Selecting a Feature

When choosing a feature to use for your inspection, consider the following guidelines to ensure the best results:

• If you’re not using a fixture, ensure that the feature is present in roughly the same location in every image, or the region is large enough to account for the expected movement of the feature.
• The Contrast Tool is useful in applications where the feature being inspected contains a mixture of greyscale values when present, and a uniform set of greyscale values when absent.
• If your application requires a more subtle differentiation between differences in brightness and contrast, consider using the Pixel Count Tool, which is more accurate in gauging those differences than the Contrast Tool.

Example

In this example, two Edge Location Tools are being used on the bottle cap to fixture two Inspection Tools: a Brightness Tool, with the region set to detect the presence or absence of the liquid, and a Contrast Tool, with the region set to detect whether or not the bottle cap is correctly fastened. The Brightness Tool is focused on the liquid, because when the liquid is present, it is roughly one greyscale value (roughly 10 to 20), and another when absent (255). The Contrast Tool is focused on the bottle cap, because if the seal is broken, there will be a mixture of greyscale values.