Patent ID: 6930772

Claim:
A flaw detection system for detecting a flaw accompanied with an optical defect if any on or in a sheet-like transparent body which is moved, comprising: a linearly extended (one-dimensional) image pickup means placed on one side of the sheet-like transparent body: an illuminating means placed on the opposite side of the sheet-like transparent body, the illuminating means comprising a lighting portion and a darkening portion, the lighting and darkening portions of the illuminating means being constituted respectively with a light source, a first light shielding plate which is placed between the light source and sheet-like transparent body to shield part of the light source such that an image of the edge of the first light shielding plate forms a visual field of the image pickup means, and a second light shielding plate is placed between the illuminating means and sheet-like transparent body so as to intercept scattered light which is a background light, out of light from the light source to thereby reduce light diffusely reflected by a flaw; and an image processing means in which two-dimensional image data are created from one-dimensional output from the image pickup means, the image data are subjected to three value based contrast enhancement to convert said data into contrast enhanced image data which are then utilized to display a contrast enhanced image, the sequential pattern (flaw pattern) of light spots and dark spots is traced which appears in the contrast enhanced image with movement of the sheet-like transparent body.