Point-spread-function computation: quasi-digital method

Abstract

Starting with an expansion of a pupil function into azimuthal Fourier harmonics, a general formula that represents the point-spread function as a weighted sum of successive Hankel transforms is derived. The corresponding transforms can rapidly be computed by using the quasi-fast Hankel transform algorithm. The method appears to be far more useful than purely digital two-dimensional fast-Fourier-transform techniques, especially for symmetrical systems.