Freeform correction polishing for optics with semi-kinematic mounting

Chien-Yao Huang; Ching-Hsiang Kuo; Wei-Jei Peng; Zong-Ru Yu; Cheng-Fang Ho; Ming-Ying Hsu; Wei-Yao Hsu

doi:10.1117/12.2195464

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12 October 2015 Freeform correction polishing for optics with semi-kinematic mounting

Chien-Yao Huang, Ching-Hsiang Kuo, Wei-Jei Peng, Zong-Ru Yu, Cheng-Fang Ho, Ming-Ying Hsu, Wei-Yao Hsu

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Proceedings Volume 9633, Optifab 2015; 963326 (2015) https://doi.org/10.1117/12.2195464
Event: SPIE Optifab, 2015, Rochester, New York, United States

Abstract

Several mounting configurations could be applied to opto-mechanical design for achieving high precise optical system. The retaining ring mounting is simple and cost effective. However, it would deform the optics due to its unpredictable over-constraint forces. The retaining ring can be modified to three small contact areas becoming a semi-kinematic mounting. The semi-kinematic mounting can give a fully constrained in lens assembly and avoid the unpredictable surface deformation. However, there would be still a deformation due to self-weight in large optics especially in vertical setup applications. The self-weight deformation with a semi-kinematic mounting is a stable, repeatable and predictable combination of power and trefoil aberrations. This predictable deformation can be pre-compensated onto the design surface and be corrected by using CNC polisher. Thus it is a freeform surface before mounting to the lens cell. In this study, the freeform correction polishing is demonstrated in a Φ150 lens with semi-kinematic mounting. The clear aperture of the lens is Φ143 mm. We utilize ANSYS simulation software to analyze the lens deformation due to selfweight deformation with semi-kinematic mounting. The simulation results of the self-weight deformation are compared with the measurement results of the assembled lens cell using QED aspheric stitching interferometer (ASI). Then, a freeform surface of a lens with semi-kinematic mounting due to self-weight deformation is verified. This deformation would be corrected by using QED Magnetorheological Finishing (MRF® ) Q-flex 300 polishing machine. The final surface form error of the assembled lens cell after MRF figuring is 0.042 λ in peak to valley (PV).

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Chien-Yao Huang, Ching-Hsiang Kuo, Wei-Jei Peng, Zong-Ru Yu, Cheng-Fang Ho, Ming-Ying Hsu, and Wei-Yao Hsu "Freeform correction polishing for optics with semi-kinematic mounting", Proc. SPIE 9633, Optifab 2015, 963326 (12 October 2015); https://doi.org/10.1117/12.2195464

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