Canon Color iR C3480, Service Manual

Page: 242 / 774

Chapter 7
7-19
UN16: patch image sensor
MEMO:
To reduce down-time, the machine forms only one patch on the ITB. If, however, the measured patch density is outside the range of correction, it forms an additional
patch. If the density is still outside the range of correction for a second time, the machine continues until it has formed as many as 4 patches.
F-7-23
7.3.6 PASCAL Control
0013-9598
Color iR C3380G / Color iR C2880G / Color iR C3380i / Color iR C3380 / Color iR C2880i / Color iR C2880 / iR C3480 / iR C3480i / iR C3080 / iR C3080i / iR
C2550
This is the control for the stabilization of the image gradation density characteristic. It is executed when 'auto gradation correction $ full correction' of the user mode
is selected. The gradation density of the test-printed patch pattern is read by the reader, and the image density correction table is created. By executing this procedure,
the correction of the image gradation density characteristic varying due to the environmental change or the deterioration of photosensitive drum.
1. Timing for Start-up
At the time of calibration (while executing 'auto gradation correction $ full correction' of the user mode)
2. Control Description
When the specified conditions are satisfied, the main controller prints three kinds of the stored patch pattern (see MEMO) on paper. Service technician sets the test
print to the reader. Reader reads the gradation density of the patch pattern from the test print. After that, the main controller creates the image gradation density
correction table from the gradation density data of the patch pattern read by the reader. In this control, the gradation correction for all colors is executed regardless
of replaced drum cartridge.
3. Operation Flow
Start-up
Patch reading
UN16
DC controller
Black D-max correction
table formation
Vdc
Density
Bk1
0
Vdc
Density
Bk2
0
Target
Correction
range
Target
Bk1
Patch pattern formation
Developing bias determination
(VDC)
Yes
No
DC controller
Within correction range?
1st patch
2nd patch
4 patches max.
DC controller