5.2 - Data Storage - Optical Media Flashcards
Examples of optical storage devices (2)
CDs
DVDs
How CDs/DVDs work (5)
laser shone at disk
arm moves laser across disk surface
laser burns pits onto disk surface
laser reads the pits and lands on disk surface
reflected light from laser shining on disk is captured by sensor
Where is data stored on the spiral track (2)
pits on the spiral track
lands on the spiral track
What is used to read and write data on CDs/DVDs
a red laser
Physical Appearance of DVDs (3)
has 2 individual record layers
2 layers joined together with transparent polycarbonate spacer
very thin reflector sandwiched between two layers
What does the R mean after DVDs or CDs
data can only be read once
What does the letter RW mean after DVDs or CDs
data can be written to and read from the disk
DVD and CD differences
DVD has larger storage capacity
DVD laser type
650 nm red laser
CD laser type
780 nm red laser
DVD construction
2 0.6 mm polycarbonate layers
CD construction
one 1.2 mm polycarbonate layer
DVD track pitch (distance between each track)
0.74 micrometers
CD track pitch (distance between each track)
1.60 micrometres
What does a shorter wavelength of laser light mean
greater storage capacity
Difference between Blu-ray and DVDs (4)
Blue ray uses blue laser - shorter wavelength
shorter wavelength allows pits and lands to be smaller - stores 5 times more data than dvd
blu ray automatically comes with encryption
blu ray data transmission is faster than dvd - 36 Mbps to 10 Mbps
storage capacity of dual-layer dvd
4.7 GB
storage capacity of single layer blu ray
27 GB
storage capacity of dual-layer blu ray
50GB
Blu-ray applications (3)
record high definition tv programs
skip quickly to any part of disk
edit programmes on disk
Wavelength of blu-ray laser
405 nm
Track pitch of blu-ray
0.30 micrometres
Construction of blu-ray single layer
1.2 mm polycarbonate layer
Construction of blu-ray double layer
two 0.6 mm polycarbonate layer
