Effect of Lens Properties on Measuring Wave Velocities by Scanning Acoustic Microscope

Abstract

In the present paper, suitable properties of the acoustic lens for the complex V(z) curve analysis using a scanning acoustic microscope are suggested. First, it is confirmed that the amplitude and the phase of the transfer function of the lens can be calculated theoretically by the transmittance function at the tip of the lens and sound field on back focal plane of the lens. To investigate the effect of the lens properties on measuring wave velocities, critical angles of waves for four kinds of glass samples are inspected by two different lenses. As a result, it is found that the transfer function of the lens in which the large amplitude decreases gradually with the normalized wave numbers, is superior in inspecting critical angles of longitudinal and transverse waves. To inspect the apparent critical angle of Rayleigh wave, it is preferable to use the lens which has the stable phase in the transfer function with respect to the normalized wave numbers.