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Fluorescent Multilayer Disc (FMD), is an optical disc format developed by Constellation 3D that uses fluorescent, rather than reflective materials to store data. Reflective disc formats (such as CD and DVD) have a practical limitation of about two layers, primarily due to interference, scatter, and intra-layer cross talk. However, the use of fluorescence allows FMDs to have up to 100 layers. These extra layers allow FMDs to have capacities up to a terabyte, while maintaining the same physical size of traditional optical discs.
Operating principles
The pits in an FMD are filled with fluorescent material. When coherent light from the laser strikes a pit the material glows, giving off incoherent light of a different wavelength. Since FMDs are clear, this light is able to travel through many layers unimpeded. The clear discs, combined with the ability to filter out laser light (based on wavelength and coherence), yield a much greater signal-to-noise ratio than reflective media. This is what allows FMDs to have many layers. The main limitation on the number of layers in a FMD is the overall thickness of the disc.
Development
A 50 GB prototype disc was demonstrated at the COMDEX industry show in November 2000. First generation FMDs were to use 650nm red lasers, yielding roughly 140GB per disc. Second and third generation FMDs were to use 405nm blue lasers, giving capacities of up to a terabyte.
After Constellation 3D shut down due to a scandal (the scandal essentially involved the prototype "demonstrated" at COMDEX 2000 being a hoax — the content was actually playing on a hard drive — the device was faked) and the company consequently running out of money, a new company called D Data Inc. was formed which acquired the entire patent portfolio of Constellation 3D in 2003. The company is determined to bring multilayer optical disc technology to the market, and so has introduced the technology again under the new name of Digital Multilayer Disk (DMD).
See also Fluorescent Multilayer Card.
External links
Computer storage media | 120 mm discs | Audio storage | Video storage
"Fluorescent Multilayer Disc"