| 摘要 |
PURPOSE:To stabilize the reference level for the binary coding of a comparator regardless of the length of the period of no light signal by digitizing the output signal of an amplifier and storing it in two storage circuits according to the output level of said comparator, and converting their intermediate value into an analog value and thus generating the reference level. CONSTITUTION:When the output signal of a photodetector 1 which is amplified by the amplifier 3 is converted by the comparator 4 into a binary signal, the output signal of the amplifier 3 is digitized by an analog-digital converting circuit 6 and written in a 1st storage circuit 7 when the output of the comparator is at 'H' level or in a 2nd storage circuit 8 when the output of the comparator is at 'L' level, an arithmetic circuit 10 calculates the center value between the digital output values stored in the 1st and 2nd storage circuits 7 and 8, and the output value of the arithmetic circuit 10 is converted into an analog value through a digital-analog converting circuit 11 for analog conversion, so that the analog value is applied as the reference level to the comparator 4. Consequently, the reference level is stable even when the period of no light signal becomes long. |
