LG DRD-820B Manual page 6

3. Structure of the Photo Diode (DVD)
(1) Focus Error Signal
• In case of DVD Disc
This signal is generated in RF AMP IC (IC201 : TA1254F) and controls the pick-up's up and down to
focus on DVD Disc.
(2) Tracking Error Signal (DPD Method)
• In case of DVD Disc
This signal is generated in RF AMP IC (IC201 : TA1254F) and controls the pick-up's left and right shift to
find the track on DVD Disc.
(3) RF Signal
• In case of DVD Disc
This signal is converted to DATA signal in DSP IC (IC401 : TC90A41AF).
(A+C) - (B+D)
(A+B+C+D)
Pick-Up module
Photo Diode
A D
B C
(As seen from light
receiving side)
Differential phase of (A+C) and (B+D)
Tracking
Red laser
Focusing
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