3.5 WHITE PLATE SCANNING
There is a white plate [A] for auto shading, located on the exposure glass [B]
underneath the left scale. When this white plate is exposed, the output from
all the CCD elements in a line should in theory be equal, but actually they
are not, because of the following:
* Variations in sensitivity between elements of the CCD
* Variations in characteristics of lens and mirror reflectivity
* Loss of brightness toward the ends of the exposure lamp
To correct for this uneven output from the CCD elements, the light reflected
from the white reference plate is scanned. This is known as auto shading.
Auto shading is done every copy cycle at the scanner home position before
starting the first scan.
3.6 SCANNER IPU BOARD
The scanner IPU board processes the RGB signal received from the CCD
board and controls the following under directions from the main control board.
1. Controls the exposure lamp on/off switching and the voltage
2. Controls the speed of the scanner drive motor
3. Detects the original paper size
4. Controls on/off switching for the four fans
5. Supplies the clock signal for the CCD board
6. Detects the home position of the scanner unit
[B]
[A]
Detailed
Section
Descriptions
SCANNER UNIT
SM 2-33 A166/A187/A189
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