| 摘要 |
PURPOSE:To make exacter long distance measurement by providing a 1st light emitting means of short distance measurement and the 2nd light emitting means for long distance measurement having the emission intensity larger than the emission intensity of the 1st light emitting means and switching the 1st and 2nd light emitting means. CONSTITUTION:A microcomputer 11 outputs a light emission command to a light emitting circuit 9 and IR light pulses for short distance measurement are emitted from an LED 3. The projected IR light pulses are reflected from an object, pass a light receiving lens 2 and are received in a position sensitive device PSD 5 which outputs current I1 and I2 to an arithmetic circuit 10. The arithmetic circuit 10 drives a lens actuator 13 to focus the lens by computing the object distance from the spot light position on the PSD 5 if the current I1, I2 are above the prescribed values. A driving circuit 7 is commanded by the microcomputer 11 to emit the IR light pulses for long distance measurement when the outputs of the PSD 5 are below the prescribed values. The device which can make the sure long distance measurement is obtd. by constituting the device in such a manner. |
