Forward Looking Infrared (FLIR)

The term “forward-looking” was historically used to distinguish fixed forward-looking thermal imaging systems from other types, such as sideways-tracking infrared systems. Line scanner systems, commonly used on aircraft and satellites, consist of a one-dimensional array of pixels that utilize the motion of the aircraft or satellite to sweep the array’s view across the ground, gradually forming a two-dimensional image. These systems do not provide real-time imaging and can only look perpendicular to the direction of travel. In contrast, FLIR systems offer real-time imaging capabilities.

FLIR cameras usually contain uncooled two-dimensional imaging detectors that produce radiometric thermal images within the infrared wavelength range. Unlike conventional visible light cameras, thermal cameras operate in the infrared spectrum, capturing images based on the thermal radiation emitted by objects. The uncooled bolometer technology used in FLIR cameras enhances reliability, cost-efficiency, and robustness compared to traditional line scanner applications, which rely on mechanical moving mirrors.

All objects above absolute zero emit thermal radiation. An optical lens system focuses these thermal variations onto a detector array in a FLIR system. Each pixel in the array corresponds to a specific area in the scene and measures the intensity of infrared radiation at that location. Depending on the infrared wavelength spectrum, sensor detectors can be based on various technologies, such as bolometers or infrared photodetectors.

When infrared radiation from objects in the camera’s field of view reaches the detector, its electrical properties change. These changes are converted into electronic signals, amplified, digitized, and processed by the camera’s electronics. Uncooled infrared cameras use a shutter mechanism that periodically corrects for offset and non-uniformity to ensure accurate intensity measurements. The camera software then translates the captured signals into temperature values, enabling non-contact temperature measurements, temperature analysis, and alarm triggering.