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3.1
Optical
Head
Erasing,
writing
and
reading are
performed by a
laser
diode
and
photo
detectors
in
the
optical
head.
The
laser
diode
driver
and
RF/servo
pre-amplifiers
are
built in
tWs
optical
head.
3.2
Laser Diode
Drive
Block
This block
drives the laser
diode
at
the
correct
power
in
each
mode
for
reading,
writing
and
erasing using
an
Automatic
Power
Control
(APC)
circuit.
The
APC
is
performed by measuring
the
writing
and
erasing
power
at
the
ALPC
area
in
the recording
format
and
holding the
level.
3.3
Data Separation Block
The
read-out
signal
from
the photo-delectors
is
divided
into
two
different
band-width
signals
for
data
separation
and
servo systems.
The
RF
signal
is
amplified,
equalized
and
differentiated for
peak
detection
of
data.
The
PLO
(Phase-Locked
Oscillator)
generates
the
phase-locked
clock
iri
order
to
separate the data
correctly.
The
demodulator decodes
the
(2,7)
RLL
in
accordance
with
this
PLO
clock.
3.4
Servo Blocks
The
SMO-D501
contains the
following four
servo
blocks.
(1)
Spindle
Servo
(2)
Focus Servo
(3)
Tracking
Servo
(4)
Slide
Servo
The
Spindle
Servo
block
rotates
the
MO
disk
at
a constant
2400rpm
by a
digital
frequency-
lock
servo
method
using the
Frequency Generator
(FG)
signal.
The
Focus Servo
block controls
a
two-axis actuator
to
focus the
laser
diode
beam
on
the disk
writing
surface
by an
astigmatism focus servo method.
The
Tracking
Servo
block
controls
a
two-axis actuator
to follow
the track
by a
DPP
(Differential
Push-Pull)
servo method.
1
6
Section
3:
System
Configuration
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