Topic
Speckle imaging
About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.
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TL;DR: In this article, a new scheme of digital speckle pattern interferometry (DSPI) for observing the entire process of dynamic deformation from the beginning of elastic deformation to the end of plastic deformation at fracture is proposed.
Abstract: A new scheme of digital speckle pattern interferometry (DSPI) for observing the entire process of dynamic deformation from the beginning of elastic deformation to the end of plastic deformation at fracture is proposed. Interesting deformation processes which consist of spatial mode division of fringes caused by plastic deformation and stress relaxation were clarified by simple experiments.
23 citations
TL;DR: A simple geometrical model was developed for calculation of the contrast of a polychromatic image-plane speckle pattern from a source of light with high spatial coherence and its validity was established by comparison with an exact solution.
Abstract: A simple geometrical model was developed for calculation of the contrast of a polychromatic image-plane speckle pattern from a source of light with high spatial coherence. It is based on counting the number of independent speckle patterns that contribute to a given point in the image plane. This results in a simple equation for the contrast as a function of imaging geometry; relative orientation of the projection direction, observation direction, and specimen normal; bandwidth of the light source; and surface roughness. Its validity was established by comparison with an exact solution: rms errors in the calculated contrast were only 0.033 over a wide range of parameter values likely to be encountered in practice.
23 citations
01 Jan 1992
TL;DR: The phase shifting speckle interferometric system has been used for both the displacement vector measurements and for the acquisition of the essential shape information, and improved algorithms concerning phase unwrapping and intensity averaging in the case of low light levels are presented.
Abstract: To determine the in-plane strain components from the 3-D displacement vector data of a loaded object, its shape has to be known. The phase shifting speckle interferometric system, described in this paper, has been used for both the displacement vector measurements and for the acquisition of the essential shape information. The numerical shape data resulting from the application of a phase shifting technique allows further calculations, e.g. the determination of the object surface normal vector. The shape measurement method (a modified two- illumination-source technique) is discussed and the experimental system is described. An overview of the basic image processing algorithms, involved in the evaluation of the speckle interference patterns, is given. Improved algorithms concerning phase unwrapping and intensity averaging in the case of low light levels are presented more extensively. Results of shape measurements on a metal cube and a glass bottle are shown. The shape measurement error is estimated at 0.1 mm r.m.s.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
23 citations
TL;DR: An experimental method for accurate polarimetric characterization of speckle field below its transverse correlation width is proposed and exhibits strong potential to analyze and differentiateSpeckle fields generated by bulk and surface scattering.
Abstract: An experimental method for accurate polarimetric characterization of speckle field below its transverse correlation width is proposed. Using a polarimetric analyzer, the speckle field under investigation is probed by a set of polarimetric projections describing the full Poincare sphere surface. Spatial polarimetric variations of the speckle field are thus observed with an accuracy of 1% for each Stokes parameter. Moreover, all the experimental data can be guaranteed by a validity criterion. Using white paper sheet and rough metal samples, the method exhibits strong potential to analyze and differentiate speckle fields generated by bulk and surface scattering.
23 citations
TL;DR: Low-speckle laser projection is demonstrated using a broad-area vertical-cavity surface-emitting laser emitting at 840 nm wavelength as the illumination source and quantitatively model the speckle contrast reduction based on polarization scrambling and the reduced temporal and spatial coherence of the VCSEL.
Abstract: We demonstrate low-speckle laser projection using a broad-area vertical-cavity surface-emitting laser (VCSEL) emitting at 840 nm wavelength as the illumination source. By driving the source in a nonmodal emission regime, we were able to achieve speckle contrast values as low as 3.5% in a realistic projection setup. This was done by driving the VCSEL with specific current pulses without using any additional or mechanically moving components to destroy the coherence of the laser beam. We quantitatively model the speckle contrast reduction based on polarization scrambling and the reduced temporal and spatial coherence of the VCSEL.
23 citations