Theoretical and Applied Optics

The Homer test bench
Presentation

The Homer test bench is a Multi-Conjugate Adaptive Optics test bench [1] (MCAO). It has been developed in the context of the study of wide field adaptive optics, associating questions of wave front multi-analysis and multi-correction with several deformable mirrors. This test bench has been financed as part of a DGA REI contract.

The purpose of this test bench is to compare different concepts of wide field AO and study the implementation of a LQG type optimal control [2] on a real system.This new approach of AO control has been developed in collaboration with the L2TI laboratory (University Paris 13) especially in the frame of the DGA-REI contract.

Description of the system

HOMER comprises two deformable mirrors (DM) and a “wide field” analyzer. It is used to test in laboratory wide field Adaptive Optics (AO) systems at visible wavelenghts.

The system comprises:

• a source module composed of numerous unresolved sources placed on a system with reconfigurable geometry, associated with a collimator,
• a collimated beam turbulent space in which phase screens simulating Kolmogorov type atmospheric turbulence may be placed,
• optical relays for pupil imaging between the first pupil plane and the DM1 deformable mirror,
• a space for correction by the first DM1 deformable mirror conjugated with the pupil of the system,
• a space for correction by the second DM2 deformable mirror conjugated either with the pupil plane or with altitude. This mirror is placed on a translation rail and the pupil imaging works via a constant envelope system,
• a wide field full pupil imaging channel,
• a multi-directional Wave Front Sensor channel downstream of the two DMs.

Figure 2: Optical architecture of the Homer test bench. The names of the various optics are given.

Principal characteristics of the test bench

The table below summarizes the main parameters of the test bench.

Characteristics of the optics

The components are installed on a test bench of dimensions 800mmx2500mm. It comprises 7 non standard Clairaut doublets and a prismatic blade manufactured by the Maris-Delfour company.

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[1] MCAO: Multi-Conjugate Adaptive Optics: Wide field AO system comprising several WFSs to analyze the volume of turbulence and several DMs to correct wide field turbulence.

[2] LQG: Linear Quadratic Gaussian: Control law of a reconstructed state feedback form based on a Kalman filtering. In AO without mirrors dynamics, the predicted value of the turbulent phase is obtained with a Kalman filtering then simply projected onto the deformable mirror(s).

Last Update: 23 August 2010 - © ONERA 2008 - Terms of use