel limit that is
furthest from the laser head. During this movement, align the head so that the return
beam is always centered on the target.
Linear
Interferom eter
Linear
Reflector
Distance
Stage
Servo
To U600/U500/U100
Controller
Figure 5-19.
5-22
Laser Head, Interferometer, and Reflector Setup
Aerotech, Inc.
Version 1.0
LZR2000
Linear Displacement and Velocity Measurements
6.
Mount and position the linear interferometer on a non-moving surface between the
laser head and the measurement reflector so that the beam hits the upper half of the
PBS opening. The retroreflector of the linear interferometer should be oriented so
that the portion of the laser beam reflected by the PBS will (1) hit the center of a
“triangle”, (2) be reflected to the opposite “triangle”, (3) return to the PBS, and (4)
be reflected back to the laser head.
7.
The linear interferometer should be mounted as closely as possible to the
measurement reflector. This distance should be minimized so that the measurement
beam is minimally effected by air temperature, pressure and humidity differences.
8.
Verify that the measurement retro does not interfere with the linear interferometer at
any point in the travel range.
9.
Block the transmitted beam between the interferometer and the reflector (using a
piece of paper, for example) and adjust the linear interferometer assembly so that the
reference portion of the return beam hits the center of the target on the laser head.
10. Remove the piece of paper and perform the same adjustment to the reflector until its
return beam is also centered on the crosshair of the lower aperture on the laser head.
There should be only one dot visible on the lower aperture, since both beams overlap
each other completely.
11. Confirm the system alignment by moving the measurement reflector back and forth to
its limits several times. Watch that the beam position doesn’t shift during the entire
distance of travel.
12. Repeat the previous steps to fine tune the system further.
13. After the system is properly aligned, rotate the shutter of the laser head to the ON
position. The laser interferometer is now ready for use.
For other configurations, the alignment procedure would be slightly different. Be sure to
perform the alignment over the full travel range of the system to ensure consistent
alignment.
Version 1.0
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5-23
Linear Displacement and Velocity Measurements
5.6.
LZR2000
Perpendicular Axis Measurements
If a measurement axis is perpendicular to the laser beam, the user should mount the
interferometer in line with the laser and at the end of the axis being measured. Figure 5-20
shows the distance measurements that are perpendicular to the laser beam for each axis.
Be sure the orientation of the interferometer is such that the tail end of one of the arrows
on its (the interferometer) side is pointed toward the laser head.
X Axis
Y Axis
Z Axis
Figure 5-20.
5-24
Positioning of Optics for Perpendicular Measurements
Aerotech, Inc.
Version 1.0
LZR2000
5.7.
Linear Displacement and Velocity Measurements
Accuracy and Potential Sources of Error
Although the LZR2000 laser system is a highly accurate and precise measurement device,
the extent of its accuracy is a function of its environment and its configuration.
Fluctuations in the measurement environment (i.e., temperature fluctuations, humidity
changes, etc.) change the refractive index of the surrounding air, thereby affecting the
wavelength of the laser beam. In addition, thermal expansion of mounting surfaces can
influence the accuracy of a measurement. Misaligned system components or improper
system configuration can cause operational problems and also add to the accumulated
error of the system. To optimize the LZR2000 System, the introduction of these types of
errors should be minimized or eliminated if possible. These sources for error are
discussed individually in the sections that follow.
5.7.1. Environmental Conditions over the Measurement Span
Recall the model of the Laser Feedback System. The measurement distance is the
distance between the linear interferometer and the other reflector. Refer to Figure 5-21.
The laser beam travels this distance twice to determine distance measurements. During
the laser beam’s trip, the density of the air (through which the beam passes) is
proportional to the refractive index of that air. Changes in the refractive index of this air
will cause changes in the wavelength of the laser beam. These changes will ultimately
affect the distance being measured. Since changes in the density of air effect the accuracy
of the distance measurement, it is important to understand what conditions affect the
density of air.
Moveable Retro
Beam Source
Beam Return
Fixed Linear
Interferometer
Figure 5-21.
Measurement
Distance
Measurement Distance of the Interferometer System
The density of air is affected by (but not limited to) air temperature, air pressure and
humidity. These three factors (individually, or in combinations) can change the air
density and therefore affect the accuracy of the measured distance. Table 5-4 shows these
three factors and the approximate variation required by each to produce a 1 parts per
million (ppm) variation in the distance measurement.
Version 1.0
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5-25
Linear Displacement and Velocity Measurements
Table 5-4.
LZR2000
Environmental Conditions Affecting Accuracy
Environmental Condition
Change
Measurement Variation
Air Temperature
-1.04° C
+1 ppm
Air Pressure
+2.7 mm Hg
+1 ppm
Humidity
-85 %
+1 ppm
In order to overcome the effects of these environmental conditions, the U600/U500
controllers provide manual or automatic ambient compensation. This gives the operator
the ability to enter temperature, pressure and humidity information directly into the
system for compensated readings. Otherwise, the system may be configured with the
optional environmental compensation package (LZR1100). This hardware automatically
sends temperature and pressure information to the motion controller for dynamic
compensation. In order to accurately correct the effects of environmental and machine
temperature on the laser reading, the user must place the sensors where they can
accurately monitor the conditions influencing the laser. The environmental compensator
(LZR1100) should always be mounted as close as possible to the actual measurement
path. This is necessary in order to monitor the conditions experienced by the laser beam.
When monitoring material temperature to account for material expansion, the material
temperature sensor (LZR1010) should be placed on the part of the machine closest to its
displacement measurement system.
The optional environmental compensation package can be used to monitor air
temperature and pressure automatically. The humidity portion of the compensation is
manual.
Plan the placement of the system components to avoid interference by obvious
environmental forces (e.g., heating/cooling ducts, radiant heat from electrical
equipment, lighting, etc.). To completely eliminate the effects of the environment,
the system can be operated in a vacuum.
5.7.2. Environmental Conditions over the Length of the Dead Path
Dead path is a term that refers to the path of the laser beam between the non-moveable
portion of the linear interferometer and reflector optics. Although this distance is not part
of the measured distance, changes in the dead path (due to the same environmental
variations discussed in the previous section) have the effect of moving the zero position
(X0). This is another possible cause of error in the system. Refer to Figure 5-22.
5-26
Aerotech, Inc.
Version 1.0
LZR2000
Linear Displacement and Velocity Measurements
Axis of Motion
Side View
Linear
Interferometer
Moveable
Reflector
Head
Dead
Path
Measurement Path
X
0
Figure 5-22.
X
Max
Location of the Dead Path in the LZR2000 System
As discussed in the previous section, environmental compensation can be incorporated for
environmental conditions over the length of the measurement path. Unfortunately, the
dead path is not part of the measurement path, therefore a separate dead path
compensation is required. Dead path compensation uses the same temperature, humidity
and pressure values that are used for measurement path compensation. To complete the
dead path compensation calculation, the software package has an input field for manually
entering the dead path distance.
Below are some guidelines used to minimize/eliminate the effects of dead path error
during measurements.
•
During installation of the system, be sure to position the fixed optical component as
close as possible to the measurement path.
In Figure 5-22, the fixed
PBS/retroreflector is positioned as close as possible to the stage that is holding the
moveable retroreflector. This helps to minimize the size of the dead path.
•
Plan the system layout so potential heat sources (e.g., stage motors, air
conditioning/heating ducts, etc.) do not directly radiate into the path of the
measurement beam.
•
Manually measure the distance of the dead path and include that measurement in the
appropriate field of the software. The dead path distance is the total distance from
the center of the linear interferometer to the center of the measurement reflector when
it is at its closest travel limit (i.e., the zero position, as shown in Figure 5-22).
•
Before the interferometer system is reset, always be sure to position the moveable
optical component in the “near” position to minimize the size of the dead path. In
Figure 5-22, the moveable reflector should be moved to the X0 position (not the XMax
position) before resetting the system.
•
Reset the LZR2000 System only when the optics are almost touching each other or
are less than 2 inches apart. At a distance equal to or less than 2 inches, the effects
due to dead path error are negligible.
Version 1.0
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5-27
Linear Displacement and Velocity Measurements
LZR2000
Mechanical compensation is another method for minimizing dead path error. This
method compensates for the dead path error by separating the PBS from the retroreflector
an amount equal to the dead path. As a result, the effects of environmental factors over
the dead path will be included in the second dead path (of the reference beam). Any
environmental effects present over the measurement path will be incorporated into the
reference path, thereby eliminating/reducing dead path error. This method is valid only if
the change is uniform. Refer to Figure 5-23 and Figure 5-24.
Figure 5-24 shows an enlargement of the fixed linear interferometer after it has been
separated. The components are placed a fixed distance apart. This distance must equal
the dead path distance between the fixed PBS and the moveable retroreflector. The fixed
components are securely held in place using a mounting post and height adjusters. The
complete assembly is mounted to the bread board or optics table.
Linear Interferometer
Mechanical
Compensation
for Dead
Path Error
Fixed
Retro
Axis of Motion
Fixed
PBS
Side View
Moveable
Retro
Head
Dead
Path
Measurement Path
X
X
0
Figure 5-23.
5-28
Max
Mechanical Dead Path Compensation (System Side View)
Aerotech, Inc.
Version 1.0
LZR2000
Linear Displacement and Velocity Measurements
Fixed Retro
Fixed linear
interferomter
(PBS/Retro)
is Separated by
the Equivalent of
the Measurement
Beam Dead Path
Distance.
Height Adjuster
Reference
Beam
Height Adjuster
Measurement Beam
Emerging from PBS
(Top) and Re-entering
PBS (Bottom).
Figure 5-24.
Fixed PBS
Optical Post
Mechanical Dead Path Compensation Close-up of Linear
Interferometer Optic and Mounting Hardware (Front View)
5.7.3. Material Temperature Compensation Due to Thermal
Expansion of Mounting Surfaces
As the temperatures of the system components (e.g., the stage onto which the optic is
mounted, the breadboard table, etc.) change, the components themselves will expand or
contract. This expansion/contraction can affect the distance that is being measured.
To compensate for the effects of thermal expansion, the LZR2000 System offers a
material temperature compensation option. The U600/U500 controllers provide manual
or automatic ambient compensation. This option includes four sensors (LZR1010) that
can be used to measure the temperature of the materials on which they are mounted. In
order to accurately correct the effects of environmental and machine temperature on the
laser reading, the user must place the sensors where they can accurately monitor the
conditions influencing the laser. The environmental compensator (LZR1100) should
always be mounted as close as possible to the actual measurement path. This is necessary
in order to monitor the conditions experienced by the laser beam. When monitoring
material temperature to account for material expansion, the material temperature sensor
(LZR1010) should be placed on the part of the machine closest to its displacement
measurement system.
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If the material compensation option is used, then up to four temperature sensors may
be used. If more than one sensor is used, the temperatures are averaged into a single
temperature value. This averaged value is then used to calculate the appropriate
compensation value.
5.7.4. Measurement Axis and Travel Axis Alignment (Cosine Error)
Depending on the configuration, the mechanical axis (i.e., the axis of motion) and the
travel axis of the laser beam should be either parallel or perpendicular to each other.
Refer to Figure 5-5 on page 5-7. If these two axes are misaligned, then the two distances
will be slightly different. This difference represents an error that is a function of the angle
of misalignment between the two axes (specifically, the cosine of this offset angle) and
the path of the laser beam. For this reason, this type of error if called Cosine error. Refer
to Figure 5-25.
Axis of the
Laser Beam
θ
Axis of Stage Motion
Figure 5-25.
Illustration of Cosine Error
To reduce the effects of cosine error, the motion axis of the reflector must be parallel (or
perpendicular depending on the configuration) to the path of the laser beam. If these axes
are misaligned, then the distance being measured by the LZR2000 System will be the
distance offset by the angle θ. Careful beam angle pitch and yaw adjustments may be
necessary to maximize accuracy and minimize the effects of cosine error.
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5.7.5. Abbé Error
Abbé error is a linear error (e.g., an incorrect distance measurement) that is caused by an
angular error (e.g., a deviation in the motion surface) and is represented mathematically as
the difference between the measured distance and the actual distance moved. Abbé error
is introduced into the LZR2000 System when the motion surface (e.g., the stage table) has
a yaw curvature, for example. As a result of this curvature, an angular error will exist
between the reported position of the stage (from an encoder, for example) and the
measured distance from the interferometer. Refer to Figure 5-26.
The effects of Abbé error can be minimized by reducing the angular error in the motion
surface (i.e., by ensuring flatness, straightness, etc.). This can be accomplished by using
laser interferometry and hardware such as special optics and LVDT sensors to measure
pitch, yaw, straightness, flatness, etc. Abbé error could be virtually eliminated by
mounting an LVDT (or similar touch probe) directly to the measurement reflector. Other
ways to minimize the effects of Abbé error include:
•
•
•
•
•
use precision mechanical components for motion
keep the measurement device (i.e., the measurement reflector) centered on the axis of
stage motion
use mechanical components with air bearings
use precision ground mounting surfaces (granite tables, etc.)
do not extend the measurement device beyond the base of the mounting surface over
the range of motion.
In Figure 5-26, the stage table has an exaggerated yaw curvature. Although the stage
table moves in a path that is parallel to the laser beam path, the stage table (and the
measurement reflector which is mounted on it) is not perpendicular to the laser path. The
amount of linear error in the measurement path due to this angular error is the Abbé error.
As the enlarged drawing illustrates, as the linear interferometer is placed further away
from the center axis of stage motion (see cutaway view), the measurement inaccuracy
increases due to Abbé error.
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Stage Table with Exaggerated
Yaw Curvature
Stage
Center
Axis of Stage
Motion
Fixed
Linear Interferometer
Measurement Linear Interferometer Centered on
Axis of Stage Motion Giving Minimal Abbé Error
Due to Stage Table with Yaw Curvature
Stage Table with Exaggerated
Yaw Curvature
Stage
Center
Axis of Stage
Motion
Fixed
Linear Interferometer
Offset from
Axis
Measurement Linear Interferometer is Offset from
Axis of Stage Motion Giving Larger Abbé Error
Due to Stage Table with Yaw Curvature
Stage Table with
Exaggerated
Yaw Curvature
Center
Axis of Stage
Motion
Linear Interferometer
Measured End Point
Traveled End Point
Abbé Error = Measured Distance - Actual Distance Moved
Figure 5-26.
Illustration of Abbé Error
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CHAPTER 6:
Plane/Flat Mirror Measurements
PLANE/FLAT MIRROR
MEASUREMENTS
In This Section:
• Introduction ....................................................................................... 6-1
• Measurement Specifications and Optical Hardware .......................... 6-1
• Layouts and Configurations............................................................... 6-3
• Aligning the System........................................................................... 6-5
6.1.
Introduction
This chapter explains how to position and setup the required optical components of the
interferometer system for plane/flat mirror measurements. These measurements are
commonly found in X-Y stage applications where movement perpendicular to the laser
axis is limited in traditional retroreflector (linear) measurement optics. The positioning
process discussed in this chapter is divided into two steps. The first provides an overview
of the process of choosing a layout and mounting surface for the application, then
mounting and positioning the optical components appropriately. The second step covers
the process of aligning the system.
6.2.
Measurement Specifications and Optical Hardware
The LZR2000 Laser Feedback System is a system capable of making plane/flat mirror
measurements. A plane/flat mirror measurement is made by measuring the change in
position of one of the optics (the mirror) while the other is held stationary. These optical
components are used in linear distance and velocity measurement applications. Table 6-1
lists the required components needed for plane/flat mirror measurements. Besides what is
listed in Table 6-1, the user may need a tripod (LZR-TRIPOD). If a tripod is not used, an
alternative type of rigid support must be provided for the laser head.
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Plane/Flat Mirror Measurements
Table 6-1.
LZR2000
Plane/Flat Mirror Measurement Hardware List
Part Number
Description
LZR2000
Laser Head
LZR2700
Plane/Flat Mirror Optical Kit
LZR2720
Plane Mirror (optional)
EDU169
Manual
Table 6-2 contains the operating specifications for plane/flat mirror measurements.
Because of the optical configuration, resolution is half that of linear displacement
measurements using a single reflector, compare to Table 6-2. Distance measurements are
accurate within the following tolerances depending on the velocity of light compensation
method and operating temperature. Values shown in Table 6-2 apply at a known material
temperature with a known coefficient of thermal expansion.
Table 6-2.
Plane/Flat Mirror Operating Specifications
Accuracy
Temp. Range
Uncompensated
Compensated
Vacuum
20°±1°C
±10 ppm
±1.5 ppm
±0.1 ppm
±14 ppm
±1.7 ppm
±0.1 ppm
20°±5°C
Measurement Range (Axial Separation)
5m (16.5 feet)
Since alignment of these optics is much more sensitive then for linear optics, linear
optics are recommended for general use.
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6.3.
Plane/Flat Mirror Measurements
Layouts and Configurations
There are several optical configurations that are available for plane/flat mirror
measurement applications. Choose a configuration that best suits the particular
application. To summarize these optical configurations, we will focus on the three
fundamental components (the laser head, the plane/flat optical kit and mirror), their
orientation to the incident laser beam (i.e., parallel or perpendicular) and their
relationship to the axis of motion (i.e., which component will move and what is the
direction of the movement).
The interferometer is always placed in between the laser head and the mirror, refer to
Figure 6-1. The interferometer will be physically attached to the spindle or stage and the
mirror will be allowed to move with respect to the other optic.
Figure 6-1.
Plane/Flat Mirror Layout
The interferometer, as compared to the interferometer in the straightness
measurement, must remain stationary and the mirror is the moving optic.
IMPORTANT
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Plane/Flat Mirror Measurements
LZR2000
When planning the setup, it is important that the tail end of one of the arrows on the
interferometer’s label points toward the laser head.
The interferometer may be attached to post-mount height adjusters (LZR1001) and then
secured onto mounting posts that are screwed into predrilled optical tables. Likewise,
stationary optical components may be vacuum mounted to precision granite tables.
Regardless of the type of mounting used, it is important to (1) begin with a surface that is
flat and (2) ensure that the stationary optical component is securely mounted to that
surface.
When mounting the mirror, be sure that it is securely fastened to the motion device (e.g.,
the stage, table or spindle). The axis of motion should be either parallel or perpendicular
(as appropriate) to the incident beam. The mirror used in the plane/flat mirror
measurement can be either the LZR2720 (Plane Mirror) or some other laser grade quality
mirror. Custom mirrors can be purchased by contacting any Aerotech sales representative.
When aligning the optical components of the system, consider using a straight edge
to aid in the coarse alignment process. This can reduce the amount of time needed to
fine tune the alignment later.
There are some important considerations that must be addressed during the installation
and alignment of the optics.
1.
The plane/flat mirror optical assembly (linear interferometer and one
retroreflector) must be located between the laser head and the mirror.
2.
The beam from the laser head must enter the interferometer at the tail end of
one of the arrows on its label.
3.
Vibrations and loose connections must be minimized by proper mounting.
Avoid long extensions and make sure that all supports are completely
stationary. A spindle, for example, must be secured by a brake so it won’t
rotate. If a brake isn’t available try using a hose clamp or a wedge.
4.
The laser beam must be returned to the bottom port on the laser head.
5.
The optics must be aligned to the laser beam well enough to keep the cosine
error at an acceptable level (see Section 5.7. Accuracy and Potential Sources
of Error).
6.
The optics must be aligned to the laser beam well enough to keep the beam
stationary on the target.
After coarsely aligning the optical components of the system, the fine tuning process can
begin. This is discussed in the next section.
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6.4.
Plane/Flat Mirror Measurements
Aligning the System
The alignment of the optical components of the system is accomplished visually using the
laser beam of the laser head. With the optical components already coarsely aligned,
supply power to the laser head using the cables discussed earlier in Chapter 4.
The laser head of the LZR2000 System emits laser radiation from the front top
aperture. Never stare directly into the laser beam or its reflections.
DANGER
It is recommended that the “Ready” LED be illuminated before beginning the alignment
process. The “Ready” LED indicates that the laser has been stabilized and is ready for
taking measurements. It takes approximately 15 minutes for the “Ready” LED to come
on after power is supplied to the laser head.
6.4.1. Coarse Alignment Process
The following pages will lead the user through the process of getting acquainted with
plane/flat mirror measurements by coarsely aligning and setting up the system. The goal
of this alignment process is to adjust the positions of the optical components (laser head,
interferometer and/or mirror) such that the beams returning from the interferometer are
superimposed to form a single spot that is centered on the return port of the laser head.
To set up the coarse alignment, perform the following:
1.
Move the moveable part of the machine as close to the laser head as possible. This
will keep the machine from hitting the laser head during a measurement and help
establish the near-end-of-travel.
The moveable part of the machine may depend on the axis being measured. Meaning,
the “X” axis moveable part may not necessarily be the “Y” axis or the “Z” axis
moveable part.
2.
Visually align the laser head parallel to the direction of travel as well as possible and
position it at an appropriate height.
Before aligning the laser head to the mirror, the interferometer optics must be in
place (between the laser head and the mirror). If it is not, all direct reflections
returning from the mirror will enter the laser head’s exit port instead of the return
port causing the laser head to become unstable.
3.
IMPORTANT
Decide where to position the optics so that:
•
The interferometer is between the plane/flat mirror and the laser head
•
The interferometer is where the tool mounts and the mirror is where the
workpiece mounts
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•
The optics are at the near-end-of-travel. This means that any subsequent
motion of the machine will separate the optics further apart instead of
bringing them closer together. Refer to Figure 6-2.
•
If measuring a perpendicular axis from the same laser head position,
position the interferometer on the part of the machine that remains stationary
and can serve as a beginning point to measure the axis. Refer to Figure 6-3
and Figure 6-4.
Installation If Spindle Moves
Quarter Wave Plate
Interferometer
Mirror
Figure 6-2.
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Position of Plane/Flat Optics (Spindle Moves)
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Plane/Flat Mirror Measurements
Figure 6-3.
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Plane/Flat Mirror Measurements
Figure 6-4.
4.
5.
LZR2000
Perpendicular Plane/Flat Mirror Measurement
If not already attached, mount the quarter wave plate (LZR2710) on the front of the
linear interferometer, see Figure 6-4 and Figure 6-6.
Be sure to orient the reflector and/or laser head so that the laser beam will hit the
center of a “triangle” and be reflected to the opposite “triangle”. See Figure 6-5.
Beam from Laser Head
Beam from Laser Head
1
6
2
5
3
4
Beam Reflected to Laser Head
Six "Triangles" in
a Retroreflector
Figure 6-5.
6-8
Proper Orientation of
a Retroreflector
Beam Reflected to Laser Head
Improper Orientation of
a Retroreflector
Front View of a Retroreflector
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Plane/Flat Mirror Measurements
The quarter wave plate (LZR2710) must be between the mirror and the
interferometer (orientation is not important).
6.
Attach the interferometer to a height adjuster and post to accommodate the position
chosen in the previous step. Refer to Figure 6-6. Attach the mirror to the moving
stage or device.
•
If the optic is mounted on a table, support the post with a base.
LZR2700 Plane/Flat Mirror Optical Kit
Height Adjuster
(LZR1001) & Post
Base (LZR1002)
Side View
Quarter Wave Plate (LZR2710)
Mounts between the Linear Interferometer and the Mirror.
Figure 6-6.
•
Plane/Flat Mirror Optics Mounting
If the optic is mounted in a spindle, do one of two things. Either attach the
height adjuster to a post like the method for table mounting or screw the
post into the height adjuster after removing the large knurled knob.
7.
Select the small opening of the laser head’s exit port by rotating the crosshairs
(target) into place over the laser head’s bottom (return) port.
8.
Attach the target to the interferometer (refer to Figure 6-7). The target is included
with the optics package.
Make sure the target is squarely positioned relative to the edges of the center optic. If
needed, use finger tips to match edges.
9.
Move the interferometer (or translate the laser head) so the beam passes through the
target’s hole.
10. Secure the entire assembly to the machine so that the interferometer is as square as
possible relative to the incoming beam (pitch limitations are ±2 degrees; yaw and roll
limitations are ±5 degrees). Using the post and height adjuster automatically takes
care of the pitch requirement.
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11. Remove the target from the interferometer.
Figure 6-7.
Attachment of Target to Interferometer (Plane/Flat Measurement)
12. Take the mirror and position it as close as possible to the interferometer. Watching
the front of the laser head, adjust the mirror until the return beams hit the laser head’s
return port target.
The return beams from both optics (the linear interferometer and the mirror) should
completely overlap the laser heads lower (return) port.
To determine which optical component(s) may be out of alignment, use the supplied
target to check the alignment of the optics.
13. Reattach the target to the interferometer (see Figure 6-7).
14. Move the interferometer up or down (after loosening the height adjuster’s large
knob), or move the base back and forth until the laser beam passes through the hole
in the interferometer’s target. Remove the target from the interferometer, there should
be two dots seen on the front of the laser head.
15. Adjust the mirror. Make sure the laser beam is centered on the crosshair of the
interferometer’s target. If necessary, adjust the mirror until it (the laser beam) is
centered on the crosshair.
16. Adjust the interferometer’s position, vertically and horizontally, until its return beam
is centered on the crosshair of the lower aperture on the laser head.
17. Perform the same adjustment to the mirror until its return beam is also centered on
the crosshair of the lower aperture on the laser head.
There should be only one dot visible on the lower aperture, since both beams overlap
each other completely.
18. Make sure that the beam position is fixed on the target.
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Plane/Flat Mirror Measurements
Once the beams are aligned and on target, verify that the alignment remains intact for the
entire range of motion of the system. Once the alignment process is complete, be careful
not to bump or jar any system components, otherwise the system may need to be realigned.
After both beams are visible, it is usually only a matter of making fine adjustments to the
components to get the beam aligned and on target. Making careful adjustments to the
tripod (if used) and leveling screws is usually sufficient to accomplish this.
6.4.2. Fine Tuning the Alignment
The above adjustment aligned the optic’s path to the laser beam. However, normal
practice is aligning the laser beam (by adjusting the laser head) to match the optics path.
In any measurement made with the laser measurement system, the laser head must be
aligned to the optic’s or the machine’s travel path. Section 5.5.2. provides the steps and
information required to adjust the laser head to the travel path of the optics.
6.5.
Perpendicular Axis Measurements
If a measurement axis is perpendicular to the laser beam, the user should mount the
interferometer in line with the laser and at the end of the axis being measured. Refer to
Figure 6-5.
6.6.
Effects on Accuracy
For effects on accuracy and sources of error, refer to Section 5.7 in Chapter: 5 Linear
Displacement and Velocity Measurements.
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CHAPTER 7:
System Maintenance
SYSTEM MAINTENANCE
In This Section:
• Introduction ...........................................................................7-1
• Storing the Components of the LZR2000 System .................7-1
• Cleaning the Laser Head........................................................7-1
• Cleaning the Optics ...............................................................7-1
• Calibration .............................................................................7-2
7.1.
Introduction
This chapter provides information for maintaining the components of the LZR2000
interferometer system.
7.2.
Storing the Components of the LZR2000 System
The LZR2000 system consists of precision components. These components are designed
to withstand the rigors of daily use for many years. However, if the system is used
infrequently, return the components to their original packaging for storage. This prevents
moisture, dust and other foreign materials from collecting on the system components.
Always store the boxes in a temperature-controlled environment that is free of excessive
vibrations and moisture.
7.3.
Cleaning the Laser Head
The LZR2000 laser head has a sturdy metal enclosure to add stability and protect the
internal components. If the metal enclosure becomes dirty, it can be cleaned with a mild
detergent using a soft, damp cloth. Be careful not to touch either of the apertures on the
laser head and be careful not to get any moisture near the electrical connectors or the
apertures.
The cleaning procedure for the laser head is only for the external surfaces. In
addition, the laser head should never be opened for cleaning or servicing. The
internal portion of the laser head contains high voltages that could result in
electrocution. There are no user-serviceable components inside the laser head. For
information on servicing, call the Technical Support Department at Aerotech, Inc.
7.4.
WARNING
Cleaning the Optics
The optical components of the LZR2000 system are precision devices. Never touch the
surface of any optical device or the apertures of the laser head. When optical devices are
touched, residue can remain on the optical surfaces, collect other contaminants and
ultimately impede the performance of the system. If the optical components have become
dirty, they may be rinsed using pure methanol. A squirt bottle can be used to spray a light
stream of methanol over the optical component. Do not wipe or rub anything over the
optical apertures. Simply spray the component lightly with pure methanol and let it air
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System Maintenance
LZR2000
dry. Note that optical components should be cleaned only when it is absolutely necessary
(e.g., if the surfaces have been touched). It is best to simply avoid touching any of the
glass surfaces of the optical components. Other acceptable cleaning fluids include
ethanol, de-ionized water and acetone.
7.5.
Calibration
The LZR2000 laser head is calibrated at the factory before it is shipped. Recalibration of
the laser head is unnecessary with normal operation.
However, the optional
Environmental Compensator (LZR1100) may need to be recalibrated periodically, even
though it is initially calibrated at the factory. Aerotech recommends that the LZR1100 be
calibrated approximately once per year or as needed. Call the Technical Support
Department for details.
∇ ∇ ∇
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CHAPTER 8:
Technical Details
TECHNICAL DETAILS
In This Section:
• Introduction .............................................................................. 8-1
• The LZR2000 Laser Head ........................................................ 8-1
• Optics and Optical Accessories ................................................ 8-4
• Environmental and Material Expansion Compensation............ 8-8
• Miscellaneous Specifications.................................................. 8-11
8.1.
Introduction
This chapter provides technical details for all of the components of the LZR2000 system.
Each of the remaining sections of this chapter discusses the technical details for separate
parts of the LZR2000 system (e.g., the laser head, optics and accessories, environment
and material compensation, and miscellaneous specifications). These details include
signals and pinouts for electrical connections, general specifications (such as power
requirements, temperature operating ranges, accuracy values, weight, etc.), dimensions,
switch settings and jumper settings.
8.2.
The LZR2000 Laser Head
This section describes technical details associated with the LZR2000 laser head.
8.2.1. Electrical Connections of the Laser Head
The LZR2000 laser head has three electrical connectors: a standard AC power connector,
a round 8-pin A-quad-B SIN/COS output connector, and a 9-pin D-type A-quad-B line
driver output connector. These connectors are illustrated in Figure 8-1.
Standard
8-pin Differential Analog
Output Signal Connector
(A-quad-B SIN/COS Output)
External AC Power
Connector
Leveling Screw
9-pin D-type Differential
TTL Output Signal Connector
(A-quad-B TTL Line Driver Output)
Figure 8-1.
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Rear View of the LZR2000 Laser Head
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8-1
Technical Details
LZR2000
The signals for the 8-pin and 9-pin connectors are listed in Table 8-1 and Table 8-2.
Table 8-1.
Pinouts for the 8-pin DIN Output Connector of the Laser Head
Pin #
Pin Name
1
SIN A
A-quad-B SIN output signal
2
SIN A
A-quad-B SIN output signal (low active)
3
COS A
A-quad-B COS output signal
4
COS A
A-quad-B COS output signal (low active)
5
GND
Ground
6
VDC
+5 Volts DC
7
Laser On
8
Stable
Table 8-2.
Description
Signal that corresponds to the “Laser On” LED
Signal that corresponds to the “Laser Ready” LED
Pinouts for the 9-pin D-type Output Connector of the Laser Head
Pin #
Pin Name
Description
1
SIN
A-quad-B line driver output signals
2
SIN
A-quad-B line driver output signals (low active)
3
COS
A-quad-B line driver output signals
4
COS
A-quad-B line driver output signals (low active)
5
GND
Ground
6
VDC
+5 VDC Output Signal
7
Laser On
8
Stable
Signal that corresponds to the “Laser Ready” LED
9
GND
Ground
Signal that corresponds to the “Laser On” LED
8.2.2. General Specifications of the Laser Head
General specifications for the LZR2000 laser head are listed in Table 8-3.
8.2.3. Dimensions of the Laser Head
Physical dimensions of the LZR2000 laser head are illustrated in Figure 8-2.
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Table 8-3.
Technical Details
General Specifications for the LZR2000 Laser Head
Specification
Description
Laser type
Helium-Neon (HeNe), single frequency
Maximum output power
1 mW
Warm-up time
15 minutes, maximum
Vacuum wavelength (λ)
632.9907 nm
Wavelength accuracy
± 0.1 ppm
Wavelength stability
± 0.002 ppm / hour, ± 0.02 ppm / month
Beam diameter
5 mm
Beam centerline spacing
11 mm
Safety classification
Class II
Power requirements
50 watts at 100-240 VAC
Output signals
λ/2 A-quad-B complimentary line driver output,
λ/2 A-quad-B complimentary sinusoidal output (0 to ±1.5 V peak)
Laser on and laser ready (TTL)
Dimensions (LxHxW)
15.38” x 5.50” x 4.04” (390,6 mm x 139,7 mm x 102,4 mm)
Weight
12 lb (5,5 kg)
Operating Temperature
15 - 40°C
Relative Humidity
0-90% Non condensing
Shock (IEC 68.2.27)
30G, 11 msec
14.12"
358,6
Laser Head Rear Panel
5.50"
139,7
4.75"
120,6
2.75"
69,8
14.00"
8-pin DIN
A-Quad-B
SIN/COS
Output
AC Power
9-pin D-type
A-Quad-B
TTL Line Driver
Output
14.88"
355,6
0.38"
3/8 - 24 Thd.
Thru., 3 Holes
9,6
377,9
Front of Laser Head
Shutter
0.197"
(6mm)
Beam
0.43"
10,9
φ
LASER ON
2.18"
0.56"
55,4
14,2
READY
0.50"
12,7
0.06"
1,5
Figure 8-2.
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Beam Exit
Beam Input
Dimensions of the LZR2000 Laser Head
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Technical Details
8.3.
LZR2000
Optics and Optical Accessories
This section summarizes technical details that relate to the optics and optical accessories
of the LZR2000 system. Technical details of the optics of the LZR2000 system are
illustrated in Figure 8-3 and Figure 8-4.
M3 x 0.5
(4 Places)
0.98"
25,0
1.57"
SQ.
40,0
1.18"
SQ.
30,0
0.78 Dia.
22,1 ∅
Figure 8-3.
Dimensions of the LZR2400 Optical Retroreflector
Retroreflector
Beam Direction
Label
Polarized Beam
Splitter (PBS)
1.18"
Knurled Screws
0.14"
10,4
Figure 8-4.
8-4
M6 x 0.5
(24 Holes Total)
30,0
SQ.
1.57"
SQ.
40,0
2.55"
64,8
Dimensions of the LZR2300 PBS/Retro Combination
Aerotech, Inc.
Version 1.0
LZR2000
Technical Details
Posts and post-mount height adjusters (LZR1001) are optical accessories that can be used
to secure all the optics to the appropriate surfaces. The dimensions of these accessories
are illustrated in Figure 8-5.
0.50" Dia.
12,7 Dia.
Knurled Screw
Clamp Knob
Knurled Screw
1.31"
33,0
Knurled Screw
1.57"
40,0
SQ.
1.18"
30,0
Clamp Knob
SQ.
Knurled Screw
8-32 Thd.
M4
Model
A
AR-4/
4.00"
AR-4M/
101,6
AR-6/
6.00"
AR-6M/
152,4
AR-8
8.00“
AR-8M
203,2
A
0.50" Dia.
12,7 Dia.
1/4-20 Thd.
M6
0.31"
7,9
Figure 8-5.
Version 1.0
Dimensions of the Post-Mount Height Adjuster and Posts
Aerotech, Inc.
8-5
Technical Details
LZR2000
The base (LZR1002) is an optical accessory that can be used to provide a means of
support for the post-mount height adjuster. This configuration offers additional flexibility
when setting up the optics. The dimensions for base are shown in Figure 8-6.
.460
0
3.040
.03 x 45%%d CHAM.
TYP.6 PLCS.
3.540
.030
.470
0
.03 x 45%%d CHAM.
TYP.4 PLCS.
0
.985
.03 x 45%%d CHAM.
TYP.4 PLCS.
1.270
DASH-1
13/64 (.203) DRL. THRU
1/4-20 TAP THRU
DASH-2
#7 (.201) DRL. THRU
M6-1.00 TAP x DP.
Figure 8-6.
Dimensions of the LZR1002 Base
The quarter wave plate (LZR2710) is used for plane/flat mirror measurements. The
dimensions for the quarter wave plate are shown in Figure 8-7.
1.5740
0.360
1.5740
Figure 8-7.
8-6
Dimensions of the LZR2710 Quarter Wave Plate
Aerotech, Inc.
Version 1.0
LZR2000
Technical Details
1.574
TURNING
MIRROR
LZR1003
Figure 8-8.
1.574
1.574
1.574
Dimensions of the Turning Mirror (Cube) LZR1003
0.502
1.574
1.574
Figure 8-9.
Version 1.0
Dimensions of the Mirror (LZR1004, LZR1005 & LZR2720)
Aerotech, Inc.
8-7
Technical Details
8.4.
LZR2000
Environmental and Material Expansion Compensation
This section contains technical details about the optional environmental compensator
(LZR1100). This package includes sensors to measure ambient air temperature and
pressure. Additional material temperature sensors (LZR1010) may be connected to the
unit to provide thermal material expansion compensation, in addition to a remote ambient
temperature sensor (LZR1020).
Technical details for the LZR1100 environmental compensator are provided in Table 8-4.
Table 8-5 contains the technical details of the material temperature sensors. Table 8-6
contains the technical details of the remote ambient temperature sensor. The LZR1100
connects directly to the Misc. I/O connector of the DR300 / DR500 / DR600 / DR800
chassis.
See the online help documentation for more information on using the LZR1100.
Table 8-4.
Environmental Compensation Specifics of the LZR1100
Specification
Measurement range
Measurement accuracy
Time constants
Maximum update rate
Wavelength compensation
Signal cable
Optional material
temperature sensor
Table 8-5.
Specifics of the Material Temperature Sensors (LZR1010)
Specification
Temperature range
Measurement Accuracy
Time Constant
Temperature compensation
8-8
Description
Temperature: 15 °C to 40 °C
Pressure: 550-790 mm of Hg
For the range 19 °C to 21 °C: 1.5 ppm
For the range 15 °C to 25 °C: 1.7 ppm
Temperature: 10 sec, typical
Pressure: 1 sec, typical
0.5 Hz
Manual (Keyboard entry) or Automatic (with air sensor);
Temperature and pressure monitored;
Humidity setting manually entered;
Wavelength computed
25-pin D-type DR500 Misc. I/O connector
Up to four (4) material temperature sensors and (1)
remote ambient temperature sensor can connect to the
LZR1100 air sensor
•
•
Description
0-50°C
0.4°C
10 sec
Manual via keyboard entry
Automatic with material temperature sensors;
temperature monitored
Aerotech, Inc.
Version 1.0
LZR2000
Table 8-6.
Technical Details
Specifics of the Remote Ambient Temperature Sensor (LZR1020)
Specification
Description
Temperature range
Temperature: 15 °C to 40 °C
Measurement Accuracy
For the range 19 °C to 21 °C: 1.5 ppm
For the range 15 °C to 25 °C: 1.7 ppm
Time Constant
Temperature: 10 sec, typical
Temperature compensation
Manual via keyboard entry
Automatic with ambient temperature sensors
The LZR1100 environmental compensator, LZR1010 material temperature sensor, and
the LZR1020 remote ambient temperature sensor are illustrated in Figure 8-10. The
dimensions for the material temperature sensor and the environmental compensator are
illustrated in Figure 8-11, Figure 8-12, and Figure 8-13.
Figure 8-10.
Version 1.0
LZR1100 Air Sensor, LZR1010 Material Temperature Sensor and
LZR1020 Remote Ambient Temperature Sensor
Aerotech, Inc.
8-9
Technical Details
LZR2000
1.31
1.75
0.47
0.25
40”
Figure 8-11.
Dimensions of the LZR1010 Material Temperature Sensor
0.28
2.02
Electro-Optical
3.00
0.65
3.50
4.75
Figure 8-12.
Dimensions of the LZR1100 Environmental Compensator
3.53
0.45
2.00
CABLE
Figure 8-13.
8-10
Dimensions of the LZR1020 Remote Ambient Temperature Sensor
Aerotech, Inc.
Version 1.0
LZR2000
8.5.
Technical Details
Miscellaneous Specifications
This section contains miscellaneous technical specifications not found in the previous
sections.
8.5.1. Resolution and Velocity for Linear Displacement
Technical details about the resolution and velocity for linear displacement are listed in
Table 8-7.
Table 8-7. Resolution and Velocity Details
Accuracy
Temp. Range
Uncompensated
Compensated
Vacuum
20°±1°C
±10 ppm
±1.5 ppm
±0.1 ppm
20°±5°C
±14 ppm
±1.7 ppm
±0.1 ppm
Measurement Range (Axial Separation)
10m (33 feet)
8.5.2. Plane/Flat Mirror Measurement Specifications
Technical operating specifications for plane/flat mirror measurements are listed in
Table 8-8.
Table 8-8.
Plane/Flat Mirror Operating Specifications
Accuracy
Temp. Range
Uncompensated
Compensated
Vacuum
20°±1°C
±10 ppm
±1.5 ppm
±0.1 ppm
20°±5°C
±14 ppm
±1.7 ppm
±0.1 ppm
Measurement Range (Axial Separation)
5m (16.5 feet)
∇ ∇ ∇
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8-11
Technical Details
8-12
LZR2000
Aerotech, Inc.
Version 1.0
LZR2000
Troubleshooting
CHAPTER 9:
TROUBLESHOOTING
In This Section:
• Introduction ................................................. 9-1
• Setup and Alignment ................................... 9-1
9.1.
Introduction
This chapter assists in diagnosing problems that may arise during the commissioning or
operation of your LZR2000 system.
9.2.
Setup and Alignment
Problems that may arise during system setup and optical alignment are listed in Table 9-1.
Possible causes and solutions are also given.
Table 9-1.
Setup and Alignment Problems
Problem
Cause/Solution
No beam appears and the
“Laser On” LED is not lit...
No power to the laser head.
No source beam appears, but
the “Laser ON” LED is lit”...
The shutter on the laser head may be in the closed
position or the laser head is still warming up.
A weak beam appears and the
“Laser On” LED blinks on and
off... after 15 minutes of
warm-up
Possible damage to laser tube. Call Aerotech.
No return beam appears...
Optical components are not properly aligned
(beam may not be centered on optical
components).
Optical components are not properly situated
(check directions of arrows on the PBS).
Retroreflector may be rotated 90 degrees (be sure
that beam strikes the center of a retroreflector’s
“triangle” and not on an edge).
The shutter on the laser head may be in the closed
position.
∇ ∇ ∇
Version 1.0
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9-1
Troubleshooting
9-2
LZR2000
Aerotech, Inc.
Version 1.0
LZR2000
APPENDIX A:
Glossary of Terms
GLOSSARY OF TERMS
In This Section:
• Terms Used In This Manual
• Abbreviations Used In This Manual
• Definitions
This appendix contains definitions of terms that are used throughout this manual.
A-quad-B output - An A-quad-B output is a two-signal output in which the two signals
are displaced 90 degrees with respect to each other. An A-quad-B output signal is a
common interface to motion controllers (e.g., the UNIDEX 600). Both line drive and
SIN/COS output signals are available on the LZR2000 laser head.
Fixed Source
P
A. A. Michelson interferometer - The A. A. Michelson interferometer was originally
built in 1881 by Michelson (1852-1931), America’s first Nobel prize winner in Science.
This model used a half-silvered mirror (rather than the modern day polarized beam
splitter) that transmitted half of the light (the reference beam) and reflected the other half
(the measurement beam). The measurement and reference beams are combined to cause
interference fringes when the measurement mirror (i.e., the modern day retroreflector) is
moved. Very accurate distances can be measured by counting the interference fringes
during this movement. The number of interference fringes counted is proportional to the
distance moved. The LZR2000 laser interferometer uses this model for its distance
calculations.
Light Leaving
Point "P"
Moveable
Mirror
Half-silvered
Mirror
Fixed Mirror
A.A. Michelson Interferometer
A
B
A-quad-B Output
Abbé error - Abbé error (named after optical designer Ernst Abbé) is a linear error (e.g.,
an incorrect distance measurement) that is caused by an angular error (e.g., a deviation in
the motion surface). Abbé error is introduced into the LZR2000 System when the motion
surface (e.g., the stage) has a yaw curvature, for example. As a result of this curvature, an
angular error will exist between the reported position of the stage (from an encoder, for
example) and the measured distance from the interferometer.
The effects of Abbé error can be minimized by reducing the angular error in the motion
surface (i.e., by ensuring flatness, straightness, etc.). This can be accomplished by using
the numerous other available optical kits. Abbé error could be virtually eliminated by
mounting an LVDT (or similar touch probe) directly to the measurement retroreflector.
Other ways to minimize the effects of Abbé error include: (1) using precision mechanical
components for motion, (2) using mechanical components with air bearings, (3) using
precision ground mounting surfaces (granite tables, etc.), and (4) keeping the
measurement device above the base of the mounting surface over the entire range of
motion (i.e., do not let the measurement device extend over the base of the mounting
surface).
absolute pressure - Absolute pressure is the ambient pressure used by the LZR2000
system for all environmental compensation calculations. If barometric pressure (the
absolute pressure corrected to sea level) is available, then an approximate absolute
pressure can be determined by decreasing the barometric pressure by 1 inch of Hg for
every 1000 feet of altitude above sea level.
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A-1
Glossary of Terms
LZR2000
accuracy - Accuracy is the difference between an expected value and an actual value.
Accuracy may also be represented as the maximum amount of deviation from the actual
value of a measurement in parts per million (ppm).
amplifier - An amplifier is a hardware device having an output that is larger than the
input signal.
axis - An axis is a direction along which movement occurs.
axis calibration - Axis calibration is the process by which the actual position of an axis is
adjusted to match the desired position of the axis.
backlash - Backlash is lost motion that occurs after a direction change.
barometric pressure - See absolute pressure.
backlash in gears
base address - A base address is a number that represents the memory location in the
computer where input/output (I/O) information can be stored. All devices (e.g., the
UNIDEX 600 card, network cards, tape backup cards, etc.) within a computer must have
unique I/O base addresses. Base addresses of PC boards may be set through hardware
(i.e., jumpers and/or switches), software (i.e., parameters) or a combination of both
hardware and software.
beam splitter - A beam splitter is a precision optical device that allows a portion of a
laser beam to be transmitted while the other portion is reflected. Beam splitters divide a
laser beam into two beams (that are usually perpendicular to each other). Beam splitters
are available with different transmission/reflection percentages (e.g., 50% transmit/50%
reflect, 30% transmit/70% reflect, etc.).
beam splitter
breadboard (optical) - In optics and laser interferometry, a breadboard refers to a
precision table top that contains aligned, pre-drilled holes for securing optical (and other
system) components.
closed-loop system - A closed-loop system is a type of drive system that uses sensors or
transducers for direct feedback of position and/or velocity. An example of a closed-loop
system is a stage which receives a position signal from an encoder. For applications that
require extreme accuracy, a laser interferometer can be used to provide the feedback.
Contrast with open-loop system.
cosine (COS) error - Depending on the system configuration, the mechanical axis (i.e.,
the axis of motion) and the travel axis of the laser beam should be either parallel or
perpendicular to each other. If these two axes are misaligned, then the two distances
would be slightly different. This difference represents an error that is a function of the
angle of misalignment between the two axes (specifically, the cosine of this angle) and the
path of the laser beam. For this reason, this type of error is called Cosine error.
To reduce the effects of cosine error, the motion axis of the retroreflector must be parallel
(or perpendicular depending on the configuration) to the path of the laser beam. If these
axes are misaligned, then the distance being measured by the LZR2000 System will be the
distance offset by the angle θ. Careful beam angle pitch and yaw adjustments may be
necessary to maximize accuracy and minimize the effects of cosine error.
A-2
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Glossary of Terms
dead path - Dead path is the distance between the fixed PBS and the measurement
retroreflector in the interferometer system when the system is zeroed. This definition
assumes that the PBS/retro components are connected. If the PBS/retro combination is
separated, the actual dead path becomes the difference between the measurement dead
path distance (the distance between the fixed PBS and the measurement retroreflector)
and the reference dead path distance (the distance between the fixed PBS and the fixed
reference retroreflector).
dead path error - Dead path error is an inaccuracy in the interferometer measurement
due to environmental changes of the air (e.g., air temperature, air pressure and humidity)
over the distance of the dead path. The effects of dead path error can be minimized by
reducing the dead path. If the PBS/retro is as close as possible to the measurement
retroreflector and measurement dead path error is still a problem, consider operating the
interferometer system (or at least the dead path portion) within a vacuum. If this is
impossible or impractical, it is also possible to offset the effects of dead path error by
introducing an equal error into the reference path. This can be done by separating the
PBS/retro combination a distance equal to the dead path of the measurement beam.
Dead path is defined as the difference in these two distances. If they are the same, then
the dead path error will be zero (or negligible).
DR 500
DR500 Drive Rack
DR500 Chassis/Drive Rack - The DR500 Chassis (or Drive Rack) is a housing for the
axis amplifiers (for microstepping, DC brush and brushless drivers) and the driver power
supply. The DR500 is available in rack mount, panel mount and desktop packaging.
dynamic link library - A dynamic link library is a set of program routines that are
available to applications at run time.
encoder - An encoder is a linear or rotary device that produces a signal based on change
in position.
stage with rotary encoder
flatness - Flatness is the condition of a surface (such as a stage) such that all points of the
surface exist in a single plane. Flatness of travel is the deviation between the theoretical
and actual axes of travel measured in the horizontal plane. Flatness of travel deviations
are primarily a function of pitch and roll errors.
floating point number format - Floating point number format is a method of
representing numbers without defining a fixed number of decimal places. Two common
forms of floating point number format are fixed-style format (e.g., 12.345, 0.000001, -2,
etc.) and scientific notation (e.g., 12.3E4, -1.2E-3, etc.). In the scientific notation method,
the number that follows the “E” represents a power of 10. For example, 12.3E4 means
12.3 x 104 or 123,000.
frequency - Frequency is the number of cycles of a wave (e.g., light) that occur within a
unit time. The standard measurement for frequency is Hertz (Hz) which represents one
cycle per second. For very large frequencies, it is common to use prefixes such as K for
1,000 (10 KHz=10,000 cycles per second) or M for 1,000,000 (50 MHz=50,000,000
cycles per second). Frequency (ƒ) of an electromagnetic (light) wave can be represented
using the equation ƒ=v/λ, where v is the velocity of light (approximately 300,000,000
m/sec [in a vacuum]) and λ is the wavelength.
Version 1.0
Aerotech, Inc.
6 cycles
1 second
frequency
A-3
Glossary of Terms
LZR2000
frequency shift - Frequency shift is a phenomenon that occurs in Doppler interferometry
when a single-frequency wave is split (into a reference beam and a measurement beam)
and then reunited to cause interference. The interference occurs as the length of the
measurement beam changes (due to motion).
hexadecimal number format - Hexadecimal number format is a method of representing
large numbers using base 16 rather than the standard base 10. In base 16 or hexadecimal
number format (often abbreviated "hex"), the number positions represent powers of 16
(rather than powers of 10 in decimal). The decimal number positions (1’s, 10’s, 100’s,
1,000’s, 10,000’s, etc.) are replaced with hexadecimal number positions (1’s, 16’s, 256’s,
4096’s, etc.). Also, while the individual numerals for the decimal system are 0-9, the
numerals for the hexadecimal number system (which requires 16 unique "numerals") are
0-9 then A-F (where A16=1010, B16=1110, C16=1210, D16=1310, E16=1410, and
F16=1510). For simplicity in this manual, hexadecimal numbers are written with a
preceding "0x" rather than using the subscript 16. For example, the hexadecimal number
12A5 is written 0x12A5. Numbers without the preceding "0x" are assumed to be decimal
unless otherwise indicated.
interferometer
interferometer - An interferometer refers to a complete system (including all of the
optics and the laser head) used to make precise measurements. The term interferometer
may also refer to an optical device that uses light interference phenomena for precise
determinations of wavelengths and small linear displacements. The LZR2300 (linear)
interferometer consists of a polarized beam splitter and a retroreflector that are connected
(PBS/retro). As a laser beam hits the internal mirrored surface of the beam splitter, a
portion is reflected from the beam splitter to a retroreflector (this portion of the wave is
called the reference beam, since the distance of its path is fixed and can be used as a
reference) and another portion is transmitted through the beam splitter (this portion of the
beam is called the measurement beam, since the distance of its pathway will vary and will
represent the distance to be measured). Both waves are reflected back to the mirror in the
beam splitter where they interfere (due to movement of the measurement retroreflector).
The resulting interference can be interpreted to determine the precise distance that the
measurement retroreflector has traveled.
jumpers - Jumpers are hardware ties that you manually position to configure the
hardware platform. A small “block” is either installed (placed over a pair of pins) or it is
removed, providing a two-state input (e.g., enable/disable, on/off, 0/1, etc.). Jumpers are
found on PC boards and are typically used to configure features (e.g., addresses,
interrupts, etc.).
jumper
laser - The term laser is an acronym for Light Amplification from the Stimulated
Emission of Radiation and refers to a device that produces such light. The LZR2000 laser
head contains a single-frequency, class II helium (He) and neon (Ne) laser. This laser
provides the single focused light beam that is the key element of the interferometer
system.
LZR2000 laser head
A-4
laser head - A laser head is an enclosure that houses and protects a laser and its
associated components and circuitry. The LZR2000 laser head contains electrical
connections for power and interference output signals. Laser beam exit and detection
apertures, an aperture shutter and diagnostic LEDs are also found on the laser head.
Aerotech, Inc.
Version 1.0
LZR2000
Glossary of Terms
laser interferometry -Laser interferometry is an extremely accurate method of distance
measurement (as well as flatness, straightness, squareness, parallelness, and others). It
involves the use of a laser, an interferometer (a precision optical device used to split the
laser beam and create interference fringes) and additional optics. The LZR2000 performs
single-axis linear displacement measurements and uses single-frequency Michelson laser
interferometry. This method of interferometry counts interference fringes (that occur as
the target moves along its axis from a known starting position to a destination position)
and accurately calculates the precise distance traversed.
least squares - A procedure in which the basic problem is to pass a curve through a set of
points, representing experimental data, in such a way that the curve shows as well as
possible the relationship between the two quantities plotted. Using one’s knowledge of the
functions that have been found useful in fitting various experimental curves, one selects a
suitable function and tries to determine the parameters left unspecified. At this point there
are certain techniques that have been worked out to choose the optimum value of the
parameters. One of the most general methods used for this purpose is least squares. In this
method one chooses the parameters in such a way to minimize the sum representing the
best line through the data.
LED - LED is an acronym for light-emitting diode. An LED is a semiconductor diode
that converts electrical energy into visible electromagnetic radiation. Several LEDs are
found on the LZR2000 laser head and are used for diagnostic purposes.
LED
LZR1001 - The LZR1001 is a post-mounted height adjuster that connects an optical
component (e.g., an LZR2400 linear reflector) to a mounting post (e.g., AR-4/, AR-4M/,
AR-6/, or AR-6M/).
LZR1002 - The LZR1002 is the base plate that provides a means of support for the postmounted height adjusters.
LZR1003 - The LZR1003 is a turning mirror (cube) used applications that require the
laser beam to be reflected or directed at an angle of 90 degrees.
LZR1004 - The LZR1004 is a mirror used with applications requiring the laser beam
reflected at an angle that is perpendicular to the mirror.
LZR1005 - The LZR1005 is a mirror used applications that require the laser beam to be
reflected or directed at an angle of 90 degrees.
LZR1010 - The LZR1010 is an optional material temperature sensor (with cable) that is
used with the LZR1100 (the environmental compensation package). Up to four material
temperature sensors can be used with the LZR1100 to improve accuracy by compensating
for measurement errors due to thermal expansion of mounting surfaces. If more than one
material temperature sensor is used, the controller’s software averages the temperatures
into a single temperature for compensation purposes.
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LZR1010
A-5
Glossary of Terms
LZR2000
LZR1020 - The LZR1020 is an optional remote ambient sensor (with cable) that is used
with the LZR1100 (the environmental compensation package). Up to four remote
ambient sensors can be used with the LZR1100 to improve accuracy by compensating for
measurement errors due to temperature. If more than one remote ambient temperature
sensor is used, the controller’s software averages the temperatures into a single
temperature for compensation purposes.
LZR1100
LZR1100 - The LZR1100 is the option environmental compensation package. This kit
contains the electronics, air sensor and 10-foot cable which connects to the Misc. I/O
connector of the DR500. With this optional package, the LZR2000 system can
automatically compensate for measurement errors due to environmental fluctuations in
temperature and pressure. A manual humidity input is also available for additional
environmental compensation.
LZR2000 - The LZR2000 is the single-frequency, helium-neon laser head component of
the LZR2000 system. The laser head is an enclosure that houses and protects a laser and
its associated components and circuitry. The LZR2000 laser head contains electrical
connections for power and interference output signals. Laser beam exit and detection
apertures, an aperture shutter and diagnostic LEDs are also found on the laser head.
LZR2000
LZR2300
LZR2400
LZR2300 - The LZR2300 is the combination PBS (polarized beam splitter) and
retroreflector. This optical component of the LZR2000 system is a precision optical
device that is placed between the laser head and the measurement retroreflector. The
PBS\retro splits the incident beam from the laser head into two beams. One beam is
reflected from the mirrored surface of the PBS, and the other beam is transmitted through
the mirrored surface of the PBS. Of these two beams, one goes to a fixed retroreflector
(creating the reference beam) and one goes to a moveable retroreflector (creating the
measurement beam).
LZR2400 - The LZR2400 is the linear reflector optical component of the LZR2000
system. A retroreflector is a precision optical device that reflects light from a laser such
that the reflected rays are parallel to the incident rays. In a linear interferometer system,
one retroreflector moves along the measurement axis (changing the distance of the
measurement beam) and the other is part of the fixed-position interferometer.
LZR2410 - The LZR2410 is an alignment target used for aligning the optics to the laser
beam.
LZR2700 - The LZR2700 is the plane mirror optical kit typically used for X-Y stage
applications where movement perpendicular to the laser axis is limited in traditional
retroreflector (linear) measurement optics.
LZR2710 - The LZR2710 is the quarter wave plate.
LZR2720 - The LZR2720 is an optical plane mirror used with the LZR2700 plane/flat
mirror optical kit.
LZR2900- The LZR2900 is the linear optical kit that contains the LZR2300 linear
retroreflector and the LZR2400 linear reflector. It is an optic that is used when the
original linear optics were not purchased.
A-6
Aerotech, Inc.
Version 1.0
LZR2000
Glossary of Terms
LZR2000 Laser Feedback System - The LZR2000 is a Laser Feedback System that
includes a laser head, optics, and cables. The LZR2000 system is used for single-axis
linear displacement measurements.
measurement beam - Measurement beam refers to one of two laser beams used in the
LZR2000 Laser Feedback System. The main laser beam (from the laser head) is split into
the measurement beam and the reference beam at the beam splitter. The reference beam
travels to a fixed retroreflector, is reflected, and returns to the beam splitter. The
measurement beam travels to a retroreflector that is attached to the moving measurement
object and is reflected back to the beam splitter where it is reunited with the fixed
reference beam to create an interference pattern. This pattern is interpreted to determine
the precise distance that was traversed by the measurement beam.
measurement beam
open-loop system - An open-loop system is a type of drive system that does not employ
feedback sensors or transducers to monitor position or velocity. Most stepper motor
applications are open loop (that is, they have no feedback). The commanded position is
the assumed motor position. Contrast with closed loop system.
PBS/retro - PBS/retro is an abbreviation for two combined optical components: the
polarized beam splitter (PBS) and a retroreflector (retro). The PBS\retro is a precision
optical device that is placed between the laser head and the measurement retroreflector.
The PBS\retro splits the incident beam from the laser head into two beams. One beam is
reflected from the mirrored surface of the PBS, and the other beam is transmitted through
the mirrored surface of the PBS. Of these two beams, one goes to a fixed retroreflector
(creating the reference beam) and one goes to a moveable retroreflector (creating the
measurement beam).
PBS/retro
photo diode - A photo diode is an electronic component that acts as a one-way “valve”,
and converts light (from a laser, for example) into electrical signals. Photo diodes are
used in the detector circuitry of the LZR2000 laser head.
pitch - Pitch is a rotation about the horizontal axis and perpendicular to the axis of travel.
Pitch is an angular movement (or error) that affects flatness of travel and positioning
accuracy (of a stage, for example).
photo diode
polarization - Polarization is the process by which one or more transverse waves (e.g.,
light) become aligned, such that only vector components that lie in the plane of wave
propagation remain.
polarized beam splitter - A polarized beam splitter (or PBS) is a precision optical device
that polarizes/reflects a portion of a laser beam and polarizes/transmits another portion.
quadrature - Quadrature is the state of two signals that are displaced 90 degrees with
respect to each other. In most rotary incremental optical encoders, light (from an LED,
for example) is measured after it is passed through slits in a grating disk (which is
attached to the axis being measured). Typically, two tracks on the disk have their gratings
displaced 90 degrees with respect to each other (that is, the tracks are said to be in
quadrature).
Version 1.0
Aerotech, Inc.
vertical polarization
A-7
Glossary of Terms
LZR2000
quarter wave plate - A quarter wave plate (QWP) is an optical device used in the
detector portion of the laser head. The QWP is an optical plane comprised of two
refractive indices. This device performs the necessary wave shifting of the returned laser
beam which allows the vector components of polarized beams to come through. The
QWP prepares the wave for fringe counting and output manipulation.
range - Range is a term used to specify the maximum recommended operational distance
of the LZR2000 system. This linear distance is measured from the front of the laser head
to the target retroreflector (at is furthest distance from the laser head). The range of the
LZR2000 system is 10 meters (or 32.8 feet). The round trip of the laser beam is actually
20 meters (or 65.6 feet) for a typical linear interferometry application (10 meters out and
10 meters back).
reference beam
reference beam - Reference beam refers to one of two laser beams used in the LZR2000
Laser Feedback System. The main laser beam (from the laser head) is split into the
reference beam and the measurement beam at the beam splitter. The reference beam
travels to a fixed retroreflector, is reflected, and returns to the beam splitter. The
measurement beam travels to a retroreflector that is attached to the moving measurement
object and is reflected back to the beam splitter where it is reunited with the fixed
reference beam to create an interference pattern. This pattern is interpreted to determine
the precise distance that was traversed by the measurement object.
Fixed
Moveable
retroreflectors
retroreflector - A retroreflector is a precision optical device that reflects light from a
laser such that the reflected rays are parallel to the incident rays. In a linear
interferometer system, one retroreflector moves along the measurement axis (changing the
distance of the measurement beam) and the other is part of the fixed-position
interferometer.
roll - Roll is rotation about an axis of movement while translating about that axis. Roll is
an angular movement (i.e., error) that effects straightness and flatness of travel.
SIN/COS signal - A SIN/COS signal is a uniform wave (i.e., an analog signal) that is
generated from a single frequency. Contrast with TTL (digital) signal.
straightness - Straightness is a condition where an element of a surface or an axis is a
straight line. For a positioning stage, straightness of travel is defined as the difference
between the theoretical and actual axis of travel measured in the vertical plane.
Straightness of travel deviations are primarily a function of yaw and roll errors.
TTL signal - A TTL (Transistor Transistor Logic) signal is a uniform square wave that is
derived from two transistors. Although TTL technology is a specific design method, the
term often generically to digital connections (e.g., a digital signal) in contrast with analog
connections (an analog signal). Contrast with SIN/COS (analog) signal.
tuning - Tuning is the process of optimizing the operation of a servo system.
A-8
Aerotech, Inc.
Version 1.0
LZR2000
Glossary of Terms
UNIDEX 600 - The UNIDEX 600 is a PC bus-based motion controller that serves as the
center of a complete Aerotech motion control system. The UNIDEX 600 provides the
required performance when synchronous coordination of a large number axes is a must.
wavelength (λ) - Wavelength is a distance measurement of the advance of a wave (a light
wave in the case of the LZR2000) from one point to the next point of corresponding
phase (i.e., one cycle). For light waves (such as those emitted from the LZR2000 laser
head), the wavelength of the laser beam equals the velocity of the wave (given as a
distance per unit time) divided by the frequency of the wave (given as a number of cycles
per unit time).
λ
wavelength λ=v/ƒ
yaw - Yaw is the rotation about the vertical axis and perpendicular to the axis of travel.
Yaw also refers to the angular movement (i.e., error) that effects straightness of travel and
positioning accuracy. Refer to Abbé error for additional information.
∇ ∇ ∇
Version 1.0
Aerotech, Inc.
A-9
Glossary of Terms
A-10
LZR2000
Aerotech, Inc.
Version 1.0
LZR2000
APPENDIX B:
Warranty and Field Service
WARRANTY AND FIELD SERVICE
In This Section:
• Laser Product Warranty
• Return Products Procedure
• Returned Product Warranty Determination
• Returned Product Non-warranty Determination
• Rush Service
• On-site Warranty Repair
• On-site Non-warranty Repair
Aerotech, Inc. warrants its products to be free from defects caused by faulty materials or
poor workmanship for a minimum period of one year from date of shipment from
Aerotech. Aerotech’s liability is limited to replacing, repairing or issuing credit, at its
option, for any products which are returned by the original purchaser during the warranty
period. Aerotech makes no warranty that its products are fit for the use or purpose to
which they may be put by the buyer, where or not such use or purpose has been disclosed
to Aerotech in specifications or drawings previously or subsequently provided, or whether
or not Aerotech’s products are specifically designed and/or manufactured for buyer’s use
or purpose. Aerotech’s liability or any claim for loss or damage arising out of the sale,
resale or use of any of its products shall in no event exceed the selling price of the unit.
Aerotech, Inc. warrants its laser products to the original purchaser for a minimum period
of one year from date of shipment. This warranty covers defects in workmanship and
material and is voided for all laser power supplies, plasma tubes and laser systems subject
to electrical or physical abuse, tampering (such as opening the housing or removal of the
serial tag) or improper operation as determined by Aerotech. This warranty is also voided
for failure to comply with Aerotech’s return procedures.
Laser Products
Claims for shipment damage (evident or concealed) must be filed with the carrier by the
buyer. Aerotech must be notified within (30) days of shipment of incorrect materials. No
product may be returned, whether in warranty or out of warranty, without first obtaining
approval from Aerotech. No credit will be given nor repairs made for products returned
without such approval. Any returned product(s) must be accompanied by a return
authorization number. The return authorization number may be obtained by calling an
Aerotech service center. Products must be returned, prepaid, to an Aerotech service
center (no C.O.D. or Collect Freight accepted). The status of any product returned later
than (30) days after the issuance of a return authorization number will be subject to
review.
Return Procedure
After Aerotech’s examination, warranty or out-of-warranty status will be determined. If
upon Aerotech’s examination a warranted defect exists, then the product(s) will be
repaired at no charge and shipped, prepaid, back to the buyer. If the buyer desires an air
freight return, the product(s) will be shipped collect. Warranty repairs do not extend the
original warranty period.
Returned Product
Warranty Determination
Version 1.0
Aerotech, Inc.
B-1
Warranty and Field Service
Returned Product Nonwarranty Determination
Rush Service
On-site Warranty Repair
LZR2000
After Aerotech’s examination, the buyer shall be notified of the repair cost. At such time
the buyer must issue a valid purchase order to cover the cost of the repair and freight, or
authorize the product(s) to be shipped back as is, at the buyer’s expense. Failure to obtain
a purchase order number or approval within (30) days of notification will result in the
product(s) being returned as is, at the buyer’s expense. Repair work is warranted for (90)
days from date of shipment. Replacement components are warranted for one year from
date of shipment.
At times, the buyer may desire to expedite a repair. Regardless of warranty or out-ofwarranty status, the buyer must issue a valid purchase order to cover the added rush
service cost. Rush service is subject to Aerotech’s approval.
If an Aerotech product cannot be made functional by telephone assistance or by sending
and having the customer install replacement parts, and cannot be returned to the Aerotech
service center for repair, and if Aerotech determines the problem could be warrantyrelated, then the following policy applies:
Aerotech will provide an on-site field service representative in a reasonable amount of
time, provided that the customer issues a valid purchase order to Aerotech covering all
transportation and subsistence costs. For warranty field repairs, the customer will not be
charged for the cost of labor and material. If service is rendered at times other than
normal work periods, then special service rates apply.
If during the on-site repair it is determined the problem is not warranty related, then the
terms and conditions stated in the following "On-Site Non-Warranty Repair" section
apply.
On-site Non-warranty
Repair
If any Aerotech product cannot be made functional by telephone assistance or purchased
replacement parts, and cannot be returned to the Aerotech service center for repair, then
the following field service policy applies:
Aerotech will provide an on-site field service representative in a reasonable amount of
time, provided that the customer issues a valid purchase order to Aerotech covering all
transportation and subsistence costs and the prevailing labor cost, including travel time,
necessary to complete the repair.
Company Address
Aerotech, Inc.
101 Zeta Drive
Pittsburgh, PA 15238-2897
USA
Phone: (412) 963-7470
Fax:
(412) 963-7459
∇ ∇ ∇
B-2
Aerotech, Inc.
Version 1.0
LZR2000
Index
Symbol
λ/2 A-quad-B differential line driver output, 8-3
λ/2 A-quad-B differential sinusoidal output, 8-3
+ position of the laser head shutter, 5-4, 5-22
8-pin A-quad-B SIN/COS output connector, 8-1
8-pin DIN Output Connector, 8-2
9-pin D-type A-quad-B line driver output connector, 81
9-pin D-type Output Connector of the Laser Head, 8-2
Choosing a location, 4-8
cleaning fluids, 7-2
cleaning optical components, 7-1, 7-2
cleaning the laser head, 7-1
Clearance for components, 4-8
Closed-loop Systems, 1-8
Coarse adjustment, 5-14
Coarse alignment process, 5-8, 5-9
Plane/flt mirror, 6-4
Components, 2-1
Configurations, 1-8, 3-6
Cosine Error, 5-30
A
D
Abbé Error, 5-31, 5-32, A-1
Absolute pressure, A-1
AC power connector, 8-1
Accessories, 1-7
optical, 5-5
Accuracy, 1-2, 1-10, 4-8, 5-25, 5-30, 8-3
acetone, 7-2
Alignment, 3-7, 4-3, 5-8, 5-9, 5-12, 5-13, 5-15, 5-16, 522, 5-23
Fine tuning, 5-15
Plane/flat mirror, 6-4, 6-5
Plane/flat mirror, 6-10
procedure summary, 5-22
Alignment aides, 3-5
Ambient compensation package, 5-26
Angle of misalignment, 5-30
Angular error, 5-31
Aperture, 1-2, 1-3, 4-1, 4-2, 4-11, 5-4, 5-8, 5-22, 6-5
Applications, 1-1, 1-8
list of, 1-1
A-quad-B differential line driver output, 8-3
A-quad-B line driver output signals, 8-2
A-quad-B signals, 1-2, 1-3, 1-9, 1-11, 4-1
A-quad-B SIN/COS output signals, 8-2
AR-4/, 1-7
AR-6/, 1-7
Attachment of target
Plane/flat mirror measurement, 6-10
Axis of motion, 4-8
B
Beam Alignment, 5-13, 5-16
Beam centerline spacing, 8-3
Beam diameter, 8-3
Beam splitter, 5-3, 5-4
C
Cables, 1-2, 1-5, 1-11, 1-12
disconnecting, 1-12
Captive set screw, 4-4
Version 1.0
Dead path, 5-26, 5-27, 5-28, A-3
measuring the distance of, 5-27
mechanical compensation, 5-29
minimizing errors, 5-27
Dead path compensation, 5-27
Defining the system configuration, 4-8
de-ionized water, 7-2
Density of air, 5-25
Detector circuitry, 5-4
Detector optics, 1-2, 4-1
Differential analog output signals, 1-3, 4-2
Differential TTL output signals, 1-3, 4-2
Dimensions, 8-3
Material temperature sensor, 8-10
Remote ambient temperature sensor, 8-11
Base LZR1002, 8-6
Environmental Compensator, 8-10
Laser Head, 8-3
Quareter Wave Plate, 8-6
disconnecting cables, 1-12
Distance measurement, 4-13
Doppler Laser Interferometry, A-5
E
Electrical connections
PC measurement board, 4-12
Environmental Compensation, 4-8, 5-27
accuracy, 1-2
effects on accuracy, 5-26
Environmental Compensation Application, 1-10
Environmental compensation electronics, 1-7
Environmental compensator, 4-12, 8-9
technical details, 8-8
Environmental Conditions Affecting Accuracy, 5-26
Error sources, 5-25
Errors, 9-1
ethanol, 7-2
External power, 4-11
Aerotech, Inc.
i
Index
LZR2000
F
L
Field Service Information, B-1
Field Service Policy, B-1
Fine adjustment, 5-15
Fine tuning, 5-15
Plane/flat mirror measurement, 6-11
Flatness, 5-31, A-3
G
General Description, 1-2
General Specifications for the LZR2000 Laser Head, 83
ground connection, 1-13, 8-2
H
Hardware, 4-13
Hardware list
Linear and Velocity measurement, 5-2
Hardware versus measurements, 4-14
Heat sources, 1-10, 5-27
Height adjusters, 3-5, 5-5
Horizontal axis, 5-19
Horizontal rotation lock, 4-4
Humidity range, 4-8
I
IC Inspection, 1-1
Illustration
Sample Single-axis LZR2000 Configuration, 1-2
The LZR2000 System, 1-1
Inaccurate readings, 1-3, 4-2
Incident beam, 5-3, 5-4, 5-7, 5-8, 6-4
Inspecting the LZR2000 Laser Head, 2-2
Installation, 4-1
Installing the laser head, 4-1
Installing the optics, 4-1
intensity, 1-13
Interference Fringes, 1-6
use in calculating distances, A-5
Interference patterns, 1-2, 4-1
Interferometer, 5-7
definition, A-4
Plane/flat mirror measurement, 6-5
Interferometer Mounting, 5-11
Interferometer Position Feedback Application, 1-11
Interferometry
definition, A-5
Doppler method, A-5
Introduction to the LZR2000 System, 1-1
ii
Labels, 1-13, 1-14
laser head, 1-2, 1-3, 1-4, 1-5, 1-6, 1-9, 1-11, 1-12, 1-13
calibration, 7-2
cleaning, 7-1
dimensions, 8-3
physical dimensions, 8-2
rear view, 8-1
Laser head, 1-2, 1-3, 3-1, 4-1, 4-2
beam alignment, 5-13
supplying power, 5-8, 6-5
rear view, 1-4, 4-3
Laser head detector circuitry, 5-4
Laser head on tripod
Setup, 4-4
Laser head power consumption, 4-11
laser head warning label, 1-3, 4-2
laser intensity, 1-13
Laser Interferometry
definition, A-5
Laser On, 1-2, 1-3, 4-1, 4-2
Laser On LED, 8-2
Laser Ready, 1-2, 1-3, 4-1, 4-2
Laser Ready LED, 1-3, 4-2, 8-2
Laser type, 8-3
Layouts, 3-6
LCD Inspection, 1-1
LED, 1-2, 1-3, 4-1, 4-2
Leveling feet, 4-5
Leveling laser head, 3-4, 4-7
Leveling screws, 3-2, 4-4, 5-15, 6-11
Linear distance, 5-1
Linear interferometer, 1-5, 2-2
Linear measurements, 5-1
Linear operating specifications, 5-2
LVDT sensors, 5-31
LZR1001, 1-7, 8-5, A-5
LZR1002, 8-6, A-5
LZR1003, 8-7, A-5
LZR1004, A-5
LZR1005, A-5
LZR1010, 1-7, 8-9, 8-10, A-5
LZR1020, 8-9, 8-11, A-6
LZR1100, 1-7, 8-9, A-6
LZR2000, 1-3, 1-4, 1-11, 2-1, 2-2, 4-2, 4-3, 5-2, A-6,
A-7
LZR2000 laser head, 8-1
technical details, 8-1
LZR2000 System Components, 1-1
LZR2300, 2-1, 5-2, 8-4, A-6
LZR2400, 5-2, 8-4, A-6
LZR2410, 2-1, 5-2, A-6
LZR2700, 6-2, A-6
LZR2710, 6-9, 8-6, A-6
LZR2720, 6-2, A-6
Aerotech, Inc.
Version 1.0
LZR2000
Index
Output signals, 8-3
peak values, 8-3
Overlapping dots, 5-18
Overview of the LZR2000, 1-1
LZR2900, A-6
M
Machine tool positioning
Tripod, 4-9
Material temperature sensor, 1-7, 8-9
Specifications, 8-8
Measurement, 3-8
Measurement beam, 1-5, 1-10, 5-3, 5-4, 5-23, 5-27. See
also transmitted beam
measurement distance, 5-25
Measurement path, 4-8, 5-27, 5-28, 5-31
measurement retroreflector, 1-11
Measurements
Types, 4-13
Mechanical compensation, 5-28
Mechanical compensation for dead path, 5-29
methanol, 7-1
Minimal Components, 2-1
Mirror, 6-3, 6-5, 6-10
Mirrored surface, 5-4
Motion axis, 4-8, 5-30
Motion control system, 4-8
Mounting hardware, 3-5, 5-5
Mounting plate, 4-5
Mounting posts, 5-1, 5-5, 5-7
Mounting surface, 3-2, 4-3, 4-8, 5-1, 5-31, 6-1
Mounting the Interferometer, 3-8
Mounting the laser head, 3-2, 3-8, 4-3, 4-4, 5-7, 5-23,
5-28, 5-29, 5-31
Multiplier, 1-9, 4-8
O
On position, 5-23
Operating specifications
Linear and Velocity measurements, 5-2
Plane/flat mirror, 6-2
Operating temperature range, 4-8
Operation Diagram, 1-4
Optical components
cleaning, 7-1
stationary, 5-7
Optical Configurations, 5-7
Optical dimensions, 8-4
Optical mounting accessories, 5-6
Optics, 1-4, 1-5, 3-5
accessories, 5-5, 8-4
interferometer definition, A-4
layouts, 5-1, 5-6, 6-1, 6-3
mounting surfaces, 5-1, 5-6, 6-1, 6-3
technical specifications, 8-4
Optics Fabrication, 1-1
Options, 1-1, 1-7
Output control shutter, 1-3, 4-1
output power, 1-13, 8-3
Version 1.0
P
packing list, 2-1
PBS, 1-5. See also Polarized Beam Splitter
PBS/retro
description, 5-3
PBS/retro combination, 3-8, 5-3, 5-9, 5-23, 5-27, 5-28,
5-31
dimensions, 8-4
PBS/Retro Combination and Retroreflector Optics, 2-2
peak output values of laser, 8-3
Perpendicular measurement, 5-24
Plane/flat mirror, 6-11
Perpendicular Plane/Flat Mirror Alignment, 6-8
Pitch, 5-30, 5-31
Plane/flat mirror alignment, 6-5
Plane/flat mirror hardware, 6-2
Plane/flat mirror interferometer, 6-10
Plane/Flat Mirror Layout, 6-3
Plane/flat mirror measurement, 6-1, 6-7
Operating specifications, 8-11
Plane/flat mirror measurements, 6-1
Plane/Flat Mirror Operating Specifications, 6-2
Plane/Flat Mirror Optical Kit, 6-2
Plane/Flat Mirror Optics Mounting, 6-9
Planning the system configuration, 4-8
polarized beam splitter, 1-2, 1-5
Polarized Beam Splitter, 1-2
Position controls
Tripod, 4-6
Position Feedback Application, 1-11
Positioning Resolution, 1-2
positioning the optical components, 5-1
Positioning Velocity
maximum, 1-2
Post-mount height adjusters, 1-7, 5-7
Post-mount height adjuster and posts
dimensions, 8-5
Power connector, 1-3, 4-1, 4-2
Power consumption of laser head, 4-11
Power cord, 4-11
Power requirements, 8-3
Power supply, 1-2, 4-1
Precautions, 1-13
Pressure sensor, 8-8
Proper Handling, 1-1, 1-12
Q
Quarter wave plate, 6-8
Aerotech, Inc.
iii
Index
LZR2000
R
Ready LED, 3-7, 5-8, 6-5
recalibration, 7-2
Reference beam, 5-3, 5-4, 5-28
Reference path, 4-8, 5-28
Reflected beam, 5-4. See also reference beam
Refractive index of air, 5-25
Remote Ambient temperature sensor, 8-9
Remote material sensor, 4-12
Resetting the system, 5-27
Resolution, 1-2, 1-9, 4-8, 8-11
Retroreflector, 1-2, 1-5, 2-2, 5-3, 5-4, 5-5, 5-6, 5-7, 5-9,
5-22, 5-25, 5-26, 5-27, 5-28, 5-30, 5-31
definition, 5-3
dimensions, 8-4
orientation, 5-3
Retroreflector Mounting, 5-12
Role of Optics, 1-5
S
Safety classification, 8-3
Semiconductor Lithography, 1-1
Shutter, 1-3, 4-1, 4-2, 5-22, 5-23
Signal multiplier, 4-8
Signal Multiplier Application, 1-9
sinusoidal signal, 1-6, 1-9
stability, 8-3
Stabilization of the laser, 3-7, 5-8, 5-22, 6-5
Storage Techniques, 1-12
storing components, 7-1
Supplying power to the laser head, 5-8, 6-5
Surface mounting, 3-2, 4-3
System Components, 2-1
System Maintenance, 7-1
U
UNIDEX 500, 1-3, 1-10
Unpacking the Components, 2-1
V
Vacuum mounting, 5-7
Vacuum wavelength, 8-3
Velocity, 8-11
maximum, 1-2
Velocity measurement, 4-13, 5-1
Velocity specifications, 5-2
Vertical axis, 5-19
Vertical lift adjustment, 4-4
Vertical lift, 4-6
Vertical lock, 4-4, 4-6
Vertical rotation adjustment, 4-7
visual inspection, 2-1
W
T
Table mounting, 3-2, 4-4
Target, 5-13, 5-14
Target Alignment Process, 5-18
Target configurations, 5-14
Target method, 5-17
Target position, 1-3, 4-2
technical details, 8-1
Technical specifications, 8-11
Temperature sensors, 5-30
Temperature, Pressure and Humidity Compensation, 110
Thermal expansion, 5-25, 5-29
Translational adjustment, 4-7
Translational lock, 4-7
Transmitted beam, 5-4
Travel limit, 3-7, 5-22, 5-27
Triangles in the retroreflector, 5-3, 5-4
iv
Tripod, 6-1
Laser head mounting, 3-3
Position controls, 4-6
Setup with laser head, 4-5
Tripod mounting, 3-2, 4-3, 4-4, 5-15, 6-11
Tripod setup, 3-3
Troubleshooting, 9-1
Turning mirror
Dimensions, 8-7
Warm-up time, 8-3
Warning label, 1-3, 4-2
warranty, 1-12
Warranty Information, 1-12, B-1
Warranty Policy, B-1
Wavelength accuracy, 8-3
wavelength of light, 1-10
Wavelength stability, 8-3
weight, 8-3
Y
Yaw, 5-30, 5-31
Z
Zero position, 5-26, 5-27
Aerotech, Inc.
∇ ∇ ∇
Version 1.0
READER’S COMMENTS
AEROTECH
R
LZR2000 and Laser Feedback System Manual
P/N EDU 169, October, 2000
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Fax number (412) 967-6870
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