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How CDs Work

This article explores the history and technology behind Compact Discs (CDs), introduced in the 1980s by Philips and Sony. Learn about their large storage capacity, the intricate design of microscopic bumps on a polycarbonate plastic surface, and the components of a CD player, including the drive motor, laser/lens system, and tracking system. Discover how the laser reads the digital signals that create audio sound waves converted by a DAC and amplified through speakers. A fascinating look at a pivotal technology in music history.

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How CDs Work

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  1. How CDsWork Stefanie Xenakis 2005

  2. History of the CD * Introduced in 1980s *Patented by Philip and SONY *Goal 1: Large storage space *Goal2: Perfect Copies

  3. CD Material *Mostly polycarbonate plastic *Impressed with microscopic bumps *Bumps arranged on CD as a spiral

  4. CD Material (cont…) *Order of materials: 1) Polycarbonate plastic 2)Thin reflective aluminum layer 3) Acrylic layer for protection

  5. CD Spiral *Starts from inside and goes to outside *Data track 0.5microns wide *1 micron= 1 millionth mm

  6. CD Spiral (cont...) *1.6microns separate one track from each other other *Stretched spiral is 3 miles

  7. CD Bumps/Pits *Minimum .83microns long *125 nanometers high *Nanometer=1 billionth of a meter *”Pits” from our view on aluminum side *”Bumps” at laser’s view

  8. CD Components *CD player reads data *Disc drive has 3 important components that each have a job

  9. 1st Important Component 1)Drive motor- spins disc(200-500rpm)

  10. 2nd Important Component 2)Laser/lens system-focus in on and reads bumps

  11. 3rd Important Component 3)Tracking system-aligns laser to follow track

  12. Laser Focus *Passes plastic layer, reads bumps *Reflects off aluminum to receptor AKA optic-electronic device *Receptor detects changes in reflectivity

  13. Laser Focus (cont…) *Reflectivity on bumps is read differently than the CD lands *Reads 0s and 1s AKA digital signal *Digital signal enters DAC *DAC=digital analouge converter

  14. Laser Focus (cont…) *DAC turns digital signal into sound waves *Sound waves go through AMP to boost sound through speakers *AMP=amplifier

  15. Before the CD

  16. Floppies

  17. Records *Needle called a stylus *Stylus held in place by arm *Simpler version of CD *Instead of laser there’s a needle *Spirals are visible to eye

  18. *Spirals are visible to eye *Amplified through speakers like CD *speed must be exact * Too slow=pitch drops;Too fast=pitch rises Records (cont…)

  19. Bibliography How CDs Work. May 3, 2005. <http://electronics.howstuffworks.com/cd.htm> Tsun-Hui, Yao Tang. Conpact Discs(CDs). May 3, 2005. <http://www.sinc.sunysb.edu/class/cei511/1.html>

  20. Bibliography What is a CD. May 3, 2005. <http://www.gsmcables.i12.con/whatiscdr.htm> Turntable History. May 3, 2005. <http://www.enjoythemusic.com/tablehistory.htm>

  21. About Me My name is Stefanie Xenakis and I am thirteen years old. I am Greek and have been to Greece about 7 times. My birthday is October 28, 1991 and my favorite animal is a monkey. I have three dogs and one cat. All of my dogs are poodles. There names are Tina, Rocky, and Lucy. I play the flute and my favorite sports are volleyball and basketball.

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