矩形超声换能器空间脉冲响应计算方法研究

Study on spatial impulse response calculation method for rectangular ultrasonic transducer

空间脉冲响应模型是一种可以高速、精确地计算平面型超声换能器瞬态声场的方法,该方法不需要对平面型探头的表面进行离散化或近轴近似处理。首先将空间点投影到换能器平面内,将构建空间脉冲响应函数转化为计算以该投影点为圆心,与换能器相交的圆弧段的圆心角。由于矩形换能器包括4个顶点和4条边线,其几何形状与圆形换能器相比较为特殊,所以当投影点位于平面内的不同位置时,其计算方法也不相同。首先将探头所在平面进行分区,当投影点位于同一分区中时,其空间脉冲响应函数的计算方法相同;然后给出了当投影点位于各个分区中时的空间脉冲响应函数的计算过程,分析了矩形换能器尺寸的变化对分区的影响;最后,对一维超声相控阵探头的瞬态辐射声场进行了计算实验,并采用动态光弹方法对瞬态声场进行观测实验。实验结果表明,不同的换能器尺寸对计算过程及结果有显著影响,本文计算方法可以有效地实现矩形超声波探头在均匀单一介质中的瞬态声场仿真计算,有利于对平面矩形类超声换能器进行优化设计。

Spatial impulse response（ SIR） model is a fast and accurate method for calculating the transient acoustic field of planar ultrasonic transducer. The SIR method does not require to perform the discretization of the planar transducer surface or paraxial approximation processing. First of all,the spatial points are projected to the transducer plane; and constructing the SIR function is transformed to calculating the central angle of the arc with the projection point as the center and intersected with the transducer. Because the rectangular transducer has four vertices and four edges,whose geometry is more complex than that of the circular transducer; the calculation procedures for the rectangular transducer are different when the projection points are located in different regions. In this paper,we analyze the relationship between the transducer dimension and the complexity of the calculation procedures. Firstly,the transducer plane is divided into four regions; the spatial impulse response calculation methods for the projection points located in the same region are the same,and the spatial impulse response calculation procedures for various regions are given. The influence of the dimension variation of the rectangular transducer on the regions is analyzed. Finally,the transient acoustic radiated field of a one-dimensional ultrasonic phased array transducer was calculated in experiment utilizing the spatial impulse response method. The dynamic photoelastic method was adopted to perform the observation experiment of the transient ultrasound field. The results demonstrate that different transducer dimension can affect the calculation procedure and the result obviously; and the presented method can effectively achieve the simulation calculation of the transient ultrasound field radiated from a rectangular ultrasonic transducer in a homogeneous medium,which is helpful to the optimization design of planar rectangular ultrasonic transducer.