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I
COPYING PROCESS
I
The
outer surface
of
the photosensitive
drum
is
a
layer
of
organic
photoconductor
(OPC).The base
is
an aluminum
(conductive)
cylinder.
Photoconductive
layer
Base
C.
Step
1
Pre-Exposure
r
- "
-
!"^
Pre-exposure
lamp
Filter
Figure
2-3
Figure
2-5
B. Electrostatic
Latent
Image
Formation Block
This stage consists
of
three steps. At the
end
of
the stage, the
drum
has a
pattern
of
negative
electrical
charges on
its
surface
corresponding
to
the
dark
parts
of
the
document
image.
The
light
areas
of
the
document image
are
represented
on
the
drum
by an absence
of
charges.
The
pattern
of
negative
charges cannot
be seen
by the
eye,
hence
it
is
called
an
electrostatic latent
image.
Time
(t)
—
/
r"\"
/
i
Light
area
-500-
/
/
/
C 3
ffl
\
Q
O
O
Dark
area
1000-
^
Q.
Ep
Image exposure
n.
g>
tk
(step
3)
Figure
2-4
Before the primary
corona
step,
light
from
the
pre-exposure
lamps
is
shone
onto the
surface
of
the
drum
(pre-exposure).
This
process
ieliminates residual
charges and
helps
to
make
the density
of
the
copy
even.
D.
Step 2 Primary
Corona
Primary
corona assembly
Figure
2-6
The
primary
corona
(negative) applies
a
uniform
layer
of
negative
charges
over
the
drum
surface.
The drum
surface
potential,
is
determined
by the
grid potential.
The
grid
is
connected
to
ground
through a
varistor,
which
holds the
drum
potential
constant
at
the
varistor
break-
down
voltage.
2-2
COPYRIGHT©
1992
CANON
INC.
CANON
NP-1550
REV.1
SEPT. 1992
PRINTED
IN
JAPAN
(IMPRIME
AU
JAPON)
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