Differential transmission for reduction of cross-talk in projective capacitive touch sensors

• US 10,423,273 B2
• Filed: 11/30/2017
• Issued: 09/24/2019
• Est. Priority Date: 12/08/2014
• Status: Active Grant

• Current Assignee: Tactual Labs Co.
• Original Assignee: Tactual Labs Co.
• Inventors: Leigh, Darren, Forlines, Clifton
• Primary Examiner(s): Awad, Amr A
• Assistant Examiner(s): Bray, Stephen A
• Application Number:
  US15/827,885
• Publication Number:
  US 20180095592A1
• Time in Patent Office: 663 Days
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 2203/04109 FTIR in optical digitiser, i.e. touch detection by frustrating the total internal reflection within an optical waveguide due to changes of optical properties or deformation at the touch location
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/042 by opto-electronic means
• 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

Differential transmission is provided in a capacitive sensor for reducing cross-talk between rows and columns. A capacitive touch sensitive device as disclosed herein includes row conductors and column conductors, a first row signal generator for transmitting a first row signal on a first row conductor, a second row signal generator for transmitting a second row signal on a second row conductor, and a touch processor for identifying a touch event on the touch interface by processing signals present on at least one of the column conductors. The first and second row signals together form a differential row group of signals that cancel each other out or at least substantially mitigate each other so as to reduce cross-talk interference in the sensor.

Claims

1. A touch sensitive device having a touch surface comprising:

touch interface comprising first conductors and second conductors such that a touch event proximate to the touch surface causes a change in coupling between at least one of the first conductors and at least one of the second conductors;

signal generator configured to transmit a plurality of unique orthogonal signals on a first plurality of first conductors, respectively;

the signal generator further configured to transmit, concurrently with the transmission of the plurality of unique orthogonal signals, a plurality of first signals on a second plurality of first conductors, respectively, wherein respective ones of the plurality of first signals and ones of the plurality of unique orthogonal signals are part of a differential group;

touch processor configured to identify a touch event on the touch interface by processing signals present on at least one of the second conductors;

wherein the differential group comprises at least one conductor from the first plurality of first conductors and one conductor from the second plurality of first conductors, wherein the at least one conductor from the first plurality of first conductors and the one conductor from the second plurality of first conductors are spaced apart by a minimum physical spacing that maintains a minimum physical distance between conductors of the first differential group, and the conductors of the first differential group are nonadjacent and at least more than one conductor apart.

2. The device of claim 1, wherein each of the plurality of unique orthogonal signals are orthogonal with each other in at least one aspect selected from a group consisting of:

time, frequency, and code.

3. The device of claim 1, wherein signals in each differential group substantially mitigate each other when combined equally, whereby cross-talk interference is substantially reduced.

4. The device of claim 1, wherein the minimum physical spacing is larger than a linear measure of a contact areas of an object affecting a touch event.

5. The device of claim 1, wherein the differential few group has a maximum physical spacing for maintaining maximum physical distance between the first first conductor and the second first conductor of the at least one differential group.

6. The device of claim 5, wherein the maximum physical spacing is small enough to ensure that signals in the differential group of signals substantially cancel each other out when combined equally when first and second conductors are fabricated from high resistivity conductors.

7. The device of claim 6, wherein the high-resistivity conductors comprise a material selected from the group consisting of:

ITO, metal-mesh, and silver nanowire.

8. The device of claim 1, wherein the differential group is one of a plurality of differential groups and the device is configured such that the plurality of differential groups are remapped between a first frame and a second frame.

9. The device of claim 8, configured such that the differential groups are remapped on a frame-by-frame basis.

10. The device of claim 1, wherein the differential group is one of a plurality of differential groups and the device is configured such that the plurality of differential groups are randomly remapped.

11. The device of claim 8, configured such that the remapping is biased according to at least one goal selected from a group consisting of:

(a) to lessen a probability of a touch event being canceled by a substantially equal contribution from all of the first signals comprising a differential group;

(b) to minimize a mean number of frames in which an undesired cancellation of a user-intended touch event occurs; and

(c) to minimize a maximum number of sequential frames in which an undesired cancellation of a user-intended touch event might occur.

12. The device of claim 1, wherein the differential group is one of a plurality of differential groups and the device is configured such that the plurality of differential groups are remapped according to a predetermined pattern.

13. The device of claim 2, configured such that the signals in the differential group are remapped on a frame-by-frame basis.

14. The device of claim 1, configured such that the signals in the differential group are remapped randomly.

15. The device of claim 1, configured such that the signals in the differential group are remapped according to a predetermined pattern.

16. The device of claim 1, wherein the touch processor is configured to determine whether a user is touching the touch interface with a body part other than and larger than a user'"'"'s finger, and thus causing an extended-area touch event.

17. The device of claim 16, configured such that at least one differential group is mapped to the first conductors that correspond with an extended-area touch event.

18. The device of claim 17, wherein the device is configured to provide sufficient physical spacing of the first conductors comprising the at least one differential group to allow for individual touch events to register on the first conductors.

19. The device of claim 1, wherein the signals in the differential group substantially mitigate each other when combined equally.

20. The device of claim 1, wherein the touch processor is configured to identify a touch event by a change in phase shift of a received second signal when and where a first conductor and second conductor are simultaneously touched.

21. The device of claim 1, wherein the touch processor is configured to identify a touch event by a change in received signal strength of a first signal of a differential group on a second conductor when and where a first conductor and second conductor are simultaneously touched.

22. The device of claim 21, configured such that a touch event decreases a first signal'"'"'s contribution to the combined signals received on a second conductor and the touch processor is configured to determine that a touch event has occurred on a particular first conductor of the differential group by measuring a combined signal and inferring which signal has decreased.

23. The device of claim 21, configured such that a touch event changes phase of a first signal'"'"'s contribution to the combined signals received on a second conductor and the touch processor is configured to determine that a touch event has occurred on a particular first conductor of a differential group by measuring a combined second signal and inferring which first signal has changed phase.

24. The device of claim 1, wherein the touch processor is configured to identify a touch event on the touch interface by processing signals present on a plurality of the second conductors.

25. The device of claim 1, further comprising a second signal generator configured to transmit first and second unique orthogonal second signals on first and second second conductors, wherein the touch processor is further configured to identify the touch event on the touch interface by processing signals present on at least one of the first conductors.

26. The device of claim 25, wherein the second signal generator is further configured to transmit a third second signal on a third column second conductor, the third second signal and the first unique orthogonal column second signal being part of a differential group.

27. The device of claim 1, further configured to transmit at least two differential groups on the first conductors.

28. The device of claim 1, further configured to transmit at least three differential groups of signals on the first conductors.

29. A non-transitory computer readable medium having code for use in identifying touch events on a touch sensitive device having first conductors, second conductors and a signals generator, the touch sensitive device identifying a touch events by processing signals present on at least one of the second conductors, the computer readable medium comprising:

code for causing the signals generator to transmit a plurality of unique orthogonal signals on a first plurality of first conductors, respectively;

code for causing the signals generator to transmit, concurrently with the transmission of the plurality of unique orthogonal signals, a plurality of first signals on a second plurality of first conductors, respectively, wherein respective ones of the plurality of first signals and ones of the plurality of unique orthogonal signals are part of a differential group, wherein the differential group comprises at least one conductor from the first plurality of first conductors and one conductor from the second plurality of first conductors, wherein the at least one conductor from the first plurality of first conductors and the one conductor from the second plurality of first conductors are spaced apart by a minimum physical spacing that maintains a minimum physical distance between conductors of the first differential group, and the conductors of the first differential group are nonadjacent and at least more than one conductor apart.

30. The computer readable medium of claim 29, wherein the unique orthogonal signals are orthogonal in at least one aspect selected from the group consisting of:

time, frequency, and code.

31. The computer readable medium of claim 29, wherein the signals in the differential group mitigate each other when combined equally, whereby cross-talk interference is substantially reduced.

32. The computer readable medium of claim 29, wherein the differential group is one of a plurality of differential groups and the plurality of differential groups are remapped between a first frame and a second frame.

33. The computer readable medium of claim 32, further comprising code for remapping the differential groups on a frame-by-frame basis.

34. The computer readable medium of claim 29, wherein the differential group is one of a plurality of differential groups and the computer readable medium further comprises code remapping the plurality of differential groups according to a predetermined pattern.

35. The computer readable medium of claim 33, further comprising code for generating the predetermined pattern according to at least one goal selected from a group consisting of:

(a) to lessen a probability of a touch event being canceled by a substantially equal contribution from all of the first signals comprising a differential group;

(b) to minimize a mean number of frames in which an undesired cancellation of a user-intended touch event occurs; and

(c) to minimize the maximum number of sequential frames in which an undesired cancellation of a user-intended touch event might occur.

36. The computer readable medium of claim 29, further comprising code for remapping the signals in the differential group on a frame-by-frame basis.

37. The computer readable medium of claim 29, further comprising code for determining whether a user is touching the touch interface with a body part other than and larger than a user'"'"'s finger.

38. The computer readable medium of claim 37, wherein first signals within the differential group that correspond with an extended-area touch event are mapped onto a location of the user'"'"'s body part for improved palm rejection.