Research On Stray Light Of The Infrared Detection System

The suppression of stray radiation is one of the key issues in the spacecraft forweak signal detection. Stray radiation makes the contrast of images decreased, colordistorted, even the target signal overwhelmed by the stray light noise.This dissevt researched the methods of the origin, transmission, evaluation andmodification of stray radiation. The PSF model of the optical systems composed ofthe stray radiation effect was established, and by taking advantage of the expressionof stray radiation PSF, the stray radiation effect can be corrected.The detection system which is on the satellite of500km earth orbit wasanalyzed for stray radiation in this dissevt, and base on the analysis, the suppressionmeasures were taken. Firstly, by evaluation, the illuminance of the target signal onthe focal plane is10-5W/m2, while the solar radiation on the entrance pupil plane is10W/m2. Base on the relationship of the illuminance, point source transmission(PST) and effective emissivity were put into use, because of PST can present thesuppression ability of the system for external stray radiation while the effectiveemissivity can present the suppression ability of the system for internal strayradiation. Secondly, the baffles of the system were built up, then the analysis modelsincluding the scatter models and the emissive models were built up. Thirdly, the PSTand effective emissivity of the detection system were evaluated by using the opticalcalculation software Tracepro, the results indicate that the PST is near10-11whenthe incidence angles are up30degree and the effective emissivity is0.0387whenthe mechanical structure surfaces were coated by black paint Martin Black, and thetemperature is293K. The effective emissivity of the system is designed around0.02to0.03, so the internal radiations need to be suppressed further. Finally, the internalradiations were suppressed by the methods of optimizing the coating, controlling thetemperature and cleaning the mirror. After suppression, the effective emissivity is0.0243.