DISPLAY TO TOUCH CROSSTALK COMPENSATION

• US 20120182251A1
• Filed: 01/14/2011
• Published: 07/19/2012
• Est. Priority Date: 01/14/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: KRAH, Christoph Horst
• Granted Patent: US 9,310,916 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04101 2.5D-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 and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

A touch sensitive display capable of compensating for crosstalk in the display is disclosed. Crosstalk in display components can be reduced, eliminated, or otherwise compensated for by reducing or eliminating parasitic capacitances that cause the crosstalk. To do so, gate voltages to the display components, such as thin film transistors (TFTs), that introduce the parasitic capacitances can be reduced or otherwise adjusted. In one approach, the gate voltage can be set at multiple different low levels to generate respective sets of touch signals having different amounts of crosstalk. The different crosstalk amounts can then be used to determine and compensate for the crosstalk in the touch signals. In another approach, gate voltage can be modulated between multiple different low levels to push crosstalk out of band with the generated touch signals. The out-of-band crosstalk can then be used to compensate for the crosstalk in the touch signals.

Claims

1. A method of compensating for crosstalk in a touch sensitive display, the method comprising:

performing multiple scans at multiple voltages to generate multiple images;

comparing the images to determine a crosstalk component introduced into the display; and

subtracting the determined crosstalk component from at least one of the images to provide a crosstalk compensated image.

2. The method of claim 1, wherein performing the multiple scans comprises:

setting an input of a display component causing the crosstalk at a predetermined level;

driving the display component at each of the multiple voltages; and

scanning pixels of the display during each driving to generate a corresponding one of the images, each corresponding image having the crosstalk therein.

3. The method of claim 1, wherein comparing the images comprises:

subtracting at least two of the images to provide a crosstalk image indicative of the crosstalk component; and

determining the crosstalk component based on the crosstalk image.

4. The method of claim 1, wherein subtracting the determined crosstalk component comprises:

averaging the multiple images; and

subtracting the determined crosstalk component from the averaged image to provide the crosstalk compensated image.

5. The method of claim 1, comprising generating a lookup table to determine the crosstalk component.

6. The method of claim 5, wherein generating the lookup table comprises:

setting a display component causing the crosstalk to display a predetermined value;

setting an input of the display component to a predetermined level;

driving the display component at each of the multiple voltages;

scanning pixels of the display during each driving to generate a corresponding crosstalk image, the corresponding crosstalk images having different amounts of crosstalk therein for each driving; and

repeating setting the display component, setting the input, driving, and scanning at multiple displayed predetermined values to acquire multiple crosstalk images.

7. The method of claim 6, wherein generating the lookup table comprises:

for each displayed predetermined value, determining the crosstalk component based on the corresponding generated crosstalk images; and

providing in the lookup table correlations between the generated crosstalk images and the determined crosstalk components.

8. The method of claim 1, comprising outputting the crosstalk compensated image.

9. A touch sensitive display comprising:

an active area including pixels having display components for displaying data and touch components for sensing a touching or hovering object;

a gate driver configured to drive the display components with an adjustable gate voltage during the sensing; and

a display controller configured to control adjustment of the gate voltage so as to compensate for crosstalk introduced by the display components during the sensing.

10. The display of claim 9, comprising a touch controller configured to drive the active area with a stimulation signal during the sensing and to receive a sense signal from the active area indicative of the touching or hovering object, the sense signal including the crosstalk.

11. The display of claim 9, wherein the gate driver drives the active area with multiple gate voltages for generating multiple sense signals having the crosstalk.

12. The display of claim 11, comprising a processor configured to determine the crosstalk in the sense signals and to compensate for the determined crosstalk.

13. The display of claim 9, wherein the display components include thin film transistors configured to receive the adjustable gate voltage.

14. A method of compensating for crosstalk in a touch sensitive display, the method comprising:

driving a display pixel with a modulating voltage to generate an output, the output having crosstalk therein;

demodulating the output to isolate the crosstalk therefrom;

determining a crosstalk compensation factor based on the isolated crosstalk; and

applying the determined crosstalk compensation factor to the output to provide a crosstalk compensated output.

15. The method of claim 14, wherein the display pixel includes display components for displaying data and touch components for sensing a touching or hovering object, and wherein driving the display pixel comprises:

driving the display components with the modulating voltage, the display components causing the crosstalk; and

driving the touch components with a stimulation voltage, the touch components generating the output indicative of the touching or hovering object.

16. The method of claim 14, wherein demodulating the output comprises:

demodulating the output at a first demodulation frequency to isolate touch components indicative of a touching or hovering object at the display; and

demodulating the output at a second demodulation frequency to isolate crosstalk components indicative of the crosstalk.

17. The method of claim 14, wherein determining the crosstalk compensation factor comprises:

retrieving from a lookup table the crosstalk compensation factor corresponding to the isolated crosstalk, the lookup table including correlations between crosstalk amounts and crosstalk compensation factors.

18. The method of claim 14, wherein applying the crosstalk compensation factor comprises:

subtracting the compensation factor from the output to provide the crosstalk compensated output.

19. The method of claim 14, comprising generating a crosstalk lookup table including:

setting at least one display component of the display pixel to display a predetermined value, the display component causing the crosstalk;

setting an input of the display component to a predetermined level;

driving the display pixel at the modulating voltage to generate an output;

demodulating the output at a first demodulation frequency to isolate signals indicative of a touch or hover at the display;

demodulating the output at a second demodulation frequency to isolate the crosstalk;

repeating setting the display component, setting the input, driving, demodulating at the first demodulation frequency, and demodulating at the second demodulation frequency at multiple displayed predetermined values to acquire multiple isolated signals and isolated crosstalks;

for each displayed predetermined value, calculating a crosstalk compensation factor based on the corresponding isolated signals and isolated crosstalk; and

providing in the lookup table correlations between the isolated crosstalks and the calculated crosstalk compensation factors.

20. A touch sensitive display comprising:

a gate voltage source configured to drive display components with a modulating voltage, the display components introducing crosstalk into the display;

a stimulation voltage source configured to drive touch components with a stimulation voltage to generate an output, the output having the crosstalk therein; and

a demodulator configured to reject the crosstalk and retain the output.

21. The display of claim 20, wherein the modulating voltage is amplitude modulated.

22. A touch sensitive display comprising:

a display pixel having a gate line;

a circuit coupled to the gate line to transmit an adjustable voltage to the pixel during a touch mode of the display; and

logic for adjusting the voltage to the pixel during the touch mode so as to compensate for crosstalk introduced into the display.

23. The display of claim 22, wherein the logic adjusts the voltage to multiple levels to generate multiple images having the crosstalk, and

wherein the logic determines the crosstalk from the images and compensates the images for the determined crosstalk.

24. The display of claim 22, wherein the logic modulates the voltage between multiple amplitudes so as to isolate the frequency of the crosstalk for removal.

25. The display of claim 22 incorporated into at least one of a mobile phone, a digital media player, or a personal computer.