Abstract

A circular harmonic (CH) filter invariant to changes of position and orientation is described in polar coordinates (ß,ψ) as F_m(ß) exp(jmψ), where F_m(ß) is the Hankel transform of the CH functions of the object. For phase-only CH filters, the function exp(jmψ) ensures the rotation invariance, and the phase of F_m(ß) contains the object information. A circular disk on the Fourier plane covers the CH filter in those segments of ß where |F_m(ß)| is small. This can improve the SNR and the discrimination ability. Experimental studies on the effect of input noise, background, and binarization of the phase-only CH filters are presented.

© 1988 Optical Society of America