JPH05181594A - Position detecting device - Google Patents

Abstract

PURPOSE:To reduce the invalid area of a sense part by obtaining the coordinates of a designated position with a 2nd coordinate value calculating means when a position pointer is moved to the invalid area. CONSTITUTION:A 2nd coordinate value calculating means 5 detects the coordinate value based on two signal levels including the highest one of those signal levels dependent on the distance between a position pointer 2 and a loop coil of a sense part 1. Then it is supposed that the pointer 2 moves to an area (an invalid area) where the coordinate value cannot be calculated by a 1st coordinate value calculating means 4 set in the position detecting direction of the part 1. Under such conditions, an area deciding/switching means 6 detects the movement of the pointer 2 and switches the means 4 to the means 5 to detect the coordinate value of the position designated by the pointer 2. Thus, the area can be increased for calculation of the coordinate value of the position designated by the pointer 2. Then the invalid area of the part 1 can be reduced and the availability of a position detector is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device utilizing electromagnetic action.

[0002]

2. Description of the Related Art Conventionally, there has been provided a position sensing device having a plurality of loop coils arranged side by side in a position detecting direction and a position pointing device having at least coils, and the position pointing device is based on an electromagnetic action between them. There is known a position detecting device that obtains coordinate values of a specified position by the.

In position detection in this type of device, one loop coil is selected from a plurality of loop coils of the sensing section, and a position indication is made when an AC signal is supplied to the one loop coil (or the coil of the position indicator). Generated in the coil of the device (or the one loop coil) or excited by the radio wave generated by the one loop coil or another loop coil The level of the alternating signal generated is detected and the loop coil that selects it is sequentially switched and repeated. At this time, a predetermined calculation is performed using the signal level depending on the distance between the position indicator and each loop coil obtained. It was done by the matter.

FIG. 2 shows the signals generated in the main part of the sense part and the respective loop coils of the conventional position detecting device of this type. In the figure, a, b, c, d, ... Are loop coils each having a width D, and are arranged side by side at a pitch P in the position detection direction, here the X direction. Also, Ea,
Eb, Ec, Ed, ... are X position indicators (not shown).
When each loop coil a, b, c, d,
...... indicates the signal that occurs.

By the way, there are various methods of calculating the coordinate value described above, but the maximum signal level, that is, the signal level when the loop coil closest to the position indicator is selected and the loop coils on both sides thereof are respectively selected. A method is generally known in which calculation is performed based on three signal levels, which are the signal levels at the time of the operation.

[0006]

However, in the vicinity of both ends in the position detecting direction of the sensing portion of the device, the above-mentioned 3
There is a region in which one signal level cannot be obtained (hereinafter referred to as an invalid area), and there is a drawback that position detection cannot be performed in the invalid area. Further, the size of the invalid area is determined by the calculation method of the width of the loop coil and the coordinate value, and the size of the entire sensing portion, in other words, the size of the area where the position can be detected (hereinafter referred to as the effective area). Since they are irrelevant, there is a problem that the ratio of the invalid area in the sense section becomes large especially in the case of being integrally combined with the liquid crystal display panel or in a small size used for an electronic notebook.

In FIG. 2, the position x ₀ at one end of the sensing portion is shown.
And a position x _{1 at} which the signals Ea and Eb intersect are an invalid area when the coordinate value calculation method based on the above-mentioned three signal levels is used, and although not shown, the other end side of the sensing unit is provided. Has a similar invalid area.

In view of the above conventional problems, it is an object of the present invention to provide a position detecting device having a small invalid area in the sensing section.

[0009]

FIG. 1 shows an outline of a position detecting device according to the present invention. In the figure, 1 is a sensing unit, 2 is a position indicator, 3 is a loop coil selection / level detecting unit, and 4 is a unit.
Is a first coordinate value calculation means, 5 is a second coordinate value calculation means,
Reference numeral 6 is an area determination / switching means.

The sense unit 1 has a plurality of loop coils (not shown) arranged in parallel in the position detecting direction.

The position indicator 2 has at least a coil (not shown).

The loop coil selection / level detection means 3 is
When one loop coil is selected from the plurality of loop coils of the sensing unit 1 and an AC signal is supplied to the one loop coil (or the coil of the position indicator 2), the coil of the position indicator 2 (or the one of the one Occurring in the loop coil), or in the one loop coil by the radio wave transmitted from the tuning circuit (not shown) of the position indicator 2 excited by the radio wave generated by the one loop coil or another loop coil. The loop coil that detects the level of the AC signal and selects it is sequentially switched and repeated. At this time, the position indicator 2
And the signal level depending on the distance between the loop coil and each loop coil is obtained.

The first coordinate value calculating means 4 comprises a position indicator 2
The coordinate value is calculated from three signal levels including the maximum signal level among the signal levels depending on the distance between the loop coil and each loop coil.

The second coordinate value calculation means 5 includes the position indicator 2
The coordinate value is calculated from the two signal levels including the maximum signal level among the signal levels depending on the distance between the loop coil and each loop coil.

The area determining / switching means 6 is an area in which the position indicator 2 can calculate the coordinate value by the first coordinate value calculating means 4 from the signal level depending on the distance between the position indicator 2 and each loop coil. Or in the area in which the coordinate value can be calculated by the second coordinate value calculating means 5, and which of the first and second coordinate value calculating means is used is switched based on the judgment result. It is like this.

[0016]

According to the present invention, when the position indicator 2 moves to an area where the first coordinate value calculating means 4 cannot calculate the coordinate values in the vicinity of both ends in the position detecting direction of the sensing section 1, this is the area determining / switching means. 6, the calculation of the coordinate value of the designated position by the position indicator 2 is switched from the first coordinate value calculation means 4 to the second coordinate value calculation means 5, whereby the designated position of the position indicator 2 is changed. The area where the coordinate value can be calculated is expanded, and the invalid area occupied in the sense unit 1 is reduced.

[0017]

FIG. 3 shows an embodiment of the position detecting device of the present invention, which is applied to a device for reciprocating a radio wave between a sense part and a position indicator to obtain coordinate values of a specified position. Here is an example: In the figure, 11 is a sense unit, 12 is a position indicator,
13 is a selection circuit, 14 is a transmission / reception switching circuit, 15 is an oscillator,
Reference numeral 16 is a signal detection circuit, and 17 is a processing device.

The sense section 11 comprises a large number of loop coils a, b, c, d, ... Shown in the prior art. The position indicator 12 has a built-in tuning circuit 18 having a tuning frequency f _{0 and including} passive elements such as a coil and a capacitor.

The selection circuit 13 selects one loop coil from the many loop coils of the sense section 11,
It operates based on the selection information from the processing device 17. The transmission / reception switching circuit 14 alternately connects the selected one loop coil to the oscillator 15 and the signal detection circuit 16, and operates based on the switching signal from the processing device 17. The oscillator 15 generates a reference clock having the same frequency as the tuning frequency f ₀ and supplies the reference clock to the transmission / reception switching circuit 14 via the processing device 17 and a low-pass filter and a drive circuit (not shown). The signal detection circuit 16 is an amplifier, and the frequency f _{0 is}
Which is a pass band, a detector and a low pass filter, and outputs a DC signal having a level according to the energy of the frequency f ₀ component in the received signal.

The processing unit 17 is composed of a well-known microprocessor or the like, and controls each circuit according to a predetermined program. FIG. 4 shows a flow of a program in the processing device 17. The program, the selection circuit 13, the transmission / reception switching circuit 14, the oscillator 15, the signal detection circuit 16 and the processing device 17 make the loop coil selection / level detection means 3 described above. And the program and processing device 1
Therefore, the first coordinate value calculating means 4, the second coordinate value calculating means 5 and the area determining / switching means 6 described above are realized.

The operation of this apparatus will be described below.

First, the processing device 17 sends information for selecting one loop coil of the sense section 11 to the selection circuit 13 and also sends a signal for selecting the transmission side to the transmission / reception switching circuit 14, and the one of the above-mentioned ones. A sine wave signal of frequency f ₀ based on the reference clock of the oscillator 15 is supplied to the loop coil to generate a radio wave of frequency f ₀ . At this time, if the position indicator 12 is placed on the sensing unit 11, the radio wave excites the tuning circuit 18 to generate an induced voltage of frequency f ₀ .

When the processing device 17 sends a signal for selecting the transmitting side to the transmission / reception switching circuit 14 for a certain period of time, it sends a signal for selecting the receiving side to extinguish the radio wave generated from the loop coil. At this time, the induced voltage generated in the tuning circuit 18 of the position indicator 12 is gradually attenuated according to the loss, and a radio wave of frequency f ₀ is emitted, but the radio wave excites the one loop coil described above in reverse. Then, an induced voltage is generated.

When the processor 17 sends a signal for selecting the receiving side to the transmission / reception switching circuit 14 for a certain period of time, it again sends a signal for selecting the transmitting side. Repeat, for example, a total of 4 times. Next, the processing device 17 changes the information sent to the selection circuit 13 to switch the loop coil to be selected.
The same radio wave transmission / reception is performed for all the loop coils of the sense unit 11 (step S1).

During the above-mentioned four reception periods, the sensing unit 11
The induced voltage generated in the loop coil of the
Of the bandpass filter, further detected, converted into a DC signal and sent to the processing device 17, and further converted into analog /
It is digital (A / D) converted. Since the level of the DC signal has a value depending on the distance between the position indicator 12 and the loop coil, the processor 17 determines whether or not the maximum value is equal to or higher than a predetermined level (step S).
By 2), it is determined whether or not the position indicator 12 is within the effective reading height of the sensing unit 11. When it is determined that the position indicator 12 is located within the height, two signals are extracted in the order of higher level than the obtained signal for each loop coil, and these are extracted as E ₀ , E ₁ (E ₀ ≧ E ₁ ) (step S3). The position indicator 12 is located within the height.
If it is determined that there is not, the process of step S1 is repeated.

Next, the processor 17 determines whether the position indicator 12 exists in the area where the coordinate value can be calculated by the coordinate value calculation method based on the three signal levels based on the obtained signals E ₀ and E ₁ . Alternatively, it is determined whether the coordinate value exists in the area where the coordinate value can be calculated by the coordinate value calculation method based on the two signal levels, here, whether it exists in the valid area or the invalid area described in the conventional example.

Specifically, it is checked whether or not the obtained coil of the signal E _{0 is} a coil at both ends of the sense section 11 (step S4), and if so, whether or not the signals E ₀ and E ₁ are equal. or the checked (step S5), and signal E ₀ of the coil the coil at a even signal E across the coil sense unit 11 or the signal E ₀ when it is not coil across the sense unit 11
₀ and E ₁ and when are equal, it is determined to be present in the effective area, and when the coil of the signal E ₀ is not a and and equal to the signal E ₀ and E ₁ coil across the sense unit 11 in the disabled area Determined to exist.

As a result of the determination, if the position indicator 12 is within the effective area, the processing device 17 causes the signals E ₀ , E ₁ and E ₂ (however, the signal E ₂ is the signal for each loop coil,
This is the next largest signal after the signals E ₀ and E ₁ . ), The coordinate calculation by the well-known three-point method is executed (step S6),
The coordinate value of the designated position by the position indicator 12 is obtained. On the other hand, if the position indicator 12 is within the invalid area, coordinate calculation by the two-point method described later is executed based on the signals E ₀ and E ₁ (step S7), and the coordinates of the position specified by the position indicator 12 are calculated. Find the value. The coordinate values thus obtained are transferred to a host computer (not shown) or the like and appropriately processed (step S8).

Next, the calculation of coordinate values by the two-point method will be described.

FIG. 5 shows the relationship between the signal obtained from two adjacent loop coils and the position designated by the position indicator, where x _a and x _b are the positions of the two adjacent loop coils. (Center position), L ₁ and L ₂ are signal levels obtained from the two loop coils, and x _p is a position designated by the position indicator.

As shown in FIG. 3A, the designated position x _p is 2
If there is an intermediate position x _c of the two loop coils, the level L ₁ ,
L ₂ is equal, and as shown in FIG. 2B, if the designated position x _p is closer to the loop coil at the position x _a than the intermediate position x _c of the two loop coils, the level L ₁ is It becomes larger than L ₂ .

The specified position x _p by the position indicator varies depending on the width D of the loop coil, the pitch P, etc., but is generally proportional to the ratio of the levels L ₁ and L ₂ of the signals obtained from the two loop coils, The difference Δx between the intermediate position x _c and the designated position x _p can be obtained from approximately Δx = k {1- (L ₂ / L ₁ )} (where k is a proportional constant).

Therefore, the coordinate value in the invalid area can be calculated by adding L ₁ = E ₀ and L ₂ = E _{1 and the} difference Δx obtained from the above equation to the intermediate position x _c (known).

6 and 7, the ratio n (= D / P) of the width D of the loop coil to the pitch P is 3.5 and 4.5, respectively.
When the specified position x _p is changed, a concrete example of changes in the levels L ₁ and L ₂ , and FIGS. 8 and 9 are shown in FIGS.
It shows the relationship between the measured value and the calculated value (k = 1) of the difference Δx based on Here, the measured value of the difference Δx (horizontal axis)
Is an arbitrary scale, but it is almost linearly proportional to the vicinity of 3D / 8 in both FIG. 8 and FIG. 9, and the coordinate value can be obtained from the end of the sense part to the line outside the second loop coil. ..

In the above embodiment, the coordinate value of the designated position in only one X direction is detected.
The other sensing section similar to the above, that is, the sensing section in the Y direction is superposed so as to be orthogonal to each other, and the selection circuit 1
3 and the same transmission / reception switching circuit 14 as the selection circuit and the transmission / reception switching circuit are connected, and an XY switching circuit is provided between these two selection circuits / transmission / reception switching circuits and the oscillator and the signal detection circuit, and the processing device 17 is also provided. It is needless to say that the coordinate values of the designated positions in the two directions of the X direction and the Y direction can be detected by slightly changing the program.

[0036]

As described above, according to the present invention, when the position indicator moves to the area where the first coordinate value calculating means cannot calculate the coordinate values near both ends in the position detecting direction of the sensing portion, the area indicating the area is detected. The coordinate value of the designated position detected by the determination / switching means is switched to the second coordinate value calculating means from the first coordinate value calculating means, whereby the coordinate of the designated position by the position indicator is switched. The area in which the value can be calculated expands, the invalid area occupied by the sense unit can be reduced, and a more useful position detection device can be realized.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an outline of a position detection device of the present invention.

FIG. 2 is an explanatory diagram showing a main part of a sense part of a conventional position detecting device and signals generated in respective loop coils thereof.

FIG. 3 is a configuration diagram showing an embodiment of a position detection device of the present invention.

FIG. 4 is a flow chart showing a program of a processing device.

FIG. 5 is an explanatory diagram showing a relationship between a signal obtained from two adjacent loop coils and a position designated by a position indicator.

FIG. 6 is an explanatory diagram showing a specific example of changes in levels L ₁ and L ₂ accompanying changes in designated position x _p .

FIG. 7 is an explanatory diagram showing another specific example of changes in the levels L ₁ and L ₂ accompanying changes in the designated position x _p .

FIG. 8 is a graph showing the correspondence between the measured value and the calculated value of the difference Δx based on FIG.

9 is a graph showing the correspondence between the measured value and calculated value of the difference Δx based on FIG. 7.

[Explanation of symbols]

1, 11 ... Sense section, 2, 12 ... Position indicator, 3 ... Loop coil selection / level detection means, 4 ... First coordinate value calculation means, 5 ... Second coordinate value calculation means, 6 ... Area determination / Switching means, 13 ... Selection circuit, 14 ... Transmission / reception switching circuit, 15 ... Oscillator, 16 ... Signal detection circuit, 17 ... Processing device, 18 ... Tuning circuit.

Claims (1)

[Claims] 1. A position detector having a plurality of loop coils arranged in parallel in a position detection direction, and a position indicator having at least the coil. The position indicator and each loop coil are based on electromagnetic action between them. In the position detecting device for obtaining the signal level depending on the distance between the position indicator and the loop position, the maximum signal among the signal levels depending on the distance between the position indicator and each loop coil is obtained. First coordinate value calculating means for calculating coordinate values from three signal levels including levels, and two signals including the maximum signal level among the signal levels depending on the distance between the position indicator and each loop coil Second coordinate value calculating means for calculating coordinate values from the level, and the position indicator by the first coordinate value calculating means from the signal level depending on the distance between the position indicator and each loop coil. It is determined whether the coordinate value can be calculated in the area in which the coordinate value can be calculated or the coordinate value can be calculated in the second coordinate value calculating means, and the first or second coordinate value calculating means is determined based on the judgment result. A position detecting device, comprising: a region determining / switching unit that switches which one of them is used.