The effect of aberrations on bispectral imaging

Abstract

Bispectral imaging is one of the most promising methods for high angular resolution imaging through turbulence. On astronomical objects, crowded star fields with individual stars as faint as 16th magnitude have been imaged by Weigelt et al. with a 1.5 m telescope in a few minutes of observing time. One virtue of the technique is its claimed insensitivity to telescope aberrations. In this paper we present a computer study of the effects of aberrations (including de-focus) on the bispectral transfer function. Two major conclusions can be drawn: (i) as the seeing deteriorates, the bispectral transfer function becomes less sensitive to telescope aberrations, and (ii) the average phase of the bispectral transfer function is not exactly zero for a finite number of images, and its departure from zero (for a fixed number of images) increases as the aberration increases.