Touch and hover sensing

Patent metadata

Field	Value
Publication number	US-9323398-B2
Application number	US-50138209-A
Country	US
Kind code	B2
Filing date	Jul 10, 2009
Priority date	Jul 10, 2009
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

Improved capacitive touch and hover sensing with a sensor array is provided. An AC ground shield positioned behind the sensor array and stimulated with signals of the same waveform as the signals driving the sensor array may concentrate the electric field extending from the sensor array and enhance hover sensing capability. The hover position and/or height of an object that is nearby, but not directly above, a touch surface of the sensor array, e.g., in the border area at the end of a touch screen, may be determined using capacitive measurements of sensors near the end of the sensor array by fitting the measurements to a model. Other improvements relate to the joint operation of touch and hover sensing, such as determining when and how to perform touch sensing, hover sensing, both touch and hover sensing, or neither.

First claim

What is claimed is:

1. A capacitive touch sensing apparatus comprising:
a cover surface;
a sensor array substantially adjacent to the cover surface;
a touch control system configured to transmit a first alternating current (AC) signal to the sensor array and measure a capacitance of the sensor array resulting from the first AC signal; and
switching circuitry capable of switching the sensor array from a mutual capacitance detection configuration to a self capacitance detection configuration, the sensor array configured to operate in the mutual capacitance detection configuration during a first detection mode, and in the self capacitance detection configuration during a second detection mode,
wherein the touch control system is further configured to:
perform a first self capacitance measurement at the sensor array;
in accordance with a determination that the first self capacitance measurement is indicative of activity of an object on the sensor array, independent of a distance of the object from the sensor array, cause the switching circuitry to alternate the sensor array between the mutual capacitance detection configuration and the self capacitance detection configuration; and
in accordance with a determination that the first self capacitance measurement is not indicative of activity on the sensor array, perform a second self capacitance measurement at the sensor array.

2. The capacitive touch sensing apparatus of claim 1 , wherein the sensor array includes an electrode including a substantially transparent conductor.

3. The capacitive touch sensing apparatus of claim 1 , further comprising:
an AC shield, wherein the sensor array is positioned substantially between the AC shield and the cover surface; and
an AC shield driving system that transmits a second AC signal to the AC shield such that a first voltage of the sensor array is substantially the same as a second voltage of the AC shield.

4. The capacitive touch sensing apparatus of claim 3 , wherein the AC shield is electrically isolated from the sensor array.

5. The capacitive touch sensing apparatus of claim 3 , wherein the AC shield includes an electrode including a non-transparent conductor.

6. The capacitive touch sensing apparatus of claim 3 , further comprising:
a second AC shield substantially surrounding at least a portion of a transmission line connecting the touch control system and the sensor array, the first AC signal being transmitted on the transmission line.

7. The capacitive touch sensing apparatus of claim 3 , wherein the first AC signal has a waveform and the second AC signal is generated from a buffered copy of the waveform.

8. A touch screen including the capacitive touch sensing apparatus of claim 3 , wherein the touch screen further comprises:
a display, wherein the touch control system and the AC shield are substantially collocated with the display, the display including display circuitry, and the AC shield is positioned substantially between the display circuitry and the sensor array.

9. The capacitive touch sensing apparatus of claim 1 , wherein the switching circuitry comprises a switch.

10. The capacitive touch sensing apparatus of claim 1 , further comprising a switching system to control the switching circuitry.

11. The capacitive touch sensing apparatus of claim 1 , wherein the activity on the sensor array comprises touch or hover activity on the sensor array.

12. A method of detecting a hover position of an object near a distal end of a sensor array and outside of a space directly above the sensor array, the method comprising:
obtaining a set of capacitance measurements of a plurality of sensors of the sensor array in a range of sensor positions near the distal end of the sensor array, the capacitance measurements being caused by the object;
fitting the set of capacitance measurements to a model that defines a curve including a local maximum with a position outside of the range of sensor positions; and
determining the hover position based on the position of the local maximum.

13. The method of claim 12 , wherein the model is based on a previous set of capacitance measurements of the object, wherein the previous set includes a local maximum.

14. The method of claim 12 , wherein the model includes a Gaussian curve.

15. The method of claim 12 , wherein the fitting includes determining a maximum likelihood estimate of parameters of the model.

16. The method of claim 15 , wherein the parameters include at least one of object conductivity and object size.

17. The method of claim 15 , wherein the fitting includes estimating a number of objects and parameters of each object.

18. The method of claim 12 , wherein the fitting includes determining a closest match between the capacitance measurement of a first sensor of the plurality of sensors and one of plurality of stored capacitance measurements of the sensor array.

19. A method of detecting a user input, including the method of detecting a hover position of claim 12 , the method further comprising:
detecting a plurality of hover positions of the object near the distal end of a sensor array and outside of the space directly above the sensor array;
determining a motion of the object corresponding to the plurality of detected hover positions; and
detecting the user input based on the determined motion of the object.

20. The method of claim 19 , further comprising:
controlling a graphical user interface (GUI) based on the detected user input.

21. A method of controlling a motion of a graphical user interface (GUI) item including the method of detecting a hover position of claim 12 , the method further comprising:
moving the GUI item in correspondence with a motion of the object inside of the space directly above the sensor array; and
continuing the motion of the GUI item when the motion of the object is detected to stop at a hover position near the distal end of the sensor array and outside of the space directly above the sensor array.

22. A capacitive touch sensing apparatus comprising:
a sensor array;
a sensor control system including a first control system configured to, during a mutual capacitance measurement mode, transmit a first alternating current (AC) signal to the sensor array and measure a mutual capacitance of the sensor array resulting from the first AC signal, and a second control system configured to, during a self capacitance measurement mode, transmit a second alternating current (AC) signal to the sensor array and measure a self capacitance of the sensor array resulting from the second AC signal; and
a switching system configured to switch the sensor control system between the mutual capacitance measurement mode and the self capacitance measurement mode,
wherein the sensor control system is configured to:
perform a first self capacitance measurement at the sensor array;
in accordance with a determination that the first self capacitance measurement is indicative of activity of an object on the sensor array, independent of a distance of the object from the sensor array, alternate between the mutual capacitance measurement mode and the self capacitance measurement mode; and
in accordance with a determination that the first self capacitance measurement is not indicative of activity on the sensor array, perform a second self capacitance measurement at the sensor array.

23. The capacitive touch sensing apparatus of claim 22 , wherein the sensor array includes common circuitry that op

Assignees

• Bernstein Jeffrey Traer
• Amm David T
• Leung Omar
• Mullens Christopher Tenzin
• King Brian Michael
• Land Brian Richards
• Cutler Reese T
• Apple Inc

Inventors

• Bernstein Jeffrey Traer
• Amm David T
• Leung Omar
• Mullens Christopher Tenzin
• King Brian Michael
• Land Brian Richards
• Cutler Reese T

Classifications

• G06F3/0486

  Drag-and-drop · CPC title

• G06F2203/04101

  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 title

• G06F3/0416

  Control or interface arrangements specially adapted for digitisers · CPC title

• G06F3/044 Primary

  by capacitive means · CPC title

• G06F3/041662 Primary

  using alternate mutual and self-capacitive scanning · CPC title