Aperture Masking Imaging

Abstract

Aperture-mask interferometry has a long history in the speckle regime � in principle equalling the performance of speckle interferometry in the low-flux, zero read-noise regime and offering superior calibration in the bright regime. Since adaptive optics has become commonplace on large telescopes, the key advantage of aperture-mask interferometry is in calibration, particularly of low spatial-frequency phase aberrations that cause quasi-static speckles. I will describe the principles of quasi-static speckle limited imaging in the Fourier plane, where bispectral phase (or Kernel-phase ) and Fourier power are the primary observables, and will show that where Strehl ratios are low or moderate, a non-redundant aperture can offer superior imaging performance. Finally, I will demonstrate the applicability of aperture-masking imaging both to laser-guide star imaging of faint (K????14) star systems and bright transition disc stars (e.g. LkCa?15) surrounded by faint (1000:1 dynamic range) structures.