22 July 2016 Effects of thermal inhomogeneity on 4m class mirror substrates
Author Affiliations +
Abstract
The new ground based telescope generation is moving to a next stage of performance and resolution. Mirror substrate material properties tolerance and homogeneity are getting into focus. The coefficient of thermal expansion (CTE) homogeneity is even more important than the absolute CTE. The error in shape of a mirror, even one of ZERODUR, is affected by changes in temperature, and by gradients in temperature. Front to back gradients will change the radius of curvature R that in turn will change the focus. Some systems rely on passive athermalization and do not have means to focus. Similarly changes in soak temperature will result in surface changes to the extent there is a non-zero coefficient of thermal expansion. When there are in-homogeneities in CTE, the mirror will react accordingly. Results of numerical experiments are presented discussing the impact of CTE in-homogeneities on the optical performance of 4 m class mirror substrates. Latest improvements in 4 m class ZERODUR CTE homogeneity and the thermal expansion metrology are presented as well.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ralf Jedamzik, Clemens Kunisch, Thomas Westerhoff, "Effects of thermal inhomogeneity on 4m class mirror substrates", Proc. SPIE 9912, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 99120Z (22 July 2016); doi: 10.1117/12.2234287; https://doi.org/10.1117/12.2234287
PROCEEDINGS
12 PAGES


SHARE
RELATED CONTENT

Metrology of IXO mirror segments
Proceedings of SPIE (October 11 2011)
Primary mirror blank fabrication of SUBARU Telescope
Proceedings of SPIE (June 01 1994)
Air flow studies in channelled mirrors
Proceedings of SPIE (July 01 1990)

Back to Top