ABB PickMaster Twin - PowerPac Applications Manual page 252

4 Working with PickMaster PowerPac
4.3.9.2 Configuring a geometric model with PatMax
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f Select Ignore polarity to ignore if the features are dark on bright or
bright on dark.
Note
PatMax will not care if a product is light on a dark background or
dark on a light background. This is useful when the background is,
for example, a grid.
g Click Adjust Granularity to define the levels in the Fine and Coarse
boxes. Granularity is a radius of influence, in pixels, which determines
the detection of a feature in a pattern. PatMax locates patterns in the
search image by first searching only for large features. After locating
one or more pattern instances, it uses smaller features to determine
the precise transformation between the trained pattern and the pattern
in the search image. PatMax uses the same range of granularity that
is computed when training the pattern to detect features in the search
image. The granularity parameters fine and coarse are auto-selected
when training the pattern and often these values are the best. These
can also be set manually. The lower limit is 1 and upper limit is 25.5.
h Click Show mask to edit a mask that determines what parts of the
model region to ignore. The effect can be verified by pressing the Train
button and checking the Show Model checkbox. This tool is useful
when the training scene contains a lot of clutter (reflections and so on).
For more information regarding the effect of the edit controls, hover
the mouse pointer over the corresponding control. Click Adjust
Granularity to define the levels in the Fine and Coarse boxes.
6 In the Search parameters part, set parameters to limit the search procedure
and the analysis time.
Score Limit indicates how closely the found item matches the trained model.
A score of 1 indicates a perfect match while a score of 0 indicates that the
pattern does not match at all. The higher a score threshold is defined the
faster PatMax will be able to perform a search.
Angle variation defines the acceptable rotation for the items. If an item has
a rotation outside the valid range it will be discarded by the vision system.
Default +/- 180 degrees.
If more settings are required, click Advanced to open the Advanced Search
Settings dialog where the following settings are found:
Items to Find is the number of items that is expected to be present in the
image. If there are more items present in the image these will not be reported
by PatMax.
Contrast Limit defines the minimum image contrast of each item that is found
in the image. The contrast is the average difference in gray-level values for
all of the boundary points that PatMax matched between the trained model
and the found item in the search image. PatMax considers only items with a
contrast value that exceeds the contrast limit.
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Application manual - PickMaster® Twin - PowerPac
3HAC064218-001 Revision: B