Segmented Phase-coding Based On Phase-shifting Coding 3D Measurement Research

With the development of computer,the traditional measurement method has undergone great changes.The new three-dimensional(3D)measurement method has been emerging.3D measurement method based on fringe projection profilometry is one of the most commonly used and effective methods in raster projection 3D measurement technology.However,its measurement speed and measurement accuracy are still needed to focus on the study of the problem.Compared with the Gray code plus phase shift method,Gray code embed the codeword into intensity,which is more sensitive to the ambient light,camera noise and the surfaces reflectivity of measured object,and the phase encoded stripe based on the phase encoding,good immunity.When the phase unwrapped,the fringe order can be accurately obtained.However,when the number of codewords used in the phase code fringes increases,there are many errors in the calculation of the stripes level.In this paper,the problem of error in the determination of the stripes based on the phase code fringes.The method of phase shift coding is proposed.At the same time,the GPU is used to accelerate the parallel computation in the 3D measurement process,and the key problems of the fast 3D measurement method for realizing high precision of complex objects are studied.The main research contents and innovation points of this paper are as follows:1.Segmented phase-coding fringe is proposed.With the increase of the number of phase-coding fringe period,the fringe order k(x,y)becomes difficult to judge,errors occur in the jump area,and the periodic dislocation problem becomes worse,ultimately leading to phase unwrapping error.In order to solve the above problems,we propose a segmented phase-coding fringe,The phase-coding is design to be a segmented fringe.In the case of not reduce the number of code words,the fringe order is easily to be juged.The feasibility of the method is verified by experiments.The experimental results show that the method is superior to the high speed and high precision 3D shape measurement.2.A new method for 3D shape measurement of segmented phase-coding fringe based on phase-shifting coding is proposed.As the number of codewords adopted in phase-coding fringes increases,the solution of fringe orders leads to many mistakes.Consequently,errors of the unwrapped phase occur.Thus,increasing the codeword approach in a phase-coding fringe remains a challenge.In this method,a modifiedsegmented stair phase-coding fringe based on phase-shifting coding is designed.This method adopts fewer codewords to replace the usual large number,which increase the pixel width of codeword and solve the problem of wrong judgment of fringe level leaded by the increase of the number of codeword.And a new phase unwrapping algorithm based on segmented phase-coding fringe based on phase-shifting coding is presented.The main idea of this method is that the frequency ratio of the sinusoidal and stair phase-coding fringes is set to n:1.At the same time,in order to achieve more rapid measurement,GPU is used to accelerate the parallel computation in the process of 3D measurement.As such,the approach gains two merits.One is that it guarantees a high measurement accuracy.The other is that it allows the measurement of isolated objects with complicated shapes.At the same time,in order to prove the validity of the method,a series of comparative experiments are carried out,the results of different width are analyzed,and the best condition is obtained,finally,the measurement accuracy is analyzed.