Calibration issues affecting the operation of infrared microscopes over large temperature ranges

Thermal imaging systems that are used in quantitative applications such as pyrometry or pulsed thermography must be calibrated to provide accurate and repeatable measurements. Several approaches are possible ranging from simple linear calibration to the characterization of detector response using polynomial relationships. This paper describes the application of these calibration techniques to a thermal imaging microscope that must operate over a broad, rapidly changing temperature range while remaining sensitive to small variations in surface temperature. Such an application requires the ability to change the infrared camera exposure and associated calibration parameters quickly. It also requires a method to compensate for variations in background thermal radiance due to the optical configuration of a thermal imaging microscope.