New speckle technique for noncontact measurement of small creep rates

Duncan, Donald D.; Mark, F.; Hunter, L. W.

doi:10.1117/12.57679

Cited by 12 publications

(7 citation statements)

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“…The crux of the problem is to calculate the shift in the speckle patterns, β, as a function of record number. From this information, the strain, ε, in the sample can be calculated directly as [1][2][3][4]…”

Section: Conceptual Experimentsmentioning

confidence: 99%

“…Various algorithms have been presented in the past for estimating the shift in a laser speckle pattern originating from an object (e.g., biological tissue) undergoing a dynamic strain. These algorithms have included the transform method of processing for speckle strain rate measurements [1,2], a maximum likelihood speckle shift estimator, and a maximum entropy estimator [3,4]. In addition, to these parametric estimators, there is the traditional approach to processing speckle data that makes use of the cross correlation between successive speckle records [3,4].…”

Section: Introductionmentioning

confidence: 99%

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Performance analysis of a maximum-likelihood speckle motion estimator

Duncan¹,

Kirkpatrick²

2002

Opt. Express

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Presented herein is a performance analysis of a maximum likelihood estimator for calculating small speckle motions. Such estimators are important in a variety of speckle techniques used in non-destructive evaluation. The analysis characterizes the performance (bias and RMS deviation) of the estimator as a function of the signal-to-noise ratio. This SNR parameter is a convenient surrogate for decorrelation of sequential speckle patterns such as are seen in biological tissues. Although the particular estimator is predicated on speckle motions that are a small fraction of a pixel, accurate performance is demonstrated for instantaneous motions of up to +/-0.8 pixel/record. Beyond this point, more conventional approaches have been shown to perform well.

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Section: Conceptual Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Performance analysis of a maximum-likelihood speckle motion estimator

Duncan¹,

Kirkpatrick²

2002

Opt. Express

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“…6(b) is a slice through this cube such that the spatial dimension is along the horizontal axis and time is along the vertical. This type of display seems to date to Oulamara et al [9] and has been called the time history of the speckle pattern (THSP) [1] and, earlier, a stacked speckle history [10]. In other fields, notably radiography and fluorescence speckle microscopy [11], such a spatio-temporal display is called a kymograph.…”

Section: ͑19͒mentioning

confidence: 99%

The copula: a tool for simulating speckle dynamics

Duncan

Kirkpatrick

2007

J. Opt. Soc. Am. A

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Use of a copula for generating a sequence of correlated speckle patterns is introduced. The chief characteristic of this algorithm is that it generates a continuous speckle sequence with a specified evolution of the correlation and does so with just two arrays of random numbers. Thus, physically realistic temporally varying speckle patterns with proper first- and second-order statistics are easily realized. We illustrate use of the algorithm for generating sequences with prescribed Gaussian, exponential, and equal-interval correlations and demonstrate how correlation times can be specified independently. This approach to generating sequences of random realizations with prescribed correlations should prove useful in modeling such phenomena as dynamic light scatter, flow-dependent laser speckle contrast, and propagation of spatial coherence.

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“…Furthermore, for the nonimaging case, the observation distance, L o , must be established in consideration of the ͑lensless͒ camera pixel pitch, p. Specifically, to meet the Nyquist sampling criteria, it must be arranged so that the mean speckle size d sp ϭL o /Dу2p where is the wavelength, and D is the length of the uniformly illuminated stripe. 15 Large speckles can be achieved through either small spot sizes or large observation distances. Too small a spot size, however, results in the speckles being too large in the far field.…”

Section: Introductionmentioning

confidence: 99%

High resolution imaged laser speckle strain gauge for vascular applications

Kirkpatrick

Cipolla

2000

J. Biomed. Opt.

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An imaged laser speckle strain gauge that yields strain rates directly is described for vascular applications. The strain gauge does not rely upon cross correlations between a reference image and subsequent strain-modulated images as most current speckle interferometric methods do. Instead, it relies upon a two-dimensional frequency transform of "stacked speckle histories" which are time series of one-dimensional views of the speckle patterns arranged into a spatio-temporal array such that space is along the abscissa and time is along the ordinate. The tilt of the stacked speckle histories is related to the time rate of speckle pattern shift. The strain gauge is sensitive only to in-plane strains. Strain rates of 30.1 +/- 3.2 and 24.83 +/- 2.1 mu epsilon/s were evaluated in vitro on a fresh human tibial artery and rat inferior vena cava, respectively. The total strains measured were 21.6 and 19.86 mu epsilon, respectively. This is at least one order of magnitude more sensitive than other current soft-tissue strain measurement techniques.

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New speckle technique for noncontact measurement of small creep rates

Cited by 12 publications

References 12 publications

Performance analysis of a maximum-likelihood speckle motion estimator

Performance analysis of a maximum-likelihood speckle motion estimator

The copula: a tool for simulating speckle dynamics

High resolution imaged laser speckle strain gauge for vascular applications

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