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1.3 AUTOMATIC ADJUSTMENT FUNCTION
A
In this system, all circuit adjustment is automatically
operated inside CD-LSI.
All adjustment is performed every time of inserting disc or
selecting CD mode by source key.
The contents about each automatic adjustment are in the
following;
1) FZD cancellation setting
It makes focus-closing performed certainly. FE offset level
at the time of POWER ON is read, and the reverse
voltage of offset value is written into CRAM inside IC, then
B
the offset is cancelled. In this way, FZD threshold level
can be set to fixed value (+240mV) and one of focus-close
conditions inside IC such as "FZD signal is latched to H" is
certainly carried out.
2) TE, FE, RF offset automatic adjustment
With this adjustment, TE, FE, RF amp offset of preamp at
the time of POWER ON are adjusted to each desired
value with REFO reference.
(The desired value: TE, FE, RF) = (0, 0, -1) [V])
Adjustment steps are;
(1) The microcomputer reads each offset during LDOFF
C
condition via servo LSI.
(2) The microcomputer calculates voltage to be corrected
from read value in step (1), and substitutes the
corrected value in the given place.
3) Tracking balance (T.BAL) automatic adjustment
With this adjustment, output difference between Ech
and Fch is equalized by changing gain of LSI internal
amp. Actually, TE waveform is adjusted to be vertical
symmetry to REFO.
Adjustment steps are;
(1) After focus-close,
D
(2) Kicking a lens toward radial direction to generate TE
waveform certainly.
(3) The microcomputer reads offset volume of TE signal
calculated inside LSI at that time via servo LSI.
(4) The microcomputer detects offset volume as which
one of 0, positive or negative.
If offset volume = 0, adjustment is finished.
If offset volume = positive or negative, change amp gain
of Ech or Fch according to certain rule.
Then, repeat step 2) - 4) until reaching "offset volume = 0"
or "limit number" and adjustment is finished.
E
F
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4) FE bias automatic adjustment
With this adjustment, RFI level is maximized by making
focus point during playing optimal. Adjustment is
performed by utilizing phase difference between 3T level
waveform of RF waveform and disturbance input of focus
error. Since disturbance is input to focus loop, the
adjustment is performed at the same timing as automatic
gain control described later.
Adjustment steps are;
(1) Filling disturbance into focus loop by microcomputer
commands (internal servo LSI)
(2) Detecting jiggle of 3T components in RF signal inside
LSI.
(3) Processing relation between 3T components described
above and disturbance inside LSI to find misalignment
of focus and its direction.
(4) The microcomputer reads out the result found above
by a command from servo LSI.
(5) The microcomputer calculates the required correction
volume and substitutes the result into bias adjustment
items inside servo LSI.
In addition, a series of adjustment steps is repeated
several times (same as automatic gain control) to
increase adjustment accuracy.
5) Focus, tracking AGC
With this adjustment, servo loop gain of focus and tracking
is adjusted automatically.
Adjustment steps are;
(1) Filling disturbance into servo loop.
(2) Acquiring G1, G2 signal by extracting error signal at
the time of filling disturbance (FE, TE) via B.P.F.
(3) Reading signal of the microcomputer, G1 and G2 via
servo LSI.
(4) The microcomputer calculates the required correction
volume and performs loop gain adjustment inside servo
LSI.
In addition, a series of adjustment steps is repeated
several times to increase adjustment accuracy.
CX-3168
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