Research On Key Technologies Of Three-Dimensional Measurement Of Dental Model

The measurement accuracy of the dental model is an important guarantee for the design and processing accuracy of the denture restoration,and it is also an important part of the oral CAD/CAM system.To this end,article designs a three-dimensional measurement system for dental jaw model based on grating structured light,and we design a new calibration scheme to improve the calibration accuracy.The main research contents are as follows:First,it introduces the development of dental jaw 3D measurement technology at home and abroad,and introduces in detail the related equipment and principles of dental jaw model measurement that have been put on the market.After that,the existing non-contact three-dimensional measurement methods were studied,and the existing non-contact three-dimensional measurement methods were studied,analyzed and compared.Finally,the grating structured light method was selected as the solution of the dental model measurement system.On this basis,the overall design architecture of the system is given based on the modular idea,the hardware modules and software modules are analyzed and designed,and the hardware selection and the scanning trajectory of the dental model are analyzed in detail according to the needs of the measurement system.Subsequently,article studies the calibration method of the camera and the rotating platform.Based on the calibration method of Zhang Zhengyou and Xia Rinpo,a camera automatic calibration scheme based on four azimuth circles is designed,which can realize the automatic ordering of the landmark points.In order to improve the efficiency of identifying the center of the calibration plate,article uses RANSAC to improve the RED ellipse center detection algorithm.Experimental verification shows that the improved RED algorithm has increased 29.34%in anti-noise interference ability and 30.10%in center detection accuracy,which effectively guarantees the measurement stability and accuracy of the measurement system.Then,with the aid of the designed calibration board,article uses the principle of three points to fit the center of rotation of the turntable,which provides a basis for the subsequent point cloud splicing.Experiments show that the back-projection error of the calibration method in article is less than 1 pixel,and the calibration accuracy is better than Zhang’s algorithm.On the basis of system calibration,this system uses sinusoidal grating structured light with multi-frequency heterodyne method for image resolution,and obtains three-dimensional point cloud data of the dental jaw model.In order to remove the outliers of the point cloud and reduce the interference of noise,article subsequently performs straight-through filtering and statistical filtering on the dental model point cloud.Then,the point cloud of the dental model is down-sampled using the Delaunay method,and a more streamlined point cloud data is obtained.Finally,the results of the turntable calibration are used to rotate and splice the point clouds at different angles.On this basis,the ICP algorithm is used to splice the point clouds from the left and right camera angles.The final measured average measurement error of the dental model is 0.035mm,the maximum average error is 0.1mm,which meets the requirements of the dental CAD/CAM system on the market.The three-dimensional measurement of the dental model developed in article has the characteristics of high precision and high stability.The measurement accuracy of the dental model has reached the requirements of clinical application,which provides theoretical and technical support for the further realization of the dental restoration CAD/CAM system.In addition,the system design in this article can also be applied to the 3D measurement of other small and complex curved objects.