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DIY Multitouch Surface Uses 2 Lasers, Webcam

A Berkeley University student has constructed a do-it-yourself multitouch surface "tablet" using only two lasers (and a power source), a webcam, and custom software.

Unlike the home made multitouch surface we reported on months ago, this formula enables the use of any surface, whether it's a desk, a cardboard box insert, or the kitchen table. The only drawback to this recipe is that the student, Yotam Mann, wrote the custom software, and currently is only demonstrating its capabilities as a cool musical instrument.

"This is not a true multitouch surface, but it is an inexpensive and useful alternative," he admits on his Berkeley webpage. The device works by scanning his fingers using both lasers, one serving as the X-axis input, and the other handling the Y-axis. Mann cut acrylic rods, measuring around one inch long, and duct-taped each rod to one laser vertically in order to refract the light horizontally. The lasers are then mounted in each back corner, facing each other and rotated 45-degrees.

Once the power supply is attached to the lasers, they are aligned so that the beam plane is parallel over the entire surface. The webcam is then placed above the surface, angled at 45-degrees and positioned to where it can view the entire "multitouch" plane. "About 6 inches works well for the size of the surface that I used," he explained. "I also find that a third-arm works well for holding light webcams." His custom-coded Max/MSP software (a visual programming language) thus reads the scan of each laser; he makes the software available for public consumption right here.

For now, his software contains only one application: a musical device that enables the user the ability to load up a sound file and control an oscillator using just the hands. By bending a finger, the sound changes frequency (x-position); the sound's volume is determined by the distance between the user's hands, and the scanned surface (y-position). Mann said that when a finger is perpendicular to the surface, a timbral change using FM synthesis occurs by moving the fingers close to the laser, and then pitching it back.

Currently the music application and the entire DIY project is heading to the Maker Faire in San Mateo this weekend, where Mann will compete against over six hundred other exhibits at the show. “It’s definitely an open-source idea,” Mann said. “For me it’s a musical instrument, but I’d like for people to see what applications they can get out of it.” Mann should be both excited and nervous, as 80,000 pairs of curious eyes are expected to attend Maker Faire this year. Mann plans to demonstrate how his device was constructed, how it works, and even distribute his custom software during the show.

Mann said that the combined cost of the lasers, power supply, clear acrylic rods, and webcam is roughly around $40. The items can also be purchased on the Internet, or a local specialty store.