When choosing an image for Particle & Pore Analysis it is essential that the user has a visual perception of what are the features to be detected (particles, pores, grains etc.). Thereby the Detection and Post Processing parameters can be adjusted so that the Particle & Pore Analysis module finds exactly what the user is looking for. Of course there will be cases, e.g. in quality control, where some objective criteria are the basis for the choice of detection parameters. This could for example be a fixed threshold used in a pass/failure test. There the “visual method” does not necessarily apply.
Before making the first detection it is important that the image has been plane corrected, which can be done by use of the Plane Correction Dialog (applies mostly for topographical images, but also SEM images may have brightness gradient imposed). Especially for Particle & Pore Analysis using the Threshold methods it is essential that the background surface is flat and horizontal. If the image has artifacts or extreme noise this should be suppressed by appropriate filtering using the Filter Module. For the Threshold methods background waviness in the image can be reduced using a filter from the Filter Dialog; this should be of considerably larger size than the features of interest. The background waviness can be reduced by subtracting filter smoothened image from the original image. Local artifacts can be excluded from the analysis using the Area of Interest tool (AOI).
In many cases it is the height of Particles, the depth of Pores or their volumes which is one of the desired measurands. When the Particles or Pores exist on a flat surface background the best way to extract their height or depth accurately is to use the group of “Raw Z Values” parameters which measure height relative to the zero height level in the image. It is therefore crucial to adjust the image zero height to be at the correct level, i.e. to the height level of the flat background. This is most easily done during the Plane Correction Step by choosing the “Bearing Height to Zero” Z Offset Method, which is selected by default. This may be the only required Plane Correction if the image is already flat and in level. Note that “Raw Z Values” will be negative for pores. Again, for non-topographical images this is irrelevant.