For many do-it-yourselfer’s out there, multi-touch displays may have been something you thought was out of your league. In reality, Maximum PC’s research guys have shown us that we can make a Frustrated Total Internal Reflection (FTIR for short) table for around $350. That is fantastic news because you can be the proud owner of your own touch-capable PC without having to spend $12,000 on the equivalent Microsoft Hardware product. In short, this makes it easier for developers such as myself to build our own touch PC’s and start working on the interfaces of tomorrow.
Many of the methods they used cut considerable corners, and with a bit more thought and research it would be easy to see that a few tweaks here and there would not only make it stronger and easier to make but also cheaper. In their implementation they used IR LED’s all around the table and a variation onf vellum and silicon to form an impression system for the surface. And while these solutions were quick, cheap and easy, there is another solution which is a bit more efficient in my opinion, and I will detail it below.
In my combined solution, there would be a thicker sheet of acrylic with one edge cut at a 45 degree angle. then using mounting hardware along that edge, we would mount a medium density amount of LED’s (one every 3/4 of an inch) that work at 850nm wavelength. Then we would obtain a sheet of vellum (or white tissue paper possibly is better) and press it against the bottom of the LED mounted sheet of acrylic, and sandwich it with a thinner piece of acrylic (not necessarily as polished of edges). By sandwhiching the vellum (tissue paper) we reduce the noise and provide a more even continuous surface of paper (making it seem more screen like) as well as enhance the touch capabilites of the screen. The single row of medium density LED count allows for fewer LED’s overall and allows for a cleaner hardware design, less interference and a clearer image when using a PS3 eye toy. In the eye toy, using a double or triple layer of colour film negative, it would filter out all light but the IR light cleanly. So we would have a noiseless, clean table surface and a clearer camera image. These improvements would overall reduce the cost of the project by significantly reducing the hardware cost for the LED’s and mounting them. I plan to put them to use when I get started on my surface HTPC (summer project). I will keep my blog posted as we move into the summer months!