Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

The IR Detectors
Infrared detectors fall into two broad categories:
■
■
thermal detectors, which have broad, uniform spectral responses,
somewhat lower sensitivities, and slower response times (on the order of
milliseconds), and
photodetectors, (or photon detectors), which have limited spectral
responses, higher peak sensitivities, and faster response times (on the
order of microseconds).
Thermal detectors will generally operate at or near room temperature, while
photodetectors are generally cooled to optimize performance. The mercury-
Cadmium-telluride (HgCdTe) detector, for example, is a photodetector cooled
to 77 K for 8.14 µm operation and to 195 K for 3.5 µm operation. Because of
its fast response, this detector is used extensively in high-speed scanning
and imaging applications.
Charlie Chong/ Fion Zhang