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In computing, sound reproduction, and video, an optical disc is flat, circular, usually polycarbonate disc whereon data is stored. This data is generally accessed when a special material on the disc (often aluminum) is illuminated with a laser diode.

The first optical disc was the video laserdisc created by Philips, appearing as early as the late 1960s, but not marketed until the mid- 1970s. The knowledge gained from this development led to the creation of the compact disc in 1980. 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 and outwardmost track.

1 Types of disc

There are many standards using optical discs:

Blu-Ray disc
Compact disc
DVD
HD-DVDHD-DVD is similar to the Blu-Ray disc: a CD size (120 mm) optical data storage media, that uses a blue laser at 405 nm wavelength. HD-DVD is promoted by Toshiba and NEC and is currently engaged in a format war with the Blu-ray Disc proposed by Sony. HD-DV
Laserdisc
Magneto-optical discMagneto-Optical disc is an optical disc format that uses a combination of optical and magnetic technologies. The sizes of discs are usually 3. 5 inch or 5. 25 inch, and disk capacities are usually one of 128MB/230MB/540MB/640MB/1. A special Magneto-optica
Minidisc

2 External link

Optical Storage Technology Association

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Topics: Optical Disc, Optical Telegraph, Optical Fiber, Optical...

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