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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >Ultrasonic Imaging in Highly Attenuating Materials With Hadamard Codes and the Decomposition of the Time Reversal Operator
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Ultrasonic Imaging in Highly Attenuating Materials With Hadamard Codes and the Decomposition of the Time Reversal Operator

机译：具有Hadamard码的高衰减材料的超声成像和时间反转算子的分解

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In this paper, defects in a high density polyethylene pipe are imaged with the total focusing method. The viscoelastic attenuation of this material greatly reduces the signal level and leads to a poor signal-to-noise ratio (SNR) due to electronic noise. To improve the image quality, the decomposition of the time reversal operator method is combined with the spatial Hadamard coded transmissions before calculating images in the time domain. Because the Hadamard coding is not compatible with conventional imaging systems, this paper proposes two modified coding methods based on sparse Hadamard matrices with +1/0 coefficients. The SNRs expected with the different spatial codes are demonstrated, and then validated on both simulated and experimental data. Experiments are performed with a transducer array in contact with the base material of a polyethylene pipe. In order to improve the noise filtering procedure, the singular values associated with electronic noise are expressed on the basis of the random matrix theory. This model of noise singular values allows a better identification of the defect response in noisy experimental data. Finally, the imaging method is evaluated in a more industrial inspection configuration, where an immersion array probe is used to image defects in a butt fusion weld with a complex geometry.
机译：在本文中，用全聚焦法对高密度聚乙烯管中的缺陷进行成像。这种材料的粘弹性衰减会大大降低信号电平，并由于电子噪声而导致较差的信噪比（SNR）。为了提高图像质量，在时域中计算图像之前，将时间反转算子方法的分解与空间Hadamard编码传输进行组合。由于Hadamard编码与常规成像系统不兼容，因此本文提出了两种基于具有+1/0系数的稀疏Hadamard矩阵的改进编码方法。演示了使用不同空间码预期的SNR，然后在模拟和实验数据上进行了验证。用与聚乙烯管的基材接触的换能器阵列进行实验。为了改进噪声过滤过程，基于随机矩阵理论来表达与电子噪声相关的奇异值。这种噪声奇异值模型可以更好地识别嘈杂的实验数据中的缺陷响应。最后，在更工业的检查配置中评估成像方法，其中使用浸没阵列探头对具有复杂几何形状的对接熔接焊缝中的缺陷成像。

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