Canon MF735C Series, Service Manual

Page: 27 / 381

Control of dust detection consists of the following two items:
• Dust detection correction
• Dust detection evasion
Execution Condition/Timing
Dust detection correction
During the period of time from the moment when the original of a stream reading job arrives just before the reading position
to the moment when reading of the original is completed (for each page)
Dust detection evasion
When a job starts
Description
Dust detection correction
If dust on the Stream Reading Glass is detected, the image is corrected to prevent the dust from being printed.
1. Before the original arrives, the White Plate is read through the Stream Reading Glass, and points where dust may exist
are detected.
2. The leading edge of the original is detected.
3. The detection results before and after the leading edge of the original appears on the Stream Reading Glass are
compared. If dust does not exist at the dust point detected in step 1, it is judged to be dust on the White Plate and dust
correction is not performed. If dust exists at the point detected in step 1, it is judged to be dust on the Stream Reading
Glass and dust correction is performed.
Dust detection evasion
If dust is detected when the last job paper is read, the reading position of the next stream reading job is changed in order to
avoid the dust.
The amount of adjustment for dust evasion is -0.5 mm (B), 0 mm (A), and +0.5 mm (C).
Each time dust is detected when reading the last paper of a stream reading job, the CIS moves to the three positions in the
order shown below.
A -> B -> C -> A ->
B A C
0.5 mm 0.5 mm
NOTE:
In the case of simultaneous duplex scanning models, this control is applied only to reading of the front side where the CIS can be
moved.
If any of the following conditions is detected 6 times in a row, it is judged that the Stream Reading Glass is soiled, and a message
prompting the user to clean the Stream Reading Glass is displayed on the Control Panel.
• Dust of 1 pixel or larger and smaller than 5 pixels is detected at 11 points or more.
• Dust of 5 pixels or larger is detected at 1 point or more.
Service Mode
• Adjustment of the image correction level at stream reading [front]
COPIER > OPTION > BODY > DFDST-L1
• Adjustment of the image correction level at stream reading [back]
COPIER > OPTION > BODY > DF2DST-L1
Additional Functions Mode/Menu
• ON/OFF of automatic correction at the time of dust detection
Menu > Adjustment/Maintenance > Adjust Image Quality > Remove Streaks from Orig. Scanning Area
2. Technical Explanation (Device)
18