Acoustic touch position sensor using higher order horizontally polarized shear wave propagation

• US 5,591,945 A
• Filed: 04/19/1995
• Issued: 01/07/1997
• Est. Priority Date: 04/19/1995
• Status: Expired due to Term

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touchsystems Incorporated (Elo Touch Solutions, Inc.)
• Inventors: Kent, Joel
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): LOOMIS, PAUL A
• Application Number:
  US08/424,216
• Time in Patent Office: 629 Days
• Field of Search: 178/18, 178/19, 345/177, 367/140, 367/168, 367/189, 367/191, 367/907
• US Class Current: 178/18.04
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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: H03K 2217/96011 with propagation, SAW or BAW
• CPC Class Codes: Y10S 367/907 Coordinate determination

Abstract

An acoustic touch position sensor having a transducer which imparts a wave, propagating along a first axis. A reflective array disposed along the first axis which reflects the wave as a set of waves having a horizontally polarized component and a non-uniform volumetric energy density along an axis normal to said surface, traveling along a different axis into the touch surface region of the substrate. The waves are partially absorbed, attenuated or perturbed by an object touching the substrate, to create a modified waveform having characteristics indicative of the axial displacement and/or contact condition of the object with the substrate. The wave perturbation is detected by collecting the set of waves with a reflective array, which redirects the wave energy to a receiving transducer. The transducers preferably produce and are responsive to Rayleigh type waves, with the reflective arrays mode-converting acoustic wave energy between higher order horizontally polarized shear waves and Rayleigh type waves.

Claims

1. A touch sensor comprising:

a substrate having at least one touch surface and being capable of propagating an acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a nonuniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface;

a transducer for producing an acoustic wave having a longitudinal component along a first axis in said substrate, said first axis being parallel to said surface; and

a first reflecting array having a length and being disposed along said first axis, for reflecting, along said length of said array, as a first reflected wave, portions of said wave having a longitudinal component, said first reflected wave having a horizontal shear-type component substantially parallel to said surface, having a nonuniform volumetric energy density along a vertical axis normal to said surface, and having energy at said surface, said first reflected wave being directed along a second axis in said substrate, different than said first axis, and having a component parallel to said surface;

whereby a proximity of an object to said substrate causes a perturbation in the power carried by said first reflected wave.

2. The touch sensor according to claim 1, further comprising a second reflecting array spaced from said first reflecting array across said substrate along said second axis of said first reflected wave, for reflecting said first reflected wave as a wave having a longitudinal component along a third axis.

3. The touch sensor according to claim 1, further comprising a reflecting member spaced from said first reflecting array across said substrate along said first axis, for reflecting said first reflected wave as a second reflected wave toward said first reflecting array along a fourth axis.

4. The touch sensor according to claim 3, wherein said fourth axis is antiparallel with said second axis, and said first reflecting array reflects said second reflected wave from said fourth axis to a fifth axis, antiparallel with said first axis as a wave having a longitudinal component.

5. The touch sensor according to claim 1, further comprising a transducer for detecting a perturbation in said first reflected wave.

6. The touch sensor according to claim 1, wherein a temporal characteristic of said perturbation corresponds to a position of said object in proximity to said substrate.

7. The touch sensor according to claim 1, further comprising:

a second transducer for producing an acoustic wave having a longitudinal component along a sixth axis in said substrate, said sixth axis being parallel to said surface; and

a second reflecting array having a length and being disposed along said sixth axis, for reflecting, along said length of said array, as a third reflected wave, portions of said wave having a longitudinal component, said third reflected wave having a horizontal shear-type component substantially parallel to said surface, having a nonuniform volumetric energy density along a vertical axis normal to said surface, and having energy at said surface, said third reflected wave being directed along a seventh axis in said substrate, different than said sixth axis, and being parallel to said surface;

a proximity of an object to said substrate cause a perturbation in the power carried by said third reflected wave, so that said proximity causes a perturbation of waves travelling along both said second axis and said seventh axis.

8. The touch sensor according to claim 7, further comprising means for detecting a perturbation of said waves travelling along said second axis and said seventh axis.

9. The touch sensor according to claim 1, wherein said wave having a longitudinal component is a Rayleigh-type wave.

10. The touch sensor according to claim 1, wherein said wave having a longitudinal component is a Lamb-type wave.

11. The touch sensor according to claim 1, wherein said first reflective array comprises a diffraction grating of acoustic scattering elements, separating modes of said horizontal shear-type component substantially parallel to said surface, having a nonuniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface, by differences in phase velocity.

12. The touch sensor according to claim 1, wherein said first reflected wave is a horizontally polarized shear wave of order greater than zero.

13. The touch sensor according to claim 1, wherein said first reflected wave is a horizontally polarized shear wave of order 4.

14. The touch sensor according to claim 1, wherein said first reflected wave is a Love wave.

15. The touch sensor according to claim 1, wherein said substrate has a thickness greater than about three times the Rayleigh wavelength of said first reflected wave.

16. The touch sensor according to claim 1, wherein said substrate has a thickness of about four times the Rayleigh wavelength of said first reflected wave.

17. The touch sensor according to claim 1, wherein said substrate is glass having a thickness of about between about 0.085" and 0.125".

18. The touch sensor according to claim 1, wherein said substrate is formed of plastic.

19. The touch sensor according to claim 1, wherein said substrate is formed of glass.

20. The touch sensor according to claim 19, wherein said substrate is formed of soda-lime glass.

21. The touch sensor according to claim 19, wherein said substrate is formed of borosilicate glass.

22. The touch sensor according to claim 19, wherein said substrate is formed of frosted glass.

23. The touch sensor according to claim 1, wherein said substrate is formed of a longitudinal laminate of a lower shear-wave-velocity material on top of a higher-shear-wave-velocity material, and wherein said first reflected wave is a Love wave.

24. The touch sensor according to claim 23, wherein said substrate comprises a borosilicate glass laminated to a soda-lime glass.

25. The touch sensor according to claim 23, wherein said first reflected wave is a Love wave.

26. The touch sensor according to claim 23, wherein said lower shear-wave-velocity material is sufficiently thin to support only the n=0 Love mode.

27. The touch sensor according to claim 1, wherein said transducer comprises a PZT piezoelectric transducer.

28. The touch sensor according to claim 27, wherein said PZT piezoelectric transducer produces compression waves and is mounted on a plastic wedge in contact with said surface of said substrate, for inducing propagation of waves having a longitudinal component in said substrate.

29. The touch sensor according to claim 1, wherein said substrate is curved.

30. The touch sensor according to claim 1, further comprising:

a receiving transducer for receiving an acoustic wave; and

a receiving reflecting array, for reflecting a wave from said first reflecting array to said receiving transducer.

31. The touch sensor according to claim 1, wherein said reflecting array comprises an acoustic diffraction grating.

32. The touch sensor according to claim 31, wherein said acoustic diffraction grating has elements of varying height.

33. The touch sensor according to claim 31, wherein said acoustic diffraction grating has elements of varying spacing.

34. The touch sensor according to claim 31, wherein said acoustic diffraction grating has elements of varying orientation.

35. The touch sensor according to claim 1, wherein said perturbation in the surface energy of said first reflected wave is detected as a perturbed wave having a differing volumetric energy distribution along said vertical axis than said first reflected wave.

36. The touch sensor according to claim 35, wherein said perturbed wave is selectively filtered from said first reflected wave.

37. The touch sensor according to claim 31, wherein said acoustic diffraction grating comprises elements which have a shear-type phase velocity which varies from a shear-type phase velocity of an adjacent area.

38. The touch sensor according to claim 1, wherein said wave having a longitudinal component is a Stoneley wave.

39. A touch sensor comprising:

a substrate capable of propagating a horizontally polarized shear-type wave having an order greater than zero, said substrate having at least one touch surface, a touch on said substrate causing a perturbation of said horizontally polarized shear-type wave;

a transducer producing a vertically polarized transverse wave having a longitudinal component in a wave propagating area;

means for converting said vertically polarized transverse wave having a longitudinal component propagating in said wave propagating area into said horizontally polarized shear-type wave having an order greater than zero propagating in said substrate; and

means for sensing a touch-induced perturbation of said horizontally polarized shear-type wave.

40. A touch position sensor comprising:

a substrate having at least one touch surface and being capable of propagating an acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface;

means for reflecting portions of a wave having a longitudinal component as at least an acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface, having an axis, along paths having differing displacements along said axis, said reflecting means being disposed on said substrate;

means for generating a wave having longitudinal component, propagating in said substrate in a direction along said axis of said reflecting means, a touch on said substrate touch surface perturbing said acoustic wave; and

means for sensing the time of occurrence of a perturbation.

41. The touch sensor according to claim 40, wherein said acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface is a shear wave having an order greater than zero.

42. The touch position sensor according to claim 40, wherein said substrate has a thickness greater than about three times the Rayleigh wavelength of said acoustic wave.

43. The touch position sensor according to claim 40, wherein said substrate has a thickness greater than about four times the Rayleigh wavelength of said acoustic wave.

44. The touch position sensor according to claim 40, wherein said substrate comprises a glass sheet.

45. The touch position sensor according to claim 40, wherein said substrate comprises a sheet selected from the group consisting of soda-lime glass, borosilicate glass, crystal glass, a laminate of borosilicate glass and soda-lime glass, a laminate of plastic and glass, frosted glass, tempered glass, plastic, metal and ceramic.

46. The touch position sensor according to claim 40, wherein said substrate is a sheet having a shape selected from the group consisting of a flat sheet, a cylindrical section, a spherical section, an ellipsoidal section and a conic section.

47. The touch position sensor according to claim 40, wherein said generating means comprises a first transducer bonded on a surface in acoustic communication with said substrate.

48. The touch position sensor according to claim 47, wherein said generating means comprises a conductive frit for bonding said transducer to said surface.

49. The touch position sensor according to claim 48, further comprising a second transducer bonded on a surface in acoustic communication with said substrate, said second transducer being proximate to said first transducer wherein said conductive frit for bonding said first transducer is continuous with conductive frit to bond said second transducer to said surface.

50. The touch position sensor according to claim 40, further comprising means for reflecting portions of said perturbed acoustic wave as a perturbed wave having a longitudinal component propagating along an axis.

51. The touch position sensor according to claim 40, wherein said sensing means comprises a receiving transducer for receiving information relating to a perturbation of said acoustic wave.

52. The touch position sensor according to claim 40, wherein said generating means and said sensing means employ a common transducer.

53. The touch position sensor according to claim 40, wherein said sensing means selects substantially a single perturbed acoustic wave mode propagating in said substrate and directs said selected perturbed acoustic wave mode to a receiving transducer.

54. The touch position sensor according to claim 40, wherein said acoustic wave propagates at substantially right angles to said wave having a longitudinal component.

55. The touch position sensor according to claim 54, wherein said acoustic wave is a horizontally polarized shear-type wave having an order greater than zero.

56. The touch position sensor according to claim 40, wherein said wave having a longitudinal component is a quasi-Rayleigh wave.

57. The touch position sensor according to claim 40, wherein said acoustic wave is a fourth order horizontally polarized shear-type wave.

58. The touch position sensor according to claim 40, wherein said substrate has a spatial variation in phase propagation velocity of shear wave energy and said acoustic wave is a Love wave of any order.

59. The touch position sensor according to claim 58, wherein said spatial variation is along an axis normal to said surface.

60. The touch position sensor according to claim 40, wherein said perturbed acoustic wave propagates in the same mode as said acoustic wave.

61. The touch position sensor according to claim 40, wherein said perturbed acoustic wave propagates in a different mode as said acoustic wave.

62. A touch sensor comprising:

a substrate having at least one touch surface and being capable of propagating an acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface;

first means for reflecting portions of a wave having a longitudinal component as a first acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface along first paths having differing displacement along a first axis of said first reflecting means; and

second means for reflecting portions of a wave having a longitudinal component as a second acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface along first paths having differing displacement along a second axis of said second reflecting means.

63. The touch sensor according to claim 62, wherein at least on of said first acoustic wave and said second acoustic wave is a horizontally polarized shear-type wave having an order greater than zero.

64. The touch sensor according to claim 62, further comprising:

a reflector for reflecting waves having a longitudinal component propagating between said first axis and said second axis; and

a transducer for transmitting a wave having longitudinal component along said first axis and for receiving information from said first and second horizontally polarized shear-type waves.

65. The touch sensor according to claim 62, wherein said first reflecting means comprises protuberances from a surface of said substrate having a spacing of an integral multiple of a wavelength of said wave having a longitudinal component and an angle with respect to said first axis such that said first acoustic wave propagates at right angles to said first axis.

66. The touch sensor according to claim 65, wherein said wave having a longitudinal component is a quasi-Raleigh wave having a frequency of about 5.5 MHz, said first acoustic wave is a fourth order horizontally polarized shear-type wave, and said protuberances are set at an angle of 52°

from said first axis.

67. The touch sensor according to claim 62, further comprising a first transducer for propagating a wave having a longitudinal component along said first axis and a second transducer for propagating a wave having a longitudinal component along said second axis.

68. The touch sensor according to claim 67, wherein said first transducer and said second transducer produce waves having the same order.

69. The touch sensor according to claim 67, wherein said first transducer is responsive to a wave propagating along said first axis and said second transducer is responsive to a wave propagating along said second axis.

70. The touch sensor according to claim 69, further comprising means for directing energy from said first acoustic wave to said first transducer and means for directing energy from said second acoustic wave to said second transducer.

71. The touch sensor according to claim 62, wherein:

said first reflecting means comprises a first reflective array disposed on said substrate and a second reflective array disposed on said substrate parallel to and spaced from said first reflective array, said first reflective array reflecting said first acoustic wave from said first axis toward said second reflective array; and

said second reflecting means comprises a third reflective array disposed on said substrate and a fourth reflective array disposed on said substrate parallel to and spaced from said third reflective array, said third reflective array reflecting said second acoustic wave from said second axis toward said second reflective array.

72. The touch sensor according to claim 62, wherein said first reflecting means comprises:

a first reflective edge of said substrate;

a second reflective edge of said substrate, said second reflective edge being disposed parallel to said first reflective edge and spaced therefrom;

a first array of reflective elements positioned adjacent said first reflective edge; and

a second array of reflective elements positioned adjacent said second reflective edge,

a wave having a longitudinal component propagating along said first axis intersecting said first array of reflective elements and being reflected by said first array of reflecting elements as said first acoustic wave toward said first reflecting edge, said first reflecting edge reflecting said first acoustic wave toward said second reflecting edge, said second reflecting edge reflecting said first acoustic wave to said second array of reflecting elements, and said second array of reflecting elements reflecting said first acoustic wave as a wave having a longitudinal component along said second axis.

73. The touch sensor according to claim 72, further comprising a transmitting acoustic transducer aligned with said first axis and a receiving acoustic transducer aligned with said second axis.

74. The touch sensor according to claim 72, wherein said wave having a longitudinal component also has a vertically polarized transverse component, further comprising members for absorbing waves having vertical components between said first reflective array and said first reflective edge.

75. The touch sensor according to claim 74, further comprising members for absorbing waves having vertical components between said second reflective array and said second reflective edge.

76. The touch sensor according to claim 69, further comprising an analog to digital converter and a digital signal processor, said analog to digital converter digitizing a signal from said first transducer and said digital signal processor receiving said digitized signal and processing said signal to filter signal components to selectively extract information relating to said first acoustic wave.

77. The touch sensor according to claim 67, further comprising means for generating a drive signal and means for controlling the application of said drive signal to said first and second transducers during respective first and second non-overlapping time periods, wherein said first transducer produces a wave having a longitudinal component in said substrate during said first time period and said second transducer produces a wave having a longitudinal component in said substrate during said second time period.

78. The touch sensor according to claim 77, wherein said first and second transducers are responsive to acoustic waves, further comprising a receiving circuit for receiving signals from said first and second transducers, and a circuit for blocking the direct effect of a drive signal from said drive signal generating means from said receiving circuit.

79. The touch sensor according to claim 63, further comprising a first reflective edge of said substrate opposite said first reflecting means and a second reflective edge of said substrate opposite said second reflecting means, said first reflective edge reflecting said first acoustic wave along its incident path to said first reflecting means and said second reflecting edge reflecting said second acoustic wave along its incident path to said second reflecting means.

80. The touch sensor according to claim 63, wherein said substrate has a thickness greater than about three times the Rayleigh wavelength for the substrate material.

81. The touch sensor according to claim 63, wherein said substrate has a thickness greater than about four times the Rayleigh wavelength for the substrate material.

82. The touch sensor according to claim 63, wherein said substrate is formed of one or more materials selected from the group consisting of glass, soda-lime glass, borosilicate glass, leaded crystal glass, silver crystal glass, soda-lime borosilicate glass laminate, tempered glass, frosted glass, plastic, glass plastic laminate, glass-organic polymer laminate, glass-silicone polymer laminate, metal, ceramic, quartz and ion-beam treated transparent sheets.

83. The touch sensor according to claim 63, wherein said substrate has a shape selected from the group consisting of a flat sheet, a curved sheet, a spheric section, an ellipsoidal section, a cylindrical section, a conic section and an aspheric section.

84. The touch sensor according to claim 63, further comprising a transducer mounted on said substrate via a plastic wedge.

85. The touch sensor according to claim 63, further comprising a transducer having a plurality of interdigital electrodes.

86. The touch sensor according to claim 85, wherein said transducer is selectively responsive to an acoustic wave mode propagating in said substrate.

87. The touch sensor according to claim 63, further comprising a transducer mounted to said substrate on a surface contiguous with a touch sensitive surface of said substrate.

88. The touch sensor according to claim 63, further comprising a first transducer and a second transducer mounted on said substrate via a conductive frit, said second transducer being proximate to said first transducer and wherein said conductive frit for bonding said first transducer is continuous with said conductive frit for mounting said second transducer.

89. The touch sensor according to claim 63, further comprising a vertically polarized transverse wave suppressor for attenuating a vertically polarized transverse wave component of said wave having a longitudinal component.

90. The touch sensor according to claim 89, wherein said first and second reflecting means each include an array of reflective elements and are each associated with a vertically polarized transverse wave component suppressor disposed on a surface of said substrate adjacent to each respective array of reflective elements.

91. The touch sensor according to claim 90, wherein said vertically polarized transverse wave component suppressor is disposed on a top surface and a bottom surface of said substrate.

92. The touch sensor according to claim 63, wherein at least one of said first acoustic wave and said second acoustic wave is selected from the group consisting of a third order shear-type wave and a fourth order shear-type wave.

93. The touch sensor according to claim 92, further comprising a bevelled edge of said substrate.

94. The touch sensor according to claim 63, further comprising a first bevelled edge of said substrate associated with said first reflecting means and a second bevelled edge associated with said second reflecting means, said bevelled edges having selective reflection characteristics for acoustic waves having differing volumetric energy density along said vertical axis.

95. An object proximity sensor comprising:

a substrate having first and second generally parallel edges, and a top touch surface and being capable of propagating an acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface;

a first transmitting transducer coupled to a surface of said substrate and responsive to a drive signal for imparting a wave having a longitudinal wave component into said substrate, said wave propagating along a first axis parallel to said first edge;

a first array of reflective elements disposed along said first axis and adjacent to said first edge, said reflective elements being positioned to reflect portions of said wave having a longitudinal wave component along first, substantially parallel paths as an acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface, a touch on said substrate top touch surface forming a perturbation in said acoustic wave propagating along a first path intersecting the position of the touch; and

a drive signal generator connected to said first transmitting transducer.

96. The object proximity sensor according to claim 95, further comprising means for generating a signal representative of a perturbed acoustic wave propagating in said substrate and means responsive to said representative signal for determining a proximity of an object to said substrate.

97. The object proximity sensor according to claim 95, further comprising a second array of reflective elements disposed along a second axis parallel to, and spaced from, said first axis, said second array of reflective elements being spaced to selectively reflect a portion of said acoustic wave propagating along said first, substantially parallel paths as a wave having a longitudinal wave component.

98. The object proximity sensor according to claim 96, further comprising:

means for storing a time at which said first transmitting transducer imparts a wave into said substrate;

means for storing temporal characteristics of said perturbed acoustic wave; and

means for calculating a position of an object in proximity to said substrate based on said stored time and said stored temporal characteristics.

99. The object proximity sensor according to claim 98, further comprising a sensor system for receiving said perturbed acoustic wave and means for determining a position of an object in proximity to said substrate along an axis having a component which is orthogonal to an axis of said first, substantially parallel paths based on said received perturbed acoustic wave.

100. The object proximity sensor according to claim 99, further comprising means for outputting information relating to a position of said object in proximity to said substrate.

101. The object proximity sensor according to claim 95, further comprising:

third and fourth edges of said substrate;

a second array of reflective elements disposed along a second axis parallel to and spaced from said first axis, said reflective elements of said second array being spaced to selectively reflect a portion of said incident acoustic waves as a wave having a longitudinal wave component propagating along said first, substantially parallel paths along a second axis;

a first receiving transducer, spaced from said first transmitting transducer and being responsive to a received wave from said second array of reflecting elements having a longitudinal wave component, and generating a signal representative thereof;

a second transmitting transducer coupled to a surface of said substrate and responsive to a drive signal for imparting a wave having a longitudinal wave component into said substrate, said wave propagating along a third axis parallel to said third edge;

a third array of reflective elements disposed along said third axis and adjacent to said third edge, said reflective elements of said third array being positioned to reflect portions of said wave having a longitudinal wave component along second, substantially parallel paths as an acoustic wave having a horizontal shear-type component substantially parallel to said surface, having a non-uniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface, a touch on said substrate top touch surface forming a perturbation in said acoustic wave propagating along a second path intersecting the position of the touch; and

a fourth array of reflective elements disposed along a fourth axis parallel to and spaced from said third axis, said reflective elements of said fourth array being spaced to selectively reflect a portion of said incident shear-type waves as a wave having a longitudinal wave component propagating along said second, substantially parallel paths along a fourth axis;

a second receiving transducer spaced from said second transmitting transducer, being responsive to a wave having a longitudinal component received from said fourth array of reflecting elements, and generating a signal representative thereof.

102. The object proximity sensor according to claim 101, wherein each of said transducers is mounted on a plastic wedge.

103. The object proximity sensor according to claim 95, wherein said wave having a longitudinal wave component also has a vertical wave component, said sensor further comprising means positioned adjacent to said first reflective array for attenuating said vertical wave component.

104. The object proximity sensor according to claim 103, wherein said attenuating means comprise strips of acoustic wave absorbing material disposed adjacent to said first array of reflective elements.

105. The object proximity sensor according to claim 103, wherein said attenuating means is disposed between said first array of reflecting elements and said first side.

106. The object proximity sensor according to claim 95, wherein said substrate has a thickness which is greater than about three Rayleigh wavelengths for the substrate material.

107. The object proximity sensor according to claim 95, wherein said substrate has a thickness which is about four Rayleigh wavelengths for the substrate material.

108. The object proximity sensor according to claim 95, wherein said substrate comprises a plate of soda-lime glass of 2 mm thickness or more laminated to a plate of borosilicate glass of 3 mm thickness or less, said first transmitting transducer being mounted on said borosilicate glass.

109. The object proximity sensor according to claim 95, wherein said substrate comprises a laminate of a first material having a first shear-type wave phase velocity and a second material having a second shear-type wave phase velocity, said phase velocity of said first material being different from said phase velocity of said second material, said laminate being formed in a manner that efficiently couples shear-type waves between said first material and said second material.

110. The object proximity sensor according to claim 108, wherein said sheet of soda-lime glass is greater than about 2 mm thick and said sheet of borosilicate glass is less than about 3 mm thick.

111. The object proximity sensor according to claim 95, wherein said substrate is transparent and is adapted for transmission of an image from a display device.

112. The object proximity sensor according to claim 95, wherein said elements of said first array of reflective elements are disposed at an angle greater than about 45°

from said first axis.

113. The object proximity sensor according to claim 95, wherein said elements of said first array of reflective elements are disposed at an angle of about 52°

from said first axis.

114. The object proximity sensor according to claim 95, wherein said first acoustic wave is a horizontally polarized shear-type wave having order greater than zero.

115. A method of detecting an object, comprising:

providing a substrate having at least one touch surface and being capable of propagating an acoustic wave having a horizontal shear-type energy component substantially parallel to said surface, having a nonuniform volumetric energy density along a vertical axis normal to said surface and having energy at said surface;

inducing a first acoustic wave having a longitudinal component along a first axis in the substrate, the first axis being parallel to said surface;

reflecting, as a second acoustic wave, portions of the energy of the first acoustic wave, the second acoustic wave having a horizontal shear-type energy component substantially parallel to the surface, having a nonuniform volumetric energy density along a vertical axis normal to the surface, and having energy at the surface, the second acoustic wave being directed along a second axis in the substrate, different than the first axis, and being parallel to said surface;

perturbing said second acoustic wave by placing an object in proximity to said surface of the substrate; and

detecting the perturbed second acoustic wave.

116. The method according to claim 115, wherein:

said perturbing step further comprises redistributing the wave energy of the second acoustic wave among available propagation modes; and

said detecting step further comprises detecting wave energy in wave propagation modes not present in said second acoustic wave.

117. The method according to claim 115, further comprising the step of:

reflecting the perturbed wave as a wave having a longitudinal component;

wherein said detecting step comprises detecting acoustic wave energy having a longitudinal component.

118. The method according to claim 115, wherein the first reflected wave is a fourth order horizontally polarized shear-type wave.

119. The method according to claims 115, wherein the induced first acoustic wave is a quasi-Rayleigh wave.

120. The method according to claims 115, wherein the substrate has a vertical variation in shear-type wave phase velocity and the first reflected wave is a Love wave.

121. The method according to claim 115, wherein a said detecting step comprises the substep of receiving the perturbed second acoustic wave with an acoustic-electric transducer, digitizing an electrical signal from the transducer, and digitally processing the digitized signal to compensate for alternate return paths of wave energy received by the transducer.

122. The method according to claim 121, wherein said digitally processing step is adaptive to changing environmental conditions.

123. The method according to claim 115, wherein the wave having a longitudinal component is a Stoneley wave.

124. The method according to claim 123, wherein said second acoustic wave is spacially dispersed over said touch surface, having a width along said second axis, and wherein said detecting step comprises the substeps of providing a transducer having a receiving aperture smaller than said width, and redirecting at least a portion of energy of said second acoustic wave over a distance along said second axis greater than said receiving aperture of said transducer to said transducer.

125. An acoustic device, suitable for coupling to a transducer for imparting a wave having a longitudinal component into the device, the wave having an axis of propagation, said device comprising:

a substrate having a surface, said substrate supporting propagation of waves having a horizontally polarized component and a non-uniform volumetric energy density along an axis normal to said surface; and

an array of acoustically reflective elements, on a surface of said substrate, disposed along the axis of wave propagation, each of said elements being disposed at an angle which reflects a wave having a longitudinal component propagating along the axis of wave propagation as a wave having a horizontally polarized component and a non-uniform volumetric energy density along an axis normal to said surface propagating at an angle of 90°

to the axis of wave propagation.