43
2. Focus Circuit
2-1. Block Diagram
Disc
Motor unit
Optical
Pick-up
HOP-8541T
A1~A4
B1~B4
(EF1~EF4)
(EF1~EF4)
DVD : (B1+B3)-(B2+B4)
CD : (EF1+EF3)-(EF2+EF4)
HAVC
LS
to
V14
FE
FE
FE
R334
C325
GND
ADC
Focusing
Compensator
DAC
FOD
FOD
R615
M63041AFP
IC601
FACT+
FACT-
FACT+
FACT-
IC101
HD153722TF
IC301
R8J32005FP
EN1
EN2
CTL1
CTL2
C608
REF
1.65V
FOIN
DVD : A1+A2+A3+A4
CD : EF1+EF2+EF3+EF4
LPF
G
HAVC
LS
to
0.8V
PE
PE
5
LPF
G
4
100
101
116
40
42
20
21
34
35
2-2. Focus Servo
The aim of Focus Servo is to maintain the distance between object lens of P/U and disc surface, so that the
detected RF signal(A1, A2, A3, A4, B1, B2, B3, B4, EF1, EF2, EF3, EF4) can be maximized.
Focus Error Signal(FE) generates from focus error detection block in RF IC(HD153722) using Double knite
Edge method (DVD), spot size Detection method(CD).
Focus Gain and path can be changed at the RF IC(HD153722) according to the disc, and the resulting output
FE(HD153722 4pin) is input to DSP IC(HD153722 100pin).
The Focus Search operation is using FE, PE Signal, therefore check FE, PE signals when Focusing is failed.
The role of DSP IC(R8J32005FP) is Focus Digital Controller. The operation path is as follows;
FE Signal is input to DSP IC(R8J32005FP 100pin), and after A/D Conversion, Digital Equalizer Block and D/A
Conversion in R8J32005FP, the output signal FOD(R8J32005FP 116pin) is input to Drive IC(M63041AFP
40pin).
The drive output signal FACT+/FACT- generated according FOIN(M63041AFP 40pin), and drives focus actuator
in the P/U unit.