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Information about Optical Disk

“Optical media” redirects here. For transmission media for light, see Medium (optics).
Optical disc authoring
Optical media types
Standards
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The optical lens of a compact disc drive.


In computing, sound reproduction, and video, an optical disc is a flat, circular, usually polycarbonate disc where 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 aluminium) 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.

In a parallel manner, 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).

While Optical Discs are significantly more durable than earlier audio/visual and data formats, they are susceptible to damage from daily usage and environmental factors. Libraries and archives should enact optical media preservation procedures to ensure continued usability.

The information on an optical disc is stored sequentially on a continuous spiral track from the innermost track to the outermost track.

A computer's peripheral device used to read or write an optical disc is an optical disc drive (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 (mainly due to cost and non-recordability); 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. The minimum size of a laser spot is proportional to the wavelength of the laser, making wavelength one factor limiting the information density. Infrared is just beyond the long-wavelength end of the visible light spectrum, so it supports less density than any visible (to humans) color of light. One example of capacity achieved with an infrared laser is 700 MB of net user data for a 12 cm compact disc. (However, many factors affect density besides minimum spot size--for example, a multi-layered disc using infrared would hold more data than an otherwise identical disc with a single layer, and other issues--such as whether CAV, CLV, or zoned CAV is used, how data is encoded, and how much margin is left clear at the center and edge--also affect how close a disc can come to taking advantage of the minimum spot size over 100% of the disc surface.)
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A Compact 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 4.7 GB of storage on a standard 12 cm, 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.

Third-generation optical discs

Major third-generation optical discs are currently in development. They are designed for holding high-definition video and support larger capacities, enabled by the use of short-wavelength visible light lasers (blue-violet for Blu-ray Disc 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.

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.

Recordable and writable optical discs

References

External links

  •  • [ e] Optical storage media
Compact Disc : CD-R | CD-RW
DVD : DVD+R | DVD+R DL | DVD-R | DVD-R DL | DVD+RW | DVD-RW | DVD-RAM Blu-Ray Disc | HD DVD | MiniDisc | Laserdisc
An optical medium is material through which electromagnetic waves propagate. It is a form of transmission medium. The permittivity and permeability of the medium define how electromagnetic waves propagate in it.
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optical disc authoring, including DVD authoring, known often as burning, is the process of recording source material—video, audio or other data—onto an optical disc (compact disc or DVD).
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disk image is a computer file containing the complete contents and structure of a data storage medium or device, such as a Hard drive, CD or DVD. The term has been generalized to cover any such file, whether originated from an actual physical storage device or not.
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optical disk drive (ODD) is a disk drive that uses electromagnetic waves as part of the process of reading and writing data. It is a computer's peripheral device, that stores data on optical discs.
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Optical disc authoring software is computer software for authoring optical discs including CD-ROMs and DVDs. They are also known by synonyms such as CD burning application or DVD authoring software. Such software is required to use an optical disc recorder.
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Disc At Once, Track At Once, Session at Once (i.e. multiple burning sessions for one disc), or packet writing modes. Each mode serves different purposes:
  • Disc At Once: writes the entire disc in one pass; preferred for duplication masters

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Disc-At-Once, Track-At-Once, and Session-At-Once.

CD Disc-At-Once

Disc-At-Once or DAO for CD-R media is a mode that masters the disc contents in one pass, rather than a track at a time as in Track At Once.
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Packet writing is an optical disc recording technology used to allow writeable CD and DVD media to be used in a similar manner to a floppy disk. Packet writing allows the user to access the contents of a CD-R or CD-RW disc directly through a mounted filesystem (Unix, Linux, Mac OS
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Laserdisc

Laserdisc (left) compared to a DVD (right).
Media type: Optical disc
Encoding: Various
Developed by: MCA
Usage: Video storage

Optical disc authoring
  • Optical disc
  • Optical disc image
  • Recorder hardware
  • Authoring software

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Compact Disc

The closely spaced tracks on the readable surface of a Compact Disc cause light to diffract into a full visible colour spectrum
Media type: Optical disc
Encoding: Various
Capacity: Typically up to 700 MB
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CD-ROM (an abbreviation of "Compact Disc read-only media") is a Compact Disc that contains data accessible by a computer. While the Compact Disc format was originally designed for music storage and playback, the format was later adapted to hold any form of binary data.
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CD-R (Compact Disc-Recordable) is a variation of the Compact Disc invented by Philips and Sony. CD-R is a Write Once, Read Many optical medium (though the whole disk does not have to be entirely written in the same session) and retains a high level of
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Compact Disc ReWritable (CD-RW) is a rewritable optical disc format. Known as CD-Erasable (CD-E) during its development, CD-RW was introduced in 1997, and was preceded by the never officially released CD-MO in 1988.
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MiniDisc

The Sony MZ1 MiniDisc player, the first to hit the market in 1992.
Media type: Magneto-optical disc
Encoding: ATRAC, linear PCM (with Hi-MD)
Capacity: 80 min (standard MiniDisc), up to 45 hours of audio (1 GB capacity) (with Hi-MD)
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DVD

Media type: Optical disc
Capacity: 4.7 GB (single layer), 8.5 GB (dual layer)
Usage: Data storage, audio, video, games

Optical disc authoring
  • Optical disc
  • Optical disc image
  • Recorder hardware
  • Authoring software

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DVD-R is a DVD recordable format. A DVD-R has a larger storage capacity than its optical predecessor, the 700 MB CD-R, typically storing 4.71 GB (or 4.382 GiB), although the capacity of the original standard developed by Pioneer was 3.95 GB (3.68 GiB).
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DVD-D is a self-destructing disposable DVD format. Like the EZ-D, it is sold in a cardboard sleeve, and begins to destroy itself after several hours.

DVD-D now exists as one time play only for movies, limited time play for video games, and recordable DVD-D.
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DVD-R DL (DL stands for Dual Layer), also called DVD-R9, is a derivative of the DVD-R format standard. DVD-R DL discs employ two recordable dye layers, each capable of storing nearly the 4.7 GB (4.
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DVD+R is a once-writable optical disc with 4.7 GB (4.377 GiB) of storage capacity (more precisely, 2295104 sectors of 2048 bytes each). It has slightly less storage capacity than the DVD-R (4.382 GiB).
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DVD+R DL (DL stands for Dual Layer, commonly mistaken as Double Layer), also called DVD+R9, is a derivative of the DVD+R format created by the DVD+RW Alliance. Its use was first demonstrated in October 2003.
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DVD-RW disc ("DVD dash RW", sometimes nicknamed "DVD minus RW") is a rewritable optical disc with equal storage capacity to a DVD-R, typically 4.7 GB. The format was developed by Pioneer in November 1999 and has been approved by the DVD Forum.
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DVD+RW is the name of a standard for optical discs: one of several types of DVD, which hold up to about 4.7GB per disc (interpreted as approximately 4.7 × 109 bytes; actually 2295104 sectors of 2048 bytes each) and are used for storing films, music or other data.
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DVD-RW DL is a rewritable optical disc standard with storage capacity of 8.5 GB. DVD-RW DL discs employ two rewritable dye layers. It's approved by DVD Forum as "DVD Specifications for Re-recordable Disc for Dual Layer (DVD-RW for DL) Physical Specifications, Version 2.0".
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DVD+RW DL is a rewritable optical disc with storage capacity of 8.5 GB. DVD+RW DL discs employ two rewritable dye layers.

In March 2006, the DVD+RW Alliance approved DVD+RW part 2: Dual Layer, volume 1; DVD+RW 8.5 Gbytes, Basic Format Specifications, version 1.
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DVD-RAM (DVD–Random Access Memory) is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM media have been used in computers as well as camcorders and personal video recorders since 1998.
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Blu-ray Disc

Media type: High-density optical disc
Encoding: MPEG-2, MPEG-4 AVC (H.264), and VC-1
Capacity: 25 GB (single layer), 50 GB (dual layer)
Read mechanism: 1x@36 Mbit/s & 2x@72 Mbit/s
Developed by: Blu-ray Disc Association
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Blu-ray Disc recordable refers to two optical disc formats that can be recorded with an optical disc recorder. BD-R discs can be written to once, whereas BD-RE can be erased and re-recorded multiple times.
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HD DVD

Media type: High-density optical disc
Encoding: VC-1, H.264, and MPEG-2
Capacity: 15 GB (single layer) 30 GB (dual layer)
Read mechanism: 1x@36 Mbit/s & 2x@72 Mbit/s
Developed by: DVD Forum
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HD DVD-R is the writable disc variant of HD DVD, and is available with a single-layer capacity of 15 GB or dual-layer capacity of 30 GB.[1] Currently, HD DVD-R has slower write speeds than the competing BD-R format (1–2x vs.
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This article contains information about a scheduled or expected .
It may contain preliminary information that does not reflect the final version of the product.

HD DVD-RAM
Media type: High-density optical disc
Capacity: 20 GB
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