Radar system detecting plural obstacles and measuring distance based on full gain and automatic gain control

A radar system for measuring a distance of an obstacle, comprising:

• a semiconductor laser diode emitting a semiconductor laser beam of pulse waveform;
• a light receiving element receiving said semiconductor laser beam reflected from said obstacle and generating a voltage signal corresponding to an intensity of said semiconductor laser beam received;
• a drive circuit actuating said semiconductor laser diode;
• a control circuit connected to said drive circuit for supplying said drive circuit with a drive signal to emit said semiconductor laser beam from said semiconductor laser diode;
• a variable gain amplifier receiving said voltage signal generated from said light receiving element and amplifying said voltage signal in response to a gain given by said control circuit;
• a comparator comparing an output of said variable gain amplifier with a reference value and generating a light receiving signal when an output of said variable gain amplifier exceeds said reference value;
• and
• a time interval measuring circuit receiving both said drive signal and said light receiving signal to measure a time interval between transmission of said drive signal and reception of said light receiving signal and sending said time interval as distance data to said control circuit,
• said control circuit calculating distance of the obstacle from said radar system based on said distance data, and
• wherein said control circuit controls a gain of said variable gain amplifier to have a standard sensitivity corresponding to a maximum value of said semiconductor laser beam receiving by said light receiving element during a first measuring period, and controls said gain of said variable gain amplifier to have its maximum sensitivity during a second measuring period.

An obstacle detecting method for a radar system having beamed energy transmission means for emitting a beam and beamed energy reception means for receiving said beam reflected from an obstacle, said radar system operating in measuring cycles, each measuring cycle comprising:

• a first controlling step of controlling a gain of said beamed energy reception means to have its maximum sensitivity;
• a first calculating step of calculating a first distance of said obstacle from said radar system based on a time interval between transmission of said beam from said beamed energy transmission means and reception of a reflected beam by said beamed energy reception means having said maximum sensitivity;
• a second controlling step of controlling said gain of said beamed energy reception means to have a standard sensitivity corresponding to a maximum value of said beam received by said beamed energy reception means;
• and
• a second calculating step of calculating a second distance of said obstacle from the radar system based on a time interval between transmission of said beam from said beamed energy transmission means and reception of a reflected beam by said beamed energy reception means having said stand sensitivity.