Canon imageRUNNER ADVANCE C255 Series, Service Manual, Page: 40 / 987

Reading Sensor
output
Original density
Standard White Plate
Characteristics
before correction
Target value
Measurement
value
Characteristics
after correction
White
Shading correction (ADF side)
Positional relationship between the CIS Reading Sensor and the Standard White Plate differs between at the Reader side and
at the ADF side. Therefore, when performing shading correction to the Reading Sensor at ADF side, the correction value stored
in advance needs to be taken into consideration. This corrects difference in image density caused by positional relationship.
■ Color Displacement Correction Processing in Vertical Scanning Direction
Color displacement correction control in the vertical scanning direction is used to correct displacement of R, G, and B by shifting
the pixels in the vertical scanning direction (by less than 1 pixel) to align the red and blue images with green when the scanned
R, G, and B images are not accurately overlapped at color scanning.
Example: A scanned image of a black line where red is displaced upward and blue is displaced downward with respect to green
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As for the color displacement correction value in the vertical scanning direction, there are 6 types of reader scans as shown below.
These correction values have been adjusted at the time of shipment, and stored as service mode values. (In COPIER > ADJUST
> CCD)
• COPIER > ADJUST > CCD > 100-RG
• COPIER > ADJUST > CCD > 100-BG
• COPIER > ADJUST > CCD > 100DF-RG
• COPIER > ADJUST > CCD > 100DF-GB
• COPIER > ADJUST > CCD > 100DF2GB
• COPIER > ADJUST > CCD > 100DF2RG
When a job is started, color displacement correction processing is performed based on the saved color displacement correction
values.
■ Gain Correction of the Reading Sensor Output, Offset Correction
The analog video signal output from the Reading Sensor has its amplification ratio aligned with a fixed value (gain correction)
and has its output voltage when there is no incident light aligned with a fixed value (offset correction).
Related service mode
• Adj CIS gain level:front,clr mode,300dpi:
COPIER > ADJUST > CCD > GAIN-CL0
• Adj CIS gain level:front,clr mode,600dpi:
COPIER > ADJUST > CCD > GAIN2CL0
• Adj CIS gain level: back,clr mode,300dpi:
COPIER > ADJUST > CCD > GAIN3CL0
• Adj CIS gain level: back,clr mode,600dpi:
COPIER > ADJUST > CCD > GAIN4CL0
2. Technology
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