Texas Instruments | DLP2010 DMD Optical engine reference design (Rev. A) | Application notes | Texas Instruments DLP2010 DMD Optical engine reference design (Rev. A) Application notes

Texas Instruments DLP2010 DMD Optical engine reference design (Rev. A) Application notes
Application Report
DLPA074A – February 2017 – Revised August 2017
Optical Engine Reference Design for DLP2010 Digital
Micromirror Device
Zhongyan Sheng and Alexander Lyubarsky
ABSTRACT
This application note provides a reference design for an optical engine. The design features TI’s DLP2010
digital micromirror device (DMD), which utilizes DLP® TRP pixel architecture to deliver high brightness and
low power consumption. Design options for optical engines are discussed.
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Contents
Scope ..........................................................................................................................
Applicable Documents ......................................................................................................
DLP2010 Key Parameters ..................................................................................................
Design Considerations ......................................................................................................
Optical Layout ................................................................................................................
Estimated Brightness ........................................................................................................
Optical Engine Specification................................................................................................
Design Variations ............................................................................................................
Summary ......................................................................................................................
Get Started ...................................................................................................................
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List of Figures
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Side Illuminated TRP Pixel ................................................................................................. 3
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Optical Design Options
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Optical System ............................................................................................................... 5
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Optical Engine Top View
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Optical Engine Front View .................................................................................................. 6
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DMD Specification ........................................................................................................... 2
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Design Summary
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Estimated Optical Engine Efficiency
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List of Tables
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Brightness at 1-W LED Power .............................................................................................
Maximum Brightness ........................................................................................................
Optical Engine Specification................................................................................................
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Pico, E2E are trademarks of Texas Instruments.
DLP is a registered trademark of Texas Instruments.
DLPA074A – February 2017 – Revised August 2017
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Optical Engine Reference Design for DLP2010 Digital Micromirror Device
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Scope
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Scope
This document provides a brief overview of a reference optical engine design for TI’s DLP2010 DMD. It
summarizes specifications and key design parameters of the optical engine. Optical engines using DLP
Pico™ technology with DLP2010 are well suited for integrating high quality display capability into ultracompact products, such as smartphones, tablets, digital cameras, mobile accessories, interactive surface
computing, digital signage, aftermarket head-up displays, and near-eye displays.
This reference design is solely intended to assist designers who are developing systems that use the
DLP2010 DMD. The performance and results listed in these documents are based on the design
simulation tool Zemax. The actual performance of the end product will depend on the final design and
manufacturing processes.
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Applicable Documents
The following TI documents contain additional information required for design of an optical engine
incorporating the DLP2010.
1. DLP2010 Datasheet
2. Geometric Optics for DLP Application Report
3. DLP Series-244 DMD and System Mounting Concepts Mechanical and Thermal Application Report
4. DLP2010 optical engine design files
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DLP2010 Key Parameters
Table 1. DMD Specification
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Features
Description
TI part number
DLP2010
Description
.2 WVGA DMD
Size
0.2 inch (5.29 mm) diagonal
Aspect ratio
16:9
Array size (pixels)
854 (h) × 480 (v)
Pixel pitch
5.4 μm
Tilt angle of mirror
17° (TRP pixel architecture)
Illumination type
Side illumination
Package size
15.9 mm × 5.3 mm × 4 mm
Optical Engine Reference Design for DLP2010 Digital Micromirror Device
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Design Considerations
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Design Considerations
This section describes the TI DLP pixel architecture, which is a key factor when beginning an optical
design. The design choices for various elements of the optical engine are also discussed.
4.1
DLP TRP Pixel Architecture
DLP TRP pixel architecture utilizes square pixels (Figure 1) and tilts by 17°. The mirror first tilts by 12°
along the hinge then rolls by 12° to either ON or OFF position, resulting in a compound 17° angle. The
TRP pixel architecture allows the DMD to be designed for side-illumination (illuminating the device from a
direction parallel to the long-axis of the device) or for bottom-illumination (illuminating the device from a
direction parallel to the short-axis of the device). Every DMD is designed for a specific illumination
direction (side or bottom), which then determines the design of the window aperture. Refer to the
datasheet for each specific DMD to determine the intended illumination direction. The recommended
illumination angle is 34°, regardless of illumination direction, and the illumination cone angle is within ±17°.
The f-number for the optical system is limited to f/1.7 maximum due to the flat state overlap. Side
illumination enables thinner optical engine. While bottom illumination reduces the size of prism in
telecentric optical design and also potential for lower cost by reducing size of projection lens.
Figure 1. Side Illuminated TRP Pixel
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Design Considerations
4.2
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Optical Design Options
Multiple components are used in an optical engine incorporating TI DLP technology. Figure 2 shows
potential design options for these components. It also highlights the choices used in this reference design.
Figure 2. Optical Design Options
NOTE: The highlighted boxes with checks are options chosen in this design.
*TIR— Total internal reflection
**RTIR— Reverse TIR
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Optical Engine Reference Design for DLP2010 Digital Micromirror Device
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Design Considerations
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4.3
Design Summary
Table 2 summarizes key attributes of this reference design:
Table 2. Design Summary
Specification
Description
Light source LED
Osram
H9RM (0.72 × 0.72) – converted green
Q6WM (0.65 × 0.65) – amber and blue in one package
LED collection angle
80°
Dichroic
Fan dichroic plate / wedge prism
- green pass
- red and blue reflect
Homogenizer
Fly Eye Array
f/#
1.7
Geometric efficiency (ray tracing only)
R – 71.6%
G – 70.2%
B – 73.1%
Offset
0%
Contrast ratio (full on/full off)
Depends on final material used, design implementation,
and manufacturing processes
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Optical Layout
5.1
Optical System
Figure 3. Optical System
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Optical Layout
5.2
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Two Dimensional View
Figure 4. Optical Engine Top View
Figure 5. Optical Engine Front View
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Optical Engine Reference Design for DLP2010 Digital Micromirror Device
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Estimated Brightness
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6
Estimated Brightness
This section calculates the estimated optical efficiency and brightness based on design simulations. The
actual efficiency will depend on the material used and the system design implementation.
6.1
Estimated Optical Engine Efficiency
The efficiency assumptions for optical elements used in Table 3 are representative of components used in
a typical projection engine for consumer applications.
Table 3. Estimated Optical Engine Efficiency
Optical Element
Estimated Transmission Efficiency
Notes
Red
Blue
Green
Collimator lens
0.96
0.96
0.96
Dichroic
0.92
0.90
0.90
Fly's eye array
0.95
0.95
0.95
RTIR prism
0.88
0.88
0.88
Estimate
DMD
0.68
0.68
0.68
Standard value
Projection lens
0.90
0.90
0.90
Total optics
transmission estimate
45.2%
44.2%
44.2%
Geometric efficiency
71.6%
73.1%
70.2%
Optical engine
efficiency
32.4%
32.3%
31.0%
Transmission
efficiency
6.2
Typical estimate
Zemax - Ray tracing
Estimated Brightness (lumens)
Table 4. Brightness at 1-W LED Power
RED
Blue
Q6WM
Green
H9RM
LED
Reference LED data
sheet
Current (mA)
350
350
Forward voltage (V)
2.2
3.4
3.0
Luminous flux
44
15
140
30%
20%
50%
Duty cycle
Available flux
Optical engine efficiency
350
13
3
70
32.4%
32.3%
31.0%
Total flux (lumens)
Mid bin LEDs
27
1.0 (1)
Total LED power (W)
(1)
Notes
Sum of LED current x forward voltage x duty cycle for each LED.
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Optical Engine Specification
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Table 5. Maximum Brightness
RED
Blue
Green
Q6WM
H9RM
LED
Notes
Reference LED data sheet
Current (mA)
1000
1000
1000
Forward voltage (V)
2.6
3.7
3.2
Corrected for high
temperature
Luminous flux
85
31
293
Flux derated for high
temperature
30%
20%
50%
25
6
146
32.4%
32.3%
31.0%
Duty cycle
Available flux
Optical engine efficiency
Total flux (lumens)
56
3.1 (1)
Total LED power (W)
(1)
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Sum of LED current x forward voltage x duty cycle for each LED.
Optical Engine Specification
Table 6 lists expected performance based on design simulation tools. Actual performance may vary from
this and will depend upon materials used, and manufacturing processes.
Table 6. Optical Engine Specification
Features
Description
Maximum brightness
Up to 56 lumens at 3.1 watts
Efficiency
Up to 27 lumens/watt
Image quality
• Contrast ratio (full on/full off)
Depends on optical engine design and management of stray, flat-state and off-state
light inside the engine
• Modulation Transfer Function (MTF)
50% at 93 lp/mm (designed)
• Uniformity
>70%
System
• Dimension (optical system only)
Does not include mechanical housing
and heat sink
29 mm ( L) × 25 mm (W) × 6.5 mm (H)
• Throw ratio
1.6
• Offset
0%
Please download "DLP2010 Optical Engine Design Files" from http://www.ti.com/lsds/ti/dlp/video-anddata-display/documents.page.
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Design Variations
For applications like near-eye displays where a very small form factor and low power consumption are
critical, brightness of up to 10 lumens is usually adequate. The design shown in this Application Report
can further be reduced in size by using a device containing red, green and blue LEDs in a single package,
which eliminates the need for dichroic optics. The optical component placement could be matched to the
form factor of the end product, for example, by unfolding the light path and using an additional optical
element to make an in-line layout.
Conversely, a light engine capable of up to 150 lumens could be designed using brighter individual red,
blue, and green LEDs.
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Optical Engine Reference Design for DLP2010 Digital Micromirror Device
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Summary
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Summary
The DLP2010 DMD enables a highly optimized and purpose built display solution for a wide range of
applications including smartphones, tablets, digital cameras, mobile accessories, interactive surface
computing, digital signage, aftermarket head-up displays and near-eye displays. The reference design
shown in this Application Report is targeted for a compact projection engine with up to 60 lumens
brightness. This class of optical engines are best suited for a small hand held battery operated product.
Variations of this basic optical architecture are possible for applications like wearables or higher-end
projectors.
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Get Started
To get started with DLP Pico technology, we recommend the following actions:
• Learn more about DLP Pico technology.
– Read the Getting Started with TI DLP® Display Technology application report.
– Browse DLP products and applications.
– Experiment with the DLP throw ratio and brightness calculator.
• Download TI Designs reference designs to speed product development, including schematics, layout
files, bill of materials, and test reports.
– DLP2010: Ultra Mobile, Ultra Low Power Display Reference Design using DLP Technology
• Evaluate DLP Pico technology with an easy to use evaluation module (EVM).
• Find optical modules and design support.
– Buy production ready modules from a worldwide optical supplier.
– Contact optical module manufacturers to help accelerate product development and speed time to
market.
– Contact DLP design houses for custom solutions.
• Contact your local TI sales representative or TI distributor representative.
• Check out TI's E2E™ community to search for solutions, get help, share knowledge and solve
problems with fellow engineers and TI experts.
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Revision History
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Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Original (February 2017) to A Revision .................................................................................................. Page
•
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Added link to DLP2010 optical engine design files in Section 2 .................................................................... 2
Revision History
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