• Coffee Table
  • Day 1
  • Day 2
  • Day 3
  • Day 4
  • Day 5
  • Day 6
  • Day 7
  • Day 8
  • Day 9
  • Day 10
  • Conclusion
• Whiteboard

Coffee Table Multitouch Surface Computer

After reading this article on the Maximum PC website and following up by reading through some of the information on the Natural User Interface Group website I decided to have a quick pass at making a multitouch surface computer myself. Unlike Maximum PC's DIY multitouch surfaces I wanted mine to be at coffee table height allowing it to take an unobtrusive role in my everyday life if even only as a coffee table. I don’t want to stand up just to use it and it would only end up being another object in my house taking up space regardless of how interesting it may be.

The very first thing that occurred to me was that the projection distance of a vertical cabinet allows for the cabinet's footprint to be as small as the screen. Such a distance could not be achieved with a coffee table height whilst maintaining the screen size as the footprint and so I made the decision to base the coffee table off of an equilateral triangle. The projector would be in one corner and the screen would be in the middle of the opposite edge with the projection reflected off of a mirror directly below it on a 45 degree angle. This makes the projection distance about the height of the triangle base plus the height of the coffee table.

After a little consideration I decided that it would be a little disappointing if the screen could not be large enough to enjoy, the seated height of my couch is 42cm and decided that the coffee table would need to be about the same height. I've had a Dell 1200MP projector hanging unused from my ceiling for upwards of two years since I brought my second-hand NEC GT-6000 and so it was immediately obvious that I would use it for this project. I used the projector throw calculator from Projector Central to settle on a 100cm screen, 80cm x 60cm at an aspect ratio of 4:3.

Conveniently the horizontal and vertical profile of a mirror the same size would turn out to be 42.43cm fitting in nicely with my intended height of about 42cm. If we consider that the intended image height is 80cm x 60cm then the mirror would need to be larger so that the vertical profile once on a 45degree angle is 60cm. However this assumes a rectangular projection however and that is not the case, as the image gets further from the projector the larger it gets and so when it reaches the mirror it still has the vertical height of the cabinet to travel before it reaches the table top and so the mirror need not be the full size which allows us to keep the height of the coffee table down.