Ultrasonic holography using an electronic reference with arbitrary wavefronts

Introduction of an electronic reference with arbitrary wavefronts to aid ultrasonic holography is described, along with simulation of the reference wave by adjusting the phase of reference signals from an oscillator. The simulated reference and object signals (originating in an object immersed in water and insonated by a 1 MHz wave) from the receiving transducer were superposed, and reconstructed from the holograms. Simulation of cylindrical and spherical wavefronts using a microcomputer to control the phase delay circuit is described.