Is a Disk Drive That Uses Laser Light to Read From or Write to Optical Discs

Type of computer deejay storage dive

A CD-RW/DVD-ROM computer drive

The CD/DVD drive lens on an Acer laptop

Lenses from a Blu-ray writer in a Sony Vaio E serial laptop

In computing, an optical disc drive (ODD) is a disc drive that uses light amplification by stimulated emission of radiation light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing information to or from optical discs. Some drives can only read from certain discs, simply recent drives tin both read and record, also called burners or writers (since they physically burn the organic dye on write-once CD-R, DVD-R and BD-R LTH discs). Compact discs, DVDs, and Blu-ray discs are common types of optical media which tin can exist read and recorded past such drives.

Drive types [edit]

Equally of 2021^[update], most of the optical disc drives on the market place are DVD-ROM drives and BD-ROM drives which read and record from those formats, forth with having astern compatibility with CD, CD-R and CD-ROM discs; compact disc drives are no longer manufactured outside of sound devices. Read-only DVD and Blu-ray drives are also manufactured, simply are less commonly establish in the consumer market and mainly express to media devices such as game consoles and disc media players. Over the last ten years, laptop computers no longer come with optical disc drives in social club to reduce costs and make devices lighter, requiring consumers to buy external optical drives.

Appliances and functionality [edit]

Optical disc drives are an integral part of standalone appliances such as CD players, DVD players, Blu-ray Disc players, DVD recorders, certain desktop video game consoles, such as Sony PlayStation 4, Microsoft Xbox I, Nintendo Wii U, Sony PlayStation 5 and Xbox Series X and also in older consoles, such equally the Sony PlayStation 3 and Xbox 360, and certain portable video game consoles, such equally Sony PlayStation Portable (using proprietary now discontinued UMDs). They are also very commonly used in computers to read software and media distributed on disc and to record discs for archival and data exchange purposes. Floppy disk drives, with chapters of 1.44 MB, have been made obsolete: optical media are cheap and have vastly college capacity to handle the big files used since the days of floppy discs, and the vast majority of computers and much consumer amusement hardware accept optical writers. USB flash drives, high-capacity, small-scale, and inexpensive, are suitable where read/write adequacy is required.

Disc recording is restricted to storing files playable on consumer appliances (films, music, etc.), relatively pocket-size volumes of data (e.grand. a standard DVD holds 4.vii gigabytes, however, higher-capacity formats such as multi-layer Blu-ray Discs exist) for local utilize, and data for distribution, only only on a pocket-sized scale; mass-producing large numbers of identical discs by pressing (replication) is cheaper and faster than individual recording (duplication).

Optical discs are used to support relatively pocket-size volumes of data, but backing upwardly of unabridged hard drives, which as of 2015^[update] typically contain many hundreds of gigabytes or even multiple terabytes, is less applied. Large backups are often instead made on external hard drives, every bit their price has dropped to a level making this viable; in professional environments magnetic tape drives are also used.

Some optical drives as well let predictively scanning the surface of discs for errors and detecting poor recording quality.^{[one] [2]}

With an option in the optical disc authoring software, optical disc writers are able to simulate the writing procedure on CD-R, CD-RW, DVD-R and DVD-RW, which allows for testing such as observing the writing speeds and patterns (e.g. constant angular velocity, constant linear velocity and P-CAV and Z-CLV variants) with different writing speed settings and testing the highest capacity of an individual disc that would be achievable using overburning, without writing any data to the disc.^[iii]

Few optical drives allow simulating a FAT32 flash drive from optical discs containing ISO9660/Joliet and UDF file systems or sound tracks (simulated as .wav files),^[4] for compatibility with most USB multimedia appliances.^[5]

Primal components [edit]

Form factors [edit]

Optical drives for computers come in 2 master form factors: half-tiptop (also known as desktop drive) and slim blazon (used in laptop computers and meaty desktop computers). They be as both internal and external variants.

Half-superlative optical drives are around four centimetres tall, while slim type optical drives are around 1 cm alpine.

Half-top optical drives operate upwardly of twice the speeds as slim type optical drives, because speeds on slim type optical drives are constrained to the physical limitations of the drive motor's rotation speed (around 5000rpm^[half-dozen]) rather than the performance of the optical pickup system.

Considering one-half-pinnacle demand much more electrical power and a voltage of 12 5 DC, while slim optical drives run on v volts, external half height optical drives require separate external power input, while external slim blazon are unremarkably able to operate entirely on power delivered through a computer's USB port. Half top drives are also faster than Slim drives due to this, since more ability is required to spin the disc at higher speeds.

Half-top optical drives agree discs in place from both sides while slim type optical drives fasten the disc from the bottom.

Half meridian drives fasten the disc using 2 spindles containing a magnet each, i under and ane above the disc tray. The spindles may be lined with flocking or a texturized silicone material to exert friction on the disc, to keep it from slipping. The upper spindle is left slightly loose and is attracted to the lower spindle because of the magnets they have. When the tray is opened, a mechanism driven by the movement of the tray pulls the lower spindle away from the upper spindle and vice versa when the tray is closed. When the tray is closed, the lower spindle touches the inner circumference of the disc, and slightly raises the disc from the tray to the upper spindle, which is attracted to the magnet on the lower disc, clamping the disc in identify. Only the lower spindle is motorized. Trays in one-half height drives oft fully open and shut using a motorized mechanism that can be pushed to close, controlled by the figurer, or controlled using a push button on the drive. Trays on half top and slim drives tin besides exist locked past whatever programme is using it, however it tin withal exist ejected by inserting the end of a newspaper clip into an emergency eject pigsty on the front of the drive. Early on CD players such as the Sony CDP-101 used a dissever motorized mechanism to clench the disc to the motorized spindle.

Slim drives utilize a special spindle with bound loaded specially shaped studs that radiate outwards, pressing confronting the inner border of the disc. The user has to put uniform pressure onto the inner circumference of the disc to clamp information technology to the spindle and pull from the outer circumference while placing the pollex on the spindle to remove the disc, flexing it slightly in the process and returning to its normal shape subsequently removal. The outer rim of the spindle may have a texturized silicone surface to exert friction keeping the disc from slipping. In slim drives about if non all components are on the disc tray, which pops out using a spring mechanism that can exist controlled by the computer. These trays cannot close on their ain; they take to be pushed until the tray reaches a stop. ^[seven]

Laser and optics [edit]

Optical pickup system [edit]

The most important part of an optical disc drive is an optical path, which is inside a pickup caput (PUH). The PUH is also known as a laser pickup, optical pickup, pickup, pickup assembly, laser assembly, laser optical assembly, optical pickup head/unit or optical assembly.^[8] It commonly consists of a semiconductor laser diode, a lens for focusing the light amplification by stimulated emission of radiation axle, and photodiodes for detecting the light reflected from the disc's surface.^[ix]

Initially, CD-blazon lasers with a wavelength of 780 nm (within the infrared) were used. For DVDs, the wavelength was reduced to 650 nm (red colour), and for Blu-ray Disc this was reduced even further to 405 nm (violet color).

Two main servomechanisms are used, the first to maintain the proper distance between lens and disc, to ensure the laser axle is focused as a small laser spot on the disc. The second servo moves the pickup caput along the disc's radius, keeping the beam on the track, a continuous spiral data path. Optical disc media are 'read' beginning at the inner radius to the outer edge.

Nearly the laser lens, optical drives are usually equipped with one to iii tiny potentiometers (usually separate ones for CDs, DVDs, and ordinarily a third i for Blu-ray Discs if supported by the drive^[ten]) that can be turned using a fine screwdriver. The potentiometer is in a series circuit with the laser lens and tin can be used to manually increase and decrease the laser power for repair purposes.^{[11] [12] [13] [14] [fifteen] [16]}

The light amplification by stimulated emission of radiation diode used in DVD writers tin can have powers of up to 100 milliwatts, such high powers are used during writing.^[17] Some CD players have automated gain control (AGC) to vary the power of the laser to ensure reliable playback of CD-RW discs.^{[18] [xix]}

Readability (the power to read physically damaged or soiled discs) may vary among optical drives due to differences in optical pickup systems, firmwares, and impairment patterns.^[20]

Read-simply media [edit]

The optical sensor out of a CD/DVD drive. The 2 larger rectangles are the photodiodes for pits, the inner one for state. This one also includes amplification and minor processing.

On factory-pressed read merely media (ROM), during the manufacturing process the tracks are formed past pressing a thermoplastic resin into a nickel stamper that was made by plating a glass 'master' with raised 'bumps' on a flat surface, thus creating pits and lands in the plastic disk. Because the depth of the pits is approximately one-quarter to one-sixth of the laser's wavelength, the reflected beam's phase is shifted in relation to the incoming beam, causing common destructive interference and reducing the reflected beam'southward intensity. This is detected by photodiodes that create respective electrical signals.

Recordable media [edit]

This section is missing information most light amplification by stimulated emission of radiation wattages for reading and writing of individual media types. Delight expand the section to include this information. Further details may exist on the talk page. (Baronial 2020)

An optical disk recorder encodes (also known as burning, since the dye layer is permanently burned) information onto a recordable CD-R, DVD-R, DVD+R, or BD-R disc (called a blank) by selectively heating (called-for) parts of an organic dye layer with a light amplification by stimulated emission of radiation.^{[ citation needed ]}

This changes the reflectivity of the dye, thereby creating marks that tin be read like the pits and lands on pressed discs. For recordable discs, the process is permanent and the media can be written to merely in one case. While the reading light amplification by stimulated emission of radiation is usually non stronger than 5 mW, the writing laser is considerably more powerful.^[21] DVD lasers operate at voltages of around 2.five volts.^[22]

The higher the writing speed, the less fourth dimension a laser has to heat a point on the media, thus its power has to increment proportionally. DVD burners' lasers oftentimes summit at nigh 200 mW, either in continuous moving ridge and pulses, although some have been driven upwardly to 400 mW before the diode fails.

Rewriteable media [edit]

For rewritable CD-RW, DVD-RW, DVD+RW, DVD-RAM, or BD-RE media, the laser is used to melt a crystalline metal blend in the recording layer of the disc. Depending on the corporeality of power applied, the substance may be allowed to melt back (modify the stage back) into crystalline form or left in an baggy form, enabling marks of varying reflectivity to exist created.

Double-sided media [edit]

Double-sided media may be used, but they are non easily accessed with a standard drive, equally they must be physically turned over to admission the information on the other side.

Dual layer media [edit]

Double layer or dual layer (DL) media have two independent data layers separated by a semi-reflective layer. Both layers are accessible from the same side, but require the eyes to change the light amplification by stimulated emission of radiation'south focus. Traditional unmarried layer (SL) writable media are produced with a screw groove molded in the protective polycarbonate layer (not in the data recording layer), to lead and synchronize the speed of recording caput. Double-layered writable media have: a first polycarbonate layer with a (shallow) groove, a first data layer, a semi-cogitating layer, a second (spacer) polycarbonate layer with some other (deep) groove, and a second data layer. The first groove spiral commonly starts on the inner edge and extends outwards, while the 2d groove start on the outer edge and extends inwards.^{[23] [24]}

Photothermal printing [edit]

Some drives support Hewlett-Packard's LightScribe, or the alternative LabelFlash photothermal printing technology for labeling specially coated discs.

Multi axle drives [edit]

Zen Technology and Sony have adult drives that apply several light amplification by stimulated emission of radiation beams simultaneously to read discs and write to them at higher speeds than what would be possible with a single light amplification by stimulated emission of radiation beam. The limitation with a unmarried laser beam comes from wobbling of the disc that may occur at high rotational speeds; at 25,000 RPMs CDs go unreadable^[xviii] while Blu-rays cannot be written to beyond 5,000 RPMs.^[25] With a single light amplification by stimulated emission of radiation beam, the only way to increase read and write speeds without reducing the pit length of the disc (which would allow for more than pits and thus bits of information per revolution, only may require smaller wavelength low-cal) is by increasing the rotational speed of the disc which reads more pits in less fourth dimension, increasing data rate; hence why faster drives spin the disc at higher speeds. In improver, CDs at 27,500 RPMs (such as to read the inside of a CD at 52x) may explode causing extensive damage to the disc'southward surround, and poor quality or damaged discs may explode at lower speeds.^{[26] [xviii]}

In Zen's system (developed in conjunction with Sanyo and licensed by Kenwood), a diffraction grating is used to split a laser beam into 7 beams, which are and then focused into the disc; a central beam is used for focusing and tracking the groove of the disc leaving 6 remaining beams (3 on either side) that are spaced evenly to read 6 split portions of the groove of the disc in parallel, effectively increasing read speeds at lower RPMs, reducing drive noise and stress on the disc. The beams then reverberate back from the disc, and are collimated and projected into a special photodiode array to be read. The commencement drives using the technology could read at 40x, later increasing to 52x and finally 72x. Information technology uses a single optical pickup.^{[27] [28] [29] [30] [31] [32]}

In Sony's organisation (used on their proprietary Optical Disc Archive system which is based on Archival Disc, itself based on Blu-ray) the bulldoze has 4 optical pickups, two on each side of the disc, with each pickup having two lenses for a total of 8 lenses and laser beams. This allows for both sides of the disc to be read and written to at the same time, and for the contents of the disc to be verified during writing.^[33]

Rotational machinery [edit]

• 

  Comparing of several forms of deejay storage showing tracks (not-to-scale); greenish denotes start and red denotes stop.
  * Some CD-R(Westward) and DVD-R(W)/DVD+R(W) recorders operate in ZCLV, CAA or CAV modes.

The rotational mechanism in an optical drive differs considerably from that of a hard disk bulldoze's, in that the latter keeps a abiding angular velocity (CAV), in other words a abiding number of revolutions per infinitesimal (RPM). With CAV, a higher throughput is mostly achievable at the outer disc compared to the inner.

On the other paw, optical drives were adult with an supposition of achieving a abiding throughput, in CD drives initially equal to 150 KiB/due south. It was a feature important for streaming audio data that always tend to require a constant bit rate. Only to ensure no disc chapters was wasted, a head had to transfer data at a maximum linear rate at all times too, without slowing on the outer rim of the disc. This led to optical drives—until recently—operating with a abiding linear velocity (CLV). The spiral groove of the disc passed under its head at a constant speed. The implication of CLV, equally opposed to CAV, is that disc angular velocity is no longer constant, and the spindle motor needed to be designed to vary its speed from betwixt 200 RPM on the outer rim and 500 RPM on the inner, keeping the data rate constant.

After CD drives kept the CLV paradigm, but evolved to achieve higher rotational speeds, popularly described in multiples of a base speed. Every bit a effect, a 4× CLV drive, for case, would rotate at 800-2000 RPM, while transferring information steadily at 600 KiB/due south, which is equal to 4 × 150 KiB/s.

For DVDs, base or one× speed is 1.385 MB/southward, equal to ane.32 MiB/s, approximately nine times faster than the CD base speed. For Blu-ray drives, base speed is 6.74 MB/due south, equal to half dozen.43 MiB/s.

The Z-CLV recording pattern is hands visible after burning a DVD-R.

Because keeping a constant transfer rate for the whole disc is not so important in most contemporary CD uses, a pure CLV approach had to be abased to keep the rotational speed of the disc safely depression while maximizing information charge per unit. Some drives work in a fractional CLV (PCLV) scheme, by switching from CLV to CAV merely when a rotational limit is reached. But switching to CAV requires considerable changes in hardware design, and then instead most drives use the zoned constant linear velocity (Z-CLV) scheme. This divides the disc into several zones, each having its own constant linear velocity. A Z-CLV recorder rated at "52×", for case, would write at 20× on the innermost zone and so progressively increase the speed in several discrete steps up to 52× at the outer rim. Without higher rotational speeds, increased read performance may be attainable past simultaneously reading more than than ane betoken of a information groove, too known as multi-beam,^[34] just drives with such mechanisms are more expensive, less compatible, and very uncommon.

Limit [edit]

Both DVDs and CDs have been known to explode^[35] when damaged or spun at excessive speeds. This imposes a constraint on the maximum prophylactic speeds (56× CAV for CDs or around 18×CAV in the case of DVDs) at which drives can operate.

The reading speeds of most one-half-height optical disc drives released since circa 2007 are limited to ×48 for CDs, ×16 for DVDs and ×12 (angular velocities) for Blu-ray Discs.^[a] Writing speeds on selected write-one time media are higher.^{[seven] [36] [37]}

Some optical drives additionally throttle the reading speed based on the contents of optical discs, such as max. 40× CAV (constant athwart velocity) for the Digital Audio Extraction ("DAE") of Audio CD tracks,^[36] 16× CAV for Video CD contents^[37] and even lower limitations on earlier models such as four× CLV (constant linear velocity) for Video CDs.^{[38] [39]}

Loading mechanisms [edit]

Tray and slot loading [edit]

Electric current optical drives use either a tray-loading mechanism, where the disc is loaded onto a motorized (equally utilized by one-half-elevation, "desktop" drives) tray, a manually operated tray (as utilized in laptop computers, besides called slim blazon), or a slot-loading mechanism, where the disc is slid into a slot and drawn in by motorized rollers. Slot-loading optical drives be in both half-summit (desktop) and slim type (laptop) course factors.^[vii]

With both types of mechanisms, if a CD or DVD is left in the drive after the computer is turned off, the disc cannot be ejected using the normal eject machinery of the bulldoze. Notwithstanding, tray-loading drives account for this situation by providing a small hole where one can insert a paperclip to manually open the drive tray to retrieve the disc.^[40]

Slot-loading optical disc drives are prominently used in game consoles and vehicle audio units. Although allowing more convenient insertion, those have the disadvantages that they cannot commonly take the smaller 80 mm diameter discs (unless fourscore mm optical disc adapter is used) or any non-standard sizes, usually accept no emergency eject hole or squirt button, and therefore have to exist disassembled if the optical disc cannot be ejected normally. However, some slot-loading optical drives have been engineered to support miniature discs. The Nintendo Wii, because of backward compatibility with Nintendo GameCube games,^{[41] [42]} and PlayStation 3^[43] video game consoles are able to load both standard size DVDs and 80 mm discs in the same slot-loading bulldoze. Its successor's slot drive however, the Wii U, lacks miniature disc compatibility.^[44]

In that location were also some early CD-ROM drives for desktop PCs in which its tray-loading mechanism volition eject slightly and user has to pull out the tray manually to load a CD^{[ citation needed ]}, similar to the tray ejecting method used in internal optical disc drives of modern laptops and modern external slim portable optical disc drives. Like the summit-loading mechanism, they have spring-loaded ball bearings on the spindle.

Summit-load [edit]

A small number of drive models, mostly meaty portable units, accept a tiptop-loading mechanism where the drive chapeau is manually opened upwards and the disc is placed direct onto the spindle^{[45] [46]} (for example, all PlayStation Ane consoles, PlayStation 2 Slim, PlayStation 3 Super Slim, Nintendo GameCube consoles, about portable CD players, and some standalone CD recorders characteristic top-loading drives). These sometimes have the reward of using spring-loaded brawl bearings to hold the disc in place, minimizing damage to the disc if the drive is moved while it is spun up.

Unlike tray and slot loading mechanisms past default, superlative-load optical drives can be opened without existence continued to power.

Cartridge load [edit]

Some early CD-ROM drives used a mechanism where CDs had to be inserted into special cartridges or caddies, somewhat similar in advent to a iii.5 inch micro floppy diskette. This was intended to protect the disc from adventitious harm by enclosing information technology in a tougher plastic casing, merely did not gain broad credence due to the additional cost and compatibility concerns—such drives would besides inconveniently require "bare" discs to be manually inserted into an openable caddy before use. Ultra Density Optical (UDO), Magneto-optical drives, Universal Media Disc (UMD), DataPlay, Professional person Disc, MiniDisc, Optical Disc Archive too every bit early DVD-RAM and Blu-ray discs employ optical disc cartridges.

Estimator interfaces [edit]

All optical disc-drives use the SCSI-protocol on a command double-decker level, and initial systems used either a fully featured SCSI autobus or as these were some what toll-prohibitive to sell to consumer applications, a proprietary price-reduced version of the bus. This is because conventional ATA-standards at the time did not back up, or take any provisions for any sort of removable media or hot-plugging of disk drives. Near mod internal drives for personal computers, servers, and workstations are designed to fit in a standard 5+ one⁄iv -inch (besides written as 5.25 inch) drive bay and connect to their host via an ATA or SATA coach interface, but communicate using the SCSI protocol commands on software level as per the ATA Package Interface standard adult for making Parallel ATA/IDE interfaces compatible with removable media. Some devices may support vendor-specific commands such equally recording density ("GigaRec"), laser power setting ("VariRec"), ability to manually hard-limit rotation speed in a way that overrides the universal speed setting (separately for reading and writing), and adjusting the lens and tray movement speeds where a lower setting reduces dissonance, every bit implmenented on some Plextor drives, as well every bit the power to strength overspeed burning, pregnant across speed recommended for the media type, for testing purposes, as implemented on some Light-ON drives.^{[47] [48] [49] [50]} Additionally, there may be digital and analog outputs for audio. The outputs may be connected via a header cable to the sound card or the motherboard or to headphones or an external speaker with a 3.5mm AUX plug cable that many early on optical drives are equipped with.^{[51] [52]} At in one case, figurer software resembling CD players controlled playback of the CD.^{[53] [54]} Today the information is extracted from the disc every bit digital information, to be played back or converted to other file formats.

Some early optical drives have dedicated buttons for CD playback controls on their front end console, assuasive them to act as a standalone compact disc player.^[51]

External drives were popular in the get-go, because the drives often required complex electronics to establish, rivaling in complication the Host estimator organisation itself. External drives using SCSI, Parallel port, USB and FireWire interfaces exist, almost modern drives being USB. Some portable versions for laptops power themselves from batteries or directly from their interface bus.

Drives with a SCSI interface were originally the only organisation interface bachelor, but they never became pop in the cost sensitive low-end consumer market which constituted bulk of the demand. They were less mutual and tended to be more expensive, because of the toll of their interface chipsets, more than circuitous SCSI connectors, and small volume of sales in comparing to proprietary cost-reduced applications, but most importantly considering most consumer market reckoner systems did not have any sort of SCSI interface in them the market place for them was minor. Even so, support for multitude of diverse cost-reduced proprietary optical bulldoze coach standards were usually embedded with audio cards which were often arranged with the optical drives themselves in the early years. Some sound card and optical drive bundles even featured a full SCSI bus. Modern IDE/ATAPI compliant Parallel ATA and Serial ATA drive command chipsets and their interface engineering science is more than complex to manufacture than a traditional 8bit 50Mhz SCSI drive interface, considering they feature properties of both the SCSI and ATA motorcoach, simply are cheaper to make overall due to economies of scale.

When the optical disc drive was first developed, it was not like shooting fish in a barrel to add to computer systems. Some computers such as the IBM PS/two were standardizing on the 3+ 1⁄2 -inch floppy and 3+ 1⁄two -inch hard disk and did non include a place for a large internal device. Also IBM PCs and clones at first just included a single (parallel) ATA drive interface, which past the time the CD-ROM was introduced, was already being used to support two difficult drives and were completely incapable of supporting removable media, a bulldoze falling off or beingness removed from the motorbus while the organization was live, would cause an unrecoverable error and crash the entire organization. Early consumer grade laptops merely had no born loftier-speed interface for supporting an external storage device. High-end workstation systems and laptops featured a SCSI interface which had a standard for externally connected devices.

HP C4381A CD-Writer Plus 7200 Series, showing parallel ports to connect between a printer and the figurer

This was solved through several techniques:

• Early audio cards could include a CD-ROM drive interface. Initially, such interfaces were proprietary to each CD-ROM manufacturer. A audio card could oftentimes have two or three different interfaces which are able to communicate with the CD-ROM drive.
• A method for using the parallel port to use with external drives was developed at some point. This interface was traditionally used to connect a printer, simply despite popular myth it is non its but employ and diverse different external auxiliary devices exist for the IEEE-1278 bus, including but non express to tape backup drives etc. This was wearisome only an pick for depression-to-midrange laptops with out integrated or PCMCIA extension bus continued SCSI.
• A PCMCIA optical drive interface was also adult for laptops.
• A SCSI card could be installed in desktop PCs to cater for an external SCSI drive enclosure or to run internally mounted SCSI Hard disk drive drives and optical drives, though SCSI was typically somewhat more than expensive than other options, with some OEMs charging a premium for it.

Due to lack of asynchrony in existing implementations, an optical drive encountering damaged sectors may crusade figurer programs trying to access the drives, such every bit Windows Explorer, to lock upwardly.

Internal mechanism of a drive [edit]

Internal mechanism of a DVD-ROM Bulldoze. See text for details.

The optical drives in the photos are shown right side up; the disc would sit on top of them. The light amplification by stimulated emission of radiation and optical system scans the underside of the disc.

With reference to the peak photograph, just to the correct of image center is the disc motor, a metal cylinder, with a greyness centering hub and blackness safe drive ring on top. In that location is a disc-shaped round clamp, loosely held inside the comprehend and free to rotate; it's non in the photo. Later the disc tray stops moving inwards, every bit the motor and its attached parts ascension, a magnet near the top of the rotating assembly contacts and strongly attracts the clamp to concord and center the disc. This motor is an "outrunner"-fashion brushless DC motor which has an external rotor – every visible part of information technology spins.

Two parallel guide rods that run betwixt upper left and lower correct in the photo behave the "sled", the moving optical read-write caput. As shown, this "sled" is close to, or at the position where it reads or writes at the edge of the disc. To move the "sled" during continuous read or write operations, a stepper motor rotates a leadscrew to motility the "sled" throughout its total travel range. The motor, itself, is the short gray cylinder simply to the left of the most-distant shock mount; its shaft is parallel to the support rods. The leadscrew is the rod with evenly-spaced darker details; these are the helical grooves that engage a pin on the "sled".

In contrast, the mechanism shown in the second photo, which comes from a cheaply made DVD player, uses less accurate and less efficient brushed DC motors to both move the sled and spin the disc. Some older drives use a DC motor to move the sled, but also take a magnetic rotary encoder to go on track of the position. Most drives in computers use stepper motors.

The grayness metal chassis is shock-mounted at its iv corners to reduce sensitivity to external shocks, and to reduce drive noise from residual imbalance when running fast. The soft shock mountain grommets are but beneath the brass-colored screws at the four corners (the left one is obscured).

In the third photo, the components under the cover of the lens mechanism are visible. The two permanent magnets on either side of the lens holder equally well as the coils that move the lens can be seen. This allows the lens to be moved up, downward, frontwards, and backwards to stabilize the focus of the beam.

In the quaternary photograph, the inside of the eyes packet tin be seen. Annotation that since this is a CD-ROM drive, in that location is only one laser, which is the blackness component mounted to the lesser left of the associates. Just above the light amplification by stimulated emission of radiation are the offset focusing lens and prism that straight the axle at the disc. The alpine, sparse object in the center is a half-silvered mirror that splits the laser beam in multiple directions. To the bottom right of the mirror is the primary photodiode that senses the beam reflected off the disc. Above the main photodiode is a 2nd photodiode that is used to sense and regulate the power of the laser.

The irregular orange textile is flexible etched copper foil supported by sparse sail plastic; these are "flexible circuits" that connect everything to the electronics (which is not shown).

History [edit]

The first light amplification by stimulated emission of radiation disc, demonstrated in 1972, was the Laservision 12-inch video disc. The video point was stored as an analog format similar a video cassette. The first digitally recorded optical disc was a 5-inch audio compact disc (CD) in a read-only format created past Sony and Philips in 1975.^[55]

The outset erasable optical disc drives were announced in 1983, by Matsushita (Panasonic),^[56] Sony, and Kokusai Denshin Denwa (KDDI).^[57] Sony somewhen released the first commercial erasable and rewritable five+ one⁄4 -inch optical disc drive in 1987,^[55] with dual-sided discs capable of holding 325 MB per side.^[56]

The CD-ROM format was developed by Sony and Denon, introduced in 1984, as an extension of Compact Disc Digital Audio and adjusted to hold any form of digital information. The CD-ROM format has a storage capacity of 650 MB. Also in 1984, Sony introduced a LaserDisc data storage format, with a larger data capacity of iii.28 GB.^[58]

In September 1992, Sony announced the MiniDisc format, which was supposed to combine the audio clarity of CD's and the convenience of a cassette size.^[59] The standard chapters holds eighty minutes of sound. In January 2004, Sony revealed an upgraded How-do-you-do-MD format, which increased the capacity to 1 GB (48 hours of audio).

The DVD format, adult by Panasonic, Sony, and Toshiba, was released in 1995, and was capable of holding 4.7 GB per layer; with the showtime DVD players aircraft on November 1, 1996, by Panasonic and Toshiba in Japan and the first DVD-ROM uniform computers being shipped on November vi of that twelvemonth by Fujitsu.^[60] Sales of DVD-ROM drives for computers in the U.South. began on March 24, 1997, when Creative Labs released their PC-DVD kit to the market place.^[61]

In 1999, Kenwood released a multi-beam optical drive that achieved called-for speeds as loftier as 72×, which would require dangerous spinning speeds to attain with single-axle called-for.^{[27] [62]} However, it suffered from reliability issues.^[29]

The offset Blu-ray prototype was unveiled by Sony in Oct 2000,^[63] and the first commercial recording device was released to market on April 10, 2003.^[64] In Jan 2005, TDK appear that they had developed an ultra-hard yet very thin polymer coating ("Durabis") for Blu-ray Discs; this was a meaning technical advance because amend protection was desired for the consumer market to protect bare discs confronting scratching and harm compared to DVD. Technically Blu-ray Disc also required a thinner layer for the narrower axle and shorter wavelength 'bluish' laser.^[65] The first BD-ROM players (Samsung BD-P1000) were shipped in mid-June 2006.^[66] The first Blu-ray Disc titles were released past Sony and MGM on June 20, 2006.^[67] The get-go mass-market Blu-ray Disc rewritable drive for the PC was the BWU-100A, released by Sony on July 18, 2006.^[68]

Starting in the mid 2010s, estimator manufacturers began to stop including congenital-in optical disc drives on their products, with the advent of cheap, rugged (scratches tin not cause corrupted data, inaccessible files or skipping audio/video), fast and high chapters USB drives and video on demand over the internet. Excluding an optical bulldoze allows for circuit boards in laptops to exist larger and less dense, requiring less layers, reducing production costs while besides reducing weight and thickness, or for batteries to be larger. Figurer case manufacturers as well began to cease including 5+ ane⁄4 -inch bays for installing optical disc drives. However, new optical disc drives are still (equally of 2020) available for purchase. Notable optical disc drive OEMs include Hitachi, LG Electronics (merged into Hitachi-LG Data Storage), Toshiba, Samsung Electronics (merged into Toshiba Samsung Storage Engineering), Sony, NEC (merged into Optiarc), Lite-On, Philips (merged into Philips & Lite-On Digital Solutions), Pioneer Corporation, Plextor, Panasonic, Yamaha Corporation and Kenwood.^[69]

Compatibility [edit]

Nearly optical drives are astern uniform with their ancestors upwardly to CD, although this is non required past standards.

Compared to a CD's ane.ii mm layer of polycarbonate, a DVD's laser axle only has to penetrate 0.6 mm in club to reach the recording surface. This allows a DVD drive to focus the beam on a smaller spot size and to read smaller pits. DVD lens supports a different focus for CD or DVD media with aforementioned light amplification by stimulated emission of radiation. With the newer Blu-ray Disc drives, the laser simply has to penetrate 0.1 mm of material. Thus the optical associates would normally have to accept an fifty-fifty greater focus range. In do, the Blu-ray optical arrangement is carve up from the DVD/CD organization.

Optical disc bulldoze	Optical disc or optical media
	Pressed CD	CD-R	CD-RW	Pressed DVD	DVD-R	DVD+R	DVD-RW	DVD+RW	DVD+R DL	Pressed CAT BD	BD-R	BD-RE	BD-R DL	BD-RE DL	BD-R XL	BD-RE Forty
Sound CD thespian	Read	Read 1	Read two12	None	None	None	None	None	None	None	None	None	None	None	None	None
CD-ROM drive	Read	Read 1	Read 2	None	None	None	None	None	None	None	None	None	None	None	None	None
CD-R recorder	Read	Write	Read	None	None	None	None	None	None	None	None	None	None	None	None	None
CD-RW recorder	Read	Write	Write	None	None	None	None	None	None	None	None	None	None	None	None	None
DVD-ROM drive	Read	Read 3	Read iii	Read	Read 4	Read four	Read 4	Read iv	Read 5	None	None	None	None	None	None	None
DVD-R recorder	Read	Write	Write	Read	Write	Read 6	Read	Read 6	Read v	None	None	None	None	None	None	None
DVD-RW recorder	Read	Write	Write	Read	Write	Read seven	Write 8	Read 6	Read 5	None	None	None	None	None	None	None
DVD+RW recorder	Read	Write	Write	Read	Read 6	Read 9	Read half dozen	Write	Read five	None	None	None	None	None	None	None
DVD+R recorder	Read	Write	Write	Read	Read 6	Write	Read vi	Write	Read five	None	None	None	None	None	None	None
DVD±RW recorder	Read	Write	Write	Read	Write	Write	Write	Write	Read 5	None	None	None	None	None	None	None
DVD±RW/DVD+R DL recorder13	Read	Write	Write	Read	Write 10	Write	Write x	Write	Write	None	None	None	None	None	None	None
BD-ROM	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	None	None
BD-R recorder	Read 11	Write 11	Write 11	Read	Write	Write	Write	Write	Write	Read	Write	Read	Read	Read	None	None
BD-RE recorder	Read 11	Write eleven	Write xi	Read	Write	Write	Write	Write	Write	Read	Write	Write	Read	Read	None	None
BD-R DL recorder	Read 11	Write xi	Write 11	Read	Write	Write	Write	Write	Write	Read	Write	Write	Write	Read	None	None
BD-RE DL recorder	Read 11	Write 11	Write xi	Read	Write	Write	Write	Write	Write	Read	Write	Write	Write	Write	None	None
BD-ROM XL	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read	Read
BD-R Xl recorder	Read 11	Write xi	Write 11	Read	Write	Write	Write	Write	Write	Read	Write	Write	Write	Write	Write	Read
BD-RE XL recorder	Read 11	Write xi	Write 11	Read	Write	Write	Write	Write	Write	Read	Write	Write	Write	Write	Write	Write

• ^ane Some types of CD-R media with less-reflective dyes may crusade problems.
• ^two May not work in not MultiRead-compliant drives.
• ^three May not work in some early-model DVD-ROM drives. CD-R would not work in any drive that did not take a 780 nm laser. CD-RW compatibility varied.^[lxx]
• ^4 DVD+RW discs did non work in early video players that played DVD-RW discs. This was non due to any incompatibility with the format but was a deliberate feature built into the firmware past one^{[ which? ]} drive manufacturer.
• ^five Read compatibility with existing DVD drives may vary profoundly with the brand of DVD+R DL media used. Also drives that predated the media did not have the book code for DVD+R DL media in their firmware (this was non an issue for DVD-R DL though some drives could only read the first layer).
• ^6 Early DVD+RW and DVD+R recorders could not write to DVD-R(Due west) media (and vice versa).
• ^7 Will work in all drives that read DVD-R every bit compatibility ID byte is the same.
• ^8 Recorder firmware may blacklist or otherwise reject to record to some brands of DVD-RW media.
• ^nine DVD+RW format was released earlier DVD+R. All DVD+RW but drives could exist upgraded to write DVD+R discs by a firmware upgrade.
• ^10 As of April 2005, all DVD+R DL recorders on the market place are Super Multi-capable.
• ^11 As of October 2006, recently released BD drives are able to read and write CD media.
• ^12 Older CD actor models might struggle with the depression reflectivity of CD-RW media.
• ^13 Also known every bit "DVD Multi Recorder"

Recording operation [edit]

During the times of CD author drives, they are often marked with three unlike speed ratings. In these cases, the first speed is for write-once (R) operations, the second speed for re-write (RW) operations, and the last speed for read-only (ROM) operations. For instance, a 40×/16×/48× CD author drive is capable of writing to CD-R media at speed of 40× (six,000 kbit/s), writing to CD-RW media at speed of 16× (2,400 kbit/s), and reading from a CD-ROM media at speed of 48× (7,200 kbit/due south).

During the times of combo (CD-RW/DVD-ROM) drives, an additional speed rating (e.g. the 16× in 52×/32×/52×/16×) is designated for DVD-ROM media reading operations.

For DVD writer drives, Blu-ray Disc combo drives, and Blu-ray Disc author drives, the writing and reading speed of their respective optical media are specified in its retail box, user'southward manual, or bundled brochures or pamphlets.

In the tardily 1990s, buffer underruns became a very mutual problem as high-speed CD recorders began to appear in home and role computers, which—for a diverseness of reasons—often could not muster the I/O operation to continue the data stream to the recorder steadily fed. The recorder, should it run brusk, would exist forced to halt the recording process, leaving a truncated rail that usually renders the disc useless.

In response, manufacturers of CD recorders began shipping drives with "buffer underrun protection" (under various merchandise names, such as Sanyo's "Burn-Proof", Ricoh's "JustLink" and Yamaha'southward "Lossless Link"). These can suspend and resume the recording process in such a manner that the gap the stoppage produces can be dealt with by the error-correcting logic built into CD players and CD-ROM drives. The first of these drives^{[ which? ]} were rated at 12× and sixteen×.

The first optical drive to support recording DVDs at sixteen× speed was the Pioneer DVR-108, released in the second one-half of 2004. At that time however, no recordable DVD media supported that high recording speed even so.^{[71] [72] [73]}

While drives are called-for DVD+R, DVD+RW and all Blu-ray formats, they practice not crave any such fault correcting recovery as the recorder is able to place the new data exactly on the cease of the suspended write effectively producing a continuous track (this is what the DVD+ technology achieved). Although afterward interfaces were able to stream data at the required speed, many drives now write in a 'zoned constant linear velocity' ("Z-CLV"). This ways that the bulldoze has to temporarily suspend the write operation while it changes speed and then recommence it once the new speed is attained. This is handled in the same fashion as a buffer underrun.

The internal buffer of optical disc writer drives is: 8 MiB or iv MiB when recording BD-R, BD-R DL, BD-RE, or BD-RE DL media; 2 MiB when recording DVD-R, DVD-RW, DVD-R DL, DVD+R, DVD+RW, DVD+RW DL, DVD-RAM, CD-R, or CD-RW media.

Recording schemes [edit]

CD recording on personal computers was originally a batch-oriented job in that it required specialised authoring software to create an "image" of the information to tape and to record information technology to disc in the one session. This was acceptable for archival purposes, but limited the full general convenience of CD-R and CD-RW discs equally a removable storage medium.

Packet writing is a scheme in which the recorder writes incrementally to disc in brusque bursts, or packets. Sequential packet writing fills the disc with packets from bottom up. To brand it readable in CD-ROM and DVD-ROM drives, the disc can be closed at whatsoever fourth dimension by writing a last tabular array-of-contents to the start of the disc; thereafter, the disc cannot exist parcel-written any farther. Packet writing, together with support from the operating system and a file arrangement like UDF, tin be used to mimic random write-access every bit in media similar wink retentiveness and magnetic disks.

Stock-still-length bundle writing (on CD-RW and DVD-RW media) divides up the disc into padded, stock-still-size packets. The padding reduces the capacity of the disc, but allows the recorder to start and stop recording on an individual packet without affecting its neighbours. These resemble the block-writable admission offered by magnetic media closely enough that many conventional file systems will piece of work as-is. Such discs, however, are non readable in near CD-ROM and DVD-ROM drives or on most operating systems without additional third-political party drivers. The partition into packets is not every bit reliable as it may seem equally CD-R(W) and DVD-R(W) drives can but locate information to within a data cake. Although generous gaps (the padding referred to higher up) are left between blocks, the drive nonetheless can occasionally miss and either destroy some existing data or fifty-fifty render the disc unreadable.

The DVD+RW disc format eliminates this unreliability by embedding more accurate timing hints in the data groove of the disc and allowing private data blocks (or even bytes) to be replaced without affecting backward compatibility (a feature dubbed "lossless linking"). The format itself was designed to deal with discontinuous recording considering it was expected to exist widely used in digital video recorders. Many such DVRs employ variable-rate video pinch schemes which crave them to record in short bursts; some allow simultaneous playback and recording by alternating apace between recording to the tail of the disc whilst reading from elsewhere. The Blu-ray Disc system also encompasses this technology.

Mount Rainier aims to brand package-written CD-RW and DVD+RW discs as convenient to use as that of removable magnetic media by having the firmware format new discs in the background and manage media defects (by automatically mapping parts of the disc which have been worn out by erase cycles to reserve space elsewhere on the disc). As of February 2007, support for Mount Rainier is natively supported in Windows Vista. All previous versions of Windows require a tertiary-party solution, every bit does Mac Bone 10.

Recorder Unique Identifier [edit]

Owing to pressure from the music industry, as represented by the IFPI and RIAA, Philips adult the Recorder Identification Lawmaking (RID) to allow media to be uniquely associated with the recorder that has written it. This standard is contained in the Rainbow Books. The RID-Code consists of a supplier code (e.m. "PHI" for Philips), a model number and the unique ID of the recorder. Quoting Philips, the RID "enables a trace for each disc back to the exact automobile on which it was made using coded information in the recording itself. The use of the RID code is mandatory."^[74]

Although the RID was introduced for music and video manufacture purposes, the RID is included on every disc written past every drive, including information and fill-in discs. The value of the RID is questionable every bit it is (currently) impossible to locate any individual recorder due to in that location being no database.

Source Identification Lawmaking [edit]

The Source Identification Code (SID) is an eight character supplier lawmaking that is placed on optical discs by the manufacturer. The SID identifies non merely manufacturer, only also the individual manufactory and machine that produced the disc.

According to Phillips, the administrator of the SID codes, the SID lawmaking provides an optical disc product facility with the means to identify all discs mastered or replicated in its plant, including the specific Laser Beam Recorder (LBR) bespeak processor or mould that produced a particular stamper or disc.^[74]

Employ of RID and SID together in forensics [edit]

The standard use of RID and SID hateful that each disc written contains a record of the machine that produced a disc (the SID), and which bulldoze wrote it (the RID). This combined knowledge may exist very useful to law enforcement, to investigative agencies, and to private or corporate investigators.^[75]

See besides [edit]

• Computer hardware
• Cue canvass (music software)
• Floptical
• ISO image
• List of optical disc authoring software
• MultiLevel Recording
• Optical disc authoring
• Optical disc recording technologies
• Optical jukebox
• Phase-change Dual
• Receiver (radio)
• Ripping

Notes [edit]

1. ^ The angular disc speeds of ×48 on CDs, ×sixteen on DVDs and ×12 on Blu-ray Discs refer to that equivalent linear velocity required for this multiple of the respective original speeds, if accessed at the outermost disc edge, and amounts to similar physical rotation speeds.

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External links [edit]

• How CDs Work at HowStuffWorks
• How CD Burners Piece of work at HowStuffWorks
• Agreement CD-R & CD-RW

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Source: https://en.wikipedia.org/wiki/Optical_disc_drive#:~:text=In%20computing%2C%20an%20optical%20disc,to%20or%20from%20optical%20discs.

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