JPH06149459A - Ultrasonic touch panel - Google Patents

Abstract

PURPOSE:To provide the ultrasonic touch panel for sensing the touch of an object to a piezoelectric panel by providing an ultrasonic transmitting/receiving means on the piezoelectric panel. CONSTITUTION:When an electric signal is inputted from an interdigital electrode T1 or T2, the electric signal is converted to a surface acoustic wave(SAW) and propagated through a piezoelectric panel 1. Among the SAWs propagated through the piezoelectric panel 1, only the SAWs at a central frequency and the adjacent frequency shown by interdigital electrodes R11-R14 or R21-R24 are converted to electric signals and outputted from the interdigital electrodes R11-R14 or R21-R24. When the propagating path of SAWs is touched, the electric signals of interdigital electrodes for output at a position corresponding to the touched part are attenuated or extinguished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic touch panel which is provided with an ultrasonic wave transmitting / receiving means on a piezoelectric plate so as to detect the contact of an object with the piezoelectric plate.

[0002]

2. Description of the Related Art Conventional touch panels mainly include a method using a resistive film and a method using ultrasonic waves. The method using the resistance film is that the resistance value of the transparent conductive film is changed by touching the transparent conductive film (resistive film), and although the power consumption is low, the response time, sensitivity,
There is a problem in terms of durability. In the method using ultrasonic waves, the surface acoustic wave is attenuated by touching a non-piezoelectric substrate on which the surface acoustic wave is excited in advance.
As a conventional method of exciting a surface acoustic wave on a non-piezoelectric substrate, there are a method of indirectly exciting a wedge-shaped transducer using a bulk wave oscillator and a method of directly exciting a piezoelectric thin film transducer. The wedge-shaped transducer is used for non-destructive inspection by ultrasonic waves, etc., but is used only in a relatively low frequency region due to the problem of the working accuracy of the wedge angle. The piezoelectric thin film transducer is a method in which a piezoelectric thin film such as ZnO is vapor-deposited on a substrate to excite surface acoustic waves by interdigital electrodes. Since the interdigital electrodes have various transmission characteristics, they are used as high frequency devices. It is limited to the VHF band and has problems in workability and mass productivity. As described above, the conventional methods have problems in response time, sensitivity, durability, working accuracy, workability, mass productivity, etc., and the frequency range used is also limited.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic touch panel which is excellent in workability, durability and mass productivity by using a light-transmissive piezoelectric plate as a substrate and which can be reduced in size and weight. It is in. Further, it is possible to efficiently excite the surface acoustic wave on the piezoelectric plate with low power consumption and low voltage, and to provide a highly sensitive ultrasonic touch panel with a short response time for the surface acoustic wave to be attenuated by contacting the piezoelectric plate. To do.

[0004]

An ultrasonic touch panel according to claim 1, wherein the ultrasonic touch panel comprises at least two ultrasonic wave transmitting / receiving means on one plate surface Z1 of a piezoelectric plate. The transmitting and receiving means is composed of N sets of interdigital electrodes P _i (i = 1, 2, ..., N) and the interdigital electrodes P _i.
N comb-shaped electrode groups Q _i (i =
1, 2, ..., N) and the interdigital electrode group Q
_i is at least two sets of interdigital electrodes Q _i-1 (i =
1, 2, ..., N) and Q _i-2 (i = 1, 2, ..., N)
Consist N), the inputs of at least one electrical signal having a frequency substantially corresponding to the interdigital periodicity of interdigital electrodes P _i to the interdigital electrodes P _i, at least having a wavelength approximately equal to the electrode period length 1 Means for exciting different kinds of surface acoustic waves on the plate surface Z1 and electric signals appearing on the interdigital electrodes Q _{i- 1} and Q _i-2 according to the wavelength of the surface acoustic waves excited on the plate surface Z1. Is provided, and the respective output ends of the interdigital transducers Q _i-1 are electrically connected to each other at a connection point N1, and the respective output ends of the interdigital transducers Q _i-2 are provided. are connected by electrical connection point N2 to each other, means for inputting an electric signal to said interdigital electrode P _i is, N number of switches having an output connected to the input terminals of the interdigital electrode P _i S _i (i =
1, 2, ..., N) and switch control means for sequentially electrically connecting and disconnecting the switches S _i at predetermined intervals, the interdigital transducer P _i in one ultrasonic wave transmitting / receiving means. SAW between the propagation path of the surface acoustic wave, and another of the said interdigital electrode P _i in ultrasonic transmitter means and said IDT group Q _i between said interdigital electrode group Q _i Of the electric signal appearing at the connection point N1 and the connection point N2, indicating that the object is in contact with a part of the propagation path of the surface acoustic wave on the plate surface Z1. It is characterized by sensing.

The ultrasonic touch panel according to claim 2 is
The switch S_iThe input ends of each are electrically
The connection point NS is connected, and the connection point N1 is connected via an amplifier.
Electrically connected to the connection point NS, The interdigital
Pole P_iTo the above-mentioned interdigital electrode Q_i-1Piezoelectric plate between
Surface acoustic wave propagation path D consisting of_i(I = 1, 2, ...,
Oscillator H using N) as a delay element_i(I = 1, 2, ...,
N) is configured, said oscillator H_iThe signal loop of
The interdigital electrode P_iAnd the propagation path D_iAnd the above blinds
Electrode Q_i-1And the amplifier,
It

The ultrasonic touch panel according to claim 3 is
There are at least _two electrode cycle lengths L1 and L2 in the interdigital electrodes P _i , Q _i-1 and Q _i-2, respectively, and an electric signal having a frequency substantially corresponding to the electrode cycle length L1 or L2 is A means for exciting the surface acoustic wave having a wavelength substantially equal to the electrode period length L1 or L2 to the plate surface Z1 by inputting it to the interdigital transducer P _i is provided.

The ultrasonic touch panel according to claim 4 is
The other plate surface Z2 of the piezoelectric plate is provided with a display screen of a display device for displaying at least one kind of color, and the frequency and the color of the electric signal input to the interdigital transducer P _i are provided. Is provided.

The ultrasonic touch panel according to claim 5 is
The piezoelectric plate is made of a substantially transparent piezoelectric ceramic, and the polarization axis of the piezoelectric ceramic is parallel to the thickness direction of the piezoelectric ceramic.

[0009]

Since the ultrasonic touch panel of the present invention has a simple structure in which at least two ultrasonic wave transmitting / receiving means are provided on one plate surface Z1 of the piezoelectric plate, the size and weight of the device can be reduced. . The ultrasonic wave transmitting / receiving means includes N sets of interdigital electrodes P _i (i = 1, 2, ..., N) and N sets of interdigital electrodes Q _i (i = 1) respectively corresponding to the interdigital electrodes P _i. ，
2, ..., N), and each of the interdigital electrode groups Q _i has at least two sets of interdigital electrodes Q _i-1 (i = 1,
2, ..., N) and Q _i-2 (i = 1,2, ..., N)
Consists of. By adopting the structure in which the interdigital electrode P _i is used for input and the electric signal is input from the interdigital electrode P _i, it is possible to excite the surface acoustic wave on the plate surface Z1 of the piezoelectric plate. Moreover, surface acoustic waves can be efficiently excited on the plate surface Z1 with low power consumption and low voltage.

The interdigital electrodes Q _i-1 and Q _i-2 are used for output, and the interdigital electrodes Q _i-1 and Q _i-2 are used to transmit and receive surface acoustic waves to and from the interdigital electrode P _i . By adopting a structure in which the directional axes are arranged in common, the surface acoustic wave excited on the plate surface Z1 can be efficiently output as an electric signal. The propagation path of the surface acoustic wave on the plate surface Z1 (that is, between the interdigital electrodes P _i and Q _i-1 and between P _i and Q _i-2 ) is excited by the object and excited on the plate surface Z1. Since the generated surface acoustic wave disappears or attenuates, the electric signals output to the interdigital electrodes Q _i-1 and Q _i-2 also disappear or attenuate. In this way, it is detected that the object has come into contact with the propagation path of the surface acoustic wave on the plate surface Z1. Moreover, the ultrasonic touch panel of the present invention has a short response time and good sensitivity. The object needs to be a substance that is softer than the piezoelectric plate and easily absorbs ultrasonic waves, and a human finger or the like also has the characteristic. Further, among the interdigital electrodes Q _i-1 and Q _i-2 , by identifying the interdigital electrode in which the output electric signal disappears or attenuates,
The contact position can be specified.

[0011] By employing at least one structure for inputting an electric signal of a frequency substantially corresponding to the interdigital periodicity of interdigital electrodes P _i to interdigital electrodes P _i, substantially to the electrode period length on the plate surface Z1 It is possible to excite at least one surface acoustic wave having an equal wavelength. Also, the plate surface Z
The surface acoustic wave excited by No. 1 can be output as an electric signal from the interdigital transducers Q _i-1 and Q _i-2 according to its wavelength.

A structure in which at least two ultrasonic wave transmitting / receiving means are provided on the plate surface Z1 is adopted, and moreover, an elastic surface between the interdigital electrode P _i and the interdigital electrode group Q _{i in} one ultrasonic wave transmitting / receiving means. By adopting a structure in which the wave propagation path and the surface acoustic wave propagation path between the interdigital transducer P _i and the interdigital transducer group Q _i in another ultrasonic wave transmitting / receiving means are orthogonal to each other, the plate surface The contact position in Z1 can be specified more delicately. As the number of ultrasonic wave transmitting / receiving means increases, more detailed identification becomes possible.

The output terminals of the interdigital transducer Q _i-1 are electrically connected to each other at a connection point N1, and the interdigital transducer Q _i is connected.
_By electrically connecting the respective output ends of _i-2 to each other at a connection point N2, it is possible to determine that a part of the propagation path of the surface acoustic wave on the plate surface Z1 is touched by the object at the connection points N1 and N2. It can be detected from the magnitude of the electric signal that appears. Interdigital electrode P as a means for inputting an electrical signal to the _i, an output connected to the input terminal of the interdigital electrodes P _i N number of switches _{S i (i = 1,2, ......} ,
N) is provided and the switches S _i are electrically connected and disconnected sequentially at a predetermined cycle. In this way, electrical signals can be sequentially input to the interdigital electrodes P _i . Therefore, for example, among the propagation paths of the surface acoustic waves on the plate surface Z1 (that is, between the interdigital electrodes P _i and Q _i-1 and between P _i and Q _i-2 ), for example, the interdigital electrodes P ₁ and Q. _In the case of contact between _1-1 and ₁ , the delayed electric signal output to the connection point N1 is attenuated or disappears only when the electric signal is input to the interdigital transducer P ₁ . In this way, the contact position can be clearly specified.

By adopting a structure in which the respective input ends of the switches S _i are electrically connected to each other at the connection point NS, and the connection point N1 is electrically connected to the connection point NS via an amplifier, the interdigital electrode is formed. Plate surface Z1 between P _i and Q _i-1
The surface acoustic wave propagation path D _i (i = 1, 2, ...,
Oscillator H _i (i = 1, 2, ..., N) as a delay element
N) can be configured. The signal loop of the oscillator H _i includes the interdigital electrode P _i , the propagation path D _i, and the interdigital electrode Q.
_It consists of _i-1 and an amplifier. In this way, since the circuit configuration is simplified, it is possible to further reduce the size and weight of the device, and it is possible to drive at low voltage with low power consumption.

Interdigital electrode P_i, Q_i-1And Q_i-2age
And each have at least two electrode period lengths L1 and L
By adopting the structure having 2, the interdigital electrode P
_iAt a frequency approximately corresponding to the electrode cycle length L1 or L2
An electric signal can be input. Therefore, on the plate surface Z1
Elastic surface with wavelength approximately equal to electrode period length L1 or L2
Can excite the waves. Also, it is excited on the plate surface Z1.
Has a wavelength almost equal to the electrode cycle length L1 or L2.
Interdigital transducers Q that generate surface acoustic waves_i-1And Q_{i -2}From
It can be output as an air signal. Ultrasonic transmitter and receiver
Interdigital electrode P in the step_iAnd interdigital transducer group Q_iTo
Make sure that the electrode fingers with smaller electrode cycle lengths are inside each other
, That is, the distance between the electrodes should be small.
Suppresses the attenuation of surface acoustic waves excited on the plate surface Z1.
You can This is because the smaller the electrode cycle length, the higher the circumference.
The surface acoustic wave of the wave is excited on the plate surface Z1 and
This is to solve the problem that surface waves are more easily attenuated.
It

A structure having a display screen of a display device for displaying at least one kind of color on the other plate surface Z2 of the piezoelectric plate is adopted, and the frequency of the electric signal input to the interdigital transducer P _i and the display screen. By adopting a structure in which the colors are associated with each other, it becomes possible to input the information separately coded by switching the frequency to the same location on the display screen. That is, it is possible to input color-coded information for each frequency by touching the above-mentioned location on the plate surface Z1 for each frequency. Therefore, the amount of information to be input is also increased. By adopting a structure in which the information of the shape corresponding to the contact position of the plate surface Z1 is displayed on the display screen for a predetermined time, for example, a character is softer than the piezoelectric plate and easily absorbs ultrasonic waves. Z1
When drawn on, the character can be displayed on the display screen. By directly writing characters, symbols, and other information on the plate surface Z1 in this manner, not only the information can be input but also an image can be displayed on the display screen.

As the piezoelectric plate, a translucent piezoelectric ceramic such as La-added zircon / lead titanate (PLZT) porcelain is used, and a structure in which the polarization axis direction of the piezoelectric ceramic and the thickness direction are parallel to each other is adopted. As a result, surface acoustic waves can be efficiently excited on the piezoelectric plate. Also, by adopting an almost transparent structure as the piezoelectric ceramic,
The information appearing on the display screen can be seen from above the plate surface Z1. In order to propagate the surface acoustic wave to the plate surface Z1 of the piezoelectric plate, the thickness of the piezoelectric plate is the interdigital electrodes P _i , Q _i-1 and Q.
It is desirable that it is three times or more the electrode period length of _i-2 . If the thickness of the piezoelectric plate is smaller than the electrode period length and is thin, the Lamb wave propagates, but if there is a mode that can function as a touch panel, the Lamb wave can also be used. As the piezoelectric plate, LiNb is used in addition to the piezoelectric ceramic.
A single crystal of O ₃ , LiTaO ₃ or the like is considered. These single crystals are transparent and have piezoelectricity. Since it has anisotropy as a crystal, it requires a device at the design stage including the electromechanical coupling coefficient and may require an extra electronic circuit, but it is promising as a piezoelectric plate. Among piezoelectric ceramics, PLZT is promising as a piezoelectric plate because it is transparent and has excellent workability and durability. By using the in-plane isotropy of the plate surface Z1 of the piezoelectric plate made of PLZT, the surface acoustic wave between the interdigital transducer P _i and the interdigital transducer group Q _{i in} one ultrasonic wave transmitting / receiving means. In the case of adopting a structure in which the propagation path of the surface acoustic wave between the interdigital transducer P _i and the interdigital electrode group Q _i in another ultrasonic wave transmitting / receiving means are orthogonal to each other, The levels of the electric signals output to the electrode group Q _i and the other interdigital electrode group Q _i can be made substantially the same. Therefore, not only can the circuit structure be simplified and the device can be made smaller and lighter, but the output signals can be made uniform at all times, so that the signal processing is accurate and the sensitivity is improved. Furthermore, since the resolution is improved, the amount of information to be input can be increased.

[0018]

1 is a plan view showing an embodiment of an ultrasonic touch panel according to the present invention. In this embodiment, each electrode crossing width is 5 m
m 14 sets of interdigital electrodes, each electrode crossing width is 0.8 mm
56 sets of interdigital electrodes, piezoelectric plate 1, and display screen 2
Consists of. However, in FIG. 1, only T1, T2, T3 and T4 are drawn for the interdigital electrodes having the electrode crossing width of 5 mm, and R11, R12, R13 and R14 for the interdigital electrodes having the electrode crossing width of 0.8 mm. , R21, R22, R23, R2
Only 4, R31, R32, R33, R34, R41, R42, R43 and R44 are depicted. Also, the display screen 2 is not drawn in FIG. Piezoelectric plate 1 has a length of 50 mm and a width of 40 m
m, thickness 0.5mm, 128 ° rotation Y-cut X-propagation Li
Consists of NbO3. Each of the interdigital electrodes is made of an aluminum thin film. The display screen 2 is provided on the other plate surface of the piezoelectric plate 1. The display screen 2 forms part of the display device. Each of the interdigital electrodes is of a regular type having an electrode period length of 160 μm and 7.5 pairs of electrode fingers.

FIG. 2 is a plan view showing the interdigital electrodes T1, T2, R11 to R14 and R21 to R24 in the ultrasonic touch panel of FIG. Interdigital electrodes T1 and T2 and R11
.About.R14 and R21 to R24 oppose each other. Similarly, the interdigital electrodes T3 and T4 and R31 to R34 and R41 to R44 are also in a relationship of being opposite to each other. The interdigital electrodes T1, T2, T3 and T4 are used for input. Interdigital electrodes R11 to R14, R21 to R24, R31 to R34
And R41 to R44 are used for output. The interdigital electrodes R11 to R14 correspond to the interdigital electrodes T1, the interdigital electrodes R21 to R24 correspond to the interdigital electrodes T2, the interdigital electrodes R31 to R34 correspond to the interdigital electrodes T3, and the interdigital electrodes R41 to R41. R44 corresponds to the interdigital electrode T4. In this way, the ultrasonic touch panel of FIG. 1 is arranged in such a manner that four sets of interdigital electrodes having an electrode crossing width of 0.8 mm are opposed to one set of interdigital electrodes having an electrode crossing width of 5 mm. ing.

FIG. 3 is a cross-sectional view of the ultrasonic touch panel of FIG. 1, showing the relationship between the input interdigital electrode and the output interdigital electrode.

FIG. 4 is a plan view showing an embodiment of interdigital electrodes used in place of the interdigital electrodes used in the ultrasonic touch panel of FIG. The interdigital electrode is a normal type electrode having an electrode cycle length of 178 μm and 5 pairs of electrode fingers and an electrode cycle length of 160 μm and 5 pairs of electrode fingers. When used, the electrode fingers having an electrode period length of 160 μm are arranged inside each other. This is because the high frequency surface acoustic wave is excited on the piezoelectric plate 1 as the electrode period length is smaller, and the higher frequency surface acoustic wave is more likely to be attenuated. In this way, the smaller the electrode cycle length, the smaller the propagation path length of the surface acoustic wave (that is, the distance between the electrodes).

FIG. 5 is a configuration diagram when the ultrasonic touch panel of FIG. 1 is driven using rf pulses. 6 is shown in FIG.
FIG. 6 is a waveform chart in each part of the configuration diagram of FIG. When the ultrasonic touch panel of FIG. 1 is driven, the continuous waves generated by the signal generator are generated by the double balanced mixers (DBM) 1 and D.M. B. M. 2 in r
f pulses are modulated into -1 and -2. D. B.
M. 1 and D.I. B. M. 2 plays a role of switching, and applies an rf pulse to the interdigital electrodes T1 and T3 (hereinafter referred to as T1 group) or an rf pulse to the interdigital electrodes T2 and T4 (hereinafter referred to as T2 group). There is. R for T1 group interdigital transducer
When the f pulse is applied, only the rf pulse having a frequency substantially corresponding to the electrode period length of the interdigital transducer of the T1 group is converted into a surface acoustic wave and propagates through the piezoelectric plate 1. Interdigital electrodes R of surface acoustic waves propagating through the piezoelectric plate 1.
Only surface acoustic waves having wavelengths substantially equal to the electrode period lengths indicated by 11 to R14 and R31 to R34 are converted into delayed electric signals and output from the interdigital electrodes R11 to R14 and R31 to R34 (hereinafter referred to as R1 group). . When an rf pulse is applied to the interdigital electrodes of the T2 group, r having a frequency substantially corresponding to the electrode period length of the interdigital electrodes of the T2 group.
Only the f pulse is converted into a surface acoustic wave and propagates through the piezoelectric plate 1. Of the surface acoustic waves propagating through the piezoelectric plate 1, only the surface acoustic waves having a wavelength substantially equal to the electrode period length indicated by the interdigital electrodes R21 to R24 and R41 to R44 are converted into delayed electric signals and the interdigital electrodes R21 to R21. It is output from R24 and R41 to R44 (hereinafter referred to as R2 group). In this way, by alternately inputting the electric signals to the interdigital electrodes of the T1 group and the T2 group, the delayed electric signals can be alternately output to the interdigital electrodes of the R1 group and the R2 group. Interdigital electrodes R11, R21, R
12 and R22, R13 and R23, R14 and R24, R31 and R41, R32
And R42, R33 and R43, and R34 and R44, respectively, not only simplifies the circuit configuration, but also makes two pairs of interdigital electrodes R11 and R21, R12 and R22, R13 and R.
23, R14 and R24, R31 and R41, R32 and R42, R33 and R4
3, and the delayed electrical signals of R34 and R44 are received in duplicate. Therefore, if the propagation path of the surface acoustic wave propagating to the piezoelectric plate 1 is contacted when an electric signal is input to the interdigital electrode of the T1 group, when the electric signal is input to the interdigital electrode of the T1 group, The surface wave corresponding to the contact position is attenuated only. Similarly, when the propagation path of the surface acoustic wave propagating to the piezoelectric plate 1 is contacted when an electric signal is input to the interdigital electrodes of the T2 group, the electric signal is input to the interdigital electrodes of the T2 group. Only occasionally, the surface wave corresponding to the contact position is attenuated. Such delayed signals and are amplified and rectified to become DC signals and, respectively. Piezoelectric plate 1
A digital signal is obtained in the comparator by setting an appropriate threshold voltage value between the DC voltage values corresponding to the case of contact with and the case of non-contact with. This digital signal is taken into the computer as a parallel signal at an appropriate timing by the computer.

FIG. 7 is a block diagram showing a case where the ultrasonic touch panel of FIG. 1 is driven by forming a delay line oscillator. Waveform diagrams in the respective portions of the configuration diagram of FIG. 7 are similar to those shown in FIG. In FIG. 7, the interdigital transducer T1
And R11 or T2 and R21 as a first delay element, and a second delay element between the interdigital electrodes T3 and R31 or T4 and R41 as a second delay element. A delay line oscillator having a loop is formed. When the ultrasonic touch panel of FIG. 1 is driven, the switches 1, 2, 3 and 4 are operated by a command from the computer. When switches 1 and 3 (hereinafter referred to as S1 group) are closed, switches 2 and 4 (hereinafter referred to as S2 group) are open. By thus opening and closing the switches of the S1 group and the S2 group, electric signals are alternately input to the interdigital electrodes T1 and T3 (hereinafter referred to as T1 group) and the interdigital electrodes T2 and T4 (hereinafter referred to as T2 group). is doing. The electrical signal input to the T1 group or the T2 group is modulated into rf pulses -1 and -2 by clock pulse -1 or -2 from the computer, respectively. When the switch of the S1 group is closed, an electric signal is sent to the interdigital electrodes of the T1 group
When 1 is input, only an electric signal having a frequency substantially corresponding to the electrode period length of the interdigital transducer of the T1 group is converted into a surface acoustic wave and propagates through the piezoelectric plate 1. Of the surface acoustic waves propagating through the piezoelectric plate 1, the interdigital electrodes R11 to R14.
And only surface acoustic waves having a wavelength substantially equal to the electrode period length of R31 to R34 are converted into delayed electric signals and the interdigital transducer R
11 to R14 and R31 to R34 (hereinafter referred to as R1 group)
Is output from. Switch of S2 group is closed and T2
When the electric signal -2 is input to the interdigital transducer of the group, only the electric signal having a frequency substantially corresponding to the electrode period length of the interdigital transducer of the T2 group is converted into the surface acoustic wave and propagates through the piezoelectric plate 1. . Of the surface acoustic waves propagating through the piezoelectric plate 1, the interdigital electrodes R21 to R24 and R41 to R
Only surface acoustic waves having a wavelength substantially equal to the electrode cycle length of 44 are converted into delayed electric signals and output from the interdigital electrodes R21 to R24 and R41 to R44 (hereinafter referred to as R2 group). In this way, by alternately inputting the electric signals to the interdigital electrodes of the T1 group and the T2 group, the delayed electric signals can be alternately output to the interdigital electrodes of the R1 group and the R2 group. Interdigital electrodes R11 and R21, R12 and R22, R13 and R23, R14 and R2
4, R31 and R41, R32 and R42, R33 and R43, and R34
And R44 are respectively connected, the circuit structure is not only simplified, but also two sets of each of the interdigital transducers R11 and R21,
R12 and R22, R13 and R23, R14 and R24, R31 and R41, R
Delayed electrical signals of 32 and R42, R33 and R43, and R34 and R44 are received in an overlapped form. However, a part of the electric signals output from the interdigital electrodes R11 and R21 of the two interdigital electrodes and the interdigital electrode R31.
A part of the electric signals output from R41 and R41 is amplified by the amplifier A and the amplifier B, respectively, and is controlled to a predetermined phase by the respective phase shifters, and then S
It is again input to the interdigital electrodes of the T1 group and the T2 group via the switches of the 1st group and the S2 group. That is, the electric signal input to the interdigital transducer T1 or T2 via the switch 1 or 2 is input to the interdigital transducer T3 or T4 after passing through the amplifier A and then the switch 3 or 4. In addition, the electric signal input to the interdigital transducer T3 or T4 via the switch 3 or 4 passes through the amplifier B, and then the switch 1 or 2
Is then input to the interdigital transducer T1 or T2. In this way, a delay line oscillator having an 8-shaped signal loop is formed. By the way, each of two sets of interdigital electrodes R11 and R21, R12 and R22, R13 and R23, R14.
And R24, R31 and R41, R32 and R42, R33 and R43, and R34 and R44 are attenuated (or) by contacting the piezoelectric plate 1. A propagation path of a surface acoustic wave propagating through the piezoelectric plate 1 when an electric signal is input to the interdigital electrodes of the T1 group (between the interdigital electrodes T1 and R11 to R14 and the interdigital electrodes T3 and R31 to
Contact with a material that is softer than the piezoelectric plate 1 and more likely to absorb ultrasonic waves, the surface wave corresponding to the contact position is attenuated only when an electric signal is input to the interdigital transducer of the T1 group. To do. Similarly, the propagation path of the surface acoustic wave propagating through the piezoelectric plate 1 when the electric signal is input to the interdigital transducer of the T2 group (the interdigital transducer T2
And R21 to R24 and the interdigital electrodes T4 and R41 to R4
4)), the surface wave corresponding to the contact position is attenuated only when an electric signal is input to the interdigital electrodes of the T2 group. Such a delayed signal,
And are amplified and rectified to become DC signals and, respectively. By setting an appropriate threshold voltage value between the DC voltage values corresponding to the case where the piezoelectric plate 1 is contacted and the case where the piezoelectric plate 1 is not contacted, a digital signal is obtained in the comparator. This digital signal is taken into the computer as a parallel signal at an appropriate timing by the computer. This delay line oscillator driving method does not require a pulse generator, so r shown in FIG.
The device can be further downsized, the power consumption can be reduced, and the voltage can be reduced as compared with the case of driving using the f pulse.

When the ultrasonic touch panel of FIG. 1 is driven, color-coded information corresponding to the contact position appears on the display screen 2 of the display device according to a command from the computer. Moreover, a system is incorporated in which the frequency of the electric signal input to the interdigital electrodes of the T1 group or the T2 group corresponds to the color thereof. The information on the display screen 2 can be seen through the piezoelectric plate 1. In this way, when the propagation path of the surface acoustic wave propagating through the piezoelectric plate 1 is contacted, the surface acoustic wave propagating along the propagation path is attenuated or disappears, and accordingly, the display screen 2 corresponds to the contact position. Then, color-coded information appears. Moreover, by performing the operation of switching the frequency of the electric signal to be inputted, the piezoelectric plate 1 at the same position is brought into contact with the display screen 2 to input information in the same position on the display screen 2 in the number of colors corresponding to the type of frequency. It becomes possible to do. That is, if two kinds of frequencies are used, it is possible to input information that is color-coded with two kinds of colors at the same position. In addition, if you introduce a system that displays information in the form corresponding to the contact position on the display screen for a predetermined time,
For example, when a character or the like is drawn on the piezoelectric plate 1 with a fingertip, the character can be displayed on the display screen 2. When the interdigital transducer of FIG. 4 is used in the ultrasonic touch panel of FIG. 1, there are two types of electrode cycle lengths of the interdigital transducer and the difference between the respective values is large. It is possible to increase the difference between the frequency values of the two types of electric signals generated. Moreover, since the frequencies of the electric signals to be input can be further subdivided into several types in correspondence with the electrode period lengths of the respective types, as a result, the types of frequencies of the electric signals to be input can be further increased.

FIG. 8 is a circuit diagram showing an embodiment of amplifiers A and B in the delay line oscillator shown in FIG.

FIG. 9 is a characteristic diagram showing an oscillation spectrum in the delay line oscillator shown in FIG. fo represents the fundamental wave and is 24.3 MHz. It can be seen that stable oscillation is obtained.

FIG. 10 is a characteristic diagram showing a relationship between loss and phase with respect to frequency in the delay line oscillator shown in FIG.

[0028]

According to the ultrasonic touch panel of the present invention,
By adopting the structure in which the interdigital electrode P _i is used for input and the electric signal is input from the interdigital electrode P _i, it is possible to excite the surface acoustic wave on the plate surface Z1 of the piezoelectric plate. Moreover, the surface acoustic wave can be efficiently generated with low power consumption and low voltage on the plate surface Z
Can be excited to 1.

The interdigital transducers Q _i-1 and Q _i-2 are used for output, and each of the interdigital transducers Q _i-1 and Q _i-2 transmits / receives a surface acoustic wave to / from the interdigital electrode P _i . By adopting a structure in which the directional axes are arranged in common, the surface acoustic wave excited on the plate surface Z1 can be efficiently output as an electric signal. The propagation path of the surface acoustic wave on the plate surface Z1 (that is, between the interdigital electrodes P _i and Q _i-1 and between P _i and Q _i-2 ) is excited by the object and excited on the plate surface Z1. Since the generated surface acoustic wave disappears or attenuates, the electric signals output to the interdigital electrodes Q _i-1 and Q _i-2 also disappear or attenuate. In this way, it is detected that the object has come into contact with the propagation path of the surface acoustic wave on the plate surface Z1. Moreover, the response time is short and the sensitivity is good.
The object needs to be a substance that is softer than the piezoelectric plate and easily absorbs ultrasonic waves, and a human finger or the like also has the characteristic. Further, the contact position can be specified by discriminating which of the interdigital electrodes Q _i-1 and Q _i-2 in which the output electric signal disappears or attenuates.

By adopting a structure for inputting an electric signal of at least one kind of frequency substantially corresponding to the electrode period length of the interdigital electrode P _i to the interdigital electrode P _i , the plate surface Z1 is made to have substantially the same electrode period length. It is possible to excite at least one surface acoustic wave having an equal wavelength. Also, the plate surface Z
The surface acoustic wave excited by No. 1 can be output as an electric signal from the interdigital transducers Q _i-1 and Q _i-2 according to its wavelength.

At least two ultrasonic wave transmitting / receiving means are provided on the plate surface Z1, and a propagation path of the surface acoustic wave between the interdigital electrode P _i and the interdigital electrode group Q _{i in} one ultrasonic wave transmitting / receiving means. , The plate surface Z by adopting a structure in which the propagation path of the surface acoustic wave between the interdigital transducer P _i and the interdigital transducer group Q _i in another ultrasonic wave transmitting / receiving means is orthogonal to each other.
The contact position in 1 can be specified more delicately. As the number of ultrasonic wave transmitting / receiving means increases, more detailed identification becomes possible.

The output terminals of the interdigital transducer Q _i-1 are electrically connected to each other at the connection point N1, and the interdigital transducer Q _i is connected.
By adopting the structure in which the respective output ends of _i-2 are electrically connected to each other at the connection point N2, it is possible to confirm that the object comes into contact with a part of the propagation path of the surface acoustic wave on the plate surface Z1. It can be detected from the magnitude of the electric signal appearing at the connection point N2. N switches S _i (i =) whose output ends are respectively connected to the input ends of the interdigital transducer P _i
1, 2, ..., N) and the structure in which the switches S _i are sequentially electrically interrupted at a predetermined cycle is used to sequentially input an electric signal to the interdigital transducer P _i. You can Therefore, when, for example, between the interdigital electrodes P ₁ and Q _{1-1 in} the propagation path of the surface acoustic wave on the plate surface Z1, the electrical signals are input to the interdigital electrode P ₁ . Only, the delayed electric signal output to the connection point N1 is attenuated or disappears. In this way, the contact position can be clearly specified.

By adopting a structure in which the respective input ends of the switches S _i are electrically connected to each other at the connection point NS, and the connection point N1 is electrically connected to the connection point NS via an amplifier, the interdigital electrodes are formed. Plate surface Z1 between P _i and Q _i-1
The surface acoustic wave propagation path D _i (i = 1, 2, ...,
Oscillator H _i (i = 1, 2, ..., N) as a delay element
N) can be configured. The signal loop of the oscillator H _i includes the interdigital electrode P _i , the propagation path D _i, and the interdigital electrode Q.
_It consists of _i-1 and an amplifier. In this way, since the circuit configuration is simplified, it is possible to further reduce the size and weight of the device, and it is possible to drive at low voltage with low power consumption.

The interdigital electrodes P _i , Q _i-1 and Q _i-2 each have at least two electrode period lengths L1 and L.
By adopting the structure having 2, the interdigital electrode P
An electric signal having a frequency substantially corresponding to the electrode cycle length L1 or L2 can be input to _i . Therefore, a surface acoustic wave having a wavelength substantially equal to the electrode period length L1 or L2 can be excited on the plate surface Z1. Further, surface acoustic waves having a wavelength substantially equal to the electrode period length L1 or L2 excited on the plate surface Z1 can be output as electric signals from the interdigital electrodes Q _i-1 and Q _{i -2} . Interdigital transducer P
_By arranging _i and the interdigital electrode group Q _{i such} that the electrode fingers having smaller electrode period lengths are inside each other, that is, the distance between the electrodes is small, the surface acoustic wave excited on the plate surface Z1 is generated. Attenuation can be suppressed.

A structure having a display screen of a display device for displaying in at least one color on the other plate surface Z2 of the piezoelectric plate is adopted, and the frequency of the electric signal input to the interdigital transducer P _i and the display screen. By adopting a structure in which the colors are associated with each other, it becomes possible to input the information separately coded by switching the frequency to the same location on the display screen. Therefore, the amount of information to be input is also increased. By adopting a structure in which the information of the shape corresponding to the contact position of the plate surface Z1 is displayed on the display screen for a predetermined time, for example, when a character is drawn on the plate surface Z1, the character is displayed on the display screen. be able to. By directly writing characters, symbols, and other information on the plate surface Z1 in this manner, not only the information can be input but also an image can be displayed on the display screen.

As the piezoelectric plate, a translucent piezoelectric ceramic such as La-added zircon / lead titanate (PLZT) porcelain is used, and a structure in which the polarization axis direction of the piezoelectric ceramic and the thickness direction are parallel to each other is adopted. As a result, surface acoustic waves can be efficiently excited on the piezoelectric plate. Also, by adopting an almost transparent structure as the piezoelectric ceramic,
The information appearing on the display screen can be seen from above the plate surface Z1. In order to propagate the surface acoustic wave to the plate surface Z1 of the piezoelectric plate, the thickness of the piezoelectric plate is the interdigital electrodes P _i , Q _i-1 and Q.
It is desirable that it is three times or more the electrode period length of _i-2 . If the thickness of the piezoelectric plate is smaller than the electrode period length and is thin, the Lamb wave propagates, but if there is a mode that can function as a touch panel, the Lamb wave can also be used. As the piezoelectric plate, LiNb is used in addition to the piezoelectric ceramic.
A single crystal of O ₃ , LiTaO ₃ or the like is considered. These single crystals are transparent and have piezoelectricity. Since it has anisotropy as a crystal, it requires a device at the design stage including the electromechanical coupling coefficient and may require an extra electronic circuit, but it is promising as a piezoelectric plate. Among piezoelectric ceramics, PLZT is promising as a piezoelectric plate because it is transparent and has excellent workability and durability. By using the in-plane isotropy of the plate surface Z1 of the piezoelectric plate made of PLZT, the surface acoustic wave between the interdigital transducer P _i and the interdigital transducer group Q _{i in} one ultrasonic wave transmitting / receiving means. In the case of adopting a structure in which the propagation path of the surface acoustic wave between the interdigital transducer P _i and the interdigital electrode group Q _i in another ultrasonic wave transmitting / receiving means are orthogonal to each other, The levels of the electric signals output to the electrode group Q _i and the other interdigital electrode group Q _i can be made substantially the same. Therefore, not only can the circuit structure be simplified and the device can be made smaller and lighter, but the output signals can be made uniform at all times, so that the signal processing is accurate and the sensitivity is improved. Furthermore, since the resolution is improved, the amount of information to be input can be increased.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of an ultrasonic touch panel of the present invention.

2 is a plan view showing interdigital electrodes T1, T2, R11 to R14 and R21 to R24 in the ultrasonic touch panel of FIG.

3 is a cross-sectional view of the ultrasonic touch panel of FIG.

FIG. 4 is a plan view showing an example of a comb-shaped electrode used in place of the comb-shaped electrode used in the ultrasonic touch panel of FIG.

FIG. 5 is a configuration diagram when the ultrasonic touch panel of FIG. 1 is driven by using an rf pulse.

FIG. 6 is a waveform diagram in each part of the configuration diagram of the ultrasonic touch panel of FIG.

FIG. 7 is a configuration diagram in the case where the ultrasonic touch panel of FIG. 1 is driven by forming a delay line oscillator.

8 is a circuit diagram showing an embodiment of amplifiers A and B in the delay line oscillator shown in FIG.

9 is a characteristic diagram showing an oscillation spectrum in the delay line oscillator shown in FIG.

10 is a characteristic diagram showing the relationship between loss and phase with respect to frequency in the delay line oscillator shown in FIG.

[Explanation of symbols]

1 Piezoelectric plate 2 Display screen T1, T2, T3, T4 Interdigital electrodes R11, R12, R13, R14, R21, R22, R23, R24
Interdigital electrodes R31, R32, R33, R34, R41, R42, R43, R44
Interdigital electrode

Claims (5)

[Claims] 1. An ultrasonic touch panel comprising at least two ultrasonic wave transmitting / receiving means on one plate surface Z1 of a piezoelectric plate, wherein said ultrasonic wave transmitting / receiving means has N sets of interdigital electrodes P _i (i =
1, 2, ..., N) and N sets of interdigital electrode groups Q _i (i = 1, 2, ...) Corresponding to the interdigital electrode P _i , respectively.
, N), and each of the interdigital electrode groups Q _i has at least two sets of interdigital electrodes Q _i-1 (i = 1, 2, ..., N) and Q _i-2.
(I = 1, 2, ..., N), and an electric signal of at least one kind of frequency substantially corresponding to the electrode period length of the interdigital transducer P _i is applied to the interdigital transducer P _i.
Means for exciting at least one type of surface acoustic wave having a wavelength substantially equal to the electrode period length on the plate surface Z1; and the means according to the wavelength of the surface acoustic wave excited on the plate surface Z1. Means for outputting electrical signals appearing on the interdigital electrodes Q _{i- 1} and Q _i-2 are provided, and the respective output ends of the interdigital electrodes Q _i-1 are electrically connected to each other at a connection point N1. The output terminals of the interdigital transducer Q _i-2 are electrically connected to each other at a connection point N2.
In is connected, means for inputting an electric signal to said interdigital electrode P _i is the N having an output connected to the input terminals of the interdigital electrode P _i switch S _{i (i} = 1,2 , ……, N),
A switch control means for electrically connecting and disconnecting the switches S _i sequentially and electrically in a predetermined cycle, between the interdigital transducer P _i and the interdigital transducer group Q _{i in} one ultrasonic wave transmitting / receiving means. The surface acoustic wave propagation path and the surface acoustic wave propagation path between the interdigital transducer P _i and the interdigital transducer group Q _i in another ultrasonic wave transmitting / receiving means are orthogonal to each other, The fact that an object contacts a part of the propagation path of the surface acoustic wave on the plate surface Z1 means that the connection point N1 and the connection point N
An ultrasonic touch panel characterized by sensing from the magnitude of an electric signal appearing in 2. 2. The switch S_iEach input end of
Are electrically connected to each other at a connection point NS, and the connection point N1
Is electrically connected to the connection point NS via an amplifier,  The interdigital electrode P_iTo the above-mentioned interdigital electrode Q_i-1Leading to
Propagation path D of the surface acoustic wave composed of the piezoelectric plate between_i(I =
Oscillator H with delay elements 1, 2, ..., N)_i(I =
1, 2, ..., N), and the oscillator H_iSignal loop of the interdigital transducer P_iWhen,
The propagation path D_iAnd the interdigital electrode Q_i-1And the amplification
The ultrasonic wave according to claim 1, characterized in that
Touch panel. 3. The interdigital electrodes P _i , Q _i-1 and Q.
There are at least _two electrode cycle lengths in _i-2, L1 and L2, respectively, and an electric signal having a frequency substantially corresponding to the electrode cycle length L1 or L2 is input to the interdigital transducer P _i , and the electrode cycle length is 3. The ultrasonic touch panel according to claim 1, further comprising means for exciting a surface acoustic wave having a wavelength substantially equal to L1 or L2 on the plate surface Z1. 4. A display screen of a display device for displaying in at least one color is provided on the other plate surface Z2 of the piezoelectric plate, and the display screen of the electric signal input to the interdigital electrode P _i is provided. 4. The ultrasonic touch panel according to claim 1, further comprising means for associating a frequency with the color. 5. The piezoelectric plate is made of a substantially transparent piezoelectric ceramic, and the direction of the polarization axis of the piezoelectric ceramic is parallel to the thickness direction of the piezoelectric ceramic. The ultrasonic touch panel according to item 4.