GRIDS
While grid patterns are neither necessary nor optimal for DIC, they may be used, with caution. Initial guesses must be
selected carefully; with a nearly-perfect grid, it’s possible for DIC to find a good match that is actually off by 1 or more grid
spacings. In addition, the subset size must be large enough that at least one grid intersection is always contained.
Subset too small – multiple matches along line Larger subset – constrained in both axes
DEALING WITH SPECULAR REFLECTION
In some of these methods, the patterning technique does not provide a matte finish for the surface. Under some
circumstances, this can cause specular reflections to produce oversaturated areas or glare. When present, this can produce
erroneous results or cause correlation to fail.
If this becomes an issue, consider changing how the specimen is being illuminated. If using heavy lighting, consider moving
the light source such that the reflections do not fall upon the camera. Using diffuse light may also be sufficient for
preventing reflection. For quasi-static tests, it may be possible to use only ambient light and higher exposer times to still
achieve high contrast images.
Another common solution is to use polarizing filters on light sources and camera lenses to prevent reflections and glare
from appearing in images.
CONCLUSIONS
This information should serve as a guideline, but very good results have been achieved in specimens and patterns that fall
far out of these guidelines. For help with challenging specimens and techniques, or for information about analyzing difficult
or poorly prepared images, please feel free to contact support@correlatedsolutions.com
, or your local representative. We’ll
be happy to help you look at options for preparation and analysis that will result in the best achievable results.
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