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 pilots 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 μm and differs significantly from that of night vision, which operates in the visible light and near-infrared ranges (0.4 to 1.0  μm).

Design 

Infrared light falls into two basic ranges: long-wave and medium-wave. Long-wave infrared (LWIR) cameras, sometimes called "far-infrared", operate at 8 to 12 μm and can see heat sources, such as hot engine parts or human body heat, several kilometers away. Longer-distance viewing is made more difficult with LWIR because the infrared light is absorbed, scattered, and refracted by air and by water vapor.

Some long-wave cameras require their detector to be cryogenically 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.

Properties
Thermal imaging cameras such as the Raytheon AN/AAQ-26 are used in a variety of applications, including naval vessels, fixed-wing aircraft, helicopters, armored fighting vehicles, and military-grade smartphones.

In warfare, they have three distinct advantages over other imaging technologies:
 The imager itself is nearly impossible to detect for the enemy, as it detects energy emitted from the target rather than sending out energy that is reflected from the target, as with radar or sonar.
 It sees radiation in the infrared spectrum, which is difficult to camouflage.
 These camera systems can see through smoke, fog, haze, and other atmospheric obscurants better than a visible light camera can.

Etymology
The term "forward-looking" is used to distinguish fixed forward-looking thermal imaging systems from sideways-tracking infrared systems, also known as "push broom" imagers, and other thermal imaging systems such as gimbal-mounted imaging systems, handheld imaging systems and the like. Pushbroom systems typically have been used on aircraft and satellites.

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.

History
In 1956, Texas Instruments began research on infrared technology that led to several line scanner contracts and, with the addition of a second scan mirror, the invention of the first forward-looking infrared camera in 1963, with production beginning in 1966. In 1972, TI invented the Common Module concept, greatly reducing cost and allowing reuse of common components.

Uses

Traffic video detection and monitoring 
Surveillance and/or capture of mammals
e.g. Detection of illegal immigrants hidden in lorries/trucks
Warning drivers about sudden road obstructions caused by deer
Location through smoke and/or haze
Search and rescue operations for missing persons especially in wooded areas or water
Target acquisition and tracking by military or civil aircraft
Drainage basin temperature monitoring and monitoring wild game habitats
Detection of energy loss or consumption, or insulation defects
e.g. insulation level mapping (pipes, walls, joints etc.) in order to reduce HVAC energy consumption
Quality control for especially electrical installations (a picture can reveal if loads are higher than expected, or show bad and potentially failing joints)
Search for drug labs and/or indoor cannabis producers (especially at night)
Piloting of aircraft in low visibility (IMC) conditions
Pinpoint sources of ignition during firefighting operations
Monitoring active volcanoes
Detecting faulty or overheating electrical joints, connections and components
Night driving
Identification or visual acquirement of hostile armour in tanks

Cost 

The cost of thermal imaging equipment in general has fallen dramatically after inexpensive portable and fixed infrared detectors and systems based on microelectromechanical technology were designed and manufactured for commercial, industrial and military application. Also, older camera designs used rotating mirrors to scan the image to a small sensor. More modern cameras no longer use this method; the simplification helps reduce cost. Uncooled technology available in many EVS products have reduced the costs to fractions of the price of older cooled technology, with similar performance. EVS is rapidly becoming mainstream on many fixed wing and rotary wing operators from Cirrus and Cessna aircraft to large business jets.

Police actions 
In 2001, the United States Supreme Court decided in Kyllo v. United States that performing surveillance of private property (ostensibly to detect high emission grow lights used in clandestine cannabis farming) using thermal imaging cameras without a search warrant by law enforcement violates the Fourth Amendment's protection from unreasonable searches and seizures.

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 infrared sensors 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.

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. 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. The American Civil Liberties Union raised concerns over the fact that new surveillance technology is implemented without judicial guidance and public discussion. 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."

See also
 Automotive night vision
 Electro-optical targeting system
 Infra-red search and track

References

External links 

 Electro-Optical Systems
 Thermal Imaging Sensors (Defence Today)
 Comparison Chart 

Film and video technology
Infrared imaging
Military electronics
Night flying
Night vision devices
Targeting (warfare)
Texas Instruments
전방 감시 적외선 장치() 또는 적외선 전방 감시 장치는 적외선 복사를 감지하는 영상 기술이다. 전방의 적외선 화상을 비디오 카메라로 촬영하는 시스템으로 특정한 시스템의 명칭이 아니고, 이런 종류의 시스템에 대한 일반 명사이다. FLIR는 비디오 출력을 위해 조립되는 '사진'을 출력하기 위해 열 에너지 감지를 사용하기 때문에, 조종사나 운전사가 구름이 끼거나 달빛이 없는 야간과 같은 완전한 어둠일 때 추운 배경에서 따뜻한 목표물을 탐지하고, 야간 및 안개에서도 그들의 탈 것을 조종하는 것을 돕는데 사용될 수 있다. FLIR가 탐지하는 적외선의 파장 길이는 가시광선 및 근적외선 범위(0.4 ~ 1.0 µm)에서 작동하는 야시경과는 다르다.

설계 
적외선은 범위에 따라 기본적으로 장파장 적외선과 중파장 적외선의 두 가지로 나눌 수 있다. 때때로 "원적외선"이라고 불리는 장파장 적외선(LWIR) 카메라는 8 ~ 12 µm에서 작동하며 몇 마일 밖에 있는 뜨거운 엔진 부분이나 인간 체온의 열을 볼 수 있지만, 적외선 빛이 공기나 수증기에 의해 흡수되고, 산란하고, 굴절되기 때문에 중파장 적외선 카메라에 비해 장거리 시야 확보가 어려운 편이다. 몇몇 장파장 FLIR는 그들의 탐지기에 극저온의 냉각이 필요하지만, 적당히 민감한 FLIR는 극저온의 냉각이 필요하지 않은 것이 생산되고 있다.

3 ~ 5 µm 범위에서 작동하는 카메라는 중파장 적외선(MWIR)이라 불린다. 중파장 적외선 카메라는 수증기 흡수로부터 영향을 덜 받기 때문에 장파장 적외선 카메라와 다르게 장거리 시야 확보가 용이한 편이지만, 일반적으로 더욱 비싼 감지기 배열과 극저온 냉각이 필요하다.

많은 FLIR 시스템은 영상 품질을 향상시키기 위해 디지털 화상 처리를 사용한다. 제조 공정에서 제한 때문에, FLIR 센서 배열은 종종 픽셀로부터 픽셀로 거칠게 불일치하는 감광도를 가진다. 이것을 개선하기 위해, 각 픽셀의 반응이 공장에서 측정되고, 대부분 선형인 변형물은 측정된 입력 신호를 출력 수준으로 측량한다.

특징 
AN/AAQ-26과 같은 FLIR는 종종 해군 함정, 고정익 항공기, 헬기 그리고 장갑 전투 차량에 사용된다. 전시에, 그것은 세 가지 큰 이점이 있다. 첫째, FLIR가 탐지하는 에너지는 이미 거기 있는 것이고, FLIR는 자신의 어떠한 에너지도 방출할 필요가 없기 때문에 영상 장치 그 자체는 적에게 발견이 거의 불가능하다. 둘째, FLIR는 위장하기 어려운 열을 감지한다. 셋째, FLIR 시스템은 연기, 안개, 연무 그리고 다른 대기 중의 방해물을 통과하여 가시광선 카메라가 볼 수 있는 것보다 더 많은 것을 볼 수 있다. 그러나 FLIR를 사용하면 적군과 아군을 구별하기 어렵기 때문에, 아군에 오인 발포하는 사건이 발생할 수도 있다.

FLIR 용어의 어원 
"전방 감시"라는 용어는 "푸시 브룸" 영상 장치로 알려진 측면 추적 적외선 시스템으로부터 FLIR 시스템을 구별하기 위해 사용된다. 그러한 시스템은 일반적으로 항공기나 위성에 사용된다. 그것들은 보통 2D 영상을 생성하기 위해 지상을 가로질러 1D 배열 전망을 움직이는 항공기나 위성의 움직임을 이용하는 픽셀의 1차원(1D) 배열을 포함한다. 그러한 시스템은 실시간 영상에는 사용할 수 없고, 비행 방향에 수직으로 봐야 한다. 어느 정도까지 측면 추적 적외선 시스템은 "전방 감시" 영상 시스템의 발달로 쓸모없게 되었다.

FLIR의 용도 
 적군 등 표적 탐지 
 유역 온도와 야생의 사냥감 서식지 감시
 HVAC 에너지 소비 감소를 위해 건물내 단열 결함 또는 에너지 손실 감지
 군용 항공기의 목표물 포착 및 추적
 저시정低視程(계기비행) 상황에서 항공기 조종
 도로에서 사슴이나 다른 동물들을 운전자에게 경고
 소방 작전중 점화의 원인을 찾아내고 생존자(연기와 벽을 통과해) 위치 찾기
 특히 숲이 우거진 지역이나 수중에서 행방불명된 사람을 탐색 구조하는 작전
 천연 가스나 다른 가스 누출 탐지
 활화산 감시
 결함이 있는 전기 접속의 열 감지
 FLIR를 갖춘 항공기는 악천후 상황에서 작전 수행 가능

가격 
FLIR 장비의 가격은 극적으로 떨어졌다. 구식 카메라 설계는 작은 센서로 영상을 스캔하기 위해 회전 반사경을 사용한다. 현대 카메라는 더이상 이 방법을 사용하지 않는다. 이러한 단순화는 가격을 낮추는데 도움이 되었다.

사생활 
2001년 미국 대법원은 법 집행자가 수색 영장 없이 사유 재산의 FLIR 감시를 수행하는 것은 부당한 수색과 압류로부터 사생활을 보호하는 수정헌법 제4조를 위반하는 것이라고 결정했다.

같이 보기 
 적외선 탐색추적
 야시경(Night vision)
 적외선 카메라
 감시
 TOD(Thermal Observation Device)

외부 링크 

 Flir Systems
 Fluke Thermal Imagers
 Electro-Optical Systems
 Thermal Imaging Sensors (Defence Today)
 Thermal Imaging Equipment
 A wide variety of FLIR applications
 OPGAL Optronics Industries (cooled and uncooled OEM cameras)

영상 기술
적외선 영상
군사 장비