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在超声显微成像领域,Fresnel声学透镜作为传统球面声学透镜的一种相互补充形式,最近受到人们的关注.Fresnel声学透镜的优点之一是平面结构,因此制作简单.另外一个优点就是它的会聚焦点可以随频率沿深度方向进行扫描.研究了圆环形Fresnel表面换能器阵在固体中产生的声场和高频聚焦特性.理论分析和实验皆表明,这种表面阵列不但可以工作在很高的频率(如400 MHz),而且当激励频率改变时,会聚声场的焦点可以沿深度方向进行扫描,即B扫描成像中的动态扫描.基于这种聚焦原理,研制了可调焦高分辨超声显微成像系统,并对已知样品的小孔缺陷进行了内部的检测和成像实验.
In the field of ultrasonic microscopy, Fresnel acoustical lenses have recently drawn the attention as a complementary form of conventional spherical acoustical lenses, one of the advantages of a Fresnel acoustical lens is its planar construction, making it easy to manufacture. Another advantage is its convergence The focus can be scanned along with the frequency in the depth direction.The acoustic field and high-frequency focusing characteristics of ring-shaped Fresnel surface transducer array in solid are studied.The theoretical analysis and experiments show that this surface array can not only work in high (Such as 400 MHz), and when the excitation frequency is changed, the focal point of the convergent sound field can be scanned in the depth direction, that is, the dynamic scan in B-scan imaging.Based on this focusing principle, a high-resolution, Micro-imaging system, and the well-known samples of small defects were detected and imaging experiments.