Calibration and characterization of a COTS thermal camera for space

This paper describes a progressive process for calibration of a shutter less Commercial off the Shelf (COTS) thermal imaging camera for small scale remote sensing applications. Usually thermal imagers are equipped with shutters which provide a uniform temperature source to correct the accumulated offset errors in the digital read outs of such cameras. This paper aims at radiometric calibration and compensatory correction methods for improved imaging via shutter less cameras. The thermal camera considered in this paper, consists of an uncooled micro-bolometer with a focal plane array of 640 ∗ 512 pixels and field of view of 45 ∗ 37 degrees. The foremost approach for calibration involved the use of a water bath, with nominal temperature control, placed in the Field of View of the camera. Following this, a different approach for calibration using a blackbody and temperature control for the camera was used. Using the Planck's Law, a relation was obtained between the digital number output from the Read out Integrated Circuit (ROIC) of the camera and the radiance of the black body. This equation allowed digital pixel value to be related to the temperature of the object being captured. Gain and offset maps for the entire FPA were obtained using this data.