Research Note

APIC

Absolute Position Interfero-Coronagraph for direct exoplanet detection

¹ ESO, European Organization for Astronomical Research in the Southern Hemisphere, Karl-Schwarzschild Strasse 2, 85748 Garching bei Mnchen, Germany e-mail: fatme.allouche@eso.org
² Laboratoire H. Fizeau, Université de Nice Sophia-Antipolis, CNRS UMR 6526, Parc Valrose, 06108 Nice Cedex 2, France

Received: 27 October 2008
Accepted: 13 March 2009

Abstract

Context. For detecting and directly imaging exoplanets, coronagraphic methods are mandatory when the intensity ratio between a star and its orbiting planet can be as large as 10⁶. In 1996, a concept of an achromatic interfero-coronagraph (AIC) was presented for detecting very faint stellar companions, such as exoplanets.

Aims. We present a modified version of the AIC not only permitting these faint companions to be detected but also their relative position to be determined with respect to the parent star, a problem that was not solved in the original design of the AIC.

Methods. In our modified design, two cylindrical lens doublets were used to remove the 180° ambiguity introduced by the AIC's original design.

Results. Our theoretical study and the numerical computations show that the axis of symmetry is destroyed when one of the cylindrical doublets is rotated around the optical axis.