Feature point extraction method of image, defect inspection method, defect inspection apparatus

摘要

PROBLEM TO BE SOLVED: To provide an image feature point extraction method for capturing a grayscale image to be inspected as an input and obtaining the coordinate value of a (conspicuous) area having a visually clear feature in the image and an index value for clearness (degree of conspicuousness), and a defect inspection method and defect inspection device for determining the presence of a defect on the basis of the index value.SOLUTION: A total gradation value of one selected pixel and pixels in its periphery, n0 pixels in total, is calculated with respect to all pixels of a given grayscale image. Also, probability distribution of gradation values of all pixels present inside a sufficiently wide area including those pixels is calculated, and the sum of probability distribution in a total of gradation values of the n0 pixels is made an index of appearance probability of a pixel of interest. When this value is smaller than a designated threshold, a (conspicuous) pixel having a visually clear feature and its peripheral region are assumed.