Kentaro Fukuchi created in 2004-2005 Laser Trail Tracker: Laser pointers tracking system with special emphasis on the shapes of a laser trails, a project to perform visually in live using laser pointers which get into the feedback generated by a camera capturing its own projected source. The interaction with the lasers over the projection get into the feedback but they also are tracked by a software which creates another shapes by the pass of the pointer. Kentaro also experimented using button widgets for bitmap image-based interaction to trigger with the laser different visual manifestations, here is an example performing using this system. See more;
"We developed a laser pointer tracking system and applied it to a live visual performance. Its basic approach is the same as that of previous systems: the computer is connected to a projector and a camera that observes the screen. We used an IEEE1394 digital camera (Fire-i, Unibrain S.A.) that can deliver uncompressed 640x480 pixels at 30 frames per second.
The projector was a standard 2000–2500 ANSI lumen XGA projector. In order to bypass expensive image processing techniques for laser detection,we used very bright green laser pointers (532nm wave length, class 3a, 5mW), and attached an ND-4 or ND-8 filter that decreases the power of an incoming ray to 1/4 or 1/8. By using this filter, we could eliminate environmental light and image on the screen from the camera’s view completely because the luminosity contrast is very high. All of the automatic parameter controls (brightness, white balance, exposure) of the camera were turned off to avoid unexpected parameter shifts during a performance. We set the exposure to almost 1/30 second, the same as the scan rate of the camera. This causes the image of a laser spot moved quickly to become a blurred and slightly dimmed trail (fig.2). This has been considered less suitable for laser spot tracking, but we feel justified in using the laser trails because the laser motion by performers is captured as trails." - Kentaro Fukuchi.
"Our laser tracking system "Laser Trail Tracker (L.T.Tracker)" recognizes laser trails and thier motions drawn on a screen with laser pointers. When a visual reflecting those laser stroke is shown on the screen, it seems to be generated via direct interaction to the screen.
There is a camera in front of a screen to capture it. The system extracts laser trails from a camera image and track their motions by using simple image processing and recognition techniques. Finally, a visual processor makes a visual from those information and projects on the screen." - Kentaro Fukuchi