19 October 2016 Ion beam figuring of Φ520mm convex hyperbolic secondary mirror
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Proceedings Volume 10154, Advanced Optical Design and Manufacturing Technology and Astronomical Telescopes and Instrumentation; 1015406 (2016) https://doi.org/10.1117/12.2243825
Event: International Symposium on Optoelectronic Technology and Application 2016, 2016, Beijing, China
Abstract
The convex hyperbolic secondary mirror is a Φ520-mm Zerodur lightweight hyperbolic convex mirror. Typically conventional methods like CCOS, stressed-lap polishing are used to manufacture this secondary mirror. Nevertheless, the required surface accuracy cannot be achieved through the use of conventional polishing methods because of the unpredictable behavior of the polishing tools, which leads to an unstable removal rate. Ion beam figuring is an optical fabrication method that provides highly controlled error of previously polished surfaces using a directed, inert and neutralized ion beam to physically sputter material from the optic surface. Several iterations with different ion beam size are selected and optimized to fit different stages of surface figure error and spatial frequency components. Before ion beam figuring, surface figure error of the secondary mirror is 2.5λ p-v, 0.23λ rms, and is improved to 0.12λ p-v, 0.014λ rms in several process iterations. The demonstration clearly shows that ion beam figuring can not only be used to the final correction of aspheric, but also be suitable for polishing the coarse surface of large, complex mirror.
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Xiaohui Meng, Xiaohui Meng, Yonggang Wang, Yonggang Wang, Ang Li, Ang Li, Wenqing Li, Wenqing Li, } "Ion beam figuring of Φ520mm convex hyperbolic secondary mirror", Proc. SPIE 10154, Advanced Optical Design and Manufacturing Technology and Astronomical Telescopes and Instrumentation, 1015406 (19 October 2016); doi: 10.1117/12.2243825; https://doi.org/10.1117/12.2243825
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