JP2012167943A - Acoustic wave type position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect whether or not a plurality of objects are actually brought into contact on a surface of a contact object when the objects are dragged on the surface in an acoustic wave type position detector.SOLUTION: An acoustic wave type position detector 100 is configured to propagate acoustic waves along a surface 2a which is a contact object of an object, detect the propagated acoustic waves to obtain electric detection signals S3 and S4, and detect a contact position on the surface 2a of the object on the basis of attenuation of the detection signals S3 and S4 when the acoustic waves are interrupted by the object. The acoustic wave type position detector 100 includes detection means 21 and 22 for detecting the presence/absence of the contact with the surface 2a of the object on the basis of the amplitude of signals indicating the state of the attenuation outputted when the plurality of objects are dragged on the surface 2a and at least one of the length of the rising part of the signals, an inter-peak distance and a waveform.

Description

  The present invention relates to an acoustic wave type position detecting device constituting a touch panel or the like.

  Conventionally, for example, as disclosed in Patent Document 1, an acoustic wave type position detection device is known. This acoustic wave type position detector basically propagates an acoustic wave along a surface that is a contact target of an object such as a human finger, and detects the propagated acoustic wave to obtain an electrical detection signal. The contact position on the surface of the object is detected based on the attenuation of the detection signal when the acoustic wave is blocked by the object.

JP 2004-164289 A

  Conventional acoustic wave type position detecting devices having such a basic configuration often generate a signal indicating the attenuation state, and based on a peak portion corresponding to the attenuation in the signal, the object It is comprised so that the contact position to a surface may be detected. More specifically, when the amplitude of the peak portion is equal to or greater than a predetermined threshold, attenuation is caused, that is, it is determined that the object is in contact with the surface, and based on the time when the peak portion occurred. The contact position is detected.

  However, in such a conventional acoustic wave type position detection device, there is a problem that a signal indicating contact cannot be obtained even though an object is actually in contact with the surface to be contacted. It recognized. Such troubles are especially common when an object such as a finger is dragging (moving while maintaining contact) on the surface to be touched, and is multi-touch (multiple touching objects). Is recognized. In consideration of such circumstances, when a signal indicating contact is not obtained, it is required to accurately know whether it is due to the above-mentioned problem or whether contact has not been made. That is, if it can be accurately grasped that the above-mentioned problem has occurred even though contact is actually made, the contact position can be obtained by an appropriate method.

  The present invention has been made in view of the above circumstances, and an object thereof is to accurately detect whether or not an object is actually in contact with a surface to be contacted in an acoustic wave type position detection device.

The acoustic wave type position detecting device according to the present invention is:
As mentioned above, while propagating the acoustic wave along the surface that is the contact target of the object,
An electrical detection signal is obtained by detecting this propagated acoustic wave,
In an acoustic wave type position detecting device configured to detect a contact position on the surface of the object based on attenuation of the detection signal when the acoustic wave is blocked by the object,
Based on at least one of the amplitude of the signal indicating the attenuation state output when a plurality of objects are dragging on the surface, the length of the rising portion of the signal, the distance between peaks, and the waveform, It is characterized by comprising detecting means for detecting the presence or absence of contact of the object with the surface.

  Note that the detection unit may be configured to predict and obtain a contact position of the object with respect to the surface at a certain time based on a contact position detected before the time.

  As described above, the acoustic wave type position detection apparatus of the present invention has the amplitude of the signal indicating the attenuation state output when a plurality of objects are dragging on the surface, and the length of the rising portion of the signal. In addition, since it is configured to detect the presence or absence of contact with the surface of the object based on at least one of the distance between peaks and the waveform, the contact is determined based only on the amplitude of the signal indicating the attenuation state. Compared with a conventional apparatus that detects presence / absence, the detection accuracy of contact presence / absence when dragged by multi-touch can be made higher.

1 is a schematic front view of an acoustic wave type position detector according to an embodiment of the present invention. Partial side view (a) and partial front view (b) showing a part of the acoustic wave type position detector The graph which shows an example of the position detection signal in the said acoustic wave type position detection apparatus The graph which shows another example of the position detection signal in the said acoustic wave type position detection apparatus The graph which shows an example of the touch signal in the said acoustic wave type position detection apparatus The graph which shows another example of the touch signal in the said acoustic wave type position detection apparatus The graph which shows another example of the touch signal in the said acoustic wave type position detection apparatus The figure explaining the problem which may arise in an acoustic wave type position detector The figure explaining the contact position detection made in the said acoustic wave type position detection apparatus

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic front shape of an acoustic wave type position detecting apparatus 100 according to an embodiment of the present invention. As shown in the figure, the acoustic wave type position detection apparatus 100 according to the present embodiment basically includes a touch panel 1, a pulse generator 20, a signal processing circuit 21, and a computer 22. It is comprised so that it may do. As will be described later, the signal processing circuit 21 and the computer 22 constitute means for detecting whether or not an object touches the touch panel 1.

  The touch panel 1 has a rectangular glass substrate 2. Four reflective arrays 6a, 6b, 6c, and 6d are formed on the surface 2a of the glass substrate 2 so as to surround the touch region 12 from four sides as a whole. That is, when the horizontal direction and the vertical direction of the glass substrate 2 are defined as the X direction and the Y direction, respectively, the reflection arrays 6a and 6b extend in the X direction along the upper edge 4a and the lower edge 4b of the glass substrate 2, respectively. The reflective arrays 6c and 6d are formed to extend in the Y direction along the left edge 4c and the right edge 4d of the glass substrate 2, respectively.

  Each reflective array 6a, 6b, 6c, 6d is formed with a large number of inclined ridges, that is, inclined lines 8, in order to reflect surface acoustic waves, which are examples of acoustic waves. These inclined lines 8 are formed by printing a paste of fine powder of lead glass on the glass substrate 2 by screen printing or the like and then sintering. In the present embodiment, each inclined line 8 is formed in a direction that forms an angle of 45 ° with respect to the edges 4 a, 4 b, 4 c, and 4 d of the glass substrate 2. More specifically, the inclined lines 8 of the reflective array 6a and the inclined lines 8 of the reflective array 6b are formed so as to form an angle of 90 ° with each other. On the other hand, each inclined line 8 of the reflective array 6c and each inclined line 8 of the reflective array 6d are also formed so as to form an angle of 90 ° with each other. As the acoustic wave, a wave other than the surface acoustic wave may be used.

  On the surface 2a of the glass substrate 2, gratings 10b and 10c, which are mode conversion elements on the acoustic wave transmission side, are disposed at two corners that are diagonal to each other. The gratings 10b and 10c are arranged so as to emit acoustic waves toward the corresponding reflection arrays 6b and 6c, respectively. Furthermore, on the surface 2a of the glass substrate 2, gratings 10a and 10d, which are reception side mode conversion elements, are arranged at another corner. These gratings 10a and 10d are arranged at positions to receive acoustic waves propagating from the reflection arrays 6a and 6d, respectively.

  Here, FIG. 2 (a) and FIG. 2 (b) show one grating 10b on the transmitting side and the side surface shape and front surface shape in the vicinity thereof. As shown in the figure, the grating 10 b is formed by forming a plurality of parallel protrusions 11 having a minute height on the surface 2 a of the glass substrate 2. A transducer 18 is attached to the back surface 2b of the glass substrate 2 at a position corresponding to the grating 10b. Although omitted in FIG. 1, transducers 18 similar to those described above are attached to positions corresponding to the other gratings 10a, 10c and 10d.

  Returning to FIG. 1, the other grating 10c on the surface acoustic wave transmitting side is basically formed in the same manner as the grating 10b. The same applies to the gratings 10a and 10d on the receiving side. The receiving-side transducers 18 provided corresponding to the gratings 10a and 10d are not bulk wave generating means but acoustic wave detecting means.

  Electric signals S1 and S2 having a frequency corresponding to the electrode period length of the transducer are applied to the transducers 18 corresponding to the gratings 10b and 10c on the transmission side from the pulse generator 20 shown in FIG. On the other hand, acoustic wave detection signals S3 and S4 output from the transducers 18 corresponding to the gratings 10a and 10d on the receiving side as described later are input to the signal processing circuit 21. The drive of the detection circuit 21 and the pulse generator 20 is controlled by a computer 22.

  Hereinafter, the operation of the position detection apparatus 100 having the above configuration will be described. First, detection of the position in the X direction will be described. When the electrical signal S1 as described above is applied from the pulse generator 20 to the transducer 18 corresponding to the grating 10b, ultrasonic vibration (bulk wave) having a frequency of about 5.5 MHz is excited from the transducer 18, for example. Is done. The bulk wave passes through the glass substrate 2 and is converted into a surface acoustic wave which is a burst wave by the grating 10b.

  The surface acoustic wave propagates in the −X direction toward the reflection array 6b, and a part of the surface acoustic wave is reflected by the inclined lines 8 constituting the reflection array 6b and propagates in the + Y direction, and each inclination constituting the reflection array 6a. The light is reflected by the line 8, propagates in the + X direction, and reaches the receiving-side grating 10a. The surface acoustic wave is converted into ultrasonic vibration (bulk wave) by the grating 10a, and this ultrasonic vibration passes through the glass substrate 2 and is electrically output by the transducer 18 provided corresponding to the grating 10a. Converted to signal S3.

  One propagation path of the surface acoustic wave at this time is indicated by 14a, 14b and 14c in FIG. That is, each inclined line 8 of the reflective array 6b is formed so as to reflect a part (about 0.5 to 1%) of the surface acoustic wave passing through the path 14a. The interval between the inclined lines 8 is an integral multiple of the wavelength of the surface acoustic wave, but this interval is such that the intensity of the surface acoustic wave propagating through the touch region 12 parallel to the path 14b is uniform. It is set so that it gradually becomes narrower as it moves away from. Thus, the arrangement density of the inclined lines 8 increases exponentially as the distance from the grating 10b increases.

  Similarly, the inclined line 8 of the corresponding reflection array 6a is set wider as it is closer to the grating 10a. However, the inclined line 8 of the reflective array 6a is formed in a direction that forms an angle of 90 ° with the inclined line 8 of the reflective array 6b. That is, the reflective array 16b and the reflective array 16a are symmetrical with respect to a center line that bisects the glass substrate 2 vertically.

  The surface acoustic wave propagates in the -X direction in the reflective array 6b, but the surface acoustic wave reflected by the inclined line 8 closer to the grating 10b in the reflective array 6b reaches the grating 10a earlier, and from the grating 10b. The surface acoustic wave reflected by the farther inclined line 8 reaches the grating 10a later. Therefore, the waveform of the output signal S3 is a waveform composed of an envelope of an electric signal obtained by converting surface acoustic waves that have successively reached the grating 10a, that is, ultrasonic vibrations that have successively reached the transducer 18. Become. Therefore, specifically, the waveform of the output signal S3 is as shown by a solid line in FIG. 3 unless a disturbance acts on the surface acoustic wave.

  However, when an object such as a finger touches the touch area 12 of the glass substrate surface 2a, the surface acoustic wave is blocked by the object, so that the output signal S3 is attenuated as shown by a broken line in FIG. Occurs. Since the time when this attenuation occurs corresponds to the X-direction position where the object touches in the touch region 12, the X-direction position of this contact can be detected based on the waveform of the output signal S3.

  The position in the Y direction of the object that has touched the touch area 12 is also detected in the same manner as described above. That is, the electrical signal S2 having a frequency corresponding to the electrode period length of the transducer is applied from the pulse generator 20 shown in FIG. 1 to the transducer 18 corresponding to the other transmission side grating 10c. Thereby, a surface acoustic wave is emitted from the grating 10c toward the reflective array 6c.

  This surface acoustic wave is reflected by the inclined line 8 of the reflecting array 6c and the inclined line 8 of the reflecting array 6d, propagates as shown by paths 16a, 16b and 16c in FIG. 1, for example, and reaches the receiving side grating 10d. . The surface acoustic wave is converted into ultrasonic vibration (bulk wave) by the grating 10d, and this ultrasonic vibration passes through the glass substrate 2 and is electrically output by the transducer 18 provided corresponding to the grating 10d. Converted to signal S4. The reflective array 16c and the reflective array 16d are symmetrical with respect to a center line that bisects the glass substrate 2 to the left and right.

  The waveform of the output signal S4 is as shown by a solid line in FIG. 4 unless a disturbance acts on the surface acoustic wave. However, here, when an object such as a finger contacts the touch region 12 of the glass substrate surface 2a, the surface acoustic wave is blocked by the object, so that the output signal S4 is attenuated as shown by the broken line in FIG. Occurs. Since the time when this attenuation occurs corresponds to the Y direction position where the object touches in the touch region 12, the Y direction position of this contact can be detected based on the waveform of the output signal S4.

  Hereinafter, the contact position detection will be described in more detail. When the signal processing circuit 21 shown in FIG. 1 receives the output signal S3 described above, the signal processing circuit 21 generates a touch signal PX corresponding to the attenuation, A / D converts it, and inputs it to the computer 22. The touch signal PX basically has a waveform obtained by vertically inverting the attenuating portion of the output signal S3, that is, the broken line portion of FIG. 3. As an example, when there is only one attenuating portion, for example, as shown in FIG. It will be a thing. That is, the touch signal PX has a peak corresponding to the place where the attenuation of the attenuation part is the largest, and the center position X1 of the peak indicates the X direction position of the contact point on the glass substrate surface 2a. Further, when two objects are in contact with the glass substrate surface 2a, two attenuation portions are generated in the output signal S3. In this case, the touch signal PX is as shown in FIG. 6, for example.

  The signal processing circuit 21 further generates a touch signal PY similar to the touch signal PX based on another output signal S4, A / D converts it, and inputs it to the computer 22. In the touch signal PY, the position where the peak occurs indicates the position in the Y direction of the contact point on the glass substrate surface 2a. Based on the touch signals PX and PY input as described above, the computer 22 outputs a position detection signal S (X, Y) indicating the X and Y coordinates of the contact point on the glass substrate surface 2a. Note that the detection of peaks in the output signals S3 and S4 can be performed using a known peak detection method.

  At this time, the computer 22 compares the amplitude of the peak portion of the touch signal PX, that is, Wh in FIG. 5 and Wh1 and Wh2 in FIG. 6, with a predetermined first amplitude threshold value Rh1. When the amplitude is lower than the first amplitude threshold value Rh1, that is, when the attenuation of the output signal S3 shown in FIG. 3 is not so significant, the amplitude is compared with the second amplitude threshold value Rh2 (Rh2 <Rh1). If the amplitude falls below the second threshold value Rh2 (this point will be described in detail later), the touch signal PX is determined not to indicate the contact of the object and is ignored. The same applies to the touch signal PY. In this way, when the touch signal PX or PY is ignored, the position detection signal S (X, Y) is not output.

  Here, in the acoustic wave type position detection apparatus 100 having the basic configuration described above, there may be a situation where the contact point is not detected even though an object is in contact with the glass substrate surface 2a. In particular, it has been found that this defect is likely to occur when there are a plurality of contact points (so-called multi-touch) as shown in FIG. 8 and they are dragged along certain paths L1 and L2. In other words, in the example of FIG. 8, the contact point at the position indicated by A is not detected, and a position detection result is obtained as if the object is separated from the glass substrate surface 2a at that position.

  Hereinafter, the point which avoids said malfunction is demonstrated. The touch signals PX and PY described above are generated each time a surface acoustic wave, which is a burst wave, is emitted once toward the reflection arrays 6b and 6c. Therefore, the touch signals obtained when the surface acoustic wave is generated for the nth time are represented as PXn and PYn, respectively.

  The computer 22 obtains touch signals PX and PY that are input when the contact point is being dragged, for example, for several consecutive inputs (when surface acoustic waves are intermittently generated several times, respectively). Only the touch signals PX and PY) are stored in the buffer memory. When the amplitude of the touch signals PXn and PYn obtained when the surface acoustic wave is generated for the nth time falls below the first threshold value Rh1, the computer 22 determines the amplitudes of the touch signals PXn and PYn. Based on the following conditions, it is determined whether there is actually no contact of the object with the glass substrate surface 2a, or whether the above problem has occurred although there is contact.

  In the present invention, in addition to the amplitude of the touch signal, at least one of the width, peak-to-peak distance, and waveform of the signal is used as the determination condition. In the present embodiment, in particular, the amplitude of the touch signal PXn, The length and waveform of the rising edge of the signal are used. Specifically, the presence / absence of contact using these is determined as follows. When the amplitude of the peak portion of the touch signal PXn, that is, Wh in FIG. 5 or Wh1 and Wh2 in FIG. 6 is lower than the first threshold value Rh1, the amplitude is then the second threshold value Rh2 (Rh2 <Rh1). ). When the amplitude falls below the second threshold value Rh2, the touch signal PXn is ignored as described above because it indicates no object contact. In this embodiment, since it is assumed that up to two contact points are detected, when there are three or more peaks in the touch signal PXn, only the two peak portions in descending order of amplitude are used as threshold values. For comparison.

  On the other hand, when the amplitude of the touch signal PXn has a value greater than or equal to the second threshold value Rh2 at one or two locations, there is a possibility that the touch signal PXn indicates an object contact. The computer 22 then compares the length Ww of the rising portion of the touch signal PXn (for example, full width at half maximum: see FIGS. 5 and 6; hereinafter simply referred to as “signal length”) with a predetermined signal length threshold Rw. . As a result of this comparison, when Ww ≦ Rw, the computer 22 has a unimodal waveform of the touch signal PXn as shown in FIG. 5, for example, and when Ww> Rw, the waveform of the touch signal PXn as shown in FIG. Judged to be bimodal. Note that the signal length Ww may be defined by, for example, the distance between portions taking 40% of the peak value, in addition to the full width at half maximum of the peak portion as described above.

  At this time, the computer 22 further determines whether the waveform of the touch signal PXn is unimodal as shown in FIG. 5 or bimodal as shown in FIG. 6 by a known method such as pattern matching.

  When the same determination result is obtained by the above two processes, the computer 22 determines whether the waveform of the touch signal PXn is unimodal or bimodal based on the determination result. If different determination results are obtained by the above two processes, the computer 22 determines that the touch signal PXn does not indicate an object contact, for example. Note that only one of the above two processes may be performed, and based on the result, it may be determined whether the waveform of the touch signal PXn is unimodal or bimodal.

  When it is determined by the above two processes that the waveform of the touch signal PXn is unimodal, the computer 22 takes a value equal to or greater than the second threshold value Rh2 at two locations of the peak portion of the touch signal PXn. Even if it is determined that only the peak portion having a larger amplitude indicates the contact of the object, the X direction position of the peak portion, that is, X1 in FIG. 5 is determined as the X direction position of the contact point. To do. In addition, although the waveform of the touch signal PXn is basically unimodal, an example of a waveform when two peaks are detected is shown in FIG.

  If it is determined that the waveform of the touch signal PXn has a bimodal shape by the above two processes, the computer 22 determines that the two peak portions of the touch signal PXn have an amplitude greater than or equal to the second threshold value Rh2. Are determined to accurately indicate the contact of the object, and the X-direction position of the peak portion, that is, X1 and X2 in FIG. 6 is determined as the X-direction position of the contact point.

  In the computer 22, the touch signal PYn is processed in the same manner as described above, thereby determining the Y-direction positions of one or two contact points on the glass substrate surface 2a. As described above, the computer 22 outputs one or two position detection signals S (X, Y) indicating the X and Y coordinates of the contact point on the glass substrate surface 2a.

  Conventionally, the presence / absence of contact is detected based only on the peak values (amplitudes) of the touch signals PX and PY. In the present embodiment, as described above, an object is dragged on the glass substrate surface 2a. In addition to the peak values of the touch signals PX and PY that are output during detection, the presence / absence of contact is detected based on the length and waveform of the rising portion of the signals, so that dragging is performed with multi-touch. Even in this case, the accuracy of this detection can be made high. That is, in the prior art, for example, when the touch signal PX is as shown in FIG. 6, the presence or absence of contact is detected based on only the magnitude relationship between the values between Wh1 and Wh2 as a threshold value. In spite of the fact that the peak appearance at position X2 is due to actual contact, it is ignored as being unrelated to contact. On the other hand, according to the present embodiment, it can be recognized that the peak appearance at the position X2 is also caused by actual contact as described above.

  In addition, when two contact points are arranged in a substantially overlapping state along the traveling direction of the surface acoustic wave, the peak of the touch signal PX or PY by the two contact points is in a substantially overlapped state. Appear. In such a case, in the conventional contact detection based only on the amplitude, there is a high possibility that only one contact point is detected. However, according to the present invention, the waveform of the touch signal PX or PY (for example, the entire rising portion of the signal) If the general height, the shape of the skirt, etc.) are also used as detection conditions, it is possible to accurately detect that there are two contact points. In other words, when the two contact points are arranged in a substantially overlapping state as described above and the case where only one contact point exists, the surface acoustic wave is attenuated more greatly in the former case. This is because the waveforms in both cases are different from each other (for example, the overall height of the rising portion of the signal is higher in the former).

  In the embodiment described above, the pattern matching technique is used to determine whether the waveform of the touch signal PXn is unimodal or bimodal, but not limited to this, the touch signal PXn is not limited thereto. It is also possible to discriminate whether it is a unimodal or a bimodal based on the value obtained by integrating the waveform or the curvature of the waveform.

  In the embodiment described above, the amplitude of the touch signal PXn, the length of the rising portion, and the waveform are used for detecting the presence or absence of the touch. In addition, the peak-to-peak distance of the touch signal PXn may be used. Is possible. For example, in the waveform as shown in FIG. 6, the peak-to-peak distance is a distance between the positions X1 and X2. For example, when the peak-to-peak distance is less than a predetermined threshold, the waveform is a single peak and the threshold When it is above, it can be determined that the shape is a bimodal. This peak-to-peak distance can be suitably used in place of the length of the rising portion of the touch signal PXn described above. However, the present invention is not limited to this. For example, when the determination results based on the length of the rising portion of the touch signal PXn, the distance between peaks, and the waveform are all bimodal, they may be regarded as bimodal.

  In the present invention, in determining whether or not there is a touch, in addition to the amplitude of the touch signal, any one or more of the three conditions of the length of the rising portion of the signal, the peak-to-peak distance, and the waveform are appropriately used. be able to. Whichever of these three conditions is used, the accuracy of the detection can be improved compared to the case where the presence / absence of the touch is detected based only on the amplitude of the touch signal.

  In the embodiment described above, the position in the X direction of the peak portion of the touch signal PXn is used as the contact position of the object as it is. However, whether there is contact with the object and whether the contact is one point or two points. It may be determined by the method in the above embodiment, and the contact position may be detected by another method. Hereinafter, an example of such another method will be described.

  As shown in FIG. 9, it is assumed that an object such as a finger is dragged (moved while maintaining contact) on a surface 2a of the glass substrate 2, for example, along a linear path L1. At this time, as described above, the contact points detected when the surface acoustic waves are generated at the (n-3) th, (n-2) th, and (n-1) th times are Dn-3, Dn-2, Dn, respectively. Set to -1. Consider the case where the contact point Dn is not detected although dragging is continued even when the surface acoustic wave is generated for the nth time following them.

  At this time, as described above, the computer 22 obtains the input touch signals PX and PY for, for example, several consecutive inputs (when surface acoustic waves are intermittently generated several times, respectively). If only the touch signals PX, PY) are stored in the buffer memory, the computer 22 can change the position change direction of the contact points Dn-3, Dn-2, Dn-1 indicated by the stored touch signals PX, PY and Based on the generation time interval of the surface acoustic wave, the position of the contact point Dn can be predicted. Therefore, when the contact point Dn is not detected, even if the predicted contact position is used as a contact point, there is little or no error between the predicted contact position and the actual contact point Dn, and this is particularly problematic in practical use. There is no invitation.

1 Touch panel 2 Glass substrate 2a Surface of glass substrate (surface to be contacted)
6a, 6b, 6c, 6d Reflective array 8 Slope 10a, 10b, 10c, 10d Grating 18 Transducer 20 Pulse generator 21 Signal processing circuit 22 Computer 100 Acoustic wave type position detector

Claims (2)

While propagating the acoustic wave along the surface that is the contact target of the object,
An electrical detection signal is obtained by detecting this propagated acoustic wave,
In an acoustic wave type position detecting device configured to detect a contact position on the surface of the object based on attenuation of the detection signal when the acoustic wave is blocked by the object,
Based on at least one of the amplitude of the signal indicating the attenuation state output when a plurality of objects are dragging on the surface, the length of the rising portion of the signal, the distance between peaks, and the waveform, An acoustic wave type position detecting apparatus comprising detecting means for detecting presence / absence of contact of an object with the surface.   2. The detection means is configured to predict and obtain a contact position of the object with respect to the surface at a certain time based on a contact position detected before the time. The acoustic wave type position detection apparatus as described.

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