Making a multitouch table: The plan
After studying some designs for multitouch displays made by other people we have began thinking of how can we incorporate all this into our design and also give it a personal touch. At the beginning I have planned to make a window-like screen, but then we have decided for the desk scenario … the way I see it it will take less space than a vertical one.
To make a multitouch screen you need the following components: a plexi-glass surface, a projecting surface, a lot of IR diodes, an IR camera, and a projector. There are also a lot of other bits of everything needed but these are the main components for the most classical multitouch setup we are aiming at. This post is just about the overall plan so I will not go into the details.
Because we have a limited choice of projectors and none of the available projectors was really wide angle we were trying to improvise a bit with a mirror reflection. This way the system becomes more complex but also smaller. Of course there was another problem: where to put the projector? Because of the reflection the projector has to be placed between the mirror and the projection surface. Of course placing it directly in-between is silly. It has to be placed on the side so that it does not occlude the picture but still close enough that the distortion angle is not too big (the name of the distortion is called keystone effect and can be to some degree fixed using a function with the same name that can be found on many projectors). We have decided to make a wide frame for the plexi-glass surface and hide the projector under it. The frame is one of the components that are in theory not really needed but the fact that all the necessary elements cannot stay in place just by themselves makes it an implicit necessity. Also a wider frame will allow people to lean on the sides of our multitouch desk not putting too much stress directly on the surface.
The next decision to be made was regarding IR diodes and wiring. The diodes should be positioned around the plexi-glass surface. Our idea was to make the frame thinner on the inner side, leaving enough room to anchor the surface and a narrow drench to put in the mount for diodes and wiring. The whole thing is then fixed in place using an aluminum cover. This probably does not make much sense now but I will elaborate in the future posts.
Less attention has been given to the sides of the desk. The main function of the sides is to protect the interior from mechanical and optical interferences. Our idea is to start with a simple aluminum cube, fix some wooden plates to it and drill some holes for the ventilation.
Anyway … here is a 3D model of our frame as it was planned before we started acquiring materials. My next post will be on the making of the actual frame (with pictures).