针对光学系统在实际工作中元件表面污染粒子对光的散射问题, 以空气中Al2O3污染粒子为例, 基于米氏散射理论, 模拟和分析了元件表面双向反射分布函数(BRDF)随散射角的变化规律, 进而定量计算了元件表面全积分散射值(TIS)。在此基础上, 进一步分析了影响表面洁净度的三个主要因素(空气洁净度、工作面朝向和曝露时间)对元件表面BRDF及其TIS值的影响。结果表明, 空气洁净度等级、工作面放置方向和曝露时间等对元件表面散射量的影响均较为明显。其中, 工作面的放置方向对元件表面的散射影响尤为突出, 水平向上放置(TIS=1.93×10-4)较之垂直放置时(TIS=8.07×10-5)散射量增大一个量级, 而较之工作面水平向下放置时(TIS=3.12×10-6)增大两个量级。最后, 以卡塞格伦望远镜为例, 针对其主镜的污染容限问题, 分析了不同空气洁净度条件下主镜表面洁净度达到污染容限所用的曝露时间, 可为实际工作中污染控制和保证系统对微弱目标信号的有效探测提供参考。

Aimed at the light scattering problem from the particles on optical surfaces of the systems in practical applications, and taken Al2O3 particles in air as an example, the variations of the bidirectional reflection distribution function(BRDF) with the scattering angle on the surfaces of optical components were simulated and analyzed based on Mie scattering theory, and then the total integral scattering (TIS) value of the surface was calculated quantitatively. On this basis, the effect of the BRDF and the TIS value were further analyzed under the conditions of different air cleanliness levels, the direction of the optical component surface, the exposure time. The results indicate that, the air cleanliness levels, the direction of the optical component surface and the exposure time have effect on scattering of the optical surface, in which the direction of optical components has significant impact on the scattering of the surfaces. When the particles buildup on horizontal upward facing surfaces(TIS=3.93×10-3), the amount of scattering increases by an order of magnitude compared with that of the vertical ones(TIS=4.07×10-4), and increases by two orders of magnitude compared with that of the downward ones(TIS=5.22×10-5). Finally, based on the Cassegrain telescope, aimed at the tolerance of the particles on the primary mirror, the exposure time reaching the tolerance was carried out with different air cleanliness levels. The results can provide reference for particle control and reliability for effective detection of the weak signal in practice.