Touch panel, signal processing device, and coupling method
A touch panel has a plurality of conductors arranged for a position detection area and can detect a position pointed to by an active stylus held by a user and a manual touch by the user holding the active stylus. The touch panel includes: a signal transmission circuit that transmits, by capacitive coupling, a signal to the active stylus that can receive the signal transmitted from the touch panel by capacitive coupling with the touch panel; an active stylus pointing position detection circuit that detects the position pointed to by the active stylus by capacitive coupling with the active stylus; a touch detection circuit that detects the manual touch by the user; and a coupling control circuit that performs coupling control to couple one or more of the plurality of conductors and a ground of the touch panel in accordance with a touch detection result of the touch detection circuit.
1. A touch panel including a sensor that has a plurality of conductors arranged for position detection and a signal processing circuit that can detect a position pointed to by an active stylus that transmits a signal to the sensor for position detection and a touch of a user on the sensor, the touch panel comprising:
a signal transmission circuit configured to capacitively transmit a signal to the active stylus via the sensor;
a position detection circuit configured to capacitively detect a position pointed to by the active stylus on the sensor by receiving the signal transmitted from the active stylus via the sensor;
a touch detection circuit configured to detect the touch of the user by receiving a signal via the sensor in response to signal transmission via the sensor; and
a coupling control circuit configured to couple at least one of the plurality of conductors of the sensor on which the touch of the user is conducted and a ground of the signal processing circuit in accordance with a touch detection result of the touch detection circuit, while a signal from the signal transmission circuit is capacitively transmittable to the active stylus via the sensor,
wherein the pointing position detection circuit is configured to detect the position pointed to by the active stylus on the sensor without using the at least one of the plurality of conductors of the sensor while the at least one of the plurality of conductors is coupled to the ground of the signal processing circuit by the coupling control circuit.
2. The touch panel of claim 1 , wherein
when the signal transmission circuit capacitively transmits the signal to the active stylus, the coupling control circuit couples the at least one of the plurality of conductors of the sensor on which the touch of the user is conducted and the ground of the signal processing circuit in accordance with the touch detection result of the touch detection circuit.
3. The touch panel of claim 1 , wherein
the plurality of conductors is arranged at least in a first direction, and
when the touch of the user is detected by the touch detection circuit, at least one of the plurality of conductors arranged where the touch of the user was detected is selectively coupled with the ground of the signal processing circuit by the coupling control circuit.
4. The touch panel of claim 3 , wherein
the plurality of conductors arranged at least in the first direction are used at least for signal transmission except for the at least one of the plurality of conductors selectively coupled with the ground of the signal processing circuit by the coupling control circuit.
5. The touch panel of claim 3 , wherein
the plurality of conductors arranged in the first direction are used to at least transmit the signal to the active stylus and detect the touch of the user.
6. The touch panel of claim 4 , wherein
the plurality of conductors arranged at least in the first direction are used for the signal transmission and signal reception, and
the signal transmission and the signal reception are switched in a time-divided manner.
7. The touch panel of claim 4 , wherein
a plurality of different kinds of transmission signals are supplied to the plurality of conductors arranged at least in the first direction.
8. The touch panel of claim 7 , wherein
one of the plurality of different kinds of transmission signals is used to capacitively transmit the signal to the active stylus, and
another signal of the plurality of different kinds of transmission signals is used to detect the touch of the user.
9. The touch panel of claim 7 , wherein
the plurality of different kinds of transmission signals are at different frequencies.
10. The touch panel of claim 1 , wherein
the plurality of conductors is arranged in a first direction and a second direction different from the first direction, and
when the touch of the user is detected by the touch detection circuit, at least one of the plurality of conductors arranged in the second direction and adjacent to an area touched by the user is selectively coupled with the ground of the signal processing circuit by the coupling control circuit.
11. The touch panel of claim 10 , wherein
the plurality of conductors arranged in the first direction are used for the signal transmission and signal reception, and
the plurality of conductors arranged in the second direction are used to receive a signal.
12. The touch panel of claim 1 , further comprising:
a plurality of conductors arranged electrically independently of the plurality of conductors used to capacitively transmit the signal to the active stylus and detect the touch of the user,
wherein, among the conductors arranged electrically independently, one or more conductors adjacent to an area touched by the user is coupled with the ground of the signal processing circuit.
13. The touch panel of claim 1 , wherein
the plurality of conductors is arranged in a first direction and a second direction different from the first direction, and
when the touch of the user is detected by the touch detection circuit, at least one of the plurality of conductors arranged in the first and second directions and adjacent to an area touched by the user is selectively coupled with the ground of the signal processing circuit by the coupling control circuit.
14. The touch panel of claim 1 , wherein
when a touched area of a predetermined size is detected by the touch panel, the coupling control circuit determines that the touched area was touched by the user.
15. The touch panel of claim 1 , wherein
the coupling control circuit couples a predetermined conductor corresponding to the position where the touch of the user was detected with the ground of the signal processing circuit.
16. The touch panel of claim 1 , wherein
the coupling control circuit couples a predetermined conductor corresponding to the position where the touch of the user was detected with a drive power supply of the touch panel.
17. A signal processing device connected to a touch panel including a sensor that has a plurality of conductors arranged for position detection and a signal processing circuit that detects a position pointed to by an active stylus that transmits a signal to the sensor for position detection and a touch of a user holding the active stylus, the signal processing device comprising:
a signal transmission circuit configured to capacitively transmit a signal to the active stylus via the sensor;
a pointing position detection circuit configured to capacitively detect a position pointed to by the active stylus on the sensor by receiving the signal transmitted from the active stylus via the sensor;
a touch detection circuit configured to detect the touch of the user by receiving a signal via the sensor in response to signal transmission via the sensor; and
a coupling control circuit configured to couple one or more of the plurality of conductors of the sensor on which the touch of the user is conducted and a ground of the signal processing circuit in accordance with a touch detection result of the touch detection circuit, while a signal from the signal transmission circuit is capacitively transmittable to the active stylus via the sensor,
wherein the pointing position detection circuit is configured to detect the position pointed to by the active stylus on the sensor without using the at least one of the plurality of conductors of the sensor while the at least one of the plurality of conductors is coupled to the ground of the signal processing circuit by the coupling control circuit.
18. The signal processing device of claim 17 , wherein
when the signal is capacitively transmitted to the active stylus, the coupling control circuit couples the at least one of the plurality of conductors of the sensor on which the touch of the user is conducted and the ground of the signal processing circuit in accordance with the touch detection result of the touch detection circuit.
19. A method of coupling an external ground and a ground of a signal processing circuit of a touch panel,
the touch panel including a sensor that has a plurality of conductors arranged for position detection and the signal processing circuit detecting a position pointed to by an active stylus that transmits a signal to the sensor for position detection and a touch of a user on the sensor, the method comprising:
capacitively transmitting a signal to the active stylus via the sensor;
capacitively detecting a position pointed to by the active stylus on the sensor by receiving the signal transmitted from the active stylus via the sensor;
detecting the touch of the user by receiving a signal via the sensor in response to signal transmission via the sensor; and
coupling at least one of the plurality of conductors of the sensor on which the touch of the user is conducted and a ground of the signal processing circuit in accordance with a result of the detecting, while a signal from the signal transmission circuit is capacitively transmittable to the active stylus via the sensor,
wherein the position pointed to by the active stylus on the sensor is capacitively detected using the at least one of the plurality of conductors of the sensor while the at least one of the plurality of conductors is coupled to the ground of the signal processing circuit.
20. The coupling method of claim 19 , wherein
when the signal is capacitively transmitted to the active stylus, the coupling is performed in response to the detecting of touch of the user.