JP3822051B2 - Ultrasonic touch panel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic touch panel that includes an ultrasonic transmission / reception device provided on a non-piezoelectric substrate, and detects that a finger or an object contacts the non-piezoelectric substrate.
[Prior art]
As a conventional ultrasonic touch panel, a method using a surface acoustic wave is widespread.
[0003]
Conventional methods using surface acoustic waves include a method of exciting a non-piezoelectric substrate such as glass indirectly with a wedge-shaped transducer using a bulk wave vibrator, a method of directly exciting with a piezoelectric thin film transducer, and the like. It is done.
[0004]
[Problems to be solved by the invention]
The method using a wedge-shaped transducer using a bulk wave vibrator indirectly excites a non-piezoelectric substrate and reflects the surface acoustic wave twice by a reflection array disposed around the non-piezoelectric substrate. Loss of elastic waves is large, and it is necessary to set the driving voltage of the transducer high, so that it is difficult to reduce power consumption.
[0005]
A piezoelectric thin film transducer is a method in which a piezoelectric thin film such as ZnO is vapor-deposited on a substrate and a surface acoustic wave is excited by an interdigital electrode. Since it exhibits various transmission characteristics depending on the configuration of an interdigital electrode, it is used as a high-frequency device. It is limited to the VHF band, the signal processing circuit becomes complicated, and it is difficult to reduce power consumption.
[0006]
An object of the present invention is to provide an ultrasonic touch panel having a simple configuration, low power consumption and excellent efficiency.
[0007]
[Means for Solving the Problems]
As means for solving the above-mentioned problem, as a first configuration,
A plurality of ultrasonic transducers having interdigital electrodes formed on one surface thereof are provided so as to face one surface of a non-piezoelectric substrate, and the propagation paths of surface acoustic waves propagating between the opposing ultrasonic transducers cross each other. An ultrasonic touch panel for selecting a pair of interdigital electrodes of the ultrasonic transducers facing each other by a selection circuit and detecting a position of a finger or an indicator from attenuation of surface acoustic waves propagating between the interdigital electrodes In
When the finger or indicator is in contact with the non-piezoelectric substrate, the interdigital electrode corresponding to the indicated position and the region adjacent to the indicated position is selected from the detection result of the indicated position of the finger or indicator. The ultrasonic touch panel is configured to have a partial scanning mode that is selected by a circuit and scans the designated position and a region adjacent to the designated position.
[0008]
As a means for solving the above-mentioned problem, as a second configuration,
A plurality of ultrasonic transducers having interdigital electrodes formed on one surface thereof are provided so as to face one surface of a non-piezoelectric substrate, and the propagation paths of surface acoustic waves propagating between the opposing ultrasonic transducers cross each other. An ultrasonic touch panel for selecting a pair of interdigital electrodes of the ultrasonic transducers facing each other by a selection circuit and detecting a position of a finger or an indicator from attenuation of surface acoustic waves propagating between the interdigital electrodes In
At least one ultrasonic transducer having a pair of comb-like electrodes arranged so that the arc-shaped electrode fingers of each other are inserted is arranged at one surface corner of the non-piezoelectric substrate, and the ultrasonic wave A scanning mode for detecting the presence or absence of contact between the finger or the indicator and the non-piezoelectric substrate from the attenuation of the surface acoustic wave emitted from the transducer to the other ultrasonic transducer on the receiving side, and the finger or the indicator The ultrasonic touch panel is configured to start detecting the position of the finger or the indicator by selecting the interdigital electrode corresponding to the detection portion by the selection circuit when the contact between the electrode and the non-piezoelectric substrate is detected. did.
[0009]
As means for solving the above-mentioned problem, as a third configuration, in addition to the second configuration,
After detecting the presence or absence of contact between the finger or the indicator and the non-piezoelectric substrate and calculating the indicated position of the finger or the indicator once, the indicated position of the finger or the indicator and the area adjacent to the indicated position The ultrasonic touch panel has a partial scanning mode in which the interdigital electrode corresponding to is selected by a selection circuit, and calculates the indicated position from the attenuation of the surface acoustic wave.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the ultrasonic touch panel according to the present invention will be described below with reference to the drawings.
[0011]
FIG. 1 is a schematic view showing the first embodiment.
[0012]
Reference numeral 1 denotes an ultrasonic touch panel body. Reference numerals 2a to 2d denote ultrasonic transducers in which interdigital electrodes Tn and Rn are formed on the surface of a piezoelectric material such as PZT. Reference numeral 3 denotes a non-piezoelectric substrate made of glass, acrylic, or the like and serving as a surface acoustic wave transmission path. Reference numeral 4 denotes a finger for inputting a designated position. In this embodiment, a finger is used as an object for indicating the position, but it is also possible to use an indicator such as a stylus pen or a cursor accompanied by the attenuation of surface acoustic waves when contacting a non-piezoelectric substrate in the same manner as the finger. It is.
[0013]
FIG. 2 is a perspective view showing the actual shape of the interdigital electrode. The interdigital electrode 11 is made of a thin metal film such as aluminum and is formed on the surface of a piezoelectric ceramic thin plate 12 made of a piezoelectric material such as PZT. The electrode finger of the interdigital electrode 11 is the wavelength of the ultrasonic wave to be transmitted or received. The electrode is formed in a comb-like shape with an electrode cycle length determined according to the interval. In addition, the interdigital electrode 11 is formed by a pair of comb-like electrodes having electrode fingers inserted between each other.
[0014]
FIG. 3 shows variations of the shape of the ultrasonic transducer. In the configuration of the ultrasonic touch panel shown in FIG. 1, the ultrasonic transducers 2a to 2d are formed to include a plurality of interdigital electrodes. However, the x-axis direction and the y-axis are set so that each interdigital electrode is included one by one. A plurality of small ultrasonic transducers may be arranged in the direction.
[0015]
FIG. 4 shows a circuit block configuration of the ultrasonic touch panel. 2 is an ultrasonic transducer, 5 is an ultrasonic transducer and a selection circuit for selecting the interdigital electrode included in the ultrasonic transducer, and 6 is an electric signal having a frequency corresponding to the electrode period length of the interdigital electrode. A pulse generator 7 is a signal processing circuit that performs processing such as rectification, smoothing, and amplification on the electrical signal converted by the ultrasonic transducer on the receiving side, and outputs a signal corresponding to the attenuation of the surface acoustic wave. A comparator 8 compares the output signal of the signal processing circuit with a reference voltage to determine whether surface acoustic waves are attenuated. A CPU 9 controls the pulse generator, the selection circuit, and the signal processing circuit, and calculates the finger pointing position from the attenuation amount of the surface acoustic wave and the positions of the selected interdigital electrodes Tn and Rn.
[0016]
FIG. 5 is a flowchart showing a scanning method of the selection circuit for selecting the interdigital electrodes Tn and Rn.
[0017]
The operation of the ultrasonic touch panel will be described based on FIG. 1 and FIGS.
[0018]
First, a case where the finger 4 is not in contact with the non-piezoelectric substrate 3 (non-contact state) will be described.
[0019]
The pulse generator 6 generates an electric signal of several MHz that is a frequency corresponding to the electrode period length of the interdigital electrode of the ultrasonic transducer 2 and outputs it as a pulse output signal. Subsequently, the pulse output signal is input to the ultrasonic transducer on the transmission side via the selection circuit 5 and converted into a surface acoustic wave. On the other hand, in the ultrasonic transducer 2 on the receiving side, surface acoustic waves are received using a non-piezoelectric substrate as a medium, converted into an electric signal, input to the signal processing circuit 7 via the selection circuit 5, and the electric signal is rectified. Then, smoothing, amplification, and comparison with a reference voltage by the comparator 8 determine the presence or absence of attenuation of the surface acoustic wave. When it is determined that the surface acoustic wave is less attenuated and is in a non-contact state, the entire surface scanning is started again.
[0020]
Next, the operation when the finger 4 is in contact with the non-piezoelectric substrate 3 (contact state) will be described.
[0021]
When the finger 4 comes into contact with the non-piezoelectric substrate 3, part of the surface acoustic wave output from the ultrasonic transducer on the transmitting side is absorbed by the finger, and the surface acoustic wave attenuated compared to the surface acoustic wave in the non-contact state is generated. It reaches the ultrasonic transducer 2 on the receiving side. By converting the surface acoustic wave into an electric signal by the ultrasonic transducer 2 on the receiving side, inputting it to the signal processing circuit 7 via the selection circuit 5, rectifying, smoothing, amplifying, and comparing with the reference voltage by the comparator 8 The presence or absence of surface acoustic wave attenuation is determined. The ultrasonic transducer selected when the surface acoustic wave is attenuated by performing a full scan in the y-axis direction to obtain the indicated position of the finger in the y-axis direction when the surface acoustic wave is greatly attenuated and determined to be in contact 2 and the position of the interdigital electrodes Tn, Rn, the CPU 9 calculates the finger pointing position.
[0022]
Further, when the interdigital electrodes corresponding to the calculation result of the pointing position of the finger 4 are Tk and Rm, for example, interdigital electrodes Tk and Rm and interdigital electrodes Tk-1, Tk + 1, Rm-1, Rm + 1 is selected (partial scan) in the order of the x-axis and y-axis directions, and the partial scan is repeated while the finger 4 is in contact with the non-piezoelectric substrate 3 and the attenuation of the surface acoustic wave is detected. The CPU 9 calculates the finger pointing position from the positions of the interdigital electrodes Tn and Rn of the ultrasonic transducer selected when the elastic wave is attenuated.
[0023]
In the case of full scan, in the first configuration of this embodiment, it is necessary to switch the selection circuit up to seven times in the x-axis direction and four times in the y-axis direction in order to calculate the finger pointing position. On the other hand, in the case of partial scanning, the selection circuit can be switched up to three times each in the x-axis direction and the y-axis direction. Accordingly, in the first embodiment, the time required to obtain the finger pointing position once is shortened as compared with the method of performing only full scan, so that the power consumption is reduced and the number of times the pointing position is output. Can be increased.
[0024]
Next, a second embodiment of the ultrasonic touch panel according to the present invention will be described.
[0025]
FIG. 6 is a schematic diagram showing the configuration of the second embodiment. In the ultrasonic touch panel of the first embodiment, for transmission during full-surface scanning, as shown in FIG. The ultrasonic transducer 2e having the same electrode periodic length and formed with arc-shaped electrode fingers that are interleaved with each other is arranged at the corner of the upper surface of the non-piezoelectric substrate 3. In the configuration shown in FIG. 6, the fan-shaped ultrasonic transducer 2e is disposed between the interdigital electrodes T1 and T11, but between the interdigital electrodes T7 and R11 according to the surface acoustic wave attenuation characteristics. For example, it is possible to arrange a plurality of ultrasonic transducers at other positions or to arrange circular ultrasonic transducers that propagate surface acoustic waves radially.
[0026]
Next, the operation in the second embodiment will be described with reference to FIG. 4 and FIGS.
[0027]
FIG. 8 is a flowchart showing a scanning method in the second embodiment of the ultrasonic touch panel.
[0028]
At the start of scanning, a pulse output signal having a frequency corresponding to the electrode period length is output from the pulse generation circuit 6 to the ultrasonic transducer 2e via the selection circuit 5, and a surface acoustic wave is transmitted from the ultrasonic transducer 2e. Next, the interdigital electrodes R1-7 and R11-14 of the ultrasonic transducer on the receiving side are sequentially selected by the selection circuit 5.
[0029]
When the finger 4 comes into contact with the non-piezoelectric substrate 3, the surface acoustic wave is attenuated and the output signal level of the ultrasonic transducer 2 on the receiving side is lowered. Therefore, the presence or absence of contact between the finger 4 and the non-piezoelectric substrate 3 can be detected by discriminating the decrease in the output signal level by the comparator 8.
[0030]
Thereafter, full scanning in the x-axis direction and y-axis direction is performed, and the CPU 9 calculates the finger pointing position from the positions of the interdigital electrodes Tn and Rn of the ultrasonic transducer selected when the surface acoustic wave is attenuated.
[0031]
In the second embodiment described above, the number of times of selection and transmission time of the non-contact ultrasonic transducer and the interdigital electrode are reduced by using the ultrasonic transducer for transmission arranged at the upper corner of the non-piezoelectric substrate. Thus, it is possible to reduce power consumption and increase the speed of finger pointing position output.
[0032]
Furthermore, as a third embodiment, by performing the partial scanning shown in the first embodiment with the configuration shown in FIG. 6 shown in the second embodiment, the ultrasonic transducer and the interdigital electrode in the contact state can be obtained. It is possible to further reduce the number of selections, thereby reducing power consumption and speeding up the finger pointing position output.
[0033]
Instead of the circuit block configuration shown in FIG. 4, the circuit shown in FIG. 9 is configured as a delay line oscillator by connecting the transmitting-side ultrasonic transducer and the receiving-side ultrasonic transducer with the amplifier 10 via the selection circuit 5. Even if the block configuration is applied, as in the first to third embodiments, it is effective for reducing power consumption and speeding up the output of the finger pointing position.
[0034]
【The invention's effect】
According to the present invention, in the first configuration having the partial scanning mode in which the selection is limited to the ultrasonic transducer and the interdigital electrode corresponding to the finger pointing position and the surrounding area from the calculation result of the finger pointing position. While the finger is in contact with the non-piezoelectric substrate, it is possible to reduce power consumption or increase the number of indication position outputs.
[0035]
According to the present invention, in the second configuration having an ultrasonic transducer in the corner of the upper surface of the non-piezoelectric substrate and using the ultrasonic transducer on the transmission side, the finger is placed on the non-piezoelectric substrate. While there is no contact, there is no need to select other ultrasonic transducers on the transmission side, and switching operation of the selection circuit on the transmission side is not necessary, reducing power consumption and speeding up finger pointing position output, etc. It is valid.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the configuration of an ultrasonic touch panel according to the present invention.
FIG. 2 is a perspective view showing the arrangement of interdigital electrodes of an ultrasonic transducer.
FIG. 3 is a schematic view showing a configuration of an ultrasonic touch panel in which a small ultrasonic transducer is arranged.
FIG. 4 is an explanatory diagram showing a circuit block configuration of an ultrasonic touch panel.
FIG. 5 is a flowchart showing a scanning method of the ultrasonic touch panel.
FIG. 6 is a schematic view showing a configuration of an ultrasonic touch panel in which ultrasonic transducers are arranged at corners of a non-piezoelectric substrate.
FIG. 7 is an explanatory view showing electrode shapes of an ultrasonic transducer of a non-piezoelectric substrate.
FIG. 8 is a flowchart showing a scanning method of an ultrasonic touch panel in which ultrasonic transducers on a non-piezoelectric substrate are arranged.
FIG. 9 is an explanatory diagram showing a circuit block configuration of an ultrasonic touch panel in which an ultrasonic transducer and an amplifier are connected and configured as a delay line oscillator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ultrasonic touch panel 2, 2a, 2b, 2c, 2d, 2e Ultrasonic transducer 3 Non-piezoelectric substrate 4 Finger 5 Selection circuit 6 Pulse generator 7 Signal processing circuit 8 Comparator 9 CPU
10 Amplifier 11 Interdigital electrode 12 Piezoelectric thin plate Tn Interdigital electrode (transmission side)
Rn interdigital electrode (receiving side)

Claims (3)

A plurality of ultrasonic transducers having interdigital electrodes formed on one surface thereof are provided so as to face one surface of a non-piezoelectric substrate, and the propagation paths of surface acoustic waves propagating between the opposing ultrasonic transducers cross each other. An ultrasonic touch panel for selecting a pair of interdigital electrodes of the ultrasonic transducers facing each other by a selection circuit and detecting a position of a finger or an indicator from attenuation of surface acoustic waves propagating between the interdigital electrodes In
When the finger or indicator is in contact with the non-piezoelectric substrate, the interdigital electrode corresponding to the indicated position and the region adjacent to the indicated position is selected from the detection result of the indicated position of the finger or indicator. An ultrasonic touch panel having a partial scanning mode for selecting by the circuit and selecting the designated position and an area adjacent to the designated position. A plurality of ultrasonic transducers having interdigital electrodes formed on one surface thereof are provided so as to face one surface of a non-piezoelectric substrate, and the propagation paths of surface acoustic waves propagating between the opposing ultrasonic transducers cross each other. An ultrasonic touch panel for selecting a pair of interdigital electrodes of the ultrasonic transducers facing each other by a selection circuit and detecting a position of a finger or an indicator from attenuation of surface acoustic waves propagating between the interdigital electrodes In
At least one ultrasonic transducer having a pair of comb-like electrodes arranged so that the arc-shaped electrode fingers of each other are inserted is arranged at one surface corner of the non-piezoelectric substrate, and the ultrasonic wave A scanning mode for detecting the presence or absence of contact between the finger or the indicator and the non-piezoelectric substrate from the attenuation of the surface acoustic wave emitted from the transducer to the other ultrasonic transducer on the receiving side, and the finger or the indicator An ultrasonic touch panel that starts detection of the position of a finger or an indicator by selecting the interdigital electrode corresponding to the detection portion by the selection circuit when detecting contact between the finger and the non-piezoelectric substrate. After detecting the presence or absence of contact between the finger or the indicator and the non-piezoelectric substrate, and calculating the indicated position of the finger or the indicator once, the indicated position of the finger or the indicator and the area adjacent to the indicated position The ultrasonic touch panel as set forth in claim 2, further comprising: a partial scanning mode in which an interdigital electrode corresponding to 1 is selected by a selection circuit, wherein the indicated position is calculated from the attenuation of the surface acoustic wave.

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