JPH067052B

PURPOSE:To lead out a signal current which has distance information propor tional to the quantity of variation in the distance of a body to be measured by dividing the resistance layer on the surface of a position detector. CONSTITUTION:This position detector is constituted by providing an N layer 23 forming a common terminal on the reverse side of a silicon substrate 22, insulating and separating a rectangular P layer which becomes a photodetection surface of the top side, and arranging signal current lead-out terminals 12 and 13 on the P layers 15 and 16. Then, H(X)+W(X)+I=W and W(X)=ax/(x+b) hold at a position which is X away from the side of the photodetection surface on a light-source side. Wherein, W is the width of the position detector, I the length of the breadthwise separation layer, H(X) the breadthwise length of the photodetection surface on the light-source side, W(X) the breadthwise length of the photodetection surface on the other side, and (a) and (b) constants, which are so defined that a=Lf(W-I)/(Lf-Ln) and b=(f.B)/Lf (where Ln is the short- distance side distance measurement limit, Lf the long-distance side distance measurement limit, B the length of a base line, and (f) image formation length). The position of the body to be measured can be detected from those equations.