METHODS AND APPARATUS FOR CAPACITIVELY DETECTING KEY MOTION AND FINGER PRESENCE ON KEYBOARD KEYS

• US 20150193008A1
• Filed: 01/09/2014
• Published: 07/09/2015
• Est. Priority Date: 01/09/2014
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Bolender, Robert J.
• Granted Patent: US 9,600,084 B2
• Time in Patent Office: 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 subset of the plurality of key assemblies each comprises:

a key cap;

a first electrode pair disposed underneath the key cap and configured to detect key motion in response to downward force applied by the input object; and

a second electrode pair disposed underneath the key cap and configured to detect positional information about the input object interacting with the key cap.

2. The keyboard of claim 1, 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;

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

and motion of the input object on the key cap.

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

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

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

6. The keyboard of claim 1, wherein the key cap comprises a first conductive portion, and the first electrode pair comprises a first transmitter and a first receiver 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 first transmitter and the first receiver.

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

8. The keyboard of claim 1, 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.

9. The keyboard of claim 8, wherein the first signal is used to disambiguate the second signal.

10. The keyboard of claim 1, wherein the key cap comprises a second conductive portion, and the second electrode pair comprises a second transmitter and a second receiver 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 second transmitter and the second receiver.

11. The keyboard of claim 9, 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 second transmitter and the second receiver.

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

13. The keyboard of claim 12, further comprising a second conductor extending across the row and electrically interconnects the other one of the first and second electrode pairs in the row.

14. The keyboard of claim 13, wherein at least one of the first and second conductors is configured to connect a plurality of transmitter electrodes.

15. The keyboard assembly of claim 1, wherein a plurality of the second electrode pairs each comprise a receiver electrode substantially surrounded by a spatially distributed transmitter electrode.

16. A processing system for a keyboard input device of the type including a plurality of keys configured to be pressed by an input object, a first plurality of capacitive sensor electrodes disposed underneath the keys, and a second plurality of capacitive sensor electrodes disposed underneath at least a subset of the keys, the processing system configured to:

determine a keystroke signal from the first plurality of sensor electrodes;

determine a finger presence signal from the second plurality of sensor electrodes; and

determine positional information for the finger based on the keystroke signal and the finger presence signal.

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

determine the keystroke signal based on a received signal on a first receiver sensor electrode of the first plurality; and

determine the finger presence signal from a first receiver sensor electrode of the second plurality.

18. A method of detecting positional information of a finger interacting with a keyboard key of the type including a keystroke sensor configured to output a keystroke signal and a finger presence sensor configured to output a finger presence signal, the method comprising:

determining a first baseline value associated with the keystroke signal;

determining a second baseline value associated with the finger presence signal;

determining whether the finger presence signal substantially corresponds to the second baseline value; and

determining positional information for the finger based on the finger presence signal and the keystroke signal.

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

20. The method of claim 18, wherein the positional information comprises at least one of:

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

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

motion of the finger on the key.