[Homestead] Computer terabyte memory storage on four disk layers
tvoivozd at infionline.net
Tue Sep 28 16:19:19 EDT 2004
*Optical technique promises terabyte disks*
17:07 27 September 04
A novel method of optical data storage could soon be used to hold a
terabyte of data on a disk the size of a normal DVD, say researchers at
Imperial College London, UK.
Information is encoded on a normal DVD in the form of microscopic
indents on the surface of the disk. The presence or absence of an indent
corresponds to a binary piece of information - a ‘1’ or a ‘0’. Indents
are detected by beaming light onto a disk with a laser and measuring the
amount of light that bounces back.
Using tracks embedded at several depths within a disk, it is possible to
store more data on the highest capacity disks. Multilayer DVDs hold
about 16 gigabytes of data, which equals about 8 hours of high quality
But the researchers realised that the polarity of light might also be
used to encode information. They developed a type of disk that
incorporates angled ridges within the pits in order to subtly alter the
polarity of the light that gets reflected. This can be used to store 10
times’ more data than is currently possible, they say.
Using the technique, the researchers think it should be possible to
create disks capable of holding 250 gigabytes in a single layer. This is
enough to store 118 hours of video, which could allow every episode of
long-running television shows to be put on one disk. Using a four-layer
disk would mean a terabyte could be stored.
In the new system, light polarised in a single direction is beamed onto
the surface of the disk. Some bounces back with a polarity at 90 degrees
to that of the original beam. By measuring how much light comes back in
each of the two directions, it is possible to work out the precise angle
of the slope.
"We’re using an added property of light not utilised by conventional
methods," researcher Peter Munro told *New Scientist*.
The most advanced optical storage disks available today use a technology
known as Blu-ray and can hold roughly 100 gigabytes of data. Blu-ray
makes use of blue light instead of red, which has a smaller wavelength
and can therefore read smaller areas of a disk's surface.
The researchers say information could be encoded using 10 different
angles of slope, corresponding to 10 bits of information in each indent.
Provided funding can be found, the team believes it should take about
five years to perfect the technology and a commercial version could be
available by 2010.
Wolfgang Schlichting, research director of the removable storage
division of US analyst firm IDC, says there should be plenty of demand
for disks that can hold so much information. He suggests that miniature
disks based on the technology would also be popular.
But Schlichting also warns that the new method could prove costly to
develop. "Typically, optical storage technology based on the polarity of
light are more difficult to implement and so more expensive," he told
Munro also says they have not yet determined out how a consumer writing
device could be made. But he believes this could be seen as a bonus.
"Creating pirate disks would be very difficult unless you bought the
mastering equipment," he says.
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