| 摘要 |
PURPOSE:To permit a wide range of light-signal differences on a sample to be reliably read by obtaining through given circuits the difference between the output of two photoelectric detectors in which the modulated light received is amplified by given circuits, and comparing the difference with a reference value to signal when the reference value is smaller. CONSTITUTION:In two photoelectric detectors Ph1, Ph2, a light-emitting element 1 actuated by a driving gear 2 scans a sheet X1, and the reflected light is detected by a photoactive element 3, and sent to an inverter 8 through an amplifier 4, detector 5, and differential amplifier 6. The output signals A and B of Ph1 and Ph2 are sent to a comparison arithmetic circuit U. A signal C which is the signal A having passed through a sensitivity regulator 9, the signal B, and a signal S from a setting 11 are sent to a substracter 10 to calculate (B-C)+S. The resultant signal D is compared with a signal F through a comparator 12 and a hysteresis setting 13 to send a binary signal to a relay 14. When B-C is larger than a reference level, a desired load is operated. Thus, a wide range of reflection differences on the sheet can be read. |
