Touch Pad

• US 20080284755A1
• Filed: 07/30/2008
• Published: 11/20/2008
• Est. Priority Date: 02/06/2002
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Soundtouch Limited
• Inventors: Hardie-Bick, Anthony Richard
• Granted Patent: US 8,319,752 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 3/0433 in which the acoustic waves are either generated by a movable member and propagated within a surface layer or propagated within a surface layer and captured by a movable member
• CPC Class Codes: Y10S 367/907 Coordinate determination

Abstract

A touch pad (101) includes transducers (201-204) for receiving acoustic signals resulting from touch events, such as the continuous movement of a fingertip across the surface (105) of the touch pad. The acoustic signals are acquired at different transducer locations in the surface. Signals from different transducers are combined, preferably in antiphase, to improve signal characteristics. The transducer signals are supplied to a stereo analogue to digital converter (407). Phase differences (706) are obtained and compared (703) with phase difference profiles (607) of known location, in order to identify the location of the touch event. An index (606) is used to identify candidate locations to reduce the amount of processing. Interpolation (705) is used to locate the touch event between profile locations.

Claims

1. A touch pad for acquiring acoustic signals resulting from touch events, comprising:

a surface having an area in which said touch events may be formed;

a plurality of transducers for acquiring said acoustic signals at a plurality of different locations in said surface;

an arrangement for electrically combining said acoustic signals from a plurality of said different locations into a combined signal; and

an output for supplying representations of said acoustic signals to an analog to digital converter in response to said combined signal.

2. A touch pad according to claim 1, including a signal conditioner arranged to emphasize preferred components of said acoustic signals.

3. A touch pad according to claim 1, wherein said arrangement includes connections for connecting together a plurality of said transducers in antiphase so as to electrically combine preferred components of said acoustic signals.

5. A touch pad according to claim 1, wherein signals from a plurality of said transducers are electrically combined by connecting said plurality of transducers in series.

6. A touch pad according to claim 1, wherein signals from a plurality of said transducers are electrically combined by connecting said plurality of transducers in parallel.

7. A touch pad according to claim 1, wherein a pair of said transducers whose signals are combined are located diagonally relative to said surface.

4. (canceled)

8-10. -10. (canceled)

11. A method for acquiring and processing acoustic signals arising from an acoustic interaction between an object and a surface, the method comprising the operations of:

(a) acquiring the said acoustic signals at a plurality of locations in said surface;

(b) extracting phase difference information from said acoustic signals; and

(c) locating the said acoustic interaction on the basis of comparisons between said phase difference information and a plurality of phase difference profiles whose respective locations are known.

13. A method according to claim 11, wherein the location of said acoustic interaction is defined by interpolating between locations of known phase difference profiles.

14. A method according to claim 11, including updating a cursor location parameter in a graphical user interface in response to an incrementally detected change in the location of said object.

15. A method according to claim 11, wherein said acoustic interaction between an object and a surface is a continuous frictional interaction.

16. A method according to claim 11, including electrically combining acoustic signals from a plurality of respective locations in said surface.

17. A method according to claim 16, wherein said acoustic signals are combined in antiphase.

27. A method according to claim 11, wherein the acoustic signals comprise a plurality of frequency components, and said step of extracting phase difference information comprises the step of transforming each said acoustic signal to generate a set of data, each said set of data defining information about a phase angle of each said frequency component of said acoustic signals.

28. A method according to claim 27, wherein said step of transforming each said acoustic signal to generate a set of data comprises a Fast Fourier Transform of said acoustic signals.

29. A method according to claim 11, wherein a first acoustic signal and a second acoustic signal are acquired from different locations in said surface, each of said first and second acoustic signals comprise a plurality of frequency components, and said step of extracting phase difference information comprises the steps of:

transforming said first and said second acoustic signals to generate a first set of data and a second set of data, said first and second sets of data defining information about a phase angle of each said frequency component of said acoustic signals; and

subtracting items of said first set of data from respective items of said second set of data to generate said phase difference information.

30. A method according to claim 29, wherein said step of transforming each said acoustic signal to generate a set of data comprises a Fast Fourier Transform of said acoustic signals.

12. (canceled)

18. (canceled)

19. A method for calibrating an acoustic touch pad by acquiring and processing acoustic signals resulting from sound supplied to said touch pad at selected locations on the surface of said touch pad;

the method comprising repeated operations of;

(a) selecting a location for calibration;

(b) supplying a sound to said surface at said selected location;

(c) acquiring the said acoustic signals from a plurality of transducers in said surface;

(d) extracting a location-related profile from said acoustic signals; and

(e) storing said location-related profile in association with said selected location.

21. A computer readable medium having program instructions encoded upon it for causing a computer to execute the method of claim 19.

20. (canceled)

22-26. -26. (canceled)