Touch pad

• US 8,319,752 B2
• Filed: 07/30/2008
• Issued: 11/27/2012
• Est. Priority Date: 02/06/2002
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touch Solutions, Inc.
• Inventors: Hardie-Bick, Anthony Richard
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): HOLTON, STEVEN E
• Application Number:
  US12/182,734
• Publication Number:
  US 20080284755A1
• Time in Patent Office: 1,581 Days
• Field of Search: 345173-178, 178 1801- 1811
• 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 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, wherein the acoustic signals comprise a plurality of frequency components;

(b) extracting phase difference information from said acoustic signals, said step of extracting phase difference information comprising 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; 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.

2. A method according to claim 1, wherein said step of transforming each said acoustic signal to generate a set of data comprises a Fast Fourier Transform of said acoustic signals.

3. A method according to claim 1, wherein the location of said acoustic interaction is defined by interpolating between locations of known phase difference profiles.

4. A method according to claim 1, including updating a cursor location parameter in a graphical user interface in response to an incrementally detected change in the location of said object.

5. A method according to claim 1, wherein said acoustic interaction between an object and a surface is a continuous frictional interaction.

6. A method according to claim 1, including electrically combining acoustic signals from a plurality of respective locations in said surface.

7. A method according to claim 6, wherein said acoustic signals are combined in antiphase.

8. 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, 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;

(b) extracting phase difference information from said acoustic signals, said step of extracting phase difference information comprising 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; 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.

9. A method according to claim 8, wherein said step of transforming each said acoustic signal to generate a set of data comprises a Fast Fourier Transform of said acoustic signals.