JPS6198433A - Tablet type coordinate input device using elastic wave - Google Patents

Abstract

PURPOSE:To attain high accuracy and high image resolution and to realize a natural handwriting action by making use of the transmission of a vertical elastic wave and therefore eliminating a specific area which produces an error input over a flat plate type medium part. CONSTITUTION:When the tip of a pen 3 has contact with an input flat plate 1, a vertical elastic wave is transmitted along the plate 1 and reaches piezoelectric elements 2a-2d set at four corner parts of the plate 1 with delay time of transmission accordant with the tip contact position of the pen 3. A pulser 4 applies a high voltage pulse to the pen 3 and also transfers a count start signal to a counter circuit 7. The signals detected by the elements 2a-2d are digitized by a waveform shaping circuit 6 and transferred to the circuit 7. Then the delay time of transmission is calculated in response to the distances between the pen 3 and the elements 2a-2d.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a tablet-type coordinate input device, and in particular detects the position coordinates of an input pen that draws a character, figure, etc. on a flat plate by counting the propagation delay time of an elastic wave. related to a device for

[Background of the invention]

Conventionally, this type of coordinate input device uses (i) air propagation method, (5) surface acoustic wave method, and (fit) board.
His method has been proposed. These are each
I II Transactions on Computers, June 1970, pp. 546-548 (IEEE
TRANSACTIONS ON COMPUTER5
, Jun, 1970゜pp546-548), I II Transactions on Electronic Computers, October 1964, 609
-Page 611 (IEEE TRANSACTIONS O
N HLECTRONIC COMPUTER8゜Oct
, 1964. pp609-611), and I
1981 Ultrasonic Symposium.

pp. 167-170 (IEEE 1981 ULTRAS
ONIC3YMPO3IUM, p p 167-17
0).

Since the method (i) is greatly affected by the surrounding environment such as temperature, it is necessary to correct it. In addition, since it is directly affected by obstacles such as hands, it cannot be used in the same way as normal handwriting, giving the user a sense of discomfort. The method (ii) also makes it impossible to accurately orient the position of the input pen when the user touches the tablet, giving the user a sense of discomfort. Although this method is suitable for a menu selection input device using finger touch,
There are difficulties in applying it to tablets that input figures.

The (fit) method does not have the drawbacks of the above two methods,
Normal handwriting is possible. An example of a transparent tablet that integrates a liquid crystal display device and an EL display device by applying this method is disclosed in Japanese Patent Laid-Open No. 56-101278.

and JP-A-58-14247. However, this method has difficulties in efficient and stable transmission and reception.

This is because plate waves have a slightly slower propagation speed than longitudinal elastic waves, so they cannot escape the influence of the longitudinal elastic waves that propagate first, and their phase changes as the propagation distance increases. Japanese Unexamined Patent Publication 1983
-101278 discloses an example using an acrylic plate. Since the acrylic plate is a low-sound velocity material, it has the advantage of being able to increase the single resolution, but because of its large attenuation constant, the method of accurately detecting the propagation time of the plate wave is complicated, and the size of the tablet is also naturally constrained.

[Purpose of the invention]

It is an object of the present invention to detect longitudinal acoustic waves with high precision, to have no specific area on the flat medium part that causes erroneous input, to have high precision and high resolution, and to be able to detect a natural wave on the flat medium part. An object of the present invention is to provide a tablet-shaped coordinate input device having a simple structure and capable of handwriting operations.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized by utilizing propagation of longitudinal elastic waves. Since longitudinal elastic waves have the fastest propagation speed, they arrive first between transmitter and receiver.

The present invention provides a flat medium section for propagating longitudinal acoustic waves, a longitudinal acoustic wave detecting section provided on a side surface or a part of the surface of an end of the medium section, and a flat plate having a sharp tip. a longitudinal elastic wave input member whose tip is freely crimped to an arbitrary position on the surface of the medium portion, and which emits a longitudinal acoustic wave from the tip; means for extracting an acoustic wave-compatible electric signal as localization information of the crimping position of the input member, the longitudinal acoustic wave detection unit is provided on a corner side surface of the flat medium portion, and the longitudinal elastic wave input member It is characterized in that the distal end portion and the flat medium portion are constructed of members having substantially equal sound image impedance.

Furthermore, the present invention uses piezoelectric elements as a part of the longitudinal acoustic wave input member and the longitudinal elastic wave detection section, and sets the resonance frequencies of the transmitting and receiving piezoelectric elements in an appropriate relationship, thereby improving efficiency. It is characterized by detecting the longitudinal elastic wave.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, 1 is an input flat plate made of a transparent member such as soda lime glass. The flat plate 1 has four corners cut off as shown in the figure, and piezoelectric elements 2a to 2d made of, for example, lead zirconate titanate are adhesively fixed to the side surfaces of these parts using an organic adhesive such as an epoxy resin. Ru.

On the other hand, in the figure, numeral 3 represents a ben for drawing characters 9, etc. by hand by touching the input plate 1 with its tip and inputting the trajectory into, for example, an electronic computer.
! FIG. 2 shows one corner of the input plate 1 and the input pen 3.
It is an enlarged view of. As shown in the figure, the piezoelectric element 2 has a cylindrical shape and is made of piezoelectric ceramics polarized in the thickness direction of the cylinder. Electrodes are provided on both bottom surfaces of the element 2, and one of the bottom surfaces is adhesively fixed to the corner side surface of the input flat plate 1. On the other hand, the input pen 3 has a conical tip 3b.
It consists of a piezoelectric element 3a and a handle 3c which are adhesively fixed to the bottom surface of the pen nib 3b. The element 3a also has the piezoelectric elements 2a to 2.
Like d, it has a cylindrical shape with electrodes on both bottoms, and is made of piezoelectric ceramics that has been polarized in the thickness direction of the cylinder. Electric signals are transmitted and received to and from the voltage ceramics 2 and 3 via lead wires 82 and 83, respectively.

In FIG. 1, in the input pen 3, a built-in piezoelectric element 3a vibrates when a high voltage pulse is applied from a pulser 4, thereby generating one elastic wave. The tip of the pen 3 is connected to the input plate 1.
When the elastic wave comes in contact with the input plate 1, the elastic wave propagates along the input plate 1, and the piezoelectric elements 2a installed at four corners of the input plate have a propagation delay time depending on the contact position of the tip of the input pen 3. ~2d, where it is converted into an electrical signal.

In an elastic wave type tablet, the performance is almost determined by counting the propagation delay time. In order to do this accurately, it is necessary to select the elastic wave mode to be used.

Efficient detection of elastic waves and highly accurate counting are essential. In the present invention, the first arriving wave of longitudinal elastic waves is detected by the efficient method described below, and the propagation is further determined by the method described below. counting time.

In FIG. 1, the balsa 4 applies a high voltage pulse to the input pen 3 and at the same time sends a counting start signal to the counting circuit 7.
Transfer to. This causes the counting circuit 7 to start counting the basic clocks. On the other hand, the elastic wave analog signals V-v4 detected by the piezoelectric elements 2a-2d are each amplified by an amplifier circuit 5 and digitized by a waveform shaping circuit 6. These digital signals D1 to D4 are transmitted to the counting circuit 7.
As a result, the counting of the basic clock described above is completed, and the input pen 3 is transferred to the piezoelectric elements 2a to 2d.
The propagation delay time is counted according to the distance.

The amplifier circuit 5 may be a commonly used high-frequency amplifier circuit, and the waveform shaping circuit 6 may be an ordinary comparator IC that inputs a certain threshold value to one side and digitizes the analog signal by comparing the signal level with this.
A circuit consisting of is fine.

By the way, FIG. 3(a) schematically depicts a situation in which elastic waves are radiated from the input pen 3 to the input flat plate 1 and propagate through the input flat plate 1.

As shown in the figure, when a high voltage pulse v2 from the pulser is applied to the piezoelectric element 3a built in the input pen 3, the inside of the conical pen tip 3b to which the bottom surface of the element 3a is glued The piezoelectric element 3a has a cylindrical shape.
Vibration components in the thickness direction and radial direction propagate simultaneously. When the input plate 1 having such a vibration component is brought into contact with the input plate 1, the vibration component is mode-converted and radiated into the input plate 1, and becomes a longitudinal wave component and a transverse wave component as shown in the figure. Elastic waves, which are a mixture of both, and plate waves caused by deformation of the sheet metal body propagate in a complex manner. However, these waves have different propagation speeds,
As shown in Figure (b), the plate wave arrives slightly later than the longitudinal elastic wave, and the transverse wave has a speed of only about 172 times that of the longitudinal wave.

Therefore, the first elastic wave to arrive is a pure longitudinal elastic wave with no other modes mixed in, and if this can be detected efficiently, the coordinate location accuracy will improve. However, since the amplitude of the longitudinal elastic wave is very small compared to the transverse wave component, it is necessary to increase the incidence efficiency from the input pen 3 to the input flat plate 1, and the first arrival of the longitudinal elastic wave How to accurately detect waves is important. Incidentally, the phase of the portion where the plate waves are superimposed shifts as the distance between the input pen 3 and the piezoelectric elements 2a to 2d increases. Furthermore, the amplitude of the superimposed portion of the transverse wave components changes in a complicated manner. On the other hand, in the case of only the longitudinal elastic wave, the piezoelectric element 2° to 2 d k, Aj'
””′3k(7)j! [[,xrb・0! No complicated amplitude changes are observed except for the effect of attenuation.

Furthermore, since the longitudinal elastic waves propagate inside the input flat plate 1, even if the flat plate 1 is touched, it is hardly affected by it.

Now, FIG. 4 shows the internal structure of the counting circuit 7 shown in FIG. 1, and FIG. 5 shows a time chart of the various signals shown in FIG. 4.

In FIG. 1, the propagation time T counted by the counting circuit 7
1 to T4 are transferred to the microcomputer 8, where the (x, y) coordinates are calculated and output to an external device. In FIG. 1, the (x, y) coordinate signal output from the microcomputer 8 is transferred to the liquid crystal drive circuit 9, and the liquid crystal display bag [ It is driving 10. Thereby, characters and figures handwritten with the input pen 3 can be input while checking them on the display directly below.

In FIG. 4, the counting circuit 7 includes a start pulse generation circuit 11, a WF generation circuit 12, a data detection circuit 13,
Oscillator 14. Counter 15, data select 16, register 17. and a multiplexer 18.

The start pulse generation circuit 11 receives a start signal (ST) from the pulser 4 and the microcomputer 8
) and the reset signal (RE) are transferred, from here,
The start pulse ST signal is transferred to the WE signal generation circuit 12 and data detection circuit 13. On the other hand, the output signals D1 to D4 of the waveform shaping circuit 6 are transmitted to the data select circuit 1.
6 is checked in the data detection circuit 13 via the start pulse ST, and transferred as a counting end signal to the counter 15 which starts counting the basic tally pulses CP generated from the oscillator 14 by the start pulse ST. Count numbers T1 to T4 of basic clocks corresponding to data signals D to D4 are stored in registers T1 to T4, respectively, and data switching signals DS are transferred from the microcomputer 8.

DS is input as data corresponding to the propagation delay time to the piezoelectric elements 28 to 2d via the multiplexer 18.

In the data detection circuit 13, the WE signal generation circuit 12 does not generate the WE multiplied signal unless all of the data signals D1 to D4 are present.

As shown in FIG. 5, the WE double signal is generated after a time t delay after sT□ is transferred, and when the WE double signal is transferred to the microcomputer 8, the data signal T~T4 of the input pen is generated. Start calculating the (X, y) coordinates. Therefore, if even one of D□ to D4 is missing, the remaining three data will be ignored as abnormal data and will not be used in coordinate calculations. This phenomenon may occur when the input pen is moved up or down. The above method prevents malfunctions at that time.

If the (xty) coordinate calculation in the microcomputer 8 is completed within the time period of the repetition period .tau. of the start pulse ST, the input speed in the tablet-type input device that varies according to the period .tau. is determined. Therefore, in order to improve the input speed, it is necessary to shorten the coordinate calculation time t1 as shown in Fig. 3 (
It is necessary to reduce the ringing of elastic waves shown in b). Furthermore, the time t from the ST operation to the WE generation is limited by the clock frequency f8 of the oscillator 14, the dimensions of the input flat plate 1, and the propagation speed c2 of the longitudinal elastic wave. Since the resolution of the tablet is determined by the ratio between the clock frequency f6 and the propagation velocity C2, settings must be made that take these into account.

An effective method for reducing the ringing of the elastic waves is to cover the peripheral side surface of the input flat plate 1 with an elastic wave absorbing member such as a rubber material. On the other hand, the reduction in the calculation time will be described in detail later.

FIG. 6 shows how a start pulse ST and a high voltage pulse are emitted from the pulser 4 until the longitudinal elastic wave propagating through the input flat plate 1 first reaches any one of the piezoelectric ceramics 2a to 2d. A method for detecting time T is shown. As shown in FIG. 6(a), the analog output waveform V of the longitudinal elastic wave that reaches the piezoelectric ceramic is amplified by the amplifier circuit 5, and then digitally output by the waveform shaping circuit 6 with a certain threshold as a reference. The counting circuit 7 detects the time from the start pulse ST to the first pulse of the digital output. However, the analog output V of the elastic wave varies with respect to a certain threshold value due to the writing pressure of the input pen 3, etc. in FIG.
). The most extreme case of this change corresponds to an instantaneous change in which the input pen 3 moves up (non-contact) and down (contact) with respect to the input plate 1.

At this time.

There are cases where the amplitude level of the first longitudinal acoustic wave that reaches a certain amount is low, resulting in malfunction. This countermeasure can be processed by the software of the microcomputer 8. However, it is desirable that the waveform change shown in FIG. 6(b) can be corrected by hardware up to the counting circuit. In the present invention, the correction is performed using a method that focuses on the time to the peak value of the waveform. That is, as the analog waveform changes from V' to v-v' for a certain value, the time until digital output changes to T.
1 to T-T', but in either case, the time to the peak value of the analog waveform remains the same and remains at a constant value T+
becomes α. Therefore, the time T when the waveform exceeds the threshold when rising
If you count the time T2 exceeding the threshold when descending from □ and define the propagation time using the value (T□+T)/2, you can achieve highly accurate time detection that is not affected by waveform fluctuations due to pen pressure, etc. I can do it. In the present invention, this is implemented by the method shown in FIG. This method eliminates the need to count T and T2 twice in order to determine one propagation time as described above. That is, in FIG. 7, the counter A counts T1 and stores it in a register. And from T1 to T
The clock of the oscillator stored in the counter A is divided into 1/2, and this is counted by the counter B via the gate circuit, added to the value of the register, and transferred to the multiplexer. do. With this method, the time to the middle of the pulse width of the digital output is counted.

The calculation time for determining the (xty) coordinates is reduced by the following method.

In FIG. 8, 81 to S are the positions of piezoelectric elements,
The point P (xt y) is the desired position of the input pen. S
1S, = a, s1s, = b, the propagation velocity of the longitudinal elastic wave is V
, then according to the delay times t1 to t4 shown in FIG.

Or.

The coordinates of point P (x+y) are found.

Locus II (
For example, the method for locating
On page 2 of issue 07, although the relationship between the wave source and the detector is reversed,
The mathematical method is described, and the formula is as follows: +VF can be regarded as a constant except for long-term gradual changes such as temperature effects, so there is no need to calculate it every time.

In the conventional example, as shown in Equation (7), a square root operation that takes a long processing time is included, so there are significant restrictions when the number of digits in the operation is increased. The above formula (1).

When calculating using equations (6) and (7), 5 additions and subtractions, 9 multiplications, 4 times, and 1 square root calculation are required. The calculation accuracy is 0.1%, that is, 10 bits, and in order to reduce the number of processing steps for 1 multiplication and square root calculation, a logic dedicated to 8-bit calculations is provided for multiplication, and an 8-bit conversion table is provided for square root calculation, and each of the remaining 2 bits is Consider the case of interpolation calculation. At this time, 10-bit addition and subtraction takes at most 3 steps, while multiplication takes about 50 steps.

Square root calculation requires approximately 125 steps 6. Therefore, 1
In the conventional example, approximately 340 steps are required to obtain one coordinate point.

On the other hand, in the present application, for example, when calculating with equations (1), (2), and (3), there are 6 additions and subtractions and 4 times 2 multiplications, which is about 218
Since only one step is required, the number of steps can be reduced to approximately two-thirds of that of the conventional example. It is obvious that the effect becomes even greater when the number of digits in the calculation increases.

In this application, three detection points are required compared to the conventional two,
The cost of the detection element, amplifier circuit, etc. increases accordingly. However, other functions can be realized by increasing the number of detection points.

When the propagation speed of the longitudinal elastic wave changes due to the influence of ambient temperature, etc., it is possible to calculate the correction coefficient using the free calculation time.In the case of the glass plate used in this application, 25
With respect to a temperature change of ±25°C, the propagation speed of longitudinal elastic waves changes by about ±5%.

For example, if the speed increases, applying the default values will result in shorter distance measurements, resulting in orientation errors.

An example of this compensation method is the detection point S in FIG.

S2, the value of X obtained at the wave source P, X□2, and the detection point S□.

Difference between the value of X13 obtained by Sl and wave gp l X1l-X
□, 1 is monitored and if the propagation speed changes,
It is sufficient to memorize the velocity value when the value of l xx2- Since it is several minutes/°C at most, it is sufficient to perform the correction calculation once every few minutes, and the orientation of the coordinate position will not be greatly affected.

As described above, by adding one detection point compared to the conventional system, the means for measuring the temperature of the propagation medium 1 can be omitted, thereby avoiding an increase in the price of the coordinate input device as a whole.

Note that although the above example has been explained based on orthogonal coordinates, it can also be applied to other coordinate systems such as polar coordinates.

It is also clear that this method can be applied to cases where the lines connecting the three detection points are not orthogonal.

Furthermore, in the present application, by providing a fourth detection point S4, it is possible to expand the correction function by software that can improve the accuracy of such a tablet.6For example, the above (1)
), (2) and (3), (x, y) is (X engineering,
Cx, y obtained using formulas (1), (4), and (5)
) is (Xz+yz), and the difference between X□ and x2 and yl and y
If the difference between 2 and 2 is not less than the allowable value, it is not adopted as the coordinate value, thereby preventing the output of a coordinate error signal when an error occurs in counting the propagation time.

Incidentally, the present inventors have stated that the frequency of the longitudinal elastic wave propagating through the input flat plate 1 is approximately equal to the frequency of the radial vibration component of the piezoelectric element 3a propagating through the conical pen tip 3b of the input pen 3. I found out the truth. According to this new fact, the piezoelectric element 3a adhered to the input pen tip 3b
The elements 2 and 3a are adjusted so that either the thickness direction resonance frequency or the radial direction resonance frequency of the piezoelectric element 2 bonded to the side surface of the input flat plate 1 matches the radial resonance frequency of the input flat plate 1.
By designing and matching the acoustic impedances of the piezoelectric element 3a and the input flat plate 1, a stable longitudinal waveform having an amplitude sufficient to count the propagation delay time was obtained.

j By the way, since the tip of the input pen has a pointed shape, the radiated energy density of elastic waves becomes extremely high, and acoustic impedance matching seems unnecessary, but research by the present inventors has revealed that Impedance matching cannot be ignored. Therefore, the present invention was provided.

For example, the acoustic impedance of two types of materials A and B that come into contact is 2. ．． Assuming 2%, when an elastic wave is incident on material B from a piezoelectric element attached to a person via the person, the reflectance of the elastic wave that is reflected by the person without being incident on material B is expressed by the following formula. Ru.

Based on this formula, the reflectance with respect to various human resources when soda lime glass is used as the B material is shown in FIG. It can be seen that the incidence rate to material B is much lower in acrylic than in cases where the personnel are made of glass or aluminum.

Fig. 11 shows the structure shown in Fig. 2, using various personnel at the tip of the input pen 3b, and applying pressure (
Voltage value vL of the longitudinal elastic wave received by the piezoelectric element 2 attached to the side surface of the input flat plate 1 when the electric element 3a is excited and the elastic wave is incident on the input flat plate 1 made of soda lime glass.
shows. According to FIG. 11, it can be seen that longitudinal elastic waves are received with a magnitude proportional to the incidence rate on material B shown in FIG.

As a specific example, when the piezoelectric elements 2 and 3b are both made of piezoelectric ceramics made of titanium and lead zirconate, the elastic wave propagating through the flat plate 1 has a power of several 100 k.
Longitudinal elastic waves with a frequency of Hz were stably obtained.

Further, when the input flat plate 1 is made of soda lime glass, as is clear from FIG. 10, it is preferable to use glass or aluminum as the pen nib 3b.

According to the present invention, the longitudinal waves propagating through the input flat plate 1 described above are obtained almost uniformly on the surface of the input flat plate 1, excluding attenuation due to distance, that is, the amplitude of the longitudinal waves is 3 and the solid-state vibrating element 2 or 2a to 2d, the piezoelectric element is made of a piezoelectric ceramic or the like, and the piezoelectric element is made of a piezoelectric ceramic or the like. is when it is attached to the side of the input flat plate 1.

Due to the influence of directivity, even if an elastic wave is emitted from a position equidistant from the element, the amplitude of the detected waveform at the element will not necessarily be the same. Figure 12 shows this schematically as a distribution of sensitivity. 1 is an input flat plate, and 2 is a piezoelectric element bonded to the side surface of the input flat plate.

As shown, according to the sensitivity distribution 10, the piezoelectric element 2
The direction perpendicular to is the most sensitive, and this is the direction of the main axis of directivity. Further, 9a and 9b show a sensitivity distribution called a side rope.

FIGS. 13 and 14 show the sensitivity distribution when the main axis of directivity of the piezoelectric element 2 attached to the side surface of the input flat plate 1 is not directed toward the center of the input flat plate 1, and when the main axis of the directivity of the piezoelectric element 2 is oriented toward the center of the input flat plate 1. These are the measurement results.

vo, v2... are amplitude voltages of the detected waveform. As shown in the figure, in the example shown in FIG. 13, points P and Q, which are equidistant from the element 2, do not have the same amplitude value, but each have Vu+V@(vi>>'vc). In this embodiment, the signal processing circuit 5 shown in FIG.
After amplifying the output waveform, a comparison is made with a certain threshold voltage, and a counting end signal is sent to the counting circuit 6. therefore,
In the example of Fig. 13, as shown in Fig. 15, the waveform at point P is 12a1 and the waveform at point Q is 12a1, despite the same distance.
2b, the delay times are T, ,T,
, and incorrect positioning is performed.

On the other hand, in the case of FIG. 14, which is an example of the present invention, as shown in the figure, the amplitude changes only due to a change in the distance.
Unlike the example shown in FIG. 13, there is no specific area where erroneous input occurs, and the position can be detected with high accuracy.

Furthermore, when the reception piezoelectric element 2 is installed on the surface of the glass plate 1 as shown in FIG. 16, it is more effective to use the radial resonance frequency of the reception piezoelectric element 2. This method is particularly effective when the glass plate 1 is thin.

In both cases, the piezoelectric element used has a thickness of 4
The larger the difference between the resonant frequencies in the radial direction and the radial direction, the more effective it is.If the two frequencies are close, the predetermined resonant frequency cannot be obtained in either direction due to interference between them.

〔Effect of the invention〕

According to the present invention, since the longitudinal waves propagating within the input plate are utilized, even if a hand touches the input plate, the input pen can be operated in a normal handwriting motion without being affected by the hand.

In addition, since the incidence efficiency and transmission/reception efficiency of elastic waves can be improved,
Longitudinal elastic waves can be detected with high precision, and since there are no specific areas on the flat plate that can cause incorrect input, the input pen can be positioned at any position on the input flat plate with high precision.

Can be detected with high resolution.

Furthermore, since the input flat plate can be made of a transparent member,
An input-integrated display can be easily implemented.

[Brief explanation of the drawing]

Fig. 1 is an embodiment of the present invention, Fig. 2 is a partially enlarged view thereof, Fig. 3 is a schematic diagram of elastic wave propagation, Fig. 4 is a schematic diagram explaining the counting circuit of Fig. 1, and Fig. 5 is a Figure 4 is a schematic diagram explaining the operation of (Figure 6 is a diagram explaining the method of detecting elastic waves, Figure 7 is a diagram explaining improvements to the counting circuit, and Figure 8 is a diagram explaining the method of determining the coordinates of the input pen. An explanatory diagram, Fig. 9 is an explanatory diagram of the delay time, Fig. 10 is a schematic diagram explaining the acoustic characteristics of the material, Fig. 11 is a data diagram showing the experimental example of Fig. 10, and Fig. 12 is an explanatory diagram.
The figure is a schematic diagram of the sensitivity distribution, Figures 13 and 14 are diagrams showing the measurement results of the sensitivity distribution, and Figure 15 is a schematic diagram explaining waveform changes.
FIG. 16 is a diagram showing another embodiment. 1... Input flat plate, 2... Solid vibration element, 2a to 2d
...Solid vibration element, 3a...Solid vibration element, 4...
・)(Lusa, 5...Amplification circuit, 6...Waveform shaping circuit, 7...Counting circuit, Yu 1 Illustration 2 Mouth η 3 z(a) P Tsuru 3(ffi(b) Taku 4( 21 Data collection S Mouth also Figure C,.Tree exclamation Cb) High 12 η 8[21 Ma54 Sea- 鵞三纂 11 Plan ゛ ゛ 13 z も 14 Plan IG Oral procedure amendment (method) u/ H++60□3., 217 Director General of the Office of Nominations Gakudono Shiga・Display of 1 to 1988 Patent Application No. 220971 Appearance of Akira
Name: Tablet-shaped coordinate input device using elastic waves? Relationship with important name゛+if'l.
Toshiro Masato

Claims (1)

[Claims] 1. A flat medium portion for propagating longitudinal acoustic waves, a longitudinal acoustic wave detection portion provided on a side surface or part of the surface of the end portion of the medium portion, and a tip having a pointed shape. a longitudinal acoustic wave input member whose tip is freely crimped to any position on the surface of the flat medium portion, and which radiates longitudinal acoustic waves from the tip; A tablet-shaped coordinate input device using elastic waves, comprising means for extracting an elastic wave-compatible electric signal detected by the input member as orientation information of the crimping position of the input member. 2. In claim 1, the longitudinal acoustic wave detection section is provided on a corner side surface of the flat medium section, and the tip of the longitudinal acoustic wave input member and the flat medium section A tablet-shaped coordinate input device using elastic waves, characterized in that it is composed of members having substantially equal impedance. 3. In claim 1, the means for converting an elastic wave-compatible electric signal detected by the detection unit by radiation of the longitudinal elastic wave into crimping position localization information of the input member includes amplifying the signal. a comparison circuit that generates a delayed pulse signal corresponding to the propagation time of the longitudinal acoustic wave by comparing the signal amplified by the amplification section with a constant threshold voltage; A counting circuit that counts the time from when an elastic wave is radiated to the flat medium section until the delayed pulse signal is emitted, and an arithmetic circuit that calculates coordinates using the time signal transferred from the counting circuit. A tablet-shaped coordinate input device using elastic waves, which is characterized by: 4. In claim 1, the longitudinal acoustic wave input member is composed of an axially symmetrical waveguide rod, and one end of the waveguide rod has a pointed tip and is connected to the flat medium. The other end of the waveguide rod has a planar shape perpendicular to the axis of symmetry of the waveguide rod, and the planar portion and the end of the flat medium portion A tablet-shaped coordinate input device using elastic waves, wherein transmitting and receiving piezoelectric elements are respectively attached to the longitudinal elastic wave detection section provided on a portion or a part of the surface. 5. In claim 4, the receiving piezoelectric element is fixed to a side surface of the flat medium portion with a surface perpendicular to the polarization direction of the receiving piezoelectric element, and the transmitting piezoelectric element is attached to the waveguide. A surface perpendicular to the polarization direction of the transmission piezoelectric element is fixed to the rod flat part, and a resonant frequency in a direction perpendicular to the polarization direction of the transmission piezoelectric element is set to the polarization direction of the reception piezoelectric element or perpendicular to the polarization direction. A tablet-shaped coordinate input device using elastic waves, characterized in that the value is equal to or close to the resonance frequency in the direction in which the coordinates are input. 6. Claim 4, wherein the receiving piezoelectric element is fixed to the surface of the flat medium portion with a surface perpendicular to the polarization direction of the receiving piezoelectric element, and the transmitting piezoelectric element is attached to the waveguide. A surface perpendicular to the polarization direction of the transmitting piezoelectric element is fixed to the rod flat part, and a resonant frequency in a direction perpendicular to the polarization direction of the transmitting piezoelectric element is set to a resonant frequency in a direction perpendicular to the polarization direction of the receiving piezoelectric element. A tablet-shaped coordinate input device using elastic waves, characterized in that the value is equal to or close to the resonance frequency. 7. In claims 4, 5, and 6, both the transmitting piezoelectric element and the receiving piezoelectric element are
A tablet-shaped coordinate input device using elastic waves, characterized in that a resonance frequency in each polarization direction and a resonance frequency in a direction orthogonal to the polarization direction are different.