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Last name: AIME
First name: Claude
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We search for the best possible transmission for an external occulter coronagraph that is dedicated to the direct observation of terrestrial exoplanets. We show that better observation conditions are obtained when the flux in the focal plane is minimized in the zone in which the exoplanet is observed, instead of the total flux received by the...
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-Le travail présenté concerne la déconvolution d'images par minimisation de divergences invariantes par changement d'échelle. L'intérêt de telles divergences est d'inclure par elles-mêmes une contrainte de somme invariante sur la reconstruction. En utilisant ce type de divergence à la fois pour le terme d'attache aux données et pour le terme de...
-Nous décrivons l'inversion de l'intégrale de Fredholm pour des images subissant un fort vignetage conduisant à des PSFs dites évanescentes car disparaissant vers un bord du champ. L'algorithme utilisé, de type gradient avec contrainte de non-négativité, utilise une régularisation adaptative et automatique faisant usage du rapport de Strehl....
In a first part of the paper we give a simple introduction to the free space propagation of light at the level of a Master degree in Physics. The presentation promotes linear filtering aspects at the expense of fundamental physics. Following the Huygens-Fresnel approach, the propagation of the wave writes as a convolution relationship, the...
We report in this communication the rst experimental results in the visible range obtained by the Probability Imaging technique applied to close binary stars. Speckle data of the well known binary Del as well as the newly discovered one Moai1 (Carbillet et al. 1996) are processed. An analysis of the probability density functions, combined with...
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Context. High-contrast hybrid coronagraphs, which combine an external occulter and a Lyot-style coronagraph became a reality in recent years, despite the lack of analytic and numerical end-to-end performance studies. The solar coronagraph ASPIICS which will fly on the future ESA Formation Flying mission Proba-3 is a good example of such a...
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International audience
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The effect of atmospheric turbulence on the imaging of scenes, for an horizontal propagation of the light over a distance of 20 km, 15 meters above the sea surface, was analyzed at visible wavelength using a 20 cm telescope. Point-sources images were recorded during the night, and the Fried parameter r 0 was derived leading to values ranging...
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Solar and stellar externally occulted coronagraphs share similar concepts, but are actually very different because of geometric characteristics. Solar occulters were first developed with a simple geometric model of diffraction perpendicular to the occulter edges. We apply this mere approach to starshades, and introduce a simple shifted circular...
The design of starshades, i.e. external occulters for stellar coronography, relies on the fast and precise computation of their associated diffraction patterns of incoming plane waves in the telescope aperture plane. We present here a method based on a polygonal approximation of the occulter's shape, that allows fast computation of their...
We develop a self-consistent automatic procedure to restore informations from astronomical observations. It relies on both a new deconvolution algorithm called LBCA (Lower Bound Constraint Algorithm) and the use of the Wiener filter. In order to explore its scientific potential for strong and weak gravitational lensing, we process a CFHT image...
We develop a self-consistent automatic procedure to restore informations from astronomical observations. It relies on both a new deconvolution algorithm called LBCA (Lower Bound Constraint Algorithm) and the use of the Wiener filter. In order to explore its scientific potential for strong and weak gravitational lensing, we process a CFHT image...
The one dimensional point spread function for long exposure frames of the whole system atmosphere-instrument is deduced from solar limb observations using data recorded at Calern Observatory (France). It is then compared to the theoretical one deduced from the Von Karman model. Good agreement is found allowing to deduce the spatial coherence...