"Blue-laser" discs are just that—discs recorded with a blue-laser diode. The capacity increase results from the diode's shorter wavelength, which measures 405nm as opposed to existing red-laser diode's 650nm. The format Toshiba and NEC are proposing is different from the "Blu-ray" format proposed earlier this year by Matsushita, Sony and others. While not compatible with Blu-ray—a format that promises up to 27GB capacity on a single-sided, single-layer disc—the Toshiba/NEC technology uses a 0.6mm substrate, the same as current red-laser discs. The companies claim that blue-laser players would be compatible with current red-laser discs, meaning that new blue-laser DVD players would still be able to play red-laser discs. The 0.1mm substrate Blu-ray, which also uses a 405nm diode, is not compatible with existing DVD media.
The other key difference between the Toshiba/NEC proposal and the Blu-ray proposal lies in the numerical aperture (NA) of the lens required to read the disc—hence, the difference in compatibility. Blu-ray uses a 0.85 NA lens, while Toshiba's proposal indicates a lens with an NA of 0.65, much closer to existing players' 0.6 lenses. Both formats propose a data transfer rate of 36Mbps, and both would result in discs with a total thickness of 1.2mm.
Toshiba and NEC say they also will soon propose a 40GB single-sided, dual-layer RW disc to the forum.
Sony showed off its Blu-ray recorder for the first time at its Sony Dream World 2002 exhibition in Japan in early September. The trial units were slightly larger than typical external DVD recorders, according to Nikkei Electronics, but offer both digital satellite and broadcast television recording capability. Sony still hasn't announced when it will bring the recorders to market.
The DVD Forum Steering Committee has established two subgroups to examine blue-laser technology, one to focus on Blu-ray's 0.1mm substrate, the other to look at the Toshiba/NEC's 0.6mm substrate. The DVD Forum is comprised of 230 companies who work together to define formats and standards, as well as to license the well-known DVD logo. Since the forum does not endorse +RW (a forum endorsed by the rival DVD+RW Alliance, which counts Forum member Sony as a member), neither of the blue-laser proposals includes DVD+RW compatibility.