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- E3
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E5400 -
6-8. JPEG encoder and decoder
Picture data are compressed and extended by JPEG
method.
7. Outline of Operation
When the shutter opens, the reset signals and the serial
signals (“TAKE A PICTURE” command) from the 8-bit
microprocessor are inputted to ASIC (IC101) and op-
eration starts. When the TG/SG drives the CCD, picture
data passes through the A/D and CDS, and is then input-
ted to the ASIC as 12-bit data. The inputted data passes
through the digital clamp and is inputted to SDRAM.
The AF, AE, AWB, shutter, and AGC values are com-
puted from this data, and three exposures are made to
obtain the optimum picture. The data which has already
been stored in the SDRAM is read by the CPU and color
generation is carried out. Each pixel, which was Ye,
Cy, Mg or Gr primary color data, is interpolated from
the surrounding data to produce R, G and B data. After
AWB and
γ
processing, matrix is generated to produce
Y, R-Y and B-Y. Aperture correction is carried out for
the Y signal, and the data is then compressed by JPEG
and is written in the card memory (compact
fl
ash).
When data is outputted to an external device, data is
taken out from the memory and outputted via USB.
When playback is done on the LCD and monitor, data is
transferred from the memory to SDRAM, and the pic-
ture data extended by the JPEG decoder is displayed on
the SDRAM display area.
8. LCD Block
The LCD display circuit is on the VF1 PCB, and is
composed of the LCD driver (IC171) and its peripheral
circuits.
The video signals from the ASIC are converted into
RGB signals by the LCD driver, and these RGB signals
and control signals which are outputted by the LCD
driver are used to drive the LCD panel. The RGB sig-
nals are reversed by 1H so that no DC component is
present in the LCD element. Two horizontal shift reg-
ister clocks drive the horizontal shift registers inside the
LCD panel and the RGB signals which are reversed by
1H are applied to the LCD panel.
As the difference in potential between COM (common
polar voltage: Fixed at AC) and RGB is larger, the LCD
elements are closed more securely. So, display is dark-
er. As the difference is smaller, the elements are opened
and display is brighter.
6. Circuit Description
6-1. Digital clamp
By subtracting the averaged value of the CCD optical
black section from the subsequent data, the black level
of the CCD output data are made uniform. The aver-
aged value of the CCD optical black section should be
the sum of the following two values: the value for the
previous line multiplied by the coef
fi
cient “k” and the
value for the current line multiplied by the coef
fi
cient
(k-1).
6-2. Signal processor
1.
γ
correction circuit
This circuit performs the
γ
correction to maintain a lin-
ear relationship between the light inputted to the camera
and the light outputted from the picture screen.
2. Color signal generation circuit
This circuit converts the CCD data into RGB signals.
3. Matrix circuit
This circuit generates the Y signals, R-Y signals and
B-Y signals from the RGB signals.
4. Horizontal/vertical aperture circuit
This circuit is used to generate the aperture signals.
6-3. AE/AWB and AF computing circuit
The AE/AWB carries out computation based on a
256-segment screen, and the AF carries out computation
based on a 11-segment screen.
6-4. SDRAM controller circuit
This circuit outputs address, RAS, CAS, CS and WE
data for controlling the SDRAM. It also refreshes the
SDRAM.
6-5. Communication control
1. SIO
This is the interface for the 8-bit microprocessor.
2. SIO for PIO/PWM/LCD
8-bit parallel input and output makes it possible to input
and output individually. It is possible to change 3-port
PWM output. It is prepared for 16-bit parallel output.
6-6. TG/SG
Timing is generated for 2 million/3 million/4 million/5
million pixels CCD control.
6-7. Digital encoder
It generates chroma signal from color difference signal.
