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CHAPTER 5. STEREO VISION 37
I
Open the Calibrate Stereo Vision System (mod) VI available in the NI myRIO
Vision Essentials Guide
3
distribution file. See the video tutorial Configure Stereo
Cameras
4
to learn how to configure the two Vision Acquisition Express VIs for
your two webcams. Figure 5.1 on the preceding page shows what is meant by the
“Left” and “Right” cameras when mounted to the tabletop copy stand. Use man-
ual settings as much as possible, especially for focus, and use 640
×
480 resolution.
I
MPORTANT
: Think of the two cameras as your two eyes looking out
towards a scene. The “left” camera is in the same position as your left
eye. The
Calibrate Stereo Vision System (mod) VI designates the
“Left” Vision Acquisition Express VI to match the “left” camera shown in
Figure 5.1 on the facing page.
I Study the video tutorial Calibrate Stereo Cameras
5
to learn how to calibrate
the stereo cameras with your dot grid target. Save the calibration file so that
you need not repeat this step.
I
Use plastic blocks of known thickness to build some shapes similar to those
shown in Figure 5.1 on the preceding page. A “step wedge” makes a good
subject to verify that the measured depth matches the true depth.
I
Study the video tutorial Measure Depth
6
to learn how to create a depth
image and how to take measurements.
4
Duplicate the step wedge results from the tutorial video. Report the mea-
sured thickness of each step compared to the actual thickness.
5
Investigate the degree to which translation and rotate of the step wedge
impacts measurement accuracy.
6
Create additional objects and take screenshots of the rectified images and
the corresponding depth image.
3
http://www.ni.com/myrio/vision-guide
4
http://youtu.be/iGqlBrg3DjM
(2:47)
5
http://youtu.be/bufXESBlzTY
(2:49)
6
http://youtu.be/UXw31LOSiHk
(3:16)