JPH11304942A - Device for detecting approach of conductor and approach position - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify signal processing, to improve noise resistance, and to eliminate the poor influence of floating capacity by receiving and processing an equivalent vibration current from a conductor such as a human body through capacitance coupling via a voltage vibration system. SOLUTION: When a vibration voltage generator 14 in a non-vibration system 2 generates a sinusoidal wave with a frequency of for example 460 kHz, the output allows an entire voltage vibration system 1 to be subjected to voltage vibration by the same phase and amplitude of 460 kHz via a ground circuit 11 of the voltage vibration system 1 or the power supply circuit of a power supply 12. At this time, when a finger 7 that is a conductor to be detected approaches a sensor panel 3, capacitance coupling 8 occurs between a film-shaped resistor 5 being formed on the panel 3 and the finger 7, and a vibration current (AC signal current) flows via the capacitance coupling 8. At this time, more signal current flows from a stripe-shaped electrode 6 that is placed near the tip of the finger 7 and has smaller face resistance than that of the resistor 5. The signal current is introduced to a signal processing part 10, and the approach position of the tip of the finger 7 on the surface of the panel 3 is detected according to the level of the signal current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitively-coupled conductor approaching and approaching position detecting device, and more particularly to an approaching and approaching approach for a human body which does not actively emit a signal and a conductor to be detected such as a finger thereof. The present invention relates to a position detecting device.

[0002]

2. Description of the Related Art Japanese Patent No. 1536723 discloses an example in which four corners of a resistive panel are driven by an operational amplifier and a driving current is simultaneously detected by a differential amplifier.
As an example of detecting a change in capacitance of a grid-like conductor of a panel including a coupling capacitance with a finger, see Japanese Patent No. 175/175.
No. 4,522 and No. 2,037,747. Alternatively, as an example of detecting the impedance of a resistive panel including a coupling capacitance with a finger, the details are not clear, but there is one disclosed in Japanese Patent No. 2603986.
As another example, the transformer touches four points on the touch panel to A
An example of applying the drive voltage component to the differential amplifier at the same time as driving by the C voltage is a finger position detecting device disclosed in Japanese Patent No. 1881208.

[0003]

In the above-mentioned prior art, the concept of absorbing an electric signal from a sensor panel to a conductor to be detected, such as a human body, is used. It was very difficult to achieve an ideal signal process. Further, since the reason for the false grounding of the conductor to be detected was uncertain (unclear), there was a potential condition that the detection became unstable.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a voltage oscillation system including a sensor panel or a sensor conductor array, a shield plate, a signal processing circuit, a ground, and a power supply circuit. Electrical vibration (AC signal) equivalently received from a conductor such as a human body belonging to a non-vibration system (in the present application, a resistor capable of flowing a necessary and sufficient current is included in the conductor) via a capacitive coupling. ) Is a conductor signal and ground position process, and a conductor approach and proximity position detecting device for transmitting the processing result to a non-vibration system via an isolator. The vibration frequency was set to 200 kHz or more, and signal detection was unconditionally stable. In this application, "approach"
Means about 1 m to 2 cm, and “proximity” means 5 cm to
It means about 0 cm (contact).

[0005]

When the conductor to be detected belonging to the non-vibration system is viewed (observed / measured) from the voltage oscillation system, the measurement is performed as if the conductor to be detected is oscillating in voltage. The apparatus measures electric vibrations (AC signals) equivalently received by the sensor panel or the sensor conductor array from the detected conductor via the capacitive coupling. In other words, it can be said that it is the theory of heaven in electrical systems. Unlike the conventional signal processing in which a finger of a human body (conductor) absorbs a signal, reception signal processing with respect to the ground can be performed in the voltage oscillation system, and the degree of freedom in circuit design is large. Further, it is easy to provide a shield, and an adverse effect due to a large stray capacitance can be easily avoided by an input circuit having a low input impedance.

When a conductor such as a human body oscillates in voltage, the conductor such as a human body acts as an antenna and radiates electromagnetic waves to some extent. The radiation impedance of the antenna generally decreases as the vibration frequency increases. Since this radiation impedance becomes a load on a conductor such as a human body, even when the conductor such as a human body (operator) is on an insulated chair or table, the vibration frequency is 200 kHz or more, and there is a voltage vibration suppression effect. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An impedance measuring system and a capacitance measuring system are not used, and a voltage oscillation system receives equivalently from a conductor such as a human body belonging to a non-oscillation system.
This is a device that detects by the C signal level. The pseudo ground effect of the conductor to be detected does not depend only on the ground capacitance of the conductor to be detected, but also the effect of suppressing the voltage oscillation due to the load of the radiation impedance as an antenna is effective. The present invention is a device that stably detects even a conductor to be detected having a size of a human body floating in the air and detects only approach, a device that detects only a proximity position, or a device having both functions.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the accompanying drawings. The conductor approach detection device shown in FIG. 2 will be described first.
For example, when the object to be detected is a human body 20 (conductive body), when the human body 20 approaches the sensor conductive plate 24 (may be a resistive film), the apparatus detects the approach.

In the present embodiment, the oscillating voltage generator 14 in the non-oscillating system 2 generates a sine wave of, for example, 460 kHz. The output is the same as the frequency 46
In order to oscillate the voltage at the same phase and the same amplitude at 0 kHz, it is connected to the ground circuit 11 or the power supply circuit of the power supply 12 in the vibration system 1.

The sensor conductive plate 24 is connected to an input circuit of the signal processing unit 25. This input circuit has a low input impedance (details will be described later), so that the sensor conductive plate 24 also oscillates in voltage, similarly to the ground circuit 11 of the voltage oscillating system. The sensor conductive plate 24 may be a resistive film formed on a glass or glass epoxy substrate by coating or vapor deposition. The shield plate 4 is not always necessary. As described above, the voltage oscillation systems 1 all perform voltage oscillation with the same amplitude and the same phase, but in the voltage oscillation system 1, there is no electrical oscillation between any two points. Only when viewed from other than the voltage oscillation system 1, it can be seen that the entire system undergoes voltage oscillation.

When the human body 20 to be detected is relatively close to the sensor conductive plate 24, a small amount of capacitance 23 exists between the human body 20 and the sensor conductive plate 24. Further, between the human body 20 and the ground (earth) 21, there is a ground impedance (Ze) 22 mainly due to the capacitance, and usually the Ze 22 is smaller than the impedance due to the capacitance 23 (pseudo-grounding effect). In addition, the ground 16 of the non-vibration system 2 is generally pseudo-grounded to the ground (earth) 21 through a capacitor or a commercial power supply line (AC100V, AC200V line) with a lower impedance than Ze22 in an AC manner. Not shown). Therefore human body 2
0 usually belongs to a non-vibrating system. The conduction resistance of the human body 20 is said to be several kΩ to 10 kΩ.

Therefore, an oscillating potential difference is generated between the human body 20 and the sensor conductive plate 24, and a small AC current flows through the coupling capacitor 23. Actually, the voltage of the sensor conductive plate 24 is oscillating, but the electrical phenomenon is relatively good on a macro basis regardless of which one is used as a reference. The human body 20 appears to vibrate in voltage (observed / measured). Accordingly, the sensor conductive plate 24 receives an electric vibration from the human body 20 equivalently vibrating as an AC signal and applies the AC vibration to an input of the signal processing unit 25. This is the reason for the "heavenly theory" in electrical systems.

In order to facilitate understanding, another example will be described. One battery is referenced to the negative terminal (ground)
In this case, the positive power supply is used. On the other hand, when the plus terminal is used as the reference (ground), the negative power supply is used. The opposite operation is performed depending on which reference is used. As another example, we all know now that the direction of current and the direction of electron movement are opposite. Because it was decided before, it still works. So it's good macro-wise. There is no need to change Kirchhoff's law, Fleming's law, or even Maxwell's electromagnetic field equation.

The signal processing section 25 only needs to perform single-ended ground signal processing on the AC signal equivalently received by the sensor conductive plate 24. There is no need to perform signal processing by complicated means using differential balance, which has been conventionally performed. Normal amplification to ground, band-pass filtering, AC / DC conversion (AM detection), A / D conversion, and the like may be performed. The signal processing unit 25 may include a microcomputer for signal processing.

Whether the detected conductor is absent, near, or distant (about 1 m) is determined from the received signal level of the sensor conductive plate 24. Since the signal level received via the coupling capacitance 23 is very low, signal losses must be avoided as much as possible. In order to reduce external noises other than the target signal, it is preferable to provide the shield plate 4.
It may be 0 to 1000 pF. 46 in the present embodiment
The impedance of the stray capacitance for a signal frequency of 0 kHz is 700Ω to 350Ω, and it has been difficult to avoid this adverse effect in the past. In this device, the input impedance of the signal processing unit 25 is set to 7.5Ω or less (details will be described later), so that the AC signal current received by the sensor conductive plate 24 is 98%.
% Or more flows into the signal processing unit 25. Also,
By doing so, the large stray capacitance depends on the temperature,
Or even if the capacity changes a little due to mechanical shock etc.,
It hardly affects the accuracy of signal measurement. This advantage is more pronounced in the device shown in FIG.

The processing result output from the signal processing unit 25 is transmitted to the interface 15 of the non-vibration system 2 through the isolator 13.
Tell The electrical information transmitted by the isolator 13 may be analog or digital. An A / D converter, a microcomputer, and the like may be provided in the interface 15. Alternatively, the microcomputer may be provided in both the voltage oscillation system 1 and the non-oscillation system 2.

Here, a case where the human body 20 is on an insulated chair or table, or a case where the conductor is in the air will be described. Naturally, the ground impedance (Ze) 22 increases, and the pseudo-ground effect decreases. The human body 20 is on the ground 20c
The grounding capacitance when standing on an insulating table of m was measured (using 10 kHz), but was less than 1 pF. However, the ground impedance (Ze) 22 is set to 460 kHz.
When it was actually measured, it was around 7 kΩ. 460 of 1 pF
The impedance at kHz is 350 kΩ, so there is a pseudo ground effect factor other than the ground capacitance. Each experiment has revealed that this factor is a pseudo-grounding effect (voltage oscillation suppression effect) caused by the electromagnetic wave radiation impedance acting as a load when the human body becomes an antenna.

Incidentally, even when the human body is on an insulating stand having a height of 1 m, the pseudo-grounding effect is not much different from the above. When an adult crouched on a table or a child in a lower grade elementary school stood on a table, the actual measurement was around 15 kΩ. When the frequency was 200 kHz, the pseudo-ground effect was reduced to 1/2 to 1 / 2.5 in any of the above cases (ground impedance (Ze) 22 was increased).

To summarize the above, the radiation impedance of the electromagnetic wave is the product of the electric vibration frequency and the size (mainly length) of the detected conductor when the size of the detected conductor is much smaller than the wavelength. Is almost inversely proportional to 200kHz ~
Since the wavelength of the 500 kHz electromagnetic wave is 1.5 km to 600 m, it will be understood that the radiation impedance is about the above when the size is about the size of a human body. If a smaller conductor to be detected is floating electrically in the air, a higher frequency electrical vibration is required for its detection.
The importance of the pseudo-ground effect with frequency is more pronounced in the device shown in FIG.

In the case of the proximity detection device shown in FIG. 2, the magnitude of the detection current received by the sensor conductive plate 24 via the coupling capacitor 23 is also important, and the noise level of the input circuit of the signal processing unit 25 is approximately the same as the detection current. It is an identification limit. The magnitude of the current flowing through the coupling capacitance 23 is proportional to the product of the frequency of the electric vibration and the coupling capacitance 23. In the present embodiment, in the case of the sensor conductive plate 24 of 20 cm × 20 cm at a vibration frequency of 460 kHz, an adult can unconditionally detect an approach from a distance of about 1 m. 0.5m when the vibration frequency is 200kHz
Approach was detected from the distance. In the case of children in lower grades of elementary school, the detection limit distance was reduced to about 2/3. From these results, the vibration frequency is desirably 200 kHz or more.

Next, a conductor (or finger) proximity position detecting device using a sensor panel having a uniform sheet resistance shown in FIG. 1 will be described. Since the description of the apparatus shown in FIG. 2 is substantially the same as that of the apparatus shown in FIG. 2, differences will be mainly described. The same reference numerals are used for parts having the same function. In the device shown in FIG. 1, when a conductor (for example, a finger) 7 is close to the surface of the sensor panel 3, the proximity position (X, Y position) of the conductor (finger) 7 on the surface of the sensor panel 3. ).

The actual structure of the sensor panel 3 will be briefly described. Two-dimensionally (in any direction) on the surface of transparent glass, resin, or opaque insulating substrate (not shown)
A resistor 5 (film-like) uniformly distributed is formed by coating, vapor deposition or the like. If the material of the resistor 5 needs to be transparent, I
TO (Indium Tin Oxide) film, NESA
(Tin oxide) film and the like, and the opaque one is a carbon film and the like. A striped electrode 6 having a sheet resistance much smaller than the sheet resistance of the resistor 5 is closely mounted on the outer peripheral portion. Various shapes of the stripe-shaped electrode 6 have been proposed, but in the present embodiment, it is a simple straight line. The four corners of the striped electrode 6 are connected to lead wires (shield wires 9) and are connected to four low input impedance current / voltage conversion circuits in the input section of the signal processing section 10. In addition, the upper surfaces (touch surfaces of the fingers) of the resistor 5 and the stripe-shaped electrode 6 are actually covered with an insulating sheet, a glass plate, or the like so that the operator and others do not directly touch the conductive parts. The shield plate 4 is not always necessary.

As shown in FIG. 1, when the fingers (conductors) 7 are close to each other on the surface of the resistor 5, an electrostatic capacitance coupling 8 exists between them, and the thickness of the insulating layer on the surface is increased. Although it depends, it is about 5 to 10 pF in the touch state. The voltage oscillation system 1 is driven by the oscillation voltage generator 14 at, for example, 460 kHz as in the example of FIG. Operator (not shown)
Belongs to the non-vibration system for the above-mentioned reason, and therefore, the coupling capacitance 8 is provided between the operator's (conductor) finger 7 and the resistor 5.
An oscillating current (AC signal current) flows through. In this embodiment, the signal current flowing through the finger 7 is at most about 20 μm.
Arms.

The resistor 5 has a uniform resistance value distribution, and more signal current flows through the striped electrode 6 on the side near the tip of the finger 7. Therefore, the proximity position of the tip of the conductor (finger) 7 on the surface of the sensor panel 3 is detected from the level of the signal current equivalently flowing into each of the low input impedance inputs of the signal processing unit 10. be able to.

Since the position of the current flowing equivalently from the tip of the finger 7 to one point (virtual center point) of the plane resistor 5 is detected, the technical concept of the PSD (light / charge position detecting element) is different. It's close. The main differences from the PSD are the following three points regarding the signals to be handled. The first point is
While the PSD handles DC signals, the device handles AC signals dynamically. Second, they are much larger than PSDs, and especially have large stray capacitances, sometimes up to 500-2000 pF when shielded. Third
The point is that noise (disturbance) voltages, which are significantly larger than the signal voltage, are usually present and are susceptible to undetectable or extreme degradation in accuracy. The present device fully addresses these three points. Although the degree of this measure largely depends on the performance of the input unit of the signal processing unit 10, the details will be described later.

When the finger 7 touches the surface of the insulating layer of the sensor panel 3, the coupling capacitance 8 is 5 to 10 pF.
At 0 pF, its impedance is 35 kΩ at 460 kHz. The ground impedance 22 for obtaining the pseudo ground effect of the human body 20 should be 30 kΩ or less. Further, regarding the S / N ratio of the detection signal, in the case of the sensor panel 3 corresponding to the A4 size, in order to obtain a positional resolution of 0.2 mm,
As a result, the S / N ratio needs to be 65 dB or more. This S
In the present embodiment, the signal current received from the finger 7 for obtaining the / N ratio depends on the processing means in the signal processing unit 10, but at least 5 μArms is required. In order to obtain the above-mentioned unconditional pseudo-grounding effect and to secure a signal current passing through the coupling capacitor 8, the oscillation frequency is desirably 200 kHz or more.

Next, the detection position distortion will be described. In the present embodiment, the stripe-shaped electrode 6 has a simple linear shape. In this structure, it has been conventionally known that as the ratio between the sheet resistance of the resistor 5 and the sheet resistance of the striped electrode 6 is increased, the curving of position detection is reduced. It has also been proposed that the curving property can be improved by devising the pattern of the surrounding electrodes. In the present embodiment, the parameters are set so as to minimize the curving property with a simple peripheral electrode pattern. The sheet resistance of the resistor 5 was 1 kΩ / □, and the resistance between both ends of each side of the striped electrode 6 was 350 Ω. FIG. 5 shows an X-direction detection isoposition line based on actual measurement at this time, and FIG.

The input impedance of the signal processing unit 10 is set to 1
If the circuit stability is lowered to about Ω while ensuring the circuit stability, the resistance value of the stripe-shaped electrode 6 is set to about 1/5 of the present embodiment, and the detection equidistant lines (detection position distortion) shown in FIGS. It is possible to make it linear. This curvature is corrected by a microcomputer (not shown) in the apparatus. As reference examples, X-direction detection equiposition lines in the case where there is no stripe-shaped electrode 6 are shown in FIG. 7, and those in the Y direction are shown in FIG.
5 to 8 show trajectories when the conductor corresponding to the finger is moved so that the following calculation results become equal. Position formula is normalized _{X = (i B + i C} -i A -i D) / (i A + i B
+ I _C + i _D) normalized _{Y = (i C + i D} -i A -i B) / (i A + i B
+ I _C + i _D ). With the center of the sensor panel 3 as the origin, FIG.
Are defined as positive directions. Also, i _A , i
_B , i _C and i _D are AC signal current values flowing from points A, B, C and D, respectively.

From FIGS. 7 and 8, when the two figures are superimposed, the area where the detection isoposition lines are nearly parallel is substantially only a one-dimensional element.
It is impossible to determine the exact position of the dimension or the position is extremely poor in accuracy, and it can be seen that the area other than the central part is a practically unusable area. From now on, the stripe-shaped electrode 6 will detect the current A,
It can be seen that there is an effect of distributing to points B, C and D along the X and Y directions.

Next, the main part of the detailed circuit which supports the present invention will be described. FIG. 3 shows that the voltage oscillation system 1
1 shows an example of a circuit that drives at the same time and supplies power and a circuit corresponding to the isolator 13. The main part is a multi-wire / common-mode / resonance transformer 30, which is a tightly-coupled coil group wound on the same closed magnetic circuit magnetic core such as a donut or an EI. L1, L3, L in the figure
The coils denoted by L4 and L5 have the same number of turns, and perform AC vibration at the same voltage and the same phase. Reference numerals 32 and 33 are large-capacity decoupling capacitors, and are multi-wire capacitors.
The coils indicated by L1 and L3 of the common mode / resonance transformer 30 are connected in parallel in an AC manner. The ground and the + 5V power supply of the voltage oscillation system 1 and the non-oscillation system 2 are connected via a coil L3 and a coil L1, respectively. The coil L1 is an inductance combined with the coil L2, and forms a parallel resonance circuit with the capacitor 35. The transistor 36 drives this resonance circuit (L1, L2, 35).

When the driving pulse is applied via the resistor 44, the waveform becomes gentle with a simple low-pass filter formed together with the capacitor 43, and the base of the transistor 36 is connected to the base of about 4 V via the AC coupling capacitor 42.
AC drive at pp. The base of the transistor 36 is 10 to
It is forward biased for 15% of the time and reverse biased at other times, and conducts intermittently between the collector and the emitter of the transistor 36 to drive the resonance circuit (L1, L2, 35) via the resistor 38. . That is, the transistor 36 operates in class C and has high efficiency. The lower end (hot end) of the coil L2 vibrates in a sine wave at about 10 Vpp, and the AC voltage divided by the coils L2 and L1 causes the voltage vibration system 1 to vibrate in a sine wave. The current consumption of the +5 V power supply of the non-vibration system 2 for driving the voltage vibration system 1 is about 2 mA. The Schottky barrier diode 37 is used for normal desaturation of the transistor 36 and has a resonance circuit (L
1, L2, 35) at a constant voltage.
For the purpose and value of each resistor and capacitor, refer to the column of description of reference numerals.

The coils L4 and L5 correspond to the isolator 1 shown in FIG.
3, which transfers analog or digital electrical information between the voltage oscillating system 1 and the non-oscillating system 2. If more electric information lines are required, the electric information lines may be provided through coils added with the same number of turns as the coils L1 and the like. The oscillation voltage of the voltage oscillation system 1 is 2
When Vpp or less and only digital electrical information by CMOS logic need to be transmitted, it is also possible to pass electrical information only through a resistor as the isolator 13 instead of the coils L4 and L5.

The power supply current and the return ground current flowing through the coils L1 and L3 have the same magnitude and opposite directions, and thus cancel each other out. Also, the current flowing through the coils L4, L5, etc., is negligibly small. Therefore, the resonance current flowing through the coil L2 becomes the main magnetic field line source, and the multi-wire common mode resonance transformer 3
The magnetic core of 0 is hardly magnetically saturated, and the multi-wire / common-mode / resonant transformer 30 can be made very small.

The circuit shown in FIG. 4 corresponds to the signal processing unit 10 shown in FIG.
Is an example of the input circuit. It is basically an AC current / AC voltage conversion circuit, and its main parts are a transistor 55 and LC parallel resonance circuits 52 and 53. The transistor 55
The base is grounded via the resistor 59, and transmits about 99.5% of the AC signal current input to the emitter to the collector.
When selected by the analog multiplexer 54, the collector circuit of the transistor 55 has a high impedance at the signal frequency, has a high trans-impedance value, and therefore has a high current / voltage conversion efficiency. Although the current / voltage conversion efficiency is high, the dynamic range is extremely large and the noise immunity is greatly enhanced, which will be described in detail later. Since the output impedance of the collector of the transistor 55 itself is large and the Q value of the parallel resonance circuits 52 and 53 is not significantly reduced, only the necessary frequency (the oscillation frequency of the voltage oscillation system 1) is converted into a voltage.

The analog multiplexer 54 connects one of the four input circuits to the parallel resonance circuits 52 and 53 so that the detection currents from the points A, B, C and D can be measured in a time sharing manner. . The diode 51 is a substitute load having a clamping action for keeping the input impedance of the present circuit at a constant value by operating the input circuit even when it is not selected by the analog multiplexer 54. Although the analog multiplexer 54 has a stray capacitance therein, it can be regarded as a part of the resonance capacitor 53 and therefore does not cause a signal loss. Further, unlike the conventional device, the present device is a signal processing for ground, so that there is no harmful spurious component added to the signal component from all the stray capacitances of the present circuit. This is also one of the features of this device.

In this embodiment, the emitter input impedance of the transistor 55 is about 20Ω, which is not a sufficiently low input impedance. Therefore, an inverting amplifier circuit using the transistor 57 is added. When the emitter voltage of the current / voltage conversion transistor 55 fluctuates, the voltage is applied to the base of the transistor 57 via the AC coupling capacitor 66 as a voltage fluctuation.
This voltage change is inverted in phase by the common emitter transistor 57 and applied to the base of the transistor 55 to modulate the base DC voltage. This modulation works in the direction of reducing the fluctuation of the emitter voltage of the transistor 55. That is, the emitter input impedance of the transistor 55 decreases. In this embodiment, 6.5Ω ± 1Ω was obtained at 640 kHz. For each circuit constant, refer to the column of description of reference numerals as a reference example.

It should be noted that the stray capacitance connected to the emitter of the transistor 55 is as large as 500 to 2000 pF. Therefore, for stable operation of the circuit,
Phase compensation by the resistor 62 and the capacitor 63 is necessary. Nevertheless, the open loop gain is 460 in this embodiment.
At kHz, it hardly drops. This circuit is 20
It is quite stable even with an input stray capacitance of 00 pF. If an operational amplifier is used instead of this circuit, the stray capacitance enters the summing point, so that it is difficult to obtain a stable operation. 20 stray capacitance
If it is much less than 00 pF, it is easy to reduce the input impedance to about 1Ω by slightly changing the constant in the circuit of FIG.

The input impedance of the circuit shown in FIG.
If the resistance value is not sufficiently smaller than the resistance between both ends of each side of the striped electrode 6 of the sensor panel 3, the current distribution ratio to the points A, B, C, and D will be small, thus causing a detection position error. . Reducing the input impedance value also prevents signal loss due to large stray capacitance, as described in paragraph 0015. In the present device using a single-layered planar resistor as a sensor panel, the position is calculated from the current ratios detected from the four corners, so that the signal loss should be as small as possible. It has been confirmed that 6.5Ω ± 1Ω in this embodiment is a sufficiently low value for practical use.

In the conventional device for absorbing a signal to a finger, the stray capacitance with a shield plate, a shielded electric wire, a device housing, and the like is also reduced by A.
Since the C signal flows out and the net component due to the absorption of the AC signal into the original finger is less than 5%, it is very difficult to secure the detection position accuracy. In this embodiment, the shield plate 4
There is no inflow AC signal from the stray capacitance of the shielded wire 9 and a little inflow from the device housing.
Since the signal current occupies about 80%, the reliability of the signal is greatly increased as compared with the related art, and more accurate and accurate proximity position detection is obtained. This is also a major feature of the present apparatus that handles a ground signal.

The noise tolerance of the circuit shown in FIG. 4 will be described. Transistor 55 transmits approximately 99.5% (almost a constant value) of the instantaneous emitter current to its collector almost irrespective of its current value until its instantaneous emitter current becomes close to zero. Good, and the linearity of the circuit is maintained. That is, the AC signal current is at most about 20 μArms, and no distortion occurs in the signal frequency component with respect to the noise mixing in which about 1.3 mA of the DC bias current becomes close to zero.
Even if noise of a different frequency component of 32 dB is mixed, the detection position is not so much shifted. That is, even if the current / voltage conversion efficiency is high, noise in a frequency band different from the signal frequency is +
Even if mixed at a level of 32 dB, this circuit does not saturate, and the dynamic range is extremely large. Further, if the input unit is AC
Due to the coupling, there is a noise tolerance of +109 dB against a power supply induced noise component of a commercial power supply of 50 to 60 Hz.

This noise resistance performance (noise margin) can be processed in a voltage oscillation system with respect to a ground signal], and is realized by a television, a personal computer, a CRT monitor, and a liquid crystal display. Provide stable operation under the environment used together with. Incidentally, the noise margin of the conventional capacitance coupling type finger touch position detecting device is at most about 0 dB at all frequencies other than the signal frequency.

It is needless to say that one of the four input circuits shown in FIG. 4 can be used for the proximity detecting device shown in FIG. 2 except for the analog multiplexer 54 and the clamp diode 51. Further, the circuit shown in FIG. 4 can be applied to a device in which an AC signal is transmitted from a pen-shaped active position indicator to a sensor panel (not a voltage oscillation system) via a coupling capacitor. Similarly, there is a margin of +32 dB for noise having a frequency component different from the AC signal frequency. +109 dB for 60 Hz
Noise margin. Those using an operational amplifier are easily saturated, and the above-described noise resistance cannot be obtained.

Next, a description will be given of a deviation in position detection when a conductor such as the finger 7 is floating above the sensor panel 3. FIG. 9 shows coupling capacitances 90 and 9 with two points on the sensor panel 3 when the finger 7 is close to the surface of the sensor panel 3.
1 is illustrated. FIG. 10 shows coupling capacitances 100 and 101 with the same two points on the sensor panel 3 when the finger 7 is slightly away from the surface of the sensor panel 3.
Is illustrated in FIG. In FIGS. 9 and 10,
The X and Y positions of the sensor panel 3 of the finger 7 are the same. The coupling capacitances 90 and 91 have a large capacitance ratio, and the coupling capacitances 100 and 101 have a small capacitance ratio.

Actually, since the coupling capacitance is distributed over the entire surface of the sensor panel 3, when the finger 7 is slightly away from the surface of the sensor panel 3, the current distribution ratio to the points A, B, C, and D is determined. Is slightly smaller, so that the detection position is calculated closer to the center of the sensor panel 3 than it is. In this apparatus, a built-in microcomputer (not shown) corrects this detection position deviation. Whether the finger 7 is near or away is determined from the sum of the AC signal current values detected from points A, B, C, and D. The correction amount differs depending on the size of the sensor panel 3.

FIG. 11 shows a grid-like sensor conductor array 1.
This shows a configuration of a voltage oscillation system of a device for detecting a proximity position of a conductor such as a finger, using the devices 11 and 112. X
And Y direction analog multiplexers 113 and 114
Sequentially switches the sensor conductor arrays 111 and 112 for X-direction and Y-direction detection and applies the signals to the input of the signal processing unit 110. From the AC signal level (current or voltage) detected (received) by each sensor conductor 111 and 112,
The proximity position of a conductor such as a finger is calculated. Although the structure of the sensor unit is more complicated than that shown in FIG. 1, since only the position between the sensor conductors 111 and 112 needs to be analog-interpolated, the detection position accuracy is better than that of FIG. This device is also capable of signal processing with respect to the ground, and has the above-mentioned advantages.

[0046]

According to the present invention, an apparatus for detecting the proximity and proximity of a conductor, which is simple and excellent in noise resistance, is obtained by signal processing to ground without performing complicated signal processing such as differential balance. In addition, the adverse effects of stray capacitance such as shields were almost eliminated. Furthermore, by clarifying the factors of the pseudo-grounding effect, it is possible to unconditionally detect the approach and proximity position of the conductor unconditionally, including the human body electrically floating in the air.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus for detecting the proximity position of a conductor such as a finger using a sensor panel having a uniform resistance surface.

FIG. 2 is a schematic configuration diagram of a conductor approach detection device.

FIG. 3 shows an example of driving and power supply of a voltage oscillation system and an isolator circuit.

FIG. 4 Detected current / voltage conversion and time division circuit example

FIG. 5 is an X-direction detection isoposition diagram.

FIG. 6 is an isometric diagram of Y direction detection.

FIG. 7 is an X-direction detection isometric diagram in a sensor panel without a low-resistance striped electrode 6;

FIG. 8 is a Y-direction detection isoposition diagram in a sensor panel having no low-resistance striped electrode 6;

FIG. 9 is an explanatory diagram of a coupling capacitance ratio when a finger is close to the surface of the sensor panel.

FIG. 10 is an explanatory diagram of a coupling capacitance ratio when a finger is slightly away from the surface of the sensor panel.

FIG. 11 uses a grid of sensor conductor arrays;
Schematic diagram of the configuration of the voltage oscillation system of the conductor proximity position detection device such as a finger

[Explanation of symbols]

Reference Signs List 1 voltage oscillation system 2 non-oscillation system 3 sensor panel 4 shield plate 5 two-dimensionally uniform resistor 6 low-resistance striped electrode 7 finger (conductor) 8 capacitance coupling between finger 7 and resistor 5 9 shield Electric wire 10 Signal processing unit 11 Voltage oscillation system ground circuit 12 Voltage oscillation system power supply 13 Isolator 14 Oscillation voltage generator 15 Interface 16 Non-oscillation system ground 20 Human body (conductor) 21 Grounding (earth) 22 Human body ground impedance 23 Human body 20 Coupling between sensor and sensor conductive plate 24 Sensor conductive plate (may be a resistive film) 25 Signal processing unit 30 Multi-wire / common-mode / resonant transformer 31 Voltage oscillation system +5 V power supply 32 Decoupling capacitor (for example, 22 μF) 33 Decoupling Ring condenser (for example, 4.7 μF) 34 Non-vibration system + 5V Source 35 resonant capacitor (e.g., 680pF) 36 C class operation of the driving transistor (e.g. 2SC4
116Y) 37 Schottky barrier diode 38 Compliance resistance (for example, 47Ω) 39 Resistance (for example, 4.7Ω) 40 Resistance (for example, 470Ω) 41 DC bias current application resistance (for example, 150 k)
Ω) 42 AC coupling capacitor (for example, 470p
F) 43 Low-pass filter capacitor (for example, 100p
F) 44 Low-pass filter resistance (for example, 1.5 kΩ) 50 +4.7 V (vibration system) 51 Clamp diode (substitute load) 52 Band-pass coil 53 Band-pass capacitor 54 Analog multiplexer 55 Current / voltage conversion transistor (for example, 2SC4)
116Y) 56 Resistance (for example, 47Ω) 57 Voltage fluctuation detection transistor (for example, 2SC41
16Y) 58 Resistance (for example, 10Ω) 59 AC and DC load resistance of transistor 57 and grounded base resistance of transistor 55 (for example, 1 kΩ) 60 DC load resistance of transistor 57 (for example, 4.
61 Decoupling capacitor (for example, 1 μF) 62 Phase compensation resistor (for example, 1 kΩ) 63 Phase compensation capacitor (for example, 7 pF) 64 DC voltage dividing resistor (for example, 68 kΩ) 65 DC voltage dividing resistor (for example, 22 kΩ) 66 Transmit voltage fluctuation Coupling capacitor (for example, 1000 pF) 67 Resistance (for example, 4.7 Ω) 68 AC coupling capacitor (for example, 0.22
μF) 69 DC current sink resistance (eg, 1.5 kΩ) 70 DC zero bias application resistance (eg, 22 kΩ) 90 Coupling capacitance between finger 7 and near point on sensor panel 91 Coupling between finger 7 and far point on sensor panel Capacitance 100 Coupling capacitance between finger 7 and near point on sensor panel 101 Coupling capacitance between finger 7 and far point on sensor panel 110 Signal processing unit 111 Sensor conductor array for X-direction detection 112 Sensor conductor array for Y-direction detection 113 X direction analog multiplexer 114 Y direction analog multiplexer

Claims (11)

[Claims] 1. An apparatus for detecting approach of a conductor, comprising a voltage oscillation system and a non-oscillation system, wherein the voltage oscillation system comprises:
A sensor conductive plate which is driven by an oscillating voltage generator having a frequency of 200 kHz or more, and which receives and detects an AC current equivalently flowing through a capacitive coupling with the conductor, and a sensor conductive plate; A signal processing unit for applying the detected AC current, a voltage oscillation ground circuit also connected to the signal processing unit, and a voltage oscillation with the same amplitude and the same phase with respect to the voltage oscillation ground circuit, The power supply circuit connected to the unit, the non-oscillating system, the oscillating voltage generator, and an interface with an external device, between the signal processing unit and the interface,
A conductor approach detection device for transferring digital or analog electrical information via an isolator. 2. An apparatus for detecting a proximity position of a conductor on a sensor panel surface, comprising a voltage oscillation system and a non-oscillation system, wherein the voltage oscillation system generates an oscillation voltage having a frequency of 200 kHz or more. Having a two-dimensionally uniform surface resistance, and a periphery of the resistor, which is driven by a heater, and receives equivalently an AC current flowing through a capacitive coupling with the conductor. A sensor panel in which low-resistance electrodes are disposed in close contact with each other, a signal processing unit for applying AC current flowing from four corners of the sensor panel, a voltage oscillation ground circuit also connected to the signal processing unit, The voltage oscillation system grounds the voltage with the same amplitude and the same phase with respect to the ground circuit, and comprises a power supply circuit connected to the signal processing unit, and the non-oscillation system includes the oscillation voltage generator and an interface with an external device. Consisting of A conductor proximity position detecting device, wherein digital or analog electrical information is exchanged between the signal processing unit and the interface via an isolator. 3. An apparatus for detecting a proximity position of a conductor on a sensor conductor array surface, comprising a voltage oscillation system and a non-oscillation system, wherein the voltage oscillation system has an oscillation voltage having a frequency of 200 kHz or more. The sensor conductor array, driven by a generator, and equivalently receiving an AC signal through a capacitive coupling between the conductor and the sensor conductor array arranged in a grid in the X direction and the Y direction; An analog multiplexer for sequentially connecting each conductor of the sensor conductor array,
A signal processing unit for applying an output of the multiplexer, a voltage oscillation ground circuit also connected to the signal processing unit and the multiplexer, and a voltage oscillation with the same amplitude and the same phase with respect to the voltage oscillation ground circuit, A non-oscillating system comprising an oscillating voltage generator and an interface with an external device, wherein an isolator is provided between the signal processing unit and the interface. An electrical conductor proximity position detecting device for transferring digital or analog electrical information via a personal computer. 4. A ground circuit, a power supply circuit, and a digital or power circuit between the voltage oscillation system and the non-oscillation system via a multi-wire common mode resonance transformer wound around the same closed magnetic circuit magnetic core. 2. The conductor approach detection device according to claim 1, wherein the analog electrical information lines are respectively connected. 5. A ground circuit, a power supply circuit, and a digital or power circuit between the voltage oscillation system and the non-oscillation system via a multi-wire common-mode resonance transformer wound around the same closed magnetic circuit magnetic core. 3. The conductor proximity position detecting device according to claim 2, wherein the analog electric information lines are respectively connected. 6. A ground circuit, a power supply circuit, and a digital or power circuit between the voltage oscillation system and the non-oscillation system via a multi-wire common mode resonance transformer wound around the same closed magnetic circuit magnetic core. 4. The conductor proximity position detecting device according to claim 3, wherein the analog electric information lines are respectively connected. 7. The multi-wire common-mode resonant transformer is driven by a class-C transistor.
The conductor approach detection device according to claim 4. 8. The multi-wire / common-mode / resonant transformer is driven by a class C transistor.
The conductor proximity position detecting device according to claim 5. 9. The multi-wire / common-mode / resonant transformer is driven by a class C transistor.
The conductor proximity position detecting device according to claim 6. 10. An apparatus for detecting a proximity position of a position indicating means on a sensor panel surface, wherein an AC signal actively or equivalently transmitted from the position indicating means is received via a capacitive coupling. A sensor panel having a two-dimensionally uniform resistor and a low-resistance electrode disposed around the resistor, and a current / voltage for applying an AC current flowing from four corners of the sensor panel. A current-to-voltage conversion circuit, wherein the current-to-voltage conversion circuit has an emitter-input transistor whose base is grounded via a resistor, an LC parallel resonance circuit that is connected to the collector of the transistor, and inverts and amplifies a voltage fluctuation of the emitter input. And an inverting amplifier applied to the base of the transistor. 11. The AC flowing from four corners of the sensor panel when the conductor contacts the sensor panel surface.
The sum of the current values is a reference measurement current value, and when the measurement is smaller than the reference measurement current value, the detected proximity position has a means for correcting the detected proximity position to the outer peripheral direction from the center position of the sensor panel surface. The conductor proximity position detecting device according to claim 2.