Optical disc
Overview
 
In computing
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...

 and optical disc recording technologies
Optical disc recording technologies
Optical disc authoring requires a number of different optical disc recorder technologies working in tandem, from the optical disc media to the firmware to the control electronics of the optical disc drive...

, an optical disc is a flat, usually circular disc which encodes binary data (bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

s) in the form of pits (binary value of 0 or off, due to lack of reflection when read) and lands (binary value of 1 or on, due to a reflection when read) on a special material (often aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

) on one of its flat surfaces. The encoding material sits atop a thicker substrate (usually polycarbonate
Polycarbonate
PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%...

) which makes up the bulk of the disc and forms a dust defocusing layer.
Encyclopedia
In computing
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...

 and optical disc recording technologies
Optical disc recording technologies
Optical disc authoring requires a number of different optical disc recorder technologies working in tandem, from the optical disc media to the firmware to the control electronics of the optical disc drive...

, an optical disc is a flat, usually circular disc which encodes binary data (bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

s) in the form of pits (binary value of 0 or off, due to lack of reflection when read) and lands (binary value of 1 or on, due to a reflection when read) on a special material (often aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

) on one of its flat surfaces. The encoding material sits atop a thicker substrate (usually polycarbonate
Polycarbonate
PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%...

) which makes up the bulk of the disc and forms a dust defocusing layer. The encoding pattern follows a continuous, spiral path covering the entire disc surface and extending from the innermost track to the outermost track. The data is stored on the disc with a laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 or stamping machine, and can be accessed when the data path is illuminated with a laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...

 in an optical disc drive which spins the disc at speeds of about 200 to 4000 RPM
Revolutions per minute
Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...

 or more, depending on the drive type, disc format, and the distance of the read head from the center of the disc (inner tracks are read at a faster disc speed). The pits or bumps distort the reflected laser light, hence most optical discs (except the black discs of the original PlayStation video game console) characteristically have an iridescent
Iridescence
Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...

 appearance created by the grooves of the reflective layer. The reverse side of an optical disc usually has a printed label, generally made of paper but sometimes printed or stamped onto the disc itself. This side of the disc contains the actual data and is typically coated with a transparent material, usually lacquer
Lacquer
In a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...

. Unlike the 3½-inch floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...

, most optical discs do not have an integrated protective casing and are therefore susceptible to data transfer problems due to scratches, fingerprints, and other environmental problems.

Optical discs are usually between 7.6 and 30 cm (3 to 12 in) in diameter, with 12 cm (4.75 in) being the most common size. A typical disc is about 1.2 mm (0.05 in) thick, while the track pitch (distance from the center of one track to the center of the next) is typically 1.6 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

.

An optical disc is designed to support one of three recording types: read-only (e.g.: CD
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

 and CD-ROM
CD-ROM
A CD-ROM is a pre-pressed compact disc that contains data accessible to, but not writable by, a computer for data storage and music playback. The 1985 “Yellow Book” standard developed by Sony and Philips adapted the format to hold any form of binary data....

), recordable (write-once, e.g. CD-R
CD-R
A CD-R 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....

), or re-recordable (rewritable, e.g. CD-RW
CD-RW
A CD-RW is a rewritable optical disc. It was introduced in 1997, and was known as "CD-Writable" during development. It was preceded by the CD-MO, which was never commercially released....

). Write-once optical discs commonly have an organic dye recording layer between the substrate and the reflective layer. Rewritable discs typically contain an alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 recording layer composed of a phase change material, most often AgInSbTe
AgInSbTe
AgInSbTe, or Silver-Indium-Antimony-Tellurium, is a phase change material from the group of chalcogenide glasses, used in rewritable optical discs and phase-change memory applications...

, an alloy of silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

, indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...

, antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

 and tellurium.

Optical discs are most commonly used for storing music (e.g. for use in a CD player), video (e.g. for use in a DVD player
DVD player
A DVD player is a device that plays discs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. These devices were invented in 1997 and continue to thrive...

), or data and programs for personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

s (PC). The Optical Storage Technology Association
Optical Storage Technology Association
The Optical Storage Technology Association is an international trade association which promotes the use of recordable optical technologies and products, and most notably it is responsible for the creation and maintenance of the UDF specification...

 (OSTA) promotes standardized optical storage formats. 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
Optical media preservation
The preservation of optical media is essential because it is a resource in libraries, and stores audio, video, and computer data to be accessed by patrons. While optical discs are generally more reliable and durable than older media types, environmental conditions and/or poor handling can result...

 procedures to ensure continued usability in the computer's optical disc drive or corresponding disc player.

For computer data backup and physical data transfer, optical discs such as CDs and DVDs are gradually being replaced with faster, smaller, and more reliable solid-state devices, especially the USB flash drive
USB flash drive
A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...

. This trend is expected to continue as USB flash drives continue to increase in capacity and drop in price. Similarly, personal portable CD players have been supplanted by portable solid-state digital audio player (MP3 players), and MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...

 music purchased or shared over the Internet has significantly reduced the number of audio CDs sold annually.

History

The optical disc was invented in 1958. In 1961 and 1969, David Paul Gregg
David Paul Gregg
Dr. David Paul Gregg was the inventor of the optical disc . Gregg was inspired to create the optical disc in 1958. He originally had it patented as the "Videodisk" in 1961. In 1968 his patents were purchased by MCA who help develop the technology further...

 registered a patent for the analog optical disc for video recording. This form of optical disc was a very early form of the DVD . It is of special interest that , filed 1989, issued 1990, generated royalty income for Pioneer Corporation's DVA until 2007 —then encompassing the CD, DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....

, and Blu-ray Disc
Blu-ray Disc
Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...

 systems. In the early 1960s, the Music Corporation of America bought Gregg's patents and his company, Gauss Electrophysics.

Later, in the Netherlands in 1969, Philips
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....

 Research physicists began their first optical videodisc experiments at Eindhoven. In 1975, Philips and MCA began to work together, and in 1978, commercially much too late, they presented their long-awaited Laserdisc
Laserdisc
LaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...

 in Atlanta. MCA delivered the discs and Philips the players. However, the presentation was a technical and commercial failure and the Philips/MCA cooperation ended.

In Japan and the U.S., Pioneer
Pioneer Corporation
is a multinational corporation that specializes in digital entertainment products, based in Kawasaki, Kanagawa, Japan. The company was founded in 1938 in Tokyo as a radio and speaker repair shop...

 succeeded with the videodisc until the advent of the DVD. In 1979, Philips and Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

, in consortium, successfully developed the audio compact disc
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

 in 1983.

In the mid-1990s, a consortium of manufacturers developed the second generation of the optical disc, the DVD.

As magnetic disks found limited applications in storing the data in large amount.So,there was the need of finding some more data storing techniques.As a result of it.it was found that by using optical means large data storing devices can be made which in turn gave rise to the optical discs.The very first application of this kind was the Compact Disc(CD) which was used in audio systems.

Sony and Philips developed the first generation of the CD's in the mid 1980's with the complete specifications for these devices.With the help of this kind of technology the possibility of representing the analog signal into digital signal was exploited to great level.For this purpose the 16 bit samples of the analog signal were taken at the rate of 44,100 samples per second which was obviously following the Nyquist Criteria.The design of first version of the CD's was to hold up to 75 minutes of music which was requiring 3GB of storage.

The third generation optical disc was developed in 2000–2006, and was introduced as Blu-ray Disc. First movies on Blu-ray discs were released in June 2006. Blu-ray eventually prevailed in a high definition optical disc format war
High definition optical disc format war
A format war took place between the Blu-ray Disc and HD DVD optical disc standards for storing high definition video and audio.These standards emerged between 2000 and 2002 and attracted both the mutual and exclusive support of major consumer electronics manufacturers, personal computer...

 over a competing format, the HD DVD
HD DVD
HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...

. A standard Blu-ray disc can hold about 25 GB of data, a DVD about 4.7 GB, and a CD about 700 MB.

First-generation

Initially, optical discs were used to store music and computer software. The Laserdisc
Laserdisc
LaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...

 format stored analog video
Analog video
Analog video is a video signal transferred by an analog signal. An analog color video signal contains luminance, brightness and chrominance of an analog television image...

 signals for the distribution of home video
Home video
Home video is a blanket term used for pre-recorded media that is either sold or rented/hired for home cinema entertainment. The term originates from the VHS/Betamax era but has carried over into current optical disc formats like DVD and Blu-ray Disc and, to a lesser extent, into methods of digital...

, but commercially lost to the VHS
VHS
The Video Home System is a consumer-level analog recording videocassette standard developed by Victor Company of Japan ....

 videocassette format, due mainly to its high cost and non-re-recordability; other first-generation disc formats were designed only to store digital data and were not initially capable of use as a digital video
Digital video
Digital video is a type of digital recording system that works by using a digital rather than an analog video signal.The terms camera, video camera, and camcorder are used interchangeably in this article.- History :...

 medium.

Most first-generation disc devices had an infrared laser reading head. The minimum size of the laser spot is proportional to its wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

, 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 700 MB of net user data for a 12 cm compact disc.

Other factors that affect data storage density include: more than one layer of data in the disc, method of rotation (Constant linear velocity
Constant linear velocity
In optical storage, constant linear velocity is a qualifier for the rated speed of an optical disc drive, and may also be applied to the writing speed of recordable discs. CLV implies that the angular velocity varies during an operation, as contrasted with CAV modes...

 (CLV), Constant angular velocity
Constant angular velocity
In optical storage, constant angular velocity is a qualifier for the rated speed of an optical disc drive, and may also be applied to the writing speed of recordable discs...

 (CAV), or zoned-CAV), the composition of lands and pits, and how much clear margin is at the center and the edge.
  • Compact Disc
    Compact Disc
    The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

     (CD) and derivatives
    • Video CD
      Video CD
      Before the advent of DVD and Blu-ray, the Video CD became the first format for distributing films on standard 120 mm optical discs. The format is a standard digital format for storing video on a Compact Disc...

       (VCD)
    • Super Video CD
      Super Video CD
      Super Video CD is a digital format for storing video on standard compact discs. SVCD was intended as a successor to Video CD and an alternative to DVD-Video, and falls somewhere between both in terms of technical capability and picture quality...

  • Laserdisc
    Laserdisc
    LaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...

  • GD-ROM
    GD-ROM
    GD-ROM is the proprietary optical disc format used by the Dreamcast games console, as well as its arcade counterparts and the Sega/Nintendo/Namco Triforce arcade system...

  • Phase-change Dual
    Phase-change Dual
    Phase-Change Dual is a rewritable optical disc format introduced by Panasonic in 1995. Much like CD-RW, PD uses a phase change layer that can be overwritten in a single pass of the read/write head. A PD disc has a capacity of 650 MB, can be rewritten 500,000 times and is enclosed in a protective...

  • Double Density Compact Disc
    Double Density Compact Disc
    Double-density compact disc is an optical disc technology developed by Sony using the same laser wave-length as compact disc, namely 780 nm...

     (DDCD)
  • Magneto-optical disc
  • MiniDisc
    MiniDisc
    The disc is permanently housed in a cartridge with a sliding door, similar to the casing of a 3.5" floppy disk. This shutter is opened automatically by a mechanism upon insertion. The audio discs can either be recordable or premastered. Recordable MiniDiscs use a magneto-optical system to record...


Second-generation

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
Numerical aperture
In optics, the numerical aperture of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light. By incorporating index of refraction in its definition, NA has the property that it is constant for a beam as it goes from one...

 allow a narrower light beam, permitting smaller pits and lands in the disc. In the DVD format, this allows 4.7 GB storage on a standard 12 cm, single-sided, single-layer disc; alternatively, smaller media, such as the MiniDisc
MiniDisc
The disc is permanently housed in a cartridge with a sliding door, similar to the casing of a 3.5" floppy disk. This shutter is opened automatically by a mechanism upon insertion. The audio discs can either be recordable or premastered. Recordable MiniDiscs use a magneto-optical system to record...

 and the DataPlay
DataPlay
DataPlay is an optical disc system developed by DataPlay Inc. and released to the consumer market in 2002. Using very small disks enclosed in a protective cartridge storing 250MB per side, DataPlay was intended primarily for portable music playback, including both pre-recorded disks and...

 formats, can have capacity comparable to that of the larger, standard compact 12 cm disc.
  • Hi-MD
    Hi-MD
    In January 2004, Sony announced the Hi-MD media storage format as a further development of the MiniDisc format. With its release in later 2004 came the ability to use newly-developed, high-capacity 1 gigabyte Hi-MD discs, sporting the same dimensions as regular MiniDiscs.- Main features :* The...

  • DVD
    DVD
    A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....

     and derivatives
    • DVD-Audio
      DVD-Audio
      DVD-Audio is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio is not intended to be a video delivery format and is not the same as video DVDs containing concert films or music videos....

    • DualDisc
      DualDisc
      DualDisc was a type of double-sided optical disc product developed by a group of record companies including EMI Music, Universal Music Group, Sony/BMG Music Entertainment, Warner Music Group, and 5.1 Entertainment Group and later under the aegis of the Recording Industry Association of America...

    • Digital Video Express
      DIVX
      DIVX was an unsuccessful attempt by Circuit City and the entertainment law firm Ziffren, Brittenham, Branca and Fischer to create an alternative to video rental in the United States.-Format:...

       (DIVX)
  • Super Audio CD
    Super Audio CD
    Super Audio CD is a high-resolution, read-only optical disc for audio storage. Sony and Philips Electronics jointly developed the technology, and publicized it in 1999. It is designated as the Scarlet Book standard. Sony and Philips previously collaborated to define the Compact Disc standard...

  • Enhanced Versatile Disc
    Enhanced Versatile Disc
    The Enhanced Versatile Disc is an optical medium-based digital audio/video format, developed to provide a means for playing HDTV content using existing optical media. It was announced on November 18, 2003, by the People's Republic of China's Xinhua News Agency as a response to the popular...

  • DataPlay
    DataPlay
    DataPlay is an optical disc system developed by DataPlay Inc. and released to the consumer market in 2002. Using very small disks enclosed in a protective cartridge storing 250MB per side, DataPlay was intended primarily for portable music playback, including both pre-recorded disks and...

  • Universal Media Disc
    Universal Media Disc
    The Universal Media Disc is an optical disc medium developed by Sony for use on their PlayStation Portable handheld gaming and multimedia platform...

  • Ultra Density Optical
    Ultra Density Optical
    Ultra Density Optical is an optical disc format designed for high-density storage of high-definition video and data.- Overview :...


Third-generation

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 and focusing optics of greater aperture, for use with discs with smaller pits and lands, thereby greater data storage capacity per layer.
In practice, the effective multimedia presentation capacity is improved with enhanced video data compression
Data compression
In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....

 codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...

s such as H.264/MPEG-4 AVC
H.264/MPEG-4 AVC
H.264/MPEG-4 Part 10 or AVC is a standard for video compression, and is currently one of the most commonly used formats for the recording, compression, and distribution of high definition video...

 and VC-1
VC-1
VC-1 is the informal name of the SMPTE 421M video codec standard, which was initially developed as a proprietary video format by Microsoft before it was released as a formal SMPTE standard video format on April 3, 2006...

.
  • Currently shipping:
    • Blu-ray Disc
      Blu-ray Disc
      Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...

       (up to 128 GB (Quad-Layer))
    • China Blue High-definition Disc

  • In development:
    • Forward Versatile Disc
      Forward Versatile Disc
      FVD, or Forward Versatile Disc, is an offshoot ofDVD developed in Taiwan jointly by the Advanced Optical Storage Research Alliance and the Industrial Technology Research Institute as a less expensive alternative for high-definition content...

    • Digital Multilayer Disk
      Digital Multilayer Disk
      Digital Multilayer Disk is an optical disc format developed by D Data Inc. It is based on the 3D optical data storage technology developed for the Fluorescent Multilayer Disc by the defunct company Constellation 3D. DMDs can store between 22 and 32 GB of binary information...

       or Fluorescent Multilayer Disc
      Fluorescent Multilayer Disc
      Fluorescent Multilayer Disc was an optical disc format developed by Constellation 3D that uses fluorescent, rather than reflective materials to store data. Reflective disc formats have a practical limitation of about two layers, primarily due to interference, scatter, and inter-layer cross talk...


  • Abandoned:
    • HD DVD
      HD DVD
      HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...

    • Versatile Multilayer Disc
      Versatile Multilayer Disc
      Versatile Multilayer Disc is a high-capacity red laser optical disc technology designed by New Medium Enterprises, Inc....


Fourth-generation

The following formats go beyond the current third-generation discs and have the potential to hold more than one terabyte (1 TB
Terabyte
The terabyte is a multiple of the unit byte for digital information. The prefix tera means 1012 in the International System of Units , and therefore 1 terabyte is , or 1 trillion bytes, or 1000 gigabytes. 1 terabyte in binary prefixes is 0.9095 tebibytes, or 931.32 gibibytes...

) of data:
  • Holographic Versatile Disc
    Holographic Versatile Disc
    The Holographic Versatile Disc is an optical disc technology developed between April 2004 and mid-2008 that can store up to several terabytes of data on an optical disc the same size as a CD, DVD or Blu-ray disc. It employs a technique known as collinear holography, whereby a green and red laser...

  • LS-R
    LS-R
    LS-R, or the Layer-Selection-Type Recordable Optical Disk, is the term coined by Hitachi in 2003 for a next-generation optical disc technology which allows much larger data storage densities than DVD, HD DVD or Blu-ray Disc, by allowing the use of a large number of data layers in a single disc...

  • Protein-coated disc
    Protein-coated disc
    Protein-Coated Disc is a theoretical optical disc technology currently being developed by Professor Venkatesan Renugopalakrishnan, formerly of Harvard Medical School and Florida International University. PCD would greatly increase storage over Holographic Versatile Disc optical disc systems...


Recordable and writable optical discs

There are numerous formats of optical direct to disk recording
Direct to Disk Recording
Direct-to-disk recording refers to methods by which analog signals and digital signals such as digital audio and digital video are digitally recorded to optical disc recording technologies such as DVDs, and CD optical discs...

 devices on the market, all of which are based on using a laser to change the reflectivity
Reflectivity
In optics and photometry, reflectivity is the fraction of incident radiation reflected by a surface. In general it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength...

 of the digital recording
Digital recording
In digital recording, digital audio and digital video is directly recorded to a storage device as a stream of discrete numbers, representing the changes in air pressure for audio and chroma and luminance values for video through time, thus making an abstract template for the original sound or...

 medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed. All formats enable reading of computer file
Computer file
A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...

s as many times as desired by the user, but writing is a different situation. Some formats such as CD-R
CD-R
A CD-R 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....

 enable writes to be made only once to each sector on the disk, while other formats CD-RW
CD-RW
A CD-RW is a rewritable optical disc. It was introduced in 1997, and was known as "CD-Writable" during development. It was preceded by the CD-MO, which was never commercially released....

 enable multiple writes to the same sector which is more like a magnetic recording hard disk drive (HDD). In August of 2011, a company named Millenniata announced a format called the M-Disk which, reverting to the original technology of optical disks, creates physical pits in a rock-like layer. The M-Disk is stable up to 500 °C (932 °F), is impervious to humidity issues, and is engineered to maintain its integrity for 1,000 years without degradation.

Specifications

Base (1×) and (current) maximum speeds by generation
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×

Capacity and nomenclature
Designation Sides Layers
(total)
Diameter Capacity
(cm) (GB
Gigabyte
The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units , therefore 1 gigabyte is...

)
| (GiB
Gibibyte
The gibibyte is a standards-based binary multiple of the byte, a unit of digital information storage. The gibibyte unit symbol is GiB....

)
BD SS SL 1 1 8 7.8
BD SS DL 1 2 8 15.6
BD SS SL 1 1 12 25
BD SS DL 1 2 12 50
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
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), +R, –RW, +RW SS SL 1 1 12 4.70 4.37
DVD-R, +R, –RW, +RW DS SL 2 2 12 9.40 8.75
DVD–RAM SS SL 1 1 8 1.46 1.36
DVD–RAM DS SL 2 2 8 2.65 2.47
DVD–RAM 1.0 SS SL 1 1 12 2.58 2.40
DVD–RAM 2.0 SS SL 1 1 12 4.70 4.37
DVD–RAM 1.0 DS SL 2 2 12 5.16 4.80
DVD–RAM 2.0 DS SL 2 2 12 9.40 8.75
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

External links

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