Abstract

A rotation-invariant single circular harmonic filter does not in general yield a maximum center autocorrelation peak. A new method for predicting the level and position of the center correlation and of sidelobes as a function of the expansion center of the circular harmonic filter was recently developed.¹ The proper expansion center that ensures the maximum peak correlation can be easily found by this method. The position of the correlation peak corresponds to the expansion center for the maximum energy of the circular harmonic component. The positions of the correlation peaks of different circular harmonic filters constitute a feature pattern of the object that can be used for rotation-invariant detection of the object against sidelobes yielded by noisy background and parasite objects in a complex scene. The discrimination ability is much improved by the use of multiple circular harmonic components. Only intensity thresholding, clustering, and matching of the simple point patterns are needed for the output of the filters. The procedure is faster and easier than the other methods.

© 1987 Optical Society of America