Phase-only circular harmonic matched filtering

The idea of a phase-only matched filter [J. L. Horner and P. D. Gianino, Appl. Opt. 23, 812-816 (1984)] is incorporated in the scheme of circular harmonic component matched filtering [Y. N. Hsu and H. H. Arsenault, Appl. Opt. 21, 4016-4019 (1982)]. Computer simulation showed that the phase-only circular harmonic matched filter possesses the rotational invariant property for 2-D recognition. Furthermore, it does a better job in recognizing closely placed targets compared with traditional circular harmonic filters. The simulation also demonstrated that a pure phase circular harmonic filter is less liable to give rise to false alarms in recognition because the sidelobe produced by it is much less pronounced and much less extensive than that produced by a traditional circular harmonic filter.