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Les optiques adaptatives grand champ : stratégie de correction et validations expérimentales

Abstract : Adaptive Optics (AO) allows to correct in real time the atmospheric perturbations thanks to the analysis of the turbulence with a WaveFront Sensor (WFS). The correction is then provided by a Deformable Mirror (DM). AO is however limited by two effects: anisoplanatism and sky coverage. To overcome these limitations, Wide Field AO (WFAO) concepts have been developed. These systems allow to probe the turbulent volume with several WFSs so as to perform a tomographic reconstruction of the turbulence. The correction is then applied in one specific direction of the Field of View (FoV) with one DM (Laser Tomography AO (LTAO)) or in a wide FoV thanks to several DMs (MultiConjugate AO (MCAO) or Multi-Object AO (MOAO)). The work performed during this PhD. is focused on the design of WFAO systems and experimental validations of these concepts. We especially study new issues related to wavefront sensing, correction and control laws. We have developed a bench called HOMER dedicated to experimental validation of WFAO concepts. The integration of the bench has allowed the study and the implementation of calibration procedures of the system, needed to obtain the best performance. These calibrations have been used in particular to implement a Linear Quadratic Gaussian (LQG) control. This control law is well adapted to WFAO since it provides an estimation and a prediction of the turbulent volume thanks to spatial and temporal a priori. Then the correction to be applied on the DMs is derived, in order to optimize the correction in a given FoV. We have implemented LQG control on HOMER for MCAO and LTAO configurations. This control leads to a significant gain in performance compared to a more standard approach based on a least-square reconstruction associated to an integrator control. This work corresponds to the first experimental results obtained with LQG control in WFAO and in closed-loop LTAO. It is also a first step towards the robustness study of LQG control with respect to model errors. In addition to these experimental results, we have also studied LGS related system design issues and have also reconsidered DM design rules in the perpective of the new VLT/ELT AO instruments.
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https://tel.archives-ouvertes.fr/tel-00447752
Contributor : Anne Costille <>
Submitted on : Friday, January 15, 2010 - 5:02:46 PM
Last modification on : Friday, June 26, 2020 - 2:00:03 PM
Long-term archiving on: : Thursday, June 17, 2010 - 10:51:00 PM

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  • HAL Id : tel-00447752, version 1

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Anne Costille. Les optiques adaptatives grand champ : stratégie de correction et validations expérimentales. Astrophysique [astro-ph]. Université Paris-Diderot - Paris VII, 2009. Français. ⟨tel-00447752⟩

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