Absolute radiance measurement based on correlated photons calibration

An absolute radiance measurement based on correlated photons calibration is proposed in this paper. A prototype of radiometer is designed with two working modes: calibration and observing modes. The radiometer is used to measure the absolute radiance of an integrating sphere and compared with a reference standard radiometer traceable to cryogenic radiometer. Uncertainty factors in measurement are analyzed and the relative difference of the two measurement methods was about 1.5%. Taking advantage of principle of correlated photon calibration and a collinear optical path of two working modes, the radiometer is theoretically insensitive to degradation, which is proved in simulation experiments. By inserting optical attenuators to simulate the degradation of the system, the relative standard deviation of the radiance measurement values under different optical decay was 0.3%.