中文摘要：

线聚焦式超声材料性质表征系统可以对水浸试样漏表面波或类漏表面波的相速度进行精确的测量,但鉴于传统超声显微镜镜头的材料昂贵且制作困难,采用厚度为40？m的聚偏氟乙烯（Polyvinylidene fluoride,PVDF）压电薄膜作为激励/接收元件,设计、制作两个应用于声学显微系统的线聚焦无镜头式PVDF超声换能器,其中心频率分别为5 MHz和11 MHz。区别于传统超声显微镜高昂的设备费用与利用单频V（z）曲线测量空间振荡周期？z的方法,基于二维傅里叶变换开发出一种改进的适用于宽频的V（f,z）分析法,并发展建立一套成本较低的用于测量材料漏表面波波速的散焦试验系统。为测试换能器、算法和整体系统的性能,对抛光熔融石英进行非接触式水浸超声试验,利用V（f,z）分析法提取出表面波波速,并将试验结果与理论值进行对比,两者吻合较好。

英文摘要：

Line-focus-beam ultrasonic material property characterization system enables accurate measurements on the phase velocities of leaky surface acoustic waves（LSAW） or rayleigh-type leaky surface acoustic waves.But in view of the lens of the conventional acoustic microscopy is expensive and difficult to produce,new method of design and fabrication of two line-focus lens-less polyvinylidene fluoride（PVDF） transducers is presented for acoustic microscopy system utilizing a 40 ？m thick piezoelectric PVDF film to construct the active element.The transducers introduced here centre around 5 MHz and 11 MHz respectively.Different from high cost of equipments and measuring the oscillation period on an operation of tone-burst mode,an improved V（f,z） method based on tow-dimensional Fourier transform is developed for the broadband measurements.A defocusing system for measuring surface acoustic waves is established and a non-contact immersion experiment of a polished fused quartz is carried out.The LSAW velocity extracted by V（f,z） analytical technique is compared with the theoretical one and they both are in good agreement.