大口径衍射望远系统由于使用透射式的薄膜衍射光学元件作为主镜, 不仅质量密度低(表面质量密度可以达到01 kg/m2), 同时面形精度要求宽松, 发射成本低。本文阐述了衍射望远系统的基本成像原理, 并推导出任意大口径系统的初始结构计算公式, 给出了口径为300 mm、系统焦距为2 m, 工作波段为058 μm到068 μm的系统设计实例并研制了原理验证系统, 进行了星点像以及分辨率板实验。成像结果接近衍射极限, 与设计结果相符。本文所做工作为大口径衍射望远系统的设计提供了良好的理论基础和初始模型结构, 能够极大地缩短设计周期, 提高成像质量。

When taking the film diffractive optical elements as main lens, large aperture diffractive telescope has the characteristics such as low mass density(surface mass density can reach 01 kg/m2), loose surface shape tolerance(surface accuracy requirements are the magnitude of centimeter) and low launch costs. In this paper, the imaging theory and the configuration of diffractive telescope are discussed. Then, the calculation process of the initial structure of this optical system is derived. A prototype system with 300-mm aperture, 2-m focal length and working wavelength from 058 μm to 068 μm is designed and star image test and resolution board test are carried out. The test result of star image is close to diffraction limit, which is agree well with the design result. The work in this paper can provide theory foundation and initial model for diffractive telescope designer, and can help them to reduce design time and increase imaging quality.