| 摘要 |
PURPOSE:To output always a signal of a prescribed voltage by using two couples of elements as one set and arranging each element couple so that the irradiating direction of light is opposite to each other in the set in a photointerruptor detecting the intermission of the light irradiated from a light emitting element to a photodetector. CONSTITUTION:An output voltage V1 of the photodetector 22b of the element pair 22 and an output voltage V2 of the photodetector 23b of the element pair 23 are added by an adder circuit 28, and the result is outputted as an output voltage V3 of a set 25. Thus, the output voltage V3 of the set 25 is the sum of the output voltage V1 of the element pair 22 and the output voltage V2 of the element pair 23 simply. A current is fed to the light emitting elements 22a, 23a, 24a from a transistor (Tr), and the current value is controlled by a base current fed to the base of the Tr from an operational amplifier OP2 via a resistor R4. Thus, the amount of light emission of the light emitting elements 22a, 23a, 24a is controlled to a constant value at all times and control error due to the change in the light emitting amount is prevented. |
