CDs and DVDs
How does a laser read data on a CD or DVD?
p. 362 Fig. 7-21
Next
laser
diode
diode
laser
diode
diode
prism
prism
light-
sensing
diode
sensing
diode
light-
sensing
diode
sensing
diode
0
1
lens
lens
pit
land
disc
label
Step 1.
Laser diode shines a light beam toward
disc.
Laser diode shines a light beam toward
disc.
Step 2.
If light strikes
a pit, it scatters. If light strikes a land, it is reflected back toward diode.
If light strikes
a pit, it scatters. If light strikes a land, it is reflected back toward diode.
Step 3.
Reflected light is deflected to a
light-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0.
Reflected light is deflected to a
light-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0.