JP2011128857A - Touch panel device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a touch position with high accuracy even when increased a size. <P>SOLUTION: A touch panel device includes a reception part receiving a charge/discharge current signal of a reception electrode responding to a drive signal (a pulse signal) applied to a transmission electrode and outputting a level signal of each electrode intersection point, the reception part includes an IV conversion part converting the charge/discharge current signal into a voltage signal, and the IV conversion part is set with a conversion property such that amplitude phases of the voltage signal corresponding to rising and falling of one pulse wave in the drive signal are nearly brought into line and that amplitude phases of the voltage signal corresponding to falling of one pulse wave and rising of the next pulse wave are nearly brought into line. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a receiving unit that receives a charge / discharge current signal of the second electrode in response to a drive signal applied to the first electrode, and outputs a level signal for each electrode intersection, to the charge / discharge current signal of the second electrode. The present invention relates to a touch panel device including an IV conversion unit that converts a voltage signal.

  There are various types of touch panel devices, such as a capacitance method, a resistance film method, and an electromagnetic induction method. In particular, the capacitance method can increase the strength of the touch surface compared to the resistance film method. There is an advantage, and there is no need for an electronic pen with a built-in oscillator etc. like the electromagnetic induction method, and it can be touched directly with the fingertip of the user or with a stylus made of a simple conductive material, so it is highly convenient have.

  In this capacitance method, the capacitance of a capacitor formed at an intersection (hereinafter referred to as an electrode intersection) between a first electrode and a second electrode arranged in a grid pattern is a conductive object (for example, a human body). A so-called projected capacitive method that utilizes the principle of changing by approaching or contacting is excellent in that the touch position can be detected with high accuracy.

  This projected capacitance method includes a so-called mutual capacitance method that detects the presence or absence of touch based on the amount of change in charge / discharge current accompanying the change in capacitance at each electrode intersection, and the capacitance of each electrode. There is a so-called self-capacitance method that detects the presence or absence of a touch based on the amount of change. In particular, the mutual capacitance method enables so-called multi-touch (multi-point detection) that simultaneously detects a plurality of touch positions (Patent Literature). 1).

  Touch panel devices are widely used in the field of personal computers and personal digital assistants, but can be used in presentations and lectures for a large number of people by combining this touch panel device with a large screen display device. A technique that can be used as a so-called interactive whiteboard is known (see Patent Document 2).

JP 2002-342033 A JP 2009-86855 A

  However, when the touch panel device is used as an interactive whiteboard, the use of a projected capacitance method, particularly a mutual capacitance method capable of multi-touch, can improve convenience. The overall capacitance between the first electrode and the second electrode is increased. For example, in the 77 inch class, the capacitance exceeds 100 pF. On the other hand, the change in the capacitance according to the touch operation by the user's fingertip or stylus is only a few hundred fF at most, and is slight. For this reason, there existed a subject that it became impossible to ensure sufficient detection accuracy with the enlargement of a touch panel apparatus.

  The touch panel device is usually provided with a band-pass filter that removes a signal having a frequency component other than the frequency of the drive signal applied to the first electrode. When external noise having a close frequency is mixed, it cannot be removed by the band-pass filter, and erroneous detection of the touch position occurs. In particular, when the touch panel device is used as an interactive whiteboard, since the electrodes become longer as the touch panel device becomes larger, it is easy to be affected by the external noise, so that an effective countermeasure against external noise is desired.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to be able to detect the touch position with high accuracy even when the size is increased. It is to provide a touch panel device. Another object of the present invention is to make it possible to avoid a decrease in touch position detection accuracy due to external noise.

  The touch panel device according to the present invention includes a panel body in which a plurality of first electrodes that run in parallel to each other and a plurality of second electrodes that run in parallel to each other are arranged in a grid pattern, and transmission that applies a drive signal to the first electrodes. A reception unit that receives a charge / discharge current signal of the second electrode in response to a drive signal applied to the first electrode, and outputs a level signal for each electrode intersection, and a level output from the reception unit A control unit that detects a touch position based on a signal and controls operations of the transmission unit and the reception unit, and the reception unit includes an IV conversion unit that converts the charge / discharge current signal into a voltage signal; The IV converter substantially matches the amplitude phase of the voltage signal corresponding to the rising and falling of one wave in the drive signal, and corresponds to the falling of one wave and the rising of the next wave, respectively. The amplitude and phase of the pressure signal so as to substantially coincide, a configuration in which conversion characteristics set.

  According to the present invention, the waveform of the voltage signal corresponding to the rising and falling of one wave is superimposed, and the waveform of the voltage signal corresponding to the falling of one wave and the rising of the next wave, respectively. By superimposing, a substantially amplified waveform can be obtained. For this reason, even if the overall capacitance between the first electrode and the second electrode increases with an increase in the size of the touch panel device, the touch position can be detected with high accuracy.

Overall configuration diagram showing a touch panel device according to the present invention Schematic configuration diagram of the receiving electrode and receiving unit shown in FIG. Schematic configuration diagram of the received signal processing unit shown in FIG. 1 is a waveform diagram showing a drive signal applied to the transmission electrode shown in FIG. 1 and a voltage signal output from the IV converter shown in FIG. Circuit diagram showing in detail the configuration of the IV converter shown in FIG.

  In order to solve the above problems, a first invention is a panel body in which a plurality of first electrodes that run parallel to each other and a plurality of second electrodes that run parallel to each other are arranged in a grid pattern, and the first electrode A transmitter for applying a drive signal to the receiver, a receiver for receiving a charge / discharge current signal of the second electrode in response to the drive signal applied to the first electrode, and outputting a level signal for each electrode intersection; A control unit configured to detect a touch position based on a level signal output from the reception unit and to control operations of the transmission unit and the reception unit, and the reception unit converts the charge / discharge current signal into a voltage signal. An IV conversion unit for converting, the IV conversion unit substantially matches the amplitude phase of the voltage signal corresponding to the rising and falling of one wave in the drive signal, and the falling and next of one wave Rise of the wave The amplitude and phase of the corresponding voltage signal so as to substantially coincide, a configuration in which conversion characteristics set.

  According to this, the waveform of the voltage signal corresponding to the rise and fall of one wave in the drive signal is superimposed, and the waveform of the voltage signal corresponding to the fall of one wave and the rise of the next wave, respectively. Is superimposed, a substantially amplified waveform can be obtained. For this reason, even if the overall capacitance between the first electrode and the second electrode increases with an increase in the size of the touch panel device, the touch position can be detected with high accuracy.

  According to a second aspect of the present invention for solving the above problem, in the first aspect of the present invention, the transmitter is configured to be able to switch the frequency of the drive signal between a plurality of frequencies, and the IV converter is The conversion characteristic is configured to be switchable between a plurality of conversion characteristics respectively corresponding to a plurality of frequencies of the drive signal, and the control unit is configured to switch the frequency of the drive signal according to the switching of the frequency of the drive signal. It is configured to control to switch the conversion characteristics.

  According to this, when the frequency of the external noise substantially coincides with any one frequency of the drive signal, the frequency of the voltage signal that is the same as the frequency of the drive signal of the first electrode by switching to another frequency, It can be different from the frequency of the external noise. For this reason, it is possible to reliably remove external noise with a bandpass filter that cuts a frequency component different from the frequency of the drive signal of the first electrode, and the detection accuracy of the touch position is reduced due to the influence of the external noise. Can be avoided.

  According to a third aspect of the present invention for solving the above-described problems, in the second aspect, the control unit is configured to output the drive signal for each frame period in which reception of charge / discharge current is completed for all electrode intersections. A configuration in which the frequency and the conversion characteristics of the IV conversion unit are controlled to be switched, the presence / absence of the influence of the external noise is determined on a frame basis, and the touch position information of the frame is discarded when the influence of the external noise is present And

  According to this, since the frequency of the drive signal applied to the first electrode is switched periodically, the influence of the external noise can be eliminated even when external noise of various frequencies is mixed. When there are only two frequencies that can be switched, the switching is alternately performed between the first frequency and the second frequency every frame period.

  In this case, the presence or absence of the influence of external noise can be determined based on the degree of variation in the touch position acquired in units of frames, and when the degree of variation is large, the touch position information for that frame may be discarded.

  It is also possible to prepare three or more frequencies that can be switched, but even when there are two frequencies that can be switched, it is very unlikely that both frequencies match the frequency of the external noise. However, if the frame period is set sufficiently small, the reliability as a touch panel device can be sufficiently ensured. .

  The transmitter selects one first electrode at a time and applies a drive signal. While applying the drive signal to the first electrode, the receiver selects one second electrode at a time. Then, by receiving the charge / discharge current of the second electrode, the charge / discharge current of all the electrode intersections is received, and the period in which the reception of the charge / discharge current is completed for all the electrode intersections is one frame period.

  4th invention made | formed in order to solve the said subject WHEREIN: The said 1st-3rd invention is equipped with the switching means which intermittently interrupts the input to the said receiving part of the charging / discharging current signal of the said 2nd electrode. The second electrode and the switching means are grouped by a predetermined number, and the corresponding switching means belonging to each group are controlled to be turned on / off in parallel.

  According to this, since the operation of the switching means is performed in parallel between a plurality of groups, it is possible to shorten the time required to receive the charge / discharge current signals of all the second electrodes. In addition, since the processing of the charge / discharge current signal in the receiving unit can be performed for each group, an increase in the size of the hardware configuration can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram showing a touch panel device according to the present invention. The touch panel device 1 includes a panel body 4 in which a plurality of transmission electrodes (first electrodes) 2 that are parallel to each other and a plurality of reception electrodes (second electrodes) 3 that are parallel to each other are arranged in a lattice pattern, and the transmission electrodes 2 receives a charge / discharge current signal of the receiving electrode 3 in response to the driving signal applied to the transmitting electrode 2 and the transmitting electrode 5 that applies a driving signal (pulse signal) to the transmitting electrode 2 and the receiving electrode 3 A receiving unit 6 that outputs a level signal at each electrode intersection where the crossing points and a control that detects the touch position based on the level signal output from the receiving unit 6 and controls the operation of the transmitting unit 5 and the receiving unit 6 Part 7.

  The touch panel device 1 is used as a so-called interactive whiteboard that can be used for presentations and lectures by being combined with a large-screen display device. In particular, the touch panel device 1 is used in combination with a projector device. The touch surface of 1 serves as a projector screen.

  Touch position information output from the touch panel device 1 is input to an external device 8 such as a personal computer, and is projected and displayed on the touch surface of the touch panel device 1 by the projector device 9 based on display screen data output from the external device 8. On the display screen, an image corresponding to the touch operation performed by the user directly with the fingertip or using the stylus on the touch surface of the touch panel device 1 is displayed, and the image is directly drawn with the marker on the touch surface of the touch panel device. It is possible to display a required image with the same feeling as described above, and to operate buttons and the like displayed on the display screen. Furthermore, an eraser that erases an image drawn by a touch operation can be used.

  In the panel body 4, a plurality (for example, 120) of transmission electrodes 2 are disposed on the surface of the sheet material 11, and a plurality (for example, 186) of the reception electrodes 3 are disposed on the back surface of the sheet material 11. The transmission electrode 2 and the reception electrode 3 are arranged at the same arrangement pitch (for example, 10 mm).

  In the panel body 4, a back board for supporting the electrode sheet is provided on the back side of the electrode sheet composed of the transmission electrode 2, the reception electrode 3, and the sheet material 11, and the electrode sheet is provided on the surface side of the electrode sheet. A protective surface board is provided. The transmission electrode 2 and the reception electrode 3 may be insulated from each other. For example, both may be configured to be disposed on the surface side of the sheet material 11 via an insulating layer.

  In the panel body 4, a capacitor is formed at an electrode intersection where the transmission electrode 2 and the reception electrode 3 intersect. When the user performs a touch operation directly with a fingertip or using a stylus, the electrostatic capacitance at the electrode intersection is changed accordingly. By substantially reducing the capacity, it is possible to detect the presence or absence of a touch operation.

  In particular, here, the mutual capacitance method is adopted, and when a drive signal is applied to the transmission electrode 2, a charge / discharge current flows to the reception electrode 3 in response to this, and at this time, according to the touch operation of the user, When the capacitance changes, the charging / discharging current of the receiving electrode 3 changes, and the amount of change of the charging / discharging current is converted into a level signal (digital signal) for each electrode intersection by the receiving unit 6 and output to the control unit 7. In the control unit 7, the touch position is calculated based on the level signal for each electrode intersection. This mutual capacitance method enables so-called multi-touch (multi-point detection) in which a plurality of touch positions are detected simultaneously.

  The transmission unit 5 selects one transmission electrode 2 at a time and applies a drive signal in synchronization with the timing signal output from the control unit 7. The receiving unit 6 receives the charging / discharging current of the receiving electrode 3 by selecting the receiving electrodes 3 one by one while applying the drive signal to one transmitting electrode 2. Thereby, the charging / discharging current for every electrode intersection can be taken out. For example, if the frame period at which the reception of the charge / discharge current is completed is 10 ms at all electrode intersections (186 × 120 (= 22320)), the drive signal output period per 120 transmission electrodes 2 is about 83 μs. It becomes.

  The control unit 7 obtains the touch position (center coordinate of the touch area) from the level signal for each electrode intersection output from the receiving unit 6 by a predetermined calculation process. In the calculation of the touch position, the level at each of a plurality of (for example, 4 × 4) electrode intersections adjacent to each other in the X-axis direction (extending direction of the transmitting electrode 2) and the Y-axis direction (extending direction of the receiving electrode 3). The touch position is obtained from the signal using a required interpolation method (for example, the center of gravity method). Thereby, the touch position can be detected with a resolution (for example, 1 mm or less) higher than the arrangement pitch (10 mm) of the transmission electrode 2 and the reception electrode 3.

  FIG. 2 is a schematic configuration diagram of the receiving electrode 3 and the receiving unit 6 shown in FIG. Each receiving electrode 3 is connected to a switching element (switching means) SW for intermittently inputting the charge / discharge current signal of the receiving electrode 3 to the receiving unit 6. The reception unit 6 includes a reception signal processing unit 21 that performs required signal processing on a charge / discharge current signal input from the reception electrode 3 via the switching element SW. Each switching element SW is individually on / off controlled in accordance with a drive signal from the control unit 7.

  The receiving electrodes 3 and the switching elements SW are grouped by a predetermined number (for example, 24), and corresponding switching elements SW belonging to each group are ON / OFF controlled in parallel. A reception signal processing unit 21 is provided for each group. In each group, the switching elements SW are controlled so as to be sequentially turned on one by one, the remaining switching elements SW are controlled to be turned off, and one receiving electrode 3 selected by turning on the switching elements SW. The charge / discharge current signal is input to the reception signal processing unit 21.

  As described above, since the switching operation of the switching element SW is performed in parallel among a plurality of groups, the time required to receive the charge / discharge current signals of all the reception electrodes 3 can be shortened. Moreover, since the process of the charging / discharging current signal in the receiving unit 6 can be divided and performed for each group, an increase in the size of the hardware configuration can be suppressed.

  In the grouping of the reception electrodes 3, the number of reception electrodes 3 belonging to each group does not need to be the same. For example, when the number of reception electrodes 3 is 186, seven groups A to G are set to 24, and the last What is necessary is just to make 18 groups H.

  FIG. 3 is a schematic configuration diagram of the received signal processing unit 21 shown in FIG. The reception signal processing unit 21 includes an IV conversion unit 31, a band pass filter 32, an absolute value detection unit 33, an integration unit 34, a sample hold unit 35, and an AD conversion unit 36.

  In the IV conversion unit 31, the charge / discharge current signal (analog signal) of the reception electrode 3 input via the switching element SW is converted into a voltage signal. In the band pass filter 32, a process for removing a signal having a frequency component other than the frequency of the drive signal applied to the transmission electrode 2 is performed on the output signal of the IV conversion unit 31. The absolute value detection unit (rectification unit) 33 performs full-wave rectification on the output signal of the bandpass filter 32. The integration unit 34 performs processing for integrating the output signal of the absolute value detection unit 33 in the time axis direction. In the sample hold unit 35, a process of sampling the output signal of the integration unit 34 at a predetermined timing is performed. The AD converter 36 AD-converts the output signal from the sample hold unit 35 and outputs a level signal (digital signal).

  FIG. 4 is a waveform diagram showing a drive signal applied to the transmission electrode 2 shown in FIG. 1 and a voltage signal output from the IV converter 31 shown in FIG. 4A shows a case according to the prior art, and FIG. 4B shows a case according to the present invention. The voltage signal shown in the figure is a waveform after the band-pass filter 32 cuts a signal having a frequency component other than the frequency of the drive signal applied to the transmission electrode 2.

  Normally, when a drive signal (pulse signal) is applied to the transmission electrode 2, as shown in FIG. 4A, waveforms A1 and A3 due to charging of the capacitor at the electrode intersection are observed at the rise of the pulse wave, and then As the transient response, waveforms A2 and A4 due to the discharge from the capacitor at the electrode intersection are observed, and thereafter a small waveform that gradually attenuates is observed. Further, at the fall of the pulse wave, a waveform B1 due to discharge from the capacitor at the electrode intersection is observed, and as a transient response, a waveform B2 due to charging of the capacitor at the electrode intersection is observed, and thereafter a small waveform that gradually attenuates. Is observed.

  Here, when there is a touch operation, the capacitance of the capacitor at the electrode intersection is reduced, so the amplitude of the voltage signal output from the IV conversion unit 31 is reduced. For this reason, the presence or absence of a touch operation can be determined based on the change in the peak value, but here the determination is made using the value obtained by integration after full-wave rectification, that is, the integrated value of the waveform area. By increasing the number of pulses at each electrode intersection, even a small change in amplitude can be determined with high accuracy.

  However, since the touch panel device 1 is used as an interactive whiteboard, the overall capacitance between the transmission electrode 2 and the reception electrode 3 increases as the size of the touch panel device 1 increases. Since the capacitance change due to is extremely small, it is easily affected by external noise, and it is necessary to increase the number of pulses per electrode intersection in order to ensure high accuracy in detecting the touch position.

  Therefore, here, the IV conversion unit 31 is output from the IV conversion unit 31 corresponding to the rising and falling of one pulse wave in the drive signal (pulse signal) applied from the transmission unit 5 to the transmission electrode 2. The conversion characteristics are set so that the amplitude phases of the voltage signals to be substantially matched and the amplitude phases of the voltage signals respectively corresponding to the fall of one pulse wave and the rise of the next pulse wave are substantially matched.

  That is, a waveform B1 due to discharge at the fall of the same pulse wave is superimposed on a waveform A2 due to discharge (transient response) at the rise of one pulse wave, and charging (transient at the fall of one pulse wave) The waveform A3 due to charging at the rise of the next pulse wave is superimposed on the waveform B2 due to (response). Such conversion characteristics can be obtained by adjusting the time constant of the conversion circuit of the IV conversion unit 31.

  In this way, a substantially amplified waveform can be obtained as shown in FIG. This is due to the cumulative addition of pulses after the main pulse in the impulse response. As a result, even if the overall capacitance between the transmission electrode 2 and the reception electrode 3 increases with an increase in the size of the touch panel device 1, the touch position can be increased without increasing the number of pulses per electrode intersection. Detection can be performed with high accuracy.

  By the way, in the reception signal processing unit 21, a band pass filter 32 is provided at the subsequent stage of the IV conversion unit 31, and even if external noise is mixed, the frequency thereof is larger than the frequency of the drive signal applied to the transmission electrode 2. If they are different, they can be removed by the band pass filter 32. However, when the amplitude phases are substantially matched as described above, the voltage signal output from the IV conversion unit 31 has the same frequency as the drive signal applied to the transmission electrode 2, and at this time, the frequency of the drive signal is substantially the same. If external noise having a matching frequency is mixed, the band-pass filter 32 cannot remove it. This makes it difficult to accurately detect the touch position. Specifically, the detected touch position (coordinate values) is not consistent and continuous, and the touch position changes randomly. Detection occurs.

  Therefore, here, the transmission unit 5 is configured to be able to switch the frequency of the drive signal between a plurality of frequencies, and the IV conversion unit 31 has a plurality of conversion characteristics respectively corresponding to the plurality of frequencies of the drive signal. The control unit 7 performs control so as to switch the conversion characteristics of the IV conversion unit 31 in accordance with the switching of the frequency of the drive signal.

  As a result, when the frequency of the external noise substantially matches one of the frequencies of the drive signal, the frequency of the voltage signal that is the same as the frequency of the drive signal of the transmission electrode 2 is changed to the external frequency by switching to another frequency. It can be different from the noise frequency. For this reason, it is possible to reliably remove external noise with a band-pass filter that cuts a frequency component different from the frequency of the drive signal of the transmission electrode 2, and the detection accuracy of the touch position decreases due to the influence of the external noise. Can be avoided.

  In particular, here, the transmission unit 5 is configured to be able to switch the drive signal applied to the transmission electrode 2 between a first frequency (for example, 5 MHz) and a second frequency (for example, 3 MHz), and the IV conversion unit 31 As will be described below, the conversion characteristics can be switched between a first conversion characteristic corresponding to the first frequency of the drive signal and a second conversion characteristic corresponding to the second frequency.

  FIG. 5 is a circuit diagram showing in detail the configuration of the IV converter 31 shown in FIG. The IV conversion unit 31 includes a first conversion circuit 51a and a second conversion circuit 51b having two different conversion characteristics, and an input switch 52 and an output switch 53 that select one of the conversion circuits 51a and 51b. It is configured.

  The first conversion circuit 51a includes an operational amplifier OPAa, a resistance component Ra, a first capacitance component Ca1, and a second capacitance component Ca2. The resistance component Ra and the first capacitance component Ca1 are the operational amplifier. The OPAa is connected in parallel between one input side and the output side. The second capacitive component Ca2 is provided on the other input side of the operational amplifier OPAa and is GND-connected. The second conversion circuit 51b includes an operational amplifier OPAb, a resistance component Rb1, a first capacitance component Cb1, and a second capacitance component Cb2, and has the same circuit configuration as the first conversion circuit 51a. is doing.

  In the first conversion circuit 51a and the second conversion circuit 51b, the resistance components Ra and Rb corresponding to each other are set to different resistance values, and the first capacitance components Ca1 and Cb1 are set to different capacitance values. The second capacitance components Ca2 and Cb2 are set to different capacitance values. As a result, the first conversion circuit 51a and the second conversion circuit 51b have different time constants.

  In each of the conversion circuits 51a and 51b, it is not necessary to set the resistance value and the capacitance value of each component to be different from each other, and the resistance of each component is obtained so that a required time constant can be obtained. What is necessary is just to set a value and a capacity | capacitance value suitably. In addition, a configuration in which the resistance value or the capacitance value of each component is set to 0, for example, the first conversion circuit 51a may have a configuration in which the capacitance of the second capacitance component Ca2 is set to 0 is possible.

  Here, the first conversion circuit 51a is set to the first conversion characteristic corresponding to the first frequency (for example, 5 MHz) of the drive signal, that is, at the first frequency, as shown in FIG. The time constant is adjusted so that amplification by matching the amplitude phase is realized. The second conversion circuit 51b is set to the second conversion characteristic corresponding to the second frequency (for example, 3 MHz) of the drive signal. That is, the second conversion circuit 51b has the amplitude and phase shown in FIG. The time constant is adjusted so that amplification by coincidence is realized.

  In the control unit 7, the first conversion circuit 51a and the second conversion circuit 51b are switched according to the switching of the frequency of the drive signal applied to the transmission electrode 2, that is, if the drive signal is the first frequency. If the first conversion circuit 51a is selected and the drive signal is the second frequency, the second conversion circuit 51b is selected.

  In particular, here, the control unit 7 converts the frequency of the drive signal applied from the transmission unit 5 to the transmission electrode 2 and the conversion of the IV conversion unit 31 every frame period in which the reception of the charge / discharge current is completed at all electrode intersections. Control to switch characteristics. In this embodiment, since there are only two frequencies of the drive signal, the first frequency and the second frequency, the frequency of the drive signal is between the first frequency and the second frequency every frame period. Are alternately switched, and the first conversion circuit and the second conversion circuit of the IV conversion unit are alternately switched.

  As described above, since the frequency of the drive signal applied to the transmission electrode 2 is periodically switched, even when external noise of various frequencies is mixed, the influence of the external noise can be eliminated. Further, even when there are two frequencies that can be switched, it is very unlikely that both of the frequencies coincide with the frequency of the external noise, and it is possible to sufficiently ensure reliability.

  Further, the control unit 7 determines the effectiveness of the touch position based on the variation degree of the touch position acquired in units of frames, and the variation degree of the touch position is large. Specifically, the variation degree has a predetermined threshold value. If it exceeds, it is determined that there is an influence of external noise, and the touch position information is discarded. Here, since the discard of the touch position information is performed in units of frames, the sampling rate is reduced to ½ as a result. However, if the frame period is set sufficiently small, sufficient reliability can be ensured. It becomes.

  By the way, when no external noise is mixed, the same touch position is detected regardless of the difference in the frequency of the drive signal applied to the transmission electrode 2, so that even if the frequency is switched periodically, there is no problem. Absent.

  In the above example, the frequency of the drive signal applied to the transmission electrode 2 is periodically switched regardless of the presence or absence of the influence of external noise, but when it is determined that there is an influence of external noise, A configuration for performing a frequency switching operation is also possible. For example, the initial operation is performed at the first frequency (for example, 5 MHz), and when the degree of variation in the detected touch position is determined to be large by comparison with a predetermined threshold value, the second frequency is set. You may make it switch to (for example, 3 MHz).

  Further, the influence of the external noise is recognized even in a situation where there is no user touch operation. When external noise that cannot be removed by the bandpass filter 32 is mixed, the level signal output from the receiving unit 6 becomes unstable. Therefore, the presence or absence of the influence of external noise may be determined based on the stability of the level signal, and the switching operation of the frequency of the drive signal and the conversion characteristic of the IV conversion unit may be performed according to the determination result. In this case, since it is not related to the touch operation, it is preferable to execute the calibration at the time of starting the apparatus.

  The touch panel device according to the present invention has an effect that the touch position can be detected with high accuracy even when the size is increased, and the charge / discharge current signal of the second electrode in response to the drive signal applied to the first electrode. It is useful as a touch panel device or the like provided with an IV conversion unit that converts a charge / discharge current signal of the second electrode into a voltage signal in a receiving unit that receives the signal and outputs a level signal for each electrode intersection.

1 Touch Panel Device 2 Transmitting Electrode (First Electrode)
3 Receiver electrode (second electrode)
4 Panel body 5 Transmitter 6 Receiver 7 Controller 21 Received signal processor 31 IV converter 32 Band pass filter 51a First converter 51b Second converter 52 Input switch 53 Output switch SW Switching element

Claims (4)

A panel body in which a plurality of first electrodes that run parallel to each other and a plurality of second electrodes that run parallel to each other are arranged in a grid pattern;
A transmitter for applying a drive signal to the first electrode;
A receiving unit for receiving a charge / discharge current signal of the second electrode in response to the drive signal applied to the first electrode, and outputting a level signal for each electrode intersection;
A control unit that detects the touch position based on a level signal output from the reception unit and controls the operation of the transmission unit and the reception unit;
The receiver includes an IV converter that converts the charge / discharge current signal into a voltage signal,
The IV converter substantially matches the amplitude phase of the voltage signal corresponding to the rising and falling of one wave in the drive signal, and corresponds to the falling of one wave and the rising of the next wave, respectively. A touch panel device, wherein the conversion characteristics are set so that the amplitude phases of the voltage signals are substantially matched. The transmission unit is configured to be able to switch the frequency of the drive signal between a plurality of frequencies,
The IV conversion unit is configured to be able to switch a conversion characteristic between a plurality of conversion characteristics respectively corresponding to a plurality of frequencies of the drive signal,
The touch panel device according to claim 1, wherein the control unit performs control so as to switch conversion characteristics of the IV conversion unit in accordance with switching of the frequency of the drive signal.   The control unit controls to switch the frequency of the drive signal and the conversion characteristics of the IV conversion unit every frame period in which the reception of the charge / discharge current is completed for all the electrode intersections, and the external noise in units of frames. The touch panel device according to claim 2, wherein the touch position information of the frame is discarded when there is an influence of external noise.   Switching means for individually switching input / output of the charge / discharge current signal of the second electrode to the receiving unit, wherein the second electrode and the switching means are grouped by a predetermined number, and the switching belonging to each group The touch panel device according to any one of claims 1 to 3, wherein corresponding ones of the means are on / off controlled in parallel.

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