JPS5887725A - Coordinates detector - 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 α) Technical Field of the Invention The present invention specifies a specific intersection of a large number of electrode intersections in which electrodes are arranged in a matrix, brings about a capacitance change in the electrode depending on the presence or absence of the instruction, and controls the capacitance change. The present invention relates to a coordinate detection device that detects the position of a designated point.

(2) Background of the Invention Various formations and methods of information input devices have been proposed, and recently a device has been proposed that detects coordinates and inputs desired information. For example, by providing a transparent detection spring y in front of the display surface of a CRT display device or the like to indicate the position, and indicating the point on the spring y that corresponds to the desired information displayed on the display surface. There is information to be entered.

(8) Prior Art and Problems An example of a coordinate detection device having such a detection spring is shown in FIG. The detection spring 1vPN has X electrodes XI-Xn and Y electrodes 7l-yn disposed on a thin Gamasu plate. Each area where the X electrode and the Y electrode intersect is a contact area TCH.
It consists of Each X electrode XI-XnK is an X-direction touch detection section X-TCH8-A! Similarly, each Y[W yl-5Q'IK is connected to a Y-direction touch detection section Y-TCH8, which is connected corresponding to each electrode. For example, the operator detects the contact portion TC at the intersection of the X electrode x1 and the Y[pole yl].
Assuming that the instructions were given by HK tentacles,
The electric current Wxx+yx becomes K if its value differs from the electrostatic capacitance before the tentacle.

When the touch detection units X-TCH8 and Y-TCHS detect that there is a change in the capacitance value, the output becomes 10.
In this example, the electrodes XI, y
Only the output of the touch detection section corresponding to l is 10# sharp,
The output of the other detectors is 11'. As a result, the indicated position of the contact part has been detected.By the way, when the conductor electrodes are arranged so as to cross adjacent to each other, the adjacent capacitance between the xH electrodes and the yt electrodes is generated as shown in FIG. 0x-x, CV-y exist, and the X electrode and Y
A counter capacitance 0X-y will exist between the electrode and the electrode. Therefore, if you touch the contact part TCHXi-y1 set at the intersection of the electrode [XL and the electrode y1, the xl poles xi-1, xi-
The H and Y electrodes yi-1゜yi+1 will also be affected by the electrodes xi and yi, and of course the touch detection section X-TCH8゜Y-TCHS will also be affected, and the tentacles This has the disadvantage that touch detection units corresponding to electrodes that do not exist are detected as if they were instructed. The present inventors have previously proposed a configuration in which the electrodes in the non-detection state are controlled so that the electrodes in the detection state are not adversely affected by capacitance. A switch means is provided corresponding to each electrode, and other electrodes other than the electrode being detected by the touch detection section are connected to earth by the switch means, as shown in FIG. 8. FIG. 8 is a block diagram illustrating its principle.

X[FMXi has a p+detection section - The TCHS is equipped with a resonant circuit, a sphere circuit SL, and a monostape μ circuit MM in order to detect the change in capacitance at the electrode xi and detect whether the electrode x1 is directed. and Koi N
The LC parallel resonant circuit connected in parallel with La is the oscillator O3.
Assuming that it is in a resonant state due to the periodic signal of C, its impedance is infinite, so a signal having a value substantially equal to the output of the oscillator O8C is input to the slice circuit SL. Since the slicing circuit SL slices the input signal using the reference voltage VR, if the voltage VR is set to be slightly smaller than the signal input during resonance, the circuit SL outputs a bus-like signal to the monostaple circuit MM.

Therefore, the monostaple circuit MM has an output of 11'
becomes.

Next, when a human body or the like contacts the electrode x1, the resonance conditions of the resonant circuit change, so its impedance decreases, and the value of the signal input to the slice circuit SL is determined by the resistance R and the voltage division ratio of the resonant circuit. becomes. Reference voltage VR
If the O value is set larger than this voltage value, the output of the circuit SL will be 'O', and therefore the output of the circuit MM will also be 50', and if the electrode x1 is instructed, the output will be 10', and if not, the output will be 11'. Therefore, the presence or absence of an instruction can be detected.

On the other hand, when the electrodes other than the electrode Xi are in the detection state by the touch detection section, the switch SW is turned on and the electrode x1
Connect to ground. As a result, even if the electrode x1 is touched, the electrode to be detected will not be adversely affected by the electrostatic capacitance Cs between adjacent electrodes.

A mechanical switch such as a relay switch can be used as a switch for use in the detection device having the above configuration. Since the switching means in such a mechanical switch is slow, a high-speed switching circuit using a transistor can be considered, but as shown in FIG. If the shown switch SW is simply replaced with a transistor switch, problems such as those described below with reference to FIGS. 4 and 5 will occur.

Figure 1) is an n-channel I as a transistor switch.
In the example using vMO8FET, G is the gate electrode and switch control terminal, S is the source, and D is the drain.

θ is earth potential or reference potential. Other symbols are the same as Koshirae, 8th figure.

A schematic connection diagram of the above MO3FET is shown in FIG.

The equivalent circuit in case of connection in this way is shown in Figure 4(c) K
show. As can be seen from this figure, when the KMO3FKT is in the off state, a diode D1 is configured between the substrate P and the drain D, so when the control potential from the switch control terminal G becomes a negative potential, that is, the MOSFET y ,
When the switch SW is in the off state, that is, when the switch SW is turned off, the oscillator of FIG. 4(a). When the sc output ■6 is a negative voltage rep μ, the drain D terminal -1ff Io)' D
The waveform VOut~ applied to the parallel resonant circuit composed of Ca and La is the 415th! ! 1(e)K The waveform VSH becomes a half wave as shown in K, and a good sine wave Ve is not applied, making it impossible to obtain a resonant state, and the impedance of the resonant circuit decreases. There is a drawback that the on/off ratio of the rounding switch sw cannot be maintained since a value much smaller than the value is applied, and the detection of non-indicated coordinates becomes a matter of national opinion.

Next, FIG. 5(a) shows an example in which a pie bow transistor is used as a transistor switch, and B is a base and is a switch control terminal, and E is an emitter and is set to a ground potential e or a reference potential. Other symbols are shown in Figure 3.

Same as Figure 4.

Even in the above circuit configuration, when the terminal of the collector C becomes a negative potential, a current path e-B-C is formed through the diode D1 formed between the base B and the collector C, and when the transistor is off, the oscillator Output of O8C Even if 8 is a sine wave, VOut is not a sine wave,
Since the resonant circuit Re becomes non-resonant and the impedance decreases, a value much smaller than the oscillator output Vs is applied to the oscillator circuit SL, similar to when a MOSFET is used as a switch transistor, and the on/off ratio of the switch sw becomes There is a drawback that detection of non-indicated coordinate points becomes a chore.

(4) Purpose of the Invention The present invention has been made in consideration of this point, and is designed to be able to output a voltage of a predetermined level only with the detection electrode, which is different from the detection electrode configured so as to be compatible with other electrode companies. It is an object of the present invention to provide a transistor switch circuit that avoids the above-mentioned erroneous detection when a high-speed transistor switch is used as a switch for sequentially switching between detection electrodes.

(5) Structure of the Invention In the present invention, the electrode in the non-detection state is in the detection state aK! l!
The basic idea is to control the electrodes so that they are not adversely affected by capacitance coupling, and each electrode is equipped with a transistor switch that selectively connects the electrodes to ground, and the touch sensor detects when the touch sensor is in the detection state. The present invention is characterized in that the electrodes other than the electrode are connected to ground by the transistor switch, and the range of change in the signal output when the switch is turned on and off is widened.

(6) Embodiment of the Invention A coordinate detection device according to the present invention will be explained in detail with reference to FIGS. 6 to 12. In the drawings from FIG. 6 onward, the same functional parts as those in FIGS. 1 to 5 will be described with the same reference numerals.

FIG. 6 is a circuit diagram illustrating the present invention in detail. -'Ca provided at the connection point of rcH3,
A feature of the present invention is that it is connected to ground or a reference potential via a capacitor C in parallel with the parallel resonant circuit made of La.

In the coordinate detection device of the present invention, it is necessary to select the capacitance of the capacitor C so that the relationship R>>1/l jwc l is established with respect to the resistor P connected between the oscillator O8C and the resonant circuit. Switch SW is on,
That is, when the electrode xi is grounded, the sum is made so that the output VOut of the oscillator O8C can be set to approximately the ○ level. Note that ω is the angular frequency of the output Vs of the oscillator O8C.

When the above-mentioned transistor switch SW is on, the equivalent circuit near the switch SW is as shown in FIG. 7, where one W pole of nine capacitors C is connected to the electrodes Xj-K and the other end is connected to the ground potential.

Next, when the transistor switch SW is off, that is, when the touch detection section X-TCH3 is in the detection state, one electrode of the diode D1 is electrically connected to the The electrode is at ground potential eK
Connected. Therefore, even if the output of the oscillator osc becomes a negative potential as in the case of conventional figures 4 and 5, the output VOut does not become the ground potential and a sine wave is applied to the resonant circuit, resulting in a resonant state. As a result, a normal on/off ratio of the switch sw can be obtained.

FIG. 9 shows the waveforms of the voltage VOut at each terminal of the transistor switch SW15g when the switch is off, and the voltage VD across the transistor, that is, across the diode D1.

It is necessary to create a circuit configuration as explained above.
High-speed switching operation can be obtained with the open collector of TI, -IC, the open drain of MO8IC, or the 8-state IC.

Next, when the comparator SL of the detection circuit is composed of a C-MO8 C, etc., it is sufficient to connect them through the capacitor C as shown in FIG. This is because the protective diode d is connected to the input of the 0MO8IC between the input terminal and ground.

FIG. 11 is a block diagram showing the entire coordinate detection device using the transistor switch SW according to the present invention. 1st
For example, a plurality of electrodes x1 to x4 arranged to extend in the X direction constitute an X electrode group, and a plurality of electrodes y1 to y4 arranged to extend in a second direction, the Y direction, Y
A transistor switch S is connected via a capacitor C to each electrode x1 to X4, which constitutes an electrode group.
W1 to SWs are provided. The switch 5Wl-3
Ws is selectively connected to ground corresponding to the detection pole. Also, corresponding to each detection unit, its output signal (ゞ1', '0'
') are provided for temporarily storing latches Ll-Ls, and latches L5 to L8 in the X direction are connected to the encoder
The latch LINL4 in the Y direction is connected to the ENC
-Input each to ENC.

FIG. 12 shows an example of a scanning circuit for electrode scanning. The pass generator PG is connected to a counter CNT, and the output of the counter CNT is input to a switch decoder 5W-DEC and a latch decoder L-DEC. The switch decoder 5W-DEC decodes the contents of the counter CNT and sequentially scans the switches SW1 to SWs, and sequentially outputs ``1'' to only one output terminal6.
When the signal 11' is sent out, only the transistor switch SW corresponding to the ninth terminal is in the off state, and the transistor switch corresponding to the terminal 10' is connected so as to be in the on state.

The latch decoder L-DEC controls the timing of latching the output information of the touch detection section with respect to the latches L1 to L8, and sequentially outputs 11' to only one terminal according to the contents of the counter CNTO.

Next, the operation will be briefly described. For convenience, the description will be made assuming that the contact part TCHxl-yx among the 16 contact parts is touched. First, the counter CNT starts counting, and the switch decoder 5W-DEC decodes the contents and only the terminal corresponding to the switch SW1 is counted. becomes 0', the switch SWI corresponding to the electrode y1 is turned off, and is detected by the touch detection unit Y-TCH8. However, the output signal of the terminal corresponding to y2 to y4°X1-X8 is ``0'', so the switches SWg to SWs are turned on.
Other vKs except for the electrodes in the detection state by TCH3,
Polar X1 to X4. i to y4 are SW2 to SW4
．． Connected to ground via SW5 N5Ws.

Since the contact parts TCHx1 to 71 are tentacled, the touch detection part y-Tcu"s detects the tentacle as described above, so its output is '0'9, and the information company latch It is controlled by the output of decoder L-DEC and stored in latch L1, but other latches L2 to L4.L
5 to Ls do not store the output of the corresponding touch detection section.

Next, the counter CNT increments and the switch decoder 5W
- Only the terminal whose DEC corresponds to switch SW2 is 10'
Therefore, in the latch decoder, only the terminal corresponding to the latch L2 becomes 1'. Therefore, the switch SW2 is turned off and is in the detection state, and the other switches SWl, S
Wa to sw8 are turned on. As a result, electrodes XI,
2. X3. ! 4,71. y3゜y4 is connected to ground via switch SW! ! ' Since it is connected, the contact part TCHXI ~
Since the electrodes XI and yl are tentacled by y1, the capacitance Cs possessed by the electrodes XI and yl has no adverse effect on the electrode y2 to be detected, and its output is 11'.

In the above manner, all electrodes Xl-X4, 71 to y4
When all scanning is completed, the detection results of each electrode are stored in the latch L.
1 to L8, and the coordinate position xi in the X direction and the coordinate position y1 in the Y direction are output from each encoder X-ENC and Y-ENC.

In the above embodiment, a MOS (MOS) fungistor was used as an example of a switch for switching between a detection electrode and a non-detection electrode, but a similar high-speed readout can be achieved by using a Paibov transistor instead.

Although an example has been described in which instructions are given by direct contact of the human body to the contact portion, instructions may be given to the contact portion by contacting the other end of a capacitor, one end of which is grounded, in the form of a pen.

In addition to detecting the instruction state by utilizing the resonance phenomenon of the resonant circuit, the touch detection unit may also detect the capacitance value by other methods, such as a balanced circuit.

(7) As described in detail, according to the present invention, a transistor switch capable of high-speed operation is used as a switch means for selectively connecting an electrode to earth, and is inserted in parallel with the resonant circuit of the detection circuit. A capacitor is connected between the transistor switch and the detection electrode, and the switch is provided corresponding to each electrode, and the transistor switch means connects the other electrodes to earth except for the electrode that is in the detection state by the touch detection section. Since the electrodes in the detection state are not adversely affected by the opposing capacitance existing between the crossing electrodes and the adjacent capacitance existing between the adjacent electrodes, and by interposing the capacitor, the switching Turning the signal on and off in the off state or detection state
Off state can be clearly determined, and detection can be performed accurately and at high speed.

[Brief explanation of the drawings] Fig. 1 is a schematic diagram showing a conventional example of a coordinate detection device using capacitance, Fig. 2 is a partially enlarged view of the detection spring y in Fig. 1, and Figs. 5 is a diagram illustrating a switch circuit used in a conventional coordinate detection device, FIGS. 6 to 8 are block diagrams illustrating a switch circuit used in a coordinate detection circuit according to the present invention, and FIG. 9 is a diagram illustrating a switch circuit used in a coordinate detection circuit according to the present invention. Figure 10 is a diagram explaining the output waveform when using the switch circuit of
FIG. 11 is a block diagram showing an example of application of the present invention when C is used, FIG. 11 is a block diagram schematically showing the entire coordinate detection device, and FIG. 12 shows an electrode scanning circuit. In the drawings, Xl-X4, yl to yQj electrodes,
X-TCH3, Y-TCH3 are touch detection parts, TCH,
TCHxi-yi and TCHx 1-yl are contact parts, and SWt to sws are switches. Fig. 1 Fig. 2 χ訃 ×i+1 3rd leap Fig. 5 Fig. 4 ((1) Fig. 4(b) Fig. 4(C1 Fig. 4(e), 9. j .-Q Lx IL- Hehe1 Figure 6 Figure 7 Figure 8 Figure 91] Figure O

Claims (1)

[Claims] It has a plurality of electrodes regularly arranged adjacent to each other corresponding to the coordinate positions to be detected, and each electrode is connected to a periodic signal oscillation circuit. In a coordinate detection device comprising a touch detection section that responds to a change in a resonance state, and a switching means that selectively connects each electrode to a reference potential, the switching means is constituted by a semiconductor switching element, and the switching means comprises a semiconductor switching element. A coordinate detection device characterized in that one terminal is set to a reference potential and the other terminal is connected to the electrode via a capacitive element.