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READING SECTION
4. IMAGE DATA PROCESSOR
After the document is read by the contact sensor, the resulting image data
undergoes various image data processing at the system controller.
The following shows a block diagram outlining the content of image pro-
cessing.
4.1
Various Image Data Processing
After the image data has been read, it undergoes various data processing
before it is sent. The following describes these processing types.
• Pre-scan
By the pre-scan, the base color of the white mylar sheet attached to the
document feed section on the contact sensor is read for one line at the start
of document reading so that the unevenness compensation values for the
output contact sensor are stored to shading memory.
• DC generation
DC generation matches the black side reference voltage of the A/D conver-
sion circuit with that of the contact sensor.
• AGC circuit
AGC (Auto Gain Control) adjusts for unevenness in the reading system
(LED, white mylar sheet and contact sensor) to prevent the maximum
value exceeding the maximum value of the A/D conversion circuit when
the background color of the white mylar sheet is read for one line.
3–14
Contact sensor
Brightness data
(analog signal)
ABC circuit
D/A
conversion
circuit
AGC
DC
generation
circuit
Shading
memory
Image processing section
A/D
conversion
Gray scale data
circuit
(digital signal)
Fig. 3-17 Block Diagram
GENESIS
(UHQ)
Binary data
To coding/decoding
processing section
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