Device for providing a hologram of an insonified object

Abstract

A device for providing a hologram of an object which may be converted to an optical image in real time. The device is part of an acoustical holographic system which uses a source of coherent acoustic radiation to irradiate the object which reflects the acoustic radiation on to a piezoelectric transducer to provide a rapidly varying sinusoidal electronic charge pattern corresponding to the reflected acoustic radiation. Electrons are released from a photocathode, illuminated by a radiation source, in a spatial distribution of electron energies corresponding in space and time to the electronic charge pattern. A first grid positioned adjacent the photocathode is maintained at a potential to provide a modulated electron current which varies in space and time linearly in accordance with the acoustic input. The electron current is modulated by a second grid energized by a coherent reference voltage of fixed phase to function as a reference signal as used in holography. A microchannel plate electron multiplier amplifies the modulated electron current, and the amplified current is imaged on a high potential phosphor screen and provides an optical image of the hologram of the insonified object. The hologram may be converted into electric signals (video) by a conventional TV camera. For displaying an image of the object itself in real time, the video signals may be processed in an electro-optical Fourier transform converter tube, or may be processed by a fast Fourier transform computer and displayed on a cathode ray tube.