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Pump Up The Volume

With the migration toward high-definition video well underway, can you ever have too much storage capacity? No, according to backers of holographic information storage systems, whose first-generation technology promises to store up to 200 GB on a single 5-inch disc, with future versions holding up to 1 terabyte (TB).

WITH THE migration toward high-definition video well underway, can you ever have too much storage capacity? No, according to backers of holographic information storage systems, whose first-generation technology promises to store up to 200 GB on a single 5-inch disc, with future versions holding up to 1 terabyte (TB).

Besides high capacity, the other big selling point for holographic versatile discs (HVDs) is transfer rates of 1 GB, which is about 40 times faster than conventional DVD technology. Those abilities — combined with a steep initial cost of about $100 per disc — make HVD a better fit for commercial applications than the consumer market when the technology makes its debut, perhaps as soon as next year.

“HVD will be introduced to the enterprise market in 2006 for data archiving,” says Yasuhide Kageyama, manager of business development and marketing at Optware, a Kanagawa, Japan-based company that's developing HVD technology. “We also see potential in the movies or other industries where a lot of multimedia files are stored.”

Rethinking volumetric recording

A 5-inch HVD disc looks like a regular DVD, except that it can store about 100 DVDs' worth of content. HVD shoehorns in more bits by taking a different approach to writing and reading data.

Conventional CDs and DVDs record data on a single, thin layer, which is buried under a protective substrate. HVDs use a process called volumetric recording, which increases capacity by recording the data on a thick layer. The depth of the recording layer is what enables higher capacity and a faster data transfer rate.

Data is written to the disc through two light beams: the information beam, which carries the encoded data as a two-dimensional bit-mapped image, and the reference beam, which carries a two-dimensional bit-mapped reference pattern. When those two beams collide in the disc's light-sensitive layer, the information is recorded.

The process sounds straightforward, and it is — except that it requires complex optical systems for focusing and tracking, as well as something to keep vibration of the beam apparatus to a minimum. Those challenges are among the reasons why holographic recording still isn't commercially viable even though the concept was hatched more than 40 years ago.

Optware claims to have solved those problems with a technique that it calls collinear holography. Past approaches used two axes: the information beam coming in at one angle, and the reference beam coming in at another. Collinear holography also uses two beams, but they're on the same axis, shooting straight down into the recording layer. Optware says that its design produces an optical pick-up that's no more complex than the ones used for conventional DVDs.

Reduced complexity translates into reduced cost, which improves the chances that holographic recording can finally become commercial reality. “While other holographic recording systems require optical components located on both sides of the disc, in collinear systems optical devices are placed only on one side of the disc,” Kageyama says. “This allows the drives to be made smaller and less expensive.”

As promising as Optware's collinear holography is, it's also proprietary, an attribute that's usually a turn-off for investors, manufacturers, and potential customers in any industry because they don't want to have their entire bet riding on a single company. The good news for Optware — and potentially for HVDs, too — is that in January 2005, Ecma TC44 — a Geneva, Switzerland-based international committee that's developing standards for holographic information storage systems — began work to standardize HVD by using Optware's technology as the standard's foundation.



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