IMAGE PROCESSING 26 January, 2001
6-16
6.5.2 SBU (SENSOR BOARD UNIT)
The CCD converts the light reflected from the original into an analog signal. The
CCD line has 7200 pixels at a resolution of 600 dpi.
The CCD has two output lines to the analog processing ASIC, one for handling odd
and one for handling even pixels. The analog processing ASIC performs the
following operations on the signals received from the CCD:
1. Z/C (Zero/Clamp)
Adjusts the black level for even pixels to match the odd pixels.
2. Signal composition
Analog signals for odd and even pixels from the CCD are merged by a
switching device.
3. Signal amplification
The analog signal is amplified by amplifiers in the AGC circuit. The maximum
gains of the amplifiers are controlled by the CPU on the BICU board.
After the above processing, the analog signals are converted to 8-bit signals by the
A/D converter. This gives a value for each pixel on a scale of 256 shades of gray.
Then, this data goes to the BICU via the SIB.
IPU
SBU
CCD
BICU
SIB
Analog
Processing
ASIC
A/D
Converter
A/D
Converter
GA
Serial Driver
8 bit Serial Data
B004D510.WMF
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