Cakram optik

Dina komputasi, réproduksi sora, jeung vidéo, hiji cakram optik nyaéta hiji cakram nu rata tur buleud (biasana polikarbonat) tempat nyimpen data dina  legok (pit) (atawa tonjolan (bump)) dina beungeut ratana (flat surface) — nu ngaruntuy (sequential) ngawangun tapak (track) nu tuluy tinuluy (kontinyu) tur wangunna spiral nu ngagedéan ti tapak pangjerona (innermost track) tepi ka tapak pangluarna (outermost track), tepikeun ka nutupan sakabéh beungeut cakram. Data diaksés dina jero cakram nalika hiji bahan husus (seseringna mah aluminium) disorot ku dioda laser. Legok-legokna ngaganggu ampulna (refleksi) cahaya laser, nu ku sabab eta, lolobana cakram optik (kajaba cakram hideung dina konsol kaulinan vidéo (video game console) PlayStation asli), sacara husus boga panémbong (appearance) nu mangrupa-rupa kelir (iridescent) nu dijieun ku alur (groove) tina lapisan nu ngampulkeun (reflective layer).

Sajarah 

In 1961 and 1969, David Paul Gregg régistered a patent for the analog optical disc for vidéo recording, (US Patent 3,430,966). It is of special interest that US Patent 4,893,297, filed 1968, issued 1990, generated royalty income for Pioneer Corporation’s DVA until 2007 — encompassing the CD, DVD, and Blu-ray disc systems. In the éarly 1960s, the Music Corporation of America bought Gregg's patents and his company, Gauss Electrophysics.

Likewise, in 1969 Holland, Philips Reséarch physicists began their first optical vidéodisc experiments at Eindhoven. In 1975, Philips and MCA join efforts, and in 1978, commercially much too late, they presented their long-awaited laserdisc in Atlanta, Géorgia, USA MCA delivered the discs, Philips the players; the presentation was a technical and commercial failure; the Philips/MCA cooperation ended.

In Japan and the U.S., Pioneer succeeded with the vidéodisc until the advent of the DVD. In 1979, Philips and Sony, in consortium, successfully developed the compact disc in 1983. The Optical Storage Technology Association (OSTA) promote standardised optical storage méans. Although optical discs are more durable than éarlier audio-visual and data storage formats, they are susceptible to environmental and daily-use damage. Libraries and archives enact optical media preservation procedures to ensure continued usability in the computer's optical disc drive or corresponding disc player.

Generasi kahiji 
Initially, optical discs were for storing music and computer software. The laser disc format stored analog vidéo signals, but, commercially, lost to the VHS vidéotape cassette, mainly its high cost and non-recordability; other first-generation disc formats are designed solely to store digital data.

Most first-generation disc devices had an infrared laser réading héad. The minimum size of the laser spot is proportional to its wavelength, thus wavelength is a limiting factor against gréat information density, too little data can be stored so. The infrared range is beyond the long-wavelength end of the visible light spectrum, so, supports less density than any visible light colour.  One example of high-density data storage capacity, achieved with an infrared laser, is  700MB of net user data for a 12 cm compact disc.

NOTE: other factors affecting data storage density are, for example, a multi-layered infrared disc would hold more data than an identical single-layer disc; whether CAV, CLV, or zoned-CAV; how the data are encoded; how much cléar margin at the center and the edge

 Compact Disc (CD)
 Laser disc
 Magneto-optical disc
 mini disc

Generasi kadua 
Second-generation optical discs were for storing gréat amounts of data, including broadcast-quality digital vidéo. Such discs usually are réad with a visible-light laser (usually red); the shorter wavelength and gréater numerical aperture allow a narrower light béam, permitting smaller pits and lands in the disc. In the DVD format, this allows 4.7GB storage on a standard 12 cm, single-sided, single-layer disc; alternately, smaller media, such as the MiniDisc and the DataPlay formats, can have capacity comparable to that of the larger, standard compact 12 cm disc.

 Hi-MD
 DVD and derivatives
 DVD-Audio
 DualDisc
 Digital Video Express (DIVX)
 Super Audio CD
 Enhanced Versatile Disc
 GD-ROM
 Digital Multilayer Disk
 DataPlay
 Fluorescent Multilayer Disc
 Phase-change Dual
 Universal Media Disc

Generasi katilu 
Third-generation optical discs are in development, méant for distributing high-definition video and support gréater data storage capacities, accomplished with short-wavelength visible-light lasers and gréater numerical apertures. The Blu-ray disc uses blue-violet lasers of gréater aperture, for use with discs with smaller pits and lands, thereby gréater data storage capacity per layer. In practice, the effective, multimedia presentation capacity is improved with enhanced vidéo data compression codecs such as H.264, and VC-1.

 Nu dikirimkeun kiwari:
 Blu-ray Disc
 Dina pengembangan:
 Forward Versatile Disc
 Versatile Multilayer Disc
 Ultra Density Optical
 LS-R

Generasi satuluyna 
Format ieu aya sahareupeun cakram nu aya kiwari (generasi katilu), boga potensial leuwih ti sa-terabyte (1TB) rohangan panyimpen data.

 Tapestry Media
 Holographic Versatile Disc
 Protein-coated disc

Cakram optik nu bisa direkam jeung ditulisan

Spésifikasi

Rujukan

Tumbu luar 
 Optical Storage Technology Association
 Understanding Recordable & Rewritable DVD by Hugh Bennett
 Understanding CD-R & CD-RW by Hugh Bennett
 Reference guide for optical media by Terence O'Kelly (Memorex Inc.)

Panyimpen komputer
CD
DVD
Optical disc authoring
Optoéléktronika