Synchronous microdeformation and first derivative dynamic measurement based on laser shearing speckle interferometry

Abstract

This paper presents a multi-carrier frequency spatial phase shift digital shearing speckle interferometry method which is capable of the first derivative and microdeformation synchronously. The dynamic deformation of the composite defects is carried out by thermal loading.The shear speckle interferometry is used to locate the defect position and holography was used to measure microdeformation of the defect. In Michelson shearing device, an optical fiber is used to introduce a reference beam,two shear images form a shear fringe pattern, and the reference beam introduced is combined with one of the shear patterns to generate a hologram. The spatial phase shifting technique is used to obtain the frequency domain after Fourier transform, holograms and shearograms are obtained at the same time. In this paper, the direct synchronous measurement of microdeformation and first derivative of deformation is realized without the need of numerical integration process. Finally, the experimental results show that the proposed method can quickly obtain the shear fringe image, which represents the first derivative of the deformation to position the defect in the composite material, and the hologram is filtered, unwrapped and 3D displayed to obtain accurate micron scale deformation values.