| 摘要 |
PURPOSE:To enable the inspection is the state that the influence of variations in the entire density is removed by calculating the difference between a detected signal and a reference signal, and further calculating the difference between a signal obtained from the previous difference and a delay signal of the same signal, and comparing it with a reference value, thereby detecting the presence or absence of a printing defect. CONSTITUTION:After an inspection signal SIS from a detector 3 is converted to a digital signal through an A/D converter 15, the signal is stored in a reference memory 17. On the other hand, a digitized inspection signal SIS is transferred directly to the first difference circuit 16. In this case, a reference signal SSS is read out, and transferred to the circuit 16, thereby obtaining a difference inspection signal DIS. The signal DIS is branched into three, one of which is fed through a delay circuit 19 to a difference circuit 18, another of which is fed directly to the circuit 18, and the other of which is transferred to a discriminator 22. A CPU14 operates as means of an alarm or a marking reject when an abnormal signal IRS is fed from a threshold circuit 20 or the discriminator 22. An inspection is performed by such a processor in the state that the influence of the variation in the entire density is alleviated. |
