Shading - Canon imageFORMULA DR-G2140 Service Manual

CHAPTER 2 FUNCTION & OPERATION

3. Shading

The CIS unit and its slide mechanism are
assembled inside the reading unit.
The CIS unit is positioned in the docu-
ment reading position when the documents
are read. Since the scanner needs to read the
white reference on a surface of the reading
glass when determining the shading correc-
tion value, it slides the CIS unit. The guide
plate is assembled for protection of the white
reference.
Reading glass
Guide plate
2-12
Document side
Figure 2-203
Figure 2-204
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The position of the CIS unit when reading
an image and white reference is shown below.
This slide plate is driven by the shading
motor. Since the white reference is attached
on a surface of the reading glass, the reflec-
tion distances during image reading and white
reference reading can be made equal.
When the power is turned ON and when
scanning starts, this machine slides the CIS
unit and reads the white reference data to de-
cide the shading correction value.
White reference
CIS unit side
CANON DR-G2140/G2110/G2090 FIRST EDITION