点源透过率测试系统精度标定与分析

点源透过率(PST)测试系统是评价光学系统杂光抑制水平高低的关键设备, 其系统精度的标定是研制难点, 针对此设计了一套用于点源透过率杂散光测试系统精度标定的校准镜头. 利用Tracepro建模分析了校准镜头在不同离轴角下的PST值, 并用此系统对校准镜头不同离轴角下的PST值进行了实测, 与其理论分析值进行比对完成设备精度的标定, 同时通过实测数据分析了测试误差, 给出了系统测试精度和测试极限水平. 结果表明, 在双柱罐内洁净度为ISO 7级的环境水平下, 系统的可见光PST测试极限水平为10^-8, 测试精度对数值优于0.5, 测量重复性为7.9%, 根据对探测系统探测能力的评估, 系统的PST极限测试水平为10^-10.

Analysis and calibration of precision for point source transmittance system

Owing to space optical system working for a long time outside the field of view, where there is strong background radiation, and the fact that the point source transmittance (PST) is an important evaluation indicator for stray light suppression of this optical system, the development of stray light equipment for testing PST has received more and more attention. Though the development of PST testing system has been extensively studied, none of them elaborate on the calibration of the PST testing system. Besides, most of the PST testing systems are at a laboratory research stage, and the calibration of neither testing stability nor accuracy is recognized. Therefore, on the basis of the PST testing system established, one calibration lens is designed to calibrate the PST testing system. By comparing the measured PST values of the calibration lens with the analyzed values, the PST testing system can be evaluated. The calibration lens model is built to analyze PST values at different off-axis angles by using the ray tracing software Tracepro. We consider the accuracy of modeling, and on the basis of simplifying the structure design, we measure bidirectional reflectance distribution function (BRDF) values of the painted surface of the calibration lens, and then estimate values of lens surface from Harvey-Shack model and PSD theory by taking these property data into the model of simulation. Ultimately PST analyzed values of calibration lens can be obtained. Finally, by comparing the measured values of calibration lens, which are tested by using PST testing system, with the analyzed values, the calibration of the PST testing system is completed. In the PST testing process of calibration lens, by analyzing the data at different off-axis angles, the accuracy of repeated measurements and threshold of PST testing system can be obtained. At the same time, testing errors caused by the stability of light source, detector linearity, air scattering and structure of double cylindrical chamber are analyzed through the testing data. The data show that when double cylindrical chamber clean class is ISO7, the PST threshold of this equipment is 10^-8, and the accuracy of repeated measurements is 7.9%. Taking into account the detection capability, the PST threshold of this equipment is 10^-10 when environmental condition is better than ISO6.