Xerox Phaser 6180, Service Manual, Page: 108 / 616

2-54 Phaser 6180 Color Laser Printer Service Manual
Theory of Operation
Color Registration Control
The printer uses a tandem electro-photographic system with Organic Photo
Conductor (OPC) Drums and direct transfer by the Transfer Belt. The images
are formed on the Drums of respective colors and they are overlapped to form
one image, and in this case, a color shift may occur. The color registration
control calculates how much the registration is shifted, and adjusts the Laser
Unit write timing.
The scan control adjusts all four colors in the process direction.
The color registration control is made from a change in inside temperature
and the print count at the execution of the process control. This control is
outlined as follows:
1. With no toner on the Transfer Belt, the output value of the ADC Sensor is
measured to determine the threshold value.
2. The patches for color registration control are generated on the Belt.
These patches are composed of 10 mm lines of K, C, K, M, K, and Y in
this order by the amount of four dispense counts, led by a black trigger.
3. The ADC Sensor reads the patch density.
4. The adjusting amount of registration shift is calculated from the threshold
value determined in step 1 and the patch density measured in step 3.
5. The Laser Unit write timing is changed from the adjusting amount of
registration shift.
10 mm
About One Half
Turn Of Belt
s6180-290
K
K
C
K
M
K
Y