Speckle-visibility spectroscopy: A tool to study time-varying dynamics
Speckle-visibility spectroscopy: A tool to study time-varying dynamics
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DOI：
10.1063/1.2037987
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发表时间：
2005-09-01
影响因子：
1.6
通讯作者：
Durian, DJ
中科院分区：
文献类型：
--
作者：
Bandyopadhyay, R;Gittings, AS;Durian, DJ
我们描述了一种多散斑动态光散射技术，能够在散射点的运动随时间系统变化的情况下解决这种运动。该方法基于由数字相机的单次曝光检测到的由散射光形成的散斑图案的可见性。虽然以前的多斑点方法依赖于图像之间的相关性，但在这里，与散射点动态的联系更简单地根据指定曝光持续时间内相机像素之间的强度变化来建立。其实质是，当散射点运动的动态与相机的曝光时间相比较慢时，散斑图案更可见，即检测到的强度级别的方差更大。给出了用电场自相关分析空间强度分布矩的理论。对两个众所周知的样品进行了测试，一个是布朗颗粒的胶体悬浮液，另一个是粗化泡沫，在这些样品中，动力学可以被视为静态的，因此可以用传统方法进行基准测试。然而，我们的散斑可见性方法特别适用于动态随时间变化的样本，无论是缓慢还是快速，仅受相机曝光时间保真度的限制。潜在的应用范围从柔软的玻璃材料，到颗粒状雪崩，再到活组织的流量测量。(C)2005年美国物理研究所。
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 camera for 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. (c) 2005 American Institute of Physics.