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Forward-looking infrared ( FLIR) cameras, typically used on military and civilian aircraft, use a thermographic camera that senses infrared radiation.
The sensors installed in forward-looking infrared cameras, as well as those of other thermal imaging cameras, use detection of infrared radiation, typically emitted from a heat source (thermal radiation), to create an image assembled for video output.
They can be used to help Aviator and drivers steer their vehicles at night and in fog, or to detect warm objects against a cooler background. The wavelength of infrared that thermal imaging cameras detect is 3 to 12 micrometre and differs significantly from that of night vision, which operates in the visible light and near-infrared ranges (0.4 to 1.0 μm).
Some long-wave cameras require their detector to be cryogenics cooled, typically for several minutes before use, although some moderately sensitive infrared cameras do not require this. Many thermal imagers, including some forward-looking infrared cameras (such as some LWIR enhanced vision systems (EVS)) are also uncooled.
Medium-wave (MWIR) cameras operate in the 3–5 μm range. These can see almost as well, since those frequencies are less affected by water-vapor absorption, but generally require a more expensive sensor array, along with cryogenic cooling.
Many camera systems use digital image processing to improve the image quality. Infrared imaging sensor arrays often have wildly inconsistent sensitivities from pixel to pixel, due to limitations in the manufacturing process. To remedy this, the response of each pixel is measured at the factory, and a transform, most often linear, maps the measured input signal to an output level.
Some companies offer advanced "fusion" technologies that blend a visible-spectrum image with an infrared-spectrum image to produce better results than a single-spectrum image alone.
In warfare, they have three distinct advantages over other imaging technologies:
Sideways-tracking imagers normally involve a one-dimensional (1D) array of pixels, which uses the motion of the aircraft or satellite to move the view of the 1D array across the ground to build up a 2D image over time. Such systems cannot be used for real-time imaging and must look perpendicular to the direction of travel.
Willardson, R. K., Weber, E. R., Skatrud, D. D., & Kruse, P. W. (1997). [https://books.google.com/books?id=5zXS_By-nQ8C&dq=advances+uncooled+infrared&pg=PP2 Uncooled infrared imaging arrays and systems (Vol. 47).] Academic press.
[http://www.sofradir-ec.com/wp-uncooled-detectors-achieve.asp White Paper: Uncooled Infrared Detectors Achieve New Performance Levels and Cost Targets],
Sofradir EC, Inc.
EVS is rapidly becoming mainstream on many fixed wing and rotary wing operators from Cirrus Aircraft and Cessna aircraft to large business jets.
In the 2004 R. v. Tessling judgment, the Supreme Court of Canada determined that the use of airborne FLIR in surveillance by police was permitted without requiring a search warrant. The Court determined that the general nature of the data gathered by FLIR did not reveal personal information of the occupants and therefore was not in violation of Tessling's Section 8 rights afforded under the Charter of Rights and Freedoms (1982). Ian Binnie distinguished the Canadian law with respect to the Kyllo judgment, by agreeing with the Kyllo minority that public officials should not have to avert their senses or their equipment from detecting emissions in the public domain such as excessive heat, traces of smoke, suspicious odors, odorless gases, airborne particulates, or radioactive emissions, any of which could identify hazards to the community.
In June 2014, the Canadian National Aerial Surveillance Program DHC-8M-100 aircraft mounted with was instrumental in the search for Justin Bourque, a fugitive who had killed three Royal Canadian Mounted Police members in Moncton. The plane's crew used its advanced heat-sensing camera to discover Bourque's heat signature in the deep brushwoods at midnight. ctvnews.ca: "Funeral for 3 fallen RCMP officers to be held Tuesday in Moncton" 7 Jun 2014
During 2015 Baltimore protests, the FBI conducted 10 aerial surveillance missions between April 29 and May 3, which included "infrared and day color, full-motion FLIR video evidence" collection, according to FBI spokesman Christopher Allen. FBI spy planes used thermal imaging tech in flights over Baltimore after Freddie Gray unrest, The Washington Post, October 30, 2015 A FLIR Talon multi-sensor camera system equipped with an infrared laser pointer (which is invisible to casual observers) for illumination purposes was used to gather data at night. Talon High Performance Multi-Sensor The American Civil Liberties Union raised concerns over the fact that new surveillance technology is implemented without judicial guidance and public discussion. FBI Documents Reveal New Information on Baltimore Surveillance Flights, ACLU, October 30, 2015 According to Nathan Wessler, an ACLU attorney, "this is a dynamic we see again and again when it comes to advances in surveillance. By the time details leak out, programs are firmly entrenched, and it's all but impossible to roll them back – and very hard to put in place restrictions and oversight."
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