System and method for detecting and localizing at least one touch on a touch-sensitive surface of an object

1. A system for detecting and localizing at least one touch on a touch-sensitive surface of an object, comprising:

at least two separate sources for transmitting bulk acoustic waves in the touch-sensitive surface, configured to generate acoustic interference between the transmitted waves;

at least one bulk acoustic wave receiver after propagation and interference thereof in the touch-sensitive surface, configured to supply a reception signal on the basis of the acoustic waves received;

means for localizing at least one touch on the touch-sensitive surface of the object by comparing certain spectral characteristics of the reception signal to a set of reference spectral characteristics;

means for measuring a temperature of the touch-sensitive surface; and

means for adapting the spectral characteristics of the reception signal or the reference spectral characteristics by a frequency shift of at least some of the spectral characteristics as a function of the temperature measured.

2. A system for detecting and localizing at least one touch according to claim 1 , wherein the adaptation means is configured to shift each spectral characteristic of the reception signal according to the temperature measured, on the basis of a predefined correspondence saved in memory, for a set of pre-determined temperatures, between a plurality of successive frequencies or frequency bands and a plurality of frequency shift values associated respectively with these successive frequencies or frequency bands.

3. A system for detecting and localizing at least one touch according to claim 1 , wherein the means for measuring temperature comprises:

a calculator for calculating a norm of the spectrum of the reception signal in a pre-determined frequency band;

a comparator of this calculated norm to a set of reference norms associated respectively with a set of temperatures;

a temperature selector on the basis of the result supplied by the comparator.

4. A system for detecting and localizing at least one touch according to claim 3 , wherein the transmission sources and the receiver are arranged asymmetrically on a periphery of the touch-sensitive surface and excitation of the transmission sources is established such that a relationship between the set of reference norms and the set of temperatures is an increasing or decreasing monotonic relationship.

5. A system for detecting and localizing at least one touch according to claim 1 , wherein the means for measuring temperature comprises a temperature sensor, or a thermistor, arranged in contact with the touch-sensitive surface.

6. A system for detecting and localizing at least one touch according to claim 1 , wherein the bulk acoustic waves being propagated in the touch-sensitive surface in a form of Lamb waves, two receivers are arranged facing each other against the touch-sensitive surface, the receivers being polarized and interconnected to only receive essentially the fundamental anti-symmetric Lamb mode and reject symmetric waves and transverse horizontal waves.

7. A system for detecting and localizing at least one touch according to claim 6 , wherein the two receivers are arranged to have symmetrically oriented polarizations relative to the median plane of the touch-sensitive surface and are electrically connected together in series.

8. A method for detecting and localizing at least one touch on a touch-sensitive surface of an object, comprising:

transmission in the touch-sensitive surface, by at least two separate sources, of mutually interfering bulk acoustic waves;

reception, by at least one receiver, of bulk acoustic waves after the propagation and interference thereof in the touch-sensitive surface, and supply of a reception signal on the basis of the acoustic waves received;

localization of at least one touch on the touch-sensitive surface of the object by comparing certain spectral characteristics of the reception signal to a set of reference spectral characteristics saved in memory;

measurement of a temperature of the touch-sensitive surface; and

adaptation of the spectral characteristics of the reception signal or the reference spectral characteristics by a frequency shift of at least some of these spectral characteristics as a function of the temperature measured.

9. A method for detecting and localizing at least one touch according to claim 8 , wherein:

each spectral characteristic of the reception signal is shifted according to the temperature measured, on the basis of a predefined correspondence, for a set of pre-determined temperatures, between a plurality of successive frequencies or frequency bands and a plurality of frequency shift values associated respectively with these successive frequencies or frequency bands; and

the frequency shift values are learned during a prior learning phase by matching spectral characteristics retrieved off-load at different temperatures with spectral characteristics retrieved off-load at the temperature for learning the reference spectral characteristics.

10. A method for detecting and localizing at least one touch according to claim 8 , wherein the bulk acoustic waves are transmitted in a form of successive pulse wavetrain transmissions at different frequencies between a minimum frequency and a maximum frequency common to the wavetrains, and wherein:

the minimum frequency is greater than one-third of the maximum frequency,

each wavetrain from the second differs from the previous one by a frequency shift of the pulse waves thereof by a fraction of the mean frequency deviation between the pulse waves.