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Florescent Disc Technology

Another contender in the battle to become the de facto high-density storage medium for the digital world could come from US data storage specialist, C3D, in the shape of its revolutionary optical storage technology that promises to deliver capacities of 140GB and above on a single multilayer disc.

With conventional optical disc drive technology signal quality degrades rapidly with the number of recording layers. This is principally because of optical interference – noise, scatter, and cross-talk resulting from the fact that the probing laser beam and the reflected signal are of the same wavelength and the nature of the highly coherent reflected signal used. The signal degradation exceeds acceptable levels with the result that no more than two recording layers are possible. However, with fluorescent readout systems, the quality degrades much more slowly, and C3D believes that up to 100 memory layers are feasible on a standard sized CD.

Fluorescent

The design of the discs is based on so-called stable photochrome, discovered by physicists and engineers in Russia. This is a transparent organic substance whose fluorescence can be triggered by a laser beam for sufficient time for it to be detected by a standard photoreceiver. This characteristic makes it possible to superimpose transparent layers on top of one another, and to write information on each level.

Once the fluorescence is stimulated by the laser light, both coherent and incoherent light are emitted. The latter has waves that are slightly out of step with each other, and the exploitation of this property is central to C3D’s technology. The out-of-sync fluorescent light beams allow data to be read through different layers of the stacked transparent discs, one beam reading data from the top layer at the same time that others are penetrating it to read from lower layers. The result is the twin benefit of huge storage capacities and greatly improved data retrieval speeds.

Its unique technological capabilities facilitate the production of a multilayer optical card, in any form factor – including a credit card or postage stamp sized ClearCard. The capacity and speed of reading for these cards is potentially enormous. For instance, as of 2001 the level of the technology allowed development of a ClearCard of 16 cm2 of area with 50 layers providing a capacity of 1TB and – through parallel access to all its layers – greater than 1 GBps reading speeds. When parallel layer reading is combined with parallel reading from multiple sectors of the same layer, data speeds can be increased still further, effectively producing 3-dimensional data transfer.

First demonstrated in Israel in the autumn of 1999, a number of leading industry players – including Philips and Matsushita – have shown an interest in the patented technology and C3D are hoping to bring a number of products to market during 2002:

  • FMD (Fluorescent Multi-layer disc) ROM: Depending on the application and the market requirements, the first generation of 120mm FMD ROM discs will hold between 20 and 100GB of pre-recorded data on 12 to 30 data layers – sufficient to store up to 20 hours of compressed HDTV film viewing – with a total thickness of under 2mm
  • FMD Microm WORM disc: a 30mm compact version of the FMD ROM – initially available as a 10-layer disc with 4GB capacity – which enables users to select the information to be stored
  • FMC ClearCard ROM Card: a 50mm credit card-sized storage medium designed to the capacity needs of the growing mobile computing marketplace which provides an initial capacity of 5GB, growing eventually to up to 20 layers, with a data density of 400 MB/cm2 and capacity of up to 10GB
  • FMC ClearCard WORM Card: a development of the ClearCard ROM – initially available with a capacity of 5GB – which enables the user to select the information to be stored.

The C3D technology is not, of course, compatible with current CD and DVD drives. However, the compatibility issue may be solved in the future since C3D claims its technology will be backwards compatible and that existing equipment can be made to read FMD ROM discs with minimal retooling.

In early 2001, progress appeared to be on schedule with the announcement of a licensing agreement with Lite-On IT Corporation of Taiwan – the third largest manufacturer of CD/DVD drives in the world – for the production of FMD/C drives. The agreement calls for Lite-On to pay a royalty to C3D on every drive produced. In addition, Lite-On will participate in the proposed FMD/C technology development consortium that will promote related media and drive manufacturing standards. The agreement also contemplates Lite-On making a strategic investment in C3D as well as appointing a Director to C3D’s Board.

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