Shaped and apodized apertures for direct imaging of extra solar planets

Abstract

In this communication, we analyze the possibility of detectingexoplanets using shaped and apodized apertures alone (withoutcoronagraphy) for the case of a perfect telescope operated inspace. In a first section, after a brief introduction to thetheory of diffraction and the determination of several usefulparameters, we show that the effects of shaped and apodizedaperture can be presented in an unified manner, making use of theRadon transform of the aperture of the telescope. This permits asimple comparison of the techniques of apodization and apertureshaping between them. An illustration of this approach is madefor a few apertures. In a second section, we introduce thesemi-classical theory of photodetection. Using simplificativeassumptions, we derive signal-to-noise ratio (SNR) expressions anddraw the corresponding curves for an experiment using a circulartelescope apodized by a prolate spheroidal function. We found thatfor given condition there is an apodization that can optimize theSNR. This apodization is generally a very strong one.