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Proceedings Paper

Worthwhile optical method for free-form mirrors qualification
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Paper Abstract

We present an optical method for free-form mirrors qualification developed by the Italian National Institute for Astrophysics (INAF) in the context of the ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) Project which includes, among its items, the design, development and installation of a dual-mirror telescope prototype for the Cherenkov Telescope Array (CTA) observatory. The primary mirror panels of the telescope prototype are free-form concave mirrors with few microns accuracy required on the shape error. The developed technique is based on the synergy between a Ronchi-like optical test performed on the reflecting surface and the image, obtained by means of the TraceIT ray-tracing proprietary code, a perfect optics should generate in the same configuration. This deflectometry test allows the reconstruction of the slope error map that the TraceIT code can process to evaluate the measured mirror optical performance at the telescope focus. The advantages of the proposed method is that it substitutes the use of 3D coordinates measuring machine reducing production time and costs and offering the possibility to evaluate on-site the mirror image quality at the focus. In this paper we report the measuring concept and compare the obtained results to the similar ones obtained processing the shape error acquired by means of a 3D coordinates measuring machine.

Paper Details

Date Published: 15 October 2013
PDF: 11 pages
Proc. SPIE 8884, Optifab 2013, 888414 (15 October 2013); doi: 10.1117/12.2029160
Show Author Affiliations
G. Sironi, INAF - Osservatorio Astronomico di Brera (Italy)
R. Canestrari, INAF - Osservatorio Astronomico di Brera (Italy)
G. Toso, INAF - IASF Milano (Italy)
G. Pareschi, INAF - Osservatorio Astronomico di Brera (Italy)

Published in SPIE Proceedings Vol. 8884:
Optifab 2013
Julie L. Bentley; Matthias Pfaff, Editor(s)

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