长波红外差分干涉仪光栅低温安装结构设计与优化

Design and optimization of cryogenic installation structure for gratings of Long-wave Infrared Spatial Heterodyne Interferometer

长波红外差分干涉仪在低温工况下会因光学元件受到非均匀应力作用产生干涉条纹的畸变,从而降低干涉仪系统性能。本文为解决低温工况干涉条纹弯曲畸变问题,基于长波红外差分干涉仪光机系统进行了干涉条纹畸变影响因素分析,结合光-机-热耦合分析方法,对干涉仪系统低温工作状态进行仿真。随后设计了针对影响条纹畸变的关键元件——光栅元件的低温微应力动态稳定支撑安装结构,结构优化后的光栅表面面形均方根(Root Mean Square,RMS)值为3.89×10^(-2) nm,面形峰谷值(Peak to Valley,PV)值为2.21×10^(-1) nm,分别较优化前初始系统的分析结果减小了5个数量级,系统仿真干涉条纹畸变小于1个探测器像元。全系统低温验证试验表明,优化结构可有效抑制干涉条纹畸变,畸变量小于2个探测器像元,试验与仿真计算结果一致性较好,验证了优化分析方法的有效性。该优化方案对提升反射式光学系统结构低温稳定性,提高系统工作能力有较大意义和价值。

The Long-wave Infrared Spatial Heterodyne Interferometer may have interference fringe distortion due to non-uniform stress acting on the optical components under cryogenic conditions,which will cause performance degradation of the interferometer system.To solve the problem of interference fringe distortion under cryogenic conditions,this paper analyzed the factors affecting interference fringe distortion based on the initial optical mechanical system of Long-wave infrared spatial heterodyne interferometer,and combined the optical-mechanical-thermal coupling analysis method to simulate the cryogenic state of the interferometer system.Then,a cryogenic micro-stress dynamic stable installation structure was designed for grating,which is the key component affecting fringe distortion.After the optimization of structure,the Root-Mean-Square(RMS)and Peak-to-Valley(PV)values of grating’s surface shape are 3.89×10^(-2) nm and 2.21×10^(-1) nm,respectively,which are five orders of magnitude lower than the initial structure analysis results.The simulated interference fringe distortion is less than 1 detector pixel.The cryogenic verification test of whole system shows that the optimized structure can effectively reduce the distortion of interference fringe,and the distortion is less than 2 detector pixels.The experimental results are highly consistent with the simulation results,which verifies the effectiveness of the optimization analysis method.The optimization analysis method has great significance and value for improving the structural stability and operating performance of the cryogenic reflective optical system.