How Does a Computer DVD Drive Work?
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The DVD
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A DVD is a plastic disk with a metal disk in the middle of it. The metal disk is coated with a special dye which becomes opaque when it is exposed to a very bright light. A special laser makes small cloudy dots on top of the otherwise clear metal disk. Each of these dots represents a bit of information about a movie. A DVD encodes an entire movie as billions of tiny pieces of information.
The DVD Player
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The DVD drive on a computer uses a dimmer laser to read the DVD. When the laser shines on a clear area of the disk , the laser bounces off the disk and is picked up by a detector in the DVD drive. When it bounces off an opaque area, it is absorbed and not bounced back. The DVD burner knows which bits are opaque and which are clear based on which reflect signals back to it. It sends this information back to the computer.
The Computer
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The computer turns the stream of bits from the DVD burner into data. The menu page, the movie, and the sounds are all encoded on the disk and deciphered by the computer. Although DVDs are usually used to store movies, they can also be used to store other kinds of information, For example, you can back up files from your computer onto DVDs. Many DVD drives nowadays also double as DVD burners. Burnable DVDs cost a few dollars each, and can store more than 4 gigabytes of information. This makes them great for creating permanent backups of documents, pictures, and home movies.
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