Position detecting device, electromagnetic resonance stylus, and position detecting system

1 . A position detecting device comprising:

a plurality of first loop coils arrayed in a first direction;

a plurality of second loop coils arrayed in a second direction perpendicular to the first direction; and

a sensor controller which, in operation, detects induced currents respectively in the second loop coils while energizing one of the first loop coils,

wherein the sensor controller, in operation, derives a position of an electromagnetic resonance stylus in at least the second direction based on a distribution of levels of the induced currents detected and acquires data transmitted by the electromagnetic resonance stylus by performing on-off keying modulation on the induced currents detected, and

wherein the sensor controller, in operation, derives the position of the electromagnetic resonance stylus and acquires the data transmitted by the electromagnetic resonance stylus,

using a current calculated by subtracting, from one of the induced currents detected in one of the second loop coils that is positioned at a first end in the second direction among the second loop coils, one of the induced currents detected in one of the second loop coils that is positioned at a second end in the second direction among the second loop coils, as the one of the induced currents detected in the one of the second loop coils that is positioned at the first end in the second direction among the second loop coils, and

using a current calculated by subtracting the one of the induced currents detected in the one of the second loop coils that is positioned at the first end in the second direction among the second loop coils from the one of the induced currents detected in the one of the second loop coils that is positioned at the second end in the second direction among the second loop coils, as the one of the induced currents detected in the one of the second loop coils that is positioned at the second end in the second direction among the second loop coils.

2 . The position detecting device according to claim 1 ,

wherein the sensor controller, in operation, performs demodulation on the induced currents based on a timing to start energizing the one of the first loop coils.

3 . The position detecting device according to claim 1 ,

wherein the sensor controller, in operation, performs:

a global scan for detecting the electromagnetic resonance stylus that is undetected, and

a local scan for detecting the electromagnetic resonance stylus that has been detected,

wherein the global scan includes a process of supplying one of the first loop coils with a drive current and detecting the induced currents respectively in the second loop coils, successively with respect to each of the first loop coils, and deriving the position of the electromagnetic resonance stylus in each of the first direction and the second direction based on a distribution in a touch surface of the levels of the induced currents detected, and

wherein the local scan includes a process of:

selecting a predetermined number of the first loop coils and a predetermined number of the second loop coils as reception loop coils and one of the first loop coils and one of the second loop coils as transmission coils based on the position of the electromagnetic resonance stylus detected,

detecting the induced currents respectively in the predetermined number of the second loop coils selected as the reception loop coils while supplying one of the first loop coils selected as a transmission loop coil with the drive current, and deriving the position of the electromagnetic resonance stylus in the second direction based on the distribution in the second direction of the levels of the induced currents detected, and

detecting the induced currents respectively in the predetermined number of the first loop coils selected as the reception loop coils while supplying one of the second loop coils selected as a transmission loop coil with the drive current, and deriving the position of the electromagnetic resonance stylus in the first direction based on the distribution in the first direction of the levels of the induced currents detected.

4 . The position detecting device according to claim 1 ,

wherein the sensor controller, in operation, derives the position of the electromagnetic resonance stylus and acquires the data transmitted by the electromagnetic resonance stylus using differences between the induced currents detected respectively in two adjacent ones of the second loop coils.

5 . An electromagnetic resonance stylus comprising:

a resonant circuit including a coil and a capacitor;

a switch element connected parallel to the capacitor; and

a processing circuit which, in operation, transmits data to a position detecting circuit by performing on/off control on the switch element according to the data to be transmitted to the position detecting circuit,

wherein the processing circuit, in operation:

detects an alternating current generated in the resonant circuit by an alternating magnetic field intermittently transmitted by the position detecting circuit, and

detects a timing for the position detecting device to newly transmit the alternating magnetic field based on a result of the detection of the alternating current, and performs the on/off control on the switch element based on the timing detected,

wherein the position detecting circuit is coupled to a plurality of first loop coils arrayed in a first direction and a plurality of second loop coils arrayed in a second direction perpendicular to the first direction, and

wherein the position detecting circuit, in operation:

derives the position of the electromagnetic resonance stylus and acquires the data transmitted by the electromagnetic resonance stylus,

using a current calculated by subtracting, from one of a plurality of induced currents detected in one of the second loop coils that is positioned at a first end in the second direction among the second loop coils, one of the induced currents detected in one of the second loop coils that is positioned at a second end in the second direction among the second loop coils, as the one of the induced currents detected in the one of the second loop coils that is positioned at the first end in the second direction among the second loop coils, and

using a current calculated by subtracting the one of the induced currents detected in the one of the second loop coils that is positioned at the first end in the second direction among the second loop coils from the one of the induced currents detected in the one of the second loop coils that is positioned at the second end in the second direction among the second loop coils, as the one of the induced currents detected in the one of the second loop coils that is positioned at the second end in the second direction among the second loop coils.

6 . A position detecting system comprising:

an electromagnetic resonance stylus; and

a position detecting device,

wherein the electromagnetic resonance stylus includes:

a resonant circuit including a coil and a capacitor,

a switch element connected parallel to the capacitor, and

a processing circuit which, in operation, transmits data to the position detecting circuit by performing on/off control on the switch element according to the data to be transmitted to the position detecting circuit,

wherein the position detecting device includes:

a plurality of first loop coils arrayed in a first direction,

a plurality of second loop coils arrayed in a second direction perpendicular to the first direction, and

a sensor controller which, in operation, detects induced currents respectively in the second loop coils while energizing one of the first loop coils, and

wherein the sensor controller, in operation, derives a position of the electromagnetic resonance stylus in at least the second direction based on a distribution of levels of the induced currents detected and acquires data transmitted by the electromagnetic resonance stylus by performing on-off keying modulation on the induced currents detected, and

wherein the sensor controller, in operation, derives the position of the electromagnetic resonance stylus and acquires the data transmitted by the electromagnetic resonance stylus,

using a current calculated by subtracting, from one of the induced currents detected in one of the second loop coils that is positioned at a first end in the second direction among the second loop coils, one of the induced currents detected in one of the second loop coils that is positioned at a second end in the second direction among the second loop coils, as the one of the induced currents detected in the one of the second loop coils that is positioned at the first end in the second direction among the second loop coils, and

using a current calculated by subtracting the one of the induced currents detected in the one of the second loop coils that is positioned at the first end in the second direction among the second loop coils from the one of the induced currents detected in the one of the second loop coils that is positioned at the second end in the second direction among the second loop coils, as the one of the induced currents detected in the one of the second loop coils that is positioned at the second end in the second direction among the second loop coils.