Optical Touch Tomography

Abstract

An optical touch-sensitive device has the capability to determine touch locations of multiple simultaneous touch events. The touch events disturb optical beams propagating across the touch sensitive surface. With multi-touch events, a single beam can be disturbed by more than one touch event. In one aspect, a non-linear transform is applied to measurements of the optical beams in order to linearize the effects of multiple touch events on a single optical beam. In another aspect, the effect of known touch events (i.e., reference touches) is modeled in advance, and then unknown touch events are determined with respect to the reference touches.

What is claimed is: 
     
         1 . A method of resolving a multi-touch event occurring at a plurality of touch regions on a touch sensitive surface, the method comprising a computer processor executing the steps of:
 receiving a plurality of beam measurement values bn resulting from the multi-touch event, wherein different beam measurement values bn result from different optical beams transmitted across the touch sensitive surface and the multi-touch event disturbs optical beams in a vicinity of the touch region;   determining binding value estimates p′, from the beam measurement values bn, the binding value estimates p′i estimating optical beam disturbance at corresponding locations Li of the touch-sensitive surface, wherein determining the binding value estimates p′i is based on modeling a transfer function from binding values pi to the beam measurement values bn as a linear transfer function; and   determining the touch regions for the multi-touch event from the binding value estimates p′ i .