随着Skysat-1卫星的成功发射，高分辨率视频相机是目前竞相开发的卫星有效载荷。为降低成本、适应小卫星平台，亟需设计与研制体积小、重量轻、易实现、能对面视场成像的长焦距光学系统。研究与设计了适于面视场成像的全视场同轴三反望远物镜，解决其固有的二次遮拦和像面引出困难等问题。由近轴几何光学理论，导出消除二次遮拦的条件和系统总长与三镜中继成像倍率的关系，讨论并得到合理的三镜中继成像倍率等参数。利用出瞳附近处的平面镜，无遮拦地引出像平面，同时用平面镜组折叠光路，减小系统总长。给出了确定初始结构参数的方法与结果，优化设计得到了有效焦距、视场角、F数分别为10 m、1.1°×1°、14.3的无二次遮拦光学系统，其总长约为有效焦距的1/8，成像质量接近衍射极限。

There is a race to develop spaceborne high-resolution video cameras since Skysat-1 is launched successfully. To reduce manufacture cost and adapt to small satellite platform, it is urgent to design and develop a long focal length optical system with small volume, light weight, easy implementation and imageable for two-dimensional field of view. The full field of view coaxial three-mirror anastigmat (CTMA) appropriate for two-dimensional field of view imaging is studied. The problems of its inherent secondary obscuration and imaging plane extraction difficulty are solved. The conditions of eliminating the secondary obscuration and the relationship between the total length of the system and the tertiary mirror relay imaging magnification are presented based on paraxial geometry optics. Then the reasonable tertiary mirror relay imaging magnification and other parameters are discussed and obtained. A flat mirror near its exit pupil can be used to deflect the image plane without obscuration. The flat mirror group is used to fold optical path and the total length of the system is decreased. The method and the result for determining the initial structural parameters are presented. The optimized optical system without secondary obscuration is designed, whose effective focal length (EFL), field of view and F number are 10 m, 1.1°×1°, 14.3, respectively. The total length of the system is 1/8 of EFL. Its imaging quality is near diffraction limit.