Acoustic condition sensor employing a plurality of mutually non-orthogonal waves

1. A method of determining information relating to a contact on a contact sensitive device comprising:

providing a member capable of supporting mechanical propagation of a vibration having a vibration frequency and at least one sensor adapted for producing a signal at the vibration frequency representing vibrations in the member;

applying a contact to the member at a location which perturbs the mechanical propagation of the vibration;

producing the signal using the at least one sensor, representing the perturbed mechanical vibration at the vibration frequency, while preserving phase information therein; and

digitally processing the signal at an oversampled rate with respect to the vibration frequency, to calculate the location of the contact based on at least a phase of the sensed signal representing the perturbed mechanical vibration.

2. A method according to claim 1 , wherein the plurality of sensors is three or more.

3. A method according to claim 1 , comprising suppressing reflected waves by placing an absorber at the edges of the member.

4. A method according to claim 1 , wherein the mechanical vibrations comprise mechanical vibrations having at least two distinct frequencies, further comprising the step of digitally processing the signal representing the at least two mechanical vibrations at an oversampled rate with respect to each of the at least two distinct frequencies.

5. A physical computer readable medium for storing a set of instructions readable by a programmable processor, for determining information relating to a contact on a contact sensitive device comprising, performing the steps of:

transducing an oscillating signal at an oscillating frequency representing vibrations within the contact sensitive device which is perturbed by the contact, into a digital signal oversampled with respect to the oscillating frequency, while preserving oscillation phase information;

calculating the location of the contact based at least a phase of the transduced oscillating signal represented in the digital signal; and

producing an output dependent on the calculated location.

6. The computer readable medium according to claim 5 , wherein the digital signal is digitized by at least two digitizers differing in respective phase sensitivity, each operating at a rate higher than a Nyquist rate for the vibrations.

7. The computer readable medium according to claim 5 , further comprising repetitively controlling a generation of the vibrations in the medium.

8. The computer readable medium according to claim 5 , wherein said calculating comprises analyzing a digital signal representing at least two superposed vibrations differing in respective oscillation frequency.

9. The computer readable medium according to claim 5 , wherein the contact on the medium changes a relative phase of a vibration proximate to the location with respect to vibrations distant from the location.

10. A contact sensitive device comprising:

a member capable of supporting propagation of vibrations having a vibration frequency;

at least one sensor mounted on the member for measuring vibrations in the member, wherein the at least one sensor transduces a vibration into an oscillating electrical waveform preserving the oscillations of the vibration at the vibration frequency while preserving phase information represented therein; and

a processor responsive to the oscillating electrical waveform of the at least one sensor and analyzing at least the preserved phase information at the vibration frequency from the oscillating electrical waveform, to determine the location of the contact on the member.

11. A contact sensitive device according to claim 10 comprising an absorber at edges of the member whereby reflected waves are suppressed.

12. A contact sensitive device according to claim 11 , wherein the absorber and the member are selected so as to reduce reflections of vibrations from the edges of the member.

13. A contact sensitive device according to claim 10 , wherein said processor separately analyzes vibrations having different respective vibration frequencies.

14. A contact sensitive device according to claim 10 , comprising four sensors on the member.

15. A contact sensitive device according to claim 10 comprising three or more sensors on the member.

16. A contact sensitive device according to claim 10 , wherein the processor analyzes time-dispersion information in the oscillating electrical waveform at the vibration frequency.

17. A contact sensitive device according to claim 10 , further comprising an emitting transducer mounted to the member to excite vibrations at the vibration frequency in the member.

18. A contact sensitive device according to claim 17 , wherein the emitting transducer also functions as one of the sensors.

19. A contact sensitive device according to claim 10 wherein the member is transparent.

20. A contact sensitive device according to claim 10 wherein the member is a liquid crystal display screen.