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Comptes Rendus Physique
Volume 8, n° 3-4
pages 349-354 (avril 2007)
Doi : 10.1016/j.crhy.2007.04.004
Speckle noise reduction techniques for high-dynamic range imaging
Techniques de réduction du bruit de tavelures pour lʼimagerie à haute dynamique
 

Pascal Bordé a, , Wesley Traub b
a Institut dʼastrophysique spatiale (IAS), bâtiment 121, université Paris-sud 11 and CNRS (UMR 8617), 91405 Orsay cedex, France 
b Jet Propulsion Laboratory (JPL), MS 301-451, 4800 Oak Grove Drive, Pasadena, CA 91109, USA 

Corresponding author.
Abstract

High-dynamic range imaging from space in the visible light range, aiming, in particular, at the detection of terrestrial exoplanets, necessitates not only the use of a coronagraph, but also of adaptive optics to correct optical defects in real time. Indeed, these defects scatter light and give birth to speckles in the image plane. Speckles can be cancelled by driving a deformable mirror to measure and compensate wavefront aberrations. In a first approach, targeted speckle nulling , speckles are cancelled iteratively by starting with the brightest ones. This first method has demonstrated a contrast better than 109 in laboratory. In a second approach, zonal speckle nulling , the total energy of speckles is minimized in a given zone of the image plane. This second method has the advantage of tackling simultaneously all speckles from the targeted zone, but it still needs better experimental demonstration. To cite this article: P. Bordé, W. Traub, C. R. Physique 8 (2007).

The full text of this article is available in PDF format.
Résumé

Lʼimagerie à haute dynamique dans le visible et depuis lʼespace, visant en particulier à la détection dʼexoplanètes telluriques, nécessite non seulement lʼutilisation dʼun coronographe, mais aussi dʼune optique adaptative pour corriger les défauts optiques en temps réel. En effet, ces défauts diffusent la lumière et donnent naissance à des tavelures dans le plan image. Les tavelures peuvent être supprimées en pilotant un miroir déformable pour mesurer, puis compenser les aberrations du front dʼonde. Dans une première approche, la suppression ciblée de tavelures , les tavelures sont supprimées itérativement en commençant par les plus brillantes. Cette première méthode a permis dʼatteindre un contraste de 109 en laboratoire. Dans une deuxième approche, la suppression zonale de tavelures , lʼénergie totale du champ de tavelures est minimisée dans une certaine zone du plan image. Cette seconde méthode a pour avantage de sʼattaquer simultanément à toutes les tavelures de la zone visée, mais elle doit encore faire ses preuves expérimentalement. Pour citer cet article : P. Bordé, W. Traub, C. R. Physique 8 (2007).

The full text of this article is available in PDF format.

Keywords : Exoplanets, Coronagraphy, Speckles

Mots-clés : Exoplanètes, Coronographie, Tavelures




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