EAS Publications Series

Issue		EAS Publications Series Volume 12, 2004 Astronomy with High Contrast Imaging II
Page(s)		293 - 298
DOI		10.1051/eas:2004043

Astronomy with High Contrast Imaging II
C. Aime and R. Soummer (eds)
EAS Publications Series, 12 (2004) 293-298
DOI: 10.1051/eas:2004043

Principle of a coaxial Achromatic Interfero Coronagraph

J. Gay¹, F. Fressin¹ and J.-P. Rivet²

¹ Dept. Gemini, Observatoire de la Côte d'Azur, BP. 4229, 06304 Nice Cedex 4, France
² Dept. Cassiopée, Observatoire de la Côte d'Azur, BP. 4229, 06304 Nice Cedex 4, France

Abstract
We describe here the principle of a new type of coronagraph, based on the incident flux division with pupil reversal and phase shift on one beam, then recombination with destructive interferences at the center orf the field. This concept of nulling has already been used in the Interferometrical Achromatic Interfero-Coronagraph (AIC, Gay & Rabbia 1996), which lies on a Michelson interferometer interferomùetry which does not allow an easy insertion in the focal facility of a telescope. The variant under consideration has a completely coaxial design with an original and very compact optical combination. It is based upon two coaxial thick lenses in the same medium, stuck one to each other with a very narrow gap in between and a proper coating of the interfaces. The very geometry of the device ensures moreover the permanent and rigorous cophasing of the interferometer. The optical combination which fulfills this problem is unique and presents a range of properties which ease its insertion in the focal instrumentation of existing telescopes or next generation ones.

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