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Posted by Bob on 11/28/05 10:37
New Scientist magazine
http://www.newscientist.com/channel/info-tech/dn8370.html
Holographic-memory discs may put DVDs to shame
A computer disc about the size of a DVD that can hold 60 times more
data is set to go on sale in 2006. The disc stores information through
the interference of light - a technique known as holographic memory.
The discs, developed by InPhase Technologies, based in Colorado, US,
hold 300 gigabytes of data and can be used to read and write data 10
times faster than a normal DVD. The company, along with Japanese
partner Hitachi Maxell announced earlier in November that they would
start selling the discs and compatible drives from the end of 2006.
"Unlike other technologies, that record one data bit at a time,
holography allows a million bits of data to be written and read in
parallel with a single flash of light," says Liz Murphy, of InPhase
Technologies. "This enables transfer rates significantly higher than
current optical storage devices."
The discs, at 13 centimetres across, are a little wider than
conventional DVDs, and slightly thicker. Normal DVDs record data by
measuring microscopic ridges on the surface of a spinning disc. Two
competing successors to the DVD format - Blu-ray and HD-DVD - use the
same technique but exploit shorter wavelengths of light to cram more
information onto a surface.
Beam-splitter
Holographic memory, by contrast, stores information in a
light-sensitive crystal material using the interference of laser
light. The process involves splitting a single light beam into two and
then passing one through a semi-transparent material. This is a grid
that acts like a filter, changing different parts of the beam to
encode bits of information.
The altered beam and the reference beam are then recombined in the
light-sensitive material and their pattern of interference provides a
record of the encoded information. Information can be recorded and
retrieved so rapidly because many bits of data can be recorded and
read in parallel.
InPhase says the technique could theoretically be used to store up to
1.6 terabytes of data on the same size of disc and to read data at 120
megabits per second. This is 340 times the capacity of an ordinary DVD
and 20 times the data rate.
High-speed streaming
Although holographic memory was first suggested in 1963, it has failed
to find commercial success so far. However, Hans Coufal, an expert in
the technology at IBM's Almaden Laboratory in California, says the
holographic memory could challenge formats such as Blu-ray and HD-DVD.
As well as offering greater storage, Coufal says the main benefit is
speed of data access. The discs developed so far by InPhase can
already stream a movie recorded in high definition television (HDTV)
format.
However, Coufal notes that the technology must also stand up to
everyday use. "It is an open race right now," he told New Scientist.
"But you have to convince the customer that it is going to be
reliable."
--
"One must realize that the world is a network of real and virtual
combat zones where the stakes are high, struggle is the primary
mode of being and only total victory is acceptable.
-- Sun Tzu, "The Art Of War"
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