JPH09212302A - Coordinate input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the influence of induction noise from finger and to precisely detect input coordinates. SOLUTION: Plural X electrodes 4 and plural Y electrode 5 are respectively formed on the upper and lower faces of a sensor board 6 so as to intersect each other at a right angle, a noise removing sheet 7 is laminated to the surface of the board 6 and a noise prevention pattern 7a is formed on the upper surface of the sheet 7 in parallel so as to be arranged on positions corresponding to gaps between respective electrodes 4. When a finger touches the sheet 7, induction noise from the finger is allowed to flow into the ground side through the pattern 7a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type coordinate input device, and more particularly to a coordinate input device for inputting coordinates using an operator's finger.

[0002]

2. Description of the Related Art In recent years, as a coordinate input device, there is known a coordinate input device which inputs an XY coordinate by touching a finger of an operator by a capacitance method.

FIG. 7 shows a main part of a conventional electrostatic capacitance type coordinate input device. A plurality of X electrodes 4 are formed on the front surface of the sensor substrate 6 along the X direction, and a plurality of Y electrodes 5 are formed on the back surface of the sensor substrate 6 along the Y direction. The Y electrodes 5 are formed in a matrix. When a pulse signal is applied to the X electrode 4 and the operator's finger is not touching,
The lines of electric force as shown in (a) are formed between the X electrode 4 and the Y electrode 5 to form the electrostatic capacitance C1. When the operator's finger 3 touches in this state, the lines of electric force between the X electrode 4 and the Y electrode 5 are absorbed by the finger 3 as shown in FIG. 7B, and the electrostatic capacitance C1 decreases to C2. The input coordinates can be detected by detecting the current change due to the decrease in the capacitance.

[0004]

However, in the above-mentioned conventional coordinate input device, when the human body is guided by radiation noise from electric equipment such as a personal computer in the vicinity, as shown in FIG. 7 (b). Since an induced current N flows from the finger 3 to the Y electrode 5, an erroneous detection occurs, which causes a problem that the cursor on the display screen with respect to the input coordinates shakes.

In view of the above conventional problems, it is an object of the present invention to provide a coordinate input device capable of preventing the influence of inductive noise from a finger and accurately detecting an input coordinate.

[0006]

SUMMARY OF THE INVENTION According to the present invention, an XY sheet having a grounding conductive pattern formed on the upper surface to which a finger touches is formed.
It will be provided on the electrode. By providing the sheet having the grounding conductive pattern formed on the XY electrodes in this way, the induction noise from the finger flows to the ground side through the grounding conductive pattern of the sheet, so that the influence of the induction noise from the finger is reduced. It is possible to prevent the input coordinate from being detected accurately.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the coordinate input device of the present invention, a plurality of first electrode groups are formed on the front surface and a plurality of second electrode groups are formed on the back surface in a direction orthogonal to the first electrode group. A sensor substrate having a group formed thereon, and a sheet provided on the sensor substrate and having a grounding conductive pattern formed on an upper surface touched by a finger are provided.

Further, it is preferable that a grounding conductive pattern is formed at a position surrounding the first and second electrode groups of the sensor substrate, and this pattern is connected to the grounding conductive pattern of the sheet.

The grounding conductive pattern of the sheet may be formed in any manner as long as it can be reliably touched by a finger. For example, the grounding conductive pattern may be formed in parallel between the first electrode groups, or It can be formed in a matrix corresponding to the first and second electrode groups.

[0010]

Embodiments will be described with reference to the drawings.
1 is an exploded perspective view showing a coordinate input device according to the present invention, FIG. 2 is a plan view showing the upper surface side of the sensor substrate of FIG. 1, FIG. 3 is a plan view showing the lower surface side of the sensor substrate of FIG. 1, and FIG. 1 is a side sectional view of the coordinate input device of FIG. 1, FIG. 5 is an explanatory diagram showing lines of electric force when a finger touches the coordinate input device of FIG. 1, and FIG. 6 is a block diagram showing the coordinate input device of FIG. is there.

The coordinate input device 1 shown in FIG. 1 is connected to a personal computer as a single unit or integrally provided on a keyboard (not shown), and an operator inputs a desired coordinate with a finger 3. ing. The coordinate input device 1 includes a sensor substrate 6 formed of a film formed on the upper surface and the lower surface of the X electrode 4 and the Y electrode 5 so as to be orthogonal to each other, and a noise removal sheet 7 attached to the upper surface of the sensor substrate 6. The shield film 8 attached to the lower surface of the sensor substrate 6 and the substrate 20 provided on the lower surface of the shield film 8 are laminated to form a schematic structure. On the back surface of the substrate 20, a CPU 16 that drives and controls the sensor substrate 6 is provided and a wiring pattern is formed.

The X electrode 4 and the Y electrode 5 are made of a conductive material such as silver and are formed in parallel at equal intervals P, so that the matrix is formed on the upper surface and the lower surface of the sensor substrate 6 as shown in FIGS. 2 and 3, respectively. It is formed into a shape. In addition, a through hole 4a for electrically connecting the X electrode 4 to the lower surface side and a strip-shaped ground pattern 9 are formed on the upper surface shown in FIG. 2, and a Y electrode 5 is formed on the lower surface shown in FIG. Land 4 electrically connected to land 5a and through hole 4a of X electrode 4
b and a strip-shaped ground pattern 9 are formed. The ground pattern 9 is connected to the GND pattern formed on the back surface of the substrate 20 by a through hole.

As shown in FIGS. 1 and 4, a plurality of noise prevention patterns 7a are formed in parallel on the upper surface of the noise removal sheet 7 at equal intervals P. These noise prevention patterns 7a are formed between the X electrodes 4. Is formed at a position corresponding to.
The noise prevention pattern 7a is formed of, for example, a printed pattern of copper, silver, ITO, or the like, and the sensor substrate 6 shown in FIGS.
It is connected to the ground pattern 9 on the side by a through hole and grounded. The noise prevention pattern 7a may be directly connected to the GND pattern of the substrate 20 through a through hole.

When the finger 3 is touched in such a structure, as shown in FIG.
Flows to the ground GND side via the noise prevention pattern 7a, so that the influence of the induced noise N from the finger 3 can be prevented. In the above embodiment, the noise prevention pattern 7
Although a is formed only in the X direction, it may be formed in a matrix in the XY directions. Further, the arrangement pitch of the noise prevention patterns 7a is not necessarily the same as that of the X electrodes 4 and the Y electrodes 5 as long as the finger 3 can be reliably touched, and further, the X electrodes 4 and the Y electrodes 5 are respectively arranged on the sensor substrate. Although it is formed on the upper surface and the lower surface of 6, it may be formed on the contrary.

When detecting input coordinates, a circuit as shown in FIG. 6 is used. The X electrode 4 has n electrodes X ₁ and X ₂
˜X _n , and these X electrodes X ₁ and X _{2 to} X _n are respectively connected to the X multiplexer 10 via the land 4b shown in FIG.
Of the switches SWX _{1 to} SWX _n . Similarly, the Y electrode 5 also has n electrodes Y ₁ , Y _{2 to} Y _n.
The Y electrodes Y ₁ and Y _{2 to} Y _n are connected to the respective ends of the switches SWY _{1 to} SWY _n of the Y multiplexer 11 via the lands 5 a shown in FIG.

Switch SWX _{1 of the} X multiplexer 10
The other ends of ～SWX _n are commonly applied signal having a predetermined frequency from the oscillation circuit 12, Y switches SWY ₁ ~SWY _n of the other end of the output voltage are both amplifying circuit 13 of the multiplexer 11, the noise absorbing filter circuit It is applied to the A / D conversion circuit 15 via 14. The digital value converted by the A / D conversion circuit 15 is taken into the CPU 16, the input coordinates are calculated, and transmitted from the CPU 16 to the host computer 17. Note that these components are mounted on the bottom surface of the coordinate input device as shown in FIG.

Then, the CPU 16 first sequentially turns on the switches SWY _{1 to} SWY _n of the Y multiplexer 11 while keeping the switches SWX _{1 to} SWX _n of the X multiplexer 10 on, and takes in the change in the capacitance as each signal. , Calculate the Y coordinate of the finger. Then X multiplexer 1
0 switches SWX _{1 to} SWX _n are grouped and sequentially turned on, and the switch SW of the Y multiplexer 11 is switched on.
The Y _{1 to} SWY _n are turned on for each group according to the Y coordinate of the finger, the change in capacitance is captured as each signal, and the X coordinate of the finger is calculated.

[0018]

As described above, according to the present invention, since the sheet having the grounding conductive pattern formed on the upper surface touched by the finger is provided on the XY electrodes, the induced noise from the finger is used for grounding the sheet. The current flows through the conductive pattern to the ground side, so that the influence of inductive noise from the finger can be prevented and the input coordinates can be accurately detected.

[Brief description of drawings]

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

FIG. 2 is a plan view showing an upper surface side of the sensor substrate of FIG.

FIG. 3 is a plan view showing a lower surface side of the sensor substrate of FIG.

FIG. 4 is a side sectional view of the coordinate input device of FIG.

5 is an explanatory diagram showing lines of electric force when a finger touches the coordinate input device of FIG. 1. FIG.

6 is a block diagram showing the coordinate input device of FIG. 1. FIG.

FIG. 7 is an explanatory diagram showing lines of electric force when a finger touches a conventional coordinate input device.

[Explanation of symbols]

 3 fingers 4 X electrode 5 Y electrode 6 sensor substrate 7 noise removal sheet 7a noise removal pattern 8 shield film 9 ground pattern

Claims (4)

[Claims] 1. A sensor substrate having a plurality of first electrode groups formed on a front surface and a plurality of second electrode groups formed on a back surface in a direction orthogonal to the first electrode group, A coordinate input device, comprising: a sheet provided on the sensor substrate and having a grounding conductive pattern formed on an upper surface touched by a finger. 2. A grounding conductive pattern is formed on the sensor substrate at a position surrounding the first and second electrode groups, and the pattern is connected to the grounding conductive pattern of the sheet. The coordinate input device according to claim 1, which is characterized in that. 3. The coordinate input device according to claim 1, wherein the grounding conductive pattern of the sheet is formed between the first electrode groups. 4. The coordinate according to claim 1, wherein the grounding conductive pattern of the sheet is formed in a matrix corresponding to the first and second electrode groups. Input device.