Patent ID: 7184898

Claim:
A contact sensitive device comprising: a member capable of supporting bending waves; a plurality of sensors for measuring bending wave vibration in the member, wherein each of the sensors determines a measured bending wave signal; and a processor responsive to the measured bending wave signals to calculate a location of a contact on the member, the processor calculating a phase angle for each measured bending wave signal and a phase difference between the phase angles of at least two pairs of sensors so that at least two phase differences are calculated and utilized in determining the location of the contact, wherein the phase difference between the phase angles of each pair of sensors is given by Δθ lm =θ 1 −θ m =k (ω 0 )Δ x lm +2π n lm , where θ l and θ m are the phase angles of respective measured bending wave signals ΔX lm =x l −x m is a path length difference of two sensors, x l and x m being respective distances from the contact location to each sensor, k(ω 0 ) is a wavevector and n lm is an integer.