Optical system for the storage of selectively erasable binary data arranged in the form of holographically recorded pages

An optical storage system for selectively erasable binary data arranged in pages holographically recorded within a photosensitive medium, said system comprising:

• a source of coherent radiation, a photosensitive medium for storing said binary data, first optical means splitting said coherent radiation into an object beam and a reference beam, a page composer device optically modulating said object beam in accordance with said binary data, second optical means causing said modulated object beam and said reference beam to intersect one another for effecting selective holographic recording and erasing of said pages within at least one portion of said photosensitive medium, third optical means cooperating with said reference beam, for selectively reading out the elementary hologram photo-induced in said photosensitive medium, and optical phase-shift means acting upon the phase of one of said beams in order to introduce an optical phase-shift acquiring the respective values 0 and .pi. for respectively effecting recording and erasing of said pages;
• said photosensitive medium being constituted by an electrically birefringent material undergoing a change in refractive index photo-induced by said coherent radiation;
• said photo-induced change in refractive index being caused by a reversible optical damage effect occuring in relation with a spatial variation in the amplitude of said coherent radiation.