Static information storage and retrieval – Read/write circuit – Optical
Patent
1998-01-08
1999-12-21
Hoang, Huan
Static information storage and retrieval
Read/write circuit
Optical
365106, 365234, G11C 700
Patent
active
06005817&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention is directed to a method and a write/read device for parallel writing and reading of data in an optical memory more specifically, the present invention is directed to such a method and device where the optical memory comprises one or more microlenses for accessing of an optical memory medium, microlens has a uniquely defined x,y position in a coordinate system assigned to the memory medium. A number of data carrying spot positions in a data carrying layer in the memory medium is assigned to each microlens. Each spot positions in a data carrying structure in the data carrying layer and is assigned a data address which is in a one-to-one correspondence with a set of angles of incidence .theta.,.phi. for light which is directed towards the microlens,. Each angle of incidence is defined as spherical coordinates in the coordinate system assigned to the memory medium.
In more general terms, the invention concerns parallel writing and reading of to data in optical memory media with high memory capacity, wherein the memory media comprise a large number of microlenses immobilized in dense arrays on or in a planar substrate which also contains a data-recording film or a data-recording volume in proximity to or adjacent to the microlenses, or in memories with low capacity, wherein each microlens forms a separate physical entity, or a memory element which includes a microlens and a data carrying surface or data carrying volume which is physically integrated with each microlens.
DESCRIPTION OF RELATED ART
As examples of a high capacity microlens-based memory medium, reference is made to NO patent applications no. 90 0443 and no. 95 2542. As an example of low capacity optical memories reference is made to the fact that there are known in the prior art objects (particles) or elements with information-bearing spot patterns, suitable for use as identification markers, etc.
The prior art includes digital optical data carriers which are widely used for storing and distributing data, typically in the form of laser-addressable, rotating discs. Recently, optical cards in a rectangular format with lower storage capacity than the discs have also been introduced. Nevertheless, compared with conventional data storage media, these types of storage media have a relatively large storage capacity, and consequently the cost of loading massive amounts of data into memories of this kind becomes a critical factor. If the data are written sequentially along a single track, operating and capital expenses may completely overshadow the cost of producing the data carrier itself. To illustrate by an example: Assume, e.g., that a data carrier has to receive 2 Gbytes of information by sequential laser writing of spots along a track in the data carrier. If the data are written at a rate of 1 Mbyte/s, fully 33 minutes will elapse before the data transfer is complete. For mass markets this is untenable. On the other hand, a substantial increase in the writing speed, e.g., beyond 1 Mbyte/s is difficult to achieve by evolutionary refinements of current single-beam writing technologies, such as increasing the spinning speed of the disc.
By writing with several lasers in parallel, the total data transfer rate can be speeded up, essentially multiplying the writing rate by the number of individually controllable lasers, as is described, for example, in Laser Focus World, August 1993, page 64. Recently, a system employing two four-beam laser arrays was announced by Asaka/Shibasoku & Co. of America, Los Angeles, Calif., USA, providing reading rates at more than 12 Mbytes/s, an improvement by a factor of ten over previous commercial technology, according to Asaka. It is not clear, however, whether their system can support similar high data rates during writing.
Parallel schemes similar to the one referred to above are currently under development at several institutions all over the world. However, they all share the same problem, namely that of simultaneously keeping all the lasers focused on the track with the required
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Gudesen Hans Gude
Nordal Per-Erik
Hoang Huan
Opticom ASA
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