Baseline management for input devices

• US 9,317,158 B2
• Filed: 03/07/2012
• Issued: 04/19/2016
• Est. Priority Date: 03/08/2011
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Schwartz, Adam, Reynolds, Joseph Kurth, Jordan, Joel C.
• Primary Examiner(s): Lee, Jr., Kenneth B
• Application Number:
  US13/414,468
• Publication Number:
  US 20120229418A1
• Time in Patent Office: 1,504 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

Embodiments of the invention generally provide a method and system that is able to minimize or remove the affect of substantially non-random electrical interference on an input device'"'"'s ability to reliably and accurately sense the position of an object. In one embodiment, the input device is configured to systematically correct for a cyclic variation in the electromagnetic interference (EMI) generated by components within the electronic system, such as interference generated by the process of refreshing or updating an image on a display module that affects the capacitive sensing measurements acquired from a plurality of capacitive sensing elements. However, in some embodiments of the invention, the performance of an input device is improved by reducing the affect that external interference generated outside of the electronic system have on the position sensing data acquired by the input device.

Claims

1. A processing system for an input device, comprising:

a sensor module comprising sensor circuitry, the sensor module coupled with a plurality of sensor electrodes, and configured to;

acquire a plurality of sensing frames comprising a first sensing frame of a first frame type, a second sensing frame of a second frame type different than the first frame type, and a third sensing frame of the second frame type,

form a first differential frame relating the first and second frame types based on a comparison of the first sensing frame with the second sensing frame, and

form a first normalized frame of the first frame type based on a comparison of the first differential frame with the third sensing frame; and

a determination module configured to compare the first normalized frame with a baseline frame.

2. The processing system of claim 1, wherein the determination module is further configured to determine positional information of an input object in a sensing region of the input device based on the comparison of the first normalized frame with the baseline frame.

3. The processing system of claim 1, wherein:

the plurality of sensing frames further comprises a fourth sensing frame of a third frame type different than the first and second frame types, and a fifth sensing frame of the third frame type,

the sensor module is further configured to form a second differential frame relating the first and third frame types based on a comparison of the first sensing frame with the fourth sensing frame, form a second normalized frame of the first frame type based on a comparison of the second differential frame with the fifth sensing frame, and

the determination module is further configured to compare the second normalized frame and the baseline frame.

4. The processing system of claim 1, wherein the comparison of the first sensing frame and the second sensing frame used to form the first differential frame further comprises subtracting the second sensing frame from the first sensing frame.

5. The processing system of claim 1, wherein the comparison of the first sensing frame and the second sensing frame used to form the first differential frame further comprises subtracting the second sensing frame from the first sensing frame and dividing the difference by a first constant.

6. The processing system of claim 1, wherein the plurality of sensor electrodes are configured for capacitive sensing.

7. The processing system of claim 1, wherein the plurality of sensor electrodes comprise a plurality of common electrodes, and wherein at least one of the plurality of common electrodes is configured for both capacitive sensing and updating a display device.

8. The processing system of claim 7, wherein the sensor module is further configured to acquire the plurality of sensing frames at a first frame rate, and

wherein the processing system further comprises a display module coupled with the plurality of common electrodes, and wherein the display module is configured to update the display device at a second frame rate, wherein the first frame rate is greater than the second frame rate.

9. The processing system of claim 1, wherein the first frame type and the second frame type correspond to different portions of a display update cycle.

10. The processing system of claim 1, wherein the difference between the first frame type and the second frame type corresponds to different types of substantially non-random interference.

11. An input device, comprising:

a plurality of sensor electrodes configured to sense input objects in a sensing region of the input device; and

a processing system coupled with the plurality of sensor electrodes, and configured to;

acquire a plurality of sensing frames comprising a first sensing frame of a first frame type, a second sensing frame of a second frame type different than the first type, and a third sensing frame of the second frame type,

form a first differential frame relating the first and second frame types based on a comparison of the first sensing frame with the second sensing frame, and

form a first normalized frame of the first frame type based on a comparison of the third sensing frame with the first differential frame, and

compare the first normalized frame with a baseline frame.

12. The input device of claim 11, wherein the processing system is further configured to determine the positional information of an input object in the sensing region of the input device based on the comparison of the first normalized frame with the baseline frame.

13. The input device of claim 11, wherein:

the plurality of sensing frames further comprises a fourth sensing frame of a third frame type different than the first and second frame types, and a fifth sensing frame of the third frame type, and

the processing system is further configured to form a second differential frame relating the first and third frame types based on a comparison of the first sensing frame with the fourth sensing frame, form a second normalized frame of the first frame type based on a comparison of the second differential frame with the fifth sensing frame, and compare the second normalized frame with the baseline frame.

14. The input device of claim 11, wherein the plurality of sensor electrodes comprise a plurality of common electrodes, and wherein at least one of the plurality of common electrodes is configured for both capacitive sensing and updating a display device,

wherein the processing system is further configured to acquire the plurality of sensing frames at a first frame rate, and

wherein the processing system further comprises a display module coupled to the plurality of common electrodes, and wherein the display module is configured to update the display device at a second frame rate, wherein the first frame rate is greater than the second frame rate.

15. The input device of claim 11, wherein the first frame type and the second frame type correspond to different portions of a display update cycle.

16. A method of sensing an input object in a sensing region of an input device, comprising:

acquiring a plurality of sensing frames with a plurality of sensor electrodes disposed in a sensing region of an input device, the plurality of sensing frames comprising a first sensing frame of a first frame type, a second sensing frame of a second frame type different than the first frame type, and a third sensing frame of the second frame type;

determining a first differential frame relating the first and second frame types based on a comparison of the first sensing frame with the second sensing frame;

determining a first normalized frame of the first frame type based on a comparison of the first differential frame with the third sensing frame; and

determining positional information of the input object in the sensing region of the input device based on a comparison of a baseline frame with the normalized sensing frame.

17. The method of claim 16, wherein the plurality of sensing frames further comprises fourth and fifth sensing frames of a third frame type different than the first and second frame types, the method further comprising:

determining a second differential frame relating the first and third frame types by comparing the first sensing frame with the fourth sensing frame; and

determining a second normalized frame of the first frame type based on a comparison of the second differential frame with the fifth sensing frame,

wherein the determining positional information of the input object in the sensing region is further based on the second normalized frame.

18. The method of claim 16, wherein the plurality of sensor electrodes comprise a plurality of common electrodes, the method further comprising:

transmitting a transmitter signal using at least a first of the plurality of common electrodes, wherein sensed effects of the transmitter signal are used to form at least a portion of at least one of the first and second sensing frames; and

transmitting a display update signal to update a display device using at least a second of the plurality of common electrodes, wherein the plurality of sensing frames are acquired at a first frame rate and the display device is updated at a second frame rate, wherein the first frame rate is greater than the second frame rate.

19. The method of claim 16, wherein the first frame type and the second frame type are formed during different portions of a cycle of a substantially non-random interference source to which the plurality of sensor electrodes are exposed.

20. The method of claim 16, wherein

the acquiring a plurality of sensing frames further comprises:

acquiring a plurality of sensing frames with the plurality of sensor electrodes, wherein every N sensing frames are different from each other, where N is greater than or equal to two, and every N+1 sensing frames are substantially similar to each other,

the determining the first normalized frame based on the comparison of the first differential frame and the third sensing frame of the plurality of sensing frames, further comprises;

determining a first sensor differential frame from each sensing frame that is P times N from the second sensing frame, where P is an integer that varies from 1 to Z, to form a set of Z normalized sensing frames, and

the determining the positional information of an input object further comprises;

determining the positional information of an input object based on a comparison of the baseline frame and the normalized sensing frames in the set of Z normalized sensing frames.