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Large aperture freeform VIS telescope with smart alignment approach

: Beier, M.; Fuhlrott, W.; Hartung, J.; Holota, W.; Gebhardt, A.; Risse, S.


Navarro, R. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II : 26 June-1 July 2016, Edinburgh, United Kingdom
Bellingham, WA: SPIE, 2016 (Proceedings of SPIE 9912)
ISBN: 978-1-5106-0203-8
ISBN: 978-1-5106-0204-5
Paper 99120Y, 10 pp.
Conference "Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation" <2, 2016, Edinburgh>
Conference Paper
Fraunhofer IOF ()

The development of smart alignment and integration strategies for imaging mirror systems to be used within astronomical instrumentation are especially important with regard to the increasing impact of non-rotationally symmetric optics. In the present work, well-known assembly approaches preferentially applied in the course of infrared instrumentation are transferred to visible applications and are verified during the integration of an anamorphic imaging telescope breadboard. The four mirror imaging system is based on a modular concept using mechanically fixed arrangements of each two freeform surfaces, generated by servo assisted diamond machining and corrected using Magnetorheological Finishing as a figuring and smoothing step. Surface testing include optical CGH interferometry as well as tactile profilometry and is conducted with respect to diamond milled fiducials at the mirror bodies. A strict compliance of surface referencing during all significant fabrication step s allow for an easy integration and direct measurement of the system's wave aberration after initial assembly. The achievable imaging performance, as well as influences of the tight tolerance budget and mid-spatial frequency errors, are discussed and experimentally evaluated.