Touch and hover sensing

• US 9,323,398 B2
• Filed: 07/10/2009
• Issued: 04/26/2016
• Est. Priority Date: 07/10/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Bernstein, Jeffrey Traer, Amm, David T., Leung, Omar, Mullens, Christopher Tenzin, King, Brian Michael, Land, Brian Richards, Cutler, Reese T.
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): Khoo, Stacy
• Application Number:
  US12/501,382
• Publication Number:
  US 20110007021A1
• Time in Patent Office: 2,482 Days
• Field of Search: 345173-178, 178 1801- 1806, 324/660, 324/686
• 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 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/04817 using icons graphical or visual programming using iconic symbols G06F8/34
• CPC Class Codes: G06F 3/04845 for image manipulation, e.g. dragging, rotation, expansion or change of colour
• CPC Class Codes: G06F 3/0486 Drag-and-drop

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.

Claims

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 operates in both the mutual capacitance measurement mode and the self capacitance measurement mode.

24. The capacitive touch sensing apparatus of claim 22, wherein the first control system includes first control system circuitry, and the second control system includes second control system circuitry, and the switching system includes a physical switch that alternatively connects the first control system circuitry to the sensor array or connects the second control system circuitry to the sensor array during the mutual capacitance measurement mode and the self capacitance measurement mode, respectively.

25. The capacitive touch sensing apparatus of claim 22, wherein the switching system includes a low-leakage analog switch.

26. A method for detecting a touch event on or near a touch sensing apparatus, the method comprising:

performing a first self capacitance measurement at a sensor array of the apparatus;

in accordance with a determination that the first self capacitance measurement is indicative of activity of an object at the sensor array, independent of a distance of the object from the sensor array;

transmitting a first alternating current (AC) signal to the sensor array, and measuring a mutual capacitance of the sensor array resulting from the first AC signal;

detecting a first touch event based on the mutual capacitance;

transmitting a second alternating current (AC) signal to the sensor array and measuring a self capacitance of the sensor array resulting from the second AC signal; and

detecting a second touch event based on the self capacitance; and

in accordance with a determination that the first self capacitance measurement is not indicative of activity on the sensor array, performing a second self capacitance measurement at the sensor array.

27. The method of claim 26, wherein the first AC signal and the second AC signal are transmitted concurrently through one of frequency multiplexing and code division multiplexing.

28. The method of claim 26, wherein the first AC signal and the second AC signal are transmitted concurrently through space multiplexing, in which the first AC signal is transmitted to a first group of sensors of the sensor array, and the second AC signal is transmitted to a second group of sensors of the sensor array.

29. The method of claim 26, wherein the first AC signal is transmitted during a first sensing phase and the second AC signal is transmitted during a second sensing phase that is non-overlapping with the first sensing phase, the method further comprising:

setting the apparatus to operate in one of a plurality of operational phases including the first sensing phase and the second sensing phase.

30. The method of claim 29, wherein setting the apparatus to operate in one of the plurality of operational phases is based on at least one of a predetermined schedule, a request from an external computer process, a current number and positions of objects detected, and a distance of an object from the sensor array.

31. A touch sensing device comprising:

a touch sensing panel having multiple sensors, each sensor capable of detecting one or more objects proximate to the panel, wherein the objects touch the panel to cause a touch event, hover over the panel to cause a hover event, or touch and hover concurrently to cause touch and hover events; and

a touch control system configured to;

perform a first self capacitance measurement at the touch sensing panel;

in accordance with a determination that the first self capacitance measurement is indicative of activity of an object on the touch sensing panel, independent of a distance of the object from the sensor array, operate the sensors in a mutual capacitance detection configuration and a self capacitance detection configuration; and

in accordance with a determination that the first self capacitance measurement is not indicative of activity on the touch sensing panel, perform a second self capacitance measurement at the touch sensing panel.

32. The device of claim 31, wherein the touch control system is further configured to switch a portion of the sensors to the self capacitance detection configuration and another portion of the sensors to the mutual capacitance detection configuration so as to partition the panel to concurrently detect mutual capacitance and self capacitance.

33. The device of claim 31, further comprising a display configured to display graphical information to select in response to the touch and hover events.

34. The device of claim 31 incorporated into at least one of a mobile phone, a digital media player, or a computer.

35. A capacitive touch sensing apparatus comprising:

a cover surface;

a sensor array substantially adjacent to the cover surface; and

a touch control system 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;

transmit a first alternating current (AC) signal concurrently with a second alternating current (AC) signal to the sensor array, and

measure a self capacitance of the sensor array resulting from the first AC signal concurrently with a mutual capacitance of the sensor array resulting from the second AC signal; 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.

36. The capacitive touch sensing apparatus of claim 35, wherein the touch control system is further configured to combine the first AC signal and the second AC signal using frequency multiplexing before transmitting the combined signal to the sensor array.

37. The capacitive touch sensing apparatus of claim 35, wherein the touch control system is further configured to combine the first AC signal and the second AC signal using code division multiplexing before transmitted the combined signal to the sensor array.

38. The capacitive touch sensing apparatus of claim 35, wherein the first AC signal has a first frequency, and the second AC signal has a second frequency, the second frequency being different than the first frequency.