The Data Processing Of 3-D Shape Measurement Based On Digital Fringe Projection And Phase-shifting Technology

The non-contact 3-D shape measuring method is an important branch of Optics, image processing and computer vision, which has a wide and urge application in the fields of product quality inspection machine vision medicine and so on. However it is an important but difficult problem to device a technology which can be used to measure 3D surface of a object nicely and rapidly. A method based on digital fringe projection and digital phase shifting technique is proposed in this thesis for 3D shape measurement.Compared to the traditional grating fringe projection systems, the new system has the following two major advantages. Firstly, with the new digital projection system, the standard sinusoid fringe patterns with exceptionally high brightness and contrast can be projected, thus improving the accuracy of surface contouring. Secondly, purely software-based digital phase shifting the fringe can be applied to improve the resolution of the contouring technique and eliminate the noise with the traditional phase-shiftingtechnique.Based on the character of projected fringes, some spin-filter methods can be creatively applied to eliminate the random-noise in the projected fringes which is not purely eliminated by the traditional digital image preprocessing, and not to damage the importance information of projected fringes. In additional, noised-free normalized fringe patterns can be established from the projected fringe patterns.For the phase wrapping and phase unwrapping research, phase shifting algorithms can be used to calculate phase map, and a new algorithm for phase unwrapping of phase map is originally proposed. It is based on the use of a queue for the processing of arbitrary shapes and the Phase reliability for the pixels to be processed. Compared with traditional phase unwrapping algorithm, it can bypass the noise automatically, solve the problem of the shade sheltering or cavity and overcome the error propagation problem.By the data processing of the experiment, some results are presented to show the influence on the precision of measuring exerted by the period of the projected fringe and the steps of phase shifting, and the performance of the Phase unwrapping algorithm based on the reliability in comparison with flood phase unwrapping algorithm.