Direct imaging with a dense aperture masking in comparison with a telescope or a hypertelelescope

Abstract

Dense Aperture Masking (DAM) is a new interferometric technique allowing high-angular resolution over a narrow field of view (FOV) imaged by the present class of mono-pupil telescopes equipped with adaptive optics (AO). DAM is realized by a suited afocal double lenslet array (BIGRE), remapping the entrance aperture (telescope pupil) into coherent sub-apertures (sub-pupils), and adopted as sub-pupils spatial filter and re-imager.We focus our attention on the point spread function (PSF) properties of DAM, highlighting those related to spatial sampling and filtering of the frequency coverage of the entrance pupil.We stress why the high spatial frequency sampling of the pupil and the low spatial frequency filtering of the sub-pupils are consistent with both a mono-pupil (telescope) and an array of sub-pupils (hypertelescope). We explain how DAM provides high Strehl and high-angular resolution images, first by filtering the low frequencies, which in turn are not so well corrected with a standard AO, second by preserving an object-image convolution relation over a narrow FOV. Finally, we make a comparison with the imaging properties of a telescope and a hypertelescope with the aim to show the complementary of DAM with other techniques adopted in high-contrast imaging.