In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc which encodes binary data (bits) 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) on one of its flat surfaces. The encoding material sits atop a thicker substrate (usually polycarbonate) 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 or stamping machine, and can be accessed when the data path is illuminated with a laser diode in an optical disc drive which spins the disc at speeds of about 200 to 4,000 RPM 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 higher disc speed). Most optical discs exhibit a characteristic iridescence as a result of the diffraction grating formed by its grooves. This side of the disc contains the actual data and is typically coated with a transparent material, usually lacquer. The reverse side of an optical disc usually has a printed label, sometimes made of paper but often printed or stamped onto the disc itself. Unlike the 3½-inch floppy disk, 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.
Computing is any activity that uses computers. It includes developing hardware and software, and using computers to manage and process information, communicate and entertain. Computing is a critically important, integral component of modern industrial technology. Major computing disciplines include computer engineering, software engineering, computer science, information systems, and information technology.
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. This article discusses some of the more important technologies.
The bit is a basic unit of information in information theory, computing, and digital communications. The name is a portmanteau of binary digit.
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) ranges from 1.6 µm (for CDs) to 320 nm (for Blu-ray discs).
The micrometre or micrometer, also commonly known by the previous name micron, is an SI derived unit of length equaling 1×10−6 metre ; that is, one millionth of a metre.
Compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony and released in 1982. The format was originally developed to store and play only sound recordings (CD-DA) but was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, CD-i, and Enhanced Music CD. The first commercially available audio CD player, the Sony CDP-101, was released October 1982 in Japan.
The nanometre or nanometer is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre. It can be written in scientific notation as 1×10−9 m, in engineering notation as 1 E−9 m, and as simply 1/1000000000 metres. One nanometre equals ten ångströms. When used as a prefix for something other than a unit of measure, nano refers to nanotechnology, or phenomena typically occurring on a scale of nanometres.
An optical disc is designed to support one of three recording types: read-only (e.g.: CD and CD-ROM), recordable (write-once, e.g. CD-R), or re-recordable (rewritable, e.g. CD-RW). Write-once optical discs commonly have an organic dye recording layer between the substrate and the reflective layer. Rewritable discs typically contain an alloy recording layer composed of a phase change material, most often AgInSbTe, an alloy of silver, indium, antimony, and tellurium.
A CD-ROM is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory.
CD-RW is a digital optical disc storage format introduced in 1997. A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written.
An alloy is a combination of metals and of a metal or another element. Alloys are defined by a metallic bonding character. An alloy may be a solid solution of metal elements or a mixture of metallic phases. Intermetallic compounds are alloys with a defined stoichiometry and crystal structure. Zintl phases are also sometimes considered alloys depending on bond types.
Optical discs are most commonly used for storing music (e.g. for use in a CD player), video (e.g. for use in a Blu-ray player), or data and programs for personal computers (PC). The Optical Storage Technology Association (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 procedures to ensure continued usability in the computer's optical disc drive or corresponding disc player.
A personal computer (PC) is a multi-purpose computer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or technician. Unlike large costly minicomputer and mainframes, time-sharing by many people at the same time is not used with personal computers.
The Optical Storage Technology Association (OSTA) 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. Representing more than 85 percent of worldwide writable optical product shipment's manufacturers and resellers, it was incorporated in 1992.
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 in lost information. This article will introduce the different types of optical media discs and offer a discussion of strategies for preservation of these materials.
For computer data backup and physical data transfer, optical discs such as CDs and DVDs are gradually being replaced with faster, smaller solid-state devices, especially the USB flash drive. [ citation needed ] This trend is expected to continue as USB flash drives continue to increase in capacity and drop in price.[ citation needed ] Additionally, music purchased or shared over the Internet has significantly reduced the number of audio CDs sold annually.
A USB flash drive, also known as a thumb drive, pen drive, gig stick, flash stick, jump drive, disk key, disk on key, flash-drive, memory stick, USB key, USB stick or USB memory, is a data storage device that includes flash memory with an integrated USB interface. It is typically removable, rewritable and much smaller than an optical disc. Most weigh less than 1 oz. Since first appearing on the market in late 2000, as with virtually all other computer memory devices, storage capacities have risen while prices have dropped. As of March 2016, flash drives with anywhere from 8 to 256 GB were frequently sold, while 512 GB and 1 TB units were less frequent. As of 2018, 2TB flash drives were the largest available in terms of storage capacity. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to last between 10 and 100 years under normal circumstances.
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The first recorded historical use of an optical disc was in 1884 when Alexander Graham Bell, Chichester Bell and Charles Sumner Tainter recorded sound on a glass disc using a beam of light.
Alexander Graham Bell was a Scottish-born scientist, inventor, engineer, and innovator who is credited with inventing and patenting the first practical telephone. He also founded the American Telephone and Telegraph Company (AT&T) in 1885.
Chichester Alexander Bell (1848–1924) was a chemist, first cousin of Alexander Graham Bell, and instrumental in developing improved versions of the phonograph.
Charles Sumner Tainter was an American scientific instrument maker, engineer and inventor, best known for his collaborations with Alexander Graham Bell, Chichester Bell, Alexander's father-in-law Gardiner Hubbard, and for his significant improvements to Thomas Edison's phonograph, resulting in the Graphophone, one version of which was the first Dictaphone.
An early optical disc system existed in 1935, named Lichttonorgel.[ citation needed ]
An early analog optical disc used for video recording was invented by David Paul Gregg in 1958 U.S. Patent 3,430,966 ). It is of special interest that U.S. Patent 4,893,297 , filed 1989, issued 1990, generated royalty income for Pioneer Corporation's DVA until 2007 —then encompassing the CD, DVD, and Blu-ray systems. In the early 1960s, the Music Corporation of America bought Gregg's patents and his company, Gauss Electrophysics.and patented in the US in 1961 and 1969. This form of optical disc was a very early form of the DVD (
American inventor James T. Russell has been credited with inventing the first system to record a digital signal on an optical transparent foil which is lit from behind by a high-power halogen lamp. Russell's patent application was first filed in 1966 and he was granted a patent in 1970. Following litigation, Sony and Philips licensed Russell's patents (then held by a Canadian company, Optical Recording Corp.) in the 1980s.
Both Gregg's and Russell's disc are floppy media read in transparent mode, which imposes serious drawbacks. In the Netherlands in 1969, Philips Research physicist, Pieter Kramer invented an optical videodisc in reflective mode with a protective layer read by a focused laser beam U.S. Patent 5,068,846 , filed 1972, issued 1991. Kramer's physical format is used in all optical discs. In 1975, Philips and MCA began to work together, and in 1978, commercially much too late, they presented their long-awaited Laserdisc in Atlanta. MCA delivered the discs and Philips the players. However, the presentation was a commercial failure, and the 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 audio compact disc.
In 1979, Exxon STAR Systems in Pasadena, CA built a computer controlled WORM drive that utilized thin film coatings of Tellurium and Selenium on a 12" diameter glass disk. The recording system utilized blue light at 457nm to record and red light at 632.8nm to read. STAR Systems was bought by Storage Technology Corporation (STC) in 1981 and moved to Boulder, CO. Development of the WORM technology was continued using 14" diameter aluminum substrates. Beta testing of the disk drives, originally labeled the Laser Storage Drive 2000 (LSD-2000), was only moderately successful. Many of the disks were shipped to RCA Laboratories (now David Sarnoff Research Center) to be used in the Library of Congress archiving efforts. The STC disks utilized a sealed cartridge with an optical window for protection U.S. Patent 4,542,495 .
The CD-ROM format was developed by Sony and Denon, introduced in 1984, as an extension of Compact Disc Digital Audio and adapted to hold any form of digital data. The same year, Sony demonstrated a LaserDisc data storage format, with a larger data capacity of 3.28 GB.
In the late 1980s and early 1990s, Optex, Inc. of Rockville, MD, built an erasable optical digital video disc system U.S. Patent 5,113,387 using Electron Trapping Optical Media (ETOM) U.S. Patent 5,128,849 . Although this technology was written up in Video Pro Magazine's December 1994 issue promising "the death of the tape", it was never marketed.
In the mid-1990s, a consortium of manufacturers (Sony, Philips, Toshiba, Panasonic) developed the second generation of the optical disc, the DVD.
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, 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 CDs in the mid-1980s 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 a great level. For this purpose, the 16-bit samples of the analog signal were taken at the rate of 44,100 samples per second. This sample rate was based on the Nyquist rate of 40,000 samples per second required to capture the audible frequency range to 20 kHz without aliasing, with an additional tolerance to allow the use of less-than-perfect analog audio pre-filters to remove any higher frequencies.The first version of the standard allowed up to 75 minutes of music which required 650MB of storage.
The DVD disc appeared after the CD-ROM had become widespread in society.
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 over a competing format, the HD DVD. A standard Blu-ray disc can hold about 25 GB of data, a DVD about 4.7 GB, and a CD about 700 MB.
Initially, optical discs were used to store broadcast-quality analog video, and later digital media such as music or computer software. The LaserDisc format stored analog video signals for the distribution of home video, but commercially lost to the VHS 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 medium.
Most first-generation disc devices had an infrared laser reading head. The minimum size of the laser spot is proportional to the wavelength of the laser, so wavelength is a limiting factor upon the amount of information that can be stored in a given physical area on the disc. The infrared range is beyond the long-wavelength end of the visible light spectrum, so it supports less density than shorter-wavelength visible light. 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: the existence of multiple layers of data on the disc, the method of rotation (Constant linear velocity (CLV), Constant angular velocity (CAV), or zoned-CAV), the composition of lands and pits, and how much margin is unused is at the center and the edge of the disc.
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 apertureallow 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 DataPlay format, can have capacity comparable to that of the larger, standard compact 12 cm disc.
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. Blu-ray Disc and HD DVD 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 codecs such as H.264/MPEG-4 AVC and VC-1.
The following formats go beyond the current third-generation discs and have the potential to hold more than one terabyte (1 TB) of data and meant for distributing Ultra HD video :
|LaserDisc (LD)||0.3 GB||1971–2001|
|Write Once Read Many Disk (WORM)||0.2–6.0 GB||1979–1984|
|Compact Disc (CD)||0.7–0.9 GB||1982–today|
|Electron Trapping Optical Memory (ETOM)||6.0–12.0 GB||1987–1996|
|MiniDisc (MD)||0.14 GB||1989–today|
|Magneto Optical Disc (MOD)||0.1–16.7 GB||1990–present|
|Digital Versatile Disc (DVD)||4.7–17 GB||1995–present|
|LIMDOW (Laser Intensity Modulation Direct OverWrite)||2.6 GB||10 GB||1996–present|
|Fluorescent Multilayer Disc||50–140 GB||1998-2003|
|Versatile Multilayer Disc (VMD)||5–20 GB||100 GB||1999-2010|
|Hyper CD-ROM||1 PB||100 EB||1999?-?|
|Ultra Density Optical (UDO)||30–60 GB||2000-present|
|FVD (FVD)||5.4–15 GB||2001-present|
|Enhanced Versatile Disc (EVD)||DVD||2002-2004|
|HD DVD||15–51 GB||1 TB[ citation needed ]||2002-2008|
|Blu-ray Disc (BD)||25 GB|
128 GB (BDXL)
|Professional Disc for Data (PDD)||23 GB||2003-2006|
|Professional Disc||23–128 GB||2003–present|
|Digital Multilayer Disk||22-32 GB||2004–2007|
|Multiplexed Optical Data Storage (MODS-Disc)||250 GB–1 TB||2004–present|
|Universal Media Disc (UMD)||0.9–1.8 GB||2004–2014|
|Holographic Versatile Disc (HVD)||6.0 TB||2004–present|
|Protein-coated Disc (PCD)||50 TB||2005–present|
|M-DISC||4.7 GB (DVD format)|
25 GB (Blu-ray format)
50 GB (Blu-ray format)
100 GB (BDXL format)
|Archival Disc||0.3-1 TB||2014–present|
|Ultra HD Blu-ray||50 GB|
There are numerous formats of optical direct to disk recording devices on the market, all of which are based on using a laser to change the reflectivity of the digital recording medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed. Formats such as CD-R and DVD-R are "Write once read many", while CD-RW and DVD-RW are rewritable, more like a magnetic recording hard disk drive (HDD). Media technologies vary, M-DISC uses a different recording technique & media versus DVD-R and BD-R.
|CD–ROM 74 min||SS SL||1||1||12||0.682|
|CD–ROM 80 min||SS SL||1||1||12||0.737|
|DVD–R 1.0||SS SL||1||1||12||3.95|
|DVD–R (2.0), +R, –RW, +RW||SS SL||1||1||12||4.7|
|DVD-R, +R, –RW, +RW||DS SL||2||2||12||9.40|
|DVD–RAM 1.0||SS SL||1||1||12||2.58|
|DVD–RAM 2.0||SS SL||1||1||12||4.70|
|DVD–RAM 1.0||DS SL||2||2||12||5.16|
|DVD–RAM 2.0||DS SL||2||2||12||9.40|
An audio optical disc is an optical disc that stores sound information such as music or speech.
In computing, an optical disc drive (ODD) is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from certain discs, but recent drives can both read and record, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives. Optical disc drives that are no longer in production include CD-ROM drive, CD writer drive, combo (CD-RW/DVD-ROM) drive, and DVD writer drive supporting certain recordable and rewritable DVD formats. As of 2015, DVD writer drive supporting all existing recordable and rewritable DVD formats is the most common for desktop PCs and laptops. There are also the DVD-ROM drive, BD-ROM drive, Blu-ray Disc combo (BD-ROM/DVD±RW/CD-RW) drive, and Blu-ray Disc writer drive.
Versatile Multilayer Disc is a high-capacity red laser optical disc technology designed by New Medium Enterprises, Inc.. VMD was intended to compete with the blue laser Blu-ray Disc format and had an initial capacity of up to 30GB per side.
Digital Multilayer Disk (DMD) 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. It is based on red laser technology, so DM discs and players can be easily made in existing production facilities with little modifications. Discs are composed of multiple data layers joined by a fluorescent material. Unlike DVDs and CDs, DMD do not have metallic layers, so they are nearly transparent. DMDs are coated with proprietary chemical compositions, and those chemicals react when the red laser shines on a particular layer. The chemical reaction then generates a signal, which is then read by the disc reader. This allows for discs to potentially have up to 100 GB of storage space.
The Holographic Versatile Disc (HVD) 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 10 cm or 12 cm in diameter. The reduced radius reduces cost and materials used. It employs a technique known as collinear holography, whereby a green and red laser beam are collimated in a single beam. The green laser reads data encoded as laser interference fringes from a holographic layer near the top of the disc. A red laser is used as the reference beam to read servoinformation from a regular CD-style aluminium layer near the bottom. Servoinformation is used to monitor the position of the read head over the disc, similar to the head, track, and sector information on a conventional hard disk drive. On a CD or DVD this servoinformation is interspersed among the data. A dichroic mirror layer between the holographic data and the servo data reflects the green laser while letting the red laser pass through. This prevents interference from refraction of the green laser off the servo data pits and is an advance over past holographic storage media, which either experienced too much interference, or lacked the servo data entirely, making them incompatible with current CD and DVD drive technology.
Kornelis Antonie "Kees" Schouhamer Immink is a Dutch scientist, inventor, and entrepreneur, who pioneered and advanced the era of digital audio, video, and data recording, including popular digital media such as Compact Disc, DVD and Blu-ray Disc. He has been a prolific and influential engineer, who holds more than 1100 U.S. and international patents. A large portion of the commonly used audio and video playback and recording devices use technologies based on his work. His contributions to coding systems assisted the digital video and audio revolution, by enabling reliable data storage at information densities previously unattainable.
Double-density compact disc (DDCD) is an optical disc technology developed by Sony using the same laser wavelength as compact disc, namely 780 nm. The format is defined by the Purple Book standard document. Unlike the compact-disc technology it is based on, DDCD was designed exclusively for data with no audio capabilities.
Professional Disc (PFD) is a digital recording optical disc format introduced by Sony in 2003 primarily for XDCAM, its new tapeless camcorder system. It was one of the first optical formats to utilize a blue laser, which allowed for a higher density of data to be stored on optical media compared to infrared laser technology used in the CD and red laser technology used in the DVD format.
Optical storage is the storage of data on an optically readable medium. Data is recorded by making marks in a pattern that can be read back with the aid of light, usually a beam of laser light precisely focused on a spinning optical disc. An older example of optical storage that does not require the use of computers, is microform. There are other means of optically storing data and new methods are in development. An optical disc drive is a device in a computer that can read CD-ROMs or other optical discs, such as DVDs and Blu-ray discs. Optical storage differs from other data storage techniques that make use of other technologies such as magnetism, such as floppy disks and hard disks, or semiconductors, such as flash memory and RAM.
In computing, external storage comprises devices that store information outside a computer. Such devices may be permanently attached to the computer, may be removable or may use removable media.
DVD recordable and DVD rewritable are optical disc recording technologies. Both terms describe DVD optical discs that can be written to by a DVD recorder, whereas only 'rewritable' discs are able to erase and rewrite data. Data is written ('burned') to the disc by a laser, rather than the data being 'pressed' onto the disc during manufacture, like a DVD-ROM. Pressing is used in mass production, primarily for the distribution of home video.
Ultra Density Optical (UDO) is an optical disc format designed for high-density storage of high-definition video and data.
DVD is a digital optical disc storage format invented and developed in 1995. The medium can store any kind of digital data and is widely used for software and other computer files as well as video programs watched using DVD players. DVDs offer higher storage capacity than compact discs while having the same dimensions.
Blu-ray or Blu-ray Disc (BD) is a digital optical disc data storage format. It was designed to supersede the DVD format, and is capable of storing several hours of video in high-definition and ultra high-definition resolution (2160p). The main application of Blu-ray is as a medium for video material such as feature films and for the physical distribution of video games for the PlayStation 3, PlayStation 4, and Xbox One. The name "Blu-ray" refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs.
HD DVD is a discontinued high-density optical disc format for storing data and playback of high-definition video. Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format.
This article provides a Comparison of popular optical data-storage systems.
Although research into optical data storage has been ongoing for many decades, the first popular system was the Compact Disc, introduced in 1982, adapted from audio (CD-DA) to data storage with the 1985 Yellow Book, and re-adapted as the first mass market optical storage medium with CD-R and CD-RW in 1988. Compact Disc is still the de facto standard for audio recordings, although its place for other multimedia recordings and optical data storage has largely been superseded by DVD.
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