| 摘要 |
PURPOSE:To readily correct the fluctuation of detected signals by setting gains so that a voltage output from a sense amplifier comes to a prescribed value with the light emitting duty of a light emitting diode standing at a prescribed value, then adjusting the light emitting duty and controlling a voltage output from a phototransistor to a prescribed value. CONSTITUTION:Through the use of a display part 17, a gain setting part 13 sets the gains of the sense amplifier 7 so that the voltage output from the sense amplifier 7, which is triggered by light reflected from the surface of a sheet 1 when the light emitting duty of the light emitting diode 3 stands at the prescribed value, comes to the prescribed value. Hence onward, duty adjusting means 11 and 18 adjust the light emitting duty of the light emitting diode 3 so that the voltage output from the phototransistor 4, which is triggered by the light reflected from the surface of the sheet 1, comes to the prescribed value. Consequently, the light reflected from the surface of the sheet 2 can be detected to readily correct the fluctuation of output voltages. Moreover, printing density can be kept constant. |
