Importance

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Abstract

An image differential unit differentiates an inspection image and a reference image on an object to be inspected. An image division unit divides an image into a predetermined number of divisions. Pixel precision position alignment unit overlays the inspection image and the reference image by carrying out the position alignment in pixel precision which is a pixel size precision. Function fitting unit detects an edge, and obtains intensity profile of the absolute pixel value in the direction orthogonal with the edge, and fits a predetermined single peak function to it. Sub-pixel precision position displacement computing unit computes a difference of the corresponding edge positions as the sub-pixel precision position displacement. Adjusted differential image forming unit forms the adjusted differential image by rewriting the pixel value so that the intensity profile of the pixel value in the direction orthogonal with the edge should follow the single peak type function form on the corresponding two edges. An image comparison unit detects the defect of the object to be inspected by comparing the adjusted divisional differential image of the inspected image with the adjusted divisional differential image of the reference image based on the position displacement of the sub-pixel precision.

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First Claim