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Proceedings Paper

Extremely aspheric mirrors: prototype development of an innovative manufacturing process based on active optics
Author(s): Zalpha Challita; Emmanuel Hugot; Marc Ferrari; Joël Le Merrer; David Le Mignant; Jean-Gabriel Cuby
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Paper Abstract

The next generation of focal-plane astronomical instruments requires technological breakthroughs to reduce their system complexity while increasing their scientific performances. Applied to the optical systems, recent studies show that the use of freeform reflective optics allows competitive compact systems with less optical components. In this context, our challenge is to supply an active freeform mirror system, using a combination of different active optics techniques. The optical shape will be provided during the fabrication using the mechanical property of metals to plasticize and will be coupled with a specific actuator system to compensate for the residual form errors, during the instrument operation phase. We present in this article the development of an innovative manufacturing process based on cold hydro-forming method, with the aim to adapt it for VIS/NIR requirements in terms of optical surface quality. It can operate on thin and flat polished initial substrates. The realization of a first prototype for a 100 mm optical diameter mirror is in progress, to compare the mechanical behaviours obtained by tests and by Finite Element Analysis (FEA), for different materials. Then, the formed samples will be characterized optically. The opto-mechanical results will allow a fine tuning of FEA parameters to optimize the residual form errors obtained through this process. It concerns the microstructure considerations, the springback effects and the work hardening evolutions of the samples, depending on the initial substrate properties and the boundary conditions applied. Modeling and tests have started with axi-symmetric spherical and aspherical shapes and will continue with highly aspherics and freeforms.

Paper Details

Date Published: 13 September 2012
PDF: 9 pages
Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 845033 (13 September 2012); doi: 10.1117/12.925540
Show Author Affiliations
Zalpha Challita, Lab. d'Astrophysique de Marseille, CNRS, Aix-Marseille Univ. (France)
Emmanuel Hugot, Lab. d'Astrophysique de Marseille, CNRS, Aix-Marseille Univ. (France)
Marc Ferrari, Lab. d'Astrophysique de Marseille, CNRS, Aix-Marseille Univ. (France)
Joël Le Merrer, Lab. d'Astrophysique de Marseille, CNRS, Aix-Marseille Univ. (France)
David Le Mignant, Lab. d'Astrophysique de Marseille, CNRS, Aix-Marseille Univ. (France)
Jean-Gabriel Cuby, Lab. d'Astrophysique de Marseille, CNRS, Aix-Marseille Univ. (France)


Published in SPIE Proceedings Vol. 8450:
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II
Ramón Navarro; Colin R. Cunningham; Eric Prieto, Editor(s)

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