Three Dimensional Profile Measurement System Based On Laser Trigonometry

Machine vision technology is a branch of artificial intelligence AI(Artificial Intelligence),it aims to replace human eyes to get scene information in the difficult places where human vision is hard to reach,and even to observe details which human eyes are difficult to identify.The basic process of reverse engineering such as 3D printing is sample-data-product,the point cloud data of the sample is obtained through the existing equipment,then the large-scale production of products is achieved,the production efficiency will be significantly improved,so obtaining point cloud data is the key link of the whole reverse engineering.In this dissertation,profile measurement is studied and explored in depth,based on the principle of laser triangulation,a 3D profile measurement system is designed and developed,and the contour scanning and contour reconstruction of the measured objects are completed.Three dimensional contour measurement system is based on the principle of laser triangulation.A single beam is sent out by the laser source and the surface of object is illuminated,the spot information of the object's surface is captured by CMOS(Complementary Metal Oxide Semiconductor)camera,then the image data is readied by computer through the Gigabit network card,finally the contour information is obtained after the upper computer software processing.The whole measurement system consists of the upper computer,the contour scanning platform and the contour scanning controller;the computer realizes the signal control of CMOS camera,the laser source,the rotating platform and other devices on the scanning platform through the contour scanning controller,the measured object placed on the rotating platform rotates with rotating platform,at the same time the camera is triggered regularly to collect image until 360 degree contour scan finished,through image processing and point cloud coordinates calculation by computer,at the lase the point cloud data of the experimental object is obtained,the reconstruction of the 3D contour is realized.In this dissertation,the hardware platform of the 3D profile measurement system is constructed,based on the Keil C51 development platform the source program of the contour scanning controller is written,and based on LabView platform the upper computer software for 3D profilometry is developed;the cause and model of the lens distortion is analyzed and the Zhang's checkerboard calibration method is used to solvethe internal,external parameters and the distortion coefficient of the camera;the calibration of system parameters is finished by displacement platform;when extracting the center of the laser line,the effect of noise and light slope on the extraction precision is considered,and an improvement method based on the extremum method is proposed;the algorithm of point cloud simplification is explored,a method of combining the bounding box method with the boundary extraction and the feature point reservation is proposed,which reduces the amount of point cloud data and keeps the details of the model;a multi group model is used to do the contour measurement experiment,the experimental results show that the system can achieve the automatic acquisition of the object's 3D contour data and model reconstruction,the reconstruction effect is lifelike,and the single point measurement error is within ±0.5mm.