Radial transducer for acoustic wave touch sensor

Abstract

Radial transducers are provided for acoustic touch sensors. Different radial transducer arrangements may allow for locating multiple simultaneous touches without ambiguity, in some embodiments without a bezel. Instead of transmitting acoustic waves along a line to be reflected at multiple points, surface acoustic waves are transmitted in a radial wave pattern. Surface acoustic waves are transmitted along different angles spread out over at least part of the touch region. Various techniques may be used to generate the radial wave pattern, such as a convex wedge of a wedge transducer, interference patterns, a curved piezoelectric element, a curved reflector, a curved edge of the substrate, a curved grating, or one or more lenses. These devices for controlling the spread of the surface acoustic waves may alternatively be used for control of the surface acoustic rays for transmission along a single line or just along two lines (e.g., X and Y axes).