Coordinate input device and display device including the same

• US 9,262,027 B2
• Filed: 04/24/2014
• Issued: 02/16/2016
• Est. Priority Date: 03/02/2010
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Japan Display Incorporated, Panasonic Liquid Crystal Company Limited
• Inventors: Mamba, Norio, Nagata, Koji, Hayakawa, Koji
• Primary Examiner(s): NGUYEN, JENNIFER T
• Application Number:
  US14/261,070
• Publication Number:
  US 20140232684A1
• Time in Patent Office: 663 Days
• Field of Search: 345173-178, 178/18.06
• 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/047 using sets of wires, e.g. crossed wires

Abstract

A coordinate input device includes: a coordinate input unit having a plurality of first detection electrodes and a plurality of second detection electrodes; an electrode drive circuit that applies a drive signal to one or more of the detection electrodes; a detection circuit that detects a signal of the first and/or second detection electrode; a selection circuit for selecting one or more of the detection electrodes to which the drive signal is not applied from among the detection electrodes which are disposed in parallel to the detection electrodes to which the drive signal is applied, as a reference electrode; a detection circuit for detecting a signal of the selected reference electrode; an input coordinate computing circuit for correcting a detection result of the detection circuit on the basis of the detected capacitance of the reference electrode and for calculating an input coordinate from the corrected detection result.

Claims

1. A coordinate input device comprising:

a plurality of first detection electrodes disposed in parallel to each other,

a plurality of second detection electrodes intersecting the first detection electrodes;

an electrode drive circuit configured to apply a drive signal to one or more of the first detection electrodes; and

a detection circuit configured to detect a signal of the second detection electrode generated by the drive signal,

wherein the electrode drive circuit is configured to select one or more of the first detection electrodes to which the drive signal is not applied as a reference electrode;

wherein the detection circuit is configured to detect a signal of the selected reference electrode as a noise signal, and

further comprising an input coordinate computing circuit configured to correct a detection result of the detection circuit on the basis of the detected noise signal of the reference electrode, and to calculate an input coordinate from the corrected detection result.

2. The coordinate input device according to claim 1, wherein the reference electrode is the first detection electrode which is disposed in parallel to the vicinity of the first detection electrode to which the drive signal is applied.

3. The coordinate input device according to claim 1,

wherein the electrode drive circuit includes a circuit configured to select one or more from among the plurality of first detection electrodes and to apply the drive signal thereto, and

the detection circuit includes a circuit configured to measure currents or voltages of the plurality of second detection electrodes generated by the drive signal.

4. The coordinate input device according to claim 3,

wherein the circuit for correcting a detection result includes a circuit configured to calculate a correction value within a predetermined range by adding or subtracting a predetermined value to or from the detection result from the reference electrode, and

the input coordinate computing circuit is configured to correct the detection result of the second detection electrode by subtracting or adding the correction value from or to the capacitance detection result of the second detection electrode.

5. The coordinate input device according to claim 1, wherein the detection circuit includes:

a first detection circuit that selects one or more of the plurality of first detection electrodes and that detects a signal of the selected first detection electrodes; and

a second detection circuit that selects one or more of the plurality of second detection electrodes and that detects a signal of the selected second detection electrodes.

6. The coordinate input device according to claim 5,

wherein the circuit configured to correct a detection result includes:

a circuit to calculate a first correction value within a predetermined range by adding or subtracting a first predetermined value to or from the detection result of the first reference electrode; and

a circuit to calculate a second correction value within a predetermined range by adding or subtracting a second predetermined value to or from the detection result of the second reference electrode,

wherein the input coordinate computing circuit is configured to correct the detection result of the first detection electrode by subtracting or adding the first correction value from or to the detection result of the first detection electrode, and to correct the detection result of the second detection electrode by subtracting or adding the second correction value from or to the detection result of the second detection electrode.

7. A coordinate input device comprising:

a plurality of first detection electrodes, which are disposed in parallel to each other,

a plurality of second detection electrodes intersecting the first detection electrodes,

an electrode drive circuit configured to apply a drive signal to one or more of the first detection electrodes;

a detection circuit configured to detect a signal of the second detection electrode charged by the drive signal;

a selecting circuit configured to select one or more of the first detection electrodes to which the drive signal is not applied from among the first detection electrodes as a reference electrode,

wherein

the detection circuit is configured to detect a signal of the selected reference electrode as a noise signal,

a correcting circuit is configured to correct a detection result of the detection circuit on the basis of the detected the noise signal of the reference electrode, and

further comprising an input coordinate computing circuit that calculates an input coordinate from the corrected detection result.

8. The coordinate input device according to claim 7, wherein the reference electrode is the first detection electrode which is disposed parallel to the vicinity of the first detection electrode to which the drive signal is applied.

9. The coordinate input device according to claim 7,

wherein the detection circuit includes a circuit configured to measure currents or voltages of the plurality of second detection electrodes as the signal of the second detection electrodes.

10. The coordinate input device according to claim 9,

wherein the corrected detection result includes a correction value within a predetermined range by adding or subtracting a predetermined value to or from the detection result from the reference electrode, and

the input coordinate computing circuit is configured to correct the detection result of the second detection electrode by subtracting or adding the correction value from or to the detection result of the second detection electrode.

11. The coordinate input device according to claim 7, wherein the detection circuit includes:

a first detection circuit that selects one or more of the plurality of first detection electrodes and detects signals of the selected first detection electrodes; and

a second capacitance detection circuit that selects one or more of the plurality of second detection electrodes and detects signals of the selected second detection electrodes.

12. The coordinate input device according to claim 11, wherein the corrected detection result includes:

a first correction value within a predetermined range by adding or subtracting a first predetermined value to or from the detection result of the first reference electrode; and

a second correction value within a predetermined range by adding or subtracting a second predetermined value to or from the second reference electrode,

wherein the input coordinate computing circuit is configured to correct the detection result of the first detection electrode by subtracting or adding the first correction value from or to the detection result of the first detection electrode, and to correct the detection result of the second detection electrode by subtracting or adding the second correction value from or to the detection result of the second detection electrode.