Capacitive touch screen having dynamic capacitance control and improved touch sensing

• US 9,001,083 B2
• Filed: 10/07/2014
• Issued: 04/07/2015
• Est. Priority Date: 08/27/2010
• Status: Active Grant

• Current Assignee: UICO, Inc.
• Original Assignee: UICO, Inc.
• Inventors: Wadia, Bahar N.
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): Martinez Quiles, Ivelisse
• Application Number:
  US14/508,294
• Publication Number:
  US 20150022498A1
• Time in Patent Office: 182 Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

Methods and apparatus for improving the sensing performance of a capacitive touch screen sensing device. The electrical potential of conductive structures proximate capacitive touch pads of the sensing device is altered to compensate for the effect of parasitic capacitance, based on external conditions such as water on the touch screen or an intervening user worn glove. The compensation for parasitic capacitance improves the signal to noise ratio and therefore the sensing performance of the device.

Claims

1. A touch pad apparatus comprising:

a capacitive touch sensing device including a plurality of respective touch sensing pads disposed on a surface of the capacitive touch sensing device;

at least one electrically manipulated conductive surface disposed on the surface of the capacitive touch sensing device proximate each respective touch sensing pad; and

a processor programmed to detect presence of water on the surface of the capacitance touch sensing device in an amount of water sufficient to attenuate capacitive coupling of a user touch with the surface of the capacitance touch sensing device, the processor further programmed to control application of an electrical potential to selected electrically manipulated conductive surfaces at a magnitude sufficient to compensate the attenuation of the capacitive coupling of the user touch with the surface.

2. The touch pad apparatus of claim 1 wherein the processor is programmed to time-multiplex the respective touch sensing pads as sensors to detect a touch of the surface of the capacitive touch sensing device and as electrically manipulated conductive surfaces.

3. The touch pad apparatus of claim 1 wherein the processor is programmed to from time to time scan each touch sensing pad of the plurality of respective touch sensing pads to detect a touch of the surface of the capacitive touch sensing device at the scanned touch sensing pad and to control application of electrical potentials to touch pads adjacent to the scanned touch sensing pad to compensate the attenuation of the capacitive coupling of the user touch with the surface.

4. The touch pad apparatus of claim 3 wherein the processor is programmed to measure a potential of the scanned touch sensing pad and to control application of the electrical potentials to the touch pads adjacent to the scanned touch sensing pad to substantially match the measured potential of the scanned touch sensing pad to compensate the attenuation of the capacitive coupling of the user touch with the surface.

5. The touch pad apparatus of claim 1 wherein the processor is programmed to determine an electrical potential of a sensed touch sensing pad and further programmed to control the application of the electrical potential to the selected electrically manipulated conductive surfaces at a potential substantially equal to the determined electrical potential of the sensed touch sensing pad to compensate the attenuation of the capacitive coupling of the user touch with the surface.

6. A method comprising:

at a capacitive touch screen device having a touch surface, a plurality of touch pads arranged for detecting touches on the touch surface and a programmable processor operable to detect conditions of the capacitive touch screen device and control electrical potentials provided to touch pads of the plurality of touch pads,

by the processor, detecting natural capacitance of each respective touch pad of the plurality of touch pads;

by the processor, detecting presence of water or a contaminant on the touch surface of the capacitive touch screen device;

scanning the plurality of touch pads to locate a touched pad experiencing a touch, including;

for each scanned touch pad, applying respective bias potentials to respective adjacent touch pads, the respective bias potentials being selected to reduce capacitive effects of the water or contaminant on capacitance of the scanned touch pad;

measuring capacitance of the each scanned touch pad; and

based on the measured capacitance, determining if the scanned touch pad experiences a touch.

7. The method of claim 6 wherein measuring capacitance of the each scanned touch pad comprises

under control of the processor, charging the each scanned touch pad to a potential;

and

measuring a rate of discharge of the each scanned touch pad from the potential.

8. The method of claim 7 wherein charging the each scanned touch pad comprises:

selecting, by the processor, an electrical potential;

providing control signals by the processor to a potential adjustment apparatus; and

applying the selected electrical potential by the potential adjustment apparatus the each scanned touch pad in response to the control signals.

9. The method of claim 7 wherein charging the each scanned touch pad comprises:

selecting, by the processor, an electrical potential; and

providing, by the processor to the each scanned touch pad, the electrical potential.

10. The method of claim 6 further comprising determining an electrical potential applied to the each scanned touch pad and wherein applying respective bias potentials to respective adjacent touch pads comprises applying electrical potentials to adjust respective capacitances between the each scanned touch pad and the respective adjacent touch pads so that parasitic capacitance added by the presence of the water or the contaminant on the touch surface of the capacitive touch screen device adds parasitic capacitance substantially equally to the each scanned touch pad and the respective adjacent touch pads.

11. The method of claim 6 further comprising determining an electrical potential applied to the each scanned touch pad and wherein applying respective bias potentials to respective adjacent touch pads comprises applying an electrical potential substantially matching the determined electrical potential to the respective adjacent touch pads to remove respective capacitances between the each scanned touch pad and the respective adjacent touch pads.

12. A method comprising:

at a capacitive touch screen device having a touch surface, a plurality of touch pads arranged for detecting touches on the touch surface and a programmable processor responsive to stored data and instructions and operable to detect conditions of the capacitive touch screen device and control electrical potentials provided to touch pads of the plurality of touch pads,

by the processor, detecting natural capacitance of each respective touch pad of the plurality of touch pads;

by the processor, determining a user of the capacitive touch screen device is wearing gloves when operating the touch surface of the capacitive touch screen device;

scanning the plurality of touch pads to locate a touched pad experiencing a touch by a gloved finger, including;

for each scanned touch pad, by the processor, applying respective bias potentials to selected respective adjacent touch pads located proximate the scanned touch pad, the respective bias potentials being selected to compensate for attenuation of capacitive coupling between the gloved finger and the scanned touch pad;

by the processor, determining capacitance of the each scanned touch pad; and

based on the measured capacitance, determining by the processor if the scanned touch pad experiences a touch by the gloved finger.

13. The method of claim 12 wherein applying respective bias potentials to selected respective adjacent touch pads comprises applying bias potentials selected to eliminate parasitic capacitance between the scanned touch pad and the selected respective adjacent touch pads.

14. The method of claim 13 further comprising applying a predetermined potential to the scanned touch pad and wherein applying respective bias potentials to selected respective adjacent touch pads comprises applying substantially the same predetermined potential to the selected respective adjacent touch pads to eliminate the parasitic capacitance between the scanned touch pad and the selected respective adjacent touch pads and increase sensitivity for determining by the processor if the scanned touch pad experiences a touch by the gloved finger.

15. A touch pad apparatus comprising:

a capacitive touch sensing device including a plurality of respective touch sensing pads disposed in a predetermined pattern on a surface of the capacitive touch sensing device so that each respective touch sensing pads has one or more adjacent touch sensing pads; and

a processor programmed to adjust sensitivity of the touch pad apparatus in response to presence of parasitic capacitance tending to attenuate capacitive coupling of a user touch by a user to a respective touch sensing pad upon the surface of the capacitance touch sensing device, the processor further programmed to control application of one or more electrical potentials to selected adjacent touch sensing pads at a magnitude sufficient to compensate the attenuation of the capacitive coupling of the user touch with the surface.

16. A digital appliance comprising the touch pad apparatus of claim 15 wherein the processor is configured to selectively scan the plurality of respective touch sensing pads to locate the user touch at the respective touch sensing pad on the surface.

17. The touch pad apparatus of claim 16 wherein the processor is configured to apply a scan potential to a selected touch sensing pad while applying selected compensating potentials to the selected adjacent touch sensing pads to eliminate parasitic capacitance between the selected touch sensing pad and the selected adjacent touch sensing pads and thereby increase sensitivity of the capacitive touch sensing device by reducing overall capacitance of the touch screen device due to natural capacitance and parasitic capacitance.

18. The touch pad apparatus of claim 17 wherein the processor is configured to select compensating potentials substantially equal to the scan potential to eliminate the parasitic capacitance between the selected touch sensing pad and the selected adjacent touch sensing pads.

19. The touch sensing apparatus of claim 17 further comprising:

potential adjustment apparatus capable of altering an output electrical potential applied to the selected adjacent touch sensing pads in response to a signal from the processor.

20. The touch pad apparatus of claim 15 wherein the processor is programmed determine a potential of a scanned touch sensing pad and to control application of the electrical potential to the selected adjacent touch pads to substantially match the measured potential of the scanned touch sensing pad to compensate the attenuation of the capacitive coupling of the user touch with the surface due to water or other contaminant on the surface or due to a gloved finger of the user.

21. A digital appliance comprising the touch pad apparatus of claim 15.