POSITION DETECTING DEVICE AND POSITION DETECTING METHOD

• US 20090065269A1
• Filed: 09/08/2008
• Published: 03/12/2009
• Est. Priority Date: 09/10/2007
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Katsurahira, Yuji
• Granted Patent: US 8,154,525 B2
• Time in Patent Office: Days
• US Class Current: 178/19.60
• CPC Class Codes: G06F 1/32 Means for saving power
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 3/046 by electromagnetic means
• CPC Class Codes: G06F 3/047 using sets of wires, e.g. crossed wires

Abstract

An excitation coil (19) surrounding the periphery of the position detecting area is connected to an oscillating circuit (21), which oscillates at a frequency f₀, through a drive circuit (20). A CPU (18) supplies control signals to a selecting circuit (12), a sample-and-hold circuit (16), an A/D conversion circuit (17), and the drive circuit (20). Based on the control signal output from the CPU (18), the drive circuit (20) controls the power of the signal output from the excitation coil (19) to ON or OFF. Further, the strength of the excitation signal supplied from the excitation coil (19) is controlled based on information obtained by analyzing a signal received from a position indicator (40), such as the position indicated by the position indicator on the position detecting area and/or a strength of the signal received from the position indicator.

Claims

1. A position detecting device for detecting an indicated position of a position indicator on a position detecting area, comprising:

an excitation coil arranged to surround a periphery of a position detecting area to supply an excitation signal to the position indicator;

a sensor configured to detect an AC signal transmitted from the position indicator based on the excitation signal supplied from the excitation coil, to thereby detect an indicated position of the position indicator on the position detecting area; and

a controller configured to control a strength of the excitation signal to be supplied from the excitation coil based on information obtained from an analysis of the detected AC signal.

2. The position detecting device according to claim 1, wherein the information obtained from an analysis of the detected AC signal is an indicated position of the position indicator.

3. The position detecting device according to claim 1, wherein the information obtained from an analysis of the detected AC signal is related to a strength of the detected AC signal.

4. The position detecting device according to claim 1,

wherein the position indicator is provided with a resonant circuit including a coil and a capacitor,

wherein a signal induced in the resonant circuit based on the excitation signal supplied from the excitation coil and transmitted from the resonant circuit is detected as the AC signal from the position indicator, and

wherein based on a voltage of the detected AC signal, the strength of the excitation signal to be supplied from the excitation coil is controlled such that a level of an AC signal to be transmitted from the position indicator and detected in the position detecting area falls within a predetermined range.

5. A position detecting device for detecting an indicated position of a position indicator on a position detecting area, comprising:

a sensor configured to be arranged on the front surface of a liquid crystal display device to detect the indicated position of the position indicator, the sensor corresponding to the position detecting area;

an excitation coil arranged to surround a periphery of the position detecting area to supply driving power to circuitry of the position indicator; and

a controller configured to dynamically control a power of a signal to be supplied to the excitation coil according to information obtained from a signal received from the position indicator.

6. The position detecting device of claim 5, wherein the information is an indicated position of the position indicator.

7. The position detecting device of claim 5, wherein the information is a strength of the signal received from the position indicator.

8. The position detecting device according to claim 5, wherein the position indicator is provided with a resonant circuit for receiving the excitation signal from the excitation coil, and the driving power is generated in the position indicator based on an AC voltage output from the resonant circuit.

9. The position detecting device according to claim 8, wherein the position indicator is provided with a diode and a capacitor for generating the driving power, and the driving power is generated by rectifying the AC voltage output from the resonant circuit to obtain a DC voltage and storing the obtained DC voltage.

10. The position detecting device according to claim 8, wherein the position indicator is included in a pen, and wherein:

the position indicator is provided with a variable capacitor whose capacitance changes according to a pen pressure applied to a pen tip of the position indicator, and

the pen pressure applied to the position indicator is detected based on a change in the capacitance of the variable capacitor.

11. The position detecting device according to claim 5,

wherein the position indicator is provided with a coil, for receiving an excitation signal from the excitation coil, and an oscillator, and

wherein the position of the position indicator on the position detecting area of the position detecting device is detected by driving the oscillator provided in the position indicator based on the excitation signal supplied from the excitation coil and received by the coil, and detecting a high-frequency signal output from the oscillator with the sensor based on the interaction between the position indicator and the sensor.

12. A method of controlling power usage in a device that includes a position detecting device for detecting an indicated position of a position indicator on a position detecting area of the position detecting device, comprising:

supplying an excitation signal to the position indicator with an excitation coil provided to surround a periphery of the position detecting area of the position detecting device;

detecting, in the position detecting area, an AC signal transmitted from the position indicator based on the excitation signal supplied from the excitation coil; and

controlling a strength of the excitation signal to be supplied from the excitation coil, based on information obtained from the AC signal transmitted from the position indicator.

13. The method according to claim 12, further comprising detecting an indicated position of the position indicator from the AC signal, wherein the strength of the excitation signal to be supplied from the excitation coil is controlled based on the indicated position of the position indicator detected by the position detecting device.

14. The method according to claim 12, wherein the strength of the excitation signal to be supplied from the excitation coil is controlled based on information indicative of a strength of the AC signal transmitted from the position indicator.

15. The method according to claim 12,

wherein the position indicator is provided with a resonant circuit including a coil and a capacitor,

wherein, in the detecting, a signal induced in the resonant circuit based on the excitation signal supplied from the excitation coil and transmitted from the resonance circuit is detected as the AC signal from the position indicator, and

wherein, in the controlling, the excitation signal to be supplied from the excitation coil is controlled such that a voltage level of an AC signal transmitted from the position indicator and detected in the position detecting area falls within a predetermined range.

16. A computer readable medium containing a sequence of instructions that are executable by a controller to perform the method of claim 12.

17. A position detecting method for detecting an indicated position of a position indicator on a position detecting area of a position detecting device, comprising:

detecting the indicated position of the position indicator on the position detecting area of the position detecting device with a sensor arranged on a front surface of a liquid crystal display device, the sensor corresponding to the position detecting area;

supplying driving power to circuitry provided in the position indicator with an excitation coil that surrounds a periphery of the position detecting area of the position detecting device; and

dynamically controlling power of a signal to be supplied to the excitation coil according to the detected indicated position of the position indicator on the position detecting area and/or according to a signal level of a signal detected by the sensor based on interaction between the position indicator and the sensor.

18. The position detecting method according to claim 17, wherein the position indicator is provided with a resonant circuit for receiving the excitation signal from the excitation coil, and the driving power is generated based on an AC voltage output from the resonant circuit.

19. The position detecting method according to claim 18, wherein the position indicator is provided with a diode and a capacitor for generating the driving power, and the driving power is generated by rectifying the AC voltage output from the resonant circuit to obtain a DC voltage and storing the obtained DC voltage.

20. The position detecting method according to claim 18, wherein the position indicator is included in a pen, and wherein:

the position indicator is provided with a variable capacitor whose capacitance changes according to a pen pressure applied to a pen tip of the position indicator; and

the pen pressure applied to the position indicator is detected based on a change in the capacitance of the variable capacitor.

21. The position detecting method according to claim 17,

wherein the position indicator is provided with a coil, for receiving an excitation signal from the excitation coil, and an oscillator, and

wherein the position of the position indicator on the position detecting area of the position detecting device is detected by driving the oscillator provided in the position indicator based on the excitation signal supplied from the excitation coil and received by the coil, and detecting a high-frequency signal output from the oscillator with the sensor, based on the interaction between the position indicator and the sensor.