Thermal Imaging or Thermography, is a type of infrared imaging. Thermal imaging camera sensors detect heat in the infrared range of the electromagnetic spectrum (roughly 900–14,000 nanometers or 0.9–14 µm) and produce color or black and white images from heat signatures.
Thermal imaging infrared imagers convert energy in the infrared wavelength into a visible light video display. All objects above 0° Kelvin emit thermal infrared energy so thermal imagers can passively see all objects regardless of ambient light.
Since infrared radiation is emitted by all objects based on their temperatures, thermal imaging cameras make it possible to "see" one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature, therefore thermography allows one to see variations in temperature (hence the name).
When viewed by a thermal imaging camera, warm objects stand out well against cooler backgrounds; humans and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography's extensive use can historically be ascribed to the military and security services.
Thermal imaging has many uses. For example, firefighters use it to see through smoke, find people, and localize the base of a fire. With thermal imaging, power lines maintenance technicians locate overheating joints and parts, a telltale sign of their failure to eliminate potential hazards.
Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning.
Thermal imaging cameras are also installed in some luxury cars to aid the driver, the first being the 2000 Cadillac DeVille. Some physiological activities, particularly responses, in human beings and other warm-blooded animals can also be monitored with thermo graphic imaging. The appearance and operation of a modern thermo graphic camera is often similar to a camcorder. Enabling the user to see in the infrared spectrum is a function so useful that ability to record their output is often optional. A recording module is therefore not always built-in.
Instead of CCD sensors, most thermal imaging cameras use the newest technologies such as low cost and un cooled microbolometers. Their resolution is considerably lower than of optical cameras, mostly 160x120 or 320x240 pixels, up to 640x480 for the most expensive models.
Thermo graphic cameras are much more expensive than their visible-spectrum counterparts, and higher-end models are often export-restricted. Older bolometers or more sensitive models as InSB require cryogenic cooling, usually by a miniature Stirling cycle refrigerator or liquid nitrogen.