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2-8. DIGIT AL AF OPERATION
2-8-1 . Operation Instructions
The IRIS signal output from Pin @ of IC91 7 (CXA1 390AR)
is amplified by 09302 after increasing the low luminance
component is increased by 09301 .
The signal is divided into nignals of more than 200 kHz and
more than 600 kHz by 09304 and input to Pins @) and @
of the standard cell . These signals are selected together
with the AE signal mentioned later by the standard cell and
are then output to Pin ® .
These time-shared multiplex signals are band limited to 2.4
MHz by the LPF of L9303, C9361 and C9362, after which
the signals are converted into digital signals by the ND
converter in the standard cell and integrated in every area
as shown in Fig. 2-1 7.
The integrated the AF evaluation value is fed to IC932
(S87C51 FC) of the microprocessor and AF operation is
carried out based on AF evaluation value of focus zones 1
and 2. The selection of these focus zones is determined by
the microprocessor using fuzzy logic, and controlled so that
the focus is on the object in the centre of the screen.
Focus zone 2
2-9. DIGITAL AE (AUTO IRIS)
This system can control counter light or excessive light
conditions by controlling the iris, AGC and gamma level
based on the luminance level of each of six video areas.
The IRIS signal from Pin @ of IC91 7 is amplified at IC935
(NJM3414M). Immediately after this, it is input to Pin @ of
IC931 and clamped by a voltage at Pin @ , after which (1 V)
AE processing is carried out for a constant period of time by
time sharing with AF.
At this time, the signal is ND converted and integrated at
every area by the standard cell and becomes an amount
(evaluation value) indicating the luminance level of each
area. Microprocessor IC932 (S87C51 FC) receives the
evaluation value at the same timing as AF and judges
whether there is a counter light or excessive light condition
using fuzzy theory based on the characteristic that most
objects are placed in the centre of the frame. This
determines the compensation values for the iris, AGC and
gamma level which are output to Pins @ and @ (as PWM
data).
Focus zone 1
Fig. 2-1 7.
The IRIS signal is detected by 09322 and input to Pin @ of
IC935 (NJM341 4M), and is then compared with the refer
ence voltage input to Pin @ and the i ris coil is driven by the
voltage d ifference.
The PWM output of Pins @ and @ of the microprocessor
®
become I RIS, REF, AGC, REF and g amma CONT signals.
When Pin
of J9001 is Low, the digital AE function is
turned O FF, which produces a standard condition where
each compensation is not done.
2-1 0. AWB (AUTO WHITE BALANCE) CIRCUIT
In the AWB circuit, the picture frame is divided i nto 8 areas
in vertical and horizontal directions respectively (a total of
64 areas) . The video information for each area is analysed
by the microprocessor, and then the colour of the object is
assumed and chroma compensation is performed. B-Y and
R - Y signals from Pin s @ and @ of IC9 1 4 (CXA 1 391 R)
pass through 09021 , are amplified by 09331 and 09332,
and then input to Pins @ and @ of IC931 (LC97000A) of
the standard cell. They are clamped by a voltage at Pin @
and ND converted for each of the 64 areas, and are then
i nput to the microprocessor.
The microprocessor analyses brightness information, colour
level, hue and the area occupied by one colour, etc. and
determines the control amount for the AWB circuit. Then the
resultant control voltages are sent to Pins @ and ® of IC932
(S87C51 FC).
The signals are i nput to Pins @ and @ of IC91 4 (CXA 1 391 R)
as B and R GAI N control signals to control the white
balance.
2-1 1 . INTERNAL COMMUNICATION
The microprocessor IC932 is linked to the ND converter
IC934, to the EEPROM loaded in the lens, to the shutter
control terminal IC91 6 (CXA1 256R) and to IC351 inside the
system control block by a serial communication bus (SK,
SO, SI) common to all of them. Selection of the object of
communication is performed at the various ports for chip
selection (Pins @, <J) and ® of IC932 and Pin ® of IC931
(LC97000A)).
The input from the switches below is read inside the system
control block and then fed to the microprocessor IC932
(S87C51 FC) by the above - mentioned serial communication
method.
AF/M F selection switch
0
Zoom switch
o
NTSC/PAL operation selection switch
0
Auto wide reset operation switch
0
Camera modeNideo mode selection switch
°
Preset mode setting switches (setting switches for sports
0
mode, auto high speed shutter mode, close-up mode,
etc.)
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