Operation; Idc Sensor Led Intensity Control; Max. Density Control; Gamma Correction Control - Konica Minolta bizhub c450 Service Manual

Theory of Operation Ver. 1.0 Mar. 2005

22.2 Operation

22.2.1

IDC Sensor LED intensity control

• Controls changes in characteristics due to change with time and contamination of the
IDC Sensor, part-to-part variations in the sensors, and change of environment.
• The intensity (current value) of the LED is adjusted on the surface of the Transfer Belt, on
which no toner sticks (background level).
22.2.2

Max. density control

• The developing bias (Vdc) is adjusted to control changes in the solid density resulting
from variations in developing characteristics and LED intensity, variations in sensitivity of
the PC Drum, and changes in the environment, durability, and the amount of charge in
toner.
• Patterns are produced on the surface of the Transfer Belt and the IDC Sensor detects the
amount of toner sticking to them.
• The correction data appropriate for each color is selected based on the correction data
with four different levels for each color.
• The developing bias and grid voltage values that result in the maximum density are cal-
culated from the detected data and stored in memory.
• Thereafter, the grid voltage (Vg) value, including the background margin adjustment
value, is calculated and stored in memory.
22.2.3

Gamma correction control

• The intensity of LED in all gradation levels is adjusted to correct changes in gradation
characteristics to a linear one. The changes in gradation characteristics are caused by
variations in the PC Drum sensitivity and developing characteristics and changes with
time and in environment.
• Patterns are produced on the surface of the Transfer Belt and the IDC Sensor detects the
amount of toner sticking to them.
• The correction data is calculated using the density measurements of different
Gamma
gradation levels. The optimum LED intensity is set for each of the different gradation lev-
els.

22.3 Operation timing

Mode
Mode 1 Reset + Stabilizer mode; a new IU is detected; a new Transfer Belt Unit is detected
Stabilizer mode; Left Door is opened and closed; Front Door is opened and closed (IU
Mode 2
removed and reinstalled)
At the end of a print cycle making a given number of printed pages*1; Power Switch is
turned ON; at the end of a print cycle following reset from Sleep; at the end of a print
Mode 3
cycle following an event, in which the interior temperature upper limit threshold value
is exceeded
Mode 4 At the end of a print cycle making a given number of printed pages
Mode 5 Gradation correction
*1: Vg and Vdc are readjusted if the gamma correction data falls outside a predetermined
range during the last image stabilization control.
22. Image stabilization control
Operation Timing
101