同轴三反射光学系统具有体积小、装调精度要求低，且成像质量好等优点，因此在高分辨率航天遥感领域有着广泛的应用前景。通过初级像差理论求解了同轴三反光学系统的初始结构参数，设计了焦距25 m，F数为12.5的同轴偏视场三反光学系统。设计结果表明，该系统采用矩形视场偏置，杂光少，引入折叠镜后系统总长f′/6.0~f′/6.6，结构紧凑，视场角达0.6°×0.3°，适合线阵时间延迟积分电荷耦合器件(TDI-CCD)传感器以推扫方式成像，空间频率50 lp/mm处，各视场的调制传递函数(MTF)均大于0.47，接近衍射极限，成像质量良好，特别适用于高分辨率对地精细观测等领域。

The coaxial three-mirror optical system has the advantage of small volume, easy to assembly and high quality image, which can be widely used in the field of aerospace remote sensing. The initial configuration parameters of the system are resolved by using the primary aberration theory, a coaxial field-bias three-mirror optical system with a focal length of 25 m and F number of 12.5 is designed. The design results show that the field of view of the system can attain to 0.6°×0.3° by offsetting the rectangle field with low parasitic light and compact structure, by using the folded mirror, the total length is about f′/6.0~f′/6.6, which is suitable for linear array time-debyed-integration charge coupled device (TDI-CCD) sensor to push-scanning image. The modulation transfer function (MTF) is higher than 0.47 at 50 lp/mm and the image quality of the optical system approaches the diffraction limit. The optical system provides a good option for the field of high-resolution space-to-earth fine observation.