Study On Optimization Of Multi-frequency Fringe Projection 3D Measurement Technology

Fringe projection technology is highly representative in the field of optical three-dimensional measurement due to its high precision,non-contact,strong universality and other advantages,and shows practical value in advanced manufacturing,entertainment,film and television,biomedicine,reverse engineering and other fields.This thesis focuses on the problems of phase extraction speed,fringe image nonlinearity and 3D measurement accuracy in the 3D measurement technology of multi-frequency fringe projection,and builds an optical experimental system based on fringe projection technology to carry out relevant research and explore corresponding solutions.Firstly,according to the principle of triangular ranging in fringe projection three-dimensional measurement,the importance of phase to experimental solution is found,and the advantages and disadvantages of different phase extraction and phase unwrapping methods are analyzed.The four-step phase shift algorithm and multi-frequency time phase unwrapping method are selected as the basic of all experimental studies in this thesis.Secondly,projector and camera equipment are indispensable in fringe projection technology,but the nonlinear effect between them will bring difficult to ignore the error influence to the subsequent phase solution,which is a very important error source in 3D measurement.At present,there are various methods to deal with nonlinear phase errors,but they often need the help of complex models or additional calculations to achieve good results.Aiming at the periodic characteristic of phase error,this thesis introduces the phase offset algorithm and designs a full-field compensation method for nonlinear phase error to correct the phase error and obtain the ideal phase.The effectiveness and robustness of the proposed method are verified by comparing with other methods.Finally,a multi-frequency time phase unwrapping method with high precision is selected to study the velocity and accuracy of fringe projection 3D measurement.In this thesis,the results of unwrapping phase with different number of fringe frequencies are obtained by experiments.Compared with the calculation process of traditional time phase unwrapping method,the steps and calculation program of multi-frequency time phase unwrapping are optimized by using the iterativeness of multi-frequency time phase unwrapping.The experimental results show that the accuracy of the proposed method is higher than that of other original methods,and the error between the proposed method and the actual data is within the range of millimeter,which ensures the accuracy of multi-frequency fringe projection 3D measurement technology and improves the measurement efficiency at the same time.