Gestetner B147, Service Manual

Page: 483 / 1081

IMAGE PROCESSING
SM 6-25 B147/B149/B190
Detailed
Des
cription
s
6.4.2 SBU BLOCK DIAGRAM
Signal Processing
1. Signal Amplification
• Odd-pixel and even-pixel RGB analog signals from the CCD are amplified by
operational amplifiers.
2. Signal Composition
• The amplified signals (even-pixel and odd-pixel for each RGB color) are
combined by the MPX circuit after A/D conversion.
A/D Conversion
•
The analog signals (CCD output) are converted to 10-bit (1024 gradations) digital
signals.
White Level Correction
A white plate is on the back of the left scale. When you turn the switch on, the
scanner scans this plate to see the actual white level. To compensate the
difference between the actual white level and the ideal white level (target white
level), the CCD-gain control is conducted.
Others
The SBU controller exchanges the R and B signals if the original is scanned by
using ARDF.
Analog Amplifier
A/D Converter
CCD
SBU
Analog Amplifier
A/D Converter
Analog Amplifier
A/D Converter
SBU
Controller
R(B) O
E
O
E
O
E
G
B(R)
10 bit
10 bit
10 bit
Field
Memory
Field
Memory
ASIC
IPU
10 bit
10 bit
10 bit
R
G
B
8 bit
8 bit
8 bit
B146D929.WMF