Image Processing Reference
In-Depth Information
TABLE 10.1
Charging Model
V p ( L ) ¼ V g 1 e a
Þ þ V p ( 0 ) e a
ð
( 10 : 9 )
where
a ¼
S
Cv
S ¼ slope of the current - voltage response curve
C ¼ capacitance per unit area
v ¼ photoconductor velocity
L ¼ charging nip length
TABLE 10.2
Parameters of Charging Model
Charging Model
Parameters
Units
0.94 10 6 A = V-m
S
v
0.254 m = s
V g
600 - 800 V
e r
3
8.854 10 12 C = V-m
e 0
d
24 m m
9.486 10 7 C = V-m 2
C
a
3.9013
V p (0)
0 V
of the integration. All uncertainties are ignored by the model; they can be handled as
disturbances in the system dynamics when this equation is used in the controller
design. More detailed charging models can be found in Refs. [4
7]. A summary of
the charging model and its related parameters is shown in Tables 10.1 and 10.2.
-
10.2.2 E XPOSURE M ODEL
A photoconductor acts like an insulator in the dark and a conductor when it is
exposed to light. A photoconductor has at the minimum two layers, a charge-
transport layer (CTL) and a charge-generation layer (CGL) or photosensitive layer.
The cross section of a dual layer PR is shown in Figure 10.6 [7]. In the CGL,
photogeneration of charge carriers takes place at the bottom of the layer when the PR
is exposed with photons. It has photoconductive material that generates electron
-
hole pairs in response to the photon exposure. These charge carriers drift and migrate
to the top surface, and neutralize the preexisting surface charges (deposited during
the charging stage) in the illuminated areas to form the latent electrostatic image. The
CTL contains materials that subsequently allow these charge carriers to be trans-
ported. The undercoat layer (UCL) is an uncharged layer used to block unwanted
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