Dirt Sensor Control - Canon H1 Service Manual

2
Technology > Controls (Reader)

■ Dirt Sensor Control

● Overview
The machine changes the original read point or executes image correction depending on
the presence/absence of dust on the stream reading glass or the platen roller of the ADF to
prevent the dust from showing up in the output. These operations are carried out only when
the ADF is in use and, in addition, is closed.
[Control timing]
• At the end of a job
• Between sheets (for each reading of a sheet)
• At the start of a job (only when any of the following conditions is true.)
Dust detected at all points of detection at the end of the previous job
Dust detection failed to end normally at the end of the previous job (e.g., ADF opened)
Main power
Start key
switch ON
ON
STBY
WMUP
Dust detection
control
2 Technology > Controls (Reader)
1st 2nd
SCAN SCAN
Dust detection
Dust detection
control
control
F-2-17
[Particulars of control]
• At the end of a job (dust detection)
CCD checks the light reflected by the surface of the platen roller of the ADF at the read
point to detect the presence/absence of dust. Presence of dust is detected at points A, B,
and C in this order. The point where least dust is detected will be used as the read position
for the next job. The point selected here will be used as the read position for the next job.
• At the start of a job (dust bypass)
Presence of dust is detected at points A, B, and C in this order in the same manner as at
the end of the job. Read will take place at the point where least dust is detected.
A B C
F-2-18
2-10
2-10