The Lead-in contains the TOC data, including
number of tracks, length of each track
and the total length of the whole tracks.
Program Area : Φ50mm ~ Φ116mm
Lead Out Area : 0.5mm wide (Φ117mm) area that comes next
to the Program area from the inside.
The data are stored in a single spiral
track of pits.
Pit
Pit Width : 0.4 ~ 0.5um
(related to the laser wavelength)
Pit Length : 3T ~ 11T
(1T = length covered per clock cycle)
CD Clock : 4.3218MHz =>7.35KHz x 588
ex) CD Constant Linear Velocity(CLV) = 1.25m/s
T = 1.25(m/s) / 4.3218(MHz) = 0.2892um
3T = 0.8677um, 11T = 3.1815um
CLV
1.2m/s
1.25m/s
1.4m/s
T
0.27766um
0.289um
0.3239um
3T
0.832986
0.8677
0.9718
11T
3.05428
3.1815
3.56333
Ref.
CLV : In Constant Linear Velocity (CLV)
systems, the relative speed between
the data spiral and the playback or record head is constant.
To achieve this, the rotational speed of the disc needs
to vary according to the radial position of the pickup.
The rate varies from 1.2 m/s ~ 1.4 m/s.
CAV : In Constant Angular Velocity (CAV)
systems, the disc rotates at the same speed.
Therefore, the relative speed between the
data spiral and the playback head increases as the pickup
moves outward.
Jitter : The time fluctuation of the pit
position.
3T jitter is the central measurement since
it's when the data get most unstable and sensitive.
Transfer rate : The speed at which a certain
volume of data is transferred from a device to
a host such as a personal computer. It is
usually measured in bits per second or bytes per second.
CD 1X = 150KB/sec , DVD 1X = 1350KB/sec
CD Diagram
CDs are digitally played back using light and not touching
the disc physically.
Basically,
CDs have one playback side.
CDs
are written onto using a laser.
Protective layer is quite strong and doesn't get scratches
easily.
ven if there are some scratches, you don't have to worry
as long as they don't affect the reflective metal layer; since a laser
beam doesn't go through the protective layer.
Scratches or dusts on the play side won't be any trouble
so long as they don't block
1mm = 625 tracks 
