Automatic optical inspection method of periodic patterns

Abstract

An automatic optical inspection method for periodic patterns includes defining regular control points in a periodic pattern, forming aligned images surrounded by the control points, obtaining a median image and a deviation image from the aligned images and defining upper- and lower-limit images to form an adaptive model, using the adaptive model to compare each point of all aligned images, defining the point of the aligned image having a gray-scale pixel greater than the upper-limit image or the smaller than the lower-limit image as a defect area. The optical inspection method is applicable for the defect detection of various periodic patterns and users simply need to manually select a first reference point to a fifth reference point from the control points and further select a rectangular range of one of the control points to create an edge image to detect a defect of the periodic pattern.

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