Build Your Own Multi-touch Surface Computer

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Maximum PC didn't feel like shelling out $12,000 for Microsoft's Surface technology, so the staff made its own multi-touch table PC for only $350

The online magazine's original task was to publish an article about future user interfaces. However, after extensive research into multi-touch applications such as Apple's iPhone and Microsoft Surface, the staff at Maximum PC uncovered a whole community of DIY engineers "perfecting the art" of creating homemade multi-touch surfaces. Home-built multi-touch surfaces should come as no surprise: there are websites dedicated to hands-on construction of unique technologies such as a Commodore 64 laptop, a speech-controlled trash can, and even a lemon-charged battery. Needless to say, if the industry can build it, then the online community will find a way to build even it better... and cheaper.

With that said, Maximum PC decided to create a multi-touch surface computer using methods found online at the Natural User Interface Group. Ultimately, the online magazine didn't go out and spend $12,000, but rather just $350. Out of various processes used to construct the homemade multi-touch surface, the staff decided to use the FTIR (Frustrated Total Internal Reflection) screen setup. This consists of a sheet of transparent acrylic, a chain of infrared LEDs, and a camera with an IR sensor. According to the site, the LEDs are arranged around the outside of the acrylic sheet so that they shine directly into the side. The IR light thus shoots into the acrylic, reflecting off the top and bottom of the material, remaining contained within.

When a finger presses against the sheet, the reflecting light hits the spot and bounces downward into the cabinet mounted underneath. A modified webcam mounted in the cabinet--altered to detect only infrared light--views the finger touch as white spots, and then sends the image to software running on a connected PC. The software maps the movements and applies the coordinates to whatever application is running. The PC thus transmits the on-screen image via a projector back onto the surface using a mirror and a piece of heat-absorbing glass. Granted this brief overview sounds rather simple, the process of creating the multi-touch surface PC takes a bit of work, from polishing the sides of the acrylic sheet to altering the webcam.

But wait... Maximum PC didn't just use any webcam; the site implemented the $35 PlayStation 3 Eye, using a rectangular razor blade to gain access to the poor camera's IR filter. As with the rest of the article, the site shows the step-by-step process of removing the unwanted filter. "The infrared sensor is the innermost piece of glass on the lens assembly," the site reads. "When it catches the light, it looks ruby red – a dead giveaway that this is the piece filtering out infrared light. In order to remove it we simply used a razor blade to gouge out the plastic in a circle around the filter, allowing us to easily pop it out." Why remove the filter? So that the PlayStation 3 Eye can pick up infrared light.

As for the connected computer, the staff didn't use anything meaty, only a PC containing a Core 2 Duo and 2 GB of memory. With that said, DIY builders won't need anything outrageously fast, but more than likely a rig that hit the market within the last few years. Additionally, the camera and PC don't necessarily need to be within the cabinet; the cables for the PS3 Eye and projector can run out of the cabinet and hook up to a laptop if needed.

Ultimately, the actual multi-touch screen was 24-inches by 30-inches, with the acrylic sheet 3/8-inches thick. The IR LEDs lining along each side were 1-inch apart, however the staff wired the LEDs together the hard way, soldering the leads together rather than just using a wire-wrap gun (that would make the task quicker and more environmentally safe... meaning no lead). The cabinet itself was constructed from 3/8-inch MDF, with a stained hardwood frame on top, standing waist high. To get the entire contraption to work, the team installed Touchlib on the PC, an open source library that takes the visual data received by the camera and parses it into touch events. Someone even wrote a driver that enables the PS3 Eye to work on the PC.

"We completed this project over the course of about two weeks' work," the article reads. "All said and done, everything worked out pretty well. We ended up with a fully functional, highly responsive multi-touch surface."

For a meager $350, the DIY multi-touch project sounds like great fun, and may end up as something we do here at Tom's just for kicks. After all, many of us don't have a whopping $12,000 stored in the underwear drawer (well, maybe Tuan). Still, this example definitely proves that anything is possible on a small budget. All it takes is a little patience, a little research, and a dedicated community to help along the way.

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