CXA2542AQ
1-1. FS4
This switch is provided between the focus error input and the focus phase compensation, and is in charge of
turning the focus servo ON and OFF.
$00
→ $08
Focus on
Focus off
1-2. Procedure of focus activation
For description, suppose that the polarity is as described below.
a) The lens is searching the disc from far to near;
b) The output voltage (Pin 5) is changing from negative to positive; and
c) The focus S-curve is varying as shown below.
A
t
Fig. 3. S-curve
The focus servo is activated at the operating point indicated by A in Fig. 3. Ordinarily, focus searching and
turning the focus servo switch ON are performed while the focus S-curve transits the point A indicated in Fig.
3. To prevent misoperation, this signal is ANDed with the focus OK signal.
In this IC, the FZC (Focus Zero Cross) signal is output from the SENS1 pin (Pin 23) as the point A transit signal.
In addition, focus OK is output as a signal indicating that the signal is in focus (can be in focus in this case).
Following the line of the above description, focusing can be well obtained by observing the following timing
chart.
(20ms) (200ms)
$02
($00)
$03
$08
Drive voltage
Focus error
The broken lines in the figure
indicate the voltage assuming
the signal not in focus.
SENS1
(FZC)
The instant when the signal is brought into focus.
Focus OK
Fig. 4. Focus ON timing chart
– 30 –
SONY [ SONY CORPORATION ]
