Design of Infrared Thermal Imager Calibration System

Aiming at the calibration problem of infrared thermal imager, a calibration system of infrared thermal imager is designed. The system is mainly composed of dual black body collimated light tube radiation source, low temperature black body radiation source, medium temperature black body radiation source, high temperature black body radiation source, standard thermocouple, standard platinum resistance, optical platform, two-dimensional turntable, precision electric translation, integrated control system for data acquisition, analysis and processing(include software), and installation accessories. The calibration of infrared thermal imager includes the calibration of temperature parameters and imaging characteristic parameters. Temperature parameters are calibrated by direct measurement. Imaging characteristic parameter calibration adopts measurement of the infrared radiation signal output from the radiation source of the dual-black-body collimating light tube. By analyzing the infrared image, the signal transfer function (SITF), noise equivalent temperature difference (NETD), distortion (DIST) and minimum distinguisable temperature difference (MRTD) of the infrared thermal imager are calculated. The integrated control system of data acquisition, analysis and processing and the design of system software are introduced in detail. The automatic calibration of infrared thermal imager is realized through the hardware composed of software control system. The calibration uncertainty of temperature indication error and the measurement uncertainty of NETD are analyzed, and the system performance is evaluated. The system was used to test the temperature parameters of Fluke Ti25 infrared thermal imager and the imaging characteristic parameters of a certain type of infrared thermal imager of a certain company. The test results show that the system can be used to calibrate the temperature indication error of infrared thermal imager when the temperature range is (−20 ∼ 1600) °C and the measurement uncertainty is 0.4% ($k=2$), and to calibrate the imaging characteristic parameters. The establishment method and testing technology of the system can provide reference for the establishment of measurement standard of infrared thermal imager.