Research On Three-Dimensional Measurement Technology Based On BI-TELECENTRIC System

In recent years, three-dimensional image measurement technology has become a hot topic in the field of modern industrial measurement. In this thesis, the principle of measuring based on telecentric optical system has been analyzed and the method has been studied. This thesis established a three-dimensional measurement system, designed three-dimensional measurement programs and verified the final result of three-dimensional measurement based on double telecentric optical system. Specific work done as follows:First of all, a three-dimensional measurement method based on double telecentric optical system was proposed and a single camera system models was established. Then, we designed the software for the system to measure and studied on the image method of the system research. To improve the measurement stability, a centroid centerline extraction algorithm was improved, using Matlab achieve triangulation reconstruction. According to the simulation results, we can safely draw the conclusion that the improved algorithm compared with the Hessian matrix, midline positioning error limited to one pixel length shortened by a third processing, simulation and experimental comparison of different density point cloud reconstruction effect can meet the measurement requirements, the system has fast calculation and accurate characteristics compared with the traditional three-dimensional measurement system;Secondly, in the three-dimensional measuring experimental system, a low distortion telecentric lens was placed as a receiving member and the 635 nm wavelength laser line was placed as the indicated light, by the rotating of the objective table, we can scanning objects for a week and complete the three-dimensional. Cylindrical and spherical are selected for multiple measurements. The recovery results of the measured data show that the new system has good linearity and low distortion error compensation than the traditional vision measurement system, the measurement accuracy can reach 0.1mm in the large field of view measurements, a single point measurement error can improve an order of magnitude with error compensation in theory and be used to measure the tiny precision parts and components quickly;Thirdly, a two-camera measurement program has been analysed. Two optical axes of the double telecentric lens form a standard Cartesian coordinate system directly, which is perpendicular to each other, when the workpiece is rotated about a specific axis or dimensional scanning by the laser is in progress, spatial point position can be obtained directly. Theoretical analysis shows that the system can improve the accuracy of three-dimensional measurement, speed and reliability further.