Patent ID: 6693703
Filing Date: 2004-02-17
Classification: G01C,G01S

Abstract:
In a distance measuring device for measuring the distance between said device and an object, which device comprises a first light source adapted to direct a first light beam toward said object for reflection therefrom, a photodetection unit adapted to receive a portion of said first light beam which is reflected from said object, said photodetection unit having means for applying a bias voltage thereto which determines the photodetection sensitivity thereof, said photodetection unit having an output electronic current proportional to the amount of light incident thereon and said bias voltage, means for alternately directing said first light beam directly toward said photodetector unit, and means for measuring the phase difference between said reflected portion and said directly directed beam so as to indicate said distance, the improvement comprisinga gain control unit adapted to change said bias voltage, a second light source adapted to direct a predetermined amount of light onto said photodetector unit, means for controlling said gain control unit in response to the amount of light reaching said photodetection unit from said second light source so as to set the bias voltage applied to said photodetection unit and thereby set said photodetection sensitivity so that said output electronic current reaches a reference value.