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7.2 Sample Imaging Setup
The following example assumes that you have determined the following:
Example: To image a feature .020" dia. on an 18" web using a LD3523 Camera.
Satisfying the Nyquist criterion, the effective y sample size
Since the maximum line rate corresponding to the minimum line period from
Table 1 is
such that the web moves 0.010" during the line period.
=
V
web
105
The required exposure
t
exp
Note 1.
The calculated exposure time guarantees the effective spatial resolution of 0.010"
at the maximum line period. Reliable imaging will require adjustment of the web
light source and/or camera gain.
PerkinElmer™ ™ Optoelectronics
•
Target width X
•
Image resolution # of pixels (By choice of camera)
•
Required feature resolution. i.e. the smallest feature
dimension "D" to be detected.
105 µ
9 .
sec
, the web velocity to assure contiguous y samples must be
. 0
010
"
=
94
.
42
/ "
−
6
9 .
*
10
sec
t
is then computed as follows:
exp
−
y
*#
of
pixels
=
eff
#
of
pixels
*
V
web
24
94
.
42
/ "
sec
=
sec
*
60
12
/ "
ft
−
X
.
010
*
2048
18
=
2048
*
94
.
42
y
=0.01".
eff
=
sec/
min
472
1 .
ft
/
min
=
−
6
12
8 .
*
10
sec
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