National Instruments IMAQ Vision for Measurement Studio - Manual (Page 57)

Chapter 5 Machine Vision
© National Instruments Corporation 5-11 IMAQ Vision for LabWindows/CVI User Manual
If you want to find points along a circular edge and find the circle that best
fits the edge, as shown in Figure 5-6, use
imaqFindCircularEdge() .
Figure 5-6. Finding a Circular Feature
These functions locate the intersection points between a set of search
lines within the search region and the edge of an object. You can specify the
search region using
imaqSelectRect() or imaqSelectAnnulus() .
Specify the separation between the lines that the functions use to detect
edges. The functions determine the intersection points based on their
contrast, width, and steepness. The software calculates a best-fit line with
outliers rejected or a best-fit circle through the points it found. The
functions return the coordinates of the edges found.
Finding Edge Points Along One Search Contour
Use imaqSimpleEdge() or imaqEdgeTool() to find edge points along
a contour. Using imaqSimpleEdge() , you can find the first edge, last
edge, or all edges along the contour. Use imaqSimpleEdge() when your
image contains little noise and the object and background are clearly
differentiated. Otherwise, use
imaqEdgeTool() .
1 Annular Search Region
2 Search Lines
3 Detected Edge Points
4 Circle Fit To Edge Points
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