Operation Outline; Lcd Block - Epson PhotoPC 850Z Service Manual

EPSON PhotoPC 850Z

2.2.2.2 Operation Outline

When the shutter opens, the reset signals (ASIC and CPU) and the serial
signals ("Take a picture" commands) from the 4-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, or B 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 JPEG and is then written to card memory
(smart media).
When data is to be output to an external device, the data is taken from the
memory and output via the USART. When played back on the LCD and
monitor, data is transferred from memory to the SDRAM, and the image is then
elongated so that it is displayed over the SDRAM display area.
Operating Principles

2.2.2.3 LCD Block

While monitoring, YUV conversion is carried out for the 10-bit CCD data which
is input from the A/D conversion block to the ASIC and is then transferred to
the DRAM so that the CCD data can be displayed on the LCD.
The data which has accumulated in the DRAM is passed through the NTSC
encoder, and after D/A conversion is carried out to change the data into a Y/C
signal, the data is sent to the LCD panel and displayed.
If the shutter button is pressed in this condition, the 10-bit data which is output
from the A/D conversion block of the CCD is sent to the DRAM (DMA transfer),
and after processor, it is displayed on the LCD as a freeze-frame image.
During playback, the JPEG image data which has accumulated in the flash
memory is converted to YUV signals, and then in the same way as during the
monitoring, it is passed through the NTSC encoder, and after D/A conversion is
carried out to change the data into a Y/C signal, the data is sent to the LCD
panel and displayed.
The two analog signal (Y/C signals) 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 horizontal shift registers
inside the LCD panel so that the 1H transposed RGB signals are applied to the
LCD panel. Since the LCD closes more as the difference in potential between
the COM (common polar voltage: fixed at DC) 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 becomes brighter.
Operating Principles of Circuit Boards
Revision A
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