National Instruments IMAQTM - Manual (Page 62)

Chapter 5 Performing Machine Vision Tasks
IMAQ Vision for Visual Basic User Manual 5-10 ni.com
Finding Lines or Circles
If you want to find points along the edge of an object and find a line
describing the edge, use
CWMachineVision.FindStraightEdge
and CWMachineVision.FindConcentricEdge .
CWMachineVision.FindStraightEdge finds edges based
on rectangular search areas, as shown in Figure 5-5.
CWMachineVision.FindConcentricEdge finds edges based
on annular search areas.
Figure 5-5. Finding a Straight Feature
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
CWMachineVision.FindCircularEdge .
1 Search Region
2 Search Lines
3 Detected Edge Points
4 Line Fit to Edge Points
2
1
4
3