Patent ID: 7352901
Filing Date: 2008-04-01
Classification: G06T

Abstract:
1. A method of inspecting a contour of a target object, said method comprising the steps of: preparing a variable-density image of said contour; extracting edge pixels along and from said contour on said image; measuring directions of said edge pixels, the direction of each of said edge pixels being defined as a direction that makes a specified angle with the direction of the density gradient on said variable-density image at, said each pixel; selecting said edge pixels sequentially one edge pixel at a time and comparing the direction of said one edge pixel with the direction of another of said edge pixels at a specified distance from said one edge pixel to obtain a comparison result; determining presence or absence of a defect in said contour from the comparison results obtained for said edge pixels; and obtaining an edge code Ec(x,y) for each of said edge pixels as follows: where (x,y) is the coordinate of said each edge pixel, and Ex(x,y) and Ey(x,y) are respectively the x-component and the y-component of the density gradient at position (x,y); and wherein the step of comparing the direction comprises the step of comparing the edge code of said each edge pixel with the edge code of said another edge pixel.