Limits of time-reversal focusing through multiple scattering: long-range correlation
Limits of time-reversal focusing through multiple scattering: long-range correlation
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DOI：
10.1121/1.429328
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发表时间：
2000-05
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影响因子：
--
通讯作者：
Derode;Tourin;Fink
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文献类型：
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作者：
Derode;Tourin;Fink
给出了高阶多次散射介质中时间反转聚焦的实验结果，并与基于统计模型的理论预测进行了比较。该介质由一组随机平行的钢棒组成。超声源(3.2 MHz)发射经过多次散射并记录在阵列上的脉冲。由阵列通过散射介质将时间反转的波发送回源。用一个简单的统计模型很好地预测了时间聚焦的质量。然而，对于较厚的样本，会出现持续性的颞叶旁瓣。我们将这些旁瓣解释为由于高阶多次散射导致样本中的交叉路径数量不断增加的结果。至于空间聚焦，分辨率实际上与阵列的孔径无关。使用16元阵列时，分辨率比均匀介质中的分辨率高30倍。获得了波长量级(0.5 mm)的分辨率。讨论了这些结果与随机介质中时间反转镜的统计性质的关系。
Experimental results of time-reversal focusing in a high-order multiple scattering medium are presented and compared to theoretical predictions based on a statistical model. The medium consists of a random collection of parallel steel rods. An ultrasonic source (3.2 MHz) transmits a pulse that undergoes multiple scattering and is recorded on an array. The time-reversed waves are sent by the array back to the source through the scattering medium. The quality of temporal focusing is very well predicted by a simple statistical model. However, for thicker samples, persistent temporal side-lobes appear. We interpret these side-lobes as a consequence of the growing number of crossing paths in the sample due to high-order multiple scattering. As to spatial focusing, the resolution is practically independent from the array's aperture. With a 16-element array, the resolution was found to be 30 times finer than in a homogeneous medium. Resolutions of the order of the wavelength (0.5 mm) were attained. These results are discussed in relation with the statistical properties of time-reversal mirrors in a random medium.