Research And Application Of The Discontinuous Optical Fringe Patterns Filtering And Phase Unwrapping Methods

Optical testing technology as a kind of whole-field,non-contact nondestructive measurement method,has been widely used in scientific research and engineering fields at present.In most optical testing technology,the measured physical quantities are related to optical phase,and shown the measurement results in the form of fringe patterns or phase patterns,so the accurate extraction of phase information is of key to the application of optical testing technology.However,the phase extraction has been a challenging problem in discontinuous optical fringe patterns.The paper makes a deeply research on the key problem for the phase extraction of discontinuous optical fringe patterns,including the filtering method of discontinuous optical fringe patterns based on spatial domain,the filtering method of discontinuous phase patterns based on frequency domain and the unwrapping method of discontinuous optical phase patterns based on orientation coherence.The main contents of this paper are as follows:(1)Concerning the research of spatial filtering methods for discontinuous optical fringe patterns,the adaptive oriented partial differential equation(PDE)filtering models are proposed from the spatial domain in the paper.The coherence of fringe orientation can be used to distinguish the continuous regions and the discontinuous regions of fringes,so the paper defines the controlling speed function as a function of orientation coherence.This controlling speed function can increase the strength of filtering for the fringe continuous regions,and reduce the strength of filtering for the fringe discontinuous regions.The experimental results show that the proposed models effectively preserve the discontinuity of fringes while filtering noise.(2)Concerning the research of frequency-domain filtering methods for discontinuous phase patterns,a filtering method based on shearlet transform is proposed from the frequency-domain in the paper.In addition,the new method is applied to the discontinuous phase patterns by this paper,and compared with the three existing filtering methods.The experimental results show that the proposed method has a good ability of noise suppression,and the better robustness and accuracy in preserving phase discontinuity.(3)Concerning the research of phase unwrapping methods for discontinuous phase patterns,a weighted least-squares phase unwrapping method based on theorientation coherence is proposed by this paper.Comparing with the traditional weighted least-squares method,the weight is set by a binary orientation coherence map in the new method.The new method is applied to the discontinuous phase patterns by this paper,and compared with the five common phase unwrapping methods.The experimental results show that the proposed method can effectively distinguish the phase continuous regions and the phase discontinuous regions,and avoid the error propagation caused by the phase discontinuous regions while unwrapping.In addition,the new method has an anti-noise ability.