TOUCH AND HOVER SENSING

• US 20110007021A1
• Filed: 07/10/2009
• Published: 01/13/2011
• Est. Priority Date: 07/10/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: CUTLER, Reese T., AMM, David T., MULLENS, Christopher Tenzin, KING, Brian Michael, LEUNG, Omar, BERNSTEIN, Jeffrey Traer, LAND, Brian Richards
• Granted Patent: US 9,323,398 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 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 and hover sensing apparatus comprising:

a cover surface;

a sensor array substantially adjacent to the cover surface;

a touch and hover control system that transmits a first alternating current (AC) signal to the sensor array and measures a capacitance of the sensor array resulting from the first AC signal;

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.

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

3. The capacitive touch and hover sensing apparatus of claim 1, wherein the AC shield is electrically isolated from the sensor array.

4. The capacitive touch and hover sensing apparatus of claim 1, wherein the AC shield includes an electrode including a non-transparent conductor.

5. The capacitive touch and hover sensing apparatus of claim 1, further comprising:

a second AC shield substantially surrounding at least a portion of a transmission line connecting the touch and hover control system and the sensor array, the first AC signal being transmitted on the transmission line.

6. The capacitive touch and hover sensing apparatus of claim 1, wherein the first AC signal has a waveform and the second AC signal is generated from a buffered copy of the waveform.

7. A touch screen including the capacitive touch and hover sensing apparatus of claim 1, wherein the touch screen further comprises:

a display, wherein the touch and hover 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.

8. 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.

9. The method of claim 8, wherein the model is based on a previous set of capacitance measurements of the object, wherein the previous set includes a local maximum.

10. The method of claim 8, wherein the model includes a Gaussian curve.

11. The method of claim 8, wherein the fitting includes determining a maximum likelihood estimate of parameters of the model.

12. The method of claim 11, wherein the parameters include at least one of object conductivity and object size.

13. The method of claim 11, wherein the fitting includes estimating a number of objects and parameters of each object.

14. The method of claim 8, 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.

15. A method of detecting a user input, including the method of detecting a hover position of claim 8, 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.

16. The method of claim 15, further comprising:

controlling a graphical user interface (GUI) based on the detected user input.

17. A method of controlling a motion of a graphical user interface (GUI) item including the method of detecting a hover position of claim 8, 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.

18. A capacitive touch and hover sensing apparatus comprising:

a sensor array;

a sensor control system including a touch control system that, during a touch sensing phase, transmits a first alternating current (AC) signal to the sensor array and measures a first capacitance of the sensor array resulting from the first AC signal, and a hover control system that, during a hover sensing phase, transmits a second alternating current (AC) signal to the sensor array and measures a second capacitance of the sensor array resulting from the second AC signal; and

a switching system that switches the sensor control system between the touch control system and the hover control system.

19. The capacitive touch and hover sensing apparatus of claim 18, wherein the first capacitance is a mutual capacitance.

20. The capacitive touch and hover sensing apparatus of claim 18, wherein the second capacitance is a self capacitance.

21. The capacitive touch and hover sensing apparatus of claim 18, wherein the sensor array includes common circuitry that operates in both the touch sensing phase and the hover sensing phase.

22. The capacitive touch and hover sensing apparatus of claim 18, wherein the touch control system includes touch control system circuitry, and the hover control system includes hover control system circuitry, and the switching system includes a physical switch that alternatively connects the touch control system circuitry to the sensor array or connects the hover control system circuitry to the sensor array during the touch sensing phase and the hover control phase, respectively.

23. The capacitive touch and hover sensing apparatus of claim 18, wherein the switching system includes a low-leakage analog switch.

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

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

detecting the touch event based on the first capacitance;

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

detecting the hover event based on the second capacitance.

25. The method of claim 24, wherein the first AC signal and the second AC signal are transmitted concurrently through one of frequency multiplexing and code division multiplexing.

26. The method of claim 24, 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.

27. The method of claim 24, wherein the first AC signal is transmitted during a touch sensing phase and the second AC signal is transmitted during a hover sensing phase that is non-overlapping with the touch sensing phase, the method further comprising:

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

28. The method of claim 24, wherein the operational phase is set 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.