Inspection Equipment

Abstract

To detect a smaller foreign substance than before in detection of foreign substances mixed in a filamentous body.SOLUTION: An inspection device 1 for a filamentous body F comprises an oscillator 10 that emits electromagnetic waves having a frequency of 30 GHz or more, a first waveguide 20 that is connected at one end to the oscillator 10 and forms a waveguide for the electromagnetic waves, a cavity resonator 30 that has an inlet 31 to which the other end of the first waveguide 20 is connected and into which the electromagnetic waves are introduced, a cavity 32 in which the electromagnetic waves resonate in a specific vibration mode, an outlet 33 from which the electromagnetic waves are derived from the cavity 32, and a communication outlet 34 that forms a communication channel 35 through which the filamentous body F is passed, a second waveguide 40 that is connected at one end to the outlet 33 and guides the electromagnetic waves from the cavity resonator 30, a receiver 50 that receives electromagnetic waves derived from the cavity resonator 30, and a calculation part 60 for evaluating the state of the filamentous body F based on fluctuations in the electromagnetic waves within the cavity resonator 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In a manufacturing line for filamentary bodies such as glass fibers, foreign objects such as metal pieces may be mixed into or attached to the filamentary bodies due to the equipment, surrounding environment, manufacturing process, etc. A metal detector utilizing the Doppler effect may be used as a method for detecting foreign objects such as metal pieces contained in an inspection object. In addition, an inspection device is used that irradiates an electromagnetic wave on the filamentary body as an inspection object in a cavity resonator in order to detect foreign objects contained in the filamentary body. When a detection wave (electromagnetic wave) is irradiated in such an inspection device, resonance occurs in the cavity resonator at a frequency determined by the internal medium and the dielectric constant of the inspection object. If a foreign object with a different dielectric constant is contained in the inspection object, this frequency changes, and by capturing this change, the foreign object can be detected (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-216687 A [Patent Document 2] Japanese Patent Application Publication No. 6-66735 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when using a metal detection method that utilizes the Doppler effect, the transport speed of the test object must be kept at a certain level or higher in order to ensure detection accuracy. When the transport speed of the test object is kept at a certain level or higher, it can be difficult to accurately determine at which position of the test object a foreign object is present. As a result, it has become necessary to discard even parts of the test object that do not contain foreign objects.

[0005] In addition, the metal detection method using the Doppler effect and the conventional inspection device described in the above patent documents have limitations in the size of foreign objects that can be detected. For example, Patent Document 1 describes a method in which a microwave is supplied to a waveguide having a through hole through which the inspection object passes, and when the inspection object contains a foreign object, the reflected wave is increased to detect a foreign object such as a metal piece. In addition, Patent Document 2 describes a method in which a microwave is supplied to a cavity resonator having a through hole through which the inspection object filament passes, and when the inspection object contains a foreign object, the waveform of the standing wave generated in the cavity resonator is changed to detect a foreign object such as a metal piece.

[0006] Here, the strength of the reflected wave weakens as the size of the foreign object becomes smaller, so that the technology described in Patent Document 1 makes it difficult to detect relatively small foreign objects. In addition, the size of detectable foreign objects varies depending on the frequency band of the electromagnetic waves used. The frequency band of the microwaves described in Patent Documents 1 and 2 is about 3 GHz or more and less than 30 GHz, and the size of foreign objects such as metal pieces that can be detected using electromagnetic waves of this frequency band is several millimeters, and at the minimum, about 100 micrometers. Therefore, when attempting to detect foreign objects mixed into a filament by applying electromagnetic waves of such a frequency band, only foreign objects that exist continuously for a certain amount or more in the length direction of the filament could be detected. Thus, the detection accuracy and the size of detectable foreign objects of the above-mentioned conventional technology were not very satisfactory.

[0007] In order to detect smaller foreign objects, it is expected that millimeter waves, which are electromagnetic waves with a shorter wavelength than microwaves and have a frequency of 30 GHz or more, will be used. However, it has been found that simply replacing microwaves with millimeter waves to realize an inspection device will not function sufficiently as an inspection device. For example, it has been found that if electromagnetic waves with shorter wavelengths are used, it becomes difficult to steadily generate a specific electromagnetic wave effective for detecting foreign objects in the space through which the filament to be inspected passes.

[0008] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an inspection device and an inspection system that are capable of detecting smaller foreign matter that has become mixed into a filament. [Means for solving the problem]

[0009] One aspect of the present invention is a filament inspection device, comprising: An oscillator that emits electromagnetic waves with a frequency of 30 GHz or more; a first waveguide having one end connected to the oscillator and forming a waveguide for an 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 output from the cavity portion, and a communication port forming a communication passage through which the filament passes; a second waveguide having one end connected to the outlet for guiding 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 filament based on a fluctuation of the electromagnetic wave in the cavity resonator; The inspection device includes:

[0010] As mentioned above, the detectable size of a foreign object depends on the wavelength of the detection (electromagnetic wave). In a conventional inspection device that uses microwaves (wavelength: several mm to about 30 cm) for this detection, the minimum size of a foreign object that can be detected is several hundred μm, and it is not possible to detect a foreign object smaller than this. In this regard, an inspection device such as that of the present embodiment uses electromagnetic waves with a frequency of 30 GHz or more, such as millimeter waves, arranges a waveguide, a cavity resonator, and a waveguide between an oscillator and a receiver, resonates in the cavity resonator, and measures the degree of fluctuation of the electromagnetic wave in the cavity resonator to evaluate the presence or absence of a foreign object, making it possible to detect foreign objects smaller than several hundred μm, for example, foreign objects of several micrometers (μm).

[0011] Inside the cavity resonator in the above-described inspection apparatus, one or more antinodes of a standing wave may be generated from the inlet to the outlet of the cavity.

[0012] The cavity resonator in the above-mentioned inspection device may be configured so that the number n of antinodes of a standing wave generated inside the cavity is an odd number.

[0013] In the above inspection device, the cavity resonator may be configured so that the number n of loops of a standing wave generated inside the cavity is 3 or more.

[0014] In the above-mentioned inspection device, the communication path may be formed at a position where the filament passes through a predetermined range from an antinode of a standing wave generated inside the cavity in a vibration mode.

[0015] In the above inspection apparatus, the cavity resonator may have a cavity portion in the shape of a rectangular parallelepiped.

[0016] In the above-mentioned inspection apparatus, the inlet and outlet may be formed by an iris.

[0017] In the above-mentioned inspection device, the inner surface of the cavity may be made of metal.

[0018] In the above-mentioned inspection device, the cavity resonator may be provided with a plurality of communication paths for passing a plurality of filaments.

[0019] In the above-described inspection device, each of the plurality of communication paths may be provided at a predetermined interval so that the filament passes through an area within a predetermined range from an antinode of a standing wave generated inside the cavity.

[0020] In the above-mentioned inspection device, the calculation unit may evaluate the condition of the filament based on at least one of the fluctuation in intensity of a predetermined resonant frequency contained in the electromagnetic wave and the fluctuation in the generation frequency of the electromagnetic wave.

[0021] In the above inspection device, the oscillator may generate a continuous wave including a first range of frequencies centered on a predetermined resonant frequency.

[0022] In the above-mentioned inspection apparatus, the oscillator may generate a chirp wave including a continuously repeated resonant frequency.

[0023] In the above-described inspection device, the calculation unit may evaluate the presence or absence of an abnormality in the filament based on at least one of the frequency difference between a first chirp wave emitted by the oscillator and received by the receiver via the cavity resonator and a second chirp wave having a different degree of frequency fluctuation over time than the chirp wave emitted by the oscillator, and the signal strength difference.

[0024] The inspection device as described above may include a protective tube disposed inside the cavity resonator and separating the communication passage from the hollow portion inside the cavity resonator.

[0025] The communication port in the above-mentioned inspection device may be set to a size such that electromagnetic waves having a frequency within a predetermined measurement range defined by the cutoff frequency of the waveguide do not leak out of the cavity.

[0026] In the above inspection device, the inner diameter of the inlet and the inner diameter of the outlet may be smaller than 15% of the cross-sectional area of ​​the cavity provided in the cavity resonator in a direction perpendicular to a line segment connecting the inlet and the outlet.

[0027] Moreover, an inspection system according to one aspect of the present invention includes a plurality of cavity resonators as described above, and is configured so that the filament passes through the communication passages of two or more of the plurality of cavity resonators. Effect of the Invention

[0028] According to the present invention, it is possible to detect foreign matter that has become mixed into a filamentous body and that is smaller than before. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of an inspection device. [Diagram 2] 1A to 1C are diagrams illustrating examples of the shape of a cavity resonator. [Diagram 3] 13 is an image showing an example of the electric field intensity in a cavity resonator when the number of loops is n=3. [Figure 4] FIG. 13 is a diagram showing how a filament is passed through a communication passage of a cavity resonator. [Diagram 5] 11 is a diagram showing electric and magnetic field lines when the communication port is viewed from above. FIG. [Figure 6] FIG. 13 shows the electric field intensity plot of TM11. [Figure 7] 1 is a graph showing the relationship between the radius of a waveguide and the cutoff frequency of a TM11 mode. [Figure 8] 13 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 object M). [Figure 10] Graph showing (A) an example of a waveform of a chirp wave, and (B) an example of change in frequency of the chirp wave. [Figure 11] FIG. 1 is a schematic diagram showing a configuration in which two different chirp waves are radiated from separate oscillators. [Figure 12] (A) A graph showing an example of two different chirp waves, and (B) a graph showing the progress of the frequency difference between the two different chirp waves. [Figure 13] Graph (A) shows the relationship between the difference in frequency (IF frequency) of two different chirp waves and the intensity of chirp wave 1, and graph (B) shows the relationship between the original frequency of chirp wave 1 and the intensity of chirp wave 1. [Figure 14] 11 is a graph showing an example of changes in resonance frequency of a normal portion of a filament and a portion containing a foreign object. [Figure 15] 11 is a graph showing examples of detected waveforms of a normal portion of a filament and a portion containing a foreign object in Example 1 of the present disclosure. [Figure 16] 1A and 1B are a perspective view and an enlarged view of a part of a cavity resonator designed in a second embodiment of the present disclosure. [Figure 17]11 is a graph showing examples of detected waveforms of a normal portion of a filament and a portion containing a foreign object; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Preferred embodiments of an inspection device and an inspection system according to the present invention will be described in detail below with reference to the drawings (see FIGS. 1 to 13).

[0031] The inspection device according to the present disclosure is a device for measuring a filament F, such as glass fiber, manufactured through various manufacturing processes, and for inspecting whether or not there is an abnormality such as the inclusion or attachment of a foreign object M, such as a metal piece, due to the equipment, surrounding environment, manufacturing process, etc. In such an inspection device, an electromagnetic wave is incident on the filament F in a cavity resonator, resonance occurs at a predetermined frequency determined by the dielectric constant of the internal medium and the filament F, and the foreign object M is detected by capturing the change in frequency that occurs when the filament F contains a foreign object M with a different dielectric constant. Moreover, the inspection device according to the present disclosure generates a standing electromagnetic wave having a predetermined resonant frequency within the cavity resonator. In this disclosure, electromagnetic waves having 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 having 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 the boundary between millimeter waves and microwaves is not strictly defined at 30 GHz.

[0032] 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.).

[0033] (Oscillator) The oscillator 10 is a device that generates a continuous wave including a predetermined range (first range) of frequencies centered on a predetermined resonant frequency. In this embodiment, the oscillator 10 and the like are configured on the assumption that electromagnetic waves belonging to the millimeter wave (30 GHz or more to less than 300 GHz) band are mainly used, but it is of course possible to apply electromagnetic waves with a frequency of 300 GHz or more.

[0034] (waveguide) The first waveguide 20 is a member for guiding the electromagnetic wave generated in the oscillator 10 to the cavity resonator 30, and one end of the first waveguide 20 is connected to the oscillator 10 and the other end to the cavity resonator 30 (see FIG. 1). The second waveguide 40 is a member for guiding the electromagnetic wave from the cavity resonator 30 to the receiver 50, and one end of the second waveguide 40 is connected to the cavity resonator 30 and the other end 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 a rectangular cross section having the same dimensions a and b (see FIG. 2) as 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 the first waveguide 20 and the second waveguide 40, for example, a waveguide (waveguide) having a shape having dimensions corresponding to electromagnetic waves of a predetermined frequency band, as specified in the EIA (Electronic Industries Alliance) standard, can be appropriately selected and used.

[0035] (cavity resonator) The cavity resonator 30 is made of a housing (structure) 39 having a cavity 32 formed therein. The cavity 32 contains a medium that transmits electromagnetic waves in the resonant frequency band well, and in this embodiment, this medium is air. The cavity resonator 30 is configured to generate a standing wave in the cavity 32. The standing wave generated in 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. In addition, as can be seen from the fact that the resonant frequency f in the case of the cavity resonator 30 having a rectangular parallelepiped shape with each dimension shown in FIG. 2 is expressed by the following formula 1, the smaller the dimension of the cavity resonator 30 is and the lower the dielectric constant of the medium (e.g., air in the internal space of the cavity resonator 30) is, the higher the electromagnetic wave generated in the cavity resonator 30 will tend to resonate at a higher frequency f. 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

[0036] Here, if the dimensions are reduced to miniaturize the cavity resonator 30, a standing wave having a predetermined resonant frequency can be generated inside the cavity resonator 30 even when a millimeter wave is used, and the generation of the standing wave can 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 way, when the filament F to be measured, which includes the foreign matter M, passes through a range of relatively strong electric field intensity, the range of change in the frequency or intensity of the electromagnetic wave that is generated becomes larger, and the detection accuracy can be improved.

[0037] As an example, in this embodiment, the cavity resonator 30 is used in which the dimensions shown in FIG. 2 are a=3.0 mm, b=1.5 mm, and n=3, i.e., 3 is adopted as the number of loops of the standing wave being an odd number, and c=7.2 mm. This allows a standing wave having a resonance frequency of 79 GHz to be generated in the cavity resonator 30. The rectangular cavity resonator 30 may be a structure conforming to the WR12 of the EIA standard, and may have dimensions adjusted to a=1.549 mm and b=3.099 mm. It goes without saying that the value of 79 GHz set as the resonance frequency will deviate by several GHz due to the presence and dimensions of the inlet 31 and outlet 33, which will be described later, and the dimensions of the communication port 34.

[0038] The above dimensions a, b, and c are merely examples, and the dimensions of the cavity resonator 30 can be appropriately adjusted based on the desired electromagnetic waves to be generated therein. According to such an inspection device, it is possible to detect smaller foreign objects compared to the conventional device, and the detection accuracy is improved.

[0039] The inspection device 1 will be described in further detail below. Compared to the conventional technique, when using millimeter waves in the high frequency band, the sensitivity to foreign matter M such as metal pieces contained in the filament F is improved, but it may be difficult to generate a predetermined electromagnetic wave inside the cavity resonator 30 (cavity 32) through which the filament F passes. For example, depending on the accuracy of the electromagnetic wave introduction method, leakage of electromagnetic waves from the cavity resonator 30, etc., it may be difficult to generate a predetermined electromagnetic wave inside the cavity resonator 30.

[0040] From the above viewpoints, it is preferable to appropriately introduce the electromagnetic wave into the space (the cavity 32) in order to generate a predetermined electromagnetic wave in the space through which the filament F to be inspected passes. The inspection device 1 in this embodiment adopts a configuration in which the electromagnetic wave generated by the oscillator 10 is introduced into the cavity 32 of the cavity resonator 30 via the first waveguide 20 and the inlet 31, and is received by the receiver 50 via the outlet 33 and the second waveguide 40. According to the above, the oscillator 10, the receiver 50, and the electromagnetic wave waveguide (the first waveguide 20 and the second waveguide 40) can be functionally separated from the space (the cavity 32 of the cavity resonator 30) in which an electromagnetic wave of a predetermined vibration mode needs to be generated in order for the inspection object to pass through, and as a result, it becomes easy to generate a desired electromagnetic wave in the cavity 32.

[0041] In this embodiment, when electromagnetic waves having a frequency of 30 GHz or more are applied, a cavity resonator 30 having the following configuration is constructed to improve a predetermined detection accuracy.

[0042] (Outline of the 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 filament F passes (see Figure 1, etc.).

[0043] The shape of the cavity 32 is not particularly limited, but may be, for example, a rectangular parallelepiped shape. The inlet 31 and the outlet 33 are arranged so as to face each other inside the cavity 32. The cavity 32 is configured so that a standing wave having one or more antinodes, the number n of which 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. In addition, among the three approximately circular electric field intensities shown in FIG. 3, the intensity is stronger toward the center. It should be noted further about FIG. 3 that, since the electric field intensity image, which was originally expressed in color, is expressed in black and white shading, the electric field intensity appears stronger on the outer side of the approximately circular shape, but the actual electric field intensity is weaker the further away from the center of the circle.

[0044] The communication port 34 is provided in the housing 39 of the cavity resonator 30 as a hole through which the filament F can pass, and forms a communication passage 35 through which the filament F passes (see FIG. 4, etc.). During measurement, the filament F moves from top to bottom (or bottom to top) in the communication passage 35 at a predetermined speed and passes through (see FIGS. 1 and 4). That is, the filament 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 ports 34 is provided on the upper surface (indicated by reference symbol 39a) in FIG. 2, which is the widest surface of the housing 39, having a width a and a length c, and on the lower surface, which is the opposite surface. It is desirable that the communication passage 35 formed by the pair of communication ports 34 is formed so as to pass through a portion of the standing wave formed in the cavity resonator 30 where the electric field intensity is strong. That is, the communication path 35 constituted by a pair of communication ports 34 is preferably formed at a location where a peak of an antinode of the standing wave formed in 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 are 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 part of the middle antinode of the three antinodes having strong electric field strength (see FIG. 4).

[0045] A protective tube 36 may be provided to separate the communication passage 35 from the hollow portion 32 in the cavity resonator 30. The protective tube 36 is preferably made of a material that absorbs little electromagnetic waves generated in the hollow portion 32, and specific examples of such a material include ceramics and resin. The protective tube 36 is preferably made of a material that does not damage the filament F, and is also preferably made of a material that does not wear out or has as small friction resistance as possible even when it comes into contact with the filament F. In this respect, ceramics are more preferable for many types of filament F in light of the above conditions, and ceramics are most preferable when the filament F to be inspected is a glass fiber. In this manner, by providing the protective tube 36, 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.

[0046] In this embodiment, one communication path 35 consisting of a pair of communication ports 34 is formed, but this is merely an example. For example, multiple communication paths 35 may be provided so that multiple filamentous bodies F can pass through each communication path 35 at the same time. 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 intensity at a predetermined interval (see FIG. 4). As a result, each of the multiple communication paths 35 consisting of a pair of communication ports 34 is formed at a location where the peak of the antinode of the standing wave formed in the cavity resonator 30 occurs.

[0047] (Diameter of communication port) When inspecting the filament F for foreign objects, the cavity resonator 30 needs to be provided with a communication port 34 for passing the filament F, and this allows communication between the cavity 32 and the external environment. The larger the diameter of the communication port 34, the easier it is to pass the filament F through and the better the operability. However, when inspecting for foreign objects using electromagnetic waves in the millimeter wave band, as described above, the influence of the electromagnetic waves leaking from the communication port 34 on the electromagnetic waves in 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 the inspection accuracy caused by the structure of the cavity resonator 30, including the diameter of the communication port 34, becomes more significant than in the past. In this case, it is desirable for the communication port 34 to have as large a hole diameter as possible while suppressing the leakage of electromagnetic waves. An example of a procedure (flow) for determining the size of the hole diameter based on these points is shown below. 1. The resonant frequency of the electromagnetic wave (standing wave) generated within the cavity resonator 30 is determined. 2. The communication port 34 of the filament F is disposed 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 filament F can be electromagnetically treated in the same way as a circular waveguide. 4. From the above resonant frequency and the length of the circular waveguide, the propagation mode within it is identified. 5. The identified propagation mode determines the k value included 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

[0048] The above-mentioned determination procedure (flow) will be supplemented below (see Figs. 6 and 7). The above-mentioned idea 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. Here, as the expression "cutoff waveguide" suggests, the circular waveguide operates as a high-pass filter and only passes electromagnetic waves above a certain frequency. Therefore, by adjusting the aperture of the circular waveguide (communication port 34) to a predetermined aperture, it is possible to prevent the electromagnetic waves from leaking from the cavity resonator 30 and generate electromagnetic waves of a desired vibration mode inside the cavity resonator 30.

[0049] As described above, the value of the constant k in the formula for the cutoff frequency (Formula 2) is determined by the propagation mode in the waveguide. The propagation mode is also determined according to the radius and length of the waveguide. As an example, as described above, when a standing wave having an electromagnetic wave with a resonant frequency of about 79 GHz is generated in the cavity resonator 30 and the length of the communication port 34 (circular waveguide) is 1.2 mm, the propagation mode is generally TM mode (Transverse Magnetic mode), and as shown in FIG. 6, it has been confirmed from the simulation results that the mode of the electromagnetic wave passing through the communication port 34 is predominantly TM11 (a mode in which there are two antinodes of the electric field in the communication port 34).

[0050] In this embodiment, as an example, as described above, when an electromagnetic wave with a resonant frequency of 79 GHz is generated in the cavity resonator 30, the cutoff frequency fc (the upper limit of the frequency included in the electromagnetic wave generated in the cavity resonator 30) is set to 82 GHz, taking into consideration the generation error of the electromagnetic wave, and the radius of the communication port 34 that does not allow electromagnetic waves having a frequency equal to or higher than the cutoff frequency fc is derived by the above-mentioned determination procedure flow. As a result, the radius of the communication port 34 needs to be 2.23 mm or less. This determines the upper limit of the hole diameter of the communication port 34 through which the filament F passes. The cutoff frequency fc may be set, for example, based on the upper limit of the frequency that the oscillator 10 used can generate.

[0051] (Inlet and outlet) The inlet 31 is a portion where the electromagnetic wave is introduced into the cavity 32 via the first waveguide 20, and the outlet 33 is a portion where the electromagnetic wave is output from the cavity 32. The inlet 31 and the outlet 33 are disposed to face each other, and have an area smaller than the cross-sectional area of ​​a cross section perpendicular to the traveling direction of the electromagnetic wave in the cavity 32. More specifically, in this embodiment, the inlet 31 and the outlet 33 have an area smaller than the cross-sectional area of ​​the cavity 32 defined by the dimensions a and b perpendicular to the traveling direction of the electromagnetic wave in the rectangular parallelepiped cavity 32.

[0052] In addition, in order to generate a standing wave having a predetermined resonant frequency in the cavity 32, the inlet 31 and the outlet 33 are preferably configured to have a size that does not allow electromagnetic waves of a predetermined frequency to leak out. That is, if the inlet 31 and the outlet 33 are too large, it becomes difficult to generate a standing wave having a predetermined resonant frequency in the cavity 32 due to the electromagnetic waves leaking from the inlet 31 and the outlet 33. This is because the first waveguide 20 and the second waveguide 40 function as resonators due to the excessive amount of electromagnetic waves leaking from the inlet 31 and the outlet 33. From the above viewpoint, in this embodiment, the inlet 31 and the outlet 33 are configured to have an area smaller than 15% of the cross-sectional area of ​​the cavity 32. The concept of calculating the upper limit of the area of ​​the inlet 31 and the outlet 33 will be described later.

[0053] 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).

[0054] The members forming the inlet 31 and outlet 33 are preferably made of a conductor so that electromagnetic waves do not pass through. 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 serve as the iris.

[0055] An example of how to obtain the upper limit of the area (size) of the inlet 31 and outlet 33 is as follows (see FIG. 9). As described above, when the areas of the inlet 31 and outlet (iris) 33 are changed in a state where a standing wave having a resonant frequency of 79 GHz is generated inside the cavity resonator 30 having a predetermined dimension, the Q factor (Quarily factor) varies depending on the areas (iris diameter) of the inlet 31 and outlet 33 as shown in FIG. 9. A large Q factor indicates that the waveform of the electromagnetic wave with the resonant frequency as a peak is relatively steep, and therefore the change in the waveform of the electromagnetic wave when the inspection object including the foreign matter M passes through is large, and the sensitivity to the foreign matter M is high. Here, in order to detect a foreign matter using the cavity resonator 30, the Q factor generally needs to be larger than 1000. Therefore, in this embodiment, the areas (iris diameter) 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.

[0056] 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 described above, the smaller the inlet 31 and outlet 33 are, 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 in the case where the cross-sectional areas of the first waveguide 20, the second waveguide 40, and the cavity resonator 30 are dimension a=3.0 mm and dimension b=1.5 mm as described above, and an electromagnetic wave having a resonance frequency of 79 GHz is used. The vertical axis of FIG. 8 shows 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, which indicates the transmittance of the electromagnetic wave passing through the inlet 31 and outlet 33, and the transmittance of the electromagnetic wave for each size of the inlet 31 and outlet 33 (diameter of the aperture 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 smaller the intensity of the electromagnetic wave after passing through them. Here, the dynamic range of a generally used measuring instrument 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 is weak, and an area outside the measurement range occurs. From the above, the diameter of the inlet 31 and outlet 33 is preferably φ0.3 mm or more. According to this, 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 more.

[0057] The upper limit of the aperture 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 aperture 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.

[0058] (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).

[0059] (calculation section) The calculation unit 60 is configured with a calculation device that evaluates the state of the filament F based on the fluctuation of the electromagnetic waves in the cavity resonator 30. The calculation unit 60 can evaluate the state of the filament F based on the fluctuation of the intensity of a predetermined resonant frequency contained in the electromagnetic waves received by the receiver 50, or can evaluate the state of the filament F based on the fluctuation of 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 filament F to be inspected by 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.

[0060] (Use of chirp waves) Here, the inspection device 1 may employ a chirp wave as the electromagnetic wave generated by the oscillator 10. This allows the frequency to be down-converted in signal processing when using electromagnetic waves in a high frequency band such as the millimeter wave band, thereby reducing loss in the arithmetic circuit that processes the signal, and compressing the amount of information to a level that makes it easy to perform AD conversion. An example of a spectrum measurement method using the difference between chirp waves with different time change rates in the inspection device 1 having the above configuration will be described below (see Figs. 10 to 12). A chirp wave refers to a waveform based on a signal (chirp signal) whose frequency changes with time (see Fig. 10). In this embodiment, two chirp waves 1 and 2 whose frequency increases with time are used.

[0061] In this embodiment, in addition to the oscillator 10, another oscillator 12 is prepared, and chirp wave 1 is emitted from the oscillator 10, and chirp wave 2 is emitted from the other oscillator 12 (see FIG. 11). For the chirp wave 2, a chirp wave having a different degree of frequency fluctuation from that of the chirp wave 1 is adopted. The chirp wave 1 is introduced into the cavity resonator 30, is affected by the resonator, and if there is a foreign object M, its intensity is changed by the object, and then the chirp wave 1 is output from the output port 33. On the other hand, the chirp wave 2 is not introduced into the cavity resonator 30, i.e., it is not affected by the detection target, and is added to the chirp wave 1 output from the cavity resonator 30 and used for multiplication.

[0062] These chirp waves 1 and 2 are configured to have different frequencies at a certain point in time (excluding the intersection between chirp wave 1 and chirp wave 2 in the graph showing the relationship between time and frequency). In this embodiment, chirp wave 1 and chirp wave 2 are configured to have different initial frequencies at the start of oscillation and different rates of increase in frequency (represented as the slope in the graph shown in FIG. 10(B)). More specifically, in this embodiment, chirp wave 1 is set so that its initial frequency at the start of oscillation is larger than that of chirp wave 2. Also, chirp wave 1 is configured so that its rate of increase in frequency over time is smaller than that of chirp wave 2.

[0063] In addition, the chirp wave 1 and the chirp wave 2 may be radiated as signals of constant intensity within the range of the radiated frequency. In other words, the intensity information of the chirp wave 2 does not need to be used. In this embodiment, the frequency information of the chirp wave 2 is used to down-convert the frequency of the chirp wave 1. According to this method, it is possible to more accurately measure the intensity (power) of the chirp wave 1 immediately after it is derived from the cavity resonator 30.

[0064] An example will be given for further explanation. It is assumed that the frequency of the chirp wave 1 passing through the cavity resonator 30 is changed from 77.005 GHz to 91.001 GHz between t=0 and t=100. It is also assumed that the frequency of the chirp wave 2 not passing through the cavity resonator 30 is changed from 77 GHz to 91 GHz between t=0 and t=100 (see FIG. 12(A)). In this case, the change in the frequency difference between the two chirp waves is as shown in the figure (see FIG. 12(B)). The difference at t=0 is 0.005 GHz (5 MHz), but at t=100, the difference becomes 0.001 GHz (1 MHz).

[0065] Here, for a graph with the frequency difference (IF frequency) on the horizontal axis and the intensity of the chirp wave emitted from the transmitter 1 (or the difference between the intensity of the chirp wave 1 emitted from the transmitter 1 and the intensity of the chirp wave 2 emitted from the transmitter 2) (not shown) on the vertical axis, if the frequency difference is Fourier transformed to obtain an intensity spectrum and the relationship between the frequency difference (IF frequency) and the intensity of the chirp wave 1 is obtained (see FIG. 13(A)), a graph is obtained with the frequency difference that varies with the elapsed time, that is, the frequency difference corresponding to the elapsed time on the horizontal axis and the intensity of the chirp wave (i.e., chirp wave 1) passing through the cavity resonator 30 on the vertical axis. Next, based on the above, if the relationship between the original frequency of the chirp wave 1 and the intensity of the chirp wave 1 is obtained (see FIG. 13(B)), the frequency can be made lower than the original frequency during this conversion. This allows the electromagnetic wave received by the receiver 50 to be down-converted to a frequency band that is easy to convert into an AD conversion. In addition, in the present disclosure using millimeter waves, which are electromagnetic waves in a high frequency band, compared to the conventional technology, when the receiver 50 performs signal processing on the received electromagnetic waves, the transmission loss in the electric circuit responsible for the arithmetic processing, especially the transmission loss due to dielectric loss proportional to the frequency, becomes large. To solve this, it is necessary to change the material of the electric circuit, especially the material of the substrate, but currently, there is no material that can significantly reduce the dielectric loss when using electromagnetic waves in the millimeter wave band and is useful for practical use. On the other hand, as described above, by performing arithmetic processing on the electromagnetic waves that have been down-converted, the arithmetic processing can be performed with reduced transmission loss. When implementing the spectrum measurement method using chirp waves as described above, the calculation unit 60 evaluates the presence or absence of an abnormality in the filament F based on the difference in frequency or the difference in signal strength between these chirp waves 1 and 2.

[0066] According to the inspection device 1 of the present embodiment as described above, electromagnetic waves such as millimeter waves having a frequency of 30 GHz or more are generated and incident on the cavity resonator 30, thereby making it possible to detect foreign bodies M that are smaller than foreign bodies of about several hundred μm, which was the limit of detection by conventional inspection devices. It is clear from the above description and also from the description of the examples described later that when applying electromagnetic waves (millimeter waves) having a frequency of 30 GHz or more to the inspection device 1 that incidents electromagnetic waves on the filament F to be inspected within the cavity resonator 30, the inspection device 1 of the present embodiment does not merely employ an oscillator 10 suitable for the application of such waves.

[0067] The above-described embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited thereto and various modifications can be made without departing from the scope 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 including a plurality of such cavity resonators 30 and allowing the filament F to pass through the communication passages 35 of two or more of the plurality of cavity resonators 30 may be configured. EXAMPLES

[0068] An attempt was made to verify the principle of anomaly detection using an actual sample of the inspection device 1. The specifications of the inspection device 1, including the shape, dimensions, and resonant frequency, are summarized and shown in Table 1. Here, a glass fiber was used as the filament F. The glass fiber was passed through the communication passage 35 of the cavity resonator 30, and the electromagnetic waves measured by the receiver 50 when the glass fiber was passed through at a speed of 5.0 m / min were measured. FIG. 14 shows a waveform when a normal part of the filament F that does not contain a foreign object of the glass fiber passes through, and a waveform when an abnormal part of the glass fiber that contains a foreign object passes through. As shown in FIG. 14, when the normal part passes through, a peak of the resonant frequency appears near 79 GHz as described above. On the other hand, when the abnormal part containing a foreign object passes through the communication passage 35 of the cavity resonator 30, the peak frequency of the resonant frequency and its intensity fluctuate. According to the inspection device 1 of the present embodiment as described above, it was found that the peak frequency and intensity of both the normal part (regular part) of the filament F and the abnormal part (metal part 1) containing a foreign matter changed significantly, and the changes were greater than the measurement error. [Table 1] It was also confirmed that the inspection device 1 disclosed herein (when the communication port diameter Φ is 1.0 mm and the iris diameter is φ0.7 mm) is capable of detecting a foreign object with a diameter α of 0.2 μm and a length of 100 μm (volume equivalent to a metal ball φ2.6 μm) (see FIG. 15). EXAMPLES

[0069] Using an electromagnetic field simulator, we tried to verify the principle of anomaly detection. Here, we designed the cavity resonator 30 so that the resonance frequency was between 76 and 81 GHz (however, the diameter of the communication port Φ: 1.5 mm, and the iris diameter φ0.6 mm), and passed a filament F containing a foreign object (metal part) M through the communication path 35 (see FIG. 16). As a result of calculation, it was found that the peak shape, peak intensity, and resonance frequency all changed significantly when the foreign object M entered the cavity resonator 30 (see FIG. 17). Note that, although the conditions in FIG. 17 were the same as those in FIG. 14, the peak positions were slightly different. This was thought to be because, in reality, the thermal expansion of the metal part of the cavity resonator 30 and the influence of the tightening method of the screws of the connection part between the cavity resonator 30 and the waveguides 20 and 40 were sensitively reflected. [Industrial Applicability]

[0070] The present invention is suitable for application to a filament inspection device and inspection system. [Explanation of symbols]

[0071] 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...Protection tube 39…Housing 39a…Top surface 40…Second waveguide 50…Receiver 60...Arithmetic section F: filamentous body M…Foreign object

Claims

1. An apparatus for inspecting a filament, comprising: An oscillator that emits electromagnetic waves with a frequency of 30 GHz or more; 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 output from the cavity portion, and a communication port forming a communication passage through which the filament passes; 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 an electromagnetic wave guided from the cavity resonator; a calculation unit that evaluates a state of the filament based on a fluctuation of the electromagnetic wave in the cavity resonator; Equipped with The cavity resonator is provided with a plurality of communication paths for passing a plurality of filaments, an inspection device, wherein each of the plurality of communication paths is provided at a predetermined interval so that the filament passes through an area within a predetermined range from an antinode of a standing wave generated inside the hollow portion.

2. An inspection device for a filament, comprising: An oscillator that emits electromagnetic waves with a frequency of 30 GHz or more; 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 output from the cavity portion, and a communication port forming a communication passage through which the filament passes; 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 an electromagnetic wave guided from the cavity resonator; a calculation unit that evaluates a state of the filament based on a fluctuation of the electromagnetic wave in the cavity resonator; Equipped with The calculation unit evaluates the presence or absence of an abnormality in the filament based on at least one of the frequency difference between a first chirp wave emitted by the oscillator and received by the receiver via the cavity resonator and a second chirp wave having a different degree of frequency fluctuation over time than the chirp wave emitted by the oscillator, and the signal strength difference.

3. 3. The inspection device according to claim 1, wherein one or more antinodes of a standing wave are generated inside the cavity resonator from an inlet to an outlet of the cavity.

4. 4. The inspection device according to claim 3, wherein the cavity resonator has a standing wave generated inside the cavity, the number of antinodes of which is an odd number, n.

5. 5. The inspection device according to claim 4, wherein the cavity resonator has a number n of loops of a standing wave generated inside the cavity, the number n being 3 or more.

6. 3. The inspection device according to claim 1, wherein the communication path is formed so that the filament passes through a predetermined range from an antinode of a standing wave generated inside the cavity in the vibration mode.

7. The inspection device according to claim 1 , wherein the cavity resonator has a cavity portion having a rectangular parallelepiped shape.

8. The inspection device according to claim 1 , wherein the inlet and the outlet are formed by an iris.

9. The inspection device according to claim 1 , wherein an inner surface of the cavity is made of a metal.

10. The inspection device according to claim 2 , wherein the cavity resonator is provided with a plurality of communication paths for passing a plurality of filaments.

11. 11. The inspection device according to claim 10, wherein each of the plurality of communication paths is provided at a predetermined interval so that the filament passes through an area within a predetermined range from an antinode of a standing wave generated inside the hollow portion.

12. The inspection device according to claim 1 , wherein the calculation unit evaluates a state of the filament based on at least one of a fluctuation in intensity of a predetermined resonant frequency contained in the electromagnetic wave and a fluctuation in a generation frequency of the electromagnetic wave.

13. 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. The inspection device according to claim 1 , wherein the oscillator generates a chirp wave including a series of resonant frequencies.

15. The inspection device according to any one of claims 1, 3 to 12 and 14, wherein the calculation unit evaluates the presence or absence of an abnormality in the filament based on at least one of the frequency difference between a first chirp wave emitted by the oscillator and received by the receiver via the cavity resonator and a second chirp wave having a different degree of frequency fluctuation over time than the chirp wave emitted by the oscillator, and the signal strength difference.

16. 16. The inspection device according to claim 1, further comprising a protective tube disposed inside the cavity resonator and separating the communication passage from a hollow portion inside the cavity resonator.

17. 17. The inspection device according to claim 1, wherein the communication port is set to a size such that electromagnetic waves having a frequency within a predetermined measurement range defined by a cutoff frequency of the waveguide do not leak out of the cavity.

18. 18. The inspection device according to claim 1, wherein an inner diameter of the inlet and an inner diameter of the outlet are smaller than 15% of a cross-sectional area of ​​a cavity provided in the cavity resonator in a direction perpendicular to a line segment connecting the inlet and the outlet.

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