National Instruments IMAQTM - Manual (Page 57)

Chapter 5 Performing Machine Vision Tasks
© National Instruments Corporation 5-5 IMAQ Vision for Visual Basic User Manual
Figure 5-3. Locating Coordinate System Axes with Two Search Areas
2. Choose the parameters you need to locate the edges on the object.
3. Choose the coordinate system axis direction.
4. Choose the results that you want to overlay onto the image.
5. Choose the mode for the method. To build a coordinate transformation
for the first time, set the
FirstRun parameter to True . To update the
coordinate transformation in subsequent images, set this parameter
to
False .
Using Pattern Matching to Build a Coordinate Transformation
You can build a coordinate transformation using pattern matching. Use
CWMachineVision.FindCoordTransformUsingPattern to define a
reference coordinate system based on the location of a reference feature.
Use this technique when the object under inspection does not have straight,
distinct edges. Follow the steps below to build a coordinate transformation
using pattern matching.
Note The object may rotate 360
° in the image using this technique if you use
rotation-invariant pattern matching.
1 Primary Search Area
2 Secondary Search Area
3 Origin of the Coordinate System
4 Measurement Area
1
3
2
4
1
3
2
4
a. b.