Rockwell Automation 5370-CVIM2 Module - Manual (Page 305)

5 Chapter Chapter 7
Inspection Tools
7–67
Note that the Sign LUT was selected for the example. Since the Laplace
kernel creates a signed image, which contains pixel values between –128 and
+127, the
Sign LUT removes negative values from the image by adding 128
to each value, thereby placing all pixel values in the 0 to 255 range that the
inspection tools require to identify and evaluate features properly.
Note also that the Absolute , S.Threshold , or S.Clip LUT could be used,
since they also remove negative values from the image. (When used with the
Laplace kernel, however, the Absolute LUT yields a somewhat indistinct
gradient compared to the S.Threshold LUT.) In any case, the choice of LUT
depends on the specific requirements for the application.
Figure 7.56 illustrates the effects on the inspected object that Absolute and
S.Threshold LUTs have when using the Laplace kernel.
Figure 7.56 Example: Effects of Absolute and S.Threshold LUTs With Laplace Kernel
Inspected object using
Absolute LUT
Inspected object using
S.Threshold LUT