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EP-4295221-B1 - COMPENSATING FOR TOUCH-SCREEN COUPLING THROUGH DISPLAY ELECTRODE

EP4295221B1EP 4295221 B1EP4295221 B1EP 4295221B1EP-4295221-B1

Inventors

  • BAREL, ELIYAHU
  • HARAN, ON

Dates

Publication Date
20260506
Application Date
20220210

Claims (15)

  1. A touch-screen display device (10A) comprising: a capacitive touch sensor (28) including a series of column electrodes (32); a series of row electrodes (30) crossing the series of column electrodes such that an electrical impedance at each crossing of a row and column electrode is responsive to proximity of a touch input to that crossing; an electronic display layer arranged behind the series of column electrodes and behind the series of row electrodes; a row-drive circuit (68) configured to apply an excitation signal to a selected row electrode of the series of row electrodes and to concurrently apply a compensation signal to one or more other row electrodes of the series of row electrodes, the compensation signal being out-of-phase with respect to the excitation signal; a column-sense circuit (70) configured to sense a first column signal from the series of column electrodes and to provide a corresponding column output; wherein the row-drive circuit is further configured to iteratively update the selected row electrode according to a predetermined sequence; characterized in that the excitation signal is a signal of an upper modulation frequency, and wherein the row-drive circuit is further configured to intermittently apply an excitation signal of a lower modulation frequency to the selected row electrode of the row electrodes of the touch-screen display device; and wherein the column-sense circuit is further configured to intermittently sense a second column signal from the series of column electrodes; and a correction circuit configured to compute a correction transform based at least partly on the first and second column signals, and to provide a corrected column output based at least partly on the first column signal and on the correction transform.
  2. The touch-screen display device of claim 1 wherein the compensation signal is 180 degrees out-of-phase with respect to the excitation signal.
  3. The touch-screen display device of claim 1 or 2 wherein the touch-screen display device includes the capacitive touch sensor (28), and wherein the series of row electrodes comprises each row electrode of the capacitive touch sensor.
  4. The touch-screen display device of any preceding claim wherein the electronic display layer includes an active-matrix organic light-emitting diode layer (14C).
  5. The touch-screen display device of any preceding claim wherein the electronic display layer includes an insulated conductor, and wherein the insulated conductor capacitively couples the series of row electrodes to the series of column electrodes absent the touch input, thereby adding an undesired component to the column signal.
  6. The touch-screen display device of claim 5 wherein an amplitude of the compensation signal is determined such as to poise the insulated conductor at a ground potential recognized by the column-sense circuit.
  7. The touch-screen display device of claim 5 or 6 wherein an amplitude of the compensation signal is A / P, where A is the amplitude of the excitation signal and P is the number of the other row electrodes in the series of row electrodes.
  8. The touch-screen display device of any one of claims 5 to 7 wherein an amplitude of the compensation signal is determined dynamically via the column-sense circuit, by sensing a response to the touch input on the column signal.
  9. The touch-screen display device of any one of claims 5 to 8 wherein the insulated conductor is within 50 microns of the nearer of the series of row electrodes and the series of column electrodes.
  10. The touch-screen display device of any one of claims 5 to 9 wherein the undesired component varies in dependence on lifetime usage of the touch-screen display device, or wherein the undesired component varies in dependence on a use condition of the touch-screen display device.
  11. A method to process touch input on a touch-screen display device (10A) having an electronic display layer arranged behind a series of column electrodes (32) and behind a series of row electrodes (30) of a capacitive touch sensor, the method comprising: applying an excitation signal of an upper modulation frequency to a selected row electrode of the series of row electrodes; sensing a first column signal from the series of column electrodes, wherein an electrical impedance at each crossing of a row and column electrode is responsive to proximity of the touch input to that crossing; intermittently applying an excitation signal of a lower modulation frequency to the selected row electrode, the lower modulation frequency being lower than the upper modulation frequency; intermittently sensing a second column signal from the series of column electrodes; characterized by computing a correction transform based partly on the first and second column signals; and providing a corrected column output based at least partly on the first column signal and on the correction transform.
  12. The method of claim 11, wherein the correction transform comprises a linear transform.
  13. The method of claim 11 or 12, wherein the electronic display layer includes an insulated conductor or degenerately doped semiconductor (36C, 36D), which capacitively couples the series of row electrodes to the series of column electrodes.
  14. The method of claim 13, wherein an undesired component of the capacitive coupling varies in dependence on lifetime usage and/or a use condition of the touch-screen display device.
  15. The method of any one of claims 11 to 14, wherein the insulated conductor or degenerately doped semiconductor is within 50 microns of the nearer of the series of row electrodes and the series of column electrodes.

Description

BACKGROUND Capacitive touch screens are used in electronic devices ranging from computer monitors and tablet computers to smartphones and other handheld devices. A capacitive touch screen may be capable of tracking touch or hover of a user's finger, of a stylus held in the user's hand, or of input devices of various other forms. In some implementations, capacitive touch-screen componentry is applied directly to the viewing surface of an electronic display, such as a liquid-crystal display (LCD) or an organic light-emitting diode (OLED) display. The resulting touch-screen display stack provides a basis for integrated display-and-input functionality. US 2015/109244 A1 describes a capacitive type touch sensor, including a plurality of driving electrodes, a plurality of sensing electrodes disposed to overlap the driving electrodes, the sensing electrodes and the driving electrodes being spaced apart from each other, a driving unit configured to supply driving signals to the respective driving electrodes, and a sensing unit configured to detect sensing signals from the sensing electrodes, wherein the driving signals supplied by the driving unit include at least one of a first driving signal having a first frequency and a second driving signal having a second frequency different from the first frequency. SUMMARY According to an aspect, there is provided an apparatus according to claim 1 and a method according to claim 5. Further features according to embodiments are set out in the dependent claims. One aspect of this disclosure is directed to a touch-screen display device comprising a capacitive touch sensor including a series of column electrodes and a series of row electrodes, with an electronic display layer arranged behind the series of column electrodes and behind the series of row electrodes. The series of row electrodes crosses the series of column electrodes such that the electrical impedance at each crossing of a row and column electrode is responsive to the proximity of a touch input to that crossing. A row-drive circuit is configured to apply an excitation signal to a selected row electrode and to concurrently apply a compensation signal to one or more other row electrodes, the compensation signal being out of phase with respect to the excitation signal. A column-sense circuit is configured to sense a first column signal from the series of column electrodes and to provide a corresponding column output; wherein the row-drive circuit is further configured to iteratively update the selected row electrode according to a predetermined sequence; and wherein the excitation signal is a signal of an upper modulation frequency, and wherein the row-drive circuit is further configured to intermittently apply an excitation signal of a lower modulation frequency to the selected row electrode of the row electrodes of the touch-screen display device; and wherein the column-sense circuit is further configured to intermittently sense a second column signal from the series of column electrodes; and a correction circuit configured to compute a correction transform based at least partly on the first and second column signals, and to provide a corrected column output based at least partly on the first column signal and on the correction transform. Another aspect of this disclosure is directed to a method to process touch input on a touch-screen display device having an electronic display layer arranged behind a series of column electrodes and behind a series of row electrodes of a capacitive touch sensor, where the electrical impedance at each crossing of a row and column electrode is responsive to proximity of the touch input to that crossing. In this method an excitation signal of an upper modulation frequency is applied to a selected row electrode and a first column signal is sensed. Intermittently an excitation signal of a lower modulation frequency is applied to the selected row electrode and a second column signal is sensed. A correction transform is then computed based partly on the first and second column signals, and a corrected column output is provided based at least partly on the first column signal and on the correction transform. This Summary is provided to introduce in simplified form a selection of concepts that are further described in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows aspects of an example touch-screen display device.FIG. 2 shows aspects of an example touch-screen display device comprising an active-matrix OLED (AMOLED) display.FIG. 3 shows aspects of an example touch-screen display device comprising an LCD.FIGS. 4 and 5 show aspects of an example capacitive touch sensor of a touch-screen display device.FIG. 6 shows aspects of example touch-screen logic of a touch-screen display devic