为了消除在实际飞行过程中温度变化对机载折反式光学系统成像质量的影响, 对该系统的光学元件、机械结构等部分进行热分析, 实现机载折反式光学系统的无热化设计。首先, 根据透镜的光焦度公式推导透镜的光焦度温度函数, 列出透镜组的消热差方程。接着, 在考虑支撑结构的影响时引入轴向放大率, 以此表现折反式系统部分元件间隔变化对系统焦距影响大的特点。最后, 结合前两者确定完整的消热差方程来指导无热化设计。仿真结果表明, 工作在486~656 nm波段, 焦距为1 850 mm的机载折反式可见光光学系统在0~40 ℃之间成像良好, 调制传递函数下降不到0.1。

In order to eliminate the influence of temperature change on the imaging quality of the airborne mirror-lens optical system during the actual flight, thermal analysis of the optical components and mechanical structures of the system was carried out to realize the athermal design of the airborne mirror-lens optical system. First, the power temperature function of the lens was derived from the power formula of the lens, and the athermal equation of the lens group was listed. Then, the axial magnification was introduced when considering the influence of the support structure, so as to show that the variation of the component spacing of the mirror-lens system had a great influence on the focal length of the system. Finally, the complete athermal equation was determined in conjunction with the former two to guide the athermal design. The simulation results show that the airborne mirror-lens visible optics system with a focal length of 1 850 mm works well in the 486~656 nm band between 0~40 ℃, and the modulation transfer function decreases by less than 0.1.