D-Half Control - Canon iR C3380 series Service Manual

Chapter 7
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

/ / / / iR C3380i / iR C3380 / iR C2880i / iR C2880
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
UN14. (See Notes.)
The machine executes gradation correction for all colors, regardless of which drum unit may have been replaced.
7-18
EX: PASCAL correction table for Y
Actual gradation
characteristics
Y63 Y64
100
Ideal gradation
characteristics
Y2
Y1
100
0
Data output(V-CON)
100
Ideal gradation
characteristics
Gradation characteristics
after correction
100
0
Data output(V-CON)
Start-up
Main controller
Patch pattern data output
DC controller
Patch pattern formation
Printing patch pattern data
(3 types) to paper
Reading the printed pattern
on reader unit
Patch reading
DC controller
Density data output
Main controller
D-half correction table creation
(Y, M, C, Bk)
F-7-24
UN16
0013-9668