JPS63104123A - Coordinate input device - Google Patents

Abstract

PURPOSE:To detect the coordinates with high accuracy based on detection of vibrations which is free from distortions, by setting the maximum width of an input plane for valid vibrations of a vibration pen at the value less than the coordinate detecting resolution. CONSTITUTION:A vibration pen 3 contains a vibrator 4 including a piezoelectric ele ment, etc., and transmits the ultrasonic vibrations produced by the vibrator 4 which is driven by a vibrator driving circuit 2 to a vibration transmitting plate 8 via a horn part 5 having a sharp tip. The vibrations of those waves transmitted into the plate 8 are detected by the vibration sensors 6 set at three corner parts of the plate 8 and the delay times of these vibrations are counted for detection of the position of the pen 3 on the plate 8. The vibration input plane of the tip part of the part 5 is formed with selection of a proper curvature so as to secure a contact with the plate at a single point at all times regardless of the contact angle of the pen 3 to the plate 8. When the area of a contact face between the part 5 and the plate 8 is set smaller than the coordinate detecting resolution, the vibrations of different phases are not supplied to the plate 8 and a vibration waveform approximate to a single wavelength free from distortions can be detected at a detecting point P. Thus, the vibration transmitting time can be accurately measured and therefore the coordinate detecting accuracy is improved.

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 sensors provided on a vibration transmitting plate. The present invention relates to a coordinate input device that detects coordinates on the top.

[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. In detecting the coordinates of a tablet in this type of device, ultrasonic vibrations generated on a vibration transmission plate by a vibrating pen equipped with a vibration generating element are detected by vibration sensors installed at multiple locations on the vibration transmission plate of the tablet. A method is known in which coordinates input by a vibrating pen are detected according to a delay time of vibration.

Compared to methods that measure the position of an input pen on a tablet using the resistance value of a resistive film or the electrostatic induction of a conductive film, this method uses a vibration transmitting plate made of a transparent material, etc. It has the advantage of being able to be used over and over again.

[Problems to be Solved by the Invention] In the above-mentioned ultrasonic method, a configuration in which the vibrator and the sensor are installed in reverse, that is, the vibrator is provided on the tablet side and the vibration sensor is provided on the vibrating pen side, is also considered. This configuration has a problem in that in order to measure the distances of the tablet from the X and Y axes, the vibrators provided at the X and Y axis positions must be driven in a time-division manner.

Therefore, a configuration in which the vibrator is attached to the vibrating pen side is common.

The conventional vibrating pen has a structure in which a vibrator made of an electrical-to-mechanical transducer such as a piezoelectric element is attached to a writing instrument-shaped body, and the vibration is transmitted to a vibration transmission plate through a horn part provided at the pen tip. has.

In order to effectively transmit the vibrations of the vibrator to the vibration transmission plate, the horn section is known to be of an exponential type having a conical shape with a pointed tip or a cross section shaped like an exponential curve. Possible materials for the horn portion include metal and ceramic.

In order for the vibrator of the vibrating pen and the horn to transmit vibrations efficiently, the dimensions of each part of the horn must satisfy the following resonance conditional expression.

α-a Dl: Diameter of large end of horn D2: Diameter of small end of horn, Il: Length of horn that resonates at half wavelength α: Wavelength constant = ω/C C: Speed of sound in horn material f: Resonance of horn Frequency ω: Resonance angular frequency of the horn = 2πf The amplitude expansion rate of the horn section is determined by DI/D2, but considering the strength of the pen tip against writing pressure, the value of D2 cannot be made that small. Therefore, the vibration input at the tip of the horn section The surface is often formed into a circular plane.

According to such a vibration input surface, when the input surface contacts the vibration transmission plate perpendicularly, the area of the input surface directly becomes the effective vibration input area.

On the other hand, the vibration input from the vibration pen is transmitted to multiple vibration sensors attached to the vibration transmission plate, and the distance to each sensor is measured by measuring the vibration transmission time, and coordinate detection is performed based on this. It is done.

In such a measurement method, when vibration is input from the vibrating pen over a certain input area as described above, microscopically, the input vibration is input from multiple input points on the vibration input surface of the vibrating pen. It becomes a composite wave of plate wave vibrations.

Therefore, the delay time of the plate wave reaching the sensor of the vibration transmission plate varies by the length of the diameter of the tip of the vibrating pen, and the detection accuracy cannot be lower than the diameter of the horn of the pen tip.

In the above, we have considered the case where the pen tip contacts the vibration transmission plate vertically, but in reality, vibrating pens are used at various angles just like ordinary writing instruments.

Therefore, it is necessary to obtain uniform coordinate detection characteristics no matter what angle the vibrating pen is used, but with the structure of the input surface of the horn part as described above, if the vibrating pen deviates even slightly from the vertical position, the horn Vibration input will be performed from one point on the edge of the tip surface.

Therefore, when a curve is drawn with a vibrating pen on the vibration transmitting plate and coordinates are input continuously, errors in detected coordinates vary and there is a problem that continuous coordinate detection cannot be performed.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, vibrations input from a vibrating pen provided with a vibration generating element are detected by a plurality of sensors provided on a vibration transmission plate. In the coordinate input device for detecting the coordinates of the vibrating pen on the vibration transmission plate, the maximum width of the effective vibration input surface for the vibration transmission plate of the vibrating pen is set to be smaller than the coordinate detection resolution.

[Operation] According to the above configuration, even if the angle of the vibrating pen is not constant, vibration is always transmitted from the vibrating pen to the vibration transmission plate via one point that is less than the coordinate detection resolution. Therefore, no matter what angle the vibrating pen contacts the vibration transmission plate, a detection error smaller than the detection resolution will not occur.

[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 of tiIJll14 is a display 11' using a liquid crystal display such as a dot matrix type.
Together with this, it constitutes an input/output device for characters, figures, images, etc.

In the figure, the reference numeral 8 is a vibration transmission plate made of acrylic, glass, etc., and a reflection plate made of silicone rubber etc. is used to prevent the vibration transmitted from the vibrating pen 3 from being reflected at the surrounding area. It is supported by the prevention material 7. Three vibration sensors 6 are attached to 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-level pulse signal from the arithmetic and control circuit l shown in FIG. . The electrical drive signal is converted into mechanical vibration by the vibrator 4 and transmitted to the vibration transmission plate 8 via the horn section 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 described above are waves called plate waves, and compared to surface waves, there are no scratches on the surface.
Waves propagating within the vibration transmission plate 8, which has the advantage of being less affected by obstacles, are detected by vibration sensors 6 provided at three corners of the vibration transmission plate 8 with a time delay corresponding to the distance.
reach. Therefore, by detecting vibration with the vibration sensor 6 and measuring its delay time, the vibration transmission plate 8
．． The position of the vibrating pen 3 above 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 11'' in FIG. 1 is driven by the arithmetic control circuit 1 via the display drive circuit 1O.

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 generates drive pulses for the vibrator drive circuit 2 shown in FIG. 1, and is started by the microcomputer 11 in synchronization with the calculation circuit. The count value of the counter 13 is
It is latched by the latch circuit 14 by the microcomputer 1.1.

The detection signal input from the waveform detection circuit 9 is the input capo)
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 11. 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.
The plate wave used in this embodiment is a unidispersive wave, which is delayed by a time tg before being transmitted to the vibration sensor via the vibration transmission plate, and therefore the detected waveform is The relationship between envelope 421 and phase 422 changes.

Let the advancing speed of the envelope be a group velocity Vg, and the velocity of the phase be a phase velocity 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 837g"tg...(1)
is given by Although the above equation relates to one of the vibration sensors 6, the same equation can measure the distance between the other two vibration sensors and the vibration pen.

Furthermore, in order to determine more accurate coordinate values, the phase waveform 42 shown in FIG.
2 specific detection point 1 For example, if the delay time of the zero contention cross point after passing the peak is tp as shown in Figure 4, then the distance d between the vibration sensor and the vibration pen is d = neλp + vpIItp - (2)
where λp is the wavelength of the elastic wave and n is an integer.

From equations (1) and (2) above, the above integral fin is: n=[(mag"tg-mapp-tp)/λp+-]
...(3) is shown. Here, N is a real number other than 0, and 0 is used as a negative value. For example, if N = = 2, if the envelope detection accuracy is within the scratching wavelength, n
can be determined. By substituting n determined as above into equation (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 transmitted to a preamplifier circuit 51.
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 signal of a predetermined waveform multiplied by tg is formed by a signal detection circuit 54 composed of a mono-multivibrator, etc., and is input to the arithmetic control circuit 1. Moreover, this Tg signal and the delay time adjustment circuit 5
From the original signal delayed by 7, a detection signal with a phase delay time T is formed by a comparator detection circuit 58 and inputted to the arithmetic control circuit 1. The circuits shown above 0 are for one vibration sensor 6. Similar circuits are provided for each of the other vibration sensors. Assuming that the number of sensors is generally h, the envelope delay time tgt~h for the arithmetic and control unit 1.

A detection signal of Tpl#h is input.

In the arithmetic control circuit of FIG. 3, the above Tgl-h.

↑The p1 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 mentioned above, the counter 13 is started in synchronization with the drive of the vibrator. Therefore, the latch circuit 14 receives data on the envelope and phase delay times.

When three vibration sensors are arranged at the corners of the vibration transmission plate 8 with symbols S and -s3 as shown in FIG. The straight line distance dl#d3 to the vibration sensor can be determined. The coordinates (x, y) of the position P of the vibrating pen 3 are 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.

As described above, the position coordinates of the vibrating pen can be detected in real time by performing calculations using the calculation control circuit 1.

According to the above configuration, since ultrasonic vibration is transmitted to the vibration transmission plate 8 as an elastic plate wave, interference caused by scratches or obstacles on the vibration transmission plate 8 is reduced, and highly accurate coordinate detection can be performed. can.

In this embodiment, the tip of the vibrating pen 3 is configured as shown in FIG. 7 to prevent variations in coordinate detection errors depending on the angle of the pen tip.

In FIG. 7, reference numeral 71 indicates the body of the vibrating pen 3, and the horn portion 5 is fixed to the tip thereof by a method such as screwing.

A base material 73 of the horn section 5 is made of metal such as aluminum, and a vibrator 4 made of a piezoelectric element or the like is fixed within the body 71 at the rear end of the horn section 5. The overall shape of the horn portion 5 is a conical shape or an exponential shape, as in the prior art, which allows effective vibration transmission.

The material and shape of the horn portion 5 are determined so as to resonate with the vibration frequency of the vibrator 4.

The vibration input surface at the tip of the horn portion 5 is formed of a curved surface as shown in the figure.

The curved surface of the vibration effective input surface has the required coordinate detection resolution,
Alternatively, an appropriate curvature can be selected and constructed as shown in FIG. 8 depending on the material of the vibration transmission plate. The curved surface can be formed by grinding the tip of the horn section 5, or by forming a tip with a curved structure from a material having an acoustic impedance close to that of the main body of the horn section, and fixing this to the tip of the horn section 5 by gluing or the like. .

According to the above configuration, the vibration input surface of the horn section 5 always contacts the vibration transmission plate 8 at one point, no matter what angle the vibration pen 3 contacts the vibration transmission plate 8. .

Therefore, the area of the effective vibration input surface does not change depending on the angle of the vibrating pen 3, unlike in the conventional case where the tip of the horn portion 5 is formed of a flat surface.

FIG. 9 shows the state of transmission of vibrations generated on the vibration transmission plate 8 by the conventional vibrating pen 3 having a flat vibration input surface.

When the vibration input surface at the tip of the horn section 5 of the vibrating pen 3 is in perpendicular contact with the vibration transmission plate 8 as shown in FIG. The vibration is input to the vibration transmission plate 8 from this point. Here, when focusing on the vibration components input from the two edges 31 and 32 of the horn section 5, the vibration waveforms input from each edge to the vibration transmission plate 8 are as shown by symbols 91 and 92. Assuming that these vibrations are transmitted to the vibration detection point P on the right side of the figure, the component of the vibration waveform 92 reaches the detection point faster than the component 91. The transmission time of waveform 91 at this time is tgl, waveform 9
The transmission time of 2 is tg2, and tgl>tg2. This time difference (phase difference) distorts the waveform detected at the detection point P and deteriorates coordinate detection accuracy.

However, if the vibration input surface of the horn section 5 is a curved surface as described above and the area of the contact surface between the horn section 5 and the vibration transmission plate 8 is set smaller than the coordinate detection resolution, as shown in FIG. Since the horn part 5 and the vibration transmission plate 8 are in contact with each other at one point, vibrations with different phases are not input to the vibration transmission plate 8 as shown in FIG. 9, and the detection point P has almost a single wavelength without distortion. Since vibration waveforms can be detected and vibration transmission time can be accurately measured, coordinate detection accuracy can be improved.

Further, according to the curved surface structure as described above, even if the vibrating pen 3 is tilted as shown in FIG. 8, the area of the effective vibration input surface of the horn portion 5 does not change, so input errors may occur depending on the operator's habits. Furthermore, even when inputting the coordinates of a curve continuously, the inclination of the vibrating pen 3 does not change, causing error variations during inputting, and making it impossible to input continuous coordinates.

In the above embodiment, the vibration input surface of the horn part has a curved structure, but the shape of the vibration input surface is not limited to a curved surface, and can be of any shape as long as the width of the effective vibration input surface is smaller than the detection resolution. I don't mind.

In addition to the above embodiments, by attaching the vibration sensor to the vibration transmission plate 8 through the same horn section as described above, and transmitting the vibration at one point on the vibration detection side, the distortion of the detected waveform can be further reduced. This allows the coordinate detection accuracy to be greatly improved.

[Effects] As is clear from the above, according to the present invention, vibrations input from a vibrating pen provided with a vibration generating element are detected by a plurality of sensors provided on the vibration transmission plate, and the vibrations of the vibrating pen are transmitted. In a coordinate input device that detects coordinates on a board,
Since the configuration is such that the maximum width of the effective vibration input surface to the vibration transmission plate of the vibrating pen is set to be smaller than the coordinate detection resolution, the vibration pen always sends a single point smaller than the coordinate detection resolution to the vibration transmission plate. This has the excellent effect of allowing highly accurate coordinate detection to be performed based on distortion-free vibration detection.

[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. Figure 4 is a waveform diagram showing the detected waveform to explain distance # measurement between the vibrating pen and the vibration sensor, and Figure 5 shows the configuration of the waveform detection circuit in Figure 1. 6 is an explanatory diagram showing the arrangement of the vibration sensor, FIG. 7 is a sectional view showing the structure of the vibrating pen, FIG. 8 is an explanatory diagram showing the function of the horn part of the vibrating pen, and FIG. FIG. 9 is a waveform diagram showing the state of vibration transmission from a conventional vibrating pen. 1... Arithmetic control circuit 3... Vibrating pen 4... Vibrator 5... Horn section 6... Vibration sensor
8... Vibration transmission plate 9... Waveform detection circuit 51
...Preamplifier 52...Envelope detection circuit 54.58...Signal detection circuit 91...Peak hold circuit 71...Body

Claims (1)

[Scope of Claims] 1) Coordinates for detecting the coordinates of the vibration pen on the vibration transmission plate by detecting vibrations input from a vibration pen provided with a vibration generating element using a plurality of sensors provided on the vibration transmission plate. A coordinate input device characterized in that the maximum width of an effective vibration input surface for the vibration transmission plate of the vibrating pen is set to be smaller than a coordinate detection resolution. 2) The coordinate input device according to claim 1, wherein the vibration input surface of the vibrating pen including the effective vibration input surface is a curved surface.