JP6214917B2 - Internal defect inspection apparatus and internal defect inspection method - Google Patents
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本発明は、各種製品を構成する物品の内部に生じた欠陥を非破壊で検出する内部欠陥検査装置及び方法に関し、特にマイクロ波の反射特性を利用して内部の層状の欠陥を検出する内部欠陥検査装置及び内部欠陥の検査方法に関する。 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.
従来、物体の内部の欠陥などを非破壊で検出する方法や装置として、例えば、特許文献１〜３に記載された方法や装置が知られている。特許文献１には従来のタイヤの剥離検査装置の一例が記載されている。タイヤの一方の表面側から加熱手段によりタイヤを加熱し、剥離部分の熱伝導が小さいことを利用して、加熱された部分の温度分布を測定することにより剥離の発生を検出するものである。 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.
特許文献２に記載の検査装置は、マイクロ波などの電磁波を測定対象となるコンクリート構造物に向けて照射し、そこからの反射波の強度や位相を検出することにより、その構造物の内部に生じたクラックや剥離などの欠陥を検出するものであり、電磁波の照射・検知手段を測定対象物上で走査することにより検出結果を画像データとして出力するものである。特許文献２においては、照射用のアンテナに対して検出用のアンテナを分離して設置し、その設置角度を照射されたマイクロ波が正反射する方向からずらすことで表面反射のノイズを減らす構成が記載されている。 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.
特許文献３に記載の装置は、主として小型の部品等の内部の欠陥などを非破壊で測定する装置であり、検出を容易に、かつ高精度に行うことを目的として、送受信共用のアンテナを用いて構成したマイクロ波の共振系の中に被測定物を配置し、欠陥によるマイクロ波の透過波又は反射波の振幅の変化を検出する構成となっている。 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.
樹脂などの板状の部材を用いた様々な工業部材や製品が使用されており、このような材料や製品において、その板状部材の張り合わせ部などの剥離や不適合層の混入のような内部に生じた層状の欠陥を短時間に簡易に、かつ高精度に検出することが望まれている。しかしながら、上記の従来の検査方法や装置では、このような要求に対しては十分な性能は得られない。 Various industrial members and products using plate-like members such as resin are used. In such materials and products, such as peeling of pasted parts of the plate-like members and mixing of incompatible layers It is desired to detect a generated layered defect easily and accurately in a short time. However, the conventional inspection method and apparatus described above cannot provide sufficient performance for such a requirement.
特許文献１の温度分布の測定による方法では、測定に一定の時間を要することや周囲環境の影響もあることから、短時間の検査や高精度の測定が難しい。 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.
一方、特許文献２に記載の検査方式はコンクリート構造物などのクラックのエッジ付近からの散乱波を測定する方式であることから、板状部材の内部に表面に対して平行に発生した剥離などのように、物体の内部の層状の欠陥を検査する場合には精度が不十分である。 On the other hand, since the inspection method described in Patent Document 2 is a method of measuring scattered waves from the vicinity of the edge of a crack of a concrete structure or the like, such as peeling that occurs parallel to the surface inside the plate member Thus, when inspecting a layered defect inside an object, the accuracy is insufficient.
また、特許文献３に記載の、アンテナと被測定物を含んだマイクロ波の共振回路を構成する方式では、アンテナと被測定物との間の距離により測定値が変化してしまうため、正確な測定を行うためには上記の距離を精度よく一定に保つ必要がある。このため、特許文献３の装置を用いて、内部の剥離欠陥を短時間に簡易に測定することは難しい。 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.
そこで、本発明は、係る問題を解決するためになされたものであり、被測定物の内部の層状の欠陥を短時間に簡易に、かつ高精度に検出することができる内部欠陥検査装置及び内部欠陥の検査方法を提供することを目的とする。 Therefore, the present invention has been made to solve such a problem, and an internal defect inspection apparatus capable of detecting a layered defect inside the object to be measured easily and with high accuracy in a short time and an internal defect inspection apparatus. An object is to provide a defect inspection method.
第１の観点では、本発明の内部欠陥検査装置は、被測定物の内部の層状の欠陥を検出する検査装置であって、前記被測定物に照射されるマイクロ波を出力する送信アンテナと、該送信アンテナと空間的に分離され、前記マイクロ波の前記被測定物からの反射波を受信する受信アンテナとを有し、前記送信アンテナから出力されるマイクロ波の強度が最大となる偏波方向と前記受信アンテナの感度が最大となる偏波方向が異なることを特徴とする。 In a first aspect, an internal defect inspection apparatus according to the present invention is an inspection apparatus that detects a layered defect inside an object to be measured, and a transmission antenna that outputs a microwave irradiated to the object to be measured; A polarization direction that is spatially separated from the transmission antenna and receives a reflected wave of the microwave from the object to be measured, and that maximizes the intensity of the microwave output from the transmission antenna And a polarization direction in which the sensitivity of the receiving antenna is maximized.
被測定物の内部の層状の欠陥に対して高い検出精度を得るためには、被測定物の欠陥からの反射波以外の信号成分、すなわち、被測定物以外からの信号成分や被測定物の表面および裏面などから生ずる反射波を除去してノイズを減らすことが重要である。しかし、送信アンテナと受信アンテナとを共用した場合、アンテナの前段に方向性結合器やサーキュレータが必要となるので、これらのデバイス内およびデバイス間の接続部での反射や、照射波のアンテナ開口部からの反射を除くことが困難であるため、十分なＳ／Ｎを得ることは難しい。本発明では送信アンテナと受信アンテナとが分離されているため、上記のような反射による信号成分を除くことができる。また、マイクロ波は電磁的な性質が異なる境界により反射されるが、その場合、一般的に偏波状態により反射率が異なるため、反射波の偏波状態は入射波とは異なり、その違いは境界を形成する材料で決定される。本発明では、受信アンテナの感度が最大となる偏波方向を、送信アンテナから出力されるマイクロ波の強度が最大となる偏波方向に一致させるのではなく、欠陥からの反射波の信号強度が最大となるように設定することや、ノイズ成分となる欠陥以外からの反射波の信号強度が最小となるように設定することで、被測定物の内部の層状の欠陥に対して、さらに高い検出精度を得ることができる。また、本発明においては、送信アンテナと受信アンテナが分離され、送信側と受信側が独立した配置となっているため、被測定物の設置位置に対する許容度は大きい。 In order to obtain high detection accuracy for a layered defect inside the object to be measured, signal components other than the reflected wave from the defect of the object to be measured, that is, signal components other than the object to be measured and It is important to reduce noise by removing reflected waves generated from the front and back surfaces. However, when the transmitting antenna and the receiving antenna are shared, a directional coupler or circulator is required in front of the antenna, so reflection at the connection between these devices and between the devices, and antenna opening of the irradiation wave Since it is difficult to remove reflection from the light, it is difficult to obtain a sufficient S / N. In the present invention, since the transmitting antenna and the receiving antenna are separated, the signal component due to reflection as described above can be removed. Microwaves are reflected by boundaries with different electromagnetic properties, but in this case, since the reflectivity is generally different depending on the polarization state, the polarization state of the reflected wave is different from the incident wave. Determined by the material forming the boundary. In the present invention, the polarization direction in which the sensitivity of the receiving antenna is maximized does not coincide with the polarization direction in which the intensity of the microwave output from the transmitting antenna is maximized, but the signal intensity of the reflected wave from the defect is Higher detection is possible for layered defects inside the object to be measured by setting it to be maximum or setting the signal intensity of the reflected wave from other than the defect that becomes a noise component to be minimum. Accuracy can be obtained. In the present invention, since the transmission antenna and the reception antenna are separated and the transmission side and the reception side are arranged independently, the tolerance for the installation position of the object to be measured is large.
第２の観点では、本発明は、前記第１の観点の内部欠陥検査装置において、前記受信アンテナの感度が最大となる偏波方向は、前記被測定物の内部に層状の欠陥がないときに受信される前記被測定物からの反射波による信号強度が最小となるように設定されることを特徴とする。これにより、ノイズ成分となる欠陥以外からの反射波の信号強度が最小となり、受信信号のＳ／Ｎを大きくすることができる。 In a second aspect, the present invention provides the internal defect inspection apparatus according to the first aspect, wherein the polarization direction in which the sensitivity of the receiving antenna is maximized is when there is no layered defect inside the device under test. It is set so that the signal intensity due to the reflected wave from the measured object to be received is minimized. Thereby, the signal intensity of the reflected wave from other than the defect that becomes a noise component is minimized, and the S / N of the received signal can be increased.
第３の観点では、本発明は、前記第１または第２の観点の内部欠陥検査装置において、前記送信アンテナから出力されるマイクロ波の周波数と異なる周波数のマイクロ波である局部波を発信する局部発振器と、前記局部波と前記受信アンテナにより受信された受信信号とを合波し両者の周波数の差の周波数を有する差周波数信号を生成するミキサと、前記差周波数信号を通過させる周波数フィルタとを有することを特徴とする。 In a third aspect, the present invention provides a local part that transmits a local wave that is a microwave having a frequency different from the frequency of the microwave output from the transmission antenna in the internal defect inspection apparatus according to the first or second aspect. An oscillator, a mixer that combines the local wave and the reception signal received by the reception antenna to generate a difference frequency signal having a frequency difference between the two, and a frequency filter that passes the difference frequency signal. It is characterized by having.
本観点の発明は、ヘテロダイン方式の検出を行うものである。本発明による内部欠陥検査装置を実用する場合、送信アンテナからのマイクロ波出力を電波法で規定されているレベルまで下げる必要があり、その周波数によっては、出力レベルを非常に小さく抑える必要が生ずる。この場合、受信信号をそのままアンプで増幅するだけでは検出信号のＳ/Ｎが低くなり欠陥の検出ができない場合が起こり得る。そこで、本観点の内部欠陥検査装置では、ヘテロダイン方式を採用し、先ず受信信号を局部波と合波することにより中間周波数へダウンコンバートする。その後、ノイズなどの不要成分をフィルタ等で除去した後に、ノイズフィギュアの小さなアンプで増幅する。これにより任意の周波数帯域でＳ/Ｎの高い検出が実現可能となる。 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.
第４の観点では、本発明は、前記第３の観点の内部欠陥検査装置において、前記局部発振器は周波数が時間的に変化する掃引型の発振器であって、前記送信アンテナから出力されるマイクロ波は、前記局部発振器により発生させた信号と固定の周波数を発振する固定発振器により発生させた信号とを合波することに得た両者の周波数の和の周波数を有し、前記受信アンテナにより受信された受信信号の振幅と位相から前記層状の欠陥の深さを検出する手段を有することを特徴とする。 In a fourth aspect, the present invention provides the internal defect inspection apparatus according to the third aspect, wherein the local oscillator is a sweep type oscillator whose frequency changes with time, and is a microwave output from the transmitting antenna. Is a sum of both frequencies obtained by combining a signal generated by the local oscillator and a signal generated by a fixed oscillator that oscillates a fixed frequency, and is received by the receiving antenna. And a means for detecting the depth of the layered defect from the amplitude and phase of the received signal.
このように周波数を掃引してマイクロ波を照射し、各周波数に対する受信信号の振幅と位相の値を逆フーリエ変換することにより反射波の時間軸に対する応答、すなわち反射波の相対的な到達時間を算出し、被測定物の内部にある層状の欠陥の深さを求めることができる。 In this way, by sweeping the frequency and irradiating the microwaves, the response to the time axis of the reflected wave, that is, the relative arrival time of the reflected wave, is obtained by inverse Fourier transforming the amplitude and phase value of the received signal for each frequency. By calculating, the depth of the layered defect in the object to be measured can be obtained.
第５の観点では、本発明は、被測定物の内部にある層状の欠陥を検出する検査方法であって、前記被測定物に照射されるマイクロ波を出力する送信アンテナと、該送信アンテナと空間的に分離され、前記マイクロ波の前記被測定物からの反射波を受信する受信アンテナとを配置し、前記送信アンテナから出力されるマイクロ波の強度が最大となる偏波方向と前記受信アンテナの感度が最大となる偏波方向が異なるように設定することを特徴とする内部欠陥の検査方法を提供する。 In a fifth aspect, the present invention provides an inspection method for detecting a layered defect in a device under test, wherein the transmission antenna outputs a microwave irradiated to the device under test; A receiving antenna that spatially separates and receives a reflected wave of the microwave from the object to be measured, and a polarization direction in which the intensity of the microwave output from the transmitting antenna is maximum, and the receiving antenna A method for inspecting an internal defect is provided in which the polarization direction is set so that the sensitivity becomes the maximum.
第６の観点では、本発明は、前記第５の観点の内部欠陥の検査方法において、前記被測定物は、板状の部分を有し、該板状の部分の内部に生じた剥離状の欠陥を検出することを特徴とする。特に、板状の被測定物において内部の剥離状の欠陥に対して高い検出精度を得るためには、欠陥による反射波とほぼ同じ向きであることが多い被測定物の表面および裏面から生ずる反射波を除去してノイズを減らすことが重要である。本発明では送信アンテナと受信アンテナとが分離されていること、および送信アンテナから出力されるマイクロ波の強度が最大となる偏波方向と前記受信アンテナの感度が最大となる偏波方向が異なるため、板状の被測定物の内部の剥離状の欠陥に対しても高い検出精度を得ることができる。 In a sixth aspect, the present invention provides the method for inspecting an internal defect according to the fifth 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 peeling-like defects in a plate-like object to be measured, reflections generated from the front and back surfaces of the object to be measured are often in the same direction as the reflected waves due to the defects. It is important to reduce noise by removing waves. In the present invention, the transmitting antenna and the receiving antenna are separated, and the polarization direction in which the intensity of the microwave output from the transmitting antenna is maximum differs from the polarization direction in which the sensitivity of the receiving antenna is maximum. Moreover, high detection accuracy can be obtained even with respect to a peeling defect inside the plate-like object to be measured.
第７の観点では、本発明は、前記第６の観点の内部欠陥の検査方法において、前記板状の部分は金属以外の層状の材料を貼り合わせた部分であることを特徴とする。特に層状構造を有する樹脂製品等においては、内部に剥離欠陥が生じた場合、その部分の誘電率の変化が大きいため、大きなマイクロ波の反射率が得られ、本発明を用いることにより、より簡易に、かつ高精度に検出することが可能となる。 In a seventh aspect, the present invention is characterized in that in the internal defect inspection method according to the sixth aspect, the plate-like portion is a portion in which a layered material other than metal is bonded. In particular, in a resin product having a layered structure, when a peeling defect occurs inside, since the change in the dielectric constant of the part is large, a large microwave reflectance can be obtained. In addition, it is possible to detect with high accuracy.
第８の観点では、本発明は、前記第６または第７の観点の内部欠陥の検査方法において、前記被測定物は、前記板状の部分の前記マイクロ波が照射される表面とは反対の裏面側に金属部分を備えることを特徴とする。被測定物の裏面に金属板などを備える製品に本発明の検査方法を適用する場合、測定対象となる板状の部分を通過したマイクロ波はすべてその金属板により反射されるので、バックグランドとなる金属板からの反射波の偏波がより大きく変化するため、欠陥以外で生じた反射波を除くための受信アンテナの偏波方向の調整が容易となる。 In an eighth aspect, the present invention provides the method for inspecting an internal defect according to the sixth or seventh aspect, wherein the object to be measured is opposite to the surface of the plate-like portion irradiated with the microwave. A metal part is provided on the back side. When applying the inspection method of the present invention to a product having a metal plate or the like on the back side of the object to be measured, all the microwaves that have passed through the plate-like part to be measured are reflected by the metal plate, Since the polarization of the reflected wave from the metal plate changes more greatly, it is easy to adjust the polarization direction of the receiving antenna in order to remove the reflected wave other than the defect.
以上のように、本発明の内部欠陥検査装置及び内部欠陥の検査方法によれば、被測定物の内部の層状の欠陥を短時間に簡易に、かつ高精度に検出することができる検査装置および検査方法が得られる。 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.
以下、図面を参照して本発明の内部欠陥検査装置を実施例により詳細に説明する。なお、図面の説明において同一の要素には同一符号を付し、その重複した説明を省略する。 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.
図１は、実施例１に係る内部欠陥検査装置２０の模式的な構成図である。図１において、本実施例の内部欠陥検査装置２０は、被測定物１０に照射されるマイクロ波８を出力する送信アンテナ１と、送信アンテナ１と空間的に分離され、マイクロ波８の被測定物１０からの反射波を受信する受信アンテナ２とを有し、被測定物１０の内部の層状の欠陥１１を検出する検査装置である。被測定物１０に照射されるマイクロ波８の偏波方向８ｐは、送信アンテナ１の設置角度を調整して水平面に垂直となるように設定されている。一方、受信アンテナ２の設置角度は、その感度が最大となる偏波方向が被測定物１０の内部に層状の欠陥がないときに受信される被測定物１０からの反射波による信号強度が最小となるように設定されている。送信アンテナ１から出力されるマイクロ波８の波源の生成および受信アンテナ２で受信された反射波からの検出信号の生成は回路部３で行われる。回路部３で生成された信号は信号処理部９に送られ、入力された信号に基づく演算などの信号処理、データの表示部やプリンタなどへの出力、記憶装置への記録などが行われる。信号処理部９にはパーソナルコンピュータなどを含んでもよい。 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 from the object 10 and detects a layered defect 11 inside the object to be measured 10. The polarization direction 8p of the microwave 8 applied to the DUT 10 is set to be perpendicular to the horizontal plane by adjusting the installation angle of the transmission antenna 1. On the other hand, the installation angle of the receiving antenna 2 is such that the signal intensity due to the reflected wave from the device under test 10 received when there is no layered defect in the device under test 10 whose polarization direction has the maximum sensitivity is minimum. It is set to become. Generation of the wave source of the microwave 8 output from the transmitting antenna 1 and generation of a detection signal from the reflected wave received by the receiving antenna 2 are performed by the circuit unit 3. The signal generated by the circuit unit 3 is sent to the signal processing unit 9, where signal processing such as calculation based on the input signal, output of data to a display unit or printer, recording to a storage device, and the like are performed. The signal processing unit 9 may include a personal computer.
図１に示すように、被測定物１０からの反射波には、被測定物１０の表面１２からの反射波２２、内部の欠陥１１からの反射波２１、被測定物１０の裏面１３からの反射波２３が含まれている。これらの反射波はそれぞれの反射面を挟む媒質が異なるため、偏波状態が異なっている。本実施例では、被測定物１０の裏面１３に金属板がある場合、そこからの反射波２３の強度が大きいので、その反射波２３の偏波方向２３ｐに対して受信アンテナ２の感度が最小となるように設定されている。欠陥１１が剥離による空隙や金属以外の異物の混入などの場合、その偏波方向２１ｐは裏面１３の金属板での反射による偏波方向２３ｐとは異なるので、欠陥１１による反射波２１は受信アンテナ２により検出される。上記のような条件で実験的に設定された一例としては、受信アンテナ２の感度が最大となる偏波方向は水平面に対して４０〜５０度程度とした。 As shown in FIG. 1, the reflected wave from the object to be measured 10 includes a reflected wave 22 from the surface 12 of the object to be measured 10, a reflected wave 21 from the internal defect 11, and a back surface 13 of the object to be measured 10. A reflected wave 23 is included. Since these reflected waves have different media sandwiching the respective reflecting surfaces, their polarization states are different. In this embodiment, when there is a metal plate on the back surface 13 of the DUT 10, the intensity of the reflected wave 23 from the metal plate is high, and therefore the sensitivity of the receiving antenna 2 is minimal with respect to the polarization direction 23 p of the reflected wave 23. It is set to become. When the defect 11 is a gap due to separation or mixing of foreign matter other than metal, the polarization direction 21p is different from the polarization direction 23p due to reflection on the metal plate of the back surface 13, so that the reflected wave 21 due to the defect 11 is a reception antenna. 2 is detected. As an example experimentally set under the above conditions, the polarization direction in which the sensitivity of the receiving antenna 2 is maximized is about 40 to 50 degrees with respect to the horizontal plane.
図２は実施例１に係る内部欠陥検査装置２０の全体の構成を示すシステム構成図である。図２に示すように、回路部３において、先ず、固定周波数ｆ１のマイクロ波を発信する固定発振器３１により生成された信号に、掃引周波数として可変の周波数ｆ２のマイクロ波を発信する掃引発振器３２により生成された信号をアップコンバータ３３により合波して周波数ｆ１＋ｆ２の送信波を生成する。この送信波をアッテネータ３４により電波法によって規定された送信強度に調整し、送信アンテナ１からマイクロ波８として放射し被測定物１０へ照射する。図１に示すように、マイクロ波８は被測定物１０の表面１２、裏面１３や欠陥１１等の誘電率が変化する境界面で反射し、それらの反射波を受信アンテナ２で受信する。受信波の振幅Ａ４は、欠陥１１からの反射波２１の情報を含んでおり、送信周波数ｆ１+ｆ２の関数で表わされる。 FIG. 2 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. 2, in the circuit unit 3, first, a sweep oscillator that transmits a microwave having a variable frequency f 2 as a sweep frequency to a signal generated by a fixed oscillator 31 that transmits a microwave having a fixed frequency f 1. The signal generated by 32 is multiplexed 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 by 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 waves are received by the receiving antenna 2. The amplitude A4 of the received wave includes information on the reflected wave 21 from the defect 11 and is expressed as a function of the transmission frequency f 1 + f 2 .
本発明の内部欠陥検査装置において、マイクロ波の周波数によっては、送信アンテナ１から放射されるマイクロ波の出力強度は電波法により非常に小さな強度に制限される。その場合、受信アンテナ２での受信強度も非常に小さくなり、アンプで増幅するだけではＳ／Ｎが不十分となり、精度よく測定することができない場合が生ずる。そこで、本実施例では、高い検出感度を得るため、送信アンテナ１から出力されるマイクロ波の周波数と異なる周波数のマイクロ波である局部波を発信する局部発振器と、局部波と受信アンテナ２により受信された受信信号とを合波し両者の周波数の差の周波数を有する差周波数信号を生成するミキサと、差周波数信号を通過させる周波数フィルタとを備え、ヘテロダイン方式により受信回路を構成している。すなわち、本実施例において、局部発振器として掃引発振器３２を使用し、受信アンテナ２により受信された受信信号をローノイズアンプ３６で増幅した後、ミキサ３５において掃引発振器３２により生成された信号と合波することにより、受信信号の周波数ｆ１＋ｆ２と掃引発振器３２の信号の周波数ｆ２の差の周波数 ｆ１を有する信号を得ている。ここで、ミキサ３５からの出力には差の周波数ｆ１、元の周波数ｆ１＋ｆ２、和の周波数ｆ１＋２ｆ２の信号が含まれるため、それをバンドパスフィルタ３７を通過させることにより差の周波数ｆ１のみを有する信号を得ている。 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.
周波数ｆ１以外の不用成分が除去された信号はローノイズアンプ３８で増幅され、欠陥情報を有する計測信号としてＩＱミキサ４０に入力され、ＩＱミキサ４０内で固定発振器３１の周波数ｆ１の参照波信号と合波され、検出信号が得られる。 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 fixed oscillator 31 in the IQ mixer 40. And a detection signal is obtained.
図３は本実施例に使用するＩＱミキサの内部構成図である。図３において、計測信号をパワーディバイダ４１で２つに分け、その分けられた同位相の２つの信号をそれぞれミキサ４３、ミキサ４４のＲＦポートに入力する。一方、参照波信号はハイブリッド４２に入力され、位相が互いに９０度異なる２つの信号に分けられ、それぞれミキサ４３、ミキサ４４のＬＯポートに入力する。ミキサ４３、ミキサ４４では、それぞれ計測信号と参照波信号の差の周波数信号と和の周波数信号が生成され、それぞれローパスフィルタ４５、ローパスフィルタ４６を通過させることにより差の周波数信号だけを取り出す。取り出される信号は、受信波の位相δと振幅Ａ５の情報を含んだｓｉｎ波成分とｃｏｓ波成分の検出信号として出力される。 FIG. 3 is an internal configuration diagram of the IQ mixer used in this embodiment. In FIG. 3, 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. Signal extracted is output as a detection signal of including phase δ and information of the amplitude A 5 of the received wave sin wave component and cos wave component.
図２に示したように、被測定物１１に照射されるマイクロ波８は周波数が掃引されており、各周波数に対するマイクロ波の波長が変化するので一定の反射面からの反射波の振幅と位相が周波数に対して変化する。そこで受信信号の周波数応答、すなわち各周波数に対する振幅と位相の値を逆フーリエ変換することにより反射波の相対的な到達時間差を算出し、反射面までの距離、すなわち被測定物の内部にある層状の欠陥の深さを求めることができる。本実施例においては、上記のように受信アンテナにより受信された受信信号の振幅と位相から欠陥１１の深さを検出する手段を信号処理部９の内部に有している。 As shown in FIG. 2, the frequency of the microwave 8 irradiated to the object to be measured 11 is swept, and the wavelength of the microwave for each frequency changes, so the amplitude and phase of the reflected wave from a certain reflecting surface. Varies with frequency. Therefore, the frequency response of the received signal, that is, the relative arrival time difference of the reflected wave is calculated by inverse Fourier transforming the amplitude and phase values for each frequency, and the distance to the reflecting surface, that is, the layered state inside the object to be measured The depth of defects can be obtained. In the present embodiment, the signal processing unit 9 has means for detecting the depth of the defect 11 from the amplitude and phase of the received signal received by the receiving antenna as described above.
図４および図５は、実施例１に係る内部欠陥検査装置による検出結果の一例を示す図であり、板状の材料を張り合わせて構成された製品における層状の剥離欠陥を測定した結果の一例を示す図である。図４は被測定物の深さ方向に対応した信号の強度分布を示す図、図５は欠陥が存在する深さでの信号強度をプロットした結果を示す図である。 4 and 5 are diagrams illustrating an example of a detection result by the internal defect inspection apparatus according to the first embodiment, and an example of a result of measuring a layered peeling defect in a product configured by laminating plate-like materials. FIG. FIG. 4 is a diagram showing the signal intensity distribution corresponding to the depth direction of the object to be measured, and FIG. 5 is a diagram showing the result of plotting the signal intensity at the depth where the defect exists.
図４の縦軸は得られた信号の深さに対応しており、横軸はマイクロ波を照射した基準点からの相対的な位置である。実際の検出装置の表示画面では横軸および縦軸の座標で示される点における信号強度が色調で表示されるが、図４においては白黒の濃淡で示し、黒色に近いほど信号強度が大きいことを示している。図４の測定結果では、被測定物の表面における反射波および深さ１００ｍｍの位置の裏面における反射波の強度が大きく示されており、その間、すなわち被測定物内の深さ４０ｍｍ程度の部分の基準位置から５０ｍｍ程度の位置に欠陥による反射波が存在していることがわかる。 The vertical axis in FIG. 4 corresponds to the depth of the obtained signal, and the horizontal axis is the relative position from the reference point irradiated with the microwave. On the display screen of the actual detection device, the signal intensity at the points indicated by the coordinates of the horizontal axis and the vertical axis is displayed in color tone. In FIG. Show. In the measurement result of FIG. 4, the intensity of the reflected wave on the surface of the object to be measured and the intensity of the reflected wave on the back surface at a position of 100 mm in depth is greatly shown. It can be seen that there is a reflected wave due to a defect at a position about 50 mm from the reference position.
図５は上記の深さ４０ｍｍの部分の信号強度をマイクロ波を照射した基準点からの相対的な位置に対してプロットしたものであり、剥離欠陥の位置が明確に示されている。 FIG. 5 is a plot of the signal intensity of the 40 mm depth portion relative to the relative position from the reference point irradiated with the microwave, and clearly shows the position of the peeling defect.
なお、上記の測定においては、被測定物の設置位置が数ｍｍ程度以上変化しても同じ測定結果が得られることが確認できた。 In the above measurement, it was confirmed that the same measurement result was obtained even when the installation position of the object to be measured was changed by several mm or more.
また、上記の測定においては、マイクロ波の照射範囲をある程度以上に広げ、製品の表面の凹凸よる反射波の変動が平均化して低減されるように考慮した。 In the above measurement, it was considered that the microwave irradiation range was expanded to a certain extent and the fluctuation of the reflected wave due to the unevenness on the surface of the product was averaged and reduced.
また、表面に周期的な凹凸を有する被測定物においては、表面の凹凸による反射波の変動によって計測信号に現れるノイズ波形は表面形状に応じてほぼ一定となるので、その波形を信号処理により除去することも可能である。 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.
以上のように、本発明により被測定物の内部の層状の欠陥を短時間に簡易に、かつ高精度に検出できることが確認できた。 As described above, it has been confirmed that the present invention can detect a layered defect inside the object to be measured easily and with high accuracy in a short time.
なお、本発明は上記の実施例に限定されるものではないことは言うまでもなく、目的や用途に応じて設計変更可能である。例えば、送信アンテナと受信アンテナの感度が最大となる偏波方向は、被測定物により、水平面に対し０〜１８０度の範囲で最適な角度に設定することができる。また、反射波から得られる信号強度が大きく、必要なＳ／Ｎが得られれば、回路部の構成は、通常のアンプと、平均化処理やフィルタなどによるノイズ低減回路と、ピーク値や振幅の検出回路などの信号処理回路を用いても構成可能であり、ヘテロダイン方式を採用しなくてもよい。また、本発明の対象とする被測定物は、金属材料以外で構成された内部に層状の欠陥を有するものであれば如何なる物体であってもよい。本発明で用いるマイクロ波の周波数は、１〜１５０ＧＨｚの帯域内で、欠陥の大きさや被測定物の物性に応じて選択可能である。この場合、一般的に低い周波数帯では分解能が低下するが、低コストとなり、高い周波数帯では分解能は高いが、高コストとなる。さらに、図２に示した回路機能と同等の機能を有するデバイスを使用することで、マイクロ波の周波数を３００ＧＨｚまで拡張することが可能である。 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, the polarization direction that maximizes the sensitivity of the transmission antenna and the reception antenna can be set to an optimum angle within a range of 0 to 180 degrees with respect to the horizontal plane depending on the object to be measured. If the signal intensity obtained from the reflected wave is large and the required S / N can be obtained, the circuit section can be configured with a normal amplifier, a noise reduction circuit such as an averaging process or a filter, and a peak value or amplitude. A signal processing circuit such as a detection circuit may be used, and the heterodyne method may not be employed. In addition, the object to be measured as an object of the present invention may be any object as long as it has a layered defect inside the metal material. The frequency of the microwave used in the present invention can be selected in the band of 1 to 150 GHz according to the size of the defect and the physical property of the object to be measured. In this case, the resolution is generally lowered in the low frequency band, but the cost is low, and the resolution is high in the high frequency band, but the cost is high. Furthermore, by using a device having a function equivalent to the circuit function shown in FIG. 2, the frequency of the microwave can be extended to 300 GHz.
１ 送信アンテナ
２ 受信アンテナ
３ 回路部
８ マイクロ波
８ｐ、２１ｐ、２３ｐ 偏波方向
９ 信号処理部
１０ 被測定物
１１ 欠陥
１２ 表面
１３ 裏面
２０ 内部欠陥検査装置
２１、２２、２３ 反射波
３１ 固定発振器
３２ 掃引発振器
３３ アップコンバータ
３４ アッテネータ
３５、４３、４４ ミキサ
３６、３８ ローノイズアンプ
３７ バンドパスフィルタ
４０ ＩＱミキサ
４１ パワーディバイダ
４２ ハイブリッド
４５、４６ ローパスフィルタ
DESCRIPTION OF SYMBOLS 1 Transmission antenna 2 Reception antenna 3 Circuit part 8 Microwave
8p, 21p, 23p Polarization direction 9 Signal processing unit 10 Object to be measured 11 Defect 12 Surface 13 Back surface 20 Internal defect inspection device 21, 22, 23 Reflected wave 31 Fixed oscillator 32 Sweep oscillator 33 Upconverter 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
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| JP6864112B2 (en) * | 2017-03-10 | 2021-04-21 | プロセク ソシエテ アノニム | Exploration of concrete structure using electromagnetic waves |
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| CN110530898B (en) * | 2019-08-13 | 2024-03-15 | 北海市产品检验检测中心 | Non-contact real-time detection device for internal and external cracking of rock test piece |
| JP7142794B1 (en) | 2022-02-24 | 2022-09-27 | 前田道路株式会社 | Delamination detection system and delamination detection method |
| JP7458598B2 (en) | 2022-09-08 | 2024-04-01 | 郁男 荒井 | Material property measuring device |
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