Optical distance measuring apparatus

摘要

An optical distance measuring apparatus is disclosed which is operable in accordance with a phase difference detecting process wherein a processing system including a central processing unit and a digital type mix-down circuit detects and calculates a phase difference between the electrical phase of a signal output from a light receiving portion in response to receipt of a reflected light beam and the electrical phase of a reference signal output from a reference oscillator so as to determine a distance between the apparatus and a object spaced at a distance to be measured with reference to the electrical phase of a local oscillation signal output from a local oscillator. A second circuit system of the processing system on the light receiving side includes a ladder resistance type attenuation circuit, a multiplexer, an veriable gain current amplifier, a wave shape correcting circuit and a signal amplitude detecting circuit. When the signal amplitude detecting circuit detects that the signal derived from the reflected light beam has an amplitude in excess of a predetermined value, the central processing unit controls the multiplexer so as to reduce a magnitude of the amplitude. In addition, an optical distance measuring apparatus operable in accordance with a time difference detecting process is disclosed.