JPS61281324A - Ultrasonic applied tablet - Google Patents

Abstract

PURPOSE:To reduce influence of the inclination of a pen by forming a write plate by a composite structure of a double layer medium, and forming an input layer medium by a medium whose longitudinal wave speed is lower than that of a propagation layer medium. CONSTITUTION:A write part of an ultrasonic applied tablet is constituted of an input pen 1 and a write device 2, and this write device 2 is constituted of a write plate 3 and receiving pieces 4 (a-d) which are installed to each corner of said plate. Also, the input pen 1 is formed by a transmitting piece 1a, a pen point 1b and a grip 1c, and a longitudinal ultrasonic wave is radiated from the pen point 1b by applying a pulse voltage by a pulse exciting circuit 5. Next, the propagated ultrasonic wave is detected by the receiving pieces 4, and a position locating operation is executed by a coordinate operating circuit 8 through a waveform shaping circuit 6 and a time counting circuit 7, and displayed by a display device 9. In such a case, the write plate 3 is formed by a propagation layer medium 3a, and an input layer medium 3b of a material whose longitudinal wave speed is lower than that of said medium, and the receiving pieces 4 are attached to the propagation layer medium 3a side. In such a way, a waveform variation caused by the inclination of the pen 1 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ultrasonic application tablet for manually inputting information into a computer or the like.

[Background of the invention]

One of the problems with the writing device of an elastic wave application tablet used as a conventional handwriting input device is that the orientation position varies depending on the inclination angle of the input pen. Especially 1
In the case of a method of locating using the propagation time of elastic waves,
Since the phase angle changes depending on the tilt angle of the input pen, this problem has been essentially unavoidable.

BACKGROUND ART Conventionally, writing devices using surface waves among elastic waves have been proposed to have a layered structure.

For example, Japanese Patent Application Laid-Open No. 50-50830 discloses a contact type position encoder using surface acoustic waves, which has a structure in which a second sheet is placed under a first sheet that transmits surface waves. Since the purpose of this is to attenuate bulk waves, a material with a high bulk wave attenuation rate is used. In this way, for writing boards combined for other purposes, 1
No consideration is given to the material required to eliminate the influence of input pen tilt as proposed in the present invention.

[Purpose of the invention]

The objects of the present invention are as follows: 1. It is possible to detect coordinates using normal handwritten input, and also to reduce waveform changes of detected waves caused by the angle of incidence of ultrasonic waves from an input pen or the rotation angle of the input pen, and in particular to prevent phase inversion. An object of the present invention is to provide an ultrasonic application tablet that can achieve high precision by preventing the above problems.

[Summary of the invention]

The principle of the longitudinal wave method according to the present invention and the problem of pen tilt will be explained.

FIG. 1 shows the configuration of an ultrasonic application tablet using longitudinal waves.The writing section is composed of an input pen 1 and a writing device 2. The writing device 2 consists of a writing board 3 and a wave receiver 4 (at by Qp d) installed at each corner of the writing board 3. The input pen 1 consists of a wave transmitter 1a, a pen tip 1b, and a grip IC, and a pulse voltage is applied by a pulse excitation circuit 5 to the pen tip 1b of the input pen 1.
Longitudinal ultrasound waves are emitted. The longitudinal ultrasound incident on the writing board 2 propagates through the writing board 3, is detected by the wave receiver 4 (a"d), and is input to the waveform shaping circuit 6. The output of the waveform shaping circuit 6 is input to a time counting circuit 7, and the propagation time from the ultrasound incident point to each receiver is measured.The output of the time counting circuit 7 is input to a coordinate calculation circuit 8, which performs positioning calculation. Thereafter, the orientation result is displayed on the display device 9.

FIG. 2 shows how the longitudinal ultrasound input to the waveform shaping circuit 6 changes depending on the inclination angle of the input pen 1. The figure shows waveforms detected by both wave receivers when wave receivers A and B are installed at both ends of the writing board 3, and longitudinal ultrasonic waves are inputted from the midpoint P by the input pen 1. (a) shows a detected waveform when the input pen 1 is placed vertically, and the first arriving wave F is detected in the same phase as the receiving wave element A. On the other hand, (b), (c), and (d) of the same figure show the detected waveforms when the input pen 1 is gradually tilted toward the wave receiver A, and the first arriving wave F at the wave receiver B. , there is a slight level change but no phase change is observed, whereas the phase of the first arriving wave F at receiver A changes with the level change, and the phase of the slope negative dog (d) changes. Therefore, when measuring the propagation time by focusing on the first arriving wave F, for example, when focusing on the peak point, the propagation time will vary depending on the inclination angle θ, which will cause a orientation error. .

The phenomenon in which the waveform of the detected wave changes when the pen is tilted is due to the fact that the component parallel to the medium surface of the ultrasonic wave incident on the medium 10 is affected by the tilt of the input pen. Proven by simulation analysis. The results are shown in FIG. 3. It can be seen that when the input pen 1 is perpendicular to the surface of the medium as shown in FIG. 3(a), the phase of the wave spreading within the medium is symmetrical about the pen. However, when the input pen 1 is tilted as shown in FIG. 3(b), the phase of the wave is reversed in the area near the surface of the medium 10 on the side where the pen is tilted.
It can be seen that the phase is asymmetric around the pen. Furthermore, when analyzed in detail, the region where the phase is reversed becomes larger as the tilt of the input pen becomes larger. From these facts, it can be seen that the tilt of the input pen 1, that is, the component of the ultrasonic waves incident on the medium 10 parallel to the medium surface, directly influences the phase of the wave component parallel to the medium surface within the medium. b Cal. Because of this phenomenon, the waveform of the detected wave changes when the pen is tilted.

However, if you look carefully, you will see that the phase on the side where the pen is tilted is not all reversed.

In other words, the phase of the wave is symmetrical about the pen at a depth below the point of incidence of the ultrasonic wave from the surface of the medium, particularly below the depth where the vortex indicated by the arrow indicating the phase of the wave is generated. Therefore, if this phase-symmetrical wave can be guided to the detection element earlier than the asymmetrical wave, the influence of the tilt of the pen can be reduced and the waveform change of the detected wave, especially phase reversal, can be prevented.

[Embodiments of the invention]

The present invention was created based on the above-mentioned idea, and an embodiment thereof is shown in FIG. In the writing device 2, the writing plate 3 has a structure consisting of at least two layers, and an input layer medium 3b made of a material having a longitudinal wave velocity lower than that of the propagation layer medium 3a is provided on the propagation layer medium 3a for propagating ultrasonic waves, The structure is such that a wave receiver 4 (B, be Qp d) is attached to the propagation layer medium 3a side.

FIG. 5 is a diagram in which the effects of the present invention were confirmed by simulation. The materials used in this analysis are shown in Table 1. When the medium is made into two layers as shown in FIG. 5, a region where the phase is symmetrical is created even when the pen is tilted, which proves that the concept of the present invention is correct. Furthermore, detailed analysis shows that this in-phase region with symmetrical phase increases as the slow input layer of the sound wave becomes thicker when the tilt of the pen is constant; The smaller the slope of , the larger the in-phase region becomes.
It was found that once the length reaches about half a wavelength, the in-phase region does not increase even if the input layer is made thicker. This shows that it is not necessary to increase the thickness of the input layer unnecessarily. Also, if you slow down the sound waves in the input layer,
It was also found that the layers could be thinner to achieve the same effect.

From a practical point of view, it is sufficient that the size of the in-phase class whose phase is symmetrical is half the wavelength of the ultrasonic wave in the propagation layer at the time of the maximum practical pen tilt. From this the thickness of the slow input layer of the sound wave is determined. in particular,
When the ultrasonic frequency is 400kHz and the materials shown in Table 1 are used, if the maximum inclination of the input pen is 40', the thickness of the input layer only needs to be 1.2mm, and if the maximum inclination is 30°, the thickness of the input layer is It was found that a thickness of 0.8 mm is sufficient.

By configuring the tablet as shown in Table 1, the density of the material used in the analysis and the speed of sound, it is possible to reduce waveform fluctuations caused by tilting the pen, and in particular to prevent phase reversals, allowing for highly accurate positioning. An ultrasonic application tablet that can be evaluated can be realized.

In addition, the materials shown in Table 1 are transparent, and tablets made of such transparent materials can be used in liquid crystal displays and CRTs.
If it is laminated on a display surface such as the like, it has the advantage of being able to realize an ultrasonic application tablet that integrates the input surface and display surface. There are many transparent materials with different longitudinal wave velocities, and combinations of them are possible. Also, with the same material, there are two acoustically
A similar effect can be obtained using layered materials.

Although the above description has been made regarding a transparent writing plate, it is of course possible to use an opaque material with the same effect.
g) and using Bakelite (longitudinal wave velocity: 2590 m/s) as the input layer medium, the effect of pen tilt can be eliminated.

Next, other embodiments will be described. FIG. 6 shows an application of the composite structure of the writing device, in which an intermediate layer medium 3ct between the propagation layer medium 3a and the input layer medium 3b of the writing board 3 is used.
The present invention is characterized in that the intermediate layer medium has a longitudinal wave velocity intermediate between the longitudinal wave velocities of the propagation layer medium and the input layer medium. The effect is based on the same idea as the embodiment shown in FIG.

Furthermore, unlike the above two embodiments, FIG. 7 shows an improved input pen. As shown in the enlarged view of the same figure,
A small contact piece 1 is provided at the tip of the nib 1b of the input pen 1, and the contact piece is made of a material whose longitudinal wave velocity is lower than the longitudinal wave velocity of the writing plate 3. In this case, it is preferable to use a material for the pen tip 1b whose longitudinal wave velocity is higher than the longitudinal wave velocity of the contact piece, and this embodiment is also effectively the same as the case in FIG. This eliminates the influence of the tilt of the input pen.

The above-mentioned composite writing board may be manufactured by bonding a plurality of boards having different sound velocities, for example.

There is a plywood method in which a polycarbonate plate or acrylic plate is laminated on top of a glass plate. Also, as another method,
There is a manufacturing method that uses the physical properties of the same material, such as differences in specific gravity, to create a two-layered medium in terms of acoustic properties during the manufacturing process.

〔Effect of the invention〕

According to the present invention, in an ultrasonic application tablet, it is possible to reduce the waveform change of the detection plate caused by the tilt of the pen,
In particular, since phase reversal can be prevented, a highly accurate tablet can be made. Additionally, compared to a tablet that corrects waveform changes using a special detector or additional circuit, it can be configured more easily.

[Brief explanation of the drawings] Figure 1 is a diagram of the principle configuration of an ultrasonic application tablet using longitudinal waves. Figure 2 shows the state of the waveform detected by the wave receiver when the input pen is tilted. The figures show the simulation results of the behavior of ultrasonic waves incident from the input pen into the writing board.
The figure shows simulation results showing the effect of compounding, and FIG. 6 shows another embodiment of the compounding writing device according to the present invention.
FIG. 7 shows other embodiments of the present invention in which improvements are made on the input pen side. DESCRIPTION OF SYMBOLS 1... Input pen, 2... Writing device, 3... Writing board, 4... Wave receiver, 5... Pulse excitation circuit, 6...
... Waveform shaping circuit, 7... Time counting circuit, 8... Coordinate calculation circuit, 9... Display device.

Claims (1)

[Claims] 1. A wave transmitter that is excited by an electric signal and generates ultrasonic waves;
An input pen with a pen tip that emits the ultrasonic waves from one point, a writing board that propagates the ultrasonic waves from the input pen, and a writing board provided at the end of the writing board that converts the propagated ultrasonic waves into electrical signals. An ultrasonic application tablet comprising a writing device comprising a wave receiver, and a signal processing device for locating the position of the input pen based on a detection signal of the writing device and displaying the position on a display device, wherein the writing plate of the writing device is at least A composite structure consisting of a two-layer medium is provided, and an input layer medium consisting of a medium having a longitudinal wave velocity lower than that of the propagation layer medium is provided on a propagation layer medium for propagating ultrasonic waves, and the wave receiver is placed on the side of the propagation layer medium. An ultrasonic application tablet characterized by being attached. 2. In the ultrasonic application tablet having the configuration of item 1 above, an intermediate layer medium is provided between the propagation layer medium and the input layer medium of the writing plate of the composite structure of the writing device, and the intermediate layer medium has a longitudinal wave velocity. An ultrasonic application tablet characterized by using a medium having a speed intermediate between that of a propagation layer medium and an input layer medium. 3. A transmitter that generates ultrasonic waves when excited by an electrical signal;
An input pen with a pen tip that emits ultrasonic waves, a writing plate that propagates the ultrasonic waves from the input pen, and a wave receiver installed at the end of the writing plate that converts the propagated ultrasonic waves into electrical signals. and a signal processing device for locating the position of the input pen based on the detection signal of the writing device and displaying the position on the display device. An ultrasonic application tablet characterized in that the contact piece is made of a medium whose longitudinal wave velocity is lower than the longitudinal wave velocity of the writing plate.