The emergence of the CD-ROM format created a standard around which optical data storage could consolidate. If the 1990s saw economic improvement from optical disk, the 21st Century is seeing technological improvement. If the diameter of a spot recorded on an optical disk is halved, the storage density is improved by a factor of four, so is the amount of energy available to write a spot. CD technology was designed for 830nm wavelength lasers, essentially giving an 830nm spot, although finally 780nm lasers were used.
The cost has been squeezed out of CD Technology. Further progress depends on technology. A new package of technologies has been developed for consumer High Density Television recording. Called Blu-Ray technology it includes a 415nm laser and is championed by Panasonic, amongst others.
The 415nm laser, accompanied with improved lens design, actually provides spot less than half the size of CD technology and thus more than four times the density. The medium is phase change, potentially a lower cost approach than magneto optical. A consortium of ten major consumer electronics companies are selling licences to use Blu-Ray.
Plasmon, a UK company with close associations with Panasonic, has introduced a format based on Blu-Ray technology known as Ultra Density Optical. The initial disk capacity is 30GB with a potential growth path to perhaps as much as 320GB. Data transfer rates are around 4.5 MBps and Dell and HP are supporting the product. UDO uses a 5.25" disk in a caddy. It is exactly compatible with Magneto-optical disk cartridges and UDO will read MO devices. Plasmon's considerable heritage in the use of optical disk for archiving gives this technology a clear path at introduction.
Sony's PDfD uses a more demanding lens design than Plasmon (0.85 numerical aperture - NA - compared to 0.7). The initial capacity is lower at 27GB but the data transfer rate is 9MBps. The technical demands of the 0.85 NA approach may be one reason why the Sony product is later to market than the one from Plasmon.
Both devices use high NA lens compared to CD technology at 0.5. This means that it is not possible to focus through a thick protective layer onto a recording surface. The protective layer is a lot thinner. The high NA also leads to a shallow depth of focus, increasing demands on the tracking system and the potential for errors. As a result, the disks are being protected from environmental degradation in caddies.
Magneto optical technology is not well placed to respond to these drives and retain compatibility with earlier generations. UDO offers MO drive users an upgrade path.
Optical tape technology at 1-3TB in a 3480 cartridge and 10-100MBps data transfer rate offers an even more aggressive road map but since LOTS Technology (an optical tape-based storage concept) failed to raise stage 3 funds in the dot com bust, the technology package has passed into the control of a major media manufacturer and no announcements about development intentions have been made.
Toshiba and NEC offer an alternative consumer format to Blu-Ray called Advanced Optical Disk. This has not been proposed as a data format.
UDO and PDfD offer the potential for optical disk to maintain its price performance improvement of the last decade, continuing to outpace magnetic tape for mid range applications.
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