Acoustic touch position sensor with first order lamb wave reflective arrays

• US 5,162,618 A
• Filed: 11/16/1990
• Issued: 11/10/1992
• 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): SCHREYER, STAFFORD
• Application Number:
  US07/614,860
• Time in Patent Office: 725 Days
• Field of Search: 178/18, 178/19, 340/706, 340/702, 267/907
• 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 wherein a Lamb wave is imparted into a substrate by a transducer mounted on the substrate, the Lamb wave propagating along a first axis. Top and bottom reflecting arrays are disposed along the first axis to reflect portions of one mode of the Lamb wave along a plurality of parallel paths extending across a touch surface of the substrate to a second pair of top and bottom reflect arrays. The second pair of top and bottom reflecting arrays reflect the Lamb waves incident thereto along an axis parallel to the first axis to a receiving transducer that provides a signal representative of the received Lamb waves. A touch on the substrate results in a partial absorption of the energy in the Lamb wave propagating along a path intersection the touch position 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 for two axes.

Claims

1. A touch position sensor comprising:

a substrate capable of supporting antisymmetric and symmetric Lamb waves propagating therein, said substrate having a touch surface;

first means coupled to said substrate for imparting a Lamb wave into said substrate, said Lamb wave propagating along a first axis;

first means disposed along said first axis for reflecting portions of said to Lamb wave along first parallel paths extending across the touch surface of said substrate, each first path representing a different axial position, a touch on said substrate touch surface forming a perturbation in a Lamb wave propagating along a first path intersecting the position of said touch; and

means for sensing the occurrence of a perturbation in said Lamb waves to determine the axial position of a touch on said substrate relative to said first axis.

2. A touch position sensor as recited in claim 1 wherein said reflecting means reflects one type of said Lamb wave, either antisymmetric Lamb wave or symmetric Lamb waves and said reflecting means suppresses the other type of said Lamb wave to prevent interference of said other type of Lamb wave with said one type of Lamb wave.

3. A touch position sensor as recited in claim 2 wherein said reflecting means includes means for suppressing said symmetric Lamb wave.

4. A touch position sensor as recited in claim 2 wherein said reflecting means includes means for suppressing said antisymmetric Lamb wave.

5. A touch position sensor as recited in claim 1 wherein said sensing means includes

second means disposed along an axis generally parallel to said first axis and positioned across said substrate touch surface from said first reflecting means for reflecting Lamb waves from said first reflecting means along said parallel axis and

means coupled to said substrate for receiving said Lamb waves propagating along said parallel axis to provide a signal representative thereof.

6. A touch position sensor as recited in claim 5 wherein said imparting means includes a transmitting transducer coupled to a side of said substrate perpendicular to said first axis and said receiving means includes a transducer coupled to said substrate side spaced from said transmitting transducer and generally perpendicular to the axis of said second reflecting means.

7. A touch position sensor as recited in claim 1 wherein said substrate includes means for reflecting Lamb waves propagating along said first paths back along said first paths to said first reflecting means, said first reflecting means reflecting said reflected Lamb waves along said first axis to said imparting means and said imparting means being responsive to Lamb waves propagated thereto to provide a signal representative of said Lamb waves, said signal being coupled to said perturbation sensing means.

8. A touch position sensor as recited in claim 1 further including

second means for imparting a Lamb wave into said substrate, said Lamb wave propagating along a second axis generally perpendicular to said first axis;

second means disposed along said second axis for reflecting portions of said Lamb wave along second parallel paths extending across the touch surface of said substrate, each path representing different axial position relative to said second axis, a touch on said substrate touch surface forming a perturbation in a Lamb wave propagating along a path intersecting the position of said touch;

said sensing means sensing the occurrence of a perturbation in said Lamb wave to determine the axial position of a touch on said substrate relative to said second axis.

9. A touch position sensor as recited in claim 1 wherein said substrate is formed of glass.

10. A touch position sensor as recited in claim 9 wherein said glass is tempered.

11. A touch position sensor as recited in claim 9 wherein said glass is frosted.

12. A touch position sensor as recited in claim 1 wherein said substrate is formed of metal.

13. A touch position sensor as recited in claim 1 wherein said substrate is formed of plastic.

14. A touch position sensor as recited in claim 1 wherein said substrate is formed of a ceramic.

15. A touch position sensor as recited in claim 1 wherein said imparting means includes a wedge mounted on said substrate and a transducer mounted on said wedge, said transducer vibrating in a manner to generate a compressional wave in said wedge wherein said compressional wave imparts a Lamb wave into said substrate.

16. A touch position sensor as recited in claim 15 wherein said wedge has a wedge angle that is equal to the arcsine of the phase velocity of either of said antisymmetric or symmetric Lamb waves divided by the phase velocity of said compressional wave.

17. A touch position sensor as recited in claim 1 wherein said imparting means includes a compression transducer mounted on a side said substrate perpendicular to said first axis for imparting said Lamb waves into said substrate.

18. A touch position sensor as recited in claim 1 wherein said imparting means includes a symmetric Lamb wave generator.

19. A touch position sensor as recited in claim 18 wherein said symmetric Lamb wave generator includes a length expander generator mounted on a side of said substrate.

20. A touch position sensor as recited in claim 18 wherein said symmetric Lamb wave generator includes a compression transducer mounted on a side of said substrate.

21. A touch position sensor as recited in claim 1 wherein said imparting means includes an antisymmetric Lamb wave generator.

22. A touch position sensor as recited in claim 21 wherein said antisymmetric Lamb wave generator includes a pair of compressional transducers mounted on a side of said substrate and vertically aligned;

and drive signal means for generating a sine wave drive signal and the compliment of said sine wave drive signal wherein the sine wave drive signal is applied to one of said transducers and the compliment drive signal is applied to the other of said transducer.

23. A touch position sensor comprising:

a substrate capable of supporting Lamb waves propagating therein said substrate having a touch surface and said Lamb waves having an antisymmetric mode and a symmetric mode;

means coupled to said substrate for imparting a Lamb wave into said substrate, said Lamb wave propagating along a first axis;

a first array of reflecting elements disposed on said substrate along said first axis for reflecting Lamb waves along first parallel paths extending across the touch surface of said substrate, each first path representing a different axial position relative to said first axis and a touch on said substrate touch surface forming a perturbation in a Lamb wave propagating along a first path intersecting the position of said touch;

means disposed on said substrate relative to said first array for suppressing one of said Lamb wave modes;

a second array of reflecting elements disposed along an axis generally parallel to said first axis for reflecting said Lamb waves along said parallel axis; and

means coupled to said substrate for sensing Lamb waves propagating along said parallel axis to provide a signal representative thereof; and

means responsive to said signal for determining the axial position of a touch on said substrate touch surface relative to said first axis.

24. A touch position sensor as recited in claim 23 wherein said first array is disposed on a first surface of said substrate and said suppressing means includes an array of reflecting elements disposed on a surface of said substrate opposite to said first surface and aligned with the elements of said first array to suppress said antisymmetric mode.

25. A touch position sensor as recited in claim 23 wherein said first array is disposed on a first surface of said substrate and said suppressing means includes an array of reflecting elements disposed on a surface of said substrate opposite to said first surface and shifted relative to the first array by an amount approximately equal to the wavelength of a symmetric mode Lamb wave divided by two to suppress said symmetric mode.

26. A touch position sensor as recited in claim 25 wherein said Lamb waves are first order Lamb waves.

27. A touch position sensor as recited in claim 25 wherein the elements of said suppressing means array are shifted from the elements of said first reflecting array in a direction at right angles to said first axis.

28. A touch position sensor as recited in claim 25 wherein the elements of said suppressing means array are shifted from the elements of said first reflecting array in a direction along said first axis.

29. A touch position sensor as recited in claim 23 further including:

second means coupled to said substrate for imparting a shear wave propagating along a second axis, said second axis intersecting said first axis;

a third array of reflecting elements disposed along said second axis for reflecting portions of said Lamb wave along second parallel paths extending across the touch surface of said substrate, each second path representing a different axial position relative to said second axis and a touch on said substrate touch surface forming a perturbation in a Lamb wave propagating along a second path intersecting the position of said touch;

means disposed on said substrate relative to said third array for suppressing one of said modes;

a fourth array of converting elements disposed along an axis generally parallel to said second axis for reflecting Lamb waves propagating on said second paths along an axis generally parallel to said second axis; and

second means coupled to said substrate for sensing shear waves propagating along said axis parallel to said second axis to provide a signal representative thereof, said position determining means being coupled to said second sensing means to determine the position of a touch on said substrate touch surface relative to said second axis.

30. A touch position sensor as recited in claim 23 wherein said substrate is formed of glass.

31. A touch position sensor as recited in claim 30 wherein said glass is tempered.

32. A touch position sensor as recited in claim 30 wherein said glass is frosted.

33. A touch position sensor as recited in claim 23 wherein said substrate is formed of metal.

34. A touch position sensor as recited in claim 23 wherein said substrate is formed of plastic.

35. A touch position sensor as recited in claim 23 wherein said substrate is formed of a ceramic.

36. A touch position sensor as recited in claim 23 wherein said imparting means includes a wedge mounted on said substrate and a transducer mounted on said wedge, said transducer vibrating in a manner to generate a compressional wave in said wedge wherein said compressional wave imparts a Lamb wave into said substrate.

37. A touch position sensor as recited in claim 36 wherein said wedge has a wedge angle that is equal to the arcsine of the phase velocity of either of said antisymmetric or symmetric Lamb waves divided by the phase velocity of said compressional wave.

38. A touch position sensor as recited in claim 23 wherein said imparting means includes a compression transducer mounted on a side said substrate perpendicular to said first axis for imparting said Lamb waves into said substrate.

39. A touch position sensor as recited in claim 23 wherein said imparting means includes a symmetric Lamb wave generator.

40. A touch position sensor as recited in claim 39 wherein said symmetric Lamb wave generator includes a length expander generator mounted on a side of said substrate.

41. A touch position sensor as recited in claim 39 wherein said symmetric Lamb wave generator includes a compression transducer mounted on a side of said substrate.

42. A touch position sensor as recited in claim 23 wherein said imparting means includes an antisymmetric Lamb wave generator.

43. A touch position sensor as recited in claim 42 wherein said antisymmetric Lamb wave generator includes a pair of compressional transducers mounted on a side of said substrate and vertically aligned;

and drive signal means for generating a sine wave drive signal and the compliment of said sine wave drive signal wherein the sine wave drive signal is applied to one of said transducers and the compliment drive signal is applied to the other of said transducer.

44. A touch position sensor comprising:

a substrate capable of supporting Lamb waves propagating therein, said substrate having a touch surface and said Lamb waves having a symmetric and antisymmetric mode;

first means coupled to said substrate for imparting a Lamb wave into said substrate, said Lamb wave propagating along a first axis;

a first array of reflecting elements disposed on said substrate along said first axis for reflecting said Lamb wave along first parallel paths extending across the touch surface of said substrate, each first path representing a different axial position relative to said first axis and a touch on said substrate touch surface forming a perturbation in a Lamb wave propagating along a first path intersecting the position of said touch;

means disposed on said substrate relative to said first array for suppressing one of said modes;

means disposed generally parallel to said first axis and spaced from said first array for reflecting Lamb waves propagating along said first parallel paths back along said first parallel paths to said first array of reflecting elements, said reflecting elements reflecting said reflected Lamb waves along said first axis to said first imparting means and said first imparting means being responsive to Lamb waves propagated thereto to provide a signal representative of said Lamb waves; and

means responsive to said signal for determining the position of a touch on said substrate relative to said first axis.

45. A touch position sensor as recited in claim 44 wherein said first array is disposed on a first surface of said substrate and said suppressing means includes an array of reflecting elements disposed on a surface of said substrate opposite to said first surface and aligned with the elements of said first array to suppress said antisymmetric mode.

46. A touch position sensor as recited in claim 44 wherein said first array is disposed on a first surface of said substrate and said suppressing means includes an array of reflecting elements disposed on a surface of said substrate opposite to said first surface and shifted relative to the first array by an amount approximately equal to the wavelength of a symmetric mode Lamb wave divided by two to suppress said symmetric mode.

47. A touch position sensor as recited in claim 46 wherein said Lamb waves are first order Lamb waves.

48. A touch position sensor as recited in claim 46 wherein the elements of said suppressing array are shifted from the elements of said first reflecting array in the direction at right angles to said first axis.

49. A touch position sensor as recited in claim 46 wherein the elements of said suppressing array are shifted from the elements of said first reflecting array in a direction along said first axis.

50. A touch position sensor as recited in claim 44 wherein said reflecting means includes a reflective edge of said substrate.

51. A touch position sensor as recited in claim 44 further including

second means coupled to said substrate for imparting a Lamb wave propagating along a second axis, said second axis intersecting said first axis;

a second array of reflecting elements disposed along said second axis for reflecting portions of said Lamb wave along second parallel paths extending across the touch surface of said substrate, each second path representing a different axial position relative to said second axis and a touch on said substrate touch surface forming a perturbation in a Lamb wave propagating along a second path intersecting the position of said touch;

means disposed on said substrate relative to said second array for suppressing one of said modes;

means disposed generally parallel to said second axis and spaced from said second array for reflecting Lamb waves propagating along said second parallel paths back along said second paths to said second array of reflecting elements, said reflecting elements reflecting said reflected Lamb waves along said second axis to said second imparting means and said second imparting means being responsive to Lamb waves propagated thereto to provide a signal representative of said Lamb waves, said position determining means being coupled to said second imparting means to determine the position of a touch on said substrate relative to said second axis.

52. A touch position sensor as recited in claim 44 wherein said substrate is formed of glass.

53. A touch position sensor as recited in claim 52 wherein said glass is tempered.

54. A touch position sensor as recited in claim 52 wherein said glass is frosted.

55. A touch position sensor as recited in claim 44 wherein said substrate is formed of metal.

56. A touch position sensor as recited in claim 44 wherein said substrate is formed of plastic.

57. A touch position sensor as recited in claim 44 wherein said substrate is formed of a ceramic.

58. A touch position sensor as recited in claim 44 wherein said imparting means includes a wedge mounted on said substrate and a transducer mounted on said wedge, said transducer vibrating in a manner to generate a compressional wave in said wedge wherein said compressional wave imparts a Lamb wave into said substrate.

59. A touch position sensor as recited in claim 58 wherein said wedge has a wedge angle that is equal to the arcsine of the phase velocity of either of said antisymmetric or symmetric Lamb waves divided by the phase velocity of said compressional wave.

60. A touch position sensor as recited in claim 44 wherein said imparting means includes a compression transducer mounted on a side said substrate perpendicular to said first axis for imparting said Lamb waves into said substrate.

61. A touch position sensor as recited in claim 44 wherein said imparting means includes a symmetric Lamb wave generator.

62. A touch position sensor as recited in claim 61 wherein said symmetric Lamb wave generator includes a length expander generator mounted on a side of said substrate.

63. A touch position sensor as recited in claim 61 wherein said symmetric Lamb wave generator includes a compression transducer mounted on a side of said substrate.

64. A touch position sensor as recited in claim 44 wherein said imparting means includes an antisymmetric Lamb wave generator.

65. A touch position sensor as recited in claim 64 wherein said antisymmetric Lamb wave generator includes a pair of compressional transducers mounted on a side of said substrate and vertically aligned;

and drive signal means for generating a sine wave drive signal and the compliment of said sine wave drive signal wherein the sine wave drive signal is applied to one of said transducers and the compliment drive signal is applied to the other of said transducer.

66. A touch position sensor comprising:

a substrate capable of supporting Lamb waves propagating therein, said substrate having a touch surface and said Lamb waves having a symmetric mode and an antisymmetric mode;

means coupled to said substrate for imparting a Lamb wave into said substrate, said Lamb wave propagating along a first axis;

a first array of reflecting elements disposed on said substrate along said first axis for reflecting said Lamb wave along first parallel paths extending across the touch surface of said substrate, each first path representing a different axial position relative to said first axis and a touch on said substrate touch surface forming a perturbation in a Lamb wave propagating along a first path intersecting the position of said touch;

means disposed on said substrate relative to said first array for suppressing one of said modes;

means disposed generally parallel to said first axis and spaced from said first array for reflecting Lamb waves propagating along said first parallel paths back along said first parallel paths to said first array of reflecting elements, said reflecting elements reflecting said reflected Lamb waves along said first axis to said first imparting means and said first imparting means being responsive to Lamb waves propagated thereto to provide a signal representative of said Lamb waves;

a second array of reflecting elements disposed along a second axis intersecting said first axis for reflecting portions of a Lamb wave along second parallel paths extending across the touch surface of said substrate, each second path representing a different axial position relative to said second axis and a touch on said substrate touch surface forming a perturbation in a Lamb wave propagating along a second path intersecting the position of said touch;

means for reflecting a shear wave propagating along said first axis to said second array for propagation along said second axis;

means disposed on said substrate relative to said second array for suppressing one of said modes;

means disposed generally parallel to said second axis and spaced from said second array for reflecting Lamb waves propagating along said second parallel paths back along said second paths to said second array of reflecting elements for reflecting said reflected Lamb waves along said second axis said reflecting means and said reflecting means reflecting said Lamb waves reflected from said second array back along said first axis to said imparting means, said imparting means being responsive to Lamb waves to provide a signal representative thereof; and

means responsive to said signals for determining the position of a touch on said substrate touch surface relative to said first and second axes.

67. A touch position sensor as recited in claim 66 wherein said substrate is formed of glass.

68. A touch position sensor as recited in claim 67 wherein said glass is tempered.

69. A touch position sensor as recited in claim 67 wherein said glass is frosted.

70. A touch position sensor as recited in claim 66 wherein said substrate is formed of metal.

71. A touch position sensor as recited in claim 66 wherein said substrate is formed of plastic.

72. A touch position sensor as recited in claim 66 wherein said substrate is formed of a ceramic.

73. A touch position sensor as recited in claim 66 wherein said imparting means includes a wedge mounted on said substrate and a transducer mounted on said wedge, said transducer vibrating in a manner to generate a compressional wave in said wedge wherein said compressional wave imparts a Lamb wave into said substrate.

74. A touch position sensor as recited in claim 73 wherein said wedge has a wedge angle that is equal to the arcsine of the phase velocity of either of said antisymmetric or symmetric Lamb waves divided by the phase velocity of said compressional wave.

75. A touch position sensor as recited in claim 66 wherein said imparting means includes a compression transducer mounted on a side said substrate perpendicular to said first axis for imparting said Lamb waves into said substrate.

76. A touch position sensor s recited in claim 66 wherein said imparting means includes a symmetric Lamb wave generator.

77. A touch position sensor as recited in claim 76 wherein said symmetric Lamb wave generator includes a length expander generator mounted on a side of said substrate.

78. A touch position sensor as recited in claim 76 wherein said symmetric Lamb wave generator includes a compression transducer mounted on a side of said substrate.

79. A touch position sensor as recited in claim 66 wherein said imparting means includes an antisymmetric Lamb wave generator.

80. A touch position sensor as recited in claim 79 wherein said antisymmetric Lamb wave generator includes a pair of compressional transducers mounted on a side of said substrate and vertically aligned;

and drive signal means for generating a sine wave drive signal and the compliment of said sine wave drive signal wherein the sine wave drive signal is applied to one of said transducers and the compliment drive signal is applied to the other of said transducer.