Chapter 5
Performing Machine Vision Tasks
IMAQ Vision for LabWindows/CVI User Manual
5-28
ni.com
Use
imaqFindLCDSegments()
to calculate the ROI around each digit
in an LCD or LED. To find the area of each digit, all the segments of the
indicator must be activated. Use
imaqReadLCD()
to read multiple digits of
an LCD or LED.
Identify Parts Under Inspection
In addition to making measurements after you set regions of inspection,
you can also identify parts using classification, optical character
recognition (OCR), and barcode reading.
Classifying Samples
Use classification to identify an unknown object by comparing a set of its
significant features to a set of features that conceptually represent classes
of known objects. Typical applications involving classification include the
following:
•
Sorting—Sorts objects of varied shapes. For example, sorting different
mechanical parts on a conveyor belt into different bins.
•
Inspection—Inspects objects by assigning each object an identification
score and then rejecting objects that do not closely match members of
the training set.
Before you classify objects, you must train the classifier session with
samples of the objects using the NI Classification Training Interface.
Go to
Start»Programs»National Instruments»Classification Training
to launch the NI Classification Training Interface.
After you have trained samples of the objects you want to classify, use the
following functions to classify the objects:
1.
Use
imaqReadClassifierFile()
to read in a classifier session that
you created using the NI Classification Training Interface.
2.
Use
imaqClassify()
to classify the object inside the ROI of the
image under inspection into one of the classes you created using
the NI Classification Training Interface.
3.
Use
imaqDispose()
to free the resources that the classifier
session used.
