Acoustic device using higher order harmonic piezoelectric element
View Patent ↗An acoustic-based system, such as a touchscreen system, is provided. The system comprises an acoustic substrate and an acoustic transducer operably coupled to the substrate. The transducer exhibits a higher order odd resonant frequency that is equal to the operating frequency of the system. As a result of using the higher resonant frequency that is substantially equal to the operating frequency, the thickness of the transducer can be increased, and thus made more durable.
1. A touch sensor having an operating frequency, comprising:
a touch sensitive substrate; and
a piezoelectric element operably coupled to the substrate, wherein the piezoelectric element is characterized by a higher order odd resonant frequency approximately equal to the operating frequency, the higher order frequency being selected from a frequency consisting of a third, fifth, and seventh order resonant frequency.
2. The touch sensor of claim 1 , wherein the higher order resonant frequency is a third order resonant frequency.
3. The touch sensor of claim 1 , wherein the piezoelectric element is a shear-mode piezoelectric element.
4. The touch sensor of claim 3 , wherein the piezoelectric element is configured for transmitting or receiving a horizontally polarized acoustic shear wave in the substrate.
5. The touch sensor of claim 4 , wherein the shear wave is selected from a wave consisting of a Love wave, a Zero Order Horizontally Polarized Shear (ZOHPS) wave, and a Higher Order Horizontally Polarized Shear (HOPS) wave.
6. The touch sensor of claim 1 , wherein the piezoelectric element is a pressure-mode transducer.
7. The touch sensor of claim 6 , wherein the piezoelectric element is configured for transmitting or receiving an acoustic wave having a longitudinal component in the substrate.
8. The touch sensor of claim 7 , wherein the wave is selected from a wave consisting of a Rayleigh wave and a Lamb wave.
9. The touch sensor of claim 1 , wherein the substrate is transparent.
10. The touch sensor of claim 1 , wherein the substrate is opaque.
11. The touch sensor of claim 1 , further comprising an acoustic transmit/receive assembly operably coupled to the substrate for transmitting and receiving acoustic waves along at least one set of parallel paths.
12. A method of sensing touches on a touch sensor, comprising:
transmitting an acoustic wave across an acoustic substrate with a piezoelectric element, the acoustic wave having a frequency approximately equal to a higher order odd resonant frequency of the piezoelectric element, the higher order frequency being selected from a frequency consisting of a third, fifth, and seventh order resonant frequency;
receiving the acoustic wave from the substrate; and
processing the acoustic wave at the higher order odd resonant frequency to determine whether the substrate has been touched.
13. The method of claim 12 , wherein the higher order odd resonant frequency is a third order resonant frequency.
14. The method of claim 12 , wherein the acoustic wave is a horizontally polarized acoustic shear wave.
15. The method of claim 14 , wherein the shear wave is selected from a wave consisting of a Love wave, a Zero Order Horizontally Polarized Shear (ZOHPS) wave, and a Higher Order Horizontally Polarized Shear (HOHPS) wave.
16. The method of claim 12 , wherein the acoustic wave is an acoustic wave with a longitudinal component.
17. The method of claim 16 , wherein the wave is selected from a wave consisting of a Rayleigh wave and a Lamb wave.
18. The method of claim 12 , wherein the substrate is transparent.
19. The method of claim 12 , wherein the substrate is opaque.
20. The method of claim 12 , further comprising processing the acoustic wave at the higher order odd resonant frequency to determine the location on the substrate that is touched.