| 摘要 |
PURPOSE:To detect the circumferential edge position of a plate-like body with high accuracy over a wide range at a low cost by using a photocurrent transducer having two electrodes for drawing of electric current at both terminals. CONSTITUTION:Electrodes (a), (b) for drawing out of electric current are disposed at both terminals of a photocurrent transducer 7 of pn junction type which is biased by a biasing power source 9 so that the sum of the electric currents generating at both electrodes (a), (b) is transmitted as an output signal (e). The output signal (e) is amplified with a current amplifying circuit 8 and is transmitted as the output voltage (e). Here the circuit 8 can be constituted most simply of one operational amplifier. A light source 5 located above said transducer 7 irradiates light of uniform illuminance onto the surface of the transducer 7. At this time, a plate-like body 6 is occupied between the transducer 7 and the light source 5. |
