An IR camera is an infrared device that creates images from infrared radiation. Also known as a thermographic camera, an IR camera uses wavelengths longer than visible light to create images even in total darkness. The two main types of cameras are cooled infrared detectors and uncooled infrared detectors.
The basic operation of an IR camera works by detecting the amount of radiation being emitted from an object based on its temperature. The hotter the object, the more radiation it emits and the more intense the image color will be. The standard IR camera shows image intensity based on the color spectrum. The hottest part of the image will reflect white, then less warm parts will reflect red and yellow. The cool parts will be the least intense or clear and will reflect as blue.
Cooled infrared detectors use cooling to produce the image. Instead of collecting radiation and converting it to an image on its own, a cooled infrared detector employs a cooling technique known as the Joule-Thomson effect. By cooling the device with cryogenics, the radiation detected in an object can be singled out to produce a much clearer image than a traditional IR camera. Special training and certification is required, and there are three levels of certification based on the amount of training and experience the applicant has.
The Joule-Thomson effect works by changing the temperature of a gas by forcing it through a valve. When done in a vacuum-sealed environment such as an IR camera, the semiconductor components are able to cool down, which allows the device to convert the radiation into a sharper image. Without the cooling effect, the image would be much fuzzier because too much radiation would be absorbed from the object when the image is being converted. Due to the expense of cooled infrared detectors, they are typically only used for military, fire fighting, and aerial applications. Law enforcement also uses this type of IR camera for night vision and anti-terrorism activities.
The other type of IR camera is an uncooled infrared detector. This type does not require cooling and simply functions at the ambient temperature. An uncooled infrared detector works by sensing the heat emitted from an object and converting it to an image using voltage or current changes. A less costly alternative to the cooled infrared detectors, an uncooled infrared detector is most often used auditing energy efficiency in buildings, detecting leaks in refrigeration systems, and mold remediation analysis.