Mitigating active stylus/touch cross-coupling

Patent metadata

Field	Value
Publication number	US-10452212-B2
Application number	US-201715485698-A
Country	US
Kind code	B2
Filing date	Apr 12, 2017
Priority date	Apr 12, 2016
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

In one aspect, the present disclosure relates to a method including determining which sense lines are potentially corrupted based on touch image information, measuring a sense signal on each sense line, and applying a trained best compensation factor to the measured sense signal on potentially corrupted sense lines in order to produce a corrected sense signal. The corrected sense signal eliminates active stylus signal that has cross-coupled to a touch contact (e.g., a finger or conductive stylus) and thereby mitigates errors in stylus location due to cross-coupled signal.

First claim

What is claimed is:

1. A method for mitigating cross-coupling in a device configured to receive input from an active stylus, comprising:
determining, during an LCD module blanking interval of a touch screen display of the device, a best compensation factor by a processor circuit based on measurements taken from one or more of a plurality of sense lines of the device and first touch image information determined by a touch sensor of the device;
determining, by the processor circuit of the device, one or more corrupted sense lines in the touch sensor based on touch image information;
measuring, by the processor circuit, a sense signal on each of the plurality of sense lines;
applying, by the processor circuit, the best compensation factor to the measured sense signal on each of the one or more corrupted sense lines to produce a corrected sense signal for each of the one or more corrupted sense lines;
determining, by the processor circuit, a stylus location based on the corrected sense signals, the stylus location being different from a detected stylus location detected by the touch sensor before applying the best compensation factor; and
generating, by the processor circuit, a stylus input made at the stylus location.

2. The method of claim 1 , wherein the training comprises:
marking, by the processor circuit, a plurality of sense lines as training pixels;
measuring, by the processor circuit, a training sense signal on each of the training pixels;
calculating, by the processor circuit, a plurality of compensation factors, wherein each of the plurality of compensation factors is a best compensation factor for one of the training pixels; and
computing, by the processor circuit, the best compensation factor from the plurality of compensation factors.

3. The method of claim 2 , wherein each of the plurality of compensation factors is calculated by the processor circuit such that a dot product of the compensation factor and the touch image information for the training pixel equals the measured training sense signal on the training pixel.

4. The method of claim 3 , wherein the processor circuit uses a least squares fit to calculate each of the plurality of compensation factors.

5. The method of claim 3 , wherein the processor circuit uses a linear fit to calculate each of the plurality of compensation factors.

6. The method of claim 2 , wherein the processor circuit marks a sense line as a training pixel when a negative phase of the active stylus signal is present on the sense line and a touch contact is present on the sense line.

7. The method of claim 1 , wherein the best compensation factor comprises a magnitude portion and a phase portion.

8. The method of claim 1 , wherein the corrected sense signal is equal to a difference between the measured sense signal for each of the one or more corrupted sense lines and a dot product of the best compensation factor and the touch image information for each of the one or more corrupted sense lines.

9. The method of claim 1 , wherein the active stylus generates a plurality of stylus drive signals.

10. The method of claim 9 , wherein the plurality of stylus drive signals comprise a ring drive signal and a tip drive signal.

11. A system for mitigating cross-coupling comprising:
an active stylus;
a touch screen display comprising a touch sensor with a plurality of sense lines;
a memory storing program instructions; and
a processor circuit coupled to the memory and configured to execute the program instructions causing the processor circuit to:
determine, during a LCD module blanking interval of the touch screen display, a best compensation factor based on measurements taken from one or more of the plurality of sense lines and first touch image information determined by the touch sensor;
determine one or more corrupted sense lines based on second touch image information determined by the touch sensor;
measure a sense signal on each of the plurality of sense lines;
apply the best compensation factor to the measured sense signal on each of the one or more corrupted sense lines to produce a corrected sense signal for each of the one or more corrupted sense lines;
determine a stylus location based on the corrected sense signals, the stylus location being different from a detected stylus location detected by the touch sensor before applying the best compensation factor; and
generate a stylus input made at the stylus location.

12. The system of claim 11 , wherein the program instructions further cause the processor circuit to:
mark a plurality of sensed lines as training pixels;
measure a training sense signal on each of the training pixels;
calculate a plurality of compensation factors, wherein each compensation factor is a best compensation factor for one of the training pixels; and
compute the best compensation factor from the plurality of compensation factors.

13. The system of claim 12 , wherein the program instructions further cause the processor circuit to calculate each of the plurality of compensation factors such that a dot product of the compensation factor and the second touch image information for the training pixel equals the measured training sense signal on the training pixel.

14. The system of claim 13 , wherein the program instructions further cause the processor circuit to use a least square fit to calculate each of the plurality of compensation factors.

15. The system of claim 13 , wherein the program instructions further cause the processor circuit to use a linear fit to calculate each of the plurality of compensation factors.

16. The system of claim 12 , wherein the program instructions further cause the processor circuit to mark a sense line as a training pixel when a negative phase of the active stylus signal is present on the sense line and a touch contact is present on the sense line.

17. The system of claim 11 , wherein the best compensation factor comprises a magnitude portion and a phase portion.

18. The system of claim 11 , wherein the corrected sense signal is equal to a difference between the measured sense signal for each of the one or more corrupted sense lines and a dot product of the best compensation factor and the second touch image information for each of the one or more corrupted sense lines.

19. The system of claim 11 , wherein the active stylus generates a plurality of stylus drive signals.

20. The system of claim 19 , wherein the plurality of stylus drive signals comprise a ring drive signal and a tip drive signal.

21. A touch-screen device comprising the system of claim 11 .

Assignees

• Apple Inc

Inventors

• Gum Leah
• Westerman Wayne C
• Navidpour Seyed Mohammad
• Shahparnia Shahrooz

Classifications

• G06F2203/04104

  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 title

• G06F3/044 Primary

  by capacitive means · CPC title

• G06F3/0446

  using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes · CPC title

• G06F3/04186 Primary

  Touch location disambiguation · CPC title

• G06F3/0442

  using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser · CPC title