CD players use an object with NA = 0.45, and laser wavelength A=780nm, whereas the new Blu-Ray disc players use NA= 0.85, λ = 405nm.
a) What is the spot use for CD players
b) What is the spot size for Blu-Ray players.
c) Calculate the ratio of the focal spot area for the Blu-Ray disc player compared to CDs (ie., Ratio= A Blu-Ray, ACD)
d) Assuming that the total information on use disc scales inversely with spot area, what would this predict for the number of Gigabytes for a Blu-Ray disc (CD ROMS are 700 MB (1 MB = 1 million byte)?
e) Is the spot-size reduction itself enough to explain the increased data storage of BluRay discs?
f) What else could account for the difference?