Methods and apparatus for machine vision template matching of images

Abstract

A machine vision apparatus of the type having a match-scoring functionality for generating a metric as a function, e.g., a correlation, of applied image signals features an improvement for estimating a location of a template in a candidate image. The improvement is characterized by a segment peak finding element that applies to the match-scoring element a plurality of pairs of image signals along a 'segment.' Each such pair includes a signal representing the template and a signal representing a respective portion of the candidate image taken along a first axis. Thus, ignoring their template components, plural pairs of signals can represent successive adjacent portions of the candidate image that are 'in line' along a first axis. Functionality within the segment peak finder determines a peak value of the metric generated by the match-scoring element in response to application of the pairs within the segment. A hill climbing element invokes the segment peak finder means to determine an image peak from among a plurality of segment peaks. To this end, the hill climber invokes the segment peak finder, e.g., with successive adjacent segments along the y-axis, where each segment itself is oriented, e.g., along the x-axis. The hill climber determines the image peak directly from the segment peaks, or by interpolation or extrapolation therefrom. The location of the template within the candidate image is, itself, determined from the position of the image peak.