随着空间技术的不断发展, 高性能、低成本的轻小型空间光学系统成为空间光学领域一个新的研究热点。离轴三反光学系统具有成像质量高、大视场、轻量化程度高等特点, 能够更好地适应轻小型、低成本空间光学系统的应用要求, 具有广泛的应用前景。以高斯光学和三反消像差理论为基础, 设计了一款第三反射镜为自由曲面的离轴三反光学系统, 焦距1 550 mm, 视场3.6°×0.45°, 相对孔径1: 6.2, 自由曲面的加入极大地提高了系统设计自由度和成像质量。设计结果表明, 在有效视场内系统成像质量良好, fMTF优于0.43@111 lp/mm, 系统最大波像差为0.049 λ(λ=632.8 nm), 平均波像差RMS值为0.034 λ, 最大网格畸变0.9%, 成像质量相对于子午面完全对称。系统的总长小于f′/3.1, 高度小于f′/4.1, 且系统的加工和装配公差较为宽松, 易于实现。该设计结果对轻小型空间光学系统的设计具有一定的参考价值。

With the increasing development of space technology, space optical system with the characteristics of high-performance, miniaturization has become a new hotspot research in space optical fields. Off-axis three-mirror optical system has the advantage of high quality image, large field of view and high level of lightweight etc., which can better suit the application of miniaturized and low-cost space optical system and has broad application prospects. Based on the Gaussian optics and three-mirror aberration theory, the off-axis three-mirror with freeform surface of tertiary mirror was designed. The focal length was 1 550 mm, field of view was 3.6°×0.45°, relative aperture was 1: 6.2, degrees of freedom and image quality were increased efficiently by the introduction of freeform surface. The design results show that system has a better performance in effective field of view, modulation transfer function value is above 0.43@111 lp/mm, wave-front error maximum value is 0.049 λ(λ=632.8 nm), RMS wave-front error value is 0.034 λ, maximum grid distortion value is 0.9%, and the imaging quality is complete symmetrical about the tangential plane. The total length of the optical system is less than f′/3.1, the height is less than f′/4.1, and is easily implemented because of the relatively loose tolerance about processing and assembling. The obtained results have a certain reference value for miniaturized space optical system.