POSITION DETECTOR USING REFLECTIVE PHOTOSENSOR

PROBLEM TO BE SOLVED: To achieve detection of a specific position like an origin position with a simple configuration at a low cost.SOLUTION: At, for example, each of both end parts of a reflecting plate 10 having reflecting surfaces sa and non-reflecting surfaces sb alternately arranged in a movement direction of a moving object, a wide reflecting surface Twider than the reflecting surface (or the non-reflecting surface) in the movement direction is provided as a peculiar pattern where an alternation pattern is peculiarly varied. A photodetector 14 of a reflective photosensor 12 is provided with three light receiving parts 14a to 14c having light receiving areas different in a movement direction of the reflecting plate 10, so that outputs signals A to C different in phase difference can be obtained from the three light receiving parts 14a to 14c. A movement position of the reflecting plate 10 is detected by outputs A and B having a 90° phase difference, and a midpoint potential is calculated from outputs A and C having a 180° phase difference, and an end position of the reflecting plate 10 (for example, a start point and an end point of a lens barrel) is detected by the wide reflecting surfaces T.