Canon iR C2880 series, Service Manual

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Chapter 7
7-24
[1] Color displacement sensor A
C. Sub Scanning Write Start Correction
1. Particulars of Control
The machine forms a sub scanning position detection pattern of each color on the ITB, and compares the measurement (A) against the reference value (B) stored
in the DC controller to detect the displacement (C) of each color. If the result indicates the presence of color displacement in sub scanning direction, the machine
varies the timing at which writing starts in sub scanning direction.
F-7-32
[1] Color displacement sensor A
The machine uses Y as the reference when measuring color displacement and, therefore, does not make correction for the reference color.
D. Main Scanning Magnification Correction
1. Particulars of Control
The machine forms a main scanning magnification detection pattern of each color on the left and right edges of the ITB. Thereafter, it uses the difference (C) between
the measurement (A) taken at the left edge and the measurement (B) taken at the right edge to detect the magnification of each color. If there is a difference in main
scanning direction, the machine increases the number of pixels in main scanning direction.
F-7-33
[1] Color displacement sensor A
[2] Color displacement sensor B
Main scanning magnification correction control computes colour displacement correction values based on the partial magnification adjustment values for the image
main scanning direction. There are eight blocks for each of the four colours, Y, M, C and Bk, giving a total of 32 values, which are programmed in the service
mode when the device is installed.
Whenever the laser scanner unit is replaced, all 32 of the partial magnification adjustment values for the image main scanning direction (which appear on a label
affixed to new laser scanner units) must be entered into the following service modes, otherwise colour displacement will occur.
COPIER > ADJUST > LASER >FSLUT-Y 1 to 8 correction values for partial magnification correction Y blocks 1 to 8
COPIER > ADJUST > LASER >FSLUT-M 1 to 8 correction values for partial magnification correction M blocks 1 to 8
A
B
C
[1]
A B
C
[1] [2]