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Analyse de front d'onde en plan focal: développement d'algorithmes temps-réel et application au cophasage de télescopes multipupilles imageurs

Abstract : Optical interferometry allows to reach the resolution of a large instrument by coupling several sub-apertures of lower diameter. However, this method requires a very accurate control of the optical paths, especially the differential aberrations between the apertures (so-called cophasing operation). In this context, focal-plane sensing appears to be an advantageous solution with a very simple opto-mechanical setup. The phase retrieval and the phase diversity techniques (based respectively on the acquisition of one or at least two images aberrated with a known phase) are now commonly used with monolithic instruments; their applicability to the cophasing of phased-array systems have also been demonstrated in laboratory. However, these estimators are iterative and consequently potentially time-consuming. In this manuscript, we propose new algorithms which are well-suited for real-time cophasing on extended objects. We demonstrate that a quadratic criterion can be derived, which allows to express the solution under a simple analytical form. We also show that the expression of this new criterion can be obtained in the case of small phase perturbations considering a linear expression of the optical transfer function. The performance we obtained on simulated data demonstrates the possibility of using the analytic algorithms in a closed-loop system at low fluxes and restoring the observed object as well. Experimental validations of both iterative and analytic estimators for various projects confirm that the focal plane approach now can be used for the cophasing of complex phased-array systems.
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Submitted on : Monday, November 2, 2009 - 10:05:16 PM
Last modification on : Tuesday, March 16, 2021 - 3:42:04 PM
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Isabelle Mocoeur. Analyse de front d'onde en plan focal: développement d'algorithmes temps-réel et application au cophasage de télescopes multipupilles imageurs. Astrophysique [astro-ph]. Université Paris Sud - Paris XI, 2008. Français. ⟨tel-00429451⟩

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