Method and apparatus for rangefinding

摘要

A multi-beam type rangefinding method and device uses three LEDs arranged along a line perpendicular to a base line, and a PSD for receiving light reflected from three measurement regions of a photographic scene. In the gain determining procedure, a selected LED emits light at least once. In the rangefinding procedure, it emits light a plurality of times. Light reflected from an object is received by the PSD which outputs two channel signals. The two channel signals are amplified by two gain control amplifiers which are adjusted to have the same gain. The gain is adjusted to be an optimum value for the two channel output signal levels. Upon changing the gain, light projection by a selected LED is stopped until the output of each gain control amplifier becomes stable. If one of the two channel output signals saturates during the rangefinding procedure, the light projection/measurement is repeated at the same gain after a lapse of predetermined delay time. If the number of times when the output signal saturates becomes a predetermined number during the rangefinding procedure, the rangefinding procedure is recommenced.