Study On Key Techniques Of 3D Surface Measurement Based On Line Structured Light

With the advancement of science and technology and the development of the social economy,the demand for 3D measurement technology is increasing in both quantity and quality in more and more fields including medical and health.Therefore 3D surface measurement technology using line structured light has become a research hotspot based on its advantages such as non-contact,high precision,low environmental requirements and low cost etc.This thesis focuses on the key technologies of 3D surface measurement based on line structured light.The main research contents and conclusions are as follows:(1)In this thesis,we first investigate the research and application of 3D measurement technology based on line structured light.Then,we design and build 3D measurement system of line structured light,which is composed of CCD industrial camera,line laser,mobile workbench and computer software system.Moreover,the mathematical model of the measurement system is deduced.(2)The calibration method of the measurement system is studied,including camera calibration and line structure light plane calibration.In the light plane calibration of measurement system,an improved method is proposed to solve the problem that there are fewer feature points in the existing calibration methods.This improved method can obtain a large number of feature points by using the plane-to-plane intersection model when using a simple calibration tool,and then fit these feature points to obtain a more accurate structured light plane equation.The experimental results show that the improved calibration method has a very significant improvement in the measurement accuracy.(3)The whole process of light stripe image processing is studied,including image filtering,image segmentation and stripe center extraction.A two-steps algorithm for light stripe center extraction is proposed.Firstly,the center of light strip is roughly extracted by one-dimensional template method,then the normal direction of the light stripe is approximated by the position of the adjacent points on the extracted light stripe center skeleton,and the more accurate center of light strip is extracted by the gray center of gravity method in the normal direction.The experimental results show that proposed algorithm has some comprehensive advantages in the extraction accuracy and speed of the strip center compared with the gray center of gravity method and Steger algorithm.In this thesis,we used Python programming language and Open CV library to implement and apply the above algorithm to the simple measurement system,and carry out a variety of experimental tests,including the measurement of the size of the standard block and the measurement and reconstruction of the irregular surface of the tooth model.The test results further verified the effectiveness of the above algorithm,and also showed that the simple measurement system has the potential of practical application value and broad market prospect after further improvement.