Forward looking infrared
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A forward looking infrared (FLIR) is the North American English term for a camera that takes pictures using the infrared portion of the electromagnetic spectrum. Elsewhere in the English speaking world, these are typically called Thermal imagers. Often these contain sub-systems known as Thermal imaging common modules or TICM. FLIRs are often described as "infrared cameras". Since FLIRs use detection of thermal energy to create the "picture" assembled for the video output, they can be used to help pilots and drivers steer their vehicles at night, and in fog, or detect warm objects against a cold background when it is completely dark (such as a cloudy, moonless night). Note that the wavelength of infrared that FLIRs detects differs significantly from that of night vision goggles, which operate in the visible light and near infrared ranges (0.4 to 1.0 micrometres).
There are two basic ranges of infrared; long-wave infrared and medium-wave infrared. The long-wave infrared (LWIR) cameras, sometimes called "far infrared", operate at 8 to 12 micrometre and can see heat such as engine exhaust or human body heat a few miles away, but longer distance viewing becomes blurred because the infra-red light is absorbed, scattered and refracted by the air.
Cameras which operate in the 3 to 5 micrometre range are called medium-wave infrared (MWIR) and can see almost as well, as those frequencies suffer from less absorbed by air, but generally require a much more expensive sensor array, and lower-temperature cooling.
Many FLIR systems use digital image processing to improve the image quality. FLIR sensor arrays often have inconsistent responses from pixel to pixel. To fix this, the response of each pixel is measured at the factory, and a transform, mostly linear, maps the measured brightness.
FLIRs are often used in naval vessels, fixed-wing aircraft, helicopters, and armored fighting vehicles. In warfare, they have three large advantages. First, the imager itself is difficult for the enemy to detect. Second, they see heat, which is hard to camouflage. Thirdly, FLIR systems can see through smoke, fog, haze, and other atmospheric obscurants better than a visible light camera can. However, it is hard to distinguish friend from foe when using the FLIR, which has led to friendly fire incidents.
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[edit] Uses of FLIR
- Surveillance of known or suspected criminals
- Watershed temperature monitoring and monitoring wild game habitats.
- Detection of energy loss or insulation defects in buildings in order to reduce heating/cooling cosume.
- Target acquisition and tracking by military aircraft.
[edit] Privacy
In 2001, the United States Supreme Court decided that by performing FLIR surveillance of private property without probable cause, law enforcement violates the Fourth Amendment's protection from unreasonable searches and seizures. United States v. Kyllo, 533 U.S. 27 (2001) [1]
