Pupil phase apodization for imaging of faint companions in prescribed regions

Abstract

We consider the ‘faint companion’ problem where substantial reduction of diffraction sidelobes is required in order to image a faint neighbour near a much brighter source. In addition to well-known pupil amplitude and shape apodization methods, we found that the required sidelobe reduction can be obtained by appropriate spatial phase modulations over an aperture. Here, our previous results on one-sided phase apodization in astronomical applications are extended in several ways. Specifically, (i) round and square pupil cases are examined via a simple computational approach based on Fourier iterations; (ii) finite target regions are considered in the image plane; (iii) the discrete (square pupil) phase functions are used to construct a segmented mirror. The mirror provides sidelobe reduction sufficient for imaging of extrasolar planets.