Abstract: 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.

Key words: Acoustic microscopy, Line-focus, Polyvinylidene fluoride (PVDF) ultrasonic transducers, V(f;z) analytical technique