FOURIER-DOMAIN-BASED ANGULAR-CORRELATION FOR QUASI-PERIODIC PATTERN-RECOGNITION - APPLICATIONS TO WEB INSPECTION

A Fourier-domain-based recognition technique is proposed for periodic and quasiperiodic pattern recognition. It is based on the angular corr elation of the moduli of the sample and the reference Fourier spectra centered at the maximum central point. As in other correlation techniq ues, recognition is achieved when a high correlation peak is obtained, and this result occurs when the two spectra coincide. The angular cor relation is a one-dimensional function of the rotation angle. The posi tion of the correlation peak indicates the rotation angle between two similar patterns in the original images. Some optimizations for the di screte calculation of the Fourier-domain-based angular correlation are also proposed. Some applications of this technique to web inspection tasks, such as pattern recognition and classification, damaged web eva luation, and detection of defects, are presented and discussed. (C) 19 96 Optical Society of America