A new generation of optical mediums – holographic discs
The pioneer in the use of three-dimensional recording of data is Pieter J. van Heerden of Polaroid. The possibilities of applying holography in data storage were introduced as early as 1963. At present, the companies engaged in the development of the new HVD format – Holographic Versatile Disc – have formed the organisation HVD Alliance (consisting of CMC Magnetics, FUJI, Nippon Paint, Optware, Pulstec, TOAGOSEI). Meanwhile in 2004, engineers from Optware presented the mediums for holographic recording, at the same time presenting a recorder which allows this type of recording of information.
How does this HVD disc differ from those which are currently universally accessible on the optical medium market. The most essential is the holographic technology itself, which enables the recording of data in three dimensions on a typical disc of 12 cm diameter (familiar to us). In this advanced optical technology two types of laser are used. One of these for recording / reading – green (532nm), the second red, positional-addressing (650nm), which is responsible for the correct positioning of the head. Data transfer of 1 Gbit/s is also impressive and as for now unique among optical discs. The speed is a plus, which counts to the detriment of High Density type mediums.
The lack of the notion of data pathways is curious in the case of holographic mediums, the memory called holographics using entire pages of data. Thanks to this, recorded information can be accessed unusually quickly.
The most important and most essential current feature of the holographic carrier, which is a breakthrough in the computer peripherals market, is the enormous capacity. The Holographic Versatile Disc can hold approximately 1TB of data, and soon even 3.9TB. The limit of capacity under current technical possibilities will surely also rise. Work on HVD discs is ongoing and at the moment we cannot talk of mass production of this type of disc.
Below is a diagram of the design and composition of a Holographic Versatile Disc
Drawing by Piotr Jaworski, 11/02/2005; POLAND, Poznań (http://wikipedia.pl)
1. Green writing/reading laser (532nm)
2. Red positioning/addressing laser (650nm)
3. Hologram carrying data
4. Polycarbon layer
5. Photopolymetric layer (with data)
6. Distancing layer
7. Dichroic layer
8. Aluminium reflecting layer
9. Transparent base
P. PIT