User Manual

Programming Basics 7-17
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13. Adjust the Search Length and Projection Length to experiment with their effect.
14. Set the Edge Polarity to Light-dark.
15. Set Minimum Contrast to 2.
> This is the lowest acceptable difference in grey-levels on opposite sides of the
edge to qualify as a transition.
16. Set Caliper Density to 2.
> A lower value will space the calipers farther apart. A higher value will
overlap them more. You can also use fractional numbers (0.5 for example).
17. Click on Teach.
18. Test the fiducial by clicking on Find Fid.
> The Test Results indicate if the fiducial was found or not, its found
coordinates and how long it took to locate the fiducial.
19. Click on Done to save the results and end this tutorial.
This concludes the tutorial on Corner Finder.
 TIP
 Caliper Sizing
 The Search Length should be optimized so that it contains only
one gray value transition (light to dark, dark to light). A longer
Caliper increases the range for finding the corner, but also
increases the chances for finding the wrong corner.
 Projection Length controls the averaging for the transition
amplification. A wider Caliper is better for rough edges or
eliminating noise caused by traces on the board. Thinner calipers
are more immune to rotated parts.
 Caliper Density controls how many calipers are used. More
calipers may help reduce the effects of edge irregularities, but will
take longer to execute. You should set the Projection Length and
Caliper Density such that you have at least five calipers along the
edge.