TOKYO Pioneer Electronics Corp. has demonstrated a 27.4-Gbyte optical disk system that can store four hours of high-definition video. The system uses a 405-nm violet laser developed by Nichia Chemical Industries Ltd.
With all work on formats for first-generation DVD products scheduled for completion by year's end, Pioneer is shifting its development focus to next-generation DVD products and hopes to leverage Nichia's newly available violet laser.
The prototype disk system, which can store four hours of high-definition video in 1,080i at variable bit rate at an average 13.4 Mbits/second, was shown at the Japan Electronics Show 1999 earlier this month. Pioneer intends to propose the system as the specs for the next-generation DVD-video system.
The desktop prototype player with the violet laser reads out signals from each layer of a two-layer disk the same structure as today's double-layered DVD-video disk with an 8.54-Gbyte capacity. The prototype disk has a track pitch of 0.37 micron, about half of the current disk, and a capacity of 27.4 Gbytes for two layers.
Since the track pitch is narrower even for the blue laser beam spot, Pioneer researchers used three-beam crosstalk cancellation. That technology divides the beam into three, with the outer two beams canceling interference from adjacent tracks while the central beam conveys the signal from the targeted track.
"The laser's performance was improved and has approached close to a level of red lasers," said Shogo Miyanabe, manager of disk system labs at Pioneer's Research & Development Group.
Nichia started sampling its violet laser early this year and began Oct. 1 to market a 405-nm laser with 5 mW of output power as the first violet semiconductor laser.
Pioneer demonstrated a 15-Gbyte disk system in 1997 using a 430-nm second-harmonic-generation laser. At that time, the numeric aperture ratio was 0.5, but since the violet laser has a shorter wavelength, Miyanabe said, aperture could be kept at 0.6, the same as current DVD players.
In the demonstration, Pioneer played back 1,080i high-definition moving pictures from the disk. For authoring, each frame is divided into four portions, encoded, then put together. But decoding is done by one decoder supplied by LG Semiconductor. Pioneer has high-resolution disk mastering technology, which originated in a semiconductor process technology called "contrast enhanced lithography."