Holographic Versatile Disc
The Holographic Versatile Disc, short HVD, is an experimental holographic storage medium - is read and written by laser - similar to the Compact Disc, DVD and Blu- ray Disc.
The Holographic Versatile Disc is planned as the next generation of optical storage media according to the Blu- ray Disc. There are two lasers used, one red and one blue - green, which are superimposed and a specific spot light on the disk. Of blue- green laser as a laser read interference pattern of a holographic data encoded layer in the upper region of the storage medium while the red laser is used to read information from an ordinary auxiliary reflective aluminum layer in the deeper layers. The auxiliary information is used to determine where you currently are on the disc, similar to sector -, head - and segment information of a normal hard drive. When a CD or DVD, this auxiliary information is distributed between the user data. A dichroic mirror layer between the holographic data and the servo data reflects the blue - green laser and red laser through the leaves. This is an improvement compared to holographic storage media, which either had too much interference, or had no auxiliary data, so they are incompatible with current CD and DVD technology.
HVDs to reach a capacity of up to 3.9 terabytes, which is about eight times the largest experimental Blu -ray discs (500 GB), and a transfer rate of 1 Gbit / s for easier rotation speed (compared to 36 Mbit / s at Blu- ray Disc, achieve 10.8 Mbit / s for DVD and 1.41 Mbit / s with the CD). This makes it the first optical storage system whose data transfer rate is comparable to today's hard drives.
The specifications for the English Holographic Versatile Disc -called holographic storage medium, in December 2004 the 44th session of the Technical Committee (English Technical Committee, therefore, also briefly called TC44 ) of the Ecma International approved.
Since December 2004, among others, the following companies and organizations are working together in the HVD Alliance:
- CMC Magnetics
- Stanford University
- Texas Instruments