| 摘要 |
PURPOSE:To accurately detect an object to a wide range of quantity of light, by using a high-pass filter for cutting a signal with frequency of 50Hz or less and a DC discriminator circuit in a photosensor. CONSTITUTION:A light emitting diode 2 is driven at certain frequency by the oscillation signal of an oscillator 1. This frequency is set to 1kHz-10kHz in order to enhance noise resistance. The light from the light emitting diode 2 is reflected by a wafer 3 to reach a phototransistor 4 and, on the basis of the signal thereof, a high-pass filter 5 removes power source frequency noise of about 50Hz from DC and a light signal with frequency (f) due to the light emitting diode 2 is taken out. After the signal of the filter 5 is amplified by an amplifier 6, an AC signal is converted to a DC signal by a DC discriminator circuit 7 while said DC signal is inputted to a slice circuit 8 and sliced at a slice level determined by a summation tone resistor 9 to output a pulse signal to an output terminal 10. |
