Positioning System Based On Four-quadrant Detector

Laser positioning technology is used to detect the target by the echo signal with the laser emitting laser signals to illuminate the target area.Due to high directivity,high monochromaticity and high concentration of energy of laser,Laser positioning technology can realize the positioning of the target by non-contact detection with high speed,so it can achieve the dynamic measurement,therefore Laser positioning technology is widely used in many diverse fields.In this paper,the laser positioning system is designed and implemented based on the four-quadrant detector,which is controlled by FPGA.The system controls the laser and emits the pulse laser signal to detect the target,and then locate the target by the echo signal.On the one hand,the target azimuth information is obtained by the light spot formed by the echo signal in the photosensitive surface of the detector.On the other hand,the target distance is obtained by the time of flight of the laser pulse.In this paper,the laser spot center positioning algorithm and the methods of laser pulse ranging are discussed and studied.First,by studying the four-quadrant detector structure and comparing the previous algorithms,a new laser spot position algorithm is proposed taking the advantage of the symmetry of the four-quadrant detector,it has high accuracy and reduces complexity of the algorithm obviously.Then,the echo signal processing circuit is designed and the principle laser pulse ranging is studied.TDC＿GP22 is used to measure the time of flight of the laser pulse,which can help figure out the distance of the target.At last,the feasibility verification has been carried out on the experimental platform of system.And experiments show that the spot position locating precision achieves 10^-4mm level at the center area of the detector and ranging precision is 20 cm,which indicates the effectiveness of the laser positioning system.