©NationalInstruments Corporation 6-1 IMAQVision for LabWindows/CVI User Manual
6
Calibration
This chapter describes how to calibrate your imaging system, save
calibration information, and attach calibration information to an image.
Afteryo u set up your imaging system, you may want to calibrate your
system.If your imaging setup is such t hatt he camera axis is perpendicular
ornearly perpendicular to the object under inspection and your len s has no
distortion,use simple calibr ation. Withsimple calibration, y ou do not need
to learn a template. Instead, you define the distance between pixels in the
horizontal and vertical directions using real-world units.
Ify our camera axis is not perpendicular to the object under inspection or
your lens is distorted, use perspectiveand nonlinear distorti on calibration
to calibrate your system.

Perspective and Nonlinear Distortion Calibration

Perspective errors and lens aberrations cause images to appear distorted.
This distortion misplaces information in an image,b ut it doesnot
necessarily destroy the information in the image. Calibrate your imaging
systemif you needto compensate for perspective errors or nonlinear lens
distortion.
Followthese general steps to calibrate your imaging system:
1. Definea calibration template.
2. Definea reference coordinate system.
3. Learnthe calibration information.
After you calibrate your imaging setup, you can attach the calibration
informationto an image. See the Attach Calibration Information section of
thischapter for more information. Depending on your needs, you can either
applythe calibration information to convert pixel coordinates to real-world
coordinatesw ithout correcting theimage, or you can create a
distortion-free image by correcting the image for perspectiveerrors and
lens aberrations. See Chapter 4, Blob Analysis,andChapter5,Machine
Vision,for more information about applying calibratio ni nformation before
making measurements.