EDGE EXTRACTING METHOD BY EXTERNAL APPEARANCE INSPECTION

摘要

PURPOSE:To accurately extract an edge of a check subject with no influence of a defective part by setting a pair of deciding picture element trains which are apart back and forth from a stick mask by plural picture elements and approximately in parallel with the stick mask and deciding a case where a prescribed value relation is satisfied between the density and the threshold value set for each deciding picture element train. CONSTITUTION:A stick mask M having a similar shape to the edge of a check subject O is moved. When the density of the picture elements set before and after the moving direction of the mask M satisfy the prescribed conditions, it is decided whether the mask M is identical with the edge of the subject O or not based on the density of said picture elements. Thus the edge of the subject O is extracted with high accuracy as compared with a case where the edge is extracted after binarizing the density. In particular, the influence of the defective parts around the edge can be eliminated. Thus the edge of the subject O can be accurately decided.