Optical disc
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In computing, sound reproduction, and video, an optical disc is a flat, circular disc (usually polycarbonate) wherein data are stored in the pits (or bumps) in its flat surface — sequentially on the continuous, spiral track extending from the innermost track to the outermost track, covering the entire disc surface. The data are accessed in the disc when a special material (often aluminium) is illuminated with a laser diode. The pits distort the reflected laser light, hence, most optical discs (except the black discs of the original PlayStation toy), characteristically have an iridescent appearance created by the grooves of the reflective layer.
In 1961 and 1969, David Paul Gregg registered a patent for the analog optical disc for video recording, (US Patent 3,430,966). It is of special interest that US Patent 4,893,297, filed 1968, issued 1990, generated royalty income for Pioneer Corporation’s DVA until 2007 — encompassing the CD, DVD, and Blu-ray disc systems. In the early 1960s, the Music Corporation of America bought Gregg's patents and his company, Gauss Electrophysics.
Likewise, in 1969 Holland, Philips Research physicists began their first optical videodisc experiments at Eindhoven. In 1975, Philips and MCA join efforts, and in 1978, commercially much too late, they presented their long-awaited laserdisc in Atlanta, Georgia, USA MCA delivered the discs, Philips the players; the presentation was a technical and commercial failure; the Philips/MCA cooperation ended.
In Japan and the U.S., Pioneer succeeded with the videodisc until the advent of the DVD. In 1979, Philips and Sony, in consortium, successfully developed the compact disc in 1983. The Optical Storage Technology Association (OSTA) promote standardised optical storage means. Although optical discs are more durable than earlier audio-visual and data storage formats, they are susceptible to environmental and daily-use damage. Libraries and archives enact optical media preservation procedures to ensure continued usability in the computer's optical disc drive or corresponding disc player.
| Generation | Base | Max | |
|---|---|---|---|
| (Mbit/s) | (Mbit/s) | × | |
| 1st (CD) | 1.17 | 65.62 | 56× |
| 2nd (DVD) | 10.55 | 210.94 | 20× |
| 3rd (BD) | 36 | 432 | 12× [1] |
| Designation | Sides | Layers (total) |
Diameter | Capacity | ||
|---|---|---|---|---|---|---|
| (cm) | (GB) | (GiB) | ||||
| DVD-1 | SS SL | 1 | 1 | 8 | 1.46 | 1.36 |
| DVD-2 | SS DL | 1 | 2 | 8 | 2.66 | 2.47 |
| DVD-3 | DS SL | 2 | 2 | 8 | 2.92 | 2.72 |
| DVD-4 | DS DL | 2 | 4 | 8 | 5.32 | 4.95 |
| DVD-5 | SS SL | 1 | 1 | 12 | 4.70 | 4.37 |
| DVD-9 | SS DL | 1 | 2 | 12 | 8.54 | 7.95 |
| DVD-10 | DS SL | 2 | 2 | 12 | 9.40 | 8.74 |
| DVD-14 | DS DL/SL | 2 | 3 | 12 | 13.24 | 12.32 |
| DVD-18 | DS DL | 2 | 4 | 12 | 17.08 | 15.90 |
| DVD-R 1.0 | SS SL | 1 | 1 | 12 | 3.95 | 3.68 |
| DVD-R 2.0 | SS SL | 1 | 1 | 12 | 4.70 | 4.37 |
| DVD-R 2.0 | DS SL | 2 | 2 | 12 | 9.40 | 8.75 |
| DVD-RW 2.0 | SS SL | 1 | 1 | 12 | 4.70 | 4.37 |
| DVD-RW 2.0 | DS SL | 2 | 2 | 12 | 9.40 | 8.75 |
| DVD+R 2.0 | SS SL | 1 | 1 | 12 | 4.70 | 4.37 |
| DVD+R 2.0 | DS SL | 2 | 2 | 12 | 9.40 | 8.75 |
| DVD+RW 2.0 | SS SL | 1 | 1 | 12 | 4.70 | 4.37 |
| DVD+RW 2.0 | DS SL | 2 | 2 | 12 | 9.40 | 8.75 |
| DVD-RAM 1.0 | SS SL | 1 | 1 | 12 | 2.58 | 2.40 |
| DVD-RAM 1.0 | DS SL | 2 | 2 | 12 | 5.16 | 4.80 |
| DVD-RAM 2.0 | SS SL | 1 | 1 | 12 | 4.70 | 4.37 |
| DVD-RAM 2.0 | DS SL | 2 | 2 | 12 | 9.40 | 8.75 |
| DVD-RAM 2.0 | SS SL | 1 | 1 | 8 | 1.46 | 1.36 |
| DVD-RAM 2.0 | DS SL | 2 | 2 | 8 | 2.65 | 2.47 |
| CD-ROM 74 min | SS SL | 1 | 1 | 12 | 0.682 | 0.635 |
| CD-ROM 80 min | SS SL | 1 | 1 | 12 | 0.737 | 0.687 |
| CD-ROM | SS SL | 1 | 1 | 8 | 0.194 | 0.180 |
| DDCD-ROM | SS SL | 1 | 1 | 12 | 1.364 | 1.270 |
| DDCD-ROM | SS SL | 1 | 1 | 8 | 0.387 | 0.360 |
| HD DVD | SS SL | 1 | 1 | 8 | 4.70 | |
| HD DVD | SS DL | 1 | 2 | 8 | 9.40 | |
| HD DVD | DS SL | 2 | 2 | 8 | 9.40 | |
| HD DVD | DS DL | 2 | 4 | 8 | 18.80 | |
| HD DVD | SS SL | 1 | 1 | 12 | 15.00 | |
| HD DVD | SS DL | 1 | 2 | 12 | 30.00 | |
| HD DVD | DS SL | 2 | 2 | 12 | 30.00 | |
| HD DVD | DS DL | 2 | 4 | 12 | 60.00 | |
| HD DVD-RAM | SS SL | 1 | 1 | 12 | 20.00 | |
Contents |
[edit] First-generation optical discs
Initially, optical discs were for storing music and computer software. The laser disc format stored analog video signals, but, commercially, lost to the VHS videotape cassette, mainly its high cost and non-recordability; other first-generation disc formats are designed solely to store digital data.
Most first-generation disc devices had an infrared laser reading head. The minimum size of the laser spot is proportional to its wavelength, thus wavelength is a limiting factor against great information density, too little data can be stored so. The infrared range is beyond the long-wavelength end of the visible light spectrum, so, supports less density than any visible light colour. One example of high-density data storage capacity, achieved with an infrared laser, is 700MB of net user data for a 12cm compact disc.
NOTE: other factors affecting data storage density are, for example, a multi-layered infrared disc would hold more data than an identical single-layer disc; whether CAV, CLV, or zoned-CAV; how the data are encoded; how much clear margin at the center and the edge
[edit] Second-generation optical discs
Second-generation optical discs were for storing great amounts of data, including broadcast-quality digital video. Such discs usually are read with a visible-light laser (usually red); the shorter wavelength and greater numerical aperture[4] allow a narrower light beam, permitting smaller pits and lands in the disc. In the DVD format, this allows 4.7GB storage on a standard 12cm, single-sided, single-layer disc; alternately, smaller media, such as the MiniDisc and the DataPlay formats, can have capacity comparable to that of the larger, standard compact 12cm disc.
- Hi-MD
- DVD and derivatives
- Super Audio CD
- Enhanced Versatile Disc
- GD-ROM
- Digital Multilayer Disk
- DataPlay
- Fluorescent Multilayer Disc
- Phase-change Dual
- Universal Media Disc
[edit] Third-generation optical discs
Third-generation optical discs are in development, meant for distributing high-definition video and support greater data storage capacities, accomplished with short-wavelength visible-light lasers and greater numerical apertures. The Blu-ray disc uses blue-violet lasers of greater aperture, for use with discs with smaller pits and lands, thereby greater data storage capacity per layer. [4] In practice, the effective, multimedia presentation capacity is improved with enhanced video data compression codecs such as H.264, and VC-1.
- Currently shipping:
- In development:
[edit] Next generation optical discs
The following formats are ahead of current (third-generation) discs, having the potential more than one terabyte (1TB) of data storage space.
[edit] Recordable and writable optical discs
- See also: Optical disc recording technologies
[edit] References
- ^ "LG 6x Blu-ray Burner Available in Korea", CDRinfo.com.
- ^ MPEG: DVD, Book A – Physical parameters
- ^ DVD in Detail
- ^ a b Format War Update: Blu-ray Wins Over HD DVD
- Inventor of the Week Archive: The Digital Compact Disc. Massachusetts Institute of Technology (December, 1999). Retrieved on 2007-07-13.
- Brier Dudley (November 29, 2004). Scientist's invention was let go for a song. The Seattle Times. Retrieved on 2007-07-13.
- David Gregg and the Optical Disk. About.com. Retrieved on 2007-07-13.
[edit] External links
- Optical Storage Technology Association
- Understanding Recordable & Rewritable DVD by Hugh Bennett
- Understanding CD-R & CD-RW by Hugh Bennett
- Reference guide for optical media by Terence O'Kelly (Memorex Inc.)
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