Electromagnetic Induction Handwriting System and Coordinate Determining Method Thereof

• US 20100206644A1
• Filed: 04/10/2009
• Published: 08/19/2010
• Est. Priority Date: 02/13/2009
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Waltop International Corp.
• Inventors: Yeh, Chia-Jui
• Granted Patent: US 8,278,572 B2
• Time in Patent Office: Days
• US Class Current: 178/18.70
• CPC Class Codes: G06F 3/03545 Pens or stylus

Abstract

The present invention discloses an electromagnetic induction handwriting system and its single side coordinate determining method for determining a coordinate of a stylus on a handwriting apparatus. The coordinate is computed by a first voltage, a second voltage, and a third voltage, where the first voltage equals the maximum detection voltage, the second voltage and the third voltage are obtained from two antennas, and both of the two antennas are arranged at the same side of the antenna that induces the maximum detection voltage.

Claims

1. An electromagnetic induction handwriting system, comprising:

a stylus;

a handwriting device;

an x-y loop antenna array arranged inside of said handwriting device;

a switch circuit;

a coordinate computation circuit;

an analog/digital (A/D) converter;

a microprocessor; and

a computer;

wherein said microprocessor instructs specific antennas of said x-y loop antenna array by switching said switch circuit to detect electromagnetic wave radiated from said stylus, the detection voltages from the antennas comprising a first voltage, a second voltage, and a third voltage are transmitted to the coordinate computation circuit to compute a coordinate of the stylus, the computed coordinate is transmitted to analog/digital (A/D) converter to convert to digital values, and said microprocessor processes the digital coordinate values then transmitting it to said computer; and

wherein the first voltage equals the maximum detection voltage, the second voltage and the third voltage are obtained from two antennas, and both of the two antennas are arranged at the same side of the antenna that induces the maximum detection voltage.

2. The system as recited in claim 1, wherein said stylus comprises cordless type or battery less type of stylus.

3. The system as recited in claim 1, wherein said stylus comprises an oscillating circuit consisting of LC (inductors and capacitors) and comprises a plurality of push buttons, the push buttons being pressed down then recovered, such that vary the capacitance of LC, and thus vary the frequency of the oscillating circuit.

4. The system as recited in claim 1, wherein said microprocessor proceeds with a full scan and a local scan to determine which side of antennas is employed for acquiring the second and third voltages.

5. The system as recited in claim 1, wherein said x-y loop antenna array is arranged inside said handwriting device in a double-faced, arrayed, and equidistant manner, and the layout of said x-y loop antenna is symmetrical and the pitch between two antenna is designed to meet the equation, aX²+bXY+cY²+dX+eY+f=0, wherein the parameters a, b, c, and d in the above equation satisfy the equations b²−

4ac=0 and d=0.

6. The system as recited in claim 1, wherein the second voltage is obtained by an antenna that is the nearest antenna to the antenna that senses the first voltage, and third voltage is obtained by an antenna that is the nearest antenna to the antenna that senses the second voltage.

7. The system as recited in claim 1, wherein the second voltage is obtained by an antenna that has double pitch with the antenna that senses the first voltage, the third voltage is obtained by an antenna that has double pitch with the antenna that senses the second voltage, and the pitch is the distance between antennas.

8. A coordinate determining method for determining a coordinate of a stylus on a handwriting device, comprising the steps of:

providing a x-y loop antenna array;

proceeding with a sequence of comparison procedure to compare the detection voltages of the x-y loop antenna array with a noise-judge value, such that a first voltage, a second voltage, and a third voltage are obtained, wherein the first voltage equals the maximum detection voltage, the second voltage and the third voltage are obtained from two antennas, and both of the two antennas are arranged at the same side of the antenna that induces the maximum detection voltage; and

computing the coordinate of the stylus according to the first voltage, the second voltage, and the third voltage.

9. The method as recited in claim 8, wherein the x-coordinate of the stylus is computed by the following equation:

10. The method as recited in claim 9, wherein the y-coordinate of the stylus is computed by the same theory.