| 摘要 |
PURPOSE:To detect a defect of printed matter on which the same patterns are printed periodically such as scattering of ink and dust during printing by detecting one pattern and a pattern conveyed next by one sensor head. CONSTITUTION:The printed matter on which the same patterns N1, N2, N3... are printed is conveyed by a driving machine at intervals of one pattern. Then, the single optical sensor head is put opposite the patterns and its output voltage is inputted to an arithmetic processor. At this time, a pulse from a pulse generator is applied to the driving machine to drive the printed matter so that one cylinder corresponds to one turn. An output voltage corresponding to the pattern N1 and an output voltage corresponding to the next pattern N2 are detected and the difference between the output voltages is digitized. This difference is patterned corresponding to the patterns which are sent periodically to correct detection characteristics, thereby detecting a defect of the printed matter. Thus, respective output voltages of the same patterns are detected to calculate their differences, so defects of the printed matter are detected automatically and precisely through the inexpensive device constitution. |
