When reading an original, the machine changes the point of reading or corrects image data in reference to the presence/absence of dust on the stream reading glass/

ADF platen roller, thereby avoiding the effects of dust on images. The machine executes this control only when the ADF is used and, in addition, when it is closed.

1. Timing of Control

(1) at the end of a job

(2) between sheets (each time a sheet is read)

(3) at the start of a job (only if any of the following is met)

(a) first job after power-on

(b) presence of dust at all points of detection at the end of the previous job

2. Particulars of Control

(1) At the End of a Job (dust detection)

The contact image sensor (CIS) checks the light reflected by the platen roller of the ADF at a point of reading to find out the presence/absence of dust. If the

presence of dust is detected, the contact image sensor moves to the next candidate point (2 times max.; A -> B -> C; B -> C -> A; or C -> A -> B).

The point identified will be used as the point of reading for the next job.

- For the control at the end of a job, the sensor will never move to point D.

- For the control at the end of a job, a message prompting cleaning of the glass surface will be indicated if an original is placed in the ADF while the presence

of dust has been detected at all points (A, B, C). The Start key is disabled until the message is cleared.

(2) At the Start of a Job (dust avoidance)

The same detection mechanism as used at the end of a job is executed; if the presence of dust is detected at all points (A, B, C), the sensor is moved to point D

for reading operation.

5-14

Original

sensor1

Main power

Start key

switch

WMUPR

STBY

Dust detection control

Copyboard glass

CIS HP