Asymmetries in the diffraction pattern of an asymmetrical aperture

The two-dimensional diffraction pattern of a line aperture can exhibit certain asymmetries when the aperture excitation is asymmetric. The four lowest moments of the aperture distribution are responsible for the distortion near the focus. When the coordinate system is chosen so that the first moment is zero, the third central moment plays the dominant role. By coupling the angle and range coordinates, image artifacts, including shape distortion, can result.