Wikijunior:How Things Work/DVD
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DVD (Although it's commonly understood as "Digital Versatile Disc" or "Digital Video Disc", the official definition is simply "DVD") is an optical disc that can be used for data storage, including movies with high video and sound quality. DVDs look like compact discs as they are the same size but they store much more information in a different format.
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[edit] Who invented it?
The DVD was not invented by one person or company. Toshiba, Philips, Sony, and Matsushita Electric all helped to develop the technology used to make DVDs. The standards used in creating DVDs are maintained by DVD Forum.
[edit] How does it get power?
A DVD player is powered by electricity. It reads the data on the media using a light.
[edit] How does it work?
DVDs are of the same diameter and thickness as CDs, and they are made using some of the same materials and manufacturing methods. Like a CD, the data on a DVD is encoded in the form of small pits and bumps in the track of the disc. A DVD is composed of several layers of plastic, totaling about 1.2 millimeters thick. Each layer is created by injection molding polycarbonate plastic. This process forms a disc that has microscopic bumps arranged as a single, continuous and extremely long spiral track of data. More on the bumps later.
Each writable layer of a DVD has a spiral track of data. On single-layer DVDs, the track always circles from the inside of the disc to the outside. That the spiral track starts at the center means that a single-layer DVD can be smaller than 12 centimeters if desired.
[edit] How dangerous is it?
The DVD is not dangerous by itself unless it is broken. Then the pieces are very sharp and could cut your fingers - or your feet if you step on them.
The most dangerous part of a DVD is its device to play the DVD disks. You should never try to open a DVD device without pulling out the plug because the laser beam used to read a DVD is dangerous. If its rays accidentally hit your eye, they can cause severe permanentl damage or occasional blindness.
[edit] What does it do?
It records digital information that can be accessed/used by a DVD player.
[edit] How does it vary?
The first DVDs could store around 4.5 GigaBytes, but later scientists found a way to make more layers so they could store more data. These are called "double layer" DVDs. But now there are two new types of DVDs called blu-ray and HD-DVD.
[edit] How has it changed the world?
The DVD has modernized the current generations of video playing devices into the digital age.
[edit] What idea(s) and/or inventions had to be developed before it could be created?
The DVD was seen as the next step from the VCR as the current generation video playing device. There are many inventions involved to make a DVD possible. First of all, the microprocessor should be invented and to invent the microproccssor all ideas related with computers should be developed. You'll realize this when you try to understand how DVD works. On a DVD disk there is coded in a binary form all the information one needs to record a picture. To record and reproduce these binary informations, one needs microporccessors.
