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F.
Measuring
the Document
Density
1.
Outline
The copier
is equipped
with
an automatic
density
control
(AE) mechanism,
which
con-
trols the DC component
of the developing
bias
to suit the density
of the document.
As long
as the
document
is uniform
overall,
copies
free
of fogging
can be made
by varying
the
DC component
of the developing
bias.
The AE sensor
is mounted
inside
the lens
unit and consists
of a photodiode
and opera-
tion amplifier.
2.
Mechanism
During the initial
rotation
(INTR), the scan-
ning
lamp
goes
ON, and the
scanner
moves
forward
about
12 cm and reverses.
The micro-
processor
on
the
DC
controller,
while
the
scanner
moves
in reverse,
reads the output
of
the AE sensor
80 times at intervals of 1 mm.
The area measured
at the time is as shown
in
Figure 3-20.
1
100mm
Figure 3-20
Area Measured
The microprocessor
calculates
the average
of the density
data of the 80 points
and con-
trols the DC component
of the developing
bias
based on its result.
3.
Adjustment
The
following
adjustment
is
performed
when
the
DC controller
or AE sensor
is re-
placed.
1) Turn the power
OFF, open the copier,
and
remove
the drum unit.
.
Cover the drum
as soon as it is out of
.
Do not leave finger
prints
or scratches
Remove
the
upper
front
cover,
and close
the, copier.
Turn the power
ON, and open the delivery
unit cover.
Place a blank
sheet
of paper
(copy
paper)
on the copyboard,
and close the document
cover.
Hold the
REDUCTION/ENLARGEMENT
and
ZOOM
MODE
keys
down,
and
close
the
delivery
unit cover.
.
The copier enters the AE adjustment
mode.
.
The count
is '00'.
6)
Select
the
DIRECT copy
mode,
and press
the COPY START
key.
*
The scanning
lamp goes ON, and the scan-
ner moves
forward
to the copy paper.
.
The
count
indicates
the
output
of the
AE
sensor
read by the microprocessor.
7)
Turn VRIOI
on the DC controller
until the
count
is '55'.
Note:
The problem
detection
circuit
of the lamp re-
gulator
will be activated
if the scanning
lamp
'--
remains
ON for
15 to' 30 seconds
to turn the
lamp
OFF. If the
lamp
goes
OFF before
the
_
count
indicates
'55'.
turn the
power
OFF and
ON, and repeat step 3) and onward.
8)
Press the CLEAR/STOP
key.
9)
Turn the power
OFF and ON.
Note:
See
Figures
3-21
and
3-22
for the
relation-
ship
between
the
count
indication
and
the
input of the microprocessor
or the DC compo-
nent of the developing
bias.
5v
ov
Figure 3-21
Figure 3-22
3-18
COPYRIGHT
01988
CANON INC.
CANON'NP-1010
AEY.0 OEC. 1988 PAINTED
IN JAPAN IIMPAIME
AU JAPDN)
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