Research And Application Of 3D Measurement System Based On Multi-line Structured Light

With the development of science and technology,the requirement of the three-dimensional measurement accuracy of the object is getting higher and higher,prompting the rapid development of three-dimensional measurement technology.Structured light method is one of the three-dimensional measurement techniques.It has the advantages of fast velocity,high precision,non-contact,and so on,which has become one of the hot spots in the field of measurement.At home and abroad,line-structured light three-dimensional measurement is conducted with a wide range of research,and has made a wealth of research results.But the camera calibration and the extraction of light bar center both should to be further studied and discussed in depth.In the camera calibration,camera distortion problems have not been effectively resolved.In the light extraction,the traditional laser center line extraction methods are susceptible to noise,and the accuracy is not high,which are more suitable for low-precision occasions.This paper proposes a three-line structured light method for three-dimensional measurement system.First of all,the importance of camera distortion to camera calibration was studied.and then the center for multi-line structured light strip was extracted.Finally,the experimental platform of 3D measurement system is set up,the 3D measurement experiment is carried out,and the experimental data is analyzed and verified.The experimental results show that the three-dimensional measurement system based on multi-line structured light can effectively improve the measurement accuracy.The main work of the dissertation is as follows:Firstly,capture the distorted light bar with the camera and then calibrate the camera.In this paper,a modified Zhang Zhengyou camera calibration method is proposed,which uses BP neural network method to improve the calibration accuracy.Secondly,a sub-pixel-level extraction method of three-line structured light strip center is proposed,which is integrated by the adaptive median filtering method,threshold segmentation method,mean square gray gradient method and weighted gray center of gravity method.The adaptive median filtering method is used to denoise the light bar image,and the threshold segmentation method is used to segment the image.The center of the light bar is preliminarily extracted by the thresholding method and the exact normal direction of the light bar is obtained by the mean square grayscale gradient method.Compared with the traditional method,this method can effectively improve the extraction accuracy.Finally,a three-line structured light three-dimensional measurement platform is developed,and the ball diameter measurement is carried out.It shows that the proposed method is valid,flexible and with high precision by experiment,and the three-line structured light three-dimensional measurement system can meet the requirements of high-precision and speed.