15
1) Focus Error Signal –> (A + C) - (B+C)
• In case of CD Disc
This signal is generated in RF AMP IC (IC101) and controls the pick-up’s up and down to
focus on CD Disc.
2) Tracking Error Signal (DPP( Differential Push Pull) )-> {(A+B) - (C+D)} - 1.9 x
{(E
1
+F
1
) - (E
2
+F
2
)}
• In case of CD 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 CD Disc.
3) RF Signal –> A+B+C+D
• In case of CD Disc
This signal is converted to DATA signal in DSP IC (IC201).
2. Structure of the Photo Diode (CD)
Infrared laser
Pick-Up module
Photo Diode
Tracking
Focusing
(As seen from light receiving side)
E
2
E
1
F
2
F
1
C
B
D
A