光瞳离轴自由曲面光学系统像差特性分析

Analysis of Aberration Properties of Pupil Off-Axis Freeform Surface Optical System

基于节点像差理论,提出了以泽尼克多项式为表征函数的光瞳离轴自由曲面光学系统像差分析方法,推导了光瞳离轴自由曲面系统的三阶像散和彗差解析表达式,分析了自由曲面对光瞳离轴系统像差节点分布的影响。根据像差分布特性,有针对性地选取和优化泽尼克系数,设计了一个光瞳离轴自由曲面空间天文光学系统,系统有效焦距为25m,口径为2m,视场为1.2°×1.2°。自由曲面的引入,使系统三阶像散和彗差节点重新回到视场中,不仅平衡了系统光瞳离轴引起的非对称像差,而且有效控制了全视场内点扩展函数(PSF)椭率,减小了星体观测时的测量误差。系统成像质量接近衍射极限,满足使用需求。

Based on the nodal aberration theory, an aberration analysis method for pupil off-axis freeform surface optical system with Zernike polynomial is proposed. The analytical expressions of third-order astigmatism and coma of the pupil off-axis freeform surface system are deduced. The impact of freeform surface on the distribution of aberration nodes of pupil off-axis system is analyzed. According to the aberration distribution properties, with pointed optimization of the Zernike terms, a pupil off axis freeform surface space telescope optical system is designed. The effective focal length is 25 m, the pupil diameter is 2 m and the field of view is 1.2＂〉（1.2~. By introducing the freeform surfaces, the third-order astigmatism and coma nodes are both moved back to the field of view. Therefore, the asymmetric aberrations induced by pupil off-axis are balanced, the point spread functions （PSF） ellipticity are controlled effectively, and the measurement errors of star observation are decreased. The final imaging quality is closed to the diffraction limit, which meets the requirements.