Holographic versatile disc (HVD) is a holographic storage format that looks like a DVD but is capable of storing far more data. Prototype HVD devices have been created with a capacity of 3.9 terabytes (TB) and a transfer rate of 1 gigabit per second (1 Gbps). At that capacity, an HVD could store as much information as 830 DVDs or 160 Blu-Ray discs.
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To increase capacity, holographic storage uses laser beams to store digital data in three dimensions, rather than in two dimensions as in CD and DVD media. HVD is, essentially, a holographic layer built on top of a conventional disc. The HVD process uses a blue-green laser beam, used for reading and writing data, collimated (made parallel) with a red laser beam, which is used for servo and tracking.
In the recording process, the initial laser is split into two beams. One of the beams passes through a device called a spatial light modulator (SLM) and combines with the direct beam to produce a hologram in the physical medium. To recover the data, another 532-nm laser is directed into the hologram, which diffracts the laser beam. The resulting image constitutes an optical reproduction of the original recorded data. A photosensitive semiconductor device converts this optical data into the original digital files.
The first working HVD systems for the enterprise are expected to be shipped in 2006, with consumer HVDs and drives to become available in 2008 or later. The initial target market is high-volume mass storage, such as digital television (DTV) broadcasts and document libraries in large businesses and government agencies.
Members of the HVD Alliance include Fujifilm, Konica Minolta and Mitsubishi. According to the Alliance, HVD will eventually replace DVD.