Display to touch crosstalk compensation

• US 9,582,114 B2
• Filed: 02/10/2016
• Issued: 02/28/2017
• Est. Priority Date: 01/14/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph H.
• Primary Examiner(s): MA, CALVIN
• Application Number:
  US15/040,928
• Publication Number:
  US 20160162119A1
• Time in Patent Office: 384 Days
• Field of Search: 345/173, 345/174, 345/211
• US Class Current: 1/1
• 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 touch sensitive display having display pixels for displaying data and touch components for sensing a touch or hover event, the method comprising:

during a touch sensing mode of operation, driving the touch components with a stimulation voltage, the touch components generating an output within a frequency band, the output indicative of the touch or hover event;

during the touch sensing mode of operation, driving the display pixels with the varying voltage at a modulation frequency, the display pixels causing the crosstalk;

wherein the modulation frequency is such as to push at least a portion of the crosstalk out of the frequency band of the output;

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.

2. The method of claim 1, 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.

3. The method of claim 1, 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.

4. The method of claim 1, wherein applying the crosstalk compensation factor comprises:

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

5. The method of claim 1, 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 modulation frequency to generate a display output signal;

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

demodulating the display output signal 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.

6. A touch sensitive display having a display mode of operation and a touch sensing mode of operation comprising:

a stimulation voltage source configured to drive touch components with a stimulation voltage to generate a sensed signal output within a frequency band, the sensed signal output indicative of a touch or hover event; and

a voltage source configured to drive display components during the touch sensing mode of operation with a voltage at a modulation frequency, the display components introducing crosstalk into the sensed signal output;

the modulation frequency such as to push at least a portion of the crosstalk out of band with respect to the frequency band of the sensed signal output; and

a demodulator configured to reject the crosstalk within the sensed signal output and provide a crosstalk a compensated output.

7. The display of claim 6, wherein the voltage is amplitude modulated.

8. An apparatus for compensating for crosstalk in a touch sensitive display comprising:

a plurality of display pixels;

a plurality of touch components;

a modulator providing a modulating voltage;

a demodulator;

a control circuitry configured for;

during a touch sensing mode of operation, driving the touch components with a stimulation voltage, the touch components generating an output within a frequency band, the output indicative of the touch or hover event;

during the touch sensing mode of operation, driving the plurality of display pixels with the modulating voltage at a modulation frequency, the display pixels causing the crosstalk;

wherein the modulation frequency is such as to push at least a portion of the crosstalk out of the frequency band of the output;

demodulating the output using the demodulator 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.

9. The apparatus of claim 8, wherein control circuitry is further configured for:

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.

10. The apparatus of claim 8, wherein control circuitry is further configured for:

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.

11. The apparatus of claim 8, wherein the control circuitry is further configured for:

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

12. The apparatus of claim 8, wherein the control circuitry is further configured for generating a crosstalk lookup table by:

setting at least one display component of the plurality of 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 plurality of display pixel at the modulation frequency to generate a display output signal;

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

demodulating the display output signal 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.