Three-Dimensional Measuring Method With Grating Projection

The application of 3D object surface measurement is more and more important in the domain of industrial inspection, quality controlling, machine vision, CAD/CAM, and medical science, etc. Fourier Transfer Profilometry is widely used among the methods of structured illumination 3D sensing, it only needs one reference grating image and one deformed grating image, and has the qualities of simple measurement system, fastness of data acquisition and high precision.Based on the method of engineering measurement of 3D object surface, this dissertation studies the theories and application of Fourier Transform Profilometry. It consists of the following contents:The principle of Morie Profilometry, Modulation Measurement Profilometry , Phase Measurement Profilometry and Fourier Transform Profilometry is analysized. With the conception of equivalent wavelength, we are able to make better choice of parameters, and can ensure the complete separation of all the spectra in frequency domain and the measuring precision of system.The mathematical model of camera imaging is studied, and a calibration method for 3D machine vision, which combines height calibration with position calibration, is introduced.The algorithm of phase unwrapping is studied, the new phase unwrapping method based on getting the blocking line by using wavelet transform is introduced. Thus, the effects of noise, height mutation and shadow can be avoided.The preprocessing methods of grating image are studied, and the 3D object surface data is reconstructed. Meanwhile, the theory of image registration is presented.A measurement system that consists of LCD, CCD, and image card is designed, it can project and obtain grating image simultaneously. At the same time, a software system that integrates the function of system calibration, image processing and also image analyzing is developed with Visual C++6.0. At the end of the dissertation, some experiment result are giving.Theoretical analysis and practical measurement prove the availability of all of the methods and algorithms.