Canon FACSIMILE BASIC 2000 Service Manual page 52

GENERAL DESCRIPTION OF A FACSIMILE
2.1.2 Flat-bed scanning
By this scanning method, a photosensor comprising linearly arranged sen-
sors is moved in the
document itself is moved while being scanned by the photosensor.
By this method, the required number of photosensors for reading a single
line in the vertical scanning direction is moved to read a single line of the
document, and the reading position is moved one line at a time in the
zontal scanning
ods of movement in the horizontal direction: movement of the document or
movement of the photosensor itself.
CCD image sensors and contact sensors are two types of photosensor used
in flat-bed scanning.
(1) CCD image sensor system
Though the CCD image sensor itself is small, the optical path up to the
document must be lengthened, which makes CCD image sensors unsuit-
able for downsizing of reading sections. Nevertheless, this system has the
advantage over a contact sensor as its reading speed is faster than that of a
contact sensor, and enlargement and reduction processing is performed
mechanically. For this reason and for the fact that it demonstrates little
image deterioration, this system is widely used on large-size machines
even now.
2–16
vertical scanning
direction to read the entire document. There are two meth-
Document
Document feed
direction
Document reading direction
The CCD image sensor reads one horizontal scanning line at a time.
Fig. 2-14 Flat-bed Scanning (CCD image sensor system)
direction to read the document or the
Fluorescent lamp
Lens
hori-
CCD image sensor