Compact Discs

COMPACT DISCS

COMPACT DISCS (CDs) are small, thin, plastic discs twelve centimeters in diameter that contain a metallized surface that holds optically recorded digital information, such as sound, images (still and motion), and computer programs. Data is recorded by creating microscopic pits along a single track on the metallized surface; playback incorporates a red laser beam reflected onto the surface that measures the pits and translates them into binary information. A standard CD can hold between 74 and 82 minutes of audio, or approximately 780 million bytes of data. CDs are nearly unaffected by the number of times they are played. The disc's durable surface tolerates fingerprints and small scratches, making it an ideal solution for optically storing and preserving digital information.

Development of the CD to replace vinyl records began in the 1970s with Royal Philips Electronics of the Netherlands and Sony Corporation of Japan. Philips produced the optical storage technologies, while Sony pioneered error correction circuitry. The result was a set of industry standards established in the late 1970s for the CD's physical and logical characteristics, which among other things, ensured compatibility among discs and players from diverse manufacturers. This standard, known as the Compact Disc Digital Audio system, was in place in the early 1980s, and in 1983, the compact disc and the first CD players were introduced to consumers.

As standards evolved, so did the uses for CDs. Changes in recording techniques allowed for specialized uses such as the CD-Read-Only Memory (CD-ROM) for use in computers, CD-Interactive (CD-I), a stand-alone audio and video hardware system designed for audio and visual data, and the Video-CD (VCD) for high-quality video playback. The rewriteable CD (CD-RW) standard, created in 1996, enabled nearly anyone with a home computer and a CD-RW drive to record music, data, and video on a compact disc.

The future remains bright for the compact disc. The Digital Versatile Disc (DVD) standard has increased storage capacities to nearly five gigabytes (4.7GB) of information, or twenty-eight times that of its CD-ROM cousin, and DVD-Video has pushed VHS videotapes from store shelves as the preferred format for popular movies. Upcoming innovations in manufacturing processes, such as the improved pinpoint light-focusing ability of the blue-violet laser beam and higher transfer rates of players and recorders, will see DVD storage capacities climb to nearly thirty gigabytes of data on one shiny disc.

BIBLIOGRAPHY

Armstrong, Elizabeth. "DVD Lasers: Why Blue Beats Red." Wired (June 2002):50.

Pohlmann, Ken C. Principles of Digital Audio. 4th ed. New York: McGraw-Hill, 2000.

Michael Regoli

See also Digital Technology .