HOME

TheInfoList




In
computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an algorithm (Euclid's algorithm) for calculating the greatest common divisor (g.c.d ...

computing
and
optical disc recording technologies Optical disc authoring requires a number of different optical disc recorder technologies working in tandem, from the optical disc drive. (CD-R), showing characteristic iridescence. In computing Computing is any goal-oriented activity ...
, an optical disc (OD) is a flat, usually circular disc that encodes binary data (
bit The bit is a basic unit of information in computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both ...
s) in the form of pits and lands on a special material, often
aluminum Aluminium (aluminum in American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the United States The United States of America (USA), commonly known as the Unit ...

aluminum
, on one of its flat surfaces. Its main uses are physical offline data distribution and long-term
archival An archive is an accumulation of historical records – in any media – or the physical facility in which they are located. Archives contain primary source In the study of history History (from Greek , ''historia'', meaning "inquiry; ...
. Changes from pit to land or from land to pit correspond to a binary value of 1; while no change, regardless of whether in a land or a pit area, corresponds to a binary value of 0. Non-circular optical discs exist for fashion purposes; see
Shaped compact disc A shaped Compact Disc is a non-circular compact disc#REDIRECT Compact disc {{redirect category shell, {{R move {{R from other capitalization, printworthy {{R yes print .... Examples include business card CDs, CDs in the shape of a star, a map ...
.


Design and technology

The encoding material sits atop a thicker substrate (usually
polycarbonate Polycarbonates (PC) are a group of thermoplastic A thermoplastic, or thermosoft plastic, is a plastic polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material co ...

polycarbonate
) that 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 are stored on the disc with a
laser A laser is a device that emits light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as ...

laser
or stamping machine, and can be accessed when the data path is illuminated with a
laser diode file:Diode laser.jpg, A packaged laser diode shown with a penny for scale file:Laser diode chip.jpg, The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD, or diode laser) ...

laser diode
in an
optical disc drive In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and ...
that spins the disc at speeds of about 200 to 4,000
RPM Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is the number of turns in one minute The minute is a unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the ...
or more, depending on the drive type, disc format, and the distance of the read head from the center of the disc (outer tracks are read at a higher data speed due to higher linear velocities at the same angular velocities). Most optical discs exhibit a characteristic
iridescence Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States Englis ...
as a result of the
diffraction grating In optics Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (phy ...

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 term lacquer is used for a number of hard and potentially shiny finishes applied to materials such as wood or metal. These fall into a number of very different groups. The term ''lacquer'' originates from the Sanskrit Sanskrit (, attri ...

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 3-inch
floppy disk A floppy disk or floppy diskette (sometimes casually referred to as a floppy or diskette) is a type of disk storage Disk storage (also sometimes called drive storage) is a general category of storage mechanisms where data is recorded by various ...

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. Blu-rays have a coating called
durabis Durabis (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republi ...
that mitigates these 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. The so-called ''program area'' that contains the data commonly starts 25 millimetres away from the center point. 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
CDs
) to 320 nm (for
Blu-ray discs
Blu-ray discs
).


Recording types

An optical disc is designed to support one of three recording types: read-only (e.g.: CD and
CD-ROM A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc The compact disc (CD) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital ...

CD-ROM
), recordable (write-once, e.g.
CD-R CD-R (Compact disc-recordable) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electronics is a field of electronics Electronics ...

CD-R
), or re-recordable (rewritable, e.g.
CD-RW CD-RW (Compact Disc-Rewritable) is a digital media, digital optical disc data storage device, storage format introduced in 1997. A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written. CD-RWs, as opposed to CDs, require sp ...
). Write-once optical discs commonly have an organic dye (may also be a (
Phthalocyanine Phthalocyanine () is a large, aromatic forms of benzene (top) combine to produce an average structure (bottom) In chemistry, aromaticity is a property of cyclic compound, cyclic (ring (chemistry), ring-shaped), plane (geometry), planar (flat) st ...

Phthalocyanine
)
Azo dye Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl. They are a commercially important family of azo compounds, i.e. compounds containing the linkage C-N=N-C. Azo dyes are widely u ...
, mainly used by
Verbatim Verbatim means word for word. Verbatim may also refer to: * Verbatim (brand) Verbatim is a brand for storage media and flash memory Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erase ...
, or an oxonol dye, used by
Fujifilm , Fujifilm, or simply Fuji, is a Japanese headquartered in , , operating in the realms of , , and , , and . The offerings from the company that started as a manufacturer of , which it still produces, include: document solutions, and diagnos ...
) recording layer between the substrate and the reflective layer. Rewritable discs typically contain an
alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts Elec ...
recording layer composed of a
phase change material A phase change material (PCM) is a substance which releases/absorbs sufficient energy at phase transition In , , and many other related fields, phase transitions (or phase changes) are the of transition between a state of a medium, identifi ...
, most often
AgInSbTeAgInSbTe, or Silver Silver is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that ...
, an alloy of
silver Silver is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same n ...

silver
,
indium Indium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that c ...

indium
,
antimony Antimony is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science t ...

antimony
, and
tellurium Tellurium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that ...

tellurium
. Azo dyes were introduced in 1996 and phthalocyanine only began to see wide use in 2002. The type of dye and the material used on the reflective layer on an optical disc may be determined by shining a light through the disc, as different dye and material combinations have different colors.
Blu-ray Disc recordable Blu-ray Disc Recordable (BD-R) refers to two direct to disc optical disc recording technologies that can be recorded on to a Blu-ray The Blu-ray Disc (BD), often known simply as Blu-ray, is a digital optical disc storage format. It is desi ...
discs do not usually use an organic dye recording layer, instead using an inorganic recording layer. Those that do are known as low-to-high (LTH) discs and can be made in existing CD and DVD production lines, but are of lower quality than traditional Blu-ray recordable discs.


Usage

Optical discs are often stored in special cases sometimes called jewel cases and are most commonly used for
digital preservation In library A library is a curated collection of sources of information and similar resources, made accessible to a defined community for reference or borrowing. It provides physical or electronic media, digital access to material, and may be ...
, storing music (e.g. for use in a
CD player A CD player is an electronic device that plays audio compact discs, which are a digital audio, digital optical disc data storage device, data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of au ...
), video (e.g. for use in a
Blu-ray The Blu-ray Disc (BD), often known simply as Blu-ray, is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electronics is a field of elect ...

Blu-ray
player), or data and programs for
personal computer A personal computer (PC) is a multi-purpose computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known a ...
s (PC), as well as offline
hard copy In information handling, the U.S. Federal Standard 1037C Federal Standard 1037C, titled Telecommunications: Glossary of Telecommunication Terms, is a United States The United States of America (USA), commonly known as the United State ...
data distribution due to lower per-unit prices than other types of media. The Optical Storage Technology Association (OSTA) promoted standardized
optical storage IBM International Business Machines Corporation (IBM) is an American multinational technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as ...
formats. Libraries and archives enact
optical media preservation The Preservation (library and archival science), preservation of Optical disc, 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 ...
procedures to ensure continued usability in the computer's optical disc drive or corresponding disc player.
File operation A computer file is a computer resource for recording data Data are units of information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and thus defines both its essence ...
s of traditional
mass storage In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and softwa ...
devices such as
flash drives A flash drive is a portable computer drive that uses flash memory Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and ...

flash drives
,
memory card A memory card is an electronic used for storing digital information, typically using . These are commonly used in , such as s, s, computers, , s, s, s, s, s and s, and allow adding memory to such devices without compromising , as the card is us ...

memory card
s and
hard drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment and the magnetic tape is a data storag ...
s can be simulated using a UDF live file system. For computer data backup and physical data transfer, optical discs such as CDs and
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electr ...

DVD
s are gradually being replaced with faster, smaller solid-state devices, especially the
USB flash drive A USB flash drive (i.e. thumb drive) is a that includes with an integrated interface. It is typically removable, rewritable and much smaller than an . Most weigh less than . Since first appearing on the market in late 2000, as with virtuall ...

USB flash drive
. This trend is expected to continue as USB flash drives continue to increase in capacity and drop in price. Additionally, music, movies, games, software and TV shows purchased, shared or streamed over the Internet has significantly reduced the number of audio CDs, video DVDs and Blu-ray discs sold annually. However, audio CDs and Blu-rays are still preferred and bought by some, as a way of supporting their favorite works while getting something tangible in return and also since audio CDs (alongside
vinyl record A phonograph disc record (also known as a gramophone disc record, especially in British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic language fi ...

vinyl record
s and
cassette tape The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape Magnetic tape is a medium for , made of a thin, magnetizable coating ...

cassette tape
s) contain uncompressed audio without the artifacts introduced by
lossy compression In information technology, lossy compression or irreversible compression is the class of data encoding methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size ...
algorithms like
MP3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio Digital audio is a representation of sound recorded in, or converted into, Digital signal (signal processing), digital form. In digital a ...

MP3
, and Blu-rays offer better image and sound quality than streaming media, without visible compression artifacts, due to higher bitrates and more available storage space. However, Blu-rays may sometimes be
torrented
torrented
over the internet, but torrenting may not be an option for some, due to restrictions put in place by
ISP#REDIRECT Internet service provider#REDIRECT Internet service provider {{Redirect category shell, 1= {{R from other capitalisation ...
{{Redirect category shell, 1= {{R from other capitalisation ...

ISP
s on legal or copyright grounds, low download speeds or not having enough available storage space, since the content may weigh up to several dozen gigabytes. Blu-rays may be the only option for those looking to play large games without having to download them over an unreliable or slow internet connection, which is the reason why they are still (as of 2020) widely used by gaming consoles, like the
PlayStation 4 The PlayStation 4 (PS4) is a home video game console developed by Sony Computer Entertainment. Announced as the successor to the PlayStation 3 in February 2013, it was launched on November 15, 2013, in North America, November 29, 2013 in Europ ...

PlayStation 4
and
Xbox One X The Xbox One is a line of home video game consoles developed by Microsoft Microsoft Corporation is an American multinational corporation, multinational technology company with headquarters in Redmond, Washington. It develops, manufactur ...
. As of 2020, it is unusual for PC games to be available in a physical format like Blu-ray. Discs should not have any stickers and should not be stored together with paper; papers must be removed from the jewel case before storage. Discs should be handled by the edges to prevent scratching, with the thumb on the inner edge of the disc. The ISO Standard 18938:2008 is about best optical disc handling techniques. Optical disc cleaning should never be done in a circular pattern, to avoid concentric cirles from forming on the disc. Improper cleaning can scratch the disc. Recordable discs should not be exposed to light for extended periods of time. Optical discs should be stored in dry and cool conditions to increase longevity, with temperatures between -10 and 23 °C, never exceeding 32 °C, and with humidity never falling below 10%, with recommended storage at 20 to 50% of humidity without fluctuations of more than ±10%.


Durability

Although optical discs are more durable than earlier audio-visual and data storage formats, they are susceptible to environmental and daily-use damage, if handled improperly. Optical discs are not prone to uncontrollable
catastrophic failure A catastrophic failure is a sudden and total failure The 1895 alt= Failure is the state or condition of not meeting a desirable or intended objective (goal), objective, and may be viewed as the opposite of Success (concept), success. The crite ...
s such as
head crash A head crash is a hard-disk failure that occurs when a disk read-and-write head, read–write head of a hard disk drive makes contact with its rotating hard disk platter, platter, slashing its surface and permanently damaging its magnetic media. ...
es,
power surge
power surge
s, or exposure to water like
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device File:Reel-to-reel recorder tc-630.jpg, On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment an ...

hard disk drive
s and
flash storage Flash memory is an electronic non-volatile Non-volatile memory (NVM) or non-volatile storage is a type of computer memory In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machine ...
, since optical drives' storage controllers are not tied to optical discs themselves like with hard disk drives and
flash memory controller A flash memory controller (or flash controller) manages data stored on flash memory and communicates with a computer or electronic device. Flash memory controllers can be designed for operating in low duty-cycle environments like Secure Digital, SD ...
s, and a disc is usually recoverable from a defective optical drive by pushing an unsharp needle into the emergency ejection pinhole, and has no point of immediate water ingress and no integrated circuitry.


Safety

As the media itself only is accessed through a laser beam, no internal control circuitry, it can not contain malicious hardware such as so-called '' rubber-duckies'' or ''
USB killer A USB Killer is a device that looks similar to a USB Universal Serial Bus (USB) is an industry standard that establishes specifications for cables and connectors and protocols for connection, communication and power supply (Interface (comp ...
s''.
Malware Malware (a portmanteau for malicious software) is any software intentionally designed to cause disruption to a computer, server (computing), server, Client (computing), client, or computer network, leak private information, gain unauthorized acc ...

Malware
is unable to spread over factory-pressed media, finalized media, or ''-ROM'' (
read only memory Read-only memory (ROM) is a type of non-volatile memory Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. In contrast, volatile memory needs const ...
) drive types whose lasers lack the strength to write data. Malware is conventionally programmed to detect and spread over traditional
mass storage In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and softwa ...
devices such as flash drives, external
solid state drive A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data Persistence (computer science), persistently, typically using flash memory, and functioning as secondary storage in the Computer ...
s and
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device File:Reel-to-reel recorder tc-630.jpg, On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment an ...

hard disk drive
s.


History

The first recorded historical use of an optical disc was in 1884 when
Alexander Graham Bell Alexander Graham Bell (; March 3, 1847 – August 2, 1922) was a Scottish-born inventor, scientist, and engineer who is credited with inventing and patenting the first practical telephone. He also co-founded the (AT&T) in 1885. , grandf ...

Alexander Graham Bell
,
Chichester Bell Chichester Alexander Bell (1848–1924) was a chemist, first cousin of Alexander Graham Bell Alexander Graham Bell (; March 3, 1847 – August 2, 1922) was a Scottish-born inventor, scientist, and engineer who is credited with inventing ...

Chichester Bell
and
Charles Sumner Tainter Charles Sumner Tainter (April 25, 1854 – April 20, 1940) was an American scientific instrument maker, engineer and inventor, best known for his collaborations with Alexander Graham Bell Alexander Graham Bell (; born Alexander Bell, March 3, ...

Charles Sumner Tainter
recorded sound on a glass disc using a beam of light. Optophonie is a very early (1931) example of a recording device using light for both recording and playing back sound signals on a transparent photograph. An early optical disc system existed in 1935, named Lichttonorgel. An early analog optical disc used for video recording was invented by David Paul Gregg in 1958 and patented in the US in 1961 and 1969. 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 The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electr ...

DVD
, and Blu-ray systems. In the early 1960s, the Music Corporation of America bought Gregg's patents and his company, Gauss Electrophysics. American inventor James T. Russell has been credited with inventing the first system to record a digital signal on an optical transparent foil that 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 ) , national_anthem = ( en, "William of Nassau") , image_map = EU-Netherlands.svg , map_caption = , image_map2 = BES islands location map.svg , map_caption2 = , image_map3 ...

Netherlands
in 1969,
Philips Koninklijke Philips N.V. (in Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () *Dutch language , spoken in Belgium (also referred as ''flemish'') Dutch may also refer t ...

Philips
Research
physicist A physicist is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of interest. In classical antiquity, there was no real ancient analog of a modern sci ...

physicist
, Pieter Kramer invented an optical
videodisc Videodisc (or video disc) is a general term for a laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym ...
in reflective mode with a protective layer read by a focused
laser A laser is a device that emits light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as ...

laser
beam , 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
Laserdisc
in
Atlanta Atlanta () is the and of the of . With an estimated 2019 population of 506,811, it is also the . The city serves as the cultural and economic center of the , home to more than 6 million people and the in the nation. Atlanta is the ...

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 Pioneer commonly refers to a settler who migrates to previously uninhabited or sparsely inhabited land. In the United States pioneer commonly refers to an American pioneer, a person in American history who migrated west to join in settling and deve ...
succeeded with the Laserdisc until the advent of the DVD. In 1979, Philips and
Sony , commonly known as Sony and stylized as SONY, is a Japanese multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body from multi ...

Sony
, in consortium, successfully developed the
audio compact disc
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 457 nm to record and red light at 632.8 nm 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 . The
CD-ROM A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc The compact disc (CD) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital ...

CD-ROM
format was developed by Sony and
Philips Koninklijke Philips N.V. (in Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () *Dutch language , spoken in Belgium (also referred as ''flemish'') Dutch may also refer t ...

Philips
, introduced in 1984, as an extension of
Compact Disc Digital Audio Compact Disc Digital Audio (CDDA or CD-DA), also known as Digital Audio Compact Disc or simply as Audio CD, is the standardization, standard format for audio compact discs. The standard is defined in the ''Red Book'', one of a series of Rainbow ...
and adapted to hold any form of digital data. The same year, Sony demonstrated a
LaserDisc
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 using Electron Trapping Optical Media (ETOM). 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 is a Japanese headquartered in , . Its diversified products and services include power, industrial and social infrastructure systems, elevators and escalators, electronic components, s, s (HDD), printers, batteries, lighting, as well as sol ...
,
Panasonic formerly is a major Japanese multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body from multiple countries * Multinational state, ...

Panasonic
) developed the second generation of the optical disc, the
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electr ...

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 that 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 In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio signal processing, sound, image processing, images, and scientific measurements. Signa ...
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 The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electr ...

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.


First-generation

From the start optical discs were used to store broadcast-quality analog video, and later digital media such as music or computer software. The
LaserDisc
LaserDisc
format stored analog video signals for the distribution of home video, but commercially lost to the VHS Videocassette#Cassette formats, 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. * Compact disc (CD) and derivatives ** Compact Disc Digital Audio, Audio CD ** Video CD (VCD) ** Super Video CD ** CD Video *
LaserDisc
LaserDisc
* GD-ROM * Phase-change Dual * Double Density Compact Disc (DDCD) * Magneto-optical disc * MiniDisc (MD) ** MD Data * Write Once Read Many (WORM)


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 apertureFormat War Update: Blu-ray Wins Over HD DVD
. Crutchfieldadvisor.com. Retrieved on 2011-10-09.
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 DataPlay format, can have capacity comparable to that of the larger, standard compact 12 cm disc. *
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electr ...

DVD
and derivatives ** DVD-Audio ** DualDisc ** DIVX, Digital Video Express (DIVX) ** DVD-RAM * Nintendo optical discs#GameCube Game Disc, Nintendo GameCube Game Disc (miniDVD derivative) * Nintendo optical discs#Wii Optical Disc, Wii Optical Disc (DVD derivative) * Super Audio CD (SACD) * Enhanced Versatile Disc * DataPlay * Hi-MD * Universal Media Disc (UMD) * Ultra Density Optical


Third-generation

Third-generation optical discs are used for distributing HDTV, high-definition video and videogames 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. *Blu-ray (up to 400 GB - experimental) *Nintendo optical discs#Wii U Optical Disc, Wii U Optical Disc (25 GB per layer) *HD DVD (discontinued disc format, up to 51 GB triple layer) *China Blue High-definition Disc, CBHD (a derivative of the HD DVD format) *HD VMD *Professional Disc Announced but not released: *Digital Multilayer Disk *Fluorescent Multilayer Disc *Forward Versatile Disc


Fourth-generation

The following formats go beyond the current third-generation discs and have the potential to hold more than one terabyte (1 Terabyte, TB) of data and at least some are meant for cold computer data storage, data storage in data centers: * Archival Disc * Holographic Versatile Disc Announced but not released: * LS-R * * Stacked Volumetric Optical Disc * 5D DVD * 3D optical data storage (not a single technology, examples are Hyper CD-ROM and Fluorescent Multilayer Disc)


Overview of optical types

;Notes


Recordable and writable optical discs

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 CD-R (Compact disc-recordable) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electronics is a field of electronics Electronics ...

CD-R
and DVD-R are "Write once read many" or write-once, while
CD-RW CD-RW (Compact Disc-Rewritable) is a digital media, digital optical disc data storage device, storage format introduced in 1997. A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written. CD-RWs, as opposed to CDs, require sp ...
and DVD-RW are rewritable, more like a magnetic recording
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device File:Reel-to-reel recorder tc-630.jpg, On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment an ...

hard disk drive
(HDD). Media technologies vary, M-DISC uses a different recording technique & media versus DVD-R and BD-R.


Surface error scanning

Optical media can Predictive failure analysis, predictively be scanned for errors and disc rot, media deterioation well before any data becomes unreadable. A higher rate of errors may indicates deteriorating and/or low quality media, physical damage, an unclean surface and/or media written using a defective optical drive. Those errors can be compensated by error correction to some extent. Error scanning software includes ''Nero DiscSpeed'', ''k-probe'', ''Opti Drive Control'' (formerly ''"CD speed 2000"'') and ''DVD info Pro'' for Windows, and QPxTool for cross-platform. Support of error scanning functionality varies per optical drive manufacturer and model.List of supported devices by dosc quality scanning software QPxTool
/ref>


Error types

There are different types of error measurements, including so-called ''"C1"'', ''"C2 error, C2"'' and ''"CU"'' errors Compact disc#Measurement, on CDs, and ''"PI/PO (parity inner/outer) errors"'' and the more critical DVD#Disc quality measurements, ''"PI/PO failures"'' on DVDs. Finer-grain error measurements on CDs supported by very few optical drives are called ''E11'', ''E21'', ''E31'', ''E21'', ''E22'', ''E32''. ''"CU"'' and ''"POF"'' represent uncorrectable errors on data CDs and DVDs respectively, thus data loss, and can be a result of too many consecutive smaller errors. Due to the weaker error correction used on Audio CDs (Compact Disc Digital Audio, Red Book standard) and Video CDs (White Book (CD standard), White Book standard), C2 errors already lead to data loss. However, even with C2 errors, the damage is unhearable to some extent. Blu-ray discs use so-called ''LDC'' (''Long Distance Code''s) and ''BIS'' (''Burst Indication Subcode''s) error parameters. According to the developer of the ''Opti Drive Control'' software, a disc can be considered healthy at an ''LDC'' error rate below 13 and ''BIS'' error rate below 15.


Optical disc manufacturing

Optical discs are made using replication. This process can be used with all disc types. Recordable discs have pre-recorded vital information, like manufacturer, disc type, maximum read and write speeds, etc. In replication, a cleanroom with yellow light is necessary to protect the light-sensitive photoresist and to prevent dust from corrupting the data on the disc. A glass master is used in replication. The master is placed in a machine that cleans it as much as possible using a rotating brush and deionized water, preparing it for the next step. In the next step, a surface analyzer inspects the cleanliness of the master before photoresist is applied on the master. The photoresist is then baked in an oven to solidify it. Then, in the exposure process, the master is placed in a turntable where a laser selectively exposes the resist to light. At the same time, a developer and deionized water are applied to the disc to remove the exposed resist. This process forms the pits and lands that represent the data on the disc. A thin coating of metal is then applied to the master, making a negative of the master with the pits and lands in it. The negative is then peeled off the master and coated in a thin layer of plastic. The plastic protects the coating while a punching press punches a hole into the center of the disc, and punches excess material. The negative is now a stamper - a part of the mold that will be used for replication. It is placed on one side of the mold with the data side containing the pits and lands facing out. This is done inside an injection molding machine. The machine then closes the mold and injects polycarbonate in the cavity formed by the walls of the mold, which forms or molds the disc with the data on it. The molten polycarbonate fills the pits or spaces between the lands on the negative, acquiring their shape when it solidifies. This step is somewhat similar to Production of phonograph records, record pressing. The polycarbonate disc cools quickly and is promply removed from the machine, before forming another disc. The disc is then metallized, covered with a thin reflective layer of aluminum. The aluminum fills the space once occupied by the negative. A layer of varnish is then applied to protect the aluminum coating and provide a surface suitable for printing. The varnish is applied near the center of the disc, and the disc is spun, evenly distributing the varnish on the surface of the disc. The varnish is hardened using UV light. The discs are then silkscreened or a label is otherwise applied. Recordable discs add a dye layer, and rewritable discs add a phase change alloy layer instead, which is protected by upper and lower dielectric (electrically insulating) layers. The layers may be sputtered. The additional layer is between the grooves and the reflective layer of the disc. Grooves are made in recordable discs in place of the traditional pits and lands found in replicated discs, and the two can be made in the same exposure process.http://www.blu-raydisc.com/Assets/Downloadablefile/White_Paper_BD-RE_5th_20180216.pdfhttp://www.blu-raydisc.com/Assets/Downloadablefile/White_Paper_General_5th_20180216.pdf In DVDs, the same processes as in CDs are carried out, but in a thinner disc. The thinner disc is then bonded to a second, equally thin but blank, disc using UV-curable Liquid optically clear adhesive, forming a DVD disc. This leaves the data in the middle of the disc, which is necessary for DVDs to achieve their storage capacity. In multi layer discs, semi reflective instead of reflective coatings are used for all layers except the last layer, which is the deepest one and uses a traditional reflective coating. Dual layer DVDs are made slightly differently. After metallization (with a thinner metal layer to allow some light to pass through), base and pit transfer resins are applied and pre-cured in the center of the disc. Then the disc is pressed again using a different stamper, and the resins are completely cured using UV light before being separated from the stamper. Then the disc receives another, thicker metallization layer, and is then bonded to the blank disc using LOCA glue. DVD-R DL and DVD+R DL discs receive a dye layer after curing, but before metallization. CD-R, DVD-R, and DVD+R discs receive the dye layer after pressing but before metallization. CD-RW, DVD-RW and DVD+RW receive a metal alloy layer sandwiched between 2 dielectric layers. HD-DVD is made in the same way as DVD. In recordable and rewritable media, most of the stamper is composed of grooves, not pits and lands. The grooves contain a wobble frequency that is used to locate the position of the reading or writing laser on the disc. DVDs use pre-pits instead, with a constant frequency wobble.


Blu-ray

''HTL'' (Blu-ray Disc recordable#HTL (high to low), high-to-low type) Blu-ray discs are made differently. First, a silicon wafer is used instead of a glass master. The wafer is processed in the same way a glass master would. The wafer is then electroplated to form a 300-micron thick nickel stamper, which is peeled off from the wafer. The stamper is mounted onto a mold inside a press or embosser. The polycarbonate discs are molded in a similar fashion to DVD and CD discs. If the discs being produced are BD-Rs or BD-REs, the mold is fitted with a stamper that stamps a groove pattern onto the discs, in lieu of the pits and lands found on BD-ROM discs. After cooling, a 35 nanometre-thick layer of silver alloy is applied to the disc using sputtering.https://www.singulus.de/fileadmin/user_upload/202003/BLULINE_II_2_2020.pdf Then the second layer is made by applying base and pit transfer resins to the disc, and are pre-cured in its center. After application and pre-curing, the disc is pressed or embossed using a stamper and the resins are immediately cured using intense UV light, before the disc is separated from the stamper. The stamper contains the data that will be transferred to the disc. This process is known as embossing and is the step that engraves the data onto the disc, replacing the pressing process used in the first layer, and it is also used for multi layer DVD discs. Then, a 30 nanometre-thick layer of silver alloy is then sputtered onto the disc and the process is repeated as many times as required. Each repetition creates a new data layer. (The resins are applied again, pre-cured, stamped (with data or grooves) and cured, silver alloy is sputtered and so on) BD-R and BD-RE discs receive (through sputtering) a metal (recording layer) alloy (that is sandwiched between two dielectric layers, also sputtered, in BD-RE), before receiving the 30 nanometre metallization (silver alloy, aluminum or gold) layer, which is sputtered. Alternatively, the silver alloy may be applied before the recording layer is applied. Silver alloys are usually used in Blu-rays, and aluminum is usually used on CDs and DVDs. Gold is used in some "Archival" CDs and DVDs, since it is more chemically inert and resistant to corrosion than aluminum, which corrodes into aluminum oxide, which can be seen in disc rot as transparent patches or dots in the disc, that prevent the disc from being read, since the laser light passes through the disc instead of being reflected back into the laser pickup assembly to be read. Normally aluminum doesn't corrode since it has a thin oxide layer that forms on contact with oxygen. In this case it can corrode due to its thinness. Then, the 98 micron-thick cover layer is applied using UV-curable liquid optically clear adhesive, and a 2 micron-thick hard coat (such as Durabis) is also applied and cured using UV light. In the last step, a 10 nanometre-thick silicon nitride barrier layer is applied to the label side of the disc to protect against humidity. Blu-rays have their data very close to the read surface of the disc, which is necessary for Blu-rays to achieve their capacity. Discs in large quantities can either be replicated or duplicated. In replication, the process explained above is used to make the discs, while in duplication, CD-R, DVD-R or BD-R discs are recorded and finalized to prevent further recording and allow for wider compatibility. (See Optical disc authoring). The equipment is also different: replication is carried out by fully automated purpose-built machinery whose cost is in the hundreds of thousands of US dollars in the used market, while duplication can be automated (using what's known as an autoloader) or be done by hand, and only requires a small tabletop duplicator.


Specifications


See also

* Disc Description Protocol * List of optical disc manufacturers * Universal Disk Format (UDF)


References


External links

* * * * * * * * * * {{DEFAULTSORT:Optical Disc Audiovisual introductions in 1884 Compact disc DVD Optical discs Optical disc authoring Optoelectronics Optical computer storage media et:Optiline andmekandja