168 Theory of operation ENWW
Color misregistration control
This controls the correction of color misregistration caused by the variation of cartridges and the
laser/scanner unit. In particular, this control corrects the following:
● Horizontal scan starting position
● Horizontal scanning scale
● Vertical scan starting position
The DC controller operates this control after a door is closed after replacement of a cartridge, or a
specified number of pages are printed after replacement of a cartridge, or a command is received
from the formatter.
The following is the sequence of this control.
1 The DC controller writes four colors’ misregistration detection patterns, the reference pattern
(right) and the pattern to be measured (left), onto the ITB.
2 The DC controller measures each color’s misregistration based on the positions of the patterns
detected by the misregistration detection (See Color misregistration control).
3 The measured information is then sent to the formatter.
4 The formatter controls each color’s VIDEO signals according to such information, making an
adjustment to the horizontal scan starting position, horizontal scanning scale, or scan starting
position.
A vertical color misregistration is also corrected by the DC controller, without communicating with
the formatter, through the speed control over the scanner motor in this printer. (See Color
misregistration control.)
In principle, the DC controller automatically sends a command to the formatter when the printer
meets the above conditions. However, when the above conditions are not met, the formatter can
send a command to the DC controller to execute this control.
Note Horizontal scanning scale: the size of the image in horizontal scanning. Every color has its own
photosensitive drum in each cartridge in this printer. The positions of each drum differ and the laser
beam lengths vary because of the variations among the cartridges; that is, the horizontal scanning
area depends on the color. This can cause a color misregistration at the edge of the image.
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