PerkinElmer Optoelectronics
22
7.2 Sample Imaging Setup
The following example assumes that you have determined the following:
· Target width X
· Image resolution # of pixels (By choice of camera)
· Required feature resolution. i.e. the smallest feature
dimension “D” to be detected.
Example:
To image a feature .020” dia. on an 18” web using a LC 3013 Camera.
Satisfying the Nyquist criterion, the effective y sample size
eff
y
=0.01”.
Since the maximum line rate corresponding to the minimum line period from
Table
1
on page 8 is
sec
9
.
208 m
, the web velocity to assure contiguous y samples
must be such that the web moves 0.010” during the line period.
min
/
4
.
239
min
sec/
60
*
/
"
12
sec
/
"
87
.
47
sec
/
"
87
.
47
sec
10
*
9
.
208
"
010
.
0
6
ft
ft
V
web
=
=
=
=
-
The required exposure
exp
t
is then computed as follows:
sec
10
*
3
.
25
87
.
47
*
2048
18
2048
*
010
.
*
#
*#
6
exp
-
=
-
=
-
=
web
eff
V
pixels
of
X
pixels
of
y
t
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.
