Acoustic touch position sensor using shear wave propagation

• US 5,260,521 A
• Filed: 06/15/1992
• Issued: 11/09/1993
• Est. Priority Date: 11/16/1990
• Status: Expired due to Term

• Current Assignee: The Whitaker Corporation (Meggitt PLC)
• Original Assignee: Exzec Incorporated
• Inventors: Knowles, Terence J.
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): LOOMIS, PAUL A
• Application Number:
  US07/898,458
• Time in Patent Office: 512 Days
• Field of Search: 178/18, 178/19, 340/206, 340/712, 367/907
• US Class Current: 178/18.04
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate
• CPC Class Codes: Y10S 367/907 Coordinate determination

Abstract

An acoustic touch position sensor is shown in which a transducer coupled to a side of a substrate imparts a shear wave into the substrate for propagation along a first axis. A reflective array is disposed along the first axis to reflect portions of the shear wave along a plurality of parallel paths extending across a touch surface of the substrate to a second reflective array the axis of which is parallel to the axis of the first reflective array. The second reflective array reflects the shear waves incident thereto to a transducer mounted on the side of the substrate and responsive to shear waves propagated thereto for providing a signal representative of these shear waves. A touch on the substrate results in a partial absorption of the energy in the shear wave so as to produce a perturbation therein which is sensed to determine the axial position of the touch on the substrate. In a second embodiment a single transducer and reflective array is provided for each axis, a coordinate on which is to be determined. In a third embodiment of the present invention, a single transducer is provided to transmit and receive shear waves propagating along perpendicular parallel paths.

Claims

1. A touch responsive panel comprising:

a substrate capable of propagating therein an acoustic wave extending through the thickness of said substrate between a first touch surface and a second touch surface;

means for propagating an acoustic wave in said substrate along a plurality of substantially parallel paths, said acoustic wave extending through the thickness of said substrate such that a touch on either said first touch surface or on said second touch surface intersecting one of said paths forms a detectable perturbation in said acoustic wave representative of the position of said touch on said substrate.

2. A touch responsive panel as recited in claim 1 wherein said propagating means includes at least one transducer mounted on said substrate for generating a shear wave for propagation in said substrate.

3. A touch responsive panel as recited in claims 2 wherein said transducer generates a zeroth order horizontally polarized shear wave for propagation in said substrate.

4. A touch responsive panel as recited in claim 1 wherein said propagating means includes at least one transducer mounted on said substrate for generating an acoustic wave with no substantial z component.

5. A touch responsive panel as recited in claim 1 wherein said propagating means includes a transducer mounted on said substrate for generating a shear wave for propagation in said substrate and an array of reflective elements aligned along an axis of said substrate for reflecting portions of said shear wave along said parallel paths.

6. A touch responsive panel comprising:

a substrate capable of propagating an acoustic wave therein, said substrate having a first edge, a second edge extending substantially perpendicular to said first edge and a third edge extending at a substantially 45°

angle with respect to said first and second edges; and

an acoustic wave generator mounted on said substrate for generating an acoustic wave propagating in said substrate along a first path substantially parallel to said first substrate edge, said first path intersecting said third substrate edge and said third substrate edge reflecting said acoustic wave along a second path substantially parallel to said second substrate edge, said acoustic wave being such that a touch on said substrate intersecting a path of an acoustic wave propagating therein forms a detectable perturbation in said acoustic wave.

7. A touch responsive panel as recited in claim 6 wherein said acoustic wave generator includes a transducer mounted on said substrate for generating an acoustic wave extending through the thickness of said substrate.

8. A touch responsive panel as recited in claim 6 wherein said acoustic wave generator includes a transducer mounted on said substrate for generating a shear wave for propagation in said substrate.

9. A touch responsive panel as recited in claim 6 wherein said propagating means includes at least one transducer mounted on said substrate for generating an acoustic wave with no z component.

10. A touch responsive panel comprising:

a substrate capable of propagating an acoustic wave therein;

a first transducer mounted on an edge of said substrate to generate an acoustic wave propagating in said substrate such that a touch intersecting said acoustic wave forms a detectable perturbation in said wave; and

conductive frit bonding said first transducer to said substrate edge.

11. A touch responsive panel as recited in claim 10 wherein said conductive frit forms a ground contact for said transducer.

12. A touch responsive panel as recited in claim 10 further including a second transducer mounted on an edge surface of said substrate adjacent to said first transducer for generating a second acoustic wave propagating in said substrate, said conductive frit extending to said mounting surface of said second transducer and bonding said second transducer to said substrate.

13. A touch responsive panel as recited in claim 12 wherein said conductive frit forms a common ground connection for said first and second transducer.

14. A touch responsive panel as recited in claim 10 wherein the height of said transducer and the height of said frit are to substantially equal to the thickness of said substrate.

15. A touch responsive panel as recited in claim 10 wherein said transducer generates a shear wave propagating in said substrate.

16. A touch responsive panel as recited in claim 10 wherein said transducer generates a zeroth order horizontally polarized shear wave propagating in said substrate.

17. An acoustic touch panel comprising:

a substrate capable of propagating an acoustic wave therein;

means coupled to said substrate for generating an acoustic wave propagating in said substrate such that a touch intersecting a path of said acoustic wave forms a detectable perturbation in said acoustic wave;

said generating means being responsive to the receipt of an acoustic wave propagating in said substrate to generate a signal representative of a received acoustic wave;

an amplifier having an adjustable gain control for amplifying said acoustic wave signal;

a demodulator for demodulating said amplified acoustic wave signal;

a threshold device coupled to the output of said demodulating means to provide an output signal that follows the input to the threshold device if the threshold device is above a predetermined level; and

a feedback loop coupled between the output of said threshold device and said amplifier to adjust the gain of said amplifier to increase the difference in amplitude of an acoustic wave signal representing an untouched point and a touched point on said substrate.

18. An acoustic touch panel as recited in claim 17 wherein said acoustic wave is a zeroth order horizontally polarized shear wave.

19. An acoustic touch panel comprising:

a substrate capable of propagating therein an acoustic wave;

first means for generating an acoustic wave propagating in said substrate along a plurality of substantially parallel paths extending across said substrate such that a touch on said substrate intersecting a path of an acoustic wave forms a detectable perturbation therein representative of the position of a touch relative to a first axis, said generating means receiving acoustic waves for generating a signal representative thereof;

means for storing the time at which a first acoustic wave is propagated in said substrate by said first generating means;

means for storing the time at which a first acoustic wave propagating along the shortest of said paths and a last acoustic wave propagating along the longest of said paths is received by said first generating means; and

means responsive to said stored times for automatically calculating the size of a touch area of said touch panel along said first axis.

20. An acoustic touch panel as recited in claim 19 further including

second means for generating an acoustic wave propagating in said substrate along a plurality of substantially parallel second paths extending across said substrate such that a touch on said substrate intersecting a path of an acoustic wave forms a detectable perturbation therein representative of the position of a touch relative to a second axis, said second axis being substantially perpendicular to said first axis, and said second generating means receiving acoustic waves for generating a signal representative thereof;

means for storing the time at which a first acoustic wave is propagated in said substrate by said second generating means;

means for storing the time at which a first acoustic wave propagating along the shortest of said second paths and a last acoustic wave propagating along the longest of said second paths is received by said second generating means; and

means responsive to said stored times for automatically calculating the size of a touch area of said touch panel along said second axis.

21. A touch responsive panel comprising:

a substrate capable of propagating therein an acoustic wave with no substantial z-axis component, said substrate having at least one touch surface thereon; and

means for propagating an acoustic wave with no substantial z-axis component in said substrate along a plurality of substantially parallel paths such that a touch on said touch surface intersecting one of said paths forms a detectable perturbation in said acoustic wave representative of the position of said touch on said substrate.

22. A touch responsive panel as recited in claim 21 wherein said propagating means includes at least one transducer mounted on said substrate for generating a shear wave for propagation in said substrate.

23. A touch responsive panel as recited in claim 22 wherein said transducer generates a zeroth order horizontally polarized shear wave for propagation in said substrate.

24. A touch responsive panel as recited in claim 21 wherein said propagating means includes a transducer mounted on said substrate for generating a shear wave for propagation in said substrate and an array of reflective elements aligned along an axis of said substrate for reflecting portions of said shear wave along said parallel paths.