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.
In speckle metrology, speckle fringe pattern includes phase information, in order to get the contains less noise in the dynamic measurement of the original speckle fringe pattern, allowing for more efficient to extract phase information,A new method is proposed to improve the quality of the original speckle pattern by changing the average speckle size on the digital shear speckle. The quantitative relationship between the optical path system parameters F number and magnification factor and the speckle size on the image surface was analyzed, and the digital shear speckle interferometry experiment based on the space carrier phase shift technology changed F number and magnification factor respectively for verification.Experimental results show that the shape of variables for fixed value, system magnification is 1, the imaging lens F value is 4.5, The average speckle size was 5.841 μm, and the image was best when it was closest to 5.86 μm, as a lens F number is 2, system magnification of 3.5, The average speckle size was 5.841 μm, and the image was best when it was closest to 5.86 μm, after filtering is cosine algorithm, the speckle fringe pattern is the most clear.It is proved that when the speckle size on the image plane is closest to the size of pixel, the quality of the speckle stripe is the best.
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