基于正交种子曲线扩展算法设计自由曲面离轴反射无焦系统

Design of Freeform Off-Axis Reflective Afocal Systems by Orthogonal Seed Curve Extension Algorithm

离轴反射无焦光学系统在空间望远镜中具有重要的应用,自由曲面能够校正离轴反射系统中的非对称像差。设计自由曲面离轴反射无焦系统的初始结构非常关键。提出了正交种子曲线扩展算法(OSCE),可直接设计自由曲面离轴反射无焦系统的初始结构。为了验证方法可行性,分别设计了放大倍率为10和20的离轴无焦三反和四反系统。设计结果表明离轴三反系统初始结构均方根(RMS)波前差为0.36 λ,离轴四反系统初始结构波前差为0.18 λ。对这两个初始结构分别进行优化,优化之后的RMS波前差小于0.02 λ。

Off-axis reflective afocal optical systems have important applications in space telescopes. Freeform surfaces can correct the asymmetric aberrations in off-axis reflective afocal systems. It is very important to design the initial layouts of freeform off-axis reflective afocal systems. In this paper, an orthogonal seed curve extension(OSCE) algorithm was proposed to design the initial layouts of freeform off-axis reflective afocal systems directly. Off-axis afocal three-mirror and four-mirror systems with magnifications of 10 and 20, respectively, were designed to verify the feasibility of the method. The results show that the root-mean-square(RMS) wavefront error of the initial layout of the off-axis three-mirror system is 0.36 λ, and that of the off-axis four-mirror system is 0.18 λ. The RMS wavefront errors of the two initial layouts after optimization are both less than 0.02 λ.