APPLICATION OF A DIFFRACTION-CORRECTED RAY THEORY TO THE SLOT LENS IN ACOUSTIC MICROSCOPY

A modified ray approach is used to model the slot lens for determining V(z) and the results are compared with experiment for several materials. The slot lens is also used to obtain V(z) of y-cut quartz for a number of slot orientations relative to the crystalline x axis. The Rayleigh wave velocity as a function of propagation direction is then deduced from these measurements and compared with accepted values. It is shown that although the angular restriction of the slot lens is introduced in the lens aperture plane in contrast to shaped electrodes in the transducer plane, it is still necessary to account for diffraction in the lens rod in order to provide agreement with experiment. The application of the slot lens to crack detection is also examined and an analysis provided that yields substantial agreement with experiment. A simple yet effective method for extracting the surface wave reflection coefficient of a crack from measurements is proposed and demonstrated.