ESD detection on a touch input device

• US 9,075,481 B2
• Filed: 12/10/2012
• Issued: 07/07/2015
• Est. Priority Date: 09/10/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Lin, Albert, O'Connor, Sean Erik, Benbasat, Ari Y., Westerman, Wayne Carl, Shih, David H. C.
• Primary Examiner(s): Hicks, Charles V
• Assistant Examiner(s): Steinberg, Jeffrey S
• Application Number:
  US13/710,318
• Publication Number:
  US 20140071092A1
• Time in Patent Office: 939 Days
• Field of Search: 345173-178, 178 1801- 1809, 178/18.11
• US Class Current: 1/1
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0425 using a single imaging device like a video camera for tracking the absolute position of a single or a plurality of objects with respect to an imaged reference surface, e.g. video camera imaging a display or a projection screen, a table or a wall surface, on which a computer generated image is displayed or projected tracking a projected light spot to determine a position on a display surface G06F3/0386
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A touch sensitive device that detects the occurrence of an electrostatic discharge event on the device by analyzing an acquired touch image for characteristics associated with the occurrence of an ESD event is provided. An acquired touch image is analyzed for characteristics that differentiate it from a touch image generated by a user input and are correlated with an expected touch image generated by an ESD event.

Claims

1. A method for detecting an occurrence of an ESD event on a touch input device, the method comprising:

applying stimulation signals to a plurality of drive lines of a touch sensor panel, wherein the stimulation signals are applied in a multi-step sequence of stimulation signals, each step having different stimulation signals;

acquiring a touch image of the touch sensor panel wherein the touch image comprises a plurality of sensed values based on the stimulation signals; and

determining a correlation of the touch image to one or more of the different stimulation signals, the correlation of one or more, but fewer than all, of the different stimulation signals indicative of the ESD event.

2. The method of claim 1, wherein the multiple steps are stored in a matrix of vectors, the matrix having a plurality of basis vectors.

3. The method of claim 2, wherein the correlation of the touch image to one or more steps in the sequence of stimulation signals further includes the touch image being correlated to one or more of the plurality of basis vectors.

4. The method of claim 2, wherein the correlation between the touch image and the plurality of basis vectors is determined by comparing a first number of positive signals within the plurality of sensed values with a second number of negative signals within the plurality of sensed values.

5. The method of claim 2, wherein determining the correlation comprises:

analyzing a first portion of the touch image corresponding to a first group of drive lines to determine a correlation of the touch image to the one or more steps in the sequence of stimulation signals;

analyzing a second portion of the touch image corresponding to a second group of drive lines to determine a correlation of the touch image to the one or more steps in the sequence of stimulation signals; and

comparing the first portion of the touch image to the second portion of the touch image.

6. The method of claim 1, wherein acquiring a touch image of the touch sensor panel further includes receiving a plurality of signals from a plurality of sense lines of the touch sensor panel, the plurality of signals being indicative of a change in capacitance at a plurality of touch nodes of the device.

7. The method of claim 1, further comprising disabling ESD detection when one or more sensed values have been detected by the touch sensor panel.

23. The method of claim 1 wherein applying the stimulation signals is performed by applying a given stimulation signal simultaneously to the plurality of the drive lines.

24. The method of claim 23, wherein determining the correlation of the touch image to one or more of the different stimulation signals comprises determining the correlation of the touch images from all of the stimulation signals in the multi-step sequence, the most strongly correlated touch image indicative of the ESD event.

8. A touch sensitive device capable of detecting the occurrence of an ESD event, the device comprising:

a touch sensor panel capable of applying stimulation signals to a plurality of drive lines of the touch sensor panel, wherein the stimulation signals are applied in a multi-step sequence of stimulation signals, each step having different stimulation signals;

a processor capable of

acquiring a touch image of the touch sensor panel, wherein the touch image comprises a plurality of sensed values based on the stimulation signals; and

determining a correlation of the touch image to one or more of the different stimulation signals, the correlation of one or more, but fewer than all, of the different stimulation signals indicative of the ESD event.

9. The device of claim 8, wherein the processor is further capable of storing the multiple steps in a matrix of vectors, the matrix having a plurality of basis vectors.

10. The device of claim 9, wherein the processor is further capable of determining the correlation of the touch image to the one or more steps in the sequence of stimulation signals by correlating the touch image to one or more of the plurality of basis vectors.

11. The device of claim 10, wherein the processor is further capable of determining the correlation between the touch image and the plurality of basis vectors by comparing a first number of positive signals within the plurality of sensed values with a second number of negative signals within the plurality of sensed values.

12. The device of claim 9, wherein determining the correlation comprises:

analyzing a first portion of the touch image corresponding to a first group of rows to determine a correlation of the touch image to one or more steps in the sequence of stimulation signals;

analyzing a second portion of the touch image corresponding to a second group of drive lines to determine a correlation of the touch image to the one or more steps in the sequence of stimulation signals; and

comparing the first portion of the touch image to the second portion of the touch image.

13. The device of claim 8, wherein acquiring a touch image of the touch sensor panel further includes receiving a plurality of signals from a plurality of sense lines of the touch sensor panel, the plurality of signals being indicative of a change in capacitance at a plurality of touch nodes of the touch sensor panel.

14. The device of claim 8, wherein the processor is further capable of disabling ESD detection when one or more of the plurality of signals from the plurality of sense lines have been detected by the touch sensor panel.

25. The device of claim 8 wherein applying the stimulation signals is performed by applying a given stimulation signal simultaneously to the plurality of the drive lines.

26. The device of claim 25, wherein determining the correlation of the touch image to one or more of the different stimulation signals comprises determining the correlation of the touch images from all of the stimulation signals in the multi-step sequence, the most strongly correlated touch image indicative of the ESD event.

15. A non-transitory computer readable storage medium having stored thereon a set of instructions for detecting ESD events in a touch sensor panel, that when executed by a processor causes the processor to:

apply stimulation signals to a plurality of drive lines of a touch sensor panel, wherein the stimulation signals are applied in a multi-step sequence of stimulation signals, each step having different stimulation signals;

acquire a touch image of the touch sensor panel wherein the touch image comprises a plurality of sensed values based on the stimulation signals; and

determining a correlation of the touch image to one or more of the different stimulation signals, the correlation of one or more, but fewer than all, of the different stimulation signals indicative of the ESD event.

16. The non-transitory computer readable storage medium of claim 15, wherein the multiple steps are stored in a matrix of vectors, the matrix having a plurality of basis vectors.

17. The non-transitory computer readable storage medium of claim 16, wherein the correlation of the touch image to one or more steps in the sequence of stimulation signals further includes the touch image being correlated to one or more of the plurality of basis vectors.

18. The non-transitory computer readable storage medium of claim 16, wherein the correlation between the touch image and the plurality of basis vectors is determined by comparing a first number of positive signals within the plurality of sensed values with a second number of negative signals within the plurality of sensed values.

19. The non-transitory computer readable storage medium of claim 15, wherein determining the correlation comprises:

analyzing a first portion of the touch image corresponding to a first group of drive lines to determine a correlation of the touch image to the one or more steps in the sequence of stimulation signals;

analyzing a second portion of the touch image corresponding to a second group of drive lines to determine a correlation of the touch image to the one or more steps in the sequence of stimulation signals; and

comparing the first portion of the touch image to the second portion of the touch image.

20. The non-transitory computer readable storage medium of claim 15, wherein acquiring a touch image of the touch sensor panel further includes receiving a plurality of signals from a plurality of sense lines of the touch sensor panel, the plurality of signals being indicative of a change in capacitance at a plurality of touch nodes of the device.

21. The non-transitory computer readable storage medium of claim 15, wherein the processor is further caused to disable ESD detection when one or more sensed value have been detected by the touch sensor panel.

27. The non-transitory computer readable storage medium of claim 15 wherein applying the stimulation signals is performed by applying a given stimulation signal simultaneously to the plurality of the drive lines.

28. The non-transitory computer readable storage medium of claim 27, wherein determining the correlation of the touch image to one or more of the different stimulation signals comprises determining the correlation of the touch images from all of the stimulation signals in the multi-step sequence, the most strongly correlated touch image indicative of the ESD event.

22. A touch sensitive device capable of detecting the occurrence of an ESD event, the device comprising:

a touch sensor panel capable of applying stimulation signals to a plurality of drive lines of the touch sensor panel, wherein the stimulation signals are applied in a multi-step sequence of stimulation signals, each step having different stimulation signals;

a processor capable of

storing a representation of the stimulation signals as a matrix of vectors having a plurality of base vectors;

acquiring a touch image of the touch sensor panel, wherein the touch image comprises a plurality of sensed values for touch pixels of the touch panel based on the stimulation signals; and

determining if a tolerance of the acquired touch image for at least one of the base vectors is below a pre-determined value, the tolerance based on a difference in amplitude of sensed values of adjacent touch pixels of the touch panel.

29. The device of claim 22 wherein applying the stimulation signals is performed by applying a given stimulation signal simultaneously to the plurality of the drive lines.

30. The device of claim 29, wherein determining the correlation of the touch image to one or more of the different stimulation signals comprises determining the correlation of the touch images from all of the stimulation signals in the multi-step sequence, the most strongly correlated touch image indicative of the ESD event.