Effect of the Speckle Size on the Quality of Speckle Pattern in DSPI System

Abstract

In order to detect the deformation and strain of materials accurately, the key is to obtain the phase information caused by dynamic loading in digital speckle pattern interferometry (DSPI). In this paper, the evaluation method of quality of the speckle pattern in DSPI system is proposed, and the influence of the size of speckle grain on the stability and contrast of speckle pattern is discussed. And then, the strain detection experiments of inactive and bioactive materials are provided with different aperture slit size under the same detection conditions. The size of speckle grain has an important influence on the quality of speckle pattern. For strain detection of inactive materials, using the small size of speckles can obtain higher quality speckle pattern under the condition of satisfying the Nyquist theorem and spectral separation. For active biomaterials, non-structural factors easily induce the instability of speckle pattern, which leads to the decorrelation of between pre-deformation and post-deformation speckle pattern. So the compromise between the stability and the information capacity of speckle images should be considered in the selection of speckle size. Experiments show that the optimum size of speckles used for strain detection active biomaterials is larger than that of inactive biomaterials under the same conditions in the same DSPI system.

Influence of average speckle size on measurement of in-plane displacement

“…Currently, laser speckle has been widely used in various fields, such as biomedical field [1], optical imaging [2], micro deformation and crack measurement [3]. In recent years, the influence of average speckle size on displacement and deformation measurement of scattering objects attracts research attentions [4][5][6][7]. Li et al [5] proposed an evaluation method of quality of the speckle pattern in digital speckle pattern interferometry system, and discussed the influence of the speckle grain size on the stability and contrast of speckle pattern.…”

“…In recent years, the influence of average speckle size on displacement and deformation measurement of scattering objects attracts research attentions [4][5][6][7]. Li et al [5] proposed an evaluation method of quality of the speckle pattern in digital speckle pattern interferometry system, and discussed the influence of the speckle grain size on the stability and contrast of speckle pattern. Yu et al [6] found a new method to improve the quality of the original speckle pattern by changing the average speckle size on the digital shear speckle, and analyzed the quantitative relationship between the system parameters of optical path and the speckle size on the image surface.…”

Orthogonally and linearly polarized green emission from a semipolar InGaN based microcavity

“…Orthogonal linearly polarized light emission is also achievable by employing two laser sources with orthogonal polar direction, which takes advantage of the inherent linear polarization properties. In addition to the laser itself, the exploitation of laser imaging and display is often hampered by the speckle effect that results from the coherent nature of laser light 22 . Two independent light sources are necessary for the above-mentioned approaches to realize orthogonally polarized emission.…”