Surface error correction of ELT primary mirror hexagonal segments by ion figuring

Xavier Tonnellier; Martin Violot; Gilles Chaussat; Yohan Drouhot; Camille Frapolli; Marc Gouedard; Hervé Leplan; André Rinchet

doi:10.1117/12.3020293

26 August 2024 Surface error correction of ELT primary mirror hexagonal segments by ion figuring

Xavier Tonnellier, Martin Violot, Gilles Chaussat, Yohan Drouhot, Camille Frapolli, Marc Gouedard, Hervé Leplan, André Rinchet

Author Affiliations +

Proceedings Volume 13100, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI; 131003W (2024) https://doi.org/10.1117/12.3020293
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

Ion Beam Figuring is a key technology after polishing, hexagonal cutting and integration to obtain ELT-M1 hexagonal segments without edge effects. This process used at REOSC over 30 years offers an efficient solution for finishing these large freeform optical components. This paper presents a dedicated figuring process strategy to maximize throughput and process convergence as well as to limit temperature increase during processing. We analysed the results of optical surface improvement over 100 ELT-M1 segments. These results highlight the high accuracy of IBF technology to correct hexagonal surfaces all the way to the edge. The final surface figure error below 10nm RMS was obtained while keeping low surface roughness. This is achieved after less than two figuring iterations leading to a throughput over one segment per day.

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

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Xavier Tonnellier, Martin Violot, Gilles Chaussat, Yohan Drouhot, Camille Frapolli, Marc Gouedard, Hervé Leplan, and André Rinchet "Surface error correction of ELT primary mirror hexagonal segments by ion figuring", Proc. SPIE 13100, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI, 131003W (26 August 2024); https://doi.org/10.1117/12.3020293

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