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Proceedings Paper

Surface error correction of a Keck 10-m telescope primary mirror segment by ion figuring
Author(s): Lynn N. Allen; Robert E. Keim; Timothy S. Lewis; James R. Ullom
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Paper Abstract

The ion figuring process has been successfully used to correct the residual surface figure error on a 1.8 m ZerodurTM off-axis segment of the new Keck telescope primary mirror. The segment is one of 36 hexagonal mirror segments composing the full aperture of the 10 m primary mirror. Ion figuring is an optical fabrication method that provides highly deterministic error correction of previously polished optical surfaces using a directed, inert, and neutralized Argon ion beam to physically sputter material from the surface. Figure error correction is accomplished by varying the velocity of the constant-output ion source as it scans across the optic surface. The surface figure error was reduced from 0.726 micrometers rms to 0.090 micrometers rms in two test-figure iterations. The demonstration provided information and requirements for future processing of ZerodurTM and other glass-ceramic materials, and clearly showed the applicability of ion beam figuring to the final correction of large, complex optics.

Paper Details

Date Published: 1 January 1992
PDF: 10 pages
Proc. SPIE 1531, Advanced Optical Manufacturing and Testing II, (1 January 1992); doi: 10.1117/12.134862
Show Author Affiliations
Lynn N. Allen, Eastman Kodak Co. (United States)
Robert E. Keim, Eastman Kodak Co. (United States)
Timothy S. Lewis, Eastman Kodak Co. (United States)
James R. Ullom, California Association for Research in Astronomy (United States)

Published in SPIE Proceedings Vol. 1531:
Advanced Optical Manufacturing and Testing II
Victor J. Doherty, Editor(s)

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