JPH10111117A - Ultrasonic digitizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic digitizer whose precision is good, in which even a distance longer than the distance corresponding to ultrasonic wave length can be measured and the area of the substrate of a tablet can be widened. SOLUTION: The digitizer is provided with a tablet 1 provided with ultrasonic sensors 2a, 2b for receiving ultrasonic vibration propagated on a substrate 1a on both the ends of one side of the substrate 1a, an ultrasonic oscillator 3 generating an ultrasonic signal, an ultrasonic generation pen 4 for converting the ultrasonic signal into ultrasonic vibration to be output, and a coordinate detection part 5 for detecting a phase difference between the ultrasonic signal from the ultrasonic oscillator and the ultrasonic signal from the ultrasonic sensor and detecting the coordinate of the position of the substrate brought into contact with the ultrasonic generation pen on the basis of the phase difference. In this case, a frequency changing-over part 3a is provided on the ultrasonic oscillator 3, and changed over to a plurality of different frequencies to be generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic digitizer, and more particularly, to an ultrasonic digitizer for calculating a distance based on a phase of an arrived ultrasonic wave.

[0002]

2. Description of the Related Art Conventionally, in a method of measuring a distance using an ultrasonic wave, a pulse-like ultrasonic wave is generated, and the arrival time (t1) of the ultrasonic wave is multiplied by a propagation velocity (S) to obtain a distance. (D
= T1 · C) and a sinusoidal ultrasonic wave are generated, and the frequency (f) is compared with the phase of the ultrasonic signal of the source and the phase of the arrived ultrasonic signal. (Φ) and the propagation velocity (S), the distance (d = S · φ / 2π
f) is calculated.

FIG. 4 is a schematic configuration diagram of a conventional ultrasonic digitizer, FIG. 5 is a diagram for explaining the principle thereof, and FIG. 6 is a waveform diagram showing problems of the conventional example. As shown in FIG. 4, the ultrasonic digitizer has an ultrasonic sensor 2a and an ultrasonic sensor 2b made of a piezoelectric material disposed at points A and B at both ends of one side of a substrate 1a on the tablet 1. The ultrasonic signal pen generated by converting the ultrasonic signal generated by the ultrasonic oscillator 3 into ultrasonic vibration is brought into contact with the desired point P above, and the coordinate detecting unit 5 causes the point A to be moved from the contact point P to the point P. Further, the distance (d1) and the distance (d2) to the point B are obtained, and the coordinates P (x, y) of the contact point P are detected from the distance.

As shown in FIG. 5, when the distance between the points A and B is (d0), the following equation (1) is obtained.
Expression (2) is satisfied, and expression (1) is subtracted from expression (2) to obtain expression (3). Further, expression (4) is obtained from expressions (1) and (3).
An expression is obtained. However, d0 is a known value, d1 and d2 are measured values, and therefore, equation (3) and (4)
The coordinates P (x, y) of the point P are obtained from the equation.

[0005]

(Equation 1)

As described above, as a method of measuring the distance from the point P to the point A or the point B, a method of generating a pulse-like ultrasonic wave and calculating from the arrival time thereof,
There is a method that generates a sine-wave ultrasonic wave and calculates it from its phase.In the former method, however, the rising point of the pulse becomes dull due to the characteristics of the ultrasonic oscillator and the like. In the method of FIG. 3, the accuracy is good, but if the measurement distance is longer than the distance corresponding to the wavelength of the ultrasonic wave,
As shown in the figure, it is not possible to distinguish between a phase difference within one wavelength or a phase difference at the second and third wavelengths, and measurement becomes impossible, so that the area of the substrate 1a of the tablet 1 is reduced. There was a problem that it could not be widened.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and is capable of measuring at a distance with a high accuracy and a distance longer than the distance corresponding to the wavelength of the ultrasonic wave, thereby increasing the area of the tablet substrate. It is an object of the present invention to provide an ultrasonic digitizer that can perform the operation.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a tablet having an ultrasonic sensor at one end of one side of a substrate for receiving ultrasonic vibrations transmitted to the substrate, And an ultrasonic generator pen that converts the ultrasonic signal into ultrasonic vibration and outputs the same, and a phase difference between the ultrasonic signal from the ultrasonic oscillator and the ultrasonic signal from the ultrasonic sensor. In the ultrasonic digitizer comprising a coordinate detection unit that detects the coordinates of the position of the substrate contacted by the ultrasonic generation pen based on the same phase difference, the ultrasonic oscillator is provided with a frequency switching unit, This is generated by switching to a plurality of different frequencies. In addition, a tablet equipped with an ultrasonic sensor at each end of one side of the board for receiving ultrasonic vibrations transmitted to the board, an ultrasonic oscillator for generating ultrasonic signals, and converting the ultrasonic signals to ultrasonic vibrations The ultrasonic generating pen to output and detect the phase difference between the ultrasonic signal from the ultrasonic oscillator and the ultrasonic signal from the ultrasonic sensor, based on the phase difference of the substrate contacted by the ultrasonic generating pen In an ultrasonic digitizer including a coordinate detecting unit for detecting a coordinate of a position, a plurality of the ultrasonic oscillators are provided, and ultrasonic waves of different frequencies are generated from the respective ultrasonic oscillators. . Further, each of the frequencies of the ultrasonic waves is a plurality of frequencies having a small prime number ratio. Further, the frequency of the ultrasonic wave is set to 2
In the case where there are two frequencies, the frequency becomes a frequency whose ratio is 3 to 5. Further, the frequencies of the plurality of ultrasonic waves are frequencies that are not in phase with each other at least within a measurement distance on the substrate. Further, the value obtained by multiplying the frequency of the plurality of ultrasonic waves by the least common multiple of the wavelength by one prime number for obtaining the same least common multiple and the value obtained by dividing the wavelength corresponding to the same prime number is the maximum value on the substrate. This is a value exceeding the value corresponding to the measurement distance.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The ultrasonic digitizer according to the present invention is constructed as described above, and generates ultrasonic waves of a plurality of frequencies from the ultrasonic wave generating pen. Since the phase is not in phase at least in the tablet substrate, the phase difference can always be detected, and even if the distance exceeds the distance corresponding to the wavelength of the ultrasonic wave, the measurement can be performed with high accuracy, and therefore, the area of the substrate can be increased. In addition, the coordinates of the position touched by the ultrasonic generating pen can be accurately detected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic digitizer according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of an ultrasonic digitizer according to the present invention, and FIG. 2 is a schematic configuration diagram showing another embodiment of the same. 1 and 2, the same functions as those in FIG. 4 use the same reference numerals and have been described in the section of the related art, so that the description thereof will be omitted. As shown in FIG. 1, the ultrasonic oscillator 3 is provided with a frequency switching unit 3a for switching a frequency to a plurality of different frequencies, or as shown in FIG. 2, a plurality of ultrasonic oscillators 3 generating a plurality of different frequencies is provided. ing.

FIG. 3 shows a phase difference (Ss1) between the ultrasonic signals (Ss1) and (Ss2) from the ultrasonic oscillator 3 and the ultrasonic signals (Sda) and (Sdb) from the ultrasonic sensor. φ1a), (φ1b), and (φ2
a) and (φ2b) are detected, and based on the phase difference, respective distances (d1) and (d2) from the ultrasonic sensor to the point P of the substrate in contact with the ultrasonic generating pen are calculated.
FIG. 4 is a main part block diagram illustrating an embodiment of a coordinate detection unit 4 that detects a coordinate P (x, y) of a point. As shown in the figure, the coordinate detecting unit 4 outputs an ultrasonic signal (S) from the ultrasonic oscillator 3.
s1) and (Ss2) and an ultrasonic signal (Sda) and an ultrasonic signal (Sdb) from the ultrasonic sensor, and a multiplier 11 for removing a high-frequency component of the signal from the multiplier 11 to obtain a phase difference signal. Output low-pass filter 12 and A / D
A conversion unit 13 and a phase difference (φ1a) based on the phase difference signal;
(Φ1b), (φ2a), and (φ2b) are calculated by the first arithmetic unit 14, and the phase differences (φ1a), (φ2a)
a), the phase difference (φ1b) and (φ2b) are temporarily stored, and the distance (d1) is calculated from the phase difference (φ1a) and (φ2a), and the distance (d2) is calculated from the phase difference (φ1b) and (φ2b). The same distances (d1) and (d2) as the second operation unit 15
And a third calculation unit 16 that calculates the coordinates of the point P from

The operation of the above configuration will now be described. First, insert the tip of the ultrasonic generating pen 4 into the tablet 1
Contacting an arbitrary position point P on the substrate 1a, and switching the frequency switching unit 3a of the ultrasonic oscillator 3 to generate an ultrasonic signal (Ss) having a frequency (f1) and transmitting the ultrasonic vibration transmitted through the substrate 1a. Is an ultrasonic signal (Sda) whose phase has been changed by each of the ultrasonic sensors 2a and 2b,
An ultrasonic signal (Sdb) is detected. From the ultrasonic signal (Sda) and the ultrasonic signal (Sdb) obtained as described above,
Phase difference (φ) with the ultrasonic signal (Ss) as follows
Is calculated, the distances from the point P to the ultrasonic sensors 2a and 2b are obtained, and the coordinates of the point P are obtained.

In obtaining the coordinates of the point P, first, the distance from the point P to each of the ultrasonic sensors 2a and 2b is calculated. Here, the method of calculating the distance from the point P to the ultrasonic sensor 2a will be described. I do. The ultrasonic signal (Ss = aSinωt) from the ultrasonic oscillator 3 and the ultrasonic sensor 2a
Ultrasonic signal from (Sda = bSin (ωt + φ))
Are adjusted (a = b), input to the multiplier 11 and multiplied, and the multiplied signal (Sin ω) from the multiplier 11 is multiplied.
t · Sin (ωt + φ) = Cosφ−Cos (2ωt +
φ)) through the low-pass filter 12
os (2ωt + φ)), the A / D converter 13 converts the phase difference signal (Cosφ) obtained by removing the phase difference signal (Cosφ) into a digital signal, and the arithmetic unit 14 calculates the phase difference signal (Cosφ).
φ), the phase difference (φ) is determined from the experimentally determined propagation velocity (C) of the substrate, and the distance (da) within one wavelength.
1 = φ · C / ω) Distance within two wavelengths (da2 = φ · C /
ω + 2π · C / ω), distance within n wavelengths (dan = φ · C)
/ Ω + 2πn · C / ω). Similarly, distances within one wavelength, distances within two wavelengths, and distances within n wavelengths are obtained for different frequencies (f2) of the ultrasonic wave, and the distances calculated at different frequencies (f1, f2) are calculated. Thus, the matched value is the distance d1 to be obtained.

Similarly, the distance d2 from the point P to the ultrasonic sensor 2b is calculated and described in the section of the prior art (3).
The coordinates P (x, y) of the point P can be obtained from the equation and the equation (4).

Now, two different frequencies (f
If 1) and (f2) are very close values, it is impossible to calculate an accurate distance because the difference of the phase difference depending on the frequency is small. For this reason, in the present invention, when the frequency of the ultrasonic waves is a plurality of frequencies whose ratio is a small prime number ratio, and when the frequency of the ultrasonic waves is two, the ratio is particularly 3 to 5. Frequency. Further, the frequency of the plurality of ultrasonic waves may be a frequency that is not in phase with each other at least within the measurement distance on the substrate, or a value whose least common multiple of the wavelength exceeds a value corresponding to the maximum measurement distance on the substrate. And so on.

[0016]

As described above, according to the ultrasonic digitizer of the present invention, ultrasonic waves of a plurality of frequencies are generated from the ultrasonic generating pen, and the plurality of frequencies are at least the tablet. Since the phase is not the same in the substrate, the phase difference can always be detected, and even if the distance exceeds the distance corresponding to the wavelength of the ultrasonic wave, the measurement can be performed with high accuracy. Therefore, the area of the substrate can be increased, and The coordinates of the position touched by the ultrasonic generating pen can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an ultrasonic digitizer according to the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the ultrasonic digitizer according to the present invention.

FIG. 3 is a block diagram showing a coordinate detecting unit of the ultrasonic digitizer according to the present invention.

FIG. 4 is a schematic configuration diagram showing a conventional ultrasonic digitizer.

FIG. 5 is an explanatory diagram for explaining the principle of coordinate detection of the ultrasonic digitizer.

FIG. 6 is a waveform diagram showing a problem of coordinate detection of a conventional ultrasonic digitizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tablet 1a Substrate 2a, 2b Ultrasonic sensor 3 Ultrasonic oscillator 3a Frequency switching part 4 Ultrasonic generating pen 5 Coordinate detection part 11 Multiplier 12 Low pass filter 13 A / D converter 14 First operation part 15 Second operation part 16 Third operation unit

Claims (6)

[Claims] 1. A tablet having, at both ends of one side of a substrate, an ultrasonic sensor for receiving ultrasonic vibration transmitted to the substrate, an ultrasonic oscillator for generating an ultrasonic signal, and an ultrasonic An ultrasonic generating pen that converts and outputs vibration, detects a phase difference between an ultrasonic signal from the ultrasonic oscillator and an ultrasonic signal from the ultrasonic sensor, and contacts the ultrasonic generating pen based on the phase difference. An ultrasonic digitizer, comprising: a coordinate detection unit that detects the coordinates of the position of the substrate that has been set; wherein a frequency switching unit is provided in the ultrasonic oscillator so that the frequency is generated by switching to a plurality of different frequencies. Ultrasonic digitizer featuring. 2. A tablet having, at both ends of one side of a substrate, an ultrasonic sensor for receiving ultrasonic vibrations transmitted to the substrate, an ultrasonic oscillator for generating an ultrasonic signal, and an ultrasonic oscillator for generating the ultrasonic signal. An ultrasonic generating pen that converts and outputs vibration, detects a phase difference between an ultrasonic signal from the ultrasonic oscillator and an ultrasonic signal from the ultrasonic sensor, and contacts the ultrasonic generating pen based on the phase difference. And a coordinate detector for detecting the coordinates of the position of the substrate, wherein a plurality of the ultrasonic oscillators are provided, and each ultrasonic oscillator generates an ultrasonic wave having a different frequency. An ultrasonic digitizer characterized in that: 3. The ultrasonic digitizer according to claim 1, wherein each of the frequencies of the ultrasonic waves is a plurality of frequencies having a small prime number ratio. 4. The ultrasonic digitizer according to claim 1, wherein, when the frequency of the ultrasonic wave is two, the ratio is 3: 5. 5. The ultrasonic digitizer according to claim 1, wherein the frequencies of the plurality of ultrasonic waves are frequencies that are not in phase with each other at least within a measurement distance on the substrate. 6. A value obtained by multiplying the frequency of the plurality of ultrasonic waves by the least common multiple of the wavelength and a value obtained by dividing a wavelength corresponding to the same prime number by one prime number for obtaining the least common multiple. 4. The ultrasonic digitizer according to claim 3, wherein the value exceeds a value corresponding to the maximum measurement distance.