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June 30, 1998
2.3.2 SBU
O
E
The CCD converts the light reflected from the original into an analog signal. The
CCD line has 5,000 pixels and the resolution is 400 dpi (15.7 lines/mm).
The CCD has two output lines, for odd and even pixels, to the analog processing
IC. There are two analog processing ICs; one handles odd pixels and the other
handles even pixels. The analog processing IC performs the following operations
on the signals from the CCD.
1. Z/C (Zero Clamp):
Adjusts the black level reference for even pixels to match the odd pixels.
2. Signal Amplification
The analog signal is amplified by operational amplifiers in the AGC circuit. The
maximum gains of the operational amplifiers are controlled by the CPU on the
SBICU board.
After the above processes, 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 grades. Then,
this data goes to the SBICU board. Two 8-bit signals are sent to the SBICU board.
SBU
Analog
A/D 1
Processing IC1
Analog
A/D 2
Processing IC2
2-21
8 bit data
G A
8 bit data
IMAGE PROCESSING
SBICU
IPU
A229D579.WMF
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