Each Optotherm thermal imaging camera contains an infrared detector called a microbolometer. A microbolometer is an array of tiny heat detecting sensors that are sensitive to infrared radiation from approximately 7 to 14µm in wavelength. Each array element is approximately 17 x 17µm in dimension.

As infrared energy strikes an individual bolometer element, the element increases in temperature, and its electrical resistance changes. This resistance change is measured and then processed into temperature values which can be represented graphically in a thermal image.

A microbolometer is an uncooled infrared sensor; the detector array does not need to be cooled in order to produce highly sensitive thermal images. Photon detectors, such as InSb (Indium Antimonide) and MCT (Mercury Cadmium Telluride) infrared detectors, can improve thermal sensitivity but require the detector to be cooled to cryogenic temperatures utilizing cooling methods such as Stirling cycle engines and liquid nitrogen. The use of photon detectors increase the cost of infrared cameras, decrease ease-of-use, and lead to more frequent and expensive maintenance.