Apparatus and method for measuring characteristics of an object under test

Abstract

This device for measuring a characteristic of an object under measurement comprises: a sound wave transmission unit 130 for transmitting a sound wave; a reception unit 140 for receiving an electromagnetic field from an object 200 under measurement that has been generated as a result of the emission of the sound wave onto the object 200 under measurement; a sound wave medium 310 that is between the sound wave transmission unit 130 and object 200 under measurement and is for temporally separating the electromagnetic field from a reverberant electromagnetic field resulting from reverberant vibration of the sound wave transmission unit 130; a despreading unit 160 for using a reference signal relating to the sound wave to despread the electromagnetic field received by the reception unit 140; and a measurement unit 170 for extracting at least one type of characteristic of the object 200 under measurement selected from the group consisting of an electrical characteristic, magnetic characteristic, electromechanical characteristic, and magnetomechanical characteristic on the basis of at least one type of measurement selected from the group consisting of the intensity, phase, and frequency of the despread electromagnetic field.

Description

[Technical Field]

[0001] The present invention relates to an apparatus for measuring characteristics of an object under test and a method for measuring characteristics of an object under test. [Background technology]

[0002] When measuring the electrical, magnetic, or other properties of an object, it is usually best to use electromagnetic waves, such as light or radio waves. However, measuring properties using light is difficult for objects that have difficulty transmitting light, such as the human body, metal, or concrete blocks. Therefore, a device and method for measuring the properties of an object using an acoustically induced electromagnetic field has been disclosed, which can measure any object while taking advantage of the characteristics of sound waves, such as high internal penetration for objects that have difficulty transmitting light, such as the human body, metal, or concrete blocks, and high spatial resolution in the depth direction and in the in-plane direction of the object compared to radio wave measurements of the same frequency.

[0003] Patent Document 1 discloses a technique for irradiating a measurement object with sound waves, measuring the electromagnetic waves generated from the measurement object, and measuring the electric, magnetic, or electromagnetic-mechanical characteristics of the measurement object from any one or a combination of the intensity, phase, and frequency characteristics of the electromagnetic waves. Patent Document 2 also discloses a technique for receiving an electromagnetic field generated by irradiating an amplitude-modulated sound wave onto the measurement object, and extracting at least one characteristic selected from the group consisting of the electric, magnetic, electromechanical, and magnetomechanical characteristics of the measurement object based on at least one measurement selected from the group consisting of the intensity, phase, and frequency of the electromagnetic field. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4919967 [Patent Document 2] Patent No. 5892623 [Non-patent literature]

[0005] [Non-Patent Document 1] E.Beaurepaire and 5 others, Appl.Phys.Lett., Vol.84, No.18, pp.3465-3467, 3. May 2004 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology disclosed in Patent Document 1 restricts the distance between the sound wave source and the object to be measured in order to avoid reverberation electromagnetic noise (hereinafter referred to as "reverberation electromagnetic field due to reverberation vibrations accompanying sound wave transmission" or simply "reverberation electromagnetic field." Note that "reverberation electromagnetic field" is also called "reverberation noise" or "vibrator noise.") from the sound wave source accompanying the transmission of sound waves, resulting in reduced measurement flexibility and signal sensitivity. The technology disclosed in Patent Document 2 solves the problem of the time required to measure the characteristics of the object to be measured in the technology disclosed in Patent Document 1 by irradiating the object with amplitude-modulated sound waves, thereby shortening the measurement time for the characteristics of the object to be measured. However, the technology disclosed in Patent Document 2 requires that the distance between the sound wave source and the object to be measured be known in advance in order to shorten the measurement time for the characteristics of the object to be measured, thereby reducing measurement flexibility. Furthermore, Patent Document 2 has lower spatial resolution in the depth direction than Patent Document 1, thereby losing the advantage of measuring characteristics using sound waves.

[0007] The present invention has been made in consideration of the above points, and aims to provide an apparatus and a method for measuring the characteristics of an object to be measured that can achieve at least one selected from the group consisting of (1) not impairing the degree of freedom in measuring characteristics using sound waves, in other words, relaxing the constraint on the distance between the source of the sound waves and the object to be measured, (2) receiving an electromagnetic field that becomes a target signal while avoiding reverberant electromagnetic fields, and (3) enabling a reduction in the measurement time for the characteristics of the object to be measured. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, one characteristic measuring device for a measured object of the present invention comprises an acoustic wave transmitting unit that transmits acoustic waves, a receiving unit that receives an electromagnetic field from the measured object generated when the acoustic waves are irradiated onto the measured object, an acoustic wave medium between the acoustic wave transmitting unit and the measured object for temporally separating the electromagnetic field from a reverberant electromagnetic field caused by reverberant vibration of the acoustic wave transmitting unit, a despreading unit that despreads the electromagnetic field received by the receiving unit using a reference signal associated with the acoustic waves, and a measuring unit that extracts at least one characteristic selected from the group consisting of electrical characteristics, magnetic characteristics, electromechanical characteristics, and magnetomechanical characteristics of the measured object based on at least one measurement selected from the group consisting of intensity, phase, and frequency of the despread electromagnetic field.

[0009] Another characteristic measuring device for a measured object of the present invention includes a reference signal generating unit that generates a reference signal based on predetermined information, a sound wave emitting unit that emits sound waves generated based on the reference signal, a receiving unit that receives an electromagnetic field generated when the sound waves are irradiated onto the measured object, a despreading unit that despreads the electromagnetic field received by the receiving unit using the reference signal, and a measuring unit that extracts at least one characteristic selected from the group consisting of electrical characteristics, magnetic characteristics, electromechanical characteristics, and magnetomechanical characteristics of the measured object based on at least one measurement selected from the group consisting of intensity, phase, and frequency of the despread electromagnetic field.

[0010] The above-mentioned characteristics measuring devices for an object under test can shorten the time required to measure the characteristics and improve the S / N ratio of the signal used to measure the characteristics. In addition, the characteristics measuring devices for an object under test can shorten the time required to measure the characteristics and eliminate the restriction on the distance between the source of the sound wave and the object under test by suppressing the reverberation electromagnetic field that accompanies the transmission of sound waves.

[0011] In one preferred embodiment, each of the despreading units correlates the electromagnetic field received by the receiving unit with the reference signal and outputs a pulse-compressed signal or a correlation signal. According to this embodiment of the device for measuring characteristics of a device under test, for example, by correlating with the reference signal, the device can be easily implemented using a digital circuit and / or software. Furthermore, outputting a pulse-compressed signal, in other words, the electromagnetic field despread in each of the despreading units is a pulse-compressed electromagnetic field, can improve the S / N ratio of the signal used to measure the characteristics and further enhance the effect of shortening the time required to measure the characteristics.

[0012] In another preferred embodiment, the reference signal generating unit generates the reference signal based on information having impulse autocorrelation characteristics as the predetermined information, or the sound wave emitting unit generates the sound wave based on information having impulse autocorrelation characteristics. This device for measuring characteristics of an object to be measured according to this preferred embodiment can further remove "noise" (for example, at least one type of noise selected from the group consisting of noise in the same frequency band as the oscillated sound wave, noise synchronized with the measuring unit (including a reverberation electromagnetic field accompanying the emission of the sound wave), noise due to external radio waves, noise caused by an amplifier or the like, and thermal noise) contained in the electromagnetic field received by the receiving unit, thereby improving the S / N ratio of the signal used to measure the characteristics. In another preferred embodiment, the information having impulse autocorrelation characteristics is an M sequence, or the information having impulse autocorrelation characteristics is an M sequence. This device for measuring characteristics of an object to be measured according to this preferred embodiment can further use an M sequence that can be generated by a shift register, making it easy to generate a reference signal. By increasing the number of shift registers, the reference signal can be lengthened without theoretical limitations, i.e., the S / N ratio can be increased.

[0013] In another preferred embodiment, the reference signal generator generates the reference signal based on information whose frequency changes continuously over time as the predetermined information, or the sound wave generator generates the sound wave based on information whose frequency changes continuously over time. According to this embodiment of the device for measuring characteristics of an object to be measured, the frequency bandwidth of the reference signal can be freely set, thereby shortening the reference signal and enabling high-speed measurement.

[0014] In another preferred embodiment, the device for measuring characteristics of an object to be measured further includes a synchronous addition unit that synchronously adds the despread electromagnetic field a predetermined number of times, and the measurement unit extracts the characteristics of the object to be measured based on the electromagnetic field synchronously added by the synchronous addition unit. According to this embodiment, the device for measuring characteristics of an object to be measured further includes a synchronous addition unit that synchronously adds the correlation signal to obtain a desired S / N ratio.

[0015] In another preferred embodiment, the device for measuring characteristics of an object to be measured further comprises a subtraction unit that subtracts a signal obtained by despreading the electromagnetic field received by the receiving unit in the absence of the object to be measured from the despread electromagnetic field. This device for measuring characteristics of an object to be measured in this embodiment can further eliminate the influence of time side lobes that may occur due to despreading.

[0016] In another preferred embodiment, the device for measuring characteristics of an object to be measured further includes a phase detection unit that detects the phase of the despread electromagnetic field at the frequency of the reference signal. According to this device for measuring characteristics of an object to be measured, the phase detection further obtains the phase delay between the incident ultrasonic wave and the electromagnetic signal induced by the ultrasonic wave, and the characteristics of the object to be measured can be extracted from the phase delay.

[0017] In another preferred embodiment, the reference signal generator generates the reference signal based on a complementary sequence as the predetermined information, or the information having the impulse autocorrelation characteristic is a complementary sequence. The device for measuring characteristics of a device under test according to this embodiment can further eliminate the influence of time side lobes that may occur due to despreading.

[0018] In addition, in order to achieve the above-mentioned object, one method for measuring the characteristics of an object to be measured of the present invention includes: an acoustic wave transmission step of transmitting acoustic waves from an acoustic wave source; a receiving step of receiving an electromagnetic field from the object to be measured, which is generated by irradiating the object with the acoustic waves from the acoustic wave source using an acoustic medium between the acoustic wave source and the object to be measured, with the electromagnetic field delayed; a despreading step of despreading the electromagnetic field received in the receiving step using a reference signal associated with the acoustic waves; and a measuring step of extracting at least one characteristic selected from the group consisting of electrical characteristics, magnetic characteristics, electromechanical characteristics, and magnetomechanical characteristics of the object to be measured based on at least one measurement selected from the group consisting of intensity, phase, and frequency of the despread electromagnetic field, and is a method for temporally separating the electromagnetic field from the reverberant electromagnetic field caused by reverberant vibration of the acoustic wave source.

[0019] Another method of measuring the characteristics of an object to be measured of the present invention generates a reference signal based on specified information, transmits sound waves generated based on the reference signal, receives an electromagnetic field generated when the sound waves are irradiated onto the object to be measured, de-spreads the received electromagnetic field using the reference signal, and extracts at least one characteristic selected from the group consisting of electrical characteristics, magnetic characteristics, electromechanical characteristics, and magnetomechanical characteristics of the object to be measured based on at least one measurement selected from the group consisting of intensity, phase, and frequency of the de-spread electromagnetic field.

[0020] The above-described method for measuring the characteristics of an object under test can shorten the time required to measure the characteristics and improve the S / N ratio of the signal used to measure the characteristics. In addition, the method for measuring the characteristics of an object under test can shorten the time required to measure the characteristics and eliminate the restriction on the distance between the source of the sound wave and the object under test by suppressing the reverberation electromagnetic field caused by the transmission of the sound wave.

[0021] In the present application, the reverberant electromagnetic field caused by the reverberant vibration of a source that generates sound waves is not limited to the reverberant electromagnetic field due to the fundamental frequency and harmonics of the source. For example, when an ultrasonic vibrator is used as the source, at least the following reverberant electromagnetic fields (a) to (c) at the source that are different from the fundamental frequency and n-th harmonic may also be included in the "reverberant electromagnetic field" in the present application. (a) Reverberation electromagnetic field due to frequencies generated by radial vibration modes (b) Reverberation electromagnetic field due to frequencies generated by thickness-shear vibration modes (c) Reverberant electromagnetic field due to frequency interference caused by multiple reflections within the probe

[0022] Therefore, it is worth noting that even if a reverberant electromagnetic field occurs due to frequencies generated by the various modes as described above, the reverberant electromagnetic field can be reduced with a high degree of certainty by using the characteristic measuring device for one object to be measured of the present invention, the characteristic measuring device for another object to be measured of the present invention, the characteristic measuring method for one object to be measured of the present invention, or the characteristic measuring method for another object to be measured. [Effects of the Invention]

[0023] According to a certain device for measuring characteristics of an object under test of the present invention and a certain method for measuring characteristics of an object under test of the present invention, it is possible to shorten the time required to measure the characteristics and improve the S / N ratio of the signal used to measure the characteristics. In addition, according to the device for measuring characteristics of an object under test and the method for measuring characteristics of an object under test, not only is the time required to measure the characteristics shortened, but the reverberation electromagnetic field of the sound wave source is suppressed, thereby eliminating the restriction on the distance between the sound wave source and the object under test. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram showing the state of an electromagnetic field induced by irradiating a part of an object to be measured with sound waves. FIG. [Figure 2] 1 is a diagram illustrating an example of the configuration of a characteristics measurement apparatus according to a first embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating an example of a signal generated by a waveform generator. [Figure 4] 10 is a graph showing an example of an electromagnetic field despread by a despreading unit. [Figure 5] This is a graph showing an example in which pulsed ultrasound is used instead of an M-sequence and integration is performed five times without despreading. [Figure 6] This is a graph showing an example in which pulsed ultrasound was used instead of an M-sequence and integration was performed 5000 times without despreading. [Figure 7] 10 is a flowchart showing the flow of a characteristic measurement process performed by the characteristic measurement device. [Figure 8] FIG. 10 is a diagram showing a case where the sound wave generator and the object to be measured are brought into close contact with each other. [Figure 9] FIG. 10 is a diagram showing a case where the sound wave generator and the object to be measured are spaced apart. [Figure 10] FIG. 1 is a diagram showing a characteristics measurement apparatus according to a first modified example of the first embodiment of the present invention. [Figure 11] FIG. 10 is a diagram showing a characteristic measurement apparatus according to a second modification of the first embodiment of the present invention. [Figure 12] FIG. 10 is a diagram showing a characteristics measurement apparatus according to a third modified example of the first embodiment of the present invention. [Figure 13] FIG. 10 is a diagram showing a characteristics measurement device according to a fourth modified example of the first embodiment. [Figure 14] 10 shows the measurement results of the device under test when using the characteristics measurement device according to the fourth modification of the first embodiment. [Figure 15] 10 shows the measurement results of the object to be measured when the comparative example was used. [Figure 16] This is a diagram for comparing the frequency spectra of the reverberation electromagnetic field corresponding to this modified example (solid line (thinner line)) and the comparative example (dotted line) in order to compare the strength of the reverberation electromagnetic field in the low frequency range. [Figure 17] FIG. 10 is a diagram showing a characteristic measurement apparatus according to another modified example of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] An example of an embodiment of the present invention will be described below with reference to the drawings. The same reference numerals are used throughout the drawings to designate identical or equivalent components and parts. The dimensional proportions of the drawings may be exaggerated for illustrative purposes and may differ from the actual proportions.

[0026] First, we will explain the electromagnetic field induced in the part of the object to be measured when sound waves are irradiated onto the object. Details of the electromagnetic field induced in the part of the object to be measured are disclosed in the above-mentioned Patent Document 1.

[0027] FIG. 1 illustrates the electromagnetic field induced by irradiating a portion of an object to be measured with sound waves. In FIG. 1, a focused sound beam 1 is shown focused on a portion 2 of the object to be measured (90), and the + and - symbols in circles represent positively charged particles 3 and negatively charged particles 4, respectively. Furthermore, in the sound-focused region 2 of the object to be measured, the balance between the concentrations of the positively charged particles 3 and the negatively charged particles 4 is disrupted, resulting in a charge distribution state in which the positively charged particles 3 outnumber the negatively charged particles 4. Additionally, arrow 5 indicates the direction of sound vibration of the focused sound beam 1, which corresponds to the direction of the electric field. Furthermore, arrow 6 indicates the magnetic field generated in a plane perpendicular to arrow 5.

[0028] As shown in FIG. 1, irradiation of the focused acoustic beam 1 causes positively charged particles 3 and negatively charged particles 4 to vibrate in the direction of the acoustic wave vibration (the direction of the arrow indicated by the symbol 5) at the frequency of the acoustic wave. The vibrations of the positively charged particles 3 and negatively charged particles 4 then result in the vibration of electric charges, which induces a magnetic field (the direction of the arrow indicated by the symbol 6) in a plane perpendicular to the vibration direction 5. The generated electromagnetic fields are out of phase with each other by π, so they cancel each other out and no electromagnetic field is induced. However, in the focused acoustic beam region 2 of the object to be measured, the positively charged particles 3 are more numerous than the negatively charged particles 4, so they cannot completely cancel each other out, and a net electromagnetic field (arrow 6) is induced. Therefore, by observing the electromagnetic field induced by the sound waves and observing a change in the intensity of the electromagnetic field, it is possible to determine that a change has occurred in the charge distribution, i.e., a change has occurred in the concentration of either the positively charged particles 3 or the negatively charged particles 4, or a change in the concentration of both. As a result, by measuring the electromagnetic field induced by the sound waves, it is possible to measure the characteristic value of the charged particles in the object being measured, in this case, the change in their concentration.

[0029] While Figure 1 illustrates an example of measuring changes in the concentration of charged particles through measurements of the electromagnetic field induced by sound waves, measurable changes in the characteristics of charged particles can include not only concentration but also changes in mass, size, shape, charge number, or the interaction force between the charged particles and the medium surrounding them. For example, if other knowledge about the state of the object being measured or knowledge obtained by some other means indicates that changes in concentration, mass, size, shape, and charge number are not possible, changes in the intensity of the measured electromagnetic field can be linked to changes in the interaction force between the charged particles and the medium surrounding them. Therefore, for example, changes in the intensity of the measured electromagnetic field can be linked to changes in the electronic polarizability or cation polarizability.

[0030] In the embodiments and modifications of the present invention described below, the electric field, dielectric constant, and spatial gradient of the electric field or dielectric constant can be measured as the electrical properties of the object under test. Furthermore, in the embodiments and modifications of the present invention described below, the magnetization caused by electron spin or nuclear spin can also be measured as the magnetic properties of the object under test. Specifically, as in the case of electric polarization, an electromagnetic field is generated even when the magnetization changes over time. According to Maxwell's equations, the radiated electric field is proportional to the second derivative of the magnetization with respect to time (see Non-Patent Document 1). Therefore, it is possible to measure the magnitude and direction of the magnetization from the electromagnetic field strength and phase.

[0031] Furthermore, in each embodiment and each modified example of the present invention described below, acoustic magnetic resonance due to electron spin or nuclear spin can be measured as a magnetic property of the object to be measured. Specifically, at a certain resonance frequency, sound waves are efficiently absorbed and the direction of electron spin or nuclear spin changes, and therefore, it is expected that the electromagnetic field intensity and phase will change significantly at that frequency. As information, the resonance frequency can be determined. In addition, as with conventional ESR (electron spin resonance) and NMR (nuclear magnetic resonance), by scanning the frequency of the sound waves, a spectrum can be obtained and information on electron spin or nuclear spin can be obtained. Furthermore, the relaxation time of electron spin or nuclear spin can be measured.

[0032] Furthermore, in each embodiment and each modified example of the present invention described below, the piezoelectric property or magnetostrictive property can be measured as the electromechanical property or magnetomechanical property of the object to be measured as follows. In principle, electric polarization occurs due to distortion in ionic crystals without inversion symmetry. Therefore, the magnitude of polarization can be obtained from the intensity of the electromagnetic field of the object to be measured, which can be called the acoustically induced electromagnetic field. By scanning the acoustic wave, the piezoelectric property of the object to be measured can be imaged. Furthermore, the piezoelectric tensor can be measured non-contact, without providing electrodes on the object to be measured, from the acoustic wave propagation direction and the angular distribution of the generated electromagnetic field.

[0033] In addition, in each embodiment and each modified example of the present invention described below, magnetostriction can be measured as an electromechanical or magnetomechanical property of an object to be measured as follows. Magnetostriction refers to the phenomenon in which crystal distortion changes electron orbitals, resulting in a change in electron spin magnetization through orbit-spin interaction. Alternatively, external distortion can change the magnetic domain structure, resulting in a change in effective magnetization in a macroscopic region (approximately the size of the acoustic beam spot). Crystal distortion can also cause changes in the crystal field splitting, which in turn changes the electronic state and the magnitude of electron spin magnetization. These temporal changes are thought to generate an electromagnetic field. Therefore, the strength of the acoustically induced electromagnetic field can determine the magnitude of magnetization, orbit-spin interaction, the sensitivity of crystal distortion to electron orbital changes, the sensitivity of crystal field splitting to distortion, the relationship between crystal field splitting and electron spin state, or the relationship between magnetic domain structure and distortion. The magnetostriction tensor can be measured non-contact from the acoustic wave propagation direction and radiation intensity without providing electrodes on the object to be measured. Magnetostriction can also be visualized, similar to piezoelectric properties.

[0034] In each embodiment and each modification of the present invention described below, a sound wave is irradiated onto an object to be measured, and an electromagnetic field generated from the object to be measured is measured. In each embodiment and each modification of the present invention, the electromagnetic field is separated in time from a reverberant electromagnetic field caused by reverberant vibration of a sound wave source by a method for measuring characteristics of the object to be measured, which includes the following steps (i) to (iv). (i) a sound wave transmission step of transmitting sound waves from a sound wave transmission source; (ii) a receiving step of receiving an electromagnetic field from the object to be measured, which is generated by irradiating the object with sound waves from the sound wave source, with a delay due to an acoustic medium between the sound wave source and the object to be measured; (iii) a despreading step of despreading the electromagnetic field received in the receiving step using a reference signal associated with the acoustic wave; (iv) a measuring step of extracting at least one characteristic selected from the group consisting of an electric characteristic, a magnetic characteristic, an electromechanical characteristic, and a magnetomechanical characteristic of the object to be measured based on at least one measurement selected from the group consisting of the intensity, phase, and frequency of the despread electromagnetic field.

[0035] From another perspective, in each embodiment and each modified example of the present invention, a measurement object is irradiated with sound waves generated based on a reference signal generated based on predetermined information, an electromagnetic field generated by the irradiation of the measurement object is received, and the received electromagnetic field is despread using the reference signal. More specifically, a correlation signal is generated by correlating the received electromagnetic field with the reference signal. At least one characteristic selected from the group consisting of an electric characteristic, a magnetic characteristic, an electromechanical characteristic, and a magnetomechanical characteristic of the measurement object can be extracted based on at least one measurement selected from the group consisting of the intensity, phase, and frequency of the correlation signal. The electric characteristic of the measurement object is a change in at least one characteristic value selected from the group consisting of an electric field, a dielectric constant, a spatial gradient of the electric field or dielectric constant, a concentration of charged particles in the measurement object, a mass, a size, a shape, a charge number, and an interaction between the charged particles and a medium surrounding the charged particles. The magnetic characteristic of the measurement object is magnetization due to electron spin or nuclear spin of the measurement object, or acoustic magnetic resonance due to electron spin or nuclear spin of the measurement object. The electromechanical and magnetomechanical characteristics of the object to be measured are the piezoelectric or magnetostrictive characteristics of the object to be measured.

[0036] First Embodiment FIG. 2 is a diagram illustrating an example of the configuration of a characteristic measurement device 100 according to this embodiment. Note that in FIG. 2(a), the source and path of the "reference signal" are simplified for clarity. However, as will be described later, the reference signal is used not only as a signal that forms the basis of the waveform generated by the waveform generator 120 but also as a signal used in the despreading unit 160 to despread the electromagnetic field. Therefore, FIG. 2(b) is shown as a more detailed diagram. The same applies to FIGS. 10, 11, 12, and 13. As shown in FIG. 2, the characteristic measurement device 100 according to this embodiment includes a reference signal generating unit 110, a waveform generator 120, a sound wave generator 130, a receiving unit 140, an amplifier / filter unit 150, a despreading unit 160, and a measuring unit 170. The characteristic measurement device 100 shown in FIG. 2 is a device that measures the characteristics of a device under test 200. In this embodiment, a ferrite magnet, an example of a ferromagnetic material, is used as the device under test 200.

[0037] Reference signal generation unit 110 generates a reference signal that serves as the basis for the waveform generated by waveform generator 120. The reference signal generated by reference signal generation unit 110 is not only the signal that serves as the basis for the waveform generated by waveform generator 120, but also a signal that is used for despreading the electromagnetic field in despreading unit 160, which will be described later. Despreading unit 160 despreads the electromagnetic field using the reference signal, thereby enabling pulse compression of the electromagnetic field.

[0038] In this embodiment, the reference signal generating unit 110 generates a reference signal based on information having an impulse autocorrelation characteristic or a sharp autocorrelation characteristic, specifically an M sequence, as the information on which the reference signal is based. An impulse is a pulse with an infinitesimal temporal width and an infinitely large height. In this embodiment, the reference signal generating unit 110 may also generate a reference signal based on information whose frequency changes continuously over time as the information on which the reference signal is based. Such a reference signal is a chirp signal whose frequency changes continuously over time. In addition, the reference signal generating unit 110 may also generate a reference signal based on a complementary sequence as the information on which the reference signal is based.

[0039] Since M sequences can be generated using shift registers, when M sequences are used as the information on which the reference signal is based, it is easy to generate the reference signal, and by increasing the number of shift registers, the reference signal can be made longer without any theoretical limit. Lengthening the reference signal leads to an increase in the S / N ratio of the electromagnetic field.

[0040] Furthermore, when a chirp signal is used as the information on which the reference signal is based, the frequency bandwidth of the reference signal can be freely set, allowing for faster measurement compared to when an M-sequence is used. The S / N ratio of pulse compression is proportional to the product of the signal length and frequency bandwidth of the reference signal. When an M-sequence is used, the bandwidth of the reference signal is an integer multiple of the center frequency. Therefore, increasing the S / N ratio of the electromagnetic field requires making the signal longer. On the other hand, when a chirp signal is used as the information on which the reference signal is based, the bandwidth of the reference signal can be wider, i.e., the reference signal can be shorter, compared to when an M-sequence is used, allowing for faster measurement of the characteristics of device under test 200.

[0041] Furthermore, the reference signal generating unit 110 may generate the reference signal based on Golay codes, Barker codes, or the like as information on which the reference signal is based.

[0042] Here, the reason for generating a reference signal will be explained. The most important thing to note about the characteristics measurement device 100 shown in FIG. 2 is to avoid oscillator noise (synonymous with reverberant electromagnetic fields in this embodiment) from the sound wave generator 130 that generates ultrasonic waves. This oscillator noise is in the same frequency band as the target signal, so it cannot be avoided even with narrowband detection. The oscillator noise is expected to be much stronger than the signal received by the receiving unit 140. For example, if the sound wave generator 130 and the object under test 200 are placed in close contact as shown in FIG. 8(a), the target signal will be buried in the oscillator noise as shown in FIG. 8(b), and the target signal will not be obtained.

[0043] Furthermore, by separating the sound wave generator 130 and the object under test 200 as shown in FIG. 9(a) and utilizing the time it takes for the sound waves to travel from the sound wave generator 130 to the object under test 200, it is possible to temporally separate the transducer noise from the target signal received by the receiver 140 from the object under test 200, as shown in FIG. 9(b). For example, the speed of sound in water is 1500 m (meters) / s (seconds), resulting in a delay of 40 μs (microseconds) for a sound wave to propagate 60 mm (millimeters). On the other hand, the propagation time of electromagnetic waves is negligibly short compared to the propagation time of sound waves. Therefore, by providing an acoustic medium between the sound wave generator 130 and the object under test 200 and using a pulse method using ultrasonic excitation pulses that are sufficiently shorter than the sound wave propagation time, it is possible to temporally separate the ultrasonic transducer noise from the target signal from the object under test 200, as shown in FIG. 9(b).

[0044] However, in pulse methods, the effective integration time is generally extremely short compared to the measurement time. For example, the time width of the signal generated by the object under test 200 receiving the sound waves is 10 μs or less, while the repetition time of the ultrasonic pulse is typically 0.1 s (100 Hz). Therefore, the effective signal integration time is only 0.01% of the measurement time. In other words, the S / N (signal / noise) ratio obtained by integrating for 1 second is small, and in many cases a clear signal cannot be obtained unless measurement is performed for a long time. This is a major obstacle to practical use.

[0045] Therefore, the characteristic measuring device 100 according to this embodiment generates sound waves from the sound wave generator 130 based on a reference signal, receives the electromagnetic field generated by the device under test 200 with the receiving unit 140, and despreads the received electromagnetic field using the reference signal that is the basis of the sound waves. By despreading the electromagnetic field received by the receiving unit 140 using the reference signal that is the basis of the sound waves, the characteristic measuring device 100 according to this embodiment can independently compress the transducer noise and the target signal from the device under test 200 that is received by the receiving unit 140, and obtain the target signal from the device under test 200.

[0046] The waveform generator 120 generates a waveform based on the reference signal generated by the reference signal generating unit 110. In the following description, the waveform generator 120 generates a waveform based on the reference signal generated based on an M sequence. M(12,11,9,5,3,1) is used as the M sequence. The waveform generator 120 generates a signal by modulating the M sequence M(12,11,9,5,3,1) with a 0.5 MHz square wave.

[0047] The sound wave generator 130 generates sound waves based on the signal generated by the waveform generator 120. The sound wave generator 130 is an example of a sound wave transmission unit of the present invention. For example, an ultrasonic transducer that vibrates based on the signal generated by the waveform generator 120 is used as the sound wave generator 130. The sound wave generator 130 may also be an array-type probe used in an ultrasonic diagnostic device or the like. FIG. 3 is a diagram showing an example of a signal generated by the waveform generator 120. The modulation frequency is the resonant frequency f0 of the sound wave generator 130, and the spatial resolution in the propagation direction of the ultrasonic waves and the ultrasonic beam spot size are determined by this resonant frequency. The code sequence used has impulse autocorrelation characteristics, in other words, a code sequence with a sufficiently sharp autocorrelation function. An example of such a code sequence is an M sequence belonging to the PN code. In this embodiment, sound waves are generated based on a signal obtained by modulating a 0.5 MHz (megahertz) square wave with M (12, 11, 9, 5, 3, 1) of the M sequence, and the sound wave generation time for one measurement is 9.190 ms (milliseconds).

[0048] In one example of this embodiment, the sound wave generator 130, which serves as a sound wave transmitter or sound wave source, emits sound waves toward the object under test 200 (sound wave emission process). The object under test 200 is placed at the bottom of a tank 300. The sound wave generator 130 is placed in water 310 (corresponding to a sound wave medium) filled in the tank 300 so that the distance between the sound wave generator 130 and the object under test 200 is 130 mm. The tank 300 is also surrounded by an electromagnetic shield 400 that blocks external electromagnetic fields so that the electromagnetic field generated by the object under test 200 can be accurately detected.

[0049] The receiving unit 140 detects (also referred to as "receiving") an electromagnetic field generated (radiated) from the object under test 200 (receiving step). The receiving unit 140 may be any device capable of detecting an electromagnetic field. For example, various antennas such as a loop antenna, an electrostatic coupling antenna, an array antenna, a sensor that detects electric charges, an electric field, a magnetic field, or an array sensor may be used as the receiving unit 140. Here, in the receiving step of this embodiment, water 310 serving as an acoustic wave medium is provided between the sound wave generator 130 and the object under test 200. This delays the time it takes for the sound waves emitted from the sound wave generator 130 to reach the object under test 200, and the electromagnetic field from the object under test 200 generated by the sound waves is received with a delay.

[0050] The amplifier / filter unit 150 amplifies and filters the electromagnetic field detected by the receiver unit 140. In this embodiment, the amplifier / filter unit 150 amplifies the electromagnetic field detected by the receiver unit 140 by a predetermined amount and passes it through a band-pass filter to remove bands other than a predetermined frequency band. The predetermined frequency band is, for example, 9.9 MHz to 10.1 MHz.

[0051] The despreading unit 160 despreads the electromagnetic field amplified and filtered by the amplifier / filter unit 150 using the reference signal generated by the reference signal generating unit 110, more specifically, the reference signal associated with the sound wave (despreading step). Note that the reference signal associated with the sound wave also means a reference signal for diffusing the sound wave or a voltage signal for exciting the diffused sound wave.

[0052] Specifically, the despreading unit 160 outputs a correlation signal obtained by correlating the electromagnetic field detected (received) by the receiving unit 140 and amplified and filtered by the amplifier / filter unit 150 with the reference signal generated by the reference signal generating unit 110, or a pulse-compressed signal obtained by correlating with the reference signal. The despreading unit 160 despreads the electromagnetic field containing the target signal using a reference signal associated with sound waves, thereby pulse-compressing the electromagnetic field or performing pulse compression processing. By pulse-compressing the electromagnetic field (i.e., the despreading unit 160 outputs the correlation signal or the pulse-compressed signal), the electromagnetic field generated by the object under test 200 can be separated from the oscillator noise generated by the sound wave generator 130 in the measurement process described below, making it possible to clearly identify the electromagnetic field generated by the object under test 200. In other words, it is possible to shorten the duration of the reverberation electromagnetic field caused by the reverberation vibration of the sound wave generator 130, and then temporally separate the electromagnetic field that serves as the target signal (the electromagnetic field from the object under test 200) from the reverberation electromagnetic field. As a result, the characteristic measuring device 100 and the characteristic measuring method of this embodiment can significantly reduce the influence of the reverberation electromagnetic field of the sound wave generator 130, improve the resolution of the electromagnetic field from the object under test 200 that serves as the target signal, and achieve a significant reduction in measurement time (in other words, faster measurement) compared to conventional techniques.

[0053] FIG. 4 is a graph showing an example of an electromagnetic field despread by the despreading unit 160. The measurement time is 10 ms, which is close to the generation time of the sound wave. In the graph of FIG. 4, the waveform generated from 0 μs is based on oscillator noise generated by the sound wave generator 130, while the waveform generated from approximately 6.5 μs is based on the electromagnetic field generated by the device under test 200 and despread by the despreading unit 160. In this way, by despreading the electromagnetic field in the despreading unit 160, the characteristic measuring device 100 according to this embodiment can clearly confirm the electromagnetic field generated by the device under test 200.

[0054] As a comparative example, an example is shown in which pulsed ultrasonic waves are used instead of M-sequences and the electromagnetic field is integrated without despreading. FIG. 5 is a graph showing an example of an electromagnetic field integrated five times using pulsed ultrasonic waves instead of M-sequences. Assuming that the measurement time per measurement is 2 [ms], the entire measurement took 10 [ms]. As shown in the graph in FIG. 5, after five integrations, the electromagnetic field is buried in the transducer noise and is impossible to observe. Therefore, the characteristic measuring device 100 according to this embodiment despreads the electromagnetic field in the despreading unit 160, thereby significantly improving the S / N ratio even with the same measurement time compared to when pulsed ultrasonic waves are used to integrate the electromagnetic field without despreading it.

[0055] As another comparative example, an example is shown in which pulsed ultrasound is used instead of an M-sequence, and the electromagnetic field is integrated a sufficient number of times without being despread. Fig. 6 is a graph showing an example in which pulsed ultrasound is used instead of an M-sequence, and integration is performed 5,000 times. If the measurement time per measurement is 2 ms, it takes 10 seconds to obtain the graph shown in Fig. 6. Therefore, by despreading the electromagnetic field in the despreading section 160, the characteristic measuring apparatus 100 according to this embodiment can significantly reduce the measurement time compared to when the electromagnetic field is integrated without being despread.

[0056] In a measurement example using the characteristic measuring device 100 according to this embodiment and employing a ferrite magnet as the object under test 200, it was confirmed that sufficient resolution was achieved even in a short time that was approximately 1 / 1000th of that required when the electromagnetic field was not de-diffused by the de-diffusion unit 160. In this example, the inventors believe that the 0.5 MHz vibrator employed as the sound wave generator 130 may have significantly exhibited the reverberation electromagnetic field due to the already-mentioned "radial vibration mode," "thickness shear vibration mode," or "interference due to multiple reflections within the probe," or a combination thereof, and therefore this resulted in a clearer improvement in resolution.

[0057] The measuring unit 170 extracts characteristics of the device under test 200 based on the electromagnetic field despread by the despreading unit 160 (measurement step). Specifically, the measuring unit 170 extracts at least one characteristic selected from the group consisting of an electric characteristic, a magnetic characteristic, an electromechanical characteristic, and a magnetomechanical characteristic of the device under test 200 based on at least one measurement selected from the group consisting of the intensity, phase, and frequency of the electromagnetic field despread by the despreading unit 160.

[0058] Specifically, as described above, the measuring unit 170 can shorten the duration of the reverberation electromagnetic field caused by the reverberation vibration of the sound wave transmitter 130, and then measure the electric field, permittivity, or spatial gradient of the electric field or permittivity as the electrical properties of the object under test 200 in a significantly shorter time than conventional techniques, while temporally separating the electromagnetic field serving as the target signal from the reverberation electromagnetic field. Furthermore, the measuring unit 170 can measure acoustic magnetic resonance caused by electron spin or nuclear spin as the magnetic properties of the object under test 200. Furthermore, the measuring unit 170 can measure the piezoelectric property or magnetostrictive property as the electromechanical property or magneto-mechanical property of the magnetic properties of the object under test 200. Furthermore, the measuring unit 170 can measure the magnetostrictive property as the electromechanical property or magneto-mechanical property of the object under test 200.

[0059] Next, a description will be given of the operation of the characteristics measurement apparatus 100. Fig. 7 is a flowchart showing the flow of the characteristics measurement process performed by the characteristics measurement apparatus 100. The characteristics measurement process performed by the characteristics measurement apparatus 100 is performed by a central processing unit (CPU) of a computer connected to the characteristics measurement apparatus 100 reading out a computer program, expanding the program into random access memory (RAM), and executing the program to control each section of the characteristics measurement apparatus 100.

[0060] In step S101, characteristic measurement apparatus 100 first generates a predetermined reference signal in reference signal generator 110. In this embodiment, characteristic measurement apparatus 100 generates the reference signal based on information having impulse autocorrelation characteristics, specifically, an M sequence, as described above. Also in this embodiment, characteristic measurement apparatus 100 generates the reference signal based on information whose frequency changes continuously over time. Such a reference signal is a chirp signal whose frequency changes continuously over time.

[0061] After generating a reference signal in step S101, characteristic measurement device 100 then generates a waveform based on the reference signal in step S102, and causes sound wave generator 130 to generate a sound wave based on the generated waveform.

[0062] In step S102, sound waves are generated from the sound wave generator 130, and then in step S103, the characteristic measuring device 100 receives the electromagnetic field emitted by the object under test 200 by receiving the sound waves generated by the sound wave generator 130 with the receiving unit 140.

[0063] In step S103, the electromagnetic field is received by the receiver 140. Then, in step S104, the characteristic measurement device 100 amplifies and filters the electromagnetic field received by the receiver 140 in the amplifier / filter unit 150. Specifically, the characteristic measurement device 100 amplifies the electromagnetic field received by the receiver 140 by a predetermined amount and passes it through a bandpass filter to remove bands other than a predetermined frequency band. The predetermined frequency band is, for example, 9.9 MHz to 10.1 MHz.

[0064] After amplifying and filtering the electromagnetic field in step S104, characteristic measurement apparatus 100 then despreads the filtered electromagnetic field using a reference signal in despreading unit 160 in step S105. For example, despreading unit 160 calculates the correlation between the filtered electromagnetic field and the reference signal and outputs a correlation signal.

[0065] After the electromagnetic field is despread in step S105, characteristic measuring apparatus 100 then causes measuring unit 170 to extract characteristics of device under test 200 based on the measurement of the despread electromagnetic field in step S106. Specifically, measuring unit 170 extracts at least one characteristic selected from the group consisting of electric characteristics, magnetic characteristics, electromechanical characteristics, and magnetomechanical characteristics of device under test 200 based on at least one measurement selected from the group consisting of the intensity, phase, and frequency of the despread electromagnetic field.

[0066] 7, characteristic measuring device 100 according to this embodiment can separate the electromagnetic field generated by device under test 200 from the oscillator noise generated by sound wave generator 130, making it possible to clearly identify the electromagnetic field generated by device under test 200. Furthermore, characteristic measuring device 100 according to this embodiment can perform the series of processes shown in FIG. 7 to despread the electromagnetic field in despreading section 160, thereby significantly shortening the measurement time compared to integrating the electromagnetic field without despreading it.

[0067] In the above embodiment, the characteristics of device under test 200 are extracted by measuring the electromagnetic field despread by despreading section 160 with measuring section 170, but the present invention is not limited to the above example.

[0068] <Modification 1 of the First Embodiment> Fig. 10 is a diagram showing a modified example of the characteristic measurement apparatus 100 according to the embodiment of the present invention described above. The characteristic measurement apparatus 100 shown in Fig. 10 has the same configuration as that shown in Fig. 2, except for the addition of a synchronous addition section 165 that synchronously adds the electromagnetic fields despread by the despreading section 160 a predetermined number of times.

[0069] In a measurement method in which the magnitude of the electromagnetic field generated by device under test 200 is assumed to be small, as in this modification, the S / N ratio may be limited by implementation limitations on the reference signal length, reference signal bandwidth, and reception bandwidth that determine the S / N ratio. Even in such a case, by synchronously adding the electromagnetic field despread by despreading section 160 a predetermined number of times, it is possible to speed up measurement while satisfying the S / N ratio required for measurement.

[0070] When the electromagnetic field is despread using a reference signal as in this modification, side lobes are generated in the despread signal. These are called time side lobes and are expected to affect discrimination of the electromagnetic field generated by device under test 200.

[0071] <Modification 2 of the First Embodiment> 11 is a diagram showing a modified example of the characteristic measurement apparatus 100 according to the embodiment of the present invention. The characteristic measurement apparatus 100 shown in FIG. 11 has the same configuration as that shown in FIG. 2 except that a subtraction unit 166 is added, which receives a signal obtained by despreading an electromagnetic field received by the receiving unit 140 in the absence of the device under test 200, and subtracts the signal from the electromagnetic field despread by the despreading unit 160, in the presence of the device under test 200. The signal can be stored, for example, in the memory of a computer connected to the characteristic measurement apparatus 100. By using the subtraction unit 166 to subtract the signal from the electromagnetic field despread by the despreading unit 160, it is possible to reduce time side lobes.

[0072] In a measurement method in which the magnitude of the electromagnetic field generated by device under test 200 is expected to be small, as in this modification, subtraction section 166 removes the time side lobes of oscillator noise that are always present, thereby improving the degree of discrimination of the electromagnetic field generated by device under test 200. Note that even when reference signal generation section 110 generates a reference signal based on a complementary sequence, characteristic measurement apparatus 100 can eliminate the influence of time side lobes that may occur due to despreading by using the reference signal.

[0073] <Modification 3 of the First Embodiment> Fig. 12 is a diagram showing a modified example of characteristic measurement apparatus 100 according to the embodiment of the present invention described above. Characteristic measurement apparatus 100 shown in Fig. 12 has the same configuration as that shown in Fig. 2, except for the addition of phase detection section 167, which performs phase detection at the frequency of a reference signal for the electromagnetic field despread by despreading section 160.

[0074] The voltage of the electromagnetic field despread by the despreading unit 160 is proportional to the piezoelectric coefficient or piezomagnetic coefficient. The measurement method used in this modification acquires the piezoelectric coefficient for dielectric materials and the piezomagnetic coefficient for magnetic materials. The characteristic measuring device 100 can acquire both the real and imaginary parts of the generalized complex piezoelectric coefficient or complex piezomagnetic coefficient by performing phase detection using the phase detector 167. The real part is the normal piezoelectric coefficient or piezomagnetic coefficient synchronized with the excitation sound wave, and the imaginary part characterizes the energy loss of the piezoelectric and piezomagnetic phenomena in the frequency band of the excitation sound wave. Therefore, by performing phase detection using the phase detector 167, the characteristic measuring device 100 can evaluate factors related to energy loss in the electrical, magnetic, electromechanical, and magnetomechanical characteristics of the device under test 200 from the imaginary part. Furthermore, by performing phase detection using the phase detector 167, the characteristic measuring device 100 can further improve the S / N ratio compared to when phase detection is not performed.

[0075] <Fourth Modification of the First Embodiment> Fig. 13 is a diagram showing a characteristic measurement apparatus 100a according to this modification. The characteristic measurement apparatus 100a shown in Fig. 13 has the same configuration as that shown in Fig. 2, except that the coil-type antenna is replaced with a metal plate (a copper plate in this modification) that serves as an electrostatic coupling antenna. Therefore, as shown in Fig. 13, the characteristic measurement apparatus 100a according to this modification includes a reference signal generation section 110, a waveform generator 120, a sound wave generator 130, a receiving section 240, an amplifier / filter section 150, a despreading section 160, and a measurement section 170. Note that a holder for holding the device under test 200 is not shown in Fig. 13.

[0076] In this modification, the Achilles tendon of a bovine, which is an example of a dielectric, is used as the object under test 200. Therefore, in this modification, the receiving unit 240 measures the characteristics of the object under test 200 by detecting (receiving) an electromagnetic field (particularly, an electric field) generated by sound waves irradiated from the sound wave generator 130. In this modification, synchronous addition processing of the electromagnetic field subjected to pulse compression processing, which is one of despreading, is performed 12 times (specifically, 5 ms x 12 times), and the measurement time was 60 ms.

[0077] Fig. 14 shows the measurement results of the device under test 200 when using the characteristics measurement apparatus 100a according to this modification. Fig. 15 shows the measurement results of the device under test 200 when using a comparative example. The comparative example shown in Fig. 15 was performed under the same measurement conditions as this modification, except that the electromagnetic field serving as the target signal was not despread, synchronous addition processing was performed 5,000 times, and the measurement time was 50 seconds (s). In each diagram, the vertical axis represents the electromagnetic field signal strength (nV), and the horizontal axis represents time (μs).

[0078] As shown in Fig. 14, in this modified example, the electromagnetic field signal from the object under test 200 is clearly displayed to the extent that it can be sufficiently distinguished from the reverberant electromagnetic field described above. It can also be seen that the electromagnetic field signal from the object under test 200 shown in Fig. 14 is separated in time from the reverberant electromagnetic field, and that the reverberant electromagnetic field associated with the transmission of sound waves is suppressed. Therefore, it can be seen that the results shown in Fig. 14 are superior to the detection accuracy of the electromagnetic field signal from the object under test 200 shown in Fig. 15. Furthermore, it is noteworthy from the perspective of realizing faster measurement times that the measurement time (60 ms) in this modified example was approximately 1 / 830 of the measurement time (50 s) in the comparative example.

[0079] 16 is a diagram for comparing the frequency spectra of the reverberation electromagnetic field from 0 to 17 μs corresponding to this modified example (solid line (thinner line)) and the comparative example (dotted line) in order to compare the strength of the reverberation electromagnetic field in the low-frequency region. As shown in FIG. 16, it was confirmed that the reverberation electromagnetic field of this modified example (solid line) in the low-frequency components different from the frequency (1 MHz) of the sound wave generator 130 is significantly reduced compared to the corresponding reverberation electromagnetic field of the comparative example (dotted line).

[0080] 16, by employing the characteristic measurement device 100a and characteristic measurement method of this modified example, it is possible to significantly reduce the frequency spectrum of the reverberation electromagnetic field from the sound wave generator 130 compared to the prior art. As a result, it is possible to shorten the duration of the reverberation electromagnetic field caused by the reverberation vibration of the sound wave generator 130, and to temporally separate the electromagnetic field that serves as the target signal (the electromagnetic field from the object under test 200) from the reverberation electromagnetic field.

[0081] In this modified example, as in the case where the characteristic measuring device 100 is adopted, the influence of the reverberant electromagnetic field of the sound wave transmitter 130 is significantly reduced, the resolution of the electromagnetic field from the measured object 200, which is the target signal, is improved, and a significant reduction in measurement time can be achieved compared to conventional technology.

[0082] In this modified example, from the viewpoints of temporally separating the electromagnetic field signal from the reverberant electromagnetic field, suppressing the reverberant electromagnetic field caused by the transmission of sound waves, and improving the S / N ratio, it can be said that synchronously adding the despread electromagnetic field is more accurate than using an electromagnetic field with a long spread signal length, and that it is easier to achieve at least one of the following (A) to (D). (A) Temporally separating the electromagnetic field signal that is the target signal from the object under test 200 from the reverberant electromagnetic field. (B) Suppressing the reverberation electromagnetic field that accompanies the transmission of waves. (C) Improving the S / N ratio (D) Drastically shortening the measurement time

[0083] <Other embodiments> Incidentally, in each of the above-described embodiments or modifications, a reference signal generating section 110 is provided, but each of the above-described embodiments or modifications does not necessarily require the reference signal generating section 110. For example, Fig. 17 is a diagram showing a characteristics measurement apparatus 100b according to another modification of an embodiment of the present invention.

[0084] 17, one aspect that can be adopted is that the reference signal is directly transmitted from the waveform generator 120. In other words, the waveform generator 120 can also serve as the reference signal generating unit 110 in the first embodiment. Specifically, a reference signal generated in advance by the waveform generator 120 is transmitted to the despreading unit 160 via a cable C2. As a result, the reference signal is used as a signal to be used for despreading the electromagnetic field in the despreading unit 160, as in the above-described embodiment or each modification example.

[0085] In this modified example, as in the case of using the characteristic measuring device 100 of the first embodiment, it is possible to shorten the duration of the reverberation electromagnetic field caused by the reverberation vibration of the sound wave generator 130, and then temporally separate the electromagnetic field that serves as the target signal (the electromagnetic field from the object under test 200) from the reverberation electromagnetic field. As a result, the characteristic measuring device 100 and characteristic measuring method of this embodiment can significantly reduce the influence of the reverberation electromagnetic field of the sound wave generator 130, improve the resolution of the electromagnetic field from the object under test 200 that serves as the target signal, and achieve a significant reduction in measurement time compared to conventional techniques.

[0086] In the above-described embodiments and modifications, water is used as the acoustic wave medium, but the acoustic wave medium is not limited to water. For example, liquids other than water (e.g., various aqueous solutions, alcohol, liquid oil), gases including air, resins, or metals may also be used as acoustic wave media for adjusting the sound velocity, as long as the effects of the above-described embodiments or modifications are not substantially lost.

[0087] Furthermore, the device and method for measuring characteristics of an object under test according to each of the above-described embodiments and modifications can nondestructively measure at least one characteristic selected from the group consisting of electrical characteristics, magnetic characteristics, electromechanical characteristics, and magnetomechanical characteristics of the object under test. Therefore, the device and method can be used in various property measurement techniques, including measurement techniques in the biotechnology field, for objects, structures, or functional devices containing any of colloidal solutions, liquid crystals, solid electrolytes, ionic crystals, semiconductors, dielectrics, metals, magnetic materials, and magnetic fluids, or composite materials thereof.

[0088] Although the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the technical scope of the present invention is not limited to the above-described embodiments or modifications. For example, even if an electromagnetic shield is not provided, at least some of the effects of the above-described embodiments and modifications can be achieved. It is clear that a person skilled in the art of the present invention can conceive of various modifications or alterations within the scope of the technical idea described in the claims, and it is understood that these modifications or alterations also fall within the technical scope of the present invention.

[0089] In the above-described embodiments and modifications, the characteristic measurement process executed by the CPU after reading software (programs) can also be executed by various processors other than the CPU. Examples of such processors include programmable logic devices (PLDs) whose circuit configuration can be changed after fabrication, such as field-programmable gate arrays (FPGAs), and dedicated electrical circuits, such as application-specific integrated circuits (ASICs), which are processors with circuit configurations specifically designed to execute specific processes. The characteristic measurement process may be executed by one of these processors, or by a combination of two or more processors of the same or different types (e.g., multiple FPGAs, or a combination of a CPU and an FPGA). The hardware structure of these processors is, more specifically, an electrical circuit that combines circuit elements such as semiconductor devices.

[0090] In addition, in each of the above-described embodiments and modifications, it is possible to employ a configuration in which the program for the characteristics measurement process is pre-stored (installed) in a ROM or storage, but the above-described embodiments and modifications are not limited to such a configuration. The program may be provided in a form recorded on a non-transitory recording medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), or a USB (Universal Serial Bus) memory. The program may also be downloaded from an external device via a network. [Industrial Applicability]

[0091] The characteristic measuring device for an object to be measured and the characteristic measuring method for an object to be measured of the present invention can be widely used in various technical fields including various industrial fields, chemical fields, power and energy fields, materials fields, medical fields, pharmaceutical fields, and life science fields. [Explanation of symbols]

[0092] 100, 100a, 100b Characteristics measuring device 110 Reference signal generation section 120 Waveform Generator 130 Sound Generator 140,240 Receiver 150 Amplifier and filter section 160 Despreading Unit 170 Measuring section 200 Object to be measured 300 Tank 310 water 400 Electromagnetic Shielding

Claims

1. a sound wave transmitting unit that transmits sound waves; a receiving unit that receives an electromagnetic field from an object to be measured, the electromagnetic field being generated by irradiating the object with the sound wave; an acoustic wave medium between the sound wave transmitter and the object to be measured for temporally separating the electromagnetic field from a reverberant electromagnetic field resulting from reverberant vibrations of the sound wave transmitter; a despreading unit that despreads the electromagnetic field received by the receiving unit using a reference signal associated with the acoustic wave; and a measurement unit that extracts at least one characteristic selected from the group consisting of an electric characteristic, a magnetic characteristic, an electromechanical characteristic, and a magnetomechanical characteristic of the object under measurement based on at least one measurement selected from the group consisting of an intensity, a phase, and a frequency of the despread electromagnetic field. A device for measuring the characteristics of the object under test.

2. a reference signal generator that generates a reference signal based on predetermined information; a sound wave transmitting unit that transmits a sound wave generated based on the reference signal; a receiving unit that receives an electromagnetic field generated by irradiating the sound wave onto an object to be measured; a despreading unit that despreads the electromagnetic field received by the receiving unit using the reference signal; and a measurement unit that extracts at least one characteristic selected from the group consisting of an electric characteristic, a magnetic characteristic, an electromechanical characteristic, and a magnetomechanical characteristic of the object under measurement based on at least one measurement selected from the group consisting of an intensity, a phase, and a frequency of the despread electromagnetic field. A device for measuring the characteristics of the object under test.

3. the despreading unit correlates the electromagnetic field received by the receiving unit with the reference signal and outputs a pulse-compressed signal.

3. The device for measuring characteristics of an object to be measured according to claim 1.

4. the sound wave generator generates the sound wave based on information having an impulse autocorrelation characteristic; the information having an impulsive autocorrelation property is an M sequence or a complementary sequence; 3. The device for measuring characteristics of an object to be measured according to claim 1.

5. The sound wave generator generates the sound wave based on information whose frequency changes continuously over time.

3. The device for measuring characteristics of an object to be measured according to claim 1.

6. a synchronous addition unit that synchronously adds the despread electromagnetic field a predetermined number of times; the measurement unit extracts characteristics of the device under test based on the electromagnetic field synchronously added by the synchronous addition unit.

3. The device for measuring characteristics of an object to be measured according to claim 1.

7. a subtraction unit configured to subtract a signal obtained by despreading the electromagnetic field received by the receiving unit in the absence of the object under test from the despread electromagnetic field; 3. The device for measuring characteristics of an object to be measured according to claim 1.

8. Further comprising a phase detection unit that detects the phase of the despread electromagnetic field.

3. The device for measuring characteristics of an object to be measured according to claim 1.

9. a sound wave transmission step of transmitting sound waves from a sound wave transmission source; a receiving step of receiving an electromagnetic field from the object to be measured, which is generated by irradiating the object with sound waves from the sound wave source by an acoustic medium between the sound wave source and the object to be measured, with a delay relative to the sound waves from the sound wave source; a despreading step of despreading the electromagnetic field received in the receiving step using a reference signal associated with the acoustic wave; a measuring step of extracting at least one characteristic selected from the group consisting of an electric characteristic, a magnetic characteristic, an electromechanical characteristic, and a magnetomechanical characteristic of the object under test based on at least one measurement selected from the group consisting of an intensity, a phase, and a frequency of the despread electromagnetic field; Temporally separating the electromagnetic field from a reverberant electromagnetic field resulting from reverberant vibrations of the acoustic source. A method for measuring the characteristics of an object under test.

10. generating a reference signal based on predetermined information; Transmitting a sound wave generated based on the reference signal; receiving an electromagnetic field generated by irradiating the sound wave onto an object to be measured; despreading the received electromagnetic field using the reference signal; extracting at least one characteristic selected from the group consisting of an electrical characteristic, a magnetic characteristic, an electromechanical characteristic, and a magnetomechanical characteristic of the object under test based on at least one measurement selected from the group consisting of an intensity, a phase, and a frequency of the despread electromagnetic field; A method for measuring the characteristics of an object under test.

11. The despreading step pulse-compresses the electromagnetic field. The method for measuring characteristics of an object to be measured according to claim 9.

12. The despread electromagnetic field is the pulse-compressed electromagnetic field. The method for measuring characteristics of an object to be measured according to claim 10.

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