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FL8370
1.7 Defect Circuit
The RFO signal bottom, after being inverted, is held with two time constants of long and short.
The short time-constant bottom hold is done for a disc mirror defect more than 0.1msec, the long time-
constant bottom hold is done with the mirror level prior to the defect. By differentiating this with a
capacitor coupling and shifting the level, both signals are compared to generate the mirror defect
detection signal.
The short time-constant bottom hold is done for a disc mirror defect more than 0.1msec, the long time-
constant bottom hold is done with the mirror level prior to the defect. By differentiating this with a
capacitor coupling and shifting the level, both signals are compared to generate the mirror defect
detection signal.
Figure 10. Defect Circuit
1.8 APC (Auto Power Control) Circuit
The laser diode has large negative temperature characteristic in its optical output when driven with a
constant current on laser diode. Therefore, the output on processing monitor photo diode, must be a
controlled current for getting regular output power, thus the APC (Auto Power Control) circuit is
composed.
constant current on laser diode. Therefore, the output on processing monitor photo diode, must be a
controlled current for getting regular output power, thus the APC (Auto Power Control) circuit is
composed.
Figure 11. APC Circuit
75
RFO
41
-
+
SSTOP/DFCT
2
BOTTOM
HOLD
5
-
+
4
DCC1
DCC2
DCB
75K
37.5K
28K
75K
VC+0.6254V
43K
DFCT
BOTTOM
HOLD
69
PD
70
-
+
LD
-
+
43.5K
150K
5.5K
150K
150K
PN (From micom command)
300K
LDON
0.75K
(From micom command)
1.25V
14
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