Non-destructive inspection system

Abstract

The present invention implements an inspection system capable of non-destructively evaluating material properties within a substance.　This non-destructive inspection system for non-destructively inspecting an internal structure of a substance comprises: a transmission unit that generates a millimeter wave and transmits the millimeter wave to the outside to irradiate the substance with the millimeter wave; a reception unit that receives the millimeter wave that has irradiated the substance from the transmission unit and has been transmitted through the substance, and outputs a transmission signal based on the millimeter wave; a measurement unit that measures the intensity of the transmission signal; an information processing unit that executes information processing using the measured intensity of the transmission signal; and a movement mechanism unit that moves the irradiation position of the millimeter wave on the substance in a predetermined direction. The information processing unit includes: a position acquisition means for sequentially acquiring, during the movement of the irradiation position by the movement mechanism unit, a two-dimensional position irradiated with the millimeter wave in the substance; and a density distribution acquisition means for acquiring a density distribution within the substance on the basis of each intensity of the transmission signal at each timing when the position is acquired by the position acquisition means.

Description

Non-destructive testing systems

[0001] This invention relates to a non-destructive testing system for non-destructively inspecting the internal structure of a material.

[0002] Wood is widely used as a sustainable natural resource, but because it is naturally derived, its internal structure exhibits significant heterogeneity. Specifically, this includes individual differences due to the growing environment, differences between heartwood and sapwood within the same individual, annual ring structure, and the presence of knots and cracks. These heterogeneities manifest as spatial variations in material properties within the wood. These variations are known to affect physical properties such as density distribution, fiber orientation, and moisture content distribution, as well as mechanical properties such as Young's modulus and compressive strength. Conventional wood quality evaluation methods have generally involved visual inspection of the wood surface or mechanical testing. However, visual inspection makes it impossible to evaluate the inside of the wood, and it is impossible to accurately evaluate material properties from surface information. Furthermore, current mechanical physical methods can only evaluate the entire piece of wood, making it difficult to grasp the spatial distribution of material properties. Under these circumstances, a non-destructive testing system using terahertz waves has been proposed (Patent Document 1).

[0003] Japanese Patent Publication No. 2008-268164

[0004] However, the non-destructive testing system using terahertz waves described in Patent Document 1 has limited penetration capability, which restricts the thickness of the sample that can be inspected, making it impossible to inspect wood of a practical thickness.

[0005] This invention has been made in view of the above circumstances and is not particularly limited to wood, but aims to realize an inspection system that can non-destructively evaluate the material properties inside a substance represented by wood.

[0006] To achieve the above objective, a non-destructive testing system according to one aspect of the present invention comprises: a transmitting unit that generates and transmits millimeter waves to the outside to irradiate a substance with the millimeter waves; a receiving unit that receives the millimeter waves irradiated from the transmitting unit to the substance and transmitted through the substance, and outputs a transmission signal based on the millimeter waves; a measuring unit that measures the intensity of the transmission signal; an information processing unit that performs information processing using the measured intensity of the transmission signal; and a moving mechanism unit that moves the irradiation position of the millimeter waves to the substance in a predetermined direction, wherein the information processing unit includes: a position acquisition means that sequentially acquires the two-dimensional position in the substance where the millimeter waves are irradiated while the irradiation position is being moved by the moving mechanism unit; and a density distribution acquisition means that acquires the density distribution inside the substance based on the intensity of the transmission signal at each timing in which the position is acquired by the position acquisition means.

[0007] According to the present invention, although not particularly limited to wood, it is possible to realize an inspection system that can non-destructively evaluate the material properties inside a substance, such as wood.

[0008] This is a schematic diagram illustrating the outline of a non-destructive testing system according to one embodiment of the present invention. This is a block diagram showing the relationships between the components of a non-destructive testing system according to one embodiment of the present invention. This is a diagram showing an example of knots as one of the heterogeneities of wood. This is a diagram showing an example of cracks as one of the heterogeneities of wood. This is a diagram showing an example of density change as one of the heterogeneities of wood. This is a diagram showing an example of fiber inclination as one of the heterogeneities of wood. This is a diagram showing an outline of the technology according to one embodiment of the present invention, in particular, a method for obtaining density distribution. This is a diagram showing the amplitude and phase of the transmitted wave and the received wave. This is a diagram where the horizontal axis represents density and the vertical axis represents the attenuation of the incident millimeter wave. This is a diagram showing an external photograph of wood having knots, which is the wood to be inspected according to one embodiment of the present invention. This is a diagram showing the density distribution inside the wood as a result of non-destructive testing of the wood shown in Figure 10 according to one embodiment of the present invention. This is a diagram showing a method for obtaining the distribution of fiber direction in wood according to one embodiment of the present invention. This is a diagram showing the state in which the polarization direction of the millimeter wave transmitted from the transmitter rotates according to one embodiment of the present invention. This is a diagram showing the experimental results of the relationship between the inclination of the fiber direction with respect to the trunk direction and the transmitted millimeter wave intensity (reaction value) according to one embodiment of the present invention. This figure shows the density distribution inside the wood as a result of non-destructive testing of a different type of wood than the wood shown in Figure 10, relating to one embodiment of the present invention. This figure shows the measurement results showing the distribution of fiber direction for the wood with the density distribution shown in Figure 15. This figure is a schematic diagram showing how millimeter waves are transmitted through the wood being measured, relating to one embodiment of the present invention. This figure shows the relationship between the global fiber direction of the wood and the polarization direction of the polarization filter and polarization detection element of the transmitting and receiving units. The polarization direction and the wood grain are parallel or perpendicular. This figure shows the relationship between the inclination of the fiber direction relative to the trunk direction and the amount of transmitted millimeter waves (reaction value) under the relationship shown in Figure 18. This figure shows the distribution of the amount of transmitted millimeter waves (reaction value) that was actually measured. This figure shows an image of the detected fiber distribution. This figure is a schematic diagram showing how millimeter waves are transmitted through the wood being measured, relating to one embodiment of the present invention. This figure shows the relationship between the global fiber direction of the wood and the polarization direction of the polarization filter and polarization detection element of the transmitting and receiving units. Unlike Figure 18, the polarization direction and the wood grain are at a 45-degree angle.This figure shows the relationship between the inclination of the fiber direction relative to the trunk direction and the transmitted millimeter wave amount (reaction value) under the relationship shown in Figure 23. This figure shows the two-dimensional distribution of the reaction value under the relationship shown in Figure 23. This is a schematic diagram showing an example of a configuration when the principle of tomosynthesis is used in the present invention. This is a block diagram showing an example of the hardware configuration of an information processing device among the non-destructive testing systems shown in Figures 1 and 2. This is a functional block diagram showing an example of the functional configuration of a non-destructive testing system including the information processing device with the hardware configuration of Figure 27. This is a flowchart showing the flow (overview) of the service according to the second embodiment of the present invention. This is a block diagram showing an example of the functional configuration of an information processing device according to the second embodiment of the present invention. This is a schematic diagram showing the measurement configuration according to the second embodiment of the present invention. This is a photograph of an actual cylindrical piece of wood used in the measurement configuration of Figure 31. This is a two-dimensional map showing the measurement results of the cylindrical piece of wood in Figure 32. This is a photograph of a glued laminated timber (a member such as a beam or column with the fiber direction laminated in the same direction, hereinafter referred to as "general glued laminated timber") that is the target of measurement. This is an image showing the measurement results for the general glued laminated timber in Figure 34 mapped with voltage values. This is data taken using X-rays for the general glued laminated timber in Figure 34. This is a composite measurement map for a surface material (Cross Laminated Timber: hereinafter referred to as "CLT") made by laminating and bonding large sheet materials (laminas) with the fiber directions perpendicular to each other. This is the moisture content analysis result, which is a more detailed analysis of the CLT measurement results. This is the moisture content analysis result, which is a more detailed analysis of other CLT measurement results. This is an actual photograph of the measurement device when applied to reinforced concrete. This shows the results of a two-dimensional analysis obtained by measuring the reflection parameters of a reinforced concrete structure. This shows the three-dimensional analysis result corresponding to the two-dimensional analysis result shown in Figure 41.

[0009] (First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. For the sake of explanation, the term "wood" is used, but the invention is not limited to wood, and any substance represented by wood is the subject of non-destructive testing.

[0010] Figure 1 is a schematic diagram illustrating the outline of a non-destructive testing system according to one embodiment of the present invention. Figure 1 shows how the transmitting and receiving unit and the wood are moved by the moving mechanism, and how a two-dimensional scan is performed on the wood.

[0011] The non-destructive testing system S comprises an information processing device 1, a transmitting unit 2 that transmits millimeter waves, a receiving unit 3 that receives millimeter waves, a sample stage 4 that supports the wood W, and a moving mechanism 5 that moves the transmitting unit 2, the receiving unit 3, and the sample stage 4.

[0012] The non-destructive testing system S operates as follows: Millimeter waves emitted from the transmitting unit 2 pass through the wood W placed on the sample stage 4 and are received by the receiving unit 3 located opposite. The transmitting unit 2, the receiving unit 3, and the wood W on the sample stage 4 are relatively movable by the moving mechanism 5, allowing scanning of a predetermined range of the wood W. The transmitted signal obtained by scanning is processed by the information processing device 1 and output as information such as the density distribution and fiber direction inside the wood W. With this configuration, it is possible to non-destructively evaluate the material properties inside the wood W.

[0013] Figure 2 is a block diagram showing the relationships between the components of a non-destructive testing system according to one embodiment of the present invention. This configuration is one embodiment, and various configurations can be adopted while maintaining functionality. The non-destructive testing system S includes an information processing device 1, a transmitting unit 2, a receiving unit 3, a sample stage 4, a moving mechanism unit 5, and a measuring unit 6. The information processing device 1 has the functional units described later and controls the non-destructive testing system S. The transmitting unit 2 includes a transmitter 21, a swivel mechanism 22, and a polarization filter 23. The transmitter 21 has the function of emitting millimeter waves, and the swivel mechanism 22 has the function of changing the polarization direction of the polarization filter 23 of the transmitting unit 2. The polarization filter 23 allows only millimeter waves with a specific polarization direction to pass through the incident millimeter waves. The polarization filter 23 is, for example, a wire grid polarizer, a beam splitter, etc. The polarization filter 23 is not necessarily required, and the polarization characteristics of the transmitting antenna may be used. That is, a configuration that does not depend on the presence or absence of the polarization filter 23 is possible. In the following description, it is assumed that a polarization filter 23 exists, but similarly, the polarization characteristics of the antenna may be used. The receiving unit 3 includes a receiver 31, a swivel mechanism 32, and a polarization detection element 33. The receiver 31 has the function of receiving millimeter waves, and the swivel mechanism 32 has the function of changing the polarization direction of the polarization detection element 33 of the receiving unit 3. The polarization detection element 33 is, like the polarization filter 23, for example, a wire grid polarizer, a beam splitter, etc. The polarization detection element 33 is not necessarily required, and the polarization characteristics of the receiving antenna may be used. That is, a configuration that does not depend on the presence or absence of the polarization detection element 33 is possible. In the following description, it is assumed that a polarization detection element 33 exists, but similarly, the polarization characteristics of the antenna may be used. The moving mechanism 5 includes an actuator 51 that changes the position of the transmitting unit 2 and the receiving unit 3, an actuator 52 that moves the sample stage 4, and a controller 53 that controls these actuators. The controller 53 is connected to the information processing device 1 and controls the position of each actuator based on instructions from the information processing device 1. The measurement unit 6 includes a lock-in amplifier 61 that receives output from the receiving unit 3 and a data acquisition device (hereinafter referred to as "DAQ"; Data Acquisition System) 62.The lock-in amplifier 61 has the function of detecting the received signal, and the DAQ 62 has the function of acquiring the detected signal as digital data.

[0014] Figure 3 shows an example of knots as one of the heterogeneities of wood W. Figure 4 shows an example of cracks as one of the heterogeneities of wood W. Figure 5 shows an example of density change as one of the heterogeneities of wood W. Figure 6 shows an example of fiber inclination as one of the heterogeneities of wood W.

[0015] One embodiment of the present invention, the non-destructive testing system S, is a system that uses millimeter waves to inspect the heterogeneity of wood W shown in Figures 3 to 6.

[0016] The non-destructive testing system S of the present invention measures the density distribution inside wood W by utilizing the material penetration characteristics of millimeter waves. The transmission characteristics of millimeter waves and the method for obtaining the density distribution using them will be described below.

[0017] Figure 7 shows an overview of the technology according to one embodiment of the present invention, in particular, a method for obtaining the density distribution. As shown in Figure 7, millimeter waves irradiated from the transmitting unit 2 are transmitted through the wood W and received by the receiving unit 3. At this time, the transmittance of millimeter waves in the material is expressed, for example, by the following formula using the complex permittivity ε and conductivity σ. In the following explanation, mathematical formulas are used in conjunction with these to make the technical explanation easier to understand, but the explanation is not limited to these, and different approximations may be applied. α = ω√(μ ０ ε ０ / 2) * √(√(1 + (σ / ωε) ２ ) - 1) ... (Equation 1) Here, α is the damping constant [Np / m], ω is the angular frequency [rad / s], μ ０ ε is the permeability of vacuum [H / m], ε ０ ε is the permittivity of vacuum [F / m], ε is the relative permittivity of the material, and σ is the conductivity [S / m]. Here, the relative permittivity is the complex permittivity, and the imaginary part represents absorption and the magnitude of dielectric loss. The intensity I(x) of the electromagnetic wave passing through the wood W is given by the incident intensity I ０ The following equation applies to this: I(x) = I ０exp(-2αx) ... (Equation 2) Here, x represents the thickness of the wood W [m]. Furthermore, the dielectric properties of wood W have a clear correlation with density and can be approximated by the following empirical formula: ε = 1 + aρ(1 + bM) ... (Equation 3) Here, a is a constant that depends on the type of wood W (usually in the range of 0.3 to 0.5), and ρ is the density of wood W [g / cm³]. ３ ], b is a coefficient representing the dependence on moisture content (approximately 0.1), and M is the moisture content [%].

[0018] From (Equation 3), it can be seen that as the density ρ of the wood W increases, the dielectric constant ε increases. This increase in dielectric constant ε leads to an increase in the attenuation constant α in (Equation 1), which in turn causes a decrease in the transmission intensity I(x) shown in (Equation 2). Figure 8 shows the amplitude attenuation and phase shift that occur between the transmitted and received waves due to this physical mechanism.

[0019] Figure 9 experimentally confirms the theoretical relationships derived from these equations. The horizontal axis represents the density of wood W in a dry state, i.e., the total dry density, and the vertical axis represents the attenuation of incident millimeter waves. Figure 9 shows that a sublinear relationship exists between the density of wood W and the attenuation of incident millimeter waves. This sublinear relationship is consistent with the theoretical trend predicted from the above equations, suggesting that the attenuation of millimeter waves in wood W is mainly caused by dielectric loss due to the dipole polarization of cellulose molecules. Dielectric loss increases as the density increases because the number of polarized molecules per unit volume increases.

[0020] FIG. 10 is a diagram showing an external photograph of a wood W to be inspected according to an embodiment of the present invention, the wood W having knots. In the case of the wood W having knots as shown in FIG. 10, since the density is different between the knot portion and other portions, the value of α in the above formula is different, and as a result, the transmission intensity I(x) also shows different values. FIG. 11 is a diagram showing the density distribution inside the wood W as a non-destructive inspection result of the wood W according to an embodiment of the present invention. The position of the high-density region in the non-destructive inspection result shown in FIG. 11 exactly coincides with the position of the knot shown in FIG. 10, demonstrating that the non-destructive inspection system S of the present invention can accurately detect the density distribution inside the wood W.

[0021] In the non-destructive inspection system S of the present embodiment, appropriate measurement conditions are set in consideration of the fact that attenuation of about 2 - 30 dB occurs in the 60 GHz band per 1 cm thickness of the wood W. Also, the influence of the moisture content is considered, and it is designed assuming a moisture content of usually about 5 - 15%. Thereby, precise measurement under practical conditions becomes possible.

[0022] Thus, according to the present embodiment, by utilizing the transmission characteristics of millimeter waves, the internal density distribution of the wood W can be measured non-destructively, and in particular, it is possible to accurately detect portions with different densities such as knots.

[0023] Next, the detection of the fiber direction of the wood W in the non-destructive inspection system S of the present invention will be described. The wood W is a material having anisotropy in the fiber direction, and its dielectric properties also show anisotropy. FIG. 12 is a diagram showing a method for obtaining the distribution of the fiber direction in the wood W according to an embodiment of the present invention. As shown in FIG. 12, in the present embodiment, the transmission unit 2 transmits millimeter waves while rotating the polarization direction of the polarization filter 23 of the transmission unit 2 to transmit through the wood W, and the receiving unit 3 receives the millimeter waves transmitted through the polarization detection element 33 while rotating the polarization direction of the polarization detection element 33. FIG. 13 is a diagram showing a state in which the polarization direction of the millimeter waves transmitted from the transmission unit 2 rotates. The rotation of the polarization direction of the millimeter waves is realized by the rotation of the polarization direction of the polarization filter 23 of the transmission unit 2. The electric field vector E of the incident millimeter wave ｌWhen the angle θ is formed from the fiber direction (x-axis) of the wood W, it is expressed by the following formula: E ｌ = E ０ exp[j(ωt - kz)] (xcosθ + ysinθ) ... (Equation 4) Here, E ０ ε is the amplitude of the electric field, ω is the angular frequency, k is the wave number, z is the propagation direction, and x and y are unit vectors. The dielectric constant tensor considering the anisotropy of wood W is expressed in the following form: ε = [ε ｌ 0 0] [0 ε ｔ 0]...(Formula 5) [0 0 ε ｔ ] Here, ε ｌ ε is the dielectric constant in the fiber direction. ｔ This is the dielectric constant in the direction perpendicular to the fiber.

[0024] Figure 14 shows experimental results relating to the relationship between the inclination of the fiber direction relative to the trunk direction and the transmitted millimeter-wave intensity (reaction value) according to one embodiment of the present invention. As shown in Figure 14, this anisotropic dielectric constant changes the polarization state of the millimeter waves transmitted through the wood W, and changes the reception intensity by the receiving unit 3. The electric field vector E after transmission through the wood W. ２ It is expressed as follows: E ２ = E ０ exp[j(ωt - k'z)] [xcosθexp(-α ｌ z) + ysinθexp(-α ｔ z)] ... (Equation 6) Here, α ｌ α is the damping constant in the fiber direction. ｔ k' is the attenuation constant in the direction perpendicular to the fiber, and k' is the wavenumber in the wood W.

[0025] The relationship shown in Figure 14 can be understood, for example, as a combination of the effects of the density and fiber direction of the wood W. When the polarization direction of the polarization detection element 33 of the receiving unit 3 is perpendicular to the incident polarization (θ + 90°), the received power P can be expressed, for example, by the following equation: P = P ０ sin ２ θ[exp(-2α)]ｔ z) - exp(-2α ｌ z)] ２ …(Equation 7) Here, P ０ is the incident power. However, this equation is simplified assuming that the fibers are uniform within the wood W.

[0026] Fig. 15 shows the density distribution inside the wood W as a non-destructive inspection result of another wood W different from the wood W shown in Fig. 10 according to an embodiment of the present invention. Fig. 16 shows the measurement result indicating the distribution of the fiber direction for the wood W from which the density distribution shown in Fig. 15 was obtained. By comparing both Fig. 15 and Fig. 16, it can be confirmed that the density change and the change in the fiber direction inside the wood W can be detected separately.

[0027] Thus, according to this embodiment, by utilizing the polarization characteristics of millimeter waves, the distribution of the fiber direction inside the wood W can be measured non-destructively.

[0028] Next, the detection of the fiber direction of the wood W, particularly its disturbance, by the non-destructive inspection system S of the present invention will be described in more detail. Fig. 17 is a schematic diagram showing a state where millimeter waves are transmitted through the wood W as the measurement target according to an embodiment of the present invention. As shown in Fig. 17, in this embodiment, the polarization direction of the polarization filter 23 of the transmitter 2 and the polarization direction of the polarization detection element 33 of the receiver 3 are made orthogonal, and the polarization directions of the polarization filters of the polarization filter 23 of the transmitter 2 and the polarization detection element 33 of the receiver 3 are arranged to be parallel and orthogonal to the fiber direction of the wood W as the measurement target. At this time, the millimeter waves irradiated from the transmitter 2 pass through the wood W and are received by the receiver 3.

[0029] Figure 18 shows the relationship between the global fiber direction of the wood W and the polarization direction of the polarization filter 23 and polarization detection element 33 of the transmitting unit 2 and receiving unit 3. The polarization direction and the grain of the wood W are parallel or perpendicular. If the grain of the wood W is oriented in the same direction from the front to the back, for example, if the fiber direction is parallel to the trunk direction, the millimeter waves from the transmitting unit 2 that have passed through the polarization filter 23 will penetrate the wood W while maintaining their polarization state. In this case, millimeter waves with a polarization state perpendicular to the polarization direction of the polarization detection element 33 of the receiving unit 3 will be incident on the polarization detection element 33. As a result, these millimeter waves cannot pass through the polarization detection element 33, and the response value will be low.

[0030] Figure 19 shows the relationship between the inclination of the fiber direction relative to the trunk direction and the transmitted millimeter wave amount (reaction value) under the relationship shown in Figure 18. As shown in Figure 19, when the fiber direction is inclined from the trunk direction, the polarization state inside the wood W changes. This is based on the physical mechanism explained above in (Equations 4) to (Equations 7). Specifically, the dielectric constant ε in the fiber direction ｌ and the dielectric constant ε in the direction perpendicular to the fiber ｔ Due to the difference, the polarization state of the incident millimeter waves changes as they pass through the wood W. This change in polarization state increases the number of millimeter waves that pass through the orthogonal polarization detection elements 33 of the receiving unit 3, resulting in a higher response value.

[0031] Figure 20 shows the distribution of the transmitted millimeter-wave amount (reaction value) that was actually measured. Regions with high reaction values ​​are identified as regions where the fibers are disordered. This is because changes in the polarization state caused by disorder in the fiber direction are detected as changes in the transmission amount by the polarization detection element 33 of the receiving unit 3. Figure 21 shows an image of the fiber distribution detected in this way. From the distribution of reaction values, the disorder in the fiber direction inside the wood W can be quantitatively evaluated.

[0032] As described above, according to this embodiment, by arranging the polarization direction of the polarization filter 23 of the transmitting unit 2 and the polarization detection element 33 of the receiving unit 3 to be perpendicular to each other, and measuring the change in the polarization state of millimeter waves transmitted through the wood W, it is possible to non-destructively detect disturbances in the fiber direction inside the wood W. This makes it possible to evaluate the internal structure of the wood W in more detail.

[0033] Next, the detection of defects in wood W using the non-destructive testing system S of the present invention will be described. Figure 22 is a schematic diagram showing the transmission of millimeter waves through the wood W to be measured according to one embodiment of the present invention. As shown in Figure 22, in this embodiment, the polarization direction of the polarization filter 23 of the transmitting unit 2 and the polarization direction of the polarization detection element 33 of the receiving unit 3 are orthogonal, and the polarization directions of the polarization filter 23 of the transmitting unit 2 and the polarization detection element 33 of the receiving unit 3 are arranged at a predetermined angle with respect to the fiber direction of the wood W. At this time, defects are detected by whether or not there is a change in the polarization state inside the wood W.

[0034] Figure 23 shows the relationship between the global fiber direction of the wood W and the polarization directions of the polarization filters and polarization detection elements of the transmitting and receiving units. Unlike Figure 18, the polarization direction and the grain of the wood W form a 45-degree angle. More specifically, as shown in Figure 23, the polarization direction of the polarization filter 23 of the transmitting unit 2 and the polarization direction of the polarization detection element 33 of the receiving unit 3 are arranged to be orthogonal to each other, and these polarization directions are set to form a 45-degree angle with the fiber direction (grain) of the wood W. This arrangement allows for a clear difference in response values ​​between normal and defective parts.

[0035] Figure 24 shows the relationship between the inclination of the fiber direction relative to the trunk direction and the transmitted millimeter wave amount (reaction value) under the relationship shown in Figure 23. In this configuration, a high reaction value is obtained in the region where the fibers are parallel to the trunk direction, i.e., where the tree is growing normally. This is because the polarization state, which is set to a 45-degree polarization direction, changes inside the wood W, generating a component that can be detected by the orthogonal detectors of the receiving unit 3. Regions with low reaction values ​​are identified as regions where the fibers are disordered. In this configuration, a high reaction value is obtained in the region where the fibers are parallel to the trunk direction, i.e., where the tree is growing normally. Furthermore, if, for example, a knot has fallen off and there is a hole in the wood W, the polarization state does not change, so the transmitted polarization is absorbed by the detector of the receiving unit, and the reaction value becomes zero. This makes it possible to detect defects (holes, etc.) in the wood W.

[0036] In the configuration shown in Figure 18, where the polarization direction of the polarization filter 23 of the transmitting unit 2 and the polarization detection element 33 of the receiving unit 3 are arranged parallel and perpendicular to the fiber direction, both areas of normal growth and defects will have low response values, making it impossible to distinguish between the two. The 45-degree arrangement shown in Figure 23 allows these differences to be detected. In Figure 24, the response value is 0 in areas where the fibers are significantly disordered. Thus, with this configuration, the presence of defects can be clearly detected as a decrease in the response value. However, the above is a theoretical explanation. The inclination of wood fibers generally falls within a range of about ±30°. Therefore, even when the polarization directions of the transmitting and receiving units are arranged parallel and perpendicular to the fibers, there will be a difference in the response values ​​between areas of normal growth and defects. However, by rotating the polarization direction of the transmitting and receiving units by 45°, the slope of the measured value in areas with large fiber disorder becomes steeper, making it easier to identify defects. Therefore, this measurement method is suitable for identifying defects.

[0037] Figure 25 shows the two-dimensional distribution of reaction values ​​under the relationship shown in Figure 23. The horizontal and vertical axes of Figure 25 represent the positions of the wood W in the horizontal and vertical directions, respectively, in a plan view. Areas with low reaction values, i.e., regions where defects are likely to exist, are shown in a dark gray color.

[0038] As described above, according to this embodiment, the polarization direction of the polarization filter 23 of the transmitting unit 2 and the polarization detection element 33 of the receiving unit 3 are arranged at a 45-degree angle with respect to the fiber direction of the wood W, and by measuring the change in the polarization state of millimeter waves transmitted through the wood W, defects inside the wood W can be detected non-destructively. In particular, the 45-degree arrangement in this embodiment makes it possible to clearly distinguish between normal and defective areas, which was difficult with parallel or orthogonal arrangements.

[0039] Next, an embodiment in which the principle of tomosynthesis is applied to the non-destructive testing system S of the present invention will be described.

[0040] Figure 26 is a schematic diagram showing an example configuration when the principle of tomosynthesis is applied to the present invention. Tomosynthesis is an image reconstruction method that reproduces depth information by superimposing multiple images taken from different angles, offsetting them to correspond to the depth of interest.

[0041] In this embodiment, transmission measurements of wood W are performed while changing the relative positions of the transmitting unit 2 and the receiving unit 3. Specifically, millimeter waves are irradiated onto the wood W from different angles, and transmission data is acquired at each angle. These transmission data are appropriately offset and superimposed according to the depth of interest. This process makes it possible to detect the density distribution and the three-dimensional distribution of fiber direction inside the wood W.

[0042] The advantages of tomosynthesis are that it enables three-dimensional reconstruction even with measurement data from a limited angular range, and requires a relatively small number of datasets. Therefore, efficient three-dimensional imaging can be achieved in the non-destructive testing system S of the present invention.

[0043] Figure 27 is a block diagram showing an example of the hardware configuration of the information processing device 1 in the non-destructive testing system S shown in Figure 2.

[0044] The information processing device 1 includes a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a bus 14, an input / output interface 15, an input unit 16, an output unit 17, a storage unit 18, a communication unit 19, a drive 18A, and a removable media 18B.

[0045] The CPU 11 executes various processes according to the program recorded in the ROM 12 or the program loaded into the RAM 13 from the storage unit 18. The RAM 13 also stores data and other information necessary for the CPU 11 to execute various processes.

[0046] The CPU 11, ROM 12, and RAM 13 are interconnected via a bus 14. An input / output interface 15 is also connected to this bus 14. An input / output interface 15 is connected to an input unit 16, an output unit 17, a storage unit 18, a communication unit 19, and a drive 18A.

[0047] The input unit 16 is configured, for example, with a keyboard, and takes in various types of information. The output unit 17 is configured with a display such as an LCD or a speaker, and outputs various types of information as images or sounds. The storage unit 18 is configured with DRAM (Dynamic Random Access Memory) or the like, and stores various types of data. The communication unit 19 communicates with other devices (for example, DAQ 62 and controller 53 in Figure 2) via a network including the Internet.

[0048] A removable media 18B, such as a magnetic disk, optical disk, magneto-optical disk, or semiconductor memory, is appropriately mounted on the drive 18A. Programs read from the removable media 18B by the drive 18A are installed in the storage unit 18 as needed. The removable media 18B can also store various data stored in the storage unit 18, just like the storage unit 18.

[0049] Figure 28 is a functional block diagram showing an example of the functional configuration of a non-destructive system including the information processing device with the hardware configuration of Figure 27. The CPU 11 of the information processing device 1 functions as follows: position acquisition unit 101, density distribution acquisition unit 102, evaluation unit 103, dielectric anisotropy distribution acquisition unit 104, node distribution acquisition unit 105, fiber direction acquisition unit 106, intensity prediction unit 107, and image composition unit 108.

[0050] The position acquisition unit 101 has the function of acquiring and managing the irradiation position of the millimeter waves on the wood W as a two-dimensional coordinate system. As shown in Figure 1, a Cartesian coordinate system is defined with the lower left end of the wood W fixed on the sample stage 4 as the origin (0,0), the longitudinal direction as the X-axis, and the width direction as the Y-axis. In this coordinate system, the positions of the transmitting unit 2 and the receiving unit 3 are acquired in units of 0.1 mm from the position information of the actuators 51 and 52.

[0051] The position acquisition unit 101 acquires position information of actuators 51 and 52 from the controller 53 at 100 msec intervals and converts the position information of each actuator into XY coordinates using a coordinate transformation matrix. Then, it records the pair of the irradiation position of the transmission unit 2 and the reception position of the reception unit 3 as a single measurement point and temporarily stores the coordinate value of the measurement point in a dedicated buffer of RAM 13. Furthermore, it saves the data to the storage unit 18 after each scan line (Y-axis scanning) is completed.

[0052] The position acquisition unit 101 also performs error processing such as (1) error detection when the actuator's position information is incorrect, (2) detection of rapid position changes and removal of abnormal values, (3) interpolation processing when measurement points are missing, and (4) correction of positional misalignment between scan lines. The position data is stored in a format that includes (1) measurement point ID (unique identifier), (2) X coordinate value (in mm), (3) Y coordinate value (in mm), (4) position coordinates (X, Y) of the transmitting unit 2, (5) position coordinates (X, Y) of the receiving unit 3, and (6) measurement time (in msec).

[0053] The density distribution acquisition unit 102 has the function of acquiring the density distribution inside the wood W based on the intensity of the transmitted signal at each measurement position acquired by the position acquisition unit 101. As shown in Figure 8, amplitude attenuation occurs between the transmitted wave and the received wave according to the internal structure of the wood W, and as shown in Figure 9, there is a sublinear relationship between this attenuation and the wood density.

[0054] The density distribution acquisition unit 102 performs calibration processing before starting measurement. Specifically, it performs (1) measurement of the reference transmission intensity with nothing placed between the transmitting unit 2 and the receiving unit 3, (2) creation of a calibration curve using a calibration test piece with a known density, (3) acquisition of a temperature correction coefficient, and (4) acquisition of a moisture content correction coefficient.

[0055] In actual density measurements, the following processes are performed at each measurement point. First, (1) the transmitted signal intensity output from the lock-in amplifier 61 of the measurement unit 6 is acquired via the DAQ 62, and (2) the attenuation is calculated from the ratio with the reference transmitted intensity. Next, (3) the attenuation is converted to a density value using a calibration curve, and (4) temperature correction and moisture content correction are applied. Then, (5) a noise reduction filter is applied to smooth the measured values. The obtained density values ​​are stored as a two-dimensional array along with the position information. Based on this two-dimensional array data, the density distribution acquisition unit 102 calculates (1) the absolute value distribution of density, (2) the relative change distribution of density, (3) the density gradient distribution, and (4) the distribution of local density anomaly regions. For example, as shown in Figure 11, these distributions are visualized as a color map or grayscale map.

[0056] To ensure data reliability, the density distribution acquisition unit 102 performs the following quality control: (1) Check the effective range of the measured value (0.3 g / cm²) ３ From 1.2 g / cm ３ (2) Detection of rapid density changes between consecutive measurement points (0.1 g / cm³) ３ (1) (2) (3) interpolation of missing areas at measurement points (using the average value of the surrounding 8 points), and (4) correction of systematic density deviations.

[0057] The density distribution acquisition unit 102 stores all acquired information as structured data in the storage unit 18. The stored data includes (1) measurement conditions (date and time, ambient temperature, relative humidity), (2) calibration data, (3) raw transmission intensity data, (4) calculated density values, (5) correction parameters, and (6) records of outliers.

[0058] The evaluation unit 103 has the function of comprehensively evaluating the quality of the wood W based on the information obtained by the density distribution acquisition unit 102, the dielectric anisotropy distribution acquisition unit 104, the knot distribution acquisition unit 105, and the fiber direction acquisition unit 106. The quality evaluation is performed in the following procedure. First, as an evaluation of the uniformity of the density distribution, the deviation distribution from the average density is calculated and areas with large deviations are identified. Next, as an evaluation of the regularity of the fiber direction, local changes in fiber direction are quantified and areas showing abrupt changes in direction are identified. Furthermore, as an evaluation of knots and defects, the size, location, and density of detected knots and defects are quantified.

[0059] The evaluation unit 103 integrates these evaluation results and performs judgments such as strength grade, appearance grade, and suitability for use. The judgment results are compared with standards such as the Japanese Agricultural Standards (JAS) to confirm compliance. The evaluation results are stored in the storage unit 18 as numerical data and an evaluation report.

[0060] The dielectric anisotropy distribution acquisition unit 104 has the function of analyzing the dielectric anisotropy inside the wood W from the intensity change of the transmitted signal acquired while changing the polarization direction of the polarization filter 23 of the transmitting unit 2 and the polarization detection element 33 of the receiving unit 3. As shown in Figure 12, the polarization state of the polarized millimeter waves irradiated from the transmitting unit 2 changes inside the wood W. This change is caused by dielectric anisotropy due to the fiber structure of the wood W, as shown in equation (7), for example.

[0061] The dielectric anisotropy distribution acquisition unit 104 performs the following processing for acquiring measurement data. First, (1) it rotates the polarization direction of the polarization filter 23 of the transmitting unit 2 in 10-degree increments from 0 degrees to 180 degrees, and at the same time rotates the polarization direction of the polarization detection element 33 of the receiving unit 3 in 10-degree increments from 90 degrees to 270 degrees, and measures the transmission intensity at each angle. Next, (2) from the angle dependence of the measured transmission intensity, for example, the dielectric constant ε in the direction of the main axis is determined.ｌ And the dielectric constant ε in the direction perpendicular to it ｔ The following is calculated: (3) The anisotropy ratio of the dielectric constant ε ｌ / ε ｔ The anisotropy strength is quantified by calculating the anisotropy strength. The acquired data is represented as a graph of the relationship between the incident polarization direction and the transmission intensity, as shown in Figure 14. The dielectric constant anisotropy distribution acquisition unit 104 separates these effects and extracts the pure anisotropy component.

[0062] The dielectric anisotropy distribution acquisition unit 104 may set the polarization direction of the polarization filter 23 of the transmitting unit 2 and the polarization detection element 33 of the receiving unit 3 based on the wood grain visible on the surface of the wood W being inspected. For example, the dielectric anisotropy distribution acquisition unit 104 may use an image sensor to detect the direction of the wood grain on the surface of the wood W, set the polarization direction of the polarization filter 23 of the transmitting unit 2 parallel to the direction of the wood grain, and set the polarization direction of the polarization detection element 33 of the receiving unit 3 perpendicular to it. Alternatively, the dielectric anisotropy distribution acquisition unit 104 may use an image sensor to detect the direction of the wood grain on the surface of the wood W, set the polarization direction of the polarization filter 23 of the transmitting unit 2 at a 45-degree angle to the direction of the wood grain, and set the polarization direction of the polarization detection element 33 of the receiving unit 3 perpendicular to the polarization direction of the polarization filter 23 of the transmitting unit 2.

[0063] The knot distribution acquisition unit 105 has the function of detecting the distribution of knots inside the wood W based on the measurement principle shown in Figures 17 to 21. The polarization directions of the polarization filter 23 of the transmitting unit 2 and the polarization detection element 33 of the receiving unit 3 are set to be orthogonal, and the polarization direction of the polarization filter 23 of the transmitting unit 2 is set to be parallel or perpendicular to the global fiber direction, as shown in Figure 18. The knot distribution acquisition unit 105 identifies the location of the knots from the intensity distribution of the transmitted signal obtained in this arrangement. Specifically, it performs (1) detection of regions with abrupt changes in transmitted intensity, (2) shape analysis of the detected region, (3) estimation of the size and direction of the knots, and (4) evaluation of the disturbance of the fiber direction around the knots.

[0064] The fiber direction acquisition unit 106 has the function of acquiring the fiber direction distribution inside the wood W based on the measurement principle shown in Figures 22 to 25, for example. The fiber direction acquisition unit 106 orthogonals the polarization planes of the polarization filter 23 of the transmitting unit 2 and the polarization detection element 33 of the receiving unit 3, and positions them at a 45-degree angle with respect to the fiber direction of the wood W, and calculates the fiber direction from the intensity distribution of the transmitted signal. Specifically, the fiber direction acquisition unit 106 performs (1) measurement of the angle dependence of the transmitted intensity at each measurement point, (2) calculation of the polarization plane rotation angle, (3) estimation of the local fiber direction, and (4) evaluation of the continuity of the fiber strike.

[0065] The strength prediction unit 107 has the function of predicting the strength of the wood W using all the measurement data obtained so far. The prediction takes into account (1) the correlation between average density and strength, (2) the effect of non-uniformity of density distribution, (3) the decrease in strength due to the presence of knots, (4) the effect of disorder in fiber orientation, and (5) the effect of moisture content. By comprehensively evaluating these factors, the mechanical properties such as bending strength, compressive strength, and tensile strength are predicted. The strength prediction unit 107 may also perform machine learning to compare all the measurement data obtained so far with data on the strength of the wood W, and estimate the above mechanical properties of the wood W based on the results of the machine learning.

[0066] The image composition unit 108 has the function of visualizing the three-dimensional structure inside the wood W based on the principle of tomosynthesis shown in Figure 26. Specifically, it performs (1) collection of multiple transmission intensity data acquired from different angles, (2) data offset processing according to the depth of interest, (3) superimposition of the offset data, and (4) reconstruction of a three-dimensional image. This makes it possible to grasp the density distribution, knot distribution, fiber orientation, etc. inside the wood W in three dimensions.

[0067] Furthermore, the information processing system to which the present invention is applied only needs to have the following configuration, and various embodiments can be taken.

[0068] A non-destructive testing system (for example, the non-destructive testing system S in Figure 1) is a non-destructive testing system for non-destructively inspecting the internal structure of a material, comprising: a transmitting unit (for example, the transmitting unit 2 in Figure 2) that generates and transmits millimeter waves to the outside to irradiate the material with the millimeter waves; a receiving unit (for example, the receiving unit 3 in Figure 2) that receives the millimeter waves irradiated from the transmitting unit to the material and transmitted through the material, and outputs a transmission signal based on the millimeter waves; a measuring unit (for example, the measuring unit 6 in Figure 2) that measures the intensity of the transmission signal; and an information processing unit (for example) that performs information processing using the intensity of the transmission signal measured by the measuring unit. The system comprises an information processing device (1) as shown in Figure 2, and a moving mechanism (5) as shown in Figure 2) that moves the irradiation position of the millimeter waves onto the material in a predetermined direction. The information processing device includes a position acquisition means (101 as shown in Figure 28) that sequentially acquires the two-dimensional position of the material irradiated with the millimeter waves while the irradiation position is being moved by the moving mechanism, and a density distribution acquisition means (102 as shown in Figure 28) that acquires the density distribution inside the material based on the intensity of the transmitted signal at each timing in which the position is acquired by the position acquisition means. This allows for non-destructive and safe inspection of the internal structure of materials such as wood. Furthermore, it enables inspection of wood W of a practical thickness, which was difficult with terahertz wave inspection devices, and allows for low-cost and safe inspection compared to X-ray inspection devices. In addition, it allows for two-dimensional understanding of the density distribution inside the material, enabling accurate evaluation of the material's quality.

[0069] Furthermore, in the non-destructive testing system, the transmitting unit can generate millimeter waves of a predetermined frequency determined according to the measurement depth or thickness of the material. This allows the use of millimeter waves with a frequency suitable for the depth and thickness of the material being inspected, meaning that millimeter waves appropriate for the material being inspected pass through the material, enabling more accurate measurement of the density distribution inside the material. In the case of wood W, it is possible to select millimeter waves with appropriate penetration capabilities for materials with practical thicknesses of a few centimeters for furniture and tens to hundreds of centimeters for building materials.

[0070] Furthermore, in a non-destructive testing system, the information processing unit may further include an evaluation means (for example, the evaluation unit 103 in Figure 28) that evaluates the spatial distribution of the material properties of the substance based on the density distribution at the position acquired by the position acquisition means. This makes it possible to evaluate the spatial distribution of the material properties of the substance from the density distribution information and to make a comprehensive judgment on the overall quality of the substance. In particular, in the case of wood, heterogeneity such as knots and cracks present inside can be detected, and the material properties can be evaluated from their distribution state.

[0071] Furthermore, in the non-destructive testing system, the measurement unit measures the intensity of the transmitted signal with the polarization direction of the transmission unit 2 (for example, the polarization direction of the polarization filter 23) set to a predetermined first direction and the polarization direction of the receiving unit 3 (for example, the polarization direction of the polarization detection element 33) set to a predetermined second direction. The information processing unit has dielectric constant distribution acquisition means (for example, dielectric constant anisotropy distribution acquisition unit 104 in Figure 28) that acquires the spatial distribution of dielectric constant anisotropy based on the polarization direction of the transmission unit 2 and the measured intensity of the transmitted signal. The evaluation means can perform the evaluation based on the density distribution and the spatial distribution of dielectric constant anisotropy. This makes it possible to acquire the spatial distribution of dielectric constant anisotropy in addition to the density distribution inside the material, enabling a more detailed evaluation of material properties. In particular, in the case of wood, detecting dielectric constant anisotropy caused by the fiber direction makes it possible to more accurately understand the internal fiber structure.

[0072] Furthermore, in the non-destructive testing system, the information processing unit further includes a knot distribution acquisition means (for example, the knot distribution acquisition unit 105 in Figure 28) that acquires the distribution of knots inside the material by detecting locations in the density distribution where the intensity of the transmitted signal shows abrupt changes, and the evaluation means can perform the evaluation based on the density distribution and the distribution of knots. This makes it possible to detect heterogeneous areas inside the material, especially the presence and distribution of knots in the case of wood. In addition, information such as the size, location, and density of knots can be quantified and evaluated, making it possible to perform a more accurate evaluation of the quality of wood.

[0073] Furthermore, in the non-destructive testing system, the information processing unit further includes a fiber direction acquisition means (for example, the fiber direction acquisition unit 106 in Figure 28) that acquires the distribution of the fiber direction of the material based on the spatial distribution of dielectric anisotropy, and the evaluation means can perform the evaluation based on the density distribution and the distribution of the fiber direction. This makes it possible to quantitatively evaluate the fiber direction inside the material from the spatial distribution of dielectric anisotropy. In particular, in the case of wood, it is possible to detect disturbances in fiber orientation and local changes in direction, and to accurately grasp the distribution state of the fiber direction, which greatly affects the strength characteristics of wood.

[0074] Furthermore, in the non-destructive testing system, the information processing unit further includes a strength prediction means (for example, the strength prediction unit 107 in Figure 28) that predicts the strength of the wood based on the density distribution and the fiber direction distribution, and the evaluation means can perform the evaluation based on the density distribution and the strength. This makes it possible to predict the strength of the wood from the density distribution and fiber direction distribution obtained by non-destructive testing. It is possible to comprehensively evaluate the influence of non-uniformity of density distribution, disorder of fiber orientation, presence of knots, etc. on strength, and to understand the performance of wood as a structural material in advance.

[0075] Furthermore, in a non-destructive testing system, the information processing unit may have an image constructing means (for example, the image constructing unit 108 in Figure 28) that constructs a three-dimensional image of the inside of a material by offsetting and superimposing the transmission signals measured from different angles relative to the depth of interest. This makes it possible to visualize the three-dimensional structure inside a material based on the principle of tomosynthesis using transmission signal data obtained from different angles. In particular, in the case of wood, it is possible to grasp the three-dimensional distribution of internal density distribution, knot distribution, fiber orientation, etc., enabling a more detailed quality evaluation.

[0076] Furthermore, in the non-destructive testing system, the material is wood, the transmitting unit and the receiving unit are arranged so that their respective polarization directions are orthogonal to each other, and the information processing unit has a knot distribution acquisition means (for example, the knot distribution acquisition unit 105 in Figure 28) that acquires the distribution of knots inside the wood by detecting locations in the density distribution where the intensity of the transmitted signal shows abrupt changes, and the evaluation means can perform the evaluation based on the density distribution and the distribution of knots. As a result, by inspecting the wood with the polarization planes of the transmitting unit and the receiving unit arranged orthogonally, knot detection can be performed with higher accuracy. In particular, changes in the polarization state due to the presence of knots can be effectively detected, making it possible to more accurately identify the location and size of knots inside the wood.

[0077] Furthermore, in a non-destructive testing system, the information processing unit may further include strength prediction means (for example, the strength prediction unit 107 in Figure 28) that predicts the strength of the wood based on the density distribution and the fiber orientation distribution. This allows strength prediction to be performed considering not only the density distribution inside the wood but also the fiber orientation distribution. In particular, it is possible to evaluate the combined effects of density non-uniformity and disorder in fiber orientation on the strength of the wood, enabling more accurate strength prediction.

[0078] Furthermore, in a non-destructive testing system, the information processing device may have an image constructing means (for example, the image constructing unit 108 in Figure 28) that constructs a three-dimensional image of the inside of a material by offsetting and superimposing a plurality of transmission signals measured from different angles relative to the depth of interest. This makes it possible to visualize the three-dimensional structure inside the material using the principle of tomosynthesis. In particular, three-dimensional reconstruction becomes possible using only measurement data from a limited range of angles, reducing the number of required datasets. Moreover, the state of the inside of the material at each depth of interest can be clearly grasped, enabling more efficient quality evaluation.

[0079] (Second Embodiment) There is a demand for non-destructive and highly accurate evaluation of the material properties inside materials such as wood. However, in millimeter-wave inspection using a single frequency band, the effects of water content inside the material and the effects of density and defects are detected superimposed, making it difficult to separate and accurately evaluate these effects.

[0080] A second embodiment of the present invention has been made in view of the above circumstances, and aims to separate and evaluate the effects of water content and density / defects within a material such as wood by utilizing the differences in the frequency dependence of measurement data in multiple frequency bands.

[0081] To achieve the above objective, a non-destructive testing system according to one aspect of the present invention is a non-destructive testing system for non-destructively inspecting the internal structure of a material, comprising: a millimeter-wave transmitting unit that transmits millimeter waves of a plurality of frequency bands to the material; a millimeter-wave receiving unit that receives the millimeter waves transmitted through or reflected by the material; a millimeter-wave measuring unit that measures the amplitude and phase of the received millimeter waves for each of the plurality of frequency bands; and a material internal structure acquisition unit that separates a first effect due to water content inside the material and a second effect due to the density and defects of the material based on the frequency dependence of the measurement results for each of the plurality of frequency bands, and acquires information about the inside of the material based on the second effect.

[0082] Each of the non-destructive testing method and program according to one aspect of the present invention corresponds to each of the method and program corresponding to the non-destructive testing system according to one aspect of the present invention.

[0083] According to the present invention, by utilizing the differences in the frequency dependence of measurement data across multiple frequency bands, it becomes possible to separately evaluate the effects of water content and density / defects within materials such as wood.

[0084] A second embodiment of the present invention will be described below with reference to the drawings. For the sake of explanation, the term "wood" is used, but the invention is not limited to wood; any substance represented by wood is subject to non-destructive testing.

[0085] Figure 1 is also a schematic diagram illustrating the outline of the non-destructive testing system S according to the second embodiment of the present invention. Figure 1 shows how the transmitting unit 2, the receiving unit 3, and the wood W are moved by the moving mechanism 5, and how a two-dimensional scan is performed on the wood W. In the second embodiment, in addition to the first embodiment, the receiving unit 3 shown in Figure 1 is positioned on the same side as the transmitting unit 2 with respect to the wood W, and the receiving unit 3 receives reflected waves from the wood W.

[0086] Referring to Figure 29, an overview of the service (hereinafter referred to as "the Service") that can be realized by an information processing system to which an information processing device according to one embodiment of the present invention is applied (see Figure 30, which will be described later) will be explained. Figure 29 is a diagram showing an overview of the Service that can be realized by an information processing system to which an information processing device according to one embodiment of the Information Processing Device of the present invention is applied.

[0087] This service enables the separate evaluation of the effects of water content within materials and the effects of density and defects in non-destructive testing of materials such as wood, which was difficult with conventional measurements using a single frequency band.

[0088] Figure 29 is a flowchart illustrating the service flow (overview). In this service, after a preparation phase for measurement, millimeter waves in multiple frequency bands are transmitted to the material under inspection, and the millimeter waves transmitted or reflected by the material are received. At this time, the amplitude and phase of the received millimeter waves are measured for each of the multiple frequency bands. The measured data is aggregated in an information processing device and analyzed. In this analysis, the service separates the first effect due to water content inside the material from the second effect due to the density and defects of the material, based on the frequency dependence of the measurement results for each of the multiple frequency bands. Then, based on the separated second effect, information about the inside of the material (e.g., true density distribution and location of defects) is obtained. This makes it possible to separate and evaluate the effects of water content and density / defects inside a material such as wood W by utilizing the differences in the frequency dependence of the measurement data in multiple frequency bands.

[0089] The following will explain the flow of this service in more detail, based on the specific example shown in Figure 29. When this service is started, first, in step S101, measurement preparation and condition setting are performed. Here, the optimal measurement parameters are set according to the type, shape, and expected thickness of the material to be inspected (e.g., wood). At this stage, a choice is also made as to whether to use a transmission type configuration where the millimeter wave transmission and reception are placed opposite each other across the material, or a reflection type configuration where they are placed on the same side of the material.

[0090] Next, in step S102, a millimeter-wave scanning measurement is performed. In this measurement, the measuring device (transmitter and receiver) is controlled based on the conditions set in step S101. Specifically, millimeter waves are sequentially irradiated onto the material not at a single frequency, but at multiple frequency bands spanning a predetermined range. The millimeter-wave signals after interaction with the material (transmission or reflection) are received, and the amplitude and phase of the signals in each frequency band are measured. This measurement is performed while scanning the beam across the material as needed.

[0091] In step S103, the measured data is uploaded to the information processing device 1 (see Figure 30) via the network. In step S104, the information processing device 1 receives the uploaded measurement data and stores it in the storage unit.

[0092] Next, in step S105, the information processing device 1 analyzes the received data. This analysis process is the core of this service. The information processing device 1 focuses on the frequency dependence of the measurement results (amplitude and phase) for each of the multiple frequency bands. Generally, moisture contained within materials such as wood has the characteristic of high dielectric loss over a wide frequency band. In contrast, changes in the density of a material and structural defects (knots, cracks, etc.) tend to exhibit strong reactions due to scattering and resonance (frequency selectivity) in specific frequency bands, depending on the relationship between their dimensions and the wavelength of electromagnetic waves. The information processing device 1 utilizes these differences in frequency characteristics to perform calculations that separate the influence of moisture content within the material (first influence) from the influence of density and defects in the material (second influence) from the signal components contained in the measurement data. Based on the separated second influence component, it obtains more accurate information about the internal structure, such as the density distribution and the presence or absence of defects, of the material, with the influence of moisture removed. In this analysis process, as will be described later, position acquisition in the depth direction and mapping processing of measurement results are also performed.

[0093] Finally, in step S106, the analysis results are notified to the user. The notified results include, for example, the separated moisture distribution map and density / defect distribution map, the location and size of detected defects, or information on the quality and strength of the material estimated based on these. This allows the user to accurately understand the internal state of the material. This concludes the series of processes of this service.

[0094] Furthermore, in one embodiment of this service, depth information is acquired during the analysis process in step S105. Specifically, the information processing device 1 applies mathematical processing such as an inverse Fourier transform to the complex spectrum (frequency domain data including amplitude and phase information) obtained from the measurement results of each of the multiple frequency bands. This converts the frequency domain data into time domain data. This time domain data includes information on the time delay from when the millimeter wave is transmitted until it is reflected (or transmitted) by each interface and scatterer inside the material and received. The information processing device 1 converts the time axis in this time domain data to the distance axis using the propagation speed of electromagnetic waves determined from the relative permittivity of the material. This obtains the reflection intensity distribution in the depth direction of the material. This process makes it possible to grasp in three dimensions where density changes and defects exist at which depths inside the material.

[0095] Furthermore, in one embodiment of this service, as described above, the arrangement of millimeter wave transmission and reception can be switched in the condition setting of step S101 in Figure 29. That is, the measurement system is configured to support both a transmission-type arrangement in which the transmitting unit and the receiving unit are positioned opposite each other with the material in between, and a reflection-type arrangement in which the transmitting unit and the receiving unit are positioned on the same side of the material. Once either arrangement is selected in step S101 according to the application, in the measurement in step S102, millimeter wave transmission and reception are performed in the selected arrangement. This makes it possible to perform flexible measurements according to the situation, for example, by using the transmission-type arrangement to perform high-precision measurements of the entire interior of lumber before sawing or materials with relatively small thickness, while using the reflection-type arrangement to perform internal inspections with access from one side for lumber such as columns and walls already used in buildings.

[0096] Furthermore, in one embodiment of this service, the measurement in step S102 can be performed while controlling the polarization direction of the millimeter waves. For example, the measurement can be performed while rotating the polarization plane of the millimeter waves radiated from the transmitter, or while switching between horizontal and vertical polarization. Then, in the analysis process in step S105, the information processing device 1 performs an analysis based on the results measured while changing the polarization direction. Materials with a fibrous structure, such as wood, have anisotropy, where the dielectric properties differ between the fiber direction and other directions. The information processing device 1 utilizes the difference in measurement results depending on the polarization direction to acquire information about the anisotropy of the material (for example, the fiber direction of wood and the disorder of its orientation) as information about the inside of the material. This makes it possible to evaluate not only information about density and defects, but also information about anisotropy, which greatly affects the strength characteristics of the material.

[0097] Furthermore, in one embodiment of this service, the measurement in step S102 can be performed while moving the irradiation position by transmitting millimeter waves to the material. For example, by using a moving mechanism to scan the transmitting and receiving units along the surface of the material, or by moving the material itself, a predetermined area of ​​the material can be measured surface-wise. Then, in the analysis process of step S105, the information processing device 1 acquires a two-dimensional distribution map of the material as information about the inside of the material, based on the results at a number of points measured while moving the irradiation position. This map includes, for example, a two-dimensional distribution of separated water content, or a two-dimensional distribution of density and defects. This makes it possible to visually grasp the distribution of characteristics inside the material as a surface, and to easily identify the location and extent of defects.

[0098] Furthermore, in one embodiment of this service, in the measurement in step S102, the material can be measured while changing the relative positions of the millimeter-wave transmitter and the millimeter-wave receiver. For example, millimeter waves are irradiated onto the material from various angles to acquire transmission data and reflection data. Then, in the analysis process in step S105, the information processing device 1 utilizes the results of multiple measurements taken from different relative positions (angles). The information processing device 1 applies, for example, the principle of tomosynthesis (tomography) to this data and performs a process of offsetting and superimposing each data to correspond to the depth of interest. This generates a three-dimensional image of the inside of the material as information about the inside of the material. This makes it possible to visualize the density distribution and the three-dimensional arrangement of defects inside the material in three dimensions, enabling a more detailed and intuitive evaluation.

[0099] The configuration of the information processing system to which the information processing device 1, an embodiment of the information processing device of the present invention, is applied, is similar to that of the first embodiment, and is exemplified by the configuration of the information processing system shown in Figure 2.

[0100] Figure 30 is a functional block diagram showing an example of the functional configuration of the information processing device 1 according to the second embodiment of the present invention.

[0101] As shown in Figure 30, the CPU 11 of the information processing device 1 includes a device control unit 151, a measurement data receiving unit 152, a time-domain conversion unit 153, a material internal structure acquisition unit 154, an anisotropy information acquisition unit 155, a mapping unit 156, and a three-dimensional image generation unit 157. In addition, one area of ​​the storage unit 18 of the information processing device 1 is provided with a measurement condition DB 71, a measurement data DB 72, a material properties DB 73, a reflectance intensity distribution DB 74, a material internal information DB 75, an anisotropy information DB 76, a two-dimensional map DB 77, and a three-dimensional image DB 78.

[0102] The device control unit 151 extracts information regarding measurement conditions from the measurement condition DB 71 in the storage unit 18, and controls the operation of the transmission unit 2, reception unit 3, sample stage 4, moving mechanism unit 5, and measurement unit 6 based on these measurement conditions. Specifically, as explained in steps S101 and S102 of Figure 29, for example, the device control unit 151 controls each unit to perform actions such as switching between transmission and reflection configurations, transmitting and receiving millimeter waves across multiple frequency bands, controlling the polarization direction, and moving the irradiation position and relative position. This enables flexible measurements according to the application and data collection to understand the anisotropy and two-dimensional and three-dimensional structure of materials.

[0103] The measurement data receiving unit 152 receives the measurement results (complex spectral data) of the amplitude and phase of millimeter waves in each of the multiple frequency bands, measured by the measurement unit 6, via the input / output interface 15. Specifically, for example, in step S104 of Figure 29, the measurement data receiving unit 152 receives the measurement data uploaded to the information processing device 1. The measurement data receiving unit 152 then stores the received measurement data in the measurement data DB 72.

[0104] The time-domain conversion unit 153 extracts the measurement results (complex spectra) for each of the multiple frequency bands from the measurement data DB 72 and converts them into time-domain data by applying an inverse Fourier transform to the complex spectra. Specifically, for example, as part of the analysis process in step S105 of Figure 29, the time-domain conversion unit 153 performs a process to convert frequency domain data into time-domain impulse response data. The time-domain conversion unit 153 then stores the obtained time-domain data (or reflection intensity distribution data obtained by converting it to distance in a process described later) in the reflection intensity distribution DB 74.

[0105] The material internal structure acquisition unit 154 separates the first influence due to water content within the material and the second influence due to the density and defects of the material based on the frequency dependence of the measurement results for each of the multiple frequency bands extracted from the measurement data DB 72, and acquires information about the inside of the material based on the second influence. Specifically, it utilizes the characteristics of water (free water and bound water), which exhibit high dielectric loss and low frequency dependence over a wide bandwidth, while density and defects tend to exhibit frequency selectivity such as scattering and resonance. The material internal structure acquisition unit 154 extracts spectral signatures of water-dominant response and density / defect-dominant response from the measurement data in multiple frequency bands, and performs factor separation processing based on the differences in their frequency dependence. In addition, the material internal structure acquisition unit 154 acquires the reflectance intensity distribution in the depth direction of the material based on time-domain data extracted from the reflectance intensity distribution DB 74. Specifically, for example, in step S105 of Figure 29, the material internal structure acquisition unit 154 performs factor separation by utilizing the difference between the broadband loss characteristics of water and the frequency-selective scattering characteristics of density and defects. Furthermore, it converts time-domain data into distance using the relative permittivity of the material (extractable from the material properties DB 73) to identify the density distribution and defect locations at each depth. The material internal structure acquisition unit 154 then stores the acquired information about the inside of the material (separated density / defect information, depth information, etc.) in the material internal information DB 75. This makes it possible to evaluate the effects of water content and density / defects separately, and to understand the three-dimensional structure inside the material.

[0106] The anisotropy information acquisition unit 155 extracts the measurement results from the measurement data DB 72 while changing the polarization direction, and based on this, acquires information about the anisotropy of the material as information about the inside of the material. Specifically, for example, using the data acquired by controlling the polarization direction in step S102 of Figure 29, in the analysis of step S105, the anisotropy information acquisition unit 155 analyzes the difference in response between the fiber direction and the direction perpendicular to it to identify the fiber orientation and disorder of the wood. Then, the anisotropy information acquisition unit 155 stores the acquired anisotropy information in the anisotropy information DB 76. This makes it possible to acquire anisotropy information that greatly affects the strength characteristics of the material.

[0107] The mapping unit 156 extracts information from the material internal information DB 75 or anisotropy information DB 76, which are generated based on the results measured while the irradiation position is moved by the moving mechanism unit 5. Based on this information, it obtains a two-dimensional distribution map of the material as information about the inside of the material. Specifically, for example, in step S105 of Figure 29, the mapping unit 156 maps the analysis results (separated density index, presence or absence of defects, fiber direction, etc.) at each scanning position on the material surface onto a plane to generate a water content distribution map, a density / defect distribution map, etc. The mapping unit 156 then stores the generated two-dimensional distribution map in the two-dimensional map DB 77. This makes it possible to grasp the density distribution and spatial extent of defects inside the material in a planar manner.

[0108] The 3D image generation unit 157 generates a 3D image of the inside of a material as information about the inside of the material by offsetting and superimposing the results of multiple measurements (extracted from the measurement data DB 72 or the reflectance intensity distribution DB 74) taken while changing the relative positions of the transmission unit 2 and the reception unit 3, so as to correspond to the depth of interest. Specifically, for example, in step S105 of Figure 29, the 3D image generation unit 157 performs reconstruction processing such as tomosynthesis using transmission data acquired from different angles to generate data that visualizes the three-dimensional structure inside the material. The 3D image generation unit 157 then stores the generated 3D image in the 3D image DB 78. This makes it possible to grasp in detail the density distribution and the three-dimensional arrangement of defects inside the material.

[0109] Figure 31 is a schematic diagram showing the measurement configuration of the wood non-destructive testing system of the present invention. A transmitting and receiving antenna 2 connected to a Vector Network Analyzer (VNA) is positioned at the top, and a cylindrical piece of wood W to be measured is placed below it. The VNA has the function of acquiring the amplitude and phase of the measurement signal as a complex spectrum (hereinafter sometimes referred to as "I / Q") for each frequency band using the Stepped Frequency Continuous Wave (SFCW) method. In the SFCW method, a continuous wave is transmitted while gradually changing the frequency, and the reflection coefficient and transmission coefficient at each frequency are measured as complex numbers, making it possible to acquire both amplitude information and phase information with high accuracy. A receiving unit 3 is positioned at the bottom, enabling transmission measurement. This configuration makes it possible to illuminate the wood (W) with radar while varying multiple frequency bands and acquire scan data over an area.

[0110] Figure 32 is a photograph showing the actual cylindrical piece of wood W used in the measurement configuration of Figure 31 (the object of measurement in step S102 of Figure 29). Inserted into the top surface of the wood W is a hardwood rod with a density higher than that of the wood W. This can be considered a knot. The "high-density hardwood rod" considered to be a knot is clearly separated from the other parts. Furthermore, a clear annual ring structure can be observed in the wood W, and the non-uniformity of the fiber direction and density distribution can be confirmed. In conventional single-frequency measurements, it was difficult to separate the effects of moisture from the effects of density and knots, but by applying multi-frequency measurements to this wood W, it is possible to separate and obtain moisture and the physical properties of the wood. Measurement data is collected from this wood W by the measurement data receiving unit 152 of Figure 30.

[0111] Figure 33 is a two-dimensional map showing the measurement results of the cylindrical wood in Figure 32. The wood W in Figure 32 was measured using the measurement configuration in Figure 31, and the image was reconstructed from data obtained by multi-frequency VNA measurement (analysis processing result of step S105 in Figure 29). The X and Y axes represent the position on the surface (range from -50 to +50), and the color bar on the Z axis shows the attenuation coefficient (ATTENUATION COEFFICIENT, range from 0 to 4). The bright area in the center showing a high attenuation coefficient is an image of the dense hardwood rod inserted into the wood W in Figure 32. Since the dense hardwood rod has a higher density than the wood W, the electromagnetic wave attenuation is greater, and it is displayed as the brightest part in this reconstructed image. The dark area around it represents the internal structure of the wood W. The distribution of physical properties inside the wood W is visualized by a separation technique that utilizes the characteristics that water has a broadband dielectric loss and low frequency dependence, while density and defects are frequency selective. The material internal structure acquisition unit 154 and the time-domain conversion unit 153 shown in Figure 30 perform this three-dimensional reconstruction process.

[0112] Figure 34 is a photograph of a glued laminated timber (a member such as a beam or column, laminated with the fiber direction in the same direction, hereinafter referred to as "general glued laminated timber") that is the target of measurement in the wood non-destructive testing system of the present invention (the target of measurement in step S102 of Figure 29). A board-shaped glued laminated timber is shown, and a clear wood grain pattern and multiple knots can be observed on the surface. General glued laminated timber is a structural material in which multiple layers of wood are laminated in parallel, and the quality and bonding state of each layer greatly affect the overall strength characteristics. Such a practical structural material has been selected as the target of application of the technology to separate the effects of moisture from the effects of density and knots. By achieving the separation of moisture and the physical properties of wood, which was difficult with conventional single-frequency measurement, through multi-frequency measurement, it is expected that the accuracy of quality evaluation of general glued laminated timber will be improved. The device control unit 151 in Figure 30 controls the measurement of such wood.

[0113] Figure 35 is an image showing the measurement results for a typical laminated timber from Figure 34 mapped to voltage values ​​(0.00-2.00V) (analysis processing and mapping results from step S105 in Figure 29). Multiple regions enclosed by dotted lines identify various characteristic parts inside the typical laminated timber. The quality distribution inside the CLT is visualized by a measurement technique that utilizes the characteristics of moisture, which has high dielectric loss over a wide bandwidth and is greatly attenuated in any frequency band, and density and defects, which tend to exhibit frequency selectivity. The changes in grayscale intensity represent changes in the electrical properties inside the wood W and include information such as moisture distribution, density changes, and the state of the adhesive layer. This two-dimensional distribution map is generated by the mapping unit 156 in Figure 30. This measurement result makes it possible to non-destructively evaluate the manufacturing quality and suitability for use of typical laminated timber.

[0114] Figure 36 shows data obtained using X-rays for the typical laminated timber shown in Figure 34. It is intended for comparison with the data in Figure 35, which was measured using millimeter waves. Numerous regions enclosed by dotted lines identify fine structural changes within the typical laminated timber with high resolution. Comparing Figure 35 and Figure 36, it can be seen that areas of high density are extracted at almost the same locations. Incidentally, there is a significant difference in the danger to the human body between millimeter waves and X-rays. X-rays, as ionizing radiation, cause direct damage at the cellular level, and the risk of cancer and genetic effects has been scientifically established. On the other hand, millimeter waves are non-ionizing radiation, and when used at appropriate power levels, the effects are mainly limited to thermal effects, and no serious health effects have been reported under current safety standards. Thus, a non-destructive testing system using millimeter waves, which are superior in safety, has been realized, and it can be confirmed that the technical goal of obtaining pure physical property values ​​of wood W by removing the influence of moisture has been achieved by this detailed mapping. By using a technology to separate the effects of moisture and density through multi-frequency measurement, it is possible to detect internal defects and quality changes that are difficult to find with conventional visual inspection. In Figure 30, the material internal structure acquisition unit 154 performs a factor separation process based on frequency dependence, and the mapping unit 156 generates a detailed two-dimensional map. The factor separation process first detects signals at each frequency, and then reduces signals common to all frequencies, such as signals of a certain intensity, from each signal. As described above, signals caused by moisture are common to angular frequencies, so by reducing the contribution of moisture to angular frequencies, it becomes possible to verify the density distribution without being affected by moisture. This highly accurate quality evaluation technology makes an important contribution to improving the reliability of general laminated materials and expanding their application as building structural materials. For example, even with wood that is not yet sufficiently dried, it is possible to predict the density distribution of the wood when it has been dried to a predetermined level, and to predict the strength of the wood.

[0115] Figure 37 is a composite measurement map for a surface material (Cross Laminated Timber: hereinafter referred to as "CLT") made by laminating and bonding large 2000 × 210 × 90 mm boards (laminae) with the fiber directions perpendicular to each other (this is the result of the surface scanning measurement in step S102 and the composite analysis in step S105 of Figure 29). The measurement was performed by dividing it into three segments, and the voltage values ​​are displayed in a wide range of 0-10.54V. Multi-frequency measurement technology makes it possible to non-destructively evaluate the internal quality of such large structural materials. By utilizing the high dielectric loss characteristics of moisture over a wide bandwidth and the frequency selectivity of density and defects, the quality distribution throughout the CLT material is quantitatively understood. The device control unit 151 in Figure 30 controls the scanning of the large piece of wood W, and the mapping unit 156 generates the composite measurement map. This large material measurement technology is a practical technology that can be directly applied to quality control at actual construction sites and quality assurance in manufacturing processes.

[0116] Figure 38 shows the analysis results related to moisture content, which are a more detailed analysis of the CLT measurement results in Figure 37 (the result of the factor separation analysis in step S105 of Figure 29). Numerical data (12.53, 7.97, 17.10, 14.52, etc.) for each measurement segment (6m_24_B, 6m_24_D, 6m_24_B-D) are displayed, and the quality distribution is visualized in the voltage range of 0.0-2.5V. By utilizing the characteristics of moisture, which has high dielectric loss over a wide bandwidth and low frequency dependence, the analysis results show the separation of the effect of moisture. The material internal structure acquisition unit 154 in Figure 30 performs a separation process of the first effect (moisture content) and the second effect (density / defects) based on frequency dependence. This analysis makes it possible to quantitatively evaluate the moisture distribution inside the CLT material and obtain the pure physical properties of wood W. By quality evaluation that removes the effect of moisture, the true structural and strength characteristics of the CLT material can be accurately grasped.

[0117] Figure 39 shows the moisture content analysis results for another CLT (0m_17 series) (comparative analysis results from step S105 in Figure 29). Numerical data (10.32, 11.22, 14.75, 12.61, 16.92, 8.02, 9.83, 12.58, etc.) for the measurement segments (0m_17_B, 0m_17_D, 0m_17_B-D) are displayed, and the voltage values ​​are shown in the range of 0-20V. By using a technique to separate the effects of moisture from the effects of density and nodes, the moisture content distribution of a CLT with different characteristics from the CLT in Figure 38 is quantitatively evaluated. The material internal structure acquisition unit 154 in Figure 30 performs factor separation processing between multiple samples, and the data is stored in the material internal information DB 75. This comparative analysis makes it possible to accurately grasp the individual differences in CLT and quality changes due to differences in manufacturing conditions, while removing the effects of moisture. This technology contributes to establishing quality standards for CLT and optimizing the manufacturing process by accumulating multiple data points.

[0118] Figure 40 is a photograph of the measuring device when the non-destructive testing system of the present invention is applied to reinforced concrete (corresponding to the measurement preparation and condition setting in step S101 and the millimeter-wave scanning measurement in step S102 of Figure 29). The transmitting antenna and receiving antenna are appropriately positioned for a structure in which reinforcing bars are placed inside a concrete block. The measuring device is covered with a radio wave absorber to block external electromagnetic noise and enable precise measurement. The device control unit 151 in Figure 30 controls the measurement of such a large concrete structure, switching between transmission type and reflection type configurations, and transmitting and receiving millimeter waves across multiple frequency bands. The relative permittivity of concrete is approximately 6, and the time-domain conversion unit 153 in Figure 30 uses this value to convert from the time axis to the distance axis. This device configuration demonstrates that this technology can be applied not only to wood but also to reinforced concrete.

[0119] Figure 41 shows the results of a two-dimensional analysis obtained by measuring reflection parameters for a reinforced concrete structure (analysis processing results from step S105 in Figure 29). The horizontal axis represents position (0-0.8 m), the vertical axis represents depth (0-250 mm), and the grayscale bars represent amplitude values ​​(0 to 0.0014). The relative permittivity of concrete (approximately 6) is used to convert from the time axis to the distance axis, and information in the depth direction is obtained. The time-domain conversion unit 153 in Figure 30 applies an inverse Fourier transform to the measurement results (complex spectra) of multiple frequency bands, converting them into time-domain data. Furthermore, the material internal structure acquisition unit 154 converts the time-domain data into distance using the relative permittivity of the material, and the reflection intensity distribution for each depth is identified. The light and dark patterns in the image reflect the position of reinforcing bars inside the reinforced concrete, changes in concrete density, voids, defects, etc. This technology enables detailed non-destructive evaluation of the internal structure, which was previously difficult, in quality control and deterioration diagnosis of building structures. The material internal information DB75 in Figure 30 stores such analysis results and is used for safety evaluation of structures.

[0120] Figure 42 shows the 3D analysis results corresponding to the 2D analysis results shown in Figure 41. Areas with particularly strong reactions have been extracted in 3D and converted into mesh data. Both the longitudinal and transverse directions of the reinforcing bars are imaged. While not apparent in Figure 41, the reaction of the transverse reinforcement becomes clear only after 3D visualization.

[0121] Although one embodiment of the present invention has been described above, the present invention is not limited to the embodiments described above, and any modifications, improvements, etc. that can achieve the objectives of the present invention are considered to be included in the present invention.

[0122] Furthermore, the system configurations shown in Figures 1, 2, and 31, and the hardware configuration of the information processing device 1 shown in Figure 27, are merely illustrative examples for achieving the objectives of the present invention and are not particularly limited.

[0123] Furthermore, the functional block diagrams shown in Figures 28 and 30 are merely illustrative and not particularly limiting. In other words, it is sufficient that the information processing device in Figure 2 is equipped with the functionality to execute the various processes described above as a whole, and the functional blocks and databases used to realize this functionality are not particularly limited to the examples in these figures.

[0124] Furthermore, the location of the functional blocks and database is not limited to Figure 28 or Figure 30, but can be any location. For example, at least a portion of the functional blocks and database located on the information processing device 1 side may be provided by another information processing device not shown.

[0125] Furthermore, the series of processes described above can be executed by hardware or by software. Also, a single functional block may consist of hardware alone, software alone, or a combination of both.

[0126] When a series of processes are executed by software, the programs that make up that software are installed on a computer or other device from a network or storage medium. The computer may be a computer built into dedicated hardware. Alternatively, the computer may be a computer capable of performing various functions by installing various programs, such as an information processing device, a general-purpose smartphone, or a personal computer.

[0127] Such recording media containing programs may consist not only of removable media (not shown) distributed separately from the main unit of the device to provide the program to the user, but also of recording media provided to the user in a state where they are pre-installed in the main unit of the device.

[0128] In this specification, the step of describing a program to be recorded on a recording medium includes not only processes that are performed chronologically in that order, but also processes that are not necessarily performed chronologically, but are executed in parallel or individually.

[0129] In summary, the information processing device to which the present invention applies only needs to have the following configuration, and can take various forms. In other words, the information processing device to which the present invention applies (for example, the information processing device 1 in Figures 2, 28, and 30) is a non-destructive testing system for non-destructively inspecting the internal structure of a material (for example, the system in Figures 1, 2, 28, and 30), comprising: a millimeter-wave transmitting unit (for example, the transmitting unit 2 in Figure 30) that transmits millimeter waves of multiple frequency bands to the material (for example, wood W); a millimeter-wave receiving unit (for example, the receiving unit 3 in Figure 30) that receives the millimeter waves transmitted or reflected by the material; a millimeter-wave measuring unit (for example, the measuring unit 6 in Figure 30) that measures the amplitude and phase of the received millimeter waves for each of the multiple frequency bands; and a material internal structure acquisition unit (for example, the material internal structure acquisition unit 154 in Figure 30, step S105 in Figure 29) that separates a first effect due to water content inside the material and a second effect due to the density and defects of the material based on the frequency dependence of the measurement results for each of the multiple frequency bands, and acquires information about the inside of the material based on the second effect. Having that will suffice.

[0130] In this way, by utilizing the differences in the frequency dependence of measurement data across multiple frequency bands, it becomes possible to separately evaluate the effects of water content and density / defects within materials such as wood.

[0131] Furthermore, the millimeter-wave measurement unit (for example, the time-domain conversion unit 153 in Figure 30) can convert the results of the measurements for each of the multiple frequency bands into time-domain data by applying an inverse Fourier transform to the complex spectra obtained from the results of the measurements for each of the multiple frequency bands, and the material internal structure acquisition unit (for example, the material internal structure acquisition unit 154 in Figure 30) can acquire the reflectance intensity distribution in the depth direction of the material (for example, the B-scan image in Figure 38) based on the time-domain data.

[0132] This allows the data to be converted into time-domain data using an inverse Fourier transform, and based on this time-domain data, the reflectance intensity distribution in the depth direction of the material can be obtained, enabling a three-dimensional understanding of the internal structure of the material.

[0133] Furthermore, the millimeter-wave transmitting unit (for example, transmitting unit 2 in Figure 30) and the millimeter-wave receiving unit (for example, receiving unit 3 in Figure 30) can be switched to either a transmissive configuration (for example, the configuration in Figure 31) where they are positioned opposite each other across the material, or a reflective configuration (for example, the configuration in Figure 40) where they are positioned on the same side of the material (for example, controlled by the device control unit 151 in Figure 30, step S101 in Figure 29).

[0134] This allows for flexible measurements tailored to the application by switching between transmissive and reflective configurations.

[0135] Furthermore, the millimeter-wave transmitting unit (for example, transmitting unit 2 in Figure 30) and the millimeter-wave receiving unit (for example, receiving unit 3 in Figure 30) are capable of controlling the polarization direction of the millimeter waves (for example, control by the device control unit 151 in Figure 30, the rotation mechanism in Figure 31), and the material internal structure acquisition unit (for example, anisotropy information acquisition unit 155 in Figure 30) can acquire information regarding the anisotropy of the material as information concerning the inside of the material, based on the results of the measurement taken while changing the polarization direction.

[0136] This makes it possible to obtain information about the anisotropy within a material by controlling the polarization direction during measurement.

[0137] Furthermore, the system further includes a moving mechanism (for example, the moving mechanism 5 in Figure 30) for moving the irradiation position by transmitting millimeter waves to the material, and the material internal structure acquisition unit (for example, the mapping unit 156 in Figure 30) can acquire a two-dimensional distribution map of the material (for example, the maps in Figures 35 to 39) as information about the inside of the material, based on the measurement results measured while moving the irradiation position by the moving mechanism.

[0138] This allows for the acquisition of a two-dimensional distribution map of the entire substance, rather than a single-point measurement, by moving the irradiation position using the moving mechanism.

[0139] Furthermore, the measurement of the material is performed while changing the relative positions of the millimeter-wave transmitting unit (for example, transmitting unit 2 in Figure 30) and the millimeter-wave receiving unit (for example, receiving unit 3 in Figure 30) (for example, controlled by the device control unit 151 in Figure 30, rotating stage in Figure 31). The material internal structure acquisition unit (for example, the 3D image generation unit 157 in Figure 30) generates a 3D image of the inside of the material (for example, the reconstructed image in Figure 33) as information about the inside of the material by offsetting and superimposing the results of multiple measurements taken from different relative positions to correspond to the depth of interest.

[0140] This makes it possible to generate a three-dimensional image of the inside of a material by superimposing measurement data from different angles using the principle of tomosynthesis.

[0141] Furthermore, the millimeter-wave measurement unit (for example, measurement unit 6 in Figure 30) may include a vector network analyzer.

[0142] This makes it possible to measure the amplitude and phase of millimeter waves in multiple frequency bands with high precision using a vector network analyzer.

[0143] S...Non-destructive testing system, 1...Information processing device, 2...Transmitter, 3...Receiver, 4...Sample stage, 5...Moving mechanism, 6...Measurement unit, 11...CPU, 12...ROM, 13...RAM, 14...Bus, 15...Input / output interface, 16...Input unit, 17...Output unit, 18...Storage unit, 18A...Drive, 18B...Removable media, 19...Communication unit, 21...Transmitter, 22...Swivel mechanism, 23...Polarization filter, 31...Receiver, 32...Swivel mechanism, 33...Polarization detection element, 51...Actuator (changes the position of the transmitter and receiver), 52...Actuator (moves the sample stage), 53...Controller, 61...Lock-in amplifier, 62... Data acquisition device (DAQ), 71...Measurement conditions DB, 72...Measurement data DB, 73...Material properties DB, 74...Reflection intensity distribution DB, 75...Material internal information DB, 76...Anisotropy information DB, 77...2D map DB, 78...3D image DB, 101...Position acquisition unit, 102...Density distribution acquisition unit, 103...Evaluation unit, 104...Dielectric constant anisotropy distribution acquisition unit, 105...Node distribution acquisition unit, 106...Fiber direction acquisition unit, 107...Intensity prediction unit, 108...Image composition unit, 151...Device control unit, 152...Measurement data reception unit, 153...Time domain conversion unit, 154...Material internal structure acquisition unit, 155...Anisotropy information acquisition unit, 156...Mapping unit, 157...3D image generation unit, W...Wood.

Claims

1. A non-destructive testing system for non-destructively inspecting the internal structure of a material, comprising: a transmitting unit that generates and transmits millimeter waves to the outside to irradiate the material with the millimeter waves; a receiving unit that receives the millimeter waves irradiated from the transmitting unit to the material and transmitted through the material, and outputs a transmission signal based on the millimeter waves; a measuring unit that measures the intensity of the transmission signal; an information processing unit that performs information processing using the measured intensity of the transmission signal; and a moving mechanism unit that moves the irradiation position of the millimeter waves to the material in a predetermined direction, wherein the information processing unit comprises: a position acquisition means that sequentially acquires the two-dimensional position in the material where the millimeter waves are irradiated while the irradiation position is being moved by the moving mechanism unit; and a density distribution acquisition means that acquires the density distribution inside the material based on the intensity of the transmission signal at each timing in which the position is acquired by the position acquisition means.

2. The non-destructive testing system according to claim 1, wherein the transmitting unit generates millimeter waves of a predetermined frequency determined according to the measurement depth or thickness of the material.

3. The non-destructive testing system according to claim 1, further comprising: an information processing unit; an evaluation means for evaluating the spatial distribution of the material properties of the substance based on the density distribution obtained by the density distribution acquisition means.

4. The non-destructive testing system according to claim 3, wherein the measuring unit measures the intensity of the transmitted signal with the polarization direction of the transmitting unit set to a predetermined first direction and the polarization direction of the receiving unit set to a predetermined second direction, the information processing unit further includes dielectric anisotropy distribution acquisition means for acquiring the spatial distribution of dielectric anisotropy based on the polarization direction of the transmitting unit and the measured intensity of the transmitted signal, and the evaluation means performs the evaluation based on the density distribution and the spatial distribution of dielectric anisotropy.

5. The non-destructive testing system according to claim 3, wherein the material is wood, the transmitting unit and the receiving unit are arranged such that their respective polarization directions are orthogonal to each other, the information processing unit further comprises a knot distribution acquisition means for acquiring the distribution of knots inside the wood by detecting locations in the density distribution where the intensity of the transmitted signal shows abrupt changes, and the evaluation means performs the evaluation based on the density distribution and the knot distribution.

6. The non-destructive testing system according to claim 4, wherein the material is wood, the information processing unit further comprises fiber direction acquisition means for acquiring the distribution of the fiber direction of the wood based on the spatial distribution of the dielectric anisotropy acquired by the dielectric anisotropy distribution acquisition means, and the evaluation means performs the evaluation based on the density distribution and the distribution of the fiber direction.

7. The non-destructive testing system according to claim 6, wherein the information processing unit further comprises strength prediction means for predicting the strength of the wood based on the density distribution and the fiber direction distribution.

8. The non-destructive testing system according to claim 1, wherein the information processing unit has an image constructing means for constructing a three-dimensional image of the inside of a material by offsetting and superimposing a plurality of transmission signals measured from different angles relative to the material so as to correspond to the depth of interest.

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