Method and system for detecting a flaw in a sample image

摘要

A method and system are described for use at a machine vision station to correctly identify flaws within a sample image by means of flexible template image comparison where the template image and a sample image suffer from a relative geometrical distortion. The method and system use the following iterative approach: 1) generate the template image; 2) register the sample image to the template image; 3) undertake an absolute image subtraction process; 4) identify all regions of image difference; 5) create sub-images of both the template and the sample images in the region of detected error; 6) repeat the registration step 2) using the sub-images; 7) undertake the absolute subtraction process on each of the sub-images; and 8) either identify the resulting differences as flaws or go to step 5) using even smaller sub-images. The invention has particular utility in the screen printing industry as well as other industries.