JPS6037493B2 - coordinate input device - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention provides an electromagnetic induction type coordinate system that is effective for inputting information such as handwritten characters and figures into an electronic device such as a converter using an input pen. This relates to input devices.

2. Description of the Related Art Structures of Conventional Examples and Their Problems In recent years, in the field of information equipment centered on computers, there has been an increasing demand for inexpensive coordinate input devices that can input handwritten characters and graphic information.

Electromagnetic induction type coordinate input devices have been known as such coordinate input devices, but in order to increase resolution, this device has many thin conductive wires densely arranged on the input board. However, it has the drawbacks that a huge number of lead wires are required and that it is difficult to arrange the conductor wires with high precision. In addition, in order to solve the above problems,
There is also a coordinate input device in which the conductor arranged on the input board is coiled to improve resolution and reduce the number of lead wires, but this has the problem that the control circuit becomes complicated and expensive.

OBJECTS OF THE INVENTION An object of the present invention is to provide an inexpensive coordinate input device that significantly reduces the number of conductors disposed on an input board, has high resolution, and does not require a complicated control circuit.

Structure of the Invention The coordinate input device of the present invention has a plurality of conductors arranged in a matrix at predetermined intervals in the X direction and the Y direction, and two of the conductors in the X or Y direction an input board configured to sequentially select the conductors of and supply current from the outside; a detection coil for coordinate input movably positioned on the surface of the input board; and the two selected conductors. comprising detection means for independently detecting the induced voltage induced in the detection coil by the current flowing through the detection coil,
In the two selected conductors, the value of the current flowing through the two conductors is relatively changed so that the sum of the value of the current flowing through one conductor and the value of the current flowing through the other conductor is constant. , the current in one of the conductors when the ratio of the values of the yield voltages generated by the magnetic fields generated by the respective conductors in the detection coil placed between the two conductors reaches a predetermined value; It is configured to determine the position of the detection coil based on the value, and is configured to superimpose a constant bias current through each of the conductors, thereby reducing the number of conductors arranged on the input surface. This can be significantly reduced, and interpolation between conductors can be performed using a simple control circuit, making it possible to realize a coordinate input device for high resolution buildings at low cost.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be specifically described based on the drawings.

FIGS. 1A and 1B are a schematic diagram showing the position detection principle of the coordinate input device of the present invention and a graph showing the magnetic field strength distribution. In FIG. 1A, 1 and 1 are conductors arranged in parallel, and 2 is a detection coil placed on the same plane as the conductor 1. This is, for example, provided at the tip of an input pen. . As shown in Figure 1A, when a current of 1 and 12 is passed through one conductor and the other conductor, the magnetic field generated between the two conductors is:
If we take the magnetic field due to 1 as a ratio, and the magnetic field due to 12 as a ratio, then
日、：Walk ． ...[1] Day 2 = death; ...[2] (however, d is the distance between both conductors).

This can be illustrated as shown in the magnetic field strength distribution graph in FIG. 1B. Next, connect the detection coil 2 to x=xp as shown in Figure 1B.
When the sensor coil 2 is placed at a position, the voltage induced in the detection coil 2 is V, the induced voltage due to V, and the yield voltage due to V2.
2, then v. =K. Day, Koyo...t3'
V2=K-day 22 bamboo reed cloth also p) ------(4)
(where K is a constant).

Therefore, from both equations {3} and {4), the position xp of the detection coil 2
is expressed as equation {5). Here, poison =
1.1.112 = 10 is constant), then the position xp of the detection coil 2 is fox = bone. ...[6] It is expressed as.

That is, when the ratio of the values of induced voltages V, V2 induced in the detection coil 2 by currents 1, 12 is 1, 1,
By checking the value of , the position xp of the detection coil 2 can be determined.

The relationship between the above-mentioned candles is illustrated in Figure 2. Therefore, when you want to output the position of the detection coil as a digital code, convert the digital code, such as a binary code, corresponding to the above position coordinates into a digital-to-analog conversion (hereinafter referred to as D/
This can be easily realized by creating 1, , 12 using A conversion). However, when the detection coil 2 is placed directly above the conductor 1, theoretically no induced voltage from the conductor 1 is generated in the detection coil 2. Therefore, it is necessary to avoid detection near the conductor, and the practical detection slope becomes narrow. Assuming that the detection areas are P, P2, the currents 1 and 12 actually flowing through the conductors are as shown in FIG. When creating the currents 1 and 12 shown in FIG. 3 using D/A conversion, it is convenient to set the position coordinates of P or P2 to 0. Therefore, by always adding the current value IB shown in FIG. 3 to 1, 12 as a bias current, the position coordinate of P or P2 can be easily set to 0. FIG. 4 is a block diagram of a coordinate input device according to an embodiment of the present invention, in which 1 is a conductor arranged in a matrix on the input board 3, and 2 is a detection coil attached to the tip of an input pen. .

6 sets the current values 1 and 12 corresponding to the binary code from the counter 8a, and the sum of the currents 1 and 12 is a constant value 1.

A D/A conversion circuit that maintains 12 is a current of 1,,1
2, a bias circuit that always gives a constant bias current, and 5, a military power supply. and a switch circuit for distributing 12 in the X direction or Y direction, 4a and 4b are counters 8
The binary code from b is a multiplexer for distributing currents 1 and 12 to conductor 1. 9 detects that the ratio between the two induced voltages V and V2 induced in the detection coil 2 becomes 1, and also detects whether the detection coil 2 is present between conductors through which current flows. It controls the latch circuit 10 which makes a judgment and temporarily stores the coordinate data. 1
1 is a modulation circuit for obtaining a high frequency current equal to the current, , 12, and 7 is a clock pulse generation circuit for driving the counter 8a, the modulation circuit 11, and the D/A conversion circuit 6.

The operation of the coordinate input device of this embodiment configured as described above will be explained below.

First, the output code of the counter 8a is sent to the multiplexer 4a,
4b and select the two conductors through which the current will flow. In this case, it is assumed that every other two conductors are selected. Next, the output code of the counter 8a is changed to change the values of the currents 1, 12. Then counter 8
Change the output code of b and select the next two conductors,
Repeat the same operation below. Z input surface 3 due to the above operation
A varying current is sequentially applied to the upper conductor. on the other hand,
In the detection coil 2, induced voltages are generated from each conductor, but current flows in the conductors on both sides of the detection coil 2, and the ratio of the two induced voltages V, , V2 induced in the detection coil 2 is 1. , the detection circuit 9 outputs a control signal and outputs the output codes of the counters 8a and 8b to the latch circuit 1.
Memorize 01. Since the output codes of the counters 8a and 8b correspond to the coordinate values of the input surface 3, the position of the detection coil 2 can be known from the output code of the latch circuit 10. As described above, according to this embodiment, when the detection area between two conductors is made narrower than the conductor interval, the current 1,,1
2, it is possible to set the coordinate value of the edge of the detection region to 0 by a simple operation of always applying a constant bias current. In addition, in this example, when selecting two conductors that carry a current, every other conductor is selected sequentially, but this is done by widening the detection area between the conductors and selecting every second conductor. It goes without saying that they may be selected sequentially and can be set arbitrarily depending on the width of the detection area. Effects of the Invention As is clear from the above explanation, when the detection area between two conductors is made narrower than the distance between the conductors, the coordinate input device of the present invention always has a Even with the simple operation of applying a constant bias current, it is possible to set the coordinate value of the edge of the detection region to 0.

Therefore, the configuration of the D/A conversion circuit is simplified, and since the coordinate values between the conductors start from 0, it is possible to obtain the coordinates of the digital code that corresponds to the coordinate values on the input board. , without performing arithmetic processing on the obtained position coordinate values of the conductor and the position coordinate values between the conductors, when the position coordinate value of the conductor is placed at the top and the position coordinate value between the conductors is placed at the bottom. can be continuously represented by one digital code. Therefore, the control circuit as a whole has a simple configuration, which also leads to cost reduction. Furthermore, even when changing the width of the detection area between conductors, this can be achieved by simply changing the bias current value and the preset value of the counter, so it is possible to change the control circuit in response to changes in specifications depending on the application. It also has the effect of being able to be used without having to use it.

[Brief explanation of the drawing]

1A and 1B are schematic diagrams and graphs showing the magnetic field strength distribution for explaining the position detection principle of the coordinate input device of the present invention, and FIG. 2 is a graph illustrating the relationship between theoretical formulas based on the above position detection principle. , FIG. 3 is a graph showing the relationship between conductor currents 1, 12 and position when the detection area between conductors is narrower than the conductor spacing, and FIG. 4 is a block diagram of an embodiment of the present invention. 1...Conductor, 2...Detection coil, 3.
...Input board, 4a, 4b...Multiplexer, 5""" switch circuit, 6...D/A conversion circuit, 7.
...Clock pulse generation circuit, 8a, 8b...
...Counter, 9...Detection circuit, 10...Latch circuit, 11...Modulation circuit, 12...Bias circuit. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 Having a plurality of conductors arranged in a matrix at predetermined intervals in the X direction and the Y direction, and
an input board configured to sequentially select two conductors among the conductors in each direction and supply current from the outside; and a detection coil for coordinate input movably positioned on the surface of the input board. , comprising detection means for independently detecting induced voltages induced in the detection coil by currents flowing through the two selected conductors, wherein the current flowing through one of the two selected conductors; The value of the current flowing through the two conductors is relatively changed so that the sum of the value of the current flowing through the other conductor and the value of the current flowing through the other conductor is relatively changed, and the current flowing through the sensing coil placed between the two conductors is The position of the detection coil is determined based on the current value of one of the conductors when the ratio of the values of each induced voltage induced by the magnetic field generated by the conductor reaches a predetermined value. . A coordinate input device characterized in that a constant bias current is superimposed and passed through each of the conductors.