Detection of a conductive object during an initialization process of a touch-sensing device

• US 9,495,038 B2
• Filed: 10/22/2014
• Issued: 11/15/2016
• Est. Priority Date: 01/14/2011
• Status: Expired due to Fees

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Inventors: Young, Kristopher L
• Primary Examiner(s): MILLER, DANIEL R
• Application Number:
  US14/520,536
• Publication Number:
  US 20150193078A1
• Time in Patent Office: 755 Days
• Field of Search: 178/18.06, 178/19.03, 324658-690, 341/33, 345/173, 345/174
• US Class Current: 1/1
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 2203/04101 2.5D-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 and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• 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 3/0418 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

A method and system for detecting a presence of a conductive object proximate to a capacitive sense element during an initialization process of a touch-sensing device. A capacitance sensing circuit measures a reference capacitance of a reference sense element. A sensing parameter of the capacitance sensing circuit is iteratively adjusted to obtain a target measurement output value for the reference sense element. With the sensing parameter set to the sensing parameter value, the capacitance measurement circuit measures a first capacitance of a first sense element. A first capacitance difference value is determined between the first capacitance and a first baseline capacitance value for the first sense element. A presence of a conductive object is detected proximate to the first sense element when the first capacitance difference value exceeds a threshold value.

Claims

1. A method comprising:

measuring a reference capacitance of a reference sense element of a touch-sensing device using a capacitance sensing circuit and adjusting a sensing parameter value of the capacitance sensing circuit until the measured reference capacitance is equal to a target measurement output value, wherein the reference sense element is disposed within the touch-sensing device such that a presence of a conductive object does not affect the reference capacitance;

measuring a first capacitance of a first sense element of the touch-sensing device using the capacitance sensing circuit having the adjusted sensing parameter value, wherein the first sense element is disposed within the touch-sensing device such that a presence of a conductive object does affect the first capacitance, wherein the reference sense element comprises at least one electrode that is identical to the at least one electrode of the first sense element with respect to at least one of size, overlay and ground clearance;

determining a first capacitance difference value between the first capacitance and a first baseline capacitance value for the first sense element; and

detecting a presence of a conductive object proximate to the first sense element when the first capacitance difference value exceeds a threshold value.

2. The method of claim 1, further comprising:

measuring a second capacitance of a second sense element of the touch-sensing device using the capacitance sensing circuit set to the sensing parameter value, wherein the second sense element is disposed within the touch-sensing device such that a presence of a conductive object does affect the second capacitance;

determining a second capacitance difference value between the second capacitance and a second baseline capacitance value for the second sense element; and

detecting a presence of a conductive object proximate to the second sense element when the second capacitance difference value exceeds the threshold value.

3. The method of claim 1, wherein the reference sense element comprises a first single electrode and the first sense element comprises a second single electrode, wherein the measuring the reference capacitance comprises measuring a first self-capacitance of the first single electrode, and wherein the measuring the first capacitance comprises measuring a second self-capacitance of the second single electrode.

4. The method of claim 1, wherein the reference sense element comprises a first pair of electrodes and the first sense element comprises a second pair of electrodes, wherein the measuring the reference capacitance comprises measuring a first mutual capacitance between the first pair of electrodes, and wherein the measuring the first capacitance comprises measuring a second mutual capacitance between the second pair of electrodes.

5. The method of claim 1, wherein the sensing parameter value is a current of a current source of the capacitance sensing circuit.

6. The method of claim 1, wherein the sensing parameter value is a voltage of a voltage source of the capacitance sensing circuit.

7. The method of claim 1, wherein the sensing parameter value is programmable by a processing device coupled to the capacitance sensing circuit.

8. The method of claim 1, wherein the measuring the reference capacitance and the adjusting the sensing parameter are performed during an initialization process of the touch-sensing device, wherein the presence of the conductive object proximate to the first sense element is detected during the initialization process of the touch-sensing device.

9. The method of claim 1, wherein the first baseline capacitance value for the first sense element is stored in a non-volatile memory.

10. A system comprising:

a processing device coupled to a capacitance sensing circuit comprising a sensing parameter, the processing device is to;

measure a reference capacitance of a reference sense element using the capacitive sensing circuit and adjust the sensing parameter value until the measured reference capacitance is equal to a target measurement output value, wherein the reference sense element is disposed within a touch-sensing device such that a presence of a conductive object does not affect the reference capacitance;

measure a first capacitance of a first sense element of the touch-sensing device using the capacitance sensing circuit having the adjusted sensing parameter value, wherein the first sense element is disposed within the touch-sensing device such that a presence of a conductive object does affect the first capacitance;

determine a first capacitance difference value between the first capacitance and a first baseline capacitance value for the first sense element; and

detect a presence of a conductive object proximate to the first sense element when the first capacitance difference value exceeds a threshold value; and

a printed circuit board comprising;

a first side upon which the first sense element is disposed; and

a second side upon which the reference sense element is disposed.

11. The system of claim 10, wherein the processing device is further to:

measure a second capacitance of a second sense element of the touch-sensing device using the capacitance sensing circuit set to the sensing parameter value, wherein the second sense element is disposed within the touch-sensing device such that a presence of a conductive object does affect the second capacitance, wherein the second sense element is disposed on the first side of the printed circuit board;

determine a second capacitance difference value between the second capacitance and a second baseline capacitance value for the second sense element; and

detect a presence of a conductive object proximate to the second sense element when the second capacitance difference value exceeds the threshold value.

12. The system of claim 10, wherein the capacitance sensing circuit is to measure the capacitance of each of a plurality of capacitive sense elements of the touch-sensing device with the sensing parameter set to the sensing parameter value.

13. The system of claim 10, wherein the first baseline capacitance value for the first sense element is stored in a non-volatile memory of the touch-sensing device.

14. The system of claim 10, wherein the presence of the conductive object proximate to the first sense element is detected during an initialization process of the touch-sensing device.

15. The system of claim 10, wherein the sensing parameter is a programmable current of the capacitance sensing circuit.

16. A system comprising:

a processing device coupled to a capacitance sensing circuit comprising a sensing parameter, the processing device is to;

measure a reference capacitance of a reference sense element using the capacitive sensing circuit and adjust the sensing parameter value until the measured reference capacitance is equal to a target measurement output value, wherein the reference sense element is disposed within a touch-sensing device such that a presence of a conductive object does not affect the reference capacitance;

measure a first capacitance of a first sense element of the touch-sensing device using the capacitance sensing circuit having the adjusted sensing parameter value, wherein the first sense element is disposed within the touch-sensing device such that a presence of a conductive object does affect the first capacitance;

determine a first capacitance difference value between the first capacitance and a first baseline capacitance value for the first sense element; and

detect a presence of a conductive object proximate to the first sense element when the first capacitance difference value exceeds a threshold value; and

a printed circuit board comprising an overlay covering the reference sense element such that the reference capacitance is not responsive to a presence of a conductive object proximate to the reference sense element.

17. A non-transitory computer-readable medium including data that, when accessed by a processing device, causes the processing device to perform operations comprising:

measuring a reference capacitance of a reference sense element of a touch-sensing device using a capacitance sensing circuit and adjusting a sensing parameter value of the capacitance sensing circuit until the measured reference capacitance is equal to a target measurement output value, wherein the reference capacitance is responsive to an environmental condition, wherein the reference sense element is disposed within the touch-sensing device such that a presence of a conductive object does not affect the reference capacitance;

measuring a first capacitance of a first sense element of the touch-sensing device using the capacitance sensing circuit having the adjusted sensing parameter value, wherein the first sense element is disposed within the touch-sensing device such that a presence of a conductive object does affect the first capacitance, wherein the reference sense element comprises at least one electrode that is identical to the at least one electrode of the first sense element with respect to at least one of size, overlay and ground clearance;

determining a first capacitance difference value between the first capacitance and a first baseline capacitance value for the first sense element; and

detecting a presence of a conductive object proximate to the first sense element when the first capacitance difference value exceeds a threshold value.

18. The non-transitory computer-readable medium of claim 17, wherein the operations further comprise:

measuring a second capacitance of a second sense element of the touch-sensing device using the capacitance sensing circuit set to the sensing parameter value, wherein the second sense element is disposed within the touch-sensing device such that a presence of a conductive object does affect the second capacitance, wherein the second sense element comprises at least one electrode that has similar characteristics as the at least one electrode of the reference sense element;

determining a second capacitance difference value between the second capacitance and a second baseline capacitance value for the second sense element; and

detecting a presence of a conductive object proximate to the second sense element when the second capacitance difference value exceeds the threshold value.

19. The non-transitory computer-readable medium of claim 17, wherein the sensing parameter value is a current of a current source of the capacitance sensing circuit, and wherein the measuring the reference capacitance and adjusting the sensing parameter value are performed during a power up of the touch-sensing device.