National Instruments IMAQTM - Manual (Page 74)

Chapter 5 Performing Machine Vision Tasks
IMAQ Vision for Visual Basic User Manual 5-22 ni.com
Defining a Search Area
Two equally important factors define the success of a color pattern
matching algorithm—accuracy and speed. You can define a search area to
reduce ambiguity in the search process. For example, if the image has
multiple instances of a pattern and only one instance is required for the
inspection task, the presence of additional instances of the pattern can
produce incorrect results. To avoid this, reduce the search area so that only
the appropriate pattern lies within the search area. For example, in the fuse
box inspection example use the location of the fuses to be inspected to
define the search area. Because the inspected fuse box may not be in the
exact location or have the same orientation in the image as the previous
one, the search area you define should be large enough to accommodate
these variations in the position of the box. Figure 5-12 shows how search
areas can be selected for different objects.
Figure 5-12. Selecting a Search Area for Color Pattern Matching
1 Search Area for 20 Amp Fuses 2 Search Area for 25 Amp Fuses
1 2