Canon ImageCLASS MF4690, Service Manual

Page: 43 / 182

Chapter 3
3-3
3.2 Various Control
3.2.1 Dirt Sensor Control
3.2.1.1 Outline
0016-1824
The machine changes the original read position or corrects the read image depending on the presence/absence of dust on the stream reading glass or ADF platen
roller, thus preventing dust from showing up in the image. This control is performed only when the ADF is used and it is closed.
[Control Timing]
- At job end
F-3-2
[Description of Control]
- At job completion:
The contact sensor (CS) detects the reflecting light from the surface of the ADF platen guide at scanning position to judge if there is dust at the point.
After the job is complete, dust detection is performed three times. First the detection is performed at "A" position and if there is no dust, then it is performed twice
more. If no duct is detected for three times, the document is scanned at "A" position. In case the dust is detected at "A" position, it moves to "B" position to perform
dust detection twice. If no dust is detected at "B" position, the document is scanned at "B" position. In case the dust is also detected at "B" position, it moves to "C"
position to perform dust detection once. In case the dust is also detected at "C" position, it returns to "A" position to scan the document.
- In the control at job completion, if dust is detected at all three positions (A/B/C), a message is displayed on the control panel to encourage cleaning of glass surface.
F-3-3
The original is read at the position determined at job end or start. If presence of dust is detected there, the read image is corrected.
Main power
switch
ON
Dust detection control
Dust detection control
STBY WMUPR
Start key
ON
1st
SCAN 2nd
SCAN
Dust detection control
Stream
reading glass
Lens
LED
Contact sensor
Platen guide
0.5mm 0.5mm
A B C