Specifying Scaling Factors; Choosing A Region Of Interest; Choosing A Learning Algorithm - National Instruments IMAQTM User Manual

Chapter 6 Calibrating Images
The user-defined ROI represents the area in which you are interested. The learning
Note
ROI is separate from the calibration ROI that is generated by the calibration algorithm.
Refer to Figure 6-6 for an illustration of calibration ROIs.
a.
IMAQ Vision for Visual Basic User Manual

Specifying Scaling Factors

Scaling factors are the real-world distances between the dots
in the calibration grid in the x and y directions and the units in
which the distances are measured. Use
CWIMAQCalibrationGridOptions.GridDescriptor
specify the scaling factors.

Choosing a Region of Interest

Define a learning ROI during the learning process to define a region of the
calibration grid you want to learn. The software ignores dot centers outside
this region when it estimates the transformation. Creating a user-defined
ROI is an effective way to increase correction speeds depending on the
other calibration options selected. Pass a CWIMAQRegions collection
representing the region you want to learn to the
CWIMAQVision.LearnCalibrationGrid
CWIMAQVision.LearnCalibrationPoints

Choosing a Learning Algorithm

Select a method in which to learn the calibration information: perspective
projection or nonlinear. Figure 6-5 illustrates the types of errors the image
can exhibit. Figure 6-5a shows an image of a calibration grid with no
errors. Figure 6-5b shows an image of a calibration grid with perspective
projection. Figure 6-5c shows an image of a calibration grid with nonlinear
distortion.
Figure 6-5. Types of Image Distortion
b.
6-6
to
parameter of
Regions
or
.
c.
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