Canon imageRUNNER ADVANCE C255 Series, Service Manual, Page: 77 / 987

Control timing
• During installation and when replacing the Drum Unit
• At last rotation on a specified print basis (1000 sheets or more)
• At last rotation when PASCAL Control is executed
Control description
1. The Main Controller PCB outputs patch data in each color (Y, M, C, and Bk) to the DC Controller PCB.
2. The DC Controller PCB forms a patch pattern of each color (Y, M, C, and Bk) on the ITB from this data.
3. The DC Controller PCB measures the patch pattern using the Registration Patch Sensor Unit (Front) (UN31) and Registration
Patch Sensor Unit (Rear) (UN32) and the result is returned to the Main Controller PCB.
4. Based on the data above, the Main Controller PCB executes gradation correction to obtain the ideal halftone image.
NOTE:
The following 3 types of patch patterns are formed with this control:
• A pattern for copy (9 patches for each color)
• A pattern for text priority (8 patches for each color)
• A pattern for photo priority (9 patches for each color)
■ ARCDAT Control (Automatic and Reciprocal Color Density Adjustment
Technology)
While reducing downtime, the ideal gradation characteristics are realized.
Control timing
• When replacing the Drum Unit
• At paper interval on a specified print basis (80 sheets or more)
• At last rotation on a specified print basis (30 sheets or more)
• At last rotation for PASCAL Control or D-half Control
Control description
1. The Main Controller PCB outputs patch data in each color (Y, M, C, and Bk) to the DC Controller PCB.
2. The DC Controller PCB forms the patch pattern of each color (Y, M, C, and Bk) on the ITB.
(Total of 12 patterns: 3 patch patterns for each color)
3. The DC Controller PCB measures the patch pattern using the Registration Patch Sensor Unit (Front) (UN31) and Registration
Patch Sensor Unit (Rear) (UN32) and the result is returned to the Main Controller PCB.
4. The Main Controller PCB compares this measured data with the reference data for ARCDAT control that has been backed
up. The difference by comparison is reflected to the D-half result as the offset value.
■ Color Displacement Correction Control
It is a control to correct color displacement caused by uneven radiation with the Laser Scanner Unit or uneven rotation of the
drum or the ITB.
Patch
ITB Unit
Short patch pattern
Long patch pattern
Medium patch pattern
Registration Patch
Sensor Unit (Rear)
(UN32)
Registration Patch
Sensor Unit (Front)
(UN31)
Patch
ITB Unit
Registration Patch
Sensor Unit (Rear)
(UN32)
Registration Patch
Sensor Unit (Front)
(UN31)
Startup timing
• Whether to execute this control is determined by the status of the host machine at power-on or recovery from sleep mode.
2. Technology
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