Focusing Characteristics Simulation of Lenses in Time-Domain with Axis-symmetric TLM Modeling

TLM nodes or elements are normally used in Cartesian coordinate systems. In the present paper, the axis-symmetric TLM node is devolved for the system of cylindrical symmetry, which only requires a little modification. The characteristic of Fresnel's zone plate lens, the dielectric convex lens and the acrylic concave lens for underwater ultrasonic are taken for the demonstration. The approach provides the visualization of the field distribution under impulsive excitation. The focal lengths obtained from the results are compared with those calculated by the ray theory.