Providing toric mirrors with Active Optics techniques will allow generating aspheric surfaces which optical quality avoid high spatial frequencies errors. In order to demonstrate the feasibility of this technique, a link has been established between analytical calculations, finite element modelling and experimental validation. A particular configuration of a flat mono-mode deformable mirror (MDM), called "degenerated configuration", has been analytically calculated, showing how to generate a third order astigmatism aberration (Astm 3) by active deformation. This mirror has been manufactured and tested. A finite element model has been produced in order to correlate simulations with experiments. The deformed optical surface is projected on a Zernike polynomial base, indicating that Astm 3 mode is, within a very high precision, the only aberration generated on the optical surface. Another spherical concave MDM has been modelled as a VLT-SPHERE toric mirror of diameter 133mm, to demonstrate the feasibility of toric surfaces from active optics deformation of a spherical shell. Projection on Zernike base shows that the simulated deformed surface is a combination of a sphere and a quasi pure Astm 3 mode, corresponding to a toroidal surface. Other terms generated, like Astm 5, could benefit of a fine adjustment from the geometry of the substrate.

Date Published: 6 July 2006
PDF: 10 pages
Proc. SPIE 6273, Optomechanical Technologies for Astronomy, 62732N (6 July 2006); doi: 10.1117/12.671906

Published in SPIE Proceedings Vol. 6273:
Optomechanical Technologies for Astronomy
Eli Atad-Ettedgui; Joseph Antebi; Dietrich Lemke, Editor(s)