Optical disc
- "Optical media" redirects here.
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In computing, sound reproduction, and video, an optical disc is a flat, circular, usually polycarbonate disc whereon data is stored in the form of pits (or bumps) within a flat surface, usually along a single spiral groove that covers the entire recorded surface of the disc. This data is generally accessed when a special material on the disc (often aluminum) is illuminated with a laser diode. The pits distort the reflected laser light. Most optical discs, with the exception of a few such as black CD-ROMs designed for the original Sony Playstation, have a characteristic prismatic or iridescent appearance created by the grooves in the reflective layer.
David Paul Gregg developed an analog optical disc for recording video and patented it in 1961 and 1969 (U.S. patent 3,430,966). Of special interest is U.S. Patent # 4,893,297, first filed in 1968 and issued in 1990, so that it will be a source of royalty income for Pioneer’s DVA until 2007. It encompasses systems such as CD, DVD, and even Blu-ray Disc. Gregg's company, Gauss Electrophysics, was acquired, along with Gregg's patents, by MCA in the early 1960s.
Parallel, and probably inspired by the developments in the U.S., a small group of physicists started their first optical videodisc experiments at Philips Research in Eindhoven, The Netherlands in 1969. In 1975, Philips and MCA decided to join forces. In 1978, much too late, the long waited laserdisc was introduced in Atlanta. MCA delivered the discs and Philips the players. It turned out to be a total technical and commercial failure, and quite soon the Philips/MCA cooperation came to an end. In Japan and the U.S., Pioneer has been successful with the videodisc until the advent of DVD.
Philips and Sony formed a consortium in 1979 to develop a digital audio disc, which resulted in the very successful introduction of the compact disc in 1983.
The promotion of standardised optical storage is undertaken by the Optical Storage Technology Association (OSTA).
The information on an optical disc is stored sequentially on a continuous spiral track from the innermost track to the outermost track.
An acronym for Optical Disc Drives is ODD.
First-generation optical discs
Optical discs were initially used for storing music and software. The Laserdisc format stored analog video, but it fought an uphill battle against VHS; other first-generation disc formats are designed to store solely digital data.
Most first-generation disc devices use an infrared laser as a read head, limiting the total capacity to, for example, 700MB for a 12cm compact disc.
- Compact disc (CD)
- Laserdisc
- Magneto-optical disc
Second-generation optical discs
Second-generation optical discs were created to store large amounts of data, including TV-quality digital video. Many, though not all, such discs use a visible light laser (usually red); the shorter wavelength allows a tighter beam, allowing the pits and lands of the disc to be smaller. In the case of the DVD format, this allows 4.7GB of storage on a standard 12cm, single-sided, single layer disc; alternately, smaller media such as the MiniDisc and DataPlay formats can have capacity approximately comparable to a much larger standard compact disc.
- Minidisc
- DVD and derivatives
- DVD-Audio
- DualDisc
- Digital Video Express (DIVX)
- Super Audio CD
- Enhanced Versatile Disc
- GD-ROM
- Digital Multilayer Disk
- DataPlay
- Fluorescent Multilayer Disc
- Phase-change Dual
- Universal Media Disc
Third-generation optical discs
Major third-generation optical discs are currently in development. They are designed for holding high-definition video and sport larger capacities, enabled by the use of short-wavelength visible light lasers (blue-violet for BluRay and HD-DVD, the most common formats so far).
In practice, effective capacity for multimedia presentations can be drastically improved by using enhanced video data compression algorithms such as MPEG-4 as well.
- Currently shipping
- Blu-ray Disc
- HD DVD
- Professional Disc for DATA
- In development
- Forward Versatile Disc
- Total HD disc
- Versatile Multilayer Disc
- Ultra Density Optical
Next Generation Optical Discs
The following formats are so advanced they can be considered to be ahead of current (third gen) discs. All of the following discs have the potential of over 1 terabyte of space.
- Tapestry Media
- Holographic Versatile Disc
- Protein-coated disc
Recordable/writable optical discs
ReferencesISBN links support NWE through referral fees
- http://web.mit.edu/invent/iow/russell.html
- http://seattletimes.nwsource.com/html/businesstechnology/2002103322_cdman29.html
- http://inventors.about.com/library/inventors/blopticaldisk.htm
External links
- Optical Storage Technology Association
- The Authoritative Blu-ray Disc (BD) FAQ by Hugh Bennett
- The Authoritative HD DVD FAQ by Hugh Bennett
- Understanding Recordable & Rewritable DVD by Hugh Bennett
- Understanding CD-R & CD-RW by Hugh Bennett
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