Patent ID: 7764276

Claim:
A touch detection apparatus comprising: a primary substrate having a surface capable of propagating acoustic waves and being so characterized that said surface is touch sensitive such that a touch on said surface causes a perturbation, in the form of at least a partial absorption of energy, of an acoustic wave propagating through a region of desired touch detection; at least one transmitter secondary substrate mounted along an edge of said primary substrate; at least one receiver secondary substrate mounted along another edge of said primary substrate opposite from said transmitter secondary substrate; at least one input transducer, coupled to a said transmitter secondary substrate, which is operative to launch a burst of acoustic waves onto said transmitter secondary substrate; at least one output acoustic wave transducer coupled to said receiver secondary substrate that detects received acoustic waves; a first coupling means disposed between said transmitter secondary substrate and said primary substrate to transfer acoustic wave components to a first edge defining a first axis of the desired touch sensing area of said primary substrate surface; a second coupling means disposed between said primary substrate and said receiver secondary substrate to transfer and redirect acoustic waves to the output transducer after propagating across the first surface at least once such that said wave components are caused to traverse said axis along a progression of paths differing in time and associated with different touch positions along the axis; at least one wave redirecting means disposed upon at least one secondary substrate which derives wave components separated in time from a launched wave, said wave components substantially perpendicular to the launched wave; and circuitry coupled to said input and output transducers which initiates acoustic wave bursts causing derived wave components separated in time across said primary substrate surface and detects touch-induced perturbations of said received waves indicative of the location of a touch along said axis, said circuit means also including means for determining, by an analysis based on the transit time of said detected perturbed wave burst component, which of a plurality of paths was traversed by said touch-perturbed wave burst component and thus determining the location of the touch along said axis of said substrate surface.