| 摘要 |
PURPOSE:To process a light receiving signal as it is a digital signal, by providing an oscillating circuit, which emits the lights impulsively, and a retriggerable monostable multivibrator which is triggered by the signal due to an AND circuit for AND between the light receiving signal and the light emission signal. CONSTITUTION:The output pulse signal from an oscillating circuit is inputted to an inverter N4 through a delay circuit consisting of resistances R7 and R8, a capacitor C2, and a diode D4, and the light reflected by a material P to be detected is received by a photodiode PD of a light receiving member and passes through an operational amplifier OP as a light receiving signal and is inputted to an NOR gate N6 after inversion of the H level and the L level. Both inputs have their delays cancelled, and no hazard is generated in the output of the NOR gate N6, and this output becomes a trigger input of a retriggerable monostable multivibrator N7. When the material P to be detected exists, this trigger input becomes retrigger inputs successively, and the output of the monostable multivibrator N7 becomes a continuous waveform. When the material P to be detected does not exist, the signal disappears after a delay of a time tl+n, and thus, the output state of the monostable multivibrator N7 is detected to discriminate whether the material P to be detected exists or not. |
