Method of measuring occluded features for high precision machine vision metrology

摘要

A method of measuring occluded features in machine vision metrology. The method allows for high precision measurement of features that are partially obscured by an extraneous object (e.g., an overlay grid of a flat panel display screen mask). The method first roughly locates the edge points of the feature to measure. In one embodiment, the rough edge location is performed by using morphology filters to delete the extraneous object (e.g., the grid) and then doing edge detection on the filtered image. Once the rough edge locations are determined, the method then returns to the original unaltered image and for each of the roughly located edge points does edge detection in a close neighborhood of the point in the original unaltered image. These refined edge points are then used to fit the feature for highly precise measurements.