The Study Of 3-D Measurement By Profile Method

With the diversification of product demand and the development of advanced manufacturing technology, the measurement of complex structure demand continues growing. When dealing with the complicated measurement tasks, traditional measurements for length, angle, straightness and plane degree etc., its limitations is increasingly prominent. In the real world, objects are in the form of three-dimensional geometry. When the amount of simple geometric measurement cannot meet the demand of a specific measurement, the measurement of complex structure will be summed up in three-dimensional shape measurement of an object.Profile measurement method of the three-dimensional shape measurement technology is performed by the parallel light projected onto the surface of the measured object, and the object is located in the stepping motor rotating platform, and then using the parallel projection of the telecentric lens to obtain the face projection of the object. With the rotation of the stepper motor, we can accurately obtain the 360° face projection of the object, through image processing of these face projection, obtaining each point of the profile line, then using OpenGL primitives composition method to put every point of the profile line together, and then the reconstruct of the three-dimensional shape of the object is completed.In this paper, we introduced the principles and methods of several commonly used to detect the three-dimensional shape in the first chapter, which focused on the optical measurement method that have much in common with this topic. At the same time, we also introduced the application and the current research status of the optical three-dimensional shape measurement method. The second chapter introduced the key technology of this measuring instrument:the parallel projection of the telecentric lens and the composition of OpenGL, focused on the two line of OpenGL-the rendering pipeline and the graphics pipeline. In the third chapter, introduced the hardware running processes of the experimental equipment, namely using telecentric system, putting the measured object on the stepper motor, measuring the profile of each angle of the object; meanwhile, this chapter presented the software modules of the device, and mainly introduced the edge detection of the image. In the fourth chapter, we explained the algorithm realization of the software, from the image denoising to the reconstruction of the three-dimensional graphics. In the fifth chapter, through comparing the differences of the measure conditions and methods, analyzing the factors affecting the results of the measurement and the application range of this equipment. In the last chapter, we summarized the main work of this topic and the shortage of this method, as well as the innovation and the prospect of this subject.In this paper, the system is based on the telecentric system, using the profile measurement method to measure the 3-D topographic parameters of the object, and to build the 3-D models. Through this process, the main work of this paper is as follows:1、Explored the principle of the profile measurement method to measure the three-dimensional topographic parameters of the object as well as the specific implementation steps, formed an experimental instrument which is based on the telecentric system, and completed the image acquisition, data processing,3-D reconstruction and so on.2、Studied the technique of the image edge detection, for the accurate extraction of the profile of the measured object, we put forward the optimization solution.3、We analyzed the strengths and weaknesses of the profile measurement method to measure the 3-D topographic parameters of the object in a large number of experimental data, and determined the range and precision of the experimental instrument.4、Wrote the algorithm program that matched the experimental instrument by C++Builder development, and connected with the actual demand, designed the different accuracy and speed of measurement model, added the full and gradually demonstration, automatic and manual measurement, etc.