Stray light separation based on the changeable veiling glare index for the vacuum radiance temperature standard facility

The vacuum radiance temperature standard facility (VRTSF) is used to determine the temperature traceability of calibration blackbodies accurately for infrared remote sensing. However, the internal surfaces of the VRTSF can emit thermal radiation, which introduces stray light and reduces measurement accuracy. Previously, background subtraction was used to eliminate stray light, without considering dynamic changes in the environment. Therefore, we propose a changeable veiling glare index (CVGI) to evaluate stray light performance based on the concept of the veiling glare index. We analyze the radiation model of the VRTSF system and simulate the attribution of stray light. CVGI can be improved considerably by cooling and by using suitable stop sizes. Experiments performed in the VRTSF show that the CVGI is suitable for analyzing stray light. Using the CVGI, we simulate a method that can significantly reduce stray light in the VRTSF.