Study On Three-dimensional Deformation Measurement Based On The Combination Of DSPI And DSCM

Three-dimensional deformation measurement plays an increasingly important role in engineering materials,biomedicine,aeronautics and astronautics,and other fields.Digital speckle pattern interferometry(DSPI)is widely used for its full-field,non-contact and high-precision characteristics.However,either out-of-plane deformations or in-plane deformations are measured in the existing DSPI system.In this paper,we developed a three-dimensional deformation measurement system based on the combination of DSPI and digital speckle correlation method(DSCM).Phase and intensity of the object wave are extracted by the Fourier transform method from the interferograms recorded before and after deformation.Out-of-plane deformations are determined by the phase difference.By applying DSCM on the intensity before and after deformation,in-plane deformations are determined.Temporal phase-shifting method,spatial carrier pixel phase-shifting method and Fourier transform method are simulated with MATLAB in different cases,such as ideal situations,uneven light intensity and vibration environment.The signal-to-noise ratio of the phase extracted by different phase detection methods is calculated.Temporal phase-shifting method,spatial carrier pixel phase-shifting method and Fourier transform method are compared.We employ the Fourier transform method to retrieve the object wave's phase and intensity distributions and an off-axis configuration is employed to introduce spatial carrier in our system.An aperture is arranged to limit the spatial frequency of the object wave to avoid frequency aliasing of the background spectrum and the interference spectrum in the Fourier domain.The aperture size and the incident angle of the reference light are calculated to avoid frequency aliasing and the experiments are conducted to validate it.The influence of the aperture size on the phase noise is investigated and the suitable aperture size is given.The influence of the intensity ratio of the reference and object wave on the phase noise is investigated as well.To demonstrate the performance of our approach,first the out-ofplane deformations of an aluminium plate due to loading of a thimble are determined.The in-plane displacements of an aluminium plate fixed on a linear translation stage are determined.