CD/DVD/Blu-Ray
DVD/CD/Blu-Ray are all optical data storage devices. All
three employ lasers and the principle of point-by-point
scanning of an object to extract the recorded information
on the disc. They differ in their capacity to store data
and by the type of laser light required to decode that
data.
Travis Harrall, Zac Spencer &
Trevor Green
The Discs
•Data stored in the series of
lands and bumps on disc
•Tracks spiral outward from
center
•1.2mm thick, maximum radius
of 12cm
The
Player
•Disc drive motor
•Lens/Laser system
•Tracking drive
How are they different?
CD
DVD
Blu-Ray
Storage Capacity
.65 GB per layer
4.7 GB per layer
23 GB per layer
Numeric Aperture
.45
.60
.85
Wavelength of Laser
780 nm (infrared)
650 nm (red)
405 nm (purple)
Track Pitch
1.6 μm
.74 μm
.32 μm
Maximum Rotating
Speed
500 rpms
1600 rpms
10,000 rpms
Minimum Size of Pits
.83 μm
.4 μm
.14 μm
Beam Diameter
NA  n sin  n  1 because the system is working in air
NA   by small angle approximat ion
  D / 2 f  NA
Radius of Laser  1.22 fD
Diameter of Laser  2 *1.22 fD
1 / NA  2 f / D
Diameter of Laser  1.22NA
CD
DVD
Blu-Ray
Storage Capacity
.65 GB per layer
4.7 GB per layer
23 GB per layer
Numeric Aperture
.45
.60
.85
Wavelength of Laser
780 nm (infrared)
650 nm (red)
405 nm (purple)
Track Pitch
1.6 μm
.74 μm
.32 μm
Maximum Rotating
Speed
500 rpms
1600 rpms
10,000 rpms
Minimum Size of Pits
.83 μm
.4 μm
.14 μm
Bibliography
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Braat, Joseph, P. Dirksen, and Augustus Janssen. Diffractive read-out of optical
discs. 2007. 1-11. Web. 19 Nov. 2010.
Kuhn, Kelin J. Laser Engineering. N.p.: Prentice Hall, 1998. Print.
Pohlmann, Ken C. The Compact Disc Handbook. 2nd ed. Vol. 5. Madison: A-R
Editions, Inc, 1992. 51-53. Web. 19 Nov. 2010.
van de Nes, A S, J J M Braat, and S F Pereira. "High-density optical data
storage." Reports of Progress in Physics 69 (2006): 2325-61. Web. 19
Nov. 2010.
http://www.explainthatstuff.com/cdplayers.html
http://electronics.howstuffworks.com/dvd.htm
http://www.blu-ray.com/faq/
http://electronics.howstuffworks.com/blu-ray.htm
http://electronics.howstuffworks.com/cd.htm
http://www.yeodoug.com/resources/handbook/image_files/text_files/beethoven
9.html