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I
OPERATIONS
AND
TIMING!
F.
Document
Density
Measurement System
1.
Outline
There
is
an
automatic
density
adjustment
(AE)
system which
adjusts
the
DC
component
of
the developing bias
to suit
the
density
of
the
original.
If
the density
of
the
original
is
more
or
less uniform,
the
AE
function varies the
DC
component
of
the
developing
bias
to suit
the density
of
the
original,
so
that
copies
of
the correct density
will
be made.
2.
Operation
The
scanner
moves
forward approxi-
mately
70mm
past the leading
edge
of
the
original
and
stops momentarily.
The
scanning lamp goes
ON
for
approximately
one
second,
the
image
density
is
read by the
AE
sensor,
and
the
sensor
output
is
interpreted
by
the
DC
controller.
The
DC
controller
then
adjusts the
DC
component
of
the developing bias
accordingly.
3.
Reading
the
Output
of
the
AE
Sensor
The
AE
sensor
consists
of
a photodiode
(Q702)
and
an
operational
amplifier
(Q701).
If
the strength
of
light
striking
the
photodiode
is
high,
the output voltage (AE)
of
the
amplifier
will
be
small.
If
the
amount
of
light
is
small,
the output voltage
will
be
large.
The
DC
controller
reads
the output
at
a
certain
time
after
the zero-cross
signal
(ZXDP)
is
received from the
DC
power
supply.
The
data representing the adjusted
AE
reference/slope values
are written
to
EEPROM
when
'CD'
or
'CI'
is
used
in
the
service
mode.
For
reference:
B6size
Approx.
A
is
the
position
of
the
AE
sensor
A
PP
rox
-
25mm
25mm
Figure 3-23
AE
sensor
PCB
DC
controller
PCB
COPYRIGHT©
1992
CANON
INC.
Figure 3-24
CANON
NP-15S0
REV.0
JAN.
1992
PRINTED
IN
JAPAN
(IMPRIME
AU
JAPON]
3-25
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