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The technology of dvd

 

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             A laser and a lens system focus in on and read the bumps. .
             A tracking mechanism moves the laser assembly so that the laser's beam can follow the spiral track. The tracking system has to be able to move the laser at micron resolutions. .
             The hardest part is keeping the laser beam centered on the data track. This centering is the job of the tracking system. The tracking system, as it plays the CD, has to continually move the laser outward. As the laser moves outward from the center of the disc, the bumps move past the laser faster -- this happens because the linear, or tangential, speed of the bumps is equal to the radius times the speed at which the disc is revolving (rpm). Therefore, as the laser moves outward, the spindle motor must slow the speed of the CD. That way, the bumps travel past the laser at a constant speed, and the data comes off the disc at a constant rate.
             A CD can store up to 74 miniutes of music, However more data can be stored on a single DVD. To put this in perspective, a standard compact disc can hold up to 650 MB of computer information. A DVD can hold up to 5 gigabytes on a disc of the same size as a standard compact disc.
             DVD stands for Digital Video Disc and is the newest way to watch movies. First launched in 1997, DVD can store up to four hours of video on a single disc using current technology. However, as they grow in popularity, DVDs will soon be able to hold even more information and the soon to be launched double sided disk will store over eight hours of film!.
             DVD Advantages.
             DVD picture quality is better, and many of DVDs have Dolby Digital or DTS sound, which is much closer to the sound you experience in a movie theater. .
             Many DVD movies have an on-screen index, where the creator of the DVD has labeled many of the significant parts of the movie, sometimes with a picture. With your remote, if you select the part of the movie you want to view, the DVD player will take you right to that part, with no need to rewind or fast-forward.


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