Manufacture and verification of M6C mirrors the pre-focal stations of the ESO-extremely large telescope

Andrew Dickins; Paul Rees

doi:10.1117/12.3017192

17 June 2024 Manufacture and verification of M6C mirrors the pre-focal stations of the ESO-extremely large telescope

Andrew Dickins, Paul Rees

Proceedings Volume 13021, Optical Fabrication and Testing VIII; 1302103 (2024) https://doi.org/10.1117/12.3017192
Event: SPIE Optical Systems Design, 2024, Strasbourg, France

Abstract

The M6C mirror of the Extremely Large Telescope is a Zerodur elliptical flat with wavefront specification of 60 nm RMS at 45 degrees angle of incidence over an optical clear area of 694 x 504 mm. The mirror is being processed at Glyndwr Innovations Ltd via small tool CNC polishing, with a sub-aperture interferometric stitching test being used to measure the surface error. Here, the design and performance of the interferometric stitching test is discussed, complete with a full uncertainty budget to ensure conformance to the specification. Current work on the stitching test has found measurements of the M6C to be repeatable to 4 nm RMS surface error, and an overall uncertainty of measurement of 12.2 nm RMS. Using this test the optic will be polished to a measured surface error of less than 17.5 nm RMS.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Andrew Dickins and Paul Rees "Manufacture and verification of M6C mirrors the pre-focal stations of the ESO-extremely large telescope", Proc. SPIE 13021, Optical Fabrication and Testing VIII, 1302103 (17 June 2024); https://doi.org/10.1117/12.3017192

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