| 摘要 |
PURPOSE:To enable the detection of foreign matters being distinguished from a specified pattern by extracting defect candidate points sequentially with a raster scanning of the inside of an inspection area to compare counts of continuous defect condidate points with a reference value. CONSTITUTION:A diferentiation image f2, a differentiation-way code image f3 and an edge image f4 are obtained from an original image f1 subjected to an A/D conversion 2 by a preprocessing 3. An average differentiation value L within an inspection area M is determined on the image f2 and compared with a specified pattern of an inscription character or the like and thresholds S1 and S2 for detecting foreign matters to judge the present of the inscription character and a foreign matter. When the presence of the inscription character or the foreign matter can not be judged with S1<L<S2, a raster scanning of the inside of an area is performed on the image f4 and a differentiation value of an edge flag searched is compared with a threshold to determine a defect candidate point. Then, the edge flag near the defect candidate point is detected to determine adjacent defect candidate points sequentially. Thus, counts B of continuous defect candidate points are compared with an adjacent defect candidate point threshold S4 and when B>S4, a foreign matter is determined to exist within the area M. |
