JP4108402B2 - Appearance inspection apparatus and appearance inspection method for aluminum extruded profile - Google Patents
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Description
【０００１】
【発明の属する技術分野】
この発明は、アルミニウム押出形材に発生する欠陥、特にストリークと称される帯状の外観欠陥が発生していないかどうかについてアルミニウム押出形材を検査し、検査したアルミニウム押出形材が良品であるか不良品であるかどうかを容易にかつ客観的に判定することができるアルミニウム押出形材の外観検査装置に関する。
【０００２】
【従来の技術】
アルミニウム又はアルミニウム合金からなるアルミニウム材のアルミニウム押出形材は、アルミニウム材の特性であるその表面の美しさに加えて、軽量であって加工性や成形性に優れ、しかも、その表面に酸化皮膜や塗装等を形成せしめると優れた耐蝕性が付与されることから、サッシ、カーテンウオール、ドア等の建材、新幹線車両、航空機等のボディ材等として幅広く利用されている。
【０００３】
そして、このようなアルミニウム押出形材は、ビレットと呼ばれるアルミニウム材の鋳塊を加熱し、押出装置により圧力をかけて各種の形状をもつダイス穴から押出すことで製造する。この方法によれば、他の加工方法では製造が困難な中空部を有した形材や、複雑な断面形状をもつ形材を比較的容易に製造することができ、また、寸法精度の厳しい形材を製造することもできるため、長手方向に一定形状を保つアルミニウム形材の製造方法として広く利用されている。
【０００４】
ところが、ビレットの溶体化処理が不十分でマクロ又はミクロの組織が不均一である場合、熱履歴を含む押出条件が不適当である場合、押出金型の状態が不適切である場合等には、押出装置によって成形されたアルミニウム押出形材の表面に、ストリークと称される外観欠陥であって、押出方向に沿って色調の異なる帯状模様が発生することがある。
そして、このようなアルミニウム押出形材の欠陥は、アルミニウム押出形材に外観上の目視の違和感を生じさせるといった問題を引き起こし、製品不良となってアルミニウム押出形材の歩留りを低下させるほか、再製造のための時間的、経済的な損害を与える。
【０００５】
このため、多くのアルミニウム押出形材の製造現場では、製品の抜き取り検査や全数検査等を実施して目視による製品検査を行い、製品中に不良品が混入しないようにしている。ところが、製品の良否の判定には、後工程での処理を考慮し、処理後のアルミニウム押出形材が良品とされるか、不良品とされるかどうかの判定をする必要があり、この判定を行う検査員はある程度の熟練者であることが要求される。また、このような検査員の判定でも個人差があるため、目視による製品検査では、判定結果にばらつきが生じ、製品の品質を一定に保つのが難しく、場合によっては、良品と判定すべきものを不良品と判定したり、反対に、不良品と判定すべきものを良品と判定してしまったりするなどして、後の工程で製品不良と判定されたときには、既にいくつかの処理を経ているため、結果的に余計なコストを掛けてしまうことがあるといった問題も生じていた。
【０００６】
そこで、目視による製品検査以外の方法がいくつか検討されている。例えば、特開平8-86,760号公報では、アルミニウム押出形材の平坦面に二方向から光を入射し、それぞれの反射光を受光して得られる明度の比率若しくは明度差を利用してアルミニウム押出形材の表面に発生する欠陥を評価する技術を教えている。この方法によれば、アルミニウム押出形材の表面の状態を客観的に評価することができるため、これまでの人による目視検査に比べて正確に検査することができる。しかし、この検査方法では、一つの検査対象に対し照射する光源の方向が互いに直交する二方向になるように少なくとも２回の測定が必要となるため、測定時間が長くなり作業性が悪いといった問題が生じ、また、この検査方法では、測定器の治具をアルミニウム押出形材に直接押圧しなければならないため、被検査材のアルミニウム押出形材形状に制約が生じるといった問題が生じる。
【０００７】
また、特開2001-281,155号公報では、光源からの放射光束を所定幅の均等光束に集束して検査対象である金属表面に放射し、集光レンズ等により所定幅にした正反射光束をラインセンサ上に結像させる検査装置が開示されている。この技術によれば、検査対象の金属表面に所定幅の照射スポットラインに同一光量を均等に照射して照射むらを回避することで、検出精度の低下を防止している。しかし、この検査装置では、所定幅の金属表面における正常部の正反射光と表面欠陥部によって減衰される散乱光との比較によるため、正常部の正反射光の安定化が重要になるが、アルミニウム押出形材の場合にはその表面特性のために比較的大きな所定幅ではベースラインとなる正常部の正反射光が安定しない。
【０００８】
【発明が解決しようとする課題】
そこで、本発明者らは、アルミニウム押出形材に発生する外観欠陥（ストリーク）を客観的にかつ確実に検出することができる外観検査の方法について鋭意検討した結果、アルミニウム押出形材の平坦面に光を照射し、この平坦面を検査画像として撮像し、得られた検査画像を小領域に分割して小領域毎の平均濃度を算出し、また、この算出した小領域の平均濃度を検査画像内で少なくとも他の２つの小領域と比較し、比較した平均濃度の差の絶対値が最大となるものを小領域の濃度差代表値とし、更に、このようにして求められた各小領域毎の濃度差代表値の中から最大のもの、すなわち検査画像内の中から濃度差代表値が最大のものに着目してこれを欠陥度とし、この欠陥度を指標として評価することにより、目視検査と整合性のとれた判定が可能であることを見出し、本発明を完成した。
【０００９】
従って、本発明の目的は、アルミニウム押出形材に発生する欠陥、特にストリークと称される帯状の外観欠陥の有無についてアルミニウム押出形材を検査し、この検査したアルミニウム押出形材が良品であるか不良品であるかどうかを容易にかつ客観的に判定することができるアルミニウム押出形材の外観検査装置を提供することにある。
【００１０】
また、本発明の他の目的は、アルミニウム押出形材に発生する欠陥、特にストリークと称される帯状の外観欠陥の有無についてアルミニウム押出形材を検査し、この検査したアルミニウム押出形材が良品であるか不良品であるかどうかを容易にかつ客観的に判定することができ、且つ、アルミニウム押出形材の製造に関する各製造工程での品質の統一が可能なアルミニウム押出形材の外観検査方法を提供することにある。
【００１１】
【課題を解決するための手段】
すなわち、本発明は、アルミニウム又はアルミニウム合金からなるアルミニウム押出形材の平坦面を検査する外観検査装置であり、アルミニウム押出形材の平坦面に光を照射する照明手段と、この平坦面を撮像して検査画像を得る撮像手段と、上記検査画像を押出方向に直交する主走査方向及び押出方向に平行な副走査方向にそれぞれ所定の幅を有する小領域に分割し、この分割された小領域に従って検査画像内を主走査方向及び副走査方向に走査する走査手段と、上記走査手段により得られた走査結果から検査画像の欠陥度を検出する欠陥度検出手段と、上記欠陥度を予め定めた基準値と比較し、欠陥度が基準値以上の場合にアルミニウム押出形材を不良品と判定する不良品判定手段とを備えており、上記欠陥度検出手段が、検査画像内の小領域毎の平均濃度を算出する平均濃度算出部と、小領域毎の平均濃度を記録する平均濃度記録部と、検査画像内のいずれか１つの小領域に注目して、この注目小領域の平均濃度と注目小領域から主走査方向に同一直線上に位置し、かつ、注目小領域との間に所定の小領域分の間隔を有する第１の対照小領域の平均濃度とを比べて第１の平均濃度の差を求めると共に、注目小領域の平均濃度と注目小領域から副走査方向に同一直線上に位置し、かつ、注目小領域との間に所定の小領域分の間隔を有する第２の対照小領域の平均濃度とを比べて第２の平均濃度の差を求め、得られた第１及び第２の平均濃度の差の絶対値が最大の値を上記注目小領域の濃度差代表値として検出する濃度差代表値検出部と、走査終了後に検査画像内の小領域毎に検出された濃度差代表値からその最大値を検査画像の欠陥度として記録する欠陥度記録部と、を備えていることを特徴とするアルミニウム押出形材の外観検査装置である。
【００１２】
また、本発明は、アルミニウム又はアルミニウム合金からなるアルミニウム押出形材の平坦面を検査する外観検査方法であり、照明手段によりアルミニウム押出形材の平坦面に光を照射し、この光が照射された平坦面から撮像手段により検査画像を撮像し、次いで走査手段により上記検査画像を押出方向に直交する主走査方向及び押出方向に平行な副走査方向にそれぞれ所定の幅を有する小領域に分割すると共に、この分割された小領域に従って検査画像内を主走査方向及び副走査方向に走査し、この走査手段により得られた走査結果から欠陥度検出手段により検査画像の欠陥度を検出し、不良品判定手段により上記走査手段で検出された欠陥度を予め定めた基準値と比較し、欠陥度が基準値以上の場合にアルミニウム押出形材を不良品と判定するに際し、上記欠陥度検出手段では、その平均濃度算出部で検査画像内の小領域毎の平均濃度を算出し、この算出された小領域毎の平均濃度を平均濃度記録部に記録すると共に、濃度差代表値検出部において、検査画像内のいずれか１つの小領域に注目して、この注目小領域の平均濃度と注目小領域から主走査方向に同一直線上に位置し、かつ、注目小領域との間に所定の小領域分の間隔を有する第１の対照小領域の平均濃度とを比べて第１の平均濃度の差を求めると共に、注目小領域の平均濃度と注目小領域から副走査方向に同一直線上に位置し、かつ、注目小領域との間に所定の小領域分の間隔を有する第２の対照小領域の平均濃度とを比べて第２の平均濃度の差を求め、得られた第１及び第２の平均濃度の差の絶対値が最大の値を上記注目小領域の濃度差代表値として検出し、走査終了後に上記検査画像内の小領域毎に検出された濃度差代表値からその最大値を検査画像の欠陥度として欠陥度記録部に記録することを特徴とするアルミニウム押出形材の外観検査方法である。
【００１３】
本発明における外観検査装置は、基本的には、照明手段、撮像手段、走査手段、欠陥度検出手段及び不良品判定手段を備えており、先ず、その照明手段によりアルミニウム押出形材の平坦面に光を照射して撮像手段により上記平坦面から所定の面積の検査画像を撮像し、次いで、走査手段により、撮像した検査画像を押出方向に直交する主走査方向及び押出方向に平行な副走査方向にそれぞれ所定の幅を有する小領域に分割しつつ、この分割された小領域に従って検査画像内を主走査方向及び副走査方向に走査し、各小領域毎の平均濃度を算出し、更に、欠陥度検出手段により、走査手段の走査結果から、検査画像の欠陥度、すなわち検査対象となったアルミニウム押出形材の欠陥度を求め、そして、不良品判定手段により、この欠陥度を予め定めた基準値と比較し、欠陥度が基準値を上回る場合にこのアルミニウム押出形材を不良品と判定するように構成されている。
【００１４】
また、本発明における外観検査装置は、上記以外にも、例えば、検査するアルミニウム押出形材を保持する保持手段、バキューム装置、アームロボット装置等を含んだ構成であってもよい。
【００１５】
そして、上記欠陥度検出手段においては、検査画像内のある小領域に注目し、この注目した小領域（注目小領域）の平均濃度をこの注目小領域の周辺に存在し、かつ、主走査方向又は副走査方向に互いに一直線上に並ばない少なくとも２つの小領域である対照小領域（このうち一方を「第１の対照小領域」といい、他方を「第２の対照小領域」という場合がある。）の平均濃度と比較し、比較した平均濃度の濃度差（注目小領域の平均濃度と第１の対照小領域の平均濃度との差を「第１の平均濃度の差」という場合がある。同様に第２の対照小領域との比較から得られたものを「第２の平均濃度の差」という場合がある。）の絶対値が最大となる値を注目小領域の濃度差代表値とし、更に、検査画像内の小領域毎に上記濃度差代表値を求め、この濃度差代表値が検査画像内で最大となるものを欠陥度として検出する。
【００１６】
ここで、上記の欠陥度については、次のように考えることができる。すなわち、予め目視検査により外観欠陥が存在すると判定されたアルミニウム押出形材のサンプルと、目視検査により外観欠陥が存在しないと判定されたアルミニウム押出形材のサンプルとを比較した場合、外観欠陥を有するサンプルの方が外観欠陥を有さないサンプルに比べて濃度差の値が大きくなる。これは、アルミニウム押出形材の表面に発生するストリーク等の外観欠陥は、正常な部分と比べてコントラストが強く発現する傾向にあるため、アルミニウム押出形材を検査画像として撮像した場合、欠陥部分と正常な部分との間の濃度差から生じていると考えられる。そのため、上記のようにして得た欠陥度が、予め定めた基準値以上である場合に、アルミニウム押出形材にストリーク等の外観欠陥が存在すると判定することができる。
【００１７】
以下、本発明の外観検査装置が備える各手段について説明する。
本発明の外観検査装置は、アルミニウム押出形材の平坦面に光を照射する照明手段を備えている。上記照明手段は、光を照射したアルミニウム押出形材の平坦面の照度を４０〜８０ルクス、好ましくは６０〜８０ルクスにする光源であるのがよい。アルミニウム押出形材の平坦面の照度が４０ルクスより小さいと、アルミニウム押出形材からの反射光が少なく、検査画像から検出できる欠陥度が小さくなって、外観欠陥の有無を正しく判定することができない。反対に、８０ルクスより大きいと、アルミニウム押出形材からの反射光が多くなり、ストリークのような色調の変化を検査画像に取り込むことができず、外観欠陥の有無を正しく判定することができない。
【００１８】
このような照明手段としては、具体的には、発光ダイオードを光源としたものが好ましく、発光ダイオードを光源とすれば、均一性と特定波長以外の波長をカットするフィルタをカメラに装着することにより外乱光を防止できる点で有利である。
【００１９】
また、本発明の照明手段は、照明手段による光の照射角度が、アルミニウム押出形材の平坦面の垂線方向に対して、１５〜４０度、好ましくは２０〜３０度であるのがよい。アルミニウム押出形材への光の照射角度がアルミニウム押出形材の平坦面の垂線方向に対し１５度より小さくても４０度より大きくてもストリークによるコントラストの変化が検査画像中で現われ難いという問題がある。
【００２０】
また、本発明の外観検査装置で用いる撮像手段は、アルミニウム押出形材の平坦面が反射した反射光を受光できるように上記照明手段と対峙してアルミニウム押出形材の平坦面の垂線方向に対し１５〜４０度、好ましくは２０〜３０度の角度で配設するのがよい。撮像手段を配設する位置が、アルミニウム押出形材の平坦面の垂線方向に対し１５度より小さくても４０度より大きくてもストリークによるコントラストの変化が検査画像中で明瞭に現われ難いという問題がある。
【００２１】
そして、この撮像手段は、アルミニウム押出形材の平坦面を検査画像として撮像する際、アルミニウム押出形材の押出方向に対し平行方向に１０〜５０mm、好ましくは２０〜３０mmであって、押出方向に対し直交方向に１０〜５０mm、好ましくは２０〜３０mmの範囲を検査画像として撮像するのがよい。このアルミニウム押出形材の平坦面を撮像する範囲が１０mmより小さいと、注目小領域と対照小領域の濃度差が小さくなり、欠陥度が目視判定と整合させ難くなるという問題が生じ、また反対に５０mmより大きいと、検査画像の解像度が悪くなるという問題が生じる。
【００２２】
また、検査するアルミニウム押出形材が、押出方向にストリーク等の外観欠陥を発生していることが目視等によって確認できる場合は、このアルミニウム押出形材の平坦面を検査画像として撮像する際、アルミニウム押出形材の押出方向に対し直交方向については、上記外観欠陥が押出方向に対し直交方向に有する幅の２〜１０倍、好ましくは３〜６倍の幅であって、押出方向に対し平行方向に１０〜５０mm、好ましくは２０〜３０mmの範囲を検査画像として撮像するのがよい。この外観欠陥を発生しているアルミニウム押出形材の平坦面を撮像する範囲が、アルミニウム押出形材の押出方向に対し直交方向が上記範囲となるように検査画像を撮像すれば十分な数の小領域を検査画像内に設定できるので、再現性よくアルミニウム押出形材に発生した外観欠陥が不良品と判定する程度のものか、良品と判定する程度のものか正しく客観的に判定することができる。この幅が２倍より小さいと、多少の位置ずれにより検査した値がずれてしまい再現性の点で問題があり、反対に１０倍より大きいと測定に時間がかかるという点で問題である。
【００２３】
本発明で用いる撮像手段としては、好ましくは、ＣＣＤカメラであるのがよい。このＣＣＤカメラとしては、検査画像を５１２画素以上×４８４画素以上で撮像することができるものがよい。撮像した検査画像が５１２画素×４８４画素より少なくなると解像度が落ちるという問題が生じる。また、撮像手段と検査するアルミニウム押出形材の平坦面との距離は、８０〜２５０mmであるのがよく、アルミニウム押出形材の平坦面との距離が８０mmより近いと検査領域が狭くなりすぎてアルミニウム押出形材全体の評価ができず、反対に２５０mmより遠くなると検査画像が小さくなり、判定の分解能が低下する。
また、上記検査画像は、ＣＣＤカメラに接続したＡ／Ｄ変換装置によりＡ／Ｄ変換してもよく、下記で説明する走査手段側でＡ／Ｄ変換してもよい。このようなＡ／Ｄ変換については、２５６階調に変換するのが好ましい。２５６階調のものであれば、判定の定量化の点で有利である。
【００２４】
また、本発明の外観検査装置に設けられた走査手段においては、検査画像を分割する小領域が矩形状の小領域であるのが好ましく、この場合、当該小領域は主走査方向に０．５〜３．０mm、好ましくは１．０〜２．０mm及び副走査方向に０．５〜３．０mm、好ましくは１．０〜２．０mmの幅を有するのがよく、この矩形状の小領域が有する幅が上記範囲内であると、注目小領域と対照小領域との距離を比較的大きくとることが可能になって、良品と不良品とを正しく判定することができる。
【００２５】
また、本発明の走査手段において、検査画像を小領域に分割しながら走査する際に、好ましくは、先に走査した小領域と次に走査する小領域とが当該小領域の主走査方向幅寸法の１／２の割合でその主走査方向に互いに重なり合うようにするのがよく、これによって、押出方向に発生する帯状の外観欠陥に対し、この帯状の外観欠陥が限りなく細いものであっても、これを確実に検出することができる。
【００２６】
上記のような走査手段として、好ましくは、撮像手段により撮像した検査画像を画素単位の情報として処理することができる装置であるのがよい。
【００２７】
そして、上記欠陥度検出手段は、上述のように、検査画像内の注目小領域の平均濃度を対照小領域の平均濃度と比較し、その濃度差の絶対値が最大となる値を注目小領域の濃度差代表値とし、検査画像内で最大の値を示す濃度差代表値を欠陥度として検出するものであり、検査画像内の小領域毎の平均濃度を算出する平均濃度算出部と、小領域毎の平均濃度を記録する平均濃度記録部と、検査画像内の注目小領域の平均濃度と少なくとも２つの対照小領域の平均濃度とを比較し、この平均濃度の差の絶対値が最大となる値を注目小領域の濃度差代表値として検出する濃度差代表値検出部と、濃度差代表値を検査画像内の小領域毎に検出し、検査画像内の濃度差代表値の最大を検査画像の欠陥度として記録する欠陥度記録部とを備えている。
【００２８】
ここで、この欠陥度検出手段については、好ましくは、注目小領域に対して２つの対照小領域と比較するものであって、これら２つの対照小領域の注目小領域に対する位置関係は、その一方が注目小領域に対してその主走査方向所定の間隔を有して直線上に位置し、また、他方が注目小領域に対してその副走査方向所定の間隔を有して直線上に位置するものであるのがよく、より好ましくは、２つの対照小領域がそれぞれ注目小領域に対して主走査方向の進行方向手前側及び副走査方向の進行方向手前側に位置するのがよい。これら注目小領域と２つの対照小領域とがこのような位置関係にあることにより、検査画像域全体の検索が可能になるという点で有利である。
【００２９】
また、上記注目小領域と対照小領域との間隔については、好ましくは、主走査方向及び副走査方向に共に４〜６小領域分の間隔を有するのがよい。これら注目小領域と対照小領域との間隔が４小領域分より短くなると注目小領域と対照小領域との間隔が近くなりすぎ、互いに同じ部分を比較することになり、反対に、６小領域分より長くなると検査画像内における注目小領域と対照小領域の比較量が少なくなるという点で好ましくない。
【００３０】
本発明における平均濃度算出部は、上記のように平均濃度を算出することができる算出装置であればよく、また、平均濃度記録部は、上記平均濃度を小領域毎に記録することができる記録装置であればよく、更に、濃度差代表値検出部は、記録された複数の小領域の平均濃度を比較し、比較した平均濃度の差のなかで絶対値が最大となるものを検出することができるような検出装置であればよく、更にまた、欠陥度記録部は、上記濃度差代表値検出装置によって検出した濃度差代表値のうち、検査画像内で最大のものを欠陥度して記録することができる記録装置であればよい。これらの装置は、各機能を発揮するような独立した装置であって、互いに算出した情報や記録情報を通信することができるように接続されたものであってもよく、また、上記いずれかの機能のうち複数を集約して処理する装置を用いてもよく、更に、欠陥度検出手段をすべて一台のパーソナルコンピューター（パソコン）等に集約させたものであってもよい。
【００３１】
更に、本発明で用いる不良品判定手段は、上記欠陥度検出手段で求められ検出された欠陥度を予め定めた基準値と比較し、この欠陥度が基準値以上の場合に検査したアルミニウム押出形材を不良品と判定できるものであればよい。
【００３２】
ここで、不良品判定手段に予め設定する欠陥度の基準値については、好ましくは濃度差２０%以上、より好ましくは濃度差３０%以上に設定するのがよい。例えば、撮像手段がＣＣＤカメラであって、Ａ／Ｄ変換装置により２５６階調に変換した場合、６４階調は濃度差２５%を意味する。基準値を濃度差２０%より小さい値で設定すると、目視による判定との不一致が生じる。
【００３３】
上記のように不良品判定のための欠陥度の基準値を設定することにより、外観欠陥が発生した不良品と発生していない良品とを正しく判定することができ、また、人による目視検査では、不良品と良品との区別がつきにくいものについても、客観的に判定することができるため、製品の品質を一定に保つことができる。このため、アルミニウム押出形材の製造において、品質管理の面からも有効であり、例えば、アルミニウム押出形材の製造に関する各製造工程間での品質を統一することができるほか、顧客との製品納入等での品質契約の明確化の点で有効である。また、本発明による外観検査装置では、上記のように検査画像から検出した欠陥度を基準値と比較することでアルミニウム押出形材を良品と不良品とに判別できるため、標準画像のような基準画像を予め記録して保持する必要がないため、外観検査装置の構成が複雑にならず、製造コストも低く抑えることができ、更には検査画像を標準画像等と比較して判定する場合とくらべ、判定の処理に要する時間も短く、容易にできることから、これまでの目視検査において要求された検査員の熟練度等を問わず誰でも容易にアルミニウム押出形材の外観検査を行うことができる。
【００３４】
また、上記のアルミニウム押出形材の外観検査装置を用いてアルミニウム押出形材の平坦面を検査するに際しては、撮像手段で検査画像を撮像する際に、アルミニウム押出形材の平坦面を１／２，０００〜１／１０，０００秒の間隔で検査画像として撮像するのがよく、検査画像を撮像する間隔が１／１０，０００秒より短いと画像が暗くなるという問題が生じ、反対に、１／２，０００秒より長くなると画像が粗くなるという問題が生じる。
【００３５】
本発明のアルミニウム押出形材の外観検査装置によれば、アルミニウム押出形材に発生する外観欠陥、特にストリークと称される帯状の外観欠陥が発生していないかどうかについて検査し、このアルミニウム押出形材が良品であるか不良品であるかどうかを正しく客観的に判定することができるため、本来不良品と判定すべきものを誤って良品と判定する判定ミスを可及的に減らすことができるほか、製造されるアルミニウム押出形材の品質を一定に保つことができ、品質管理の面からも有効である。また、上記のように検査画像から検出した濃度差に基づく欠陥度を予め設定した欠陥度の基準値と比較してアルミニウム押出形材を良品と不良品とに判別するため、標準画像を予め記録しておき、検査毎にこの標準画像と比較して判定していくような場合と比較して、判定の処理に要する時間が短く、不良品と判定された場合には直ちにアルミニウム押出形材を製造するアルミニウム押出形材の製造装置を停止することができるため、アルミニウム押出形材を製造しながらの抜き取り検査で用いる場合でも有効である。
【００３６】
【発明の実施の形態】
以下、実施例に基づいて、本発明の好適な実施の形態を具体的に説明する。
【００３７】
〔試験例１〕
図１は、予め人による目視検査で外観欠陥が発生していると判定されたアルミニウム押出形材のサンプル３０個と、目視検査により外観欠陥が発生していないと判定されたアルミニウム押出形材のサンプル４５個とを用意し、それぞれについて本発明の外観検査装置を用いて求めた欠陥度をグラフ化したものである。
【００３８】
ここで、上記欠陥度を検出した条件は次のとおりである。
先ず、各サンプルに対し、赤色ＬＥＤ（波長６６０nm）を並べて１８０mm×１３５mmとした光源を、光の照射角度が平坦面の垂線方向に対して３０度となり、また、サンプルの平坦面までの距離が１３０mmとなるように配置し、更に、ＣＣＤカメラ（２４７８０８画素）を、サンプルの平坦面が反射する反射光が正面から入射するように、平坦面の垂線方向に対して３０度となり、サンプルの平坦面までの距離が１３０mmとなるように配置した。
【００３９】
光源から発射され、平坦面で反射された反射光をＣＣＤカメラで受光し、Ａ／Ｄ変換装置にて２５６階調に変換して検査画像（２０mm×４０mm）を撮像した。得られた検査画像（２０mm×４０mm）をサンプル（アルミニウム押出形材）の押出方向に対して直交する主走査方向に１０画素（１．５mm）及び押出方向に対し平行な副走査方向に１０画素（１．５mm）の正方形状の小領域に分割し、主走査方向の検査画像の走査については、上記の如く分割して走査する小領域が先に主走査方向に走査した隣接小領域とこの小領域の幅の１／２（半分）づつ重なり合うように走査した。
【００４０】
次いで、上記走査による矩形状の小領域について平均濃度を算出し、検査画像内の小領域毎について平均濃度を記録した。そして、検査画像内のある１つの小領域に注目し、この注目小領域の平均濃度を、この注目小領域と主走査進行方向手前側に６小領域分の間隔を有して注目小領域と直線上に並んだ主走査方向対照小領域の平均濃度と比較して平均濃度の差を求め、また、この注目小領域と副走査進行方向手前側に６小領域分の間隔を有して注目小領域と直線上に並んだ副走査方向対照小領域の平均濃度と比較して平均濃度の差を求めた。そして、上記平均濃度の差のうち、その絶対値が大きい方を当該注目小領域の濃度差代表値とした。上記と同様にして、検査画像内のすべての小領域について濃度差代表値を求め、この濃度差代表値が検査画像内で最大のものを当該検査画像の欠陥度として求めた。
【００４１】
上記のようにして各サンプルについて求めた欠陥度は、図１から分かるように、欠陥度８０（濃度差３１.２５％）を境にして二極に分布しており、欠陥度が大きい方に目視検査で外観欠陥あり（不良品）と判定されたサンプルが分布し、欠陥度が小さい方に目視検査で外観欠陥なし（良品）と判定されたサンプルが分布している。したがって、欠陥度８０付近を基準値とすることで、アルミニウム押出形材の外観検査が可能であることが分かる。
【００４２】
〔実施例１〕
図２〜４に、アルミニウム押出形材の平坦面を検査するために本発明が適用された実施例１に係るアルミニウム押出形材の外観検査装置が示されている。
本発明における外観検査装置１は、成形されたアルミニウム押出形材２を吸着して保持するバキューム保持機３と、赤色ＬＥＤ（波長６６０nm）を並べて１８０mm×１３５mmの大きさの光源とし、アルミニウム押出形材２の平坦面への光の照射角度が当該平坦面の垂線方向に対して３０度となり、かつ、この平坦面までの距離が１３０mmとなる位置に配置された照明と４と、上記アルミニウム押出形材２の平坦面から反射した反射光を正面から受光するようにアルミニウム押出形材２の平坦面の垂線方向に対して３０度となり、かつ、この平坦面までの距離が１３０mmとなる位置に配置された検査画像を撮像するＣＣＤカメラ５と、パソコン６とを備えており、このパソコン６には、上記ＣＣＤカメラ５で撮像された検査画像を採り込み、この検査画像を押出方向に直交する主走査方向及び押出方向に平行な副走査方向にそれぞれ所定の幅を有する小領域に分割し、この分割された小領域に従って検査画像内を主走査方向及び副走査方向に走査する走査手段と、この走査手段により得られた走査結果から検査画像の欠陥度を検出する欠陥度検出手段と、上記欠陥度を予め定めた基準値と比較し、欠陥度が基準値以上の場合にアルミニウム押出形材を不良品と判定する不良品判定手段と、液晶モニタ画面とが設けられている。尚、ＣＣＤカメラ５で撮像された検査画像は、ＣＣＤカメラ５によりＡ／Ｄ変換されてもよく、また、検査画像を採り込んだパソコン６によりＡ／Ｄ変換されてもよい。
【００４３】
そして、上記走査手段においては、図５に示すように、検査画像を押出方向に直交する主走査方向ＭＤ及び押出方向に平行な副走査方向ＳＤにそれぞれ１０画素（１．５mm）×１０画素（１．５mm）の大きさを有する多数の小領域７に分割し、この分割された小領域７に従って、主走査方向ＭＤには小領域の幅寸法の１／２づつ〔すなわち、５画素（０．７５mm）〕、また、検査画副走査方向ＳＤには小領域の幅寸法の１／２づつ〔すなわち、５画素（０．７５mm）〕走査するようになっている。
【００４４】
また、上記欠陥度検出手段は、図５に示すように、検査画像内の小領域７毎の平均濃度を算出する平均濃度算出部と、小領域７毎の平均濃度を記録する平均濃度記録部と、検査画像内のいずれか１つの小領域７ａに注目し、この注目小領域７ａの平均濃度と、この注目小領域７ａから小領域４個分の比較間隔ｘ及びｙだけ主走査方向ＭＤ及び副走査方向ＳＤの進行方向手前側に位置する２つの対照小領域７ｂ，７ｃの平均濃度とを比較し、その平均濃度の差の絶対値が最大の値を上記注目小領域の濃度差代表値として検出する図示外の濃度差代表値検出部と、走査終了後に検査画像内の小領域毎に検出された濃度差代表値からその最大値を検査画像の欠陥度として記録する図示外の欠陥度記録部とを備えている。
【００４５】
更に、上記不良品判定手段には、良品と不良品とを判別するための欠陥度の基準値として上記試験例１で得られた欠陥度８０の値が記憶されており、上記欠陥度検出手段で求められ検出された欠陥度がこの欠陥度の基準値８０と比較され、欠陥度がこの基準値未満である場合には良品と判定され、また、この基準値以上である場合には不良品として判定されるようになっている。
【００４６】
【発明の効果】
本発明のアルミニウム押出形材の外観検査装置及び外観検査方法によれば、アルミニウム押出形材に発生する欠陥、特にストリークと称される帯状の外観欠陥の有無についてアルミニウム押出形材を検査し、この検査したアルミニウム押出形材が良品であるか不良品であるかどうかを容易にかつ客観的に判定することができる。
【図面の簡単な説明】
【図１】 図１は、目視検査で不良品と判定したアルミニウム押出形材と、良品と判定したアルミニウム押出形材の欠陥度を表すグラフである。
【図２】 図２は、本発明の実施例１に係るアルミニウム押出形材の外観検査装置の概略を示す側面説明図である。
【図３】 図３は、図２の正面説明図である。
【図４】 図４は、図２の平面説明図である。
【図５】 図５は、図２の外観検査装置に搭載されている走査手段における走査方法と欠陥度検出手段における注目小領域と対照小領域との位置関係を示す説明図である。
【符号の説明】
１…外観検査装置、２…アルミニウム押出形材、３…バキューム保持機、４…照明、５…ＣＣＤカメラ、６…パソコン、７…領域、7a…注目小領域、7b,7c…対照小領域、ＭＤ…主走査方向、ＳＤ…副走査方向、ｘ,ｙ…比較間隔。[0001]
BACKGROUND OF THE INVENTION
The present invention inspects an aluminum extruded shape for defects occurring in an aluminum extruded shape, particularly a strip-like appearance defect called streak, and whether the inspected aluminum extruded shape is a good product. It is related with the external appearance inspection apparatus of the aluminum extrusion shape material which can determine easily whether it is inferior goods objectively.
[0002]
[Prior art]
Aluminum extrusions made of aluminum or aluminum alloys are lightweight and have excellent workability and formability in addition to the beauty of the surface, which is a characteristic of aluminum materials. Since excellent corrosion resistance is imparted when a coating is formed, it is widely used as a building material for sashes, curtain walls, doors, etc., as a body material for Shinkansen vehicles, aircraft, etc.
[0003]
And such an aluminum extrusion shape material is manufactured by heating the ingot of aluminum material called a billet, and extruding it from the die hole which has various shapes, applying a pressure with an extrusion apparatus. According to this method, it is possible to relatively easily manufacture a shape having a hollow portion, which is difficult to manufacture by other processing methods, or a shape having a complicated cross-sectional shape. Since a material can also be manufactured, it is widely used as a method for manufacturing an aluminum profile that maintains a constant shape in the longitudinal direction.
[0004]
However, when the billet solution treatment is inadequate and the macro or micro structure is uneven, the extrusion conditions including the heat history are inappropriate, the extrusion mold is in an inappropriate condition, etc. On the surface of the aluminum extruded shape formed by the extrusion apparatus, there may be a band-like pattern having an appearance defect called streak and having a different color tone along the extrusion direction.
Such defects in the extruded aluminum profile cause problems such as a visually uncomfortable appearance on the extruded aluminum profile, resulting in a defective product and reducing the yield of the extruded aluminum profile. For time and economic damage.
[0005]
For this reason, in many aluminum extrusion shape manufacturing sites, product sampling inspections, 100% inspections, etc. are performed to visually inspect products so that defective products are not mixed in the products. However, in determining the quality of a product, it is necessary to determine whether the processed aluminum extruded shape is a non-defective product or a defective product in consideration of processing in the subsequent process. The inspector who performs the inspection is required to have some skill. In addition, because there are individual differences even in such inspector judgments, in visual product inspections, the judgment results vary and it is difficult to keep the product quality constant. When it is determined that the product is defective in a later process, such as when it is determined as a defective product, or conversely, a product that should be determined as a defective product is determined as a non-defective product. As a result, there has been a problem that extra costs may be incurred.
[0006]
Therefore, several methods other than visual product inspection have been studied. For example, in JP-A-8-86,760, light is incident on a flat surface of an aluminum extruded shape member from two directions, and the ratio of brightness obtained by receiving each reflected light or the difference in brightness is used to make an aluminum extruded shape. Teaching techniques for evaluating defects on the surface of materials. According to this method, since the surface state of the aluminum extruded profile can be objectively evaluated, it can be inspected more accurately than conventional visual inspections by humans. However, this inspection method requires at least two measurements so that the direction of the light source irradiated to one inspection object is two directions orthogonal to each other. In addition, in this inspection method, since the jig of the measuring instrument must be pressed directly onto the aluminum extruded shape, there is a problem that the shape of the aluminum extruded shape of the material to be inspected is restricted.
[0007]
In JP-A-2001-281,155, a radiated light beam from a light source is converged to a uniform light beam having a predetermined width and radiated to a metal surface to be inspected, and a regular reflected light beam having a predetermined width is collected by a condenser lens or the like. An inspection apparatus that forms an image on a sensor is disclosed. According to this technique, the detection accuracy is prevented from deteriorating by uniformly irradiating the irradiation target spot surface of the predetermined width with the same amount of light to avoid irradiation unevenness. However, in this inspection apparatus, because of the comparison between the regular reflected light of the normal part on the metal surface of a predetermined width and the scattered light attenuated by the surface defect part, stabilization of the regular reflected light of the normal part becomes important. In the case of an aluminum extruded shape, the regular reflection light of the normal part serving as the baseline is not stable at a relatively large predetermined width because of the surface characteristics.
[0008]
[Problems to be solved by the invention]
Therefore, as a result of intensive studies on an appearance inspection method capable of objectively and reliably detecting appearance defects (streaks) occurring in an aluminum extruded shape, the present inventors have found that the flat surface of the aluminum extruded shape is Light is irradiated, this flat surface is imaged as an inspection image, the obtained inspection image is divided into small areas, the average density for each small area is calculated, and the calculated average density of the small areas is also inspected image Compared with at least the other two small regions, the one having the largest absolute value of the difference in the average density compared is set as the representative value of the density difference of the small region. Further, for each small region thus obtained, Focusing on the largest density difference representative value, that is, the largest density difference representative value in the inspection image, this is regarded as the defect degree, and this defect degree is evaluated as an index, thereby visual inspection. And consistent Found that constant is possible, the present invention has been completed.
[0009]
Therefore, the object of the present invention is to inspect the aluminum extruded shape for defects occurring in the aluminum extruded shape, particularly the presence of a strip-like appearance defect called streak, and whether the inspected aluminum extruded shape is good. An object of the present invention is to provide an appearance inspection apparatus for an extruded aluminum profile that can easily and objectively determine whether or not it is a defective product.
[0010]
Another object of the present invention is to inspect the aluminum extruded shape for defects occurring in the aluminum extruded shape, particularly for the presence of a strip-like appearance defect called streak, and the inspected aluminum extruded shape is a non-defective product. A method of inspecting the appearance of an aluminum extruded profile that can easily and objectively determine whether it is a defective product or not, and that can unify the quality in each manufacturing process related to the production of aluminum extruded profiles It is to provide.
[0011]
[Means for Solving the Problems]
That is, the present invention is an appearance inspection apparatus for inspecting a flat surface of an aluminum extruded profile made of aluminum or an aluminum alloy, and an illumination means for irradiating light on the flat surface of the aluminum extruded profile, and imaging the flat surface. Imaging means for obtaining an inspection image, and dividing the inspection image into small regions each having a predetermined width in a main scanning direction orthogonal to the extrusion direction and a sub-scanning direction parallel to the extrusion direction, and according to the divided small regions Scanning means for scanning the inspection image in the main scanning direction and the sub-scanning direction, a defect degree detecting means for detecting the defect degree of the inspection image from the scanning result obtained by the scanning means, and a reference for determining the defect degree in advance A defective product judging means for judging that the aluminum extruded profile is a defective product when the defect degree is equal to or higher than a reference value, and the defect degree detecting means is provided in the inspection image. An average density calculation unit that calculates an average density for each region, an average density recording unit that records an average density for each small region, and any one small region in the inspection image, the average of this small region of interest The first density is compared with the average density of the first control small area that is located on the same straight line from the small area of interest in the main scanning direction and has a predetermined small area between the small area of interest. A difference between the average density of the target small area and the target small area located on the same straight line in the sub-scanning direction and having a predetermined small area interval between the target small area and the target small area. Comparing the average density of the two control subregions to determine the difference in the second average density, Obtained first and second A density difference representative value detection unit that detects a value with the maximum absolute value of the average density difference as a density difference representative value of the target small area, and a density difference representative value detected for each small area in the inspection image after the scan is completed. And a defect degree recording unit for recording the maximum value as the defect degree of the inspection image.
[0012]
Further, the present invention is an appearance inspection method for inspecting a flat surface of an aluminum extruded shape made of aluminum or an aluminum alloy, and the light is irradiated to the flat surface of the aluminum extruded shape by an illuminating means. The inspection image is picked up by the image pickup means from the flat surface, and then the inspection image is divided by the scanning means into small regions each having a predetermined width in the main scanning direction orthogonal to the extrusion direction and the sub-scanning direction parallel to the extrusion direction. The inspection image is scanned in the main scanning direction and the sub-scanning direction according to the divided small areas, and the defect degree of the inspection image is detected by the defect degree detection means from the scanning result obtained by the scanning means, and the defective product is determined. The degree of defect detected by the scanning means is compared with a predetermined reference value, and if the degree of defect is equal to or greater than the reference value, the extruded aluminum shape is determined to be defective. In doing so, in the defect degree detection means, the average density calculation unit calculates the average density for each small region in the inspection image, and records the calculated average density for each small region in the average density recording unit, In the density difference representative value detection unit, paying attention to any one small area in the inspection image, the average density of the target small area and the target small area are located on the same straight line in the main scanning direction, and A difference between the first average density is obtained by comparing the average density of the first control small area having an interval of a predetermined small area with the area, and the sub-area is calculated from the average density of the small area of interest and the small area of interest. A difference in the second average density is obtained by comparing with the average density of the second control small area located on the same straight line in the scanning direction and having a predetermined small area distance from the target small area. , Obtained first and second The maximum absolute value of the average density difference is detected as the representative density difference value of the target small area, and the maximum value is inspected from the representative density difference value detected for each small area in the inspection image after the scan is completed. It is an appearance inspection method for an aluminum extruded profile, which is recorded as a defect degree of an image in a defect degree recording section.
[0013]
The visual inspection apparatus according to the present invention basically includes illumination means, imaging means, scanning means, defect degree detection means, and defective product determination means. First, the illumination means applies a flat surface to the aluminum extruded profile. A test image of a predetermined area is picked up from the flat surface by irradiating light with the imaging means, and then the main scanning direction orthogonal to the extrusion direction and the sub-scanning direction parallel to the extrusion direction by the scanning means The image is divided into small areas each having a predetermined width, the inspection image is scanned in the main scanning direction and the sub-scanning direction according to the divided small areas, and the average density for each small area is calculated. The degree detection means obtains the defect degree of the inspection image from the scanning result of the scanning means, that is, the defect degree of the aluminum extruded shape which is the inspection object, and the defect judgment means predicts this defect degree. It compared with a reference value determined, and is configured so that the aluminum extruded profile determined as defective when the defective degree exceeds a reference value.
[0014]
In addition to the above, the appearance inspection apparatus according to the present invention may be configured to include, for example, a holding means for holding an aluminum extruded profile to be inspected, a vacuum apparatus, an arm robot apparatus, and the like.
[0015]
Then, in the defect degree detection means, attention is paid to a certain small area in the inspection image, and the average density of the focused small area (focused small area) exists around the focused small area, and the main scanning direction Or at least two small areas that are not aligned with each other in the sub-scanning direction (One of these may be referred to as a “first control subregion” and the other may be referred to as a “second control subregion”.) Compared with the average concentration of, the difference in concentration of the compared average concentration (The difference between the average density of the target small area and the average density of the first control small area is sometimes referred to as “first average density difference.” Similarly, the difference was obtained from the comparison with the second control small area. (In some cases, this is referred to as “second average density difference”.) As a representative value of the density difference of the target small area, the density difference representative value is obtained for each small area in the inspection image, and this density difference representative value becomes the maximum in the inspection image. A thing is detected as a defect degree.
[0016]
Here, the above-described defect degree can be considered as follows. That is, when comparing a sample of an aluminum extruded profile that has been determined in advance by visual inspection to have an appearance defect and a sample of an aluminum extruded profile that has been determined by visual inspection to have no appearance defect, the sample has an appearance defect. The sample has a larger density difference value than the sample having no appearance defect. This is because appearance defects such as streaks that occur on the surface of the aluminum extruded profile tend to exhibit a stronger contrast than normal portions, so when an aluminum extruded profile is imaged as an inspection image, It is thought that it is caused by the difference in density from the normal part. Therefore, when the degree of defect obtained as described above is equal to or greater than a predetermined reference value, it can be determined that there are appearance defects such as streaks in the aluminum extruded profile.
[0017]
Hereinafter, each means with which the external appearance inspection apparatus of this invention is provided is demonstrated.
The appearance inspection apparatus according to the present invention includes illumination means for irradiating light onto a flat surface of an aluminum extruded profile. The illuminating means may be a light source that adjusts the illuminance of the flat surface of the aluminum extruded profile irradiated with light to 40 to 80 lux, preferably 60 to 80 lux. If the illuminance on the flat surface of the aluminum extruded profile is less than 40 lux, the reflected light from the aluminum extruded profile is small, the degree of defects that can be detected from the inspection image is small, and the presence or absence of appearance defects cannot be determined correctly. . On the other hand, if it is larger than 80 lux, the amount of reflected light from the aluminum extruded profile increases, so that a change in color tone such as streak cannot be taken into the inspection image, and the presence or absence of an appearance defect cannot be determined correctly.
[0018]
Specifically, such illumination means preferably uses a light emitting diode as a light source. If the light emitting diode is used as a light source, a filter that cuts off wavelengths other than the uniformity and specific wavelength can be mounted on the camera. This is advantageous in that ambient light can be prevented.
[0019]
In the illumination means of the present invention, the irradiation angle of light by the illumination means is such that the flat surface of the aluminum extruded profile is Normal direction On the other hand, it is 15 to 40 degrees, preferably 20 to 30 degrees. The angle of light irradiation on the aluminum extruded profile is the flat surface of the aluminum extruded profile. Normal direction On the other hand, there is a problem that the contrast change due to the streak hardly appears in the inspection image even if it is smaller than 15 degrees or larger than 40 degrees.
[0020]
Further, the imaging means used in the appearance inspection apparatus of the present invention is adapted to face the illumination means so as to receive the reflected light reflected by the flat surface of the aluminum extruded shape member. Normal direction It is good to arrange | position with respect to 15-40 degree | times with respect to this, Preferably it is 20-30 degree | times. The position where the imaging means is disposed is the flat surface of the aluminum extruded profile. Normal direction On the other hand, there is a problem that the contrast change due to the streak hardly appears clearly in the inspection image even if it is smaller than 15 degrees or larger than 40 degrees.
[0021]
And when this imaging means images the flat surface of an aluminum extrusion shape material as a test | inspection image, it is 10-50 mm in a parallel direction with respect to the extrusion direction of an aluminum extrusion shape material, Preferably it is 20-30 mm, Comprising: On the other hand, a range of 10 to 50 mm, preferably 20 to 30 mm in the orthogonal direction may be taken as an inspection image. If the range for imaging the flat surface of the aluminum extruded profile is less than 10 mm, the density difference between the target small area and the control small area becomes small, and the defect degree becomes difficult to match with the visual judgment. If it is larger than 50 mm, there arises a problem that the resolution of the inspection image is deteriorated.
[0022]
In addition, when it is possible to visually confirm that the aluminum extruded profile to be inspected has appearance defects such as streaks in the extrusion direction, the aluminum extruded profile is subjected to aluminum imaging when the flat surface of the aluminum extruded profile is imaged as an inspection image. About the direction orthogonal to the extrusion direction of the extruded profile, the width of the external defect is 2 to 10 times, preferably 3 to 6 times, the direction parallel to the extrusion direction. In this case, a range of 10 to 50 mm, preferably 20 to 30 mm is taken as an inspection image. If the inspection image is imaged so that the range in which the flat surface of the aluminum extruded profile in which the appearance defect is generated is in the above-mentioned range is perpendicular to the extrusion direction of the aluminum extruded profile, it is sufficiently small. Since the area can be set in the inspection image, it is possible to accurately and objectively determine whether the appearance defect generated in the aluminum extruded shape is a defective product or a non-defective product with good reproducibility. . If this width is smaller than 2 times, the inspected value is shifted due to a slight positional deviation, which causes a problem in reproducibility. On the other hand, if it is larger than 10 times, it takes a long time to measure.
[0023]
The imaging means used in the present invention is preferably a CCD camera. As this CCD camera, a camera capable of capturing an inspection image with 512 pixels or more × 484 pixels or more is preferable. When the captured inspection image is smaller than 512 pixels × 484 pixels, there is a problem that the resolution is lowered. The distance between the imaging means and the flat surface of the aluminum extruded profile to be inspected should be 80 to 250 mm. If the distance between the flat surface of the aluminum extruded profile is closer than 80 mm, the inspection area becomes too narrow. The entire aluminum extruded profile cannot be evaluated. Conversely, when the distance is longer than 250 mm, the inspection image becomes small, and the determination resolution is lowered.
The inspection image may be A / D converted by an A / D conversion device connected to a CCD camera, or A / D converted on the scanning means side described below. Such A / D conversion is preferably converted to 256 gradations. The 256 gradations are advantageous in terms of quantification of the determination.
[0024]
In the scanning means provided in the appearance inspection apparatus of the present invention, it is preferable that the small area for dividing the inspection image is a rectangular small area. In this case, the small area is 0.5 in the main scanning direction. This rectangular small region should have a width of ~ 3.0 mm, preferably 1.0-2.0 mm and 0.5-3.0 mm in the sub-scanning direction, preferably 1.0-2.0 mm. If the width of the is within the above range, the distance between the target small region and the control small region can be made relatively large, and a good product and a defective product can be correctly determined.
[0025]
In the scanning means of the present invention, when the inspection image is scanned while being divided into small areas, the first scanned small area and the next scanned small area are preferably the width dimension in the main scanning direction of the small area. It is preferable to overlap each other in the main scanning direction at a ratio of 1/2 of this, even if the band-like appearance defect is extremely narrow with respect to the band-like appearance defect generated in the extrusion direction. This can be reliably detected.
[0026]
Preferably, the scanning unit as described above is a device that can process an inspection image captured by the imaging unit as information in units of pixels.
[0027]
Then, as described above, the defect degree detection means compares the average density of the target small area in the inspection image with the average density of the control small area, and determines the value with the maximum absolute value of the density difference as the target small area. A density difference representative value indicating the maximum value in the inspection image is detected as a defect degree, and an average density calculating unit for calculating an average density for each small region in the inspection image; The average density recording unit for recording the average density for each area, the average density of the target small area in the inspection image and the average density of at least two control small areas are compared, and the absolute value of the difference between the average densities is the maximum A density difference representative value detection unit that detects the value as a representative value of the density difference of the target small area, and a density difference representative value is detected for each small area in the inspection image, and the maximum density difference representative value in the inspection image is inspected. A defect degree recording unit that records the defect degree of the image.
[0028]
Here, the defect degree detection means preferably compares the small target area with two control small areas, and the positional relationship between the two small control areas with respect to the small target area is one of them. Is positioned on a straight line with a predetermined interval in the main scanning direction with respect to the small target region, and the other is positioned on a straight line with a predetermined interval in the sub scanning direction with respect to the small target region. More preferably, the two small control areas are respectively positioned on the front side in the main scanning direction and the front side in the sub scanning direction with respect to the target small area. This positional relationship between the target small area and the two small control areas is advantageous in that the entire inspection image area can be searched.
[0029]
In addition, the interval between the target small region and the control small region preferably has an interval of 4 to 6 small regions in both the main scanning direction and the sub-scanning direction. If the interval between the target small region and the control small region is shorter than the size of the four small regions, the interval between the target small region and the control small region becomes too close, and the same part is compared with each other. If the length is longer than 5 minutes, the amount of comparison between the target small area and the control small area in the inspection image is not preferable.
[0030]
The average density calculation unit in the present invention may be a calculation device that can calculate the average density as described above, and the average density recording unit is a recording that can record the average density for each small area. In addition, the density difference representative value detection unit compares the average densities of a plurality of recorded small areas, and detects the maximum difference among the compared average density differences. In addition, the defect level recording unit records the maximum density difference value detected by the density difference representative value detection apparatus as the defect level in the inspection image. Any recording device that can do this is acceptable. These devices are independent devices that perform each function, and may be connected so that information calculated or recorded information can be communicated with each other. A device that aggregates and processes a plurality of functions may be used, and all defect degree detection means may be integrated into one personal computer (personal computer) or the like.
[0031]
Furthermore, the defective product determination means used in the present invention compares the defect degree obtained and detected by the defect degree detection means with a predetermined reference value, and inspected when the defect degree is equal to or greater than the reference value. Any material can be used as long as it can determine that the material is defective.
[0032]
Here, the reference value of the degree of defect preset in the defective product determination means is preferably set to a density difference of 20% or more, more preferably a density difference of 30% or more. For example, when the imaging means is a CCD camera and converted to 256 gradations by an A / D converter, 64 gradations means a density difference of 25%. If the reference value is set to a value smaller than the density difference of 20%, a discrepancy with the visual judgment occurs.
[0033]
By setting the standard value of the defect degree for defective product determination as described above, it is possible to correctly determine defective products with appearance defects and non-defective products that have not occurred. Since it is also possible to objectively determine a product that is difficult to distinguish between a defective product and a non-defective product, the quality of the product can be kept constant. For this reason, it is effective from the aspect of quality control in the manufacture of aluminum extruded profiles, for example, it is possible to unify the quality between manufacturing processes related to the manufacture of aluminum extruded profiles, and deliver products to customers. This is effective in clarifying quality contracts. Further, in the appearance inspection apparatus according to the present invention, the aluminum extruded profile can be discriminated as a non-defective product and a defective product by comparing the degree of defect detected from the inspection image with a reference value as described above. Since it is not necessary to record and hold the image in advance, the configuration of the appearance inspection apparatus is not complicated, the manufacturing cost can be kept low, and compared with the case where the inspection image is compared with a standard image or the like. Since the time required for the determination process is short and easy, anyone can easily perform the appearance inspection of the aluminum extruded profile regardless of the skill level of the inspector required in the conventional visual inspection.
[0034]
Further, when inspecting the flat surface of the aluminum extruded shape member using the above-described aluminum extruded shape appearance inspection apparatus, when the inspection image is picked up by the imaging means, the flat surface of the aluminum extruded shape member is halved. The inspection image is preferably imaged at intervals of 1,000 to 1 / 10,000 seconds, and if the interval at which the inspection image is captured is shorter than 1 / 10,000 seconds, the image becomes dark. When the time is longer than / 2,000 seconds, there is a problem that the image becomes rough.
[0035]
According to the appearance inspection apparatus for an aluminum extruded profile of the present invention, the aluminum extruded profile is inspected for occurrence of an appearance defect, particularly a strip-shaped appearance defect called streak. Since it is possible to correctly and objectively determine whether a material is a non-defective product or a defective product, it is possible to reduce as much as possible the determination mistakes that erroneously determine that a material should be determined as a defective product. Therefore, the quality of the extruded aluminum material to be produced can be kept constant, which is also effective in terms of quality control. In addition, a standard image is recorded in advance so that the degree of defect based on the density difference detected from the inspection image as described above is compared with a preset reference value for the degree of defect to determine whether the aluminum extruded profile is good or defective. In addition, the time required for the determination process is short compared to the case where determination is made by comparison with this standard image for each inspection. Since the manufacturing apparatus of the aluminum extruded shape member to be manufactured can be stopped, it is effective even when used in a sampling inspection while manufacturing the aluminum extruded shape member.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be specifically described based on examples.
[0037]
[Test Example 1]
FIG. 1 shows 30 samples of aluminum extruded profiles that have been determined in advance by visual inspection by humans and aluminum extruded profiles that have been determined by visual inspection to have no appearance defects. 45 samples are prepared, and the degree of defects obtained by using the appearance inspection apparatus of the present invention for each sample is graphed.
[0038]
Here, the conditions for detecting the defect degree are as follows.
First, for each sample, a red LED (wavelength 660 nm) is arranged in a light source of 180 mm × 135 mm, and the light irradiation angle is flat. Normal direction The CCD camera (247808 pixels) is further arranged so that the reflected light reflected from the flat surface of the sample is incident from the front. On a flat surface Normal direction The sample was disposed so that the distance to the flat surface of the sample was 130 mm.
[0039]
The reflected light emitted from the light source and reflected by the flat surface was received by a CCD camera, converted into 256 gradations by an A / D converter, and an inspection image (20 mm × 40 mm) was taken. The obtained inspection image (20 mm × 40 mm) is 10 pixels (1.5 mm) in the main scanning direction orthogonal to the extrusion direction of the sample (aluminum extruded profile) and 10 pixels in the sub-scanning direction parallel to the extrusion direction. (1.5 mm) is divided into small square areas, and the scan of the inspection image in the main scanning direction is performed by dividing the small area to be scanned as described above with the adjacent small area previously scanned in the main scanning direction. Scanning was performed so as to overlap by half (half) of the width of the small region.
[0040]
Next, the average density was calculated for the rectangular small areas obtained by the scanning, and the average density was recorded for each small area in the inspection image. Then, attention is paid to one small area in the inspection image, and the average density of the small area of interest is determined as the small area of interest with an interval of six small areas on the front side in the main scanning direction with respect to the small area of interest. A difference in average density is obtained by comparison with the average density of the reference small areas in the main scanning direction arranged on a straight line, and there is an interval corresponding to the six small areas on the front side in the sub-scanning traveling direction. The difference in average density was obtained by comparing with the average density of the sub-scanning direction control small areas arranged in a line with the small area. Of the average density differences, the larger absolute value is used as the density difference representative value of the target small area. In the same manner as described above, the density difference representative value was obtained for all the small areas in the inspection image, and the density difference representative value having the maximum value in the inspection image was obtained as the defect degree of the inspection image.
[0041]
As can be seen from FIG. 1, the degree of defect obtained for each sample as described above is distributed in two poles with a defect degree of 80 (concentration difference of 31.25%) as a boundary. Samples that are judged to have an appearance defect (defective product) by visual inspection are distributed, and samples that are judged to have no visual defect (good product) by visual inspection are distributed in a smaller defect degree. Therefore, it is understood that the appearance inspection of the aluminum extruded shape can be performed by setting the vicinity of the
[0042]
[Example 1]
2 to 4 show an appearance inspection apparatus for an aluminum extruded profile according to Example 1 to which the present invention is applied in order to inspect a flat surface of an aluminum extruded profile.
An appearance inspection apparatus 1 according to the present invention includes a
[0043]
In the scanning means, as shown in FIG. 5, the inspection image is respectively 10 pixels (1.5 mm) × 10 pixels in the main scanning direction MD perpendicular to the extrusion direction and the sub-scanning direction SD parallel to the extrusion direction. Is divided into a large number of
[0044]
Further, as shown in FIG. 5, the defect degree detecting means includes an average density calculating unit that calculates an average density for each
[0045]
Further, the defective product determination means stores the value of the
[0046]
【The invention's effect】
According to the appearance inspection apparatus and appearance inspection method for an aluminum extruded shape of the present invention, the aluminum extruded shape is inspected for the presence or absence of defects occurring in the aluminum extruded shape, in particular, strip-shaped appearance defects called streaks. It is possible to easily and objectively determine whether the inspected aluminum extruded shape is a good product or a defective product.
[Brief description of the drawings]
FIG. 1 is a graph showing the degree of defect between an aluminum extruded shape determined to be defective by visual inspection and an aluminum extruded shape determined to be good.
FIG. 2 is an explanatory side view showing an outline of an appearance inspection apparatus for an aluminum extruded profile according to Embodiment 1 of the present invention.
FIG. 3 is an explanatory front view of FIG. 2;
4 is an explanatory plan view of FIG. 2; FIG.
FIG. 5 is an explanatory diagram showing a positional relationship between a scanning method in the scanning means mounted in the appearance inspection apparatus in FIG. 2 and a small area of interest and a small contrast area in the defect degree detection means.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Appearance inspection apparatus, 2 ... Aluminum extrusion shape material, 3 ... Vacuum holding machine, 4 ... Illumination, 5 ... CCD camera, 6 ... Personal computer, 7 ... Area | region, 7a ... Small attention area, 7b, 7c ... Control small area | region, MD: main scanning direction, SD: sub-scanning direction, x, y: comparison interval.
Claims (16)
アルミニウム押出形材の平坦面に光を照射する照明手段と、この平坦面を撮像して検査画像を得る撮像手段と、上記検査画像を押出方向に直交する主走査方向及び押出方向に平行な副走査方向にそれぞれ所定の幅を有する小領域に分割し、この分割された小領域に従って検査画像内を主走査方向及び副走査方向に走査する走査手段と、上記走査手段により得られた走査結果から検査画像の欠陥度を検出する欠陥度検出手段と、上記欠陥度を予め定めた基準値と比較し、欠陥度が基準値以上の場合にアルミニウム押出形材を不良品と判定する不良品判定手段とを備えており、
上記欠陥度検出手段が、
検査画像内の小領域毎の平均濃度を算出する平均濃度算出部と、
小領域毎の平均濃度を記録する平均濃度記録部と、
検査画像内のいずれか１つの小領域に注目して、この注目小領域の平均濃度と注目小領域から主走査方向に同一直線上に位置し、かつ、注目小領域との間に所定の小領域分の間隔を有する第１の対照小領域の平均濃度とを比べて第１の平均濃度の差を求めると共に、注目小領域の平均濃度と注目小領域から副走査方向に同一直線上に位置し、かつ、注目小領域との間に所定の小領域分の間隔を有する第２の対照小領域の平均濃度とを比べて第２の平均濃度の差を求め、得られた第１及び第２の平均濃度の差の絶対値が最大の値を上記注目小領域の濃度差代表値として検出する濃度差代表値検出部と、
走査終了後に検査画像内の小領域毎に検出された濃度差代表値からその最大値を検査画像の欠陥度として記録する欠陥度記録部と、
を備えていることを特徴とするアルミニウム押出形材の外観検査装置。It is an appearance inspection device for inspecting a flat surface of an aluminum extruded profile made of aluminum or an aluminum alloy,
Illumination means for irradiating light onto the flat surface of the aluminum extruded shape member, imaging means for imaging the flat surface to obtain an inspection image, and the inspection image obtained by subtracting the inspection image in a main scanning direction and a direction parallel to the extrusion direction. From the scanning results obtained by the scanning means obtained by dividing the inspection image in the main scanning direction and the sub-scanning direction according to the divided small areas by dividing into small areas each having a predetermined width in the scanning direction. Defect degree detection means for detecting the defect degree of the inspection image, and a defective article determination means for comparing the defect degree with a predetermined reference value and determining that the aluminum extruded profile is defective when the defect degree is equal to or greater than the reference value And
The defect degree detecting means is
An average density calculator for calculating an average density for each small area in the inspection image;
An average density recording section for recording the average density for each small area;
Paying attention to any one of the small areas in the inspection image, the average density of the small area of interest is located on the same line in the main scanning direction from the small area of interest, and a predetermined small area between the small area of interest. Comparing the average density of the first control small area having an interval of the area to obtain the difference of the first average density, the average density of the target small area is located on the same straight line from the target small area in the sub-scanning direction. and, and, of interest determines the difference between the second average density than the average density of the second control small area having a predetermined distance of a small area fraction between the small area, the first and second obtained A density difference representative value detection unit that detects a value having a maximum absolute value of the difference between the average densities of the two as a density difference representative value of the small region of interest;
A defect degree recording unit for recording the maximum value as the defect degree of the inspection image from the density difference representative value detected for each small region in the inspection image after the end of scanning;
An apparatus for inspecting the appearance of an extruded aluminum member characterized by comprising:
照明手段によりアルミニウム押出形材の平坦面に光を照射し、この光が照射された平坦面から撮像手段により検査画像を撮像し、次いで走査手段により上記検査画像を押出方向に直交する主走査方向及び押出方向に平行な副走査方向にそれぞれ所定の幅を有する小領域に分割すると共に、この分割された小領域に従って検査画像内を主走査方向及び副走査方向に走査し、この走査手段により得られた走査結果から欠陥度検出手段により検査画像の欠陥度を検出し、不良品判定手段により上記走査手段で検出された欠陥度を予め定めた基準値と比較し、欠陥度が基準値以上の場合にアルミニウム押出形材を不良品と判定するに際し、
上記欠陥度検出手段では、その平均濃度算出部で検査画像内の小領域毎の平均濃度を算出し、この算出された小領域毎の平均濃度を平均濃度記録部に記録すると共に、濃度差代表値検出部において、検査画像内のいずれか１つの小領域に注目して、この注目小領域の平均濃度と注目小領域から主走査方向に同一直線上に位置し、かつ、注目小領域との間に所定の小領域分の間隔を有する第１の対照小領域の平均濃度とを比べて第１の平均濃度の差を求めると共に、注目小領域の平均濃度と注目小領域から副走査方向に同一直線上に位置し、かつ、注目小領域との間に所定の小領域分の間隔を有する第２の対照小領域の平均濃度とを比べて第２の平均濃度の差を求め、得られた第１及び第２の平均濃度の差の絶対値が最大の値を上記注目小領域の濃度差代表値として検出し、走査終了後に上記検査画像内の小領域毎に検出された濃度差代表値からその最大値を検査画像の欠陥度として欠陥度記録部に記録することを特徴とするアルミニウム押出形材の外観検査方法。It is an appearance inspection method for inspecting a flat surface of an aluminum extruded profile made of aluminum or an aluminum alloy,
Light is irradiated on the flat surface of the aluminum extruded shape member by the illumination means, an inspection image is picked up by the image pickup means from the flat surface irradiated with this light, and then the main scanning direction orthogonal to the extrusion direction by the scanning means. The image is divided into small areas each having a predetermined width in the sub-scanning direction parallel to the extrusion direction, and the inspection image is scanned in the main scanning direction and the sub-scanning direction according to the divided small areas. The defect degree of the inspection image is detected by the defect degree detection means from the obtained scanning results, the defect degree detected by the scanning means by the defective product determination means is compared with a predetermined reference value, and the defect degree is equal to or higher than the reference value. In determining the aluminum extruded profile as defective,
In the defect degree detection means, the average density calculation unit calculates the average density for each small region in the inspection image, records the calculated average density for each small region in the average density recording unit, and displays the density difference representative. In the value detection unit, paying attention to any one small area in the inspection image, the average density of the target small area and the target small area are located on the same straight line in the main scanning direction, and A first average density difference is obtained by comparing with the average density of the first control small area having a predetermined small area interval between them, and the average density of the target small area and the target small area in the sub-scanning direction. A difference in the second average density is obtained by comparing with the average density of the second control small area that is located on the same straight line and has a predetermined small area distance from the small area of interest. the first and the target small area absolute value of the maximum value of the difference between the second average concentration Detecting as a density difference representative value, and recording the maximum value from the density difference representative value detected for each small area in the inspection image as a defect degree of the inspection image in the defect degree recording unit after scanning is completed. Appearance inspection method for aluminum extrusions.
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