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CHAPTER 12. GAUGING STATION 93
LabVIEW Techniques
Once your Vision Assistant script is packaged into an Express VI the LabVIEW
project is almost done, however, interpreting and using the output of the Caliper
step takes some care. See “Gauging Demo” Connections
14
to learn how to
extract specific values from the 2-D array output of the Caliper step.
Take a screen capture of Figure 12.3 on page 90 and then paste this onto the
front-panel of your application. Place frameless numerical indicators near the
dimensional symbols as shown in Figure 12.1 on page 87 and then connect these
indicators to your Vision Assistant Express VI.
12.2 Development Tips
Representative Images
• Set up the camera on a table-top camera copy stand with an optically
black background. Adjust the field of view to accommodate a single
component. Allow for the component to tilt and translate somewhat. Set
all of the camera attributes to manual, and adjust the brightness, contrast,
and exposure to ensure that the background looks completely black while
the foreground component maintains good contrast.
•
Use a relatively high resolution, e.g., 1280
×
720, but do not go too high,
otherwise myRIO may not have enough memory to perform the needed
grid calibration tasks. You could also convert the LabVIEW project to
target the desktop and thereby eliminate any concerns about memory use.
IMPORTANT
: All of the ROIs that look for specific object features
depend on a specific resolution, therefore you need to make this choice
at the beginning of development. Changing the resolution after the Vi-
sion Assistant script is complete requires editing of nearly every step!
•
Collect one image in which the component bottom and right-side edges
are aligned with the pixel array.
• Collect additional images in which the component is translated and tipped
to the right and left.
• Make additional cutouts that contain “defects,” e.g., incorrect bevel angle,
slot width or depth, and hole radius.
14
http://youtu.be/auw8OBj_7m4
(6:54)