Method and apparatus for detecting hold condition on an acoustic touch surface

• US 8,659,579 B2
• Filed: 05/14/2010
• Issued: 02/25/2014
• Est. Priority Date: 05/22/2009
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc., Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Elo Touch Solutions, Inc., Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Nadjar, Hamid Sheikhzadeh, Babb, Joe Henry, Brennan, Robert L., Haungs, Steven W., Kent, Joel C., Wynne, James R. Jr.
• Primary Examiner(s): Bibbins, Latanya
• Application Number:
  US12/780,033
• Publication Number:
  US 20110025649A1
• Time in Patent Office: 1,383 Days
• Field of Search: 345/177
• US Class Current: 345/177
• CPC Class Codes: G06F 3/043 using propagating acoustic waves

Abstract

A bending wave touch system includes at least one sensor and a touchscreen controller. The at least one sensor is coupled to a substrate and is responsive to vibrations in the substrate. The at least one sensor outputs signals. The controller receives the signals from the at least one sensor and identifies touch coordinates based on high frequency components of the signals when a touch on the substrate includes at least one of a tap, a drag and a lift-off. The controller identifies a status of a hold condition of the touch based on at least two different time averages of low frequency components of the signals.

Claims

1. A bending wave touch system, comprising:

at least one sensor coupled to a substrate and responsive to vibrations in the substrate, the at least one sensor outputting signals; and

a controller configured to receive the signals from the at least one sensor, the controller further configured to identify touch coordinates based on high frequency components of the signals when a touch on the substrate comprises at least one of a tap, a drag and a lift-off, the controller further configured to identify a status of a hold condition of the touch based on at least two different time averages of low frequency components of the signals.

2. The system of claim 1, further comprising a frequency transform module configured to accomplish fast Fourier transformation (FFT) on the signals, and wherein the low frequency components are based on FFT Bin 0.

3. The system of claim 1, further comprising a frequency transform module to receive the signals from the at least one sensor, the frequency transform module including high and low pass filters to output the high and low frequency components over a high frequency channel and a low frequency channel, respectively, to the controller.

4. The system of claim 1, further comprising a signal processing circuit configured to process the signals and output a non-monotonic frequency response.

5. The system of claim 1, wherein the two different time averages comprise a fast averaged envelope and a slow averaged envelope, the system further comprising a hold detection module configured to calculate absolute values of the low frequency components and to calculate the fast averaged envelope and the slow averaged envelope wherein the absolute values are averaged over relatively shorter and relatively longer periods of time, respectively.

6. The system of claim 1, wherein the two different time averages comprise a fast averaged envelope and a slow averaged envelope, the system further comprising a hold detection module configured to calculate the slow averaged envelope based on the low frequency components, the hold detection module further configured to hold the slow averaged envelope to a level of background activity when the at least one of the tap, the drag and the lift-off are identified.

7. The system of claim 1, wherein the controller is further configured to prevent the hold condition when the hold condition is identified without at least one of the tap and the drag being detected prior to the hold condition.

8. A method for identifying a hold condition on a bending wave touch panel, comprising:

detecting signals with at least one sensor bonded with a substrate, the signals indicative of vibrations on the substrate of a bending wave touch panel;

identifying at least one of a tap and a drag based on the signals;

calculating two different time averages based on low frequency components of the signals; and

identifying a hold condition following the at least one of the tap and the drag based on amplitude levels of the two different time averages.

9. The method of claim 8, further comprising fast Fourier transforming (FFT) the signals, wherein the low frequency components are based on FFT Bin 0.

10. The method of claim 8, further comprising:

low pass filtering the low frequency components to pass frequency components below 100 Hz;

decimating the frequency components below 100 Hz; and

forming an envelope based on absolute values of the frequency components, the envelope comprising one of the two different time averages, the identifying the hold condition being further based on the envelope.

11. The method of claim 8, further comprising:

low pass filtering the low frequency components to pass frequency components below 100 Hz;

forming a fast averaged envelope based on the low frequency components wherein an absolute value of the low frequency components is quickly averaged over time; and

forming a slow averaged envelope wherein the absolute value of the low frequency components are slowly averaged over time, wherein the fast and slow averaged envelopes comprise the two different time averages, and wherein the hold condition is identified when a ratio of the slow averaged envelope to the fast averaged envelope is less than a predetermined threshold.

12. The method of claim 8, further comprising:

determining an average background activity when no touch is present on the substrate;

forming a fast averaged envelope based on the low frequency components wherein absolute values of the low frequency components are quickly averaged over time; and

forming a slow averaged envelope based on the low frequency components wherein the absolute values of the low frequency components are slowly averaged over time, wherein the fast and slow averaged envelopes comprise the two different time averages, wherein the hold condition is identified when a ratio of the slow averaged envelope to the fast averaged envelope is less than a predetermined threshold and a ratio of the fast averaged envelope to the background activity is greater than a second predetermined threshold.

13. The method of claim 8, further comprising:

low pass filtering the low frequency components to pass frequency components below 100 Hz;

decimating the frequency components below 100 Hz; and

detecting a lift-off when a ratio of the decimated frequency components to an envelope based on absolute values of the decimated frequency components exceeds a predetermined threshold, the envelope comprising one of the two different time averages.

14. The method of claim 8, further comprising detecting a lift-off event when the low frequency components comprise at least a predetermined signal amplitude and a phase variance of the signals is less than a predetermined threshold.

15. The method of claim 8, further comprising setting the low frequency components to one of zero and a level based on a background activity for a predetermined period of time after the tap or a lift-off is detected, and wherein the background activity is based on signals received when no touch is present on the substrate.

16. The method of claim 8, further comprising:

holding the hold condition for a predetermined delay period; and

terminating the hold condition if the hold condition is not valid after the delay period.

17. A method for determining touch coordinates on a bending wave touch surface, comprising:

detecting signals with at least two sensors bonded with the bending wave touch surface, the signals indicative of vibrations on the bending wave touch surface;

low pass filtering the signals to pass low frequency components below 100 Hz; and

determining the touch coordinates of a single touch on the touch surface based on ratios of the low frequency components;

wherein at least one of the ratios is determined based on at least one averaged envelope of the low frequency components.

18. The method of claim 17, wherein the single touch condition is determined when a phase variance of the signals is less than a predetermined threshold.

19. The method of claim 17, wherein the low pass filtering further comprising separately low pass filtering the signals from different ones of at least two sensors, and wherein the touch coordinates of the single touch are further determined based on ratios of low frequency components associated with the at least two sensors.

20. The method of claim 17, further comprising:

determining touch coordinates of at least two touches held simultaneously on the bending wave touch surface such that the touch coordinates of a single touch remaining on the touch surface is based on the ratios of the low frequency components.