ABB PickMaster Twin - PowerPac Applications Manual page 290

4 Working with PickMaster PowerPac
4.4 Using color vision
Continued
When using color filtering it is easier to distinguish between colors if they are
dissimilar. The level of similarity may be interpreted as the distance between the
colors in color space. The difference may be more pronounced in one or the other
of the two color spaces and for this reason it is wise to try out filters in both color
spaces.
Lighting
Because a color system provides more information about the color contents of an
image it is also more sensitive to lighting conditions. It is very important to provide
uniform light, that is consistent over time.
Computer performance
Color vision is very resource consuming; acquisition, warping, and filtering all take
more time. It is important to keep the number of cameras and frame rate moderate.
The performance limit can vary greatly as it is a combination of the vision task and
the computer resources.
Color vision in PickMaster PowerPac
PickMaster PowerPac provides color vision in the form of a filter except the
histogram. This filter is accessible from the PatMax, Blob and Caliper configuration
dialogs, both as standalone, alignment and sub-inspection models. The filter is a
pre-processing step which takes place before the object recognition or
measurement. Every model can have its own individual filter setting.
The camera acquires a color image, that is converted into a grayscale image by
passing it through a color filter, as shown in the following figure. The histogram
tool takes a slightly different approach to color vision as it skips the filtering step
and instead performs the measurement directly on each of the three color channels
of the image.
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Vision model
Color image
Color filter
grayscale image
Object recognition
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Application manual - PickMaster® Twin - PowerPac
3HAC064218-001 Revision: B