Canon NP6012 Service Manual page 85

Il. Measuring the Density of
the Original (AE)
1. Outline
The copier is equipped with an automat-
ic density adjustment (AE) mechanism which
adjusts the DC component of the developing
bias. As long as the original has an even
overall density, the AE mechanism ensures
the generation of copies without fogging by
varying the DC component of the developing
bias to suit the density of the original.
The copier's AE mechanism does not
execute an AE scan; rather, it measures the
density of the original during initial rotation at
the scanner home position; for this reason,
the copying speed remains the same in both
AE and non-AE modes.
Figure 3-322 shows the circuit that con-
trols the measurement of the density of origi-
nals.
Copyboard glass
AE sensor
ls]
s
Scanning lamp
rs
!
'
aie.
b=
2 —
6
:
i
Photosensitive)
Developing
Ww
drum
cylinder
i
_
DC bias
Developing DC bias
edt
—|
Microprocessor
circuit
.
_|Developing DC bias
Microprocessor | peyeloping
.
on signal (DVDCON) DC bias
control signal
z AE
_AE signal
(DCBPWM)
|
Composite power supply PCB
Amolifier c circuit
DC controller PCB
Figure 3-322
3-40
COPYRIGHT © 1995 CANON INC.
CANON NP6O12 /NPGO{2F/NPS212 REV.{ SEPT. 1995 PRINTED IN JAPAN (IMPRIME AU JAPON)