JPS5985584A - Tablet - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy of coordinates with a simple constitution by using two sheets having electrodes formed at two counter sides of resistance sheet having uniform surface resistance and superposing these sheets to make the sides of the electrodes orthogonal to each other. CONSTITUTION:The currents conducting to lead wires 28-31 are equal to the currents conducting to feedback resistances 48-51. Therefore the voltage change generated at output terminals 44-47 of amplifiers 32-35 when the non-conductive state between transparent resistance sheets 21 and 22 changes to a short circuited state at a contact point 54 is proportional to the current conducting to the wires 28-31. Therefore the horizontal and vertical coordinates of the point 54 are obtained from the voltage change ratio generated between output terminals 44 and 45 and output terminals 46 and 47 respectively. Then the offset voltage of the amplifiers 34 and 35 is set at zero with no contact secured between lead wires 30/31 and electrodes 25/26. In such a way, the vertical coordinates of the point 54 can be obtained by a coordinate discriminating circuit 52 from the output voltage ratio between amplifiers 34 and 35.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tablet constructed using a resistive sheet.

Figure 1 shows a conventional example of a conventional transparent tablet.
Reference numeral 1 denotes a transparent resistance sheet with uniform sheet resistance, and a large number of dot-like projections 2 are formed on the surface.

3 is a transparent electrode sheet. The transparent resistance sheet 1 and the transparent electrode sheet 3 are overlapped, and the projections 2 serve as spacers that electrically separate the transparent resistance sheet 1 and the transparent electrode sheet 3. Diode groups 8 to 11 are connected to sides 4 to 7 of the transparent resistance sheet 104, respectively. 12 is the power supply, 1
3 is a two-pole, double-throw switch for polarity switching. When the a side of switch 13 is closed, current flows from the positive terminal of power supply 12 to switch 13. Diode group 10. Transparent resistance sheet 1. Diode group 11. It flows through a loop through switch 13 to the negative pole of power supply 12. Therefore, equipotential lines approximately parallel to the sides 6 and 7 are generated in the transparent resistance sheet 1. When the b side of switch 13 is closed, current flows from the positive terminal of power supply 12 to switch 13 and diode group 8. Transparent resistance sheet 1
1 diode group9. The flow passes through the switch 13 to the negative electrode of the power supply 12, and the transparent resistance sheet 1 has sides 4 and 5.
Equipotential lines approximately parallel to are generated. When point 15 on the transparent electrode sheet 3 is pressed down with the pen 14 from above the transparent electrode sheet 3, the transparent resistance sheet 1 and the transparent electrode sheet 3 are connected to the point 15.
The contact point 16 on the transparent resistive sheet 1 corresponds to this point. Therefore, the potential at the point 16 is transmitted to the transparent electrode sheet 3. Since the potential of point 16 corresponds to the coordinates of point 16, when the detection circuit 17 detects the potential of point 16, the coordinates of the pressed point are identified. The potential at point 16 corresponds to the X coordinate when the a side of the switch 13 is closed, and to the X coordinate when the b side is closed, so by switching the switch 13, the X, Both y coordinates can be identified.

When writing characters or figures with the pen 14, the dot 15 moves quickly, so the switch 13 needs to be switched quickly, and in reality, an electronic switch is used. The timing of this switching needs to coincide with the timing at which the detection circuit 17 distinguishes between the X coordinate and the X coordinate.

In the above tablet, it is necessary to generate completely parallel equipotential lines on the transparent resistance sheet 1,
Because current flows through a group of diodes, it is difficult for the equipotential lines to be parallel, leading to errors in the detected coordinates. In order to reduce the error, a large number of diodes are required, which requires a lot of man-hours to manufacture. However, this method has the disadvantage that it takes a long time to measure the potential at point 16 in synchronization with the circuit configuring the switch 13 and the switch 13.

This invention has been made in view of the above points, and by configuring a transparent resistance sheet for detecting the X direction and a transparent resistance sheet for detecting the X direction to be stacked, a group of diodes is not required, This allows coordinate signals in the X direction and the X direction to be obtained simultaneously.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention.

21 and 22 are transparent resistance sheets with uniform sheet resistance, and have electrodes 23, 24 and 25° 26 at both ends, respectively. A group of dot-shaped protrusions 27 made of an insulating material are provided on the surface of the transparent resistance sheet 220. The transparent resistor sheets 21 and 22 are stacked with the protrusion group 27 in between. The protrusion group 27 has the function of a spacer. Amplifiers 32-35 having sufficiently large amplification factors are connected to the electrodes 23-26 via lead wires 28-31. Lead Iw28
-31 are connected to amplifiers 32-350 and inverting input terminals 36-39. Non-inverting input terminal 4 of amplifier 32.33
A power supply 53 is connected to 0.41.

Non-inverting input terminals 42,43 of amplifiers 34,35 are grounded. 44 to 47 are output terminals of the amplifiers 32 to 35, 48 to 51 are feedback resistors, 52 is a coordinate identification circuit, 53 is the aforementioned power source, and 54 is a contact point when pressed.

Next, the operation will be explained. Transparent resistance sheets 21 and 22
contacts at a contact point 54. Transparent resistance sheets 21 and 22
When they come in contact with each other, a current flows to the output terminal 44 of the amplifier
．． 45 to feedback resistors 48-49. It flows through the leads 28, 29 into the transparent resistive sheet 21, through the contact point 54 into the transparent resistive sheet 22, through the leads 30.31, through the feedback resistor 50.51 and into the amplifier 34.35. (feedback resistors 48, 49, 50 and 51 have equal resistance values, respectively). At this time, amplifiers 32 to 35
The potentials of the inverting input terminals 36 to 39 of the non-inverting input terminal 40
It becomes the same potential as ~43 (imaginal short). Therefore, when a short circuit occurs between the transparent resistive sheets 21 and 22 at the contact point 54, the magnitude of the current flowing through the lead wires 28 to 31 and the transparent resistive sheets 21 and 22 is
．． The current is equal to the current flfHn when the power supply 53 is connected to the terminal 29 and the lead wires 30 and 31 are grounded. Therefore, the ratio of the currents flowing in the leads 28, 29 is equal to the ratio of the distance from the contact point 54 to the electrode 24 and the distance from the contact point 54 to the electrode 23, and the lead? The ratio of the currents flowing through the IMs 30 and 31 is determined by the distance from the contact point 54 to the electrode 26 and the contact point 5.
4 to the electrode 25.

Although the current flowing through the lead wires 28 to 31 is equal to the current flowing to the feedback resistors 48 to 51, when the transparent resistance sheets 21 and 22 change from a non-contact state to a short circuit state at the contact point 54, the amplifier The voltage change occurring at the output terminals 44-47 of
It is proportional to the current flowing through the Therefore, output terminal 44.45
The abscissa of the contact point 54 is determined from the ratio of the voltage changes at the output terminals 46, 47, and the ordinate of the contact point 54 is determined from the ratio of the voltage changes at the output terminals 46, 47. Lead wires 30.31 are connected to electrodes 25.
If the offset voltage of the amplifier 34 and 35 is adjusted to zero when it is not connected to the amplifier 34 and 35,
Since the output voltage of the amplifier 34.35 is proportional to the current flowing through the lead wire 30.31, the contact point 54
The ordinate of can be determined by the coordinate identification circuit 52.

The coordinate identification circuit 52 can be constructed using, for example, an A/D':3 inverter and a microcomputer.

FIG. 3 is a modified circuit diagram of a portion of the circuit of FIG. 55 is a differential amplifier that outputs a voltage proportional to the potential difference between the output voltage of the amplifier 32 and the power supply 53;
is a differential amplifier that outputs a voltage proportional to the potential difference between the output voltage of the amplifier 33 and the power supply 53. Differential amplifier 5
5.56 has the same amplification factor. The output terminal 57.5El is connected to the coordinate identification circuit 52. lead 828.29
Amplifier 3 with electrode 24.25 VC not connected
If the offset voltages 2.33 and 55.56 are adjusted to zero, the output voltage of the amplifier 55.56 will be proportional to the current flowing through the lead wire 28.29. Contact point 54
The abscissa of is calculated using the following formula.

X/χ0 2V2/(V++Vx) where X is the distance between the contact point 54 and the electrode 23.

is the distance between the electrodes 23.24, and V, , V2 are the voltage changes before and after the transparent resistive sheets 21.22 are short-circuited at the contact point 54 of the output terminal 44.45 or the output terminal 57.58, respectively. V, , V2 is the amplifier 32.33
, 55, 56 are adjusted, it may be used as the output voltage of the amplifier 55, 56. Contact point 5
The ordinate of 4 is also based on the output voltage of amplifier 34.35,
It can be calculated in the same way as the abscissa.

FIG. 4 is an example of a circuit showing another embodiment of the present invention. Resistors 59-62 are connected to leads @28-31. For this reason, at the contact point 54 a transparent resistance sheet)21.
22, current flows from the power supply 63 to the resistor 59.
60 and into the transparent resistive sheet 21 at the contact point 54, forming a resistor 61.62.
flows through to the ground. The voltage drop across resistors 59-62 is proportional to the current flowing through leads 28-31. 6
4 to 67 detect voltage drops across the resistors 59 to 62;
This is an amplifier for amplifying as necessary. 64 and 65
is a differential amplifier. Amplifiers 64 and 65 and amplifier 6
The amplification factors of 6 and 67 are equal. Lead wire 28-3
1 is not connected to the electrodes 23-26, the amplifier 6
If the offset voltage of 4 to 67 is adjusted, the output voltage of amplifiers 64 and 65 is V64 r V6B.
The ordinate of the contact point 54 is determined from 66°v67. The abscissa of the contact point 54 is approximately expressed by the following equation.

However, X is the distance from the contact point 54 to the electrode 23,
is the distance between the electrodes 23, 24, r is the resistance value of the resistor 59, 60, R1 is the resistance value between the electrode 23 and the contact point 54, R
2 is the resistance value between the electrode 24 and the contact point 54. The ordinate of the contact point 54 is also V, 6. It can be obtained from V, 7 by a similar calculation.

The transparent resistance sheets 21 and 22 are made of, for example, a transparent film such as polyester and indium oxide or tin oxide.

It can be made by depositing gold or the like by sputtering or vapor deposition. Although the transparent resistive sheets 21, 22 can be formed on glass plates, it is necessary to select a highly flexible glass for the transparent resistive sheet 21. The dotted spacers can be formed by printing ink based on transparent resin.

Further, the spacer may not be in the form of a dot but may be in the form of a thin line.

In the above, the transparent resistance sheet 2L is used as the resistance sheet.
22 was used, but this may also be opaque. As the opaque resistance sort, a carbon sheet formed by applying carbon-containing ink to paper or the like, a conductive rubber sheet, or the like can be used.

As explained in detail above, in the tablet of the present invention, two resistive sheets having uniform sheet resistance and electrodes formed on two opposing sides are used, and both resistive sheets are arranged so that the electrode sides are perpendicular to each other. Since the configuration is such that signals corresponding to the abscissa and ordinate can be obtained simultaneously, there is no need to provide a switching circuit for identifying the abscissa and the ordinate. Furthermore, a circuit for obtaining a signal corresponding to the coordinates can be constructed from several amplifier circuits. 5. In this invention, the coordinate identification circuit is significantly simplified, and since one resistor sheet detects coordinates in only one direction, electrodes can be provided on the entire two opposing sides, and There is no need for a diode group as in the past.

Therefore, there are advantages in that the coordinate detection accuracy is high and the configuration is simple.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional transparent tablet, Fig. 2 is a circuit diagram showing an embodiment of the present invention, and Fig. 4 is a block diagram showing an example of a conventional transparent tablet.
The figure is a diagram showing the configuration of another embodiment of the present invention. In the figure, 21 and 22 are transparent resistance sheets, 23 to 26 are electrodes at both ends, 27 is a group of point-like projections, 28 to 31 are lead wires,
32 to 35 are amplifiers, 36 to 39 are inverting input terminals, 40
-43 are non-inverting input terminals, 44-47 are output terminals, 48
~51 is a feedback resistor, 52 is a coordinate identification circuit,
53 is a power supply, 54 is a contact point, 55.56 is a differential amplifier,
59-62 are resistors, and 64-67 are amplifiers. Figure 1 Figure 2 Figure 5]

Claims (1)

[Claims] Two resistor sheets with electrodes formed on two opposing sides and having a uniform sheet resistance are stacked with a spacer in between so that the sides on which the electrodes are formed are orthogonal to each other. The configured input section, an amplifier that detects the magnitude of the current flowing through the two sets of lead wires connected to each of the electrodes when the two resistor sheets are short-circuited by pressing down, and an amplifier that detects the magnitude of the current flowing through the two sets of lead wires connected to each of the electrodes, and A tablet comprising a coordinate identification circuit for identifying the coordinates of a point.