Method For Determining The Locations Of One Or More Impacts Or Touches On A Surface Of An Object Including Two Or More Transducers

• US 20120120031A1
• Filed: 05/26/2010
• Published: 05/17/2012
• Est. Priority Date: 06/19/2009
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touch Solutions, Inc.
• Inventors: Thuillier, Bruno
• Granted Patent: US 9,459,732 B2
• Time in Patent Office: Days
• US Class Current: 345/177
• CPC Class Codes: G06F 3/043 using propagating acoustic waves
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate

Abstract

The invention relates to a method for determining the locations of one or more impacts or touches on a surface of an object including two or more transducers which improves the precision of localisation even for low signal to noise ratios and furthermore provides the possibility to identify multi touch or multi impact situations. To achieve these objects the method comprises the steps of: a) receiving a signal, in particular an acoustic signal, from each one of the transducers, wherein the signals correspond to at least one impact at least one location on the surface; b) determining a representative value based on the signals received in step a) and predetermined properties, in particular acoustic properties, of the object at a given location on the surface of the object; and c) deciding whether the at least one impact at the at least one location on the surface of step a) corresponds to the given location on the surface based on a comparison of the representative value and the corresponding value of the at least two signals.

Claims

1. A method for determining the locations of one or more impacts or touches on a surface of an object including two or more transducers comprising the steps of:

a) receiving a signal, in particular an acoustic signal, from each one of the transducers, wherein the signals correspond to at least one impact at least one location on the surface;

b) determining a representative value based on the signals received in step a) and predetermined properties, in particular acoustic properties, of the object at a given location on the surface of the object; and

c) deciding whether the at least one impact at the at least one location on the surface of step a) corresponds to the given location on the surface based on a comparison of the representative value and the corresponding value of the at least two signals.

2. The method according to claim 1, wherein step b) comprises a step b1) of determining a reconstructed source signal for the given location based on the properties of the object at the given location and the at least two signals received in step a).

3. The method according to claim 2, wherein step b) further comprises a step b2) of determining at least two reconstructed signals for a given location based on the reconstructed source signal and the properties of the surface of the object at the given location.

4. The method according to claim 3, wherein in step c) the comparison comprises determining an error energy, in particular the numerical expression

5. The method according to claim 1, wherein step b) and c) are combined by directly determining the error energy using the expression

6. The method according to claim 1, wherein step b) comprises a filtering step b3) for removing background noise around the maximum of the reconstructed source signal, in particular, in time domain.

7. The method according to claim 6, wherein step b3) comprises the steps of:

transforming the reconstructed input source signal of step b1) in the time domain;

then determining a time (t_max) at which the reconstructed input signal has a maximum amplitude;

then filtering out a time window around t_max to obtained a modified reconstructed source signal corresponding to a given impact at the given location on the surface of the object;

retransforming the modified reconstructed source signal into frequency domain, and using the modified reconstructed source signal in the frequency domain in step b2) as the reconstructed source signal.

8. The method according to claim 1, wherein the steps a) through c) are repeated for a plurality of locations on the surface of the object.

9. The method according to claim 1, wherein step b) comprises a triggering step to carry out step b3) only for locations close to the location of a real impact.

10. The method according to claim 4, wherein step c) comprises determining the signal energy of the signals received in step a), in particular determining the value

11. The method according to claim 4, wherein step c) comprises deciding that the given location corresponds to one location of an impact when the error energy represents an absolute or relative minimum value compared to the error energy of neighbouring locations.

12. The method according to claim 10, wherein the minimum of the error energy or the maximum of the ratio is determined after having analysed all locations i of the surface of the object for which predetermined properties have been determined, or is determined by comparing the value for a given location with the value of a previously analysed location and only keeping the smaller one in case of error energy or the larger one in case of the ratio.

13. The method according to claim 1, wherein both the amplitude and phase information of the received signals of step a) are used in step b).

14. Computer program product comprising computer executable instructions for carrying out a method for determining the locations of one or more impacts or touches on a surface of an object including two or more transducers comprising the steps of:

a) receiving a signal, in particular an acoustic signal, from each one of the transducers, wherein the signals correspond to at least one impact at least one location on the surface;

b) determining a representative value based on the signals received in step a) and predetermined properties, in particular acoustic properties, of the object at a given location on the surface of the object; and

c) deciding whether the at least one impact at the at least one location on the surface of step a) corresponds to the given location on the surface based on a comparison of the representative value and the corresponding value of the at least two signals.

15. Touch sensitive device comprising an interaction surface and at least two transducers and a control unit configured to a) receive a signal, in particular an acoustic signal, from each one of the transducers, wherein the signals correspond to at least one impact at at least one location on the surface;

b) determine a representative value based on the signals received in step a) and predetermined properties, in particular acoustic properties, of the object at a given location on the surface of the object; and

c) decide whether the at least one impact at the at least one location on the surface of step a) corresponds to the given location on the surface based on a comparison of the representative value and the corresponding value of the at least two signals.