空间激光通信离轴两镜反射望远镜自由曲面光学天线设计

同轴两反结构作为空间激光通信光学天线时常存在接收视场小、发射效率低等缺点。同时，因中心遮拦造成的能量损失，也会大大降低通信系统的瞄准和捕获概率。针对此缺陷，提出采用离轴两反天线结构并引入自由曲面设计以提高通信系统的性能。由初级像差理论推导得出离轴两反系统的初始结构，并采用Zernike多项式自由曲面面形，增加系统设计自由度，提高系统平衡像差的能力。给出入瞳口径与焦距相同的同轴两反和离轴两反系统的设计实例，并比较二者的光学传递函数MTF、点列图、衍射包围圆能量、波前误差等。结果表明:离轴两反自由曲面天线的像质明显优于同轴两反天线，因而该种天线结构的使用可提升空间激光通信系统的整体性能。

Optical antenna design of off-axis two-mirror reflective telescope with freeform surface for space laser communication

The coaxial two-mirror reflective structure has the disadvantage of small receiving field of view and low emission efficiency when being used as optical antenna in space laser communication. At the same time, the energy loss caused by central obscuration will greatly reduce the aiming and capturing probability of communication system. For this inherent defects, an off-axis two-mirror reflective structure with freeform surface was designed to improve the performance of space laser communication. The initial structure of the off-axis two-mirror reflective structure was deduced according to the basic aberration theory. Zernike polynomial freeform surface was introduced to improve the ability of designing freedom and balancing the freeform surfaces aberration. A design example was given whose coaxial and off-axis two-mirror reflective system had same pupil aperture and focal length, and the modulation transfer function, spot diagram, diffraction encircled energy and wavefront error were compared. The results show that the image quality of the off-axis two-mirror reflective antenna with freeform surface is better than that of the coaxial, thus, the structure of the off-axis two-mirror reflective antenna structure could improve entire performance of space laser communication system.