| 摘要 |
PROBLEM TO BE SOLVED: To enable updating an arbitrary reference image in accordance with factors which change with time, by updating the reference image at every spe cific frequency, on the basis of an inspected image which is judged to be not defective. SOLUTION: An image having no defects in printing is decomposed into picture elements and detected 1 by the line sensor of an area camera, and smoothed and stored in a memory bank (a), as a reference image picture 2. In eight picture elements around a picture element, the maximum value 3 and the minimum value 4 are stored in memory banks (b), (c), as reference values. As image to be inspected is taken in by the same method, and smoothed. A differential signal for one sheet is stored in a memory bank (d), as an inspected image 6. From the differential signal, differential signals of the maximum reference value 3 and the minimum reference value 4 are deducted, and values (values exceeding the upper limit or the lower limit) 7, 8 are obtained and stored in memory banks (e), (f). The values 7, 8 are binary-coded 9, 10 by a previously determined threshold value. By the logical add 11, whether defects exist is judged 12. By the inspected image 6 having no defects, the reference image 2 is updated at every specific frequency. |
