JPS6218928B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tablet input device, and more particularly to a tablet input device using a resistive sheet.

One type of information input device that has been researched and developed in recent years is a tablet input device that uses a resistive sheet. This device uses a uniform resistor to convert the positional coordinates of an input point into a voltage or current ratio, and has the advantage of a simple structure and low cost. 1 and 2 show a current ratio type tablet input device using a capacitive coupling method. In FIG. 1, the input section consists of an input pen 1 and a tablet 2. An electrode 3 is provided at the tip of the input pen 1, and this electrode 3 is connected to an external AC power source 4. The tablet 2 has electrodes 5 on two opposing sides perpendicular to the X-axis.
A rectangular X-axis resistance sheet 7 provided with a It is composed of a rectangular Y-axis resistance sheet 10 provided with numbers 8 and 9, and an insulating protection plate 11 provided on the upper surface of the X-axis resistance sheet 7. To explain the operation of this input section, when the input pen 1 is brought into contact with a point P (x, y) on the tablet 2 to specify the position, the input pen 1 is Then, a current flows from the AC power source 4 to a point Px on the X-axis resistance sheet 7 and a point Py on the Y-axis resistance sheet 10. The current flowing into the X-axis resistance sheet 7 is divided according to the magnitude of electrical resistance between the point Px and the electrodes 5 and 6 at both ends, and then flows to the ground as currents I ₁ and I ₂ . The relationship x/Lx=I ₁ /I (I=I ₁ +H ₂ ) holds between the ground current and the X coordinate at this time, and by performing this calculation, the specified position can be The X coordinate can be found.
FIG. 2 shows a schematic block diagram of the X-coordinate detection section that performs this calculation. In the figure, the X coordinate detection section is
Current-voltage conversion circuits 12 and 13 to which the ground currents I ₁ and I ₂ are input;
Rectifier circuit 1 connected to each output side of 13
4, 15, an adder circuit 16 connected to the output sides of these rectifier circuits 14, 15, and the rectifier circuit 1.
5 and a division circuit 17 connected to the output side of the addition circuit 16. The current-voltage conversion circuits 12 and 13 each have a function of converting the ground currents I ₁ and I ₂ into voltages proportional to each other, and the rectifier circuits 14 and 15 have the function of converting the ground currents I 1 and I 2 into voltages proportional to each other. It has the function of rectifying the output to DC voltage. Further, the adder circuit 16 includes the rectifier circuit 1
It has the function of adding the output values of 4 and 15.
The division circuit 17 has a function of dividing the output value of the rectification circuit 15 by the output value of the addition circuit 16. In the X-coordinate detection section configured as described above, first, the ground currents I ₁ and I _{2 are converted into voltages proportional to each other by the current-voltage conversion circuits 12 and 13, and then the ground currents I 1 and I 2} are converted into voltages proportional to each other, and then the ground currents are converted to voltages proportional to each other. Therefore, it is converted into DC voltage as _I1 component and _I2 component. Then, an addition circuit 16 further calculates the I component, and finally a division circuit 17 calculates a value proportional to the position coordinate X based on the above-mentioned relationship. Although only the X-coordinate component has been described here, the same applies to the Y-coordinate component. In this manner, the position can be easily detected in the tablet input device using the resistance sheet.

However, in a tablet input device using such a resistor sheet, the shunt pattern of the current flowing into the resistor sheet from the input pen within the resistor sheet changes in a complicated manner depending on the contact position of the input pen. However, the ratio of the ground current is not necessarily proportional to the coordinates of the contact position, and the resistance sheet has always had the disadvantage that the distortion is particularly large at the edge portion.

The present invention improves the drawbacks of the above-mentioned conventional technology and makes it possible to accurately detect a specified position from the current ratio by making the shunt pattern uniform within the resistor sheet. It is an object of the present invention to provide a tablet input device having an excellent feature of being able to input coordinates.

The present invention aims to achieve the above-mentioned object by forming a resistance sheet with a plurality of resistors formed in a strip shape and arranged slightly apart from each other.

Hereinafter, one embodiment of the present invention will be described based on FIGS. 3 and 4.

FIG. 3 shows a portion of a tablet of a tablet input device according to the present invention. In the figure, the X-axis resistance sheet 20 is formed into a strip shape and includes a plurality of resistors 21, 21, .
21, . . . and electrodes 22 and 23 integrally provided at one end portion 21A, 21A, . The Y-axis resistance sheet (not shown) is also configured in exactly the same way as the X-axis resistance sheet 20,
The other constituent parts are formed substantially in the same manner as in the prior art.

Next, the operation of the above embodiment will be explained.
Now, when the input pen is brought into contact with point P (x, y) on the tablet and the position is specified, as mentioned above, the
Point Px of the X-axis resistance sheet 20 from the AC power source
current flows into. Here, X-axis resistance sheet 2
Since the resistors 21, 21, . , most of which flows into
Then, from the point Px of the resistor 21, the electrodes 2 at both ends
Depending on the magnitude of the electrical resistance between 2 and 23, the currents are shunted and flow to ground as currents I ₁ and I ₂ .

At this time, the shunt pattern within the resistor 21 is such that only the vicinity of the inflow point Px diverges, as shown in FIG. Resistor 2
Since the width of resistor 1 is narrow and almost no current flows into other resistors 21, 21 adjacent to resistor 21, the current flows approximately parallel to the X axis. Therefore, the inflow point
In areas other than the vicinity of Px, an equipotential surface is generated perpendicular to the X axis, and is approximately the same as when the current is divided by a normal linear resistance wire. Therefore, the relative ratio _{I 2 /} I ₁ +I ₂ of the ground currents I 1 and I ₂ is approximately proportional to the relative x-coordinate position x/Lx. Therefore, if a detection circuit (not shown) performs calculations to determine the relative ratio of ground currents, the x-coordinate of the position specified by the input pen can be obtained.

The above explanation is exactly the same even when the inflow point Px is biased in the width direction of the resistor 21 as shown in FIG.
No matter what position on 0 is designated by the input pen, its x coordinate can be detected accurately. This also applies to the Y-axis resistance sheet (not shown).

According to this embodiment, the divided current pattern within the resistor sheet can be made substantially uniform except for the vicinity of the inflow point, and thereby the designated position can be accurately detected from the ground voltage ratio.

In the above embodiment, the strip-shaped resistors are only arranged with a slight distance from each other, but a high-resistance layer having an internally grounded conductor is interposed between the resistors. You may. In this way, the leakage current between the resistors can be further reduced,
It becomes possible to further improve detection accuracy.

As described above, according to the present invention, it is possible to provide a tablet input device capable of inputting coordinates at low cost and with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a tablet using a resistive sheet according to the prior art, FIG. 2 is a schematic block diagram showing a coordinate detection section, FIG. 3 is a schematic diagram showing a resistive sheet according to the present invention, and FIG. FIG. 5 is an explanatory diagram of the action of the resistance sheet shown in FIG. 3, respectively. 7, 20... Resistance sheet for X axis, 10... Resistance sheet for Y axis, 21... Resistor.

Claims (1)

[Claims] 1. A tablet input device using a resistive sheet, characterized in that the resistive sheet is formed into a rectangular shape and constituted by a plurality of resistors arranged slightly apart from each other.