Holographic Storage Technology
Holographic data storage technology is a relatively new type of data storage offering compact storage capacity, higher data transfers rates and significantly longer archival life. The technology is based on the recording and reading of data in the form of holograms. Holographic data storage has been discussed since the 1960s, but has only recently become a commercially viable technology.
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Definition
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Holography is the technique of recording the scattered light off an object, and then displaying this recorded image so that it appears as if the object is present is the same position as before, relative to the viewer. In other words, holography represents a three-dimensional image of an object. Holograms are volumetric images of objects within a two-dimensional medium.
History
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Holography was first discovered in 1947, but the techniques of holography didn't really advance until the development of the laser in 1960. In 1968, the invention of white-light transmission holography enabled holographs in ordinary white light and the mass production of the type of holographs most commonly seen today.
Benefits
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According to Jet Propulsion Laboratories, holographic data storage offers the ability to store much greater volumes of data by taking advantage of the depth of the recording medium, not just its surface area, and high-speed data transfer rates. Other benefits include high-fidelity data recovery, high-fidelity imaging of data pages, low levels of noise in data recovery and a long archival life (up to 50 years at current estimates).
Difficulties
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One of the biggest difficulties facing developers of holographic data storage is the consistent alignment of data layers with the reader. Reading one layer of holographic image is relatively easy; reading multiple layers (otherwise known as "multiplexing") is a lot more difficult. The slightest defect in the recording medium or the position of the medium to the optical reader reduces the clarity of output. Furthermore, to overcome the problem of decreasing efficiency of each holographic layer, "the exposure time for each hologram had to be different to compensate for the recording order."
Layout of Holograms
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InPhase Technologies developed a two-part approach to the construction of materials for holographic data storage: a high-index photopolymerizable monomer and a low-index matrix precursor. One of the problems with these photopolymer materials is that its photosensitivity decreases relative to the layers of data recorded. To compensate for this lost of sensitivity, layers are recorded not as overlapping but as "shifted from previous ones by at least one...dimension in the plane of the media."
Commercially Available Products
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As of March 2010, there are no products on the market. InPhase Technologies, which was set to release the first commercially available holographic data storage device, Tapestry, was seized by the Colorado Department of Revenue on February 8, 2010 for non-payment of taxes. InPhase was granted a joint patent with Nintendo to produce a multiplexing holograph data storage system, but this project seems to have been put on hold. Holographic Versatile Disks, which share many of the same technologies as holographic data storage, are still not on the market. All of these products are expected to be initially priced out of the range of the common consumer. Target markets will be enterprises with very large data storage needs.
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References
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