User Guide

The DC controller controls the color misregistration unit under the following conditions:
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At power on or door close after cartridge replacement
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After job completion in every specified number of printings
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At a command from the formatter
The following is the operational sequence of the color misregistration corrective control:
1. The DC controller forms two pattern images for color misregistration detection with four colors
on the ETB when the color misregistration corrective control starts. The two pattern images are
the same pattern, one formed on the left side and the other on the right side.
2. The DC controller measures the position of each pattern image and calculates the
misregistration amount of each color by controlling the color misregistration unit.
3. The calculated misregistration information of each color is sent to the formatter.
4. The formatter controls each color’s video signals according to this information and optimizes the
main-scanning start position, the main-scanning scale, and the sub-scanning start position.
The color misregistration in sub-scanning direction is corrected at printer engine side by the DC
controller controlling the speed of the scanner motor.
NOTE Horizontal magnification is the size of the image in the horizontal direction. Every
color has its own photosensitive drum in each cartridge in this MFP. The positions of each
drum differ and the laser beam lengths vary because of the variations among the cartridges,
so the horizontal scanning area depends on the color. This causes a color misregistration at
the edge of image.
Color misregistration detection
In this MFP, the positions of each color’s misregistration pattern images formed on the ETB are
detected to measure the misregistration amount. The DC controller controls the color misregistration
unit during the foregoing color misregistration corrective control. The color misregistration unit is
placed under the ETB and consists of two detection sensors, each one having a light emitter (LED)
and a light receiver (PD).
The following is the operational sequence of the color misregistration detection.
1. The DC controller allows the LED to emit light by sending the LED DRIVE signal when the color
misregistration detection starts.
2. The ETB reflects the light from the LED and the PD in the color misregistration sensor receives
the light. This reflected light intensity differs depending on whether the light is reflected from the
area of toner.
3. The light receiver converts the received light intensity into voltage and sends it in the form of the
color misregistration signal to the DC controller.
4. The DC controller detects the positions of the pattern images according to the timing of the color
misregistration signal.
Figure 5-31 Color misregistration detection on page 190 illustrates this process.
ENWW Image formation system 189