In this video Shahriar dives into the amazing science & engineering of cryogenically cooled thermal cameras. This particular model, Inframetrics 760 Imaging Radiometer, was manufactured in the 1990's and leverages a range of clever engineering techniques. It includes a miniaturized Stirling engine cryocooler, galvanometer based mirrors for 2D field scanning as well as a low-noise Mercury-Cadmium-Tellurite (HgCdTe) MCT detector sensitive in the 4-15um wavelength.
Teardown of the unit along with a detailed theory of operation is presented. The semiconductor profile and properties of MCT detectors are also discussed. Furthermore, a different thermal camera using a Joule-Thomson cryocooler and high-pressure (3000 PSI) Argon source is also shown.
After reverse engineering the critical detector interfaces, an experiment is devised to measure the thermal signature of a resistor. The setup includes a triangle wave driving a resistor to generate a time varying thermal source, Lakeshore M81 source-measure lock-in amplifier and chopper in front of the MCT detector and BLDC motor driver for running the cryocooler. The measurement demonstrates the functionality & sensitivity of the detector to capture black body radiation.
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