Sensing frame averaging for cancelling display noise in simultaneous display and touch sensing

• US 9,645,670 B2
• Filed: 09/30/2015
• Issued: 05/09/2017
• Est. Priority Date: 09/30/2015
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Khazeni, Kasra, Reynolds, Joseph Kurth
• Primary Examiner(s): Cheng, Joe H
• Application Number:
  US14/871,473
• Publication Number:
  US 20170090641A1
• Time in Patent Office: 587 Days
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/04164 Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/044 by capacitive means
• 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

Techniques for removing display-based corrupting components from a capacitive sensing signal when display and capacitive sensing is performed at or nearly at the same time. A routing carrying display related signals (e.g., a source signal for sub-pixel updating) may induce a corrupting current into a routing for carrying capacitive sensing signals. This corrupting current would reduce the ability to determine presence of an input object via the sensing signal. Therefore, the corrupting signal is effectively removed by averaging sensing signals from two consecutive frames together. Because displays perform frame inversion, in which the voltage polarity provided to a sub-pixel for updates is reversed each frame, the corrupting current reverses in polarity each frame. Therefore, adding two subsequent frames together cancels out the corrupting signal.

Claims

1. A processing system configured for simultaneously updating a display and performing capacitive sensing, the processing system comprising:

a source driver configured to drive a source line with a first source driver voltage during a first time period and to receive resulting signals on a routing trace coupled to a sensor electrode during a second time period that at least partially overlaps with the first time period, the routing trace and the source line being routed proximate each other; and

an interference remover configured to acquire first resulting signals during a first display update period and second resulting signals during a second display update period, and to remove display interference from the second resulting signals by combining the first resulting signals and the second resulting signals,

wherein first display signals provided for display updates during the first display update period are frame-inverted with respect to second display signals provided for display updates during the second display update period.

2. The processing system of claim 1, wherein the interference remover is configured to combine the first resulting signals and the second resulting signals by:

adding the first resulting signals to the second resulting signals.

3. The processing system of claim 1, wherein the interference remover is configured to combine the first resulting signals and the second resulting signals by:

averaging the first resulting signals with the second resulting signals.

4. The processing system of claim 3, wherein removing the display interference from the second resulting signals comprises:

producing an interference-filtered set of resulting signals corresponding to the second sensing frame.

5. The processing system of claim 1, wherein:

the first resulting signals comprise resulting signals for a first sensing frame; and

the second resulting signals comprise resulting signals for a second sensing frame that is consecutive to the first sensing frame.

6. The processing system of claim 5, wherein:

the second sensing frame is subsequent to the first sensing frame.

7. The processing system of claim 1, wherein:

the source line and the routing trace are disposed in a common layer.

8. The processing system of claim 1, wherein:

the source line and the routing trace are disposed in separate layers; and

the source line is parallel to the routing trace.

9. The processing system of claim 1, wherein the interference remover is further configured to:

drop an initial sensing frame.

10. An input device configured for simultaneously updating a display and performing capacitive sensing, the input device comprising:

a display element coupled to a source line;

a sensor electrode coupled to a routing trace, the routing trace and the source line being routed proximate each other; and

a processing system coupled to the source line and the routing trace, the processing system comprising;

a source driver configured to drive the source line with a first source driver voltage during a first time period and to receive resulting signals on the a routing trace during a second time period that at least partially overlaps with the first time period; and

an interference remover configured to acquire first resulting signals during a first display update period and second resulting signals during a second display update period, and to remove display interference from the second resulting signals by combining the first resulting signals and the second resulting signals,

wherein first display signals provided for display updates during the first display update period are frame-inverted with respect to second display signals provided for display updates during the second display update period.

11. The input device of claim 10, wherein the interference remover is configured to combine the first resulting signals and the second resulting signals by:

adding the first resulting signals to the second resulting signals.

12. The input device of claim 10, wherein the interference remover is configured to combine the first resulting signals and the second resulting signals by:

averaging the first resulting signals with the second resulting signals.

13. The input device of claim 12, wherein removing the display interference from the second resulting signals comprises:

producing an interference-filtered set of resulting signals corresponding to the second sensing frame.

14. The input device of claim 10, wherein:

the first resulting signals comprise resulting signals for a first sensing frame; and

the second resulting signals comprise resulting signals for a second sensing frame that is consecutive to the first sensing frame.

15. The input device of claim 14, wherein:

the second sensing frame is subsequent to the first sensing frame.

16. The input device of claim 10, wherein:

the source line and the routing trace are disposed in a common layer.

17. The input device of claim 10, wherein:

the source line and the routing trace are disposed in separate layers; and

the source line is parallel to the routing trace.

18. The input device of claim 10, wherein the interference remover is further configured to:

drop an initial sensing frame.

19. A method for simultaneously updating a display and performing capacitive sensing, the method comprising:

driving a source line with a first source driver voltage during a first time period;

receiving resulting signals on a routing trace coupled to a sensor electrode during a second time period that at least partially overlaps with the first time period, the routing trace and the source line being routed proximate each other;

acquiring first resulting signals during a first display update period and second resulting signals during a second display update period;

removing display interference from the second resulting signals by combining the first resulting signals and the second resulting signals,

wherein first display signals provided for display updates during the first display update period are frame-inverted with respect to second display signals provided for display updates during the second display update period.

20. The method of claim 19, wherein combining the first resulting signals and the second resulting signals comprises:

averaging the first resulting signals with the second resulting signals.