METHOD AND APPARATUS FOR DETECTING CUT IN PROFILE OF OBJECT

PROBLEM TO BE SOLVED: To detect a cut in the outer circumferential edge line of an object directly and reliably with no missing or overdetection by scanning on a line running slightly on the inside of outer circumferential edge line using a highly accurate displacement gauge thereby detecting irregularities on the scanning line. SOLUTION: At first, a specimen is shifted directly under an image processing camera by means of an X-Y table and the outer circumferential profile thereof is recognized through image processing. The outer circumferential edge line 1 is then shifted directly under a displacement gauge S by means of the X-Y table which operates to scan along a line, shifted by a micro amount (e) from the outer circumferential edge line, by means of the displacement gauge S and a measured displacement (h) is compared with an appropriate threshold displacement (a) thus detecting a cut in the outer circumferential edge line. Minimum dimensions of the cut depend on the combined accuracy of X-Y table and image processing camera and assuming the combined accuracy is ± (e) μm, a line shifted inward by (e) μm from the outer circumferential edge line is scanned by means of the displacement gauge S and a detection accuracy higher than 2e μm is ensured.