Processing an acoustic microscope’s spatiotemporal signal to determine the parameters of an isotropic layer

Abstract

This paper presents a method for measuring the thickness and velocities of body waves and the density of an isotropic layer by a pulse scanning acoustic microscope. The method is based on recording the microscope signal as a function of the displacement magnitude of the focused ultrasonic transducer along its axis perpendicular to the sample surface and on the decomposition of the recorded 2D spatiotemporal signal into the spectrum of plane pulse waves. The velocities of the longitudinal and transverse waves and the layer’s thickness are calculated from the relative delays of the components of the spectrum of plane waves reflected from the surfaces of the layer and the density is computed by the amplitudes of these components. An experimental investigation of a test sample in the form of a glass plate carried out in the 50-MHz range shows that the error in measuring the thickness and velocities of body waves does not exceed 1% and the density measurement error does not exceed 10%.