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IBM defines optical storage as "any storage method that uses a laser to store and retrieve data from optical media." '' Britannica'' notes that it "uses low-power laser beams to record and retrieve digital (binary) data."
Compact disc The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in O ...
(CD) and DVD are examples of '' optical media''.


Overview

Optical storage is the storage of data on an optically readable medium.
Data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...
is recorded by making marks in a pattern that can be read back with the aid of
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
, usually a beam of
laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...
light precisely focused on a spinning
optical disc In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc that encodes binary data ( bits) in the form of pits and lands on a special material, often aluminum, on one of its flat surface ...
. An older example of optical storage that does not require the use of
computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...
s, is
microform Microforms are scaled-down reproductions of documents, typically either films or paper, made for the purposes of transmission, storage, reading, and printing. Microform images are commonly reduced to about 4% or of the original document size. ...
. There are other means of optically storing data and new methods are in development. An
optical disc drive In computing, an optical disc drive is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only r ...
is a device in a computer that can read
CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both com ...
s or other
optical disc In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc that encodes binary data ( bits) in the form of pits and lands on a special material, often aluminum, on one of its flat surface ...
s, such as DVDs and
Blu-ray The Blu-ray Disc (BD), often known simply as Blu-ray, is a digital optical disc data storage format. It was invented and developed in 2005 and released on June 20, 2006 worldwide. It is designed to supersede the DVD format, and capable of st ...
discs. Optical storage differs from other data storage techniques that make use of other technologies such as
magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...
, such as
floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined ...
s and
hard disk A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magn ...
s, or
semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...
s, such as
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 NAND flash, are named for the NOR and NAND logic gates. Both use ...
. Optical storage in the form of discs grants the ability to record onto a compact disc in real time. Compact discs held many advantages over audio tape players, such as higher sound quality and the ability to play back digital sound. Optical storage also gained importance for its
green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combin ...
qualities and its efficiency with high energies. Optical storage can range from a single drive reading a single CD-ROM to multiple drives reading multiple discs such as an optical jukebox. Single CDs (
compact discs The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in October ...
) can hold around 700 MB (
megabyte The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix ''mega'' is a multiplier of (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes o ...
s) and optical jukeboxes can hold much more. Single-layer DVDs can hold 4.7 GB, while dual-layered can hold 8.5 GB. This can be doubled to 9.4 GB and 17 GB by making the DVDs double-sided, with readable surfaces on both sides of the disc. HD DVDs were able to store 15 GB with a single-layer and 30 GB with a dual-layer. Blu-ray discs, which won the HDTV optical
format war A format war is a competition between similar but mutually incompatible technical standards that compete for the same market, such as for data storage devices and recording formats for electronic media. It is often characterized by political ...
by defeating HD DVDs, can hold 25 GB for single-layer, 50 GB for dual-layer and up to 128 GB for quad-layer discs. Optical storage includes CDs and DVDs.


History

In 1985, the ''New York Times'' said about optical storage, "the rumor refuses to die." The 1978-introduced
LaserDisc The LaserDisc (LD) is a home video format and the first commercial optical disc storage medium, initially licensed, sold and marketed as MCA DiscoVision (also known simply as "DiscoVision") in the United States in 1978. Its diameter typical ...
and 1982-introduced audio/music CD had made a data-storing optical media format, introduced in 1984 at a trade show, seem feasible. In 2005, the patent for an Optical Storage Device in the form of a compact disc recorder was published by Peter J. Keller and Michael J. Kelley. The Optical Storage Technology Association (OSTA) was an international
trade association A trade association, also known as an industry trade group, business association, sector association or industry body, is an organization founded and funded by businesses that operate in a specific industry. An industry trade association partic ...
formed to promote the use of recordable optical data storage technologies and products.


See also

* 5D optical data storage * 3D optical data storage


References

{{DEFAULTSORT:Optical Storage Storage media