JP3865675B2 - Ultrasonic flaw detection result display method and ultrasonic flaw detector - Google Patents

Description

この数１に示すように、処理(Ｓ７０３)では、受信波の伝播時間Δｔと参照波からホログラムを作成する。ここで、注意すべき点は、参照波の引数として用いる伝播時間Δｔに対しては補正が必要な点である。何故なら、平面波の場合と異なり、集束超音波は、焦点位置を中心として、放射状に超音波が拡がる波面を持つからである。
【００９６】
このため、伝播時間を求める際の伝播時間の基準として、平面波の場合はアレイセンサ１０１上に位置する超音波送信位置を時間０とおくのに対して、集束超音波の場合は、放射状に拡がる波面の原点である焦点位置を伝播時間の基準とするため、通常の伝播時間から焦点位置までの伝播時間を減算し、焦点位置からの伝播時間を、補正された伝播時間Δｔ'として採用する。
【００９７】
また、数１では、参照波の値そのものをホログラムとして採用しているため、ホログラムが−１から＋１までを連続的に変化する値を取る。しかし、連続値のホログラムに代えて、図１４に示した２値化ホログラムを用いてもよい。
【００９８】
次に、図１８の処理における第２段階として、ホログラム再生処理に移る。このときのホログラム再生方法の例を数２に示す。
【００９９】
【数２】

そして、ホログラム作成のための角振動数ωによって定められる波数ｋを持った球面波を加算することで、ホログラム再生処理を行う(Ｓ７０４)。ここで、角振動数ωと波数ｋは、被検査体１００を伝播する超音波音速Ｖを用いて、ｋ＝ω／Ｖと書き表すことができる。
【０１００】
次に、このホログラムの再生値に対して、或るしきい値(閾値)を定め、その値以上のものを反射源の映像として使用する)。このときのしきい値による処理の流れの具体例は、図２０のフローチャートに示すように、Ｓ７０５１による判定処理の結果でＳ７０５２を実行する処理になっている。
【０１０１】
この後、全てのデータに対する再生処理の終了を確認し(Ｓ７０６)、再生値を含む再生用データを、表示処理部２１８により２次元又は３次元的の映像に処理し、表示部２１９に表示(Ｓ８０)させ、処理を終了する。
【０１０２】
従って、この実施形態１によれば、欠陥などの反射源の近傍に焦点を合わせた集束超音波を作り出し、これを用いてエコーを検出しているので、ノイズが少なくＳＮ比が高くいエコーが得られ、この結果、得られたホログラムにおけるノイズの影響を最小限に抑えることができる。
【０１０３】
このとき、一旦、フラットな超音波を送信し、エコーの最短時間に着目して反射源位置を検出し、その近傍に焦点を持つ集束超音波の発生に必要な焦点位置の設定が自動的に与えられるようにしているので、操作が簡単で容易に高精度を保つことができる。
【０１０４】
また、この実施形態１では、アレイセンサを用い、電子走査による探傷が得られるようにしているので、探傷処理に要する時間が短くでき、且つ、ＳＮ比の高いエコーから作成されるノイズの少ないホログラムにより、最終的に、ノイズの影響の少ないホログラム再生像による欠陥映像を得ることができる。
【０１０５】
次に、本発明の実施形態２(第２の実施形態)について説明する。なお、この実施形態２も、被検査体の中に複数個の反射源が存在し、しかも、それらが異なった深さを持っている場合を想定し、この場合に好適な超音波探傷装置を提供するものである。
【０１０６】
従って、この実施形態２でも、アレイセンサ１０１とシステム全体２００は図２と図３で説明した実施形態１と同じで、その他、ホログラムの再生までの基本的な動作も、実施形態１と同じであり、従って、以下、図１０〜図１３により、実施形態１と異なっている点に重点をおいて説明する。
【０１０７】
まず、ここでも、図１０に示すように、被検査体１００の内部に深さ位置の異なる反射源が複数(ここでは反射源Ａ、Ｂの２個)存在する場合の探傷に、この実施形態２が適用されたとする。
【０１０８】
ところで、この場合も、実施形態１と同じく、図１５に示したフローチャートに従って動作させ、被検査体１００の各位置において、フラットな波面を持つ超音波を入射し、反射源Ａ、反射源Ｂまでの深さを推定た後、集束超音波を入射して欠陥を映像化することは可能である。
【０１０９】
この場合は、まず、図１０に示すように、被検査体内部の浅い位置に存在する反射源Ａを探傷するには、遅延時間パターンＰ１(波形９ａ〜９ｅ)をアレイセンサ１０１に供給し、反射源Ａの深さと焦点位置を合わせて探傷する。
【０１１０】
このように反射源位置と焦点位置が比較的近い場合には、実施形態１においても説明したように、超音波の強度が十分に強いため、小さな反射源からのエコーを逃すことも少なく、また焦点位置では超音波の拡がりが少ないため、反射源の大きさを過大に評価することもない。
【０１１１】
しかし、やや深い場所に位置する反射源Ｂを探傷する場合には、同じ遅延時間パターンＰ１では、反射源位置と焦点位置がずれてしまうため、これも実施形態１において説明したように、信号強度が弱く、しかも超音波の拡がりの影響を受けた不明瞭なエコーしか得られないため、正確な探傷が困難である。
【０１１２】
ここで、このような焦点位置からずれた反射源によるＢスコープ(超音波送受信位置と伝播時間の関係を示した図)の例は、図７に示した通りである。
【０１１３】
そこで、深さの異なる複数個の反射源を適切に検査するためには、それぞれの反射源毎に集束超音波の焦点を変え、例えば図１０の反射源Ｂに対しても集束超音波の焦点を合わせるためには、例えば遅延時間パターンを多数用意し、焦点の異なる集束超音波を繰り返し被検査体内部に送信し、最も信号強度の強いエコーの得られる遅延時間、すなわち、遅延パターンＰ２(波形９ｆ〜９ｊ)による反射源Ｂのエコーが得られるまで、深さ方向に少しずつ焦点位置を変化させながら、遅延時間を変更して探傷を繰り返えす必要がある。
【０１１４】
しかし、このように、遅延時間パターンを多数用意し、それらを順次使い分けして超音波探傷を行うようにしたのでは、探傷に多大の時間が必要になり、被検査体内に多数の欠陥が存在した場合には、実用的とはいえない。
【０１１５】
そこで、この実施形態２では、焦点位置から大きくずれた欠陥でも、１回の集束超音波による探傷だけで高精度の映像が得られるようにしたもので、このために図１１に示す探傷方法を採用し、図２２のフローチャートに示す処理が実行されるようにしたものである。
【０１１６】
これら図１１と図２２において、まず、始めに初期設定として、焦点距離１１００に対応した遅延時間の遅延時間パターン(波形１０ａ〜１０ｅ)を素子遅延時間設定部２１２に設定する(Ｓ１００)。このときの焦点距離１１００としては、上記した板厚の半分程度の距離とする。
【０１１７】
次に、探傷を開始する(Ｓ２００)。そうすると、素子遅延時間設定部２１２で設定された遅延時間に基づいて、遅延器２１４から送受信器２１６に信号が送られ、これにより、このときの遅延時間パターン(波形１０ａ〜１０ｅ)に従って焦点距離１１００に集束する波面を持つ超音波１１０１が、アレイセンサ１０１から被検査体１００の内に送信される。
【０１１８】
そして、反射源によるエコーが現われると、これがアレイセンサ１０１により捉えられ、送受信器２１６で受信された後、遅延器２１４により再び素子毎に時間的な遅延が与えれてから加算器２１７で加算され、加算された波形がＡ／Ｄ変換器２１５でディジタル信号に変換され、記憶装置２１３に収録されることになる(Ｓ３００)。
【０１１９】
この後、画像データ演算(1)が施され(Ｓ４００)、送信位置と受信信号の伝播時間又は伝播距離から、Ｂスコープ画像データを加工する。なお、ここでの処理は、基本的には実施形態１とほぼ同様である。
【０１２０】
但し、実施形態１では、図１６で説明したように、処理Ｓ４０３を備え、最も伝播時間が短い値を２回目の焦点距離と設定し、ホログラム作成に際して伝播時間Δｔを補正している。
【０１２１】
しかし、この実施形態２では、図２３に示すように、最初に与えた焦点距離によって、伝播時間Δｔを補正する点が異なっている。つまり、この場合は、上記した処理Ｓ４０３を備えていない点が異なっており、ホログラムの作成にあたって、最初に与えた焦点距離の基準の位置として、ホログラムを作成し、その位置を基準にホログラム再生処理を行う。
【０１２２】
ここで、この実施形態２で表示されるＢスコープ画像においては、被検査体に送信される集束超音波の焦点距離は、この被検査体内部に想定される反射源の深さとは必ずしも一致していないことに留意を要する。
【０１２３】
つまり、この場合、反射源から離れた位置に焦点を持つ集束超音波を用いて探傷を行い、その焦点位置を基準としてホログラムを作成、再生することで、実際の反射源位置近傍に反射源の再生像が映像化されることになる。
【０１２４】
このため、被検査体内部に傷などの反射源が存在した場合、この反射源からの信号は、焦点からずれて拡散した超音波１１０１(図１１)により、図７で説明したように、水平方向に広がって受信される。ここで、この図７は、被検査体が内部に加工された横穴を有する場合の受信波の例である。
【０１２５】
この場合、反射源は、ある深さ(Ｚ軸)位置に局所的に存在しているにもかかわらず、送信位置(Ｘ軸)が移動したとき拡散した超音波が反射源に当たってしまうため、反射信号が左右に円弧状に広がった形で受信されてしまうことが判る。
【０１２６】
次のＢスコープ表示処理(Ｓ５００)では、受信信号を送信位置(横軸)と伝播時間又は伝播距離(縦軸)の関係を２次元のグラフとして表示する。そして、以上の探傷処理を１回実行したら、次の画像データ演算(2)処理(Ｓ７００)に進む。
【０１２７】
なお、このとき被検査体の板厚及び超音波の音速から、反射源による受信信号が得られるまでの時間を予測し、その予測時間で決まる時刻の前後に時間幅(ウィンドウ)を設定して時間ゲートとし、ゲート時間内での受信信号の有無を２値化して表示しても良い。
【０１２８】
また、時間ゲートによらず、受信信号の強度に応じた白黒濃淡や色分けを用いて受信波形を表示するようにしてもよい。
【０１２９】
ここで、この実施形態２では、上記したように、反射源の実際の位置或いは形状よりも広がってしまう画像から、本来の反射源の状態(位置或いは形状)を復元するための信号処理が、次の画像データ演算(2)処理(Ｓ７００)で施されるようになっている。
【０１３０】
このＳ７００による処理は、焦点位置がずれた超音波で得られてしまう、横に広がったＢスコープ画像データからホログラムを作成し、本来の反射源の正確な画像を再生する処理となるが、ここで、この画像データ演算(2)の処理手順も、基本的には、図１８に示した実施形態１と同じである。
【０１３１】
しかして、この実施形態２では、この処理Ｓ７００の内容が、図２４に示すようになっている。そして、この図２４による処理手順が、図１８に示した実施形態１の処理手順と異なっている点は、ホログラムを作成する際の焦点距離設定処理(Ｓ７０２０)にあり、その他の点はおなじである。
【０１３２】
つまり、図１８の処理(Ｓ７０２)では、フラットな波面をもつ超音波の伝播時間の最小値を焦点距離として設定しているが、図２４の処理(Ｓ７０２０)では、超音波探傷を実行する際、予め設定しておいた集束超音波の焦点距離がそのまま設定されるようになっている点で異なっているだけである。
【０１３３】
従って、この図２４による処理手順では、この予め設定しておいた集束超音波の焦点距離を基準にしてホログラムが作成され、その位置を基準にしてホログラム再生処理が実行されることになるが、ここで、この図２４による処理も、基本的な点では、図１８で説明した処理と同じなので、詳しい説明は割愛する。
【０１３４】
そして、以下では、この実施形態２の場合、焦点距離と反射源の位置がずれていた場合でもホログラムを用いることで、傷や欠陥などの反射源の映像が正確に復元できる理由についてだけ詳細に説明する。
【０１３５】
まず、図１１の(a)に示すように、予め設定した焦点距離とは異なる深さに反射源が存在していた場合においても、超音波探傷を実行すればＢスコープ画像データが得られる。
【０１３６】
このとき、焦点距離１１００に設定して、アレイセンサ１０１から送信された集束超音波の波面を見てみると、集束点１１０２を仮想音源として、ここから拡散されてゆく集束超音波１１０１と見做すことができる。
【０１３７】
このことから、アレイセンサ１０１から送信された集束超音波による探傷結果は、集束点１１０２を仮想音源とし、ここから送信され拡散してきた超音波による探傷結果として取り扱えることが判る。
【０１３８】
具体的には、アレイセンサ１０１による探傷で求めた伝播時間から、焦点距離１１００までの伝播時間を減算することにより、仮想の探傷面１１０３上にある仮想音源１１０２からの伝播時間に換算できるのである。
【０１３９】
そこで、この仮想音源１１０２による伝播時間と参照波を比較して、図１１の(b)に示すように、仮想探傷面に移動したホログラム１１０４を作成し、ホログラムを再生する。このときのホログラムの再生は、既に説明したように、数２式が用いられる。
【０１４０】
ここで、この数２式は、ホログラムの強度をもった球面波(exp(ikr)/r)を加算(積分)した数式になっている。従って、これを模式的に表せば、図１１(b)に白黒の２値で表現してあるホログラムの強度をもった球面波が、図示のように、ホログラムの各点から送信され、これらの球面波が重ね合わされ、再生波になることを意味する。
【０１４１】
このホログラム１０８の再生にあたっては、仮想音源１１０２が水平に移動して作られる仮想探傷面１１０３に正しくホログラムを位置させることが肝要である。この仮想探傷面に移動したホログラム１１０４からホログラムの強度を持った球面波が重ね合わされてこそ、実際に反射源が存在した位置、又は大きさの再生像１１４が得られるからである。
【０１４２】
以上のように、この実施形態２では、反射源から離れた位置に焦点をもった集束超音波を用い、その焦点位置を基準にしてホログラムを作成し再生することにより、実際の反射源の位置の近傍に、反射源の再生像が得られるようにしたものである。
【０１４３】
ここで、図１２は、このときのホログラムの一例で、図１３は、再生像の一例であるが、これら図１２と図１３のホログラム処理のもとになったＢスコープ画像は図７に示した画像である。
【０１４４】
従って、この実施形態２によれば、水平方向に広がったＢスコープ画像から仮想的な探傷面を設定し、この仮想の探傷面においてホログラムを作成し、このホログラムから反射源の映像が再構成させるようにしたので、反射像の拡がりによる影響が低減でき、本来の反射源の形状、位置、大きさに良く類似した欠陥の画像を容易に得ることができる。
【０１４５】
また、この実施形態２によれば、予め焦点距離１１００を１パターンにしているため、被検査体に深さの異なる複数個の欠陥が存在していた場合でも、仮想探傷面によるホログラフィ処理による映像化により、反射源が存在する本来の位置に、当該反射源を映像化することができる。
【０１４６】
以上説明したように、上記実施形態によれば、アレイセンサによる高速走査を実現する効果に加えて、被検査体内部に深さの異なる複数個の反射源が存在していても、最初に設定した焦点位置を基準とした伝播時間からホログラムを作成、再生することで、焦点位置のずれの内場合の映像と同等の高精度な欠陥映像を得ることができる。
【０１４７】
【発明の効果】
本発明によれば、アレイセンサを用いた電子走査により反射源からの反射波を用いてホログラムを作成することで、従来のセンサを機械走査による２次元走査を用いる場合に比べて、高速なデータ収録が可能になる。
【０１４８】
また、アレイセンサの遅延時間を変更することで、焦点位置が可変で、且つ、波面の乱れのなくい集束超音波で得られた波形から正確なホログラムを作成することができ、高精度な欠陥映像化が可能となる。
【図面の簡単な説明】
【図１】本発明の超音波探傷装置における超音波ホログラフィ法の動作原理の概略を示す説明図である。
【図２】本発明による超音波探傷装置の実施形態を示すブロック図である。
【図３】本発明による超音波探傷装置の実施形態におけるシステム構成の一例を示す説明図である。
【図４】本発明の一実施形態におけるアレイセンサの動作説明図である。
【図５】本発明の一実施形態における超音波探傷動作の説明図である。
【図６】本発明の一実施形態におけるＢスコープ像の一例を示す説明図である。
【図７】本発明の一実施形態におけるＢスコープ像の他の一例を示す説明図である。
【図８】本発明の一実施形態における探傷波形の一例を示す説明図である。
【図９】本発明による超音波探傷装置の第１の実施形態による動作の一例を示す説明図である。
【図１０】本発明による超音波探傷装置の第１の実施形態による動作の他の一例を示す説明図である。
【図１１】本発明による超音波探傷装置の第２の実施形態による動作の一例を示す説明図である。
【図１２】本発明による超音波探傷装置の第２の実施形態におけるホログラムの一例を示す波形図である。
【図１３】本発明による超音波探傷装置の第２の実施形態におけるホログラム再生像の一例を示す説明図である。
【図１４】本発明の超音波探傷装置におけるホログラムの作成方法の説明図である。
【図１５】本発明による超音波探傷装置の第１の実施形態における処理手順の一例を示すフローチャートである。
【図１６】本発明による超音波探傷装置の第１の実施形態における画像データ演算(1)の処理手順を示すフローチャートである。
【図１７】本発明による超音波探傷装置の第１の実施形態におけるＢスコープデータの説明図である。
【図１８】本発明による超音波探傷装置の第１の実施形態における画像データ演算(2)の処理手順を示すフローチャートである。
【図１９】本発明による超音波探傷装置の一実施形態におけるホログラム再生結果データの一例を示す説明図である。
【図２０】本発明による超音波探傷装置の第１の実施形態におけるホログラム再生値のしきい値処理を示すフローチャートである。
【図２１】本発明による超音波探傷装置の第１の実施形態におけるホグラム処理のための初期データの説明図である。
【図２２】本発明による超音波探傷装置の第２の実施形態における処理手順の一例を示すフローチャートである。
【図２３】本発明による超音波探傷装置の第２の実施形態における画像データ演算(1)の処理手順を示すフローチャートである。
【図２４】本発明による超音波探傷装置の第２の実施形態における画像データ演算(2)の処理手順を示すフローチャートである。
【符号の説明】
１００ 被検査体
１０１ アレイセンサ(一次元探触子)
１０３ 反射源
１０４ 反射源からのエコー
１０５ 底面エコー
１０８ ホログラム
１１０ 参照波
１１１ 径路差
１１２ 再生領域
１１４ 再生像
２００ 本発明による超音波探傷システム
２０１ 映像処理部
２０２ 素子遅延時間計算部
２０３ 演算処理部
２０４ 表示部
２０５ 記憶装置
２１１ 多チャンネル探傷部
２１２ 素子遅延時間設定部
２１３ 記憶装置
２１４ 遅延器
２１５ Ａ／Ｄ変換器
２１６ 送受信器
２１７ 加算器
２１８ 表示処理部
２１８ 表示部
３０１ 計算機
３０２ キーボード
３０３ ポインタデバイス
３０６ アレイセンサ固定用治具
１１００ 焦点距離
１１０１ 集束超音波
１１０２ 仮想音源
１１０３ 仮想探傷面
１１０４ 仮想探傷面に移動したホログラム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for displaying ultrasonic flaw detection results, and more particularly to a method and apparatus for displaying flaw detection results by an ultrasonic holography method.
[0002]
[Prior art]
Conventionally, the A scope method (A scan graphic), the B scope method (B scan graphic), and the C scope method (C scan graphic) are used to display the ultrasonic flaw detection results.
[0003]
First, the A scope method is a method in which time is taken on the horizontal axis and the intensity of the reflected wave (echo) is taken on the vertical axis, and a graphic display is made. The position on the inspection object and the sound wave propagation time are displayed in rectangular coordinates (X, Z axes), and the flaw detection result can be expressed as a cross-sectional view of the object to be inspected.
[0004]
On the other hand, the C scope method expresses the flaw detection result in the form of a plan view (X and Y axes) as viewed from above the inspection object. Therefore, the flaw detection result by each of the A, B, and C scope methods. In this display technique, the time and intensity of the signal obtained by ultrasonic flaw detection are used as they are for display.
[0005]
However, in ultrasonic flaw detection, it may be difficult to identify whether the obtained signal is due to a defect due to the following two factors, and flaw detection may be difficult.
[0006]
The first factor is due to the diffusion of the ultrasonic wave with the distance. The transmitted ultrasonic wave is diffused and the reflected wave from a wide range is received, so the position and number of the reflection sources cannot be specified.
[0007]
The second factor is that ultrasonic waves originating from other than the reflection source due to a defect or the like to be inspected are received depending on the internal state (welded part or shape) of the inspection object.
[0008]
Due to these factors, in ultrasonic flaw detection, an ultrasonic probe is used at a position away from a reflection source such as a defect in the inspection object or at a position where there is no reflection source such as a defect to be inspected. There is a case where some signal is received.
[0009]
Therefore, in order to realize the flaw detection result display in which the number and position of the reflection sources can be clearly understood, not only the propagation time and intensity of the received ultrasonic wave, but also the flaw detection method focusing on the ultrasonic wave waveform and phase information, and There is a need for a display method. One such technique is an ultrasonic holography method that applies the principle of optical holography.
[0010]
Here, the optical holography method is a method in which phase-matched light such as laser light is incident on an object, phase information of light scattered from the object is recorded on a film as an interference pattern of incident light and scattered light, Thereafter, the phase information of the scattered light is reproduced again by applying light to the film.
[0011]
At this time, in general, an interference pattern of light scattered by an object and incident light (three-dimensional geometric information of the object) recorded on a film is a hologram, and light that interferes with a reflected wave from the object (incident wave in this example) Is referred to as a reference wave, and reproduction of interference information by applying light to the hologram is called reproduction of the hologram, and light applied to the hologram for hologram reproduction is called a reproduction reference wave.
[0012]
By the way, in the initial ultrasonic holography method, similarly to optical holography, a received wave and a reference wave are caused to interfere with each other to create a hologram. A three-dimensional image can be obtained by displaying the flaw detection result using this method.
[0013]
Here, the wavelength of ultrasonic waves is considerably longer than that of light, and there is no recording medium such as a film. However, several methods for realizing the method based on this principle have been proposed. One is a digital ultrasonic holography flaw detection method (see, for example, Patent Document 1).
[0014]
This digital ultrasonic holography flaw detection method uses a pulse echo by a spike-like transmission wave and creates a hologram by coincidence of a reception wave and a clock pulse instead of interfering with a reference wave. And the time resolution of the received wave are improved, and the measurement accuracy of the flaw detection result can be improved.
[0015]
[Patent Document 1]
JP-A-54-8484
[0016]
[Problems to be solved by the invention]
The above prior art has not considered the point that two-dimensional movement of the ultrasonic probe is required for ultrasonic scanning, and has the following problems.
[0017]
In the conventional ultrasonic holography method including the digital ultrasonic holography flaw detection method, in order to receive the ultrasonic wave from the object to be inspected, the ultrasonic probe is precisely moved and scanned at a fine interval in two dimensions. The method is adopted.
[0018]
However, the scanning method employed in this conventional technique has a problem that it takes a long time for scanning.
[0019]
In addition, when a sufficient S / N ratio cannot be obtained, such as flaw detection of a welded portion, a focusing probe is required. In this case, a medium (shoe material) for adjusting the incident angle of ultrasonic waves is required. ) Is also necessary, and at this time, the presence of this medium may disturb the wavefront, making it impossible to create an accurate hologram.
[0020]
An object of the present invention is to provide an ultrasonic flaw detection result display method and apparatus capable of displaying high-accuracy ultrasonic flaw detection results at high speed.
[0021]
[Means for Solving the Problems]
  The purpose is to transmit ultrasonic waves of a predetermined mode from the probe to the object to be inspected, receive echoes reflected from the reflection source due to internal flaws, etc., and determine the position of the reflection source from the reception time of the echoes. In order to display the reflection source graphic, flaw detection data including the reception time of the echo is collected for each transmission / reception position of the probe, B scope graphic data is created from the flaw detection data for one line, and the B scope graphic An area including data is used as a reproduction area, a hologram is created by numerically interfering with a reference wave having a wave number k with respect to the flaw detection data, and hologram reproduction is performed using the sound velocity of the designated mode ultrasonic wave in the reproduction area, In the ultrasonic flaw detection result display method for displaying a reproduced image on the screen, a line sensor in which M (M = plural) ultrasonic transmission / reception elements are arranged in a line is used as the probe. The ultrasound transmission and reception time by each signal element sequentially individually selected from one to the other of the arrayed direction, the ultrasonic transmitting and receiving position relative to the object to be inspected is scanned in the arrangement direction of the ultrasonic transmitting and receiving elementsAfter that, the ultrasonic transmitting / receiving element is placed adjacent to N. ( N = multiple <M ) By dividing the element group into individual elements and setting the delay time of the drive pulse to be supplied to each element in the element group to a predetermined pattern, ultrasonic flaw detection by focused ultrasound can be obtained, and the echo The reception time is measured based on the focal position of the focused ultrasound.To be achieved.
[0022]
  At this time, the plurality of elements selected as the element group are sequentially changed from one of the arranged directions to the other, and the distance to the reflection source is measured by the shortest time of the signal received by each element.You may make it.
[0023]
Furthermore, at this time, the delay time of the drive pulse by the predetermined pattern may be reset based on the distance to the reflection source measured by the shortest time.
[0024]
  Further, the object is to transmit an ultrasonic wave of a predetermined mode to the object to be inspected, and to receive an echo reflected from a reflection source due to internal scratches, etc., and from the reception time of the echo, the reflection source In the ultrasonic flaw detector comprising a multi-channel flaw detector that creates the reflection source graphic data by determining the position of the reflection source, and an imaging processor that displays the generated graphic data on the screen, a plurality of the ultrasonic probe parts are provided. It is composed of a line sensor in which a plurality of ultrasonic transmission / reception elements are arranged in a line, and the multi-channel flaw detection unit sequentially transmits and receives ultrasonic transmission / reception times by each of the ultrasonic transmission / reception elements from one to the other in the arranged direction. And an element selection unit that scans an ultrasonic transmission / reception position with respect to the object to be inspected in an arrangement direction of the ultrasonic transmission / reception elements, and the imaging processing unit performs the process for each ultrasonic transmission / reception position. Means for collecting flaw detection data including the reception time of-, means for generating B scope graphic data from flaw detection data of one line scanning, and an area including the B scope graphic as a reproduction area, and ultrasonic waves in a designated mode Means for reproducing a hologram image by ultrasonic holography using the speed of sound and means for displaying the reproduced image on a screen in two or three dimensionsIn addition, the ultrasonic transmitting / receiving element of the line sensor is connected to the adjacent N ( N = multiple <M ) By dividing the element group into individual elements and setting the delay time of the drive pulse to be supplied to each element in the element group to a predetermined pattern, ultrasonic flaw detection by focused ultrasound can be obtained, and the echo Means are provided for measuring the reception time with reference to the focal position of the focused ultrasound.This is also achieved.
[0026]
  At this time, beforeMeans for sequentially changing a plurality of elements selected as the element group from one of the arranged directions to the other, and means for measuring the distance to the reflection source by the shortest time of the signal received by each element It may be provided.
[0027]
Furthermore, at this time, the delay time of the driving pulse by the predetermined pattern may be reset based on the distance to the reflection source measured by the shortest time.
[0028]
As a result, the focal length can be automatically set with respect to the distance to the reflection source, and an ultrasonic signal having a focus near the position of the reflection source can be obtained even in the inspection of an object whose position is not known. Since a signal having a high S / N ratio can be obtained at a wide range of ultrasonic transmission / reception positions, a more accurate hologram can be created and a defect image can be formed with high accuracy.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an ultrasonic flaw detector according to the present invention will be described in detail with reference to embodiments shown in the drawings.
[0030]
First, the imaging procedure of the flaw detection result by the ultrasonic holography method of the present invention will be outlined with reference to FIG.
[0031]
First, FIG. 1A is a schematic diagram of an ultrasonic flaw detector, in which an ultrasonic wave 102 is incident from an array sensor 101 into an object to be inspected 100, and an echo signal 102 from a reflection source 103 such as a flaw is transmitted to the array sensor 101. And processing so that the position and shape of the reflection source 103 can be displayed.
[0032]
Here, the array sensor 101 is a probe in which a plurality of ultrasonic transmission / reception elements are linearly arranged so that the ultrasonic transmission / reception position can be moved electrically, so that so-called electronic scanning can be performed. Therefore, in the X direction shown in the drawing, the transmission / reception position can be changed at a higher speed than in the conventional mechanical scanning, and a reception waveform described later can be recorded at each transmission / reception position.
[0033]
Next, FIG. 1 (b) is a received waveform (flaw detection waveform) of the flaw detection result, the horizontal axis is time t, and the vertical axis is the amplitude A of the signal intensity, which is reflected behind the ultrasonic transmission pulse. It is shown that an echo (reflected wave) 104 from the source 103 appears, and then an echo 105 from the bottom surface appears. Then, as shown in the figure, the flaw detection waveform corresponds to each transmission / reception position x according to the scanning of the transmission / reception position.₁, X₂, ..., x_n Every time, it is recorded each time.
[0034]
Next, FIG. 1 (c) shows a B-scope image 107 as a result of flaw detection, which indicates the amplitude intensity of the received signal with the horizontal axis as the ultrasonic flaw detection position direction X and the vertical axis as the depth direction Z of the inspection object. It is shown in shades of color.
[0035]
When comparing the B-scope image 107 and the reflection source 103, the defect image by the B-scope image 107 is displayed as a curved image spreading from side to side due to the influence of ultrasonic diffusion. I understand.
[0036]
Next, FIG. 1 (d) shows the creation status of the hologram. As shown in the figure, by making the reference wave 110 (for example, cos function) interfere numerically with the data of each point of the echo signal, A hologram 108 is created.
[0037]
Here, with reference to FIG. 14, a method for creating a hologram will be briefly described by taking as an example a binarized hologram in which hologram values are recorded in binary values of “+1” and “−1”.
[0038]
First, the received waveform recorded at a certain ultrasonic transmission / reception position, for example, the received waveform x in FIG.₁ , The propagation time Δt is obtained from the time difference between the transmission pulse and the echo as shown in the figure, and a hologram is created depending on what value the reference wave 110 takes in this propagation time Δt.
[0039]
For example, in the case of the figure, as shown in (1), when the propagation time is Δt, the reference wave takes a value +1 at this time Δt. Therefore, in this way, when the reference wave takes a value of 0 or more, the value of the hologram is determined as +1.
[0040]
Further, at the propagation time Δt ′ in the case (2), the reference wave has a value of −1. Therefore, when the reference wave takes a value less than 0, the value of the hologram is set to -1.
[0041]
Thus, when the propagation time Δt of the echo signal and the reference wave are compared in this way and the holograms obtained by numerical interference are accumulated at each transmission / reception position, the hologram 108 is obtained.
[0042]
Next, FIG. 1E shows a reproduction image creation process. The image of the reflection source 103 can be reproduced from the hologram 108 in the reproduction area 112 at the sound speed in the designated mode. The main calculation for reproducing the hologram at this time is a process of adding the spherical wave described by the path difference r indicated by 111 with the phase difference weight of the hologram 108 added.
[0043]
FIG. 1 (f) is a display of a reproduced image. The reflection source 103 originally present at the non-focal position is separated from the reflection source 103 by a reproduction wave 113 which is a superposition of spherical waves having the phase of the hologram. At the same position, a situation where the reproduced image 114 is visualized is shown.
[0044]
According to this holographic processing, the influence of ultrasonic diffusion is reduced, so that a higher-accuracy video can be obtained as compared with the display using the B scope image.
[0045]
Therefore, the present invention will be described more specifically below with reference to a plurality of illustrated embodiments.
[0046]
First, FIG. 2 is Embodiment 1 (first embodiment) of the present invention. In the figure, 200 represents the entire ultrasonic flaw detection system (the entire system). It is roughly divided into a multi-channel flaw detection unit 211 and a video processing unit 201.
[0047]
First, the array sensor 101 functions to generate and receive ultrasonic waves, and a so-called one-dimensional sensor (line) in which a plurality of (M) elements (ultrasonic transmitting / receiving elements) are arranged in a straight line. In this case, an electrostrictive element is usually used as the element at this time, but of course, a magnetostrictive element can also be used.
[0048]
Next, the multi-channel flaw detector 211 includes a transmitter / receiver 216 connected to the array sensor 101, a delayer 214 connected to the transmitter / receiver 216, an adder 217 connected to the delayer 216, and an adder 217. A connected A / D converter 215, an element delay time setting unit 212 connected to the delay unit 214, a display processing unit 218 that performs display processing of the received signal, a display unit 219, and a storage device that records the delay time and the received signal 213.
[0049]
The imaging processing unit 201 performs graphic display by an ultrasonic holography method. For this reason, the imaging processing unit 201 includes a display unit 204, an arithmetic processing unit 203, and a storage device 205.
[0050]
Here, the multi-channel flaw detector 211 will be described in more detail. First, the transmitter / receiver 216 supplies an ultrasonic wave generation drive signal to each element of the array sensor 101 and also receives an ultrasonic reception signal detected by each element. Next, the delay unit 214 functions to shift (shift) the driving signal for generating ultrasonic waves to be supplied to each element of the array sensor 101 for each element.
[0051]
The adder 217 functions to add the ultrasonic reception signals detected by the respective elements of the array sensor 101 and received by the transmitter / receiver 216, and the A / D converter 215 is added by the adder 217. It functions to convert ultrasonic reception signals into digital data.
[0052]
The element delay time setting unit 212 functions to set the delay time for each element of the drive signal for generating ultrasonic waves to be supplied to each element of the array sensor 101. As a result, the array sensor 101 has Based on the delay time determined by the delay time setting unit 212, the transmission / reception position with respect to the object to be inspected can be electrically changed, that is, electronic scanning can be performed.
[0053]
Therefore, the multi-channel flaw detector 211 constitutes element selection means for individually controlling the ultrasonic transmission / reception time of each element of the array sensor 101 from one to the other in the direction in which they are arranged. It will be.
[0054]
Next, FIG. 3 shows a configuration example of the flaw detection system according to the first embodiment. The entire system 200 includes a multi-channel flaw detector and a receiver, and at least one A / D converter. Unit 211, and a video processing unit comprising a microcomputer provided with a computer 301 and a display device 204. Here, as shown in the figure, one or both of a data input keyboard 302 and a pointer device 303 are provided. It may be attached.
[0055]
On the other hand, the array sensor 101 is held by a jig 306 and is positioned in contact with the surface of the object to be inspected 100. At this time, the jig 306 includes a mechanical movement mechanism, and the array sensor 101 is simply moved. In addition to being placed on the surface of the inspected object 100, it may be moved in the Y-axis direction in the figure to have a function of scanning the surface of the inspected object 100 in the Y-axis direction.
[0056]
The array sensor 101 corresponds to, for example, longitudinal ultrasonic waves having a frequency of 5 MHz. Here, for example, 72 piezoelectric elements having a width of 0.5 mm (M = 72) are arranged. The entire system 200 is connected by data lines 304 and 305.
[0057]
Next, the operation of the first embodiment will be described. FIG. 4 shows the operation of the delay unit 214 and the transceiver 216 of the multi-channel flaw detection unit 211 and the array sensor 101. Here, the depth is taken as an example. The case where two flawed reflection sources A and B are flaw-detected with focused ultrasound focused at a depth near one of the reflection sources A will be described.
[0058]
Here, the generation and reception of focused ultrasonic waves will be described. First, in such an ultrasonic flaw detection system, pulsed ultrasonic waves are sequentially generated at a predetermined cycle, and echoes are received once each time. The flaw detection operation is performed, and the period for one time at this time is the flaw detection period.
[0059]
At this time, in the first embodiment, the plurality of (here, 72) elements provided in the array sensor 101 are not used individually, but a plurality of adjacent elements, for example, N (N <M) A plurality of elements can be used simultaneously as an element group, and the delay time of the drive pulse to be supplied to each element in the element group can be set according to a predetermined pattern so that focused ultrasound is generated. In addition, a multi-channel flaw detection unit 211 is configured.
[0060]
Here, in the first embodiment, as described above, the array sensor 101 includes 72 elements, but at this time, the number of elements in the element group described above is limited to five (N = 5). explain. However, in implementing the present invention, it is not necessary to limit the number N of elements used simultaneously to five.
[0061]
At this time, the above-described electronic scanning can be obtained by further switching the element group from one end of the array sensor 101 toward the other end and selecting the element group. Similarly, the multi-channel flaw detection part 211 is configured.
[0062]
Specifically, when the first to fifth elements of the 72 elements arranged in a line in the array sensor 101 are the first element group, the next element group is the second to sixth elements. . However, instead of shifting the elements one by one at this time, the elements may be shifted every two or three. For example, if the first to fifth elements are the first element group, the next element group may be the third to seventh element, or the next may be the fourth to eighth element.
[0063]
Returning to FIG. 4, the focused ultrasonic waves from the element group consisting of the five elements of the array sensor 101 into the inspected object 100 according to the delay time patterns (waveforms 4 a to 4 e) determined by the element delay time setting unit 212. It is sent.
[0064]
Here, this delay time pattern has the above-described flaw detection period as one cycle, and plays the role of a trigger signal for the transceiver. Then, the waveform 4a and the waveform 4e in the delay time pattern at this time means that transmission is performed earlier than the central waveform 4c.
[0065]
Therefore, if the five elements in the element group at this time are a, b, c, d, and e, first, in the above-described flaw detection period, first, the two elements a and e at both ends of the five elements first generate ultrasonic waves. Then, the second two elements b and d from both ends generate ultrasonic waves, and finally the central element c generates ultrasonic waves.
[0066]
As a result, the wavefront of the ultrasonic wave propagating inside the object to be inspected 100 progresses quickly at both ends and becomes a wavefront delayed at the center, so that a focused ultrasonic wave is formed. On the other hand, in the case of reception, the signal received at the center is received with a slight delay compared to the signals obtained at the elements at both ends, and this is added by the adder 217, so that the echo is also superposed. It will be received as a sound wave.
[0067]
When electronic scanning is performed in this state and the ultrasonic transmission / reception position is scanned at a high speed, the delay time pattern is constant, but the combination of elements to which the pattern is applied is sequentially changed to have the same focal position. The flaw detection is performed while the focused ultrasonic wave moves in the right direction in the drawing from the vicinity of the reflection source A to the vicinity of the reflection source B.
[0068]
By the way, in the conventional ultrasonic holography method, a method of mechanically moving the ultrasonic probe has been adopted in order to realize scanning of the ultrasonic transmission / reception position. Here, in the case of such mechanical scanning, the moving speed of the probe is about several tens mm / second to about 100 mm / second.
[0069]
On the other hand, in the case of electronic scanning, it is only necessary to switch the signal. Therefore, the moving speed is 10 times or more easier than mechanical scanning. Therefore, according to this embodiment, the flaw detection time can be sufficiently shortened. be able to.
[0070]
Next, as examples of flaw detection results according to this embodiment, B scope images at the ultrasonic transmission / reception position A (501) and the ultrasonic transmission / reception position B (502) shown in FIG. 5 are shown in FIGS. FIG. 8 is an example of an echo waveform in the case of FIG.
[0071]
Here, first, in the case of the B scope image of the reflection source A at the transmission position A in FIG. 6, since the reflection source A is located at the focal position of the ultrasonic wave as apparent from FIG. A sharp B-scope image that is hardly affected by this is obtained.
[0072]
On the other hand, in the case of the B scope image of the reflection source B at the transmission position B in FIG. 7, since the reflection source B is located at a position away from the focal position of the ultrasonic wave, it is greatly affected by the diffusion of the ultrasonic wave. It can be seen that only the B-scope video that has spread widely is obtained.
[0073]
As can be easily understood from FIGS. 6 and 7, in the defect imaging method by the conventional ultrasonic flaw detection method using the array sensor, when the reflection source position is close to the focal position of the incident ultrasonic wave, actual reflection is performed. Although the image is formed in a shape almost the same as that of the source, the more the image deviates from the focal position, the more influenced by the diffusion, and only the expanded image can be obtained, and the error from the actual shape and position of the reflection source increases.
[0074]
Therefore, according to the present invention, the influence of such diffusion can be reduced, and the shape and position of the reflection source can be obtained with high accuracy. Therefore, in the above embodiment, the processing shown in the flowchart of FIG. It is configured to be executed so that the focus of the focused ultrasound by the array sensor is automatically tied to the depth of the reflection source, such as a defect.
[0075]
Here, the processing according to the flowchart of FIG. 15 is executed by the computer 301 in the entire system 200. When this processing is started, first, as an initial setting, the element delay time setting unit 212 is set. Thus, as shown in FIG. 9A, delay time patterns (waveforms 8a to 8e) having the same delay time are set for each element (S10), and then flaw detection is started (S20).
[0076]
In the process of S20, a signal is sent from the delay unit 214 to the transmitter / receiver 216 based on the delay time set by the element delay time setting unit 212. As a result, the array sensor 101 receives a delay time pattern at this time. In accordance with (waveforms 8 a to 8 e), an ultrasonic wave 801 having a flat wavefront is transmitted to the inside of the inspection object 100.
[0077]
The ultrasonic wave 801 transmitted into the inspection object 100 is reflected on the bottom surface of the inspection object 100, and when the inspection object has a reflection source such as a defect, it is also reflected by this reflection source. Each echo (reflected wave) is returned to the array sensor 101 and detected.
[0078]
Thus, these echoes received by the array sensor 101 are received by the transmitter / receiver 216, and a delay is given again for each element by the delay unit 214 and added by the adder 217. The added waveform is converted to a digital signal by the A / D converter 215 and recorded in the storage device 213 (S30).
[0079]
At this time, since the defect inside the object to be inspected exists between the surface and the bottom surface, if the echo includes a reflected wave whose propagation time is shorter than the echo from the bottom surface of the object to be inspected Can be regarded as having a reflection source that seems to be defective.
[0080]
Therefore, the process S40 executed next to the process S30 is set as image data calculation (1), and FIG. 16 is a flowchart showing the processing procedure.
[0081]
The process of FIG. 16 is a process for determining whether or not the propagation time of the received signal is between the front surface and the bottom surface of the device under test 100. For this reason, first, the device under test 100 is stored from the storage device 213. Are read into the arithmetic processing unit 203 (S401).
[0082]
Thereafter, in the arithmetic processing unit 203, a process of comparing whether the propagation time is shorter than the bottom echo (S402) is executed, and then whether or not the propagation time is the shortest value in the propagation time is determined. (S403) and the minimum value of the propagation time is stored in the storage device 205 (S404).
[0083]
On the other hand, when the propagation time is not the minimum value, the arithmetic processing unit 203 creates data for B scope display (S405). The data at this time includes at least the ultrasonic transmission / reception position, propagation time, and reception intensity, and FIG. 17 is an example of B scope display data at this time.
[0084]
The B scope data created in this way is supplied to the display processing unit 218, processed into a two-dimensional B scope image, supplied to the display unit 219, and the B scope image is displayed.
[0085]
By the way, in actual flaw detection, except in exceptional cases, it is unclear at which depth in the body to be inspected a defect serving as a reflection source. As shown in FIG. 9A, the shortest propagation time in the reception time corresponds to the propagation time corresponding to the distance 810 to the reflection source.
[0086]
Accordingly, if there is a reflector inside the object to be inspected, the distance from the surface of the object to be inspected to the reflection source corresponds to this distance 810. Therefore, the propagation time corresponding to the shortest distance is set to the distance to the reflection source. Assuming that a focused ultrasonic wave having a focal length corresponding to the shortest distance 810 is transmitted, an echo having a high intensity can be received from the reflection source.
[0087]
Therefore, as shown in FIG. 9 (a), after flaw detection is performed once with the delay time patterns (waveforms 8a to 8e) having the same delay time for each element, a focused ultrasonic wave is transmitted to perform flaw detection again. . At this time, the element delay time setting unit 212 changes the delay time pattern (waveforms 8f to 8j) corresponding to the focused ultrasound.
[0088]
The focal length of the focused ultrasonic wave at this time is the shortest propagation time obtained when the element delay time calculation unit 202 performs flaw detection with the first delay time pattern (waveforms 8a to 8e). It is calculated by multiplying the ultrasonic propagation sound velocity (S25).
[0089]
As in the case of flaw detection using the first delay time pattern, flaw detection data is collected (S30), B scope data is created (S40), and the B scope is displayed (S50).
[0090]
When the flaw detection is completed in the second delay time (S60), the process proceeds to the image data calculation (2) process including the hologram process (S70). Here, the processing procedure of the image data calculation (2) by this processing S70 is shown in the flowchart of FIG.
[0091]
In the processing of FIG. 18, first, parameters necessary for holography processing are read into the arithmetic processing unit 203 (S701). As shown in FIG. 21 as an example, the initial parameters read at this time include the frequency and sound velocity of the ultrasonic wave used for flaw detection, and the refraction angle, as well as the angular frequency ω for creating the hologram. Instead of the angular frequency ω, a frequency or wave number that is an amount proportional to the angular frequency ω may be used as the creation parameter.
[0092]
The first stage of the process of FIG. 18 is a hologram creation process, which uses the read initial parameters to create a hologram from the propagation time of the received waveform and the reference wave (S703). At this time, the transmission ultrasonic wave from the array sensor 101 becomes a focused ultrasonic wave 802 as shown in FIG. 9B, and should have a focus in the vicinity of the reflection source.
[0093]
Since the focal point is concentrated in the vicinity of the defect in this manner, the ultrasonic wave is concentrated near the defect rather than the normal transmission wave, so that an echo with less noise and a higher S / N ratio is obtained. As a result, in the obtained hologram, the noise is reduced. The impact of has been reduced.
[0094]
In creating the hologram (S703) described above, the focal position of the focused ultrasonic wave in the second flaw detection, that is, the minimum value of the propagation time obtained in the first flaw detection is read into the arithmetic processing unit 203 as focal position information. (S702). Here, Formula 1 shows an example of a hologram creation method in the above-described processing (S703).
[0095]
[Expression 1]

As shown in Equation 1, in the process (S703), a hologram is created from the propagation time Δt of the received wave and the reference wave. Here, it should be noted that the propagation time Δt used as the argument of the reference wave needs to be corrected. This is because, unlike the case of a plane wave, the focused ultrasound has a wavefront in which the ultrasound spreads radially around the focal position.
[0096]
For this reason, as a reference for the propagation time when obtaining the propagation time, the ultrasonic transmission position located on the array sensor 101 is set to time 0 in the case of a plane wave, whereas in the case of a focused ultrasonic wave, it spreads radially. In order to use the focal position which is the origin of the wavefront as a reference for the propagation time, the propagation time from the normal propagation time to the focal position is subtracted, and the propagation time from the focal position is adopted as the corrected propagation time Δt ′.
[0097]
Further, in Equation 1, since the value of the reference wave itself is adopted as the hologram, the hologram takes a value that continuously changes from −1 to +1. However, the binarized hologram shown in FIG. 14 may be used instead of the continuous value hologram.
[0098]
Next, as a second stage in the process of FIG. An example of the hologram reproducing method at this time is shown in Equation 2.
[0099]
[Expression 2]

Then, a hologram reproduction process is performed by adding spherical waves having a wave number k determined by the angular frequency ω for hologram creation (S704). Here, the angular frequency ω and the wave number k can be expressed as k = ω / V using the ultrasonic sound velocity V propagating through the inspection object 100.
[0100]
Next, a certain threshold value (threshold value) is determined for the reproduced value of this hologram, and a value exceeding that value is used as the image of the reflection source). A specific example of the flow of processing based on the threshold at this time is processing for executing S7052 as a result of the determination processing in S7051 as shown in the flowchart of FIG.
[0101]
Thereafter, the completion of the reproduction process for all data is confirmed (S706), and the reproduction data including the reproduction value is processed into a two-dimensional or three-dimensional image by the display processing unit 218 and displayed on the display unit 219 ( S80) to finish the process.
[0102]
Therefore, according to the first embodiment, a focused ultrasonic wave focused on the vicinity of a reflection source such as a defect is generated, and an echo is detected by using the focused ultrasonic wave. As a result, the influence of noise in the obtained hologram can be minimized.
[0103]
At this time, once the flat ultrasonic wave is transmitted, the position of the reflection source is detected by paying attention to the shortest echo time, and the focal position necessary for generating a focused ultrasonic wave having a focal point in the vicinity is automatically set. Since it is provided, the operation is simple and high accuracy can be easily maintained.
[0104]
In the first embodiment, since an array sensor is used to obtain flaw detection by electronic scanning, the time required for flaw detection processing can be shortened, and a hologram with less noise created from an echo having a high S / N ratio. Thus, finally, it is possible to obtain a defective image by a hologram reproduction image with little influence of noise.
[0105]
Next, a second embodiment (second embodiment) of the present invention will be described. In addition, this Embodiment 2 also assumes a case where a plurality of reflection sources exist in the object to be inspected, and they have different depths. It is to provide.
[0106]
Therefore, also in the second embodiment, the array sensor 101 and the entire system 200 are the same as those in the first embodiment described with reference to FIGS. 2 and 3, and other basic operations until the reproduction of the hologram are the same as those in the first embodiment. Therefore, hereinafter, points different from the first embodiment will be described with reference to FIGS.
[0107]
First, also in this embodiment, as shown in FIG. 10, this embodiment is used for flaw detection when a plurality of reflection sources (here, two reflection sources A and B) exist in the inspected object 100. 2 is applied.
[0108]
In this case as well, as in the first embodiment, the operation is performed according to the flowchart shown in FIG. 15, and ultrasonic waves having a flat wavefront are incident on each position of the inspected object 100 to the reflection source A and the reflection source B. After estimating the depth, it is possible to image the defect by injecting focused ultrasound.
[0109]
In this case, first, as shown in FIG. 10, in order to detect the reflection source A existing at a shallow position inside the object to be inspected, a delay time pattern P1 (waveforms 9a to 9e) is supplied to the array sensor 101. The flaw detection is performed by matching the depth of the reflection source A and the focal position.
[0110]
In this way, when the reflection source position and the focal position are relatively close, as described in the first embodiment, since the intensity of the ultrasonic wave is sufficiently strong, it is less likely to miss an echo from a small reflection source. Since the ultrasonic wave has little spread at the focal position, the size of the reflection source is not overestimated.
[0111]
However, when flaw detection is performed on the reflection source B located at a slightly deeper location, the reflection source position and the focal position are shifted in the same delay time pattern P1, so that the signal intensity is also described as described in the first embodiment. However, since only an unclear echo affected by the spread of ultrasonic waves is obtained, accurate flaw detection is difficult.
[0112]
Here, an example of a B scope (a diagram showing the relationship between the ultrasonic wave transmission / reception position and the propagation time) by the reflection source deviated from the focal position is as shown in FIG.
[0113]
Therefore, in order to appropriately inspect a plurality of reflection sources having different depths, the focus of the focused ultrasound is changed for each of the reflection sources, and for example, the focus of the focused ultrasound is also applied to the reflection source B of FIG. For example, a large number of delay time patterns are prepared, and focused ultrasonic waves with different focal points are repeatedly transmitted to the inside of the inspected object. It is necessary to repeat the flaw detection by changing the delay time while changing the focal position little by little in the depth direction until the echo of the reflection source B according to 9f to 9j) is obtained.
[0114]
However, if a large number of delay time patterns are prepared in this way and they are used sequentially to perform ultrasonic flaw detection, a great deal of time is required for flaw detection, and there are a large number of defects in the inspected body. If so, it is not practical.
[0115]
Therefore, in the second embodiment, even if the defect is greatly deviated from the focal position, a high-accuracy image can be obtained only by flaw detection by one focused ultrasonic wave. For this purpose, the flaw detection method shown in FIG. The process shown in the flowchart of FIG. 22 is employed.
[0116]
11 and 22, first, as an initial setting, a delay time pattern (waveforms 10a to 10e) corresponding to the focal length 1100 is set in the element delay time setting unit 212 (S100). The focal length 1100 at this time is a distance that is about half of the above plate thickness.
[0117]
Next, flaw detection is started (S200). Then, based on the delay time set by the element delay time setting unit 212, a signal is sent from the delay unit 214 to the transmitter / receiver 216, and thereby the focal length 1100 according to the delay time pattern (waveforms 10a to 10e) at this time. An ultrasonic wave 1101 having a wavefront that converges on the object is transmitted from the array sensor 101 into the object to be inspected 100.
[0118]
Then, when an echo from the reflection source appears, this is captured by the array sensor 101 and received by the transceiver 216, and then a time delay is again given to each element by the delay unit 214 and then added by the adder 217. The added waveform is converted into a digital signal by the A / D converter 215 and recorded in the storage device 213 (S300).
[0119]
Thereafter, image data calculation (1) is performed (S400), and the B scope image data is processed from the transmission position and the propagation time or propagation distance of the received signal. The processing here is basically the same as in the first embodiment.
[0120]
However, in the first embodiment, as described with reference to FIG. 16, the process S403 is provided, and the value with the shortest propagation time is set as the second focal length, and the propagation time Δt is corrected when the hologram is created.
[0121]
However, as shown in FIG. 23, the second embodiment is different in that the propagation time Δt is corrected depending on the initial focal length. That is, in this case, the point that the above-described processing S403 is not provided is different, and in the creation of the hologram, a hologram is created as a reference position of the first given focal length, and the hologram reproduction process is performed based on the position. I do.
[0122]
Here, in the B scope image displayed in the second embodiment, the focal length of the focused ultrasonic wave transmitted to the object to be inspected does not necessarily match the depth of the reflection source assumed inside the object to be inspected. Note that it is not.
[0123]
In other words, in this case, flaw detection is performed using focused ultrasonic waves having a focal point at a position away from the reflection source, and a hologram is created and reproduced using the focal position as a reference, so that the reflection source is located near the actual reflection source position. The reproduced image is visualized.
[0124]
For this reason, when a reflection source such as a scratch is present inside the object to be inspected, the signal from the reflection source is horizontal as described with reference to FIG. 7 by the ultrasonic wave 1101 (FIG. 11) diffused out of focus. Received spreading in the direction. Here, FIG. 7 is an example of a received wave when the object to be inspected has a lateral hole machined therein.
[0125]
In this case, although the reflection source is locally present at a certain depth (Z-axis) position, the diffused ultrasonic wave hits the reflection source when the transmission position (X-axis) is moved. It can be seen that the signal is received in the form of an arc extending left and right.
[0126]
In the next B scope display process (S500), the received signal is displayed as a two-dimensional graph of the relationship between the transmission position (horizontal axis) and the propagation time or propagation distance (vertical axis). When the above flaw detection process is executed once, the process proceeds to the next image data calculation (2) process (S700).
[0127]
At this time, the time until the reception signal by the reflection source is obtained is predicted from the thickness of the object to be inspected and the sound speed of the ultrasonic wave, and the time width (window) is set before and after the time determined by the prediction time. A time gate may be used, and the presence / absence of a received signal within the gate time may be binarized and displayed.
[0128]
Further, the received waveform may be displayed using black and white shading or color coding according to the intensity of the received signal regardless of the time gate.
[0129]
Here, in the second embodiment, as described above, the signal processing for restoring the original state (position or shape) of the reflection source from the image that is wider than the actual position or shape of the reflection source, The following image data calculation (2) process (S700) is performed.
[0130]
The process in S700 is a process of creating a hologram from B-scope image data spread laterally, which is obtained by an ultrasonic wave whose focal position is shifted, and reproducing an accurate image of the original reflection source. Thus, the processing procedure of the image data calculation (2) is basically the same as that of the first embodiment shown in FIG.
[0131]
Therefore, in the second embodiment, the contents of this process S700 are as shown in FIG. The processing procedure shown in FIG. 24 is different from the processing procedure of the first embodiment shown in FIG. 18 in the focal length setting process (S7020) when creating a hologram, and the other points are the same. is there.
[0132]
That is, in the process of FIG. 18 (S702), the minimum value of the propagation time of the ultrasonic wave having a flat wavefront is set as the focal length, but in the process of FIG. 24 (S7020), when ultrasonic flaw detection is executed. The only difference is that the focal length of the focused ultrasound set in advance is set as it is.
[0133]
Therefore, in the processing procedure according to FIG. 24, a hologram is created with reference to the focal length of the previously set focused ultrasound, and the hologram reproduction processing is executed with reference to the position. Here, the processing according to FIG. 24 is also the same as the processing described with reference to FIG.
[0134]
In the following, in the case of the second embodiment, only the reason why the image of the reflection source such as a scratch or a defect can be accurately restored by using the hologram even when the focal length and the position of the reflection source are deviated. explain.
[0135]
First, as shown in FIG. 11A, even when a reflection source exists at a depth different from a preset focal length, B-scope image data can be obtained by performing ultrasonic flaw detection.
[0136]
At this time, when the focal length 1100 is set and the wavefront of the focused ultrasonic wave transmitted from the array sensor 101 is viewed, the focused ultrasonic wave 1101 that is diffused from the focal point 1102 is regarded as a virtual sound source. I can do it.
[0137]
From this, it can be seen that the flaw detection result by the focused ultrasonic wave transmitted from the array sensor 101 can be handled as the flaw detection result by the ultrasonic wave transmitted from and diffused from the focal point 1102 as a virtual sound source.
[0138]
Specifically, the propagation time from the virtual sound source 1102 on the virtual flaw detection surface 1103 can be converted by subtracting the propagation time up to the focal length 1100 from the propagation time obtained by the flaw detection by the array sensor 101. .
[0139]
Therefore, by comparing the propagation time by the virtual sound source 1102 and the reference wave, as shown in FIG. 11B, a hologram 1104 moved to the virtual flaw detection surface is created, and the hologram is reproduced. For reproducing the hologram at this time, Equation 2 is used as described above.
[0140]
Here, Equation 2 is an equation obtained by adding (integrating) a spherical wave (exp (ikr) / r) having the intensity of the hologram. Therefore, if this is schematically represented, a spherical wave having the intensity of the hologram expressed in black and white binary in FIG. 11 (b) is transmitted from each point of the hologram as shown in the figure. It means that spherical waves are superimposed and become a regenerative wave.
[0141]
When reproducing the hologram 108, it is important to correctly position the hologram on the virtual flaw detection surface 1103 created by moving the virtual sound source 1102 horizontally. This is because the reproduced image 114 having the position or size where the reflection source actually exists can be obtained only by superimposing the spherical wave having the intensity of the hologram from the hologram 1104 moved to the virtual flaw detection surface.
[0142]
As described above, in the second embodiment, the position of the actual reflection source is obtained by using the focused ultrasonic wave having a focal point at a position away from the reflection source and generating and reproducing the hologram with reference to the focal position. The reproduction image of the reflection source is obtained in the vicinity of.
[0143]
Here, FIG. 12 shows an example of the hologram at this time, and FIG. 13 shows an example of the reproduced image. FIG. 7 shows the B scope image that is the basis of the hologram processing of FIG. 12 and FIG. It is an image.
[0144]
Therefore, according to the second embodiment, a virtual flaw detection surface is set from the B scope image spread in the horizontal direction, a hologram is created on the virtual flaw detection surface, and the image of the reflection source is reconstructed from the hologram. As a result, the influence of the spread of the reflected image can be reduced, and an image of a defect that closely resembles the shape, position, and size of the original reflection source can be easily obtained.
[0145]
Further, according to the second embodiment, since the focal length 1100 is set to one pattern in advance, even when a plurality of defects having different depths exist in the inspection object, an image obtained by holographic processing using the virtual flaw detection surface By the conversion, the reflection source can be imaged at the original position where the reflection source exists.
[0146]
As described above, according to the above-described embodiment, in addition to the effect of realizing high-speed scanning by the array sensor, even if a plurality of reflection sources having different depths exist in the inspected object, the first setting is performed. By creating and reproducing a hologram from the propagation time with reference to the focal position, it is possible to obtain a highly accurate defect image equivalent to the image in the case of the deviation of the focal position.
[0147]
【The invention's effect】
According to the present invention, a hologram is created by using a reflected wave from a reflection source by electronic scanning using an array sensor, so that high-speed data can be obtained compared with a case where a conventional sensor uses two-dimensional scanning by mechanical scanning. Recording is possible.
[0148]
In addition, by changing the delay time of the array sensor, it is possible to create an accurate hologram from the waveform obtained from the focused ultrasound with variable focal position and no wavefront disturbance. Visualization becomes possible.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of an operation principle of an ultrasonic holography method in an ultrasonic flaw detector according to the present invention.
FIG. 2 is a block diagram showing an embodiment of an ultrasonic flaw detector according to the present invention.
FIG. 3 is an explanatory diagram showing an example of a system configuration in an embodiment of an ultrasonic flaw detector according to the present invention.
FIG. 4 is an operation explanatory diagram of an array sensor in one embodiment of the present invention.
FIG. 5 is an explanatory diagram of an ultrasonic flaw detection operation in one embodiment of the present invention.
FIG. 6 is an explanatory diagram showing an example of a B scope image according to an embodiment of the present invention.
FIG. 7 is an explanatory diagram illustrating another example of the B scope image according to the embodiment of the present invention.
FIG. 8 is an explanatory diagram showing an example of a flaw detection waveform in one embodiment of the present invention.
FIG. 9 is an explanatory diagram showing an example of an operation according to the first embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 10 is an explanatory diagram showing another example of the operation according to the first embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 11 is an explanatory diagram showing an example of the operation of the ultrasonic flaw detector according to the second embodiment of the present invention.
FIG. 12 is a waveform diagram showing an example of a hologram in the second embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 13 is an explanatory diagram showing an example of a hologram reproduction image in the second embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 14 is an explanatory diagram of a hologram creation method in the ultrasonic flaw detector of the present invention.
FIG. 15 is a flowchart showing an example of a processing procedure in the first embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 16 is a flowchart showing a processing procedure of image data calculation (1) in the first embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 17 is an explanatory diagram of B scope data in the first embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 18 is a flowchart showing a processing procedure of image data calculation (2) in the first embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 19 is an explanatory diagram showing an example of hologram reproduction result data in an embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 20 is a flowchart showing a threshold value process of a hologram reproduction value in the first embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 21 is an explanatory diagram of initial data for hologram processing in the first embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 22 is a flowchart showing an example of a processing procedure in the second embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 23 is a flowchart showing a processing procedure of image data calculation (1) in the second embodiment of the ultrasonic flaw detector according to the present invention.
FIG. 24 is a flowchart showing a processing procedure of image data calculation (2) in the second embodiment of the ultrasonic flaw detector according to the present invention.
[Explanation of symbols]
100 Inspected object
101 Array sensor (one-dimensional probe)
103 Reflection source
104 Echo from reflection source
105 Bottom echo
108 hologram
110 Reference wave
111 path difference
112 Playback area
114 Reconstructed image
200 Ultrasonic flaw detection system according to the present invention
201 Video processing unit
202 Element delay time calculation unit
203 arithmetic processing unit
204 display
205 storage device
211 Multi-channel flaw detector
212 Element delay time setting section
213 storage device
214 Delayer
215 A / D converter
216 transceiver
217 Adder
218 Display processing unit
218 display
301 computer
302 keyboard
303 Pointer device
306 Jig for fixing array sensor
1100 Focal length
1101 Focused ultrasound
1102 Virtual sound source
1103 Virtual flaw detection surface
1104 Hologram moved to virtual flaw detection surface

Claims (6)

Transmits ultrasonic waves in a predetermined mode from the probe to the object to be inspected, receives echoes reflected from the reflection source due to internal flaws, etc., and determines the position of the reflection source from the reception time of the echoes. To display flaw detection data including the reception time of the echo for each transmission / reception position of the probe, create B scope graphic data from flaw detection data for one line, and include the B scope graphic data Is used as a reproduction area, a hologram is created by numerically interfering with a reference wave having a wave number k with respect to the flaw detection data, and hologram reproduction is performed in the reproduction area using the sound velocity of the designated mode ultrasonic wave. In the ultrasonic flaw detection result display method of the display method,
As the probe, a line sensor in which M (M = plural) ultrasonic transmitting / receiving elements are arranged in a line is used.
The ultrasonic transmission / reception time by each of the ultrasonic transmission / reception elements is individually selected sequentially from one of the arranged directions to the other,
After the ultrasonic transmission / reception position with respect to the object to be inspected is scanned in the arrangement direction of the ultrasonic transmission / reception elements ,
The ultrasonic transmission / reception elements are divided into adjacent element groups consisting of N ( N = plurality <M ) elements,
By making the delay time of the drive pulse to be supplied to each element in the element group into a predetermined pattern,
Ultrasonic flaw detection with focused ultrasound is obtained,
An ultrasonic flaw detection result display method , wherein the reception time of the echo is measured with reference to a focal position of the focused ultrasonic wave. The ultrasonic flaw detection result display method according to claim 1,
A plurality of elements selected as the element group are sequentially changed from one of the arranged directions to the other,
An ultrasonic flaw detection result display method characterized in that the distance to the reflection source is measured by the shortest time of a signal received by each element . The ultrasonic flaw detection result display method according to claim 2,
The ultrasonic flaw detection result display method , wherein a delay time of the drive pulse by the predetermined pattern is reset based on a distance to the reflection source measured by the shortest time . An ultrasonic probe that transmits ultrasonic waves in a predetermined mode to the object to be inspected and receives echoes reflected from the reflection source due to internal flaws, etc., and obtains the position of the reflection source from the reception time of the echoes and reflects it In an ultrasonic flaw detector equipped with a multi-channel flaw detector for creating source graphic data and an imaging processing unit for displaying the generated graphic data on the screen ,
The ultrasonic probe is
Consists of a line sensor in which a plurality of ultrasonic transmitting and receiving elements are arranged in a line,
The multi-channel flaw detection unit is
The ultrasonic transmission / reception time of each of the ultrasonic transmission / reception elements is individually controlled sequentially from one of the arranged directions to the other, and the ultrasonic transmission / reception position with respect to the inspection object is scanned in the arrangement direction of the ultrasonic transmission / reception elements. Comprising element selection means for
The imaging processing unit
Means for collecting flaw detection data including the reception time of the echo for each ultrasonic transmission / reception position;
Means for creating B-scope graphic data from flaw detection data for one-line scanning;
Means for reproducing a hologram image by an ultrasonic holography method using an ultrasonic velocity of a designated mode as a reproduction area, wherein the area including the B scope graphic is a reproduction area;
With a means for displaying the reconstructed image in two or three dimensions on the screen,
The ultrasonic transmission / reception elements of the line sensor are divided into adjacent element groups composed of N ( N = plurality <M ) elements,
By making the delay time of the drive pulse to be supplied to each element in the element group into a predetermined pattern,
Ultrasonic flaw detection with focused ultrasound is obtained,
Wherein the reception time of the echo, the focused ultrasonic testing apparatus characterized by means for measuring in the ultrasonic reference focal position of are provided. The ultrasonic flaw detector according to claim 4,
Means for sequentially changing a plurality of elements selected as the element group from one of the arranged directions to the other;
The means for measuring a distance to the reflection source by the shortest time of the signal received by each element is provided an ultrasonic flaw detection apparatus according to claim. The ultrasonic flaw detector according to claim 4 ,
An ultrasonic flaw detection apparatus comprising: means for resetting a delay time of the driving pulse according to the predetermined pattern based on a distance to the reflection source measured by the shortest time .

Images