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D. Document Size Identification
1.
Outline
The copier is equipped
with auto ljaper
selection
and
auto
reproduction
ratio
selection
mechanisms.
These mechanisms
call for identification
of the document size as
described below.
To enable
such
identification,
three
circuits are'attached
under the copyboard
glass (Figure
3-17);
when
the copyboard
cover is lowered,
the DC controller
checks
the output
of the&
circuits
twice, thereby
identifying
the document
as A3, A4, A4R, or
A5R.
The document
identification
circuit
causes its LED to emit light to illuminate the
document;
the
reflected
light
is then
checked
by the phototransistor,
whose
output is sent to the DC controller.
2.
Mechanism
The DC controller checks the output of
the document
identification
circuit when the
copyboard
cover is lowered to about 20 deg.
(SW4 ON) and about 1 set second after the
over
has been
lowered
to about
5 deg.
(SW5 ON).
The'DC
controller
recognized
the
presence
of
a document
if
the
two
measurements
are identical;
conversely,
it
recognizes
the absence of a,document
if the
measurements
are different.
1
DC conboller
PCB
DC controller PCB
I
(The thickness of the arrows represents the degree of the level.)
Figure 3-17
When a document
is present, the light
reflected by the document
is checked by the
document identification
circuit; therefore,
the
output of the circuit is constant regardless of
the angle of the copyboard
cover.
When
no document
is present,
the
output of the circuit from the first measure-
ment
is low or none
at all;
the output
of the circuit from the second measurement,
on the other hand, is high because the light
is reflected by the document
sheet.
If the
document
is too
thick
and,
therefore,
if only
SW4
goes
ON,
the
document
size is Identified
based
on the
current output level.
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