Research On Phase In 3D Measurement Of Single Fringe

Fringe projection 3D measurement technology,as a new type of modern measurement technology,is widely used in various fields,such as reverse engineering,information security,medical diagnosis and other fields with its advatantages of non-contact,high precision,and rapid measurement.Among them,the single fringe 3D measurement requires only one deformed fringe image to recover the phase distribution that containing the object imformation,thus it is widely used in for 3D measurement of dynamic objects.It is a key issue to extract complete and accurate phase imformation from single fringe.In this thesis,the some key phase problems of single fringe 3D measurement are analyzed and researched based on a new method,Bidmensional Sinusoids-assisted Empirical Mode Decomposition(BSEMD).The main work and innovation are as follows:1)A fast phase unwrapping method for region-division quality map based is proposed.On the one hand,the traditional phase unwrapping methods based on the quality map rely on the rationality of the establishment of quality map.On the other hand,its computation time will increase significantly with increase of the image size.In this regard,this thesis proposes to use the instantaneous frequency of the fundamental frequency component,where be obtained in the process of extracting phase using BSEMD and Hilbert transform,as a parameter basis for establishing the quality map.Then,because of the multi-scale analysis capability of BSEMD,regions that prone to phase unwrapping errors can be partitioned from different modes of their decomposition results.In these regions,phase unwrapping based on quality map is performed,while in other regions,the direct method is applied.Experiments have proved that this method ensures the accuracy of the global quality map method and significantly reduces the computation time.2)The nonlinear phase error correction based on the Fourier spectrum gamma calibration method is improved,and the parameter constraint conditions applied to the gamma calibration method are proposed.Firstly,the effect of projector Gamma nonlinearity on phase demodulation method of BSEMD is analyzed,and the necessity of gamma correction for single fringe is analyzed.Then analyze and improve the influence of Gamma calibration results on nonlinear harmonic order selection,spectral leakage,non-uniform period of fringe,and precoding value based on Fourier spectrum gamma calibration method,furthermore proposed the parameter constraint conditions of the gamma calibration method.Finally,the experiment verifies that using the gamma value pre-coded projection fringe calibrated in this paper can well solve the phase nonlinearity correction problem of single fringe.