摘要 |
PROBLEM TO BE SOLVED: To make inspectable surface defects of a flat object in a production process or the like by calculating a binarization threshold optimized for defect detection of a predetermined range by a binarization threshold operate means. SOLUTION: An image of the surface of a plastic card as an example of a flat object is picked up in an image pickup process of a step 1, thereby obtaining an image pickup signal. Next, the obtained image pickup signal is inputted to an A/D conversion means in an A/D conversion process in a step 2, and converted to digital data, whereby a pickup image is generated. The pickup image is differentiated by a differentiation means in a differentiation process of a step 3, whereby a differential image is generated. A binarization threshold is calculated for every predetermined area based on the image by a binarization operation means in a binarization threshold operation process of a step 4. The differential image of every predetermined area is formed into a binary image with the use of the binarization threshold for every predetermined area in a step 5. Whether the plastic card is good or not is judged on the basis of the binary images by a judgment means in a step 6. Whether the surface inspection is to be continued or terminated is judged in a step 7, and the step is returned to the step 1 when the surface inspection is to be continued, thereby repeating the processes. |