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

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

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

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

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

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

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

13. *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…)

14. *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 *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

18. *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. Tsun-Hui, Yao Tang. Conpact Discs(CDs). May 3, 2005.

20. Bibliography What is a CD. May 3, 2005. Turntable History. May 3, 2005.

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.