JPS60181914A - Coordinate detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a coordinate detection device, and in particular, a resistive film is provided on a substrate of a display device, etc., and coordinate values are two-dimensionally detected when an appropriate position is indicated. The present invention relates to a coordinate detection device configured as described above.

[Technology background]

With the computerization and digitization of office equipment, transparent switch-notches, light-touch switches, keyboard switches, and the like have come to play a major role as input operation parts. In particular, transparent switches and other panel switches that can be operated while looking at the display using a finger or pen from above various displays have begun to be widely used because the surface design can be selected relatively freely, and the pointing point of these input devices can be detected. As a coordinate detection device for this purpose, for example, a transparent conductive film is provided on the surface of a transparent film, etc., and upper and lower transparent electrode patterns are arranged facing each other in a grid pattern at regular intervals, and data can be input by lightly touching it with a fingertip without using a keyboard. What it does is known. This device had a problem in that the accuracy of inputting coordinates was determined by the density of the arranged patterns.

[Problems with conventional technology]

In order to solve these problems, the applicant first
As shown in the figure, when the equivalent impedance seen from one terminal side of the resistive film 1 is clamped by a buffer circuit added to both ends of the resistive film, the coordinate relationship with the indicated point is a specific function relationship. We proposed a detection device that detects coordinates from equivalent impedance values.

Regarding FIG. 1, in detail, 1 is a resistive film of uniform quality, one end 2 of the resistive film 1 is connected to an output terminal 5, and the positive input of an operational amplifier 6 constituting a buffer circuit. The other end 3 is connected to the output of the operational amplifier 6, and is further connected to the negative input of the operational amplifier 6 itself. Reference numeral 4 denotes a pointing point indicating an appropriate position on the resistive film 1, and there is an impedance 8 between the pointing point and the ground 7. Note that the impedance is assumed to be Zo. The impedance is a capacitance component generated between the human body and the ground when the resistive film 4 is pointed with a fingertip. Now, the coordinate of one end 2 of the resistive film 1 is "0", the other end 3 is "1", and the coordinate of the indicated point 4 is X.
shall take a value of 0≦X≦1. Furthermore, the ground potential of the indicating point 4 is set to va.

Let the potential of one end 2.3 of the resistive film with respect to the ground be V, and the resistance value between the one end 2.3 of the resistive film l and the pointing point 4 is Rx.

The resistance value between the one end 3 of the resistive film 1 and the indicating point 4 is R8-8, and the output terminal 5 is a composite of the above-mentioned impedance Zo and resistance values R'x and R1-8 between the output terminal 5 and the ground 7.
When the equivalent impedance seen from the side is divided by Z, the equivalent impedance is calculated. First, the current V a /Z o flowing to the impedance Z[+ is the sum of the current flowing to RX via the pointing point 4 (v va )/Rx and the current flowing to Rl-X (v va ) / R+-x ( va/Zo) = (v-va) ((1/RX) + (1/R,-
, )) ・ ・ ・ ・ ・ (1) However, since the other end of the resistive film is clamped by a buffer circuit (voltage torque lower β-1,0), the resistor R1-
The current flowing through 8 is supplied independently from the buffer circuit.

Therefore, the current flowing through the output terminal 5 is the current flowing through the resistor Rx itself. From this, the current v/7° flowing through the equivalent impedance Z is the current flowing through Rx (v-
va)/Rx, (■/Z)-(v-va)/R
X...(2). +11. + Subtracting the equal 1i11i impedance from formula 21, Z=Rx4-Z o ((Rx +R1-8) /R+
-x)...(3) Here, set R8゜RI so that Ry + R+-x is sufficiently smaller than the absolute value 1Zol of impedance ZO.
If −X + and Za are set, equation (3) becomes approximately Z″=−Zo ((RX+R1−X)/R1,8) ・
...(4) can be done.

On the other hand, from FIG. 1, the resistance value of the resistive film 1 is proportional to the length of the resistor, so the coordinates X of the indicated point 4 are x=R, /(RX+RI−
Subtracting R1-8 from X), R+-x= ((1-x)/
xi Rx ---・-(51. In equation (4), 15
Substituting equation 1 and substituting X gives x -1-(Zo/Z) ・
・・・・・・(6) As can be seen from equation (6), the indicated point 4
The coordinate of

In the above equation (6), if the impedance Z is the capacitance between the human body and the ground indicated by a fingertip, or a capacitive pen, etc., a capacitive variable oscillator 9 and its pulse width measuring device IO should be added to the output terminal 5. In principle, the coordinates of the designated point 4 can be determined from the output 11. However, it is very effective when the capacitive impedance Zo has a constant value, such as in a capacitive pen, but in the case of human body capacitance caused by fingertip touch, the above method cannot be used directly because the capacitance value fluctuates. was there. Furthermore, resistive film 1
When there is a stray capacitance 12.13 (the capacitance value is CsX+C3l-X) between both ends 2.3 of 2.3 and the ground, there is a problem that the error in calculating the equivalent impedance Z cannot be ignored.

[Purpose of the invention]

The present invention has been made in view of the above drawbacks, and when determining coordinates by calculating the equivalent impedance Z described above, the equivalent impedance seen from both ends of the resistive film is measured multiple times, and the results are averaged to determine the coordinates indicated by the fingertip. It is an object of the present invention to provide a coordinate detection device that can provide instructions and also detect two-dimensional coordinates of a resistive film in the X and Y axis directions.

[Structure of the invention]

According to the present invention, the above object is achieved by a coordinate input panel means having a resistive film formed on a substrate, and a diode connected in the X-axis direction or Y-axis direction of the panel when an appropriate position of the panel means is specified. bias switching means for forward biasing or reverse biasing the group; buffer means for maintaining a constant voltage between the diode groups connected in the X-axis or Y-axis direction of the panel means; , a switching means for alternately switching both ends of the buffer means, a detection means for detecting the impedance seen from one end of the buffer means switched by the switching means, and a designated position of the panel means based on the output value of the detection means. This can be achieved by providing a coordinate detection device characterized by comprising a control means for calculating.

[Embodiments of the invention]

The invention will now be described in detail with reference to the drawings. A principle diagram of the coordinate detection device of the present invention is shown using FIGS. 1 and 2. FIG. In the present invention shown in FIG. 1 described as the conventional example described above, it is assumed that the impedance Zo indicates the pointing point 4 with a fingertip, and the impedance value ZO has a capacitance value C that fluctuates, for example. Also, stray capacitance 12.13
To find the equivalent impedance 2 including
When B, zo = 1/jωC, (7) (where j is a complex number and ω is an angular frequency). Substituting the above impedance ZO into equation (4), the equivalent impedance Z is Z=1/ [jωCa (R+-x/ (Rx +R+
−x) ) ]・・・・・・(8) Therefore Z = CB[R+-x / (Rx RI-X)
)...(9), but in addition, the stray capacitance 12.
13, the stray capacitance value CS l-X can be ignored since no current flows through terminal 3, and the stray capacitance value C A. is connected in parallel with the impedance Zo=CB, and the equivalent impedance Z is Z=Cs x + [CB (Rt-x/ (Rx +
R+-x) ) ]... (10) It is expressed as follows.

FIG. 2 shows a state in which the operational amplifier 6 and the variable capacitance digital oscillator 9 are connected to one end 2 and 3 of the resistive film 1 in a completely opposite manner to that shown in FIG. If the switching is performed in a very short time of about 5 m5 ec, it can be considered that the stray capacitance value Csx+Cs5-x and the human body capacitance value CB do not change. The equivalent impedance Za seen from the output terminal 5a side in Fig. 2 is Z
a=CH-x+ [CB (Rx/ (Rx+R+, x
)lco・ ・ ・ ・ ・ (11) Therefore, C can be eliminated from equations (10) and (11). That is, R, −, = ((z − ct x)/ (z − cs, −
,))R.

...(12) becomes. Therefore, the coordinate X of the indicated point 4 is x = Rx / (Rx + R+-x) = (Z
a Cs +-x) / ((Z Cs x) + CCs x Cs+-x)
1. ・ ・ ・ ・ (13)

Therefore, the output pulse from the pulse width measuring device 10 is output 1
1 and find the coordinate X of the indicated point 4. Now, the first
If the oscillation period of the variable capacitance digital oscillator 9 shown in the figure is TX+, then T x + ”k-Z ...... (14)
(However, k is a constant).

Similarly, if the oscillation period in the case of Fig. 2 is T, 2, then Tx 2-k -Za ・ ・ ・ ・ ・ ・ ・
(15). Furthermore, if the oscillation period of the stray capacitance C5X shown in FIG. 1 when there is no fingertip touch is 'r, then TsX=-Csx (16).

Similarly, if the oscillation period when there is no finger touch in the stray capacitance CS I-X shown in Fig. 2 is T i l-X, then T1+4=-Cs+-x'... (17)
Detected as .

The above equations (14), (15), (16), and (17) are converted to (1)
3) Substituting into the formula, x = (T X 2 T s + - x) / ((Tx
+ Tsx)+ (Tx + Tg+-x)1...
... (18) can be calculated. That is, in the present invention, the oscillation period when there is no finger touch 〇 in each state of FIG. 1 and FIG.
8) The 40 coordinates X of the indicated point can be calculated from the equation.

In the above principle, it is assumed that the human body capacitance does not change because the switching is performed in a short time while the oscillation period T x + + T There is a limit to detection accuracy because the change is slight. Therefore, the measurement is repeated multiple times (preferably 7!-2 to 4 times) and the measured value Tx11°T, 21 for each time is measured by the control device (computer).
(Tx + + Ts X),
(Tx 2 +-'rs,-,) and set the value to n
After integrating measurements and calculations over several times, the X coordinate is calculated and detected as follows (19). This value is a weighted average of the detected coordinate values xl in each measurement cycle, and is expressed as follows, x I = (T, 2 i-T, t-x) / ((Tx
+ i Ty, x) + (Ty 2 i Tsx
-X)... (20) It is possible to perform X coordinate detection with high accuracy by well averaging the variations in detected coordinate values due to changes in human body capacitance during T x + + + T x 21. .

An embodiment of the coordinate detection device of the present invention based on the above-described principle will be described in detail with reference to FIG.

In FIG. 3, reference numeral 14 denotes a panel, which has a transparent resistive film formed on, for example, a glass substrate. The glass transparent resistive film is uniformly sputtered to have a resistance value of 500 to IKΩ/hole. Furthermore, silicon oxide (SiO2) is formed as an insulating film on the transparent resistive film to a thickness of about 2 μm. A plurality of diodes D1x+D2x are arranged in the X-axis direction and the Y-axis direction of the panel 14 formed in a substantially rectangular shape.
+D 3 X I...+D + x' +
D 2 x ′+ D 3 x ′.

” '+ DI V+ D2 v+ D3 v+ ・・
・.

Dr v'+ D2 v'+ D3'V'+ ・
..., connect. DIXID2 connected in the X-axis direction
A first diode group 15X consisting of XID3X,...
connects the cathode to one end of the panel in the X-axis direction, each anode side is commonly connected to the first line LA, and the diodes D + x' + D2X', D3
A second diode group 15X' consisting of X... has its cathode commonly connected to the second line LB, and each anode connected to the other end of the panel in the X-axis direction.

Furthermore, a diode D+v is installed at one end of the panel in the Y-axis direction.
A third diode group 16Y consisting of + D2 v+ D3 v+ DI v+ . Connect to line LA. A diode D' is installed at the other end of the panel in the Y-axis direction.
v Z D2 v ′+ D3 v ZDav'...
- A fourth diode group 16Y' consisting of the following is arranged, the cathode of each diode is connected to the other end of the panel 14 in the Y-axis direction, and each anode is commonly connected to the second line LB.

8 is the capacitance (capacitance value C+s) generated between the human body and the ground 7 when an appropriate position is indicated with a fingertip. SL is the first switch means, which is composed of two switches 17 and 18;
The movable contact a of the switch 17 is connected to the first line LA via voltage dividing resistors R2 and R1, and the movable contact a of the switch 17
The movable contact a is connected to the second line LB via voltage dividing resistors R3 and R4. first and second switch 1
7゜18 fixed contacts S and C are grounded, and the first
Fixed contacts C and b of the second c17, 1B are connected to a terminal EO connected to a DC voltage source (12V). Furthermore, blocking capacitors CI and C2 with relatively large capacities are connected to the respective connection points of the resistors R1, R2 and R3, Ra for blocking alternating current from the operational amplifier 6,
The other end of the capacitor is commonly connected to the output side of the operational amplifier 6 described in FIGS. 1 and 2. operational amplifier 6
The positive input of 9 is connected to the variable capacitance digital oscillator 9 described in FIGS. 1 and 2 via a blocking capacitor C4. X applied to the control device (computer) 20 from the output 11 of the conversion circuit 19 consisting of the panel width measuring device 10, etc.
Based on the coordinate signals, the controller outputs the coordinate output 20a and the first
and a control signal 20b for controlling the second switch means Sl, S2.

20c to control the first and second switch means. The second switch means S2 is composed of two switches 21 and 22, and the movable contact a of the third switch 21 is connected to the positive terminal of the operational amplifier 6, and the fourth switch 22 is connected to the positive terminal of the operational amplifier 6.
Through the movable contact a and the blocking capacitor C3!
The third switch 21 is connected to the output side of the operational amplifier 6.
The fixed contact C is connected to the second line LB, and the fixed contact C is connected to the first line LB.
is connected to line LA. Further, the fixed contact of the fourth switch 22 is connected to the first line LA, and the fixed contact C of the fourth switch 22 is connected to the second line LB.

To explain the operation of the above configuration, if an appropriate position on the panel 14 is indicated with a fingertip, <If a capacitor MCB between a person and ground is formed including a silicon oxide film on a transparent resistive film treated as a flannel base, The control device 20 is connected to the switch S1 of
The first switch means SI
As a result of the switching operation, the contact piece of the movable contact a of the first switch 17 is connected to the fixed contact, and a DC 12V power supply is applied to the first line via the resistor R2°R1, and the first diode group 15X is sequentially Although the third diode group 16Y is biased in the opposite direction, the third diode group 16Y is reverse biased. Further, since the contact piece of the movable contact a of the second switch 18 of the first switch means S+ is connected to the fixed contact C, the second line LB becomes a ground line and the second diode group 15X' has a pole. A current flows in the X-axis direction of the panel from left to right as shown in the resistors RX, R, . . . not shown in the equivalent circuit of FIG. That is, the first
The voltage VLA on the line LA side is compared with the voltage VL& on the second line LB side, so that VLA>VLI! 1, the diode in the X-axis direction is in the "on" state.

At this time, the fourth diode group 16Y' is inversely biased, non-conducting, and virtually open, and no current flows from the fourth diode group 16Y' to the third diode group 16Y.

In this state, the second switch means S2 is also controlled by the control signal 20C of the control device 20, and the contact pieces of the movable contacts a of the third and fourth switch notches 21 and 22 are in contact with the fixed contact C side. There is. Therefore, the operational amplifier 6 is in the same state as shown in the equivalent circuit of FIG. A corresponding output pulse is obtained and output to the control device 20. The oscillation period of the output pulse is measured by a counter, a timer, etc. in the control device 20 and stored. Further, the oscillation cycle TsX when the fingertip is not touched in this state is stored in advance in the control device 20.

Next, the contacts of the movable contacts a of the third and fourth switches 21 and 22 of the second switch means S2 are switched to the b side, and the operational amplifier 6 is equivalent to that shown in FIG. An output pulse with an oscillation period TX2 corresponding to the impedance Za is obtained, measured and stored by the control device 20.

Further, the oscillation cycle T It l−X when there is no fingertip touch in this state is also measured and stored in advance in the control device.

TXI, TX2 and Ts X obtained by the above operations
By calculating equation (18) within the control device 20 using ITss-x, the X coordinate of the pulse 14 in the X-axis direction is output.

Next, a control signal is applied to the first switch means S1, and the contacts of the movable contacts a of the first switch and the second switch 17 and 18 are switched to the fixed contact side. Therefore, the first line LA becomes a ground line, and the second line LB receives DC 12V power via the resistor R3゜R4, so the second diode group 15X' is reverse biased and the fourth diode group 16Y ' is forward biased, and the voltage VLA of the first line LA is lower than the voltage VL& of the second line LB, and the relationship of VLA < VjB is established, so the X-axis direction of the panel 14 is in an open state, and the fourth A current flows from the diode group 16Y' direction to the third diode group 16Y.

The following operation is performed in the same way as above with the panel switched in the Y-axis direction to detect the X coordinate and control the control device 20.
Output 20a is detected. In addition, the above-mentioned switch S
The switching time of 2 can be selected to be approximately 5m5ec.

Furthermore, in the case of weighted averaging, the above-mentioned measurements may be repeated within the control device 20.

According to the above-described configuration and operation, the AC bones that should normally flow only to the human body flow from lines LA and LB to R1, R2, and R.
3. Earth and power source E via Ra.

A blocking capacitor CI is used to prevent the DC component from flowing to the operational amplifier 6 and to prevent the DC component from flowing to the operational amplifier 6.
, C2, and the first and second lines LA, LB
A blocking capacitor C3, Ca is required around the operational amplifier 6 to allow direct current to flow between X and Y.
There is a problem in that the detection speed becomes slow because it is necessary to wait until the transient phenomenon that occurs when switching the axis subsides.

Other embodiments that do not cause such problems are detailed in FIGS. 4 and 5.

FIG. 4 is a circuit diagram showing another embodiment, in which the indicated point position signal is detected only from the X-axis direction by a group of diodes arranged on the panel 14, and FIG.
FIG. 4 is a connection diagram showing still another embodiment showing a method of connecting diodes disposed in FIG.

In the circuit diagram in FIG. 4, the anodes of diodes D2 x and D3 x are commonly connected to one end of the panel 14 in the X-axis direction, and the switch S of the switching means 25 is
4, the cathodes of each of the diodes are connected to one end of the panel 14, and a diode, Da XI D 5X+ D 6y, is connected in series with each cathode.
and connect the corresponding diode D
Switching means 2 by connecting the cathodes of 6 x in common
Connect to the movable contact a of the switch S3 of No. 5. In this way, the first diode group 23X is connected to one end of the panel 14 in the X-axis direction. Similarly, at the other end of the panel 14 in the X-axis direction, a diode D + x' + D2X'
The anodes of l D 3
.

The anodes of D5x'+D6X' are connected in common to the movable contact a of the switch Sθ of the switching means 25.
connected to. Diode DIX'.

The cathodes of D 2 x ′ + 03 x ′ are connected in common to the movable contact a of the switch S7 of the switching means 25. Thus, the second diode group 2
3X' is connected to the other end of the panel 14 in the X-axis direction.

Similarly, there is a diode D l v in the Y-axis direction of the panel 14.
+ D 2 v + D 3 v and diode D
5 v+ D 6 v+ D 7v are connected in series, and the series connection point is connected to one end of the Y-axis direction panel, and the diode D l v + D 2v r D
3V cathodes are commonly connected and connected to the movable contact a of the switch S6 of the switching means 25, and the diode D5V
, D6111 Dvv anodes are commonly connected and connected to the movable contact a of the switch S5, and the third diode group 24
Y is connected to one end of the panel 14 in the Y-axis direction.

Furthermore, in the Y-axis direction of the panel 14, a diode DIv',
D2. ', D3V' and D5v'+D6. ′, Dt, and ′ are connected in series, and the intersection of each series connection is connected to the other end of the panel in the Y-axis direction, and the diode D l v ′ +
The anodes of D 2 v ′+ D 3 v ′ are commonly connected and connected to the movable contact a of the sui-nochi rib 0, and the diodes D 11v ′ + D 8 v ′+D 7 v
The cathodes of ' are connected in common and connected to the movable contact a of the switch S9. Thus, the fourth diode group 24Y'
is connected to one end of the panel 14 in the Y-axis direction. 1st above
~ The fourth diode group each has three sets of series circuits connected to the panel, but it goes without saying that the number of these can be selected as appropriate.

In addition, the connection between the diode group and the panel is as shown in Figure 5, using one pair of diodes D+ instead of connecting them in series.
x + D a x : D 2 X I D 5 X
The anode and cathode of each of the D 3

81 fixed contacts of the switch means 25, fixed contacts C of the switch S6, and fixed contacts of the switch S7.

A fixed contact C of the switch S9 is connected to a positive terminal of a first voltage source Vp, and the negative side of the first voltage source is grounded. The fixed contact C of the first switch S3 is connected to the terminal in contact with the first line LA mentioned in FIG. 3, and the fixed contact C of the switch S7 is similarly connected to the terminal in contact with the second line LB. .

The fixed contacts C of the switch S4 and the fixed contacts of the switch S5 are connected to the terminals connected to the first line LA.

Each of the fixed contacts C of the switch S6 is connected, and the second
A fixed contact C of the switch Se, a fixed contact S of the switch S9, and a fixed contact S of the switch S+o are connected to the terminal connected to the line LB. Further, one end of the fixed contact S of the switch S4, the fixed contact C of the switch S5, the fixed contact C of the switch Se, and the fixed contact C of the switch Sho are connected to the negative terminal of the second voltage source V, and the second voltage source V is connected to the negative terminal of the second voltage source V. The positive terminal of the source is grounded. It is assumed that the terminals LA and L13 are connected to coordinate detection means having an operational amplifier 6, a control device 20, etc. similar to those shown in FIG.

According to the above configuration, the switch means 25 is connected to the control device 20 (
(see Fig. 3), and the contact piece on the movable contact a side of the switches 83 to S4 in the switch means is connected to the fixed contact C.
When in contact with the side, the thirteenth and fourth diode groups 24Y and 24Y' connected in the Y-axis direction of the panel 14 are reverse biased and substantially open,
First and second diode groups 23 in the X-axis direction of the panel
X.

Only 23X' is turned on, and the terminal LA.

Data corresponding to the X coordinate of the panel pointing point can be extracted from between LB. Of course, in this case the first voltage source V is lower than the maximum voltage for driving the first and second diode groups.
The voltage of p is selected to be high, and the voltage of the second voltage source ■N is selected to be lower than the minimum driving voltage.

In order to detect coordinates in the Y-axis direction, switch/7 switch means 25 is used.
If the control device 20 controls the contact pieces of the movable contacts a of all the switches 83 to S+o to fall toward the fixed contact C side, the X-axis direction will be in an open state.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible not only to detect coordinates two-dimensionally, but also to specify coordinate positions with a fingertip. Additionally, since diodes are used, it is only necessary to reverse bias a group of diodes, eliminating the need for complex analog switches or ICs around the panel. Furthermore, the embodiments shown in FIGS. 4 and 5 have the feature that coordinate detection can be performed without using a blocking capacitor.

[Brief explanation of drawings]

FIG. 1 is an equivalent circuit diagram of a detection device for explaining the principle of a conventional coordinate detection device and a coordinate detection device of the present invention, and FIG. 2 is an equivalent circuit diagram of a detection device for explaining the principle of a coordinate detection device of the present invention. 3 is a circuit diagram showing one embodiment of the coordinate detection device of the present invention, FIG. 4 is a circuit diagram of a switching part showing another embodiment of the coordinate detection device of the present invention, and FIG. 5 is an equivalent circuit diagram. 5 is a circuit diagram of a diode group and a panel connection portion showing another modification of FIG. 4. FIG. DESCRIPTION OF SYMBOLS 1... Resistive film, 2... Resistive film - side end, 3... Resistive film other end, 4... Indication point, 5... Output terminal, 6
... operational amplifier, 7... grounding, 8... impedance, 9... variable capacitance digital oscillator, lO・
...Pulse width measuring device, 12.13... Stray capacitance,
14...Panel, 15X, 23X...First diode group, 15X', 23X'...Second diode group, 16Y, 24Y...Third diode group, 16Y
', 24Y'... Fourth diode group, 17... First switch, 18... Second switch, 19.
...Conversion circuit, 20...Control device, 21...Third
switch, 22... fourth switch, Sl...
First switch means, S2... Second switch means, LA... First line, LB... Second line, D I X I D l x '+ D 2 x +
D 2 x ′+ D 3 x +D 3X ”, D
4 X I D a x ' + D a x r
Dsx'+D6x, D68'...Diode, 25...Switch means, 83~Sho...
...Switch, Vp...First voltage source, vN...Second voltage source. Figure 1 Figure 2

Claims (2)

[Claims] (1) A panel means for inputting coordinates with a resistive film formed on a substrate, and a group of diodes connected in the X-axis direction or Y-axis direction of the panel when the appropriate position of the panel means is indicated, and a group of diodes connected in the X-axis direction or Y-axis direction of the panel is forward biased or bias switching means for biasing; buffer means for maintaining a constant voltage between a group of diodes connected in the X-axis or Y-axis direction of the panel means; a switching means for alternately switching both ends; a detection means for detecting the impedance seen from one end of the buffer means switched by the switching means; and a control means for calculating the indicated position of the panel means based on the output value of the detection means. A coordinate detection device comprising: (2) The group of diodes connected to the panel means is composed of two diodes connected in series in the same direction as one unit, and the cathodes and anodes of the unit of diodes are commonly connected, and the panel In the direction of coordinate detection in the X or Y axis direction of the means, the output of the anodes and cathodes of the diode group commonly connected together is connected to the buffer 1 means for coordinate detection, and in the direction of coordinate detection in the X or Y axis direction where coordinate detection is not performed. 2. The coordinate detecting device according to claim 1, wherein the anodes and cathodes of the diode groups in the direction are commonly connected to each other so as to be reverse biased.