Capacitive touch screen sensing and electric field sensing for mobile devices and other devices

• US 8,547,360 B2
• Filed: 07/08/2011
• Issued: 10/01/2013
• Est. Priority Date: 07/08/2011
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Posamentier, Joshua
• Primary Examiner(s): Cheng, Joe H
• Application Number:
  US13/179,135
• Publication Number:
  US 20130009906A1
• Time in Patent Office: 816 Days
• Field of Search: 345/173, 345/174, 345/179, 178/18.06, 178/18.07, 178/19.03
• US Class Current: 345/174
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• 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 3/0443 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
• 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 system includes a touch screen having multiple electrodes. The system also includes a processing unit configured to use the electrodes to (i) detect an object contacting the touch screen or within a first distance from the touch screen in a first mode and (ii) detect the object within a second distance from the touch screen in a second mode. The second distance is larger than the first distance. The processing unit can be configured to use the multiple electrodes in the first mode to perform capacitive touch screen sensing. The processing unit can also be configured to use the multiple electrodes in the second mode to perform electric field sensing.

Claims

1. A system comprising:

a touch screen comprising multiple electrodes;

a touch screen processor comprising;

a drive signal generator, wherein the drive signal generator is configured to provide touch screen or electric field sensing drive signals to one or more of the electrodes;

a detections unit, wherein the detection unit receives signals from one or more of the electrodes and is configured to analyze the signals received from one or more of the electrodes and perform capacitive touch screen sensing and electric field sensing;

wherein the touch screen processor is configured to use the drive signal generator and the detection unit to;

detect an object contacting the touch screen or within a first distance from the touch screen in a first mode; and

detect the object within a second distance from the touch screen in a second mode, the second distance larger than the first distance;

wherein the first mode is configured for;

each of multiple pairs of electrodes, drive one of the electrodes in the pair and measure a mutual capacitance using another of the electrodes in the pair; and

use mutual capacitance measurements to detect the object contacting the touch screen or within the first distance from the touch screen; and

wherein the second mode is configured to;

drive a first group of the electrodes and measure a self-capacitance of the group of electrodes; and

use self-capacitance measurements on the first group of electrodes to detect the object within the second distance from the touch screen.

2. The system of claim 1, wherein the touch screen processor is configured to:

use the multiple electrodes in the first mode to perform capacitive touch screen sensing; and

use the multiple electrodes in the second mode to perform electric field sensing.

3. The system of claim 1, wherein the touch screen processor is configured to repeatedly switch between the first and second modes.

4. The system of claim 1, further comprising:

an application processor configured to execute one or more applications that are configured to use a location of the object during execution.

5. The system of claim 1, wherein:

the electrodes comprise first electrodes arranged in rows and second electrodes arranged in columns; and

each electrode comprises multiple conductive pads that are electrically coupled together.

6. An apparatus comprising:

a touch screen processor configured to be coupled to multiple electrodes in a touch screen and to use the multiple electrodes to;

detect an object contacting a touch screen or within a first distance from the touch screen in a first mode; and

detect the object within a second distance from the touch screen in a second mode, the second distance larger than the first distance;

wherein the touch screen processor is comprised of;

a drive signal generator, wherein the drive signal generator is configured to provide touch screen or electric field sensing drive signals to one or more of the electrodes;

a detections unit, wherein the detection unit receives signals from one or more of the electrodes and is configured to analyze the signals received from one or more of the electrodes and perform capacitive touch screen sensing and electric field sensing;

wherein the touch screen processor in the first mode is configured for;

each of multiple pairs of electrodes, drive one of the electrodes in the pair and measure a mutual capacitance using another of the electrodes in the pair; and

use mutual capacitance measurements to detect the object contacting the touch screen or within the first distance from the touch screen;

wherein the touch screen processor in the second mode is configured to;

drive a first group of the electrodes and measure a self-capacitance of the first group of electrodes; and

use self-capacitance measurements to detect the object within the second distance from the touch screen.

7. The apparatus of claim 6, wherein the processing unit is configured to:

use the multiple electrodes in the first mode to perform capacitive touch screen sensing; and

use the multiple electrodes in the second mode to perform electric field sensing.

8. The apparatus of claim 6, wherein the processing unit is configured to repeatedly switch between the first and second modes.

9. A method comprising:

using multiple pairs of electrodes in a touch screen to detect an object contacting the touch screen or within a first distance from the touch screen in a first mode; and

using a first group of electrodes in the touch screen to detect the object within a second distance from the touch screen in a second mode, the second distance larger than the first distance;

wherein using the multiple pairs of electrodes in the first mode comprises;

for each of multiple pairs of electrodes, driving one of the electrodes in the pair and measuring a mutual capacitance using another of the electrodes in the pair; and

using mutual capacitance measurements to detect the object contacting the touch screen or within the first distance from the touch screen;

wherein using the multiple electrodes in the second mode comprises;

driving a first group of the electrodes and measuring a self-capacitance of the group of electrodes; and

using self-capacitance measurements to detect the object within the second distance from the touch screen.

10. The method of claim 9, further comprising:

repeatedly switching between the first and second modes.

11. The method of claim 9, further comprising:

outputting a first indication in response to detecting the object contacting the touch screen or within the first distance from the touch screen; and

outputting a second indication in response to detecting the object within the second distance from the touch screen.

12. The method of claim 9, wherein:

using the multiple pairs of electrodes in the first mode comprises using the multiple electrodes to perform capacitive touch screen sensing; and

using the first group of electrodes in the second mode comprises using the multiple electrodes to perform electric field sensing.