JP2007093283A - Method and system for measuring distance fluctuations by phase conjugate wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure distance fluctuations between two points with sufficient measurement accuracy even when there are heterogenities such as an ocean current, a water mass, and a vortex between two points at the bottom of the sea, which are objects of distance measurement. <P>SOLUTION: A sound source system 10 and a measurement processing system 20 are installed on the top surface of a sea side plate 16 and the bottom of the sea of a land side plate 22, respectively. A first acoustic probe wave is sent from the sound source system to the measurement processing system. In response, an acoustic phase conjugate wave is sent from the measurement processing system back to the sound source system and is stored as a standard probe wave. A second acoustic probe wave is then sent from the sound source system to the measurement processing system. In response, a plurality of acoustic modulation phase conjugate waves are sent from the measurement processing system back to the sound source system sequentially in order of the size of the amount of phase modulation and are generated as measurement probe waves, respectively. These measurement probe waves and the standard probe wave are sequentially allowed to interfere with each other to generate an interference wave. The amount of fluctuations in the distance between the sound source system and the measurement processing system is determined through the amount of phase modulation minimizing the amplitude of the interference wave. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for measuring a change in distance between two points using a phase conjugate wave and a system for realizing the method.

  One of the measurements that lead to earthquake prediction is crustal strain measurement. At the boundary where the plates composing the earth's crust contact each other, the displacement between the plates is accumulated as strain energy. Since this strain energy causes an earthquake, there is a need for a method for accurately measuring the displacement of the crust across the boundary between two plates. When the boundary where two plates meet is in the sea, it is necessary to accurately measure the crustal displacement of the seabed in the sea.

  Usually, the speed at which the crustal displacement of the seabed occurs is very gradual, and the amount of displacement is as small as several centimeters per year. Therefore, a measurement time interval of about one month or one year is sufficient, but with a measurement accuracy (hereinafter sometimes referred to as “sufficient measurement accuracy”) capable of measuring a displacement of several centimeters or less. Therefore, it is necessary to measure the crustal displacement in the sea.

  Conventionally, an attempt has been made to measure the distance between two points on the sea floor based on the propagation time of a sound wave propagating in the sea (hereinafter, simply referred to as “sound wave”) (for example, non-patent literature). 1).

  However, this method has a problem that the propagation time of sound waves is easily affected by the presence of inhomogeneities such as ocean currents, water masses, and vortices in the sound wave propagation path. In other words, due to the presence of the above-mentioned inhomogeneity, there can be many sound wave propagation paths from one point of the seabed to the other point, and it is not possible to measure the exact propagation time of sound waves propagating between two points. It is difficult and the distance between these two points cannot be measured accurately.

Further, since this method is a method of measuring an actual distance between two points (hereinafter also referred to as “absolute distance”), a measurement error increases as the distance between the two points increases. For this reason, it has been difficult to measure crustal displacement with sufficient measurement accuracy for displacements of several centimeters or less.
Akira Asada “A New Approach to Observational Observations of Undersea Crustal Movements—AUV Observations and Future Concepts” 2005 First Ocean Acoustic Society Meeting, June 9, 2005

  Therefore, the present invention has sufficient measurement accuracy to measure the distance fluctuation between these two points even if there are inhomogeneities such as ocean currents, water masses, vortices, etc. between the two points on the seabed. It is an object of the present invention to provide a method that can be measured and a system for realizing the method.

  In the following explanation, to avoid confusion, the following terms may be used. That is, a probe wave as an electric wave may be described separately from an electric probe wave, and a probe wave as a sound wave may be distinguished from an acoustic probe wave. A phase conjugate wave as an electrical wave may be described separately from an electrical phase conjugate wave, and a phase conjugate wave in a sound wave state as an acoustic phase conjugate wave. Electric probe waves generated inside the sound source device are transmitted electric probe waves, electric probe waves obtained by converting the acoustic probe waves transmitted from the sound source device inside the measurement processing device are received electric probe waves, and It may be distinguished and described. A modulated phase conjugate wave as an electrical wave may be described separately from an electrically modulated phase conjugate wave, and a modulated phase conjugate wave as a sound wave may be distinguished from an acoustically modulated phase conjugate wave.

In order to solve the above problem, the distance variation measuring method of the present invention includes the following steps.
(A) The first acoustic probe wave is generated by the sound source device, and the first acoustic probe wave is sent from the sound source device to the measurement processing device. (B) The measurement processing device is based on the first acoustic probe wave. The second step of sending the acoustic phase conjugate wave generated in step (C) to the sound source device (C) The step of converting the acoustic phase conjugate wave into the reference probe wave and storing it in the storage unit of the sound source device (D) (2) Generate a second acoustic probe wave and send the second acoustic probe wave from the sound source device to the measurement processing device. (E) In the measurement processing device, the phase modulation amount is stepwise based on the second acoustic probe wave. 5th step of generating multiple different acoustic modulation phase conjugate waves and sequentially sending the multiple acoustic modulation phase conjugate waves to the sound source device according to the order of magnitude of the phase modulation amount (F) Multiple multiple acoustic modulation phase conjugate waves Convert the measurement probe wave to that of the measurement probe wave Then, the reference probe wave read from the storage unit is sequentially interfered to generate an interference wave, and the phase modulation amount of the measurement probe wave that generates the interference wave having the smallest amplitude among the interference waves is determined, A sixth step in which the phase modulation amount is converted into a distance value using a phase / distance conversion means and output.

  Furthermore, it is preferable that the first, second, fourth and fifth steps described above each include the following sub-steps.

That is, it is preferable that the first step includes the following three substeps.
(A1) Step of generating first transmission electric probe wave by probe wave generation unit of sound source device (A2) Step of converting first transmission electric probe wave to first acoustic probe wave (A3) Measuring first acoustic probe wave Sending to the processing unit.

It is preferable that the second step includes the following four substeps.
(B1) The step of converting the first acoustic probe wave into the first received electrical probe wave (B2) The step of converting the first received electrical probe wave into the first electrical phase conjugate wave (B3) The first electrical phase conjugate wave is acoustically Step of converting into phase conjugate wave (B4) Sending acoustic phase conjugate wave to sound source device.

It is preferable that the fourth step includes the following three substeps.
(D1) Step of generating the second transmission electric probe wave in the probe wave generator of the sound source device (D2) Step of converting the second transmission electric probe wave into the second acoustic probe wave (D3) Measuring the second acoustic probe wave Sending to the processing unit.

It is preferable that the fifth step includes the following five substeps.
(E1) Step of converting the second acoustic probe wave into a second electric probe wave (E2) Step of converting the second electric probe wave into a second electric phase conjugate wave (E3) Based on the second electric phase conjugate wave Next, a step of sequentially generating a plurality of electrically modulated phase conjugate waves having phase modulation amounts that differ in stages (E4) a step of sequentially converting a plurality of electrically modulated phase conjugate waves to an acoustically modulated phase conjugate wave (E5) a plurality of acoustic waves Sending the modulated phase conjugate wave to the sound source device sequentially at intervals in the order of the magnitude of the phase modulation amount;

  A system for realizing the above-described distance variation measuring method is configured as follows. That is, the distance variation measuring system of the present invention includes a sound source device and a measurement processing device. The measurement processing apparatus can be configured with only a single measurement processing unit, but generally includes a plurality of measurement processing units.

  The sound source device generates first and second acoustic probe waves and transmits them to the measurement processing device, and converts the acoustic phase conjugate wave sent from the measurement processing device into a reference probe wave and stores it in the storage unit. Further, the sound source device converts a plurality of acoustic modulation phase conjugate waves into a plurality of measurement probe waves, and sequentially interferes each of the measurement probe waves with the reference probe wave read from the storage unit to generate an interference wave, The phase modulation amount of the measurement probe wave that generates the interference wave having the minimum amplitude is determined. Then, the sound source device outputs a distance value obtained by using a phase / distance conversion means for the phase modulation amount.

  Here, as described above, the term “sound source device” refers to the function of generating the first and second acoustic probe waves, and the distance between the amplitude of the interference wave and the reference probe wave and the measurement probe wave. It is used to mean a device having a plurality of functions such as an output function. In addition, the term measurement processing device is used to mean a device configured by assembling a plurality of measurement processing devices in an array, but in cases where it is exceptionally configured with only one measurement processing device, measurement is also performed. Include in processing equipment. Further, as will be described later, the term “measurement processor” is used to mean a functional block having a plurality of functions such as generating an acoustic phase conjugate wave and an acoustic modulation phase conjugate wave and transmitting them to a sound source device. .

  The sound source device preferably includes a probe wave generation unit, a first transducer, a storage unit, a signal interference / minimum point detection unit, and an output unit such as interference information.

  Here, the probe wave generator generates the first and second transmission electric probe waves. The first transducer converts the first and second transmission electrical probe waves into first and second acoustic probe waves, respectively, and converts the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave into a reference probe wave and a measurement probe wave, respectively. Convert to The storage unit stores the reference probe wave and stores conversion means for phase and distance. The signal interference / minimum point detection unit generates interference waves by sequentially causing interference between each of the plurality of measurement probe waves and the reference probe wave read from the storage unit, thereby generating an interference wave having the minimum amplitude. The probe wave is specified and the phase modulation amount is determined. The output unit such as the interference information reads the phase / distance conversion unit from the storage unit, converts the phase modulation amount into a distance value using the conversion unit, and outputs the distance value.

  The measurement processing device transmits an acoustic phase conjugate wave generated based on the first acoustic probe wave to the sound source device, and a plurality of acoustic waves having different phase modulation amounts based on the second acoustic probe wave. Modulated phase conjugate waves are sequentially generated, and a plurality of acoustic modulation phase conjugate waves are sequentially sent to the sound source device in the order of the magnitude of the phase modulation amount.

  The measurement processing device preferably includes a second transducer, a time reversing unit, and a modulated conjugate wave generating unit.

  Here, the second transducer converts the first and second acoustic probe waves into the first and second received electrical probe waves, respectively, and the first electrical phase conjugate wave and the electrically modulated phase conjugate wave respectively. Wave and acoustic modulation phase conjugate wave. The time inverting unit converts the first and second received electrical probe waves into a first electrical phase conjugate wave and a second electrical phase conjugate wave, respectively. The modulation conjugate wave generation unit performs phase modulation on the second electric phase conjugate wave to generate an electric modulation phase conjugate wave.

  The first and second transmission electrical probe waves generated by the probe wave generation unit described above are converted into first and second acoustic probe waves by a first transducer included in the sound source device. Therefore, the time waveforms of both the first and second transmission electrical probe waves and the first and second acoustic probe waves are similar. Further, a tone burst wave composed of a sine wave can be used as the probe wave such as the first and second transmission electric probe waves or the first and second acoustic probe waves.

  As described above, the distance variation measuring method of the present invention comprises (A) the first step, (B) the second step and (C) the third step, (D) the fourth step, (E) the fifth step, (F ) 6th step.

  According to this, in the first to third steps, the first acoustic probe wave is sent from the sound source device to the measurement processing device, where phase conjugation processing is performed and sent back to the sound source device as an acoustic phase conjugate wave. In the sound source device, the acoustic phase conjugate wave is converted into a reference probe wave that is an electrical phase conjugate wave, and the reference probe wave is stored in a storage device.

  Similar to the conventional measurement method, when the acoustic probe wave is transmitted from the sound source device, it is reflected many times on the sea surface and the sea floor, and further reaches the measurement processing device due to scattering and refraction due to the inhomogeneity of the seawater. For this reason, the acoustic probe wave spreads both spatially and temporally, and is greatly different from the shape first transmitted from the sound source device, so the arrival time cannot be accurately read.

  Therefore, in the present invention, the spread acoustic probe wave is subjected to phase conjugation processing and re-radiated. The sound wave is shrunk both spatially and temporally, and at the position of the sound source device, it is the same as the first wave transmitted. When an acoustic probe wave is transmitted again after a certain period of time, and subjected to phase conjugation processing and re-radiated by the measurement processing device, a sound wave having the same shape as that obtained last time is obtained at the position of the sound source. However, during this time, if the distance between the sound source device and the measurement processing device changes due to crustal movement, a time difference occurs between the two waves, so the distance between the sound source device and the measurement processing device is changed. Can be sought. The reason for this will be described first based on what the phase conjugate wave is and based on the properties of the phase conjugate wave.

  A phase conjugate wave refers to a wave having the same spatial amplitude distribution as a certain wave and having a traveling direction opposite to that of the wave, and is sometimes referred to as a time reversal wave. A sound wave emitted from the sound source device is received by a measurement processing device composed of a plurality of measurement processors, and by reversing the received sound wave on the time axis, a phase conjugate wave for the received sound wave is generated, When this phase conjugate wave is transmitted from this measurement processing device, the sound wave converges at the position (receiving point) of the original sound source device. In this case, the receiving point is the focal point of the sound wave. That is, the convergence by the phase conjugate wave is such that the reflected wave and the refracted wave generated before the phase conjugate wave emitted from the measurement processing device reaches the receiving point that is the position of the original sound source device are temporally and spatially. It is a phenomenon realized by gathering together.

  This phenomenon can be explained from another viewpoint as follows. When the phase conjugate wave is transmitted from the measurement processing device, the sound wave propagation phenomenon including the reflected wave and the refracted wave occurs with the time reversed from the time when the sound wave is transmitted from the sound source device. In this position, the traveling direction is opposite to that when the sound wave is transmitted. That is, the phase conjugate wave has the same spatial distribution shape of the sound pressure and is a sound wave having the opposite traveling direction only. Therefore, the phase conjugate wave has the same spatial shape as that transmitted from the sound source device, and the original sound source. It will return to the position of the device and the sound wave will converge to the focal point.

  As a result, the acoustic phase conjugate wave received by the sound source device is not spread in time and space, so the distance between the sound source device and the measurement processing device is determined based on the propagation time or phase of the acoustic probe wave. It becomes possible to measure correctly. In the distance fluctuation measuring method of the present invention, as will be described later, the distance between the sound source device and the measurement processing device is measured based on the phase of the acoustic phase conjugate wave. As described above, in the first to third steps, the reference probe wave is stored in the storage device of the sound source device. The reference probe wave is used for generating an interference wave with a measurement probe wave described later. The relative fluctuation amount of the distance between the sound source device and the measurement processing device is obtained from the amplitude of the interference wave.

  Next, in the fourth to sixth steps, a plurality of measurement probe waves are generated, and these measurement probe waves and the above-described reference probe wave are sequentially interfered to generate an interference wave. The amplitude of the interference wave Is required. A fluctuation amount of the distance between the sound source device and the measurement processing device is obtained from the amplitude of the interference wave. First, in the fourth step, the second acoustic probe wave is sent from the sound source device to the measurement processing device, and in the fifth step, a plurality of acoustic modulation phases whose phase modulation amounts differ stepwise based on the second acoustic probe wave. A conjugate wave is generated.

  In the fifth step, the measurement processing device can sequentially modulate the phase of the second received electrical probe wave step by step without losing the phase conjugate property together with the phase conjugate processing. As a result, the phase of the acoustically modulated phase conjugate wave received by the sound source device can be sent while being changed stepwise. That is, it is possible to accurately transmit a plurality of acoustic modulation phase conjugate waves whose phases are sequentially changed stepwise from the measurement processing device to the sound source device.

  Here, the meaning of modulating the phase of the second received electrical probe wave without impairing the phase conjugation will be described. This means that the phase of the second received electrical probe wave is modulated without changing the frequency spectrum obtained by time-reversing the second received electrical probe wave and Fourier transforming it.

  In general, a probe wave is composed of a number of frequency components. If the same phase change is given to each of the Fourier components having different frequencies constituting the probe wave, the phase of the probe wave can be modulated without changing the frequency spectrum of the probe wave. In this case, even though the phase shifts of all these Fourier components are the same, the magnitudes of shifts on the time axis for the respective Fourier components are different. However, the frequency spectrum of the probe wave does not change even if a phase change having the same magnitude is applied to each Fourier component having a different frequency constituting the probe wave.

  The second received electrical probe wave is time-reversed, and then the second received electrical probe wave is converted from the time domain to the frequency domain. When the above-described phase conversion is given in the frequency domain and then converted again into the time domain, the time waveform of the electric modulation phase conjugate wave obtained by the conversion is not different from the time waveform of the second reception electric probe wave. This is because the shape of the frequency spectrum does not change before and after the phase modulation, and the time waveform of the electrically modulated phase conjugate wave obtained by converting the frequency spectrum after the phase modulation as a time domain wave is as described above. It is concluded that the time waveform is the same as that of the second received electrical probe wave.

  That is, an electric modulation phase conjugate wave obtained by phase-modulating the second electric phase conjugate wave with respect to a second electric phase conjugate wave obtained by phase conjugate processing (time reversal processing) of the second received electric probe wave The phase conjugation is not impaired.

  As described above, the distance variation measuring method according to the present invention utilizes the property that the phase conjugate wave originally converges on the position of the original sound source device. Therefore, even when the sound waves of the first and second acoustic probe waves change due to underwater propagation conditions, etc., the acoustic phase conjugate wave and the acoustic modulation sent from the measurement processing device to the sound source device The phase conjugate wave converges at the position of the sound source device at the time when the first and second acoustic probe waves are transmitted. Therefore, it is possible to transmit from the measurement processing device to the sound source device while accurately maintaining the phase modulation amounts of the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave.

  As described above, the plurality of acoustic modulation phase conjugate waves are sequentially sent from the measurement processing device to the sound source device according to the order of the magnitude of the phase modulation amount while keeping the phase modulation amount accurately. In the sixth step, the reference probe wave and the measurement probe wave converted from the plurality of acoustic modulation phase conjugate waves are sequentially interfered to generate an interference wave, and the amplitude is the smallest of the plurality of interference waves. From the amount of phase modulation of the measurement probe wave that caused the interference wave, the relative distance variation between the sound source device and the measurement processing device is obtained. Therefore, unlike the method for obtaining the absolute distance obtained from the round-trip time of the underwater acoustic wave between the sound source device and the measurement processing device, the measurement error increases as the absolute distance between the sound source device and the measurement processing device increases. There is no such thing as to do.

  The distance fluctuation measuring method of the present invention is realized by a distance fluctuation measuring system including a sound source device and a measurement processing device. The first, third, fourth and sixth steps can be realized by a sound source device, and the second and fifth steps can be realized by a measurement processing device.

  Further, in the distance variation measuring method of the present invention, as described above, the first step includes three substeps, the second step includes four substeps, and the fourth step includes three substeps. It is possible to include substeps, and the fifth step may include five substeps.

  In sub-step A1, which constitutes the first step, a first transmission electrical probe wave is generated, which is executed centering on a probe wave generator provided in the sound source device. In sub-step A2, the first transmission electrical probe wave is converted into the first acoustic probe wave, which is executed by the first transducer included in the sound source device. In sub-step A3, the first acoustic probe wave is sent from the sound source device to the measurement processing device.

  Therefore, in the first step, the above-mentioned sub-steps A1 to A3 are executed, and as a result, the first acoustic probe wave is transmitted from the sound source device to the measurement processing device.

  In sub-step B1, which constitutes the second step, the first acoustic probe wave is converted into a first received electrical probe wave, which is executed by a second transducer provided in the measurement processing device. In sub-step B2, the first received electrical probe wave is converted into a first electrical phase conjugate wave, which is executed centering on a time reversing unit provided in the measurement processing device. In sub-step B3, the first electrical phase conjugate wave is converted into an acoustic phase conjugate wave, which is executed by a second transducer included in the measurement processing device. In sub-step B4, an acoustic phase conjugate wave is sent from the measurement processing device to the sound source device.

  Therefore, in the second step, the above-described sub-steps B1 to B4 are executed, and as a result, the acoustic phase conjugate wave generated based on the first acoustic probe wave is transmitted from the measurement processing device to the sound source device. It is transmitted.

  In the third step, the acoustic phase conjugate wave is converted into a reference probe wave and stored in the storage unit of the sound source device in order to execute the step of generating an interference wave by interfering with the measurement probe wave, which is a subsequent step. The

  In sub-step D1, which constitutes the fourth step, a second transmission electrical probe wave is generated, which is executed centering on a probe wave generator provided in the sound source device. In sub-step D2, the second transmission electrical probe wave is converted into a second acoustic probe wave, which is executed by a first transducer included in the sound source device. In sub-step D3, the second acoustic probe wave is sent from the sound source device to the measurement processing device.

  In sub-step E1 constituting the fifth step, the second acoustic probe wave is converted into a second received electrical probe wave, which is executed by a second transducer provided in the measurement processing device. In sub-step E2, the second received electrical probe wave is converted into a second electrical phase conjugate wave, which is executed centering on a time reversing unit provided in the measurement processing device. In sub-step E3, based on the second electrical phase conjugate wave, a plurality of electrical modulation phase conjugate waves having different phase modulation amounts are generated step by step. This is a modulated conjugate wave generation unit provided in the measurement processing device. Run around. In sub-step E4, a plurality of electrical modulation phase conjugate waves are sequentially converted into acoustic modulation phase conjugate waves, which is executed by a second transducer provided in the measurement processing device. In sub-step E5, a plurality of acoustic modulation phase conjugate waves are sequentially sent to the sound source device at time intervals in the order of the magnitude of the phase modulation amount.

  Therefore, in the fifth step, by executing the above-described sub-steps E1 to E5, as a result, a plurality of acoustic modulation phase conjugate waves having different phase modulation amounts in stages based on the second acoustic probe wave are generated. The plurality of acoustic modulation phase conjugate waves are generated and sequentially transmitted to the sound source device in the order of the magnitude of the phase modulation amount.

  In the sixth step, a plurality of acoustically modulated phase conjugate waves are converted into a plurality of measurement probe waves, which is executed by the first transducer. In addition, the measurement probe wave and the reference probe wave read from the storage unit are sequentially interfered to generate an interference wave, and the measurement probe that generates the interference wave having the smallest amplitude among the interference waves A wave is identified and the amount of phase modulation is determined, which is executed by a signal interference / minimum point detector provided in the sound source device. Further, the phase modulation amount is converted into a distance value using a phase / distance conversion means, and this is executed by an output unit such as interference information provided in the sound source device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The block configuration diagram and the like illustrate one configuration example according to the present invention, and the present invention is not limited to the illustrated example. In addition, a block diagram showing a configuration example of the present invention schematically shows an arrangement relationship of each component to the extent that the present invention can be understood.

<Distance variation measurement using phase conjugate wave>
With reference to FIG. 1, an example of measuring the distance fluctuation between fixed points installed on the seabed will be taken up, and the basic matters of the principle of the distance fluctuation measuring method using the phase conjugate wave of the present invention will be described. FIG. 1 is a diagram for explaining a method for measuring the variation in the distance between fixed points in the sea.The sound source device 10 that is one of the fixed points in the sea and the measurement processing device 20 that is the fixed point in the sea are respectively connected to the seaside plate 16. It shows a state where it is installed on the sea bottom 28 which is the upper surface and the sea bottom 26 which is the upper surface of the land side plate 22.

  The boundary where the sea-side plate 16 and the land-side plate 22 that make up the crust on the surface of the earth are in contact with each other has a structure generally shown in FIG. The sea side plate 16 is on the mantle 18 and is in contact with the plate 24 as shown in the figure. At the boundary where the sea side plate 16 and the land side plate 22 contact each other, the sea side plate 16 moves by moving the sea side plate 16 relative to the land side plate 22 in the direction indicated by an arrow in the sea side plate 16. An activity is happening to sink under the land side plate 22.

  As a result, distortion is applied to the land-side plate 22 and the sea-side plate 16 in the vicinity of the boundary where the sea-side plate 16 and the land-side plate 22 are in contact (portion surrounded by a broken line in FIG. 1). When the magnitude of the strain exceeds the threshold value, the strain on the land side plate 22 and the sea side plate 16 is eliminated at once. At this time, an earthquake occurs when the land-side plate 22 and the sea-side plate 16 are suddenly displaced. Since the amount of sliding movement of the sea side plate 16 relative to the land side plate 22 reflects the magnitude of the distortion, a fixed point on the sea bottom plate 28 that is the upper surface of the sea side plate 16 riding on the mantle 18 and the mantle 24 By measuring the change in distance between the fixed point on the sea floor 26, which is the upper surface of the land side plate 22 that is on top, the magnitude of the strain applied to the land side plate 22 and the sea side plate 16 can be determined. It is possible to estimate.

  Therefore, the sound source device 10 is installed at a fixed point on the sea floor 28, and the measurement processing device 20 is installed at a fixed point on the sea floor 26, and the distance between the sound source device 10 and the measurement processing device 20 is measured. As shown in FIG. 1, since the sound source device 10 and the measurement processing device 20 are installed in the seawater 14, even if there is inhomogeneity in the seawater 14, the distance between the sound source device 10 and the measurement processing device 20 Measures must be taken to accurately measure fluctuations.

  In addition, in order to estimate the magnitude of the distortion applied to the land side plate 22 and the sea side plate 16, it is not necessary to know the absolute distance between the sound source device 10 and the measurement processing device 20 accurately. It is sufficient to know the amount of change in the distance to the processing device 20. Therefore, it is preferable to measure the variation in the distance between the sound source device 10 and the measurement processing device 20 from the amount of variation in the phase of the phase conjugate wave using the phase conjugate wave. If the phase conjugate wave is used, as described above, even if inhomogeneity exists in the seawater 14, the measurement result is not affected, and the absolute distance is accurately measured from the amount of phase change of the phase conjugate wave. This is because the distance variation can be accurately measured even if it is not possible.

  An acoustic probe wave S (first and second acoustic probe waves) is transmitted from the sound source device 10 toward the measurement processing device 20, and an acoustic phase conjugate wave R or an acoustic modulation phase conjugate wave R is transmitted from the measurement processing device 20 to the sound source device. It shows a state of being transmitted toward 20. Hereinafter, when referring to both the first and second acoustic probe waves, they may be simply referred to as acoustic probe waves.

  The measurement processing device 20 is configured by arranging a total of seven measurement processors 20-1 to 20-7 in a straight line in the vertical direction. In FIG. 1, the measurement processing device 20 including a total of seven measurement processors is shown, but the number of measurement processors is not necessarily limited to seven. Further, the measurement processors constituting the measurement processing device 20 are arranged in a line in the vertical direction. However, it is not necessary to arrange the measurement processors in a line in this way, and the arrangement shape may be arbitrary. The greater the number of measurement processors provided in the measurement processing device 20, the higher the convergence performance of the phase conjugate wave, which will be described later, and the higher the accuracy of distance fluctuation measurement, but the measurement processing device 20 becomes larger and manufactured and installed in the sea Work becomes big.

  On the other hand, if the number of measurement processors provided in the measurement processing device 20 is small, the convergence of the phase conjugate wave deteriorates and the accuracy of distance fluctuation measurement decreases instead of reducing the manufacturing and installation work of the measurement processing device 20. To do. Therefore, the number of measurement processors constituting the measurement processing device 20 is such that the depth of the phase conjugate wave is sufficient so that the measurement processing device 20 can be sufficiently manufactured and installed in the sea. Depending on the distance between the sound source device 10 and the measurement processing device 20, etc., the necessary number is sufficient.

  The acoustic probe wave S transmitted from the sound source device 10 is reflected by the sea bottom surfaces 26 and 28 and the seawater surface 12 (reflected wave), or refracted (refracted wave) due to nonuniform sound velocity distribution of the seawater 14, etc. In addition, each measurement processing unit (measurement processing units 20-1 to 20-7) that constitutes the measurement processing apparatus 20 is scattered and diffracted (scattered wave, diffracted wave) by the sound wave scatterer existing in the seawater 14. ). In the following description, the reflected wave, refracted wave, diffracted wave, and scattered wave described above may be referred to as a multipath wave.

  When the acoustic probe wave S is transmitted from the sound source device 10, the acoustic probe wave S immediately after being transmitted from the sound source device 10 is generated in the vicinity of the measurement processing device 20 while generating a multipath wave while propagating through the seawater 14. An acoustic probe wave having a deformed wavefront is received by the measurement processing device 20.

  2A and 2B show spatial distribution shapes of sound pressures of sound waves in water between the sound source device 10 and the measurement processing device 20. FIG. FIG. 2 (A) shows the spatial distribution shape of sound pressure of sound waves across the sound source device 10 and the measurement processing device 20, and FIG. 2 (B) shows the sound pressure sound space in the vicinity of the sound source device 10. The general distribution shape is enlarged for easy viewing.

  The part where the sound pressure is strong is shown in white, the part where the sound pressure is weak is shown in black, and the sound pressure of the intermediate intensity is shown in gray with gradation to approach white in proportion to the intensity. 2 (A) and 2 (B), the horizontal axis indicates the distance in m units, and the vertical axis indicates the water depth in m units. In FIG. 2 (A), the measurement processing device 20 is arranged inside a dashed rectangle indicated by N. 2A and 2B, the position indicated by M is the position where the sound source device 10 is disposed. The horizontal axis (position at a depth of 100 m) corresponds to the sea floor. 2 (A) and 2 (B), it can be seen that the acoustic phase conjugate wave has converged at the position of the sound source device 10. The interval between the sound source device 10 and the measurement processing device 20 is set to 5 km.

  In order for the acoustic phase conjugate wave to completely converge at the position of the sound source device 10, effects such as reflection, refraction, diffraction, scattering, etc. on the propagation of sound waves in the middle of the sound source device 10 and the measurement processing device 20 The element that gives the sound is the process in which the acoustic probe wave is transmitted from the sound source device 10 and received by the measurement processing device 20, and the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave are transmitted from the measurement processing device 20 The process received by the device 10 needs to be in the same state.

  For example, due to the ocean current, the refractive index distribution of the seawater 14 is obtained when the acoustic probe wave is transmitted from the sound source device 10 and received by the measurement processing device 20, and the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave. Is different from when the sound is transmitted from the measurement processing device 20 and received by the sound source device 10, the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave do not converge completely. However, the time from when the acoustic probe wave is received by the measurement processing device 20 until the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave are transmitted is not so long, in fact, the refractive index distribution of the seawater 14, etc. Elements that give effects such as reflection, refraction, diffraction, and scattering to the propagation of sound waves do not greatly change the situation.

  Next, the time waveform of the first acoustic probe wave transmitted from the sound source device 10 and the time waveform of the acoustic phase conjugate wave transmitted from the measurement processing device 20 are shown in FIG. ) And (B). 3 (A) and 3 (B) are converted based on the time waveform of the first transmission electrical probe wave and the time waveform of the acoustic phase conjugate wave, which are the basis for generating the first acoustic probe wave, respectively. The time waveform of the electric phase conjugate wave (reference probe wave to be described later) generated in this way is shown. 3 (A) and 3 (B), the horizontal axis indicates time scaled in units of seconds, and the vertical axis indicates sound pressure amplitude scaled on an arbitrary scale.

  3A is a diagram illustrating an example of a time waveform of the first transmission electrical probe wave that is the source of the first acoustic probe wave transmitted from the sound source device 10. The first transmission electrical probe wave illustrated in FIG. As will be described later, the first transmission electrical probe wave is converted into a first acoustic probe wave by a first transducer provided in the sound source device 10, and is transmitted from the sound source device 10 toward the measurement processing device 20. . In the case of this example, as shown in FIG. 3 (A), the first transmission electric probe wave is an electric wave consisting of eight sine waves, so the first acoustic probe wave transmitted from the sound source device 10 is also It is a tone burst wave consisting of 8 sine waves.

  The electrical phase conjugate wave (reference probe wave described later) shown in FIG. 3 (B) is an example of a time waveform of the first electrical phase conjugate wave that is the source of the acoustic phase conjugate wave transmitted from the measurement processing device 20. FIG. As will be described later, the first electrical phase conjugate wave is converted into an acoustic phase conjugate wave by a second transducer provided in the measurement processing device 20, and is transmitted from the measurement processing device 20 toward the sound source device 10. . In the case of this example, as shown in FIG. 3 (B), the first electrical phase conjugate wave is an electrical wave consisting of eight sine waves, so the acoustic phase conjugate wave transmitted from the measurement processing device 20 is also It is a tone burst wave consisting of 8 sine waves.

  The time waveform of the electric phase conjugate wave shown in FIG. 3 (B) hardly changes with respect to the time waveform of the first transmission electric probe wave shown in FIG. 3 (A). That is, the amplitude of each sine wave constituting the electric phase conjugate wave only fluctuates by several percent. In addition, small wave components appear at the start time (around 0.50 seconds on the horizontal axis) and the end time (around 0.52 seconds on the horizontal axis) of the electrical phase conjugate wave. The amplitude of this small wave is Less than a few percent of the amplitude. The fluctuation of the amplitude of the electric phase conjugate wave and the small wave components appearing at the start time (around 0.50 seconds on the horizontal axis) and the end time (around 0.52 seconds on the horizontal axis) are noise components.

  That is, these noise components can be reduced by increasing the number of measurement processors constituting the measurement processing device 20. When constructing a distance variation measurement system using a phase conjugate wave, the measurement processor 20 constituting the measurement processing device 20 is configured in accordance with the design guideline regarding how much the magnitude of the noise component should be set below. It is necessary to select the number.

  Here, as a first step, the acoustic probe wave S is sent from the sound source device 10 to the measurement processing device 20, the acoustic phase conjugate wave R is generated and sent back to the sound source device 10, and the reference probe wave (in the following explanation) The electric phase conjugate wave obtained in the first stage is referred to as a reference probe wave.) And stored. Thereafter, a case is considered in which the distance between the sound source device 10 and the measurement processing device 20 (sometimes referred to as “distance between fixed points”) fluctuates by several centimeters. After the distance between the fixed points fluctuates, as a second step, the acoustic probe wave is sent again from the sound source device 10 to the measurement processing device 20, an acoustic phase conjugate wave is generated and sent back to the sound source device 10, and the electrical phase is similarly Assume that a conjugate wave is obtained.

  Thereafter, an electrical phase conjugate wave obtained in the second stage (the electrical phase conjugate wave obtained in the second stage is sometimes referred to as an electrically modulated phase conjugate wave because it has undergone phase modulation). It is described as a wave. If the distance between fixed points varies between the reference probe wave and the measurement probe wave, the pulse shape will also change, but the amount of change that appears in the pulse shape is small, and it is difficult to accurately grasp. is there. Therefore, an interferometry is used to numerically read a minute change amount between the reference probe wave and the measurement probe wave.

  FIG. 4 is a time waveform diagram of the reference probe wave and the measurement probe wave obtained by converting the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave received by the sound source device 10. The horizontal axis indicates time in units of seconds, and the vertical axis indicates amplitude on an arbitrary scale.

  In FIG. 4, the total of 10 waveforms indicated by symbols (a) to (j) are respectively, in order from (a), the amount of phase modulation applied in the measurement processing device 20 is indicated by an arc method. The time waveforms of the reference probe wave and the measurement probe wave with respect to the case where the amount is changed by an amount corresponding to the π / 4 phase are shown. That is, the waveform indicated by the symbol (a) is the waveform of the measurement probe wave received by the sound source device 10 when the phase modulation amount of the acoustic modulation phase conjugate wave sent from the measurement processing device 20 is 5π / 4. A time waveform is shown. Similarly, the waveform indicated by symbol (b) to symbol (j) indicates the phase modulation amount of the acoustic modulation phase conjugate wave as 4π / 4, 3π / 4, 2π / 4, π / 4, 0, −1π, respectively. 4 shows time waveforms of measurement probe waves when / 4, -2π / 4, -3π / 4, and -4π / 4. The reference probe wave is the same as the waveform indicated by the symbol (f) having a phase modulation amount of zero.

  As shown in FIG. 4, each waveform indicated by symbol (a) to symbol (j) is only shifted in phase on the time axis, and the shape of these time waveforms themselves changes. I can read that I have not done it. This means that the phase information can be sent from the measurement processing device 20 to the sound source device 10 without breaking the shape of the second acoustic probe wave transmitted from the sound source device 10.

  In addition, the fact that phase information can be transmitted without destroying the shape of the second acoustic probe wave transmitted from the sound source device 10 means that the measurement processing device does not depend on the shape of the second acoustic probe wave to the sound source device. It also means that phase information can be sent. That is, the example shown in FIG. 4 shows a case where a tone burst wave composed of a sine wave is used, but the acoustic probe wave is not limited to a sine wave.

  Generally, as a probe wave (transmitted electric probe wave and acoustic probe wave), any waveform that can modulate only the phase without changing the frequency spectrum obtained by Fourier transform can be used. In other words, any waveform wave can be used as a probe wave as long as it can give the same magnitude of phase change to all Fourier components with different frequencies constituting the probe wave. It is.

  The distance measuring method of the present invention is a method of obtaining a reference probe wave in advance and obtaining a distance variation amount from the amplitude of the interference wave between the reference probe wave and the measuring probe wave. The reference probe wave is acquired at a certain time as a measurement reference and stored in a storage device included in the sound source device 10. That is, the first to third steps of the distance variation measuring method of the present invention are executed on a certain date as a measurement reference (first stage). Then, after acquiring the reference probe wave, the measurement probe wave is acquired about six months or a year later, and an interference wave between the reference probe wave and the measurement probe wave acquired in advance is generated. That is, the first to third steps are executed in advance, and the fourth to sixth steps are executed after about six months or one year (second stage).

  If the distance between the sound source device 10 and the measurement processing device 20 does not vary between the acquisition of the reference probe wave (first stage) and the acquisition of the measurement probe wave (second stage), phase modulation is performed. The amplitude of the interference wave with the measurement probe wave whose amount is 180 ° (π in the arc method display) becomes zero. However, if this distance varies, the amplitude of the interference wave does not become zero, and the amplitude of the interference wave with the measurement probe wave subjected to the phase modulation of a phase modulation amount different from 180 ° is zero. It becomes. The amount of fluctuation in the distance between the sound source device 10 and the measurement processing device 20 during this period is obtained from the phase amount corresponding to the difference from 180 ° of the modulation amount value applied to the measurement probe wave.

  Therefore, in the fifth step executed by the measurement processing device 20, the phase modulation amount based on the second acoustic probe wave is, for example, 180 °, (180 ± δ) °, (180 ± 2δ) °, (180 ± 3δ) °, ..., (180 ± Nδ) ° (where N is a sufficiently large integer), generating multiple acoustic modulation phase conjugate waves in stages, The phase conjugate wave is sequentially sent to the sound source device 10 in the order of the magnitude of the phase modulation amount.

  Here, for the sake of convenience, different values are used for the phase modulation amount stepwise at equal intervals (parameter δ). However, in principle, the phase modulation amounts need not be equal intervals. However, as will be described later, in order to take measures such as counting the amplitude of the interference wave and determining the minimum value thereof, it is convenient to set them at equal intervals. In the following description, it is assumed that the interval δ ° is set to an equal interval.

  Further, in principle, the measurement accuracy increases as the interval δ ° of the minimum phase modulation amount is smaller, but the measurement system is limited by the waveform distortion of the pulse. Therefore, the minimum phase modulation amount determined by the absolute distance between the sound source device 10 and the measurement processing device 20, the state of the seabed 26 and seawater 14 between them, or the number of measurement processing devices constituting the measurement processing device 20, etc. It is necessary to decide the interval.

  Next, the relationship between the phase modulation amount of the acoustic modulation phase conjugate wave sent from the measurement processing device 20 and the amplitude of the interference wave will be described with reference to FIG. FIG. 5 is a diagram showing the relationship of the amplitude of the interference wave (interference wave obtained by the interference between the reference probe wave and the measurement probe wave) with respect to the phase modulation amount. The vertical axis shows the amplitude of the interference wave on an arbitrary scale. The horizontal axis represents the minute angle Δ ° by converting the phase modulation amount into an angle. FIG. 5 shows the amplitude of the interference wave when there is no variation in the distance between the measurement processing device 20 and the sound source device 10, and the distance varies by 8.3 cm (corresponding to a phase variation of −10 ° as will be described later). ) Is indicated by a broken line.

  Here, the minute angle Δ ° is Nδ °, and the value of δ ° is shown as small enough that the phase modulation amount seems to change almost continuously. Therefore, it should be understood that FIG. 5 shows how the amplitude of the interference wave changes when the phase modulation amount is continuously changed.

  As described above, the distance between the sound source device 10 and the measurement processing device 20 between the time point when the reference probe wave is acquired (first stage) and the time point when the measurement probe wave is acquired (second stage). If there is no fluctuation, the amplitude of the interference wave between the measurement probe wave whose phase modulation amount is 180 ° (π in the arc method display) and the reference probe wave (the phase modulation amount is 0 °) is 0. Should be. The amplitude of the interference wave shown in FIG. 5 is (180-Δ) ° when the phase modulation amount for the measurement probe wave is 180 ° (when the small angle Δ ° is 0 °) is 0 °. The amplitude of the interference wave between the measurement probe wave and the reference probe wave is shown.

  The value of the minute angle Δ ° corresponds to the distance fluctuation amount between the sound source device 10 and the measurement processing device 20. That is, if the frequency f and velocity v of the acoustic probe wave are given, the distance variation is converted into a unit of length from the value of the minute angle Δ °.

  When there is no change in the distance between the measurement processing device 20 and the sound source device 10, as shown by the solid line in FIG. 5, the measurement probe wave and the reference probe wave whose minute angle Δ ° is 0 ° are Since the phases are shifted by 180 ° and added together, the amplitude of the interference wave becomes zero. That is, the minimum angle Δ ° is 0 ° and takes a minimum. Similarly, when the value of the minute angle Δ ° is 360 °, the amplitude of the interference wave is 0 because the phase of the measurement probe wave and that of the reference probe wave are opposite to each other.

  On the other hand, when the distance between the measurement processing device 20 and the sound source device 10 is fluctuating, the position of the minute angle Δ ° is different from 0 ° (in this case, as indicated by a broken line in FIG. 5) It is a curve with a minimum value at the -10 ° position. Also in the curve indicated by the broken line, the minimum positions appear at intervals of 360 ° as in the curve indicated by the solid line. The amount of deviation of the minimum position from 0 ° (in this case, −10 °) corresponds to the distance fluctuation amount between the measurement processing device 20 and the sound source device 10.

  The example shown in FIG. 5 is a simulation result using an acoustic probe wave having a distance of 5 km between the sound source device 10 and the measurement processing device 20 and a frequency f of 500 Hz. According to FIG. 5, it can be seen that the amplitude of the interference wave when the value of the minute angle Δ ° is changed gradually changes near the maximum, but rapidly changes near the minimum. That is, it can be seen that the upward convex portion giving the maximum value of the curve representing the amplitude of the interference wave changes gently, whereas the downward convex portion giving the minimum value changes abruptly. . Therefore, the value of the minute angle Δ ° taking the minimum value can be accurately obtained. Since the distance fluctuation amount ΔL is obtained from the position of the minimum amplitude of the interference wave (the value of the minute angle Δ ° that gives the minimum), it can be seen that it is convenient for accurate measurement of the distance fluctuation amount.

The relationship between the value of the minute angle Δ ° and the distance variation ΔL is as follows. If the wavelength of the acoustic probe wave in seawater is λ, the average velocity is v, and the frequency is f, there is a relationship of λf = v, and the distance variation ΔL corresponding to the phase modulation amount of 360 ° is equal to λ. . That is,
ΔL = (Δ ° / 360 °) λ (1)
There is a relationship. The positive and negative signs of ΔL correspond to the case where the distance increases and the case where the distance decreases, respectively.

  From FIG. 5, it can be seen that the values of the minute angle Δ ° at which the amplitude of the interference wave indicated by the broken line is minimum are −10 ° and 350 °. The amount of distance fluctuation ΔL when the value of the minute angle Δ ° at which the amplitude of the interference wave is minimized is −10 ° is | ΔL | = (10/360) × 3 (m) = 8.3 cm When the angle is 350 °, the magnitude ΔL of the distance fluctuation amount is | ΔL | = (350/360) × 3 (m) = 291.7 cm. However, the average velocity of sound waves between the sound source device 10 and the measurement processing device 20 was set to 1500 m / s. That is, the wavelength λ of the acoustic probe wave in seawater was set to 3 m (= v / f = 1500/500 = 3 m).

  At the boundary where the plates composing the earth's crust contact each other, there is an activity that moves so that the other plate (sea side plate) sinks into one plate (land side plate), The distance between the two points across the boundary where the plates touch each other shrinks over time. Therefore, the value of the minute angle Δ ° at which the amplitude of the interference wave is minimized takes a negative value.

  As described above, according to the distance variation measuring method of the present invention, it is possible to accurately estimate only the amount of variation in the distance between the sound source device 10 and the measurement processing device 20 without knowing the absolute distance. In order to know the value of the amount of crustal strain required for earthquake prediction, the absolute distance between the sound source device 10 and the measurement processing device 20 is not required, and it is sufficient if the amount of change in the distance between the two is known. Therefore, the distance variation measuring method of the present invention, in which the distance variation amount is accurately obtained, is an extremely useful method as a strain measuring method required for earthquake prediction.

<Measurement procedure of distance fluctuation>
A procedure for measuring the distance variation will be described with reference to FIGS.

  FIG. 6 is a flowchart for explaining the steps constituting the distance variation measuring method of the present invention. As described above, the distance variation measuring method of the present invention includes the first step, step A, the second step, step B, the third step, step C, the fourth step, step D, and the fifth step. Step E that is, and Step F that is the sixth step. Each of the first to sixth steps includes substeps. In particular, step A includes substeps A1 to A3, step B includes substeps B1 to B4, step D includes substeps D1 to D3, and step E includes substeps E1 to E5.

  FIG. 6 shows the processing order of each step for the first to sixth steps. First, as a first step of the distance variation measuring method of the present invention, step A is executed in the sound source device 10 and the first acoustic probe wave is sent to the measurement processing device 20. In the measurement processing device 20, step B is executed and an acoustic phase conjugate wave is sent to the sound source device 10. In the sound source device 10, Step C is executed, and the acoustic phase conjugate wave is converted into a reference probe wave and stored in the storage unit. As a second stage, Step D is executed in the sound source device 10 and the second acoustic probe wave is sent to the measurement processing device 20. In the measurement processing device 20, step E is executed, and the acoustic modulation phase conjugate wave is sent to the sound source device 10. In the sound source device 10, Step F is executed, and the amount of variation in distance is obtained.

  FIG. 7 is a detailed flowchart of Step A. Step A is a step executed in the sound source device 10, in which the first transmission electric probe wave is generated by the probe wave generation unit (substep A1), and the first transmission electric probe wave is converted into the first acoustic probe wave. Then (substep A2), and transmitted to the measurement processing device 20 (substep A3). Sub-steps A2 and A3 are performed around the first transducer.

  FIG. 8 is a detailed flowchart of Step B. Step B is a step executed in the measurement processing device 20. By executing the above sub-step A3, the first acoustic probe wave transmitted from the sound source device 10 is converted into the first reception electric probe wave by the second transducer (sub-step B1), and the time reversing unit Is converted into a first electric phase conjugate wave (substep B2). The first electrical phase conjugate wave is converted into an acoustic phase conjugate wave by the second transducer (substep B3) and transmitted to the sound source device 10 (substep B4).

  FIG. 9 is a detailed flowchart of Step C. Step C is a step executed in the sound source device 10, and the acoustic phase conjugate wave transmitted from the measurement processing device 20 by the execution of the above-described step B4 causes the first transducer to generate a reference probe wave. (Substep C1) and stored in the first storage unit included in the sound source device 10 (substep C2).

  FIG. 10 is a detailed flowchart of Step D. The steps after Step D are the second stage of the distance variation measuring method of the present invention. The probe wave generator generates a second transmission electric probe wave (substep D1), the second transmission electric probe wave is converted into a second acoustic probe wave (substep D2), and is transmitted to the measurement processing device 20 (Substep D3). Sub-steps D2 and D3 are performed around the first transducer.

  FIG. 11 is a detailed flowchart of Step E. Step E is a step executed in the measurement processing device 20. By executing step D3 described above, the second acoustic probe wave transmitted from the sound source device 10 is converted into the second received electrical probe wave by the second transducer (sub step E1), and the time reversing unit Conversion into a second electric phase conjugate wave (substep E2). A modulation conjugate wave generation unit provided in the measurement processing device 20 generates a plurality of electric modulation phase conjugate waves having different phase modulation amounts in stages (substep E3), and the plurality of these are centered on the second transducer. The electric modulation phase conjugate wave is sequentially converted into an acoustic modulation phase conjugate wave (substep E4), and is sequentially transmitted to the sound source device 10 at time intervals in accordance with the order of the magnitude of the phase modulation amount (substep E5). .

  FIG. 12 is a detailed flowchart of Step F. Step F is a step executed in the sound source device 10. By executing Step E5 described above, the plurality of acoustic modulation phase conjugate waves transmitted from the measurement processing device 20 are sequentially converted into measurement probe waves around the first transducer (sub-step F1). In the signal interference / minimum point detection unit, an interference wave between the reference probe wave and the measurement probe wave is generated, and the amplitude of this interference wave is sequentially measured (sub step F2), and the phase modulation that minimizes the amplitude of the interference wave The amount is determined, and this phase modulation amount is converted into a distance variation amount, which is output from the interference information output unit to an external distance variation information acquisition device (sub step F3).

  The period from the execution of the first stage to the execution of the second stage is determined for each object of distance fluctuation measurement, for example, the fluctuation of the crustal strain described with reference to FIG. When the distance variation measuring method of the present invention is used to measure the distance, it is set to several months, half a year, or one year.

<Sound source device>
The structure and function of the sound source device 10 will be described with reference to FIG. FIG. 13 is a schematic block diagram of the sound source device 10. As shown in FIG. The sound source device 10 generates an acoustic probe wave and transmits it to the measurement processing device (Step A, Step D), and converts the acoustic phase conjugate wave sent from the measurement processing device 20 into a reference probe wave to generate a first probe wave. Store in the storage unit (Step C), convert multiple acoustic modulation phase conjugate waves into multiple measurement probe waves, and sequentially interfere each of the measurement probe waves with the reference probe wave read from the storage unit to generate interference waves Generate and confirm the phase modulation amount of the measurement probe wave that produced the interference wave with the smallest amplitude, and output the amount of variation in the distance obtained using the phase-to-distance conversion means. Step F).

  The sound source device 10 includes a first transducer 34 and a probe wave generation / distance information output unit 30 as basic components.

  The first transducer 34 has a function of converting an electric signal into a sound wave signal and converting the sound wave signal into an electric signal. Accordingly, the first transducer 34 converts the first and second transmitted electrical probe waves into the first and second acoustic probe waves 35, respectively.

  Hereinafter, the first and second transmission electrical probe waves may be referred to as transmission electrical probe waves 51, and the first and second acoustic probe waves may be referred to as acoustic probe waves 35. Further, when the first and second transmission electrical probe waves are distinguished from each other within a range where no confusion occurs, they may be referred to as a first transmission electrical probe wave 51 and a second transmission electrical probe wave 51, respectively. Similarly, when the first and second acoustic probe waves are distinguished from each other, they may be referred to as a first acoustic probe wave 35 and a second acoustic probe wave 35.

  The acoustic phase conjugate wave and the acoustic modulation phase conjugate wave are converted into a first sub reception electrical phase conjugate wave and a first sub reception electrical modulation phase conjugate wave, respectively. Hereinafter, the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave are referred to as an acoustic modulation phase conjugate wave 65 within a range where no confusion occurs (the acoustic phase conjugate wave is regarded as an acoustic modulation phase conjugate wave having a phase modulation amount of 0). The first sub reception electrical phase conjugate wave and the first sub reception electrical modulation phase conjugate wave are described as a first sub reception electrical modulation phase conjugate wave 59 (the phase modulation amount of the first sub reception electrical phase conjugate wave is 0) It may be regarded as the first sub-receiving electrical modulation phase conjugate wave.)

  Further, in the received electrical phase conjugate wave or the received electrical modulation phase conjugate wave, it may be necessary to distinguish between the outputs from the first transducer 34 or the first preamplifier 36. In such a case, the first or second sub-received electrical modulation phase conjugate wave may be distinguished from the first and second sub-acoustic words with the words “first”, “second”, or “sub”. Similarly, a transmission electric probe wave or a reception electric probe wave, which will be described later, may be described separately with the words “first”, “second”, or “sub”.

  As the first transducer 34, a commercially available acoustic transducer having any suitable configuration can be used. For example, it is commercially available as an underwater acoustic transducer.

  The probe wave generation / distance information output unit 30 includes a probe wave generation / phase conjugate wave processing unit 32 and a first controller 56.

  The probe wave generation / phase conjugate wave processing unit 32 has a function of converting the acoustic phase conjugate wave into a reference probe wave and storing it in the first storage unit 54 (function of executing step C). The probe wave generation / phase conjugate wave processing unit 32 reads each of the plurality of measurement probe waves generated by converting the plurality of acoustic modulation phase conjugate waves by the first transducer 34 from the first storage unit 54. The reference probe wave is sequentially interfered with each other to generate an interference wave. In addition, the probe wave generation / phase conjugate wave processing unit 32 determines the phase modulation amount of the measurement probe wave that generates the interference wave having the minimum amplitude, and uses the phase and distance conversion means to convert the phase modulation amount. It has a function of outputting the obtained distance fluctuation value 71 to the distance fluctuation information acquisition device 70 provided as appropriate separately from the sound source device 10 (function to execute step F).

  The probe wave generation / phase conjugate wave processing unit 32 includes a probe wave generation unit 46, a first output unit 48, a first input unit 38, a signal interference / minimum point detection unit 40, and an interference information output unit 44. . The function of generating a transmission electrical probe wave and transmitting it as the acoustic probe wave 35 (the function of executing sub-steps A1 to A3 and sub-steps D1 to D3) includes the probe wave generation unit 46 and the first output unit 48. It is realized centering on. In addition, the function of generating interference waves by sequentially interfering each of the measurement probe waves and the reference probe wave, and the function of determining the phase modulation amount and calculating and outputting the variation value of the distance (substeps F1 to F3) The function to be executed) is realized mainly by the first input unit 38, the signal interference / minimum point detection unit 40, and the interference information output unit 44.

  As will be described below, the signal interference / minimum point detection unit 40 sequentially interferes with each of the plurality of measurement probe waves and the reference probe wave read from the first storage unit 52 to generate an interference wave, and the amplitude The phase modulation amount of the measurement probe wave that generates the interference wave having the smallest is determined. Further, the signal interference / minimum point detection unit 40 converts the phase modulation amount as a distance variation value using a phase / distance conversion unit.

  The phase / distance conversion means is stored in the first storage unit 54, and when the phase modulation amount is converted into an actual distance (amount of fluctuation in the interval between the sound source device 10 and the measurement processing device 20), it is appropriately selected. Called and used. As a specific example of the phase / distance conversion means, the value of the small angle Δ ° and the distance fluctuation amount ΔL are defined as the relationship given by the above equation (1), and the value of Δ ° is If given, it is a program that outputs ΔL.

  The first control device 56 is constituted by a microcomputer. The first control device 56 includes a first instruction unit 42, a first control unit 52, and a first storage unit 54. The first control unit 52 is configured by a so-called central processing unit (CPU), and the probe wave generation / phase conjugate wave processing unit 32 is operated according to a processing program stored in the first storage unit 54. Control. The first storage unit 54 stores a processing program for controlling the probe wave generation / phase conjugate wave processing unit 32, and is used and processed in the probe wave generation / phase conjugate wave processing unit 32. Save data temporarily. That is, the first storage unit 54 is a program that outputs the above-described ΔL, a transmission electrical probe wave 51, a reception electrical modulation phase conjugate wave 39, and the like that are processed by a probe wave generation / phase conjugate wave processing unit 32 described later. The required data and control information are temporarily saved.

  The received electrical modulation phase conjugate wave 39 is a reference probe wave in the case of an electrical wave obtained by converting the acoustic phase conjugate wave, and the electrical modulation phase conjugate wave obtained by converting the acoustic modulation phase conjugate wave. If it is a wave, it is a measurement probe wave. Hereinafter, when it is necessary to distinguish between the reference probe wave and the measurement probe wave, the received electrical modulation phase conjugate wave 39 is described as the reference probe wave 39 and the measurement probe wave 39 according to each case. To distinguish. In the case of an argument that holds in either case without distinguishing between the reference probe wave and the measurement probe wave, the reference probe wave and the measurement probe wave are expressed as a received electrical modulation phase conjugate wave 39.

  In FIG. 13, the probe wave generation / phase conjugate wave processing unit 32 and the first control device 56 are shown connected by a double-headed arrow, but this is necessary between each component of the first control device 56. FIG. 2 conceptually shows that the first control unit 52 controls the operation of each component of the probe wave generation / phase conjugate wave processing unit 32.

  When the probe wave generation / distance information output unit 30 starts operating, each component of the probe wave generation / phase conjugate wave processing unit 32 is started in response to a control signal from the first control unit 52.

  The probe wave generator 46 generates first and second sub-transmission electric probe waves. Hereinafter, when referring to both the first and second sub-transmission electric probe waves, they may be simply referred to as sub-transmission electric probe waves. Therefore, the probe wave generator 46 generates the sub transmission electrical probe wave 47.

  As the probe wave generator 46, a commercially available device having any suitable configuration may be used. For example, since waveform forming apparatuses equipped with software for arbitrarily generating output waves such as tone burst waves are commercially available, it is possible to select and use an apparatus with any suitable configuration from these. (For example, see the Internet <URL: http://www.toyo.co.jp/awg/ARB_SOFT.html> (searched on June 17, 2005)).

  When the above-described distance variation measurement method is executed, the probe wave generation unit 46 generates the first sub transmission electric probe wave 47 in response to the probe wave generation instruction signal from the first control unit 52. The first sub transmission electric probe wave 47 is sent to the first output unit 48 in response to the probe wave transfer instruction signal from the first control unit 52. As will be described later, the first output unit 48 adjusts the timing for transmitting the first sub-transmission electrical probe wave 47 and sends it to the first amplifier 50 as the second sub-transmission electrical probe wave 49 (Step A). Including sub-step A1). The timing at which the second sub-transmission electric probe wave 49 is sent to the first amplifier 50 indicates that the first transducer 34 is not in an operating state in which the acoustic modulation phase conjugate wave 65 is received from the first input unit 38. The first control unit 52 makes a determination based on the operation signal, and adjusts by sending an operation start signal from the first control unit 52 to the first output unit.

  The second sub transmission electrical probe wave 49 sent from the first output unit 48 to the first amplifier 50 is amplified by the first amplifier 50 to a level at which the first transducer 34 can operate, and the transmission electrical probe wave 51 To the first transducer 34. The transmission electrical probe wave 51 is converted from an electrical signal into an acoustic probe wave 35 that is a sound wave signal by the first transducer 34 (substeps A2 and D2). Then, the acoustic probe wave 35 is transmitted toward the measurement processing device 20 (substeps A3 and D3).

  On the other hand, the acoustic modulation phase conjugate wave 65 transmitted from the measurement processing device 20 is received by the first transducer 34, and the acoustic modulation phase conjugate wave 65 that is a sound wave signal is the first sub reception electrical modulation that is an electric signal. It is converted into a phase conjugate wave 59 and sent to the first preamplifier 36.

  In the first preamplifier 36, the first sub reception electrical modulation phase conjugate wave 59 is amplified and sent to the first input unit 38 as the second sub reception electrical modulation phase conjugate wave 37. In addition, the first preamplifier 36 transmits a signal having a large energy that may be mixed into the first sub reception electrical modulation phase conjugate wave 59 to the first input unit 38 when the acoustic probe wave 35 is transmitted. It also plays a role in preventing input.

  The first control unit 52 responds to the input of the second sub reception electrical modulation phase conjugate wave 37 to the first input unit 38, and the filtering instruction signal and timing instruction stored in advance in the first storage unit 54 The signal is read, and the filtering instruction signal is sent to the first input unit 38 and the timing instruction signal is sent to the first output unit 48.

  The first input unit 38 is instructed to perform temporal filtering on the second sub reception electrical modulation phase conjugate wave 37, and at the same time, the first output unit 48 receives the first sub transmission electrical probe wave. An indication of the timing to transmit 47 is given. In accordance with this instruction, the first input unit 38 performs temporal filtering on the second sub reception electrical modulation phase conjugate wave 37.

  That is, a so-called time that passes the signal for a time equal to the time width of the tone burst wave transmitted to the measurement processing device 20 as the acoustic probe wave 35 by this filtering instruction signal and blocks signal components in other time zones. Filter processing by the window is executed in the first input unit 38. On the other hand, as described above, the second output electric probe wave 49 is output from the first output unit 48 by the timing instruction signal. The acoustic modulation phase conjugate wave 65 received by the first transducer 34 is slightly mixed with noise components. This noise component is removed from the second sub reception electric modulation phase conjugate wave 37 by the filtering process by this time window.

  The noise component is removed from the second sub reception electrical modulation phase conjugate wave 37, and the amplified reception electrical modulation phase conjugate wave 39 is output from the first input unit 38 and input to the signal interference / minimum point detection unit 40. Is done. In the signal interference / minimum point detection unit 40, step C for storing the reference probe wave in the first storage unit 54 is executed as described below. Further, the signal interference / minimum point detection unit 40 sequentially interferes each of the plurality of measurement probe waves with the reference probe wave to generate an interference wave, and the measurement probe wave that has generated the interference wave having the minimum amplitude. Step F for determining the amount of phase variation and determining the amount of variation in distance is executed.

  In response to the reception electrical modulation phase conjugate wave 39 being input to the signal interference / minimum point detection unit 40, the first control unit 52 receives the signal interference / minimum point detection unit 40 from the first input unit 38. An instruction to capture the output received electrical modulation phase conjugate wave 39 into the first storage unit 54 is given.

  When the sound source device 10 receives an acoustic phase conjugate wave as a first step of the measurement processing method of the present invention, the received electrical modulation phase conjugate wave 39 is a reference probe wave, so the first control unit 52 gives an instruction to capture the received electrical modulation phase conjugate wave 39 into the reference probe wave storage area of the first storage unit 54. On the other hand, when the sound source device 10 receives the acoustic modulation phase conjugate wave as the second step, the received electrical modulation phase conjugate wave 39 is a measurement probe wave. An instruction to capture the received electrical modulation phase conjugate wave 39 into the measurement probe wave storage area of the first storage unit 54 is given. Of course, in this case, since a plurality of measurement probe waves having different phase modulation amounts are sequentially transmitted, each of the plurality of measurement probe waves and the phase modulation amount have a one-to-one correspondence. It is stored in the first storage unit 54.

  Subsequently, the first control unit 52 reads the reference probe wave stored in the first storage unit 54 and the plurality of measurement probe waves described above and provides them to the signal interference / minimum point detection unit 40. At the same time, the first control unit 52 sequentially calculates the interference wave by causing the reference probe wave and the plurality of measurement probe waves to sequentially interfere according to the procedure for generating the interference wave stored in the first storage unit 54. Is given to the signal interference / minimum point detection unit 40.

  In the signal interference / minimum point detection unit 40, an interference wave with the reference probe wave is generated for each of the plurality of measurement probe waves, and in response to the interference wave capturing signal output from the first control unit 52, These interference waves are temporarily and temporarily stored in the first storage unit 54. Subsequently, in the signal interference / minimum point detection unit 40, in response to the interference wave amplitude comparison signal output from the first control unit 52, the above-described interference wave is called from the first storage unit 54 to increase the amplitude. The phase modulation amount 41 added to the measurement probe wave having the smallest length is output to the phase information output unit 44.

  In response to the conversion work start signal output from the first control unit 52, the phase information etc. output unit 44 calls the conversion means between the phase and distance from the first storage unit 54 to detect the signal interference / minimum point. The step of converting the above-described phase modulation amount input from the unit 40 into the distance fluctuation amount ΔL is executed. Information regarding the distance fluctuation amount ΔL obtained by conversion in this way is stored in the first storage unit 54.

  The information on the distance fluctuation amount ΔL stored in the first storage unit 54 is, for example, the distance fluctuation mounted on this observation ship etc. by anchoring the observation ship etc. in the area where the sound source device 10 is installed. The information may be transferred to the information acquisition device 70. In order to transfer the information related to the distance fluctuation amount ΔL stored in the first storage unit 54 to the distance fluctuation information acquisition device 70, the following is performed.

  A transmission command signal is sent from the distance variation information acquisition device 70 to the first instruction unit 42, a transmission command signal is sent from the first instruction unit 42 that has received the transmission command signal to the first control unit 52, In response to this transmission command signal, the 1 control unit 52 reads out information related to the distance variation ΔL from the first storage unit 54 and sends the information to the interference information output unit 44. Upon receiving the transmission instruction signal from the first control unit 52, the interference information output unit 44 transfers information regarding the distance variation amount ΔL to the distance variation information acquisition device 70. When the reception of the information related to the distance fluctuation amount ΔL is completed, a transmission end signal is sent from the distance fluctuation information acquisition device 70 to the first instruction unit 42, and the first control unit 52 responds to the transmission end signal according to the interference information. The information transfer operation related to the distance fluctuation amount ΔL of the equal output unit 44 is terminated.

《Measurement processing device》
With reference to FIG. 14, the configuration and function of the converter constituting the measurement processing device 20 will be described. The measurement processing device 20 generates an acoustic modulation phase conjugate wave 65 based on the acoustic probe wave 35 transmitted from the sound source device 10, and sends the acoustic modulation phase conjugate wave 65 to the sound source device 10 (steps B and E). (Function to execute).

  All the measurement processors constituting the measurement processing device 20 have the same configuration. Therefore, FIG. 14 shows a schematic block configuration diagram of the measurement processor 20-1 on behalf of one measurement processor constituting the measurement processor 20. The measurement processor 20-1 includes a second transducer 64 and a phase conjugate wave generation / transmission device 60 as basic components.

  Similar to the first transducer 34, the second transducer 64 has a function of converting an electric signal into a sound wave signal and converting the sound wave signal into an electric signal. Accordingly, the second transducer 64 converts the acoustic probe wave 35 into the first sub reception electrical probe wave 57 (substeps B1 and E1), and the transmission electrical modulation phase conjugate wave 85 into the acoustic modulation phase conjugate wave 65. Converted (substeps B3 and E4). The second transducer 64 can be used by selecting any suitable configuration from ordinary acoustic transducers in the same manner as the first transducer 34.

  When the phase conjugate wave generation / transmission device 60 starts operation, each component of the phase conjugate wave generation / phase modulation unit 62 is started in response to the control signal from the second control unit 88. The phase conjugate wave generation / transmission device 60 includes a phase conjugate wave generation / phase modulation unit 62 and a second control device 92.

  The phase conjugate wave generation / phase modulation unit 62 includes a second input unit 68, a time inversion unit 72, a modulation conjugate wave generation unit 94, and a second output unit 82. The phase conjugate wave generation / phase modulation unit 62 has a function of receiving the acoustic probe wave 35 transmitted from the sound source device 10 and generating an electrical phase conjugate wave 73 for the acoustic probe wave 35. . Further, it has a function of generating a second sub-transmission electric modulation phase conjugate wave 83 by applying phase modulation to the electric phase conjugate wave 73.

  The second control device 92 is composed of a microcomputer. The second control device 92 includes a second instruction unit 86, a second control unit 88, and a second storage unit 90. The second control unit 88 includes a so-called central processing unit (CPU), and controls the phase conjugate wave generation / phase modulation unit 62 in accordance with a processing program stored in the second storage unit 90. The second storage unit 90 stores a processing program for controlling the phase conjugate wave generation / phase modulation unit 62, and also uses data processed and processed in the phase conjugate wave generation / phase modulation unit 62. Memorize temporarily. That is, the second storage unit 90 is a signal processed in the phase conjugate wave generation / phase modulation unit 62, for example, an acoustic probe wave 35 that is a received signal, an electrical phase conjugate wave 73, a frequency spectrum 75, a modulation signal 77, a frequency The modulated wave 79, the first sub-transmission electric modulation phase conjugate wave 81, and the like are stored.

  In FIG. 14, the phase conjugate wave generation / phase modulation unit 62 and the second control device 92 are shown connected by a bidirectional arrow, but this is the second control unit that is a main component of the second control device 92. 88 and the respective components constituting the phase conjugate wave generation / phase modulation unit 62, and the second control unit 88 uses the phase conjugate wave generation / phase modulation unit to exchange required data. 62 conceptually indicates that the operation control of each of the 62 constituent elements is performed.

  The function of receiving the acoustic probe wave 35 transmitted from the sound source device 10 and generating the electric phase conjugate wave 73 based on the acoustic probe wave 35 includes the second transducer 64, the second preamplifier 66, This is realized by the second input unit 68 and the time reversing unit 72.

  The acoustic probe wave 35 that is a sound wave signal is received by the second transducer 64, converted into a first sub reception electric probe wave 57 that is an electric signal, and input to the second preamplifier 66 (substep). B1 and E1). The second preamplifier 66 amplifies the first sub reception electric probe wave 57 and outputs it as a second sub reception electric probe wave 67 and inputs it to the second input unit 68. In addition, the second preamplifier 66 transmits a signal having a large energy that may be mixed into the first sub reception electric probe wave 57 to the second input unit 68 when the acoustic modulation phase conjugate wave 65 is transmitted. It also plays a role in preventing input.

  In response to the second sub reception electrical probe wave 67 being input to the second input unit 68, the second control unit 88 receives the filtering instruction signal and the timing instruction signal stored in advance in the second storage unit 90. Then, the filtering instruction signal is sent to the second input unit 68 and the timing instruction signal is sent to the second output unit 82.

  That is, the second control unit 88 gives an instruction to the second input unit 68 to perform temporal filtering on the second sub reception electric probe wave 67, and at the same time, the second output unit 82 Is given an instruction to input the first sub-transmission electrical modulation phase conjugate wave 81. In accordance with this instruction, the second input unit 68 performs temporal filtering on the second sub reception electrical probe wave 67. In other words, a so-called time window filter that passes the signal for a time slightly longer than the time width of the tone burst wave transmitted as the acoustic probe wave 35 and extended by multipath, and blocks signal components in other time zones. Processing is executed in the second input unit 68. That is, a part of the noise component mixed in the second sub reception electric probe wave 67 is removed by the filtering process by this time window, and is output as the third sub reception electric probe wave 69 and input to the time inverting unit 72. The

  The time reversing unit 72 has a function of converting the third sub reception electric probe wave 69 into an electric phase conjugate wave 73 (function of executing sub-steps B2 and E2).

  The time reversing unit 72 sets a time window for the third sub reception electrical probe wave 69 and reverses the time axis. This is because the third sub-reception electric probe wave 69 is allowed to pass for a time equal to the width of the transmitted tone burst wave on the time axis, and the passed time waveform is stored in the second storage unit 90 in the order of time. Remember me temporarily. When all the signal components that have passed through the time window for the third sub-received electrical probe wave 69 are stored in the second storage unit 90, the signal components stored last in time, contrary to the order of the stored time The signal components are extracted from the second storage unit 90 and rearranged on the time axis so that the signal components stored first in time in order are last. By performing such an operation between the time reversing unit 72 and the second storage unit 90, in the time reversing unit 72, the electric phase conjugate wave 73 whose time axis is reversed from the third sub reception electric probe wave 69 is obtained. Is generated.

  In the first stage, the electric phase conjugate wave 73 is input to the second output unit 82 based on the input instruction signal to the second output unit 82 supplied from the second control unit 88, and the second sub transmission electric wave 73 The phase conjugate wave 83 is output. The second sub transmission electrical phase conjugate wave 83 is amplified by the second amplifier 84 to an intensity at which the second transducer 64 can operate, and is output from the second amplifier 84 as a transmission electrical phase conjugate wave 85. The transmission electrical phase conjugate wave 85 is converted into an acoustic phase conjugate wave 65 by the second transducer 64 (substep B3) and transmitted to the sound source device 10 (substep B4).

  In the second stage, the electrical phase conjugate wave 73 is input to the modulation conjugate wave generation unit 94 based on the input instruction signal to the second output unit 82 supplied from the second control unit 88. The function of generating a plurality of first sub-transmission electrical modulation phase conjugate waves 81 whose phase modulation amounts differ in stages from the electrical phase conjugate wave 73 (function of executing sub-step E3) is realized by the modulation conjugate wave generation unit 94. The The plurality of first sub-transmission electrical modulation phase conjugate waves 81 are sequentially input to the second output unit 82 and sequentially output as the plurality of second sub-transmission electrical modulation phase conjugate waves 83. The plurality of second sub-transmission electrical modulation phase conjugate waves 83 are amplified by the second amplifier 84 to an intensity at which the second transducer 64 can operate, and sequentially transmitted from the second amplifier 84 as transmission electrical modulation phase conjugate waves 85. Is output. The plurality of transmission electrical modulation phase conjugate waves 85 are sequentially converted into the acoustic modulation phase conjugate wave 65 by the second transducer 64 (sub step E4) and transmitted to the sound source device 10 (sub step E5).

  The modulation conjugate wave generation unit 94 includes a spectrum analysis unit 74, a sweep phase generation unit 76, a phase modulation unit 78, and a pulse wave generation unit 80.

  The spectrum analysis unit 74 has a function of obtaining a frequency spectrum by performing a Fourier transform on the electric phase conjugate wave 73 and outputting it as a frequency spectrum 75.

  The frequency spectrum 75 is input to the phase modulation unit 78. Further, the modulation signal 77 is also input from the sweep phase generation unit 76 to the phase modulation unit 78. In response to the frequency spectrum 75 being input to the phase modulation unit 78, the second control unit 88 sends an output instruction signal that instructs the sweep phase generation unit 76 to output the modulation signal 77. The sweep phase generation unit 76 outputs a modulation signal 77 to the phase modulation unit 78 in synchronization with the frequency spectrum 75 based on the output instruction signal.

  More specifically, outputting the modulation signal 77 to the phase modulation unit 78 in synchronization with the frequency spectrum 75 is as follows. In other words, the frequency spectrum 75 is supplied from the spectrum analysis unit 74 to the phase modulation unit 78 at regular time intervals. On the other hand, from the sweep phase generation unit 76, modulation signals 77 having different modulation amounts in stages are output to the phase modulation unit 78 at regular time intervals in the order of the modulation amount. Therefore, the second modulation signal 77 supplied from the sweep phase generation unit 76 and the frequency spectrum 75 supplied from the spectrum analysis unit 74 are supplied to the phase modulation unit 78 with the timing matched in time. A supply timing signal is supplied from the control unit 88 to the sweep phase generation unit 76 and the spectrum analysis unit 74, respectively.

  In response to the input of the set of the frequency spectrum 75 and the modulation signal 77 to the phase modulation unit 78, the phase modulation unit 78 performs phase modulation on the frequency spectrum 75 based on the modulation signal 77, and the frequency A modulated wave 79 is generated. Such an operation is performed at regular time intervals according to the above-described timing signal, and a plurality of frequency modulation waves 79 having different modulation amounts in stages are sequentially generated.

  In the phase modulation unit 78, modulation is continuously and linearly applied to the phase of the electric phase conjugate wave 73 without impairing the phase conjugate property. This means that the phase of the electrical phase conjugate wave 73 is modulated without changing the frequency spectrum 75 obtained by Fourier transforming the electrical phase conjugate wave 73. The electric phase conjugate wave 73 is composed of a number of frequency components. Therefore, in the phase modulation unit 78, the same phase change is given to all the Fourier components having different frequencies constituting the electric phase conjugate wave 73. Although the phase modulation amounts of all these Fourier components are the same, the magnitudes of the deviations on the time axis for the respective Fourier components are different. That is, the phase modulation unit 78 modulates the phase of the electrical phase conjugate wave 73 without changing the frequency spectrum of the electrical phase conjugate wave 73 and outputs it as a frequency modulated wave 79.

  In the pulse wave generation unit 80, the frequency modulation wave 79 is subjected to inverse Fourier transform to generate and output a first sub-transmission electric modulation phase conjugate wave 81. The first sub-transmission electrical modulation phase conjugate wave 81 is input to the second output unit 82. In all measurement processors constituting the measurement processing device 20, the second output unit 82 adjusts the transmission timing of the first sub transmission electrical modulation phase conjugate wave 81 to the second amplifier 84. The second sub-transmission electric modulation phase conjugate wave 83 is sent.

  The timing adjustment performed by the second output unit 82 is performed by the second control unit 88 that determines the time zone in which the second sub reception electrical probe wave 67 is not input to the second input unit 68. Based on this, the second sub-transmission electric modulation phase conjugate wave 83 input permission signal to the second amplifier 84 is output to the second output unit 82. Then, in response to the input of the second sub reception electrical probe wave 67 from the second input unit 68, the reception signal of the second sub reception electrical probe wave 67 is sent to the second control unit 88. The second control unit 88 selects a time zone during which this received signal is not transmitted from the second input unit 68, and outputs a second sub-transmission electric modulation phase conjugate wave 83 input permission signal to the second amplifier 84. Second sub-transmission electrical modulation phase conjugate wave 83 until second sub-transmission electrical modulation phase conjugate wave 83 input permission signal to second amplifier 84 is output from second control unit 88 to second output unit 82 Is stored in the second storage unit 90.

  The second amplifier 84 amplifies the second sub-transmission electrical modulation phase conjugate wave 83 to a level at which the second transducer 64 operates, and sends it to the second transducer 64 as a transmission electrical modulation phase conjugate wave 85. In the second transducer 64, the transmission electrical modulation phase conjugate wave 85 is converted into the acoustic modulation phase conjugate wave 65 (sub step E4) and transmitted to the sound source device 10 (sub step E5).

  The second instruction unit 86 has a function of instructing the sweep phase generation unit 76 regarding the modulation signal 77 to be supplied from the sweep phase generation unit 76. That is, an instruction is given as to which range of modulation amount to be applied to the frequency spectrum 75 is set and supplied at what interval. That is, the instruction related to the modulation signal 77 to be supplied from the sweep phase generation unit 76 is information on how much it is preferable to set the parameter δ, and as described above, the sound source device 10 and the measurement process It relates to parameters determined by the absolute distance from the apparatus 20, the conditions of the sea floors 26 and 28 and the seawater 14 during this period, the number of measurement processors constituting the measurement processing apparatus 20, and the like.

  Therefore, optimum conditions must be set for each measurement object to which the distance variation measuring method of the present invention is applied. Therefore, the distance variation measuring device of the present invention is installed on the seabed, and data related to the modulation amount to be added to the frequency spectrum 75 is set in advance in the second instruction section 86 before the measurement is started. The phase information input to the second instruction unit 86 is sent to the sweep phase generation unit 76 via the second control unit 88, and a modulation signal 77 corresponding to the input phase information is generated.

It is a figure where it uses for description of the distance fluctuation | variation measuring method between underwater fixed points. It is a figure which shows the sound pressure distribution of the sound wave between a measurement processing apparatus and a sound source device. FIG. 4 is a diagram showing a time waveform of a first acoustic probe wave transmitted from a sound source device and a time waveform of an acoustic phase conjugate wave transmitted from a measurement processing device. It is a figure which shows the time waveform of the acoustic modulation phase conjugate wave received with the sound source device. It is a figure which shows the relationship of the amplitude of the interference wave of a reference | standard probe wave and a measurement probe wave with respect to a phase modulation amount. It is a flowchart of the distance fluctuation | variation measuring method of this invention. 4 is a detailed flowchart of Step A. 4 is a detailed flowchart of Step B. 4 is a detailed flowchart of Step C. 4 is a detailed flowchart of Step D. 5 is a detailed flowchart of Step E. 4 is a detailed flowchart of Step F. It is a schematic block block diagram of a sound source device. It is a schematic block block diagram of the measurement processor which forms a measurement processing apparatus.

Explanation of symbols

10: Sound source device
12: Sea level
14: Seawater
16: Sea side plate
18, 24: Mantle
20: Measurement processing equipment
22: Land side plate
26, 28: Bottom of the sea
30: Probe wave generation / distance information output section
32: Probe wave generation / phase conjugate wave processing section
34: 1st transducer
36: 1st preamplifier
38: First input section
40: Signal interference / minimum point detector
42: First indicator
44: Output section for interference information, etc.
46: Probe wave generator
48: 1st output section
50: First amplifier
52: First control unit
54: First memory
56: First controller
60: Phase conjugate wave generator / transmitter
62: Phase conjugate wave generator / phase modulator
64: 2nd transducer
66: Second preamplifier
68: Second input section
70: Distance fluctuation information acquisition device
72: Time reversal part
74: Spectrum analysis section
76: Sweep phase generator
78: Phase modulation section
80: Pulse wave generator
82: Second output section
84: Second amplifier
86: Second indicator
88: Second control unit
90: Second memory
92: Second controller
94: Modulated conjugate wave generator

Claims (9)

(A) In the sound source device, a first step of generating a first acoustic probe wave and sending the first acoustic probe wave from the sound source device to the measurement processing device;
(B) a second step of sending an acoustic phase conjugate wave generated based on the first acoustic probe wave to the sound source device in the measurement processing device;
(C) a third step of converting the acoustic phase conjugate wave into a reference probe wave and storing it in the storage unit of the sound source device;
(D) a fourth step of generating a second acoustic probe wave in the sound source device and sending the second acoustic probe wave from the sound source device to the measurement processing device;
(E) In the measurement processing device, a plurality of acoustic modulation phase conjugate waves having different phase modulation amounts are generated stepwise based on the second acoustic probe wave, and the plurality of acoustic modulation phase conjugate waves are phase-modulated. A fifth step of sequentially sending to the sound source device according to the order of the magnitude of the quantity;
(F) converting the plurality of acoustic modulation phase conjugate waves into a plurality of measurement probe waves, and sequentially interfering each of the measurement probe waves with the reference probe wave read from the storage unit to generate an interference wave Determining the phase modulation amount of the measurement probe wave that has produced the interference wave having the smallest amplitude among the interference waves, and converting the phase modulation amount into a distance value using a phase and distance conversion means. A distance variation measuring method comprising: a sixth step of converting and outputting. The first step includes
(A1) generating a first transmission electrical probe wave in the probe wave generator of the sound source device;
(A2) converting the first transmission electrical probe wave into the first acoustic probe wave;
2. The distance variation measuring method according to claim 1, further comprising: (A3) sending the first acoustic probe wave to the measurement processing device. The second step includes
(B1) converting the first acoustic probe wave into a first received electrical probe wave;
(B2) converting the first received electrical probe wave into a first electrical phase conjugate wave;
(B3) converting the first electrical phase conjugate wave to the acoustic phase conjugate wave;
2. The distance variation measuring method according to claim 1, further comprising: (B4) sending the acoustic phase conjugate wave to the sound source device. The fourth step is
(D1) generating a second transmission electric probe wave in the probe wave generation unit of the sound source device;
(D2) converting the second transmission electrical probe wave into the second acoustic probe wave;
2. The distance variation measuring method according to claim 1, further comprising: (D3) sending the second acoustic probe wave to the measurement processing device. The fifth step includes
(E1) converting the second acoustic probe wave into a second received electrical probe wave;
(E2) converting the second received electrical probe wave into a second electrical phase conjugate wave;
(E3) sequentially generating a plurality of electrical modulation phase conjugate waves having phase modulation amounts that differ in stages based on the second electrical phase conjugate wave;
(E4) sequentially converting the plurality of electrically modulated phase conjugate waves into the acoustically modulated phase conjugate wave;
2. The distance variation measurement according to claim 1, further comprising the step of: (E5) sending the plurality of acoustic modulation phase conjugate waves to the sound source device sequentially at intervals in the order of the magnitude of the phase modulation amount. Method. The first and second acoustic probe waves are generated and transmitted to the measurement processing device, and the acoustic phase conjugate wave transmitted from the measurement processing device is converted into a reference probe wave and stored in the storage unit, and a plurality of acoustic waves are stored. An interference wave having a minimum amplitude by converting a modulated phase conjugate wave into a plurality of measurement probe waves and sequentially interfering each of the measurement probe waves with the reference probe wave read from the storage unit. A sound source device that determines the phase modulation amount of the measurement probe wave that has caused the error and outputs the value of the distance obtained by using the phase and distance conversion means for the phase modulation amount;
The acoustic phase conjugate wave generated based on the first acoustic probe wave is transmitted to the sound source device, and the plurality of acoustics whose phase modulation amounts differ stepwise based on the second acoustic probe wave And a measurement processing device configured to include a measurement processor that generates a modulated phase conjugate wave and sequentially sends the plurality of acoustic modulation phase conjugate waves to the sound source device in the order of the magnitude of the phase modulation amount. Distance variation measurement system characterized by   7. The distance variation measuring system according to claim 6, wherein the measurement processing device includes a plurality of the measurement processors. The sound source device is
A probe wave generator for generating first and second transmission electric probe waves;
The first and second transmission electric probe waves are converted into the first and second acoustic probe waves, respectively, and the acoustic phase conjugate wave and the acoustic modulation phase conjugate wave are converted into the reference probe wave and the measurement probe wave, respectively. The first transducer to convert to
A storage unit for storing the reference probe wave and storing a conversion means between the phase and the distance;
Each of the plurality of measurement probe waves and the reference probe wave read from the storage unit are sequentially interfered to generate an interference wave, and the measurement probe wave that has generated the interference wave having the minimum amplitude is identified. A signal interference / minimum point detector for determining the phase modulation amount;
An output unit for interference information, etc., which reads out the phase / distance conversion means from the storage unit and converts the phase modulation amount into a distance value using the conversion means; The distance variation measuring system according to claim 6 or 7. The measurement processor is
The first and second acoustic probe waves are converted into first and second received electrical probe waves, respectively, and the first electrical phase conjugate wave and the electrical modulation phase conjugate wave are converted into an acoustic phase conjugate wave and an acoustic modulation phase conjugate wave, respectively. A second transducer to convert,
A time reversing unit for converting the first and second received electrical probe waves into the first electrical phase conjugate wave and the second electrical phase conjugate wave, respectively;
8. The distance variation measuring system according to claim 6, further comprising: a modulation conjugate wave generation unit that performs phase modulation on the second electric phase conjugate wave to generate the electric modulation phase conjugate wave.