ABSTRACT
With any complicated combination of microscopic analog devices, mechanical mechanisms, and compensatory digital software, a great deal can go wrong, and thermal imagers are no exception. When should an imager be returned for factory recalibration? Thermal imagers measure microbolometer leaflet resistance, not temperature; they must be recalibrated at the factory using a series of known blackbody temperatures and sensing the resultant resistance values – an expensive procedure. This chapter discusses in detail how to check the thermal offset, gain, and image “flatness” of an imager using inexpensive equipment and techniques that can be done in a thermography clinic. The use of thermopile non-contact thermometers (NCTs) and contact-type thermometers makes these verification steps possible. Even a black-painted bucket of hot water can be useful for imager calibration. Laboratory blackbody calibrators are also discussed for verifying imager calibration across the physiologic range, and plans for making a room-temperature blackbody are included. Calibration of the calibration devices is also discussed, using fixed physical principles as calibration standards.
