This is a control that main controller PCB executes the gradation correction based on result of the halftone density measurement that is executed by DC controller

PCB.

After D-max control, DC controller PCB and main controller PCB execute the D-half control in the following procedure.

1. DC controller PCB measures the each color density detection pattern on ITB that is made by the appropriate primary charge bias that is determined at D-max

control and developing bias, and sends the density data to main controller PCB.

2. Main controller PCB executes the gradation correction to realize the ideal halftone image based on the data.

2.4.3.4 Color displacement correction control

This control is to correct the color displacement that appears due to the variation of laser scanner unit or toner cartridge.

The following objects are controlled by this color displacement correction.

- Write start position in main scanning direction

- Magnification in main scanning direction

- Write start position in sub scanning direction

When one of the following conditions is met, DC controller PCB controls the color displacement/density sensor and displacement sensor.

- At power ON

At power ON, Out-of-Register Colors Correction is suspended until the initial print process is completed and the machine is ready or until 15 min passes after

the power ON. The time setting can be changed from Option > Device Settings > Startup Settings in printer status window.

Startup Settings

Execute Later

Execute Immediately (Level 1)

Execute Immediately (Level 2)

- When closing the door after toner cartridge replacement

- After a specified sheet number printing (150 sheets)

- 60 minutes after the power is turned ON

- 240 minutes after the printing is completed, or 240 minutes after color displacement adjustment control execution

- If there is major environment change

MEMO:

- When the calibration is executed, sheet counter reading and elapsed time timer are cleared.

- Calibration is not executed in sleep mode.

The following is the sequences of this control.

1) DC controller calculates the degree of each color displacement by the color displacement detection pattern made on ITB and sends the color displacement infor-

mation to main controller.

2) Main controller controls the each color video signal according the color displacement data and adjusts the write start position in main scanning direction, the

magnification in main scanning direction and the write start position in sub scanning direction.

At printer engine side, DC controller PCB also controls the scanner motor speed to correct the color displacement in sub scanning direction.

Scanning magnification

This indicates the image size in the main scanning direction.

Since this machine is equipped with the independent photosensitive drum for each color, the photosensitive drum position differs due to the toner cartridge variation

and that leads to the laser wave length difference. Thus, image range differs depending on a color in main scanning direction so that the color displacement occurs

at the edge of the image.

2.4.4 Drum Cartridge

2.4.4.1 Developing roller engagement/disengagement control

The developing cylinder engagement/disengagement control engages the required developing cylinder with the photosensitive drum according to the print mode,

full-color mode or monochrome mode.

The necessary developing cylinder is engaged with the photosensitive drum only when required, preventing a deterioration of the drums and making maximum use

of the life.

The engagement/disengagement of the developing cylinder is controlled by the DC controller rotating the main motor and changing the direction of the developing

disengagement cam. The DC controller controls the developing cylinder state, whether engaged or disengaged, by counting the main motor rotation after it detects

the signal from the developing homeposition sensor.

All four colors' developing cylinders disengage from the photosensitive drums when the printer is turned on and when a print operation is completed. All four colors'

developing cylinders engage with the photosensitive drums when the full-color mode is designated. Only black's developing cylinder engages with the photosensi-

tive drum when the monochrome mode is designated.

The DC controller determines an abnormality of the developing cylinder engagement/disengagement function and notifies the main controller when it does not

sense the signal from the developing homeposition sensor for a specified period during the developing cylinder engagement/disengagement operation.

Performed 15 minutes later

Execute Immediately

T-2-3

Calibration

Performed 15 minutes later

Execute Immediately

Out-of-Register Colors Correction

Performed 15 minutes later

Execute Immediately

Chapter 2

0021-1317