Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1997-11-24
2000-11-21
Tran, Thang V.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
3692751, G11B 700
Patent
active
061512877
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the design and fabrication of optical mass memory devices, such as optical discs (or laser discs), as well as to recording and reading out information data as stored in such memories using a beam of laser light. It must be understood however that while the configuration of so-called compact discs in standard dimensions fulfil important industrial needs, it is not limitative, and mass data storage memories with similar composition and structure can be formed on other types of substrates, for example tapes or films.
BACKGROUND OF THE INVENTION
The storage capacity of present optical memory devices appear quite inadequate for many applications. One does not know how to do more than storing information data at the surface of a photo-sensitive layer covering the disc side. Most often, micro-dips on which the light beam is focused are engraved on such an optical coating, which form elementary cells for data recording that are distributed over the photo-sensitive surface. Owing to the area each of them occupies and to their necessary spacing, their number is limited.
With a view to increasing the memory capacity of optical discs, several solutions are currently been studied. One may mention:--double-sided discs,--the use of blue laser light, allowing a slight size reduction for the elementary cells in agreement with the theory of diffraction,--the superposition of several photo-sensitive layers, in limited number however (six for example or up to ten), which in addition requires as many lenses to focus the light on the different layers, both for recording and read-out.
These different solutions allow only to increase the capacity of current optical discs by at most ten times, which is not a sufficient increase for the needs of industry.
One can also envisage to use substrates bearing several differently coloured layers, as is the case in color photographic films. But, in fact, it is difficult to have more than a few layers, owing to the interactions among the coloured light beams to be used both for recording and read-out, and therefore the memory increase remains limited.
SUMMARY OF THE INVENTION
The problem that the present invention intends to solve is to provide an optical-type mass memory with much improved memory density, compared to that of current optical discs, by allowing advantageously to record hundreds of data bits in a zone corresponding to the Airy peak of a microscope lens, said peak being generally approximately one micron wide.
To this end, the invention proposes to resort to the aptitudes for volume holography of photo-sensitive mediums volume that have been explored in another field, and to combine thereby, for data storage, a high lateral density over the surface of the optical layer with a high vertical density in depth.
To this effect, an object of the present invention a is a mass optical memory, of the kind having a photo-sensitive layer, preferably formed on an optical disc, which includes elementary cells distributed across its free surface, for recording data reaching it in a laser beam to which it is exposed, the data thus recorded being retrieved through read-out with a laser beam.
The memory according to the invention comprises, for each elementary cell, a light guiding rod operative as a single-mode optical fibre, made from a photo-sensitive material, the axis of which is approximately orthogonal to the free recording surface.
When a fibre in such layer is exposed to a data carrying beam, it is created therein, through Lippmann's effect, standing waves with multiple wavelenghts that, by acting on the light-sensitive material, generate a structure comprised in each fibre of a pile of periodic stratifications superposed along the rod axis and forming an interferogram.
In each rod within a photo-sensitive layer according to the invention, having a structure forming a lattice of monomode fibres directed transversally to the accessible exposure face, data are recorded in a retrievable form as a stratification of its optical properties which, through the ad
REFERENCES:
patent: 3912391 (1975-10-01), Fleischer et al.
patent: 5283777 (1994-02-01), Tanno et al.
patent: 5377176 (1994-12-01), Redfield
patent: 5377179 (1994-12-01), Redfield et al.
patent: 5477347 (1995-12-01), Redfield et al.
patent: 5566387 (1996-10-01), Dewald
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