JPH0981301A - Resistance pressure sensitive tablet and its pen-on detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the detection method which can set the pen-on detection threshold of every resistance pressure sensitive tablet and can decide the pen-on in a state the contact resistance is satisfactorily reduced. SOLUTION: The reference detection voltage VCC is applied to one of both sides of a detection voltage applied resistance plate via the control resistance RP, and the other side of the resistance plate is grounded. The voltage drop due to the RP referred to as the 1st potential difference VA is compared with the voltage drop due to the contact resistance (r) referred to as the 2nd potential difference VB. Thus the resistance value can be compared with each other between both resistance RP and (r). The pen-on detection threshold VTR decided by the difference VA can be easily set when the resistance value of the RP is set equal to the threshold (contact resistance threshold rc) that is optimum to decide a pen-on state. Then it is possible to decide the pressing of the resistance plate when the resistance (r) is equal to the threshold rc without being affected by the plate pressing position, if the pressing of the resistance plate is decided to be the time when the difference VB is less than the threshold VTR after they are compared with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance pressure-sensitive tablet that detects a pressing position of a stylus pen, a finger, or the like, and more specifically, a resistance pressure-sensitive tablet that detects that a resistance plate is pressed in a standby mode. It relates to the pen-on detection method.

[0002]

2. Description of the Related Art As shown in FIG. 9, a conventional resistance pressure-sensitive tablet has an X coordinate resistance plate 101 and a Y coordinate resistance plate 102.
While being separated from each other at a slight interval by an insulating dot spacer (not shown) or the like, they are polymerized so that their resistance layers face each other.

This resistive layer is formed of a uniform resistive element. Therefore, when a voltage for coordinate detection is applied to one electrode of the resistive plate and the other electrode is grounded, the distance from the electrode at each position of the resistive plate is increased. Proportional potentials are created and potential gradients of equal slope are formed.

When the resistance pressure-sensitive tablet having the above structure is used to detect coordinates, first, the CPU 103 controls the switches 103 and 104 on the X side to be closed to apply a potential gradient to the X coordinate resistance plate 101. At this time, A / D
Switch 107 connected to the input terminal of converter 106
Is connected to the output electrode side of the Y coordinate resistance plate 102.

Here, point P (x,
When y) is pressed by a stylus pen or the like, the potential V _P at the point _P has a resistance of x2 from the X input electrode 111 and a resistance of x1 from the X output electrode 110 as shown in the figure.
Then, V _CC × x1 ÷ (x1 + x2), and the x coordinate (x) is detected by reading this potential V _P with the A / D converter 106.

Next, the switches 103 and 104 on the X side are opened, the switches 108 and 109 on the Y side are closed, and the switch 107 connected to the input terminal of the A / D converter 106 is connected to the X output of the X coordinate resistance plate 101. Electrode 110
Connect to.

The potential V _P at the point _P is similarly the Y input electrode 1
If the resistance at the distance from 12 is y2 and the resistance at the distance from the Y output electrode 113 is y1, then V _CC × y1 ÷ (y1 + y
2), and the y coordinate (y) is detected by reading this potential V _P with the A / D converter 106.

As described above, in the coordinate detection mode, since a potential gradient is alternately applied to either the X coordinate resistance plate 101 or the Y coordinate resistance plate 102, a large amount of power is consumed.

Therefore, in the conventional resistance pressure-sensitive tablet, in the standby mode as shown in, for example, Japanese Patent Laid-Open No. 6-309086 shown in FIG. The detection mode is set.

That is, in the standby mode, the X coordinate resistance plate 1
01 one switch 103 is closed, the other switch 1
04 is opened to keep the X coordinate resistance plate 101 at the potential of V _CC , while the Y coordinate resistance plate 102 is such that the switch 108 is opened and the switch 109 is closed to be grounded.

At this time, the switch 107 connected to the input terminal of the A / D converter 106 is connected to the X coordinate resistance plate 101.
If it is connected to the electrode side of, the potential of the input terminal is V _CC as described above.

Here, the position P of the X coordinate resistance plate 101 is
When pressed with a stylus pen or the like, a current flows from the pressed point to the ground side through the Y coordinate resistance plate 102 and the switch 109, and the potential at the electrode 110 of the X coordinate resistance plate 101, that is, the input terminal of the A / D converter 106. Potential drops to a predetermined potential.

[0013] In CPU105 compares the stylus pressure detecting threshold value V _T is set to this potential in advance, when it becomes less stylus pressure detecting threshold value V _T, and determines that the resistance plate is pressed, the aforementioned coordinates The detection mode is set.

[0014]

The potential V _P dropped by the pen-on is V _CC × (y1 +) when the contact resistance is r.
r) ÷ (x2 + y1 + r), and changes from the pre-pressing potential V _{CC as the} contact resistance r decreases as shown in FIG. 10A, and stabilizes at the potential V _PL when the contact resistance r becomes the smallest. .

Therefore, the pen-on detection threshold value V _T is shown in FIG.
As shown in 0 (a), set a potential slightly higher than this,
This value is stored in advance in a ROM (not shown) and compared with the potential V _P that drops when the pen is turned on to determine that the resistance plate has been pressed.

However, since the potential V _PL when the contact resistance r becomes the smallest changes depending on the resistance values x2 and y1 of the X coordinate resistance plate 101 and the Y coordinate resistance plate 102, the material of the resistance layer of the resistance plate. , It may vary from tablet to tablet due to the thickness of the resistive film.

[0017] Thus, in stylus pressure detecting threshold value V _T set in FIG. 10 (a), the setting the the stylus pressure detecting threshold value V _T 1 of another tablet, as shown in FIG. 10 (b), the potential V _PL In the following cases, the pressing of the resistance plate could not be determined.

For example, in a tablet in which the resistance layer is made of carbon and a tablet in which ITO (Indium tin Oxide) is used, it is necessary to use a ROM in which different pen-on detection thresholds V _T are stored, and the ROM cannot be shared. was there.

In order to solve this problem, FIG.
It is conceivable to stylus pressure detecting threshold value V _T 2 by pulling the stylus pressure detecting threshold V _T to slightly lower than the potential V _CC in the standby mode as shown in, stylus pressure detecting threshold value V _T When the value exceeds 2, the contact resistance r has not decreased to a negligible level as compared with the internal resistance of the A / D converter 106, so it is determined that the resistance plate is pressed in this state, and the subsequent coordinate detection is performed. When shifting to the mode, there arises a problem that the coordinate detection is affected by the change in the contact resistance r.

That is, when detecting, for example, the x-coordinate (x) in the coordinate detection mode, the potential V _P at the point P is detected by the A / D converter 106 as shown in FIG. 9 as described above. However, this is because the stable contact resistance r at point P is the internal resistance R _A of the A / D converter 106.
It is premised that it is negligibly smaller than (1 M to 10 MΩ), and the contact resistance r immediately after the potential V _P at the point _P exceeds the pen-on detection threshold V _T 2 is:
It has a large value.

At this time, the potential V _P ′ read by the A / D converter 106 is V _P × R _A ÷ (R _A + r)
When the contact resistance r becomes a large value that cannot be ignored with respect to R _A, a change in the contact resistance r appears in the read potential V _P ′, which causes a coordinate detection error.

In particular, while the contact resistance r is high, the influence of noise from the outside is also great, which hinders coordinate detection.

On the other hand, a timer of time T ₀ from when it is determined that the resistance plate is pressed by the pen-on detection threshold V _T 2 until the contact resistance r is sufficiently reduced is set, and the coordinate detection thereafter. It is also known to delay the transition to the mode, but it requires an extra timer circuit and becomes expensive,
There was a problem that the circuit became complicated.

Further, the time until the contact resistance is sufficiently reduced varies depending on the pen-on pressing condition, and it is difficult to uniformly set the time T ₀ .

After all, in FIG. 10A, the pen-on detection threshold V _T needs to be equal to or higher than the potential V _PL determined by the material of the resistor, the thickness of the resistive film, etc., and the contact resistance r decreases. Therefore, it is necessary to set the potential below the potential V _PC when the change does not affect the coordinate detection, but since the potentials V _PL and V _PC are unique potentials for each tablet, the pen-on detection threshold V _T is set. RO for each tablet
M had to remember.

On the contrary, once the data is stored in the ROM, it cannot be used for other models, and the ROM needs to be replaced each time.

To solve this problem, the applicant of the present invention has filed a patent application for a resistance pressure sensitive tablet in which the pen-on detection threshold V _T is set by the voltage division ratio of the resistor R1 and the variable resistor R2 as shown in FIG. (Japanese Patent Application No. Hei 7th year No. 63527).

That is, resistors R1 and R2 connected in series
The reference detection voltage V _CC is applied to one end of the
The intermediate tap T is connected to the input terminal IY ⁺ of the A / D converter 114. The potential at the intermediate tap T is A / D
If the pen-on detection threshold V _T of the converter 114 is set, the potential at the intermediate tap T is the potential obtained by dividing the reference detection voltage V _CC by the resistors R1 and R2, and thus the resistance value R2 of the variable resistor R2 is changed. The pen-on detection threshold value V _T can be set only by itself.

This pen-on detection threshold V _T is a potential equal to or higher than the minimum potential V _{PL of the} pen-on and equal to or lower than the potential V _PC when the contact resistance is reduced to such an extent that the change in the contact resistance between the resistance plates can be ignored. In order to set to, the operation of the tablet is confirmed by repeating the pen-on of the tablet on a trial basis, and the resistance value of the variable resistor R2 is set. That is, the resistance value of the variable resistor R2 is adjusted so that the pressing force of the tablet can be detected and the influence of the change of the contact resistance does not appear after the detection.

The value of the variable resistance R2 adjusted in this way is from the contact resistance value r _MIN and the pressing position P'to the electrode when the contact resistance decreases and becomes stable when the tablet is pressed experimentally. The resistance value is slightly larger than the sum of the resistance values r _y and r _x of both resistance plates (r _MIN + r _y + r _x ).

On the other hand, in the standby mode for detecting a stylus pressure, one end of the variable resistor R2 (PCHK ^-) is turned off and grounded electrode X side resistance sheet 115 as shown, the potential of the intermediate tap T by the Pen-on is determined by comparing with the set pen-on detection threshold V _T.

Therefore, even if the material of the resistive pressure sensitive tablet is different, the pressing of the tablet can be accurately detected by pressing in the vicinity of the position where the tablet is pressed during the adjustment, and after the detection, the contact resistance r The effect of the change of does not appear.

However, when the position P'where the tablet is pressed to adjust the variable resistance and the pressing position P of the pen-on to be actually detected are different, as shown in FIG. There is a problem that the resistance values r _y ′ and r _x ′ of both resistance plates up to the electrodes are different, and even if the stable contact resistance value r _MIN is reached, the pen-on detection threshold value V _T is not exceeded and the pen-on cannot be detected. Occurs.

That is, when pressing the pressing position P farther from the electrode than the pressing position P ′ of the tablet when adjusting the variable resistance, r _y ′ + r _x ′> r _y + r _x , and the potential of the intermediate tap T becomes However, if a pressing position P closer to the electrode is pressed than a pressing position P ′ of the tablet when adjusting the variable resistance, the problem that the pen-on cannot be detected rises, and conversely, r _y ′ + r _x ′ <r _y + r _x becomes, the potential of the intermediate tap T is lowered, and the pen-on is discriminated before the contact resistance r is sufficiently lowered, which causes a problem that the cursor moves in the subsequent coordinate detection.

This problem cannot be solved no matter how the pen-on detection threshold value V _T is set, because the pressing position P at the time of detecting the pen-on is different each time.

Further, in the resistance pressure-sensitive tablet shown in FIG. 11, the variable resistor R2 used when setting the pen-on detection threshold V _T is set in the standby mode and the coordinate detection mode in which the pen-on is subsequently detected. A / D converter 11
4 so as not to affect the input voltage of 4 (PCHK
^- ) Must be turned off, and a switch circuit for that was required, and the circuit configuration was complicated.

The present invention has been made to solve the above problems, and the pen-on detection threshold value V _TR for each resistance pressure-sensitive tablet can be set with a simple structure.
Moreover, it is an object of the present invention to provide a resistance pressure sensitive tablet capable of discriminating pen-on when the contact resistance is sufficiently reduced regardless of the pressing position P of the tablet, and a pen-on detection method for the resistance pressure-sensitive tablet.

[0038]

In order to achieve the above object, the resistance pressure-sensitive tablet according to claim 1 has an X coordinate in which an X input electrode and an X output electrode are formed along two sides at both ends in the X direction. A resistance plate, a Y input electrode and a Y output electrode are formed along the two sides of both ends in the Y direction orthogonal to the X direction, and the Y coordinate resistance plate is superposed with the X coordinate resistance plate with a slight insulating gap. In the mode, the CPU detects the resistance plate being pressed from the potential of the resistance plate changed by pen-on by applying the reference detection voltage V _CC to one resistance plate and controlling the other resistance plate to be grounded. In a resistance pressure-sensitive tablet including and, a reference detection voltage is applied to an input electrode of one resistance plate via an adjustment resistor R _P, and an output electrode of the other resistance plate is grounded, and an A / D converter is used. , Inspection Detecting an output electrode and the input electrode of the voltage application side resistance sheet, each potential of the input electrode of the ground side resistance sheet,
By the CPU, the first potential difference V _A between the potential of the input electrode of the detection voltage applying side resistance plate and the reference detection voltage, the potential of the output electrode of the detection voltage applying side resistance plate and the potential of the input electrode of the ground side resistance plate The second potential difference V _B is compared, and it is determined that the resistance plate is pressed when the second potential difference V _B becomes equal to or less than the pen-on detection threshold V _TR defined from the first potential difference V _A. And

[0039] When pressing the tablet in stylus pressure detecting state, from one end of the adjusting resistor R _P of applying the reference detection voltage, adjusting resistor R _P, the input electrode of the detection voltage application side resistance sheet, the detection voltage application side resistance sheet, the pressing position An electric current flows through the contact resistance at, the ground side resistance plate, and the output electrode of the ground side resistance plate.

At this time, since no current flows through the output electrode of the detection voltage application side resistance plate and the input electrode of the ground side resistance plate,
The first potential difference V _A represents a voltage drop due to the adjustment resistor R _P ,
The second potential difference V _B represents the voltage drop due to the contact resistance r. Further, since the adjustment resistance value and the current value flowing through the contact resistance are equal, if the second potential difference V _B and the first potential difference V _A are compared,
The resistance value of the changing contact resistance and the resistance value of the adjusting resistance R _P can be compared.

If the resistance value of the adjusting resistance R _P is adjusted with reference to the resistance value when the resistance value of the contact resistance r is so low that it can be ignored (hereinafter referred to as the contact resistance threshold value r _C ),
The pen-on detection threshold V _TR determined from the potential difference V _A and the second
The potential difference V _B is compared, and when the second potential difference V _B becomes equal to or less than the pen-on detection threshold value V _TR , the resistance plate is pressed as if the contact resistance r has decreased to the contact resistance threshold value r _C. Can be identified as a thing.

That is, although the current value flowing through the tablet differs depending on the pressing position of the tablet, the pressing of the resistance plate can be discriminated without being affected by the pressing position by comparing the adjustment resistance value and the voltage drop of the contact resistance.

If the contact resistance threshold value r _C of the tablet can be known in advance, the pen-on detection threshold value V _TR can be set by using the adjustment resistance R _P of the resistance value r _{P corresponding} to it. You can

According to a second aspect of the pressure-sensitive tablet, an X-coordinate resistance plate having an X input electrode and an X output electrode respectively formed along two sides in the Y direction, and two in the X direction orthogonal to the Y direction.
Y input electrodes and Y output electrodes are formed along the sides, respectively, and the Y coordinate is overlapped with the X coordinate resistance plate and a slight insulating gap.
In the coordinate resistance plate and the standby mode, the reference detection voltage V _CC is applied to one resistance plate and the other resistance plate is controlled to be grounded, and the resistance plate is pressed from the potential of the resistance plate changed by pen-on. In a resistance pressure-sensitive tablet equipped with a CPU for detecting the fact that the reference detection voltage is applied to the input electrode of one resistance plate, and the output electrode of the other resistance plate is grounded via the adjustment resistance R _P. , A / D converter detects the respective potentials of the output electrode of the detection voltage application side resistance plate and the input and output electrodes of the ground side resistance plate, and C
By the PU, the first potential difference V _A between the output electrode potential of the ground side resistance plate and the ground voltage, and the second potential difference between the output electrode potential of the detection voltage application side resistance plate and the input electrode potential of the ground side resistance plate. It is characterized in that the resistance plate is pressed when the second potential difference V _B becomes equal to or less than the pen-on detection threshold V _TR defined from the first potential difference V _A by comparing V _B.

When the tablet is pressed in the pen-on detection state, from the input electrode of the detection voltage application side resistance plate to which the reference detection voltage is applied, the detection voltage application side resistance plate, the contact resistance at the pressing position, the ground side resistance plate, the ground side resistance. A current flows through the output electrode of the plate and the adjusting resistor R _P.

At this time, since no current flows through the output electrode of the detection voltage application side resistance plate and the input electrode of the ground side resistance plate,
The first potential difference V _A represents a voltage drop due to the adjustment resistor R _P ,
The second potential difference V _B represents the voltage drop due to the contact resistance r. Further, since the adjustment resistance value and the current value flowing through the contact resistance are equal, if the second potential difference V _B and the first potential difference V _A are compared,
The resistance value of the changing contact resistance and the resistance value of the adjusting resistance R _P can be compared.

The first and the potential difference V stylus pressure determined from _A detection threshold V _TR comparing the second potential difference V _B, when the second potential difference V _B becomes equal to or lower than the stylus pressure detecting threshold value V _TR, the resistor plate If is pressed, it is possible to determine the pressing of the resistance plate by directly comparing with the contact resistance threshold value r _C.

That is, although the current value flowing through the tablet differs depending on the pressing position of the tablet, the pressing of the resistance plate can be discriminated without being affected by the pressing position by comparing the adjustment resistance value and the voltage drop of the contact resistance.

If the contact resistance threshold value r _C of the tablet can be known in advance, the pen-on detection threshold value V _TR can be set by using the adjustment resistance R _P of the resistance value r _{P corresponding} to it. You can

The resistance pressure-sensitive tablet according to claim 3 is characterized in that the adjusting resistor R _P is a variable resistor.

Since the adjusting resistor R _P is a variable resistor, the resistance value r _P of the adjusting resistor R _P can be easily changed. Therefore, the pen-on of the tablet is repeated on a trial basis, the resistance value r _P of the variable resistance is changed while confirming the operation of the tablet, and the pressure of the tablet can be detected, and after the detection, the influence of the change of the contact resistance does not appear. It is possible to set a different pen-on detection threshold V _TR .

Since the pen-on detection threshold value V _TR is adjusted by only the variable resistor and is not obtained by the voltage division ratio with other resistors connected in series, after the pen-on detection threshold value V _TR is set, No switch is needed to disconnect the other resistors from the circuit.

The resistance pressure-sensitive tablet according to claim 4 is characterized in that the pen-on detection threshold value is equal to the first potential difference V _A.

Pen-on detection threshold V _TR and first potential difference V
_{Since A} is equal, if the adjustment resistance R _P having the same resistance value as the contact resistance threshold value r _C is used, the contact resistance becomes contact resistance when the second potential difference V _B becomes equal to or lower than the pen-on detection threshold value V _TR. becomes equal to or less than threshold r _C, it can determine the pressing of the resistance plate is directly compared with the contact resistance threshold r _C.

The resistance pressure-sensitive tablet according to claim 5 is characterized in that the pen-on detection threshold value is a value obtained by multiplying the first potential difference V _A by a correction constant N larger than 1.

A pen-on detection threshold value V _TR which can be discriminated as a pen-on when the contact resistance r becomes equal to or lower than the contact resistance threshold value r _C is set by using the adjustment resistance R _P having a resistance value r _P of 1 / N. Therefore, the influence on the coordinate detection circuit is small, and the potential gradient can be formed on the resistance plate through the adjustment resistor R _P as it is even after shifting to the coordinate detection mode.

According to a sixth aspect of the resistance pressure sensitive tablet pen-on detection method, the X-coordinate resistance plate and the Y-coordinate resistance plate are superposed with a slight insulating gap, and in the standby mode, one of the resistance plates has a reference detection voltage V _CC. Is applied to control the other resistance plate to be grounded, and the resistance plate is detected from the potential of the resistance plate that changes when the pen is turned on. , The reference detection voltage is applied via the adjustment resistor R _P , the other resistance plate is grounded, and the first potential difference V _A which is the potential difference between both ends of the adjustment resistor R _P and the second potential difference which is the potential difference between the resistance plates. The potential difference V _B is compared, and the second potential difference V _B is compared with the first potential difference V _B.
It is characterized in that it is determined that the resistance plate has been pressed when it becomes equal to or less than the pen-on detection threshold V _TR determined from _A.

According to a seventh aspect of the present invention, there is provided a pen-on detection method for a resistance pressure-sensitive tablet, wherein the X-coordinate resistance plate and the Y-coordinate resistance plate are superposed with a slight insulating gap, and one resistance plate has a reference detection voltage V _CC in the standby mode. Is applied to control the other resistance plate to be grounded, and the resistance plate is detected from the potential of the resistance plate that changes when the pen is turned on. While applying the reference detection voltage,
Adjusting resistor R _P through the ground, comparing the first potential difference V _A is the voltage across the adjustment resistive R _P, the second potential difference V _B is the potential difference in the resistance plates, the second potential difference V _B No. 1 potential difference V _A
It is characterized in that it is determined that the resistance plate has been pressed when it becomes equal to or less than the pen-on detection threshold V _TR determined by

In the invention of claim 6 and claim 7, the second
The ratio of the potential difference V _B and the first potential difference V _A is such that the contact resistance r changes.
And the resistance value r _P of the adjustment resistance R _P.

The pen-on detection threshold value V _TR determined from the first potential difference V _A and the second potential difference V _B are compared, and when the second potential difference V _B becomes equal to or less than the pen-on detection threshold value V _TR , the resistance plate If is pressed, it is possible to determine the pressing of the resistance plate by directly comparing with the contact resistance threshold value r _C.

[0061] Since the adjusting resistor R _P is a variable resistor, by changing the resistance value r _P of the adjustment resistor R _P, it can be easily set the stylus pressure detecting threshold V _TR.

The pen-on detection threshold V _TR is adjusted only by the variable resistor and is not obtained by the voltage division ratio with other resistors connected in series. Therefore, after the pen-on detection threshold V _TR is set, No switch is needed to disconnect the other resistors from the circuit.

[0063]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show a resistance pressure-sensitive tablet 20 according to the first embodiment of the present invention.
In, the CPU 1 has a built-in A / D converter 2,
This A / D converter 2 has three input terminals AD1, A
Equipped with D2 and AD3, the potentials of the input terminals can be detected at the same time.

The CPU 1 has five input / output terminals PCH.
K, IX ⁺ , OX ⁻ , IY ⁺ , and OY ⁻ are provided, and electronic switches 3 to 7 that switch the connection between these input terminals and the internal circuit are connected in the subsequent stage of each input / output terminal. Each of the electronic switches 3 to 7 operates individually under the control of the CPU 1, and C
The connection with the internal circuit in PU1 can be switched.

Reference numerals 8 and 9 are an X coordinate resistance plate and a Y coordinate resistance plate, which are separated from each other by a printing spacer (not shown) printed in dots on the resistance plates 8 and 9 with a slight gap therebetween. Polymerization is performed so that the uniformly formed resistance layers face each other.

As shown in the figure, the X coordinate resistance plate 8 is provided with an X input electrode 8a and an X output electrode 8 along two sides at both ends in the X direction.
b is formed, the X input electrode 8a is connected to the PCHK terminal via the IX ⁺ terminal of the CPU 1 and the variable resistance R _P which is the adjustment resistance, and the X output electrode 8b is connected to the OX ⁻ terminal of the CPU 1. .

A Y input electrode 9a and a Y output electrode 9b are formed on the Y coordinate resistance plate 9 along the two sides at both ends in the Y direction. The Y input electrode 9a is connected to the IY ⁺ terminal of the CPU 1. The Y output electrode 9b is connected to the OY ⁻ terminal of the CPU 1.

Before use, the resistance pressure-sensitive tablet thus configured initializes the pen-on detection threshold V _TR which is the detection sensitivity for detecting the pressing of the resistance plate in the standby mode.

When the pen-on detection threshold value V _TR is initialized, the electronic switches 3 to 7 of the CPU 1 are operated as shown in FIG. 1, and the input / output terminals of the CPU 1 are connected to the internal circuit. .

That is, the PCHK ⁺ terminal is connected to the switch 3
Power V _CC and connected, and applying a reference detection voltage V _CC via the variable resistor R _P to the X input electrode 8a of the X-coordinate resistance sheet 8 by.

The input / output terminals of IX ⁺ , OX ⁻ and IY ⁺ are connected to the input terminals AD1, AD2 and AD3 of the A / D converter 2 by switches 4, 5 and 6, respectively, and X
The potentials of the X input electrode 8a, the X output electrode 8b of the coordinate resistance plate 8 and the Y input electrode 9a of the Y coordinate resistance plate 9 are detected.

The remaining OY ^- input / output terminal is the electronic switch 7
Is connected to the ground terminal, and the Y output electrode 9b of the Y coordinate resistance plate 9 is set to the GND level.

[0074] In the present embodiment, by pressing the tablet on a trial basis in this state, while checking the operation of the pressure sensitive resistor, by adjusting the resistance value r _P of the variable resistor R _P, stylus pressure detecting threshold Set the value V _TR .

The setting of the pen-on detection threshold value V _TR will be described below with reference to FIG.

FIG. 2 is an equivalent circuit diagram of the resistance pressure sensitive tablet of FIG. In the resistance pressure-sensitive tablet 20, the X coordinate resistance plate 8 is at the reference detection voltage V _CC level and the Y coordinate resistance plate 9 is GND when the tablet is not pressed.
Level.

As shown in the figure, when the X coordinate resistance plate 8 is pressed from this state, at the pressing position P ', the current i _t changing from the X coordinate resistance plate 8 to the Y coordinate resistance plate 9 due to the change of the contact resistance. Flowing. At this time, since the A / D converter 2 is connected to each of the IX ⁺ , OX ⁻ , and IY ⁺ input / output terminals, ignoring the minute currents flowing in these directions, the variable resistance R _P and the contact resistance r are ignored. An equal current i flows through each.

Therefore, the potential difference between the both ends is set to the first
Potential difference V _A, as a second potential difference V _B, can be compared to the first potential difference V _A and the second potential difference V _B, compares the resistance value r _P and the contact resistance r of the variable resistor R _P.

As is apparent from the figure, the first potential difference V _A is the known reference detection voltage V _CC and the potential V ₁ of the input terminal AD1 of the A / D converter 2, and the second potential difference V _B is A /
It can be obtained from the potentials V ₂ and V ₃ of the input terminals AD2 and AD3 of the D converter 2.

In the present embodiment, the resistance value r _P of the variable resistor R _P is adjusted to a value equal to the contact resistance threshold value r _C ,
The first potential difference V _A across the variable resistor R _P at this time as stylus pressure detecting threshold value V _TR, stylus pressure detecting threshold value V _TR
And the second potential difference V _B are compared with each other to substantially compare the contact resistance threshold value r _C with the contact resistance r that changes due to the pressing of the tablet (hereinafter referred to as pen-on).

[0081] In order to adjust the variable resistance R equal to the contact resistance threshold r _C the resistance value r _P of _P, for each changing the resistance value r _P of the variable resistor R _P, pressed tablet, the The operation of the tablet is confirmed by determining that the pen-on is detected when the second potential difference V _B becomes equal to or less than the first potential difference V _A.

[0082] Variable resistance R resistance value r _P of _P does not detect the minimum stable value r _MIN smaller than the stylus pressure of contact resistance r, the internal resistance and the contact resistance r is the A / D converter is too large R
Since it is determined that the pen is on before it becomes so small that it can be ignored compared to _A , the change in the contact resistance r appears as an error in the coordinate detection data, and the cursor moves with the change in the contact resistance r.

That is, when the pen-on is surely detected, and when the pen-on is discriminated so that the change of the contact resistance r after detecting the pen-on does not affect the coordinate detection after the detection of the pen-on, the resistance of the variable resistance R _P is changed. The value r _P is sufficiently smaller than the internal resistance R _A of the A / D converter, and the minimum stable value r
_It is adjusted to a value equal to the contact resistance threshold value r _C, which is slightly larger than _MIN .

In this embodiment, the adjustment resistor R _P is used as a variable resistor to adjust the first potential difference V _A , but the adjustment resistor R _P having a different resistance value is replaced as appropriate to change the first potential difference V _A. You may adjust _A. In particular, in the above embodiment, and check the operation of the tablet while tentatively repeated stylus pressure on the tablet, obtains a resistance value r _P of the variable resistor R _P, make adjustments by changing the resistance value r _P However, if the contact resistance threshold value r _C can be known in advance, the adjustment resistance R _P having a resistance value r _{P that} is substantially the same as the contact resistance threshold value r _C can be connected to make adjustment without repeating the pen-on for the above adjustment. be able to.

In this way, pen-on is discriminated by the tablet of FIG. 1 in which the adjustment resistance R _P is adjusted to the value equal to the contact resistance threshold value r _C.

In the standby mode for monitoring the pen-on, as in the initial setting of the pen-on detection threshold V _TR , the electronic switches 3 to 7 of the CPU 1 are operated as shown in FIG. 8 is the reference detection voltage V _CC level, and the Y coordinate resistance plate 9 is the GND level.

In this standby mode, the X coordinate resistance plate 8 and Y
Since no current flows between the coordinate resistance plate 9 and the coordinate resistance plate 9, the adjustment resistance R
The potentials at both ends of _P are equal, and the first potential difference V _A is 0V. The potentials of the OX ⁻ and IY ⁺ input / output terminals are V _CC and 0 V, respectively, and the second potential difference V _B is V _CC, which is larger than the first potential difference V _A.

As shown in FIG. 2, when the tablet is pressed from this state, the contact resistance r at the contact position P between the resistance plates 8 and 9 changes from infinity to rapidly as the contact pressure gradually increases. Decrease.

[0089] In a state where the contact resistance is changing, if the current flowing through the i _t, the first potential difference V _A, an r _P * i _t, the resistance value r _P, the contact resistance threshold r since adjusted to equal to _C value, stylus pressure detecting threshold location V _TR equal to the first potential difference V _a can be expressed by the product of r _C and i _t. On the other hand, the second electrical potential difference V _B can be expressed by the product of the contact resistance r and i _t that varies by the change of the pressing force.

Therefore, IX ⁺ input / output terminals and OX ⁻ , IY ⁺
The potentials V ₁ , V ₂ and V ₃ of the input / output terminals are detected by the A / D converter 2, and the pen-on detection threshold V _TR and V ₂ are obtained by the difference between the reference detection voltage V _CC and the potential V _1. When the second potential difference V _B obtained by the potential difference of V ₃ is compared by the CPU 1, the contact resistance threshold value r _C and the contact resistance r are directly compared.

That is, since the resistance value of the resistance plates 8 and 9 is not included in the pen-on detection threshold V _TR and the second potential difference V _B , no matter which position of the resistance plate is pressed, the same condition is applied. Can be compared.

When the contact resistance r becomes equal to or less than the contact resistance threshold value r _C , the second potential difference V _B becomes equal to or less than the pen-on detection threshold V _TR , and at this time, the CPU 1 determines the pen-on.

Therefore, the pen-on is detected without exception, and when it is determined that the pen-on is detected, the contact resistance r is A /
Since the internal resistance R _A of the D converter 2 is so small that it can be ignored, the change does not affect the coordinate detection in the coordinate detection mode later.

When the pen-on is detected in the standby mode, the mode is shifted to the coordinate detection mode and the X coordinate resistance plate 8 and the Y coordinate resistance plate 9 are detected.
An electric potential gradient is alternately formed in and the X and Y coordinates of the pressing position P are detected. In the coordinate detection mode, the electronic switch 3 turns off the PCHK ⁺ terminal to disconnect the adjusting resistor R _P from the resistor plate circuit.

FIG. 3 shows a resistance pressure-sensitive tablet in which a potential gradient is formed on the X-coordinate resistance plate 8 in order to detect the X-coordinate.

That is, the IX ⁺ input terminal is connected to the power source V _CC by the electronic switch 4, the reference detection voltage V _CC is applied to the X input electrode 8a of the X coordinate resistance plate 8 from the IX ⁺ input terminal, and the OX ⁻ input is applied. The output terminal is grounded by the electronic switch 5, the other X output electrode 8b of the X coordinate resistance plate 8 is grounded, and the X coordinate resistance plate 8 is formed with a uniform potential gradient.

Further, the Y coordinate resistance plate 9 has a Y output electrode 9b.
The electronic switch 7 turns off the OY ^- input / output terminal connected to the terminal so that current does not flow from the contact position with the X-coordinate resistance plate 8 to the Y-coordinate resistance plate 9, and the IY ⁺ input / output terminal is connected to the electronic switch 6 Is connected to the input terminal AD3 of the A / D converter 2 by the Y input electrode 9a of the Y coordinate resistance plate 9.
Therefore, the electric potential at the pressing position P is detected.

Then, from the potential V _X detected at the input terminal AD3, the X coordinate (V _X / V _CC ) of the pressing position P is calculated by the CPU.
Calculate with 1 and detect.

After detecting the X coordinate, the Y coordinate is detected by the same method.

FIG. 4 shows a resistance pressure sensitive tablet in a state where a potential gradient is formed on the Y coordinate resistance plate 9.

As shown in the figure, by operating the electronic switches 6 and 7, the reference detection voltage V _CC is applied to the Y input electrode 9a of the Y coordinate resistance plate 9 and the other Y output electrode 9b is applied.
Is grounded to form a uniform potential gradient on the Y coordinate resistance plate 9.

By the operation of the electronic switches 4 and 5,
The X output electrode 8b terminal of the X coordinate resistance plate 8 is turned off so that the current does not flow from the contact position with the Y coordinate resistance plate 9 to the X coordinate resistance plate 8, and the IX ⁺ input connected to the X input electrode 8a is input. The output terminal is the input terminal AD of the A / D converter 2.
1, and the electric potential at the pressing position P is detected from the X input electrode 8a.

Thus, similarly to the X coordinate, the CPU 1 calculates and detects the Y coordinate (V _Y / V _CC ) of the pressing position P from the potential V _Y detected at the input terminal AD1.

When the detection of the X and Y coordinates is completed, C
The PU 1 controls the operation of the electronic switches 3 to 7, and the PU 1 shown in FIG.
Then, the pen-on detection is repeated.

In the pen-on detection, if the second potential difference V _B is equal to or less than the pen-on detection threshold V _TR, it can be determined that the pen has been continuously pressed after the coordinate detection, and the X coordinate, Y detected immediately before is detected. The coordinates are output as effective position information to a higher-level processing device (not shown) such as a personal computer.

At this time, if it cannot be determined that the pen is on, it is determined that the pen has moved away during coordinate detection, and the position information of the X coordinate and the Y coordinate detected immediately before is invalidated.

In any case, once the pen-on is detected and the coordinate detection is executed, a predetermined time (for example, 5 m
sec), the standby mode is resumed and the pen-on detection is repeated.

In the first embodiment described above, the first
While the electric potential difference V _A as stylus pressure detecting threshold value V _TR it is compared with the second potential difference V _B, as pressure sensitive resistor shown in FIG. 5, the contact a 'resistance r _P' of the adjustment resistor R _P 1 / N of the threshold resistance r _C (N is greater than 1 correction constant) to adjust the resistance value r _C / N of stylus pressure to N times the potential difference between the first potential difference V _a across the regulation resistor R _P ' As the detection threshold V _TR , the pen-on detection threshold V _TR and the second potential difference V _B may be compared.

As in the above-described embodiment, if the current flowing while the contact resistance is changing is i _t , the pen-on detection threshold V _TR is N * V _A, that is, N * r _P ″. i _t
And the resistance value r _P ′ is 1 / N of the contact resistance threshold value r _C.
Since the adjustment of the resistance value, eventually stylus pressure detecting threshold location V _TR is expressed by the product of r _C and i _t.

Therefore, IX ⁺ input / output terminals and OX ⁻ , IY ⁺
A pen-on detection threshold V _TR obtained by detecting the respective potentials V ₁ , V ₂ , V ₃ of the input / output terminals by the A / D converter 2 and multiplying the difference between the reference detection voltage V _CC and the potential V ₁ by N. , The second potential difference V _B obtained by the potential difference between V ₂ and V ₃ is compared by the CPU 1, the contact resistance threshold value r _C and the contact resistance r are directly compared as in the first embodiment described above. You can

[0111] be changed to 'adjust the resistance R _P of' thus adjusting resistor R _P of the resistance value r _P a smaller resistance value r _P, by comparing the contact resistance r and the contact resistance threshold r _C, stylus pressure Can be determined.

In the present invention, it is not always necessary to separate the adjustment resistor R _P from the circuit of the resistance plates 8 and 9 in the coordinate detection mode, but as in the second embodiment, the adjustment resistor R _P ′ is not provided. When the resistance value r _P ′ is reduced, even if the resistance plates 8 and 9 are directly connected to the circuit, the influence on the coordinate detection resolution is small.

That is, in the coordinate detection mode for detecting the X coordinate shown in FIG. 3, the reference detection voltage V _{CC is} temporarily applied to the X input electrode 8a from the PCHK input / output terminal through the adjustment resistor R _P.
Is applied, the potential of the X input electrode 8a becomes lower than the reference detection voltage V _CC by the voltage drop V _RP due to the adjustment resistor R _P.

In the first embodiment, the resistance value r _P of the adjustment resistor R _P is equal to the contact resistance threshold value r _C , and the coordinate detection mode is connected in series with the resistance layer of the X coordinate resistance plate 8. At, V _RP becomes a non-negligible size compared to V _CC .

Therefore, both electrodes 8a, 8 of the X coordinate resistance plate 8 are
The potential difference between b is V _CC −V _RP , and since V _RP is a size that cannot be ignored, the coordinate detection accuracy of the X coordinate obtained from V _X / (V _CC −V _RP ) is impaired.

However, in the resistance pressure-sensitive tablet shown in FIG. 5, in the X coordinate detection mode, even if the reference detection voltage V _CC is applied to the X input electrode 8a from the IX ⁺ output terminal through the adjustment resistor R _P ′. , 'resistance r _P' of the adjustment resistor R _P
However, since it is a value obtained by dividing the contact resistance threshold value r _C by the correction constant N, V _RP is small and the coordinate detection accuracy of the X coordinate is not impaired.

In the first and second embodiments of the present invention described above, in the standby mode, the reference detection voltage V _CC is applied to the resistance plate on the reference voltage application side through the adjustment resistor R _P to turn on the pen. Detecting, but connecting the adjustment resistor R _P to the ground side resistance plate to which the reference detection voltage V _CC is not applied, and connecting the ground side resistance plate to the ground terminal via the adjustment resistor R _P to detect the pen-on. You may

The resistance pressure-sensitive tablet 30 according to the third embodiment will be described with reference to FIGS. 6 and 7.

FIG. 6 shows a resistance feeling in a state where a variable resistor R _P which is an adjusting resistor is connected to the Y output electrode 9b of the Y coordinate resistor plate 9 which is a ground side resistor plate, and the other end of the variable resistor R _P is grounded. A pressure type tablet is shown, and in the state shown in the figure, the resistance value of the adjustment resistor R _P is initialized, and a standby mode for detecting pen-on is set.

This resistance pressure-sensitive tablet 30 has different internal circuits of the CPU 1 which can be switched by the electronic switches 3 to 7, and the adjustment resistor R _P connected to the PCHK terminal.
The configuration is almost the same as that of the first embodiment (see FIG. 1) except that the other end of is connected to the Y output electrode 9b of the Y coordinate resistance plate 9.

In the same manner as in the first embodiment, also in this resistance pressure-sensitive tablet, pen-on is repeated on a trial basis before use, and the resistance value r _P of the adjustment resistor RP is adjusted while confirming the operation. , The pen-on detection threshold value V _TR is initialized.

The setting of the pen-on detection threshold value V _TR will be described below with reference to FIG.

FIG. 7 is an equivalent circuit diagram of the resistance pressure sensitive tablet of FIG. In the resistance pressure-sensitive tablet of FIG. 6, when the tablet is not pressed, the X coordinate resistance plate 8 is at the reference detection voltage V _CC level and the Y coordinate resistance plate 9 is GN.
It is at the D level.

As shown in FIG. 7, when the X coordinate resistance plate 8 is pressed from this state, a current i _t flows from the X coordinate resistance plate 8 to the Y coordinate resistance plate 9 at the pressing position P '. The relationship between the variable resistance R _P and the contact resistance r at this time can be compared from the potential difference between both ends of each resistance, as described above.
Comparing a first potential difference V _A between the potential V ₁ of the input terminal AD1 of the A / D converter 2 and a known ground potential GND and a second potential difference V _B between the input terminals AD2 and AD3 of the A / D converter 2. Required by.

[0125] Therefore, as in the first embodiment, while confirming the operation to adjust the resistance value r _P of the variable resistor R _P, or the contact resistance threshold r _C is, if known, the corresponding resistor The adjustment value R _P of the adjustment resistance is connected to the resistance value r of the adjustment resistance R _{P.
Make P} equal to the contact resistance threshold r _C.

The pen-on detection threshold value V _TR is the first potential difference V _A across the adjustment resistor R _P adjusted to the contact resistance threshold value r _C when it is determined to be pen-on.

As described above, the pen-on is discriminated by the tablet for which the pen-on detection threshold value V _TR is set. Even in the standby mode in which the pen-on is monitored, the electronic switches 3 to 7 of the CPU 1 are connected to the internal circuit of the CPU 1 at the same positions shown in FIG. 6 as in the initial setting of the pen-on detection threshold V _TR .

When the tablet is pressed in the standby mode, the contact resistance r at the contact position P between the resistance plates 8 and 9 shown in FIG. 7 decreases from infinity to abruptly as the contact pressure gradually increases. To do.

[0129] In a state where the contact resistance r is changing, if the current flowing through the i _t, stylus pressure detecting threshold location V _TR equal to the first potential difference V _A is r _C * i _t, the second Potential difference V
_B is the contact resistance r * i _t.

Therefore, OY ⁻ input / output terminals and OX ⁻ , IY ⁺
Each potential V _1, V _2, V ₃ of the input and output terminals is detected by the A / D converter 2, and the stylus pressure detecting threshold location V _TR obtained by the difference between the potential V ₁ and the ground potential GND, V ₂ and V ₃ When the second potential difference V _B obtained by the potential difference of 1 is compared by the CPU 1, the contact resistance threshold value r _C and the contact resistance r are directly compared.

That is, since the pen-on detection threshold V _TR and the second potential difference V _B do not include the resistance values of the resistance plates 8 and 9, no matter which position of the resistance plate is pressed, the same condition is applied. Can be compared.

When the contact resistance r becomes equal to or lower than the contact resistance threshold value r _C , the second potential difference V _B becomes equal to or lower than the pen-on detection threshold V _TR , and at this time, the CPU 1 determines the pen-on.

Therefore, also in the third embodiment, when the pen-on is detected without fail and when the pen-on is determined, the contact resistance r is negligibly smaller than the internal resistance R _A of the A / D converter 2. Therefore, the change does not affect the coordinate detection in the subsequent coordinate detection mode.

As for the adjusting resistor R _P connected to the ground side resistance plate, the resistance value r _P of the adjusting resistor R _P is set to 1 / the contact resistance threshold value r _C as in the second embodiment. N (N
Can be replaced with an adjustment resistor R _P ′ having a resistance value r _P ′ of a correction constant greater than 1.

FIG. 8 shows a resistance pressure sensitive tablet 40 according to a fourth embodiment different from the above.

In the resistance pressure sensitive tablet of FIG. 8, the pen-on detection threshold V _TR is N * V _A, that is, N * r _P.
'* I is _t, the resistance value r _P', the contact resistance threshold r _C
Since the resistance value is 1 / N, the pen-on detection threshold V
_TR is a r _C * i _t.

Therefore, OY ⁻ input / output terminals and OX ⁻ , IY ⁺
Pen-on detection threshold V _TR, which is obtained by detecting each potential V ₁ , V ₂ , V ₃ of the input / output terminal by the A / D converter 2 and multiplying the difference between the ground potential GND and the potential V ₁ by N, _When the second potential difference V _B obtained by the potential difference between ₂ and V ₃ is compared by the CPU 1,
Similar to the third embodiment described above, the contact resistance threshold value r
_C and contact resistance r can be directly compared.

[0138] In other to 'adjust the resistance R _P of' thus adjusting resistor R _P of the resistance value r _P a smaller resistance value r _P, directly, by comparing the contact resistance r and the contact resistance threshold r _C, Pen-on can be discriminated, and even if the adjustment resistors R _P ′ are directly connected to the circuits of the resistance plates 8 and 9 as in the second embodiment, the influence on the coordinate detection resolution is small.

Further, in the above embodiment, the CPU
Although the example in which the AD converter 2 is built in 1 has been described, the AD converter 2 and the CPU 1 may be separate components as long as the potentials at at least three locations can be read. The converter 2 may be used.

Further, in the above embodiment, AD
The converter 2 obtains the potentials across the adjusting resistor R _P and the potential across the contact resistor r, and compares the pen-on detection threshold value determined from the second potential difference and the first potential difference.
It is also possible to input the potential difference between both ends of the adjustment resistor R _P and the potential difference between both ends of the contact resistance r to a comparison circuit, and compare the second potential difference with the pen-on detection threshold value to determine pen-on.

[0141]

As described above, according to the present invention,
Even if the resistance material of the pressure-sensitive tablet and the thickness of the resistance film are different, the pen-on detection threshold V _{T is set} to RO in advance.
Since it does not need to be stored in M, the pen-on detection threshold V _TR can be easily modified by changing the resistance value of the adjustment resistor, and the pen-on detection can be performed under optimum conditions for each tablet.

Further, since the pen-on detection threshold value V _TR is set by the resistance value r _P of the adjustment resistor R _P , the storage unit for storing the pen-on detection threshold value V _T is not required unlike the conventional case.

Further, when the pen-on is discriminated, the current value flowing in the tablet differs depending on the pressing position of the tablet, but since it is discriminated by comparing the respective voltage drops in the contact resistance r and the adjustment resistance R _P , Pen-on can be identified without being affected by the pressed position.

Further, if the contact resistance threshold value r _C of the tablet can be known in advance, the pen-on detection threshold value V _TR can be easily set by using the adjustment resistance of the resistance value r _{P corresponding} thereto. You can

According to the inventions of claim 3, claim 6, and claim 7, since the adjusting resistor R _P is a variable resistor, the resistance value r _P of the adjusting resistor can be easily changed. Therefore, the pen-on of the tablet is repeated on a trial basis, the resistance value r _P of the variable resistance is changed while confirming the operation of the tablet, and the pressure of the tablet can be detected, and after the detection, the influence of the change of the contact resistance does not appear. It is possible to set a different pen-on detection threshold V _TR .

Since the pen-on detection threshold value V _TR is adjusted only by the variable resistance and is not obtained by the voltage division ratio with other resistors connected in series, after the pen-on detection threshold value V _TR is set, No switch is needed to disconnect the other resistors from the circuit.

[0147] According to the invention of claim 5, the stylus pressure detecting threshold V _TR that can be identified as the stylus pressure when the contact resistance r is equal to or less than the contact resistance threshold r _C, the contact resistance of the threshold r _C Since it can be set by using the adjustment resistance R _P ′ having the resistance value r _P ′ of 1 / N, even if the adjustment resistance is connected to the resistance plate and the mode is changed to the coordinate detection mode, the influence on the coordinate detection circuit is small.

[0148]

[Brief description of drawings]

FIG. 1 is a circuit diagram of a resistance pressure sensitive tablet 20 according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the resistance pressure-sensitive tablet 20 of FIG.

FIG. 3 is a circuit diagram showing a coordinate detection mode of an X coordinate in the resistance pressure sensitive tablet 20 of FIG.

FIG. 4 is a circuit diagram showing a coordinate detection mode of a Y coordinate in the resistance pressure sensitive tablet 20 of FIG.

FIG. 5 is a circuit diagram showing a resistance pressure-sensitive tablet according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram of a resistance pressure-sensitive tablet 30 according to a third embodiment of the present invention.

FIG. 7 is an equivalent circuit diagram of the resistance pressure-sensitive tablet 30 of FIG.

FIG. 8 is a circuit diagram showing a resistance pressure sensitive tablet 40 according to a fourth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a conventional resistance pressure-sensitive tablet.

FIG. 10 is a waveform diagram showing the relationship between the voltage V _P at the pressing point P where the voltage changes due to pen-on and the pen-on detection threshold V _T, and FIG. 10A shows a stable contact resistance. Waveform diagram of tablet with relatively low voltage V _PL , (b)
FIG. 4 is a waveform diagram of a tablet having a relatively high voltage V _PL when the contact resistance is stable.

FIG. 11 is a circuit diagram showing a resistive pressure-sensitive tablet in a state where a pen-on detection threshold V _T is set.

FIG. 12 is a circuit diagram showing a resistance pressure-sensitive tablet in a state where pen-on is detected.

[Explanation of symbols]

1 CPU 2 A / D converter 8 X coordinate resistance plate 8a X input electrode 8b X output electrode 9 Y coordinate resistance plate 9a Y input electrode 9b Y output electrode V _TR Pen-on detection threshold V _CC Reference detection voltage V _A First potential difference V _B Second potential difference V ₁ Potential of input electrode of resistance plate on detection voltage application side V ₂ Potential of output electrode of resistance plate on detection voltage application side V ₃ Potential of input electrode of ground side resistance plate N Correction constant R _P Adjustment resistance

Claims (7)

[Claims] 1. Along each of the two sides at both ends in the X direction, X
X with the input electrode (8a) and the X output electrode (8b) formed
A coordinate resistance plate (8) and a Y input electrode (9a) and a Y output electrode (9b) are formed along the two sides of both ends in the Y direction orthogonal to the X direction,
In the standby mode, the X-coordinate resistance plate (8) and the Y-coordinate resistance plate (9) that overlaps with each other with a slight insulation gap, and the reference detection voltage V
A resistance pressure-sensitive tablet having a CPU (1) that applies _CC and controls the other resistance plate to be grounded, and detects that the resistance plate is pressed from the potential of the resistance plate that changes with pen-on, The reference detection voltage V _CC is applied to the input electrode of one resistance plate via the adjustment resistance R _P, and the output electrode of the other resistance plate is grounded, and the detection voltage application side is applied by the A / D converter (2). The respective potentials of the input electrode and the output electrode of the resistance plate and the input electrode of the ground side resistance plate are detected, and the CPU (1) detects the potential V ₁ of the input electrode of the detection voltage application side resistance plate and the reference detection voltage V _CC . The first potential difference V _A of
The second potential difference V _B is determined from the first potential difference V _A by comparing the second potential difference V _B between the output electrode potential V _{2 of the} detection voltage application side resistance plate and the input electrode potential V ₃ of the ground side resistance plate. A resistive pressure-sensitive tablet characterized in that it is determined that the resistance plate has been pressed when the pen-on detection threshold value V _{TR is} less than or equal to the threshold value. 2. An X coordinate resistance plate (8) having an X input electrode (8a) and an X output electrode (8b) formed along two sides in the Y direction, and two sides in the X direction orthogonal to the Y direction. A Y input electrode (9a) and a Y output electrode (9b) are formed along the Y coordinate electrode (9a) and the Y coordinate resistor plate (9) which overlaps with the X coordinate resistor plate (8) with a slight insulating gap, and in the standby mode, The reference detection voltage V is applied to one resistance plate.
A resistance pressure-sensitive tablet having a CPU (1) that applies _CC and controls the other resistance plate to be grounded, and detects that the resistance plate is pressed from the potential of the resistance plate that changes with pen-on, The reference detection voltage V _CC is applied to the input electrode of one of the resistance plates, and the output electrode of the other resistance plate is grounded via the adjustment resistor R _P , and the detection voltage application side is applied by the A / D converter (2). The respective potentials of the output electrode of the resistance plate, the input electrode and the output electrode of the ground side resistance plate are detected, and the first potential difference V ₁ between the potential V ₁ of the output electrode of the ground side resistance plate and the ground voltage is detected by the CPU (1). compared with _a, the second potential difference V _B between the potential V ₃ of the input electrodes and the potential V ₂ of the output electrode of the detection voltage application side resistance sheet ground side resistance sheet, the second electrical potential difference V _B
Is the pen-on detection threshold V _TR determined from the first potential difference V _A
A resistive pressure-sensitive tablet characterized in that it is determined that the resistive plate has been pressed when the following occurs. 3. The resistance pressure-sensitive tablet according to claim 1, wherein the adjusting resistor R _P is a variable resistor. 4. The resistance pressure-sensitive tablet according to claim 1, wherein the pen-on detection threshold value V _TR is equal to the first potential difference V _A. 5. The resistance according to claim 1, wherein the pen-on detection threshold value V _TR is a value obtained by multiplying the first potential difference V _A by a correction constant N larger than 1. Pressure-sensitive tablet. 6. The X-coordinate resistance plate (8) and the Y-coordinate resistance plate (9) are superposed with a slight insulating gap, and one resistance plate has a reference detection voltage V in a standby mode.
C _C is applied, the other resistance plate is controlled to be grounded, and the resistance of the resistance plate is detected from the potential of the resistance plate that changes when the pen is turned on. The reference detection voltage V is applied to the plate through the adjustment resistor R _P.
While applying _CC , the other resistance plate is grounded, and the first potential difference V _A , which is the potential difference between both ends of the adjustment resistor R _P , and the second potential difference V _B , which is the potential difference between the resistance plates, are compared to determine the second potential difference. _A pen-on detecting method for a resistance pressure-sensitive tablet, characterized in that it is determined that the resistive plate has been pressed when V _B becomes equal to or less than a pen-on detecting threshold value determined from the first potential difference V _A. 7. The X-coordinate resistance plate (8) and the Y-coordinate resistance plate (9) are superposed with a slight insulating gap, and one resistance plate has a reference detection voltage V in a standby mode.
_In the pen-on detection method for a pressure-sensitive tablet that detects when the resistance plate is pressed from the potential of the resistance plate that changes by pen-on by applying _CC and controlling the other resistance plate to be grounded, one of the resistance plates The reference detection voltage V _CC is applied to
The other resistance plate, grounded via a control resistor R _P, compares a first potential difference V _A is the voltage across the adjustment resistive R _P, the second potential difference V _B is the potential difference in the resistance plates, the _A pen-on detection method for a resistance pressure-sensitive tablet, characterized in that it is determined that the resistance plate has been pressed when the two-potential difference V _B becomes equal to or less than the pen-on detection threshold value determined from the first potential difference V _A.