Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1997-12-23
2000-04-18
Tran, Thang V.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369100, G11B 700
Patent
active
060523549
DESCRIPTION:
BRIEF SUMMARY
The invention concerns an optical data storage medium comprising a data storage area formed by a substantially transparent homogeneous base material and with a number of optically active structures in the form of diffractive optical elements adjacent to one side of the data storage area, wherein the diffractive optical elements each are adapted to focus a light beam incident on the data storage area onto one or more points which each corresponds to a uniquely addressable location of a data-carrying structure which is to be generated or a generated data-carrying structure in the data storage area and/or to focus a redirected light beam or emitted light radiation from this point or these points onto a point outside the optical storage medium. The invention also concerns methods for writing of data according to the introduction to claims 13 and 14 together with methods for reading of data according to the introduction to claims 17 and 18 respectively. Furthermore the invention also concerns a method for parallel writing of data according to the introduction to claim 20 and a method for parallel reading of data according to the introduction to claim 21.
The present invention is intended to be used in optical data storage media in the form of rotating discs, rectangular cards or sheets or tapes in the form of strips or spools.
The present invention is especially intended to be employed in connection with a data carrying medium and a method for generating a data carrying structure in such a data carrying medium, as described in International Published Application WO96/37888, titled "Optical data storage" assigned to present applicant and to which reference will be made here.
In digital optical data storage according to the state of the art a sharply focused laser beam is systematically scanned over the surface of the data carrying medium, typically a rotating disc, and the data content is deduced by recording changes in reflected light from the disc when the laser beam passes microscopic pits or spots which have been encoded on to the medium. High data densities can be achieved when the pits or the spots are small and are located close together. The pits or spots which form the data carrying structures can either be moulded or pressed into the disc at the time of manufacture, or a scanning laser beam may be used to encode data into the disc by means of short, intense bursts of light which cause the data carrying structures to be formed, e.g. in the form of pits.
FIELD OF THE INVENTION
This method of optical data storage and accessing has a number of drawbacks. A highly precise optomechanical system is required in order to position the laser beam accurately along the track containing the data, and the data are read out serially. This entails mechanically operative restrictions and also reduces random access speed. The latter problem is particularly serious in many applications, and comprehensive research is currently in progress with a view to the development of lighter optical head designs which permit faster mechanical positioning. Mechanically based methods, however, are not suited to the attainment of very high access rates and considerable resources have therefore beer invested on research in order to develop addressing schemes for light beams based on acoustooptic or elctrooptic effects. Since such schemes now could be implemented in compact and preferably low-cost physical packages, integrated optical structures have been of particular interest to researchers.
Even though the above mentioned ongoing research will eventually result in practical hardware, due to sequential access to the stored information and as a result of the tracking method employed, the data transfer rates will be a serious problem. In order to eliminate his, research has been carried out on multi-track solutions where data are transferred in parallel by optical heads which write and read a number of adjacent tracks. Only a few neighbouring tracks can be covered in this fashion by a single servo-controlled optical head, and several in
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Gudesen Hans Gude
N.ae butted.ringsrud Thormod
Nilsen Rolv M.o slashed.ll
Nordal Per-Erik
Thin Film Electronics ASA
Tran Thang V.
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