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Proceedings Paper

Progress in 4m class ZERODUR mirror production
Author(s): Thomas Westerhoff; Steffen Gruen; Ralf Jedamzik; Christopher Klein; Thomas Werner; Alexander Werz
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Paper Abstract

The first monolithic ZERODUR® 4 m class mirror was ordered by the German Max Planck Institute for Astronomical Physics in 1968. A ratio of 1:6 for thickness to diameter ratio ensured the necessary stiffness to minimize deformation under gravity load. The technological ability to actively compensate the bending of the mirror substrate under gravity initiated the development from heavy non active thick mirror substrates to ever thinner thicknesses starting with the NTT, the New Technology Telescope of ESO. The thinner the mirror substrates are becoming the more demanding are the requests on homogeneity of material properties to ensure best performance over the clear aperture at every spot. In this paper we present results on material properties achieved for the 4 m class mirror substrates recently delivered by SCHOTT. The CTE homogeneity, the internal quality regarding striae, bubbles and inclusions as well as stress birefringence data are reported. Improvements in CNC processing and overall manufacturing process for the very thin 4 m class blanks are discussed.

Paper Details

Date Published: 26 September 2011
PDF: 10 pages
Proc. SPIE 8126, Optical Manufacturing and Testing IX, 81260A (26 September 2011); doi: 10.1117/12.894419
Show Author Affiliations
Thomas Westerhoff, SCHOTT AG (Germany)
Steffen Gruen, SCHOTT AG (Germany)
Ralf Jedamzik, SCHOTT AG (Germany)
Christopher Klein, SCHOTT AG (Germany)
Thomas Werner, SCHOTT AG (Germany)
Alexander Werz, SCHOTT AG (Germany)

Published in SPIE Proceedings Vol. 8126:
Optical Manufacturing and Testing IX
James H. Burge; Oliver W. Fähnle; Ray Williamson, Editor(s)

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