针对离轴三反光学系统初始结构求解复杂、视场宽度小的问题, 提出了利用光学传递矩阵求解三反系统初始结构的计算方法, 推导了三反系统焦距和后截距的表达式, 求解了光阑位于次镜的三反系统初始结构。采用引入高次非球面以增加系统设计自由度的技术路线, 基于ZEMAX光学设计软件, 通过对同轴初始结构进行离轴优化, 得到了一个矩形视场17°×2°, 焦距1 440 mm, F数4.8的离轴三反光学系统。该系统三个反射面均为高次非球面, 可同时满足宽视场角和高分辨率的要求, 在空间频率50 lp/mm处, 调制传递函数大于0.6, 接近衍射极限。结果表明: 该系统搭载线阵/面阵时间延迟积分电荷耦合元件(TDI-CCD)用于推扫/多通道式空间对地成像时, 可有效扩大空间对地成像系统的地面覆盖范围, 提高信息获取效率。

To the problem that off-axis three-mirror optical system has narrow field and complicating initial structure solving process, a method by using optical transfer matrix to solve initial structure was proposed, the focus length and rear cut-off distance of three-mirror system was deduced, then an initial structure parameter of three-mirror system with aperture stop on secondary mirror was given. High order aspheric surface was used to increase system design variance, and making off-axial optimization design to coaxial system based on optical design software ZEMAX, finally got an off-axis three-mirror optical system with wide rectangle field of view 17°×2°, focus length of 1 440 mm, F number of 4.8. The system has three high order aspheric optical elements, it can satisfy the requirement of high resolution and large field, the MTF is more than 0.6 at 50 lp/mm, approaches to the diffraction limitation. The designed result shows that the system can be used in space of imaging system with Timed Delay and Integrated Charge-couple Device(TDI-CCD), can expand the ground coverage of system obviously, and achieves high information retrieval efficiency.