为了解决空间相机高分辨率与大视场的难题，在共轴三反的基础上，通过对以往离轴三反系统改进设计，提出了一种长焦距、大视场、大相对孔径无中心遮拦的离轴三反系统设计方法，并利用ZEMAX软件设计了一种焦距为1 200 mm，视场角11°×3°，相对孔径F/4,工作谱段在0.4~2.5 μm的光学系统，该系统在全视场空间频率 50 lp/mm处，MTF均值大于0.42，接近衍射极限，弥散斑直径RMS值小于10 μm，表明其具有良好的成像质量。

For resolving the problem in space camera with high resolution and wide field of view, based on the coaxialthree-mirror system，improving the former off-axis three-mirror system，the design method of the center unabscuredoff-axis three-mirror system with long focal length，wide field of view and large relative aperture is put forward. Withthe help of ZEMAX software，designing a optical system which has a focal length of 1 200 mm，the field of view is 11°×3°，the relative aperture is 1∶4，and the wave length is 0.4~2.5 μm. The system MTF is more than 0.42 at 50lp/mm on the total field of view，and the MTF approaches the diffraction limit，the RMS diameter of disc of confusionis less than 10 μm， which shows that the imaging quality of the system is very good.