DVD Technology (Encyclopedia of Science)
DVD stands for digital versatile disc, although it is also commonly referred to as digital video disc, due to the popularity of DVDs in the video industry. DVD technology allows for the storage of a large amount of data using digital technology. DVDs can store up to 17 gigabytes, compared to the storage capacity of a compact disc (CD), which is approximately 680 megabytes (1 gigabyte is equal to 1,024 megabytes).
Construction of a DVD
A DVD is a thin, circular wafer of clear plastic and metal measuring 4.75 inches (12 centimeters) in diameter with a small hole in its center. In its most basic form, a DVD is one 0.02-inch-thick (0.06-centimeter-thick) disc; at its greatest capacity, a DVD is two such discs, compressed together to create a double-sided disc 0.04 inch (0.12 centimeter) thick.
The digital data (the binary language of ones and zeroes common to all computers) used in DVDs is encoded onto a master disc. This disc is then used to create copies of itself. A laser (a device used to create a narrow, intense beam of very bright light) burns small holes, called pits, into a microscopic layer of metal, usually aluminum. These pits correspond to the binary ones; smooth areas of the disc untouched by the laser, called land, correspond to the binary zeroes. Once the pits have been burned, the metal is coated with a protective, transparent...
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