Fast Pattern Recognition Using Gradient-Descent Search in an Image Pyramid

A new technique for fast pattern recognition using normalized grey-scale correlation (NGC) is described. While NGC has traditionally been slow due to computational intensity issues, the introduction of both a pyramid structure and a local estimate of the correlation surjace gradient allows for recognition in 10-50 ms using modest microcomputer hardware. The algorithm is designed to analyze the target ofline prior to starting the search. Issues surrounding determining an appropriate depth for the pyramid representation and peiforming sub-pixel localization of the target instance are discussed. The speed and robustness of the method makes it attractive for industrial applications.