Selectively erasable optical memory system utilizing a photo excitable ferroelectric storage plate
AssigneeThomson-CSF
InventorsMarie Vergnolle, Jean Marc Rouchon, Francois Micheron
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Abstract
The present invention relates to photo excitable ferroelectric optical memory system designed to store, erase, and display light traces. In accordance with the invention, there is provided a system wherein a photo-ferroelectric plate is placed between a polarizer and a polarization analyzer. Under the combined action of a recording radiation and an external electric field, a photo induced electric is formed in the illuminated zones of the plate. Erasure is obtained by re-illuminating the plate without applying any external field. The optical display is achieved by means of an electric read-out field.
Claims14
Selectively erasable optical memory system for storing erasing and displaying data in form of at least one light trace, said system comprising:
- a storage plate having two substantially parallel major faces, electrical biasing means arranged for providing within said storage plate an external electric field having an orientation substantially parallel to said major faces, optical means provided for respectively recording and erasing said data through the selective illumination of said storage plate along one of said major faces, read-out means arranged for optically displaying the data stored in said storage plate, and control means for simultaneously controlling said electrical biasing means and said optical means to successively effect storage erasure and display of said data;
- said storage plate being cut from a photo excitable ferroelectric material whose birefringent property is a quadratic function of the applied electric field;
- said read-out means comprising a source of radiant energy for illuminating said storage plate along one of said major faces, polarizer means positioned between said source and said storage plate, and analyser means arranged for receiving from said storage plate said radiant energy;
- said optical means comprising a further source of radiant energy selectively illuminating said storage plate in the course of the recording and erasing of said data;
- said electrical biasing means comprising switching means actuated by said control means for setting the value of said external electric field to a predetermined value in the course of the storage of said trace for forming in the portion of said storage plate receiving said selective illumination of photo-induced electric field balancing said external electric field;
- said switching means making the value of said external field to reduce to zero for causing the erasure of data stored in any portion of said storage plate under the selective re-illumination thereof with said optical means.
Dependencies are inferred from the claim text.