JPS63106821A - Coordinate input device - Google Patents

Abstract

PURPOSE:To contrive the improvement of the coordinate detection accuracy by arranging a vibration sensor on a vibration transmitting plate with a prescribed distance larger than a reflection interference distance of vibration apart from the boundary face where the specific acoustic impedance of a vibration transmitting plate ridge is changed so as to prevent the distortion in the vibration detection waveform at the boundary face of the ridge of the vibration transmitting plate caused by a reflection wave. CONSTITUTION:When the distance between the vibration sensor 6 and the reflection boundary face 82 is parted only by a reflection interference distance L as shown in figure (A), the effective transmission range 84 is linear, but in parting the vibration sensor 6 from the reflection boundary face 82 over the reflection interference range L as shown in figures (B)-(D), the effective transmission range 84 of the direct wave is being spread sectorially. That is, the vibration sensor 6 is parted sufficiently from the reflection interference range as shown in the figure (D). Thus, the distortion due to the combination of the reflected wave from the boundary face 82 where the specific acoustic impedance of the vibration delivery plate 8 changes onto the detected waveform is avoided and the coordinate detection accuracy based on the vibration detection is improved remarkably.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects vibrations input from a coordinate input device, particularly a vibrating pen, using a plurality of vibration sensors provided on a vibration transmitting plate, and transmits the vibrations of the vibrating pen. This invention relates to a coordinate input device that detects coordinates on a board.

[Prior Art] Coordinate input devices using various input pens, tablets, etc. have been known as devices for inputting handwritten characters, figures, etc. to a processing device such as a computer. The following various methods are known for detecting the coordinates of a tablet in this type of device.

1) A method that detects changes in the resistance value of a sheet material placed opposite the resistive film.

2) A method that detects electromagnetic or electrostatic induction from conductive sheets placed opposite each other.

3) A method that detects ultrasonic vibrations transmitted from the input pen to the tablet.

[Problem that the invention attempts to solve] Each of the above conventional methods has the following problems.

First, in the resistive film method (1), the uniformity of the resistive film determines the detection accuracy, so it requires a highly uniform and expensive resistive film, or the tablet cannot be made transparent, so it is used on top of a display etc. There are drawbacks such as not being able to do so.

The induction method (2) is also difficult to make transparent, and moreover, it is difficult to construct a large tablet because a large number of matrix-like electrodes are provided.

On the other hand, in the ultrasonic method (3), a vibration transmission plate made of a transparent material such as acrylic or glass plate and provided with a vibration sensor such as a piezoelectric element can be used as the tablet.

However, this ultrasonic method has a problem in that the detection accuracy decreases due to scratches or obstacles on the vibration transmission plate-L of the tablet.

Therefore, a technology has been proposed in which the vibration transmission plate of the tablet is vibrated using a plate wave among the elastic waves to reduce the effects of scratches and obstacles on the vibration transmission plate. In this type of conventional method using elastic waves, the vibration transmission plate is supported by an anti-reflection material made of anti-vibration material such as silicone rubber in order to prevent the reflection of elastic waves from the periphery of the vibration transmission plate. be done.

However, even with this structure, there is a problem in that reflected waves from the interface between the vibration transmission plate and the anti-reflection material are combined with the detected vibration, causing distortion and reducing detection accuracy.

The present invention aims to improve the above-mentioned detection error problem in an ultrasonic vibration method which has various advantages such as easy transparency and relatively inexpensive construction compared to other methods.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, vibrations input from a vibrating pen are detected by a plurality of vibration sensors provided on a vibration transmission plate, and the vibration pen In a coordinate input device for detecting the coordinates of a vibration transmission plate, the vibration transmission plate is placed at a distance of a predetermined pressure greater than the vibration reflection interference distance from the boundary surface where the characteristic acoustic impedance of the edge of the vibration transmission plate changes. A configuration was adopted in which the vibration sensor was placed at the top.

[Function] According to the above configuration, the reflected waves from the boundary surface where the natural acoustic impedance of the vibration transmission plate changes are not synthesized into the detected waveform and cause distortion, and the accuracy of coordinate detection based on vibration detection is greatly increased. "Mukai" - Can be done.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 shows the structure of a coordinate input device employing the present invention. The coordinate input device shown in FIG. 1 constitutes an input/output device for characters, figures, images, etc. together with a display 11' using a liquid crystal display such as a dot matrix type.

The reference numeral 8 in the figure is a vibration transmission plate made of acrylic, glass, etc., and is made of silicone rubber or the like in order to prevent the vibrations transmitted from the vibrating pen 3 from being reflected in the surrounding area. It is supported by an anti-reflection material 7. Three vibration sensors 6 are arranged at the corners of the vibration transmission plate 8, and detect elastic waves transmitted from the vibration pen 3.

A vibration transmission plate 8 is disposed on a display 11' composed of a liquid crystal display or the like, and constitutes an information input/output device. The display 11' feeds back characters and figures input via the vibration transmission plate 8, or displays prompts for input operations on the vibration transmission plate.

The vibrating pen 3 transmits ultrasonic vibration to the vibration transmitting plate 8,
It has a vibrator 4 made of a piezoelectric element or the like inside, and transmits ultrasonic vibrations generated by the vibrator 4 to a vibration transmission plate 8 via a horn portion 5 having a sharp tip. FIG. 2 shows the structure of the vibrating pen 3. A vibrator 4 built into the vibrating pen 3 is driven by a vibrator drive circuit 2. Vibrator 4
The drive signal is supplied as a low 1/bel pulse signal from the operator and control circuit 1 shown in FIG. is applied to The electrical drive signal is converted into mechanical vibration by the vibrator 4 and transmitted to the vibration transmission plate 8 via the horn portion 5.

The vibration frequency of the vibrator 4 is selected to be a frequency that generates plate waves in the vibration transmission plate 8 made of acrylic, glass, or the like. Further, an operation mode is selected in which the vibrator 4 mainly vibrates in the vertical direction in FIG. 2 with respect to the vibration transmission plate 8. By selecting the vibration frequency of the vibrator to be the resonance frequency of the vibrator 4, efficient vibration generation can be achieved.

The elastic waves transmitted to the vibration transmission plate 8 as shown in - are waves called plate waves, and have the advantage of being less affected by surface scratches, obstacles, etc. than surface waves. The waves propagating within the vibration transmission plate 8 reach the vibration sensors 6 provided at the three corners of the vibration transmission plate 8 with a time delay corresponding to the distance. Therefore, by measuring the vibration with the vibration sensor 6 and measuring its delay time, the position of the vibrating pen 3 on the vibration transmission plate 8-H can be detected.

Referring again to FIG. 1, the output signal of the vibration sensor 6 composed of a piezoelectric element, etc. is input to the waveform detection circuit 9, and is converted into a detection signal that can be processed by the arithmetic control circuit 1 composed of a microcomputer, memory, etc. be done.

The arithmetic control circuit 1 detects the position of the vibrating pen 3 on the vibration transmission plate 8 based on the above-mentioned delay time arithmetic processing.

The display 1/11' shown in FIG. 1 is driven by the arithmetic control circuit 1 via the display drive circuit 10.

FIG. 3 shows the structure of the arithmetic control circuit of FIG. Here, except for the control system of the drive circuit for the display 11' shown in FIG. 1, only the circuit that processes vibration generation from the vibrating pen and vibration detection from the vibration transmission plate is shown.

The microcomputer 11 includes an internal counter, ROM, and RAM. The drive signal generation circuit 12
It generates drive pulses for the vibrator drive circuit 2 shown in FIG. 51, and is started by the microcomputer 11 in synchronization with the calculation circuit. The count value of the counter 13 is latched into the latch circuit 14 by the microcomputer 11.

The detection signal inputted from the waveform detection circuit 9 is inputted to the input port 15, and is compared with the count value in the latch circuit 14° by the determination circuit 16, and the result is transmitted to the microcomputer-1. Driving of the display 11' and input/output with other processing devices such as a computer system are performed via the input/output port 17.

FIG. 4 explains the detected waveform input to the waveform detection circuit 9 of FIG. 1 and the delay time measurement process based on the detected waveform. In FIG. 4, reference numeral 41 is a drive signal pulse applied to the vibrating pen 3. Due to such a waveform, the ultrasonic signal generated by the driven vibrating pen 3 is transmitted as an elastic wave within the vibration transmission plate 8, and is detected by the vibration sensor 6, and is detected by the symbol 42 in FIG. Form a waveform. The detected waveform is transmitted from the vibration pen to the vibration transmission plate 8.
There is a delay of time tg before the signal is transmitted to the vibration sensor via. The plate wave used in the non-example is a dispersive wave, and therefore the relationship between the envelope 421 and phase 422 of the detected waveform changes with respect to the propagation distance within the vibration transmission plate.

Let the advancing speed of the envelope be the group velocity Vg, and the velocity of the phase be the phase method 11' map p.

The distance between the vibrating pen 3 and the sensor can be detected from the group velocity and phase velocity. First, if we focus only on the envelope 421, its speed is mag, and when a certain point, for example the peak of the envelope, is detected as indicated by reference numeral 43 in FIG. 4, the vibration pen and vibration sensor 6
The distance d between them is d=vgIltg=(1) where the delay time is tg.
is given by Although the two equations relate to one of the vibration sensors 6, the same equation can be used to measure the distance between the other two vibration sensors and the vibration pen.

Furthermore, in order to determine coordinate values with higher precision, processing based on phase signal detection is performed. Phase waveform 42 in Figure 4
If the delay time of the second specific detection point, for example the zero-crossing point after passing the peak, is tp as shown in Fig. 4, then the distance d between the vibration sensor and the vibration pen is d=n-λp+vpitp・...(2
). Here, the wavelength of the input pIi elastic wave, n, is an integer.

From the above equations (1) and (2), the above integer n is n = [(vglltg-vpIItp)/λp+
−]−(3). Here, N is a real number other than O, and an appropriate value is used. For example, if N=2, n can be determined if the envelope detection accuracy is within the wavelength range. −N obtained as above is (2
), the distance between the vibrating pen and the sensor can be accurately measured.

Distance measurement based on the two delay times tg and tp shown in FIG. 4 is performed by the waveform detection circuit 9 shown in FIG.

The waveform detection circuit is constructed as shown in FIG. In FIG. 5, the output signal of the vibration sensor 6 is
is amplified to a low level. The amplified signal is input to the envelope detection circuit 52, only the envelope is taken out, and the envelope peak detection circuit 53 detects the timing of the peak of the envelope of the detection signal. For peak signal detection, a Tg times signal of a predetermined waveform is formed by a signal detection circuit 54 composed of a mono-multivibrator, etc., and is inputted to the arithmetic control circuit 1. Moreover, this Tg multiplied signal delay time adjustment circuit 5
A phase delay time Tp detection signal is formed by the comparator detection circuit 58 from the original signal delayed by 7, and is input to the arithmetic control circuit 1. The circuit shown below is for one vibration sensor 6, and similar circuits are provided for each of the other vibration sensors. Assuming that the number of sensors is generally h, the envelope delay time Tgl~h for the arithmetic and control unit 1.

Detection signals Tp1 to Tph are input.

In the arithmetic control circuit of FIG. 3, the above 7g1 to h.

Tp1 to h signals are input from the input port 15, and the count value of the counter 13 is taken into the latch circuit 14 using each timing as a trigger. As described above, since the counter 13 is started in synchronization with the drive of the vibrator, the latch circuit 14 receives data on the delay times of the envelope 0 and phase.

As shown in FIG. 6, three vibration sensors are arranged at the corners of the vibration transmission plate 8 as indicated by symbols S1 to S3.

By the process described in connection with FIG. 4, the straight-line distances d1 to d3 from the position P of the vibrating pen to each vibration sensor can be determined. The coordinates of the position P of the vibrating pen 3 (x
, y) is obtained from the 3-square theorem. Here, X and Y are S2. This is the distance from the origin of the vibration sensor at the position S3.

By performing the above calculations using the calculation control device l,
The position coordinates of the vibrating pen can be detected in real time.

In the above embodiment, the vibration sensors 6 are provided at the three corners of the vibration transmission plate 8, but in such a configuration, the anti-reflection I
Although the reflected waves are reduced by the material, the waves reflected from the two interfaces at the corners of the vibration transmission plate 8 and the anti-reflection material 7, which have two different acoustic impedances, cause the detected waveform of the vibration sensor 6 to change. There is a problem of distortion.

Therefore, in the embodiment shown below, as shown in FIG. 7, the vibration sensor 6 is provided at the center of the three sides.

According to such a configuration, there is only one interface with the anti-reflection material 7 for each vibration sensor, which causes reflection of elastic waves, making it easier to process counter-waves.

Here, the position of the vibration sensor 6 on the vibration transmission plate 8 and the influence of reflected waves corresponding thereto are shown in FIGS. 8 and 9. Here, in order to simplify the explanation, a case will be considered in which no antireflection material is provided.

When the vibration sensors 6 are mounted at different distances from the boundary surface 82 of the edge of the vibration transmission plate 8 as shown in FIGS. 8(A) to (C), the distances shown in FIGS. 9(A) to (C) The detected waveforms will differ as shown in the following. As is clear from FIGS. 8(A) to 8(C), as the distance between the boundary surface 82 and the vibration sensor 6 increases, the distance between the direct wave from the vibrating pen 3 indicated by symbol a and the reflected wave from the symbol pen increases. The difference becomes larger.

Therefore, when the vibration sensor 6 is far from the boundary surface as shown in FIG. 8(A), the path of the reflected wave is longer than the path a of the direct wave, so as shown in FIG. 9(A). The reflected wave reaches the vibration sensor 6 with a much higher R than the direct wave a. If the vibration input time from vibration vent 3 is short, Figure 9 (
Since the reflected wave does not overlap the direct wave as shown in A), the influence of the reflected wave can be completely removed by detecting the waveform for a time t corresponding to the vibration input time. In FIG. 9(A), a' is the detected waveform of the direct wave, b' is the detected waveform of the reflected wave, 0 is the respective wave head, S is the detection time point by the above detection process, and ti is the detected waveform of the direct wave and the reflected wave. The delay time between wave crests 0, ts, indicates the time from the wave crest of the direct wave to the detection time point S.

However, if the distance between the vibration sensor 6 and the interface 82 is brought closer as shown in FIG. 8(B), the difference in path length between the direct wave and the reflected wave becomes smaller, so the detected waveform becomes as shown in FIG. 9(B). ), the waveform is a superimposition of direct waves and indirect waves, and distortion occurs due to interference between the direct waves and reflected waves. In this case, the delay time t1 between the wave crests of the direct wave and the indirect wave is short, and a pure direct wave waveform can only be obtained during this time. The above distortion greatly affects the accuracy of coordinate detection based on the waveform detection.

In the case of Fig. 9(B), the waveform is not yet distorted at the detection time S, but if the vibration sensor 6 is arranged as shown in Fig. 8(C), there will be an additional delay time as shown in Fig. 9(C). Since t1 becomes shorter, t sat is 1, and the detected waveform is already distorted at the detection time S. Accurate coordinate detection cannot be expected with such a detection waveform.

Therefore, the following conditions are necessary to perform accurate detection.

tl>ts = (6) Now,
Letting the group velocity of the plate wave of the vibration transmission plate 8 be Vg, and making it correspond to the distances a and b in Fig. 8, the above equation becomes tl・Vg=b−
It can be seen that it is sufficient if a>Vg·ts −·−(7). In other words, the vibration sensor 6 has a distance of at least V g -t s / 2 or more from the reflective boundary surface 82 #1. Just place it. Here, let this Vg-ts/2=L,
This L will be called the reflection interference distance.

Although FIG. 8 shows a case where the vibration sensor 6 and the vibration vent 3 are lined up on a straight line perpendicular to the reflective boundary surface 82, in reality the vibration vent 3 is located in the same position as shown in FIG. Possible. As is clear from the figure, the difference in the transmission distance between the reflected wave and the direct wave, -a, is smaller when the vibration vent 3 is at the position MH than when it is at the position 2JD.

Therefore, the position of the vibration ben 3 on the vibration transmission plate 8 such that ba≧Vg・Ls −(8), that is, the effective direct wave transmission area is not parallel to the reflection boundary surface 82. Recognize. For example, FIGS. 11(A) to 11(A) show the difference in the effective direct wave transmittable area that satisfies the above conditions according to the distance from the reflective boundary surface 82 of the vibration sensor 6.
Shown in D).

As shown in FIG. 11(A), the vibration sensor 6 and the reflective boundary surface 82
If the distance is only the reflected interference pressure #L, the effective transmission range 84 becomes a straight line. However, as the vibration sensor 6 is moved away from the reflective boundary surface 82 by more than the reflected interference pressure #L as shown in FIGS. . In other words, by separating the vibration sensor 6 sufficiently from the reflection interference distance as shown in FIG. 11(D), interference of reflected waves can be avoided, and
A wide vibration detection range can be achieved.

In order to expand the effective transmission range 84, L should be made small and the vibration sensor 6 should be placed as close to the edge of the vibration transmission plate 8 as possible. For this purpose, Vg constituting L=Vg・ts
It is desirable to make ts small. For example, the fourth
When detecting an odor using the detection method shown in the figure, if the detection is performed closer to the wavefront of the detection waveform, the time ts to the inspection point in FIG. 9 can be shortened, and the reflection interference distance can be shortened.

Figure 12 shows one vibration sensor 6 on a rectangular vibration transmission plate 8.
10 shows the effective coordinate input range when the device is attached as shown in FIG. As shown in the figure, when the vibration sensor 6 is attached to the reflective boundary surface 121 according to this embodiment, there is no reflection by the boundary surface 121, so the effective coordinate input range is the boundary recommendation corresponding to each of the reflective boundary surfaces 122 to 124. line 14
2 to 144, and the effective input range is widened by one reflective boundary surface.

Figure t513 shows the input range of Figure 12 superimposed on the effective coordinate input range for the four vibration sensors 6 that are actually attached. As shown in FIG. 13, the actual effective coordinate input range 150 is an overlapping area of the effective transmission range 84 when the vibration sensor 6 of FIG. 12 is provided at the center of each side of the vibration transmission plate 8.

Each vibration sensor 6 is placed at a distance that is sufficiently larger than the reflection interference distance ML, but its installation position is outside the effective coordinate input range 150 in FIG. 13. Therefore, when the vibration transmission plate 8 is used in combination with a transparent material binding indicator,
If the range other than the effective coordinate input range 150 is configured to be blocked by a light shielding member or the like, the vibration sensor 6 will not be prevented from viewing the display.

This means that the size of the vibration transmission plate 8 that achieves the same input area can be made smaller, and the entire device can be made smaller.

FIG. 14 shows a configuration in which the vibration transmission plate 8 is supported via the anti-reflection material 7. In this configuration, the vibration transmission plate 8
The periphery of is covered with an anti-reflection material 7. In such a configuration, the reflected waves are absorbed by the anti-reflection material 7 to a large extent, so the effect is greatly reduced compared to the case where the anti-reflection material 7 is not provided, but the anti-reflection material 7 and the vibration transmission plate 8 are Since the acoustic impedance is greatly different, the boundary surface 82
becomes a reflective surface, and a slight reflection occurs on this surface.

Therefore, also in the configuration shown in FIG. 14, the vibration transmission plate 8
The reflective boundary surface 82 at the edge of the vibration transmitting plate 8 and the anti-reflection material 7
By simply replacing it with the boundary surface, the influence of reflected waves can be reduced in the same way as in item 1-.

According to such a configuration, the reflected waves are reduced by the antireflection material 7, and the antireflection effect described in "2" can be expected, so that distortion of the detected waveform due to the influence of the reflected waves can be almost completely eliminated.

Further, according to the above configuration, it is possible to expand the effective coordinate input range. This will be explained using FIG. 15.

15(A) to 15(C) are detected waveforms when the anti-reflection material 7 is provided. FIG. 15(A) shows the detected waveforms when the direct wave a is not interfered with by the reflected wave. B) shows a case where reflected waves are causing interference from the detection point S of the direct waves. FIG. 15 CC') shows an enlarged view of the reflected wave b (FIG. 15 (A)), where h is the detection threshold of the aforementioned detection circuit.

As shown in the figure, according to the configuration shown in Fig. 14, the amplitude of the reflected wave is small, so the part that directly affects wave a is shown in Fig. 15 (
As in B), the time tr is shorter.

This time tr is determined by the allowable variation level h of the reflected wave of the detection circuit at the detection time point S, and is determined by the permissible fluctuation level h of the reflected wave of the detection circuit at the detection time point S.
) is the time it takes for the wave crest and waveform to exceed the threshold. Therefore, the effective vibration transmission distance in this case is tlsVg=ba-a>Vg(ts-tr)-(9)
The position of the vibrating pen is such that it satisfies the following. That is, in this case as well, the vibration sensor 6 is tolerated by keeping a sufficient distance from the reflection interference distance, but the effective coordinate input range becomes larger as Vgetr becomes shorter. The reflection interference distance in this case is indicated by (ts-tr) in Vg.

When the vibration sensor 6 is provided on the side of the vibration transmission plate 8, the sixth
Although the coordinate calculation method shown in the figure is slightly different, as long as the sensors are not lined up in a straight line due to parallel movement of the coordinate axes, coordinate calculations can be performed using calculation formulas equivalent to equations (4) and (5). .

[Effects of the Invention] As is clear from the above, according to the present invention, vibrations input from a vibrating pen are detected by a plurality of vibration sensors provided on a vibration transmission plate, and vibrations inputted from a vibration pen are detected on the vibration transmission plate of the vibrating pen. In a coordinate input device for detecting coordinates, the vibration sensor is arranged on the vibration transmission plate at a predetermined distance greater than a vibration reflection interference distance from a boundary surface where the characteristic acoustic impedance of the edge of the vibration transmission plate changes. This prevents distortion of the vibration detection waveform due to reflected waves at the boundary surface of the edge of the vibration transmission plate, and greatly improves coordinate detection accuracy.
This has the excellent advantage of being able to expand the effective coordinate input range.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the configuration of a coordinate input device adopting the present invention, Fig. 2 is an explanatory diagram showing the structure of the vibrating pen shown in Fig. 1, and Fig. 3 is an explanatory diagram showing the structure of the vibrating pen shown in Fig. 1. A block diagram showing the structure, FIG. 4 is a waveform diagram showing detected waveforms to explain distance measurement between the vibrating pen and the vibration sensor, and FIG. 5 is a block diagram showing the configuration of the waveform detection circuit in FIG. 1. , FIG. 6 is an explanatory diagram showing the arrangement of vibration sensors, FIG. 7 is an explanatory diagram showing different configurations of the coordinate detection device according to the present invention, and FIG. 8 (A)
~(C) are explanatory diagrams showing the influence of reflected waves depending on the mounting position of the vibration sensor, and Figures 9(A) to (CC) are diagrams showing the detection of reflected waves corresponding to Figures 8(A) to (C). A waveform diagram explaining the influence on the waveform, Fig. 10 is an explanatory diagram showing the difference in the vibration transmission path depending on the position of the vibrating pen, and Fig. 11 (
A) to (D) are explanatory diagrams each showing the effective direct wave transmission range, FIGS. 12 and 13 are explanatory diagrams each showing the effective coordinate detection range in the present invention, and FIG. 14 is an explanatory diagram showing the effective transmission range of direct waves. FIGS. 15A to 15C are waveform diagrams showing vibration detection waveforms in the configuration of FIG. 14. 1... Arithmetic control circuit 3... Vibration pen 4... Vibrator 6... Vibration sensor 7... Anti-reflection material 8... Vibration transmission plate 9... Waveform detection circuit 5
1... Preamplifier 52... Envelope detection circuit 54.58... Signal detection circuit 82... Reflection boundary surface

Claims (1)

[Claims] In a coordinate input device that detects vibrations input from a vibrating pen using a plurality of vibration sensors provided on a vibration transmitting plate to detect the coordinates of the vibrating pen on the vibration transmitting plate, A coordinate input device characterized in that the vibration sensor is arranged on the vibration transmission plate at a predetermined distance greater than a vibration reflection interference distance from a boundary surface where impedance changes.