用于无运动部件变焦的球面变曲率镜设计及试验

摘要

将无运动部件变焦技术引入空间光学相机的设计中，能够在不干扰卫星平台工况的情况下使空间相机在通过目标区域上空时获取蕴含有目标不同层次信息的图像，从而为后续的识别、判读甚至超分辨率重建提供依据。无运动部件变焦的关键在于：基于光学杠杆效应的光学设计和可以产生较大尺度曲率变化的变曲率反射镜。目前已设计出一种无运动部件变焦原型光学系统，其中变曲率反射镜的有效口径不超过100mm，初始曲率半径为1740mm，且具备曲率增减双向变形能力。文章针对上述指标，设计了变曲率反射镜，并进行了有限元分析，利用具有高韧性、高抗拉断性以及高极限许用应力的碳纤维复合材料研制了反射镜，通过与13点高精度压电驱动器的集成，最终实现了变曲率镜的研制。试验结果表明，该球面变曲率镜可以实现1705~1760mm的曲率半径变化，对应的中心形变量接近23μm，优于国外同等规模器件所能达到的水平。%Optical zoom imaging without introducing moving elements makes space camera own the capability of capture multiple images having different resolution that can reveal different details of interested object. These images can be used to carry out object recognitions, classification and even super-resolution construction. The key to this technique lies in two aspects: optical system design based on optical leveraging effect and variable curvature mirror(VCM)capable of generating large variation of curvature radius. In our previously published paper, a prototype non-moving element optical zooming system is proposed. According to the design, the VCM has a diameter of less than 100mm, initial curvature radius of 1 740mm and can change its curvature bi-directionally. In this paper, a VCM satisfying the requirements is designed and finite element analysis(FEA) is provided. Besides, the carbon fiber reinforced polymer(CFRP), which is robust enough, requires less force to be deformed and has high ultimate strength, is used to manufacture the mirror of VCM. Finally, by integrating 13 point PIEZO drivers with the CFRP mirror, a VCM is successfully fabricated and the test results demonstrate that the curvature radius of VCM can be changed between 1 705mm and 1 760mm, corresponding to a relatively large center deflection of approximately 23μm.