Method and system for detecting touch events based on magnitude ratios

• US 8,378,974 B2
• Filed: 07/02/2007
• Issued: 02/19/2013
• Est. Priority Date: 07/02/2007
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touch Solutions, Inc.
• Inventors: Aroyan, James L., D'Souza, Henry M., Fry, Charles David, Kent, Joel C.
• Primary Examiner(s): Kumar, Srilakshmi K
• Application Number:
  US11/824,965
• Publication Number:
  US 20090008160A1
• Time in Patent Office: 2,059 Days
• Field of Search: 345/156, 345173-178, 178 1801- 1807
• US Class Current: 345/173
• 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

Abstract

A method for detecting a touch event on a touch panel comprises obtaining at least first and second signals from at least two sensors where the at least first and second signals are responsive to a touch event. A first amplitude magnitude associated with the first signal is calculated and a second amplitude magnitude associated with the second signal is calculated. A magnitude ratio is determined between the first and second amplitude magnitudes, and a touch location is identified based on the magnitude ratio.

Claims

1. A method of detecting a touch event on a touch panel, comprising:

obtaining a first signal from at least a first sensor and a second signal respectively from at least a second sensor, where the first and second signals are responsive to a touch event;

digitizing the first signal to form a first set of digitized signals and the second signal to form a second set of digitized signals;

performing a frequency transform upon the first and second sets of digitized signals to form respectively first and second frequency transform data sets of frequency components;

calculating a first amplitude magnitude associated with the first signal and calculating a second amplitude magnitude associated with the second signal, the first amplitude magnitude being calculated based on the first frequency transform data set and the second amplitude magnitude being calculated based on the second frequency transform data set;

determining a magnitude ratio between the first amplitude magnitude associated with the first frequency transform data set and the second amplitude magnitude associated with the second frequency data set; and

identifying a location of the touch event based on the magnitude ratio, the magnitude ratio being gauge-invariant.

2. The method of claim 1, wherein the calculating includes calculating a series of magnitude ratios.

3. The method of claim 1, wherein the identifying the touch location includes analyzing the magnitude ratio in connection with a calibration file of template magnitude ratios, wherein each of the template magnitude ratios is associated with a known location on the touch panel.

4. The method of claim 1, wherein the identifying the touch location further comprises comparing the magnitude ratio to a plurality of template magnitude ratios within a calibration file to determine associated scoring relations, wherein each of the template magnitude ratios is associated with a known location on the touch panel, the identifying the touch location further comprising identifying at least one of the template magnitude ratios based on the scoring relations.

5. The method of claim 1, further comprising obtaining a third signal from a third sensor, wherein the magnitude ratio is determined based on amplitude magnitudes associated with the first, second and third signals.

6. A touch system, comprising:

a touch panel;

at least two sensors configured to obtain at least two signals associated with a touch event on the touch panel, the at least two signals comprising a first signal obtained from a first sensor and a second signal obtained from a second sensor, the at least two sensors including the first and second sensors; and

a processor module configured to

digitize the first signal to form a first set of digitized signals;

digitize the second signal to form a second set of digitized signals;

perform frequency transforms based on the first and second set of digitized signals to form respectively first and second frequency transform data sets;

calculate a first amplitude magnitude associated with the first signal, the first amplitude magnitude being calculated based on the first frequency transform data set;

calculate a second amplitude magnitude associated with the second signal, the second amplitude magnitude being calculated based on the second frequency transform data set; and

compare a magnitude ratio of the first and second amplitude magnitudes to a calibration file of template fingerprints associated with known locations on the touch panel to determine a coordinate location associated with the touch event, the template fingerprints being at least in part based on magnitude ratios between magnitude frequency spectra of the first and second sensors for the known locations, the magnitude ratio being gauge-invariant.

7. The system of claim 6, wherein the magnitude ratio of the first and second amplitude magnitudes represents at least a portion of a live fingerprint associated with the touch event.

8. The system of claim 7, wherein the live fingerprint is at least one of a function of (A₁(ω

)/A₂(ω

), a function of (A₂(ω

)−

A₁(ω

)/(A₂(ω

)+A₁(ω

)), a function of (A₂(ω

)²−

A₁(ω

)²/(A₂(ω

)²+A₁(ω

)²), and a function of arctan(A₂(ω

)/A₁(ω

)), wherein A₁(ω

) is a first amplitude magnitude as a function of frequency and A₂(ω

) is a second amplitude magnitude as a function of frequency.

9. The system of claim 6, wherein the processor module is further configured to obtain a phase difference based on the first and second frequency transform data sets, the phase difference and the magnitude ratio being used to construct a live fingerprint associated with the touch event.

10. The system of claim 9, comprising M signals wherein M is at least three.

11. The system of claim 10, wherein the processor module is further configured to produce a phase φ

₁(ω

), φ

₂(ω

) . . . φ

_M(ω

) for each of the M signals, wherein a linear-combination constant C₁, C₂, . . . C_M is associated with each of the M phases and wherein the sum of the M linear-combination constants is zero, the processor module forming a gauge-invariant phase difference C₁φ

(ω

)+C₂φ

₂(ω

) . . . +C<sub>N φ

N</sub>(ω

) based on the sum of the products of each linear-combination constant and phase.

12. The system of claim 9, wherein the live fingerprint is a trajectory having two dimensions wherein a first coordinate of the trajectory is based on π

/2−

2 arctan(A₂(ω

)/A₁(ω

) and a second coordinate of the trajectory is based on Δ

φ

(ω

)=φ

₂(ω

)−

φ

₁(ω

).

13. The system of claim 9, wherein the template fingerprints within the calibration file are further based on phase differences associated with the known locations on the touch panel, the processor module further configured to generate scores based on a comparison between the live fingerprint and the template fingerprints.

14. The system of claim 9, wherein the processor module is further configured to calculate and store with one-bit resolution at least one of the magnitude ratio and the phase difference.

15. A non-transitory computer readable medium for use in an acoustic fingerprint based touch system, comprising;

Instructions to process digitized signals from at least two sensors where the digitized signals are responsive to a touch event on a touch panel, the digitized signals comprising at least first and second signals, the first signal associated with a first sensor and the second signal associated with a second sensor, the at least two sensors including the first and second sensors;

instructions to digitize the first signal to form a first set of digitized signals;

instructions to digitize the second signal to form a second set of digitized signals;

instructions to perform a frequency transform upon the first and second sets of digitized signals to form respectively first and second frequency transform data sets of frequency components;

instructions to calculate a first amplitude magnitude associated with the first signal, the first amplitude magnitude being calculated based on the second frequency transform data set;

instructions to determine a magnitude ratio between the first amplitude magnitude associated with the first frequency transform data set and the second amplitude magnitude associated with the second frequency data set; and

instructions to identify a touch location associated with the touch event based on the magnitude ratio, the magnitude ratio being gauge-invariant.

16. The non-transitory computer readable claim 15, further comprising instructions to compare the magnitude ratio to a calibration file of template magnitude ratios associated with known locations on the touch panel.

17. The non-transitory computer readable medium of claim 15, further comprising:

instructions to calculate first phase information associated with the first signal and second phase information associated with the second signal; and

instructions to further identify the touch location associated with the touch event based on phase differences between the first and second phase information.

18. The non-transitory computer readable medium of claim 15 further comprising instructions to compute a calibration file of template fingerprints associated with known locations on the touch panel, the template fingerprints being based on at least amplitude magnitude information associated with each of the known locations, the touch location being further identified based on a comparison of the magnitude ratio to the template fingerprints.