| 摘要 |
PURPOSE:To enable the accurate measurement of both a short distance and a long distance, by a method wherein a plurality of light-emitting elements provided in different positions in the direction perpendicular to the base line and the optical axis of a projected light are made to emit a light selectively so that lights for a short distance and a long distance be outputted selectively. CONSTITUTION:Infrared-ray-emitting LED 6 as a light-emitting element is provided with two light-emitting elements L1 and L2 having similar light-emitting intensities, in different positions in the direction perpendicular to a base line A. When a switch 8 is turned ON, infrared-ray pulses for measurement of a long distance are emitted from the light-emitting elements L1 and L2 by a light-emission circuit 7 according to an instruction of a microcomputer 11 and reflected by a subject 4, and electric currents I1 and I2 are outputted from PSD 5 as a photosensing element to an arithmetic processing circuit 8. Then, it is determined in this circuit whether the currents I, I1 and I2 are in a saturated state or not, and when they are in the saturated state, the light-emitting element L2 alone, as an element for measurement of a short distance, is made to emit a light by the circuit 7 according to a re-instruction. Then, a distance R to the subject is computed in the arithmetic processing circuit 8 on the basis of an output current from PSD 5 generated by these operations. When said currents are not is the saturated state, the light-emitting element L1 and L2, as elements for measurement of a long distance, are made to emit lights, and the same processings as stated above are executed.
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