Capacitive sensing with high pass filtering for segmentation

• US 10,095,363 B2
• Filed: 03/28/2016
• Issued: 10/09/2018
• Est. Priority Date: 03/28/2016
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Ling, Yi, Mani, Sanjay
• Primary Examiner(s): Merkoulova, Olga
• Application Number:
  US15/083,184
• Publication Number:
  US 20170277293A1
• Time in Patent Office: 925 Days
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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

Embodiments described herein include a method for using multiple filtered images. The method includes acquiring changes of capacitance in a sensing region at a plurality of sensor electrodes in a capacitive sensor. The method also includes generating a capacitive frame based on the changes of capacitance and calculating one or more filtered capacitive frames by modifying the capacitive frame with a spatial filter. The method also includes performing clump detection on the one or more filtered capacitive frames, where clump detection includes detecting locations in each filtered capacitive frame exceeding a first threshold near locations that exceed a second threshold in the corresponding capacitive frame.

Claims

1. A method of input detection, comprising:

detecting changes of capacitance in a sensing region of a capacitive sensor;

generating a first capacitive frame based on the detected changes of capacitance;

filtering the first capacitive frame using a high pass spatial filter to produce at least one filtered capacitive frame; and

detecting an input in the sensing region coinciding with a location at which an amplitude of the at least one filtered capacitive frame exceeds a first threshold and an amplitude of the first capacitive frame exceeds a second threshold.

2. The method of claim 1, wherein the changes of capacitance are detected using transcapacitive sensing, and the first capacitive frame is a two-dimensional image.

3. The method of claim 1, wherein the changes of capacitance are detected using absolute capacitive sensing, and the first capacitive frame is a capacitive profile.

4. The method of claim 1, further comprising calculating low frequency noise by comparing two or more filtered capacitive frames.

5. The method of claim 1, further comprising calculating low frequency noise by comparing the first capacitive frame to one or more filtered capacitive frames.

6. The method of claim 1, further comprising determining a bending amount of the capacitive sensor based on comparing two capacitive frames.

7. The method of claim 1, wherein the high pass spatial filter comprises a first order derivative for an edge pixel of the capacitive sensor.

8. The method of claim 1, wherein the high pass spatial filter comprises a third order derivative for a non-edge pixel of the capacitive sensor.

9. An input device, comprising:

a plurality of capacitive sensing electrodes configured to receive a signal; and

a processing system coupled to the plurality of capacitive sensing electrodes, the processing system configured to;

detect changes of capacitance in a sensing region associated with the plurality of capacitive sensing electrodes;

generate a first capacitive frame based on the detected changes of capacitance;

filter the first capacitive frame to produce at least one filtered capacitive frame; and

detect an input in the sensing region coinciding with a location at which an amplitude of the at least one filtered capacitive frame exceeds a first threshold and an amplitude of the first capacitive frame exceeds a second threshold.

10. The input device of claim 9, wherein the processing system is to filter the first capacitive frame using a high pass spatial filter.

11. The input device of claim 10, wherein the high pass spatial filter comprises a first order derivative for an edge pixel of a capacitive sensor.

12. The input device of claim 10, wherein the high pass spatial filter comprises a third order derivative for a non-edge pixel of a capacitive sensor.

13. The input device of claim 9, wherein the processing system is to detect the changes of capacitance using transcapacitive sensing, and wherein the first capacitive frame is a two-dimensional image.

14. The input device of claim 9, wherein the processing system is to detect the changes of capacitance using absolute capacitive sensing, and wherein the first capacitive frame is a capacitive profile.

15. A processing system for capacitive sensing, comprising:

a filter configured to filter a first capacitive frame to produce at least one filtered capacitive frame;

a segmentation module configured to detect a location at which an amplitude of the at least one filtered capacitive frame exceeds a first threshold and an amplitude of the first capacitive frame exceeds a second threshold; and

a classifier configured to classify an input associated with the detected location.

16. The processing system of claim 15, wherein the filter is a high pass spatial filter.

17. The processing system of claim 16, wherein the high pass spatial filter comprises a first order derivative for an edge pixel of a capacitive sensor.

18. The processing system of claim 16, wherein the high pass spatial filter comprises a third order derivative for a non-edge pixel of a capacitive sensor.

19. The processing system of claim 15, wherein the first capacitive frame is generated using transcapacitive sensing, and wherein the first capacitive frame is a two-dimensional image.

20. The processing system of claim 15, wherein the first capacitive frame is generated using absolute capacitive sensing, and wherein the first capacitive frame is a capacitive profile.