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CD and DVD. How CD and DVD works By: Mark Jiang. History of the Compact Disk. Compact disk (CD) started in the 1970’s with the videodisk in the form of Video Long Play (VLP) read-only systems. In 1982 the CD-DA (compact disk-digital audio) was introduced to the market. - PowerPoint PPT Presentation
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CD and DVD
How CD and DVD works
By: Mark Jiang
History of the Compact Disk
Compact disk (CD) started in the 1970’s with the videodisk in the form of Video Long Play (VLP) read-only systems.
In 1982 the CD-DA (compact disk-digital audio) was introduced to the market.
In 1985, the technology was extended to computer storage as CD-ROM (compact disk-read only memory).
In November of 1996 the high-density compact disk DVD (Digital Versatile Disc) was introduced to the market.
CD: Material
Polycarbonate PlasticAluminumAcrylicLabel
CD: Spiral
A CD has a single spiral track of data, circling from the inside of the disc to the outside.
the picture on the right does not show how small the data track is, it is approximately 0.5 microns wide, with 1.6 microns separating one track from the next. (A micron is a millionth of a meter.) And the bumps are even smaller.
CD: Spiral
Low-magnification (X32) image of a CD showing an edge of the data zone.
CD: Bumps
The bumps are each 0.5 microns wide, a minimum of 0.83 microns long and 125 nanometers high. (A nanometer is a billionth of a meter.) We often call it "pits" on a CD instead of bumps.
CD: Pits
How Small are the Pits?
Did You Know?
The incredibly small dimensions of the bumps make the spiral track on a CD extremely long. If you could lift the data track off a CD and stretch it out into a straight line, it would be almost 3.5 miles (5 km) long!
DVD: Different Types
DVD versus CD
CD Drive: Components
How CD Drive Read Data: Optics
How CD Drive Read Data: Surface
The laser beam (wavelength ~ 780 nm) is focused ontothe data side of the disk (focused spot diameter ~ 1mm).
How CD Drive Read Data: Laser Focus
How CD Drive Read Data: Tracking
How CD Drive Read Data: Tracking
CD Drive: Motor
VIDEOVIDEO
ENDENDThank YouThank You
Information From:Information From:
HowStuffWorksHowStuffWorkshttp://www.howstuffworks.com/cd.htmhttp://www.howstuffworks.com/cd.htm
M. MansuripurM. MansuripurOptical Sciences CenterOptical Sciences CenterThe University of Arizona TucsonThe University of Arizona Tucson
