A two-step calibration method for measuring the optical transmittance of a cooled infrared imager

Abstract

Optical transmittance is a critical index that determines an infrared imaging system's detection capability, stray light suppression performance, and radiometry accuracy. This paper presents a novel two-step calibration method, consisting of optical system radiometric calibration and detector calibration techniques, for measuring the optical transmittance of cooled infrared imaging systems. The advantage of this method is that it allows transmittance measurements of infrared lenses to be realized under normal operating conditions rather than only in the laboratory, as previously, thus facilitating the performance evaluation of infrared optical systems and the investigation of stray radiation properties. Experimental results show that the proposed method yields high measurement accuracy and is almost independent of the ambient temperature.