Correcting Image Displacement; Outline - Canon imagerunner C5180 Service Manual

8.3.5 Correcting Image Displacement

8.3.5.1 Outline

The following factors can displace images of individual colors:
- displacement of the photosensitive drum caused by replacement of the drum unit/toner container
->displacement in sub scanning direction
- displacement of laser path caused by replacement of laser unit
->displacement/angle in main scanning direction
- displacement in laser path length caused by changes in temperature inside machine
->variation in magnification
To correct the discrepancies in images, the machine executes corrective control for image position; it detects
displacement in color by forming a pattern of a specific color on the transfer belt and reading it against the
correct position.
Detecting displacement in color
• Forms an image position correction pattern on the transfer belt (direct transfer).
• Reads the individual pattern (of different colors) using the pattern reader
photo sensors.
• Identifies displacement in color with reference to the pattern signals in the
DC controller.
Displacement in sub scanning
direction
Displacement in main scanning
direction
Angle in main scanning
direction
Discrepancy in reproduction
ratio in main scanning direction
corrects the write start position in
sub scanning direction.
corrects the start position in main
scanning direction.
corrects the laser path inside the
laser unit.
corrects image data generation timing
in main scanning direction
F-8-13
Chapter 8
8-15