On Acoustic Field Focusing Caustics caused by Material Anisotropy and Inhomogenity

The work is concerned with acoustic field focusing caustics related, on one side, to material anisotropy, and, on the other side, by local inhomogenity of isotropic materials. Angular spectrum technique in combination with 2D FFT algorithm applied by the authors in case of anisotropic materials demonstrates high accuracy of calculated results with measurements. In the case of functionally graded materials (FGM), THE inhomogenity of acoustic properties and wave dispersion are taken into account. In both cases acoustic microscopy with phase contrast was employed to reveal material properties. Authors discuss the influence of field focussing effects on the microscopic imaging and the possibility of appropriate results correction.