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首页> 外文会议>Photons Plus Ultrasound: Imaging and Sensing 2006; Progress in Biomedical Optics and Imaging; vol.7, no.9 >Experimental investigation of time-reversal of photo-acoustic waves
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Experimental investigation of time-reversal of photo-acoustic waves

机译：光声波时间反转的实验研究

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摘要

Ultrasound focusing through complex media can be achieved using time-reversal techniques. These techniques make use of back-propagating ultrasonic waves generated by localized sources. Such sources generally consist of high acoustic contrasts echoing ultrasonic waves generated by an incident ultrasonic field, or directly by point-like transducers inserted at the desired focusing location. In this work, we experimentally investigate time-reversal of acoustic waves generated by photo-acoustic emission. A frequency-doubled Q-switched Nd:YAG laser was used to illuminate phantom with 5-ns laser pulses. A 128-element ultrasonic transducer array, with a center frequency of 1.5 MHz, was used to detect acoustic waves generated by optically absorbing targets suspended in water. A dedicated 32-channel electronics was used to time-reverse and re-emit the detected ultrasonic field. Gel spheres dyed with India ink (diameter approximately 1-2 mm) illuminated by the laser beam were used to generate the photo-acoustic waves. Time-reversal of the detected field was performed to focus ultrasound in the presence of highly defocusing media in front of the transducer array. We demonstrate how this allows correcting for the aberration in order to provide good quality images in the isoplanetic region surrounding the photo-acoustic source.
机译：通过时间反转技术可以实现通过复杂介质进行超声聚焦。这些技术利用了局部源产生的反向传播超声波。这样的源通常由高声对比度组成，该高声对比度回波由入射超声场或直接由插入在所需聚焦位置的点状换能器产生的超声波。在这项工作中，我们实验研究由光声发射产生的声波的时间反转。倍频调Q的Nd：YAG激光器用于以5 ns的激光脉冲照亮体模。中心频率为1.5 MHz的128元素超声换能器阵列用于检测由光学吸收悬浮在水中的目标产生的声波。专用的32通道电子设备用于时间倒转并重新发射检测到的超声场。用被激光束照射的印度墨水（直径约1-2毫米）染色的凝胶球体用于产生光声波。在换能器阵列前面存在高度散焦的介质时，对检测到的场进行时间反转以聚焦超声。我们演示了这如何允许校正像差，以便在围绕光声源的等平面区域中提供高质量的图像。

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