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Holographic storage

Aug 1, 2006 12:00 PM, BY BRAD DICK, EDITORIAL DIRECTOR

The storage medium

Figure 3. To read the data, the reference beam deflects off the hologram, thus reconstructing the stored information. The resulting hologram is projected onto the detector, which reads the data out in parallel.
Click image to enlarge.

The holograms are stored on photopolymer media. Today's DVDs provide about 120Mb/in² of storage capacity. The holographic disc will provide 515Gb/in² of storage capacity.

The two beams write the pages of data in the 1.5mm recording layer of the 3.5mm-thick disc. This layer is filled with two photopolymers sandwiched between the upper and lower 1mm substrates. The InPhase Tapestry recorder uses a 407nm blue laser, providing average record and readout times of 2ms.

More than 300 pages are recorded in a single location, and this collection of pages forms a book. Each page can hold 1.2Mb of user data.

The first question asked by potential users is: How much storage can holographic technology provide? Figure 4 compares the holographic storage capacities for some typical applications. Depending on the task, even small form factors can provide high capacity and performance. For instance, a 2cm postage-stamp-sized recorder (e.g., a Flash-like device) could provide from 2GB to 20GB of storage. A Maxell optical disc provides enough storage to hold 462 CD-ROMs. Or, the same optical disc can store up to 24 hours of SD video or seven hours of HD video.

The second question from potential users concerns transfer rates. Here again holographic performance is good. A Tapestry disc can provide a transfer rate of 20MB/s, which equates to 160Mb/s.

Other vendors

While InPhase was the first to launch the technology as a professional product, other vendors are vying to produce similar items for consumer products.

Figure 4. Holographic storage provides tremendous data storage in small form factors. A postage-stamp-sized space can contain up to 20GB of storage, a disk can store 300GB.
Click image to enlarge.

Last year, Toshiba, Intel Capital and others invested in another holographic optical storage developer, Optware. Optware is proposing a Holographic Versatile Disc (HVD), which is the same size as a DVD. The HVD will store 1TB of information. That's 200 times more data than what a typical DVD holds. The company claims transfer rates of 1Gb/s, or about 40 times a DVD's throughput.

While still a holographic storage technology, the Optware system relies on coherent-path laser beams. This means the reference and data beams move along the same axis. The company believes this will allow the development of more consumer-friendly (i.e., low-cost) players. Optware has proposed the HVD be declared a standard with the modest capacities of 100GB for ROMs and 200GB for cartridge-enclosed HVD-R products.

Broadcast applications

While all this may sound like future hardware, it's not. Pappas Telecasting has announced it will be the first to integrate holographic storage into a broadcast facility. The company is building new, state-of-the-art studios to serve KAZR-TV/KREN-TV in Reno, NV.

The company's new automated master control facility, called the Crystal Palace, is being constructed at an indoor Reno shopping mall. The facility will house two local high-definition news studios, one for each station. The HD studios will integrate the InPhase holographic storage platform into an automated program archive system.

Just when you thought the stoage race was only between Blu-ray and HD-DVD, something new and potentially better pops up. Stay tuned; the storage front is getting exciting.