Inspection device and inspection system

Abstract

To detect foreign matter that is smaller than before from among foreign matter mixed into powder-like and liquid-like measurement objects.SOLUTION: An inspection device 1 with a hairy element, powder, and liquid as measurement objects F comprises: an oscillator 10 for generating electromagnetic waves; a first waveguide 20 for forming a waveguide of electromagnetic waves while one end is connected to the oscillator 10; an inlet 31 for introducing electromagnetic waves while the other end of the first waveguide 20 is connected; a cavity resonator 30 having a cavity section 32 in which electromagnetic waves resonate in a specific vibration mode, an outlet 33 for leading out electromagnetic waves from the cavity section 32, and a columnar communication path 35 disposed in the cavity section 32; a second waveguide 40 for leading out electromagnetic waves from the cavity resonator 30 while one end is connected to the outlet 33; a receiver 50 for receiving electromagnetic waves led out of the cavity resonator 30; and an arithmetic section 60 for evaluating the state of the measurement object F. The communication path 35 is disposed along a pair of communicating openings comprising an insertion opening into which the measurement object F is inserted and an outlet from which the measurement object is led out.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inspection device and an inspection system. [Background technology]

[0002] One method for detecting foreign objects such as metal pieces contained in a measurement object is to use a cavity resonator. In an inspection device using a cavity resonator, when a detection wave (electromagnetic wave) is incident, resonance occurs within the cavity resonator at a frequency determined by the internal medium and the dielectric constant of the object being inspected. If a foreign object with a different dielectric constant is contained in the measurement object, this frequency changes, and this method detects the foreign object by capturing this change (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-79990 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while such a detection method using a cavity resonator is effective for detecting foreign objects in measurement objects with fine, fixed shapes such as filaments, further improvement in the accuracy of foreign object detection is desired for measurement objects with irregular shapes such as powders and liquids.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an inspection device that can accurately detect foreign matter in an object to be measured that has an irregular shape, such as a powder or liquid, as well as in a thread state.

[0006] The inventors investigated the reasons why detection accuracy cannot be achieved in detection methods using cavity resonators when the measurement object is in the form of an irregular object such as a powder or liquid. As a result, they found that detection accuracy cannot be achieved for reasons such as the fact that if an irregular measurement object is passed directly through the inside of a box-shaped cavity resonator made of metal walls, it will become clogged inside the resonator, or the electromagnetic wave inlet and outlet will be blocked, and that it is difficult to efficiently insert an irregular measurement object directly into the connecting passage.

[0007] Therefore, the present invention aims to provide an inspection device and an inspection system that can detect smaller foreign matter than before that has become mixed into a filament, and that can detect foreign matter in various forms of measurement objects, such as filaments, powders, and liquids. [Means for solving the problem]

[0008] After careful consideration, the problem was solved by selecting a material that absorbs little electromagnetic waves, forming a columnar communication passage along a pair of communication ports that form the path (communication passage) through which the measurement object passes inside the cavity resonator, and providing a guide to lead the irregularly shaped measurement object into the communication passage.

[0009] The following are examples of aspects of the present invention that can solve such problems. (1) An inspection device for measuring filamentous bodies, powders, and liquids, an oscillator that emits electromagnetic waves; a first waveguide having one end connected to the oscillator and forming a waveguide for the electromagnetic wave; a cavity resonator having an inlet port to which the other end of the first waveguide is connected and through which an electromagnetic wave is introduced, a cavity portion in which the electromagnetic wave resonates in a specific vibration mode, an outlet port through which the electromagnetic wave is led out of the cavity portion, and a columnar communicating path disposed in the cavity portion; a second waveguide having one end connected to the outlet and configured to guide the electromagnetic wave from the cavity resonator; a receiver for receiving the electromagnetic wave guided from the cavity resonator; a calculation unit that evaluates a state of the measurement target based on fluctuations in the electromagnetic waves within the cavity resonator; Equipped with In the inspection device, the communication path is arranged along a pair of communication ports each including an insertion port through which the measurement object is inserted and an outlet port through which the measurement object is discharged.

[0010] (2) The inspection device according to (1), wherein the material used for the peripheral wall portion that defines the communication passage is a material that does not absorb the electromagnetic waves used.

[0011] (3) The inspection device according to (1) or (2), wherein a funnel-shaped structure is disposed at a communication port that introduces the measurement target of the cavity resonator into the communication path.

[0012] (4) The inspection device according to any one of (1) to (3), wherein the cavity inside the cavity resonator is filled with a material that has low absorption of the frequency of the electromagnetic wave used.

[0013] (5) The inspection device according to any one of (1) to (4), wherein the cavity resonator has a cavity portion in the shape of a rectangular parallelepiped.

[0014] (6) An inspection device described in any one of (1) to (5), in which the shape of the cavity in which the electromagnetic wave resonates in a specific vibration mode is cylindrical, with an inlet for the object to be measured at one end and an outlet for the object to be measured at the other end, and the inlet for introducing the electromagnetic wave and the outlet for emitting the electromagnetic wave facing each other on the side of the cylinder.

[0015] (7) The inspection device according to any one of (1) to (6), wherein the cavity resonator is made of metal.

[0016] (8) The inspection device according to any one of (1) to (7), wherein the cavity resonator is provided with a plurality of communication paths for passing a plurality of measurement targets.

[0017] (9) An inspection device described in (1) to (8), wherein each of the plurality of communication paths is provided at a predetermined interval so that the object to be measured passes through an area within a predetermined range from the antinode of a standing wave generated inside the cavity.

[0018] (10) An inspection device described in any one of (1) to (9), wherein the communication path is set to a size that prevents electromagnetic waves having a frequency within a predetermined measurement range defined by the cutoff frequency of the waveguide from leaking out of the cavity.

[0019] (11) The inspection device according to any one of (1) to (10), comprising a plurality of cavity resonators.

[0020] (12) An inspection device described in any one of (1) to (11), wherein the calculation unit estimates the state of the object to be measured based on at least one of fluctuations in the intensity of a predetermined resonant frequency contained in the electromagnetic wave and fluctuations in the generation frequency of the electromagnetic wave.

[0021] (13) The inspection device according to any one of (1) to (12), wherein the oscillator generates a continuous wave including a first range of frequencies centered on a predetermined resonant frequency.

[0022] (14) An inspection system comprising a plurality of cavity resonators according to any one of (1) to (13), wherein an object to be measured passes through the communication passages of two or more of the plurality of cavity resonators. [Effects of the Invention]

[0023] According to the present invention, it is possible to detect foreign matter that has become mixed in a measurement object and is smaller than before, and foreign matter in various forms such as filaments, powders, and liquids can be detected. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the configuration of an inspection device. [Figure 2] 1A and 1B are diagrams illustrating examples of the shape of a cavity resonator. [Figure 3] 10 is an image showing an example of the electric field intensity inside the cavity resonator when the number of loops is n=3. [Figure 4] FIG. 10 is a diagram showing how a filament is passed through a communication passage of a cavity resonator. [Figure 5]FIG. 10 is a diagram showing electric and magnetic field lines when the communication opening is viewed from above. [Figure 6] FIG. 10 shows the electric field intensity plot of TM11. [Figure 7] 10 is a graph showing the relationship between the radius of the waveguide and the cutoff frequency of the TM11 mode. [Figure 8] 10 is a graph showing a comparison of spectra when the iris diameter is changed. [Figure 9] 1 is a graph showing the relationship between the iris diameter and the Q value (sensitivity to a foreign substance M). [Figure 10] Graphs showing (A) an example of a waveform of a chirp wave and (B) an example of a change in frequency of the chirp wave. [Figure 11] FIG. 1 is a diagram showing a schematic configuration in which two different chirp waves are emitted from separate oscillators. [Figure 12] (A) A graph showing an example of two different chirp waves, and (B) a graph showing the change in frequency difference between the two different chirp waves. [Figure 13] (A) A graph showing the relationship between the difference in frequency (IF frequency) of two different chirp waves and the intensity of chirp wave 1, and (B) a graph showing the relationship between the original frequency of chirp wave 1 and the intensity of chirp wave 1. [Figure 14] 10 is a graph showing a waveform when a measurement object F containing no foreign matter passes through, and a waveform when a measurement object F containing a metallic foreign matter passes through. [Figure 15] 1 is a schematic diagram of an inspection device and the like for explaining abnormality detection in the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, preferred embodiments of an inspection device and an inspection system according to the present invention will be described in detail with reference to the drawings (see FIGS. 1 to 13).

[0026] The inspection device according to the present disclosure is a device for inspecting a filament F, such as glass fiber, manufactured through various manufacturing processes, to determine whether or not there are any abnormalities, such as the inclusion or attachment of metal particles or other foreign matter M, due to the equipment, surrounding environment, manufacturing process, etc. Such an inspection device performs inspections based on the principle that electromagnetic waves are incident on the measurement object F within a cavity resonator, causing resonance at a predetermined frequency determined by the internal medium and the dielectric constant of the measurement object F, and detecting the frequency change that occurs when a foreign matter M with a different dielectric constant is present. Furthermore, the inspection device according to the present disclosure generates a standing electromagnetic wave having a predetermined resonance frequency within the cavity resonator. In this disclosure, electromagnetic waves with a frequency of 3 GHz or more and less than 30 GHz, and a wavelength of approximately 10 to 1 centimeter, are referred to as microwaves, and electromagnetic waves with a frequency of 30 GHz or more and less than 300 GHz, and a wavelength of the millimeter range, are referred to as millimeter waves. However, it goes without saying that millimeter waves and microwaves are not strictly defined with 30 GHz as the boundary.

[0027] The inspection device 1 of this embodiment is configured as a device including an oscillator 10, a first waveguide 20, a cavity resonator 30, a second waveguide 40, a receiver 50, and a calculation unit 60 (see FIG. 1, etc.).

[0028] (oscillator) The oscillator 10 is a device that generates a continuous wave including frequencies in a predetermined range (first range) centered on a predetermined resonant frequency. In this embodiment, the oscillator 10 is configured assuming that electromagnetic waves belonging to the millimeter wave band (30 GHz or more to less than 300 GHz) are mainly used, but it is of course also possible to apply electromagnetic waves with frequencies of 300 GHz or more.

[0029] (waveguide) The first waveguide 20 is a component for guiding the electromagnetic waves generated in the oscillator 10 to the cavity resonator 30, with one end connected to the oscillator 10 and the other end connected to the cavity resonator 30 (see FIG. 1). The second waveguide 40 is a component for guiding the electromagnetic waves from the cavity resonator 30 to the receiver 50, with one end connected to the cavity resonator 30 and the other end connected to the receiver 50 (see FIG. 1). The first waveguide 20 and the second waveguide 40 may each have the same configuration as those used in conventional inspection devices. Note that these are shown in a simplified form in the schematic diagram shown in FIG. 1. The cross-sectional areas of the first waveguide 20 and the second waveguide 40 can be determined by the resonant frequency of the electromagnetic waves generated inside the cavity resonator 30. In this embodiment, the first waveguide 20 and the second waveguide 40 have rectangular cross sections with the same dimensions a and b (see FIG. 2) as those of the cavity resonator 30. The cross-sectional areas and cross-sectional shapes of the first waveguide 20 and the second waveguide 40 do not have to be the same as those of the cavity resonator 30. The lengths of the first waveguide 20 and the second waveguide 40 are not particularly limited. For example, the first waveguide 20 and the second waveguide 40 can be appropriately selected and used from waveguides (waveguides) having shapes with dimensions corresponding to electromagnetic waves in a predetermined frequency band, as defined in the EIA (Electronic Industries Alliance) standard.

[0030] (cavity resonator) The cavity resonator 30 comprises a housing (structure) 39 having a cavity 32 formed therein. The cavity 32 contains a medium that allows electromagnetic waves in the resonant frequency band to pass through easily. In this embodiment, this medium is air. The cavity resonator 30 is configured to generate a standing wave within the cavity 32. The standing wave generated within the cavity 32 has a predetermined resonant frequency component. At least the inner peripheral surface of the cavity 32 is made of metal. In this embodiment, the housing 39 is made of a metal wall. Furthermore, as can be seen from the following equation 1, where the resonant frequency f is expressed for the rectangular parallelepiped cavity resonator 30 having the dimensions shown in FIG. 2 as an example, the smaller the dimensions of the cavity resonator 30 and the lower the dielectric constant of the medium (e.g., air in the internal space of the cavity resonator 30), the higher the frequency f of the electromagnetic waves generated within the cavity resonator 30 that will resonate. 2 indicate the dimensions of the cavity 32, that is, the dimensions of the space that generates a standing wave having a predetermined resonant frequency component.

number

[0031] Here, by reducing the dimensions and downsizing the cavity resonator 30, a standing wave having a predetermined resonant frequency can be generated inside the cavity resonator 30 even when millimeter waves are used, and the generation of the standing wave makes it possible to adjust the electric field intensity distribution inside the cavity resonator 30. As a result, the amplitude of the standing wave having a predetermined resonant frequency can be increased, that is, the electric field intensity can be strengthened in a specific range (region). In the cavity resonator 30 configured in this manner, when the measurement object F including the foreign object M passes through a range of relatively strong electric field intensity, the range of change in the frequency or intensity of the generated electromagnetic wave becomes larger, thereby improving detection accuracy.

[0032] As an example, in this embodiment, the cavity resonator 30 shown in FIG. 2 has dimensions a = 3.0 mm, b = 1.5 mm, and n = 3, i.e., the number of loops of the standing wave is an odd number, so that c = 7.2 mm. This allows a standing wave having a resonant frequency of 79 GHz to be generated within the cavity resonator 30. The rectangular cavity resonator 30 may be a structure conforming to EIA Standard WR12, with dimensions adjusted to a = 1.549 mm and b = 3.099 mm. It goes without saying that the resonant frequency of 79 GHz may deviate by several GHz depending on the presence and dimensions of the inlet 31 and outlet 33, which will be described later, and the dimensions of the communication port 34.

[0033] The above dimensions a, b, and c are merely examples, and the dimensions of the cavity resonator 30 can be adjusted appropriately based on the desired electromagnetic waves to be generated therein. Such an inspection device can detect smaller foreign objects and improve detection accuracy compared to conventional devices.

[0034] The inspection device 1 will be described in further detail below. Compared to conventional methods, when millimeter waves in the high frequency band are used, sensitivity to foreign matter M such as metal pieces contained in the measurement object F is improved. However, it can be difficult to generate a predetermined electromagnetic wave inside the cavity resonator 30 (cavity 32) through which the measurement object F passes. For example, it can be difficult to generate a predetermined electromagnetic wave inside the cavity resonator 30 depending on the accuracy of the electromagnetic wave introduction method, leakage of electromagnetic waves from the cavity resonator 30, etc.

[0035] From the above viewpoints, it is preferable to appropriately introduce the electromagnetic waves into the space (cavity 32) in order to generate predetermined electromagnetic waves in the space through which the object of measurement F of the inspection target passes. The inspection device 1 in this embodiment employs a configuration in which the electromagnetic waves generated by the oscillator 10 are introduced into the cavity 32 of the cavity resonator 30 via the first waveguide 20 and the inlet 31, and are received by the receiver 50 via the outlet 33 and the second waveguide 40. As a result, the oscillator 10, the receiver 50, and the electromagnetic wave waveguides (the first waveguide 20 and the second waveguide 40) can be functionally separated from the space (cavity 32 of the cavity resonator 30) in which electromagnetic waves of a predetermined vibration mode must be generated in order for the object of inspection to pass through. As a result, it is easy to generate the desired electromagnetic waves in the cavity 32.

[0036] In this embodiment, when electromagnetic waves with a frequency of 30 GHz or more are applied, a cavity resonator 30 having the following configuration is constructed to improve predetermined detection accuracy.

[0037] (Outline of cavity resonator) The cavity resonator 30 of this embodiment has an inlet 31 through which electromagnetic waves are introduced, a hollow portion 32, an outlet 33 through which the electromagnetic waves are output from the hollow portion 32, and a pair of, i.e., at least two, communication ports 34 that form a communication passage 35 through which the object to be measured F passes (see Figure 1, etc.).

[0038] The shape of the cavity 32 is not particularly limited, but may be, for example, a rectangular parallelepiped. The inlet 31 and the outlet 33 are arranged facing each other inside the cavity 32. The cavity 32 is configured so that a standing wave with one or more antinodes, where the number n of antinodes is an odd number, is generated from the inlet 31 toward the outlet 33. As an example, in this embodiment, the number n of antinodes of the standing wave generated inside the cavity 32 is set to 3 (see FIG. 3), so that the electromagnetic wave resonates in a specific vibration mode. Note that among the three approximately circular electric field intensities shown in FIG. 3, the intensity is stronger toward the center. It should be noted that, since the electric field intensity image, which was originally expressed in color, is now expressed in shades of black and white, the electric field intensity appears stronger outside the approximately circular shapes, but the actual electric field intensity is weaker the further away from the center of the circle.

[0039] The communication opening 34 is provided in the housing 39 of the cavity resonator 30 as a hole through which the measurement object F can pass, forming a communication path 35 through which the measurement object F passes (see FIG. 4, etc.). During measurement, the measurement object F moves and passes through the communication path 35 from top to bottom (or bottom to top) at a predetermined speed (see FIGS. 1 and 4). That is, the measurement object F passes through the cavity 32 of the cavity resonator 30 in the direction of the amplitude of the standing wave generated in the cavity 32. In this embodiment, a pair of communication openings 34, each consisting of an insertion opening through which the measurement object F is inserted and an exit opening through which the measurement object F is exited, is provided on the top surface (denoted by reference numeral 39a in FIG. 2 ), which is the widest surface of the housing 39 and has a width a and a length c, and on the opposite bottom surface. It is desirable that the communication path 35 formed by the pair of communication openings 34 be configured to pass through a portion of the standing wave generated in the cavity resonator 30 where the electric field intensity is strong. That is, the communication path 35 formed by the pair of communication ports 34 is preferably formed at a location where a peak of an antinode of the standing wave formed inside the cavity resonator 30 occurs. In this embodiment (see FIG. 3), in which the number n of antinodes of the standing wave generated inside the cavity 32 is set to 3, a pair of communication ports 34 is provided in the center of each of the upper surface 39a and the lower surface of the housing 39 so that the communication path 35 passes through the center of the middle antinode of the three antinodes with strong electric field strength (see FIG. 4).

[0040] A cylindrical communicating passage 35 is disposed along the pair of communicating ports 34. More specifically, the communicating passage 35 is a cylindrical region (a space with a circular cross section) defined by a cylindrical peripheral wall portion 36. The cylindrical peripheral wall portion 36 defining the communicating passage 35 is made of a material that exhibits low absorption of the electromagnetic wave frequency being used. Specific examples include ceramic and resin (PE, PLA, PET). Furthermore, the peripheral wall portion 36 defining the communicating passage 35 is preferably made of a material that will not damage the object F to be measured, and that will not wear out or will exhibit minimal frictional resistance even when it comes into contact with the object F to be measured. In this regard, ceramic is more preferable for many types of object F in light of the above conditions. In particular, ceramic is most preferable when the object F to be inspected is glass fiber. Additionally, the size of the opening for the object F to be measured in the communicating passage 35 matches the size of the communicating port 34, enabling efficient and reliable introduction. The shape of the communication passage 35 may be a polygonal prism such as a square prism or a hexagonal prism depending on the shape of the communication port 34, or may be a cylindrical or polygonal prism independently of the shape of the communication port 34.

[0041] Furthermore, the hollow portion 32 inside the cavity resonator 30 may be filled with a material that has little absorption of the frequency of the electromagnetic waves used. The substance filled in the hollow portion 32 is preferably a material that has little absorption of electromagnetic waves, such as gas, resin, or ceramic. Nitrogen, for example, is a preferable gas. When the material is resin or ceramic, it is preferably the same material as that used for the peripheral wall portion that defines the communicating passage 35.

[0042] Furthermore, by providing the communication passage 35, it is possible to prevent dust and the like generated in the external environment from entering the cavity resonator 30. As a result, even when the inspection device 1 is implemented in a production line and used continuously, it is possible to maintain high inspection accuracy.

[0043] In this embodiment, one communication path 35 is formed from a pair of communication ports 34, but this is merely an example. For example, multiple communication paths 35 may be provided so that multiple measurement targets F can pass through each communication path 35 simultaneously. In this case, if the number of antinodes of the standing wave is n=3 as in this embodiment, it is preferable to provide each communication port 34 so that each communication path 35 passes through a region within a predetermined range from each of three antinodes with strong electric field strength at a predetermined interval (see FIG. 4). As a result, each of the multiple communication paths 35 formed by a pair of communication ports 34 is formed at a location where a peak of an antinode of the standing wave formed in the cavity resonator 30 occurs.

[0044] (Communication port diameter) When inspecting a measurement object F for foreign objects, the cavity resonator 30 must be provided with a communication opening 34 through which the measurement object F passes, thereby connecting the cavity 32 to the external environment. The larger the diameter of the communication opening 34, the easier it is to pass the measurement object F and the easier it is to operate. However, as described above, when inspecting for foreign objects using millimeter-wave electromagnetic waves, the influence of electromagnetic waves leaking from the communication opening 34 on the electromagnetic waves within the cavity resonator 30 is greater than in the past, making it difficult to generate the desired electromagnetic waves useful for the inspection. Therefore, the influence on inspection accuracy due to the structure of the cavity resonator 30, including the diameter of the communication opening 34, becomes more significant than in the past. Therefore, it is desirable for the communication opening 34 to have as large a diameter as possible while suppressing electromagnetic wave leakage. An example of a procedure (flow) for determining the size of the hole diameter based on these considerations is shown below. 1. The resonant frequency of the electromagnetic wave (standing wave) generated in the cavity resonator 30 is determined. 2. The communication port 34 of the measurement object F is placed directly above the antinode of the electromagnetic wave (standing wave) having the above-mentioned resonant frequency. 3. Considering the length of the communication opening 34 (in other words, the thickness of the metal wall of the cavity resonator 30 in which the communication opening 34 is formed), it is considered that the communication opening 34 of the measurement object F can be treated electromagnetically in the same way as a circular waveguide. 4. The propagation mode within the circular waveguide can be determined from the above resonant frequency and length. 5. The identified propagation mode determines the k value in the cutoff frequency formula (Equation 2). 6. fc is set as the upper limit of the frequency included in the electromagnetic waves generated within the cavity resonator 30, and the hole diameter (radius) r of the communication port 34 is determined by the following formula 2 for the cutoff frequency.

number

[0045] The above-described determination procedure (flow) will be explained in more detail below (see FIGS. 6 and 7). The above-described concept is to consider the communication port 34 as a cutoff waveguide and reduce the electromagnetic waves (power) leaking from the cavity 32. As described above, the communication port 34 functions as a circular waveguide having a length equal to the thickness of the housing (metal wall) constituting the cavity resonator 30. As the term "cutoff waveguide" suggests, the circular waveguide functions as a high-pass filter, passing only electromagnetic waves above a certain frequency. Therefore, by adjusting the diameter of the circular waveguide (communication port 34) to a predetermined diameter, it is possible to prevent electromagnetic waves from leaking from the cavity resonator 30 and generate electromagnetic waves of a desired vibration mode inside the cavity resonator 30.

[0046] As mentioned above, the value of the constant k in the formula for the cutoff frequency (Equation 2) is determined by the propagation mode within the waveguide. The propagation mode is also determined by the radius and length of the waveguide. For example, as mentioned above, when a standing wave having electromagnetic waves in a frequency band with a resonant frequency of approximately 79 GHz is generated within the cavity resonator 30 and the length of the communication opening 34 (circular waveguide) is 1.2 mm, the propagation mode is generally the TM mode (Transverse Magnetic mode). Furthermore, as shown in FIG. 6, simulation results confirm that the mode of the electromagnetic waves passing through the communication opening 34 is predominantly the TM11 mode (a mode in which there are two antinodes of the electric field within the communication opening 34).

[0047] In this embodiment, as an example, when an electromagnetic wave with a resonant frequency of 79 GHz is generated in the cavity resonator 30 as described above, the cutoff frequency fc (the upper limit of the frequencies included in the electromagnetic wave generated in the cavity resonator 30) is set to 82 GHz, taking into account the electromagnetic wave generation error, and the radius of the communication opening 34 that does not allow electromagnetic waves with frequencies equal to or higher than the cutoff frequency fc to pass through is derived using the above-described determination procedure flow. As a result, the radius of the communication opening 34 needs to be 2.23 mm or less. This determines the upper limit of the hole diameter of the communication opening 34 through which the measurement object F passes. Note that the cutoff frequency fc may be set, for example, based on the upper limit of the frequency that can be generated by the oscillator 10 used.

[0048] (inlet and outlet) Inlet 31 is a portion through which the electromagnetic wave is introduced into cavity 32 via first waveguide 20, and outlet 33 is a portion through which the electromagnetic wave is extracted from cavity 32. Inlet 31 and outlet 33 are disposed opposite each other and have an area smaller than the cross-sectional area of ​​a cross section perpendicular to the propagation direction of the electromagnetic wave in cavity 32. More specifically, in this embodiment, inlet 31 and outlet 33 have an area smaller than the cross-sectional area of ​​cavity 32 defined by dimensions a and b perpendicular to the propagation direction of the electromagnetic wave in rectangular parallelepiped cavity 32.

[0049] Furthermore, in order to generate a standing wave having a predetermined resonant frequency within cavity 32, inlet 31 and outlet 33 are preferably configured to be large enough to prevent leakage of electromagnetic waves of the predetermined frequency. That is, if inlet 31 and outlet 33 are excessively large, it becomes difficult to generate a standing wave having a predetermined resonant frequency within cavity 32 due to the electromagnetic waves leaking from inlet 31 and outlet 33. This is because an excessive amount of electromagnetic waves leaking from inlet 31 and outlet 33 causes first waveguide 20 and second waveguide 40 to function as resonators. From this perspective, in this embodiment, inlet 31 and outlet 33 are configured to have an area smaller than 15% of the cross-sectional area of ​​cavity 32. The concept of calculating the upper limit of the area of ​​inlet 31 and outlet 33 will be described later.

[0050] The inlet 31 and the outlet 33 may be arranged by forming a predetermined through-hole in the cavity resonator 30, or may be formed by placing an iris having a through-hole with a predetermined area between the cavity resonator 30 and the first waveguide 20 or the second waveguide 40. In this embodiment, the inlet 31 and the outlet 33 are formed by an iris (small hole).

[0051] The members forming the inlet 31 and outlet 33 are preferably made of a conductor so as not to transmit electromagnetic waves. The thickness of the members forming the inlet 31 and outlet 33 (thickness of the iris) is preferably thin while ensuring a length that does not allow electromagnetic waves to pass through. Such a length is, for example, 1 μm or more and less than 100 μm. In this embodiment, the inlet 31 and outlet 33 are formed in a metal plate with a thickness of 50 μm to form the iris.

[0052] An example of how to determine the upper limits of the areas (sizes) of the inlet 31 and outlet 33 is shown below (see FIG. 9 ). As described above, when a standing wave having a resonant frequency of 79 GHz is generated inside the cavity resonator 30 having predetermined dimensions and the areas of the inlet 31 and outlet (iris) 33 are varied, the Q factor (Quality factor) varies depending on the areas (iris diameters) of the inlet 31 and outlet 33, as shown in FIG. 9 . A large Q factor indicates that the waveform of the electromagnetic wave, which peaks at the resonant frequency, is relatively steep. This means that when an inspection object containing a foreign object M passes through, the waveform of the electromagnetic wave changes significantly, resulting in high sensitivity to the foreign object M. Here, to detect foreign objects using the cavity resonator 30, a Q factor of greater than 1000 is generally required. Therefore, in this embodiment, the areas (iris diameters) of the inlet 31 and outlet 33 are preferably φ0.9 mm or less, which is preferably 15% or less of the cross-sectional area of ​​the cavity 32. From the above, it is preferable that the inner diameter of the inlet 31 and the inner diameter of the outlet 33 of the cavity resonator 30 are smaller than 15% of the cross-sectional area of ​​the cavity portion 32 provided in the cavity resonator 30 in a direction perpendicular to the line connecting the inlet 31 and the outlet 33.

[0053] The lower limit of the area (iris diameter) of the inlet 31 and outlet 33 is not particularly limited as long as it is greater than 0 and allows measurement of electromagnetic waves. On the other hand, it is preferable that the inlet 31 and outlet 33 have a predetermined size or larger so that the intensity of the electromagnetic waves acquired by the receiver 50 is at a certain level or higher. As mentioned above, the smaller the inlet 31 and outlet 33, the lower the level of the electromagnetic wave after passing through these through holes. For example, Fig. 8 shows a comparison of the electromagnetic wave level when the area of ​​the inlet 31 and outlet 33 is changed, assuming that the cross-sectional areas of the first waveguide 20, the second waveguide 40, and the cavity resonator 30 are a = 3.0 mm and b = 1.5 mm, and an electromagnetic wave with a resonant frequency of 79 GHz is used. The vertical axis of Fig. 8 represents the ratio between the intensity of the electromagnetic wave generated by the oscillator 10 and the intensity of the electromagnetic wave received by the receiver 50, and indicates the transmittance of the electromagnetic wave passing through the inlet 31 and outlet 33. The graph also shows the transmittance of the electromagnetic wave for each size of the inlet 31 and outlet 33 (the diameter of the inlet 31 and outlet 33) shown in the upper right. As shown in FIG. 8, the smaller the area of ​​the inlet 31 and outlet 33, the weaker the intensity of the electromagnetic wave that passes through them. Here, the dynamic range of commonly used measuring instruments with high measurement accuracy is approximately −110 dB (see the −110 dB line in FIG. 8). In light of this, if the diameter of the inlet 31 and outlet 33 is less than 0.3 mm, the intensity of the electromagnetic wave received by the receiver 50 will be weak, resulting in an area outside the measurement range. For these reasons, the diameter of the inlet 31 and outlet 33 is preferably φ0.3 mm or greater. Accordingly, the area of ​​the inlet 31 and outlet 33 relative to the cross-sectional area of ​​the first waveguide 20, the cavity 32, and the second waveguide 40 is preferably 1.6% or greater.

[0054] The upper limit of the diameter determined by the ratio of the area of ​​the inlet 31 and the outlet 33 to the cross-sectional area of ​​the cavity 32 of the cavity resonator 30, and the lower limit of the diameter determined by the ratio of the area of ​​the inlet 31 and the outlet 33 to the cross-sectional area of ​​the first waveguide 20, the cavity 32, and the second waveguide 40, as explained above, can be applied even if the shapes and dimensions of the first waveguide 20, the cavity resonator 30, and the second waveguide 40 are changed.

[0055] (funnel-shaped structure) In the present invention, a funnel-shaped structure is placed at the communication port that introduces the measurement object into the communication path, which makes it possible to efficiently introduce the measurement object into the communication path. The material type of the funnel-shaped structure is preferably a material that will not damage the measurement object F, and that will not wear out or will have as little frictional resistance as possible even when it comes into contact with the measurement object F. In this regard, ceramic is more preferable for many types of measurement objects F in light of the conditions above.

[0056] (Receiver) The receiver 50 receives the electromagnetic wave that is guided out of the cavity resonator 30 and passes through the second waveguide 40 (see FIG. 1).

[0057] (calculation section) The calculation unit 60 is configured with a calculation device that evaluates the state of the measurement object F based on fluctuations in the electromagnetic waves within the cavity resonator 30. The calculation unit 60 can evaluate the state of the measurement object F based on fluctuations in the intensity of a predetermined resonant frequency contained in the electromagnetic waves received by the receiver 50, or can evaluate the state of the measurement object F based on fluctuations in the generation frequency of the electromagnetic waves. In this embodiment, the inspection device 1 generates a standing wave of an electromagnetic wave having a predetermined resonant frequency within the cavity 32 of the cavity resonator 30, receives the electromagnetic wave derived from the cavity 32 with the receiver 50, and evaluates the presence or absence of a foreign object in the measurement object F to be inspected with the calculation unit based on the degree of fluctuation of the electromagnetic wave received by the receiver 50, for example, the degree of fluctuation of at least one of the frequency of the resonant frequency and the amplitude.

[0058] As described above, the inspection device 1 of this embodiment generates electromagnetic waves such as millimeter waves with a frequency of 30 GHz or more and inputs them into the cavity resonator 30, thereby making it possible to detect foreign particles M that are even smaller than foreign particles of about several hundred μm in size, which was the limit of detection by conventional inspection devices. Note that, when applying electromagnetic waves (millimeter waves) with a frequency of 30 GHz or more to the inspection device 1 that inputs electromagnetic waves to the measurement object F that is the inspection target within the cavity resonator 30, it is clear from the description above and from the description of the examples that will be described later that the inspection device 1 of this embodiment does more than simply employ an oscillator 10 that is suitable for this purpose.

[0059] Although the above-described embodiment is one example of a preferred embodiment of the present invention, the present invention is not limited to this embodiment and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the inspection device 1 including a single cavity resonator 30 has been described, but an inspection system may be configured including a plurality of such cavity resonators 30, and the measurement object F passes through the communication paths 35 of two or more of the plurality of cavity resonators 30. [Example]

[0060] An attempt was made to verify the principle of anomaly detection using an actual sample of the inspection device 1. Table 1 summarizes the specifications of the inspection device 1, including its shape, dimensions, and resonant frequency. Here, a ceramic connecting passage (φ1.5 mm) was used, and wheat flour was used as the measurement object F. The dielectric constant of wheat flour is known to be 2.5 to 3. The electromagnetic waves were measured by the receiver 50 after the measurement object F passed through the connecting passage 35 (see FIG. 15). FIG. 14 shows the waveforms obtained when the measurement object F did not contain any foreign matter and when the measurement object F contained a metal foreign matter. As shown in FIG. 14, when the measurement object F did not contain any foreign matter, a resonant frequency peak appeared near 77.23 GHz, as described above. On the other hand, when the measurement object F contained a foreign matter passed through the connecting passage 35 of the cavity resonator 30, the peak frequency of the resonant frequency and its intensity fluctuated. According to the inspection device 1 of this embodiment as described above, it was confirmed that the peak frequency of both the normal part (regular part) of the measurement object F and the abnormal part containing a foreign substance (metal part 1) changed by 20 kHz or more and the intensity changed by 2.3 bB or more, which is a change greater than the measurement error. [Table 1] [Industrial Applicability]

[0061] The present invention is suitable for application to an inspection device and an inspection system that measure filamentous bodies, powders, and liquids. [Explanation of symbols]

[0062] 1...Inspection equipment 10...Oscillator 12...Another oscillator 20...First waveguide 30...Cavity resonator 31...Entrance 32...Cavity part 33... Outlet 34...Communication port 35…Communication path 36...Peripheral wall part 37... Guide 39…Case 39a…Top surface 40...Second waveguide 50...Receiver 60...Arithmetic section F...Measurement target M…Foreign object

Claims

1. An inspection device for measuring filamentous bodies, powders, and liquids, an oscillator that emits electromagnetic waves; a first waveguide having one end connected to the oscillator and forming a waveguide for the electromagnetic wave; a cavity resonator including an inlet port to which the other end of the first waveguide is connected and through which the electromagnetic wave is introduced, a cavity portion in which the electromagnetic wave resonates in a specific vibration mode, an outlet port through which the electromagnetic wave is led out of the cavity portion, and a columnar communicating path disposed in the cavity portion; a second waveguide having one end connected to the outlet and configured to guide the electromagnetic wave from the cavity resonator; a receiver for receiving electromagnetic waves guided from the cavity resonator; a calculation unit that evaluates a state of the measurement object based on fluctuations of the electromagnetic wave in the cavity resonator; Equipped with The communication path is arranged along a pair of communication ports each including an insertion port through which the measurement object is inserted and an outlet port through which the measurement object is discharged.

2. 2. The inspection device according to claim 1, wherein a material used for a peripheral wall portion that defines the communication passage is a material that does not absorb the electromagnetic waves used.

3. 2. The inspection device according to claim 1, wherein a funnel-shaped structure is disposed at a communication port of the cavity resonator through which the measurement object is introduced into the communication path.

4. 2. The inspection device according to claim 1, wherein the cavity inside the cavity resonator is filled with a material that has low absorption of the frequency of the electromagnetic wave used.

5. 5. The inspection device according to claim 1, wherein the cavity resonator has a cavity portion in the shape of a rectangular parallelepiped.

6. 5. The inspection device according to claim 1, wherein the cavity in which the electromagnetic wave resonates in a specific vibration mode is cylindrical in shape, has an inlet for an object to be measured at one end and an outlet for an object to be measured at the other end, and the inlet through which the electromagnetic wave is introduced and the outlet through which the electromagnetic wave is extracted are opposed to each other on the side surface of the cylinder.

7. 5. The inspection device according to claim 1, wherein the cavity resonator is made of metal.

8. 5. The inspection device according to claim 1, wherein the cavity resonator is provided with a plurality of communication paths for passing a plurality of measurement targets.

9. 9. The inspection device according to claim 8, wherein each of the plurality of communication paths is provided at a predetermined interval so that the measurement object passes through an area within a predetermined range from an antinode of a standing wave generated inside the cavity.

10. 5. The inspection device according to claim 1, wherein the communicating path is set to a size that prevents electromagnetic waves having a frequency within a predetermined measurement range defined by the cutoff frequency of the waveguide from leaking out of the cavity.

11. 5. The inspection device according to claim 1, comprising a plurality of the cavity resonators.

12. The inspection device according to any one of claims 1 to 4, wherein the calculation unit estimates the state of the object to be measured based on at least one of a fluctuation in intensity of a predetermined resonant frequency contained in the electromagnetic wave and a fluctuation in the generation frequency of the electromagnetic wave.

13. 5. The inspection device according to claim 1, wherein the oscillator generates a continuous wave including a first range of frequencies centered on a predetermined resonant frequency.

14. a plurality of cavity resonators according to any one of claims 1 to 4; an inspection system configured so that the measurement object passes through communication passages of two or more of the plurality of cavity resonators;

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