| 摘要 |
PURPOSE:To make a titled converter hardly susceptible to a change in temp. by disposing a shutter displacing according to physical quantity between a light emission part and a photodetection part, controlling periodically the transmission quantities of light in the two regions of the shutter reverse from each other and obtaining the ratio of the sum and difference of the outputs from the photodetection part. CONSTITUTION:The regions 16, 17 of a shutter 15 of a liquid crystal cell are periodically controlled reverse from each other by a switch 24. The outputs of a photodetection part 12 are supplied through an amplifier 26 to smoothing circuits 28, 29 after the outputs are selected with a switch 27 operating in synchronization with the switch 24. Since the photodetection areas of the region 16 and region 17 changes reverse from each other with a displacement (x), the outputs V1, V2 of the circuits 28, 29 are V1= kQL1(l-x), V2=kQL1(l-x), wherein (k) is the photoelectric conversion efficiency of the part 12, and Q is the quantity of light of a light emission part 11. V1, V2 are supplied to a differential amplifier 35 and are added to each other. A power source 14 is controlled by the differential output from a reference voltage Vs so that the difference between said outputs is made zero. The output V0 of a differential amplifier 37 is V0= V2-V1=Vs.x/l and is hardly affected by the fluctuation in temp. or the like. |
