JP5035205B2 - Touch panel device - Google Patents

Description

  The present invention relates to an apparatus and method for measuring a phase of a detection signal of a touch position in a capacitive touch panel device that detects a touch position on a sensor panel with a finger or a coordinate indicator, and correcting a positional coordinate shift. It is.

The touch panel device provides a simple and intuitive interface for a computer or other data processing device. In particular, in a transparent touch panel device, the user can send information via the touch panel device by touching an icon on the screen or drawing a character or a picture instead of using a keyboard for data input. A typical example of this technical field is a capacitive coupling type, which is derived from the fact that an AC current path can be formed by the human body having a grounding effect.
FIG. 4 shows the prior art. This is an example of a capacitive coupling type touch panel device, and a resistive surrounding electrode 43 surrounding a uniform surface resistor 42 is arranged on the surface of the glass substrate of the sensor panel 41, and connection electrodes 4A at the four vertices. 4B, 4C, and 4D are provided with lead wires 44 and connected to the signal processing unit 45.
In the conventional sensor panel 41, an ITO (indium oxide) film formed by sputtering or a tin oxide film formed by CVD is formed on the surface of a glass substrate as a surface resistor 42 at about 700Ω / □. As the glass substrate, for example, soda glass is used. On the surface resistor 42, a resistive surrounding electrode 43 is formed so that the resistance value between the apexes is about 70Ω. The resistive surrounding electrode 43 is formed by, for example, using conductive ink, printing and baking in a desired pattern. If necessary, the connecting electrode at each apex portion may be printed and baked with a solderable conductive ink for connecting the lead wire 44, or may be protected with insulating ink except for each apex portion. .

As the coordinate detection means of the sensor panel 41, each part of the surface resistor 42 is signal-driven, and the entire surface resistor 42 is vibrated by an AC voltage, thereby forming a capacitive coupling formed between the finger 46 and the surface resistor 42. There is a method of detecting the position of a point touched via the touch panel.
The signal processing unit 45 includes a measurement circuit for measuring the AC vibration voltage from the finger 46, an AD conversion circuit for converting the measured signal into a DC value, and a driver for causing the surface resistor 2 to vibrate. A circuit, a CPU for converting measured signals into coordinate data, and arithmetic software / storage devices thereof are included.

JP 2000-132319 (direct contact type touch panel device) Japanese Patent Application No. 11-278734 (parasitic signal elimination touch panel device)

In a capacitive touch panel device, the signal processing unit uses the coordinate position where the finger actually touched the surface resistor due to the parasitic signal due to the installation environment of the sensor panel and the degree of grounding effect of the human body, that is, the change in grounding impedance. There was a phenomenon in which the coordinate detection position was shifted between the calculated coordinate positions.
The internal resistance component of the ground impedance of the human body cannot be ignored due to the surrounding conditions of the human body or the contact state between the human body and the system housing and its grounding platform, and the footwear material. As a result, parasitic signals (occurrence of parasitic signals) Will be described later.) And the original signal from the finger (capacitance coupling amount generated when the operator touches the finger with the surface resistor), a phase difference occurs, and the scalar amount is combined (mixed). ), But a vector composite signal. If the vector composite signal is used as a scalar quantity to perform coordinate calculation as it is, it is different from the original AC signal component, which causes a coordinate shift.

  The phase difference between the parasitic signal and the original signal consisting of the capacitance generated when the operator's finger contacts the surface resistor is captured as a vector composition, and the operator's finger becomes the surface resistor. A method of forcibly applying a removal signal having an opposite phase and the same amplitude in an AC signal state to a parasitic signal due to electromagnetic radiation from a sensor panel and a parasitic signal due to parasitic capacitance, as a method of eliminating a shift in touch position coordinates when abutting. Is disclosed.

Assuming the stray capacitance between the sensor panel and the system casing and the parasitic signal due to electromagnetic radiation from the sensor panel, the means forcibly applies a signal with the same phase and amplitude as the vector, This is an effective removal method for touch position deviation. However, as a condition in the above method, a removal signal having an opposite phase and the same amplitude as that of a parasitic signal component generated in an environment where the sensor panel is attached to the system casing must be forcibly applied.
That is, before the sensor panel is attached to the system casing, the amplitude and phase of the parasitic signal, which is the stray capacitance between the sensor panel and the system casing, is not known.
Further, it is possible to apply a removal signal having the opposite phase and the same amplitude assuming a parasitic signal component to some extent, but this method cannot completely remove the parasitic signal.
In order to reduce the stray capacitance between the sensor panel and the system casing, shield the surface resistor on the sensor panel mounting part on the back or front of the panel (means for preventing parasitic signals from entering the sensor circuit mounting part) In the following text, it is used in the above-mentioned meaning), and the current due to electromagnetic radiation from the back surface or the sensor panel front surface mounting portion does not flow into the signal processing portion, but it can be reduced, but the parasitic signal cannot be completely removed. (In actuality, there is a method of shielding the surface resistor by applying a transparent surface resistor to the back of the panel part, but there is no material that can make the surface resistance of the transparent surface resistor zero, and the shield is completely shielded. (Since the touch panel cannot shield the sensor panel mounting part on the surface, the parasitic signal cannot be completely removed.)

  An object of the present invention is to generate a phase difference between a signal generated when an operator's finger actually touches a surface resistor and a parasitic signal, and to generate a signal that is not vector synthesis (mixing) but vector synthesis. The object is to correct the original AC signal component (converted to a scalar amount) and eliminate the coordinate shift.

  The present invention is an apparatus used for detecting a contact position of a finger or a conductive stylus on a sensor panel surface, and a surface resistor in which a resistive film material is uniformly formed on the sensor panel surface In addition, in order to drive the surface resistor with an AC voltage, a resistive peripheral electrode provided with connection electrode points is provided on the periphery of the sensor panel surface, and is proportional to the AC current flowing through the connection electrode. A touch panel device having a circuit for measuring the amplitude of an AC voltage and a circuit for measuring the phase of the AC voltage, and the AC voltage phase when the finger or the conductive stylus is not in contact with the surface resistor The amplitude is a contactless vector signal, the AC voltage amplitude and phase when the finger or conductive stylus contacts the surface resistor is the contact vector signal, and the finger or conductive stylus is The AC voltage amplitude and phase when abutting against the resistor is used as a contact vector signal, and the result obtained by calculating the contactless vector signal and the contact vector signal is obtained by a finger or a conductive stylus. A touch panel device having an arithmetic processing unit for calculating a coordinate as a scalar amount of an original AC current touched on the surface resistor, and using the scalar amount as an original AC current proportional to the contacted position flowing through the connection electrode This is a proposal.

  By treating the AC voltage due to the parasitic signal when the finger is not near the surface resistor, the phase difference of the amplitude due to the finger of the capacitive ground human body or the resistive ground human body as a combined vector, and eliminating the parasitic signal, The original detection signal can be measured even when the installation environment of the touch panel device or the impedance of the grounded human body changes constantly.

  As a result of the means obtained in the present invention, the touch position is detected from the AC signal current flowing in the surface resistor when the operator touches the sensor panel. Regardless of the operator's grounding status of the capacitive touch panel device, and regardless of the installation environment of the sensor panel in the device, the sensor panel may be installed before or after being installed in the system chassis. Even if the inflow amount of the incorporated parasitic signal into the signal processing unit changes, the touch detection position shift can be eliminated.

  In the sensor panel, a resistive film material is uniformly formed on the surface of a resin or glass as a base, and a resistive peripheral electrode surrounding the periphery of the resistive film is disposed. A conductor cable is connected, and includes a circuit for measuring the amplitude of the AC voltage proportional to the touch position from the four vertices of the surrounding electrodes and a circuit for measuring the phase from the four vertices of the surrounding electrodes. There is an arithmetic processing unit that calculates using the cosine theorem, and uses the calculated scalar amount as an original touch position detection signal as a touch panel device having means for calculating the coordinates of the finger contact position on the sensor panel surface. is there.

Hereinafter, the details of the present invention will be described in detail with reference to FIG.
In the sensor panel unit 1, a transparent surface resistor film 2 such as ITO (indium tin oxide) or NESA (tin oxide) was formed on a rectangular glass substrate so as to have a resistance of about 700Ω / □.
Next, a resistive surrounding electrode 3 (hereinafter referred to as a surrounding electrode) surrounding the surface resistor film 2 was placed in contact with a conductive ink such as carbon or silver carbon. The resistance value between the four vertices of the peripheral electrode is set to about 70Ω, and lead wires 4 that are conductor cables are connected to the four vertices A, B, C, and D that are connection electrodes.
Each lead line 4 is connected to a respective input of the current-voltage conversion circuit 9. An oscillating voltage generator 8 serving as an AC signal source applies an oscillating voltage to each input of the current-voltage conversion circuit 9 with a low impedance. Therefore, the transparent surface resistor 2 is driven by an AC voltage.

  A simple practical example of the current-voltage conversion circuit 9 is that the base of the transistor is vibrated with an AC voltage, the emitter is connected to the sensor panel unit 1, and the collector is single-ended (isolated from the AC voltage oscillation system). An output signal voltage is applied to the analog multiplexer 10. This output signal voltage is proportional to the signal current flowing through the lead wire 4. Further, in order to measure the output voltage, it is converted to DC by an AM detection unit in the signal processing unit 12.

  The finger 5 touches or approaches the transparent surface resistor 2 that is voltage-driven. The same applies when a conductive stylus (not shown) touches or approaches instead of the finger 5. The human body is conductive and is illustrated with an equivalent resistance 6. As is known in the art, the human body has a grounding effect and is represented by a grounding impedance 7 (Z).

Reference numeral 11 denotes a phase measuring unit which, as a simple embodiment, amplifies an output voltage proportional to an AC signal current and forms a waveform into a rectangular wave. If the waveform from the output part of the oscillating voltage generator 8 is a sine wave, it is shaped into a rectangular wave. A rectangular wave having a duty ratio proportional to the phase is obtained from the both rectangular waves by an AND circuit. A DC signal proportional to the phase can be measured by converting the rectangular wave into DC in the signal processing unit 12.
As described above, when the human finger 5 touches or approaches the transparent surface resistor 2 (through capacitive coupling when close), the AC signal current path through the transparent surface resistor 2 and the finger 5 is It was possible to measure the amplitude voltage of the detection signal and the phase at the same time.

  In the example shown in FIG. 1, the AC current flowing through the transparent surface resistor 2 is eventually distributed to the connection electrodes A, B, C, and D, and in the case of the touch position of the finger 5 shown in FIG. Current flows little at the connection electrode C point. From the AC signal current values flowing through these connection electrodes A, B, C, and D, that is, the input AC signal voltage values of the analog multiplexer 10 proportional to them, the finger 5 is touched or located close to the transparent surface resistor 2. Is detected.

  Here, a parasitic signal that flows in addition to the finger 5 will be described. FIG. 3 is an explanatory diagram of the cause of parasitic signal generation. Generally, when a conductor vibrates with voltage, electromagnetic radiation is more or less accompanied by a radiated current flowing through a driving point. In this embodiment, the sensor panel unit 1 is driven by a sine wave of 460 kHz and 0.5 Vrms, and the wavelength of the radiated electromagnetic wave 35 (see FIG. 3) is 650 m. The size of the sensor panel unit 1 is about A5 to A3, and is extremely small compared to the wavelength. Therefore, the radiation impedance is almost capacitive only, and the resistance component can be ignored.

  There is another cause of parasitic signal generation, and the sensor panel 1 of this apparatus is attached to a casing 31 of a system that uses this apparatus. Usually, the system casing 31 is made of metal and is a conductor. The system casing 31 is in a low impedance relationship with the circuit ground and the noise filter, stray capacitance, etc. of the power supply unit at the signal frequency of the apparatus. As shown in the figure, the transparent touch panel device particularly has a parasitic capacitance 34 because the sensor panel unit 1 is mounted in the immediate vicinity of the casing 31 of the system. Further, the sensor panel unit 1 is often used by being overlapped with a liquid crystal display, and a large parasitic capacitance is generated on the back surface.

  This parasitic signal current is capacitive and its phase advance is 90 degrees ahead of the drive voltage. The parasitic signal current varies greatly depending on the attachment state of the sensor panel 1 to the housing 31 of the system, and is about 5 μA to 300 μA. Similarly, in the phase, the parasitic signal increases as the sensor panel 1 approaches the system casing 31 or the facing area increases.

  The electromagnetic radiation impedance from the sensor panel 1 and the parasitic signal current due to the parasitic capacitance 34 from the system casing 31 are placed on the back of the sensor panel 1 and connected to the vibration voltage generator 8 from the back. The current is reduced by not flowing into the signal processing unit 12 but does not become zero. Further, since there is a touch input surface on the surface of the sensor panel 1, electromagnetic radiation cannot be stopped.

  As described above, the almost capacitive radiation current from the surface of the sensor panel 1 and the parasitic signal current of the capacitive 34 between the sensor panel 1 and the system housing 31 are combined, and each lead line 4 in FIG. Parasitic currents iA, iB, iC, iD having phases advanced from the drive voltage phase always flow to the input circuit of the signal processing unit 12 via the current / voltage conversion circuit 9 and the analog multiplexer 10 as shown in the figure.

  According to the present invention, the original touch detection signal can be obtained by the means for measuring the current value and phase of the parasitic signal current, the means for measuring the combined current value and phase of the parasitic signal and the touch detection signal, and the arithmetic processing thereof. The finger touch position shift can be eliminated, details of which will be described later.

  Next, the grounding effect of the human body will be described. A sensor panel 1 of the present apparatus is attached to a casing 31 of a system that uses the present apparatus. The human body 30 touches and operates the sensor panel 1 with its right hand. When the left hand of the human body 30 is in contact with the metallic system casing 31 as shown in the figure, the human body 30 and the system casing 31 are in a resistive impedance relationship. Its resistance value is about 1 kΩ. Further, when the left hand of the human body 30 is separated from the system casing 31, other ground effect factors play a leading role, the capacity 33 between the system casing 31 and the human body 30, the ground capacity 32 of the human body 30, and the finger When the sensor panel 1 is touched, the human body 30 also vibrates a little, but it is a combination of the ground effect due to the electromagnetic radiation impedance.

The grounding effect (the effect of suppressing voltage vibration of the human body) due to electromagnetic radiation from the human body 30 is described in detail in the aforementioned patent application number [Japanese Patent Application No. 10-321508].
Therefore, if the footwear of the human body 30 is insulative, the ground impedance 7 of the human body shown in FIG. 1 is capacitive when the system housing 31 is not touched, and when the footwear is touching the system housing 31. The ground impedance 7 is resistive, and the impedance is a small value compared to the capacitive.

FIG. 2 is an explanatory diagram in which parasitic signals and touch signals are displayed as vectors.
In FIG. 2, for easy understanding, the voltage phase of the oscillating voltage generator 8 is the reference phase axis 20, and the vertical direction is the direction in which the phase has advanced. Vector 22 is the combined signal component of the actual parasitic signal and the capacitive ground human body. Vector 21 is a parasitic signal component. A difference between the vector 22 and the vector 21 is an original AC signal component by the finger 5 of the ground human body. In the case of a capacitive ground human body having the same phase as the parasitic signal 21, the vector 22 is in the same direction. Therefore, after DC conversion (AM detection) as a scalar quantity, the amplitude of the vector 21 is subtracted from the amplitude of the vector 22 by the original finger. Even if the amplitude (magnitude) of the AC signal component is detected, the touch position does not shift.

However, in the case of a signal from the finger 5 of the grounded human body whose resistance component is greater than that of the parasitic signal, the vector 23 is obtained by combining the parasitic signal component 21 with the original AC signal component 24. As can be seen from the figure, when the amplitude of the vector 21 is subtracted from the amplitude of the vector 23 by the above-described method, it becomes smaller than the original AC signal 24 and an accurate coordinate cannot be obtained.
Countermeasures against this phenomenon are impossible with only the scalar amount that has been conventionally used. The cause is the phase shift due to the change in the phase of the parasitic signal component 21 and the resistance / capacitance of the human ground. As described above, it is impossible to provide a complete shield, which is a conventional measure, and the structure of the sensor panel 1 is complicated and the cost is increased.

As another effective measure, there is a method of canceling the parasitic signal by forcibly applying a signal having the same magnitude (same amplitude) as that of the parasitic signal component by changing the phase by 180 degrees (reverse phase). However, in the above method, it is necessary to apply an antiphase signal having the same magnitude as the parasitic signal component in the environment where the sensor panel 1 is attached to the system casing 31. The signal applied to must be adjusted. Further, in the touch panel device alone before the sensor panel 1 is attached, it is difficult to completely adjust the signal having the same amplitude because the phase and amplitude of the parasitic signal must be predicted.
In the present invention, the current amount and phase of the parasitic signal and the touch detection signal are measured and treated as each vector signal to extract the original touch signal (convert to a scalar amount).

Next, operation processing for eliminating parasitic signals will be described. The amplitude of the detection signal in a state where the finger is not close to or in contact with the sensor panel surface is measured as a DC value, and the symbol in FIG. The phase is measured. The phase angle here is 90 degrees from the drive voltage signal because of the capacitive signal, but it is measured because it is not accurate 90 degrees due to circuit processing for DC conversion. Next, the DC value of the amplitude (c) and the phase angle of the detection signal at the time of touch is measured. The detection signal at the time of touch is a combined signal including a parasitic signal. Next, if the difference between the phase angle when the finger is not touching (contactless vector) and the phase angle when touching (contact vector) is (α), the amplitude (a) of the original detection signal to be obtained is obtained from the cosine theorem.

a = √ (b2 + c2-2bc cos α)

It can be calculated with

Incidentally, since the phase measurement circuit does not require absolute value accuracy in order to detect the phase difference as described above, it can be configured with a simple circuit.
As a result of the vector processing described above, an original touch detection signal (scalar amount) to be obtained in which the parasitic signal is excluded from the non-contact vector (parasitic signal) and the contact vector (synthetic signal) is obtained.
Next, the vector processing described above is performed for each point (point A, B, C, D) on the sensor panel, and coordinate calculation processing based on the original signal is performed.
For the measurement of the non-contact vector, when the power is turned on or when the amplitude becomes minimum, the non-contact vector is used, and if the value of the non-contact vector is updated, more accurate calculation processing can be performed.

In this embodiment, the connection electrodes A, B, C, and D are arranged at the four vertices of the resistive surrounding electrode 3, but the connection electrodes may be arranged between the vertices, and the coordinate calculation is complicated. However, the resistive surrounding electrode 3 may be eliminated, and the connection electrode may be disposed directly around the surface resistor 2. In the above description, a rectangular panel has been described. However, a panel having an arbitrary shape may be used, and even one-dimensional (coordinates) does not change the effectiveness of the present invention.
As a result of the means obtained by the present invention, a capacitive touch panel device that detects a touch position from an AC signal current flowing in a surface resistor when an operator touches a sensor panel, and a non-contact vector (parasitic signal) and By correcting the original detection signal using the cosine theorem from the contact vector (synthetic signal), the sensor panel can be used regardless of the grounding condition of the operator and the sensor panel installation environment. There was no need for adjustment even before installation, after it was installed, or even when the built-in electrical environment changed, and the touch detection position shift could be eliminated.

Explanatory drawing of the touch panel device of the present invention Vector explanatory diagram of parasitic AC signal and synthesized AC signal Illustration of sensor panel parasitic capacitance and human body grounding Explanatory drawing of a conventional capacitively coupled coordinate input device

Explanation of symbols

A, B, C, D Connection electrode point 4A, 4B, 4C, 4D Connection electrode point 1 Sensor panel 2 Surface resistor 3 Resistive surrounding electrode 4 Lead wire 5 Finger 6 Human body equivalent resistance 7 Human body ground impedance 8 Vibration voltage Generator 9 Current / Voltage Conversion Circuit 10 Analog Multiplexer 11 Phase Detection Circuit 12 Signal Processing Unit 20 Reference Phase Axis 21 Parasitic Signal Component 22 Synthesized Actual Parasitic Signal and Capacitive Ground Human Body 23 Parasitic Signal Component 21 24 AC signal component 30 Human body 31 System housing 32 Human body grounding capacity 33 Capacity 33 between housing 31 and human body 30
34 Parasitic capacitance 35 Radiated electromagnetic wave

Claims (1)

A device used for detecting a contact position of a finger or a conductive stylus on a sensor panel surface, and a surface resistor in which a resistive film material is uniformly formed is disposed on the sensor panel surface. In addition, in order to drive the surface resistor with an AC voltage, a resistive surrounding electrode provided with connection electrode points is provided on the periphery of the sensor panel surface, and the amplitude of the AC voltage is proportional to the AC current flowing through the connection electrode. A touch panel device having a circuit for measuring the AC voltage and a circuit for measuring the phase of the AC voltage, wherein the AC voltage phase and amplitude when the finger or the conductive stylus is not in contact with the surface resistor are contactless A vector signal, the AC voltage amplitude and phase when a finger or a conductive stylus contacts the surface resistor as a contact vector signal, the contactless vector signal, and the contact vector The result obtained by calculating the signal is the scalar amount of the original AC current that the finger or conductive stylus touches on the surface resistor, and the abutted position where the scalar amount flows to the connection electrode A touch panel device comprising an arithmetic processing unit that calculates coordinates as an original AC current proportional to