Acoustic touch position sensor using a low acoustic loss transparent substrate

• US 6,441,809 B2
• Filed: 05/22/2001
• Issued: 08/27/2002
• Est. Priority Date: 01/24/1995
• Status: Expired due to Term

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touchsystems Incorporated (Elo Touch Solutions, Inc.)
• Inventors: Tsumura, Masahiro, Kent, Joel
• Primary Examiner(s): Brier, Jeffery
• Assistant Examiner(s): Blackman, Anthony J.
• Application Number:
  US09/862,672
• Publication Number:
  US 20010033275A1
• Time in Patent Office: 462 Days
• Field of Search: 345/177, 345/173, 345/176, 178/18.01, 178/18.03, 178/18.04
• US Class Current: 345/177
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate

Abstract

An acoustic touch panel or “touch screen” utilizes acoustic waves within a sensor substrate to determine the position of touch. The substrate is made of a temperable glass having an attenuation coefficient of less than or equal to about 0.6 dB/cm as determined at the substrate surface for 5.53 MHz Rayleigh waves as measured by the slope of a plot of amplitude versus distance for a signal through a pair of facing 0.5-inch wide wedge transducers mounted on a sample of the glass type under test having sufficient thickness to support Rayleigh wave propagation. An acoustic touch panel with a tempered low-acoustic-loss glass substrate. This makes possible large tempered acoustic touch panels.

A glass substrate of the touch sensor comprises SiO₂ as the main component with a total content of Na₂O, CaO and MgO of 20% by weight or less and a total content of Al₂O₃, ZrO₂, TiO₂, B₂O₃, Y₂O₃, SnO₂, PbO₂, In₂O₃ and K₂O of 5% by weight or more.

Claims

1. A touch position sensor comprising:

a substrate capable of supporting Rayleigh-type waves propagating therein, said substrate having a touch surface, said substrate being formed of a glassy silica matrix in which silicon-oxygen bonds are replaced with alternate covalent bonds, strong ionic bonds, or sterically constrained ionic bonds sufficient to reduce an acoustic loss to less than or equal to about 0.5 dB/cm;

means, coupled to said substrate, for imparting a Rayleigh-type wave propagating along an axis into said substrate; and

means disposed along said axis for reflecting portions of said Rayleigh-type wave along a set of mutually displaced paths extending across the touch surface of said substrate, and for subsequently superposing acoustic energy propagating along said mutually displaced paths in time-displaced manner, a touch on said substrate touch surface perturbing propagation of the Rayleigh-type wave intersecting the position of said touch.

2. The touch position sensor according to claim 1, wherein said substrate is formed of B270 glass.

3. The touch position sensor according to claim 1, wherein said substrate is formed of barium-containing glass.

4. The touch position sensor according to claim 1, wherein said substrate comprises a faceplate for a cathode ray tube.

5. The touch position sensor according to claim 1, wherein said substrate contains about 2.1% Barium oxide.

6. The touch position sensor according to claim 1, wherein said substrate has a 3:

4 aspect ratio and a diagonal measurement of 21″

.

7. The touch position sensor according to claim 1, wherein said substrate has a 3:

4 aspect ratio and a diagonal measurement of 31″

.

8. The touch position sensor according to claim 1, wherein said substrate is heat tempered.

9. The touch position sensor according to claim 1, wherein said substrate is chemically hardened.

10. The touch position sensor according to claim 1, further comprising means for sensing the occurrence of a perturbation in said Rayleigh-type wave to determine the axial position of a touch on said substrate.

11. The touch position sensor according to claim 1, wherein said means for imparting is an electroacoustic transducer having a transmit-burst amplitude of about 10 Volts peak-to-peak or less.

12. The touch position sensor according to claim 1, further comprising an acoustically absorptive seal adapted to cause significant acoustic signal absorption of the Rayleigh-type wave in contact with the substrate.

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

14. The touch position sensor according to claim 1, wherein said substrate has a chemical composition which minimizes the number of unconstrained broken links Si—

O−

/−

O—

Si therein.

15. The touch position sensor according to claim 1, wherein said substrate comprises a glass having SiO₂ as the main component, and having additional components that prevent said SiO₂ from forming a regular crystalline lattice by disruption of Si—

O—

Si covalent links, and wherein said added components provide sufficiently strong alternate links through strong ionic bonding, alternate covalent bonding, or steric constraints.

16. The touch position sensor according to claim 1, wherein an attenuation coefficient of said substrate is less than or equal to about 0.5 dB/cm as determined at the substrate surface for a 5.53 MHz Rayleigh waves as measured by the slope of a plot of amplitude versus distance for a signal through a pair of facing 0.5 -inch wide wedge transducers, mounted on a sample of said substrate under test having sufficient thickness to support Rayleigh wave propagation.

17. The touch position sensor according to claim 1, wherein said substrate comprises a projection video surface.

18. The touch position substrate according to claim 1, wherein said reflecting means comprises an array of elements formed on said touch surface.

19. The touch position sensor according to claim 1, wherein said substrate comprises between about 55-90% by weight SiO₂, and 0 to 18% by weight Al₂O₃, ZrO₂, TiO₂, B₂O₃, Y₂O_{3 SnO2}, PbO₂, In₂O₃ and K₂O.

20. The touch position sensor according to claim 1, further comprising BaO, ZnO, BeO, Li₂O, TeO₂, V₂O₅, or P₂O₅.