Tuesday, November 13, 2012

A stereovision primer

When it comes to 3D machine vision, my preferred technique is laser triangulation. However, it needs relative motion between laser and object under inspection, which isn’t always feasible. One alternative is to use two cameras and do stereo imaging.
If you’re interested in learning more, especially about the underlying math, let me refer you to “A Guide to Stereovision and 3D Imaging” by Dinesh Nair of National Instruments and published on the NASA Tech Briefs website October 1st, 2012.
This article gets in to the whole area of “disparity”, (which is the key concept in stereo imaging,) but is a little light on the subject of accuracy. The best information I’ve seen on the accuracy of stereo imaging was given by Dr. Lau, (one of my “friends” over on the right of this page,) in a webcast he delivered for Vision Systems Design. If you visit that site and look under their “webcasts” tab you should be able to find it (unless they’ve rearranged their titles.)
Whether stereo is better than triangulation rather depends on your application, but remember: there’s usually more than one way to skin the cat.

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