| 摘要 |
PURPOSE:To measure the distance to a subject efficiently by laminating plural PDS as light receiving elements in parallel to the axes of a projection lens and a photodetection lens and finding an angle of incidence from relative position shifts of incidence of the individual PSDs and layer thicknesses. CONSTITUTION:A beam L from an infrared-ray emitting diode LED is reflected by the subject 21 and the reflected beam S is made incident on a 1st PSD-1 as a photodetecting element at a point Q-1. The specific resistance value of the PSD-1 which varies owing to the incidence is inputted to a CPU, which finds the position of the point Q-1. The reflected light S passed through the PSD-1 is made incident on a PSD-2 at a point Q-1 and the position of the point Q-2 is calculated by the CPU from variation in its specific resistance value; and the phase difference between both the points is found, S1/d is calculated from it and the layer thickness (d) of the PSD-1, and the angle theta of incidence of the reflected beam S on a PSD is found from S1/d= tantheta. The angle theta of incidence is equal to the angles of the optical axes 30 and 10 of the photodetection lens and projection lens 11 and the reflected beam S and the distance Y between the projection lens 11 and subject 21 is found from an equation I based upon the distance between the optical axes 30 and 10 and base line length K. |
