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VL-C780S/H/X
\VL-C7400E
VL-CGS0S/H/X
VL-CG400E
7-2 Description of action
1. Filter circuit
In the auto focus circuit, the luminance signal Y}; (A/F-Y, P706 pin (1)) outputted from the camera processing
circuit is used. In this signal, noise is reduced by synthesizing the signals of OH and 1H.
After passing through the buffer (Q904), the signal is distributed to the two kinds of band pass filter (0.1
MHz~1.0 MHz, 1.0:-MHz~2.0 MHz), where the high frequency component is ectracted. The band pass filter is
the active filter composed of Q905, Q906, resistor and condenser.
The two kinds of signals passed through the filters are switched with a timing of f4/2 by analog switch 1C908,
becoming the line sequential signal. Then, after passing through the amplification circuit (Q908) and buffer
(Q911), the signal is sent to the A/D conversion circuit.
fyl2
CAMERA SIGNAL
PROCESSING
«()
Q304
Q908
AMPLIFI-
|
CATION
CIRCUIT
IC908
ANALOG SW
Figure 7-2 (a). Filter Circuit
2. A/D conversion circuit
The signal processed in the filter circuit is inputted in A/D converter 1C903 pin (12). By means of the pin (10)
and pin (11) terminal voltage, the range of A/D conversion is set (upper limit: 3.14 V, lower limit: 1.57 V). The
reference voltage is obtained from the constant voltage circuit of IC909.
This reference voltage (1.57 V) is
also used for the bias voltage of filter circuit, ete.
The result of A/D converston is outputted by means of the binary code (B1 - B6, 81 = LSB, B6 = MSB) and sent
to A/F gate array |C902.
FROM FILTER
CIRCUIT Q911
R939
R940
R941
IC909
1C903
.
1c902
CONSTANT VOLTAGE
A/D CONVERTER
A/F GATE ARRAY
CIRCUIT
'
-S
:
Figure 7-2 (b). A/D Conversion Circuit
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