Image Processing Reference
In-Depth Information
Photoconductor
voltage
Charging
Dark decay
Exposure
(PID)
Light
decay
Time
FIGURE 10.7
Photoconductor charge - discharge cycle.
h 0
p
h( E ) ¼
(
10
:
10
)
E c
E E r
1
þ
where
E is the electric
field
E c is a scaling parameter that depends on the initial state of the photoconductor
p is the shape of the
field dependence
h 0 is the high
field limit of the CE
E r is the residual
field
Figure 10.8 shows the Melnyk
Springett CE for different values of p. Given the
differential number of photons per unit area (exposure energy per unit area in
ergs
-
cm 2 ) absorbed by the CGL, dX, the differential charge density produced is
=
ds ¼ e h( E )d X
(
10
:
11
)
1.0
0.8
0.6
0.4
p = 0.5
p = 1.0
p = 2.0
p = 4.0
0.2
0.0
0
1
2 3
Scaled electric field ( E / E c )
4
5
FIGURE 10.8
Melnyk - Springett collection efficiency curves.
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