How does a Laser 3-D Scanner Work

Here's a quick post about a few things I learned about laser 3-D scanners.

In the classification of 3-D scanners, laser scanners fall in to the category of 'Non-Contact Active'. There several types of scanners in this category, but the most common type used is the Laser Triangulation scanner. These are used in scanning relatively small objects with high accuracy.

How does it work? A triangulation scanner shines a laser dot to the object and uses a camera to look for the location of the laser dot. Depending of the distance from the laser emitter to the surface of the object, the dot appears at different places on the camera's field of view, as seen on the following diagram.

Operating principle of a triangulation laser scanner

Since the distance between the laser emitter and camera and the angle between them is known, using the position of the laser dot on the camera's field of view, the distance between the emitter and the surface can be calculated. Most object scanners that use this principle use a laser stripe instead of a dot to speed up the scanning process.

Triangulation with a laser stripe

Triangulation scanners have a limited range - only a few meters, but their accuracy is high - accurate to a few micrometers.

There are other types of laser scanners such as time-of-flight scanners, conoscopic holography scanners etc. If anyone's interested, I could do few articles on them too...

References
http://en.wikipedia.org/wiki/3D_scanner

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