He Chuanwang, Huang Peng, He Yiwei, Dong Xiaochun, Fan Bin
Appl Opt. 2020 Feb 20;59(6):1660-1666. doi: 10.1364/AO.379922.
An unobscured optical system provides a good solution for a high-performance diffractive telescope. However, the unobscured diffractive telescope, such as an off-axis three-mirror diffractive telescope (OTDT), suffers from the complex calculation of initial parameters, strict tolerance, and fabrication of aspheric mirror diffractive optical elements (DOE). In this paper, a simplified unobscured design method, which is effective in achieving compact and loose tolerance, is proposed. Combining the deflection of an optical path and Schupmann achromatic theory, a novel unobscured diffractive telescope is rapidly converted from a coaxial transmissive system. Not only is the loose tolerance obtained, but the fabrication of an aspheric mirror DOE is avoided. The designed system, with a focal length of 400 mm, $f$f-number of 5, and working waveband of 612.8-652.8 nm, is analyzed. The results show that the imaging quality approached the diffraction limit within a field of view of ${0.04}^\circ \times {0.02}^\circ $0.04×0.02. Compared with the OTDT, the designed system has great advantages in design step, DOE fabricating, and system alignment. It also provides a reference for unobscured diffractive telescope development.
无遮拦光学系统为高性能衍射望远镜提供了一个很好的解决方案。然而，无遮拦衍射望远镜，如离轴三镜衍射望远镜（OTDT），存在初始参数计算复杂、公差要求严格以及非球面镜衍射光学元件（DOE）制造等问题。本文提出了一种简化的无遮拦设计方法，该方法在实现紧凑结构和宽松公差方面是有效的。结合光路偏折和舒曼消色差理论，一种新型无遮拦衍射望远镜由同轴透射系统快速转换而来。不仅获得了宽松的公差，而且避免了非球面镜DOE的制造。对设计的焦距为400mm、f数为5且工作波段为612.8 - 652.8nm的系统进行了分析。结果表明，在视场为${0.04}^\circ \times {0.02}^\circ $0.04×0.02范围内成像质量接近衍射极限。与OTDT相比，设计的系统在设计步骤、DOE制造和系统对准方面具有很大优势。它也为无遮拦衍射望远镜的发展提供了参考。
