FOCUSED FIELD OF THE SPHERICALLY CONVERGING ACOUSTIC WAVE ON ANISOTROPIC MEDIA

In this letter, a theoretical method based on Huygen's principle used by Green and Kino to predict the radiation fields of the two-dimension transducers on anisotropic substrates is extended to the three-dimension case, i.e., to the focused acoustic fields of the spherically converging waves. In terms of the expression of the diffraction integral developed here, the acoustic intensity distributions in the focal plane and on the beam axis are given. It is shown that the transversal width of the focus in anisotropic media is the same as that in isotropic case but the focal length, the longitudinal length of the focal region and the tolerance of the focus are changed by a factor of 1/（1-2b） compared with that in the isotropic media situation, b is the anisotropy factor of the media. It means that the focus position in anisotropic media is more tolerant than in isotropic media.