Forward looking infrared
Encyclopedia
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
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
source, to create the "picture" assembled for the video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
output, they can be used to help pilot
Aviator
An aviator is a person who flies an aircraft. The first recorded use of the term was in 1887, as a variation of 'aviation', from the Latin avis , coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne...
s and drivers steer their vehicles at night, and in fog, or detect warm objects against a cooler background. The wavelength of infrared that thermal imaging cameras detect differs significantly from that of night vision
Night vision
Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range...
, which operates in the visible light and near infrared ranges (0.4 to 1.0 μm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
).
Design
There are two basic ranges of infraredInfrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
; long-wave infrared and medium-wave infrared. The 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
Body heat
Body Heat is a 1981 film by Lawrence Kasdan.Body Heat may also refer to:*Body heat or thermoregulation, the ability of an organism to keep its body temperature within certain boundaries*Body Heat...
, a few miles away, but longer-distance viewing is made more difficult because the infrared light is absorbed, scattered
Scattering
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of...
, and refracted
Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...
by the air and water vapor. Some long-wave cameras require their detector to be cryogenically
Cryogenics
In physics, cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures. A person who studies elements under extremely cold temperature is called a cryogenicist. Rather than the relative temperature scales of Celsius and Fahrenheit,...
cooled, typically for several minutes before use, although moderately sensitive infrared cameras are produced that do not require cryogenic cooling. Many thermal imagers including some forward looking infrared cameras are uncooled such as some LWIR Enhanced Vision Systems (EVS).
Cameras which operate in the 3 to 5 μm range are called medium-wave infrared (MWIR) and can see almost as well, as those frequencies suffer less from water-vapor absorption, but generally require a more expensive sensor array and cryogenic cooling.
Many camera systems use digital image processing
Digital image processing
Digital image processing is the use of computer algorithms to perform image processing on digital images. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing...
to improve the image quality. infrared imaging sensor arrays often have wildly inconsistent sensitivities from pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
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 AN/AAQ-26AN/AAQ-26
The AN/AAQ-26 is a second generation infrared detection set manufactured by Raytheon. The infrared detecting set is a high-performance multipurpose thermal imaging sensor, providing long-range navigation, surveillance, and fire control capabilities....
, are often used in a variety of applications, including naval vessels, fixed-wing aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
, helicopter
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
s, and armored fighting vehicles. In warfare, they have three large advantages. First, the imager itself is nearly impossible for the enemy to detect, as it detects energy that's already there and doesn't have to send out any energy of its own. Second, it sees heat, which is hard to camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
. Third, these camera systems can see through smoke, fog, haze, and other atmospheric obscurants better than a visible light camera can.
Origin of the term
The term "forward looking" is used to distinguish fixed forward looking thermal imaging systems from sideways tracking infrared systems, also known as "push broomPush broom scanner
A Push broom scanner is a technology for obtaining satellite images with optical cameras. It is used for passive remote sensing from space. In a push broom sensor, a line of sensors arranged perpendicular to the flight direction of the spacecraft is used. Different areas of the surface are imaged...
" 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. They 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 of the forward looking infrared systems
In 1956 Texas InstrumentsTexas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
began research on infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
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
- SurveillanceSurveillanceSurveillance is the monitoring of the behavior, activities, or other changing information, usually of people. It is sometimes done in a surreptitious manner...
of living things (e.g. people or other animals) - WatershedDrainage basinA drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
temperature monitoring and monitoring wild game habitats - Detection of energy loss or insulationThermal insulationThermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...
defects in buildings in order to reduce HVACHVACHVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...
energy consumption - Target acquisition and tracking by military aircraftAircraftAn aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
- Piloting of aircraft in low visibility (IFR) conditions
- Warning drivers about sudden road obstructions caused by animals (e.g. deer)
- Locating living beings (through smoke) and pinpointing sources of ignition during firefighting operations
- Search and rescueSearch and rescueSearch and rescue is the search for and provision of aid to people who are in distress or imminent danger.The general field of search and rescue includes many specialty sub-fields, mostly based upon terrain considerations...
operations for missing persons especially in wooded areas or water. - Detecting leaks of natural gas and other gasses.
- Monitoring active volcanoes.
- Detecting heat in faulty electrical joints.
- Searching for drug-labs at night.
Cost
The cost of thermal imaging equipment in general has fallen dramatically. 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 of older cooled technology to fractions of the price with similar performance measures. EVS is rapidly becoming mainstream on many fixed wing and rotary wing operators from Cirrus and Cessna aircraft to large business jets.Privacy
In 2001, the United States Supreme Court decided that performing surveillance of private property (ostensibly to detect high emission grow lightGrow light
A grow light or plant light is an artificial light source, generally an electric light, designed to stimulate plant growth by emitting an electromagnetic spectrum appropriate for photosynthesis. Grow lights are used in applications where there is either no naturally occurring light, or where...
s used in clandestine marijuana farming) using thermal imaging cameras without a search warrant
Search warrant
A search warrant is a court order issued by a Magistrate, judge or Supreme Court Official that authorizes law enforcement officers to conduct a search of a person or location for evidence of a crime and to confiscate evidence if it is found....
by law enforcement violates the Fourth Amendment's
Fourth Amendment to the United States Constitution
The Fourth Amendment to the United States Constitution is the part of the Bill of Rights which guards against unreasonable searches and seizures, along with requiring any warrant to be judicially sanctioned and supported by probable cause...
protection from unreasonable searches and seizures. Kyllo v. United States
Kyllo v. United States
Kyllo v. United States, , held that the use of a thermal imaging device from a public vantage point to monitor the radiation of heat from a person's home was a "search" within the meaning of the Fourth Amendment, and thus required a warrant...
, 533 U.S. 27, 121 S.Ct. 2038, 150 L.Ed.2d 94 (2001).
In R v. Tessling Canada's Supreme court determined that the use of thermal imagers in surveillance by police was permitted without requiring a search warrant. The Court determined that the general nature of the data gathered by thermal imagers 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).
See also
- Infra-red search and trackInfra-red search and trackAn infra-red search and track system is a method for detecting and tracking objects which give off infra-red radiation such as jet aircraft and helicopters. IRST is a generalized case of Forward Looking Infra-Red , i.e. from Forward-Looking to allround situational awareness...
- Night visionNight visionNight vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range...
- Infrared camera
- SurveillanceSurveillanceSurveillance is the monitoring of the behavior, activities, or other changing information, usually of people. It is sometimes done in a surreptitious manner...