Numerical analysis of frequency characteristics of a prototype planate acoustic lens constructed by phononic crystal structures

The imaging system with acoustic lens was applied in the research of underwater field. In previous study, we calculated the basic characteristics of a planate acoustic lens constructed with phononic crystal structure. For confirming the basic property of the acoustic lens to obtain by the calculation, we manufactured a prototype of the planate lens made by stainless steel rods. In this study, for obtaining the frequency characteristics of a prototype of the planate lens, we calculated focusing field by a prototype of planate acoustic lens using elastic finite difference time domain (FDTD) method with sub-grid techniques. In addition, we calculated frequency characteristics of a planate lens by varying the diameter of steel rods a changed from 0.75 to 1.35 mm for the designing of high gain lens. As a result, measurement result is good agreement with simulation result using elastic FDTD method. The maximum gain appeared 700 kHz at centre frequency when diameter of rod equal 1.0 mm.