Characterization of layered materials by the Lamb wave lens

The Lamb wave lens is a type of lens that can replace the conventional lens of an acoustic microscope for some applications. When it insonifies a layered solid structure, it excites a single mode in the structure, provided that the frequency is properly adjusted. Measuring the return signal as a function of frequency results in a characteristic curve showing the excited modes. Since the number of excited modes, the frequencies at which they are excited, and the efficiency of excitation are highly dependent on the elastic and physical parameters of the layered solid, a characterization method emerges. The authors describe this characterization method for the layered structures using the Lamb wave lens. Theoretical and experimental results are presented.