红外探测器光学元件表面疵病、污染可能会降低系统的探测性能。杜瓦中窗片、滤光片表面存在不同程度的麻点、划痕，采用光学仿真软件LightTools计算分析光学元件表面不同疵病等级情况下的光学参数，引入杂散辐射系数和信杂比的概念对杜瓦光学特性进行评估，合理判断光学元件的表面疵病容限。同时仿真分析滤光片位置造成的表面疵病对杜瓦光学特性的影响。结果表明：随着窗片、滤光片表面疵病等级增加，接收像面非均匀性增加、信号强度减弱，且在相同疵病等级情况下，滤光片与芯片距离越近，疵病对杜瓦光学特性影响越大，因此在杜瓦设计时必须严格控制光学元件表面疵病容限，并合理设置滤光片封装位置。

Surface defects and contamination of optical elements may reduce the infrared detector ability. There are different level of surface defects on the window and filter in dewar. Optical simulation software LightTools was used to calculate the optical parameter. Meanwhile, to evaluate the optical characteristics of the systems, the concepts of stray radiation coefficient and signal-to-clutter ratio were introduced, so the defect tolerance can be reasonably judged. Then, when the filter position changed, the effect of surface defects on Dewar was analyzed by simulation. The results show that with the level of surface defects increasing, the non-uniformity of the image increased and the signal strength decreased. And at the same grade of defects, the closer the filter is to the chip, the more defects affect the Dewar optical characteristics, as a result, when encapsulating Dewar, it is important to strictly control the surface defect tolerance and arrange the location of the filter reasonably.