POSITION DETECTING DEVICE

• US 20130249854A1
• Filed: 03/01/2013
• Published: 09/26/2013
• Est. Priority Date: 03/23/2012
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Katsurahira, Yuji
• Granted Patent: US 9,046,978 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• 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 2203/04808 Several contacts: gestures triggering a specific function, e.g. scrolling, zooming, right-click, when the user establishes several contacts with the surface simultaneously; e.g. using several fingers or a combination of fingers and pen
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/041661 using detection at multiple resolutions, e.g. coarse and fine scanning; using detection within a limited area, e.g. object tracking window
• 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 3/0443 using a single layer of sensing electrodes
• 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 position detecting device is provided, which is capable of stably detecting an indicator with less susceptibility to the influence of noise by using a differential amplifier circuit and multi-touch. The device includes a sensor having an electrode pattern formed of plural first electrodes arranged in a first direction and plural second electrodes arranged in a second direction. The device selects two sets of the first electrodes separate from each other by a distance equivalent to a predetermined number of electrodes and supplies two drive signals having phases inverted from each other. The device selects two sets of the second electrodes separate from each other by a distance equivalent to a predetermined number of electrodes and connects the selected second electrodes to two differential inputs of a differential amplifier circuit. The device controls selection of two sets of the first electrodes and two sets of the second electrodes.

Claims

1. A position detecting device including a sensor having an electrode pattern formed of a plurality of first electrodes arranged in a first direction and a plurality of second electrodes arranged in a second direction intersecting with the first direction, the position detecting device supplying a drive signal to the first electrodes and detecting a position of an indicator on the electrode pattern from a reception signal obtained from the second electrodes, the position detecting device comprising:

a first selection circuit configured to select two sets of the second electrodes, which are separate from each other by a distance equivalent to a second predetermined number of electrodes, from the plurality of second electrodes;

a second selection circuit configured to select two sets of the first electrodes, which are separate from each other by a distance equivalent to a first predetermined number of electrodes, from the plurality of first electrodes;

a drive signal supply circuit configured to supply the drive signal to each of the two sets of the first electrodes selected by the second selection circuit and to output two signals having phases inverted from each other;

a differential amplifier circuit having a non-inverting input terminal, to which one set of the two sets of the second electrodes selected by the first selection circuit is connected, and an inverting input terminal, to which the other set of the two sets of the second electrodes is connected; and

a detection circuit configured to detect the position of the indicator on the electrode pattern from an output signal of the differential amplifier circuit.

2. The position detecting device according to claim 1, further comprising

a control circuit that controls selection by the first and second selection circuits and determines the first and second predetermined numbers in such a manner that only one intersection among four intersections, which are respectively formed by the two sets each of electrodes selected by the first and second selection circuits, is near the position of the indicator when positions of a plurality of indicators are detected by the detection circuit.

3. The position detecting device according to claim 1, wherein

a plurality of electrodes are included in each of the two sets each of electrodes selected by the first selection circuit and the second selection circuit, and the plurality of electrodes included in each set are simultaneously connected to the drive circuit and the differential amplifier circuit by the first selection circuit and the second selection circuit to detect a rough position of the indicator.

4. The position detecting device according to claim 1, wherein

the first electrodes and the second electrodes are formed of transparent electrodes and the sensor is obtained by forming the electrode pattern on a transparent substrate.

5. The position detecting device according to claim 4, wherein

the sensor is provided on a display surface of a display device.

6. A position detecting device including a sensor having a lattice-shaped electrode pattern formed of a plurality of first electrodes arranged in a first direction and a plurality of second electrodes arranged in a second direction intersecting with the first direction, the position detecting device supplying a transmission signal to the first electrodes and detecting a position of an indicator on the electrode pattern from a reception signal obtained from the plurality of second electrodes, the position detecting device comprising:

a drive signal supply circuit configured to supply a predetermined drive signal to the first electrodes;

a first selection circuit configured to select two sets of the second electrodes, which are separate from each other by a distance equivalent to a predetermined number of electrodes, from the plurality of second electrodes;

a second selection circuit configured to select the first electrode, to which the drive signal is supplied;

a differential amplifier circuit having a non-inverting input terminal, to which one set of the two sets of the second electrodes is connected, and an inverting input terminal, to which the other set is connected;

a detection circuit configured to detect the position of the indicator on the electrode pattern from an output signal of the differential amplifier circuit; and

a control circuit that carries out, for the first selection circuit, first selection control to select the two sets of the second electrodes in such a manner that a signal from the second electrode, at a position other than a detection position of the indicator, is supplied to one terminal of the non-inverting input terminal and the inverting input terminal of the differential amplifier circuit when a signal from the second electrode at the detection position of the indicator is supplied to the other terminal, based on plural pieces of position information detected when positions of plural indicators are detected by the detection circuit.

7. The position detecting device according to claim 6, wherein

in the first selection control for the first selection circuit, the control circuit changes the distance equivalent to the predetermined number of electrodes in the selection of the two sets of the second electrodes.

8. The position detecting device according to claim 6, wherein

two signals in phase opposition to each other are employed as the drive signal,

the second selection circuit is controlled by the control circuit in such a manner as to select two sets of the first electrodes, which are separate from each other by a distance equivalent to a predetermined number of electrodes, from the plurality of first electrodes,

one signal of two signals in phase opposition to each other as the drive signal is supplied to one set of the two sets of the first electrodes selected by the second selection circuit and the other signal is supplied to the other set of the two sets of the first electrodes, and

the control circuit carries out, for the second selection circuit, second selection control to select the two sets of the first electrodes in such a manner that one signal of two signals in phase opposition to each other as the drive signal is supplied to the first electrode, at a position other than the detection position of the indicator, when the other signal is supplied to the first electrode at the detection position of the indicator, based on plural pieces of position information of the indicator.

9. The position detecting device according to claim 8, wherein

in the second selection control for the second selection circuit, the control circuit changes the distance equivalent to the predetermined number of electrodes in the selection of the two sets of the first electrodes.

10. The position detecting device according to claim 8, wherein

the control circuit executes first detection processing of detecting the position of the indicator over an area of the lattice-shaped electrode pattern by controlling the selection of the two sets of the second electrodes in the first selection circuit and by controlling the selection of the two sets of the first electrodes in the second selection circuit,

when the indicator is detected by the first detection processing, the control circuit carries out control to execute second detection processing of detecting the position of the indicator over a partial area centered at a position at which the indicator is detected, by controlling the selection of the two sets of the second electrodes in the first selection circuit in such a manner that each of a plurality of second electrodes included in the partial area forms one set of the second electrodes and each second electrode separate from the second electrode in said one set by a distance equivalent to a predetermined number of electrodes forms the other set, and

the control circuit carries out said first selection control for the first selection circuit only in the second detection processing, and repeatedly alternates between the first detection processing and the second detection processing.

11. The position detecting device according to claim 10, wherein

after executing the first detection processing and the second detection processing, the control circuit carries out control to execute third detection processing of detecting the position of the indicator in the first direction over the partial area centered at the position at which the indicator is detected, by controlling the selection of the two sets of the first electrodes in the second selection circuit in such a manner that each of a plurality of first electrodes included in the partial area forms one set of the first electrodes and each first electrode separate from the first electrode in said one set by a distance equivalent to a predetermined number of electrodes forms the other set, and

the control circuit carries out said second selection control for the second selection circuit only in the third detection processing.

12. The position detecting device according to claim 6, wherein

the position of the indicator on the electrode pattern is detected by detecting change in capacitance between the electrode pattern and the indicator.