Study of acoustic signatures for non-spherical curved acoustic lens

In this paper, we first evaluate the Acoustical Material Signature used in acoustic microscopy by a method based on the Rayleigh-Sommefeld field integration. Different to the conventional geometry ray or Fourier optics method the field integration method needs no approximate conditions and can take into consideration the near field phenomenon and the diffraction effect in an acoustic lens. Moreover, with this model, the lens can have any special designed geometry. Using this method, we compared the calculated results with that of the experimental ones obtained from a three-layered bonding structure, the concordance is very significant. We then take the case of a conical ring lens which is convenient to the selected Lamb wave excitation and detection for a multilayered structure. A physical model is given to explain the fringes obtained in V(z) curve using such a lens