The Research Of Image Processing On Digital Speckle Pattern Interferometry Based On Spatial Carrier Phase-shifting

With the development of manufacturing and engineering materials,Digital Speckle Pattern Interferometry(DSPI)is urgently needed to achieve high-precision and real-time dynamic measurement.The dynamic measurement performance of DSPI depends on the phase-shifting technique,in which the spatial carrier phase-shifting can not only achieve dynamic measurement,but also has a simple optical structure and is suitable for multi-dimensional deformation measurement.However,at present,the research on multi-dimensional deformation measurement of DSPI based on spatial carrier phase-shifting is still in the initial stage in China,so the theoretical analysis and research on DSPI based on spatial carrier phase-shifting is very meaningful.The precision of DSPI mainly depends on the phase unwrapping algorithm in the image processing of speckle.The weighted least-square phase-unwrapping method in the global algorithm can not only generate a smooth solution,but also suppress the smoothing error by weighting coefficient generated by quality map.But the current quality map have their own defects,so it is necessary to study the weighted least-square phase-unwrapping algorithm based on quality map of high quality.In this thesis,the theoretical analysis and experimental verifications of one-dimensional and two-dimensional deformation measurement based on spatial carrier phase-shifting are presented,and an improved weighted least-square phase-unwrapping algorithm based on reliability mask is proposed.Simulated and experimental verifications of the improved algorithm were carried out.Firstly,the principles of speckle interferometry,one-dimensional speckle interferometry based on spatial carrier phase-shifting and two-dimensional speckle interferometry based on spatial carrier phase-shifting are deduced in detail.The key of experiments is analyzed,including experimental observation indexes and experimental parameters.Then speckle image processing technology is analyzed,including image filtering technology and phase-unwrapping technology.The principles,advantages and disadvantages of several commonly used filters and phase-unwrapping algorithms are studied.According to the advantage of 0-1 mask that the correct solution can be obtained in the unit weighted region and the smoothing solution can be obtained in the zero weighted region,and the merit that the reliability in the path-following algorithm can detect the residuals reliably,a novel weighted least-square phase-unwrapping algorithm based on reliability mask is proposed.In order to verify the performance of the improved algorithm,simulated and experimental tests are carried out,and GBCA,WLSA-PDV and PCA were used as comparison algorithms.Firstly,the simulated test was carried out,and the noises that may appear in actual wrapped phase were added in the simulated wrapped phase,including weak global noise,strong local noise,misalignment and cut-off.The simulated results show that in these noise cases,the improved algorithm is not only more accurate than the other three algorithms,but also generates a smooth solution in the noise regions.It proves that the improved algorithm can not only effectively suppress the smoothing error,but also has a powerful ability to process noise.Then the experimental test is carried out to unwrap the large wrapped phase with low signal-to-noise ratio,which is obtained from the DSPI based on spatial carrier phase-shifting.The experimental results show that the improved algorithm is superior to the other three comparison algorithms in both accuracy and speed,which proves that the improved algorithm is effective and accurate for the actual wrapping phase of large size and low signal-to-noise ratio.What's more,in order to verify the feasibility of the system of DSPI based on spatial carrier phase-shifting,the optical systems of one-dimensional DSPI based on spatial carrier phase-shifting and two-dimensional DSPI based on spatial carrier phase-shifting are built,and one-dimensional off-plane and in-plane deformation measurements are performed,and two-dimensional off-plane,in-plane,and off-plane and in-plane simultaneous measurements were performed.The experiments verify the feasibility of the one-dimensional and two-dimensional DSPI systems based on spatial carrier phase-shifting and the theoretical analysis of the key of experiments.