| 摘要 |
PROBLEM TO BE SOLVED: To satisfactorily process the unclear circumferential edge image of a low wafer by taking images of a plurality of edges, determining the approximate expression of the edge within the image or the coordinate in a prescribed point on the approximate expression by image processing, and expressing the wafer circumferential part by a numerical expression. SOLUTION: An image processing means 106 has a binarized level setting means, a profile tracking means or the like. The average luminance within a threshold determining area is calculated by the binarized level setting means. The value obtained by multiplying the average luminance by a constant is taken as the initial threshold. In the profile tracking means, the edge detecting area is scanned from the upper right to the left by use of the initial threshold. When a continuation of black picture elements is present after the continuation of a regulated number or more of while picture elements, the boundary between the initial white picture element and black picture element is taken as one point on the edge. In a straight line calculating means, linear expression calculation and abnormal data removing processing are performed. The processing is repeated until conversion is attained. Since the binarized level is regulated to determine the final approximate expression while judging the quality of the approximate expression calculated by the picture element recognized as the edge, the edge can be satisfactorily enciphered. |
