| 摘要 |
PURPOSE:To discriminate the contamination on leaves of paper with good reproducibility even if the conveying speed thereof fluctuates by changing the time for starting and ending integration according to the conveying speed of the leaves of paper. CONSTITUTION:The output signal of a photodetector 4 is inputted via an amplifier 11, an integrating circuit 12, etc. to an arithmetic processing and discriminating part 14. The reference level for the quantity of the light reflected from the leaves of paper, i.e., the reference level for discriminating the contamination is stored in a ROM 15 connected to the discriminating part 14. The conveying speed detected by a conveying detector 2 is inputted to an integrating gate signal generating circuit 16, which detects the front end of the leaves of paper by the output signal from the amplifier 11, generates the gate signal for starting and ending the integration on the basis of the detected front end and feeds the signal to the circuit 12. The circuit 16 changes the generation timing of the gate signal according to the conveying speed detected by the detector 2, thereby changing the time for starting and ending the integration of the circuit 12. The discriminating part 14 adds the correction by the conveying speed detected by the detector 12 to the output of an A/D converter 13, and compares the corrected value thereof and the reference level of the ROM 15 to discriminate the contamination on the leaves of paper and therefore, the discrimination is not affected by the fluctuation of the conveying speed even if said speed fluctuates. |
