Patent ID: 8508720
Filing Date: 2013-08-13
Classification: G01C,G01S

Abstract:
1. A rangefinding system comprising: a light-emitting device for emitting pulsed light toward an object; a light-detecting device for detecting reflected light from the pulsed light, and producing an output signal depending on the energy of reflected light that is detected; a control device for controlling the light-emitting device and the light-detecting device; and an arithmetic device for calculating a distance up to the object according to a time-of-flight process using the output signal from the light-detecting device; the light-detecting device further comprising: a photodetector for detecting the reflected light and generating photoelectrons by the detected reflected light; first through fourth capacitors for storing the photoelectrons from the photodetector; a photoelectron discharger for discharging the photoelectrons from the photodetector; first through fourth gate electrodes disposed between the photodetector and the first through fourth capacitors, for allotting the photoelectrons with respect to the first through fourth capacitors in synchronism with emission of the pulsed light; and a fifth gate electrode disposed between the photodetector and the photoelectron discharger, for controlling supply of the photoelectrons from the photodetector and the photoelectron discharger; wherein, if it is assumed that a time at which the pulsed light starts to be emitted is referred to as time Teu, a time at which the pulsed light stops being emitted is referred to as time Ted, a time at which the reflected light stops being exposed to the photodetector is referred to as time Trd, respective times at which the first through fourth gate electrodes are opened are referred to as times Tg respective times at which the first through fourth gate electrodes are closed are referred to as times Tg a period from the time Tg a period from the time Tg a period from the time Tg a period from the time Tg a period from the time Tg a photoelectron quantity stored in the first capacitor during the period P a photoelectron quantity stored in the second capacitor during the period P a photoelectron quantity stored in the third capacitor during the period P a photoelectron quantity stored in the fourth capacitor during the period P a period during which the pulsed light is emitted, reflected by the object, and returned as the reflected light is referred to as round trip time ΔP, and a distance between the rangefinding system and the object is referred to as distance D, then the control device controls emission of the pulsed light from the light-emitting device and opening and closing of the first through fourth gate electrodes so as to satisfy the following relationships: (1) P (2) P (3) Tg the control device opens the fifth gate electrode to discharge the photoelectrons when all of the first through fourth gate electrodes are closed; the arithmetic device acquires light energy information of the reflected light during the period P the arithmetic device acquires light energy information of the reflected light during the period Psr based on the difference between the photoelectron quantity Q the arithmetic device calculates the round trip time ΔP based on a ratio of the light energy information of the reflected light during the period P the arithmetic device measures the distance D based on the round trip time ΔP.