Stabilized range finder for use with an electronically controlled camera

Abstract

A range finding device having a plurality of LEDs for projecting toward a scene to be photographed a plurality of spot beams of light disposed in a horizontal line, and a PSD for receiving light reflected from the object. Two channel signals from the PSD are amplified by gain control amplifiers and converted into digital signals. The two channel digital signals are obtained for each LED, and the ratio between the two digital signals is used for calculating a distance datum. Of a plurality of distance data obtained for respective LEDs, an optimum one is selected. For the calculation of a distance datum, there is used a microcomputer which controls an image taking sequence. The gain of the gain control amplifier is automatically adjusted by the measured data obtained in accordance with pulsed light emitted during the initial period of driving the LED. Digital signals obtained prior to the light emission of the LED are used for calculating an offset correction value. Each LED emits a pulsed light beam at a predetermined interval. An average value of digital signals for the pulsed light beams is used for calculating a distance datum. Several pulsed light beams during the initial period are not used for range finding or gain control. If the gain of the gain control amplifier is not proper, the range finding is interrupted and a distance datum specific to the then-existing gain value is used.