Research On Three Dimensional Measurement System Of Tooth Jaw Based On Grating Projection

With the continues improvement of people's living standards and the development of population aging in China, the population of people who needs mouth rehabilitation grows constantly. However, the design and manufacture cycle of the technology of traditional restoration manufacturing is long and difficult to guarantee the quality of restoration with more manual intervention,it has been unable to meet clinical needs. As an important part of the CAD / CAM technology on Prosthodontics, creating three-dimensional digital tooth jaw model is the precondition of achieving the digital design and manufacture of tooth jaw restorations. The precision of restoration depends largely on the measurement accuracy of tooth jaw. Therefore, in this paper the three dimensional measurement system of tooth jaw based on grating projection is studied and main contents are as follows.This paper describes the measurement principle and the approach used in the system and proposes the overall framework of the measurement system based on the idea of modular, which includes the tooth jaw positioning module, optical path adjustment module, the visual measurement module, product appearance modules, system calibration module, encoding and decoding modules, three-dimensional reconstruction of the module and point cloud merging module. Meanwhile, this paper gives some details on the selection of the instruments used in the measurement system and the design of the listed modules above, which provides the basic guarantee for the measurement system to achieve the function.This paper studies calibration methods of camera and projector and compares the pros and cons of various calibration methods. On the basis of Zhang-Zhengyou calibration method widely used, the calibration method combined measurement objects and system characters is studied for application,which provides an important support for the overall accuracy of the system. It establishes a three-dimensional reconstruction model of non-geometric constraint, which makes a significant reduction of the demand of the precision of the system in the processing and assembly while the system may be relatively more stable.In view of non-contact optical three dimensional measurement of tooth jaw, A jig design method which integrates the calibration function is proposed for realizing spatial coincidence during the process of objects to be measured and calibration target. The coordinate systems are defined monocular vision measurement process involved. A coordinate matching-based point clouds registration technology is proposed for simplifying the process of point clouds registration and simultaneously realizing the zero error of point clouds registration theory. With the experimental verification, cloud registration data with some precision is obtained, which significantly support the overall accuracy of dental measurement system.The three dimensional measurement device in this article is used for tooth jaw measurement, the experimental process is stable, the period of single measurement is not more than 1 minute and a certain accuracy is achieved, which provides a digital measurement platform for CAD / CAM technology to access to the original point cloud. Meanwhile, the research in this article can be used for other objects to be measured with complex surface features, such as precision Measurement, Heritage, etc.