JP2011128858A - Touch panel device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid deterioration of detection accuracy of a touch position by influence by exogenous noise. <P>SOLUTION: A touch panel device includes a reception part 6 receiving a charge/discharge current signal of a reception electrode 3 responding to a drive signal applied to a transmission electrode and outputting a level signal of each electrode intersection point. The reception part has: an IV conversion part 31 converting the charge/discharge current signal of the reception electrode into a voltage signal; an absolute value detection part 33 rectifying an output signal thereof; an integration part 34 integrating the output signal to a temporal axis direction; a sample hold part 35 sampling the output signal in prescribed timing; and an AD conversion part 36 performing A/D-conversion of the output signal and outputting the level signal. A control part detects a variation degree of the level signal output from the reception part, and sets the sample timing of the sample hold part such that the variation degree becomes small. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention samples an integration signal at a predetermined timing in a receiving unit that receives a charge / discharge current signal of a second electrode in response to a drive signal applied to the first electrode and outputs a level signal for each electrode intersection. The present invention relates to a touch panel device including a sample hold unit.

  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, 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 avoid a decrease in touch position detection accuracy due to the influence of external noise. It is providing the touch panel apparatus comprised in this.

  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 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; and a level signal output from the receiving unit And a control unit that controls the operation of the transmission unit and the reception unit, and the reception unit is a voltage obtained by performing IV conversion on the charge / discharge current signal of the second electrode. The signal is rectified and integrated in the time axis direction, the integrated signal is sampled at a predetermined timing by the sample and hold unit, and a level signal is output, and the control unit outputs from the receiving unit Be done By detecting the variation degree of the bell signal, a configuration for setting at least one operating condition of the transmission unit and the reception unit such sampling is performed at the timing when the variation degree is reduced.

  According to the present invention, it is possible to suppress variations in the level signal output from the receiving unit, and thus it is possible to obtain a stable output signal that is not affected by external noise. A decrease in accuracy can be avoided.

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. The figure explaining the point of the setting of the sample timing in the sample hold part shown in FIG. The flowchart which shows the procedure of the sample timing setting process performed in the control part shown in FIG. Schematic block diagram showing another example of the touch panel device according to the present invention

  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 that detects a touch position based on a level signal output from the reception unit and controls operations of the transmission unit and the reception unit, and the reception unit receives a charge / discharge current signal of the second electrode. The voltage signal obtained by IV conversion is rectified and integrated in the time axis direction, and the integrated signal is sampled at a predetermined timing by a sample and hold unit to output a level signal. Part By detecting the variation degree of the level signal output from the section, a configuration for setting at least one operating condition of the transmission unit and the reception unit such sampling is performed at the timing when the variation degree is reduced.

  According to this, since it is possible to suppress variations in the level signal output from the receiving unit, it is possible to obtain a stable output signal that is not affected by the external noise. Decreasing can be avoided.

  According to a second aspect of the present invention for solving the above problem, in the first aspect of the present invention, the control unit sets a sample timing of the sample hold unit so that a variation degree of the level signal is small. To do.

  According to this, since it is only necessary to change the set value of the timer in order to change the sample timing, an increase in manufacturing cost can be suppressed.

  According to a third aspect of the present invention for solving the above-described problem, in the first and second aspects, the control unit may change the level signal from the transmission unit to the first electrode so that a variation degree of the level signal is reduced. The frequency of the applied drive signal is set.

  According to this, since a means for changing the frequency of the drive signal is required in the transmission unit, the manufacturing cost increases, but it is not necessary to change the sample timing, so that it is possible to avoid a decrease in the frame rate. it can.

  In a fourth invention made to solve the above-described problem, in the first to third inventions, the control unit executes the operation condition setting process at the time of calibration performed at the time of starting the apparatus. The configuration.

  According to this, the operation condition setting process can be performed without hindering the user's operation.

  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 diagram for explaining the procedure for setting the sample timing in the sample hold unit 35 shown in FIG. This is an example of simulation, and the drive signal applied to the transmission electrode 2 is a sine wave here, but is actually a pulse wave. In addition, it is assumed that the phase of the external noise changes randomly.

  Since the output signal of the absolute value detection unit 33 is integrated in the time axis direction, the output signal of the integration unit 34 gradually increases with the passage of time and changes randomly due to the influence of external noise. For this reason, for example, when sampling is performed at the sample timing T0, the output signal of the sample hold unit 35 varies, and a stable output signal cannot be obtained.

  However, in the output signal of the integration unit 34, a node having a small variation degree appears at a timing that is a common multiple of the period of the drive signal and the period of the external noise. If sampling is performed at the timing (time T1 and T2) at which this section appears or in the vicinity thereof, variations in the output signal of the sample hold unit 35 can be suppressed, and a stable output signal that is not affected by external noise can be obtained. .

  Therefore, here, the control unit 7 detects the degree of variation of the level signal output from the receiving unit 6, and at least one of the transmission unit 5 and the receiving unit 6 is performed so that sampling is performed at a timing when the variation degree becomes small. Set the operating conditions. In particular, here, the sample timing of the sample hold unit 35 is set so that the variation degree of the level signal becomes small.

  FIG. 5 is a flowchart showing the procedure of the sample timing setting process performed by the controller 7 shown in FIG. This sample timing setting process is executed at the time of calibration performed when the apparatus is started up.

  First, when the power is turned on, the sample timing is set to the initial value T0 (ST101), sampling is performed by the sample hold unit 35 at the sample timing T0, and the level signal for each electrode intersection is received from the receiving unit 6. The signals are sequentially output and the level signal for one screen is acquired (ST102). This is repeated a predetermined number of times (here, 5 times) (ST103). When the predetermined number of times is reached, the level signal variation degree is calculated (ST104). Then, it is determined whether or not the variation degree of the level signal is equal to or less than a predetermined reference value (here, 4) (ST105). If the variation degree is equal to or less than the predetermined reference value, it is determined that the level signal is not affected by external noise. Judgment is made, and the sample timing remains at the initial value T0, and the process is terminated.

  On the other hand, if the degree of variation exceeds a predetermined value (No in ST105), it is determined that the signal is affected by external noise, the sample timing is changed, and the above-mentioned is performed until the degree of variation becomes equal to or less than the predetermined value. Repeat the process. At this time, the sample timing is shifted little by little, and a sample timing with a small variation degree is searched. For example, as shown in FIG. 4, first, the sample timing is first shifted in time (A direction) from the initial value T0. In addition, it is preferable to set new sample timings both backward (in the B direction) in time, calculate the degree of variation of each, and finely set the new sample timing in the direction of small variation degree. In the example of FIG. 4, the variation degree becomes smaller when the sample timing is changed in the B direction, and a new sample timing is set in the B direction finely to find a sample timing with a small variation degree.

  As a result, variations in the level signal output from the receiving unit 6 can be suppressed, and a stable output signal that is not affected by external noise can be obtained. Decreasing can be avoided. Further, in order to suppress the influence of external noise only by the bandpass filter 32, it is necessary to adopt a bandpass filter 32 having a steep characteristic. Here, a high-cost band having such a steep characteristic is used. Since no pass filter is required, the cost can be reduced.

  In this configuration, when the frequency of the external noise coincides with the frequency of the drive signal, no node appears in the output signal of the integration unit 34, so that variation in the level signal cannot be suppressed. Is unlikely to match the frequency of the drive signal, and a practically sufficient effect can be obtained.

  FIG. 6 is a schematic configuration diagram showing another example of the touch panel device according to the present invention. Here, the control unit 7 sets the frequency of the drive signal applied from the transmission unit 5 to the transmission electrode 2 so that the variation degree of the level signal value output from the reception unit 6 becomes small. The transmission unit 5 includes an oscillator 61 and a frequency conversion unit (PLL) 62, and can change the frequency of the drive signal applied to the transmission electrode 2.

  The control unit 7 may perform processing in the same procedure as in the example shown in FIG. 5, but here, processing for setting the frequency of the drive signal is performed instead of processing for setting the sample timing (ST101). Then, the frequency of the drive signal is shifted little by little to find a frequency with a small variation degree. Other configurations are the same as those in the above example, and the same reference numerals are given and detailed description thereof is omitted.

  When the frequency of the drive signal applied to the transmission electrode 2 is changed in this way, the timing of nodes appearing in the output signal of the integration unit 34 can be shifted back and forth as shown in FIG. What is necessary is just to set the frequency of the drive signal applied to the transmission electrode 2 so that the node appearing in the signal coincides with or is close to a predetermined sample timing.

  If the period of the drive signal and the period of the external noise are close to each other, the timing at which a node appears in the output signal of the integrating unit 34, that is, the common multiple of the period of the drive signal and the period of the external noise is delayed. In the configuration in which the sample timing is changed, the time required for acquiring the level signal for each electrode intersection becomes longer, resulting in a decrease in the frame rate. However, in the configuration in which the frequency of the drive signal is changed, the sample timing is changed. Since this is not necessary, there is an advantage that the frame rate does not decrease.

  Note that, as in the example shown in FIG. 3, the operating condition of the receiving unit 6, that is, the configuration for setting the sample timing of the sample hold unit 35, and the operating condition of the transmitting unit 5 as in the example shown in FIG. The configuration for setting the frequency of the drive signal applied to the electrode 2 may be selected in consideration of the manufacturing cost, but a configuration in which both are combined is also possible.

  The touch panel device according to the present invention has an effect of avoiding deterioration in detection accuracy of the touch position due to the influence of external noise, and the charge / discharge current signal of the reception electrode in response to the drive signal applied to the transmission electrode Is useful as a touch panel device or the like provided with a sample-and-hold unit that samples an integrated signal at a predetermined timing in a receiving unit that receives a signal and outputs a level signal for each electrode intersection.

DESCRIPTION OF SYMBOLS 1 Touch panel apparatus 2 Transmission electrode 3 Reception electrode 4 Panel main body 5 Transmission part 6 Reception part 7 Control part 21 Reception signal processing part 31 IV conversion part 32 Band pass filter 33 Absolute value detection part 34 Integration part 35 Sample hold part 36 AD conversion part 61 Oscillator 62 Frequency converter 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 that receives a charge / discharge current signal of the second electrode in response to the drive signal applied to the first electrode and outputs 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 receiving unit rectifies a voltage signal obtained by performing IV conversion on the charge / discharge current signal of the second electrode and integrates the voltage signal in a time axis direction, and the integration signal is obtained at a predetermined timing in the sample hold unit. Sampling and outputting a level signal,
The control unit detects a variation degree of the level signal output from the reception unit, and at least one of the operating conditions of the transmission unit and the reception unit is performed so that sampling is performed at a timing when the variation degree becomes small A touch panel device characterized by setting.   The touch panel device according to claim 1, wherein the control unit sets a sample timing of the sample hold unit so that a variation degree of the level signal becomes small.   The said control part sets the frequency of the drive signal applied to the said 1st electrode from the said transmission part so that the dispersion | variation degree of the said level signal may become small, The Claim 1 or Claim 2 characterized by the above-mentioned. Touch panel device.   The touch panel device according to any one of claims 1 to 3, wherein the control unit executes the setting process of the operation condition at the time of calibration performed when the device is activated.

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