Nikon Coolpix 5700 Repair Manual page 37

1-2. CP1 & VF1 CIRCUIT DESCRIPTION
1. Circuit Description
1-1. Digital clamp
The optical black section of the CCD extracts averaged
values from the subsequent data to make the black level
of the CCD output data uniform for each line. The
optical black section of the CCD averaged value for
each line is taken as the sum of the value for the
previous line multiplied by the coefficient k and the
value for the current line multiplied by the coefficient
1-k.
1-2. Signal processor
1. γcorrection circuit
This circuit performs (gamma) correction in order to
maintain a linear relationship between the light input to
the camera and the light output from the picture screen.
2. Color 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 and vertical aperture circuit
This circuit is used gemerate the aperture signal.
1-3. AE/AWB and AF computing circuit
The AE/AWB carries out computation based on a
64-segment screen, and the AF carries out computations
based on a 6-segment screen.
1-4. SDRAM controller
This circuit outputs address, RAS, CAS and AS data for
controlling the SDRAM. It also refreshes the SDRAM.
1-5. Communication control
1. SIO
This is the interface for the 8-bit microprocessor.
2. PIO/PWM/SIO for LCD
8-bit parallel input and output makes it possible to
switch between individual input/output and PWM
input/output.
1-6. TG/SG
Timing generated for 2 million/3 million/4 million/5
million pixels CCD control.
1-7. Digital encorder
It generates chroma signal from color difference signal.
1-8. JPEG encorder and decorder
It is compressed and elongated the data by JPEG
system.
2. Outline of Operation
When the shutter opens, the reset signals (ASIC
(IC102) and CPU (IC101)) and the serial signals ("take
a picture" commands) from the 8-bit microprocessor
are input and operation starts. When the TG/SG drives
the CCD, picture data passes through the A/D and CDS,
and is then input to the ASIC as 10-bit data. The AF,
AE, AWB, shutter, and AGC value are computed 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 is interpolated
from the surrounding data as being either Ye, Cy, Mg
and Gr primary color data to produce R, G and B data.
At this time, correction of the lens distortion which is a
characteristic of wide-angle lenses is carried out. After
AWB and γ processing are carried out, a matrix is
generated and aperture correction is carried out for the
Y signal, and the data is then compressed by the JPEG
method by (JPEG) and is then written to card memory
(compact flash).
When the data is to be output to an external device, it is
taken data from the memory and output via the UART.
When played back on the LCD and monitor, data is
transferred from memery to the SDRAM, and the data
elongated by JPEG decorder is displayed over the
SDRAM display area.
3. LCD and EVF Block
LCD Block is in the VF1 board, and it is constructed by
LCD driver (IC171) and around circuits.
The video signal (Y color difference signal) from the
ASIC are converted into RGB signals by the LCD
driver, and these RGB signals and the control signal
which is output by the LCD driver are used to drive the
LCD panel. The RGB signals are 1H transposed so that
no DC component is present in the LCD element, and
the two horizontal shift register clocks drive the hori-
zontal shift registers inside the LCD panel so that the
1H transposed RGB signals are applied to the LCD
panel. Because the LCD closes more as the difference
in potential between the COM (common polar voltage)
and the R, G and B signals becomes greater, the display
becomes darker; if the difference in potential is smaller,
the element opens and the LCD become brighter.
Also, EVF Block is in the CP1 board, and it is con-
structed by EVF driver (IC801) and around circuits.
The operation is the same as the LCD block.
- E3 ･ E5700 -
VAA11801-R.3578.A