JPH05324166A - Cordless digitizer - Google Patents

Abstract

PURPOSE:To make it possible to omit an external circuit for driving a position indicator and a cord for connecting the external circuit to the position indicator. CONSTITUTION:When sine and cosine wave signals are respectively applied to two driving coils x1, x2 in a tablet 1, the position indicator 2 held in electromagnetically coupled status with the tablet 1 is driven and generates a magnetic field and the position of the indicator 2 can be calculated from voltage induced in the 1st and 2nd receiving coils y1, y2, so that an external circuit for driving the indicator 2 or a cord can be omitted. Since the whole positions of the indicator 2 in the X and Y directions are detected from the 1st and 2n detecting coil groups Zx, Zy, the partial position in the Y direction is calculated from the induced voltage values of the receiving coils y1, y2 and the partial position in the X direction can be calculated from a phase difference between the induced voltages and the driving signals applied to the driving coils x1, x2, a scanner for detecting the position is made unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordless digitizer which comprises a tablet and a position indicator wirelessly connected to the tablet and detects the position of the position indicator mounted on the tablet.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 5, a conventional digitizer comprises a tablet 1 having a plurality of coils arranged in the X and Y directions and a position indicator 2. The drive circuit 4 for driving the motor 2 and the position indicator 2 are of a wired type connected by a cord 3. When the position indicator 2 is placed on the tablet 1 and the position indicator 2 is driven by the drive circuit 4, the LC resonance circuit including the coil and the capacitor provided in the position indicator 2 resonates. The resonance of the position indicator 2 detects the voltage induced in the coil arranged on the tablet 1, whereby the XY plane position of the position indicator 2 is detected.

In addition, in this type of digitizer, a so-called cordless digitizer in which the cord 3 and the driving circuit 4 are omitted has been proposed in recent years. In such a cordless digitizer, when detecting the position of the position indicator 2 by an electromagnetic induction method, for example, the tablet 1
On the side, an oscillation coil group arranged in the X direction, a reception coil group arranged in the Y direction orthogonal to the transmission coil group, and an oscillator for giving a current signal of a predetermined frequency to the oscillation coil group are provided. The current signals are sequentially selected by the Y-axis scanner and applied to the oscillation coil group, and the induced voltage generated on the receiving coil group side by electromagnetic coupling with the oscillation coil group when the position indicator is placed on the tablet is set. The position of the position indicator is detected by detecting it through the scanning of the X-axis scanner.

[0004]

However, in the case of the first example of the related art, since the position indicator 1 and the drive circuit 4 are of a wired type connected by the cord 3, there is a drawback that the operability is poor. there were. Further, in the case of making the cordless as in the second example, there is a drawback that an expensive scanner such as an X-axis scanner or a Y-axis scanner is required, and the apparatus cannot be economically constructed.

[0005]

In order to solve such a problem, the present invention provides a first and second drive coils on the tablet side, in which a position indicator electromagnetically coupled to the tablet is provided with at least a coil and a capacitor. Is configured to generate a magnetic field by the energization of the first drive coil and the first drive coil arranged in a zigzag shape at equal intervals, and the first drive coil has a gap of 1/2 from that of the first drive coil A second drive coil arranged in a zigzag shape, a drive circuit for driving the first and second drive coils by supplying drive signals of a sine wave and a cosine wave, respectively, and first and second drive coils Of the first receiving coil, which is arranged orthogonal to the direction of arrangement and is arranged at equal intervals and in a zigzag shape to generate an induced voltage due to the magnetic field of the position indicator, and the distance between the first receiving coil and 1 / Evenly spaced with a gap of 2 The second receiving coil, which is arranged in a zigzag shape and generates an induced voltage by the magnetic field of the position indicator, and the second receiving coil, which are arranged in the same direction as the direction in which the first and second drive coils are arranged, The first detection coil group that detects the overall position in the first direction and the overall position in the second direction of the position indicator that is arranged so as to be orthogonal to the arrangement direction of the first and second drive coils A second detection coil group for detecting, a means for calculating a partial position of the position indicator in the second direction from the induced voltage, and a phase difference between the drive signal and the induced voltage signal in the first direction of the position indicator. The tablet is provided with means for calculating a partial position.

[0006]

When a sine wave signal and a cosine wave signal are applied to the first and second drive coils in the tablet, respectively, the position indicator placed on the tablet and in an electromagnetically coupled state with the tablet is driven to generate a magnetic field. The generated magnetic field induces a voltage in the first and second receiving coils, and as a result, the position of the position indicator is calculated. Therefore, when detecting the position of the position indicator, an external circuit for driving the position indicator and a code for connecting the external circuit and the position indicator can be omitted. In addition, the entire position of the position indicator in the first and second directions is detected from the first and second detection coil groups, and the partial position of the position indicator in the second direction is the induced voltage value of the receiving coil. Further, the partial position in the first direction is calculated from the phase difference between this induced voltage and the drive signal applied to the drive coil. As a result, the scanner is not required when detecting the position of the position indicator.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a cordless digitizer according to the present invention. In the figure, a tablet 1 for detecting the position of a position indicator 2 includes a first grid plate, first and second receiving coils y1 and y2 arranged in the X-axis direction, and a second grid plate. First and second drive coils x arranged in a zigzag pattern in the Y-axis direction at regular intervals.
1, x2, drive circuits 11, 12, phaser 13, oscillator 1
4, an amplifier 15, 16 and a processing circuit 17. In addition, z _X and z _Y are the Y direction and X of the position indicator 2.
It is a detection coil group for detecting a rough position in the direction.

Next, the general operation of the digitizer will be described with reference to FIG. When the sine wave voltage signal e _d1 and the cosine wave voltage signal e _d2 are applied to the drive coils x1 and x2 when detecting the position of the position indicator 2 in the X direction, FIG.
As shown in, the position indicator 2 including the coil and the capacitor is in a resonance state, and the alternating current i _c flows on the coil. As a result, an alternating magnetic field is generated from the position indicator 2. On the other hand, at this time, voltages e ₁ and e ₂ are induced in the receiving coils y1 and y2 by the alternating magnetic field, and the amplifiers 15,
It is sent to the processing circuit 17 via 16. Processing circuit 17
In, calculates a position in the induced voltage e _1, e ₂ of the position indicator from the value Y direction, X-direction position of the position indicator from the phase difference between the drive voltage e _d to be applied to the induced voltage e and the driving coil To calculate.

The position indicator 2 is composed of a coil and a capacitor as described above, and the LC resonance circuit resonates to generate a magnetic field when a current signal is applied to the drive coils x1 and x2. Therefore, it is a cordless type that does not require the separate drive circuit 4 and the cord 3 for connecting the drive circuit 4 and the position indicator 2 as in the conventional case. Here, the coil diameter D of the coil is set to be approximately 1/2 of the coil arrangement intervals L _x and L _y which will be described later, and the position indicator 2 has a plurality of other switches and this switch. A plurality of capacitors corresponding to is provided, and the switch information can be transmitted from the change in the frequency of the LC resonant circuit when the switch is pressed.

Next, FIG. 3 is a diagram showing the principle of position detection of the tablet for detecting the position of the position indicator 2. The position detection in this case is partial position detection within a predetermined arrangement interval of the drive coil and the reception coil arranged on each grid plate. In FIG. 3A, the drive coils x1 and x2 arranged on the second grid plate are both at a constant distance L.
_The driving coil x2 is disposed at a position L _X / 4 apart from the driving coil x1. Now, assuming that the voltage signal sinωt is applied only to the drive coil x1, the current i _cs flowing through the coil of the position indicator 2
Is i _cs = K cos φ · sin ωt (1)

Similarly, the voltage signal c is applied only to the drive coil x2.
If osωt is applied, the current i _cc flowing through the coil of the position indicator 2 is i _cc = Ksinφ · cosωt (2).

Accordingly, at the same time a voltage signal sin .omega.t to the driving coil x1, x2, current i _c flowing through the coil of the position indicator 2 when cos .omega.t is _{applied, i c = i cs + i} cc = Kcosφ · sinωt + Ksinφ · cosωt = Ksin (ωt + φ) (3)

Here, in FIG. 3A, assuming that the position of the position indicator 2 in the X direction is x, there is a relationship of φ = 2πx / L _X (4). When the equation (4) is modified, x = Since φ / 2πL _X (5), it can be seen that the position x of the position indicator 2 in the X direction is proportional to the phase φ.

Therefore, the current flowing through the position indicator 2 is i _{c as} follows: i _c = Ksin {ωt + (2πx / L _X )} (6)

When a current i _c as shown in the above equation (6) flows on the coil of the position indicator 2, the receiving coils y1 and y2 are received.
A voltage is induced in. That is, the induced voltage e ₁ of the receiving coil y1 is e ₁ = K ₂ cos θ · sin (ωt + φ) (7) where K ₂ is a proportional constant, φ = 2πx / L _X.

Further, the induced voltage e ₂ of the receiving coil y2 is e ₂ = K ₂ sin θ · sin (ωt + φ) (8)

Here, in FIG. 3B, assuming that the position of the position indicator 2 in the Y direction is y, there is a relationship of θ = 2πy / L _Y (9) and the above equations (7) and (8) are satisfied. Therefore, the induced voltages e ₁ and e ₂ of the receiving coils y1 and y2 are proportional to the position y. Therefore, if the induced voltages e ₁ and e ₂ are measured, the position y of the position indicator 2 is determined from these values.

However, the positions x and y thus obtained are the positions within the disposition interval of the drive coil and the receiving coil, and it is not possible to determine where the position indicator 2 is located on the entire tablet. .. In general, FIG.
As shown in (a), the direction of the current flowing through the coil z0 differs depending on whether the position indicator 2 that generates a magnetic field is present in the region A or in the region B. Here, when the position indicator 2 is in the area A, the direction of the current generated in the coil is “ON”, and when it is in the area B, the direction of the current generated in the coil is “OFF”, and the first detection is performed. Coil z _x
1, z _X 2 are drive coils x1, as shown in FIG.
If it is arranged so that it is twice or four times the arrangement interval of x2,
It is possible to identify four areas. When it is desired to identify eight areas, three detection coils are provided as shown in FIG. In this way, if the tablet surface is wide and a large number of drive coils are distributed and you want to increase the number of area identifications, add the number of detection coils and
The additional detection coils are arranged so as to have a pitch 16 times, 32 times, ...

By arranging the first detection coil group in this way, it is possible to transmit to the processing circuit 17 rough position information indicating where the position indicator 2 exists in the eight regions. As a result, the position of the position indicator 2 is roughly determined in the processing circuit 17, and the position indicator in the X-axis direction is determined from the rough position (overall position) and the partial position x within the coil arrangement interval described above. Two exact positions can be determined. If the second detecting coil group z _Y is provided and the second detecting coil group is arranged in the receiving coil arranging direction, the overall position of the position indicator 2 in the Y-axis direction can be similarly obtained. You can

[0020]

As described above, according to the present invention, when a sine wave signal and a cosine wave signal are respectively applied to the first and second drive coils in the tablet, they are placed on the tablet and electromagnetically coupled with the tablet. Since the position indicator in is driven to generate a magnetic field and the generated magnetic field detects the voltage induced in the first and second receiving coils, the position of the position indicator is calculated. An external circuit for driving the position indicator and a code for connecting the external circuit and the position indicator can be omitted when detecting the position of the indicator. The entire position of the position indicator in the first and second directions is detected from the first and second detection coil groups, and the partial position of the position indicator in the second direction is the induced voltage value of the receiving coil. Further, since the partial position in the first direction is calculated from the phase difference between this induced voltage and the drive signal given to the drive coil, an expensive scanner can detect the position of the position indicator. It becomes unnecessary and the device can be economically constructed.

[Brief description of drawings]

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

FIG. 2 is a diagram illustrating an outline of an operation of detecting a position of a position indicator in the digitizer.

FIG. 3 is a diagram showing a principle of detecting a partial position of a position indicator in the digitizer.

FIG. 4 is a diagram showing a principle of detecting the entire position of a position indicator in the digitizer.

FIG. 5 is a block diagram of a conventional digitizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 tablet 2 position indicator 11,12 drive circuit 13 phaser 14 oscillator 15,16 amplifier 17 processing circuit x1, x2 drive coil y1, y2 receiving coil z1-z3 first detection coil

Claims (1)

[Claims] 1. A cordless digitizer, comprising a tablet and a position indicator electromagnetically coupled to the tablet, for detecting the position indicated by the position indicator mounted on the tablet, wherein the cordless digitizer has a regular interval and a zigzag shape. A first drive coil arranged in a zigzag shape and a second drive coil arranged in a zigzag shape at equal intervals with a gap of 1/2 between the first drive coil and the first drive coil; , A drive circuit for driving the second drive coil by applying drive signals of a sine wave and a cosine wave, respectively, and the first and second drive coils.
The position indicator that generates a magnetic field in response to energization of the second drive coil and the position indicator that are arranged orthogonal to the direction in which the first and second drive coils are arranged and are arranged at equal intervals in a zigzag shape. A first receiving coil that is installed and generates an induced voltage by the magnetic field of the position indicator;
Second receiving coils which are arranged in a zigzag shape with a gap of / 2 and which generate an induced voltage by the magnetic field of the position indicator, and the disposing directions of the first and second drive coils. And a first detection coil group that is arranged in the same direction as the position indicator and detects the entire position of the position indicator in the first direction, and is arranged so as to be orthogonal to the direction in which the first and second drive coils are arranged. A second detection coil group for detecting the overall position of the position indicator in a second direction orthogonal to the first direction, and a partial position of the position indicator in the second direction are calculated from the induced voltage. A cordless digitizer comprising: means and means for calculating a partial position of the position indicator in the first direction from a phase difference between the drive signal and the induced voltage signal.