NHK Accelerates Disc Speed
June 6, 2007
The Science and Technical Research Laboratories of NHK, Japan's public broadcaster, is fine-tuning a disc recording system that can spin as fast as 15,000 rpm--about 5,000 rounds-per-minute higher than current speed limits. The increased spin speed (necessary to record and play back large amounts of HD content) is based on Blu-ray disc technology.
Broadcast-quality HD signals used by NHK and others typically stream at about 250 Mbps--necessitating a very fast-spinning optical disc. By comparison, a regular Blu-ray Disc records at closer to 36 Mbps. Therefore, the new system NHK is working on is nearly seven times Blu-ray's speed.
If current discs spin too fast, they could disintegrate inside the disc drive, destroying the disc, the drive, and all the data contained on the disc. Excessive speeds also can create a wobble effect that makes reliable recording difficult, according to Tech.co.com.
The stress factor on the disc has been sharply reduced by NHK, using a flexible prototype disc that is only 0.1 mm thick. The disc (co-developed with Ricoh Corp.) is basically the same recording layer from a Blu-ray disc--but without the 1.1 mm plastic substrate that makes the disc rigid and, therefore, more practical to use. To solve the rigidity problem, a stabilizing plate will be built into the disc drive itself.
Hitachi Maxell has a similar technology known as Stacked Volumetric Optical Disc. However, unlike the NHK prototype system, the SVOD's internal drive stabilizer physically rotates, which NHK, for its part, said leaves it open to possible mechanical problems.