红外成像系统冷反射的定量分析

Quantitative Analysis of the Narcissus of Infrared Imaging System

冷反射指红外系统中制冷型探测器能"看到"自身的反射像的现象。制冷型红外光学成像系统在进行设计时需要对冷反射进行严格控制,所以准确、迅速地进行冷反射分析就显得十分重要。利用噪声等效温差(NETD)的定义推导出冷反射信噪比公式;利用ASAP和Code V对冷反射进行仿真分析;用Code V选择出冷反射比较严重的光学面;将系统在ASAP中建模,并赋予系统模型合理的光学属性,通过光线追迹得到像面"冷斑"的大小和平均辐照度。把仿真结果带入冷反射信噪比公式中计算出各个表面以及系统总的冷反射信噪比大小。最后,以某红外单镜头为例,对其冷反射进行了仿真分析和成像实验,仿真结果与实验现象基本一致。

Narcissus refers to the case that cooled detector can ‘see＇ its own reflecting image, which must be controlled strictly in the process of optical design. So, it is very important to analyze the narcissus quickly and accurately. This paper derived the signal to noise ratio formula of narcissus from the definition of noise equivalent temperature difference. The narcissus was analyzed by simulation software Code V and ASAP and the optical surface whose narcissus was serious in Code V was screened out. Then reasonable surface properties of the system was modeled and added in ASAP. The size and the average irradiance of the ‘cold spot＇ were got by real ray tracing. Finally, the SNR of narcissus was calculated by putting the value of average irradiance into the previous formula. On this basis, the simulation analysis and experimental test about the narcissus of an infrared lens were performed and the experimental phenomenon is consistent with the result of simulation analysis.