Methods and apparatus for capacitive sensing

• US 8,749,523 B2
• Filed: 08/23/2010
• Issued: 06/10/2014
• Est. Priority Date: 10/24/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Pance, Aleksandar, Leung, Omar S., Amm, David Thomas
• Primary Examiner(s): Dharia, Prabodh M
• Application Number:
  US12/861,640
• Publication Number:
  US 20110043227A1
• Time in Patent Office: 1,387 Days
• Field of Search: 345156-184, 324/669, 324/681, 324/686, 361/679.4, 361/752, 361/679.3, 361/681, 340/5, 340/54, 273/237
• US Class Current: 345/175
• CPC Class Codes: G06F 1/1616 with folding flat displays, e.g. laptop computers or notebooks having a clamshell configuration, with body parts pivoting to an open position around an axis parallel to the plane they define in closed position
• CPC Class Codes: G06F 1/1643 the display being associated to a digitizer, e.g. laptops that can be used as penpads details related to the relative motion of the display enclosure with respect to the body enclosure, e.g. to move between laptop and tablet PC configuration G06F1/1615
• CPC Class Codes: G06F 1/169 the I/O peripheral being an integrated pointing device, e.g. trackball in the palm rest area, mini-joystick integrated between keyboard keys, touch pads or touch stripes G06F1/1643 takes precedence; constructional details of pointing devices G06F3/033
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 2203/04108 Touchless 2D- 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 without distance measurement in the Z direction
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 17/975 using a capacitive movable element
• CPC Class Codes: H03K 17/98 having a plurality of control members, e.g. keyboard
• CPC Class Codes: H03K 2217/96077 comprising an electrode which is floating

Abstract

The present disclosure addresses methods and apparatus facilitating capacitive sensing using a conductive surface, and facilitating the sensing of proximity to the conductive surface. The sensed proximity will often be that of a user, but can be another source of a reference voltage potential. In some examples, the described systems are capable of sensing capacitance (including parasitic capacitance) in a circuit that includes the outer conductive surface, and where that outer conductive surface is at a floating electrical potential. In some systems, the systems can be switched between two operating modes, a first mode in which the system will sense proximity to the conductive surface, and a second mode in which the system will use a capacitance measurement to sense contact with the conductive surface.

Claims

1. A sensing device, comprising:

a conductive sensing member having a sensing surface and an opposite surface, wherein the sensing surface comprises an outer surface of an electronic device housing, wherein the sensing member is at a floating potential;

a conductive reference member in spaced relation to the opposite surface of the sensing member, wherein the conductive reference member forms a capacitor with the conductive sensing member; and

a capacitance sensing device coupled to both the conductive reference member and to ground, wherein the capacitance sensing device is configured to determine a change in capacitance between the conductive reference member and ground resulting from proximity of a human.

2. The sensing device of claim 1, wherein the conductive sensing member comprises a metal sensing surface.

3. The sensing device of claim 1, wherein the conductive sensing member is electrically insulated from other portions of the sensing device, to allow the conductive sensing member to be at the floating potential relative to the other portions of the sensing device.

4. The sensing device of claim 3, further comprising a switch assembly coupled to the sensing member and configured to switch the sensing member from a floating potential to a reference voltage potential.

5. The sensing device of claim 1, wherein the capacitive sensing device is configured to determine conditions indicative of likely contact between the human and the sensing surface of the sensing member.

6. The sensing device of claim 1, wherein the sensing device is an integral part of a portable electronic device.

7. The sensing device of claim 1, wherein the sensing device is an input device to a portable electronic device.

8. A method of determining the proximity of a user to an electronic device having a metal surface component, comprising:

measuring a total capacitance between a reference electrode and a ground, wherein the total capacitance comprises a first capacitance between the metal surface component and the reference electrode and a second capacitance between the metal surface component and a reference, wherein the second capacitance is responsive to proximity of an external source of electric potential, and wherein the metal surface component comprises an outer surface of an electronic device housing.

9. The method of claim 8, further comprising:

determining parameters of the total capacitance indicating that contact between the external source of electric potential and the metal surface component is likely.

10. The method of claim 8, wherein the electronic device is a portable electronic device, selected from the group consisting essentially of:

a laptop computer, a phone, and a computer input device.

11. The method of claim 8, wherein the metal surface component of the electronic device is at a floating voltage potential relative to other components of the electronic device.

12. A method of operating an electronic device, comprising the acts of:

determining a first capacitance between a metal surface component and a reference electrode, the reference electrode tied to a sensing device and placed proximate the metal surface component, with the metal surface component at a floating potential;

identifying a second capacitance between the floating potential metal surface component and a reference, the second capacitance responsive to the presence of an external source of electric potential;

identifying the proximity of a user to the metal surface component in response to a parameter of a capacitance measurement comprising a change in the second capacitance;

in response to an identified proximity of a user, coupling the metal surface component to a direct current voltage reference; and

identifying a contact with the metal surface component causing deflection of a portion of the metal surface component by measuring a change in capacitance between the metal surface component and the reference electrode resulting from the deflection, wherein the metal surface component comprises a location that in a first state forms an invisible contact location and in a second state forms a visible contact location, and wherein the method further comprises transitioning the location from the first state to the second state in response to the identified proximity of a user.

13. The method of operating an electronic device of claim 12, wherein the parameter of a capacitance measurement comprising a change in the second capacitance comprises the magnitude of the capacitance measurement.

14. The method of operating an electronic device of claim 12, wherein the parameter of a capacitance measurement comprising a change in the second capacitance comprises the rate of change of the capacitance measurement.

15. The method of operating an electronic device of claim 12, further comprising the act of receiving the identified contact with the metal surface as a touch input, and initiating a control function of the electronic device in response to the touch input.

16. The method of operating an electronic device of claim 15, wherein the touch input is a multi-touch input.

17. The method of operating an electronic device of claim 12, wherein the invisible contact location is not configured to sense touch input when the location is in the first state, and wherein the method further comprises transitioning the location to receive a touch input in response to the identified proximity of a user.

18. An electronic assembly, comprising:

a capacitance sensing assembly that is operable in two states, a first state in which the assembly detects proximity of a source of electric potential and a second state in which the assembly detects contact with a source of electric potential, the sensing assembly comprising,

a metal sensing member having a sensing surface and an opposite surface, and

a first capacitive reference member in spaced relation to the opposite surface of the metal sensing member, and forming a capacitor with the metal sensing member,

a switching assembly to selectively connect the metal sensing member between a first state in which the metal sensing member is at a floating potential and a second state in which the metal sensing member is coupled to a reference voltage, and

a capacitance sensing device coupled to both the first capacitive reference member and the reference voltage, the capacitance sensing assembly configured to,

determine a first parameter of change in capacitance between the conductive reference member and ground resulting from proximity of a source of electric potential relative to the metal sensing member when the metal sensing member is in the first floating state,

generate a sensed proximity signal in response to the determined first parameter; and

determine a second parameter of change in capacitance between the conductive reference member and the metal sensing resulting from contact of a source of electric potential with the metal sensing member causing deflection of the metal sensing member when the metal sensing member is in the second state, and

generate a touch input signal in response to be determined second parameter.

19. The electronic assembly of claim 18, wherein the electronic assembly is configured to make a first change in an operating parameter of the assembly in response to a sensed proximity signal, and is further configured to make a second change in an operating parameter of the assembly in response to a touch signal.

20. The electronic assembly of claim 18, wherein the first determined parameter of change in capacitance comprises a magnitude of the change in capacitance.

21. The electronic assembly of claim 18, wherein the first determined parameter of change in capacitance comprises a rate of change of the change in capacitance.

22. The electronic assembly of claim 19, wherein the metal sensing member further comprises a contact location that is invisible in a first state and visible in a second state, and wherein the first change in an operating parameter of the assembly in response to a sensed proximity signal comprises changing the contact location appearance from the first invisible state to the second visible state.

23. A laptop computer moveable between a closed lid state and an open lid state, comprising:

at least one processor;

a capacitance sensing mechanism proximate a selected region of an external surface of the computer when the computer is in the closed lid state; and

machine readable storage media containing instructions comprising,

instructions to enable the capacitance sensor to detect a change in capacitance proximate the selected region of the external surface of the computer, when the computer is in the closed lid state,

instructions to receive the detected capacitance as a touch input; and

instructions to execute a touch responsive functionality in response to the sensed touch input.

24. The laptop computer of claim 23, wherein the instructions to detect a change in capacitance proximate the selected region of the external surface of the computer when the computer is in the closed lid state, comprise:

instructions to configure the capacitance sensor in a proximity sensing mode;

instructions to detect the proximity of a user to the selected region;

instructions to determine that a touch input from the user is likely; and

instructions to configure the capacitance sensor in a touch sensing mode in response to the determination that a touch input is likely.

25. The laptop computer of claim 23, wherein the touch responsive functionality comprises determining a system status parameter of the laptop computer.

26. The laptop computer of claim 23, wherein the touch responsive functionality comprises checking for updated data information.

27. The laptop computer of claim 23, wherein the one or more processors comprises a system processor and an auxiliary processor;

wherein the auxiliary processor is a relatively low power processor; and

wherein at least a portion of the identified instructions are executed by the auxiliary processor.

28. The laptop computer of claim 27, wherein the laptop computer is configured to maintain the auxiliary processor in an operable state when the computer is in a sleep mode.