JPH06186328A - Ultrasonic range-finding device - Google Patents

Abstract

PURPOSE:To significantly improve coordinate specifying resolution of a coordinate input device by transmitting/receiving two frequencies and obtaining respective phases, and then, based on these phases, obtaining the distance between a transmitter and a receiver. CONSTITUTION:A transmission circuit (a) cuts out continuous waveform of fundamental frequency f1 from an oscillator b, and drives a transmitter c. Ultrasonic waves, propagating in the air, are converted into electrical signals by a receiver and then amplified (e), after that, inputted into a phase detector f. In phase detection, firstly, two multiplication waveforms (sin and cos) having the same frequency f1 but of but of different phase by 90 degrees from each other, are multiplied together by a multiplier, and only low-frequency component is extracted by an LPF, and then their ratio (tan 2pifx1) is obtained, further, from its inverse function tan<-1> (tan 2pifx1), instantaneous phase X1 of reception signal is obtained, and then averaged. In a similar manner, phase X2 of fundamental frequency f2 is obtained, and an analysis part g, based on phase X1 and phase X2 of two frequencies, corrects the sound velocity and phase, to obtain the distance L between a transmitter and a receiver. By using phase for measuring distance, precision of about 1/40 wavelength is available.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic distance measuring device for measuring distance using ultrasonic waves, and in particular, it uses ultrasonic waves to personalize movement and position of a pen tip, a human finger, a head or the like. The present invention relates to an ultrasonic distance measuring device suitable for being applied to a coordinate input device for inputting to a computer, a workstation, CAD, or the like.

[0002]

2. Description of the Related Art FIG. 13 is a block diagram showing a coordinate input device for inputting coordinates using ultrasonic waves. In this example, three ultrasonic wave receivers 2a, 2b, 2c are fixed to a position adjacent to a monitor screen 5a such as a CRT, while the ultrasonic wave transmitter 1 is attached to the tip of a pencil type operator, This operator is operated by the operator on the front surface of the monitor screen 5a. The operator is provided with a switch (not shown), and when the operator presses this switch, an ultrasonic wave pulse is emitted from the ultrasonic transmitter 1 attached to the tip of the operator. This ultrasonic pulse is received by each of the three ultrasonic transmitters 2a, 2b, 2c, and each received signal is input to the coordinate calculation unit 3. A transmission trigger signal indicating the timing at which the ultrasonic wave is emitted from the ultrasonic transmitter 1 is also input to the coordinate calculation unit 3, and the coordinate calculation unit 3 receives three-dimensional coordinate information of the ultrasonic transmitter 1 (operator). Is required. The obtained coordinate information is input to the computer 4, converted into coordinates to be displayed on the monitor screen 5a, and sent to the monitor 5 as display information. For example, a stereoscopic view is displayed on the monitor screen 5a, and the three-dimensional coordinates superposed on the stereoscopic view and instructed by the operator are displayed. Thereby, for example, the operator thinks as if the three-dimensional structure displayed on the monitor screen 5a exists on the front surface of the monitor screen 5a, and operates the operator to select an arbitrary three-dimensional structure of the three-dimensional structure. You can specify the position. Although the coordinate calculator 3 is provided separately from the calculator 4 here, the coordinates may be calculated inside the calculator 4. In addition, although it has been described here that the operator side includes the ultrasonic transmitter, the operator side may include the ultrasonic receiver and the monitor side may include the ultrasonic transmitter.

FIG. 14 is a diagram schematically showing a transmission / reception waveform of ultrasonic waves for conventional coordinate analysis. The transmitted waveform is
As shown in the figure, it is a pulse-like waveform that is repeatedly generated every time the operator presses the switch or at a predetermined time interval after pressing the switch. On the other hand, the received waveform is a waveform that repeatedly changes sinusoidally so as to have a predetermined envelope. Conventionally, as shown in the reception waveform of FIG. 14 (a), the reception waveform is monitored with a predetermined threshold, and the propagation time τ from the start of transmission until the reception waveform crosses the predetermined threshold is Measured with ultrasonic receiver, distance L = τ ×
C (C is the speed of sound) is calculated, and based on this, the ultrasonic transmitter 1
The coordinates of the (operator) were obtained (Japanese Patent Laid-Open No. 52-1271).
29).

[0004]

By the way, since spatial ultrasonic waves are strongly attenuated and the attenuation is proportional to the square of the ultrasonic frequency, only ultrasonic waves in a considerably low frequency range such as 40 kHz are practically used. I can't. In addition, since the attenuation is large, the amplitude of the received waveform changes considerably depending on the distance between the ultrasonic transmitter and the ultrasonic receiver. Therefore, the propagation time τ easily changes for one cycle depending on, for example, whether the first wave of the received waveform exceeds a predetermined threshold, and the ultrasonic wave of 40 kHz does not change the propagation time for this one cycle. The distance is equivalent to about 8.5 mm, and the resolution is too low for the coordinate designating means, and only coarse coordinates can be designated, which is far from practical use.

Several methods have been proposed in an attempt to solve this problem. For example, JP-A-59-102127
As shown in the received waveform of FIG. 14 (b), the publication discloses a method in which envelope detection is performed and a zero cross point closest to the peak of this envelope is used as the propagation time τ. However, this envelope usually has a fairly gentle slope, and therefore, an error of about one cycle is included in obtaining the peak of the envelope, and eventually the coordinate pointing resolution cannot be improved.

In Japanese Patent Laid-Open No. 63-283863, a typical received waveform is stored in advance, and a cross-correlation operation between this received waveform and a received waveform obtained by an ultrasonic receiver is performed. Has proposed a method of correcting the rising time of the received waveform. However, in this case, the waveform obtained by the cross-correlation calculation also becomes a repetitive waveform having the same shape as the received waveform, and thus also includes an error of about one period.

Further, Japanese Patent Laid-Open No. 63-159779 proposes a method using a chirp wave compression technique. A chirp wave is a waveform whose frequency changes continuously. It has been theoretically shown that a correlation calculation waveform with a sharp peak can be obtained by employing this chirp wave and performing a correlation calculation, for example, but since aerial ultrasonic waves are severely attenuated, they are originally narrowband and wideband. It is extremely difficult to manufacture an airborne ultrasonic transducer of
Only about 2 kHz can be changed with respect to z, and even if the frequency is changed to this extent, the accuracy is hardly improved.

In view of the above circumstances, it is an object of the present invention to provide an ultrasonic distance measuring device suitable for greatly improving the coordinate pointing resolution of a coordinate input device.

[0009]

An ultrasonic distance measuring apparatus according to the present invention for achieving the above object comprises: (1) an ultrasonic wave transmitter for transmitting an ultrasonic wave and an ultrasonic wave transmitted from the ultrasonic wave transmitter. One or a plurality of ultrasonic transducers that have the functions of both of the ultrasonic receivers or share the functions (2) Generate drive signals for transmitting ultrasonic waves of at least two different frequencies from the ultrasonic transmitter Transmitting section (3) Phase detecting section for detecting respective phases of ultrasonic waves of at least two frequencies received by the ultrasonic receiver (4) Ultrasonic wave transmitter based on at least two phases detected by the phase detecting section And a distance analysis unit for determining the distance along the propagation path of the ultrasonic wave between the ultrasonic receivers.

Here, when the frequencies of different ultrasonic waves are f ₁ and f ₂ , the sound velocity is c, and the maximum value of the measurement distance range is L _max , the transmitting unit is given by the formula | f ₂ −f ₁ | <c / L _max (1) The ultrasonic transmitter is driven so that ultrasonic waves of at least two frequencies f ₁ and f ₂ satisfying (1) are output from the ultrasonic transmitter. The ultrasonic transmitter may be driven so that the ultrasonic waves of these at least two frequencies f ₁ and f ₂ are sequentially transmitted at a time interval from the ultrasonic wave transmitter, or from the ultrasonic wave transmitter. The ultrasonic transmitter may be driven so that ultrasonic waves of at least two frequencies f ₁ and f ₂ are transmitted one after another. Alternatively, the transmitting unit applies a drive signal including at least two frequencies f ₁ and f ₂ to the ultrasonic transmitter, and the ultrasonic distance measuring device includes:
A configuration including a filter unit that extracts at least two ultrasonic waves of frequencies f ₁ and f ₂ from the ultrasonic waves received by the ultrasonic receiver may be provided.

Further, it is preferable that the phase detecting section in the ultrasonic distance measuring apparatus of the present invention has means for storing a correction value for correcting the phase detected by the phase detecting section. It is also a preferable aspect that the ultrasonic distance measuring device includes a temperature sensor for correcting the distance calculated by the distance analyzing unit.

When the ultrasonic distance measuring device of the present invention is constructed as a device for obtaining two-dimensional coordinates or three-dimensional coordinates,
The ultrasonic distance measuring device of the present invention includes a plurality of first ultrasonic transducers, which are arranged at predetermined positions different from each other and are used as either one of an ultrasonic transmitter or an ultrasonic receiver, and the first ultrasonic transducers. A second ultrasonic transducer, which is movably provided with respect to the other ultrasonic transducer and is used as the other one of the ultrasonic transmitters or the ultrasonic receivers different from the above one. Of the second ultrasonic transducer based on the plurality of distances obtained using the second ultrasonic transducer and the second ultrasonic transducer.
A configuration including a coordinate analysis unit for obtaining dimensional coordinates or three-dimensional coordinates is adopted.

[0013]

In the following, regarding the ultrasonic distance measuring apparatus of the present invention, a case where one set of ultrasonic transmitter and ultrasonic receiver is used will be described for the sake of simplicity. However, a reflector using one ultrasonic transmitter / receiver is used. The same applies when the distance between and is obtained. If the distance between the ultrasonic transmitter and the ultrasonic receiver is L, then L = (n ₁ + x ₁ ) λ ₁ (2) Here, n is an integer of 0 or more, λ is a wavelength, x
Is a numerical value between 0 and 1, and xλ is the remainder of dividing the distance L by nλ. The subscript number 1 indicates that it relates to the ultrasonic wave of the first frequency. The information obtained when the phase of the received signal is detected is only x. In other words, it has been generally accepted that the distance L cannot be obtained unless n is known, and thus the absolute distance cannot be obtained by phase detection.

The present inventor proposes a method for obtaining n here. It seeks absolute coordinates with extremely high accuracy based only on phase information. Therefore, using ultrasonic waves of two or more frequencies, the phase of the received signal is detected for each ultrasonic wave. That is, x ₂ shown in L = (n ₂ + x ₂ ) λ ₂ (3) is measured by using an ultrasonic wave having a wavelength λ ₂ (that is, a different frequency) different from that of the above formula (1). Here, n ₂ is an integer.
In equations (2) and (3), the unknowns are L,
Since there are 3 of n ₁ and n ₂ , it cannot be solved as it is.

Therefore, restrictions are given. The difference between n ₁ and n ₂ is 1
Set λ ₁ and λ _{2 so} that The reason for this is
This is because, if the difference between n ₁ and n ₂ differs by 2 or more, the solution cannot be obtained because the difference between n ₁ and n ₂ cannot be obtained in principle only by the phase information. n ₁ is approximately L / λ ₁ from the equation (1), n ₂ is approximately L / λ ₂ from the equation (2), and the difference between n ₁ and n ₂ is the maximum at the maximum value of L | (L _{The condition of max} / λ ₂ )-(L _max / λ ₁ ) | <1 (4) is given. Here, L _max is the maximum value of the measured distance. (4) is deformed and the above-described (1) Expression | f ₂ -f ₁ | obtain _{<c / L max ... (1} ). Where c is the speed of sound, and f ₁ and f ₂ are wavelengths λ, respectively.
It is the frequency of the ultrasonic wave having ₁ and λ ₂ . For example, when f ₁ is 40 kHz, the maximum value L _max of the measurement distance is 300
It is derived from the equation (4) that f ₂ should be 41 kHz (39 kHz may be used) in order to obtain mm. Although it is extremely difficult to manufacture a wideband aerial ultrasonic transducer, it is possible to easily provide a band of this degree, which is not a practical obstacle. Although L _max is defined as the maximum value of the measurement distance in the above, it is more accurate to set it to the maximum value of the measurement distance range. For example, when L _{max is set} to 300 mm, 30 is set when the short range detection limit is set to 0 mm.
The maximum value of the measurement distance is 0 mm, but the maximum value of the measurement distance is 400 when the detection limit of the short distance is 100 mm.
mm. When the distance to the reflector is obtained using one ultrasonic transmitter / receiver, ultrasonic waves propagate back and forth. Therefore, for example, in order to set the maximum value of the measurement distance to 300 mm, L _max in the equation (4) is calculated to be 600 mm.

A method for obtaining n ₁ from the equations (2) and (3) in the case of f ₁ <f ₂ will be described below. f ₁ <
In the case of f ₂ , λ ₁ > λ ₂ . In the case of f ₁ > f ₂ , ultrasonic waves of two frequencies may be considered in alternation, and therefore, even if f ₁ <f ₂ , generality is not lost. λ ₁ ＞ λ
_In the case of ₂ , if conditional expression (4) is satisfied, n ₂ = n ₁ −1
However, n ₂ = n ₁ or n ₂ = n ₁ +1.

First, n₂= N₁The case will be described.
At this time, from equations (2) and (3), n₁= (X₂λ₂-X₁λ₁) / (Λ₁−λ₂)… (5) For simplicity, n shown in FIG.₂= N₁= 3
The analysis method will be described using the example of. Check at 2 frequencies
Phase to be emitted x₁, X₂From x₁λ₁, X₂λ ₂Total
Calculate x₁λ₁, X₂λ₂Respectively the distance L to λ₁，
λ₂It is the remainder divided by. Using equation (5), n₁Seeking
This n₁By substituting into equation (2)
L can be obtained.

Next, n₂= N₁If +1 then
From the formula (3), n₁= (X₂λ₂-X₁λ₁+ Λ₂) / (Λ₁−λ₂) ... (6) N in FIG.₁= 4, n₂= 5 is shown. x₂λ
₂X₂λ₂+ Λ₂Then n ₂= N₁= 4,
It can be seen that the formula (5) can be applied.

As shown above, n₂= N₁Or n₂= N₁
The formula applied by +1 is different from the formulas (5) and (6). n
₂= N₁Or n₂= N₁Known because +1 is unknown
Λ ₁, Λ₂, X₁, X₂Need to determine this using
There is. The determination method will be described below. n₂= N₁When
Then, rearranging equations (2) and (3), x₂λ₂-X₁λ₁= N₁(Λ₁−λ₂)… (7), and n₂= N₁Organize equations (2) and (3) as +1
Then x₂λ₂-X₁λ₁= N₁(Λ₁−λ₂) −λ₂ … (8). Where λ₁−λ₂> 0, that is, frequency f₁<
f₂Consider the case.

First, when n ₂ = n ₁ , it can be seen from equation (7) that x ₂ λ ₂ > x ₁ λ ₁ . Then n ₂
= N ₁ +1, n ₁ is smaller than L _max / λ _{1 and} the right side of equation (8) is transformed to n ₁ = (λ ₁ −λ ₂ ) −λ ₂ <L _max (λ ₁ −λ ₂ ) / λ ₁ −λ ₂ = L _max −L _max λ ₂ / λ ₁ −λ ₂ = λ ₂ (L _max / λ ₂ −L _max / λ ₁ −1) (9). The inside of the brackets of λ ₂ or less in the expression (9) is 0 or less according to the conditional expression given by the expression (4). Therefore, n ₂ = n ₁ +
When ₁ , it is understood that x ₂ λ ₂ <x ₁ λ ₁ is always satisfied.

From the above, x₂λ₂> X₁λ₁Then n
₂= N₁And n using the equation (8) ₁, X₂λ₂
<X₁λ₁Then n₂-N₁+1 and use equation (9)
N₁You can see that Finally check the accuracy
Debate. Λ of the numerator on the right side of equation (5)₁And λ₂Haho
Since both are equal, λ₁And denominator λ₁−λ₂And Δλ
If you put it, equation (5) is n₁= (X₂-X₁) λ₁It can be approximated as / Δλ (10). From now on, n₁The precision of x₂-X₁You
That is, it can be seen that it is determined by the accuracy of phase detection.

Of the experiment using hollow ultrasonic waves by the present inventor
As a result, even if the simplest circuit is used, the phase detection accuracy is
It was confirmed that about 1/40 of the wavelength can be easily achieved.
ing. N is an integer₁The accuracy of is less than 1.
For this purpose, if the phase detection accuracy is about 1/40, λ
₁It is a necessary condition to set / Δλ to 40 or less.
λ₁/ Δλ is approximately f₁/ (F₂-F₁). Above
f₁= 40 kHz, f ₂= 41kHz in the example₁The spirit of
Degree is equal to the limit of this condition. n₁The accuracy of
There are two possible ways to do this. One is f₁Small
One is f₂-F₁To make
And. However, the former is n₁Effective in improving the accuracy of
However, since the wavelength λ becomes large, it is shown in equation (2).
The measurement accuracy of the distance L is reduced.

On the other hand, in the latter, the accuracy of the distance L does not decrease.
As is clear from the equation (1), L _maxDecrease
Ku. L_maxIn order to increase the accuracy without lowering the
, It is important to improve the accuracy of phase detection. actually
Is L determined by the usage environment_{ma x}For n₁sand
Wachi L_max/ Λ₁Is close to the reciprocal of the phase detection accuracy
As λ₁, The frequency f₁To decide.

The speed of sound is about 2 when the temperature changes by 10 ° C.
It is said to change%. It can easily be seen from the equation (10) that the influence of the speed of sound on n ₁ is very small.
As shown in the equation (1), when the final distance L is obtained, the variation of the wavelength becomes an error as it is. As a countermeasure for this, for example, there is a method in which the device is equipped with a thermometer to measure the temperature to correct the sound velocity, and this error can be canceled.

Further, there is a difference between the value of x _{1 in the} equation (2) and the value of the actually detected phase x ₁ ′. This is due to the time delay that the oscillator and the transmission / reception circuit system have. Since this difference is a constant that does not depend on the distance L, it can be easily corrected by performing calibration for each device.

[0026]

EXAMPLES Examples of the present invention will be described below. 3 is a block diagram of the first embodiment of the ultrasonic distance measuring apparatus of the present invention, and FIG. 4 is a block diagram of the second embodiment of the ultrasonic distance measuring apparatus of the present invention. Further, FIG. 5 is a diagram showing an example of a transmission / reception waveform. The difference between the first embodiment (FIG. 3) and the second embodiment (FIG. 4) is that the first embodiment (FIG. 3) is an example in which separate transmitter 13 and receiver 14 are used. The second embodiment (FIG. 4) is an example using a transmitter / receiver having the functions of both the handset and the receiver. The distance L between the transmitter 13 and the receiver 14 is measured in the first embodiment, and the distance L between the transceiver and the reflector is measured in the second embodiment. Since the method of analyzing the received signal is the same for both,
An example will be described.

The oscillator first generates a continuous waveform of fundamental frequency f ₁ . The transmitter circuit amplifies this waveform if necessary and drives the transmitter. In the transmitter circuit, as shown in FIG.
The transmitter is driven by the waveform obtained by cutting out the continuous waveform from the oscillator. The ultrasonic wave propagates through the air, is received by a receiver, and is converted into an electric signal. These transmitters and receivers are composed of piezoelectric porcelain such as PZT, electrostatic microphones, electromagnetic coils and the like. The received signal is amplified by the amplifier 15 and the phase is detected by the phase detector 16.

FIG. 6 is a block diagram showing a quadrature detector which is an example of a phase detector. First, the received signal is multiplied by the multiplication waveform having the same frequency as the received signal by the multiplier. Multiplying waveforms are generally 90 ° out of phase with each other 2
Frequency (sin and cos) signals are used. As these signals, one uses a continuous waveform from the oscillator as it is, and the other uses a signal obtained by adding a 90 ° phase delay to the continuous waveform from the oscillator by an LC delay line or the like. The ratio of the output of the multiplier is calculated after extracting only low frequencies by the LPF. This ratio is the phase of the received signal (tan2πfx
₁ ) The inverse function tan of this tan2πfx ₁
The instantaneous phase x ₁ of the received signal can be obtained by obtaining ⁻¹ (tan2πfx ₁ ). These inverse functions tan ⁻¹ can be obtained by calculation or by using a ROM table. Since quadrature detection is generally vulnerable to noise, for example, several consecutive x ₁
It is desirable to average

[0029] Thus after obtaining a phase x ₁ at frequency f _1, the oscillator generates a continuous waveform of the fundamental frequency f _2, to obtain the phase x ₂ by the same method as above. The oscillator includes, for example, two oscillators each of which emits at a single frequency f ₁ and f ₂ as shown in FIG. 7, and outputs two fundamental frequencies f ₁ and f ₂ by switching these oscillators. In the case of the above-described embodiment, it was necessary to perform transmission and reception twice in order to measure one distance, but the point is to radiate two frequencies from the transmitter. An example of measuring the distance by one transmission and reception is shown in FIGS. 8 and 9.

FIG. 8 is a block diagram showing a third embodiment of the ultrasonic distance measuring apparatus of the present invention, and FIG. 9 is a diagram showing an example of transmission / reception waveforms adopted in the third embodiment shown in FIG. Is. The transmitter first emits a frequency f ₁ for a predetermined time t, followed by an ultrasound of frequency f ₂ . On the receiving side, the frequency f ₁
Phase detection is performed according to. After about t time has passed, phase detection is performed in accordance with the frequency f ₂ . A simple threshold circuit 1 at the start of ultrasonic wave reception.
If there is one, it can be detected.

FIG. 10 shows an ultrasonic distance measuring apparatus according to the present invention.
FIG. 11 is a block diagram of a fourth embodiment, and FIG. 11 is a fourth diagram shown in FIG.
3 is an example of a drive waveform adopted in the embodiment of FIG. Here, send
The signal waveform is pulsed as shown in FIG. Pulse is
It has a wide frequency band. Received waveforms of transmitter and receiver
Due to the frequency band, it becomes narrower than the transmission waveform,
The above two frequencies are included. From this received wave
With a pass filter ₁, F₂Of the two frequencies of
Detect the phase. When phase detection is performed by quadrature detection
It is also possible to omit the band pass filter.
In this case, f₁, F₂Multiply the frequency of
Then, only the DC component should be extracted by the low pass filter that follows.
Yes.

FIG. 12 is a flow chart showing the analysis algorithm in the analysis unit. Based on the phases x ₁ and x ₂ at the two frequencies obtained as described above, the analysis unit of FIG.
Calculate the distance according to the algorithm shown in. This algorithm has already been fully described in the section of action, and its explanation is omitted here. Note that this algorithm also performs phase correction of the difference between the phase x ₁ and the actually detected phase x ₁ ′, and sound velocity correction. Phase correction is easy because each device is provided with a correction constant and only the addition or subtraction of the constant is performed. For speed of sound correction, a speed table according to temperature is stored in ROM
The sound velocity corresponding to the temperature measured by the temperature sensor is used.

The distance information thus obtained can be applied to a system as shown in FIG. 13 to detect two-dimensional and three-dimensional coordinates.

[0034]

As described above, the ultrasonic distance measuring apparatus of the present invention transmits and receives ultrasonic waves of two predetermined frequencies to obtain the phase of each received signal, and the distance is calculated based on these phases. Since the measurement is performed, the distance is accurately measured, and an ultrasonic measurement device suitable for the coordinate input device is realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a distance measuring principle in the present invention.

FIG. 2 is an explanatory diagram of a distance measuring principle in the present invention.

FIG. 3 is a block diagram of a first embodiment of the ultrasonic distance measuring apparatus of the present invention.

FIG. 4 is a block diagram of a second embodiment of the ultrasonic distance measuring apparatus of the present invention.

FIG. 5 is a diagram showing an example of transmission / reception waveforms.

FIG. 6 is a block diagram showing a quadrature detector.

FIG. 7 is a block diagram showing an example of an oscillator.

FIG. 8 is a block diagram of a third embodiment of the ultrasonic distance measuring apparatus of the present invention.

9 is a diagram showing a transmission / reception waveform example adopted in the third embodiment shown in FIG.

FIG. 10 is a block diagram of a fourth embodiment of the ultrasonic distance measuring apparatus of the present invention.

11 is an example of drive waveforms adopted in the fourth embodiment shown in FIG.

FIG. 12 is a flowchart showing an analysis algorithm in the analysis unit.

FIG. 13 is a block diagram showing a coordinate input device for inputting coordinates using ultrasonic waves.

FIG. 14 is a diagram schematically showing a transmission / reception waveform of ultrasonic waves for conventional coordinate analysis.

[Explanation of symbols]

 1 Ultrasonic Transmitter 2a, 2b, 2c Ultrasonic Receiver 3 Coordinate Calculator 4 Calculator 5 Monitor 5a Monitor Screen

Claims (8)

[Claims] 1. One or a plurality of ultrasonic transducers that share or share the functions of both an ultrasonic transmitter that transmits ultrasonic waves and an ultrasonic receiver that receives ultrasonic waves transmitted from the ultrasonic transmitters. A transmitter for generating a drive signal for transmitting ultrasonic waves of at least two different frequencies from the ultrasonic transmitter, and phases of the ultrasonic waves of at least two frequencies received by the ultrasonic receiver. And a distance analysis unit that determines a distance along the propagation path of the ultrasonic wave between the ultrasonic transmitter and the ultrasonic receiver based on at least two phases detected by the phase detection unit. An ultrasonic distance measuring device comprising: 2. When the transmitting section sets the frequencies of different ultrasonic waves to f ₁ and f ₂ , the sound velocity to c, and the maximum value of the measurement distance range to L _max , the formula | f ₂ −f ₁ | <c _2. The ultrasonic transmitter is driven so that ultrasonic waves of at least two frequencies f ₁ and f ₂ satisfying / L _max are output from the ultrasonic transmitter. Ultrasonic distance measuring device. 3. The transmitting unit drives the ultrasonic transmitter so that ultrasonic waves of at least two frequencies are sequentially transmitted at time intervals from the ultrasonic transmitter. The ultrasonic distance measuring device according to claim 1. 4. The transmitting unit drives the ultrasonic transmitter so that ultrasonic waves of at least two frequencies are transmitted in succession from the ultrasonic transmitter. Item 1. The ultrasonic distance measuring device according to item 1. 5. The transmitting unit applies the drive signal including at least two frequencies to the ultrasonic transmitter, and the ultrasonic distance measuring device is received by the ultrasonic receiver. The ultrasonic distance measuring device according to claim 1, further comprising a filter unit that extracts the ultrasonic waves of at least two frequencies from the ultrasonic waves. 6. The ultrasonic distance measuring apparatus according to claim 1, wherein the phase detecting unit has a unit that stores a correction value for correcting the phase detected by the phase detecting unit. 7. The ultrasonic distance measuring apparatus according to claim 1, wherein the ultrasonic distance measuring apparatus includes a temperature sensor for correcting the distance calculated by the distance analyzing unit. 8. A plurality of first ultrasonic transducers, wherein the ultrasonic distance measuring device is used as either one of an ultrasonic transmitter or an ultrasonic receiver arranged at respective predetermined positions different from each other, and Movably provided with respect to the first ultrasonic transducer,
A second ultrasonic transducer that is used as the other one of the ultrasonic transmitters or the ultrasonic receivers, which is different from the above one, and is obtained using the first ultrasonic transducer and the second ultrasonic transducer. An ultrasonic distance measuring apparatus, comprising: a coordinate analysis unit that obtains two-dimensional coordinates or three-dimensional coordinates of the second ultrasonic transducer based on a plurality of the calculated distances.