How CDs Work

Stefanie Xenakis2005

History of the CD

* Introduced in 1980s*Patented by Philip and SONY*Goal 1: Large storage space*Goal2: Perfect Copies

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

*Order of materials:1) Polycarbonate plastic2)Thin reflective aluminum layer 3) Acrylic layer for protection

CD Material (cont…)

CD Spiral

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

*1.6microns separate one track from each other other*Stretched spiral is 3 miles

CD Spiral (cont...)

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

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

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

2)Laser/lens system-focus in on and reads bumps2nd Important Component

3)Tracking system-aligns laser to follow track3rd Important Component

Laser Focus

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

*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

Laser Focus (cont…)

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

Before the CD

Floppies

Records*Simpler version of CD*Instead of laser there’s a needle

*Needle called a stylus*Stylus held in place by arm*Spirals are visible to eye

*Spirals are visible to eye*Amplified through speakers like CD*speed must be exact* Too slow=pitch drops;Too fast=pitch rises

Records (cont…)

BibliographyHow 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>

BibliographyWhat is a CD. May 3, 2005.

<http://www.gsmcables.i12.con/whatiscdr.htm>

Turntable History. May 3, 2005. <http://www.enjoythemusic.com/

tablehistory.htm>

About MeMy 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.