空间相机温度-离焦特性分析与试验

Study and test of thermal-defocusing property in space camera

为了提高空间相机在不同温度条件下的成像质量,本文建立了空间相机光-机-热集成分析模型,以此模型为基础,对系统的温度-离焦特性进行研究,得到了相机温度调焦曲线,并开展了热光学试验。首先,分析了温度变化对光学系统的影响,特别是对最佳像面位置的影响,得到了相机离焦量与光学元件参数的关系;介绍了光机热集成分析的一般方法,即将热分析的温度场,经过映射,作为结构分析的边界条件,然后进行结构有限元的热弹性分析,通过对变形结果中光学元件曲率和刚体位移做拟合,得到敏感因素的温度-离焦敏感度矩阵;在此基础上得到了相机温度调焦曲线;最后,开展了相机热光学试验。试验结果表明,基于集成分析结果的温度调焦,空间相机在20℃±8℃内的最大误差小于0.1mm,基本满足相机在轨自动调焦的要求,并指出了进一步提高相机温度调焦精度的方法。

In order to improve the image quality of space camera in different temperature fields, a integrated analysis model of structure-thermal-optical performance （STOP） model was established. According to the model, the thermal-defocusing property of the system was studied and test, and focusing curve of camera temperature was obtained. Then, thermo-optical experiment was developed. Firstly, influence of temperature changes on optical system, especially influence on optimal image plane position, was analyzed to obtain relationship of defocusing amount and optical element parameters; then, general method of STOP integrated analysis was introduced. In this method, temperature field of thermal analysis was as boundary condition of structural analysis by mapping, and a thermo-elastic performance of finite element model was analyzed. Then, temperature-defocusing sensitivity matrix of sensitive factors was obtained by fitting the curvature of optical elements and rigid body displacement in deformation result. On the basis of above, Temperature-focusing curve of camera was obtained. Finally thermo-optical test of camera was carried out. Experimental result indicates that maximum error of temperature focusing based on integrated analysis result is less than 0.1 mm in 20℃8℃. The results basically satisfy camera requirements of on-orbit automatic focusing and method of further increasing camera precision of temperature focusing is pointed out.