Multitouch screen

Overview

A touchscreen interface that allows for multiple points of contact for uniquely manipulating objects and information on screen.

Design concepts

• Ideally would be linked to screen resolution rather than physical size making it highly scalable.
• A transparent layer capable of being laid over any existing screen, projected or otherwise.
• System software would control generic interaction techniques that would work with all existing applications as well as newly developed ones.

Existing designs

• Jeff Han's: Acrylic sheet backed with a difuser(a solid surface to project on) and lined along the side with LEDs in a mobile frame capable of holding the projector and camera below the screen. A small solid lip surrounds the edge of the acrylic to prevent the light from escaping at acute angles causing the light to be reflected internally along the full length of the sheet. Placing a finger or other object on the surface causes light to scatter in a mostly perpendicular direction to the sheet making a bright spot on the difuser below which the camera then picks up and registers as a manipulation point. It is unknown that type LEDs Jeff Han uses, but other examples use infrared LEDs, which most digital cameras/webcams are capable of picking up. This is likely the cheapest way to produce large multitouch screens.

Preliminary notes

Working off the Jeff Han design, that is to say acrylic sheet with IR LEDs, projector from underneath, and IR sensitive camera, I'm going to see how shallow I can get the table by use of a concave mirror. The concave mirror should make the image larger, thereby decreasing the distance the projector needs to be from the projection surface, but will flip this image(easily corrected on the projector itself).

Progress

• 05/13/2007: Obtained a dinner plate sized convex mirror. Testing on focal length distance and size increase can begin.