Canon iR C6800 Series, Service Manual

Page: 292 / 1404

Chapter 7
7-26
PS2: patch image sensor
DCCON: DC controller
<Flow of Operations>
The following shows the flow of operations executed under this control:
F-7-21
7.4.8 Dhalf Control
0003-7416
The machine executes Dhalf control (image gradation correction control) to bring about an ideal set of gradation
characteristics.
When specific conditions exist, the main controller sends patch pattern data for individual colors (Y, M, C, Bk) to
the DC controller, which in response forms patch patterns of individual colors (Y, M, C, Bk) on the ITB.
Thereafter, the DC controller measures the density of the patch pattern using the patch image read sensor (PS2), and
sends the result to the main controller, where gradation correction is executed so that ideal halftone images may be
obtained.
The machine executes Dhalf control for the following:
when the power is turned on/when the toner cartridge is replaced*1
after jam recovery/after return from a sleep state*1
in response to changes in the environment
during execution of PASCAL
*1: if there is a history of 500 or more fullcolor prints with the temperature of the fixing upper roller being less than
100 deg C.
Starts up
Creates a patch pattern
Reads the patches
ITB
PS2
DC controller
Creates a D-max correction table (M, Y, C)
DC controller
Determines the developing bias (VDC)
Vdc
T
arget density
M3
M1
M2
M4 M5
0
EX: D-max Correction Table for M