Analysis of Reference Sources for the Characterization and Calibration of Infrared Cameras

Abstract

This paper gives an analysis of the radiometric properties of different types of reference sources applied for the characterization and calibration of infrared cameras. For the absolute radiance measurement with an infrared camera, a metrological characterization and calibration of the instrument are essential. Similar to the calibration of radiation thermometers, this calibration is generally performed with reference sources of known radiance. As infrared cameras are optically and electronically more complex than radiation thermometers, which are equipped with a single element detector, the applied reference sources have to be carefully characterized and limitations in their performance have to be considered. Each pixel of the image measured with an infrared camera should depict correctly the desired physical quantity value of the projected object area. This should be achieved for all relevant conditions of observation, e.g., at different distances or at different incident angles. The performance of cavity radiators and plate radiators is analyzed based on ray-tracing calculations and spatially and angularly resolved radiance measurements with radiation thermometers and cameras. Relevant components of a calibration facility for infrared cameras at PTB are presented with their specifications. A first analysis of the relevant characteristics of the applied infrared calibration sources and infrared cameras is presented as the essential basic information for the realization of the calibration of infrared cameras.