In the horizontal scan direction, the document feed speed is changed depending on the magnification rate whether or not the image is enlarged or reduced. When

the magnification rate is 100% copy, the speed is 78.66 mm/sec. Data is not processed by the image processor PCB.

4.3.2 Dirt Sensor Control

4.3.2.1 Outline

The machine changes the document read position or corrects the read image depending on the presence/absence of dust on the stream reading glass or ADF platen

guide, thus preventing dust from showing up in the image.

[Control Timing]

- At job end

[Description of Control]

- At job end

The contact image sensor (CIS) checks the light reflected by the ADF platen guide surface at the read position for presence/absence of dust.

After job end, presence/absence of dust is detected three times. First presence/absence of dust is detected at position A. If no dust is detected at position A, presence/

absence of dust is detected twice. If no duct is detected three times, the document is read at position A. If duct is detected at position A, presence/absence of dust

is detected at B twice. If no duct is detected at position B, the document is read at position B. If dust is also detected at position B, presence/absence of dust is

detected at position C once. If dust is also detected at position C, the relevant message is displayed on the operation panel. If dust is also detected at position C, the

sensor returns to position A and the document is read.

If dust is detected a all positions A, B, and C at job end, a message prompting to clean the glass surface appears on the operation panel.

4-6

Shading

position

1.black shading/

white shading/

Original scan

Main power

Start key

switch

STBY