User Manual - FLIR PathfindIR II

User Manual - FLIR PathfindIR II
User Manual
334-0001-00-10-LE, rev. 100
May ’08
334-0001-00-10-LE, rev. 100
May ’08
© FLIR Systems, Inc.. All rights reserved worldwide. No parts of this
manual, in whole or in part, may be copied, photocopied, translated, or
transmitted to any electronic medium or machine readable form without
the prior written permission of FLIR Systems, Inc.
Names and marks appearing on the products herein are either registered
trademarks or trademarks of FLIR Systems, Inc. and/or its subsidiaries. All
other trademarks, trade names, or company names referenced herein are
used for identification only and are the property of their respective owners.
This product is protected by patents, design patents, patents pending, or
design patents pending.
Your Source for Modern Thermal Imaging Systems
P.O. BOX 4242
Middletown, NY 10941
PH: + 1 888 919 2263
PH Intl: + 1 845 343 4077
FX: + 1 845 343 4299
[email protected]
w w
Warnings and Cautions
Getting Started
Caring for your PathFindIR LE
Options and Accessories
Technical Data
Infrared Technology
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1 Warnings and Cautions
1.1 Cautions ................................................................................. 1
1.2 General Information ................................................................. 2
2 Introduction
Overview ................................................................................. 3
Thermal Imaging Driver Vision Enhancement System .................. 3
What is Thermal Imaging? ........................................................ 5
Vehicles that use PathFindIR LE ............................................... 5
Part Numbers .......................................................................... 6
3 Getting Started
Using your PathFindIR LE ........................................................ 7
Initial System Startup .............................................................. 7
Heater Element ....................................................................... 8
Automatic Shutter ................................................................... 8
In Case of Difficulty ................................................................. 8
Troubleshooting ....................................................................... 9
4 Caring for your PathFindIR LE
4.1 Product Cleaning ................................................................... 11
4.2 Temperature ......................................................................... 11
4.3 Maintenance ......................................................................... 11
5 Options and Accessories
5.1 Accessories ........................................................................... 13
5.1.1 PathFindIR Interface Cable ........................................... 13
5.1.2 PathFindIR LE Vision Enhancement Kit .......................... 14
6 Technical Data
6.1 Performance Specification ...................................................... 15
6.1.1 Side View .................................................................... 16
6.1.2 Side View, Additional Dimensions .................................. 17
6.1.3 Front View ................................................................... 18
7 Installation
PathFindIR LE Installation ..................................................... 19
Preparation ........................................................................... 19
Installation ........................................................................... 20
Installation Guidelines and Precautions ................................... 20
Installation Assistance ........................................................... 21
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7.6 Mounting Assistance .............................................................. 21
8 Infrared Technology
8.1 History of Infrared ................................................................ 23
8.2 How do Infrared Cameras Work? .............................................. 27
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Warnings and Cautions
1.1 Cautions
Caution! This guide uses the term Caution to indicate a potentially
hazardous situation, which, if not avoided, may result in injury, damage
to the vehicle or PathFindIR LE, or other property damage.
Do not operate any function that takes your attention away from safely driving
your vehicle.
Any function that requires your prolonged attention should only be
performed after coming to a complete stop. Always stop the vehicle in a
safe location before performing these functions. Failure to do so may
result in an accident.
Consult your local and state driving regulations prior to installation.
In many states using active monitors in view of the driver is prohibited.
Consult your local and state driving regulations for laws and guidelines.
User assumes all risks and indemnifies the manufacturer from any
Minimize display viewing while driving.
Viewing the display may distract the driver from looking ahead and may
result in an accident. The PathFindIR LE thermal imaging system should
not be used as a substitution for head lamps or head lamp assisted human
vision during vehicle operation.
Use this product for mobile 12VDC applications.
Use for other applications may result in excess heat, fire, and equipment
When installing the PathFindIR LE, do not block the vehicle’s vents or radiator
Doing so may result in heat buildup, equipment breakage, and/or fire.
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1 – Warnings and Cautions
1.2 General Information
Caution! The PathFindIR LE thermal imaging system is not intended to
be used as the primary navigation system. The PathFindIR LE should not
to be used as a substitution for head lamps or head lamp assisted human
vision during vehicle operation. It should be used only as an aid to
cautious night-time driving.
Do not open the camera body for any reason. Disassembly of the camera
(including removal of the cover) can cause permanent damage and will
void the warranty.
Operating the camera outside of the specified input voltage range or the
specified operating temperature range can cause permanent damage.
Do not image extremely high intensity radiation sources, such as the sun,
lasers, arc welders, etc.
The camera is a precision optical instrument and should not be exposed to
excessive shock and/or vibration. Refer to paragraph 6.1 “Performance
Specification” on page 15 for detailed environmental requirements.
Great care should be used with your camera optics. They are delicate and
can be damaged by improper cleaning. Refer to Chapter 4 “Caring for your
PathFindIR LE” on page 11.
All thermal imaging systems are subject to export control. Please
contact FLIR for export compliance information concerning your
application or geographic area.
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PathFindIR LE - See More, Be Safer!
2.1 Overview
Congratulations! You have purchased one of the most sophisticated and
important instruments you will have on your vehicle. The FLIR
ThermoVision®PathFindIR LE is a state-of-the-art thermal imaging system
that will provide you with excellent night visibility and situational
awareness, even in absolute darkness.
The PathFindIR LE system is designed for simple, intuitive operation. The
PathFindIR LE camera is a sophisticated thermal sensor that converts
thermal content (heat) of a scene into a 2-dimensional image for display
on a video monitor inside your vehicle.
2.2 Thermal Imaging Driver Vision Enhancement System
The FLIR Systems, Inc. PathFindIR LE camera is a high performance,
rugged, thermal imaging camera designed to provide driver vision
enhancement in adverse weather conditions and better situational
awareness than with traditional head lamps.
Many serious accidents occur at night because the driver is not able to see
the cause of the accident in time to prevent the collision. PathFindIR LE
directly addresses this problem, allowing drivers to see farther ahead on
nighttime roadways and identify potential problems earlier. The majority of
trucking accidents occur in rural areas, where visibility is severely reduced
at night. Humans and other warm blooded animals offer significant
thermal contrast to driving backgrounds and are easy to spot with the
PathFindIR LE. The system allows drivers to see without any additional
lighting and provides real-time imaging at any speed.
Different than visible light cameras, thermal imagers do not display
reflected light as seen with human eyes. Rather, thermal imaging cameras
only 'see' temperature differences which are converted into shades of grey,
from black to white. The PathFindIR LE camera displays cold objects as
black and hot objects as white.
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2 – Introduction
When using a thermal imager in darkness, the image is created based on
temperature differences of objects in the field of view, rather than
reflected light from headlights.
Furthermore, because thermal imaging cameras only 'see' heat sources
and not reflected light, they are ideal to assist with driver vision and
situational awareness for oncoming obstructions such as animals, people,
and other vehicles
Figure 2-1: PathFindIR Makes the Difference
The above images show a comparison of typical night time driving
compared to using the PathFindIR LE thermal imager. The image on the
left is from an ordinary digital camera and shows the amount of visible
light as illuminated by headlights; the image on the right is a thermal
image created by the PathFindIR LE thermal imaging camera. Note the
PathFindIR LE camera is sensitive to warm objects, such as the deer, and
provides visibility over a much greater distance.
Some of the objects that are most critical for a driver to avoid are people
and animals. Because these objects are naturally warm, they are
particularly easy to see with the PathFindIR LE and clearly stand out in the
video image.
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2 – Introduction
2 – Introduction
Although adverse conditions such as heavy fog will affect any driver vision
enhancement system, thermal imaging cameras such as the PathFindIR
LE have been shown to continue to provide useful information in
conditions of reduced visibility, such as haze and smoke. While the
PathFindIR LE can assist drivers with detection of obstructions in the
vehicle’s path, thermal imagers should not be used as the sole vision
method of the driver.
PathFindIR LE is specifically designed to withstand a harsh environment,
with a hermetically-sealed external housing resistant to rocks, sand, salt,
and under-hood contaminants. Additionally, the wide operating
temperature range allows the PathFindIR LE to maintain high performance
in severe weather conditions.
2.3 What is Thermal Imaging?
With our eyes, we see visible light. With a thermal imager, we can see
infrared - a form of light just beyond the visible spectrum. Thermal
imagers show subtle differences in temperature; warm objects appear
white and cooler objects appear black.
In addition to driver vision enhancement, FLIR's thermal imaging cameras
are used in a wide variety of applications, including fire fighting, security,
maritime, industrial and medical applications. They continue to be used
by militaries worldwide to navigate at night and in battlefield conditions.
Over the last few years, volume production of these systems has allowed
FLIR to offer the same high performance cameras designed for military use
to the commercial market.
2.4 Vehicles that use PathFindIR LE
PathFindIR LE can increase the detection time for hazards and reduce the
probability of an accident - providing confidence and saving lives and
property. PathFindIR LE provides improved situational awareness often
necessary when performing investigations and when responding to
Emergency vehicles - Emergency vehicles' high speeds and degraded
stopping distances increase the chance of an accident - PathFindIR LE
improves hazard detection at high speeds.
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2 – Introduction
Open rural roads - PathFindIR LE can reveal people, animals and
obstructions at long ranges in complete darkness. This early detection
capability can significantly increase reaction time.
Hard-to-see conditions - PathFindIR LE improves awareness in conditions
that render eyesight and daylight cameras useless. The PathFindIR LE can
see clearly through dust and smoke, increasing safety for everyone on the
job site.
2.5 Part Numbers
The PathFindIR LE kit (part number 421-0034-00) contains the standard
PathFindIR camera (part number 334-0001-00, 30Hz, NTSC format) as
well as a monitor, bracket, and cables required for a complete installation.
Refer to Chapter 5 “Options and Accessories” on page 5-13 for more
All thermal imaging systems are subject to export control.
Standard NTSC (30Hz) and PAL (25Hz) units are subject to
export restrictions and licensing by the United States
Government. Models with video frame rates at or below 9Hz do
not require licensing but do require compliance with other export
requirements. Please contact FLIR for details concerning export
compliance for your application or geographic area.
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Getting Started
The thermal imaging camera inside the PathFindIR LE is completely
sealed and extremely rugged. The camera has been qualified for operation
in all types of weather conditions over the specified operating temperature
range and includes an automatic window heater that will prevent icing
under most conditions.
3.1 Using your PathFindIR LE
The PathFindIR LE is easy to use, but you should take a moment to
carefully read this section so you fully understand what you are seeing on
your display. While the imagery you will see on the monitor may look like
black and white daylight video, it isn’t! A few tips on how to interpret some
of the imagery will help you to make the most of your system.
The camera automatically adjusts to changing scene conditions so no
additional camera control is necessary. Scenes with familiar objects will be
easy to interpret with some experience. The camera automatically
optimizes the image to provide you with the best contrast in most
The thermal imager inside the camera does not sense light like
conventional cameras; it senses heat or temperature differences. As you
experiment with the system during nighttime operation, you will notice
variances in the “picture quality”; this is normal. The camera senses small
“differences” in apparent radiation from the objects in view, and displays
them as either white (or lighter shades of gray) for warmer objects, and
black (or darker shades of gray) for colder objects.
3.2 Initial System Startup
The PathFindIR LE camera requires power and a connection to an external
monitor to provide imagery. Make sure to test the system prior to
installation to assure the system is functioning properly. Be sure to remove
the protective window sticker prior to test and installation.
Upon initial power up you will hear a slight clicking sound. This click is
the internal image correction. This noise is the mechanical shutter
assembly which will cause the image to momentarily “freeze.” This noise
and image freezing will occur until the unit has reached a thermally stable
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3 – Getting Started
temperature and periodically thereafter. See “Automatic Shutter” on
page 8.
3.3 Heater Element
The PathFindIR LE has a built-in heating element to stabilize the window
and prevent ice build-up in cold weather conditions. The heating element
is automatically turned on when the temperature of the window falls below
4ºC and is tuned off when the temperature reaches 6ºC.
3.4 Automatic Shutter
The PathFindIR LE incorporates an automatic image correction feature via
the internal calibration shutter. This shutter will activate every 2 minutes
or more frequently during initial start up and large environmental
temperature changes. During this function the image will be “frozen” for
approximately half a second.
The frozen image will display a small white box in the left middle portion
of the image during this calibration, as shown in the image below.
3.5 In Case of Difficulty
The PathFindIR LE comes with a 12 month limited warranty from the date
of purchase. DO NOT OPEN, MODIFY, or ALTER the PathFindIR LE unit or
accessories. Doing so will void any warranty and may cause system
malfunction, loss of performance, fire, or bodily harm.
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3 – Getting Started
3 – Getting Started
The PathFindIR LE is a highly sophisticated electronic imaging system.
Should the system fail for any reason do not attempt to fix the system or
wiring cables yourself. Check wiring connections, power input, video
output. If system is not performing please contact the manufacture at
+1.888.747.3547 or +1.805.964.9797 and ask to speak to the service
department. You will need the serial number of the unit to obtain a Return
Material Authorization.
3.6 Troubleshooting
No Video but the system is running and has power supplied to it.
Place your ear next to the PathFindIR LE unit. If you hear the mechanical
shutter (clicking noise, see section 3.2 “Initial System Startup” on page
7) but you are not getting an image, check the video connections. The
PathFindIR LE works with most standard NTSC or PAL monitors that have
75 ohm input.
No Video, no clicking.
If video is not displayed and you do not hear a "clicking" sound from the
PathFindIR LE, check the power inputs. The PathFindIR LE runs on 6V to
16V power through the optional 20 foot standard cable power leads. If this
voltage is exceeded the unit will not function and may be damaged.
The image is cloudy or hazy, or the window has fog or ice built up.
The PathFindIR LE is equipped with an automatic heating element which
turns on at cold temperatures. The heater requires a few moments to
stabilize the window. Once the window is thermally stabilized the heating
element will turn off automatically.
The image has "lines" or screen door appearance.
Check to see if the image "freezes" or if you hear a mechanical "clicking
noise" from the PathFindIR LE unit. If you do not see the image freeze
momentarily (this may take a few minutes), the internal shutter may be
damaged. Contact the manufacturer.
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3 – Getting Started
The image is shaky.
Check your mounting. The PathFindIR LE does not incorporate image
stabilization and must be mounted soundly and securely.
Image is dim.
Check your monitor and video connections. It is recommended that you
use separate power supplies for the PathFindIR LE and the local display to
make sure you have clean uninterrupted power. Also, verify the PathFindIR
LE is connected to the 75 ohm input on the monitor. The image may be
dim if the camera is connected to an input that requires a different
The image is dark and no objects are seen.
Recycle the power and see if you get the "Splash Screen" (as seen below)
on the display. If you get the Splash Screen but no image afterwards (only
a black screen), check to make sure that the window is clear of all
obstructions (refer to the maintenance section for information on window
cleaning). If you do not see the Splash Screen, check the power input and
video output.
If you see the Splash Screen but no image afterwards, it is possible the
mechanical shutter is stuck in the on position. Contact FLIR customer
service for additional help.
Figure 3-1: Startup Splash Screen
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Caring for your PathFindIR LE
4.1 Product Cleaning
Caution! Do not open the camera body for any reason. Disassembly of the
camera (including removal of the cover) can cause permanent damage
and will void the warranty.
Your PathFindIR LE camera images through an infrared transparent
window. This window is designed for the harsh automotive environment of
normal driving, but may require occasional cleaning. FLIR Systems Inc.
suggests that you clean the window of the PathFindIR LE when image
quality degradation is noticed or excessive contaminant build-up is seen
on the window.
The camera housing has a durable coating and the rugged protective
window is designed to withstand normal cleaning. Rinse the camera
housing with low pressure fresh water to keep it clean. If the front window
of the PathFindIR LE gets water spots, wipe it with a clean soft cotton
cloth dampened with fresh water. If the window requires further cleaning,
use a soft moist cotton-based cloth with isopropyl alcohol or dish soap.
Do not use abrasive materials, such as paper or scrub brushes as this will
possibly damage the window by scratching it. Only clean the window when
you can visually see contamination on the surface.
4.2 Temperature
The PathFindIR LE camera has an operating temperature range of -40 to
80oC. Choose an installation location so that the PathFindIR LE is not
subject to temperature extremes that exceed this range.
4.3 Maintenance
If you have problems do not attempt to repair the PathFindIR LE unit
yourself. The PathFindIR LE camera is a water-tight sealed unit and can
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4 – Caring for your PathFindIR LE
not be opened or serviced in the field. Consult your installation dealer or
FLIR Systems Inc. for repair information.
If the camera will not produce an image, check the video connection at the
camera and at your display. If the connectors appear to be properly
engaged but the camera still does not produce an image, have an
authorized service representative make the appropriate repairs.
Figure 4-1: Front Window
Caution! Improper care of the camera window can cause damage to the
anti-reflective coating, degrade the camera’s performance, and void the
camera warranty.
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Options and Accessories
5.1 Accessories
Camera options and accessories are subject to change. Refer to the FLIR
web site or contact your local dealer to obtain up-todate information regarding available accessories such as mounting kits,
monitor options, cables and accessories.
5.1.1 PathFindIR Interface Cable
Part Number: 308-0121-00
The standard 20 foot system cable ensures a sealed connection to the
PathFindIR LE, a requirement for harsh vehicle environments. Cable
includes sealed PathFindIR connector at one end and two open power
leads and a BNC video connection at the other end.
Power Leads
Video output
Connect to
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5 – Options and Accessories
5.1.2 PathFindIR LE Vision Enhancement Kit
The FLIR PathFindIR LE Vision Enhancement Kit, part number 4210034-00, is made available to facilitate installation in most Law
Enforcement vehicle applications. The kit contains:
PathFindIR LE camera
Universal Mounting Bracket and hardware
PathFindIR Interface Cable 308-0121-00
Safety Vision 7” Monitor with Mounting Bracket and Sun Shield
Monitor Interface Cable SV-513
The following diagram shows how to connect the PathFindIR LE using the
cables in the kit.
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Technical Data
6.1 Performance Specification
Thermal Imaging Performance
Sensor type
Uncooled microbolometer
Field of view
36° h x 27° v
Spectral band
8 - 14 μ
320 x 240 pixels
Time to Image
< 2 sec.
Focal Length
19 millimeters
Connector types
12-pin automotive connector for power in, video
30-Hz for NTSC Video, 25 Hz for PAL video
Frame Rate
Note: Hz is equivalent
to frames per second < 9 Hz Export Compliant
Power requirements
12 VDC nominal (range 6V to 16V)
Power consumption
2 Watts (nominal)
8 Watts with heater turned on
Operating temperature -40º C to +80ºC
Impact protection
High-impact resistant window with heating
Weather Resistance
Hermetically sealed, pressurized enclosure
For additional information, contact FLIR.
Dimensions and Weight
Dimensions (Width x
Height x Length)
58mm x 57mm x 72mm (2.3” x 2.2” x 2.8”)
excluding connector
Connector adds 25.7 mm to height
less than 0.4 kg (0.88 lb.)
Mounting Points
2 per side, M4x0.7
6mm screws required
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6 – Technical Data
6.1.1 Side View
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6 – Technical Data
6 – Technical Data
6.1.2 Side View, Additional Dimensions
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6.1.3 Front View
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7.1 PathFindIR LE Installation
The PathFindIR LE is a compact, sealed imaging system that fits easily
behind vehicle grilles and in other compact locations. It includes an
internal heater to keep the lens clear in icy conditions, and delivers
superior image quality. It can be ordered as a camera module with a
commercial grade cable.
The PathFindIR LE must be mounted in a location where it is not
obstructed by the windshield or other glass materials. Although glass is
transparent to the human eye, it is opaque in the infrared spectrum.
The PathFindIR LE should be installed by an installer or dealer trained by
FLIR Systems, Inc. If one is not available in your area we recommend that
you use a reputable car audio/video installation shop that specializes in
mobile video system integration. The wiring and installation requires
special care and integration techniques. Improper installation may result
in damage to the camera and may void the warranty.
Some modifications to the vehicle’s exterior may be required, as well as
integration into various display units, including factory LCD or aftermarket
multi-functional display units.
7.2 Preparation
The PathFindIR LE Standard 20 foot system cable has two open power
leads to be connected to a power source operating between 6V - 16V. The
standard cable accessory also includes a BNC male end. Refer to the
model number for your specific analog video output format.
It is recommended that power to the monitor be supplied separately from
power to the PathFindIR LE unit to assure clean (low noise) power to both
items. Otherwise the video image may appear to have interference,
ghosting, or undesirable video artifacts.
Caution: Before wiring the camera, disconnect all power from the
battery. Failure to do so may result in shock, bodily harm, or damage to
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7 – Installation
7.3 Installation
Installation using incorrect connections may result in system malfunction
or risk of shock. FLIR Systems, Inc. recommends the standard 20-foot
cable for proper installation (refer to Chapter 5.1 “Accessories” on page 513). This cable is sealed and provides two power input leads and video
output via the connected BNC adapter.
The proper mating connector must be used when installing the PathFindIR
LE. The use of other connectors may result in damage to the camera that
is not covered by the limited product warranty.
The Standard 20 foot System cable has a BNC connector for video output.
You may need to purchase connectors/converters to connect to aftermarket
or factory-installed video monitors.
Caution: Supplying power to the unit outside of the recommended and
stated values will result in system malfunction and void the warranty.
This may also result in excessive heat build up, shock, or fire.
7.4 Installation Guidelines and Precautions
Do not splice cables or tap into existing cables for power or video. Doing so
may result in shock, fire, or damage to electrical system/equipment. Power
connections should be made to the fused side of the vehicle’s power
distribution block.
Do not install in areas where the unit will hinder vehicle operation, i.e.
radiator, steering, head lamps, braking systems. Doing so may interfere
with the vehicle's operation and cause an accident.
Do not install in areas of high moisture, dust or air intake paths. Doing so
may hinder the performance of the PathFindIR LE unit and cause image
degradation or window damage.
Use only authorized parts and accessories. Doing so helps assure proper
mounting and connectivity and limits external issues associated with
poorly secured mounting and wiring.
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7 – Installation
Disconnect the negative (-) battery terminal prior to installation.
Connect the unit to the vehicle power distribution block using an available
fused (2 amp) connection. Be sure to connect each lead to the correct
polarity (red-positive and black-negative).
Be sure to securely mount the system to assure reliable connections and
stable system performance.
Record the serial number, date of purchase, location of purchase and keep
in a safe place.
When making connections to the vehicle’s electrical system be aware of
the vehicle’s installed components (i.e. on board computer system).
Do not mount a display where it will distract the driver or adversely affect
the driver’s vision.
7.5 Installation Assistance
FLIR offers installation kits which are suitable for many applications.
Refer to Chapter 5.1.2 “PathFindIR LE Vision Enhancement Kit” on page
5-14 for more information.
If your company has applications for a specific vehicle utilizing
PathFindIR LE cameras please contact FLIR Systems, Inc. directly to
discuss your needs.
7.6 Mounting Assistance
The following are some general guidelines which will assist your
professional service and installer with good mounting positions and
The PathFindIR LE is a thermal imaging system. As such, it will not “see
through” windows or obstructions. The system should be mounted outside
the vehicle's cabin (interior) and in such a location to assure a similar
driving viewing field of view as normal head lamps and human vision.
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FLIR Systems Inc. is not liable for any modifications made to the vehicle's
body, or aftermarket parts. Owner assumes all risk when modifying
vehicles body, frame, grill, or any other structure. Care should be taken
when drilling or cutting into parts. Contact your vehicle manufacture to
assure that the mounting location does not affect the performance,
operation, or safety features of your vehicle.
Mounting should be performed by a FLIR-authorized service center or
professional installer of automotive aftermarket equipment. Many shops
familiar with rear vision cameras will be able to assist in the mounting and
location of the PathFindIR LE system, as well as proper display mounting
and integration.
Caution: Contact your vehicle manufacture to assure that your mounting
location does not affect any sensors found in bumpers or grills (such as
air bag deployment devices). Mounting the PathFindIR LE should never
interfere with the mechanical or electrical components or airways to
maintain vehicle performance or operations.
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Infrared Technology
History of Infrared
Less than 200 years ago the existence of the infrared portion of the
electromagnetic spectrum wasn't even suspected. The original significance
of the infrared spectrum, or simply ‘the infrared’ as it is often called, as a
form of heat radiation is perhaps less obvious today than it was at the time
of its discovery by Herschel in 1800.
Figure 8-1: Sir William Herschel (1738–1822)
The discovery was made accidentally during the search for a new optical
material. Sir William Herschel—Royal Astronomer to King George III of
England, and already famous for his discovery of the planet Uranus—was
searching for an optical filter material to reduce the brightness of the sun’s
image in telescopes during solar observations. While testing different
samples of colored glass which gave similar reductions in brightness he
was intrigued to find that some of the samples passed very little of the
sun’s heat, while others passed so much heat that he risked eye damage
after only a few seconds’ observation.
Herschel was soon convinced of the necessity of setting up a systematic
experiment, with the objective of finding a single material that would give
the desired reduction in brightness as well as the maximum reduction in
heat. He began the experiment by actually repeating Newton’s prism
experiment, but looking for the heating effect rather than the visual
distribution of intensity in the spectrum. He first blackened the bulb of a
sensitive mercury-in-glass thermometer with ink, and with this as his
radiation detector he proceeded to test the heating effect of the various
colors of the spectrum formed on the top of a table by passing sunlight
through a glass prism. Other thermometers, placed outside the sun’s rays,
served as controls.
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8 – Infrared Technology
As the blackened thermometer was moved slowly along the colors of the
spectrum, the temperature readings showed a steady increase from the
violet end to the red end. This was not entirely unexpected, since the
Italian researcher, Landriani, in a similar experiment in 1777 had
observed much the same effect. It was Herschel, however, who was the
first to recognize that there must be a point where the heating effect
reaches a maximum, and those measurements confined to the visible
portion of the spectrum failed to locate this point.
Figure 8-2: Marsilio Landriani (1746–1815)
Moving the thermometer into the dark region beyond the red end of the
spectrum, Herschel confirmed that the heating continued to increase. The
maximum point, when he found it, lay well beyond the red end—in what is
known today as the ‘infrared wavelengths’.
When Herschel revealed his discovery, he referred to this new portion of
the electromagnetic spectrum as the ‘thermometrical spectrum’. The
radiation itself he sometimes referred to as ‘dark heat’, or simply ‘the
invisible rays’. Ironically, and contrary to popular opinion, it wasn't
Herschel who originated the term ‘infrared’. The word only began to appear
in print around 75 years later, and it is still unclear who should receive
credit as the originator.
Herschel’s use of glass in the prism of his original experiment led to some
early controversies with his contemporaries about the actual existence of
the infrared wavelengths. Different investigators, in attempting to confirm
his work, used various types of glass indiscriminately, having different
transparencies in the infrared. Through his later experiments, Herschel
was aware of the limited transparency of glass to the newly-discovered
thermal radiation, and he was forced to conclude that optics for the
infrared would probably be doomed to the use of reflective elements
exclusively (i.e. plane and curved mirrors). Fortunately, this proved to be
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true only until 1830, when the Italian investigator, Melloni, made his great
discovery that naturally occurring rock salt (NaCl)—which was available in
large enough natural crystals to be made into lenses and prisms—is
remarkably transparent to the infrared. The result was that rock salt
became the principal infrared optical material, and remained so for the
next hundred years, until the art of synthetic crystal growing was mastered
in the 1930’s.
Figure 8-3: Macedonio Melloni (1798–1854)
Thermometers, as radiation detectors, remained unchallenged until 1829,
the year Nobili invented the thermocouple. (Herschel’s own thermometer
could be read to 0.2 °C (0.036 °F), and later models were able to be read
to 0.05 °C (0.09 °F)). Then a breakthrough occurred; Melloni connected a
number of thermocouples in series to form the first thermopile. The new
device was at least 40 times as sensitive as the best thermometer of the
day for detecting heat radiation—capable of detecting the heat from a
person standing three meters away.
The first so-called ‘heat-picture’ became possible in 1840, the result of
work by Sir John Herschel, son of the discoverer of the infrared and a
famous astronomer in his own right. Based upon the differential
evaporation of a thin film of oil when exposed to a heat pattern focused
upon it, the thermal image could be seen by reflected light where the
interference effects of the oil film made the image visible to the eye. Sir
John also managed to obtain a primitive record of the thermal image on
paper, which he called a “thermograph”.
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Figure 8-4: Samuel P. Langley (1834–1906)
The improvement of infrared-detector sensitivity progressed slowly.
Another major breakthrough, made by Langley in 1880, was the invention
of the bolometer. This consisted of a thin blackened strip of platinum
connected in one arm of a Wheatstone bridge circuit upon which the
infrared radiation was focused and to which a sensitive galvanometer
responded. This instrument is said to have been able to detect the heat
from a cow at a distance of 400 meters.
An English scientist, Sir James Dewar, first introduced the use of liquefied
gases as cooling agents (such as liquid nitrogen with a temperature of 196 °C (-320.8 °F)) in low temperature research. In 1892 he invented a
unique vacuum insulating container in which it is possible to store
liquefied gases for entire days. The common ‘thermos bottle’, used for
storing hot and cold drinks, is based upon his invention.
Between the years 1900 and 1920, the inventors of the world ‘discovered’
the infrared. Many patents were issued for devices to detect personnel,
artillery, aircraft, ships—and even icebergs. The first operating systems, in
the modern sense, began to be developed during the 1914–18 war, when
both sides had research programs devoted to the military exploitation of
the infrared. These programs included experimental systems for enemy
intrusion/detection, remote temperature sensing, secure communications,
and ‘flying torpedo’ guidance. An infrared search system tested during this
period was able to detect an approaching airplane at a distance of 1.5 km
(0.94 miles), or a person more than 300 meters (984 ft.) away.
The most sensitive systems up to this time were all based upon variations
of the bolometer idea, but the period between the two wars saw the
development of two revolutionary new infrared detectors: the image
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converter and the photon detector. At first, the image converter received
the greatest attention by the military, because it enabled an observer for
the first time in history to literally ‘see in the dark’. However, the
sensitivity of the image converter was limited to the near infrared
wavelengths, and the most interesting military targets (i.e. enemy soldiers)
had to be illuminated by infrared search beams. Since this involved the
risk of giving away the observer’s position to a similarly-equipped enemy
observer, it is understandable that military interest in the image converter
eventually faded.
The tactical military disadvantages of so-called 'active’ (i.e. search beamequipped) thermal imaging systems provided impetus following the 1939–
45 war for extensive secret military infrared-research programs into the
possibilities of developing ‘passive’ (no search beam) systems around the
extremely sensitive photon detector. During this period, military secrecy
regulations completely prevented disclosure of the status of infraredimaging technology. This secrecy only began to be lifted in the middle of
the 1950’s, and from that time adequate thermal-imaging devices finally
began to be available to civilian science and industry.
8.2 How do Infrared Cameras Work?
Infrared energy is part of a complete range of radiation called the
electromagnetic spectrum. The electromagnetic spectrum includes gamma
rays, X-rays, ultraviolet, visible, infrared, microwaves (RADAR), and radio
waves. The only difference between these different types of radiation is
their wavelength or frequency. All of these forms of radiation travel at the
speed of light (186,000 miles or 300,000,000 meters per second in a
vacuum). Infrared radiation lies between the visible and RADAR portions
of the electromagnetic spectrum. Thus infrared waves have wavelengths
longer than visible and shorter than RADAR.
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Figure 8-5: Electromagnetic Spectrum
The primary source of infrared radiation is heat or thermal radiation. Any
object which has a temperature radiates in the infrared portion of the
electromagnetic spectrum. Even objects that are very cold, such as an ice
cube, emit infrared. When an object is not quite hot enough to radiate
visible light, it will emit most of its energy in the infrared. For example, hot
charcoal may not give off light, but it does emit infrared radiation which
we feel as heat. The warmer the object, the more infrared radiation it
Infrared cameras produce an image of invisible infrared or “heat” radiation
that is unseen by the human eye. There are no colors or “shades” of gray
in infrared, only varying intensities of radiated energy. The infrared imager
converts this energy into an image that we can interpret. Several detector
technologies exist; the sensor in the PathFindIR LE is of the latest solid
state design, offering long life and fully automatic image optimization
(contrast and gain). True thermal imagers should not be confused with
infrared illuminator cameras that are often presented as simply “infrared
cameras.” There are hundreds of low cost infrared illuminated cameras on
the market at prices below $100. These cameras do not produce the same
image because they do not detect heat. They operate in wavelengths near
visible, and require an IR illuminator to provide an image. IR illuminators
have very short range, and require a lot of power to see beyond 5 meters.
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Document History
Table -1: Revision History
May 15, 2008
Initial release
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Your Source for Modern Thermal Imaging Systems
P.O. BOX 4242
Middletown, NY 10941
PH: + 1 888 919 2263
PH Intl: + 1 845 343 4077
FX: + 1 845 343 4299
[email protected]
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