Samsung RCD-750 - Page 18

(4) FOCUS AND TRACKING SERVO
(1)
FOCUSING
SERVO
:
It
vertically
shifts
the
objective
lense
so
that
the
beam
correctly
fall
on
the
disc
surface
to
read
out
the
data
recordeda
on
the
disc.
(2) TRACKING SERVO : It controls the objective lense to maintain proper tracking.
@ Normal Tracking Servo: it shifts the objective lense for proper tracking (1.6 um).
@ Feed Servo: it shifts the optical pick up itself for tracking.
(5
—
DSP (Digital signal Processor)
DSP(Digital
Signal
Processor)
is
basically
composed
of
the
EFM(Eight
to
Fourteen
Modulation)
decoder
and
Error
Correction
System.
:
The
EFM
decoder
converts
the
serial
14
bit
EFM
code
to
an
8
bit
parallel
code
which
is
directed
to
a
bi-directional
bus
and
placed
in
the
RAM.
The
contents
of
the
RAM
are
read
by
the
Error
Detection
Circuit.
The
Error
Detection
Circuit
extracts
the
interleaved
data
samples
so
that
the
signal
is
deinterleaved
and
detects
most
of
the
errors
present in the
present
in
the
signal
dued
to
flaws
on
the
disc.
The
decoded
signal,
with
error
correction,
is
output
from
the
Memory
Control
circuit
in
a
16
bit
serial
code
and
‘directed
to
the
D/A
Converter.
The
Memory
circuit
also
output
a
signal,
derived
from
the
Clock,
which
denotes
the
linear
velocity
of
the
disc.
These
signals
are
directed
to
the
CLV
(Constant
Linear
Velocity)
circuit
to
correct
any
error
in the
disc speed.
(6) D/A CONVERTER
The
signal
output
from
the
Memory
Control
in
the
Error
Correction
circuit
is
a
serial
16
Bit
NRZ
(Non-Rerurn
to
Zero),
error
corrected
and
de-interleaved
digital
code.
The
signal
must
now
be
converted
to
an
analog
signal
suitable
for
application
to
a
stereo
pre-amplifier.
This
is
the
function
of
the
D/A
(Digital
to
Analog)
Converter
and
Analog
Amplifier.
47-
RCD-750