Department of Physics Papers

Document Type

Journal Article

Date of this Version

2005

Publication Source

Review of Scientific Instruments

Volume

76

Issue

9

Start Page

093110-1

Last Page

093110-11

DOI

10.1063/1.2037987

Abstract

We describe a multispeckle dynamic light scattering technique capable of resolving the motion of scattering sites in cases that this motion changes systematically with time. The method is based on the visibility of the speckle pattern formed by the scattered light as detected by a single exposure of a digital camera. Whereas previous multispeckle methods rely on correlations between images, here the connection with scattering site dynamics is made more simply in terms of the variance of intensity among the pixels of the camerafor the specified exposure duration. The essence is that the speckle pattern is more visible, i.e., the variance of detected intensity levels is greater, when the dynamics of the scattering site motion is slow compared to the exposure time of the camera. The theory for analyzing the moments of the spatial intensity distribution in terms of the electric-field autocorrelation is presented. It is tested for two well-understood samples, a colloidal suspension of Brownian particles and a coarsening foam, where the dynamics can be treated as stationary and hence can be benchmarked by traditional methods. However, our speckle-visibility method is particularly appropriate for samples in which the dynamics vary with time, either slowly or rapidly, limited only by the exposure time fidelity of the camera. Potential applications range from soft-glassy materials, to granular avalanches, to flowmetry of living tissue.

Copyright/Permission Statement

This article was originally published by the American Institute of Physics. You can find the original article at: http://aip.scitation.org/doi/10.1063/1.2037987

Keywords

speckle, spin valves, cameras, speckle patterns, light scattering

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Date Posted:10 October 2017

This document has been peer reviewed.