Weighting for display noise removal in capacitive sensors

• US 9,454,278 B2
• Filed: 03/27/2015
• Issued: 09/27/2016
• Est. Priority Date: 04/25/2014
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Keppel, Drew Garvin, Ramakrishnan, Shubha
• Primary Examiner(s): Marinelli, Patrick F
• Application Number:
  US14/671,989
• Publication Number:
  US 20150309618A1
• Time in Patent Office: 550 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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

Abstract

A processing system for a capacitive sensing input device comprises a sensor module and a determination module. The sensor module acquires a plurality of capacitive resulting signals by operating a plurality of sensor electrodes for capacitive sensing. The determination module weights values of the plurality of capacitive resulting signals to achieve a plurality of weighted capacitive resulting signals, wherein a first capacitive resulting signal of the plurality of capacitive resulting signals is weighted according to a weighted noise parameter derived from a component of a variable noise associated with a respective sensor electrode used for acquisition of the first capacitive resulting signal, wherein the variable noise varies across the plurality of sensor electrodes. The determination module also determines positional information for an least input object in a sensing region of the capacitive sensing input device based on resulting signals processed from the weighted capacitive resulting signals.

Claims

1. A processing system for a capacitive sensing input device, said processing system comprising:

a sensor module configured to acquire a plurality of capacitive resulting signals by operating a plurality of sensor electrodes for capacitive sensing; and

a determination module configured to;

weight values of said plurality of capacitive resulting signals to achieve a plurality of weighted capacitive resulting signals, wherein a first capacitive resulting signal of said plurality of capacitive resulting signals is weighted according to a weighted noise parameter derived from a component of a variable noise associated with a respective sensor electrode used for acquisition of said first capacitive resulting signal, wherein said variable noise varies across said plurality of sensor electrodes; and

determine positional information for an least input object in a sensing region of the capacitive sensing input device based on resulting signals processed from said weighted capacitive resulting signals,

wherein said determination module is further configured to;

filter said weighted capacitive resulting signals to remove common noise and to achieve a plurality of filtered capacitive resulting signals; and

de-weight said filtered capacitive resulting signals according to said weighted noise parameters to achieve a plurality of processed capacitive resulting signals.

2. The processing system of claim 1, wherein said sensor module is configured to acquire said first capacitive resulting signal by driving a first sensor electrode of said plurality of sensor electrodes with a transmitter signal and receiving said first capacitive resulting signal with a second sensor electrode of said plurality of sensor electrodes, wherein said first and second sensor electrodes are different sensor electrodes, and wherein said first capacitive resulting comprises effects corresponding to said transmitter signal.

3. The processing system of claim 1, wherein said sensor module is configured to acquire said first capacitive resulting signal by driving a first sensor electrode of said plurality of sensor electrodes with a transmitter signal and receiving said first capacitive resulting signal with said first sensor electrode.

4. The processing system of claim 1, wherein said determination module is further configured to:

determine a transcapacitive image from said plurality of processed capacitive resulting signals.

5. The processing system of claim 1, wherein said determination module is further configured to:

acquire a control set of capacitive resulting signals when no input object is determined to be interacting with said plurality of sensor electrodes;

subtract baseline values from said control set of capacitive resulting signals to achieve a set of differences;

determine absolute values of a set of weights needed to normalize the set of differences; and

estimate said weighted noise parameters by dividing each of said absolute values of said set of weights by a maximum absolute value of said absolute values.

6. The processing system of claim 1, said determination module is further configured to:

weight a second capacitive resulting signal of said plurality of capacitive resulting signals according to a second weighted noise parameter derived from a second component of said variable noise associated with a second respective sensor electrode used for acquisition of said second capacitive resulting signal, wherein different weighted noise parameters are used for weighting said first capacitive resulting signal and said second capacitive resulting signal.

7. The processing system of claim 1, wherein said variable noise is a display coupled noise coupled from a display to said plurality of sensor electrodes.

8. The processing system of claim 1, wherein said weighted noise parameters are fixed values.

9. The processing system of claim 1, wherein said weighted noise parameters are adaptive values.

16. The capacitive sensing input device of claim 1, wherein said processing system is further configured to:

determine a transcapacitive image from said plurality of processed capacitive resulting signals.

10. A method of capacitive sensing comprising:

operating, by a processing system, a plurality sensor of electrodes to acquire a plurality of capacitive resulting signals of capacitive resulting signals;

weighting, by said processing system, values of said plurality of capacitive resulting signals to achieve a plurality of weighted capacitive resulting signals, wherein a first capacitive resulting signal of said plurality of capacitive resulting signals is weighted according to a weighted noise parameter derived from a component of a variable noise associated with a respective sensor electrode used for acquisition of said first capacitive resulting signal, wherein said variable noise varies across said plurality of sensor electrodes;

filtering, by said processing system, said weighted capacitive resulting signals to remove common noise and to achieve a plurality of filtered capacitive resulting signals;

de-weighting, by said processing system, said filtered capacitive resulting signals according to said weighted noise parameters to achieve a plurality of processed capacitive resulting signals; and

determining, by said processing system, a capacitive image from said processed capacitive resulting signals.

11. The method of claim 10, further comprising:

acquiring, by said processing system, a control set of capacitive resulting signals when no input object is determined to be interacting with said plurality of sensor electrodes;

subtracting, by said processing system, baseline values from said control set of capacitive resulting signals to achieve a set of differences;

determining, by said processing system, absolute values of a set of weights needed to normalize the set of differences; and

estimating said weighted noise parameters by dividing each of said absolute values of said set of weights by a maximum absolute value of said absolute values.

12. The method of claim 10, wherein said weighting values of said plurality of capacitive resulting signals to achieve a plurality of weighted capacitive resulting signals further comprises:

weighting a second capacitive resulting signal of said plurality of capacitive resulting signals according to a second weighted noise parameter derived from a second component of said variable noise associated with a second respective sensor electrode used for acquisition of said second capacitive resulting signal, wherein different weighted noise parameters are used for weighting said first capacitive resulting signal and said second capacitive resulting signal.

13. A capacitive sensing input device, comprising:

a display;

a plurality of sensor electrodes; and

a processing system configured to;

acquire a plurality of capacitive resulting signals by operating a plurality of sensor electrodes for capacitive sensing;

weight values of said plurality of capacitive resulting signals to achieve a plurality of weighted capacitive resulting signals, wherein a first capacitive resulting signal of said plurality of capacitive resulting signals is weighted according to a weighted noise parameter derived from a component of a variable noise associated with a respective sensor electrode used for acquisition of said first capacitive resulting signal, wherein said variable noise varies across said plurality of sensor electrodes; and

determine positional information for an least input object in a sensing region of the capacitive sensing input device based on resulting signals processed from said weighted capacitive resulting signals,

wherein said processing system is further configured to;

filter said weighted capacitive resulting signals to remove common noise and to achieve a plurality of filtered capacitive resulting signals; and

de-weight said filtered capacitive resulting signals according to said weighted noise parameters to achieve a plurality of processed capacitive resulting signals.

14. The capacitive sensing input device of claim 13, wherein said processing system is further configured to:

acquire said first capacitive resulting signal by driving a first sensor electrode of said plurality of sensor electrodes with a transmitter signal and receiving said first capacitive resulting signal with a second sensor electrode of said plurality of sensor electrodes, wherein said first and second sensor electrodes are different sensor electrodes, and wherein said first capacitive resulting signal comprise effects corresponding to said transmitter signal.

15. The capacitive sensing input device of claim 13, wherein said processing system is further configured to:

acquire said first capacitive resulting signal by driving a first sensor electrode of said plurality of sensor electrodes with a transmitter signal and receiving said first capacitive resulting signal with said first sensor electrode.

17. The capacitive sensing input device of claim 13, wherein said processing system is further configured to:

acquire a control set of capacitive resulting signals when no input object is determined to be interacting with said plurality of sensor electrodes;

subtract baseline values from said control set of capacitive resulting signals to achieve a set of differences;

determine absolute values of a set of weights needed to normalize the set of differences; and

estimate said weighted noise parameters by dividing each of said absolute values of said set of weights by a maximum absolute value of said absolute values.

18. The capacitive sensing input device of claim 13, wherein said processing system is further configured to:

weight a second capacitive resulting signal of said plurality of capacitive resulting signals according to a second weighted noise parameter derived from a second component of said variable noise associated with a second respective sensor electrode used for acquisition of said second capacitive resulting signal, wherein different weighted noise parameters are used for weighting said first capacitive resulting signal and said second capacitive resulting signal.