An application of holographic interferometry to acoustical holography

Holographic interferometry with a phase-modulated reference beam is applied to an acoustic holography. A very thin, flexible, optically reflective membrane, called a pellicle, is used in the liquid as an acousto-optic interface. The method involves three processes: the motion of a pellicle caused by an ultrasonic wave is recorded as an optical hologram using holographic interferometry; the optical hologram is reconstructed to form an image on the pellicle which is used as an acoustic hologram; the acoustic hologram is finally used to reconstruct an image of the original object by illuminating it by laser light. A preliminary experiment is done with an ultrasound of frequency 1 MHz.