Point contact transducer of waveguiding structure for high-frequency operation

Time-of-flight measurements with point-like contact transducers have successfully been applied for the detection of anisotropy, and for in situ measurements of film thickness and temperature. This paper presents a new type of Hertzian-contact transducer of waveguiding structure operating in the MHz range. The transducer is composed of a fused quartz tube and a radially-polarized annular piezoelectric element bonded to one of its ends. The edge-bonded shear-wave transducer effectively excites a surface wave on the interior surface of the tube. A small bullet pin made of quartz is inserted and fixed on the other end of the tube to make a point contact and transmit the wave energy to a specimen to be inspected. Using a pair of these transducers, we have succeeded in the excitation and detection of surface acoustic waves as well as Lamb waves in the 3 MHz frequency range.