Great article on DVD-RAM and magneto-optical drives.............
Go to the link to see a good table.
japanbiztech.com
Japan Targets Year 2000 for 5-10GB Optical Disks
September 29, 1997 (TOKYO) -- Japanese makers are targeting the year 2000 as the launch
date for next-generation optical disks, which will follow the recently standardized DVD-RAM
and extend storage capacity to 5GB to 10GB.
The Japanese manufacturers are pursuing two methods for achieving data read/write capabilities:
optical disks and magneto-optical disks, the latter of which combine light and magnetism (see table).
In the optical camp, NEC Corp. has successfully developed a rewritable optical disk with 5.4GB
of capacity.
Hot on NEC's heels are Matsushita Electric Industrial Co., Ltd. and Sony Corp., both of which are
developing optical disks with more than 10GB of capacity.
The magneto-optical disk camp is led by Imation Corp. of the United States and an international
consortium of 15 firms that are jointly developing the 6GB advanced storage magneto optical
(ASMO) disk. The group has set the year 1998 as the target launch date for the disk.
Whatever paths they have chosen, the manufacturers are in a hurry. What is at stake is the leadership
of the multibillion dollar market for next-generation storage devices.
DVD-RAM: Insufficient Capacity for Video Storage
Matsushita and Hitachi Ltd. will ship the first batch of 2.6GB DVD-RAM drives sometime before
the end of 1997 for less than 100,000 yen (US$833) per unit. The rewritable disk follows the
read-only DVD-ROM introduced in 1996.
In the meantime, Japanese manufacturers are fast at work to develop and standardize next-generation
optical disks with much larger storage capacities.
Japan's consumer electronics makers expect a post-VCR megahit out of a DVD capable of storing
huge digital video contents pouring in from Internet Web sites as well as emerging digital TV
broadcasting.
However, DVD-RAMs with a capacity of only 2.6GB are not large enough to store video data. That
is the primary driving force behind the frantic development efforts for the next generation of
DVD-RAMs.
There are ongoing efforts among manufacturers to standardize the DVD-RAM with a 4.7GB capacity,
the same as that of the DVD-ROM. However, that capacity is not enough either.
Manufacturers are now trying two methods to increase storage capacity. One is to develop a laser
with a short light wavelength and new magnetic modulation record/playback technology. The other
is to stretch the capacity of the magneto-optical disk.
Blue Laser Expected to Increase Storage Capacity
The recording density of optical disks such as the DVD-RAMs will increase if the wavelength of the
laser, which is used for writing and reading, becomes shorter.
Today's DVD-RAM drives use a red laser with a wavelength of 650nm. So development efforts are
now focused on a blue laser with a shorter wavelength.
One of Matsushita's current targets is to develop such a blue laser. Matsushita Electronics Corp.,
a Matsushita subsidiary, and CBL Technologies Inc. of the United States are jointly developing a
blue laser for commercial use around the year 2000.
For its part, Matsushita is developing a second harmonics generation (SHG) device that can cut the
wavelength of an existing 850nm blue laser in half.
Matsushita is planning to put the technology into commercial use by the end of 1999, but it has yet to
solve the problem of the SHG's low efficiency and the high heat generation caused by the high-power
laser used for the method.
Sony announced the development of a blue-green laser with a 515nm wavelength. Sony's laser
is longer than that of Matsushita, but it has a smaller diameter beam spot achieved by the extended
numerical aperture of the objective lens.
Sony plans to manufacture a video recorder based on the technology in 1999.
Theoretically, Sony said, if a 410nm blue laser was developed in the future, a disk with a capacity of
18GB per side will be possible.
The drawback of using a short wavelength laser is that the drive will require another lens with a smaller
numerical aperture to maintain compatibility with commercially available DVD-RAM drives. The
thickness of the protective layer over the recording layer must be reduced.
NEC will continue to use the same 680nm red laser used for DVD-ROMs, but improve the read
signal processing technology to increase capacity.
NEC's disk will store 5.4GB of data per side and 10.8GB per disk, equivalent in capacity to
DVD-ROMs.
NEC already has completed the prototype, and is believed to be the forerunner in the race for
commercial production. The company is planning to produce home video recorders by the end
of 1998.
Move for 6.1GB Magneto-Optical ASMO
Also, there is an industry-wide movement to increase the storage capacity of the 120mm
magneto-optical (MO) disk as the 6.1GB ASMO standard.
MO disks have a leg up on optical disks as a rewritable, large-capacity medium.
If the ASMO camp were able to come up with a commercial product with prices identical to those
of DVD-RAM drives by the end of 1998, industry experts said the standard will have a good chance
of occupying a leadership position in the markets for post-VCR home video recorders as well as for
PC storage devices.
An international industry forum called "Advanced Storage Technology Conference" (ASTC),
consisting of 15 drive and medium makers, is developing the ASMO standard.
Nine firms -- Imation Corp. of the United States, Philips Electronics NV of the Netherlands, and
Fujitsu Ltd., Hitachi Ltd., Sharp Corp. and Sony of Japan -- are core members. Six other members,
including LSI Logic Corp. of the United States, LG Electronics Inc. of Korea and Matsushita, also
are participating in the forum's meetings.
The forum in September will announce the Standard Version 0.9 for developing prototypes of drives
and media.
The ASMO disk employs magnetic field modulation and is not compatible with PC MO disks that
use light modulation. But the ASMO drive can read DVD-ROM disks.
ASMO also uses a laser strobe magnetic field modulation method, which can write recording marks
finer in diameter than the laser beam spot.
To suppress mutual interference of data contiguous to each other, magnetically introduced super
resolution technology will be adopted.
ASMO has the potential to increase storage capacity to more than 10GB. Magnetic amplifying
magneto-optical system (MAMMOS) technology, announced by Hitachi Maxell Ltd. and Sanyo
Electric Co., Ltd. in October 1996, can be used for that purpose.
By means of magnifying small recording marks through magnetic amplifiers, this technology enables
reading of small recording marks the MSR cannot handle.
The MAMMOS technology also can be applied to current MO disks with light modulation.
Fujitsu is trying to increase the storage capacity of existing 3.5-in. MO disks by using MSR and
MAMMOS technology.
Table: Next-Generation Rewritable Optical Disks Under Development
go to link for table |
