DEFECTIVE PORTION DETECTOR AND DEFECTIVE PORTION DETECTING METHOD FOR INSPECTED OBJECT HAVING PERIODIC PATTERN

PROBLEM TO BE SOLVED: To provide a defective portion detecting method and detector capable of detecting accurately a fault portion to detect a bright fault as the bright fault and a dark fault as the dark fault, without detecting an end part of the pattern as a defect, in an inspected object having a periodic pattern, and requiring no reference image of the periodic pattern of the normal inspected object to be stored preliminarily. SOLUTION: In this defective portion detecting method of the present invention for the inspected object having the periodic pattern, a relative position between the inspected object and a line sensor camera for imaging it is linearly moved at a fixed speed to image the inspected object continuously by the line sensor camera. A difference between an intensity of an image signal in each time point and an intensity of the image signal after one period is calculated as the first differential signal, and a difference between the intensity of the image signal in the each time point and an intensity of the image signal before one period is calculated as the second differential signal, in a periodic change in the intensity of the picked-up image signal. The first differential signal is compared with the second differential signal in the each time point, and the signal having a lower absolute value is adopted as a defect image signal from the inspected object. COPYRIGHT: (C)2006,JPO&NCIPI