F. Measuring the
Density
1. Outline
The
has
exposure
mechanism, which
the DC component of
the development bias according to the density of the
document. the document uniform density, the
mechanism varies the DC omponent of the
development bias to enable reproduction of fog-free
copies.
2. Mechanism
The scanner moved forward about 70 mm from
the image leading edge with the scanning lamp kept
the
sensor reads the document density, and
the output sent to the DC controller.
Based
the output from the
sensor, the DC
controller
the DC component of the
opment bias.
N O T E : A
s e n s o r
Figure 3-30
3. Fteading the
Sensor Output
The
sensor
of a photodiode (Q702)
and operation amplifier (Q701); when the light
ceived by the photodiode
by the
ment) strong, the output
of the
operation amplifier low;
the other hand, if the
The DC controller reads the output
of the
sensor based
the zero-cross
(ZXDP) sent
by the lamp
Thelimitercircuitconsistsof
(2) anddiodes
and
to cut
output of 5 V or more to prevent
to the microprocessor (Q302).
1
be assumed; if the
output rises
the setting
of
it lowered to maintain the setting.
D C
P C B
I N C .
-
-
-
- -
-
-
-
P C B
Figure 3-31
C A N O N
J A N .
I N J A P A N
At,
Summary of Contents for NP-2120
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