JPS63100530A - Coordinate input device - Google Patents

Abstract

PURPOSE:To obtain a transparent and high-precision coordinate input device convenient for use by providing a frequency dividing circuit, an AND circuit, and a logic circuit and driving an oscillating pen with the driving signal which is outputted from the logic circuit and has the waveform modulated. CONSTITUTION:Both of the group velocity and the phase velocity due to dispersion of a plane wave of an elastic wave are measured, and the coordinate position is operated based on these velocities to improve the resolution. Since the driving waveform of a signal which drives an oscillating pen is modulated, an inflection point is given near the head of the detection waveform obtained from a detecting means, and it is difficult that detection of this inflection point is affected by the reflected wave. Thus, the distance from a reflecting face to the detection point of the detection waveform is shortened, and the coordinate input device is formed which accurately detects the position coordinate and has a wide effective area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a coordinate input device that detects coordinate positions based on the propagation delay time of elastic waves, and is particularly intended to improve detection accuracy.

[Prior Art] Conventionally, as a coordinate input device called a digitizer or the like for inputting a coordinate position, for example, the following ones 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,
This pen tip is wired in a matrix on the panel, and the coordinate position of the pen tip is detected and input by bringing the pen tip close to one of the electrode wires, making an electromagnetic connection, and measuring the current generated in the electrode wire. thing.

■ 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.

[Problem to be solved by the invention] 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 graphic input.
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 induction type does not become transparent because the electric wires are arranged in a matrix.

Furthermore, if the ultrasonic type used in item 0 above uses surface waves or sound waves, if there is a flaw or an obstacle such as a hand between the sound wave transmitting part and the receiving part. However, such obstacles may cause problems such as erroneous detection of measurement points or failure to measure. 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 An object of the present invention is to eliminate the above-mentioned drawbacks and provide a coordinate input device that is transparent, highly accurate, and easy to use.

[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 board made of a vibration propagation medium, and transmits the vibration! ! The elastic wave propagated through the medium is detected by a conversion element that converts mechanical vibration into an electrical signal, which is placed at a predetermined position on the vibration propagation medium, and the propagation delay time of the elastic wave is measured based on the detected electrical signal. In a coordinate input device that detects the position coordinates of a vibrating pen using A logic circuit that weights the output signal of the product circuit and the pulse signal by a predetermined coefficient and then adds them to each other is provided, and the vibrating pen is driven by a drive signal having a modulated waveform output from the logic circuit. It is characterized by

[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. Since the driving waveform of the driving signal is modulated, the detection waveform obtained from the detection means has an inflection point near the beginning, and when detecting this inflection point, it is less susceptible to the influence of reflected waves. As a result, the distance from the reflecting surface to the detection point of the detection waveform can be made closer, and a coordinate input device with a wide effective area capable of accurate position coordinate detection can be provided.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the overall configuration of a coordinate input device 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 receiving vibrations, 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 input 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 electric 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 signal 14 serving as a carrier 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 depending on which part of the group of small waves of the signal 14 in FIG. Approximately 172 wavelengths may be generated.

For example, if a predetermined threshold S is set for the signal 14 and the detection signal 15 is extracted as shown in B in FIG. 3, the position of small waves will be affected by the dispersion as described above. (phase) changes with the distance between Ben 3 and sensor 6, so even if Ben 3's B distance is extremely small, the detection delay time is approximately one wavelength λ, as shown by A-D in Figure 3. Sometimes it moves. 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 rg 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 TX signal detection circuit (for example, a zero-cross comparator) that outputs a signal 22' representing the point at which 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;
23 is a monostable multivibrator circuit that opens the gate for a certain period of time (creating a so-called window) from the rise of the signal 22' representing the propagation delay time Tg, and 24 is the time period during which the gate created by the monostable multivibrator 23 is open. This is a comparator level supply circuit that provides a comparator level to the comparator 26. 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 comparator level created by the comparator level supply circuit 24 to the comparator 26 is detected representing the propagation delay time Tp based on the phase velocity. Signal.

Using both signals 22' and 26' representing these propagation delay times Tg and Tp, the arithmetic control circuit 1 performs calculations to detect the coordinate position. Step 9 of detecting this coordinate position
An example is detailed below.

As described above, the propagation delay time Tg based on the group velocity is determined by counting from the time when the drive pulse signal 12 is output, and this time is the envelope of the detected wave.

Since the detection is from a lobe, the detection accuracy is lower than the propagation delay time detected from a single detected wave. 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 λ and the propagation time t becomes Tpi (
However, i=1.2. ). That is, as the tip position of the pen 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 a
The peak was the wave , but gradually the wave b became the peak. Next, the movement will be such that the C wave will reach its peak. If the pen 3 is moved in the opposite direction, its peak movement will also be the opposite of that described above. When the movement of this peak is shown as a function of propagation time t and propagation distance 1, Tp in Fig. 6 is shown.
This results in a step-like movement curve as shown by i. Also, a,
Similar movements occur for the zero crossing points of waves 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 l 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 Tp. A concrete example of this is shown below.

Assuming that the propagation delay times Tg and Tp are detected as described above, Tpt in the range of Lp+ for Tg+ in the range of Lgr in FIG. 6, Tg2 in the range of f-g2, Tp2 in the range of tp2,
It is possible to sequentially detect one Tp for one sensor 6, such as with respect to Tg+ in the range of f-gs, and calculate the distance based on this Tpi. That is, in Fig. 6, if the propagation distance is °C, one wavelength of the detected wave is λ, and the phase velocity is υp, then the following equation (1) is obtained.
holds true.

λ=υPTP+nλ...(1) This above formula (
The distance @J2 based on 1) can be detected.

However, when n is Tg is in the range of jg+, nto1Tg is jg2. When the range is jg3, n=1. 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 of the arithmetic control circuit 1 (see Fig. 1). ) and this table I
Using A, Tg is converted to the value of n in the arithmetic control circuit 1, and phase velocity υp, propagation delay time Tp, constant n,
The statement is calculated by substituting each value of wavelength λ into equation (1).

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.

Furthermore, in this embodiment, in the transducer drive circuit 2 shown in FIG. 1, the waveform of the transducer drive signal (!SIA IIJ pulse signal) is modulated to create an inflection point in the waveform of the detection signal (sensor output signal) I try to give. Then, the inflection point is detected and the detection signal of this inflection point is used as a signal indicating the group propagation delay time Tg due to the group velocity instead of the above-mentioned Tg signal. Thereafter, in the same manner as described above, a signal indicating the phase propagation delay time Tp due to the phase velocity is detected, and further calculations are made from these values of Tg and Tp to detect the true position coordinates.

In FIG. 10, the waveform A is the waveform of a normal vibrator drive signal, and is the same as the waveform 12 in FIG. 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, and the phase propagation delay time Tp is detected from this Tg to calculate the phase coordinates. In this embodiment, the waveform of the vibrator drive signal is, for example, When the vibrator 4 of the pen 3 is driven with a waveform modulated as shown in , the detection signal obtained by the sensor 6 has a waveform as shown by D in FIG.

The waveform of the detection signal D 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 differentiating the envelope twice 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.
, Tp 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 the tree deer example, the first inflection point is placed close to the beginning of the detected wave using the waveform shown by D in Figure 10, so the position coordinates can be detected accurately without being affected by reflection. 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 frequency-dividing the signal 1' by 174. 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'
31 is an amplification drive circuit, which adds the outputs of the two coefficient number circuits 30 and 30 and drives the Drive signal 3 that is amplified to a voltage and drives the fJAII] child of pen 3
1'' waveform (see Figure 12) is output.

What is indicated by D in FIG. 10 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
The numerical values showing the relationship are stored in the internal table LA (see Figure 1), and from this table, the highly accurate Tg' is re-obtained from the highly accurate value of Tp. Since Tg and Tp' form a continuous straight line, , directly x using this value of Tg'
, y-coordinate position can also be calculated.

Furthermore, 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 obtained by twice differentiating the envelope of the detected wave. It is also possible. By this double differentiation, a steeper detection point can be obtained than when detecting a zero cross point with a single differentiation, that is, when detecting an envelope peak point, and detection can be performed with higher accuracy than envelope peak detection. When detecting a peak, it is affected by pen pressure, detection wave (7;) S/N, etc., but in the case of zero cross detection, accurate phase delay time Tp is detected without being affected by these factors. can.

That is, 211 in FIG. 8 is a two-time differentiating circuit, and the fourth
It is connected in place of the envelope peak detection circuit 21 shown in the figure, and outputs the twice differentiated output waveform 211'' shown in FIG. 9 to the τ8 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 when detecting this inflection point, A coordinate input device with a wide effective area that can be made less susceptible to the effects of reflected waves, thereby shortening the distance from the reflecting surface to the detection point of the detected waveform, and enabling accurate position coordinate detection. can be provided.

Further, according to the present invention, by storing the relationships among group propagation delay time Tg, phase propagation delay time Tp, and propagation path @jQ in a table in advance, and using this table, signal processing time can be shortened, and accuracy can be improved. 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 affected by the shadow U, 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 input 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... Pen (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...Synchronization circuit, 29...AND circuit, 30...Coefficient circuit, 31...Amplification drive circuit, 211...2-time differentiator circuit. The right name of the row of flowers /) Yutomo lsugi - />'J star link 'green' 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 frequency divider circuit that divides the frequency of a pulse signal of a continuous pulse train; an AND circuit that ANDs the output signal of the frequency divider circuit and the pulse signal; and each of the output signal of the AND circuit and the pulse signal. and a logic circuit that adds weights to each other by a predetermined coefficient, and the vibrating pen is driven by a drive signal having a modulated waveform outputted from the logic circuit. .