An optical disc is a flat, usually disc-shaped object that stores information in the form of physical variations on its surface that can be read with the aid of a beam of light. Optical discs can be reflective, where the light source and detector are on the same side of the disc, or transmissive, where light shines through the disc to be detected on the other side.
In computing, an optical disc drive (ODD) 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 read from certain discs, but recent drives can both read and record, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives.
A DVD recorder is an optical disc recorder that uses optical disc recording technologies to digitally record analog or digital signals onto blank writable DVD media. Such devices are available as either installable drives for computers or as standalone components for use in television studios or home theater systems.
The Blu-ray Disc Association (BDA) is the industry consortium that develops and licenses Blu-ray technology and is responsible for establishing format standards and promoting business opportunities for Blu-ray Disc. The BDA is divided into three levels of membership: the board of directors, contributors, and general members.
Verbatim is a brand for storage media and flash memory products currently owned by CMC Magnetics Corporation (CMC), a Taiwanese company that is known for optical disc manufacturing. Formerly a subsidiary of Mitsubishi Chemical, the global business and assets of Verbatim were sold to CMC Magnetics in 2019 at an estimated price of $32 million USD.
The double-density compact disc (DDCD) is an optical disc technology developed by Sony and Philips using the same 780 nm laser wavelength as a compact disc. The format was announced in July 2000 and 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.
Mini CDs, or pocket CDs, are CDs with a smaller diameter and one-third the storage capacity of a standard 120 mm disc.
Optical storage refers to a class of data storage systems that use light to read or write data to an underlying optical media. Although a number of optical formats have been used over time, the most common examples are optical disks like the compact disc (CD) and DVD. Reading and writing methods have also varied over time, but most modern systems as of 2023 use lasers as the light source and use it both for reading and writing to the discs. Britannica notes that it "uses low-power laser beams to record and retrieve digital (binary) data."
In computing, external storage refers to non-volatile (secondary) data storage outside a computer's own internal hardware, and thus can be readily disconnected and accessed elsewhere. Such storage devices may refer to removable media, compact flash drives, portable storage devices, or network-attached storage. Web-based cloud storage is the latest technology for external storage.
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.
A combo drive is a type of optical drive that combines CD-R/CD-RW recording capability with an ability to read DVD media; some manufacturers refer this as CD-RW/DVD-ROM drive. The term was used almost exclusively by Apple as a name for the low-end substitute for their high-end SuperDrive, as the latter was designed to both read and write CD and DVD recordable media. The device was created as a mid-range option between a CD burner and a DVD burner, which at the time the combo drive was introduced was generally an expensive option costing in excess of US$300 a unit.
Optical disc authoring requires a number of different optical disc recorder technologies working in tandem, from the optical disc media to the firmware to the control electronics of the optical disc drive.
CD-RW is a digital optical disc storage format introduced in 1997. A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written.
Calimetrics was an American technology company 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 grant to conduct research and development on pit-depth modulated optical data storage systems. 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.
The DVD is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind of digital data and has been widely used to store video programs, software and other computer files. DVDs offer significantly higher storage capacity than compact discs (CD) while having the same dimensions. A standard single-layer DVD can store up to 4.7 GB of data, a dual-layer DVD up to 8.5 GB. Variants can store up to a maximum of 17.08 GB.
Blu-ray is a digital optical disc data storage format designed to supersede the DVD format. It was invented and developed in 2005 and released worldwide on June 20, 2006, capable of storing several hours of high-definition video. 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, PlayStation 5, Xbox One, and Xbox Series X. The name 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 an 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, but lost to Blu-ray, supported by Sony and others.
As of 2021, multiple consumer-oriented, optical-disk media formats are or were available:
Toshiba Samsung Storage Technology Corporation is an international joint venture company of Toshiba (Japan) and Samsung Electronics. Toshiba used to own 51% of its stock, while Samsung used to own the remaining 49%. The company specialized in optical disc drive manufacturing. The company was established in 2004.
A CD-ROM 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. Some CDs, called enhanced CDs, hold both computer data and audio with the latter capable of being played on a CD player, while data is only usable on a computer.
