Canon Color iR C3480, Service Manual

Page: 243 / 774

Chapter 7
7-20
F-7-24
MEMO:
This control creates the following 3 types of patch patterns.
- pattern for copy (64-patch for each color)
- character pattern (64-patch for each color)
- photo pattern (64-patch for each color)
7.3.7 D-half Control
0013-9668
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
The machine uses the main controller to execute gradation correction to enable ideal gradation characteristics.
1. Start-Up Timing
- when the drum unit is replaced with a new one
- during post-rotation executed every 1000 prints
- during execution of calibration (user mode)
2. Particulars of Control
In the presence of a specific condition, the main controller sends the patch data of individual colors (Y, M, C, Bk) to the DC controller, which in turn forms a patch
pattern of each color (Y, M, C, Bk) on the ITB. Thereafter, the DC controller uses the patch image sensor (UN14) to measure the patch pattern, and sends the result
back to the main controller, which executes gradation correction based on the data so that ideal halftone images may be obtained.
In this control, the machine also forms a reference patch for use by abridged D-half control, and stores the reference data for abridged D-half control collected from
Patch pattern formation
Patch reading
UN16
D-half correction table creation
(Y, M, C, Bk)
EX: PASCAL correction table for Y
Actual gradation
characteristics
Ideal gradation
characteristics
0
100
Density data(D-CON)
Data output(V-CON)
DC controller
Main controller
Density data output
100
Gradation characteristics
after correction
Ideal gradation
characteristics
0
100
Density data(D-CON)
Data output(V-CON)
100
Start-up
Patch pattern data output
Main controller
DC controller
Printing patch pattern data
(3 types) to paper
Reading the printed pattern
on reader unit
Y1
Y2
Y63Y64