| 摘要 |
PROBLEM TO BE SOLVED: To perform a precise judgment in a short time by extracting a specified part from the contrast of image data, extracting a defect candidate from coordinate data and density data, and cutting and extending the defect candidate and the periphery to judge the quality. SOLUTION: A computer 4 stores the output of a CCD line sensor 3 as two-dimensional contrast image in a memory element 5. An arithmetic element 9 compares each picture element of the contrast image with an adjacent picture image density to determine the peak point, calculate the sum of density of 10×10 picture elements around it and stores the result as compression data in a memory element 6. The hole of defect candidate of a shadow mask 1 is extracted according to the program of a memory element 7, and it and the periphery thereof are cut, pseudo enlarged, and stored in a memory element 8. This image data is binarized to detect the transmitted part (cluster) of light, and when two or more clusters are present in one hole, adhesion of a foreign matter to the hole is judged. The circularity of the hole is then determined and compared with a prescribed threshold, and the shadow mask 1 is judged as non-defective when the circularity is large and as defective when it is small.
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