JPH06309085A - Coordinate reader - Google Patents

Abstract

PURPOSE:To reduce the size and weight of the coordinate reader and to simplify a coordinate detecting circuit while securing necessary readable height and coordinate calculation precision. CONSTITUTION:The coordinate reader consisting of a coordinate indicator 1, the coordinate detecting device 3 having a detection part 2 which detects a magnetic field produced by the coordinate indicator 1, and a shield plate 4 which has a function for preventing the influence of magnetic field variation by a control substrate 5 and other components uses a magnetic thin plate made of 'Permalloy(R)' or amorphous metal of <=0.2mm thick as the shield plate 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate reader having coordinate input means using radio waves or magnetism.

[0002]

2. Description of the Related Art A conventional coordinate reading device is described in Japanese Patent Application Laid-Open No. 2-249019 invented by the present applicant. FIG. 11 is a perspective view showing the configuration of a conventional coordinate reading device. In FIG. 11, the coordinate indicator 1 has a resonance circuit that resonates with an alternating magnetic field generated from an excitation line included in a coordinate detecting device 3 described later, and the resonance action generates an alternating magnetic field necessary for coordinate calculation. Have a function. The detection unit 2 has a function of detecting the alternating magnetic field generated by the coordinate indicator 1 and converting it into an induction signal. The coordinate detection device 3 includes an excitation line, a detection unit 2, and a coordinate detection circuit (not shown) that processes an induction signal generated by the detection unit 2. The shield plate 4 has a function of preventing the influence of an unnecessary magnetic field generated from the control board 5 arranged under the coordinate detection device 3, other circuits, or peripheral devices. Spacer 10
1 is used to hold the distance between the coordinate detection device 3 and the shield plate 4.

FIG. 12 is a perspective view showing another structure of a conventional coordinate reading device. FIG. 12 shows a structure in which a metallic part 9 such as a hard disk drive for generating a partial magnetic field change is arranged below the coordinate detecting device 3 similarly to the control board 5 in FIG. When the metallic part 9 is arranged below the coordinate detection device 3, the magnetic field changes around the metallic part 9, which adversely affects the coordinate calculation accuracy. Therefore, not only to prevent the unnecessary magnetic field generated from the circuit such as the control board 5 in FIG. 11 but also to prevent the influence of the partial magnetic field change due to the metallic component 9, the shield plate 4
Is valid.

FIG. 13 is a block diagram of the coordinate detecting device 3.
The excitation line group S1 includes excitation lines y1 to yn having a function of generating an alternating magnetic field. The sense line group S2 is a sense line x1 to xm corresponding to the detection unit 2 that detects the alternating magnetic field generated by the coordinate indicator 1 in FIGS.
including. The excitation line scanning circuit 10 includes an excitation line group S1
Has a function of selecting one excitation line. The sense line scanning circuit 11 has a function of selecting one sense line of the sense line group S2. The excitation circuit 12 has a function of supplying an excitation signal to the excitation line group S1. The coordinate detection circuit 13 calculates coordinates from the guidance signal generated in the sense line group S2.

In the conventional coordinate reading device, the influence of the unnecessary magnetic field generated by the control board 5 shown in FIG. 11 and the partial magnetic field change generated by the metallic component 9 such as the hard disk drive shown in FIG. 12 is prevented. In order to perform accurate coordinate detection, the shield plate 4 made of an electromagnetic steel plate such as silicon steel is required. Further, a spacer 101 made of a non-magnetic and non-conductive material such as acrylic is required between the coordinate detecting device 3 and the shield plate 4.

[0006]

The conventional coordinate reading device has the following problems. First, when the coordinate detecting device 3 and the shield plate 4 are brought into close contact with each other, the inductive signal generated in the sense line group S2 is significantly attenuated by the shield plate 4, so that the coordinate indicator 1 and the coordinate detecting device 3 capable of detecting the coordinate. There is a problem in that the readable height that indicates the distance to and cannot be secured and the coordinate calculation accuracy decreases. Further, in order to compensate for the attenuation of the induced voltage, it is necessary to greatly amplify the induced signal, and as a result, the coordinate detection circuit 13 becomes complicated and the coordinate reading device becomes expensive.

On the contrary, in order to reduce the attenuation of the induced signal by the shield plate 4 and to secure the readable height of the coordinate indicator 1, a spacer 101 is arranged between the coordinate detection device 3 and the shield plate 4. Then, it is necessary to separate the coordinate detecting device 3 and the shield plate 4 by a predetermined distance. As described above, when the spacer 101 is arranged between the coordinate detecting device 3 and the shield plate 4 to increase the distance, there is a problem that the thickness and weight of the coordinate reading device increase. Especially in a small coordinate reading device used for a pen input computer,
It is difficult for the structure using the spacer 101 to satisfy the thickness and weight specifications required by the market.

Therefore, a first object of the present invention is to realize a compact and lightweight coordinate reading device by bringing the coordinate detecting device and the shield plate into close contact with each other. The second purpose is to prevent the reduction of the readable height of the coordinate indicator in addition to the first purpose.

A third object is to prevent a decrease in coordinate calculation accuracy in addition to the first and second objects.
Furthermore, in addition to the above-mentioned first to third objects, a fourth object is to enable simplification of a coordinate detecting circuit for compensating for the attenuation of the induction signal induced in the detecting section of the coordinate detecting apparatus, and to provide an inexpensive coordinate reading apparatus. To do.

[0010]

In order to solve the above-mentioned problems, according to the present invention, a coordinate detector having a coordinate indicator and a detector for detecting a magnetic field generated by the coordinate indicator, and a lower portion of the coordinate detector. In the coordinate reading device configured with the shield plate arranged, a magnetic thin plate made of permalloy or amorphous metal having a plate thickness of 0.2 mm or less is used as the shield plate.

[0011]

First, the purpose of using the shield plate is to shield an unnecessary magnetic field generated by a circuit such as a control board arranged below the coordinate detecting device. Therefore, the shield ratio S is used as an index showing the effect of shielding the unnecessary magnetic field (shield effect).
There is E. FIG. 3 is an explanatory diagram of the shield rate. Figure 3
When E1 is an input voltage, E2 is an output voltage, R is a reflection loss, A is an absorption loss, and B is an internal loss in the shield plate 4 of, the shield ratio SE is represented by the following equation.

SE = 20log (E1 / E2) = R + A + B In a general electromagnetic induction type coordinate reading device, the frequency range of the unnecessary magnetic field that needs to be shielded is several hundreds KHz or less, so the shield rate SE is A The absorption loss of The thickness of the shield plate is t, the relative permeability is μ,
Assuming that the specific conductivity is σ, the absorption loss A is proportional to t · μ · σ, so that a material having a large μ · σ, that is, a ferromagnetic material is advantageous.

In order to bring the shield plate into close contact with the coordinate detecting device, it is necessary to minimize the eddy current flowing through the shield plate and minimize the attenuation of the induced voltage by the shield plate. Therefore, it is necessary to use a material having a low specific conductivity σ for the shield plate.

From the above, when a material having a high relative magnetic permeability and a low relative electric conductivity, that is, a material having a high effective magnetic permeability μe is selected as the material for the shield plate, a shield having the same degree as an electromagnetic steel plate such as silicon steel is selected. It is possible to reduce the attenuation of the induced voltage induced in the detection unit of the coordinate detection device while securing the rate. As a result, it is possible to prevent a decrease in the readable height of the coordinate indicator and a decrease in coordinate calculation accuracy, simplify the coordinate detection device, and provide an inexpensive coordinate reading device. Further, even when the shield plate is brought into close contact with the coordinate detecting device, the required readable height of the coordinate indicator and the coordinate calculation accuracy can be ensured, so that a compact and lightweight coordinate reading device can be realized. .

[0015]

1 is a perspective view showing the structure of an embodiment of a coordinate reading apparatus according to the present invention. FIG. 2 is a cross-sectional view showing an example of the cross section AA ′ shown in FIG. 1 and the magnetic field distribution.

The configuration according to the present invention will be described. Figure 1
In, the coordinate indicator 1 has a function of generating a magnetic field necessary for coordinate calculation. The coordinate detecting device 3 has an exciting line group S1 similar to the structure of the conventional coordinate detecting device shown in FIG.
And the sense line group S2 and the excitation line scanning circuit 10,
It has a sense line scanning circuit 11, an excitation circuit 12, and a coordinate detection circuit 13. The shield plate 4 made of permalloy having a plate thickness of 0.2 mm or less is arranged without disposing a spacer below the coordinate detecting device 3.

The operation of the coordinate reading apparatus according to the present invention is the same as the operation shown in the conventional example, and the description thereof will be omitted. Next, the role of the shield plate 4 in this embodiment will be described. In the coordinate reading device having the configuration of FIG.
As shown in FIG. 2, the unnecessary magnetic field 6 generated from the control board 5 is shielded by the shield plate 4 made of permalloy and does not reach the coordinate detection device 3 side.

Here, although the shield ratio decreases as the shield plate 4 becomes thinner, when a material having a high maximum magnetic permeability and a high saturation magnetic flux density, such as Permalloy in Table 1 described later, is used as the shield plate, Normally, since the unnecessary magnetic field 6 is not so large, the shield ratio will not be insufficient unless the plate thickness is very thin. If the unnecessary magnetic field 6 affects the coordinate calculation accuracy, increase the shield rate by using a configuration in which permalloy is laminated as a shield plate or a metal material such as iron or aluminum is placed under the permalloy. Is also possible.

[0019]

[Table 1] Table 1 shows the magnetic properties of permalloy and silicon steel. Thus, it can be seen that there is a difference in the effective magnetic permeability μe depending on the material of the shield plate, and in particular, the effective magnetic permeability of PC-based permalloy is high.

Further, in FIG. 2, the magnetic field 7 generated from the coordinate indicator 1 passes through the coordinate detecting device 3 and a part of the magnetic field reaches the shield plate 4, but the effective transmission of the shield plate 4 made of permalloy. Since the magnetic susceptibility μe is high, the iron loss is reduced and the attenuation of the induction signal can be reduced.

A part of the magnetic field 8 generated from one excitation line yL of the excitation line group S1 also reaches the shield plate 4, but since the effective permeability μe of the shield plate 4 made of permalloy is high, the excitation line yL. It is also possible to reduce the attenuation of the generated magnetic field 8.

FIG. 4 is a graph showing frequency characteristics of effective magnetic permeability μe of permalloy. The frequency characteristic of the effective magnetic permeability varies not only with the material but also with the plate thickness t, and it can be seen that the thinner the plate thickness t, the higher the effective magnetic permeability μe. FIG. 5 is a graph showing the relationship between the spacer thickness and the induced voltage generated in the sense line group. It can be seen from FIG. 5 that there is a correlation between the material and thickness of the shield plate 4 and the induced voltage, and the higher the effective magnetic permeability μe, the higher the induced voltage.

FIG. 6 is a graph showing the relationship between the thickness of the spacer and the readable height from the upper surface of the coordinate reading device to the coordinate indicator. From this FIG. 6, the coordinate detection device 3 and the shield plate 4 are shown.
In the state where they are closely attached with a distance of 0 mm from the plate thickness of 0.
In the case of a PC-based permalloy shield plate 4 of 2 mm, the readable height from the upper surface of the coordinate detection device 3 is about 15 mm, and a PB-based permalloy shield plate of 0.2 mm thickness and a PC system of 0.5 mm thickness. It can be seen that the readable height of the Permalloy shield plate is about 10 mm. Although the standard of the readable height differs depending on the type of the coordinate reading device, it is possible to satisfy the readable height of 10 mm that is normally required in a state where the shield plate 4 is used and brought into close contact with the coordinate detecting device 3. Become.

From the above results, the condition of the shield plate that can ensure the necessary readable height and the coordinate calculation accuracy even when the shield plate is in close contact with the coordinate detecting device is that the plate thickness is 0.2 mm.
And 0.5 mm PC-based permalloy and 0.2 mm thick P
B type permalloy. However, among these three conditions, the PC-based permalloy having a thickness of 0.5 mm has a thickness of 0.2 m.
Compared with the PC-based permalloy of m, there are many demerits such as an increase in weight and an increase in material cost and a decrease in readable height. On the other hand, the PB-based permalloy with a plate thickness of 0.2 mm has a merit that the readable height is lower than that of a PC-based permalloy with a plate thickness of 0.2 mm, but the material cost is low. Therefore, the condition of the shield plate in this embodiment is limited to a plate thickness of 0.2 mm or less.

In the first embodiment, permalloy is used as the shield plate, but as the second embodiment, a case where amorphous metal is used will be described. Table 2 shows the magnetic characteristics of amorphous metals. It can be seen from Table 2 that the initial permeability of amorphous metal is considerably higher than that of PB-based permalloy. FIG. 7 is a graph showing frequency characteristics of effective magnetic permeability of amorphous metal. It can be seen from FIG. 7 that the iron-based amorphous metal has a higher effective permeability than the PB-based permalloy, and the cobalt-based amorphous metal has a higher effective permeability than the PC-based permalloy. .

FIG. 8 is a graph showing the relationship between spacer thickness and induced voltage when permalloy and amorphous metal are used as the shield plate. FIG. 9 is a graph showing the thickness and readable height of the spacer when permalloy and amorphous metal are used as the shield plate. 8 and 9, compared with PB-based permalloy, amorphous metal has a higher induced voltage and a readable height of 10 m.
It is clear that m can be secured.

[0027]

[Table 2] On the other hand, since the shield plate made of an amorphous metal has a thickness limited to 0.05 mm or less depending on the manufacturing method, the shield ratio is lower than that of a shield plate made of permalloy having a plate thickness of about 0.2 mm. Therefore, if the unnecessary magnetic field generated from the control board or the like affects the coordinate calculation accuracy due to the low shield ratio, a configuration in which amorphous metal is laminated as a shield plate or a metal material such as iron or aluminum under the amorphous metal is used. It is also possible to increase the shield rate by arranging. Therefore, in the configuration shown in the first embodiment,
Even if a shield plate made of iron-based amorphous metal or cobalt-based amorphous metal is provided instead of the shield plate made of permalloy having a plate thickness of 0.2 mm or less,
The same effect as the effect shown in the first embodiment can be obtained.

Next, a coordinate reading device using an electromagnetic induction phenomenon, which uses a coordinate detecting device different from the method shown in the conventional example, will be described. FIG. 10 shows a configuration diagram of another example of the coordinate detection device. The coordinate detection device 3 shown in FIG. 10 includes an amplifier circuit 16 and a first scanning circuit 14
The first sense line group S3 connected to the output of the amplifier circuit 16 via the amplifier circuit 1 and the amplifier circuit 1 via the second scanning circuit 15
A second sense line group S4 connected to the input of 6 and a coordinate detection circuit 13. When the coordinate indicator 1 approaches the coordinate detecting device 3, the resonance circuit included in the coordinate indicator 1 includes the first sense line group S3 included in the coordinate detecting device 3.
One of the sense lines (first sense line) and one sense line of the second sense line group S4 (second sense line) are electromagnetically coupled. As a result, the first
The sense line, the resonance circuit, the second sense line, and the amplifier circuit 16 form a positive feedback loop to form an oscillation circuit that oscillates at the resonance frequency of the resonance circuit.
Obtains position information of the coordinate indicator 1 from amplitude information of oscillation generated by the positive feedback loop. The present invention can be applied to a coordinate reading device including the coordinate detecting device having the above-described configuration, and the same effects as the effects shown in the first and second embodiments can be obtained.

Further, according to the present invention, at least an alternating magnetic field, such as a coordinate reader having a power source and a resonance circuit mounted in the coordinate indicator or a coordinate indicator and a coordinate detecting device electrically connected to each other by wire. Electromagnetic induction phenomenon composed of a coordinate indicator having a function to generate, and a coordinate detection device including a detector for detecting an alternating magnetic field generated from the coordinate indicator and converting it into an induction signal for detecting the position of the coordinate indicator. The present invention can also be applied in principle to a coordinate reading device using the above, and the same effects as those of the first and second configurations can be obtained.

[0030]

As described above, according to the present invention, the magnetic thin plate made of permalloy or amorphous metal having a plate thickness of 0.2 mm or less is provided as the shield plate under the coordinate detecting device, which is necessary for the coordinate calculation. The unnecessary magnetic field from the control board can be shielded without attenuating various inductive signals and lowering the readable height, enabling simplification of the coordinate detection circuit and downsizing and weight reduction of the coordinate reading device. There is an effect that.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structure of an embodiment of a coordinate reading device according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a cross section AA ′ shown in FIG. 1 and a magnetic field distribution.

FIG. 3 is an explanatory diagram showing a shield rate of a shield plate.

FIG. 4 is a graph showing frequency characteristics of effective magnetic permeability of permalloy.

FIG. 5 is a graph showing the relationship between spacer thickness and induced voltage.

FIG. 6 is a graph showing the relationship between spacer thickness and readable height.

FIG. 7 is a graph showing frequency characteristics of effective magnetic permeability of amorphous metal and permalloy.

FIG. 8 is a graph showing the relationship between spacer thickness and induced voltage.

FIG. 9 is a graph showing the relationship between spacer thickness and readable height.

FIG. 10 is a configuration diagram showing another example of the coordinate detection device.

FIG. 11 is a perspective view showing an example of a structure of a conventional coordinate reading device.

FIG. 12 is a perspective view showing another example of the structure of a conventional coordinate reading device.

FIG. 13 is a configuration diagram of a conventional coordinate detection device.

[Explanation of symbols]

 1 Coordinate Indicator 2 Detecting Section 3 Coordinate Detection Device 4 Shield Plate 5 Control Board 6 Unwanted Magnetic Field 7 Magnetic Field Generated from Coordinate Indicator 8 Magnetic Field Generated from Excitation Line 9 Metal Parts 10 Excitation Line Scan Circuit 11 Sense Line Scan Circuit 12 Excitation circuit 13 Coordinate detection circuit 14 First scanning circuit 15 Second scanning circuit 16 Amplifier circuit 101 Spacer S1 Excitation line group S2 Sense line group S3 First sense line group S4 Second sense line group

Claims (1)

[Claims] 1. A coordinate reader comprising a coordinate indicator, a coordinate detector having a detector for detecting a magnetic field generated by the coordinate indicator, and a shield plate arranged below the coordinate detector. The coordinate reading device is characterized in that the shield plate is made of permalloy having a plate thickness of 0.2 mm or less, or amorphous metal.