– 19 –

CXA1372BQ/BS

The instant the signal is brought into focus.

$08

$03

($00)

$02

(20ms) (200ms)

Drive voltage

Focus error

SENS pin

(FZC)

Focus OK

1-1. FS4

This switch is provided between the focus error input (Pin 47) and the focus phase compensation, and is in

charge of turning the focus servo ON and OFF.

$00

→ $08

Focus OFF

← Focus ON

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.

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 when 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, FZC (Focus Zero Cross) signal is output from the SENS pin (Pin 27) as the point A transit signal.

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.

∗

The broken lines in the figure

indicate the voltage assuming

the signal is not in focus.

t

A

Fig. 3. S-curve

Fig. 4. Focus ON timing chart