Detecting Dust In Stream Reading Mode - Canon iR8500 Servise Manual

CHAPTER 2 NEW FUNCTIONS

2.1.8 Detecting Dust in Stream Reading Mode

In addition to the stream reading position, the machine has six reading points at intervals
of 0.5 mm (six each for small-size and large-size sheets) used to avoid areas where dust may
exist. In all, there are seven reading points for small-size and seven for large-size.
Normally, stream reading takes place at the same point as in the GP605 (iR600). If dust is
found, the point of stream reading is changed to avoid reproducing the dust in images. At
each end of a stream reading job, the ADF belt is rotated idly to execute stream reading; if a
black line is detected, the presence of dust will be assumed.
When the presence of dust is detected, the present stream reading point is cleared, and
dust detection is executed by returning to the point of reference on the left edge. If dust is
detected, the stream reading position is shifted by a single point (= 0.5 mm) to the right, and
dust detection is executed once again. If no dust is detected at the new point, the selected
stream reading point will be used.
If, however, dust is detected also at the new stream reading point, dust detection is ex-
ecuted once again after a shift to a new point. If dust is detected at all seven points, a mes-
sage to this effect will be indicated: "The platen glass is dirty." The message will remain un-
til the ADF is opened and the copyboard glass is cleaned; while the message remains, the
machine will operate in fixed reading mode only.
Dust
Shows as a
black line
2-12
F02-201-06
COPYRIGHT© 2001 CANON INC.
3 mm (7 points)
2000 2000 2000 2000 CANON iR8500 REV.0 MAR. 2001