title: Approximate analytic astigmatism of unit-magnification multipass system.
abstract: We develop a way to estimate the approximate analytic astigmatism with a high accuracy for any unit-magnification multipass system (UMS). The coaxial optical transmission model for UMS is simplified based on the system's features. Furthermore, astigmatism is derived as a distinct form of vector addition and, thus, feasible analytic astigmatism can be obtained. The effectiveness of our method is verified by simulations for a Bernstein-Herzberg White cell. In our cases, the relative error of optimization for astigmatism correction by our method is smaller than 5 per thousand, which is only one-tenth of that by Kohn's method. Our method significantly improves the efficiency for astigmatism correction, and further benefits the optical design of a UMS.
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments,Tsinghua University, Beijing 100084, China. ckx03@mails.tsinghua.edu.cn
authors.forename: Kexin
authors.initials: K
authors.lastname: Chen
authors.forename: Huaidong
authors.initials: H
authors.lastname: Yang
authors.forename: Liqun
authors.initials: L
authors.lastname: Sun
authors.forename: Guofan
authors.initials: G
authors.lastname: Jin