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 on one of its flat surfaces.
Videodisc is a general term for a laser- or stylus-readable random-access disc that contains both audio and analog video signals recorded in an analog form. Typically, it is a reference to any such media that predates the mainstream popularity of the DVD format.
A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon a magneto-optical disc. Both 130 mm (5.25 in) and 90 mm (3.5 in) form factors exist. In 1983, just a year after the introduction of the Compact Disc, Kees Schouhamer Immink and Joseph Braat presented the first experiments with erasable magneto-optical Compact Discs during the 73rd AES Convention in Eindhoven. The technology was introduced commercially in 1985. Although optical, they appear as hard disk drives to the operating system and can be formatted with any file system. Magneto-optical drives were common in some countries, such as Japan, but have fallen into disuse.
DVD-RAM is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM media have been used in computers as well as camcorders and personal video recorders since 1998.
MiniDVD is a DVD disc which is 8 centimetres (3.15 in) in diameter. It refers two separated formats as well. One is a pseudo-format that uses 80mm CD-R(W) to store contents with the same structure as the standard DVD-Video so that standalone DVD players can play it like standard DVD. The other format is a real DVD format, but in a smaller 80mm size, which holds 1.4 GB of data.
Versatile Multilayer Disc is a high-capacity red-laser optical disc technology designed by New Medium Enterprises, Inc.. VMD was intended to compete with the blue-laser Blu-ray Disc format and had an initial capacity of up to 30GB per side.
The Holographic Versatile Disc (HVD) is an optical disc technology developed between April 2004 and mid-2008 that can store up to several terabytes of data on an optical disc 10 cm or 12 cm in diameter. The reduced radius reduces cost and materials used. It employs a technique known as collinear holography, whereby a green and red laser beam are collimated in a single beam. The green laser reads data encoded as laser interference fringes from a holographic layer near the top of the disc. A red laser is used as the reference beam to read servoinformation from a regular CD-style aluminium layer near the bottom. Servoinformation is used to monitor the position of the read head over the disc, similar to the head, track, and sector information on a conventional hard disk drive. On a CD or DVD this servoinformation is interspersed among the data. A dichroic mirror layer between the holographic data and the servo data reflects the green laser while letting the red laser pass through. This prevents interference from refraction of the green laser off the servo data pits and is an advance over past holographic storage media, which either experienced too much interference, or lacked the servo data entirely, making them incompatible with current CD and DVD drive technology.
GD-ROM is a proprietary optical disc format originally used for the Dreamcast video game console, as well as its arcade counterpart, the Sega NAOMI and select Triforce arcade board titles. It was developed by Yamaha to curb piracy common to standard compact discs and to offer increased storage capacity without the expense of the fledgling DVD-ROM. It is similar to the standard CD-ROM except that the pits on the disc are packed more closely together, resulting in a higher storage capacity of 1 gigabyte, a 42% increase over a conventional CD's capacity of 700 megabytes.
Double-density compact disc (DDCD) is an optical disc technology developed by Sony using the same laser wavelength as compact disc, namely 780 nm. The format is defined by the Purple Book standard document. Unlike the compact-disc technology it is based on, DDCD was designed exclusively for data with no audio capabilities.
Professional Disc (PFD) is a digital recording optical disc format introduced by Sony in 2003 primarily for XDCAM, its tapeless camcorder system. It was one of the first optical formats to utilize a blue laser, which allowed for a higher density of data to be stored on optical media compared to infrared laser technology used in the CD and red laser technology used in the DVD format.
Plextor is a Taiwanese brand, best known for solid-state drives and optical disc drives.
In computing, external storage comprises devices that store information outside a computer. Such devices may be permanently attached to the computer, may be removable or may use removable media.
DVD recordable and DVD rewritable are optical disc recording technologies. Both terms describe DVD optical discs that can be written to by a DVD recorder, whereas only 'rewritable' discs are able to erase and rewrite data. Data is written ('burned') to the disc by a laser, rather than the data being 'pressed' onto the disc during manufacture, like a DVD-ROM. Pressing is used in mass production, primarily for the distribution of home video.
Ultra Density Optical (UDO) is an optical disc format designed for high-density storage of high-definition video and data.
Calimetrics was founded in 1994 by Terrence Wong, Michael O'Neill, and Thomas Burke. Based on Dr. Wong and Dr. O'Neill's UC Berkeley research, the company received startup funding of $1.8M from an Advanced Technology Program (ATP) grant to conduct research and development on pit depth modulated optical data storage systems."Status Report - Number 2 NIST SP 950-2". Performance of 50 Completed ATP Projects. Archived from the original on 2015-06-30. Retrieved 2015-06-27. Over the years, Calimetrics raised approximately $50M from government, venture, angel, and corporate sources. Calimetrics was acquired in 2003 by LSI Logic and ceased operations in 2004.
This article compares the technical specifications of multiple high-definition formats, including HD DVD and Blu-ray Disc; two mutually incompatible, high-definition optical disc formats that, beginning in 2006, attempted to improve upon and eventually replace the DVD standard. The two formats remained in a format war until February 19, 2008, when Toshiba, HD DVD's creator, announced plans to cease development, manufacturing and marketing of HD DVD players and recorders.
DVD is a digital optical disc storage format invented and developed in 1995 and released in late 1996. The medium can store any kind of digital data and is widely used for software and other computer files as well as video programs watched using DVD players. DVDs offer higher storage capacity than compact discs while having the same dimensions.
Blu-ray Disc (BD), often known simply as Blu-ray, is a digital optical disc data storage format designed to supersede the DVD format, capable of storing several hours of video in high-definition. The main application of Blu-ray is as a medium for video material such as feature films and for the physical distribution of video games for the PlayStation 3, PlayStation 4, and Xbox One. The name "Blu-ray" refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs.
HD DVD is a discontinued, obsolete high-density optical disc format for storing data and playback of high-definition video. Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format.
