JPH0562769B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a coordinate input device that inputs coordinates using elastic waves generated by a piezoelectric element, and is particularly intended to improve coordinate detection accuracy.

[Prior Art] Conventionally, this type of coordinate input device generally brings a vibrating pen incorporating a piezoelectric element as a vibration generation source into contact with a signal input plate made of a vibration propagation body, and generates a plate-wave acoustic wave propagated by this. The mechanical vibration is detected as an electrical signal by a sensor including a piezoelectric element attached to the signal input board, and from this the position coordinates of the vibrating pen are detected.

[Problems to be Solved by the Invention] However, in this type of conventional coordinate input device, the frequency of the electric signal that drives the piezoelectric element of the vibrating pen (hereinafter referred to as the drive frequency),
Nothing has taken into account the resonant frequency of the vibrating pen, and furthermore, the matching with the resonant frequency of the sensor. If the driving frequency is different from the resonance frequency of the vibrating pen and sensor, not only will the coordinate detection efficiency be poor, but the detection signal waveform will be distorted, so the position coordinates are detected from this detection signal waveform. In some cases, there was a problem that detection accuracy deteriorated.

In view of the above-mentioned problems, the present invention makes it possible to efficiently detect a signal waveform without distortion by matching the driving frequency with the resonant frequency of the vibrating pen and sensor, thereby providing highly accurate position coordinates. An object of the present invention is to provide a coordinate input device that enables detection.

[Means for Solving the Problems] In order to achieve the above object, the present invention brings vibration input means having a vibration generating element into contact with each other, thereby transmitting the vibration transmitted to the vibration transmission member to the vibration propagation member. In a coordinate input device that detects with a provided vibration detection element and derives a coordinate position of contact of the vibration input means with the vibration transmission member, the vibration generation element is capable of generating a plate wave in the vibration transmission member. The frequency of the drive signal, the resonance frequency of the vibration input means, and the resonance frequency of the vibration detection element are substantially equal to or coincide with each other.

[Operation] In the present invention, by bringing the vibration input means having the vibration generating element into contact with the vibration transmission member, the vibration transmitted to the vibration transmission member is detected by the vibration detection element, and this detection causes the vibration transmission of the vibration input means to be detected. Derive the coordinate position of contact with the member. In particular, in the coordinate input device of the present invention, the frequency of the drive signal of the vibration generating element capable of generating a plate wave in the vibration transmission member, the resonance frequency of the vibration input means, and the resonance frequency of the vibration detection element are approximately Since they are made to be equal or coincident, a distortion-free signal waveform can be efficiently obtained from the vibration detecting element, thereby making it possible to input highly accurate coordinate data.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of the entire coordinate input device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a vibrating pen, which has a piezoelectric element 2 as a vibration generation source and a horn 3 with a pointed tip connected to the piezoelectric element. 4 is a tablet-shaped signal input board consisting of a vibration propagator 5; 6 is a horn 3 and a vibration propagator 5;
It is a point of contact with

Sensors 7 include piezoelectric elements for detecting vibrations, and are mounted at multiple (for example, three) corners or corners of the vibration propagation body 5 of the signal input board 4 .

8 is a lead wire for taking out the detection output from the sensor 7, 9 is a vibration absorbing material for anti-reflection attached to the lower part of the vibration propagation body 5, and the above-mentioned signal input plate 4 is connected to the vibration propagation body 5, the sensor 7, It is composed of a lead wire 8 and a vibration absorbing material 9. 10 is a pulse generator that generates a driving pulse to be applied to the piezoelectric element 2 of the vibrating pen 1; 11 is a pulse generator that outputs a start signal to the pulse generator 10, and based on the output signal from the sensor 7, the elastic wave vibrating pen 1 This is an amplification calculation circuit that measures the propagation delay time from to the sensor 7 and calculates and detects the position coordinates of the contact 6 of the vibrating pen 1.

Furthermore, the drive frequency of the electric signal that drives the piezoelectric element 2 of the vibrating pen 1, the resonance frequency of the piezoelectric element 2, the resonance frequency of the horn 3, and the resonance frequency of the piezoelectric element of the sensor 7 are set to be approximately equal to each other in advance or mutually. Fix it to a close value. Further, when the sensor 7 is composed of a piezoelectric element and a horn, the resonance frequencies of the horns are also made to be approximately the same. For example, as described later, the difference between the driving frequency and the resonant frequency of the vibrating pen 1 and the sensor 7 is set within the difference between the resonant frequency and the anti-resonant frequency of the vibrating pen 1 and the sensor 7.

Further, the vibration directions of the piezoelectric element 2 and the horn 3 of the vibrating pen 1 and the piezoelectric element and the horn of the sensor 7 are, for example, the longitudinal direction or the thickness direction of the piezoelectric element, and the elastic waves propagating through the vibration propagation body 5 are, for example, transverse waves. A plate wave asymmetric mode mainly composed of the following components is used.

In the above configuration, first, a start signal is output from the amplification calculation circuit 11 to the pulse generator 10.
In response to this start signal, the pulse generator 10 generates a pulsed electrical signal. The higher the frequency of this pulse electric signal, the higher the resolution, but at the same time the attenuation rate also increases, so it is 50 [kHz] to 5 [MHz],
More preferably, a range of 200 [kHz] to 1 [MHz] is suitable. The piezoelectric element 2 of the vibrating pen 1 to which this pulse electric signal is applied expands and contracts, generating vibration. This vibration is magnified by horn 3,
Vibration is transmitted to the vibration propagation body 5 at the contact point 6,
Propagates as a plate elastic wave. As the material of the vibration propagation body 5, for example, a transparent plate such as glass or acrylic can be considered. The plate wave elastic wave propagated through the vibration propagation body 5 is detected as a piezoelectric voltage by the piezoelectric elements of the three vibration detection sensors 7, and is sent to the amplification calculation circuit 11 through the lead wire 8.

The amplification calculation circuit 11 detects the delay time required for the vibration propagation described above in synchronization with the start signal described above. This detection is preferably repeated about 50 to 300 times per second. The vibration signal waveform is detected based on the peak of the envelope of the waveform or the peak of the carrier wave. Using the delay times for the three vibration detection sensors 7 obtained in this manner, the position coordinates of the vibrating pen 1 are calculated as follows, for example.

That is, as shown in FIG. 2, the position coordinates of the vibrating pen 1 are (x, y), and the coordinates of each of the three vibration detection sensors 7 are (x ₁ , y ₁ )=(0, 0),
If (x ₂ , y ₂ ) = (x ₂ , 0), (x ₃ , y ₃ ) = (0, y ₃ ), then the position coordinates (x, y) of the vibrating pen 1 are calculated using the following formula.
Determined by (1) and (2).

x= _x2 /2+ ^v2 / _2x2 ( _t1 + _t2 )(t1- _t2 )...(1) y= _y3 / ₂ + ^v2 / _2y3 ( _t1 + _t3 )( _t1 - _t3 )...(2) However, t ₁ to _{t 3} are the propagation times of the elastic waves, and v is the degree of propagation of the elastic waves. Therefore, by sequentially performing calculations based on the above equations (1) and (2) in the amplification calculation circuit 11, the position coordinates of the movement of the vibrating pen 1 can be accurately obtained.

Further, when the vibration in the vibration propagation body 5 reaches the vibration absorbing material 9, the amplitude of the elastic wave is attenuated here. The material for the vibration absorbing material 9 is, for example, silicone rubber mixed with metal powder in order to have a high damping rate and to match the characteristic acoustic impedance with the glass of the vibration propagation body 5. Furthermore, it is desirable to use a plate thickness of the vibration propagation body 5 of, for example, 0.3 to 2.0 mm. That is, as the thickness of the plate decreases, the amplitude of the propagated and detected elastic waves increases, but the strength of the material decreases.

Here, the frequency (drive frequency) of the pulse electric signal generated from the pulse generator 10 described above is as close as possible to the resonant frequency of the vibrating pen 1 and the resonant frequency of the sensor 7, and more preferably, the three frequencies are made to match each other. When set, sensor 7
A distortion-free detection signal waveform can be obtained from this method, which is effective in increasing the accuracy of position detection.

Figure 3 shows the frequency characteristics when the driving frequency, the resonant frequency of the vibrating pen 1, and the resonant frequency of the sensor 7 are mismatched. The frequency characteristics are shown when the resonant frequencies match each other.

3 and 4, 12 and 16 are positions indicating the driving frequency, 13 and 17 are frequency characteristic curves of the vibrating pen 1, 14 and 18 are frequency characteristic curves of the sensor 7, and 15 and 19 are frequencies of the detection signal. It is a spectral curve. As shown in FIG. 3, the driving frequency 12 and the frequency characteristic curve 1 of the vibrating pen 1
If the respective peaks in the frequency characteristic curve 14 of the sensor 3 and the sensor 7, that is, the respective resonance frequencies, do not match but are shifted, the frequency spectrum 15 of the signal detected from the sensor 7 (detection signal) will have multiple peaks. Therefore, the detected signal will contain several frequency components at the same level. Therefore, the detection signal waveform becomes distorted as shown in FIG. 5, and it is extremely difficult to detect this waveform with high precision.

On the other hand, as shown in FIG. 4, the drive frequency 16 and the peaks in the frequency characteristic curve 17 of the vibrating pen 1 and the frequency characteristic curve 18 of the sensor 7, that is, the respective resonance frequencies, are consistent with each other. In a case like the embodiment, one peak appears at the matched frequency in the frequency spectrum 19 of the detected signal (detection signal). The waveform of the detection signal containing the single frequency component is free from distortion, as shown in FIG. 6, so that highly accurate position coordinate detection is possible using this waveform. Furthermore, in this case, the detection signal waveform can have a large amplitude, so detection efficiency is improved and the S/N ratio is also improved.

Note that the resonant frequency of the vibrating pen 1 changes slightly depending on the bonding state of the piezoelectric element 2 and the horn 3 in the vibrating pen 1, so as mentioned above, the resonant frequencies of the piezoelectric element 2 and the horn 3 are set to values close to each other. To,
More preferably, they match, and it is also preferable to adjust the bonding conditions such as the thickness of the adhesive at the time of bonding in advance so that they match the drive frequency and the resonance frequency of the sensor 7.

Furthermore, by using an asymmetric mode mainly consisting of transverse wave components as the plate wave elastic wave, the drive mode of the piezoelectric elements of the vibrating pen 1 and the sensor 7 is set to longitudinal vibration or thickness direction vibration, and the vibrating pen 1 and the sensor 7 are It is preferable to match the resonance frequencies of the two. This is because, as an elastic wave propagating through the vibration propagation body 5, it is easier to detect a plate wave asymmetric mode, which mainly consists of transverse wave components, which can obtain a larger amplitude level than a plate wave symmetric mode, which mainly consists of longitudinal wave components. This is preferable because it is easy.

In this embodiment, a piezoelectric element for vibration detection is used as the sensor 7, but a sensor composed of a piezoelectric element and a horn, which can detect vibration with a higher accuracy than a point area, may also be used. In this case, as in the case of the vibrating pen 1, the resonant frequency of the sensor 7 is set to match the driving frequency and the resonant frequency of the vibrating pen 1, paying attention to the connection between the piezoelectric element and the horn. In addition, when using a piezoelectric element with vertical vibration, that is, thickness direction driving mode, the horns of the vibrating pen 1 and sensor 7 are also set so that the driving frequency and the resonant frequency of the piezoelectric element match in the vertical vibration. do.

Further, in this embodiment, as an example, the sensor 7
Although three pieces were used, four or more pieces may be used. In that case, by performing position calculations that match the number of sensors 7, the accuracy can be further improved.

Furthermore, in the above description of the present embodiment, it was stated that if the drive frequency and the resonance frequencies of the vibrating pen 1 and the sensor 7 are close to each other, the frequency component of the detection signal will have only one peak. , the allowable value for the difference between the frequencies that are close to each other is within ±a of the difference between each resonant frequency and anti-resonant frequency. FIG. 7 shows this limit (tolerable range) state.
In FIG. 7, 20 is, for example, a frequency characteristic curve of the vibrating pen 1, 21 is, for example, a frequency characteristic curve of the sensor 7, 22 and 24 are the resonance frequencies of the vibrating pen 1 and the sensor 7, respectively, and 23 and 25 are the vibrating pen 1 and the sensor, respectively. 7 anti-resonant frequency. It is preferable to obtain as large an amplitude level as possible, and it is necessary to obtain a waveform as shown in FIG.
It is desirable for detection efficiency to be within a. This permissible range of frequency deviation is also the same for the drive frequency.

[Effects] As explained above, according to the present invention, the frequency of the drive signal of the vibration generating element that can generate ripples in the vibration transmission member, the resonance frequency of the vibration input means, and the resonance frequency of the vibration detection element are substantially equal or coincide with each other, it is possible to efficiently obtain a distortion-free signal waveform from the vibration detecting element, thereby achieving the effect that highly accurate coordinate data can be input.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the overall configuration of a coordinate input device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing a method of calculating position coordinates according to an embodiment of the present invention, and Fig. 3 is a diagram showing drive frequency and resonance. A frequency characteristic diagram showing the frequency characteristics when the frequencies do not match. FIG. 4 is a characteristic diagram showing the frequency characteristics when the driving frequency and the resonant frequency match in the embodiment of the present invention. FIG. 5 shows the frequency characteristics when the frequencies do not match in FIG. 3. A waveform diagram showing the waveform of the detection signal in the case of
FIG. 6 is a waveform diagram of the detection signal in the case of frequency matching in FIG. 4, and FIG. 7 is an explanatory diagram showing the allowable range of frequency deviation in the embodiment of the present invention. 1... Vibration pen, 2... Piezoelectric element, 3... Horn, 4... Signal input board, 5... Vibration propagation body, 6...
... Contact, 7 ... Sensor (piezoelectric element), 8 ... Lead wire, 9 ... Anti-reflection vibration absorbing material, 10 ... Pulse generator, 11 ... Amplification calculation circuit.

Claims (1)

[Scope of Claims] 1. By bringing a vibration input means having a vibration generating element into contact with each other, the vibration transmitted to the vibration transmission member is detected by a vibration detection element provided on the vibration transmission member, and the vibration input means A coordinate input device for deriving a coordinate position of contact with the vibration transmission member, comprising: a frequency of a drive signal for the vibration generation element capable of generating a plate wave in the vibration transmission member;
A coordinate input device characterized in that the resonance frequency of the vibration input means and the resonance frequency of the vibration detection element are substantially equal or matched.