Research on the magnetorheological finishing of large aperture off-axis aspheric optical surfaces for zinc sulfide

Yunfei Zhang; Wen Huang; Yongcheng Zheng; Fang Ji; Min Xu; Zhixin Duan; Qing Luo; Qian Liu; Hong Xiao

doi:10.1117/12.2267813

8 March 2017 Research on the magnetorheological finishing of large aperture off-axis aspheric optical surfaces for zinc sulfide

Yunfei Zhang, Wen Huang, Yongcheng Zheng, Fang Ji, Min Xu, Zhixin Duan, Qing Luo, Qian Liu, Hong Xiao

Author Affiliations +

Proceedings Volume 10255, Selected Papers of the Chinese Society for Optical Engineering Conferences held October and November 2016; 102550R (2017) https://doi.org/10.1117/12.2267813
Event: Selected Papers of the Chinese Society for Optical Engineering Conferences held October and November 2016, 2016, Jinhua, Suzhou, Chengdu, Xi'an, Wuxi, China

Abstract

Zinc sulfide is a kind of typical infrared optical material, commonly produced using single point diamond turning (SPDT). SPDT can efficiently produce zinc sulfide aspheric surfaces with micro-roughness and acceptable figure error. However the tool marks left by the diamond turning process cause high micro-roughness that degrades the optical performance when used in the visible region of the spectrum. Magnetorheological finishing (MRF) is a deterministic, sub-aperture polishing technology that is very helpful in improving both surface micro-roughness and surface figure.This paper mainly investigates the MRF technology of large aperture off-axis aspheric optical surfaces for zinc sulfide. The topological structure and coordinate transformation of a MRF machine tool PKC1200Q2 are analyzed and its kinematics is calculated, then the post-processing algorithm model of MRF for an optical lens is established. By taking the post-processing of off-axis aspheric surfacefor example, a post-processing algorithm that can be used for a raster tool path is deduced and the errors produced by the approximate treatment are analyzed. A polishing algorithm of trajectory planning and dwell time based on matrix equation and optimization theory is presented in this paper. Adopting this algorithm an experiment is performed to machining a large-aperture off-axis aspheric surface on the MRF machine developed by ourselves. After several times’ polishing, the figure accuracy PV is proved from 3.3λ to 2.0λ and RMS from 0.451λ to 0.327λ. This algorithm is used to polish the other shapes including spheres, aspheres and prisms.

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Yunfei Zhang, Wen Huang, Yongcheng Zheng, Fang Ji, Min Xu, Zhixin Duan, Qing Luo, Qian Liu, and Hong Xiao "Research on the magnetorheological finishing of large aperture off-axis aspheric optical surfaces for zinc sulfide", Proc. SPIE 10255, Selected Papers of the Chinese Society for Optical Engineering Conferences held October and November 2016, 102550R (8 March 2017); https://doi.org/10.1117/12.2267813

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