Match Pattern FAQs

NI Vision Builder

Check for Presence Locate Features Tab

Match Pattern FAQs

Q: Reposition Region of Interest and Reference Coordinate System are dimmed. How can I make these options available?

Insert a Set Coordinate System step before this step to make the Reposition Region of Interest and Reference Coordinate System controls available.

Q: What does the green dot in the template image indicate?

The green dot indicates the point on the template whose coordinate location you want returned when the step finds matches of the template in the inspection image.

Q: When should I mirror the search angle?

Mirror the search angle when the fixture of the part under inspection constrains the location of the part along a specified axis. Another typical use for this parameter is to find templates that are symmetric along one axis.

Q: What is the difference between the green and red overlays?

The green overlay indicates the region of the image in which you want to search for matches to the template. The red overlay indicates an area that matches the template.

Q: Why does the Matches table sometimes contain one match more than I requested?

The Matches table displays one extra match, in a different color with the match number in parentheses, if the step can find one. The score for the extra match is an estimation of the Minimum Score required for the step to return the object as a match. The actual Minimum Score required to return the object as a match may vary from the estimated score. However, you can use the estimated score of the extra match to adjust the Minimum Score, as follows:

  • If the step does not find all of the matches you specified in the Number of Matches to Find control, set the Minimum Score to be less than the score of the match you want.
  • If the step finds all of the matches you specified in the Number of Matches to Find control, set Minimum Score to be between the scores of the last expected match and the extra match listed in the Matches table.

The Minimum Score must be low enough to detect the expected patterns properly but high enough to avoid detecting mismatches—areas of the image with some degree of similarity to the learned template. To build a reliable inspection process, maximize the range between the lowest score of the expected matches and the highest score of the extra matches. Also, take into account the usual variations of your process when setting the Minimum Score.