Rockwell Automation 48MS MultiSight Vision Sensor - Manual (Page 37)

MultiSight™ User Manual
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Contour Matching
The Contour Matching detector type is essentially a simplified pattern matching algorithm. Instead of the fully detailed pattern with
relative grey scale levels and complex area evaluation used for comparison in the Pattern Matching detector type, the Contour
Matching detector type compares simple line contours and shapes. In contour mode, the teach process identifies the borders
between dark and bright areas on the image. These borders between dark and light are highlighted with a blue line and
subsequently represent what the MultiSight looks for in run mode. When the MultiSight performs an inspection in run mode, it
identifies these line shapes and determines if they match the taught line contour. The threshold settings affect how closely the
found line shapes match the taught line shape.
As an example, a solid black circle on a white background would cause a single circular contour line. A black ring on a white
background would cause a large circular contour line (at the outer diameter) and within it a smaller circular contour line (the inner
diameter). There is a contour line tracing border between black and white.
The primary advantage of Contour Matching (in comparison to Pattern Matching) is that this detector type is fully tolerant of shape
rotation, i.e. the object may appear in any angular position and still be detected. Another advantage is that the taught contour can
be edited by the user to remove parts of the contour that are not to be used for the inspection. The primary disadvantage of Contour
Matching (in comparison to Pattern Matching) is that it cannot detect as complex a pattern. Contour Matching is also typically
slower.
To edit the taught line contour, place the cursor over the pattern in the Pattern section of the software on the right hand side of the
screen. The cursor becomes an eraser. The size of the eraser is determined by the Eraser Size parameter under the pattern. It is
recommended to use the Zoom button (in the Pattern section) to work with a larger image. This eraser can be used to eliminate
portions of the taught line contour (depicted as a blue line) that should not be included in the inspection. For example, another
component near the part to be inspected, or even a shadow, may cause a contour shape in the taught image. The blue contour lines
created by these conditions can be eliminated by placing the cursor-eraser over those sections and clicking the mouse button. If a
desired blue contour line is accidentally deleted, the entire contour must be re-taught.
There are several additional parameters that appear when the Contour Matching detector type is used. These parameters affect
either the teach process or the inspection process. They are described in more detail below. For most applications these can remain
in their default states.
For a repeatable inspection results using the Contour Matching
detector type, a high-contrast image is essential.