多谱段相机红外光学系统杂散辐射分析

Stray radiation analysis of infrared optical system in multispectral camera

杂散辐射是影响多谱段红外相机成像性能的主要因素。为了确保系统在各种工作状况下正常运行,需要分析并抑制相机光学系统中的杂散辐射。在详细分析了其红外光学系统中杂散辐射主要来源的基础上,针对系统特殊的光机结构,在杂光分析软件中建立光机系统模型;围绕遮光罩选取了8个太阳方位、16个离轴角进行光线追迹,得到太阳杂光在像面上产生的辐照度,据此来评价系统杂散辐射水平;同时分析了指向镜滚动轴和俯仰轴在两个方位内的转动以及地球大气杂散辐射对像面辐照度的影响。最后,对于影响严重的杂散辐射,进行了有效的抑制措施。结果表明,可以忽略地球大气的杂散辐射,当太阳杂光入射角大于58°时,系统能满足对像面辐照度的技术要求,多谱段相机红外光学系统可在此范围内正常工作。

The performance of the multispectral infrared camera is seriously influenced by the stray radiation. In order to ensure that the camera can work properly in all situations, the stray radiation in different working conditions needs to be analyzed. The main sources of the stray radiation in the infrared optical system of a camera were analyzed. The model of the multispectral infrared camera was established in the stray light analysis software. The irradiance of the imaging plane was used to evaluate the stray radiation level. Taking the influence of the solar azimuth and the off-axis angle into consideration, around the hood, 8 solar azimuths and 16 different off-axis angles were selected to carry out the ray tracing. Thus the irradiance of the imaging plane for every certain condition was obtained. And the effect to the irradiance of the imaging plane caused by the rotation of the pointing mirror which was composed of roller shaft and pitching axis was analyzed. Meanwhile the influence of the earth atmosphere stray radiation was also discussed. The results show that the earth atmosphere stray radiation is tolerable. And the system can basically satisfy the requirement to the imaging plane irradiance when the off-axis angle is greater than 58°. The infrared optical system of the multispectral camera can work well within this range.