Contaminant processing system for an acoustic touchscreen

• US 6,366,277 B1
• Filed: 10/13/1999
• Issued: 04/02/2002
• Est. Priority Date: 10/13/1999
• Status: Expired due to Fees

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touchsystems Incorporated (Elo Touch Solutions, Inc.)
• Inventors: Armstrong, Don
• Primary Examiner(s): Jankus, Almis R.
• Assistant Examiner(s): Tran, Henry N.
• Application Number:
  US09/417,872
• Time in Patent Office: 902 Days
• Field of Search: 345/173, 345/177
• 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

A method for minimizing the shadowing effects of a contaminant on a surface acoustic wave touchscreen is provided. The disclosed system compares the measured waveform against a baseline waveform for each axis and validates the new touch if the measured waveform is different from the baseline waveform for either axis. As a consequence of this approach, even if the new touch lies within the shadow created by a contaminant in one axis, the new touch is still validated as it is not within the shadow created by the contaminant in the second axis. In one embodiment, after the system determines that the measured response is different from the baseline in at least one axis, the system compares the new touch to one or more selection criteria to insure that it is a valid touch and not due to a contaminant, electrical noise, or other improper source. Preferably the duration of the new touch is monitored, thus allowing the new touch to be invalidated if the duration is too short, indicating system noise, or too long, indicating for example, a contaminant. Also preferably the size of the new touch is determined, thus allowing the touch to be invalidated if the size is too large which may be indicative of a contaminant or other foreign body resting on the touchscreen surface.

Claims

1. A method of operating an acoustic wave touchscreen, comprising the steps of:

periodically measuring a first waveform for a first axis of said touchscreen and a second waveform for a second axis of said touchscreen;

comparing said first waveform to a first baseline waveform;

determining if said first waveform and said first baseline waveform are substantially equivalent;

comparing said second waveform to a second baseline waveform;

determining if said second waveform and said second baseline waveform are substantially equivalent;

returning to an initial monitoring state if said first waveform and said first baseline waveform are substantially equivalent and if said second waveform and said second baseline waveform are substantially equivalent; and

establishing a new touch if said first waveform and said first baseline waveform are not substantially equivalent or if said second waveform and said second baseline waveform are not substantially equivalent.

2. The method according to claim 1, further comprising the steps of:

measuring a duration of said new touch;

validating said new touch if said duration is greater than a predetermined duration; and

invalidating said new touch if said duration is less than said predetermined duration.

3. The method according to claim 1, further comprising the steps of:

measuring a duration of said new touch;

validating said new touch if said duration is less than a predetermined duration; and

invalidating said new touch if said duration is greater than said predetermined duration.

4. The method according to claim 3, further comprising the steps of:

replacing said first baseline waveform with said first waveform if said first waveform and said first baseline waveform are not substantially equivalent and if said new touch is invalidated; and

replacing said second baseline waveform with said second waveform if said second waveform and said second baseline waveform are not substantially equivalent and if said new touch is invalidated.

5. The method according to claim 1, further comprising the steps of:

measuring a touch size corresponding to said new touch;

validating said new touch if said touch size is less than a predetermined size; and

invalidating said new touch if said touch size is greater than said predetermined size.

6. The method according to claim 5, further comprising the steps of:

replacing said first baseline waveform with said first waveform if said first waveform and said first baseline waveform are not substantially equivalent and if said new touch is invalidated; and

replacing said second baseline waveform with said second waveform if said second waveform and said second baseline waveform are not substantially equivalent and if said new touch is invalidated.

7. The method according to claim 1, further comprising the step of computing a pair of coordinates for said new touch.

8. The method according to claim 7, further comprising the step of transmitting said first pair of coordinates to a touchscreen operating system.

9. The method according to claim 1, wherein said first baseline waveform includes at least one attenuation dip, and wherein said second baseline waveform includes at least one attenuation dip.

10. A method of operating an acoustic wave touchscreen, comprising the steps of:

periodically measuring a first waveform for a first axis of said touchscreen and a second waveform for a second axis of said touchscreen;

comparing said first waveform to a first baseline waveform, wherein said first baseline waveform includes at least one attenuation dip;

determining if said first waveform and said first baseline waveform are substantially equivalent;

comparing said second waveform to a second baseline waveform, wherein said second baseline waveform includes at least one attenuation dip;

determining if said second waveform and said second baseline waveform are substantially equivalent;

returning to an initial monitoring state if said first waveform and said first baseline waveform are substantially equivalent and if said second waveform and said second baseline waveform are substantially equivalent;

establishing a new touch if said first waveform and said first baseline waveform are not substantially equivalent and if said second waveform and said second baseline waveform are substantially equivalent;

determining a waveform difference between said first waveform and said first baseline waveform;

determining a first axis touch coordinate from said waveform difference; and

determining a second axis touch coordinate based on said second axis attenuation dip.

11. The method according to claim 10, further comprising the steps of:

measuring a duration of said new touch;

validating said new touch if said duration is greater than a predetermined duration; and

invalidating said new touch if said duration is less than said predetermined duration.

12. The method according to claim 10, further comprising the steps of:

measuring a duration of said new touch;

validating said new touch if said duration is less than a predetermined duration; and

invalidating said new touch if said duration is greater than said predetermined duration.

13. The method according to claim 12, further comprising the steps of replacing said first baseline waveform with said first waveform if said first waveform and said first baseline waveform are not substantially equivalent and if said new touch is invalidated.

14. The method according to claim 10, further comprising the steps of:

measuring a touch size corresponding to said new touch;

validating said new touch if said touch size is less than a predetermined size; and

invalidating said new touch if said touch size is greater than said predetermined size.

15. The method according to claim 14, further comprising the steps of replacing said first baseline waveform with said first waveform if said first waveform and said first baseline waveform are not substantially equivalent and if said new touch is invalidated.