Three basic categories of laser discs, or optical discs, exist--one of which that is specifically designed to store data files (CD-ROM), one that is specifically designed to store audio files (CD) and one that is specifically designed to store video files (DVD). However, within and between these three categories, there are three different types: read only, write once and rewrite. The combination of the three categories and types produces a multitude of different optical discs.
Inventors
The laser disc as we know it today is a combination of the work of two different inventors.
In 1958, David Paul Gregg visualized what he called a "videodisk," which was eventually patented in 1961 and 1969. Shortly thereafter, Music Corporation of America (MCA) bought his company, Gauss Electrophysics, and his patents and began mass producing his technology in 1978.
In 1965, James Russell of General Electric (GE), who was an avid music lover, invented what he called a "compact disk" as a way to prevent him from having to carry around a lot of cassette tapes. He later received more than 20 patents that covered all of the aspects of the technology. These patents were later acquired by the Dutch company Koninklijke Philips Electronics N.V. (Royal Philips Electronics)
First Generation
From the concepts established by the two inventions, Philips created the compact disc (CD); Pioneer Corporation created the Digital Versatile Disc (DVD) and the LaserDisc (LD); and Sony Corporation created the compact disc for read-only memory (CD-ROM) and the MiniDisc (MD).
These are all known as first generation optical discs and were characterized by their initial high cost, non-recordability and use of infrared light.
Second Generation
Second generation optical discs include the DVD-Audio (DVDA), the Super Audio CD (SACD), the Video CD (VCD), the Enhanced Versatile Disc (EVD), Sony's Hi-MD (HMD) and Universal Media Disc (UMD), Circuit City's Digital Video Express (DIVX) and Sega Dreamcast's Giga Disc ROM (GD-ROM).
These optical discs are all known for their high storage capacity and use of visible light.
Third Generation
In 2002, nine major electronics corporations (Sony, Panasonic, Pioneer, Philips, Thomson, LG (Lucky GoldStar) Electronics, Hitachi, Sharp and Samsung) joined forces to launch the Blu-Ray Disc (BD) to start third generation optical disc technology. Other competing discs are the High Density Video Multilayer Disc (HD-VMD), the High-Definition/High-Density DVD (HD-DVD) and the China Blue High-Definition Disc (CBHD).
Other Optical Disc Formats
Several other optical disc formats also exist or have existed. The list below includes some, but not all, of them.
CD formats: CD-R, CD-RW, PhotoCD
DVD formats: DVD-R, DVD-RW, DVD+RW, DVD-RAM
Blu-Ray formats: BD-R, BD-RE
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