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Proceedings Paper

Influence of striae on the homogeneity of the linear thermal expansion coefficient of ZERODUR
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Paper Abstract

The ZERODUR production, consisting of established processes used in the manufacturing of high homogeneous optical glasses, results in excellent blanks with low stress birefringence, striae content and outstanding homogeneity of the coefficient of thermal expansion. For future extremely large telescope projects like OWL (OverWhelmingly Large Telescope) or TMT (Thirty Meter Telescope), with at least several hundreds of mirror blanks, the material homogeneity within a single blank is extremely important. Previously, the stress birefringence of 2m class mirror blanks could be reduced to amounts far below our catalog values. Striae in ZERODUR, if present, are weak band-like density fluctuations within the material with only minimum influence on the properties of the material. This paper presents the results of dilatometric measurements on the influence of standard grade striae within ZERODUR on the homogeneity of the CTE. All CTE measurements have been carried out using our new dilatometer setup with improved reproducibility.

Paper Details

Date Published: 31 August 2006
PDF: 12 pages
Proc. SPIE 6288, Current Developments in Lens Design and Optical Engineering VII, 62880M (31 August 2006); doi: 10.1117/12.674751
Show Author Affiliations
Ralf Jedamzik, SCHOTT AG (Germany)
Peter Hartmann, SCHOTT AG (Germany)

Published in SPIE Proceedings Vol. 6288:
Current Developments in Lens Design and Optical Engineering VII
Pantazis Z. Mouroulis; Warren J. Smith; R. Barry Johnson, Editor(s)

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