Methods and apparatus for capacitively detecting key motion and finger presence on keyboard keys

• US 9,600,084 B2
• Filed: 01/09/2014
• Issued: 03/21/2017
• Est. Priority Date: 01/09/2014
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Bolender, Robert J.
• Primary Examiner(s): Sitta, Grant
• Assistant Examiner(s): BOGALE, AMEN W
• Application Number:
  US14/150,824
• Publication Number:
  US 20150193008A1
• Time in Patent Office: 1,167 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/018 Input/output arrangements for oriental characters
• CPC Class Codes: G06F 3/0202 Constructional details or processes of manufacture of the input device
• CPC Class Codes: G06F 3/0233 Character input methods
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/96062 with tactile or haptic feedback
• CPC Class Codes: H03K 2217/960775 Emitter-receiver or "fringe" type detection, i.e. one or more field emitting electrodes and corresponding one or more receiving electrodes

Abstract

A keyboard including a plurality of key assemblies configured to be pressed by an input object. A subset of the plurality of key assemblies each includes a key cap and a first electrode pair underneath the key cap and configured to detect key motion in response to downward force applied by the input object. The key cap also includes a second electrode pair disposed underneath the key cap and configured to detect positional information about the input object interacting with the key cap.

Claims

1. A keyboard including a plurality of key assemblies configured to be pressed by an input object, wherein a first subset of the plurality of key assemblies each comprises:

a key cap;

a first conductive portion disposed on the key cap, wherein the first conductive portion is configured to operate at a substantially constant voltage;

a second conductive portion disposed on the key cap, wherein the second conductive portion is an electrically floating conductor;

a base;

a first electrode pair disposed underneath the key cap and on the base, the first electrode pair configured to generate a keystroke signal in response to movement of the first conductive portion on the key cap toward the base by the input object; and

a second electrode pair disposed underneath the key cap and on the base, the second electrode pair configured to generate a finger presence signal in response to a change in capacitive coupling between a finger and the second conductive portion at the key cap,

wherein the finger presence signal with no finger present at the key cap corresponds to a baseline value of the finger presence signal, and

wherein the keystroke signal is used by a processing system to determine that the key cap is in a pressed position when the keystroke signal is above the baseline value.

2. The keyboard of claim 1, wherein the first and second electrode pairs comprise capacitive sensing electrodes.

3. The keyboard of claim 1, wherein the subset of key assemblies comprises at least one wide key cap, and wherein a plurality of electrode pairs are disposed underneath the at least one wide key cap.

4. The keyboard of claim 3, wherein the plurality of electrode pairs are configured to detect directional motion of the input object interacting with the at least one wide key cap.

5. The keyboard assembly of claim 3, wherein the plurality of electrode pairs each comprise a receiver electrode substantially surrounded by a spatially distributed transmitter electrode.

6. The keyboard of claim 1, wherein the first electrode pair comprises a transmitter electrode and a receiver electrode configured to detect keystroke motion based on at least one of:

a change in capacitance between the first electrode pair and the first conductive portion; and

a change in capacitance between the first conductive portion and a variable capacitance between the transmitter electrode and the receiver electrode.

7. The keyboard assembly of claim 6, wherein the first conductive portion comprises a ferromagnetic material.

8. The keyboard of claim 1, wherein the second electrode pair comprises a transmitter electrode and a receiver electrode configured to detect positional information based on at least one of:

a change in capacitance between the second electrode pair and the input object;

a change in capacitance between the second electrode pair and the second conductive portion; and

a change in capacitance between the second conductive portion and a variable capacitance between the transmitter electrode and the receiver electrode.

9. The keyboard of claim 8, wherein the positional information comprises at least one of:

a binary indication of the presence or absence of the input object on the key cap;

a location of the input object on a surface of the key cap; and

motion of the input object on the key cap.

10. The keyboard of claim 8, wherein the first electrode pair is configured to generate a first signal, the second electrode pair is configured to generate a second signal, and further wherein the positional information is determined based on the first and second signals.

11. The keyboard of claim 10, wherein the first signal is used to disambiguate the second signal.

12. The keyboard of claim 8, wherein the key cap comprises a top surface and a bottom surface, and wherein the second conductive portion is affixed to the bottom surface and spaced apart from the transmitter electrode and the receiver electrode.

13. The keyboard of claim 1, wherein a second subset of the key assemblies are arranged in a substantially horizontal row, and wherein the first conductive portion extends across the substantially horizontal row and electrically interconnects one of the first and second electrode pairs in the substantially horizontal row.

14. The keyboard of claim 13, wherein the second conductive portion extends across the substantially horizontal row and electrically interconnects the other one of the first and second electrode pairs in the substantially horizontal row.

15. A processing system for a keyboard input device of a type including a plurality of key assemblies configured to be pressed by an input object, the processing system configured to:

determine a keystroke signal from a first plurality of sensor electrodes, wherein the first plurality of sensor electrodes are disposed on a base of a key cap among the plurality of key assemblies, wherein the keystroke signal changes in response to movement of a first conductive portion operating at a substantially constant voltage and disposed on the key cap towards the base;

determine a finger presence signal from a second plurality of sensor electrodes, wherein the finger presence signal changes in response to a change in capacitive coupling between a finger at the key cap and a second conductive portion disposed on the key cap, and wherein the second conductive portion is an electrically floating conductor; and

determine, in response to determining that the keystroke signal is above a baseline value, that the key cap from the plurality of key assemblies is in a pressed position,

wherein the baseline value corresponds to the finger presence signal with no finger present at the key cap.

16. The processing system of claim 15, wherein the first plurality of sensor electrodes and the second plurality of sensor electrodes comprise a transmitter electrode and a receiver electrode, and wherein the processing system is configured to:

determine the keystroke signal based on a received signal from the receiver electrode; and

determine the finger presence signal using the received signal.

17. A method of detecting positional information of a finger interacting with a keyboard key of the type including a keystroke sensor and a finger presence sensor, the method comprising:

obtaining a keystroke signal from the keystroke sensor, wherein the keystroke signal changes in response to movement of a first conductive portion disposed on a key cap of the keyboard key toward a base, wherein the first conductive portion is configured to operate at a substantially constant voltage;

obtaining a finger presence signal from the finger presence sensor, wherein the finger presence signal changes in response to a change in capacitive coupling between the finger and a second conductive portion disposed on the key cap, wherein the second conductive portion is an electrically floating conductor;

determining a first baseline value associated with the keystroke signal, wherein the first baseline value corresponds to the keystroke signal of an unpressed keyboard key;

determining a second baseline value associated with the finger presence signal, wherein the second baseline value corresponds to the finger presence signal with no finger present at the keyboard key;

determining whether the keystroke signal is above the second baseline value; and

determining, in response to determining that the keystroke signal is above the second baseline value, that the keyboard key is in a pressed position.

18. The method of claim 17, further comprising disambiguating the finger presence signal using the keystroke signal.

19. The method of claim 17, wherein the positional information comprises at least one of:

a binary indication of the presence or absence of the finger on the keyboard key;

a location of the finger on a surface of the key cap; and

motion of the finger on the keyboard key.