COORDINATE INPUT DEVICE AND DISPLAY DEVICE WITH THE SAME

• US 20100085322A1
• Filed: 10/06/2009
• Published: 04/08/2010
• Est. Priority Date: 10/06/2008
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Japan Display Incorporated
• Inventors: Anno, Kouichi, Kajiwara, Hisayoshi, Nagata, Koji, Furuhashi, Tsutomu, MAMBA, Norio, Hayakawa, Koji, Kumagai, Toshiyuki
• Granted Patent: US 9,395,850 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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 capacitance detection device of a capacitance system includes: a capacitance sensor electrode for detecting a capacitance; a power source for supplying charges to be charged in the capacitance sensor electrode; an electric charge storage capacitor in which an amount of charges to be charged therein changes according to the electric charges charged in the capacitance sensor electrode; and a switch for changing a reference potential of the electric charge storage capacitor. The reference potential of the electric charge storage capacitor is changed in a period of measuring the capacitance.

Claims

1. A capacitance detection device of a capacitance system, comprising:

an electrode for detecting a capacitance;

a power source for supplying electric charges to be charged in the electrode;

an electric charge storage capacitor in which an amount of charges to be charged therein changes according to the electric charges charged in the electrode; and

a switch for changing a reference potential of the electric charge storage capacitor,

wherein the reference potential of the electric charge storage capacitor is changed in a period of measuring the capacitance.

2. A capacitance detection device according to claim 1, wherein the switch sets the reference potential of the electric charge storage capacitor as a potential of a portion which causes noise to be generated in a charging potential at which the charges are charged in the electric charge storage capacitor.

3. A capacitance detection device according to claim 2, wherein a period in which the switch sets the reference potential of the electric charge storage capacitor as the potential of the portion which causes the noise to be generated in the charging potential at which the charges are charged in the electric charge storage capacitor overlaps with at least one of a period in which the electric charges charged in the electrode of a measuring target are moved to the electric charge storage capacitor and a period in which the charges are charged in the electrode of the measuring target.

4. A capacitance detection device according to claim 1, further comprising a filter in a portion for connecting a terminal to which the reference potential of the electric charge storage capacitor is input with a portion which causes noise to be generated in a charging potential at which the charges are charged in the electric charge storage capacitor.

5. A coordinate input device of a capacitive coupling system, comprising:

a capacitance sensor electrode for detecting a capacitance;

a first switching element for applying a fixed potential to the capacitance sensor electrode;

a second switching element for transferring electric charges charged in the capacitance sensor electrode; and

an integration circuit for detecting the charges transferred from the capacitance sensor electrode via the second switching element, wherein;

the capacitance sensor electrode is connected to a voltage source for supplying the fixed potential via the first switching element, and is connected to an input terminal of the integration circuit via the second switching element;

the input terminal of the integration circuit is connected to a third switching element for short-circuiting to a reference level of the integration circuit, and is connected to one terminal of an adjustment capacitor; and

another terminal of the adjustment capacitor has an adjustment signal applied thereto.

6. A coordinate input device according to claim 5, wherein:

in a first procedure, the first switching element, the second switching element, and the third switching element are turned OFF to reset an output signal of the integration circuit;

in a second procedure, the first switching element is turned ON to apply the fixed potential to the capacitance sensor electrode;

in a third procedure, the first switching element is turned OFF while the second switching element is turned ON to transfer the electric charges charged in the capacitance sensor electrode to the integration circuit;

in a fourth procedure, the second switching element is turned OFF to change the adjustment signal by an amount equal to an adjustment voltage;

in a fifth procedure, the third switching element is turned ON to reset the adjustment signal to a potential before the change;

in a sixth procedure, the third switching element is turned OFF; and

the first procedure to the sixth procedure constitute a capacitance detection cycle for the capacitance sensor electrode.

7. A coordinate input device according to claim 6, wherein when the capacitance of the capacitance sensor electrode is detected by repeating the capacitance detection cycle n times, n being an integer of 2 or more, at a first time of the capacitance detection cycle, the resetting of the output signal of the integration circuit is performed in the first procedure, and at a second time and thereafter of the capacitance detection cycle, the resetting of the output signal of the integration circuit is stopped in the first procedure.

8. A display device, comprising:

the coordinate input device according to claim 6; and

a display unit for displaying a video based on a display control signal output from a display control unit, wherein;

the coordinate input device further comprises;

a coordinate input unit in which an X electrode having

a plurality of the capacitance sensor electrodes arrayed in a lateral direction and a Y electrode having a plurality of the capacitance sensor electrodes arrayed in a longitudinal direction are disposed so as to intersect each other via an insulating layer;

a plurality of capacitance detection circuits for detecting the respective capacitances of the X electrode and the Y electrode; and

an input coordinate detection control unit for generating a control signal for controlling the plurality of capacitance detection circuits;

the coordinate input unit is formed transparent to overlap the coordinate input unit and the display unit; and

the coordinate input device detects touching position coordinates in a display area by capacitance detection.

9. A display device according to claim 8, wherein the control signal for the plurality of capacitance detection circuits is generated so that change timing of a potential of a display electrode of the display device is within a period of the fifth procedure of the capacitance detection cycle.

16. A coordinate input device according to claim 5, wherein:

the input terminal of the integration circuit is connected to an adjustment current source in place of the adjustment capacitor; and

the adjustment current source supplies an adjustment current in place of applying the adjustment signal to the another terminal of the adjustment capacitor.

17. A coordinate input device according to claim 16, wherein:

in a first procedure, the first switching element, the second switching element, and the third switching element are turned OFF to reset an output signal of the integration circuit, and the adjustment current source is controlled so that an output current is zero;

in a second procedure, the first switching element is turned ON to apply the fixed potential to the capacitance sensor electrode;

in a third procedure, the first switching element is turned OFF while the second switching element is turned ON to transfer the electric charges charged in the capacitance sensor electrode to the integration circuit;

in a fourth procedure, the second switching element is turned OFF to output the adjustment current from the adjustment current source for a given period of time;

in a fifth procedure, the third switching element is turned ON; and

in a sixth procedure, the third switching element is turned OFF; and

the first procedure to the sixth procedure constitute a capacitance detection cycle for the capacitance sensor electrode.

10. A coordinate input device of a capacitive coupling system, comprising:

a scanning sensor electrode;

a detection sensor electrode disposed so as to intersect the scanning sensor electrode via an insulating layer;

a scanning circuit comprising;

a first switching element for applying a fixed potential to the scanning sensor electrode; and

a second switching element for resetting a potential of the scanning sensor electrode; and

a detection circuit comprising an integration circuit for detecting charges flowing into the detection sensor electrode, wherein;

an input terminal of the integration circuit of the detection circuit is connected to a third switching element for short-circuiting to a reference level of the integration circuit, and is connected to one terminal of an adjustment capacitor; and

another terminal of the adjustment capacitor has an adjustment signal applied thereto.

11. A coordinate input device according to claim 10, wherein:

in a first procedure, the first switching element and the third switching element are turned OFF while the second switching element is turned ON to reset the potential of the scanning sensor electrode, and to reset an output signal of the integration circuit;

in a second procedure, the second switching element is turned OFF while the first switching element is turned ON to apply the fixed potential to the scanning sensor electrode, and the integration circuit detects a current flowing via a capacitance generated in a vicinity of an intersection between the scanning sensor electrode and the detection sensor electrode;

in a third procedure, the first switching element is turned OFF to change the adjustment signal by an amount equal to an adjustment voltage;

in a fourth procedure, the third switching element is turned ON to reset the adjustment signal to a potential before the change, and the second switching element is turned ON to reset the potential of the scanning sensor electrode;

in a fifth procedure, the second switching element and the third switching element are turned OFF; and

the first procedure to the fifth procedure constitute a capacitance detection cycle in which the detection circuit detects a capacitance.

12. A coordinate input device according to claim 11, wherein the adjustment voltage is set so that an output signal of the detection circuit is small in a state where there is no input operation for an input capacitance detection unit including the scanning sensor electrode and the detection sensor electrode.

13. A coordinate input device according to claim 12, wherein when an input capacitance input to the input capacitance detection unit is detected by repeating the capacitance detection cycle n times, n being an integer of 2 or more, at a first time of the capacitance detection cycle, the resetting of the output signal of the integration circuit and the potential of the scanning sensor electrode is performed in the first procedure, and at a second time and thereafter of the capacitance detection cycle, the resetting of the output signal of the integration circuit and the potential of the scanning sensor electrode is stopped in the first procedure.

14. A display device, comprising:

the coordinate input device according to claim 11; and

a display unit for displaying a video based on a display control signal output from a display control unit, wherein;

the coordinate input device further comprises;

a coordinate input unit in which an X electrode having a plurality of the detection sensor electrodes arrayed in a lateral direction and a Y electrode having a plurality of the scanning sensor electrodes arrayed in a longitudinal direction are disposed so as to intersect each other via an insulating layer;

a plurality of the detection circuits are connected to the X electrode;

a plurality of the scanning circuits are connected to the Y electrode; and

an input coordinate detection control unit for generating a control signal for controlling the plurality of the detection circuits and the plurality of the scanning circuits;

the coordinate input unit is formed transparent to overlap the coordinate input unit and the display unit; and

the coordinate input device detects touching position coordinates in a display area by capacitance detection.

15. A display device according to claim 14, wherein the control signal for the plurality of the detection circuits is generated so that change timing of a display electrode of the display device is within a period in which the third switching element is in an ON state from the fourth procedure to the fifth procedure of the capacitance detection cycle.

18. A coordinate input device according to claim 10, wherein:

the input terminal of the integration circuit is connected to an adjustment current source in place of the adjustment capacitor; and

the adjustment current source supplies an adjustment current in place of applying the adjustment signal to the another terminal of the adjustment capacitor.

19. A coordinate input device according to claim 18, wherein:

in a first procedure, the first switching element and the third switching element are turned OFF while the second switching element is turned ON to reset the potential of the scanning sensor electrode, and to reset an output signal of the integration circuit;

in a second procedure, the second switching element is turned OFF while the first switching element is turned ON to apply the fixed potential to the scanning sensor electrode, and the integration circuit detects a current flowing via a capacitance generated in a vicinity of an intersection between the scanning sensor electrode and the detection sensor electrode;

in a third procedure, the first switching element is turned OFF to output the adjustment current from the adjustment current source for a given period of time;

in a fourth procedure, the third switching element is turned ON to reset the adjustment signal to a potential before the change, and the second switching element is turned ON to reset the potential of the scanning sensor electrode;

in a fifth procedure, the second switching element and the third switching element are turned OFF; and

the first procedure to the fifth procedure constitute a capacitance detection cycle in which the detection circuit detects a capacitance.

20. A coordinate input device according to claim 18, wherein the adjustment current is set so that an output signal of the detection circuit is small in a state where there is no input operation for the detection sensor electrode.