| Laser Digital Speckle Pattern Interferometry(DSPI)is widely used for real-time dynamic measurement in industrial manufacturing,biomedical detection and other fields due to its full-field,non-contact and high-precision measurement characteristics.In order to obtain accurate measurement information in real time,3D dynamic deformation and strain measurement of objects are required in various fields,but the current digital speckle pattern interference technology can't truly achieve real-time measurement of 3D deformation and strain.In light of this situation,this paper designs and sets up a 3D DSPI deformation and strain measurement system based on space carrier.Dynamic measurement can be realized by using space carrier phase-shifting technology.Usually Fourier transform is used to extract phase distribution information from single speckle interferogram,in which Fourier spatial filtering is needed to separate items with phase information from the spectrum.The traditional spatial filter needs human intervention,especially the multi-dimensional spectrum needs to separate multiple items,which undoubtedly increases a lot of analysis time,so it is of great significance to research the fast and automatic spatial filter method.In this paper,the theoretical analysis and experimental verification of 3D deformation,strain and simultaneous deformation and strain measurement of digital speckle interference based on space carrier are presented.An automatic Fourier spatial filtering algorithm based on adaptive local threshold segmentation is proposed,and the algorithm has been experimentally verified.Firstly,the relationship between the amount of deformation and its derivative and the phase difference,the principle of 3D synchronous deformation measurement,the principle of strain measurement,and the principle of simultaneous measurement of deformation and strain are analyzed in detail.Then,the key parameters affecting the frequency spectrum distribution and image processing techniques in the spatial carrier DSPI are analyzed,and several common phase filtering methods and unwrapping methods and their advantages and disadvantages are compared.Finally,combining with region recognition technology and local threshold segmentation,an automatic Fourier spatial filtering method based on adaptive local threshold is proposed.In order to verify the performance of the proposed automatic spatial filtering algorithm,experimental tests were performed.Compared with the area recognition algorithm based on iterative threshold,the recognition results under different spectral intensities are compared,and the results show that the proposed algorithm can identify spectral terms that need to be separated for the same and different spectral brightness.Compared with the phase obtained by manual spatial filtering algorithm,the proposed algorithm can accurately extract the target spatial terms of the 3D speckle interferogram.The automatic analysis of multiple speckle interferograms shows that the algorithm can realize the real-time measurement of three-dimensional dynamic deformation.In addition,in order to verify the feasibility of the spatial carrier DSPI deformation and strain measurement system,a spatial carrier DSPI three-dimensional deformation synchronous measurement experimental configuration was designed to measure the out-of-plane deformation,in-plane horizontal deformation and in-plane vertical deformation separately and simultaneously.A Michelson digital Shearography strain measurement optical path was designed to measure out-of-plane strain.A synchronous optical path for deformation and strain measurement combining DSPI and digital Shearography was designed,and the out-of-plane deformation and strain were measured simultaneously,which verified the system's feasibility and theoretical analysis of the key parameters of the experiment.It also provides a good research foundation for the practical three-dimensional dynamic deformation and strain measurement system. |
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