Journal ArticleDOI
Electronic speckle photography: analysis of an algorithm giving the displacement with subpixel accuracy.
Mikael Sjödahl,Lars Benckert +1 more
TLDR
An algorithm based on a two-dimensional discrete cross correlation between subimages from different images is presented, and the reliability and accuracy is analyzed by using computer-generated speckle patterns.Abstract:
Replacing photographic recording by electronic processing has some obvious advantages. An algorithm used for electronic speckle pattern photography is presented, and the reliability and accuracy is analyzed by using computer-generated speckle patterns. The algorithm is based on a two-dimensional discrete cross correlation between subimages from different images. Subpixel accuracy is obtained by a Fourier series expansion of the discrete correlation surface. The accuracy of the algorithm was found to vary in proportion to sigma/n(1 - delta)(2), where sigma is the speckle size, n is the subimage size, and delta is the amount of decorrelation, with negligible systematic errors. For typical values the uncertainty in the displacement is approximately 0.05 pixels. The uncertainty is found to increase with increased displacement gradients.read more
Citations
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Journal ArticleDOI
Two-dimensional digital image correlation for in-plane displacement and strain measurement: a review
TL;DR: In this article, a review of the 2D digital image correlation (2D DIC) technique for displacement field measurement and strain field estimation is presented, and detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided.
Journal ArticleDOI
Review of experimental techniques for high rate deformation and shock studies
TL;DR: In this paper, a variety of techniques used to obtain the mechanical properties of materials at high rates of strain (⩾10 s−1) are summarised, including dropweight machines, split Hopkinson pressure bars, Taylor impact and shock loading by plate impact.
Journal ArticleDOI
Equivalence of digital image correlation criteria for pattern matching.
TL;DR: This paper focuses on three robust and most widely used correlation criteria, i.e., a zero-mean normalized cross-correlation (ZNCC) criterion, a Zero normalized sum of squared difference criterion, and a parametric sum of squares difference (PSSD(ab) criterion with two additional unknown parameters, since they are insensitive to the scale and offset changes of the target subset intensity and have been highly recommended for practical use in literature.
Journal ArticleDOI
Electronic speckle photography: increased accuracy by nonintegral pixel shifting.
TL;DR: The improved algorithm was found to determine displacement components with an uncertainty of less than 1% of a pixel and with negligible systematic errors in ideal experimental conditions.
Journal ArticleDOI
Full-field strain mapping by optical correlation of micrographs acquired during deformation
TL;DR: The fundamental aspects of optical correlation are presented, with emphasis on the applicability of the technique to the analysis of micrographs obtained during in situ deformation studies.
References
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Journal ArticleDOI
Applications of digital-image-correlation techniques to experimental mechanics
Journal ArticleDOI
Determination of displacements using an improved digital correlation method
TL;DR: An improved digital correlation method is presented for obtaining the full-field in-plane deformations of an object by numerically correlating a selected subset from the digitized intensity pattern of the undeformed object.
ReportDOI
Statistical properties of laser sparkle patterns
TL;DR: In this article, the first order statistics of the observed electric-field strength, the observed light intensity, and observed light phase are examined, and the autocorrelation functions of the complex field and intensity processes are investigated, and that of the electric field is found to be proportional to the Fourier transform of the light intensity distribution incident on the scattering surface.
Journal ArticleDOI
Digital image correlation using Newton-Raphson method of partial differential correction
TL;DR: In this paper, the authors developed and limited experimental verification of a method which can determine displacements and gradients using the Newton-Raphson method of partial corrections, which was shown to be accurate in determining displacement and certain gradients, while using significantly less CPU time than the current coarse-fine search method.
Book ChapterDOI
Statistical Properties of Laser Speckle Patterns
TL;DR: In this article, the first-order statistics of the complex amplitude, intensity and phase of speckle are derived for a free-space propagation geometry and for an imaging geometry.