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8. OPERATION OF PICKUP
8-1. CIRCUIT CONFIGURATION OF PICKUP
The pickup unit reads signals from the disk, and the flexible cable is connected to the board. The following signals flow
through the cable.
8-2. EQUIVALENT CIRCUIT OF PICKUP
ACTUATOR
HIGH-FREQUENCY CONVOLUTION
HOLOGRAM LASER UNIT
8-3. POLARITIES OF SIGNAL
Focus
FO+, FO-
Tracking
TR+, TR-
Gain switching
Sga
8-4. SIGNALS OF PICKUP
8-4-1. Tracking drive signal (TR+, TR-)
The signal drives the tracking servo mechanism which projects the beam on the track by moving the objective lens (OL)
to the outer or inner circumference (at a right angle against the track) of the disk.
Since an eccentricity error of 25 µmP-P is generated due to the eccentricity of 100 µmP-P of the DVD disk when the disk
is fixed, the error is reduced to ± 0.22 µm or less with the tracking servo.
FO+
TR–
TR+
FO–
V
OS
OSC
LD
PD
VA
–
+
VB
–
+
VC
–
+
VD
–
+
Sga
V
raf
V
cc
GND
When electric current is flowed from FO+ to FO-, the lens comes to near the disk.
When electric current is flowed from TR+ to TR-, the lens goes toward the outer
circumference.
DVD one Layer
Low gain
DVD two Layer
High gain Sga : +5V
CD
Power adjust
Sga : GND
8-1
TR–
1
FO+
2
TR+
3
FO–
4
VR
5
PD
6
V
7
CC
GND
8
(NC)
LD
9
GND
10
V
11
OS
NC
12
NC
13
V
(VCC/2)
14
ref
VA
15
VC
16
Sga
17
GND
18
VB
19
VD
20
1
DV-550U
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