| 摘要 |
PURPOSE:To detect the number of revolutions with stability and high accuracy by regulating electric conductivity of a doping layer at the incident side of light of amorphous silicon optical electromotive force elements having pin junctions to <=10<-5>(OMEGAcm)<-1> and >=10<-10>(OMEGAcm)<-1>. CONSTITUTION:An encoder 13 is connected with a motor shaft 12 and rays of light from plural diodes 14 are reflected by a mirror 15 and irradiated on a photodetector 2 on an optical detecting plate 1 through a hole 16. Transparent electrodes 31 and 32 of the tops of photodetectors of two couples of optical detecting elements are arranged in a comb shape meshed with mutually on the plate 1. The photodetector is constituted of a hydrogenated amorphous silicon film (a-Si:H). At this time, first, a-Si:H layer 21 of P-type and a real a-Si:H layer 22 are laminated on a conductive base 10. Next, a-Si:H layer 23 film of N-type is formed so that the electric conductivity is made in a range of 10<-5>-10<-10>(OMEGAcm)<-1>. Then, a leakage current flowing between the transparent electrodes 31 and 32 via the doping layer is reduced and two couples of optical electromotive force elements are made in the insulated states and a difference between electrical signals generating by on and off of optical signals attaining these is clear and the number of revolutions can be detected with the improved stability and accuracy. |
