POSITION DETECTING DEVICE

• US 20140078101A1
• Filed: 08/21/2013
• Published: 03/20/2014
• Est. Priority Date: 09/20/2012
• Status: Abandoned Application

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Katsurahira, Yuji
• Application Number:
  US13/972,744
• Publication Number:
  US 20140078101A1
• 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 3/03545 Pens or stylus
• 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 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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 detects both a finger and a stylus radiating an electric field. The device includes: a substantially transparent sensor disposed on a display device and formed by X-electrodes and Y-electrodes; an X-selecting circuit for selecting two sets of X-electrodes as a positive terminal and a negative terminal; a Y-selecting circuit for selecting two sets of Y-electrodes as a positive terminal and a negative terminal; a driving signal generating circuit for generating signals shifted in phase from each other by 180° as a positive signal and a negative signal; a differential amplifier for amplifying a difference between signals occurring in the positive terminal and the negative terminal selected by one, or respectively each, of the X-selecting circuit and the Y-selecting circuit; and a balanced switching circuit for switching connection of the positive terminal and the negative terminal to the driving signal generating circuit or to the differential amplifier.

Claims

1. A position detecting device for detecting and inputting a position indicated by a finger or a stylus on a display device capable of refreshing display in each fixed period, the position detecting device comprising:

a substantially transparent sensor disposed on the display device and formed by arranging a plurality of electrodes in each of an X-direction and a Y-direction orthogonal to each other, the electrodes being formed of a transparent conductive material or a conductive material having a width such that the conductive material is regarded as substantially transparent;

a stylus for radiating an alternating-current electric field from an electrode at a tip portion, the stylus including a power supply retained by a battery or a capacitor, an alternating-current signal generating circuit for generating an alternating-current signal, a pen pressure detecting circuit for detecting pressure applied to the tip portion as switch information or pen pressure information, and a modulating circuit for changing a frequency or amplitude of the signal output from the alternating-current signal generating circuit on a basis of the information detected by the pen pressure detecting circuit;

an X-selecting circuit for selecting two sets of electrodes as a positive terminal and a negative terminal from the plurality of X-electrodes arranged in the X-direction;

a Y-selecting circuit for selecting two sets of electrodes as a positive terminal and a negative terminal from the plurality of Y-electrodes arranged in the Y-direction;

a driving signal generating circuit for generating signals shifted in phase from each other by 180°

to be sent out from the transparent sensor as a positive driving signal and a negative driving signal;

a differential amplifier for amplifying a difference between signals occurring in the positive terminal and the negative terminal selected by one, or respectively each, of the X-selecting circuit and the Y-selecting circuit;

a balanced switching circuit for performing switching so as to connect the positive terminal and the negative terminal selected by the Y-selecting circuit or the X-selecting circuit to the driving signal generating circuit at a time of touch detection and connect the positive terminal and the negative terminal selected by the Y-selecting circuit or the X-selecting circuit to the differential amplifier at a time of stylus detection; and

a processing circuit for determining the position indicated by the finger or the stylus from a distribution of strengths of signals output to the differential amplifier when the electrodes selected by the X-selecting circuit and the Y-selecting circuit are changed sequentially;

wherein at the time of the touch detection, the positive signal and the negative signal from the driving signal generating circuit are supplied respectively to the positive terminal and the negative terminal of one of the Y-selecting circuit and the X-selecting circuit, and the differential amplifier is connected to the positive terminal and the negative terminal of the other selecting circuit, and

at the time of the stylus detection, the positive terminal and the negative terminal of one, or respectively each, of the X-selecting circuit and the Y-selecting circuit are connected to the differential amplifier to detect a signal from the stylus.

2. The position detecting device according to claim 1,

wherein output of the differential amplifier is connected to a band-pass filter circuit, and a center frequency of the band-pass filter circuit is controlled to coincide with a frequency of the signals from the driving signal generating circuit at the time of the touch detection and is controlled to coincide with a frequency of the electric field radiated from the stylus at the time of the stylus detection.

3. The position detecting device according to claim 2,

wherein the frequency of the electric field radiated from the stylus is higher than the frequency of the signals from the driving signal generating circuit at the time of the touch detection.

4. The position detecting device according to claim 2,

wherein the band-pass filter circuit includes a parallel resonance circuit including a coil and a capacitor, and a switch connected in parallel with the parallel resonance circuit and controlled to be on or off, and the switch is controlled to be on for only a certain period each time the electrodes selected by the X-selecting circuit or the Y-selecting circuit are changed.

5. The position detecting device according to claim 2,

wherein the stylus includes a pen pressure detecting circuit for detecting pen pressure and digitizing the pen pressure, and an ASK modulation circuit for changing the alternating-current signal applied to the electrode in time series by turning on or off the alternating-current signal on a basis of digital information output by the pen pressure detecting circuit.

6. The position detecting device according to claim 1,

wherein selection of the electrodes by the X-selecting circuit or the Y-selecting circuit is changed in timing synchronized with the refreshing period of the display device.

7. The position detecting device according to claim 1,

wherein, at the time of the touch detection, the X-selecting circuit or the Y-selecting circuit selects the two sets of electrodes that are separated by an interval larger than a diameter of a finger contact area.

8. The position detecting device according to claim 1,

wherein, at the time of the stylus detection, the X-selecting circuit or the Y-selecting circuit selects the two sets of electrodes that are separated by an interval larger than a diameter of a radiation pattern of the alternating-current electric field from the stylus.

9. The position detecting device according to claim 1,

wherein a number of electrodes selected by the X-selecting circuit or the Y-selecting circuit as the positive terminal is the same as a number of electrodes selected by the X-selecting circuit or the Y-selecting circuit as the negative terminal.

10. The position detecting device according to claim 1, wherein the display device is a liquid crystal display device.

11. A combined sensor and display device for detecting and inputting a position indicated by a finger or a stylus thereon, comprising:

a display device capable of refreshing display in each fixed period,

a substantially transparent sensor disposed on the display device and formed by arranging a plurality of electrodes in each of an X-direction and a Y-direction orthogonal to each other, the electrodes being formed of a transparent conductive material or a conductive material having a width such that the conductive material is regarded as substantially transparent;

an X-selecting circuit for selecting two sets of electrodes as a positive terminal and a negative terminal from the plurality of X-electrodes arranged in the X-direction;

a Y-selecting circuit for selecting two sets of electrodes as a positive terminal and a negative terminal from the plurality of Y-electrodes arranged in the Y-direction;

a driving signal generating circuit for generating signals shifted in phase from each other by 180°

to be sent out from the transparent sensor as a positive driving signal and a negative driving signal;

a differential amplifier for amplifying a difference between signals occurring in the positive terminal and the negative terminal selected by one, or respectively each, of the X-selecting circuit and the Y-selecting circuit;

a balanced switching circuit for performing switching so as to connect the positive terminal and the negative terminal selected by the Y-selecting circuit or the X-selecting circuit to the driving signal generating circuit at a time of touch detection and connect the positive terminal and the negative terminal selected by the Y-selecting circuit or the X-selecting circuit to the differential amplifier at a time of stylus detection; and

a processing circuit for determining the position indicated by the finger or the stylus from a distribution of strengths of signals output to the differential amplifier when the electrodes selected by the X-selecting circuit and the Y-selecting circuit are changed sequentially;

wherein at the time of the touch detection, the positive signal and the negative signal from the driving signal generating circuit are supplied respectively to the positive terminal and the negative terminal of one of the Y-selecting circuit and the X-selecting circuit, and the differential amplifier is connected to the positive terminal and the negative terminal of the other selecting circuit, and

at the time of the stylus detection, the positive terminal and the negative terminal of one, or respectively each, of the X-selecting circuit and the Y-selecting circuit are connected to the differential amplifier to detect a signal from the stylus.

12. The combined sensor and display device according to claim 11,

wherein output of the differential amplifier is connected to a band-pass filter circuit, and a center frequency of the band-pass filter circuit is controlled to coincide with a frequency of the signals from the driving signal generating circuit at the time of the touch detection and is controlled to coincide with a frequency of an electric field radiated from the stylus at the time of the stylus detection.

13. The combined sensor and display device according to claim 12,

wherein the frequency of the electric field radiated from the stylus is higher than the frequency of the signals from the driving signal generating circuit at the time of the touch detection.

14. The combined sensor and display device according to claim 12,

wherein the band-pass filter circuit includes a parallel resonance circuit including a coil and a capacitor, and a switch connected in parallel with the parallel resonance circuit and controlled to be on or off, and the switch is controlled to be on for only a certain period each time the electrodes selected by the X-selecting circuit or the Y-selecting circuit are changed.

15. The combined sensor and display device according to claim 12,

wherein the processing circuit is further configured to determine a pen pressure detected by the stylus and ASK modulated onto the electric field radiated from the stylus.

16. The combined sensor and display device according to claim 11,

wherein selection of the electrodes by the X-selecting circuit or the Y-selecting circuit is changed in timing synchronized with the refreshing period of the display device.

17. The combined sensor and display device according to claim 11,

wherein, at the time of the touch detection, the X-selecting circuit or the Y-selecting circuit selects the two sets of electrodes that are separated by an interval larger than a diameter of a finger contact area.

18. The combined sensor and display device according to claim 11,

wherein, at the time of the stylus detection, the X-selecting circuit or the Y-selecting circuit selects the two sets of electrodes that are separated by an interval larger than a diameter of a radiation pattern of an electric field radiated from the stylus.

19. The combined sensor and display device according to claim 11, wherein a number of electrodes selected by the X-selecting circuit or the Y-selecting circuit as the positive terminal is the same as a number of electrodes selected by the X-selecting circuit or the Y-selecting circuit as the negative terminal.

20. The combined sensor and display device according to claim 11, wherein the display device is a liquid crystal display device.