JP2825601B

PURPOSE:To clean a printing roller effectively by inspecting printing defects certainly in good yield by a method wherein at least two items among inspection items for the number of total dots corresponding to pixels of a binary coded signal printing part, the number of group binding components, and the number of dots corresponding to pixels of a printing part of each block enclosing the printing part are compared with standard ranges, and a cleaning mechanism part is controlled by driving by a printing defect detecting signal. CONSTITUTION:A number of total dots inside a window W1 corresponding to pixels of a printing part detected from a binary coded signal read at detection synchronous signal timing from a binary coded frame memory 14, the number of bonding components, and the number of dots corresponding to pixels of a printing part of each divided block inside an inspection mask W2 are compared with three kinds of standard widths established with a standard width establishing part. When any one of inspected results of those three kinds of printing defects is outside the standard, a defect detecting signal is outputted. When a generating rate of this defect detecting signal becomes not less than the established value, a cleaning mechanism part K is operated.