JP2012112805A - Wood imaging device and wood inspection method - Google Patents

Wood imaging device and wood inspection method Download PDF

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JP2012112805A
JP2012112805A JP2010262164A JP2010262164A JP2012112805A JP 2012112805 A JP2012112805 A JP 2012112805A JP 2010262164 A JP2010262164 A JP 2010262164A JP 2010262164 A JP2010262164 A JP 2010262164A JP 2012112805 A JP2012112805 A JP 2012112805A
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wood
measured
electromagnetic wave
radiation pattern
electromagnetic waves
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JP5682952B2 (en
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Hiroyoshi Toko
浩芳 都甲
Shoji Mochizuki
章志 望月
Naoya Kukutsu
直哉 久々津
Yoshihisa Fujii
義久 藤井
Hiroko Fujiwara
裕子 藤原
Soichi Tanaka
聡一 田中
Shogo Okumura
正悟 奥村
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Kyoto University
Nippon Telegraph and Telephone Corp
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Nippon Telegraph and Telephone Corp
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PROBLEM TO BE SOLVED: To shorten the measuring time of the quality of wood, and to further accurately determine an inside structure or a defect.SOLUTION: An electromagnetic wave radiated by a transmission antenna 12 is converted into a plane wave by a lens 13, and emitted on wood 100 to be measured. A detector 15 detects the electromagnetic wave outgoing from a surface of the wood 100 to be measured, and interference fringes are obtained, which are produced by the interference of the electromagnetic waves outgoing respectively from a fiber (grain) traveling structure of the wood 100 to be measured. Therefore, without two-dimensionally scanning the wood 100 to be measured, a traveling interval, a direction, and an inside defect of fibers (grains) of the wood 100 to be measured can be detected, and an inspection cost can be reduced.

Description

本発明は、木材の内部構造を調べ、木材の品質を検査する技術に関する。   The present invention relates to a technique for examining the internal structure of wood and inspecting the quality of the wood.

木材や木質構造物の品質は繊維（木理）の走行方向や節の有無、虫食いなどによる欠陥の有無などのパラメータにより規定されている。品質は木材加工現場、工場、卸売業者などすべての現場において管理されるべきであるが、現実的には点検コストを理由にすべての現場で実施されていない。そのような背景の中で、より簡便に低コストで品質検査を行う方法が開発されている。   The quality of timber and wood structures is defined by parameters such as the direction of fiber (wood), the presence or absence of nodes, and the presence or absence of defects due to worms. Quality should be managed at all sites, such as timber processing sites, factories, and wholesalers, but in reality it is not implemented at all sites because of inspection costs. In such a background, a method of performing quality inspection more easily and at low cost has been developed.

例えば、特許文献１は、超音波を用いて木材の内部構造を検査する。ＣＴ技術により優れた空間分解能を有するが、被測定対象に反射防止液剤を塗布してセンサを密着させる必要があるため、非侵襲性や作業コストの点に課題がある。   For example, Patent Document 1 inspects the internal structure of wood using ultrasonic waves. Although it has an excellent spatial resolution by the CT technique, it is necessary to apply an antireflection liquid agent to the measurement object and to bring the sensor into close contact with each other.

特許文献２のＸ線ＣＴを用いた検査方法は超音波による検査方法の課題を克服しているが、安全管理や作業者に免許や特殊な技能が必要なため汎用性に課題を残している。   Although the inspection method using X-ray CT in Patent Document 2 overcomes the problems of ultrasonic inspection methods, it remains a problem in versatility because it requires safety management and licenses and special skills for workers. .

特許文献３のマイクロ波からテラヘルツ波の電磁波を用いる方法は、上記の超音波による検査方法およびＸ線ＣＴによる検査方法の上記の課題を克服している。図５に従来の木材イメージング装置の構成を示す。従来の木材イメージング装置は、信号源５１で発生したマイクロ波からテラヘルツ波の電磁波を送信アンテナ５２から放射し、その電磁波をレンズ５３で集束させて被測定木材１００に照射し、被測定木材１００を透過した電磁波を受信アンテナ５４で受信して検出器５５で検出する。送受信アンテナもしくは被測定木材１００を２次元に走査することにより電磁波の透過強度の２次元マップを得て、内部構造や欠陥を検出することができる。   The method of using electromagnetic waves of terahertz waves from microwaves in Patent Document 3 overcomes the above-described problems of the inspection method using ultrasonic waves and the inspection method using X-ray CT. FIG. 5 shows the configuration of a conventional wood imaging apparatus. A conventional wood imaging apparatus radiates terahertz electromagnetic waves from microwaves generated by a signal source 51 from a transmission antenna 52, focuses the electromagnetic waves on a lens 53, and irradiates the wood to be measured 100. The transmitted electromagnetic wave is received by the receiving antenna 54 and detected by the detector 55. By scanning the transmission / reception antenna or the measured wood 100 two-dimensionally, a two-dimensional map of electromagnetic wave transmission intensity can be obtained to detect internal structures and defects.

特開２００６−０５３０４５号公報JP 2006-053045 A 特開２００６−０７８２５１号公報JP 2006-078251 特開２００５−０４３２３０号公報Japanese Patent Laid-Open No. 2005-043230

しかしながら、従来の電磁波による木材イメージング装置には、以下に示す問題があった。   However, the conventional wood imaging apparatus using electromagnetic waves has the following problems.

従来の木材イメージング装置においては被測定木材を２次元に走査しながら、被測定木材を透過する電磁波を検出する。内部構造や欠陥を検出するために検出信号を被測定木材の各点に２次元マッピングした画像を作成するので、走査時間がかかり点検コストが高いという問題があった。   In a conventional wood imaging apparatus, an electromagnetic wave transmitted through the wood to be measured is detected while the wood to be measured is scanned two-dimensionally. In order to detect internal structures and defects, an image in which the detection signal is two-dimensionally mapped to each point of the wood to be measured is created.

また、被測定木材内を伝搬する電磁波は被測定木材の厚さ方向の構造の影響で回折されるため、走査した各点の検出信号は回折した電磁波が加算されたものとなり、画像が不鮮明で内部構造や欠陥を判別することが困難であるという問題があった。   In addition, since the electromagnetic wave propagating through the wood to be measured is diffracted by the influence of the structure in the thickness direction of the wood to be measured, the detection signal at each scanned point is the sum of the diffracted electromagnetic waves, and the image is unclear. There was a problem that it was difficult to distinguish internal structures and defects.

本発明は、上記に鑑みてなされたものであり、木材の品質の測定時間を短縮し、点検コストを低減すること、および、より正確に内部構造や欠陥を判別することを目的とする。   The present invention has been made in view of the above, and it is an object of the present invention to shorten the measurement time of wood quality, reduce inspection costs, and more accurately determine internal structures and defects.

第１の本発明に係る木材イメージング装置は、電磁波を被測定木材へ照射し、当該被測定木材を透過した電磁波を受信して当該被測定木材の内部構造を撮像する木材イメージング装置であって、電磁波を放射する送信アンテナと、前記送信アンテナが放射した前記電磁波を平面波に変換して前記被測定木材へ照射するレンズと、前記被測定木材を透過した前記電磁波による干渉縞が観察できる位置に配置され、当該電磁波を受信して放射パターンを測定する検出手段と、を有することを特徴とする。   A wood imaging apparatus according to a first aspect of the present invention is a wood imaging apparatus that irradiates a target wood with electromagnetic waves, receives the electromagnetic waves transmitted through the target wood, and images the internal structure of the target wood, A transmitting antenna that radiates electromagnetic waves, a lens that converts the electromagnetic waves radiated from the transmitting antenna into plane waves and irradiates the wood to be measured, and an interference fringe due to the electromagnetic waves that have passed through the wood to be measured are disposed at positions where they can be observed And detecting means for receiving the electromagnetic wave and measuring a radiation pattern.

上記木材イメージング装置において、前記検出手段は、前記被測定木材を原点とする円周上で前記電磁波を受信することを特徴とする。   In the wood imaging apparatus, the detection means receives the electromagnetic wave on a circumference having the wood to be measured as an origin.

上記木材イメージング装置において、前記検出手段は、前記被測定木材を原点とする円周上に複数配置されたことを特徴とする。   In the wood imaging apparatus, a plurality of the detection means are arranged on a circumference having the wood to be measured as an origin.

上記木材イメージング装置において、前記原点は、前記被測定木材の中心であることを特徴とする。   In the wood imaging apparatus, the origin is a center of the wood to be measured.

上記木材イメージング装置において、前記電磁波の波長は、対象とする前記被測定木材の内部の欠陥の相当径よりも大きな波長であることを特徴とする。   In the wood imaging apparatus, the wavelength of the electromagnetic wave is larger than an equivalent diameter of a defect inside the target wood to be measured.

第２の本発明に係る木材検査方法は、電磁波を被測定木材へ照射し、当該被測定木材から出射された電磁波を受信して当該被測定木材の内部構造を撮像する木材検査方法であって、送信アンテナから電磁波を放射するステップと、レンズを用いて前記送信アンテナが放射した前記電磁波を平面波に変換し、前記被測定木材へ照射するステップと、前記被測定木材から出射する前記電磁波の干渉縞が観察できる位置に配置された検出手段により当該電磁波を受信して放射パターンを測定するステップと、前記放射パターンから前記被測定木材の品質を判定するステップと、を有することを特徴とする。   A wood inspection method according to a second aspect of the present invention is a wood inspection method for irradiating an electromagnetic wave to a measurement wood, receiving the electromagnetic wave emitted from the measurement wood, and imaging an internal structure of the measurement wood. Radiating an electromagnetic wave from the transmitting antenna; converting the electromagnetic wave radiated from the transmitting antenna into a plane wave using a lens; irradiating the measured wood; and interference of the electromagnetic wave emitted from the measured wood It has the step which receives the said electromagnetic wave by the detection means arrange | positioned in the position which can observe a fringe, measures a radiation pattern, and determines the quality of the said to-be-measured wood from the said radiation pattern, It is characterized by the above-mentioned.

上記木材検査方法において、前記判定するステップは、前記放射パターンの周波数解析に基づき、高い空間周波数のスペクトル強度が強い場合に前記被測定木材の内部に欠陥があると判定することを特徴とする。   In the wood inspection method, the determining step is characterized in that, based on the frequency analysis of the radiation pattern, it is determined that there is a defect inside the wood to be measured when the spectral intensity of a high spatial frequency is strong.

上記木材検査方法において、前記判定するステップは、前記放射パターンを理想的な放射パターンと比較することを特徴とする。   In the wood inspection method, the determining step compares the radiation pattern with an ideal radiation pattern.

本発明によれば、木材の品質の測定時間を短縮し、点検コストを低減すること、および、より正確に内部構造や欠陥を判別することができる。   ADVANTAGE OF THE INVENTION According to this invention, the measurement time of the quality of wood can be shortened, inspection cost can be reduced, and an internal structure and a defect can be discriminate | determined more correctly.

本実施の形態における木材イメージング装置の構成を示す図である。It is a figure which shows the structure of the wood imaging apparatus in this Embodiment. 本実施の形態における別の木材イメージング装置の構成を示す図である。It is a figure which shows the structure of another wood imaging apparatus in this Embodiment. 本実施の形態における木材イメージング装置で検出される放射パターンの例を示す図である。It is a figure which shows the example of the radiation pattern detected with the timber imaging apparatus in this Embodiment. 木材に欠陥があるときの放射パターンの例を示す図である。It is a figure which shows the example of the radiation pattern when there exists a defect in wood. 従来の木材イメージング装置の構成を示す図である。It is a figure which shows the structure of the conventional wood imaging apparatus.

以下、本発明の実施の形態について図面を用いて説明する。   Hereinafter, embodiments of the present invention will be described with reference to the drawings.

図１は、本実施の形態における木材イメージング装置の構成を示す図である。同図に示す木材イメージング装置は、信号源１１、送信アンテナ１２、レンズ１３、受信アンテナ１４、および検出器１５を備える。本実施の形態における木材イメージング装置は、被測定木材１００の繊維（木理）走行構造をスリットもしくはスラブ導波管としてみなし、電磁波を被測定木材１００へ入射して被測定木材１００の繊維（木理）走行構造内を分離伝搬させて、各走行構造から出射される電磁波が干渉することにより生成される干渉縞を観察することで、繊維（木理）の走行間隔や方向などの構造、内部欠陥（虫穴や腐朽による空洞部や密度低下部）を検出する。以下、各部について説明する。   FIG. 1 is a diagram showing a configuration of a wood imaging apparatus in the present embodiment. The wood imaging apparatus shown in the figure includes a signal source 11, a transmission antenna 12, a lens 13, a reception antenna 14, and a detector 15. The wood imaging apparatus according to the present embodiment regards the fiber (wood) running structure of the wood to be measured 100 as a slit or slab waveguide, and enters the electromagnetic waves into the wood to be measured 100 to cause the fibers (wood) of the wood to be measured 100 F) By separating and propagating through the traveling structure and observing the interference fringes generated by the interference of electromagnetic waves emitted from each traveling structure, the structure of the fiber (wood), such as the traveling interval and direction, Detect defects (cavities and reduced density due to insect holes and decay). Hereinafter, each part will be described.

信号源１１は、数Ｈｚから数ＴＨｚまでの周波数の電磁波を出力する。本実施の形態では、被測定木材１００の内部欠陥の相当径よりも大きな波長となる周波数の電磁波を用いる。   The signal source 11 outputs an electromagnetic wave having a frequency from several Hz to several THz. In the present embodiment, an electromagnetic wave having a frequency having a wavelength larger than the equivalent diameter of the internal defect of the measured wood 100 is used.

送信アンテナ１２は、信号源１１の出力した電磁波をレンズ１３を介して被測定木材１００に対して放射する。送信アンテナ１２から放射された電磁波はレンズ１３により平面波に変換され、被測定木材１００へ照射される。電磁波が照射される範囲は、被測定木材１００の繊維（木理）が複数本含まれる必要がある。   The transmission antenna 12 radiates the electromagnetic wave output from the signal source 11 to the measured wood 100 through the lens 13. The electromagnetic wave radiated from the transmitting antenna 12 is converted into a plane wave by the lens 13 and irradiated to the measured wood 100. The range irradiated with the electromagnetic wave needs to include a plurality of fibers (wood) of the measured wood 100.

受信アンテナ１４が取り付けられた検出器１５は、被測定木材１００の内部を伝搬して被測定木材１００の側面もしくは電磁波の入射面に対向する反対側の面から出射された電磁波を受信して放射パターンを測定する。検出器１５は、走査ステージ（図示せず）上に配置され、制御部（図示せず）により、被測定木材１００を原点として被測定木材１００から一定距離離れた円周上を移動するように制御されて電磁波を検出する。例えば、図１に示すように、検出器１５を被測定木材１００の中心を円周の原点とした円周上で移動させて走査する。被測定木材１００の中心を原点として信号源１１の正対称の位置が零次回折点となる。図１では、零次回折点の方向を円周の９０度と表示している。円周の原点を被測定木材１００の中心にとり、観察面を円周上にとることが干渉縞の観測に適している。被測定木材１００から一定距離離れた直線上を観察面としても電磁波の干渉は観測できるが、円周上で観測することによって、被測定木材１００からの遠方界を過不足なく最小の労力で観察することができる。検出器１５が測定した放射パターンに基づく被測定木材１００の品質の判定については後述する。   The detector 15 to which the receiving antenna 14 is attached receives and radiates electromagnetic waves emitted from the side surface of the measured wood 100 or the side opposite to the incident surface of the electromagnetic waves while propagating through the measured wood 100. Measure the pattern. The detector 15 is arranged on a scanning stage (not shown), and is moved by a control unit (not shown) on the circumference away from the measured wood 100 by a certain distance from the measured wood 100 as an origin. Controlled to detect electromagnetic waves. For example, as shown in FIG. 1, the detector 15 is moved and scanned on the circumference with the center of the measured wood 100 as the origin of the circumference. A positively symmetric position of the signal source 11 with the center of the measured wood 100 as the origin is the zero-order diffraction point. In FIG. 1, the direction of the zero-order diffraction point is displayed as 90 degrees of the circumference. It is suitable for observing interference fringes that the origin of the circumference is at the center of the wood 100 to be measured and the observation surface is on the circumference. Although the interference of electromagnetic waves can be observed even if the observation surface is a straight line away from the measured wood 100 by a certain distance, the far field from the measured wood 100 can be observed with a minimum amount of effort by observing on the circumference. can do. The determination of the quality of the measured wood 100 based on the radiation pattern measured by the detector 15 will be described later.

図２は、本実施の形態における別の木材イメージング装置の構成を示す図である。同図に示す木材イメージング装置は、検出器１５を円周上で走査する代わりに、複数の検出器１５を円周上に配置したものである。繊維（木理）走行方向は木種や年齢によってある程度の範囲に収まっているため、電磁波の波長および被測定木材１００と検出器１５との距離によって検出器１５の配置数や配置間隔を設計することができる。   FIG. 2 is a diagram showing a configuration of another wood imaging apparatus in the present embodiment. The wood imaging apparatus shown in the figure has a plurality of detectors 15 arranged on the circumference instead of scanning the detectors 15 on the circumference. Since the fiber (wood) traveling direction is within a certain range depending on the tree type and age, the number of detectors 15 and the arrangement interval of the detectors 15 are designed according to the wavelength of the electromagnetic wave and the distance between the wood to be measured 100 and the detector 15. be able to.

また、図２に示す木材イメージング装置は、遮蔽板１６を備えて、送信アンテナ１２から放射される電磁波の主ローブのみをレンズ１３に伝搬させている。遮蔽板１６の代わりに、送信アンテナ１２のホーン部分を緩やかに広げてレンズ１３に直結することにより放射効率を向上することもできる。   The wood imaging apparatus shown in FIG. 2 includes a shielding plate 16 and propagates only the main lobe of the electromagnetic wave radiated from the transmitting antenna 12 to the lens 13. Instead of the shielding plate 16, the radiation efficiency can be improved by gently expanding the horn portion of the transmitting antenna 12 and directly connecting it to the lens 13.

次に、観測される干渉縞について説明する。   Next, the observed interference fringes will be described.

被測定木材１００の組織構造は、入射された電磁波の波長が年輪などの組織構造の周期よりも大きいときはスリット、小さいときはスラブ導波管として機能する。被測定木材１００内を伝搬した電磁波は組織構造の周期間を波源として被測定木材１００の表面から出射される。組織構造の周期間から出射された電磁波は互いに干渉するため、検出器１５で測定した放射パターンは図３に示すような干渉縞を形成し、零次回折を中心として一次回折、二次回折、・・・の干渉縞が観察される。図３は、横軸に検出した電磁波の強度、縦軸に検出器１５の位置を示している。零次回折縞は必ずしも被測定木材１００の中央の位置（信号源の正対称の位置）に出現するわけではなく、組織構造の走行方向によって変化する。例えば、図３のように、図上で上向きに組織構造が走行しているときは、干渉縞は０度に近い位置に偏る。このことから、干渉縞の位置から組織構造の走行方向を判別することができる。   The tissue structure of the wood to be measured 100 functions as a slit when the wavelength of the incident electromagnetic wave is larger than the period of the tissue structure such as an annual ring, and functions as a slab waveguide when the wavelength is small. The electromagnetic wave propagated through the measured wood 100 is emitted from the surface of the measured wood 100 using the period of the tissue structure as a wave source. Since electromagnetic waves emitted from the period of the tissue structure interfere with each other, the radiation pattern measured by the detector 15 forms interference fringes as shown in FIG. 3, and the first-order diffraction, the second-order diffraction, Interference fringes are observed. FIG. 3 shows the detected electromagnetic wave intensity on the horizontal axis and the position of the detector 15 on the vertical axis. The zero-order diffraction fringes do not necessarily appear at the center position of the measured wood 100 (the position of positive symmetry of the signal source), but varies depending on the traveling direction of the tissue structure. For example, as shown in FIG. 3, when the tissue structure is traveling upward in the figure, the interference fringes are biased to a position close to 0 degrees. From this, the traveling direction of the tissue structure can be determined from the position of the interference fringes.

続いて、組織構造の周期の算出について説明する。   Subsequently, calculation of the period of the tissue structure will be described.

組織構造の周期ｄは、干渉縞の間隔Ｄ、電磁波の波長λ、被測定木材１００の電磁波の出射面と検出器１５の距離Ｌを用いて次式（１）により求めることができる。   The period d of the tissue structure can be obtained by the following equation (1) using the distance D between the interference fringes, the wavelength λ of the electromagnetic wave, and the distance L between the electromagnetic wave emission surface of the measured wood 100 and the detector 15.

Figure 2012112805
Figure 2012112805

上記の式を変形して干渉縞の間隔Ｄは次式（２）で表される。   By transforming the above formula, the interference fringe spacing D is expressed by the following formula (2).

Figure 2012112805
Figure 2012112805

続いて、被測定木材１００の電磁波の出射面と検出器１５との距離について説明する。   Next, the distance between the electromagnetic wave emission surface of the measured wood 100 and the detector 15 will be described.

アンテナをコニカルホーンアンテナなどの単純な円形開口を有する開口アンテナとすると、アンテナの実効長ｌｅはアンテナ利得Ｇを用いて次式（３）で表される。 When the antenna is an aperture antenna having a simple circular aperture such as a conical horn antenna, the effective length l e of the antenna is expressed by the following equation (3) using the antenna gain G.

Figure 2012112805
Figure 2012112805

電磁波の放射パターンを正確に測定するためには標本化定理から干渉縞の間隔Ｄがアンテナの実効長ｌｅの半分よりも大きくなるように検出器１５を配置する必要がある。したがって、被測定木材１００の電磁波の出射面と検出器１５の距離Ｌは以下の条件を満たす必要がある。 In order to accurately measure the radiation pattern of electromagnetic waves, it is necessary to arrange the detector 15 so that the interference fringe spacing D is larger than half of the effective length l e of the antenna from the sampling theorem. Therefore, the distance L between the electromagnetic wave emission surface of the measured wood 100 and the detector 15 needs to satisfy the following conditions.

Figure 2012112805
Figure 2012112805

また、干渉縞を形成するためにはフラウンフォーファー回折領域での測定が必要であるため距離Ｌは波長λの１０倍以上となる。   Further, since it is necessary to measure in the Fraunhofer diffraction region in order to form the interference fringes, the distance L is 10 times or more the wavelength λ.

次に、木材の品質の判定について説明する。   Next, the determination of the quality of wood will be described.

放射パターン上の干渉縞の次数は組織構造の周期性を、縞間隔は周期を表しており、木材内部に虫害による孔や節が存在するときは図４のように複雑なパターンとなる。これは、対象とする内部欠陥の相当径よりも大きな波長の電磁波を用いることにより、欠陥を回折した電磁波が繊維（木理）走行構造から出射される電磁波と干渉するためである。品質の良い木材は繊維（木理）の周期性が高いため干渉縞は単純であり、放射パターンを観察することにより品質を判別することができる。すなわち、放射パターンに一次や二次などの低い次数の回折による干渉縞のみが観察されるときは木材の内部に欠陥が存在しない。これに対して、低い次数の回折による干渉縞だけでなく高い次数の回折による干渉縞が観察されるときは木材内部に欠陥が存在している。したがって、高次の回折パターンを抽出するために、例えば、周波数解析を行い、高い空間周波数のスペクトル強度が強い場合には木材内部に欠陥が存在していると判定する。または、予め周期構造が分かる場合は、理想的な干渉縞パターンを計算によって生成するか、もしくはメモリに記憶しておき、そのパターンと観測した干渉パターンとを比較することで、品質を判定しても良い。   The order of the interference fringes on the radiation pattern represents the periodicity of the tissue structure, and the fringe interval represents the period. When holes or nodes due to insect damage are present inside the wood, the pattern becomes complicated as shown in FIG. This is because the electromagnetic wave diffracted by the defect interferes with the electromagnetic wave emitted from the fiber (wood) traveling structure by using the electromagnetic wave having a wavelength larger than the equivalent diameter of the target internal defect. Good quality wood has a high periodicity of fibers (wood), so the interference fringes are simple, and the quality can be discriminated by observing the radiation pattern. In other words, when only interference fringes due to low-order diffraction such as primary and secondary are observed in the radiation pattern, there is no defect inside the wood. On the other hand, when not only interference fringes due to low-order diffraction but also interference fringes due to high-order diffraction are observed, defects are present in the wood. Therefore, in order to extract a higher-order diffraction pattern, for example, frequency analysis is performed, and it is determined that there is a defect inside the wood when the spectral intensity at a high spatial frequency is strong. Alternatively, if the periodic structure is known in advance, an ideal interference fringe pattern is generated by calculation or stored in a memory, and the quality is determined by comparing the pattern with the observed interference pattern. Also good.

なお、一般に使用される木材の組織構造の周期は木種や樹齢にもよるがほぼ一定であり、数ｍｍから十数ｍｍである。使用する木種などがあらかじめ分かっていれば、式（２）から干渉縞間隔は推定できる。すなわち、検出器１５は全領域を走査したり、配置する必要はなく、被測定木材１００の組織構造に応じて推定される干渉縞の位置にのみ配置すればよい。その結果、測定時間を短縮し、点検コストの低減を図ることができる。   Note that the period of the tissue structure of wood generally used is almost constant, depending on the type of tree and the age of the tree, and is several mm to several tens of mm. If the tree type to be used is known in advance, the interference fringe interval can be estimated from equation (2). In other words, the detector 15 does not need to scan or be arranged over the entire area, and may be arranged only at the position of the interference fringes estimated according to the tissue structure of the measured wood 100. As a result, the measurement time can be shortened and the inspection cost can be reduced.

以上説明したように、本実施の形態によれば、送信アンテナ１２が放射する電磁波をレンズ１３で平面波に変換して被測定木材１００に照射し、検出器１５により、被測定木材１００の表面から出射する電磁波を検出し、被測定木材１００の繊維（木理）走行構造それぞれから出射する電磁波が干渉することで生成される干渉縞を観察することにより、被測定木材１００を２次元に走査することなく、被測定木材１００の繊維（木理）の走行間隔や方向、内部の欠陥を検出することができ、点検コストの低減を図ることができる。   As described above, according to the present embodiment, the electromagnetic wave radiated from the transmitting antenna 12 is converted into a plane wave by the lens 13 and irradiated to the measured wood 100, and the detector 15 detects the surface of the measured wood 100. The measured wood 100 is two-dimensionally scanned by detecting the emitted electromagnetic waves and observing the interference fringes generated by the interference of the electromagnetic waves emitted from the fiber (wood) running structures of the measured wood 100. Therefore, it is possible to detect the travel interval and direction of the fibers (wood) of the measured wood 100 and internal defects, and to reduce the inspection cost.

本実施の形態によれば、電磁波を円周上で検出することによって、被測定木材１００からの遠方界を過不足なく最小の労力で観察することができる。このとき、円周の原点を被測定木材１００の中心にとることが干渉縞の観測に適している。また、繊維（木理）走行構造は木種や樹齢によってある程度の範囲に収まっているため、電磁波の波長、観察面と検出器１５との距離によって検出器１５の配置数や配置間隔を想定することができ、測定時間を短縮し、点検コストの低減を図ることができる。   According to the present embodiment, by detecting electromagnetic waves on the circumference, it is possible to observe the far field from the measured wood 100 with a minimum effort without excess or deficiency. At this time, taking the origin of the circumference at the center of the measured wood 100 is suitable for observation of interference fringes. Further, since the fiber (wood) running structure is within a certain range depending on the tree type and age, the number of detectors 15 and the spacing between the detectors 15 are assumed based on the wavelength of the electromagnetic wave and the distance between the observation surface and the detector 15. Therefore, the measurement time can be shortened and the inspection cost can be reduced.

さらに、対象とする内部欠陥の相当径よりも大きな波長の電磁波を用いることにより、欠陥を回折した電磁波が繊維（木理）走行構造から出射する電磁波と干渉するため、観察される干渉縞が変化し、容易に内部の欠陥を判別することができ、被測定木材１００の内部の欠陥の検査精度の向上を図ることができる。   Furthermore, by using an electromagnetic wave having a wavelength larger than the equivalent diameter of the target internal defect, the electromagnetic wave diffracted by the defect interferes with the electromagnetic wave emitted from the fiber (wood) traveling structure, so that the observed interference fringe changes. In addition, the internal defects can be easily determined, and the inspection accuracy of the internal defects of the measured wood 100 can be improved.

１１…信号源
１２…送信アンテナ
１３…レンズ
１４…受信アンテナ
１５…検出器
１６…遮蔽板
１００…被測定木材 DESCRIPTION OF SYMBOLS 11 ... Signal source 12 ... Transmission antenna 13 ... Lens 14 ... Reception antenna 15 ... Detector 16 ... Shielding plate 100 ... Wood to be measured

Claims (8)

電磁波を被測定木材へ照射し、当該被測定木材を透過した電磁波を受信して当該被測定木材の内部構造を撮像する木材イメージング装置であって、
電磁波を放射する送信アンテナと、
前記送信アンテナが放射した前記電磁波を平面波に変換して前記被測定木材へ照射するレンズと、
前記被測定木材を透過した前記電磁波による干渉縞が観察できる位置に配置され、当該電磁波を受信して放射パターンを測定する検出手段と、
を有することを特徴とする木材イメージング装置。 A wood imaging device that irradiates a measured wood with electromagnetic waves, receives electromagnetic waves transmitted through the measured wood, and images the internal structure of the measured wood,
A transmitting antenna that radiates electromagnetic waves;
A lens that converts the electromagnetic wave emitted by the transmitting antenna into a plane wave and irradiates the wood to be measured;
A detector that is arranged at a position where the interference fringes due to the electromagnetic waves transmitted through the wood to be measured can be observed, and that receives the electromagnetic waves and measures a radiation pattern;
A wood imaging apparatus comprising: 前記検出手段は、前記被測定木材を原点とする円周上で前記電磁波を受信することを特徴とする請求項１記載の木材イメージング装置。   2. The wood imaging apparatus according to claim 1, wherein the detection means receives the electromagnetic wave on a circumference having the wood to be measured as an origin. 前記検出手段は、前記被測定木材を原点とする円周上に複数配置されたことを特徴とする請求項２記載の木材イメージング装置。   3. The wood imaging apparatus according to claim 2, wherein a plurality of the detection means are arranged on a circumference having the wood to be measured as an origin. 前記原点は、前記被測定木材の中心であることを特徴とする請求項２又は３記載の木材イメージング装置。   4. The wood imaging apparatus according to claim 2, wherein the origin is a center of the wood to be measured. 前記電磁波の波長は、対象とする前記被測定木材の内部の欠陥の相当径よりも大きな波長であることを特徴とする請求項１乃至４のいずれかに記載の木材イメージング装置。   5. The wood imaging apparatus according to claim 1, wherein a wavelength of the electromagnetic wave is a wavelength larger than an equivalent diameter of a defect inside the target wood to be measured. 電磁波を被測定木材へ照射し、当該被測定木材から出射された電磁波を受信して当該被測定木材の内部構造を撮像する木材検査方法であって、
送信アンテナから電磁波を放射するステップと、
レンズを用いて前記送信アンテナが放射した前記電磁波を平面波に変換し、前記被測定木材へ照射するステップと、
前記被測定木材から出射する前記電磁波の干渉縞が観察できる位置に配置された検出手段により当該電磁波を受信して放射パターンを測定するステップと、
前記放射パターンから前記被測定木材の品質を判定するステップと、
を有することを特徴とする木材検査方法。 A wood inspection method for irradiating an electromagnetic wave to a wood to be measured, receiving an electromagnetic wave emitted from the wood to be measured, and imaging an internal structure of the wood to be measured,
Radiating electromagnetic waves from the transmitting antenna; and
Converting the electromagnetic wave radiated from the transmitting antenna using a lens into a plane wave and irradiating the wood to be measured;
Measuring the radiation pattern by receiving the electromagnetic wave by a detecting means arranged at a position where the interference fringes of the electromagnetic wave emitted from the measured wood can be observed;
Determining the quality of the measured wood from the radiation pattern;
A method for inspecting wood, comprising: 前記判定するステップは、前記放射パターンの周波数解析に基づき、高い空間周波数のスペクトル強度が強い場合に前記被測定木材の内部に欠陥があると判定することを特徴とする請求項６記載の木材検査方法。   7. The wood inspection according to claim 6, wherein the determining step determines, based on frequency analysis of the radiation pattern, that there is a defect in the measured wood when the spectral intensity of a high spatial frequency is strong. Method. 前記判定するステップは、前記放射パターンを理想的な放射パターンと比較することを特徴とする請求項６記載の木材検査方法。   7. The wood inspection method according to claim 6, wherein the determining step compares the radiation pattern with an ideal radiation pattern.
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