Image Processing - Canon imageRUNNER ADVANCE C255 Series Service Manual

Control timing
Dust detection
• At job completion
Dust evasion
• When a job starts
Control description
At job completion (dust detection)
The Reading Sensor performs dust detection at a reading position. When it detects any dust, the sensor is moved to the
position B if the sensor position is A, or to the position C if the position is B. This position will be the reading position for the
next job.
At the start of a job and paper interval (dust evasion)
The Scanner Unit does not move.
Reading is performed at the position determined by the control performed at job completion or at the start of a job, and image
correction is performed if dust is detected at that position.
Related service mode
• Adj dust detect level: ppr intvl, DADF:
Service mode > COPIER > OPTION > IMG-RDR > DFDST-L1
• ON/OFF dust detection: ppr intvl, back
Service mode > COPIER > OPTION > IMG-RDR > DF2DSTL1

Image Processing

The functions of the PCB related to image processing are shown below:
• Main Controller PCB
Shading correction (executed per job)
Color displacement correction in vertical scanning direction
• Scanner Unit PCB
Scanner Unit drive, analog image processing, A/D conversion
Image processing is performed by the Main Controller PCB for each line of the images. The main functions are indicated below.
Main Controller PCB
• Shading correction
• Color displacement correction in vertical scanning direction
Scanner Unit PCB (in the Scanner Unit)
• Scanner Unit Drive
• Gain correction of the Reading Sensor output, Offset correction
Main power
Start key
switch ON
ON
WMUP STBY
Dust avoidance
C
1st 2nd
SCAN SCAN
control
B A
27
Dust detection
control
2. Technology