JP2013195219A - Internal defect inspection device and internal defect inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection device and an inspection method which can easily detect a layered defect inside a measured object with high accuracy in a short period.SOLUTION: An inspection device comprises: a transmission antenna 1 outputting a microwave 8 applied to a measured object 10; and a reception antenna 2 which is spatially separated from the transmission antenna 1 and which receives a reflected wave 9 of the microwave 8 reflecting on the measured object 10, so as to detect a layered defect 11 inside the measured object 10. The microwave 8 applied to the measured object 10 includes a frequency causing interference due to multiple reflection between a surface 12 of the measured object 10 and the defect 11. The intensity of the reflected wave 9 at the frequency is measured, so that the defect 11 inside the measured object 10 is detected.

Description

  The present invention relates to an internal defect inspection apparatus and method for nondestructively detecting defects generated inside articles constituting various products, and in particular, internal defects for detecting internal layered defects using microwave reflection characteristics. The present invention relates to an inspection apparatus and an internal defect inspection method.

  Conventionally, methods and devices described in Patent Documents 1 to 3, for example, are known as methods and devices for nondestructively detecting defects inside an object. Patent Document 1 describes an example of a conventional tire peeling inspection apparatus. The occurrence of delamination is detected by measuring the temperature distribution of the heated portion by utilizing the fact that the tire is heated from one surface side of the tire by a heating means and the heat conduction of the delamination portion is small.

  The inspection apparatus described in Patent Document 2 irradiates an electromagnetic wave such as a microwave toward a concrete structure to be measured, and detects the intensity and phase of the reflected wave from the inside of the structure. A defect such as a crack or a peeling that occurs is detected, and the detection result is output as image data by scanning an irradiation / detection means of electromagnetic waves on the measurement object. In Patent Document 2, the detection antenna is separated from the irradiation antenna, and the installation angle is shifted from the direction in which the irradiated microwave is regularly reflected to reduce the noise of the surface reflection. Have been described.

  The device described in Patent Document 3 is a device that mainly measures non-destructive internal defects such as small parts, and uses a shared antenna for the purpose of easy and high-precision detection. An object to be measured is arranged in a microwave resonance system configured as described above, and a change in the amplitude of the transmitted wave or reflected wave of the microwave due to a defect is detected.

Japanese Patent Laid-Open No. 2005-207763 JP 2007-121214 A Japanese Patent No. 3754556

  Various industrial members and products using plate-like members such as rubber plates and resin plates are used. In such materials and products, peeling of the laminated parts of the plate-like members and mixing of incompatible layers It is desired to detect such a layered defect generated inside easily and accurately in a short time. However, the conventional inspection method and apparatus described above cannot provide sufficient performance for such a requirement.

  In the method based on the temperature distribution measurement of Patent Document 1, it takes a certain amount of time for measurement and the influence of the surrounding environment, so that it is difficult to perform a short-time inspection and high-accuracy measurement.

  On the other hand, since the inspection method described in Patent Document 2 is a method for the purpose of defect inspection of concrete structures and the like, a small portion of a defect such as a defect inside a plate member or a thin object The accuracy is insufficient when inspecting the layered defects inside. In addition, the inspection apparatus becomes complicated and large.

  Further, in the method of configuring a microwave resonance circuit including an antenna and a device under test described in Patent Document 3, the measured value changes depending on the distance between the antenna and the device under test. In order to perform measurement, it is necessary to keep the above distance constant with high accuracy. For this reason, it is difficult to easily measure internal peeling defects in a short time using the apparatus of Patent Document 3.

  Therefore, the present invention has been made to solve such a problem, and an inspection apparatus and an inspection method capable of easily and accurately detecting a layered defect inside a measurement object in a short time. The purpose is to provide.

  In a first aspect, the present invention is an inspection apparatus for detecting a layered defect in an object to be measured, the transmitting antenna outputting a microwave irradiated to the object to be measured, the transmission antenna and the space And a receiving antenna that receives a reflected wave of the microwave from the object to be measured, and the microwave has a frequency that causes interference due to multiple reflections between the surface of the object to be measured and the defect. And an internal defect inspection apparatus that detects the defect by measuring the intensity of the reflected wave at the frequency.

  In the present invention, the transmitting antenna and the receiving antenna are separated, and the frequency of the irradiated microwave is set so as to cause interference due to multiple reflection between the surface of the object to be measured and the defect. When there is a defect and the above-mentioned interference occurs, the reflected wave has the maximum amplitude or the minimum amplitude at a specific frequency. Therefore, when the defect is identified by simply detecting the intensity or phase of the reflected wave without using the interference. Compared to the sensitivity improvement. In addition, in order to obtain high detection accuracy, it is necessary to reduce noise by removing the reflected wave generated from a defect other than the surface of the object to be measured and the surface, but when the transmitting antenna and the receiving antenna are shared, Since a directional coupler or isolator is required in the previous stage, it is difficult to eliminate reflection at the connection between these devices and between devices, and reflection from the antenna opening of the irradiation wave. / N is difficult to get. In the present invention, since the transmitting antenna and the receiving antenna are separated, high detection accuracy can be obtained even for a layered defect inside the object to be measured. As described above, the layered defect can be detected easily and with high accuracy in a short time.

  Further, in the present invention, the shape of the irradiation region of the microwave is the optimum shape for the object to be measured within a range where the reflected wave intensity of a certain level or more can be secured on the object to be measured by effectively using the output power of the microwave. Can be. If there is unevenness on the surface of the object being measured and the reflected wave fluctuates, the fluctuation can be reduced by making the microwave irradiation range optimal for the object to be measured so as to cover these uneven parts widely. It becomes possible to remove by averaging.

  In a second aspect, the present invention provides the internal defect inspection apparatus according to the first aspect, further comprising a transflective plate that transmits a part of the microwave, and a part of the microwave output from the transmission antenna. Is transmitted through the semi-transmissive reflector and irradiated to the surface of the object to be measured substantially perpendicularly, and a part of the reflected wave from the object to be measured is reflected by the semi-transmissive reflector and enters the receiving antenna. It is comprised so that it may be comprised.

  In a third aspect, the present invention provides the internal defect inspection apparatus according to the first aspect, further comprising a transflective plate that transmits a part of the microwave, and a part of the microwave output from the transmission antenna. Is reflected by the transflective reflector and irradiated almost perpendicularly to the surface of the object to be measured, and a part of the reflected wave from the object to be measured is transmitted through the semitransmissive reflector and enters the receiving antenna. It is comprised so that it may be comprised.

  The internal defect inspection apparatus according to the second and third aspects has a configuration similar to a Fizeau optical interferometer conventionally used for measuring flatness and the like, and uses a transflective plate. The surface of the object to be measured can be irradiated almost perpendicularly to the surface of the object to be measured, and the transmitting antenna and the receiving antenna can be spatially separated. By irradiating the surface of the object to be measured almost perpendicularly to the surface of the object to be measured, it is possible to increase the setting tolerance for the distance between the transmitting antenna and the receiving antenna and the object to be measured, and the fluctuation of the detection signal with respect to the distance. Can be suppressed.

  In a fourth aspect, the present invention depends on the surface shape of the object to be measured included in the received signal received by the receiving antenna in the internal defect inspection apparatus according to any one of the first to third aspects. It has a means to specify a signal, and a means to remove the specified signal. When the surface shape of the object to be measured is fixed, the received signal always includes a certain noise signal depending on the surface shape of the object to be measured. By grasping in advance the noise signal waveform corresponding to the surface shape, it can be removed from the received signal. Thereby, unnecessary noise can be removed and the S / N of the detection signal can be improved.

  In a fifth aspect, the present invention provides the internal defect inspection apparatus according to any one of the first to fourth aspects, wherein a local wave that is a microwave having a frequency different from the frequency of the microwave output from the transmission antenna is detected. A transmitting local oscillator, a mixer for combining the local wave and the received signal received by the receiving antenna to generate a difference frequency signal having a frequency difference between the two, and a frequency for allowing the difference frequency signal to pass And a filter. The invention according to this aspect performs heterodyne detection. When the internal defect inspection apparatus according to the present invention is put into practical use, it is necessary to reduce the microwave output from the transmission antenna to a level defined by the Radio Law, and depending on the frequency, it is necessary to keep the output level very small. In this case, there is a possibility that the S / N of the detection signal is lowered and the defect cannot be detected by simply amplifying the received signal with an amplifier as it is. Therefore, the internal defect inspection apparatus according to this aspect employs a heterodyne system, and first down-converts the received signal to an intermediate frequency by combining with the local wave. Thereafter, unnecessary components such as noise are removed by a filter or the like, and then amplified by an amplifier having a small noise figure. Thereby, detection with high S / N can be realized in an arbitrary frequency band.

  In a sixth aspect, the present invention is an inspection method for detecting a layered defect in an object to be measured, wherein a transmitting antenna causes interference due to multiple reflections between the surface of the object to be measured and the defect. Outputting a microwave including a frequency and irradiating the object to be measured; and a receiving antenna spatially separated from the transmission antenna receiving a reflected wave of the microwave from the object to be measured. A method for inspecting an internal defect is provided, wherein the intensity of the reflected wave at the frequency is measured.

  In a seventh aspect, the present invention provides the method for inspecting an internal defect according to the sixth aspect, wherein the object to be measured has a plate-like portion, and a peeled shape generated inside the plate-like portion. It is characterized by detecting a defect. In particular, in order to obtain high detection accuracy for internal layered defects in a plate-like object to be measured, noise is reduced by removing reflected waves generated from parts other than the object and the front and back surfaces of the object to be measured. is important. In the present invention, since the transmitting antenna and the receiving antenna are separated, high detection accuracy can be obtained even for a layered defect inside the plate-like object to be measured.

  In an eighth aspect, the present invention is characterized in that in the internal defect inspection method according to the seventh aspect, the plate-like portion is a portion in which layered rubber is bonded. Especially in layered rubber products, when a peeling defect occurs inside, the change in the dielectric constant of that part is large, so that a sufficient microwave reflectivity to cause multiple interference can be obtained. Thus, detection can be performed more easily and with high accuracy. An example of a layered rubber product is a tire.

  As described above, according to the internal defect inspection apparatus and the internal defect inspection method of the present invention, an inspection apparatus capable of easily and accurately detecting a layered defect inside the object to be measured in a short time, and An inspection method is obtained.

1 is a schematic configuration diagram of an internal defect inspection apparatus according to Embodiment 1. FIG. The figure which shows the intensity | strength of the reflected wave with respect to the frequency of the microwave to irradiate. 1 is a system configuration diagram showing the overall configuration of an internal defect inspection apparatus according to Embodiment 1. FIG. 1 is an internal configuration diagram of an IQ mixer used in an internal defect inspection apparatus according to Embodiment 1. FIG. The figure which shows an example of the result of having measured the peeling defect inside a layered rubber product using the internal defect inspection apparatus which concerns on Example 1. FIG. FIG. 6 is a schematic configuration diagram of an internal defect inspection apparatus according to a second embodiment. FIG. 6 is a schematic configuration diagram of an internal defect inspection apparatus according to a third embodiment.

  Hereinafter, an internal defect inspection apparatus of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description thereof is omitted.

  FIG. 1 is a schematic configuration diagram of an internal defect inspection apparatus 20 according to the first embodiment. In FIG. 1, an internal defect inspection apparatus 20 according to the present embodiment includes a transmission antenna 1 that outputs a microwave 8 that is irradiated onto a device under test 10 and a transmission antenna 1 that is spatially separated from the transmission antenna 1. The inspection apparatus includes a receiving antenna 2 that receives a reflected wave 9 from an object 10 and detects a layered defect 11 inside the object to be measured 10. The microwave 8 applied to the object to be measured 10 includes a frequency that causes interference due to multiple reflections between the surface 12 of the object to be measured 10 and the defect 11, and the object to be measured is measured by measuring the intensity of the reflected wave 9 at that frequency. 10 internal defects 11 are detected. The circuit unit 3 generates a wave source of the microwave 8 output from the transmitting antenna 1 and generates a detection signal from the reflected wave 9 received by the receiving antenna 2.

In FIG. 1, the distance between the surface 12 of the object to be measured 10 and the defect 11 is d, the incident angle of the microwave 8, that is, the angle formed with the normal of the surface 12, θ, the frequency of the microwave 8 is f, If the relative permittivity of the measured object 10 is ε _r and the relative permittivity of the defect 11 is smaller than ε _r as in the case of a void due to peeling, the reflected wave is reflected by interference due to multiple reflection between the surface 12 and the defect 11. The intensity of 9 is minimum when Expression (1) is satisfied, and is maximum when Expression (2) is satisfied. Here, m is an arbitrary integer, and c is the speed of light in vacuum.

FIG. 2 is a diagram showing the intensity of the reflected wave 9 with respect to the frequency of the microwave 8 to be irradiated. In a portion where the defect 11 of the object to be measured 10 is not present, the multiple reflection between the front surface 12 and the rear surface 13 is performed at a frequency satisfying the expressions (1) and (2), with the value of d as the thickness between the front and back surfaces. Interference occurs, and the characteristics shown by the broken line in FIG. 2 are obtained. On the other hand, in the portion where the defect 11 exists, the value of d is smaller than the thickness between the front and back surfaces. Therefore, the frequency satisfying the equations (1) and (2) becomes larger than the case where the defect 11 does not exist. The characteristic indicated by the solid line 2 is obtained. For example, the frequency at which the reflected wave has the minimum intensity is F _{1 in} the portion where the defect 11 is not present and F _{2 in the} portion where the defect 11 is present, and the intensity of the reflected wave 9 is measured while moving the DUT 10 at the frequency F ₂ . In this case, the strength of the portion having the defect 11 is greatly reduced. The frequency satisfying the equations (1) and (2) varies depending on the depth d from the surface of the defect 11, but the intensity of the reflected wave 9 depends on the presence of the defect that causes interference due to multiple reflection between the surface 12 and the defect 11. Since it changes greatly, in the present invention, it is possible to detect easily and with high accuracy in a short time as compared with the case of simply detecting the reflection intensity or phase from the microwave defect 11 without using interference due to multiple reflection. is there.

  Here, in order to simplify the detection circuit in the present invention, it is necessary to clearly cause interference due to multiple reflections. For this purpose, is the surface 12 of the DUT 10 and the defect 11 substantially parallel? Or if not parallel, it is desirable that the amount of change in depth from the surface of one defect is sufficiently small with respect to the wavelength of the irradiated microwave, for example, 1/5 or less of the wavelength of the microwave, Furthermore, it is desirable that the frequency of the microwave to be irradiated is set to be larger than the frequency satisfying m = 1 in the equation (1) and within the range of the commonly used microwave frequency.

FIG. 3 is a system configuration diagram illustrating the overall configuration of the internal defect inspection apparatus 20 according to the first embodiment. As shown in FIG. 3, in the circuit unit 3, first, a sweep oscillator 32 that transmits a microwave having a variable frequency f ₂ as a sweep frequency to a signal generated by an oscillator 31 that transmits a microwave having a fixed frequency f _1. Are combined by the up-converter 33 to generate a transmission wave of frequency f ₁ + f ₂ . The transmission wave is adjusted to a transmission intensity defined by the radio wave law by an attenuator 34, and is emitted as a microwave 8 from the transmission antenna 1 and applied to the object 10 to be measured. As shown in FIG. 1, the microwave 8 is reflected on the boundary surface where the dielectric constant changes, such as the front surface 12, the back surface 13, and the defect 11 of the DUT 10, and the reflected wave 9 is received by the receiving antenna 2. The amplitude A4 of the received wave includes interference information as shown in FIG. 2 and is represented by a function of the transmission frequency f ₁ + f ₂ .

In the internal defect inspection apparatus of the present invention, depending on the frequency of the microwave, the output intensity of the microwave radiated from the transmitting antenna 1 is limited to a very small intensity by the radio wave method. In that case, the reception intensity at the reception antenna 2 also becomes very small, and the signal-to-noise ratio becomes insufficient just by amplifying with the amplifier, and there is a case where the measurement cannot be performed with high accuracy. Therefore, in this embodiment, in order to obtain high detection sensitivity, a local oscillator that transmits a local wave that is a microwave having a frequency different from the frequency of the microwave output from the transmission antenna 1, and the local wave and the reception antenna 2 receive the signal. The received signal is combined with the received signal to generate a difference frequency signal having a frequency difference between the two and a frequency filter that allows the difference frequency signal to pass therethrough, and a receiving circuit is configured by a heterodyne method. That is, in this embodiment, the sweep oscillator 32 is used as a local oscillator, the received signal received by the receiving antenna 2 is amplified by the low noise amplifier 36, and then combined with the signal generated by the sweep oscillator 32 in the mixer 35. it allows to obtain a signal having a frequency f ₁ of the difference between the frequency _{f 2} of the frequency _f 1 + _{f 2} and the signal of the sweep oscillator 32 of the received signal. Here, since the output from the mixer 35 includes signals of the difference frequency f ₁ , the original frequency f ₁ + f ₂ , and the sum frequency f ₁ + 2f ₂ , the difference is obtained by passing the signal through the band-pass filter 37. to obtain a signal having only the frequency f _1.

The signal from which unnecessary components other than the frequency f ₁ are removed is amplified by the low noise amplifier 38 and input to the IQ mixer 40 as a measurement signal having defect information, and the reference wave signal of the frequency f ₁ of the oscillator 31 in the IQ mixer 40. The signals are combined to obtain a detection signal.

  FIG. 4 is an internal configuration diagram of an IQ mixer used in this embodiment. In FIG. 4, the measurement signal is divided into two by the power divider 41, and the divided two signals having the same phase are input to the RF ports of the mixer 43 and the mixer 44, respectively. On the other hand, the reference wave signal is input to the hybrid 42, divided into two signals whose phases are different from each other by 90 degrees, and input to the LO ports of the mixer 43 and the mixer 44, respectively. In the mixer 43 and the mixer 44, a frequency signal that is the sum of the difference between the measurement signal and the reference wave signal is generated, and only the difference frequency signal is extracted by passing through the low-pass filter 45 and the low-pass filter 46, respectively. The extracted signal is output as a detection signal of a sin wave component and a cos wave component including information on the phase δ and amplitude A4 of the received wave.

Next, an internal defect inspection method according to the present invention will be described. First, as shown in FIG. 1, the transmission antenna 1 and the reception antenna 2 are set so that the microwave 8 output from the transmission antenna 1 is regularly reflected by the surface 12 of the object to be measured 10 and enters the reception antenna 2 as a reflected wave 9. Deploy. In FIG. 3, the frequency f ₁ + f ₂ of the microwave 8 satisfies the formula (1) in a range of m ≧ 1, and a fixed frequency is generated so as to cause interference due to multiple reflection between the surface 12 of the object to be measured 10 and the defect 11. setting the f ₁ and the sweep frequency _{f 2.} The intensity of the reflected wave 9 is measured by changing the frequency f ₁ + f ₂ of the microwave 8 by changing the sweep frequency f ₂ , and the defect is determined from the intensity for a specific frequency or the magnitude of the intensity change with respect to the frequency change. Is detected.

  FIG. 5 is a diagram illustrating an example of a result of measuring a peeling defect of a layered rubber product using the internal defect inspection apparatus 20 of Example 1. A microwave having a frequency of 28 to 29 GHz is swept and irradiated from the transmitting antenna 1 onto the surface of the object to be measured, and the difference between the maximum value and the minimum value of the amplitude of the detection signal obtained from the IQ mixer is calculated. And plotted. The horizontal axis is the relative position from the reference point irradiated with the microwave. As shown in FIG. 5, a clear increase in signal output was obtained at the position where there was a peeling defect, and the detection of the intended defect could be confirmed.

  In the measurement of the layered rubber product, the microwave irradiation range was considered so that the fluctuation of the reflected wave due to the surface irregularities was averaged and reduced.

  In addition, in the object to be measured having periodic unevenness on the surface, the noise waveform that appears in the measurement signal due to the fluctuation of the reflected wave due to the unevenness on the surface becomes almost constant according to the surface shape, so the waveform is removed by signal processing It is also possible to do.

  FIG. 6 is a schematic configuration diagram of the internal defect inspection apparatus 21 according to the second embodiment. In FIG. 6, the internal defect inspection apparatus 21 of the present embodiment is spatially separated from the transmission antenna 1 that outputs the microwave 8 irradiated to the device under test 10 and the transmission antenna 1, as in the first embodiment. The inspection apparatus includes a receiving antenna 2 that receives a reflected wave 19 from a microwave measurement object 10 and detects a layered defect 11 inside the measurement object 10. The microwave 8 applied to the object to be measured 10 includes a frequency that causes interference due to multiple reflections between the surface 12 of the object to be measured 10 and the defect 11, and measures the intensity of the reflected wave 19 at the frequency. 10 internal defects 11 are detected. The circuit unit 3 generates a wave source of the microwave 8 output from the transmitting antenna 1 and a detection signal from the reflected wave 19 received by the receiving antenna 2.

  In this embodiment, it has a transflective plate 4 that transmits a part of the microwave, and a part of the microwave 8 output from the transmitting antenna 1 transmits through the transflective plate 4 to be measured 10. The surface 12 is irradiated almost perpendicularly, and a part of the reflected wave from the object to be measured 10 is reflected by the semi-transmissive reflecting plate 4 and enters the receiving antenna 2 as a reflected wave 19. In the present embodiment, the component reflected by the transflective plate 4 of the microwave 8 is reflected by the absorber 5 in order to avoid the microwave 8 being reflected by the part other than the device under test 10 and entering the receiving antenna 2. Absorbs. The transflective plate 4 may be a plate-like material having a function of reflecting and transmitting a part of the microwave at the microwave frequency to be used. For example, an acrylic plate can be used.

  In the configuration of the first embodiment shown in FIG. 1, when the device under test 10 is replaced while the antenna position is fixed, the microscopic light that enters the measurement location due to the distance between the transmission antenna 1 and the reception antenna 2 and the device under test 10. The incident angle θ of the wave 8 changes, and as a result, the frequency that gives the minimum intensity and the maximum intensity satisfying the expressions (1) and (2) slightly changes. For this reason, the DUT 10 needs to be installed at the same position to some extent. On the other hand, in the present embodiment, the incident angle θ is always 0 by irradiating the surface of the object to be measured substantially perpendicularly using the transflective plate 4, and theoretically, The frequency satisfying the expressions (1) and (2) does not depend on the distance between the two. As a result, in this embodiment, the setting tolerance for the device under test 10 can be increased, and the fluctuation of the detection signal with respect to the set position of the device under test 10 can be suppressed.

  FIG. 7 is a schematic configuration diagram of the internal defect inspection apparatus 22 according to the third embodiment. In FIG. 7, the internal defect inspection apparatus 22 according to the present embodiment is similar to the first and second embodiments in that the transmission antenna 1 that outputs the microwave 8 that irradiates the DUT 10 and the transmission antenna 1 are spatially separated. The inspection apparatus includes a receiving antenna 2 that receives a reflected wave 29 from the object to be measured 10 of the microwave 8 and detects a layered defect 11 inside the object to be measured 10. The microwave 8 radiated to includes a frequency that causes interference due to multiple reflections between the surface 12 of the object to be measured 10 and the defect 11, and by measuring the intensity of the reflected wave 29 at the frequency, The defect 11 is detected. Similarly to the second embodiment, in this embodiment, the microwave is applied to the surface 12 of the DUT 10 almost perpendicularly.

  However, in this embodiment, it has a transflective plate 4 that transmits part of the microwave, and a part of the microwave 8 output from the transmitting antenna 1 is reflected by the transflective plate 4 to be measured. The surface 12 of the object 10 is irradiated substantially perpendicularly, and a part of the reflected wave from the object to be measured 10 is transmitted through the transflective plate 4 and enters the receiving antenna 2 as a reflected wave 29. The component of the microwave 8 that has passed through the transflective plate 4 is absorbed by the absorber 5. As shown in FIG. 7, the angle of the transflective plate 4 with respect to the traveling direction of the microwave 8 depends on the incident angle such as the transmittance, reflectivity, and polarization characteristics of the microwave of the transflective plate 4. In consideration, it can be arbitrarily set to obtain an optimum configuration.

  Also in the present embodiment, as in the second embodiment, the setting tolerance for the device under test 10 can be increased, and the variation of the detection signal with respect to the set position of the device under test 10 can be suppressed.

  Needless to say, the present invention is not limited to the above-described embodiments, and the design can be changed according to the purpose and application. For example, if the signal intensity obtained from the reflected wave is large and the required S / N is obtained, the circuit configuration can be as follows: a normal amplifier, a noise reduction circuit using an averaging process or a filter, a peak value or an amplitude A signal processing circuit such as a detection circuit may be used, and the heterodyne method may not be employed. The object to be measured as an object of the present invention may be any object as long as it has a layered defect that causes interference due to multiple reflection between the surface and the defect.

DESCRIPTION OF SYMBOLS 1 Transmitting antenna 2 Receiving antenna 3 Circuit part 4 Transflective board 5 Absorber 8 Microwave
9, 19, 29 Reflected wave
DESCRIPTION OF SYMBOLS 10 Measured object 11 Defect 12 Front surface 13 Back surface 20, 21, 22 Internal defect inspection apparatus 31 Oscillator 32 Sweep oscillator 33 Up converter 34 Attenuator 35, 43, 44 Mixer 36, 38 Low noise amplifier 37 Band pass filter 40 IQ mixer 41 Power divider 42 Hybrid 45, 46 Low-pass filter

Claims (8)

  An inspection apparatus for detecting a layered defect inside an object to be measured, the transmitting antenna outputting a microwave irradiated to the object to be measured, and the transmission antenna spatially separated from the microwave A reception antenna that receives a reflected wave from the object to be measured, and the microwave includes a frequency that causes interference due to multiple reflections between the surface of the object to be measured and the defect, and the intensity of the reflected wave at the frequency An internal defect inspection apparatus, wherein the defect is detected by measuring the defect.   A transflective plate that transmits a part of the microwave, and a part of the microwave that is output from the transmitting antenna is transmitted through the transflective plate and irradiated to the surface of the object to be measured substantially perpendicularly; 2. The internal defect inspection apparatus according to claim 1, wherein a part of the reflected wave from the object to be measured is reflected by the transflective plate and is incident on the receiving antenna.   A transflective plate that transmits a part of the microwave, and a part of the microwave output from the transmitting antenna is reflected by the transflective plate to irradiate the surface of the object to be measured substantially perpendicularly; The internal defect inspection apparatus according to claim 1, wherein a part of the reflected wave from the object to be measured is configured to pass through the transflective plate and enter the receiving antenna.   2. The apparatus according to claim 1, further comprising: means for specifying a signal depending on a surface shape of the object to be measured included in a reception signal received by the reception antenna; and means for removing the specified signal. 5. The internal defect inspection apparatus according to any one of 4 above.   A local oscillator that transmits a local wave that is a microwave having a frequency different from the frequency of the microwave output from the transmitting antenna, and the received signal received by the local wave and the receiving antenna are combined to The internal defect inspection apparatus according to claim 1, further comprising: a mixer that generates a difference frequency signal having a difference frequency; and a frequency filter that passes the difference frequency signal. An inspection method for detecting a layered defect in an object to be measured,
A step of transmitting a microwave including a frequency that causes interference due to multiple reflection between the surface of the object to be measured and the defect and irradiating the object to be measured;
A receiving antenna spatially separated from the transmitting antenna receives the reflected wave of the microwave from the object to be measured, and measures the intensity of the reflected wave at the frequency Internal defect inspection method.   The internal defect inspection method according to claim 7, wherein the object to be measured has a plate-like portion, and a peeling-like defect generated inside the plate-like portion is detected.   The internal defect inspection method according to claim 8, wherein the plate-like portion is a portion where layered rubber is bonded.

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