JPS63100532A - coordinate input device - Google Patents

Abstract

PURPOSE:To accurately detect position coordinates by providing a signal modulating means and a inflection point detecting means and detecting the position coordinates of an oscillating pen based on a detected inflection point. CONSTITUTION:In an oscillator driving circuit, the waveform of an oscillator driving signal (driving pulse signal) is modulated to give an inflection point to the waveform of a detection signal (sensor output signal). This inflection point is detected, and the detection signal of this inflection point is used as a signal indicating a group propagation delay time Tg due to the group velocity instead of the signal Tg. A signal indicating a phase propagation delay time Tp due to the phase velocity is detected similarly, and values of signals Tg and Tp are calculated to detect true position coordinates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a coordinate human-powered device that detects a coordinate position based on the propagation delay time of an elastic wave, and is particularly aimed at improving detection accuracy.

[Prior Art] Conventionally, as a coordinate input device called a digitizer or the like that manually inputs coordinate positions, the following devices are known.

■ Layer the resistive films for the X-coordinate and the X-coordinate with the - side as a resistor, apply voltage or current to each resistive film, and apply pressure to the point (coordinate input point) with a pen or fingertip. On the other hand, the type that uses a resistive film measures the ratio of voltage or current and detects and inputs the coordinate position of that point.

■ Generate a local magnetic field pulse from the pen tip,
A type that uses electromagnetic 8 conductors, which detects and inputs the coordinate position of the pen tip by bringing the pen tip close to one of the electrode wires that are wired in a matrix on the panel, making an electromagnetic connection, and measuring the current generated in the electrode wire. Of things.

■ Types that use ultrasound include those that measure position coordinates by detecting the propagation delay time of surface waves through the ultrasound propagation medium, or those that transmit ultrasound into the air and measure the propagation time of the ultrasound. There are things to measure.

[The problem that the invention aims to solve] However, these conventional devices have the following drawbacks.

In other words, in the above-mentioned 0-term resistive film type, the uniformity of the resistor directly affects the accuracy of the graphic design.
In particular, it requires a resistor with excellent uniformity, which makes it very expensive. Furthermore, since two resistive films are required, one for the X-coordinate and one for the X-coordinate, there is also a drawback that the transparency is reduced.

Next, the above-mentioned 0-term electromagnetic 8 conductor type does not become transparent because the electric wires are arranged in a matrix.

Furthermore, if a surface wave or sound wave is used, such as the ultrasonic type described in Item 0 above, if there is a flaw or an obstacle such as a hand between the sound wave transmitting part and the receiving part,
There is a drawback that such obstacles may cause problems such as the measurement point being detected incorrectly or the measurement being impossible. On the other hand, in the case of conventional coordinate input devices that use plate waves of elastic waves, dispersion occurs, and the group velocity and phase velocity of the elastic waves are different, so it is necessary to detect the peak of the envelope and set a predetermined threshold. This detection had the disadvantage that an error of ±172 wavelengths occurred.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and provide a transparent, highly accurate, and easy-to-use coordinate system.

[Means for Solving the Problems] In order to achieve the above object, the present invention brings a vibrating pen that generates mechanical vibration into contact with a signal input plate made of a vibration propagation medium, and generates elastic waves propagated to the vibration propagation medium. is detected by a conversion element that converts mechanical vibration into an electrical signal placed at a predetermined position in the vibration propagation medium, and the position coordinates of the vibrating pen are determined by measuring the propagation delay time of the elastic wave based on the detected electrical signal. The coordinate input device for detection includes signal modulation means for modulating the waveform of the drive signal and supplying it to the vibrating pen, and inflection point detection means for detecting the inflection point of the waveform of the electric signal output from the conversion element. , the position coordinates of the vibrating pen are detected based on the detected inflection point.

[Function] In the present invention, the resolution is improved by measuring both the group velocity and the phase velocity due to the dispersion of the plate wave of the elastic wave, and calculating the coordinate position based on these velocities, and the vibrating pen is Since the drive waveform of the driving signal is modulated, the detection waveform obtained from the detection means has an inflection point near the beginning, making it less susceptible to the influence of reflected waves when detecting this inflection point. As a result, the distance from the reflecting surface to the detection point of the detection waveform can be made closer, and it is possible to provide a coordinate input device 3 with a wide effective area capable of accurate position coordinate detection.

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

FIG. 1 shows the overall configuration of a coordinate system according to an embodiment of the present invention. In this figure, reference numeral 1 denotes an arithmetic control circuit that performs arithmetic operations and control according to the present invention, and is composed of, for example, a microcomputer, a RAM, and the like. Reference numeral 2 denotes a vibrator drive circuit, which generates a pulse signal for driving the vibrator in response to a synchronization signal from the arithmetic control circuit 1. Reference numeral 3 denotes a vibrating ben for inputting coordinates, which includes a vibrator 4 such as a piezoelectric element that expands and contracts in response to a pulse signal from the vibrator drive circuit 2, and a horn with a pointed end that magnifies the amplitude of the vibration of the vibrator 4. 5, and a rod-shaped shaft portion that supports them.

6 is a sensor for photographing and receiving, 7 is an anti-reflection material, and 8 is a transparent propagation medium such as glass that propagates vibrations. The sensors 6 are arranged at a plurality of predetermined locations (three corners in this example) of the propagation medium 8 constituting the signal power board, and perform mechanical-electrical conversion of the vibration waves (plate wave elastic waves) of the Ben 3 propagated through the propagation medium 8. It is made of, for example, a piezoelectric element and is extracted as an electrical signal.

The antireflection material 7 is made of silicone rubber, for example, and absorbs vibrations from the ben 3 and prevents the vibrations from being reflected at the ends of the propagation medium 8.

9 is a received waveform detection circuit, which processes the signal received by the sensor 6 as described below and converts it into a signal indicating the propagation time of the elastic wave that has propagated in the propagation medium 8 from the ben 3 to the sensor 6; Output to the arithmetic control circuit 1. The calculation control circuit 1 detects the propagation delay time from the signals indicating the propagation time sent from the three sensors 6 via the reception waveform detection circuit 9, and calculates the Ben 3 according to a predetermined calculation formula based on the propagation delay time. Calculate the coordinate position of the contact point.

Reference numeral 10 denotes a display 11 that is integrally disposed below a transparent propagation medium (for example, glass) 8 and displays characters, images, etc.
This is a display drive circuit that drives the . The coordinate information of the Ben 3 calculated by the arithmetic control circuit 1 can be displayed on the display 11 through the display drive circuit 10 almost in real time, so that characters, figures, etc. drawn with the Ben 3 can be displayed as they are on the display 11 instantly.

FIG. 2 shows signal waveforms and timing in the embodiment of FIG. In FIG. 2, reference numeral 12 is a drive pulse signal applied to the vibrator 4 from the vibrator drive circuit 2, and the pulse width of this pulse signal 12 is set to the resonance frequency of the vibrator 4. 14 is a sensor signal (received signal) output from the sensor 6, and 15 is an output signal of the received waveform detection circuit 9 obtained by processing this signal 14.

When the tip of Ben 3 touches the glass plate 8 which is the propagation medium,
The vibration of the vibrator 4 driven by the pulse signal 12 as shown in FIG. 2 passes through the horn 5, amplifies its amplitude, and is transmitted to the glass plate 8. The vibration then becomes an elastic wave (ultrasonic wave) and propagates within the glass 8. At this time, plate waves are used as elastic waves. Using plate waves in this way,
Even if there are scratches or objects placed on the surface of the glass plate 8, there is almost no effect on the glass plate 8, and the sensor 6 can receive waveform elastic wave signals and can easily detect the position coordinates. It is.

By the way, the vibration waveform due to this plate wave does not have a constant shape because the group velocity and phase velocity differ due to dispersion. That is, the velocity (group velocity) at which the overall shape (envelope) shown by 13 in FIG. This is because, since the velocities (phase velocities) are different, a phenomenon occurs in which the phase of the carrier signal 14 becomes different with respect to the overall waveform 13 depending on the distance between the ben 3 and the sensor 6. Therefore, when detecting the propagation delay time, it is necessary to detect it using a method that minimizes the error caused by the difference between the group velocity and the phase velocity.

Next, specific means for detecting propagation delay time will be described in detail.

As mentioned above, the error in the detected delay time varies by ±1 depending on which part of the group of small waves of the signal 14 in FIG. / Two waves may occur.

For example, if a predetermined threshold S is set for the signal 14 and extracted as a detection signal 15 as shown in B in FIG. 3, the position of small waves ( Since the phase (phase) changes depending on the distance between Ben 3 and sensor 6, as shown in A to D in Figure 3, even if the distance between Ben 3 and B is extremely small, the detection delay time is approximately one wavelength λ. It may move. Therefore, in this embodiment, in order to eliminate this one-wavelength error, the propagation delay is calculated based on the velocity of a group of small waves (group velocity) and the velocity of each small wave (phase velocity). The coordinate position is calculated based on this delay time.

For example, the received waveform detection circuit 9 detects the envelope 13 from the sensor output signal 14 shown in FIG. 2, and detects the peak of the envelope 13. This peak is taken as a signal with a delay time Tg based on the group velocity. The accuracy of the signal resolution of the detected delay time Tg is lower than when small waves are detected because a collection of small waves is measured as one wave. However, the signal of this delay time Tg can also roughly detect the distance with respect to the coordinates of the vibration occurrence position.

Therefore, in this embodiment, after detecting the signal with the delay time Tg, the zero-crossing rising point of one of the first small waves is detected, and this detected rising point is taken as the signal with the propagation delay time Tp. When the arithmetic control circuit 1 calculates the coordinate position from the rise of each signal of the propagation delay times Tg and Tp obtained using the group velocity and phase velocity and the rise of the first pulse of the drive pulse signal, an error occurs. It is possible to detect coordinate positions with high resolution (accuracy).

FIG. 4 shows an example of the configuration of a received waveform detection circuit 9 that detects a signal representing the above-mentioned propagation delay time Tg-Tp for one sensor 6 among the sensors 6.

Moreover, FIG. 5 shows the waveform of the output signal of the circuit of FIG. 4.

Here, 6' indicates one of the plurality of sensors 6 in FIG. 19 is a preamplifier circuit that amplifies the signal received by this sensor 6'; 20 is an envelope detection circuit that detects the envelope 13 from the signal 14 amplified by the preamplifier circuit 19; and 21 is a signal detected by the envelope detection circuit 20. This is an envelope peak detection circuit (for example, a differentiating circuit) that differentiates the envelope in order to detect the peak of the envelope 13.

22 is a T that outputs a signal 22' representing the point where the signal 21' obtained by differentiating the envelope 13 crosses zero, that is, the propagation delay time Tg detected using the above-mentioned group velocity.
g signal detection circuit (e.g. zero cross comparator), 2
3 opens the gate for a certain period of time from the rise of the signal 22' representing the propagation delay time τg (creating a so-called window)
The monostable multivibrator circuit 24 is a comparator level supply circuit that provides the comparator level of the comparator 26 during the time when the gate formed by the monostable multivibrator 23 is open. 25 is an envelope detection circuit 20. Envelope peak detection circuit 21. Tg
Signal detection circuit 22) Monostable multivibrator 23.
This is a delay time adjustment circuit that adjusts the amount of time delayed through each circuit of the comparator level supply circuit 24. A signal 26' obtained by manually inputting the signal passing through the delay time adjustment circuit 25 and the comparison level created by the hump rate level supply circuit 24 to the comparator 26 is detected representing the propagation delay time Tp based on the phase velocity. Signal.

Using both of the signals 22' and 26' representing the propagation delay times rg and Tp, the arithmetic control circuit l calculates the coordinate position to detect the coordinate position. An example of the procedure for detecting this coordinate position will be described in detail below.

As mentioned above, the propagation delay time T8 based on the group velocity is determined by counting from the time when the drive pulse signal 12 is output, but since this time is detected from the envelope of the detected wave, The detection accuracy is lower than the propagation delay time detected from . Therefore, calculating the distance between Ben 3 and the sensor 6 from the propagation delay time Tp detected from one of the detected waves is much more accurate than calculating from the propagation time Tg based on the group velocity.

However, as described above, the phase of each detected wave shifts due to dispersion. Therefore, when detecting the peak with the highest level in the signal 14 in FIG. 2, the relationship between the propagation distance 11jik and the propagation time t becomes Tp in FIG.
It will be shown as i (however, i=1, 2, . . . ). That is, as the tip of the ben 3 continuously moves away from the sensor 6, the peaks change in the order shown by (A)-(B)-(C) in FIG. That is, at a certain distance, the a wave is at its peak, but gradually the b wave becomes the peak. Next, the movement will be such that the C wave will reach its peak. If Ben 3 were to move in the opposite direction, its peak movement would also be the opposite of what was described above. When this peak movement is shown as a function of propagation time t and propagation distance l, it becomes a step-like movement curve as shown by Tpi in FIG. Also,
Similar movements occur for the zero crossing points of waves a, b, and c.

By the way, since the propagation distance is calculated by counting the delay time, in the case of Tpi in FIG. 6, two values are obtained for the propagation distance 1 for one propagation delay time t. Therefore, by reading the value of the propagation delay time Tp based on the propagation delay time Tg, one propagation distance can be calculated with a highly accurate value based on 79. A specific example of this is as follows.

Assuming that the propagation delay times Tg and Tp are detected as described above, T9+s in the jil+ range for Tg+ in the tg1 range in FIG. 6, tri's tri for Tgz in the tg2 range, Tg2) in the range
It is possible to sequentially detect one Tp for one sensor 6, such as for Tgs in the range of tg, and so on, and calculate the distance based on this Tpi. That is, in FIG. 6, when the propagation distance is l, one wavelength of the detected wave is λ, and the phase velocity is υp, the following equation (1) holds true.

f=vpTp+nλ - (1) This above equation (1)
The distance @i based on can be detected.

However, when Tg is in the range of jg+, n=o, 1 is t
g2. When the range is tg3, n=1, n=i Therefore, when the propagation delay times Tg and Tp are detected as described above, data conversion based on the above equation (1) is performed using the internal table IA ( (see Figure 1), and using this table l^, the arithmetic control circuit 1 calculates T.
Convert g to the value of n, phase velocity vp, propagation delay time T
By substituting the values of p, constant n, and wavelength λ into equation (1), we obtain 2
Calculate. Through such calculations, sensor output signals are detected using the plurality of sensors 6, and the X and y coordinate positions are calculated and output.

Further, in this embodiment, in the vibrator drive circuit 2 shown in FIG. 1, the waveform of the vibrator drive signal (drive pulse signal) is modulated to give an inflection point to the waveform of the detection signal (sensor output signal). I have to. Then, detect the inflection point,
The detection signal of this inflection point is expressed as the group propagation delay time T due to the group velocity.
It is used as a signal indicating g in place of the above-mentioned Tg signal. Hereinafter, in the same manner as described above, a signal indicating the phase propagation delay time Tp due to the phase velocity is detected, and these Tg, T
The true position coordinates are detected by calculating from the pO value.

In FIG. 1O, the waveform A is the waveform of a normal vibrator drive signal, and is the same as the waveform 12 in FIG. 2. When the vibrator 4 is driven by the waveform of the vibrator drive signal A, the waveform detected by the sensor 6 becomes as shown by B in FIG. The group propagation delay time Tg is detected from Tg, the phase propagation delay time Tp is detected from this Tg, and the phase coordinate is calculated. When the vibrator 4 of the Ben 3 is driven with a modulated waveform as shown in FIG. 10, the detection signal obtained by the sensor 6 has a waveform as shown by D in FIG.

The waveform of this D detection signal is passed through the received waveform detection circuit 9 as shown in FIG. 8, and the first zero-crossing point of the waveform (211'' in FIG. 9) obtained by dividing the envelope into two equal parts is detected,
The signal at this zero crossing point is assumed to be a signal indicating the group propagation delay time Tg. Hereinafter, as described above, the phase propagation delay time T
A signal indicating p is detected, and the arithmetic control circuit 1 determines its Tg.
, and the TpO value to calculate more accurate position coordinates.

By modulating the vibrator drive signal in this manner, the range affected by reflection from the end face of the glass 8 serving as the propagation medium or the wall surface of the antireflection material 7 can be reduced.

In other words, in the case of the detected waveform as shown in B in Fig. 11, when reflection occurs, the reflected waves overlap from behind the waveform, and the waveform is distorted, resulting in accurate group propagation delay time Tg and phase propagation delay. The time Tp becomes undetectable. Therefore, in order to minimize the influence of reflected waves, the propagation time T should be
g and Tp must be detected. In this embodiment, the first inflection point is set close to the beginning of the detected wave using the waveform shown by D in FIG. 10, so the position coordinates can be accurately detected without being affected by the reflection U. Can be done.

Note that even the antireflection material 7 cannot completely absorb reflected waves, and some reflection may occur even in the antireflection material 7, which may affect the detected waveform.

FIG. 11 shows a vibrator drive circuit 2 that executes the above-mentioned modulation process.
An example of the configuration is shown below. In FIG. 11, 1 is a vibrator drive signal outputted from the arithmetic control circuit 1 to the vibrator drive circuit 2, and has a pulse waveform as shown in FIG.

Further, 27 is a frequency dividing circuit, which outputs a signal 27' (see FIG. 12) having a waveform obtained by dividing the frequency of the signal 1' by 1/4. 28
is a synchronous circuit, which aligns the rising edges of the waveforms of signals 1' and 27'.

Reference numeral 29 denotes an AND circuit (logical product circuit) which performs the logical product of signals 1' and 27' to obtain a signal having the waveform shown at 29' in FIG. 30 is a coefficient circuit, and a signal 29'
and 1' at different predetermined amplification factors. 31 is an amplification drive circuit, and two coefficient circuits 30.3
The waveform of the drive signal 31' (see FIG. 12) for driving the vibrator of the pen 3 is output by adding the outputs of 0 and amplifying it to a drive voltage.

What is indicated by D in Fig. 1θ and 31' in Fig. 12 is
This shows an example of a modulated drive waveform, and the present invention can be applied to drive waveforms that are modulated differently.

Note that the delay time adjustment circuit 25 in FIG.
This circuit is not necessary if the delay time adjustment is counted from the beginning. Also, Tg and Tp
With the numerical values showing the relationship in the internal table, we retake the highly accurate Tg' from the highly accurate value of rp from this table IA (see Figure 1), and since Tg and Tp' form a continuous straight line, , it is also possible to directly calculate the x and y coordinate position using this value of Tg'.

In addition, as shown in Figures 8 and 9, in group velocity detection, instead of envelope peak detection, the group velocity is detected by detecting the zero-crossing point of a waveform that is equal to two parts of the envelope of the detected wave. It is also possible. By detecting the zero-crossing points for two aircraft, a steeper detection point can be obtained than when detecting the envelope peak point using one aircraft, and the detection accuracy can be improved compared to envelope peak detection. When detecting peaks, it is affected by pen pressure, S/N of detected waves, etc.
In the case of zero-cross detection, accurate phase delay time ip can be detected without being influenced by these factors.

In other words, 211 in Fig. 8 is a circuit for two machines, and the fourth
It is connected in place of the envelope peak detection circuit 21 shown in the figure, and outputs the output waveform 211'' of the two machines in FIG. 9 to the Tg signal detection circuit 22.

[Effects of the Invention] As explained above, according to the present invention, by measuring both the group velocity and the phase velocity due to dispersion of plate waves of elastic waves, and calculating the coordinate position based on these velocities, Since the resolution has been improved and the drive waveform of the signal that drives the vibrating pen is modulated, the detection waveform obtained from the detection means has an inflection point near the beginning, and this inflection point can be detected. Coordinates with a wide effective area that can be made less susceptible to the influence of reflected waves, thereby making the distance from the reflecting surface to the detection point of the detected waveform closer, allowing accurate position coordinate detection. Human powered equipment can be provided.

Further, according to the present invention, the relationship between the group propagation delay time Tg, the phase propagation delay time Tp, and the propagation distance sentence is stored in advance in a table, and by using this table, the signal processing time can be shortened, and the accuracy can be reduced. A high level of detection is possible.

Further, according to the present invention, by providing a detection window using a monostable multivibrator and a comparator level supply circuit, it is possible to detect position coordinates with high accuracy without being affected by erroneous detection.

Further, according to the present invention, by providing a delay adjustment circuit, accurate group delay time Tg and phase delay time Tp can be detected from the envelope and the detected wave, and position coordinates can be detected with high precision.

Furthermore, according to the present invention, when detecting the phase delay time Tp, instead of detecting the peak of the detected wave, by detecting the zero cross, the pen pressure when detecting the peak, the S/N of the detected wave, etc. It is possible to detect an accurate phase delay time Tp without being influenced by the above, and to detect highly accurate position coordinates.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a coordinate human-powered device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the drive pulse signal of the vibrator shown in FIG. 1, the output signal of the sensor, and the propagation delay time detection signal. A waveform diagram showing the waveform and output timing. Figure 3 is a waveform diagram showing the principle that a detection error occurs when the waveform of the propagation delay time detection signal is detected at a certain threshold. Figure 4 is a waveform diagram showing the reception of Figure 1. A block diagram showing an example of the configuration of a waveform detection circuit. Fig. 5 is a waveform diagram showing the waveform and output timing of the output signal of the circuit in Fig. 4. Fig. 6 shows the relationship between the distance and time of the propagation delay times Tg and Tp. Figure 7 (A), (B), and (C) are explanatory diagrams showing enlarged peaks and zero-crossing points near the peak of the detected wave;
FIG. 8 is a block diagram showing a modification of the embodiment of the present invention, FIG. 9 is a waveform diagram showing the waveform and output timing of the output signal of the circuit in FIG. 8, and FIG. 11 is a block diagram showing a configuration example of a vibrator drive circuit according to an embodiment of the present invention that outputs a modulated drive waveform, and FIG. 12 is a waveform diagram showing a detection waveform based on a modulated drive waveform.
FIG. 2 is a waveform diagram showing the waveform of an output signal of the circuit shown in FIG. 1; DESCRIPTION OF SYMBOLS 1... Arithmetic control circuit, 2... Vibrator drive circuit, 3... Ben (vibrating pen), 4... Vibrator, 5... Horn, 6... Sensor, 7... Antireflection material, 8... Propagation medium (glass), 9... Received waveform detection circuit, 10... Display drive circuit, 11... Display, 20... Envelope detection circuit, 21... Envelope Peak detection circuit, 22...T
g signal detection circuit, 23... Monostable multivibrator, 24... Comparator level supply circuit, 25... Delay time adjustment circuit, 26... Comparator (Tp detection circuit), 27...
Frequency dividing circuit, 28... Synchronous circuit, 29... AND circuit, 30... Coefficient circuit, 31... Amplification drive circuit, 211... 2-equipment division circuit. Torazu V Imo, Ren 1j's I-sango s Risome 1 Butcher 1 Mei Sugu Gin-no-N Pekinaku-ku Figure 3

Claims (1)

[Claims] 1) A vibrating pen that generates mechanical vibration is brought into contact with a signal input plate made of a vibration propagation medium, and an elastic wave propagated to the vibration propagation medium is disposed at a predetermined position of the vibration propagation medium. A coordinate input device that detects the positional coordinates of the vibrating pen by detecting mechanical vibrations generated by a transducer with a conversion element that converts them into electrical signals, and measuring the propagation delay time of the elastic waves based on the detected electrical signals, A signal modulating means for modulating the waveform of a drive signal and supplying the modulated waveform to the vibrating pen; and an inflection point detecting means for detecting an inflection point of the waveform of the electric signal output from the conversion element, A coordinate input device characterized in that the position coordinates of the vibrating pen are detected based on the inflection point. 2) In the device according to claim 1, the propagation delay time to be counted includes both a group propagation delay time related to group velocity due to dispersion of the elastic wave and a phase propagation delay time related to phase velocity. A coordinate input device characterized by: