How to use Geometric Matching

Template Selection Interface

1. Draw a region of interest around an area of the image for which you want to search in your inspection images. This region becomes the geometric pattern matching template.
2. Click OK to accept the template.

When you specify a template, the step automatically tries to find the template in the image. Template matches appear inside red rectangles in the image. The green rectangle indicates the region of interest in which the step searches for matches.

Main Tab

3. In the Step Name control, enter a descriptive name for the step.
4. Choose one of the following methods to specify the region of interest for the step:
   • Create a new region of interest.
     1. Select Constant from the Region of Interest listbox.
     2. Select a tool from the menu toolbar that matches the type of region of interest you want to specify.
     3. Draw a region of interest on the image.
   • Select a previously defined region of interest from the Region of Interest listbox.
5. Verify that the Reposition Region of Interest option is enabled if you want to link the region of interest specified in this step to a previously defined coordinate system.

   Link the region of interest to a coordinate system if the position of the object under inspection changes from image to image, and you need to adjust the position of the region of interest to match the new location of the object.

   Note  This step can find rotated instances of the template without the assistance of a Set Coordinate System step.

Template Tab

By default, the center of the template is used as the focal point of the template. You can change the location of the focal point to any position in the template.

6. Change the focal point of the template by adjusting the Match Offset values.

Curve Tab

By default, the values of the parameters in this tab are initialized to the values you selected in the training interface. You can adjust these values to improve edge detection in the inspection image.

7. If necessary, modify the Extraction Mode, Edge Threshold, Edge Filter Size, Minimum Length, Row Search Step Size, and Column Search Step Size to improve edge detection.

Settings Tab

8. Set Number of Matches to Find and Minimum Score.
9. Enable Rotated, Scaled, or Occluded to indicate that a match may be a rotated, scaled, or occluded version of the template. Specify an acceptable range for each parameter to restrict the amount of rotation, scale, or occlusion allowed in a valid match.

Limits Tab

10. Set the minimum and/or maximum number of matches you expect to find.