Sony spin-off prototypes Tbyte holographic storage

Tokyo - While HD-DVD and Blu-ray disks jockey for position as the next-generation optical storage format, a Sony Corp. spin-off is developing a holographic data storage system with a much higher disk capacity. The system handles 200 Gbytes to 1 terabyte and has the potential to become a future-generation optical storage medium.

The developer, Optware Corp. (www.optware.co.jp/english/), reports that it has successfully recorded and played back digital video footage on a holographic disk with a reflective layer and preformatted address pits. The preformatted pits, considered a main hurdle for commercial holographic storage systems, make the holographic disk similar to those widely used in present-day CDs and DVD video disks, opening the door to compatibility between the systems.

Optware's system uses proprietary collinear holography technology. The approach differs from other holographic systems, which usually perform read/write operations by employing two laser beams-one a reference beam, the other an information beam-on two axes.

Hideyoshi Horimai, Optware's founder and chief evangelist, said collinear holography uses two laser beams emitted on the same axis, from the same direction. That enables a disk system similar to present optical disk systems, he said.

The preformatted address pits in Optware's holographic storage system will allow the company to enter the commercial market with a system that's a compatible successor to today's optical disk systems, Horimai said.

In its prototype system, Optware recorded video data on a disk using previously cut pits to hold address and servo information, then played back the moving images by reading the pits. "It is the first time that holographic data has been written and read from a rotating disk," an Optware spokesman said.

To develop a system that enables a smooth transition from present optical disk systems, Optware is proposing a hologram disk structure similar to conventional optical disks, with a reflective layer featuring preformatted pits for address and servo information. To date, holographic disks have been transparent and have not been able to store servo information, the company said.

In prior holographic systems, the laser beam for the read/write operation and the laser beam for servo information interfered with each other on the disk's reflective layer and generated diffusion noise. Such noise causes serious signal deterioration and makes it difficult to use prepitted disks for holographic recording, the company said.

Optware has cleared this hurdle by introducing a dichroic mirror layer between the disk's recording photopolymer layer and reflective layer. The mirror layer only passes a red laser beam for the servo information and blocks the diffusion noise generated at the address pits.

Optware demonstrated its system's playback capability for investors and some major electronics companies in early July. The company will present the technology at the COST Action P8 event, to be held in Paris on Sept. 16-17.

The company plans to introduce a holographic data storage system for the business and professional market in early 2006 and for the consumer market sometime in 2007.