Key Technologies Of High Precision And Low Cost Galvanometer Scanning Laser 3D Vision System

Intelligent system is an important part of national science and technology development. Collecting 3D image information of environment with high precision is urgent needed in this area. Laser 3D Vision System is one of most effective technologies of collecting 3D image information of environment currently. It becomes an important mean of information collecting for intelligent system for its strong information acquisition ability, long working range and strong anti-jamming ability. However, in a practical application, laser 3D vision system is facing some problems such as difficult in technique, high price of device. Based on these, this paper has put forward a design scheme of high precision low cost galvanometer scanning laser 3D vision system. From key problems and technologies, developed a set of galvanometer scanning laser 3D vision system principle prototype. Imaging experiments showed that, overall performance of system has reached advanced level of domestic similar research. Main studies of this paper is as follows:(1) The overall structure of laser galvanometer scanning 3D vision system was designed. Adopted galvanometer scanning as imaging method, got the spatial position information of laser radiation by closed loop control, get targets echo signals by the high sensitivity characteristic of APD, measured distances of targets environment with high precision by time of flight method. Finally, fused position information and distance information of the targets area into the 3D image information. Derived theoretical formula of atmospheric transmittance and optical properties of targets. Estimated and choose laser pulse transmitter which meeting the requirement under condition of direct detection lidar range equation. Analyzed working principle of galvanometer and determined selection basis of galvanometer from perspective of key parameters. Choose unit APD as photoelectric detective means, analyzed working principles and characteristics of APD, selected APD which meets the requirements of the system according to key parameters.(2) Studied low cost laser two-dimensional galvanometer, scanning technology with high speed and high efficiency. Discussed and selected scanning track which is suitable for laser galvanometer scanning 3D vision system by analyzing scanning track of two-dimensional galvanometer, and simulated scanning track distortion,obtained effective correction method. Put correction algorithm into driving voltage input of two-dimensional galvanometer to measure scanning track correction results,obtained uniform space dot array. In order to get 360° full field scanning, calculated and selected turntable suitable for laser galvanometer scanning 3D vision system.(3) Designed and manufactured monostatic polarization isolated optical system.Designed and manufactured beams collimating expanding optical system with divergence angle less than 0.75 mrad and output beams diameter 4mm. Designed and manufactured polarization isolated photo switch, which transmittance of P light was more than 90%, reflectivity of S light was more than 90%, P light and S light was separated as 90 degree. Designed and manufactured four times beams expanding Galileo telescopic scanning system with ±10° scanning angle. Designed and manufactured APD optical system, the dispersion circle was 51μm, focal length was40 mm. Discussed and analyzed stray light problems, put forward solution methods.One method was using principle of polarization isolation to isolate the stray light from reflective surface of Galileo telescopic scanning system. Second method was isolating the stray light of quarter wave plate surface reflection by rotating fixed angle. Both of the two methods obtained better stray light isolation effect.(4) Studied key techniques of high precision time interval measurement time discrimination. Improved the ranging measurement precision of system from two aspects of time measurement and time discrimination. Choose time to digital converter to measure time interval. Compared the traditional analog time interval measurement techniques between the popular TDC time interval measurement techniques, choose delay-line interpolation method to improve measurement precision, calculated theoretical time measurement error of TDC according to the device parameters. Choose constant fraction discriminator as time discrimination method. based on the total measurement error and time measurement error of the system, determined the time discrimination error. Analyzed the time drifting of CFD and false alarm rate, obtained the corresponding threshold setting, determined threshold setting as 112 m V, and choose 4 channels CFD with the error of time discrimination less than 100 ps. Discussed and analyzed the problem of system time synchronization, determined laser trigger scheme which is more more precise.(5)Built laser galvanometer scanning 3D vision system for experiments.Including measurement of system farthest working range, calibration of system fixed time delay, calibration of laser ranging precision and system scanning imaging experiments. From the experimental results can get that, indicator of the high precision and low cost galvanometer scanning laser 3D vision system has reached the expected value, 100 m working range, 60 mm ranging precision, 10??10? large field of view which can be 360° full field scanning with turntable, and high resolution as 10k(high frame rate) to 100k(low frame rate). At the same time,application of mature galvanometer scanning technology made system achieve the target of miniaturization and low cost, which will be widely used.