LG CED-8081B Service Manual page 38

3. Signal detection of the P/U
1) Focus Error Signal ==> (A+C)-(B+D)
This signal is generated in RF IC (IC401 : CXA2551R) and controls the pick-up's up and down to focus on
Disc.
2) Tracking Error Signal (DPP Method) ==> {(A+D)-(B+C)}-
This signal is generated in RF IC (IC401 : CXA2551R) and controls the pick-up's left and right shift to find
to track on Disc.
3) RF Signal ==> (A+B+C+D)
This signal is converted to DATA signal in DSP IC (IC201 : OTI-9790).
Tp/2
Main
Sub2
Offset
TE
24
Pick-Up module
Photo Diode
Track Center
Tp
k x {(F+H)-(E+G)}
Sub1
D,C
A,B
H,G
k[(F+H) - (E+G)]
(A+D) - (B+C)
(A+D) - (B+C) - k[(F+H) - (E+G)]
Infrared Iaser
Focusing
Tracking
F,E