Gestetner A265, Service Manual

Page: 58 / 855

IMAGE PROCESSING
A265/A267 2-6 SM
2.2.2 SBU (SENSOR BOARD UNIT)
The CCD converts the light reflected from the original into an analog signal. The
CCD line has 7,450 pixels and the resolution is 600 dpi (23.6 lines/mm).
The CCD has two output lines, for odd and even pixels, to the analog processing
IC. 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
BICU board.
After the above processing, the analog signals are converted to 8-bit signals by the
A/D converter. This will give a value for each pixel on a scale of 256 grades. Then,
the digitized image data is sent to the BICU board.
S B U
I P U
BICU
Analog
Processing IC1
A/D 1
8 bit data
Analog
Processing IC2
A/D 2
8 bit data
E
G A
CCD
O
A265D501.WMF
CÓPIA NÃO CONTROLADA
CÓPIA NÃO CONTROLADA