JP3120256B2 - Cordless digitizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordless digitizer comprising a tablet and a position indicator wirelessly connected to the tablet, for detecting the position of a position indicator mounted on the tablet.

[0002]

2. Description of the Related Art In a conventional cordless digitizer of this type, when detecting the position of a position indicator by an electromagnetic induction method, for example, an oscillating coil group and a transmitting coil group arranged in the X direction on the tablet side, for example. A receiving coil group arranged in the Y direction orthogonal to the oscillator, and an oscillator for providing a current signal of a constant frequency to the oscillation coil group. The current signal from the oscillator is sequentially applied to the oscillation coil group, and the position indicator is a tablet. When mounted above, the position of the position indicator is detected by detecting an induced voltage generated on the receiving coil group side due to electromagnetic coupling with the oscillation coil group. That is, when the position indicator is placed on the tablet, the oscillation coil supplied with the current and the position indicator are electromagnetically coupled, and as a result, an induced voltage is generated on the receiving coil group side. The induced voltage generated in the receiving coil group is sequentially scanned and detected, and the plane position of the position indicator on the tablet is determined from the X direction position of the transmitting coil to which the current is supplied and the Y direction position of the receiving coil where the induced voltage is generated. I try to detect. The position indicator is provided with an oscillator, and a current signal having a constant frequency is applied to the coils in the position indicator to generate a magnetic field. The position and the like can also be detected.

[0003]

However, when the position of the position indicator is detected by such an electromagnetic induction method, a method of generating a magnetic field from a group of oscillating coils on the tablet side or a coil of the position indicator is used. In any of the methods for generating a magnetic field from the above, there is an oscillator for generating a magnetic field, and there is a disadvantage that the device configuration becomes complicated.

[0004]

SUMMARY OF THE INVENTION In order to solve such a problem, the present invention provides a position indicator as an electric circuit having at least one of a coil and a capacitor. A grid group which is configured and for which a voltage is induced by electromagnetic coupling between a second loop coil group and a position indicator arranged in the Y-axis direction, for example;
1. A tablet comprising: an adder for adding a sum of induced voltages generated in each grid line; and an amplifier for amplifying an output signal from the adder and transmitting the amplified signal to a second loop coil group. It is.

[0005]

As a result, when measuring the position pointer, a self-oscillation system including the second loop coil group, the position pointer, the grid group, the adder and the amplifier is formed, and the second loop coil group is disposed in the X direction. The position of the position indicator in the X direction is detected based on the output of one loop coil group, and the position in the Y direction is detected based on the output of the amplifier.

[0006]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of a cordless digitizer according to the present invention. FIG. 1A shows the configuration of a position indicator 1 and FIG. 1B shows the configuration of a tablet. ing.

In FIG. 1A, a position indicator 1 includes a coil 10, a first capacitor 11, and a second capacitor 1.
2 and a switch 13. Here, the first
The capacity of the capacitor 11 varies according to the contact pressure with the tablet unit 20. Further, the second capacitor 12 is connected in parallel with the first capacitor 11 via the switch 13, and serves to identify the ON / OFF operation (operation information) of the switch 13.

In FIG. 1B, an X-side loop coil group x1, formed on a first grid plate and sequentially arranged in the X direction and insulated from each other, is
, xn, and Y-side loop coil groups y1, which are formed on a second grid plate different from the X-axis loop coil group, are sequentially arranged in the Y direction, and are insulated from each other.
, yn and a third grid group 21 formed on the third grid plate. One end of each loop coil of the X-side loop coil group and the Y-axis loop coil group is connected to the ground,
The other ends are connected to an X-axis scanner SCNX and a Y-axis scanner SCNY, respectively. Similarly, the third grid group 21 formed on the third grid plate has one end connected to the ground, and the other end connected to the input side of the adder 22.

Here, the Y-axis scanner SCNY sequentially selects the Y-axis loop coil group based on an address signal Y from a control circuit (not shown). At this time, an AC current from an amplifier 24 described later is selected. Applied to the Y-axis loop coil. On the other hand, the X-axis scanner SCNX sequentially selects a group of X-axis loop coils based on an address signal X from the control circuit when a certain Y-axis loop coil is selected by the Y-axis scanner SCNY. If the position indicator 1 is placed on the tablet unit 20 at this time, a voltage is induced in the X-axis loop coil, and the output information (induction voltage) of the selection result by the X-axis scanner SCN
Are amplified by the amplifier 25 and output as position information a of the position indicator 1 in the X direction.

At this time, the signal from the third grid group 21 via the adder 22 is output almost in synchronism with the signal applied to the Y-axis loop coil. After amplification, it is output as Y-direction position information b of the position indicator 1. The Y-direction position information b is further amplified by the above-described amplifier 24, output to an external circuit as attribute information c, and sent to the Y-axis scanner SCNY.

FIG. 4 is a diagram showing the structure of the tablet unit 20, which includes a Y-axis loop coil group formed on a second grid plate and a third grid group 21 formed on a third grid plate. Shows the arrangement status of. As described above, when the driving loop coil yi (coil driven by the output of the amplifier 24) is disposed at the center point of the inter-coil width W of the third grid group 21 and an alternating current is applied, the position indicator 1 When not present in the vicinity, the magnetic fields generated between the adjacent loop coils cancel each other and no electromagnetic coupling occurs, so that no current is induced in the third grid group 21. However, when the position indicator 1 is moved closer, a current is induced in the third grid group 21 in the direction of the arrow to form a self-oscillation system. FIG.
FIG. 2 is a diagram showing the principle of a self-oscillation system having such a current loop. In the drawing, L0, Li, and Lj indicate the inductance of each coil, and c indicates the capacitance of the capacitor.

FIG. 2 is a timing chart showing a measuring operation of the digitizer for measuring the position information and the like of the position indicator 1, and FIG. 3 is a diagram showing an induced voltage generated in the X-axis loop coil group and the Y-axis loop coil group. It is a figure showing the measurement result of.
The detailed operation of the cordless digitizer will be described with reference to FIGS. As described above, the Y-axis scanner SCNY
, The loop coil y1 is selected and the amplifier 24
[FIG. 2 (a)]. If the position indicator 1 is placed close to the loop coil y1 at this time, a self-oscillation system is formed to be in an oscillating state. , A voltage is induced [FIG. 2 (b)]. That is, a self-oscillation system including the loop coil y1, the position indicator 1, the third grid group 21, the adder 22, the amplifier 23, and the amplifier 24 is formed, and a current flows in this system.
In this case, a magnetic field is generated from the coil 10 of the position indicator 1, and a voltage is induced on the X-axis loop coil group side.

In this case, the X-axis scanner SCNX sequentially scans the loop coils x1 to xn according to the address signal X [FIG. 2 (c)]. The scanning result of the X-axis scanner SCNX is amplified by the amplifier 25, and as a result, for example, measurement data of the X-axis loop coil group as shown in FIG. 3A is obtained. The position in the X direction of the position indicator 1 is calculated from three points A, B, and C near the peak value among these measurement data.

On the other hand, at this time, the sum of the voltages induced on each grid line in the third grid group 21 is added in the adder 14, and the output of the adder 14 is amplified by the amplifier 15. As a result, for example, as shown in FIG.
Measurement data of the shaft loop coil group is obtained. The position in the Y direction of the position indicator 1 is calculated from three points D, E, and F near the peak value among these measurement data. As described above, the present digitizer can detect the position of the position indicator 1 without using an oscillator, so that the configuration can be simplified.

[0015]

As described above, according to the present invention, at the time of measuring the position indicated by the position indicator, for example, the second loop coil group, the position indicator, the grid group, and the adder disposed in the Y direction. A self-oscillation system including an amplifier and an amplifier is formed, and the positions of the position indicator in the X and Y directions are detected from the output of the first loop coil group disposed in the X direction and the output of the amplifier. Oscillator for driving the loop coil can be omitted, so that the device configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a cordless digitizer according to the present invention.

FIG. 2 is a timing chart showing a scanning situation of each loop coil group of the digitizer.

FIG. 3 is a graph showing a measurement result of an induced voltage generated in each of the loop coils.

FIG. 4 is a diagram showing an arrangement state of each coil of the digitizer.

FIG. 5 is a diagram showing the principle of detecting the position of a position indicator in the digitizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Position indicator 10 Coil 11, 12 Capacitor 13 Switch 20 Tablet part SCNX X-axis scanner SCNY Y-axis scanner 21 Third grid group 22 Adder 23-25 Amplifier a X-direction position information b Y-direction position information c Attribute information

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-307522 (JP, A) JP-A-2-253419 (JP, A) JP-A-4-7720 (JP, A) JP-A-5-205 241722 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G06F 3/03

Claims (1)

(57) [Claims] 1. A tablet provided with first and second loop coil groups disposed in the X-axis and Y-axis directions and insulated from each other, and the tablet via the first and second loop coil groups. A cordless digitizer for detecting a position indicated by the position indicator mounted on the tablet, the position indicator having at least one of a coil and a capacitor. And a voltage guide formed by a plurality of grid lines and induced by electromagnetic coupling between one of the first and second loop coil groups and the position indicator. A group, an adder for adding the sum of the induced voltages generated in each of the grid lines, an output signal from the adder, and an amplified signal, An amplifier for transmitting to one of the second loop coil groups; and an output of the amplifier and one of the first and second loop coil groups. A cordless digitizer characterized by detecting an indicated position of the position indicator from an output of the cordless digitizer.