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Proceedings Paper

Large optical glass blanks for the ELT generation
Author(s): Ralf Jedamzik; Uwe Petzold; Volker Dietrich; Volker Wittmer; Olga Rexius
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Paper Abstract

The upcoming extremely large telescope projects like the E-ELT, TMT or GMT telescopes require not only large amount of mirror blank substrates but have also sophisticated instrument setups. Common instrument components are atmospheric dispersion correctors that compensate for the varying atmospheric path length depending on the telescope inclination angle. These elements consist usually of optical glass blanks that have to be large due to the increased size of the focal beam of the extremely large telescopes.

SCHOTT has a long experience in producing and delivering large optical glass blanks for astronomical applications up to 1 m and in homogeneity grades up to H3 quality in the past.

The most common optical glass available in large formats is SCHOTT N-BK7. But other glass types like F2 or LLF1 can also be produced in formats up to 1 m. The extremely large telescope projects partly demand atmospheric dispersion components even in sizes beyond 1m up to a range of 1.5 m diameter. The production of such large homogeneous optical glass banks requires tight control of all process steps.

To cover this demand in the future SCHOTT initiated a research project to improve the large optical blank production process steps from melting to annealing and measurement. Large optical glass blanks are measured in several sub-apertures that cover the total clear aperture of the application. With SCHOTT's new stitching software it is now possible to combine individual sub-aperture measurements to a total homogeneity map of the blank. In this presentation first results will be demonstrated.

Paper Details

Date Published: 22 July 2016
PDF: 12 pages
Proc. SPIE 9912, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 99123E (22 July 2016); doi: 10.1117/12.2230647
Show Author Affiliations
Ralf Jedamzik, SCHOTT AG (Germany)
Uwe Petzold, SCHOTT AG (Germany)
Volker Dietrich, SCHOTT AG (Germany)
Volker Wittmer, SCHOTT AG (Germany)
Olga Rexius, SCHOTT AG (Germany)

Published in SPIE Proceedings Vol. 9912:
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II
Ramón Navarro; James H. Burge, Editor(s)

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