JP3138972B2 - 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 Generally, a conventional digitizer comprises a tablet 1 having a plurality of coils arranged in X and Y directions and a position indicator 2, as shown in FIG. The drive circuit 4 for driving the drive 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 drive circuit 4 drives the position indicator 2, the LC resonance circuit including the coil and the capacitor provided in the position indicator 2 resonates. By detecting the voltage induced in the coil disposed on the tablet 1 by the resonance of the position indicator 2, the XY plane position of the position indicator 2 is detected.

In addition, among these types of digitizers, a so-called cordless digitizer in which the code 3 and the drive circuit 4 are omitted in recent years has been proposed. In such a cordless digitizer, for example, when detecting the position of the position indicator 2 by an electromagnetic induction method, 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 that supplies a current signal of a predetermined frequency to the oscillation coil group are provided. Are sequentially selected by the Y-axis scanner and applied to the oscillation coil group, and the induced voltage generated on the reception coil group side by electromagnetic coupling with the oscillation coil group when the position indicator is mounted on the tablet. The position of the position indicator is detected by detecting through scanning of the X-axis scanner.

[0004]

However, in the case of the first example of the prior art, since the position indicator 1 and the drive circuit 4 are of a wired type in which the cords 3 are connected, the operability is poor. there were. Further, in the case of cordless as in the second example, expensive scanners such as an X-axis scanner and a Y-axis scanner are required, and there is a disadvantage that the apparatus cannot be configured economically.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a position indicator that is electromagnetically coupled to a tablet and includes at least a coil and a capacitor. And a first drive coil disposed at regular intervals and in a zigzag manner, and at a regular interval having a deviation of 1/2 from that of the first drive coil. A second drive coil disposed in a zigzag pattern, a drive circuit for applying drive signals of sine and cosine waves to the first and second drive coils, respectively, and first and second drive coils A first receiving coil, which is disposed orthogonally to the direction of disposition and is disposed at equal intervals and in a zigzag manner, and generates an induced voltage due to the magnetic field of the position indicator; Equally spaced with 2 shifts A second receiving coil, which is arranged in a zigzag manner and generates an induced voltage by the magnetic field of the position indicator, and a position indicator which is arranged in the same direction as the direction in which the first and second drive coils are arranged. A first detection coil group for detecting an entire position in a first direction, and an entire position in a second direction of a position indicator that is disposed so as to be orthogonal to an arrangement direction of the first and second drive coils. A second detection coil group to be detected, means for calculating a partial position of the position indicator in the second direction from the induced voltage, and a position indicator in the first direction from the phase difference between the drive signal and the induced voltage signal Means for calculating a partial position are provided in the tablet.

[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. As a result, a voltage is induced in the first and second receiving coils by the generated magnetic field, so that 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 to 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 an induced voltage value of the receiving coil. And the partial position in the first direction is calculated from the phase difference between the induced voltage and the drive signal applied to the drive coil. As a result, a scanner becomes unnecessary when detecting the position of the position indicator.

[0007]

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. In FIG. 1, a tablet 1 for detecting the position of a position indicator 2 and the like includes a first and a second receiving coils y1, y2 arranged in the X-axis direction on a first grid plate, and a second grid plate. First and second drive coils x disposed at regular intervals in a zigzag manner in the Y-axis direction
1, x2, drive circuits 11 and 12, phase shifter 13, oscillator 1
4. It comprises amplifiers 15 and 16 and a processing circuit 17. Here, z _X and z _Y are the Y direction of the position indicator 2 and X
This is a detection coil group for detecting a rough position in the direction.

Next, a schematic operation of the present digitizer will be described with reference to FIG. When the sine wave voltage signal _ed1 and the cosine wave voltage signal _ed2 are applied to the drive coils x1 and x2, respectively, when detecting the position of the position indicator 2 in the X direction, FIG.
As shown in the figure, the position indicator 2 composed of a coil and a capacitor enters a resonance state, and an alternating current _ic 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, the receiving coils y1 and y2 are
Voltages e ₁ and e ₂ are induced by the BR> th magnetic field, and the amplifier 1
The data is sent to the processing circuit 17 via the processing circuits 5 and 16. The processing circuit 17 determines the position indicator Y based on the values of the induced voltages e ₁ and e _2.
Calculates a position in the direction, it calculates the 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.

The position indicator 2 is composed of a coil, a capacitor, and the like as described above, and generates a magnetic field by resonating the LC resonance circuit by applying a current signal to the drive coils x1 and x2. Therefore, it is a cordless type which does not require a separate drive circuit 4 and a cord 3 for connecting the drive circuit 4 and the position indicator 2 as in the related art. The coil diameter D of the coil is a coil arrangement distances L _x to be described later, is defined so as to be substantially 1/2 of the L _y, also, a plurality of switches and switch to another in the position indicator 2 Are provided, and switch information can also be transmitted from a change in the frequency of the LC resonance circuit when the switch is pressed.

FIG. 3 is a view showing the principle of detecting the position of the tablet for detecting the position of the position indicator 2. Note that the position detection in this case is a partial position detection within a predetermined arrangement interval of the drive coils and the reception coils 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 interval L.
_The driving coil x2 is shifted from the driving coil x1 by L _X / 4. Now, when the voltage signal sinωt and is applied only to the driving coil x1, current i _cs flowing through the coil of the position indicator 2
Is a _{i cs = Kcosφ · sinωt (1} ).

Similarly, the voltage signal c is applied only to the driving coil x2.
When osωt is applied, the current i _cc flowing through the coil of the position indicator 2 becomes _{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, if the position of the position indicator 2 in the X direction is x, there is a relationship of φ = 2πx / L _X (4). φ / 2πL _X (5), which indicates that the position x of the position indicator 2 in the X direction is proportional to the phase φ.

[0014] Thus, the current i _c flowing to the position indicator 2, and _{i c = Ksin {ωt + (} 2πx / L X)} (6).

When a current _ic as shown in the above equation (6) flows on the coil of the position indicator 2, the receiving coils y1, y2
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 and φ = 2πx / L _X.

Further, the induced voltage e ₂ of the receiving coil y2 is as follows: 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) Therefore, the induced voltages e ₁ and e ₂ of the receiving coils y 1 and y ₂ 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 obtained in this manner are positions within the arrangement interval of the driving coil and the receiving coil, and it is not possible to obtain the position of the position indicator 2 on the whole tablet. . Generally, FIG.
As shown in (a), the direction of the current flowing through the coil z0 differs between the case where the position indicator 2 that generates the magnetic field exists in the region A and the case where the position indicator 2 exists in the region B. Here, the direction of the current generated in the coil when the position indicator 2 is in the area A is “ON”, and the direction of the current generated in the coil when the position indicator 2 is in the area B is “OFF”. Coil z _X
1 and z _X 2 as shown in FIG.
When it is arranged so as to be twice or four times the arrangement interval of x2,
Four types of areas can be identified. When it is desired to identify eight types of regions, three detection coils are provided as shown in FIG. As described above, when the tablet surface is wide and a large number of drive coils are arranged and distributed, and it is desired to increase the number of region identifications, the number of detection coils is added, and
The added detection coils are arranged so as to be further 16 times, 32 times,... The arrangement pitch of the drive coils.

By arranging the first detection coil group in this manner, rough position information indicating where the position indicator 2 exists in the eight areas can be transmitted to the processing circuit 17. 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 approximate position (entire position) and the partial position x within the above-described coil arrangement interval. 2 accurate positions can be obtained. Incidentally, a second detection coil group z _Y, if provided the second detection coil group in the laying direction of the receiving coils, be determined in the same manner the entire position in the Y-axis direction of the position indicator 2 Can be.

[0020]

As described above, according to the present invention, when a sine wave signal and a cosine wave signal are applied to the first and second drive coils in the tablet, respectively, the tablet is placed on the tablet and is in an electromagnetically coupled state with the tablet. Is driven to generate a magnetic field, and a voltage induced in the first and second receiving coils by the generated magnetic field is calculated to calculate the position of the position indicator. When detecting the position of the pointer, an external circuit for driving the position indicator and a code for connecting the external circuit to the position indicator can be omitted. Further, 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 determined by the induced voltage value of the receiving coil. And the partial position in the first direction is calculated from the phase difference between the induced voltage and the drive signal applied to the drive coil. Therefore, when detecting the position of the position indicator, an expensive scanner is used. This is unnecessary, and the apparatus can be configured economically.

[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 diagram schematically illustrating an operation of detecting the 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 the 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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-24717 (JP, A) JP-A-58-199101 (JP, A) JP-A-1-113822 (JP, A) JP-A-4-113 326418 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06F 3/03

Claims (1)

(57) [Claims] 1. A cordless digitizer, comprising a tablet and a position indicator electromagnetically coupled to the tablet, for detecting a position indicated by the position indicator mounted on the tablet, comprising: A first drive coil disposed in the first drive coil, a second drive coil disposed in an equidistant and zigzag manner with a shift of 間隔 from the distance between the first drive coils, and the first drive coil; , A driving circuit that supplies sine-wave and cosine-wave driving signals to the second driving coil, respectively;
The position indicator for generating a magnetic field in accordance with the energization of the second drive coil; and a position indicator that is disposed orthogonal to the direction in which the first and second drive coils are disposed and that is disposed at equal intervals and in a zigzag shape. A first receiving coil for generating an induced voltage by a magnetic field of the position pointing device;
/ 2, a second receiving coil which is arranged in a zigzag manner at regular intervals and has a zigzag shape and which generates an induced voltage by the magnetic field of the position indicator, and an arrangement direction of the first and second drive coils. And a first detection coil group that is disposed in the same direction as the first direction and detects the entire position of the position indicator in a first direction, and is disposed so as to be orthogonal to the direction in which the first and second drive coils are disposed. And a second detection coil group for detecting an entire 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 is calculated from the induced voltage. And a means for calculating a partial position of the position indicator in a first direction from a phase difference between the drive signal and the induced voltage signal.