Inspection Equipment

Abstract

To provide an inspection device capable of inspecting non-uniformity or the like of material substances in an object to be inspected, targeting a wider range of materials than before, in a shorter time than before.SOLUTION: An inspection device includes: a transmitting / receiving antenna 4 that radiates a millimeter wave 2 toward an object 1 to be inspected and receives a reflected wave signal 3; a transmitting / receiving circuit 5 connected to the transmitting / receiving antenna 4; a motorized stage 6 that moves the object 1 to be inspected; and synthetic aperture processing means for performing synthetic aperture processing using a plurality of reflected wave signals received at a plurality of relatively different positions between the object 1 to be inspected and the transmitting / receiving antenna 4, and their position data. The inspection device obtains distribution of an amount of phase shift by the object 1 to be inspected and thereby evaluates distribution in an xy plane of substances forming the object to be measured.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inspection device that irradiates an object with electromagnetic waves such as microwaves or millimeter waves in order to inspect the non-uniformity of materials constituting the object, and determines the phase distribution shape of the reflected waves that pass through the object and are reflected back. [Background technology]

[0002] In the manufacturing process of various industrial products or in the inspection and evaluation of completed products, when the materials constituting the products are created by mixing, synthesizing, or the like, multiple substances, it is necessary to understand whether the mixing state, density distribution, dispersion state, etc. of these substances are as designed or within an acceptable range. Conventionally, such evaluations have been performed using various measurement means and various analytical and evaluation methods for each individual product. Examples include a method of collecting samples from each location and performing a gravimetric analysis, a method using optical transmittance or reflectance, and an analytical and evaluation method using images captured by a camera, optical microscope, scanning microscope, X-ray, or the like. Patent Document 1 describes an evaluation method for quantitatively evaluating the distribution state of specific points over a wide range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-202729 Summary of the Invention [Problem to be solved by the invention]

[0004] In cases where it is necessary to immediately feed back inspection results such as unevenness of materials within an object to correct the material mixing process, or when it is necessary to inspect many products in the inspection process of manufactured finished products, the above inspections must be performed in a short time. Conventional methods of collecting samples or evaluation methods using images, etc., take time to produce inspection results and are not suitable for the above purposes. In addition, optical evaluation is limited in the objects that can be evaluated, making it difficult to apply to a wide range of materials.

[0005] Therefore, the present invention has been made to solve such problems, and aims to provide an inspection device that can inspect a wider range of materials than conventionally possible and inspect the non-uniformity of material substances in an object to be inspected in a shorter time than conventionally possible. [Means for solving the problem]

[0006] In a first aspect, the inspection device of the present invention comprises: means for emitting electromagnetic waves toward the surface of an object to be inspected, the object being composed of a single or multiple substances, at a plurality of relatively different positions relative to the object, and receiving reflected wave signals of the electromagnetic waves including waves reflected from the back surface of the object to be inspected; synthetic aperture processing means for performing synthetic aperture processing using the received reflected wave signals and position data indicating the plurality of relatively different positions; and means for determining, by the synthetic aperture processing means, a distribution of phase shift amounts of the reflected wave signals due to the presence of the object to be inspected, and is characterized in that the distribution of phase shift amounts is used to evaluate the in-plane distribution of the substances in the object to be inspected in a direction parallel to the surface.

[0007] In the present invention, electromagnetic waves refer to microwaves, millimeter waves, or terahertz waves. Generally, microwaves have a frequency range of 0.3 to 30 GHz, millimeter waves have a frequency range of 30 to 300 GHz, and terahertz waves have a frequency range of 300 GHz to 10 THz. In the present invention, as described above, electromagnetic waves are emitted toward the surface of an object to be inspected, and a reflected wave signal including a wave reflected from at least the back surface of the object is received. If the thickness of the object to be inspected is approximately uniform, the phase of the received electromagnetic wave will change if there are portions with different dielectric constants in the object. In the present invention, materials with different dielectric constants are detected as differences in the amount of phase shift. Different densities of the materials in the object to be inspected can also be detected as differences in the amount of phase shift. Furthermore, if materials with different reflectivities of the electromagnetic wave are present on the surface or inside the object, the reflection positions will be different, and this can also be detected as a change in the phase of the reflected wave. In other words, the present invention can determine the in-plane distribution of electromagnetic waves in the object to be inspected for a wide range of materials with different dielectric constants and reflectivities. Furthermore, the present invention uses synthetic aperture processing technology to determine the two-dimensional distribution shape of the in-plane direction of the object under inspection with high resolution. In the present invention, synthetic aperture processing is performed using multiple reflected wave signals received by transmitting and receiving antennas of electromagnetic waves at different positions relative to the object under inspection, thereby enabling detection with significantly higher resolution than when the shape of the electromagnetic waves is simply determined from the distribution of the intensity and phase of the reflected waves. In other words, the two-dimensional in-plane distribution of the abundance of a non-uniform material, etc., integrated in the thickness direction within the object under inspection can be detected with high resolution. Furthermore, even if materials with different dielectric constants and reflectivities exist within the object, their positions within the plane can be detected.

[0008] The object to be inspected has one or more substances as its constituent elements, and the present invention evaluates the distribution of one or more of the constituent substances within the object to be inspected. For example, the density distribution, dispersion state, localized areas, etc. of the substance can be evaluated. The target substance, the accuracy of the distribution shape, whether or not quantification is required, etc. can be selected depending on the evaluation items required for the object to be inspected.

[0009] In the present invention, the phase shift due to the presence of an object to be inspected refers to the amount of change in the phase of the reflected wave signal caused by the electromagnetic wave being reflected on the surface or inside of the object to be inspected, or by the electromagnetic wave passing through the object and being reflected on the back surface, when compared with the phase of the reflected wave signal of the electromagnetic wave when there is no object to be inspected but a reflector is present on the back surface of the object. In order to perform synthetic aperture processing, the electromagnetic wave transmitting and receiving antennas used must have a relatively wide radiation angle, and for example, a probe antenna, patch antenna, horn antenna, etc. can be used. It is also possible to use transmitting and receiving antennas for millimeter-wave radar used in vehicles, etc.

[0010] In the present invention, to perform synthetic aperture processing, electromagnetic wave signals at relatively different positions between the object to be inspected and the transmitting and receiving antennas of the electromagnetic waves are required, but as means for emitting electromagnetic waves to the object to be inspected from a plurality of transmitting and receiving antennas at relatively different positions and receiving reflected waves, either means for moving at least one of the transmitting and receiving antennas or the object to be inspected, or means for providing a plurality of transmitting and receiving antennas, or both of these means may be provided. In other words, either or both of the object to be inspected and the transmitting and receiving antennas may be moved, or a plurality of transmitting and receiving antennas may be arranged, as long as the electromagnetic waves are irradiated over the entire required inspection area.

[0011] In synthetic aperture processing, for example, the reflection position in the range direction can be determined using an FM-CW radar system or the like. In this case, an electromagnetic wave reflector is installed in advance at a reference position where the object to be inspected is located, and the reflected signal of the electromagnetic wave is acquired. By referring to this signal, the reflection position within the object to be inspected can be determined more accurately, achieving higher resolution. As an example of synthetic aperture processing in the azimuth direction, range migration correction is performed, and the complex conjugate of the transfer function at each range position is analytically generated from the measurement conditions. This is then used as a two-dimensional or one-dimensional reference signal for correlation processing with the measurement data to obtain synthetic aperture processing data.

[0012] In a second aspect, the present invention is characterized in that the inspection device of the first aspect further comprises means for determining the distribution of the substance to be measured present in the object to be inspected in an in-plane direction parallel to the surface, using a correlation between the amount of the substance present in the object to be inspected and the amount of phase shift, which correlation is determined by a previous measurement.

[0013] Here, the constituent materials of the object under test refer to various materials, such as raw materials, mixtures of multiple materials, air bubbles generated by foaming, fibrous materials such as wool and the air between those fibers, and foreign materials if they may be present. The target material for which the distribution shape is to be determined is a material composed of one or more of the above materials. The abundance refers to the density of the material under test, the composition ratio with other materials, etc. For example, in an object under test that is a mixture of two or more materials with different densities or dielectric constants, by measuring the phase shift characteristics of each material, i.e., the phase shift versus thickness, in advance, the composition ratio and the dispersion of the materials can be determined from the phase shift of the mixture. For example, in an object under test that is composed of multiple materials, samples of the mixture containing different amounts of one material can be prepared, and the relationship between the amount of each material and the phase shift can be determined using the inspection device of the present invention, thereby obtaining the correlation. In addition, for an object to be inspected that is made of a single substance or a substance that is a uniform mixture of multiple materials, samples with different densities can be prepared and the phase shift amounts can be calculated to obtain a correlation between the density and the phase shift amount, which can be used to determine the density distribution of the substance to be measured that exists in the object to be inspected.

[0014] The present invention can be used in a variety of applications, including the following: (1) In the manufacturing process of rubber products such as tires, one or more mixed substances are used as the measured substances, and the kneaded state of the rubber is measured and quantified using a correlation determined in advance, and its distribution is determined. (2) One or more substances mixed into the ceramic material before sintering and the moisture contained therein are used as the measured substances, and the mixed state and moisture content are measured and quantified to determine their distribution. (3) For amorphous materials made of fibers such as nonwoven fabrics and glass wool, the density of the fiber material is measured and converted into a numerical value to determine the distribution shape. (4) In materials containing bubbles, such as foam rubber and urethane, the density of the raw material or bubbles is measured as the substance to be measured, and the density distribution is calculated. (5) The filler contained in the resin material is measured as the substance to be measured and quantified to determine the distribution of its dispersion state. (6) In the food manufacturing process, the density of powdered materials such as wheat flour is measured and converted into numerical values, and the distribution pattern is determined and used to determine the degree of mixing. (7) In the pharmaceutical manufacturing process, one or more components are used as the substance to be measured, and their density, etc. is measured and quantified to determine the distribution shape. (8) In a product or manufacturing process in which multiple liquids are mixed, one or more liquids are measured as the substance to be measured and converted into numerical values, and the distribution shape is determined and used to determine the degree of mixing. (9) In the manufacturing process of products made of gel-like materials such as toothpaste and compounds, one or more of the materials are measured as the substance to be measured, quantified, and their distribution pattern is determined and used to determine the degree of mixing. (10) Fibers such as carbon nanotubes and cellulose are measured as the substance to be measured and converted into numerical values, and their distribution patterns are obtained and used to determine the dispersion state. (11) In the manufacturing process of building boards, one or more of the materials to be kneaded are measured as the substance to be measured, quantified, and their distribution shape is determined. (12) In the manufacturing process of explosives, one or more of the raw materials are measured as the substance to be measured, quantified, and the distribution shape is determined. (13) In a process in which foreign matter is mixed into and dispersed in rubber, such as in studless tires, the density and other properties of the foreign matter are measured as the substance to be measured, and the distribution shape is determined. (14) In the cement manufacturing process, one or more raw materials are measured as the substance to be measured, quantified, and their distribution pattern is determined to determine the degree of mixing.

[0015] In a third aspect, the present invention is characterized in that the inspection device according to the first or second aspect further comprises an interpolation processing means that presets the plurality of relatively different positions, receives the reflected wave signals of the electromagnetic waves, estimates and interpolates data of the reflected wave signals of the electromagnetic waves obtained between the set positions based on data of the reflected wave signals of the electromagnetic waves obtained for each of the preset positions, and determines a distribution of the amount of phase shift based on the data obtained for each of the set positions and the interpolated data.

[0016] In this aspect of the invention, data obtained by measuring reflected wave signals of electromagnetic waves at a plurality of predetermined relatively different positions is used to calculate interpolated data that is estimated to be obtained by measurements between the above-mentioned set positions, and this interpolated data is added to data actually obtained from reflected wave signals to determine the distribution of phase shift amounts of the object to be inspected or the distribution of the substance to be inspected present in the object to be inspected. This makes it possible to grasp the distribution shape with even higher resolution. Furthermore, by performing interpolation processing by calculation without actually measuring at the interpolated positions, it is possible to significantly reduce the time required for measurement and processing of the measurement results.

[0017] In a fourth aspect, the present invention is characterized in that the inspection device according to any one of the first to third aspects is provided with a plurality of at least one of transmitting antennas for transmitting the electromagnetic waves or receiving antennas for receiving the reflected wave signals, and the synthetic aperture processing is performed using reflected wave signals that are individually separated and received via the plurality of antennas.

[0018] The invention of this aspect applies MIMO (Multiple Input Multi Output) radar technology. By using multiple transmitting or receiving antennas, reflected wave signals from multiple measurement locations can be measured without moving the antenna or the object being measured, enabling high-speed measurement. Multiple transmitting or receiving antennas may be provided, or multiple both may be provided. By using a MIMO millimeter-wave radar transmitting and receiving antenna for vehicles configured with multiple transmitting or receiving antennas arranged in a compact space, a low-cost, compact inspection device can be realized.

[0019] In a fifth aspect, the present invention is characterized in that, in the inspection device of the fourth aspect, the plurality of transmitting antennas or the plurality of receiving antennas include a virtual antenna that is set by adding or subtracting a phase amount of a transmitting signal or a receiving signal.

[0020] In the invention of this aspect, when MIMO radar technology is applied to the present invention, the number of apparent transmitting and receiving antennas can be increased by adding reflected wave signals from virtual antennas, thereby further improving the measurement speed and accuracy in measuring the distribution shape.

[0021] In a sixth aspect, the present invention provides the inspection apparatus according to any one of the first to fifth aspects, characterized in that the back surface of the object to be inspected has a reflector that reflects the electromagnetic waves. By providing an electromagnetic wave reflector on the back surface of an object to be inspected whose back surface has insufficient reflectivity of the electromagnetic waves, the invention of this aspect can increase the intensity of the reflected wave signal that returns after going back and forth between the front and back surfaces of the object to be inspected, thereby increasing the S / N ratio for the desired information and improving the measurement accuracy of the distribution shape of the amount of phase shift in the object to be inspected. A metal plate, metal film, or the like can be used as the reflector, and any material other than metal can be used as long as it has a higher reflectivity of the electromagnetic waves than the object to be measured.

[0022] In a seventh aspect, the present invention provides the inspection apparatus of any one of the first to sixth aspects, further comprising means for measuring the distance between the front and back surfaces of the object to be inspected, and means for correcting the amount of phase shift based on the measurement result of the distance. When measuring an object whose thickness is not uniform or whose thickness varies in parts, the difference in thickness will cause a difference in the amount of phase shift, preventing accurate measurement of the amount of phase shift due to the target material, etc. Therefore, in the invention of this aspect, the distance between the front and back surfaces of the object to be inspected, i.e., the thickness of the object to be inspected at the measurement point, is constantly measured, and the measurement value obtained from the reflected wave signal is corrected based on the amount of phase shift due to an increase or decrease in the thickness, thereby eliminating the effect of thickness.

[0023] In an eighth aspect, the present invention is characterized in that the inspection apparatus according to any one of the first to seventh aspects further comprises means for automatically determining the frequency and intensity of the electromagnetic wave for determining the distribution of the amount of phase shift of the object to be inspected by irradiating a condition setting electromagnetic wave of which frequency and intensity are changed toward the surface of the object to be inspected in advance, receiving the reflected wave, and analyzing the characteristics of the received wave with respect to the frequency and intensity.

[0024] In the inspection device of the present invention, for an object to be inspected whose electromagnetic wave characteristics are not fully known, it is necessary to select the frequency and intensity of the electromagnetic waves to be used and adjust the transmitter / receiver to match those conditions, which requires a lot of work.The invention of this aspect is equipped with an auto-calibration function that automatically determines the optimal frequency and intensity of the electromagnetic waves and makes it possible to set those conditions.By having this function, it is easy to select and adjust the electromagnetic waves even for new objects to be inspected. [Effects of the Invention]

[0025] As described above, the inspection apparatus of the present invention can inspect a wider range of materials than ever before, and can inspect for non-uniformity of material substances in an object to be inspected in a shorter time than ever before. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a block diagram of an inspection device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of a flowchart of an inspection procedure according to the first embodiment. [Figure 3] FIG. 10 is a perspective view showing the main components of an inspection device according to a second embodiment. [Figure 4] FIG. 10 is a diagram schematically illustrating the configuration of transmitting and receiving antennas and a MIMO system used in a second embodiment. [Figure 5] FIG. 10 is a diagram showing an example of a first experimental result using the inspection device of the second embodiment. [Figure 6] FIG. 10 is a diagram showing an example of a second experimental result using the inspection device of the second embodiment. [Figure 7] FIG. 11 is a perspective view showing the main components of an inspection device according to a third embodiment. [Figure 8] FIG. 10 is a perspective view showing the main components of an inspection device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0027] The inspection device of the present invention will be described in detail below by way of examples with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals and redundant description will be omitted. [Example]

[0028] FIG. 1 is a block diagram of an inspection apparatus according to a first embodiment of the present invention. In FIG. 1, the inspection apparatus 10 of this embodiment includes a transmitting / receiving antenna 4, which functions as a transmitting antenna for emitting millimeter waves 2 toward an object under inspection 1 and a receiving antenna for receiving a reflected wave signal 3 reflected from the object under inspection 1; a transmitting / receiving circuit 5 connected to the transmitting / receiving antenna 4; and a motorized stage 6 as a moving means for carrying and moving the object under inspection 1. The object under inspection 1 has a plate-like shape, and the millimeter waves 2 radiated from the transmitting / receiving antenna 4 are radiated substantially perpendicular to the surface 1a of the object under inspection 1. The motorized stage 6 moves the object under inspection 1 in a plane parallel to the surface 1a, i.e., in the xy plane, so that different portions of the object under inspection 1 are sequentially positioned in the direction of radiation of the millimeter waves 2 from the transmitting / receiving antenna 4. In this embodiment, a probe antenna is used as the transmitting / receiving antenna 4.

[0029] In this embodiment, the object 1 to be inspected is made of a dielectric material in the form of a substantially parallel plate, in which substances with different dielectric constants are mixed non-uniformly, and on the back side of the object 1 is the upper surface of an electric stage made of a metal plate. As a result, the reflected wave signal 3 from the object 1 to be inspected is mainly composed of a reflected wave that travels back and forth between the front and back surfaces of the object 1 to be inspected, and the amount of phase shift at each measurement point on the object 1 to be inspected reflects the value obtained by integrating the density and composition ratio of the mixed substances with different dielectric constants in the z-axis direction, i.e., in the thickness direction.

[0030] The inspection device 10 also includes a synthetic aperture processing means that performs synthetic aperture processing using a plurality of reflected wave signals received from a plurality of relatively different positions between the object under inspection 1 and the transmitting / receiving antenna 4 and position data indicating these relatively different positions, and this synthetic aperture processing means is provided as a piece of software in the personal computer 7. Specifically, as the object under inspection 1 moves, reflected wave signals reflected from the object under inspection 1 are received at preset movement intervals, for example, every 0.5 to 5.0 mm, and synthetic aperture processing is performed using the plurality of reflected wave signals received at each movement position and position data indicating the position of the object under inspection 1 relative to the transmitting / receiving antenna 4 at each reception position. The synthetic aperture processing means determines the distribution of phase shift amounts in the xy plane due to the presence of the object under inspection 1, and the shape of this distribution is displayed on the display 8 of the personal computer 7.

[0031] The motorized stage 6 is controlled by a controller 9, which is in turn controlled by a control signal 11 from a personal computer 7. In addition, as the stage moves, the controller 9 sends a trigger signal 12 to the personal computer 7 to receive a received signal and to the transmitter / receiver circuit 5 to send a transmitted signal. It is also possible to make the movement speed in the x and y directions constant, thereby eliminating the need for a trigger signal.

[0032] The inspection procedure of the inspection method using the inspection device 10 of this embodiment will be described below. FIG. 2 is a diagram showing an example of a flowchart of the inspection procedure of this embodiment. First, measurement conditions are set. As a specific example, when the FM-CW radar system shown in FIG. 1 is used, a chirp signal is used in which the frequency of the millimeter wave radiated from the transmitting / receiving antenna 4 is periodically and linearly changed, so the frequency, the amount of change, the period, etc. are set. Based on these set conditions, a millimeter wave transmission signal is created and supplied to the transmitting / receiving antenna 4. Note that the millimeter wave frequency can be swept between 77 GHz and 81 GHz, for example.

[0033] Next, when the object to be inspected 1 reaches the set movement position, the received data is processed by receiving the reflected wave signal 3 from the object to be inspected 1 via the transmitting / receiving antenna 4, converting the frequency of the received wave to a low frequency range, and performing voltage value conversion using an AD converter, outputting the raw data of the received signal in the range direction. Next, correlation processing is performed in the range direction, i.e., the depth z direction of the object to be inspected 1 in Figure 1. Specifically, a reference signal is created based on the transmitted signal, and correlation processing is performed between the received signal and the reference signal to obtain range compressed data. Note that if measurement accuracy in the depth z direction is not required, the above correlation processing in the range direction is not necessary.

[0034] In this embodiment, in the correlation processing in the range direction, a millimeter wave is emitted from a predetermined position in the area where the object 1 to be inspected is placed, for example, from the position of the front surface 1a of the object 1 to be inspected, and a wave signal reflected by the metal plate of the motorized stage 6 on the back side of the object 1 to be measured is received, and this received data can be used to correct the entire measurement system including the transmitting / receiving antenna 4 and the transmitting / receiving circuit 5. In this case, the correlation processing is performed using the wave signal reflected by the metal plate, and the reference signal is corrected so that data correctly indicating the metal plate is output as a result, and then the correlation processing is performed. By performing this correction, distortion in the entire transmitting / receiving system can be corrected, and data on the amount of phase shift due to the presence of the object 1 to be inspected with little error can be obtained.

[0035] Next, to correct for the change in distance between the analysis point and the antenna when the object under test 1 is moved in the azimuth direction, range migration correction is performed on the range compression data, and correlation processing is performed in the azimuth direction, i.e., the direction of movement of the object under test 1 in Figure 1. The reference signal in the azimuth direction used in correlation processing is created by analytically finding the complex conjugate of the transfer function at each range position based on the transmitted signal. Synthetic aperture processing data is obtained using multiple received data in the movement direction using a procedure similar to general synthetic aperture processing. After performing synthetic aperture processing over the entire predetermined area while moving the object under test 1, the distribution of phase shift amounts in the xy plane direction caused by the object under test 1 is displayed on the display unit 8 using the obtained synthetic aperture processing data.

[0036] However, in this embodiment, data obtained from the reflected wave signal at each set movement interval is used to calculate interpolated data estimated to be obtained by measurement between the movement intervals, and this interpolated data is added to the data obtained from the actual reflected wave signal to determine the distribution shape of the phase shift amount of the object under test. Specifically, reference signals in the azimuth direction are generated not only at positions where reflected wave signal data is obtained but also at interpolated positions between them, and correlation processing is performed with the reflected wave signal data to obtain synthetic aperture processing data at the interpolated positions. The interpolated data is then added to determine the phase distribution shape of the object under test 1. For example, reference signals for interpolation processing are generated at intervals one-fifth the movement interval at which received signals are obtained, and correlation processing is performed with the obtained received signals. In this way, by performing interpolation processing by calculation without actually performing measurements at the interpolated positions, it is possible to significantly reduce the time required for measurement and processing of the measurement results, and it has been confirmed that the resolution of the measured distribution shape is also significantly improved. [Example]

[0037] FIG. 3 is a perspective view showing the main components of an inspection apparatus according to a second embodiment of the present invention. In FIG. 3, the inspection apparatus 20 of this embodiment includes a MIMO millimeter-wave radar 23 equipped with two transmitting antennas that radiate millimeter waves from above toward an object under inspection 21 and four receiving antennas that receive reflected wave signals from the object under inspection 21. The object under inspection 21 is placed on a metal sample stage 22, which is moved in the y direction by a motorized stage 26. The millimeter-wave radar 23 is attached to a motorized stage 27 via a mounting jig 25 and moves in the x direction. The motorized stages 26 and 27 are controlled by a controller 28. Although not shown, the inspection apparatus 20, like the first embodiment, includes a synthetic aperture processing unit as part of its software and a personal computer 7 with a display unit 8. The millimeter-wave radar 23 also includes a transmitting / receiving circuit for processing transmitted and received signals, and its input / output data is exchanged with the personal computer 7 via communication. The controller 28 is controlled by a control signal from the personal computer 7, and as the robot moves, the controller 28 sends a trigger signal to the personal computer 7 and the millimeter-wave radar 23. It is also possible to make the movement speed in the x and y directions constant, thereby eliminating the need for a trigger signal.

[0038] Furthermore, the inspection device 20 of this embodiment is equipped with a laser displacement meter 24 integrated with the millimeter-wave radar 23 in order to measure the thickness of the object to be inspected 21 at the measurement location and correct the measurement value obtained from the reflected wave signal based on the amount of phase shift due to an increase or decrease in the thickness.

[0039] In this embodiment, the millimeter-wave radar 23 is used in the transmitting and receiving section including the transmitting and receiving antennas, so that a small transmitting and receiving section can be configured at low cost. Furthermore, since the millimeter-wave radar 23 has multiple transmitting and receiving antennas, it can simultaneously acquire reflected wave signals from multiple measurement locations, enabling high-speed measurement.

[0040] The inspection procedure of this embodiment is similar to that of the first embodiment, except that the number of reflected wave signals from the multiple transmitting and receiving antennas is large. As the object under inspection 21 and the millimeter-wave radar 23 move in the x and y directions, reflected wave signals from the object under inspection 21 are received at preset intervals, e.g., approximately 0.5 to 5.0 mm. Synthetic aperture processing is performed using the multiple reflected wave signals received at each movement position and position data indicating the position of the object under inspection 21 relative to the transmitting and receiving antennas of the millimeter-wave radar 23 at each reception position. This synthetic aperture processing means determines the distribution of phase shifts in the x-y plane of the object under inspection 21, and the distribution is displayed on the display 8 of the personal computer 7. It is also possible to generate azimuth-direction reference signals at interpolated positions between positions where reflected wave signal data is obtained, perform correlation processing with the received signal data to obtain synthetic aperture processing data at the interpolated positions, and then use this to determine the distribution of phase shifts of the object under inspection 21.

[0041] FIG. 4 is a diagram showing a schematic diagram of the transmitting and receiving antennas and the MIMO system configuration used in this embodiment. As shown in FIG. 4, a millimeter-wave radar 23 disposed above an object under inspection 21 includes two transmitting antennas 31 and 32 spaced at a regular interval, and four receiving antennas 33, 34, 35, and 36 spaced at regular intervals from the transmitting antennas 31 and 32. Four measurement points 21a, 21b, 21c, and 21d on the object under inspection 21 are irradiated with millimeter waves by the transmitting antenna 31, and the reflected wave signals are detected by the receiving antennas 33, 34, 35, and 36, respectively. Simultaneously, four measurement points 21e, 21f, 21g, and 21h are irradiated with millimeter waves by the transmitting antenna 32, and the reflected wave signals are detected by the receiving antennas 33, 34, 35, and 36, respectively. In other words, this fixed arrangement of the transmitting and receiving antennas and the object to be measured allows for simultaneous measurement of eight points, and when measuring by moving the transmitting and receiving antennas or the object to be measured, the movement interval can be increased by eight times, enabling high-speed measurement.

[0042] FIG. 5 is a diagram showing an example of the results of a first experiment using the inspection device 20 of this embodiment, and is an image showing the inspection results of a sample in the process of mixing clays of different densities. In this experiment, in the process of kneading high-density white clay 51 and low-density black clay 52, the sample was cut into a flat shape and used as the measurement object in each of the following states: state A before kneading, state B during kneading, and state C after kneading. The in-plane density distribution of each sample was determined. In the above measurement, the phase shift amount was measured in advance using samples with different densities, and the correlation between density and phase shift amount was determined.

[0043] Figures 5(a), (b), and (c) show photographs of the samples in states A, B, and C, respectively. Figures 5(d), (e), and (f) show the density distributions within the planes of the samples in states A, B, and C, respectively. Figures 5(g), (h), and (i) show graphs showing the density frequency and standard deviation values ​​within the samples in states A, B, and C, respectively. The planar dimensions of the samples are approximately 10 cm in the x direction and 10 cm in the y direction. The density distributions in Figures 5(d)–(f) are actually displayed using different colors, with density increasing in the order blue (B), green (G), yellow (Y), and red (R). Figures 5(g)–(i) show that in state A, the density frequency is limited to two values, corresponding to the high-density white clay 51 and the low-density black clay 52, respectively. In state B, the density values ​​are widely distributed within the plane due to insufficient mixing, while in state A, the density is uniformly intermediate across the entire plane.

[0044] Figure 6 shows an example of the results of a second experiment using the inspection device 20 of this embodiment. It is an image showing the measurement results of the bubble distribution in a polyurethane resin containing bubbles. A sample in the process of mixing bubbles was cut into a flat plate to serve as the measurement object. Figure 6(a) is a photograph of the appearance, and Figure 6(b) shows the distribution of phase shift in a plane. The planar shape of the sample is approximately 5 cm in the x direction and 5 cm in the y direction. The phase shift distribution in Figure 6(b) is actually displayed using different colors, with the phase shift increasing in the order blue (B), green (G), yellow (Y), and red (R). As Figure 6(b) shows, areas with many bubbles are blue (B) and have a small phase shift, while areas with few bubbles have a large phase shift and are red (R). This allows us to determine the distribution of bubbles inside the sample, and by inspecting the sample during the foaming process, we can measure the degree of foaming.

[0045] As in the above experiment, by determining the density distribution and calculating its standard deviation, it is possible to quantify the dispersion and density distribution of materials. Furthermore, in manufacturing processes where materials are mixed, feeding back the calculated standard deviation to upstream processes makes it possible to manufacture uniform products. By setting thresholds for density and standard deviation, it is also possible to use them to determine whether a product is good or bad.

[0046] Furthermore, by utilizing the correlation between the amount of phase shift and density, the inspection device of this embodiment can be effectively used in many of the applications mentioned above, such as measuring and evaluating the mixing state in the manufacturing process of rubber products such as tires, measuring the mixing state and moisture content distribution of ceramic materials, and measuring and inspecting the mixing state of multiple materials such as liquid materials and cement. [Example]

[0047] FIG. 7 is a perspective view showing the main components of an inspection apparatus according to a third embodiment of the present invention. In FIG. 7, the inspection apparatus 30 of this embodiment includes a MIMO millimeter-wave radar 43 that emits millimeter waves from above toward a plate-shaped object under inspection 41 moving in the y direction on a belt conveyor and receives reflected wave signals from the object under inspection 41. The millimeter-wave radar 43 has a configuration similar to the millimeter-wave radar 23 of the second embodiment, and includes two transmitting antennas and four receiving antennas. As the object under inspection 41 passes over a reflector 42 that is an object that reflects millimeter waves and is installed between belt conveyors 45 and 46, millimeter waves are emitted from above and the reflected wave signals are detected. The millimeter-wave radar 43 is attached to a motorized stage 47 and is controlled to move in the x direction above the reflector 42 and to obtain x-direction reflected wave signal data corresponding to the position of the object under inspection 41 in the y direction as it passes. Although not shown in the drawings, the inspection device 30 includes a synthetic aperture processing means as one piece of software, and includes a personal computer 7 having a display unit 8, similar to the first embodiment.

[0048] Furthermore, the inspection device 30 of this embodiment is equipped with a laser displacement meter 44 for measuring the thickness of the object 41 at the measurement location and correcting the measurement value obtained from the reflected wave signal based on the amount of phase shift caused by an increase or decrease in the thickness. This laser displacement meter 44 measures the distance between the surface of the reflector 42 and the surface of the edge of the object 41, making it possible to constantly measure and correct the thickness of the object 41.

[0049] As in the second embodiment, the present embodiment also uses a millimeter-wave radar 43 in the transmitting and receiving section including the transmitting and receiving antennas, making it possible to configure a small transmitting and receiving section at low cost. Furthermore, since the millimeter-wave radar 43 has multiple transmitting and receiving antennas, it is possible to simultaneously acquire reflected wave signals from multiple measurement locations, enabling high-speed measurement.

[0050] This embodiment can also be applied to inspections in which it is necessary to inspect the density and distribution of the constituent ratio of materials, etc. of materials or intermediate products as the object 41 to be measured in the manufacturing process of a product or the like, and feed back the results to the previous process. For example, by measuring intermediate products produced in an extrusion process, rolling process, pressing process, etc. immediately after production, it is possible to achieve manufacturing with less waste.

[0051] The inspection procedure of this embodiment is almost the same as that of Embodiment 2. As the object 41 moves in the x and y directions, reflected wave signals from the object 41 are received at preset movement intervals, and synthetic aperture processing is performed using the multiple reflected wave signals received at each movement position and position data indicating the position of the object 41 relative to the transmitting and receiving antennas of the millimeter-wave radar 43 at each receiving position. This synthetic aperture processing means determines the distribution of phase shift amounts in the xy plane of the object 41, and these are displayed on the display 8 of the personal computer 7. It is also possible to create a reference signal in the azimuth direction at an interpolation position between positions where reflected wave signal data is obtained, perform correlation processing with the received signal data to determine synthetic aperture processing data at that interpolation position, and add this to determine the distribution shape of the phase shift amounts. [Example]

[0052] FIG. 8 is a perspective view showing the main components of an inspection device according to a fourth embodiment of the present invention. In FIG. 8, the inspection device 40 of this embodiment has five millimeter-wave radars 51, 52, 53, 54, and 55, each of which has a similar configuration to the millimeter-wave radar 43 of the third embodiment, arranged at regular intervals in the x direction while being slightly offset in the y direction. This differs from the inspection device 30 of the third embodiment in that it does not require the millimeter-wave radar to be moved in the x direction for measurement and that it does not include a laser displacement meter. Specifically, the millimeter-wave radar is positioned so that it can measure necessary measurement points in the x direction, eliminating the need for movement in the x direction. By simultaneously acquiring reflected wave signals at necessary measurement points in the x direction, it is possible to achieve even faster measurement. Other basic inspection processes and functions are the same as those of the third embodiment. The laser displacement meter can also be positioned upstream or downstream of the belt conveyor, separate from the millimeter-wave radar. Furthermore, thickness measurement is not necessary if the thickness is uniform.

[0053] As described above, it has been confirmed that the present invention provides an inspection apparatus that can inspect a wider range of materials than ever before for non-uniformity of material substances in an object to be inspected in a shorter time than ever before.

[0054] Needless to say, the present invention is not limited to the above-described embodiments, and the design can be modified depending on the purpose and application. For example, electromagnetic waves other than those in the millimeter wave band may be used. The type and configuration of the transmitting and receiving antennas, the arrangement of the transmitting and receiving antennas and the object to be inspected, the means of movement, the number of transmitting and receiving antennas, the material and position of the reflecting object, the interpolation interval for the interpolation process, and other factors can be selected as desired depending on the purpose. Furthermore, the frequency of the electromagnetic waves can be selected to suit the physical properties of the object to be measured. For example, since electromagnetic waves attenuate when the object to be inspected contains a large amount of moisture, using a lower frequency can reduce the effects of attenuation. [Explanation of symbols]

[0055] 1, 21, 41 Inspected object 1a surface 2 mmWave 3 Reflected wave signal 4 Transmitting and receiving antennas 5 Transmitting and receiving circuit 6, 26, 27, 47 Motorized Stage 7. Personal Computers 8 Display 9, 28 Controller 10, 20, 30, 40 Inspection equipment 11 Control Signals 12 Trigger Signal 21a, 21b, 21c, 21d, 21e, 21f, 21g, 21h measurement points 22 Sample stage 23, 43, 51, 52, 53, 54, 55 Millimeter wave radar 24, 44 Laser displacement meter 25 Mounting jig 31, 32 Transmitting antenna 33, 34, 35, 36 Receiving antenna 37 White Clay 38 Black Clay 42 Reflector 45, 46 Belt conveyor

Claims

1. a means for emitting electromagnetic waves toward a surface of an object to be inspected, the surface of the object being inspected being composed of a single or multiple substances, at a plurality of relatively different positions with respect to the object, and receiving reflected wave signals of the electromagnetic waves including reflected waves from a back surface of the object to be inspected; a synthetic aperture processing means for performing synthetic aperture processing using the received reflected wave signals and position data indicating the relatively different positions; and means for determining a distribution of a phase shift amount of the reflected wave signal due to the presence of the object to be inspected by the synthetic aperture processing means. an inspection apparatus for evaluating a distribution of the amount of phase shift in an in-plane direction parallel to the surface of the substance in the object to be inspected based on the distribution of the amount of phase shift, An inspection device characterized by having a means for determining the distribution of the substance present in the object to be inspected in an in-plane direction parallel to the surface, using the correlation between the amount of the substance present in the object to be inspected and the amount of phase shift, which has been determined by a previous measurement.

2. a plurality of relatively different positions are preset, and the reflected wave signal of the electromagnetic wave is received; an interpolation processing means for estimating and interpolating data based on the reflected wave signals of the electromagnetic waves obtained between the set positions based on data based on the reflected wave signals obtained at each of the preset positions; 2. The inspection apparatus according to claim 1, wherein the distribution of the phase shift amounts is determined based on the data obtained for each of the set positions and the interpolated data.

3. 3. The inspection device according to claim 1, further comprising at least a plurality of transmitting antennas for transmitting the electromagnetic waves or a plurality of receiving antennas for receiving the reflected wave signals, and performing the synthetic aperture processing using the reflected wave signals received individually and separately via the plurality of antennas.

4. 4. The inspection device according to claim 1, further comprising a reflector on a rear surface of the object to be inspected, the reflector reflecting the electromagnetic waves.

5. 5. An inspection device according to claim 1, further comprising: means for measuring the distance between the front and back surfaces of the object to be inspected; and means for correcting the amount of phase shift based on the measurement result of the distance.

6. 6. An inspection device according to claim 1, further comprising means for automatically determining the frequency and intensity of electromagnetic waves for determining the distribution of the amount of phase shift of the object to be inspected by irradiating a surface of the object to be inspected with electromagnetic waves for setting conditions, the frequency and intensity of which are changed, receiving the reflected waves, and analyzing the characteristics of the received waves with respect to the frequency and intensity.

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