基于米氏散射理论, 建立了光学元件基板不同疵病等级光学元件的散射模型, 进而定量分析了元件表面存在粒子污染时的基板缺陷复制引起的表面散射特性。在此基础上, 以R-C光学系统为例, 利用ASAP(Advanced System Analysis Program)光学分析软件, 针对主镜表面存在粒子污染的情况, 仿真计算和分析系统主镜基板不同疵病等级的杂散辐射特性, 并根据信噪比的计算方法, 对系统信噪比进行了计算和分析。结果表明: 当天空背景辐射温度不变时, 随着主镜基板疵病等级的增加, 系统信噪比明显减小。当主镜基板疵病等级不变时, 随着天空背景辐射温度的升高, 主镜基板不同疵病等级对信噪比的影响逐渐减小。当天空背景温度为200 K时, 对于主镜表面粒子污染为300等级(粒子表面覆盖率为0.03%), 且其基板疵病等级分别为I-10、I-20、I-30、II和III五种情况, 计算得到系统相对信噪比(相对于理想主镜)分别为0.932、0.920、0.906、0.832和0.807。由此可见, 当元件光学特性变差时, 为保证微弱信号的有效探测, 必须将疵病等级严格控制在II级以内。

A scattering model of the optical component substrate under different levels of defects has been established based on Mie scattering theory, and then the scattering characteristics of the replication of substrate defect have been analyzed quantitatively when the particle contamination exists on the surface of the optical component. On this basis, a R-C optical system has been taken as an example, and stray radiation characteristics of the system have been simulated and analyzed by using the ASAP optical analysis software for the case of the primary mirror substrate under different levels of defects. Furthermore, according to the calculation method of the signal to noise ratio(SNR), the SNR of the system has also been carried out and analyzed. The results indicate that the SNR of the system decreases with the increasing of the defect levels of primary mirror substrate for a given radiant temperature of the sky background, and the influence of the SNR decreases with the increasing of the radiant temperature of the sky background for a fixed defect level of primary mirror substrate. Finally, for the primary mirror particle contamination of 300 grades (the particle surface coverage is 0.03%) and its substrate defect levels under five cases such as I-10, I-20, I-30, II and III, the relative SNR(relative to the ideal primary mirror) of the system are 0.932, 0.920, 0.906, 0.832 and 0.807, respectively when the radiant temperature of the sky background is 200 K. Thus, when the optical properties of components become worse, the levels of optical component defects should be strictly controlled within II level to ensure the effective detection of the weak signal with low SNR.