17
1) Focus Error Signal –> {(a+c) - (b+d)} - 1.17 x {(e
2
+ f
2
+ e
4
+ f
4
) - (e
1
+ f
1
- e
3
+ f
3
)}
• In case of DVD Disc
This signal is generated in RF AMP IC (IC101) and controls the pick-up’s up and down to
focus on DVD Disc.
2) Tracking Error Signal (DPP Method) –> {(a+b) -(c+d)} - 1.17 x {(e
1
+ f
1
+ e
2
+ f
2
)
- (e
3
+ f
3
+ e
4
+ f
4
)}
• In case of DVD Disc
This signal is generated in RF AMP IC (IC101) and controls the pick-up’s left and right shift to find the track
on DVD Disc.
3) RF Signal –> A+B+C+D
• In case of DVD Disc
This signal is converted to DATA signal in DSP IC (IC201).
4. Structure of the Photo Diode (DVD-RAM)
(As seen from light receiving side)
Red laser
Pick-Up module
Photo Diode
Tracking
Focusing
d
a
c
b
e
4
e
1
e
3
e
2
f
4
f
1
f
3
f
2
