National Instruments IMAQTM 用户手册

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

 to 

specify the scaling factors.

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 

Regions

 parameter of 

CWIMAQVision.LearnCalibrationGrid

 or 

CWIMAQVision.LearnCalibrationPoints

.

The user-defined ROI represents the area in which you are interested. The learning 

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.

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

a.

c.

b.