Compact Discs Rebecca Martin May 2005. The CD in General Invented in 1980s Used to hold music, data,...
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Transcript of Compact Discs Rebecca Martin May 2005. The CD in General Invented in 1980s Used to hold music, data,...
Compact
DiscsRebecca Martin
May 2005
The CD in General
• Invented in 1980s
• Used to hold music, data, or computer software
• Cheap and easy to distribute a lot of information
Making a CD
• Digital data is encoded on a master disc as bumps
• Changed to binary language of one and zeroes in reading
• Strong laser burns small holes and bumps
Audio CDs
• Smaller and have a better sound quality than phonograph records and audio tapes
CD-ROM's
• Computer data stored on this format
• Stands for Compact Disc- Read Only Memory
• 650 MB
Even More About CD-ROM's
• Can store many images that take up more memory than words
• Can store contents of an encyclopedia with images
How CDs Work:CD Player
• Read out system retrieves sound signal
• Goes to amplifier and pair of headphones
How CDs Work:Laser
• Continually moving outward from center
• As it moves bumps move faster past laser
• Works because of tangential speed
How CDs Work:More About the Laser
• Cannot be extended gaps between bumps
• Incredibly precise to read track
How CDs Work:Bumps or Pits
• Actually bumps on the side that the laser reads, not pits• 1.6 microns away from bump on the left or right of it
How CDs Work:Bumps or Pits Again
• Bumps are 0.5 microns wide, minimum of 0.83 micron long, and 125 nanometers high
• Small dimensions make track very long
How CDs Work:Track
• Lifted and stretched out in straight line, would be 0.5 microns wide and 3.5 miles long
• Incredibly precise mechanism to read
How CDs Work:
Drive Motor
• Spins the disc and controls it to rotate between 200 and 500 rpm (revolutions per minute)
How CDs Work:Laser and Lens System
• Laser and lens system focus in on and read the bumps on the CDs.
How CDs Work:
Tracking Mechanis
m• Tracking
mechanism moves laser assembly so laser beam can follow track
How CDs Work:Layers
• Injection-molded clear polycarbonate plastic• Plastic is impressed with bumps during
manufacturing.
How CDs Work:The Layers Again
• Reflective aluminum
• Thin acrylic layer
• Label
About Me• My name is Rebecca
Martin. I am 13 years old and go to Hanes Middle School. I enjoy playing sports and cheering for Duke. Duke is my favorite college. My favorite sports are soccer and volleyball. I also enjoy talking to my friends and hanging out with them.
Bibliography•“How CDs Work.” U-X-L Encyclopedia of Science. Second Edition, 2002.•Marshall Brain. How CDs Work. HSW MediaNetworks. 29 April 2005. <http://electronics.howstuffworks.com/cd.htm>.•Ian Graham. How Things Work. Italy: Facts On File.1995.•David Macaulay. The New Way Things Work. Boston: Houghton Mifflin Company, 1998.•How Does a CDs Work? 2004. MLK. 5 May 2005. <http://www.copy-cd.biz/technical-area-compact- discs-explained.jsp>.