对于长焦距摄远光学系统，大相对孔径意味着成像亮度更加优秀，但是也伴随着孔径边缘像差变差而难以校正的难题。利用折反系统减小光学系统总长，采用反射结构为基础，搭配前后两组校正镜构成光学系统，设计出大相对孔径，总长较短的摄远光学系统。光学系统工作波段为可见光波段，焦距1 000 mm，F数2.1，摄远比0.52，光学总长远小于焦距，遮拦比45%，全视场MTF在空间频率80 lp/mm处大于0.3，像面直径11 mm。该光学系统镜片全部采用球面镜，光学系统由2片反射镜和7片透射镜组成，结构紧凑，成像质量好。对摄远物镜进行公差分析，得出该设计公差较宽松。

For the optical system with long focal length, the large relative aperture means that the imaging brightness is better, but it is difficult to correct with the variation of aperture edge aberration as well. The refractive system was used to reduce the total length of the optical system. Based on the reflection structure, the optical system was composed of two sets of correcting lens before and after, and the telephoto optical system with large relative aperture and short total length was effectively designed. The operating band of the optical system is the visible band, the focal length is 1 000 mm, the F number is 2.1, the telephoto ratio is 0.52, the optical total length is less than the focal length, the obstruction ratio is 45%, the full-field MTF is greater than 0.3 at the space frequency 80 lp/mm, and the image plane diameter is 11 mm. All the lenses of this optical system are spherical mirrors, and the system is composed of two reflectors and seven transmission mirrors, with compact structure and good imaging quality. The tolerance analysis of telephoto objective lens shows that the tolerance is good.