Patent ID: 6392167
Filing Date: 2002-05-21
Classification: G06F

Abstract:
A touch position sensing system for detecting a location of a touch on a substrate having a four sided perimeter, comprising:a transducer including a pseudo random noise generator, and configured to transmit and modulate by pseudo random coding acoustic waves and to decode reflected waves generated by the acoustic waves by autocorrelating said pseudo random coding; a substrate configured to propagate the acoustic waves, including a touch surface having a first axis along a side of the perimeter of said substrate and a second axis which is perpendicular to the first axis and located along a second side of the perimeter; and, a first reflective array configured to reflect the acoustic waves transmitted by said transducer such that reflected waves are generated traveling parallel to the second axis, having a length substantially as long as the side of said perimeter corresponding to the first axis including partially reflective grating along said length and disposed lengthwise along said first axis of said substrate; wherein a touch to the touch surface attenuates the reflected waves such that said modulation by pseudo random coding of acoustic waves is varied, said transducer configured to detect the location of the touch based on variation in autocorrelation of the varied pseudo random coding included in the reflected waves.