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CHAPTER 13. PRODUCT LABEL INSPECTOR 99
to learn how to use the Particle Analysis step to count the remaining particles
(now assumed to represent the product label defects) and to report their areas.
LabVIEW Techniques
The following LabVIEW techniques are required for this project:
•
(qsm) initialize: Front-Panel
6
– Use an Invoke Node to reset the numerical
front-panel indicators when the application starts up, and
• Select Image Palette
7
– Use a
Property Node
to select either the “Grayscale”
or “Binary” palette for the image display; the Particle Filter step produces
a binary output that appears like an all-black screen unless the “Binary”
palette is selected.
13.2 Development Tips
Representative Images
• Use double-sided tape to bond the defect-free paper product label to a
stiff paper card or piece of cardboard. The product label need to be as flat
as possible when presented to the camera, and mounting the label to a
card makes handling more convenient and prevents wrinkling.
•
Create additional product label cards in which you introduce defects such
as pencil mark smudges, tears, and holes of varying degrees of severity.
•
Set up the camera on a table-top camera copy stand and adjust the field
of view to accommodate a single product label. Allow for the label to be
tilted and translated somewhat. Adjust the camera mode to obtain rea-
sonably high resolution and the camera attributes to obtain good contrast
without over or underexposure.
IMPORTANT : Ensure that the camera’s physical setup remains
undisturbed throughout this project! The conditions under which you
create the golden template image must be identical to the way that
your finished vision application collects images of the product label.
• Collect one image to serve as the basis of your golden template. The
product label must be free of defects. Align the product label with the
pixel array to the best of your ability.
6
http://youtu.be/eBtBy__PNwU
(1:49)
7
http://youtu.be/M53-QmPsSq4
(2:09)