Short interest was up? Numbers are reported as of the 15th of each month. Sony's 12 Gig storage disc..............................
October 27, 1997, Issue: 977
Section: News
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Sony shows 12-Gbyte home video-disk recorder
By Yoshiko Hara
Tokyo - Sony Corp. demonstrated last week a prototype of a would-be video-disk recorder with a 12-Gbyte capacity per side employing a semiconductor blue-green laser.
The phase-change-disk approach has achieved the largest-ever capacity in a rewritable optical-disk system, Sony claimed. It was demonstrated as a potential prototype that Sony plans to introduce as a video-disk recorder early in the next century.
"When marketing the video-disk recorder, we want to offer three- to four-hour recording time in NTSC quality. That will make a 10-Gbyte capacity the minimum target," said Katsuaki Tsurushima, president of Sony's Advanced Development Laboratory. "Current VCRs do not necessarily satisfy all the needs of consumers," he said. "In tandem with the disk-recorder development, we are developing user-friendly software for the home-disk recorder so that it works as a home server."
The basic technologies were announced last May (see May 26, page 10) and Sony researchers integrated the technologies such as a laser, a tracking system and a rewritable disk into the 12-Gbyte disk recorder. They used a 515-nm blue-green laser and an 8-Gbyte recorder with a 635-nm read laser. In the demonstration, MPEG-2 compressed-video images were recorded and played back at a 6-Mbit/second rate with the 8-Gbyte system and 12-Mbit/s rate with the 12-Gbyte system.
The disk system format is completely different from any other rewritable format such as phase-change-rewritable or DVD-RAM announced so far.
"The capacity will jump one digit larger from DVD," said Tsurushima. "If we stick on maintaining the same structure of disks in the past, a new, innovative system can hardly be developed." He also said that the disk system is not linked to the phase-change-rewritable, a 3-Gbyte rewritable-disk system that six companies, lead by Sony, Philips Electronics N.V. and Hewlett-Packard Co., are proposing. "The phase-change-rewritable is for computer applications and satisfies a vigorous standard for that purpose. This optical system is for home use, which does not require, for example, 10,000 times rewriting on one disk."
The disk system features a wide numerical aperture (NA) of 0.85, which is equivalent to lenses of a 100x microscope. The wide NA enables a smaller beam spot, but limits the working distance to 0.3 mm. As the result, the recording layer is set at just a 0.1 mm depth from the disk surface. "It is just like using a compact disk from the backside," said Tsurushima.
Masanobu Yamamoto, general manager of the Optical Media Laboratory, said, "To achieve a capacity of 10 Gbytes to 100 Gbytes so that it is competitive with video tapes, all parameters should be upgraded from those of DVD."
The recording density will be three times that of DVD video with the 515-nm laser and 4.6 times with a 410-nm blue laser when it becomes available. With the blue laser, the system's theoretical capacity will exceed 20 Gbytes.
The disks use land-and-groove recording with track pitch at 0.5 micron for the 635-nm recorder and 0.40 micron for the 515-nm recorder.
Sony researchers have extended to 1,000 hours the life of a zinc-selenide blue-green laser, which was used for the prototype recorder. In reading mode, the laser stands for about 1,000 hours with 0.3-mW output power. In writing mode, 4-mW to 5-mW output power is needed. The output power is low compared with the 20-mW power needed for DVD-RAM drives, since the small beam spot requires less power-and the life of the laser, at several hours, is still short, Yamamoto said.
In terms of the laser, "The 635-nm red laser has a long enough life," said Yamamoto. The laser writes in data with a peak output of 20 mW. The 8-Gbyte prototype recorder was demonstrated as more practical at present.
High NA lenses are expensive in general, said Tsurushima, but the lens won't increase cost. If high NA were achieved by one lens, it would be more expensive, he said, but Sony used two lenses to achieve the NA and each is an inexpensive, common lens.
Copyright (c) 1997 CMP Media Inc.
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