High-resolution imaging using pupil segmentation

Abstract

Recentering and selecting short-exposure images result in significant improvements in spatial resolution compared with that for classical long-exposure images. A maximum gain in resolution of the order of 3 is possible for a D/r0 between 3 and 6, depending on the selection rates. A pupil-segmentation experiment has been performed at the Cassegrain focus of the Canada–France–Hawaii telescope to match the optimum values of D/r0. A photon-counting camera records short-exposure images. The software processing is made after acquisition of the data. Recentering is made by cross correlation of the short-exposure images with a long-exposure image of a star or a contrasted object. We present results obtained on the gravitational lens Q2237+030. A full width at half-maximum of 0.29 arcsec has been achieved with this method. The gain in resolution is approximately 2.3 compared with that for classical imaging. However, we need to count enough photons for reliable recentering; this prevents us from achieving the theoretical gain in resolution. We expect to overcome this limitation in the case of crowded fields or with the use of new object-reconstruction methods.