Active optics: deformable mirrors with a minimum number of actuators

M Laslandes,E Hugot,M Ferrari

doi:10.2971/jeos.2012.12036

Abstract

We present two concepts of deformable mirror to compensate for first order optical aberrations. Deformation systems are designed using both elasticity theory and Finite Element Analysis in order to minimize the number of actuators. Starting from instrument specifications, we explain the methodology to design dedicated deformable mirrors. The work presented here leads to correcting devices optimized for specific functions. The Variable Off-Axis paraboLA concept is a 3-actuators, 3-modes system able to generate independently Focus, Astigmatism and Coma. The Correcting Optimized Mirror with a Single Actuator is a 1-actuator system able to generate a given combination of optical aberrations.

Highlights

IntroductionActive optics allows a wave-front control at nanometric precisions, ensuring optimal performance for the optical instrument [1]
Using deformable mirrors, active optics allows a wave-front control at nanometric precisions, ensuring optimal performance for the optical instrument [1]
Developed and proved by Wilson on the ESO New Technology Telescope [2], these systems are widely used on 8-10 m-class telescopes, such as Gemini North and South, Keck, Gran Telescopio Canarias (GTC) or Very Large Telescope (VLT)

Summary

Introduction

Active optics allows a wave-front control at nanometric precisions, ensuring optimal performance for the optical instrument [1]. The first application of active optics is the maintaining of large mirrors optimal shape with actuators located under their optical surfaces. Proposed in the 1930’s by Schmidt [5] for the polishing of the entrance correcting lens of his wide field telescope, this method has been improved by Lemaitre in 1974 [6]. It allows the achievement of an aspherical mirror without high spatial frequency errors, by polishing a deformed optical substrate, under constraints, with a full size tool. As we can see through these three types of use, the key element of active optics is a deformable mirror, designed and optimized to fit specific requirements

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Conclusion