JP2004301752A

JP2004301752A - Method and apparatus for detecting surface defect

Info

Publication number: JP2004301752A
Application number: JP2003096728A
Authority: JP
Inventors: Akinori Tanimoto; 明徳谷本
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2003-03-31
Filing date: 2003-03-31
Publication date: 2004-10-28

Abstract

PROBLEM TO BE SOLVED: To provide an optical surface defect detection method and an optical surface defect detector for reliably detecting even minute defects with high S/N ratio. SOLUTION: The method and apparatus for detecting surface have a process for setting a strip of inspection region on the surface of a magnetic tape 12, irradiating an irradiation region including the strip of inspection region with beams of light La, Lb from an inspection light irradiator, forming strip of long light source image regions 18A, 18B in the direction of the width of a tape adjacent to both the outside of the strip of inspection region, further inclining the light axis of a camera 22 of a CCD line camera with an inclination angle of β (0<β≤10°) for setting to a first virtual plane 16 including a center line in the width direction of the light source image region while orthogonally crossing the surface of the magnetic tape, allowing the irradiation light axis of the beams of light La, Lb to pass the mirror image position of the CCD line camera, setting an inclination angle α between a set straight line passing the center in the width direction of the strip of inspection region from a light projection opening and a camera symmetrical light axis 23 of a camera light axis to 0<α<25°, and outputting a defect detection signal in a judging apparatus 24 when a reception signal by the CCD line camera becomes at least a constant level. COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、光沢を有する材料、例えば磁気テープ等の磁気記録媒体の磁性層表面やバックコート層表面、圧延材、研磨した金属等の表面、光反射率の高い樹脂の表面、ガラス表面、等の、各種材料の表面における非常に微細な塗布時の欠陥、付着物、押し傷等の表面欠陥を検出することができるようにした表面欠陥検出方法及び装置に関する。
【０００２】
【従来の技術】
従来の磁気記録媒体、例えば磁気テープの検査方法は、磁気ヘッドにより信号を磁気テープに記録し、且つ、再生し、その再生レベルから磁気テープの欠陥の有無を判定するものが一般的であった。
【０００３】
このような検査方法は、磁気記録媒体の傷と再生信号に表われる実害との相関が大きいので、最も信頼性の高い検査方法とされていた。
【０００４】
この従来の磁気記録媒体の検査方法は、具体的には、磁気記録媒体を高速で走行させて多チャンネル固定磁気ヘッドを信号再生ヘッドとして使用することにより、高速、且つ、高能率に検査するようにしていた。
【０００５】
このような磁気記録媒体の欠陥検査の分野においては、近年の、磁気記録媒体における記録情報の高密度化に対応するために、従来よりも微細・微小な欠陥までも検出可能な高分解能が要求されている。
【０００６】
ところが、上記のような多チャンネル固定磁気ヘッドによる磁気記録媒体表面の欠陥検査方法では、その磁気ヘッドの製作技術上の限界から、検出の分解能を高くすることが容易でなく、この分解能は、磁気記録媒体幅方向で５０μｍ程度が実用上の限界であり、装置の条件を調整して熟練者が検査を行なったとしても２０μｍ程度が限界であった。しかも、チャンネル数が多くなるほど装置が大掛かりとなり、コスト増大の原因となっていた。
【０００７】
又、上記のような多チャンネル固定磁気ヘッドを利用した場合よりも高い検査分解能を得られる磁気記録媒体検査方法としては、特許文献１あるいは特許文献２に開示されるような、光学的に磁気記録媒体の表面欠陥を検査する方法がある。
【０００８】
特許文献１の磁気テープ検査方法は、赤色ＬＥＤ（発光ダイオード）光源から照射した光を磁気テープ表面で反射させ、これをセンサヘッドで受光・検出するに際して、センサヘッドの受光軸方向を磁気テープの主面法線方向に対して一定角度傾けることにより、欠陥部分の信号を高ＳＮで検出できるようにしたものである。
【０００９】
又、特許文献２の磁気記録媒体の表面検査方法は、ハロゲン光を磁性層表面に照射して、その反射光をＣＣＤカメラで受光・検出するに際し、投受光角度を特定範囲とし、更に入射光の光軸位置を反射点から偏倚させることにより、信号出力レベルを最大、システムノイズを最小とするようにしたものである。
【００１０】
更に、特許文献３の磁気ディスクの光学的検査方法は、磁気ディスク面の垂直線に対して傾斜角を有する方向から光線を入射し、ディスクの面上方に散乱された光を結像して暗視野像を得ると共に、該暗視野像を受光素子を列設したラインセンサで受光して散乱光強度を測定するものであって、入射する光線をディスク面の検査領域を走査せしめ、ラインセンサの１又は複数の素子が所定レベル以上の強度の信号を所定時間以上取得したとき欠陥部として検出するようにしたものである。
【００１１】
特に、近年の高密度記録技術を駆使した磁気記録媒体装置等では、例えば磁性層塗布時の欠陥、付着物、押し傷等の欠陥の場合は、その高さが低く、全体としてなだらかな形状であるため再生信号に及ぼす影響は比較的ゆるやかではあるものの、欠陥が多く集中するとエラーレートが増加する。又、その大きさが１０〜２０μｍの場合には再生信号にエラーレートの増加が認められる。このような大きさが１０〜２０μｍ程度の欠陥を安定して、且つ、簡単に検出できる方法や装置が望まれている。
【００１２】
【特許文献１】
特開平８−２０１３０９号公報
【特許文献２】
特開平８−２３３５６０号公報
【特許文献３】
特開平１０−１４３８０１号公報
【００１３】
【発明が解決しようとする課題】
しかしながら、上記特許文献１に開示される方法は、ＬＥＤ光源の光量が少なく、又全反射方式の検出であるため大きな異物等の検出は可能であるものの、大きさが１０〜２０μｍの欠陥を安定して検出することは困難であった。
【００１４】
又、特許文献２の磁気記録媒体の表面検査方法も、全反射方式の検出であるために、大きさが１０〜２０μｍの欠陥を安定して検出することが困難であったという問題点がある。
【００１５】
更に、特許文献３の磁気ディスクの光学的検査方法では、照射光による直接照射領域からの散乱光を結像して暗視野像を得るようにしているので、微小欠陥に対しては、欠陥部からの散乱光の強い波光値が低いレベルであり、ＳＮ比が低いという問題点がある。
【００１６】
又、上記各特許文献に開示されているような表面欠陥検査方法は、磁気記録媒体の表面以外の分野、例えば圧延過程におけるストリップ表面の欠陥検査、メッキ表面の欠陥検査、ガラス基板等のガラス製品の表面欠陥検査、機械加工工程における研磨金属表面の検査等に用いられているが、いずれの場合でも、欠陥部での散乱光とそのバックグラウンド光との比が小さいため、検出が困難であることが多かった。
【００１７】
この発明は、上記従来の問題点に鑑みてなされたものであって、微小欠陥でも高ＳＮ比で確実に検出することができるようにした光学的な、表面欠陥検出方法及び装置を提供することを目的とする。
【００１８】
【課題を解決するための手段】
本発明者は、磁気テープ等の表面の検査方法について鋭意研究を重ね、検査対象物の表面の垂線に対して一定角度傾斜したカメラ光軸のカメラによる検査領域、及び、この領域から僅かにずらして、光出射口の鏡像が位置する光源像領域を設定し、該領域よりも暗い領域、即ちバックグラウンドの光量が小さい領域での、表面欠陥からの散乱光をカメラにより受光し、高ＳＮ比で表面欠陥を検出できることが分かった。又、このとき、表面欠陥の種類によっては磁気テープの走行方向によって検出感度が異なり、検出できない場合があり、これを、検査領域の両側を２つの光出射口からの光で照射することによって解決できることが分った。
【００１９】
即ち、以下の本発明により上記目的が達成可能となる。
【００２０】
（１）検査対象物表面に、カメラによる検査領域を設定し、且つ、前記検査対象物の表面に、複数の光出射口からの光を入射したときの、前記検査領域を含む該光による照射領域中であって、前記検査領域の外側に隣接し、且つ、少なくとも該検査領域を間にする２個所の位置に、前記複数の光出射口の鏡像が位置するように、該光出射口を設定し、前記検査領域からの散乱光を前記カメラにより受光して、受光信号に変換し、この受光信号が前記検査領域の無欠陥部からの受光信号の強度よりも一定値以上大きいとき、前記検査対象物の表面欠陥として検出することを特徴とする表面欠陥の検出方法。
【００２１】
（２）検査対象物表面に、カメラによる検査領域を設定し、且つ、この検査領域の中心を通るカメラ光軸を、前記検査対象物表面の法線に対する傾斜角βが０＜β≦１０°となるように傾けて設定し、前記検査対象物の表面に、２つの光出射口から光を入射したときの、該光による、前記検査領域を含む照射領域中であって、前記検査領域の両外側に隣接する位置に、前記２つの出射口の鏡像が位置するように、該２つの光出射口を設定し、且つ、これらの光出射口の中心と前記検査領域の中心とを通る設定直線を、前記法線を中心とする前記カメラ光軸のカメラ対称光軸から両側に、それぞれ傾斜角αを０＜α＜２５°に設定し、前記検査領域からの散乱光を前記カメラにより受光して、受光信号に変換し、この受光信号が前記検査領域の無欠陥部からの受光信号の強度よりも一定値以上大きいとき、前記検査対象物の表面欠陥として検出することを特徴とする表面欠陥の検出方法。
【００２２】
（３）前記傾斜角αを、０＜α＜５°としたことを特徴とする（２）に記載の表面欠陥の検査方法。
【００２３】
（４）前記傾斜角αを、５°≦α＜１０°、１０°≦α＜１５°、又は、１５°≦α＜２５°のいずれかに設定したことを特徴とする（２）に記載の表面欠陥の検査方法。
【００２４】
（５）前記検査対象物の表面における、前記光出射口の鏡像が位置する２つの光源像領域の、前記検査領域からの隣接方向の全長をＷとしたとき、前記光源像領域の前記隣接方向中心位置から前記検査領域までの距離Ｄを、Ｗ／２＜Ｄ≦３Ｗ／２としたことを特徴とする（２）乃至（４）のいずれかに記載の表面欠陥の検出方法。
【００２５】
（６）前記光を、前記カメラにより前記光出射口の鏡像が位置する光源像領域が直線帯形状となると共に、照射光軸が、前記光源像領域の幅方向中心線と平行な平面内にあるように設定し、且つ、前記検査領域が、前記直線状の光源像領域と平行な直線帯形状になると共に、前記カメラ光軸が、前記法線に対して、前記光出射口を通る前記設定直線と反対側に傾斜角βで傾斜され、前記直線帯形状の検査領域における幅方向中心線を含む平面内にあるように設定したことを特徴とする（２）乃至（５）のいずれかに記載の表面欠陥の検出方法。
【００２６】
（７）前記光源像領域及び検査領域それぞれの幅方向中心線と平行、且つ、検査対象物表面と垂直な第１の仮想平面に対して、この第１の仮想平面及び前記検査対象物表面に垂直な第２の仮想平面内で、前記２本の光の照射光軸を前記カメラ対称光軸に対して、その両側でそれぞれ傾斜角αに傾け、且つ、前記カメラ光軸を、照射光軸とは反対側に前記第１の仮想平面に対して傾斜角βに傾けて設定したことを特徴とする（６）に記載の表面欠陥の検出方法。
傾斜角βに傾けて設定したことを特徴とする表面欠陥の検出方法。
【００２７】
（８）前記検査対象物が帯状材のとき、前記光源像領域及び検査領域を、該帯状材を幅方向に横断する直線帯形状に設定すると共に、該帯状材を長手方向に走行させつつ表面欠陥を検出することを特徴とする（６）又は（７）に記載の表面欠陥の検出方法。
【００２８】
（９）前記カメラをＣＣＤラインカメラとし、このＣＣＤラインカメラの複数の入射光軸を含む入射光軸面を、前記検査領域の幅方向中心線を含む平面と一致して設定したことを特徴とする（６）、（７）又は（８）に記載の表面欠陥の検出方法。
【００２９】
（１０）検査対象物を、その少なくとも一部の表面が、厚さ方向定位置で検査位置を通過又は検査位置に静止するように支持する支持装置と、前記検査位置における前記表面に検査領域が設定され、且つ、カメラ光軸が、前記表面での法線に対して、傾斜角βが、０＜β≦１０°となるように傾けて配置され、入射光強度に比例する強度の受光信号を出力するカメラと、前記検査対象物の表面に、２つの光出射口から光を照射したときの、該光による、前記検査領域を含む照射領域中であって、前記検査領域の両外側に隣接する位置に、該２つの光出射口の鏡像が位置する２つの光源像領域を形成し、且つ、これらの光出射口の中心と前記検査領域の中心とを通る直線が、前記カメラ光軸の、前記法線を中心とするカメラ対称光軸から両側に、それぞれ傾斜角αが０°＜α＜２５°に設定された検査光照射装置と、前記カメラからの前記受光信号の強度が前記検査領域における無欠陥部分からの入射光による受光信号の強度よりも一定値以上大きいとき欠陥検出信号を出力する判定装置と、を有してなる表面欠陥検出装置。
【００３０】
（１１）前記検査光照射装置における前記傾斜角αを、０＜α＜５°としたことを特徴とする（１０）に記載の表面欠陥の検査装置。
【００３１】
（１２）前記検査光照射装置における前記傾斜角αを、５°≦α＜１０°、１０°≦α＜１５°、又は、１５°≦α＜２５°のいずれかに設定したことを特徴とする（１０）に記載の表面欠陥の検査装置。
【００３２】
（１３）前記カメラは、前記検査領域から見て前記光源像領域の中心に向かう方向における該光源像領域の全長をＷとしたとき、前記光源像領域の前記方向の中心位置から前記検査領域までの距離Ｄが、Ｗ／２＜Ｄ≦３Ｗ／２となるように設定されたことを特徴とする（１０）乃至（１２）のいずれかに記載の表面欠陥検出装置。
【００３３】
（１４）前記検査光照射装置は、前記光源像領域が直線帯形状となると共に、前記光の照射光軸が、前記光源像領域の幅方向中心線と平行な平面内にあるように設定され、且つ、前記カメラは、前記検査領域が、前記直線帯形状の光源像領域と平行な直線帯形状になると共に、前記カメラ光軸が、前記法線に対して、前記光出射口を通る前記設定直線と反対側に傾斜角βで傾斜され、前記直線帯形状の検査領域における幅方向中心線を含む平面内にあるように設定されたことを特徴とする（１０）乃至（１３）のいずれかに記載の表面欠陥検出装置。
【００３４】
（１５）前記検査光照射装置は、前記光源像領域及び検査領域それぞれの幅方向中心線と平行、且つ、検査対象物表面と垂直な第１の仮想平面に対して、この第１の仮想平面及び前記検査対象物表面に垂直な第２の仮想平面内で、前記２本の光出射口を通る前記設定直線が傾斜角αに傾けて設けられ、且つ、前記カメラは、前記カメラ光軸を、前記設定直線とは反対側に傾斜角βに傾けて設けられたことを特徴とする表面欠陥検出装置。
【００３５】
（１６）前記検査対象物が帯状材であり、前記支持装置は、該帯状材を長手方向に走行させる構成とされ、前記検査光照射装置及び前記カメラは、前記光源像領域及び検査領域が、該帯状材を幅方向に横断する直線帯形状となるように設定されたことを特徴とする（１４）又は（１５）に記載の表面欠陥検出装置。
【００３６】
（１７）前記カメラはＣＣＤラインカメラであり、このＣＣＤラインカメラの複数の入射光軸を含む入射光軸面が、前記検査領域の幅方向中心線を含む平面と一致して設定されたことを特徴とする（１４）、（１５）又は（１６）に記載の表面欠陥検出装置。
【００３７】
上記のように、検査光の照射光軸及びカメラの検査領域とそのカメラ光軸を設定すると、高ＳＮ比で欠陥部からの散乱光に基づく受光信号を得ることができる。
【００３８】
【発明の実施の形態】
以下本発明の実施の形態の例を図面を参照して詳細に説明する。この実施の形態の例は、検査対象物を磁気記録媒体としたものである。
【００３９】
この実施の形態の例に係る表面欠陥検出装置１０は、図１に示されるように、磁気記録媒体である磁気テープ１２の検査部１２Ａを直平面状に支持する支持装置１４と、この支持装置１４の、前記直平面状に支持される磁気テープ１２の表面との法線１６Ａ（図２参照）を含み、且つ、磁気テープ１２を幅方向に横断する第１の仮想平面１６（図２参照）と磁気テープ１２の表面との交線上に設定された帯状検査領域２２Ａの幅方向中心線２２Ｂ（図４参照）を通るカメラ光軸２１が、前記第１の仮想平面１６に対して傾斜角βが、０＜β≦１０°となるように傾けて配置されたＣＣＤラインカメラ２２と、前記帯状検査領域２２Ａを含む照射領域３０に、２つの光照射口２５Ａ、２５Ｂから２本の光Ｌａ、Ｌｂを照射し、照射領域３０内で、帯状検査領域２２Ａから見てその幅方向両外側（図２において左側及び右側）に隣接して接近した位置に、磁気テープ１２を幅方向に横断する２本の帯状の光源像領域（光Ｌａ、Ｌｂの光出射口２５Ａ、２５Ｂの鏡像が位置する領域）１８Ａ、１８Ｂを形成する検査光照射装置２０と、前記ＣＣＤラインカメラ２２からの受光信号の強度が、前記帯状検査領域２２Ａにおける無欠陥部分からの入射光による受光信号の強度よりも一定値以上大きいとき欠陥信号を出力する判定装置２４と、を備えて構成されている。
【００４０】
前記傾斜角βは、前記法線１６Ａを含み、且つ、前記第１の仮想面１６と検査部１２Ａの表面とに直角な第２の仮想平面１７内での角度である。
【００４１】
前記カメラ光軸２１の、前記第１の仮想平面１６を対称面とするカメラ対称光軸２３は、前記第１の仮想平面１６に対して第２の仮想平面１７内で、カメラ光軸２１と反対側に角度β傾斜している。前記光出射口２５Ａ、２５Ｂを通る２照射光軸１９Ａ、１９Ｂは、前記検査部１２Ａの表面を対称面とする前記ＣＣＤラインカメラ２２の鏡像を観察するための仮想位置２２Ｍと、光出射口２５Ａ、２５Ｂとを結ぶように設定され、且つ、検査光照射装置２０の光出射口２５Ａ、２５Ｂは、その中心と前記帯状検査領域２２Ａの幅方向中心線２２Ｂとを通る２本の設定直線２９Ａ、２９Ｂが前記カメラ対称光軸２３に対してその両側から傾斜角αで交わるように設定されている。
【００４２】
前記支持装置１４は、図３に示されるように、平行に配置された一対の円筒状ガイド部材２６Ａ、２６Ｂを備え、これら円筒状ガイド部材２６Ａ、２６Ｂの、磁気テープ１２が巻き掛けられる範囲では、多数のエア吹出し細孔２７が形成され、ここから圧縮空気を吹出すことによって円筒状ガイド部材２６Ａ、２６Ｂに巻き掛けられる磁気テープ１２を、ガイド部材表面とは非接触の状態で且つ磁気テープ１２を直平面状に維持しつつ走行させるようにしている。なお、この直平面状に維持されている磁気テープ１２の部分が検出部１２Ａである。
【００４３】
前記支持装置１４は、磁気テープ１２を直平面状に維持しつつ走行させることができるものであればよく、磁気テープに対して非接触なものに限定されない。
【００４４】
前記光出射口２５Ａ、２５Ｂの中心と、帯状検査領域２２Ａの幅方向中心とを通る前記設定直線２９Ａ、２９Ｂは、前記カメラ対称光軸２３及び帯状検査領域２２Ａの幅方向中心線を含むカメラ対称光軸２３Ａに対して、前記ＣＣＤラインカメラ２２のカメラ光軸２１側及びその反対側に傾斜角αだけ傾けて配置されている。この傾斜角αは、０＜α＜２５°の範囲で後述のように設定される。
【００４５】
なお、前記照射光軸１９Ａ、１９Ｂ及びカメラ光軸２１は、共に磁気テープ１２の幅方向に連続して複数あり、図４に示されるように、これらによって照射光軸面１９Ｃ及びカメラ光軸面２１Ａが形成される。カメラ光軸面２１Ａは、前記仮想平面１６に対して傾斜角βで傾斜され、照射光軸面１９Ｃは、光源像領域１８Ａ、１８Ｂの幅方向中心線１８Ｃを通って形成されている。
【００４６】
又、図５に示されるように、磁気テープ１２の走行方向から見て光Ｌａ、Ｌｂとカメラ光軸２１は、磁気テープ１２に対して垂直かつ重なり合うように設定されている。
【００４７】
前記検査光照射装置２０は、図１に示されるように、ハロゲンランプ２８と、その光を２本の光Ｌａ、Ｌｂとして導くための光ファイバー束２８Ａ、２８Ｂとを備えて構成され、前記支持装置１４により直平面状に支持された磁気テープ１２の表面を照射して、前述のように、磁気テープ１２をその幅方向に横断する前記２本の帯状の光源像領域１８Ａ、１８Ｂを含む照射領域３０（図４参照）を形成するようにされている。この照射領域３０は、前記２つの光源像領域１８Ａ、１８Ｂと、それぞれの両側の、光源像が観察されないが光Ｌａ、Ｌｂが照射される光源像外側領域１８Ｄ（図４参照、詳細後述）とからなっている。前記帯状検査領域２２Ａは２本の帯状の光源像領域１８Ａ、１８Ｂの両方に付属する光源像外側領域１８Ｄにあることになる。
【００４８】
ここで、前記帯状の光源像領域１８Ａ、１８Ｂの幅方向中心線１８Ｃに対する帯状検査領域２２Ａの距離Ｄは、図２に示されるように、前記光源像領域１８Ａ、１８Ｂの幅をＷとしたとき、Ｗ／２＜Ｄ≦３Ｗ／２の範囲とする。Ｄ≦Ｗ／２の場合は、強い照射光が、外乱光として入射することがある。Ｄ＞３Ｗ／２とすると帯状検査領域２２Ａは、前記光源像外側領域１８Ｄ内での光源像領域１８Ａ、１８Ｂから離れた位置となるので照射光が弱く、従って、この領域から得られる散乱光が弱くなる。
【００４９】
前記判定装置２４は、前記磁気テープ１２の長手方向の一定間隔、即ち、所定のライン走査周期で、テープ幅方向の分解能に対応する位置毎に、ＣＣＤラインカメラ２２から同ＣＣＤラインカメラ２２に入射する光エネルギーに対応して輝度信号を受けて、この輝度信号と、上記帯状検査領域２２Ａにおける無欠陥部分での輝度信号のレベル（ローレベル）とを比較して、一定値以上の差があるとき、欠陥信号を出力するようにされている。
【００５０】
詳細には、ＣＣＤラインカメラ２２からは、入射する光エネルギーが蓄積して得られた積分値が輝度信号として出力され、判定装置２４では、前記輝度信号を、比較器２４Ａで予め設定されている、前記ローレベルの輝度に所定値を加えた輝度の信号（比較値）と比較して、入力した輝度信号が比較値よりも大きい場合に、欠陥信号を出力するようにされている。
【００５１】
上記のような表面欠陥検出装置１０により、磁気テープ１２の表面の欠陥を検出する場合、帯状検査領域２２Ａが、２本の光Ｌａ、Ｌｂによる光源像領域１８Ａ、１８Ｂに対して、これらの間に、且つ、隣接して設定されているので、磁気テープ１２表面における欠陥のない部分ではＣＣＤラインカメラ２２で得られる輝度信号はほとんど黒レベルに近く、磁気テープ１２の平面性や光学系に起因して輝度が上がる度合が少ない。
【００５２】
更に詳細には、図４にも示されるように、上記帯状検査領域２２Ａは、２本の光Ｌａ、Ｌｂによる光源像領域１８Ａ、１８Ｂの間に隣接する光源像外側領域１８Ｄに含まれ、且つ、上述のように、カメラ光軸２１のカメラ対称光軸２３に対して傾斜角αの設定直線２９Ａ、２９Ｂ上に光出射口２５Ａ、２５Ｂがあるので、光Ｌａ、Ｌｂの前記光源像領域１８Ａ、１８Ｂでの正反射光はＣＣＤラインカメラ２２に入射することがない。
【００５３】
一方、磁気テープ１２の表面に何らかの欠陥がある場合は上記帯状検査領域２２Ａで照射光が散乱し、散乱光の一部がＣＣＤラインカメラ２２に入射する。
【００５４】
前述のように、光源像外側領域１８Ｄでの磁気テープ１２の輝度はほとんど黒レベルに近いので、欠陥部からの散乱光がこの黒レベルに対して高い輝度となり、結果として検出信号のＳＮＲが大幅に向上される。これに対して、従来のように帯状光源像領域と検査領域とを一致させた場合、欠陥のない部分の輝度が高く欠陥部の輝度が立ち下がってある程度の輝度差は得られるものの、欠陥検出の波高値が低いため本発明のような高いＳＮＲは得られない。
【００５５】
ここで、前記傾斜角αの設定、磁気テープ１２表面の欠陥の種類及び２本の光Ｌａ、Ｌｂの関係について説明する。
【００５６】
図６に示されるように、押し疵等の凹部３２が磁気テープ１２の表面にあるとき、この凹部３２からの散乱光量は少なくＳＮ比のレベルがかなり小さく、且つ、特異的に散乱光量の多い角度が磁気テープ１２表面の法線１６Ａ又は第１の仮想平面１６に接近している。従って、ＳＮ比のレベルを高くするためには、傾斜角αを５°以下且つ可能な限り０°に近づける。
【００５７】
傾斜角αが０に近くなると、光Ｌａ、Ｌｂの照射光軸１９Ａ、１９Ｂとカメラ対称光軸２３とが平行且つ接近するので、磁気テープ１２がその走行時にばたつくと誤検出を生じる。従って、検査時の磁気テープ１２の平担性を保つべく、走行テンション、速度変動、テープガイド形状等を調整するとよい。
【００５８】
このように調整しても、凹部３２の形状がテープ走行方向に非対称の場合、例えば図７（Ａ）に示されるような右上りの傾斜面３２Ａと左上りの傾斜面３２Ｂとでは、散乱光の反射方向が異なるので、テープ走行方向によって、一方が検出できても他方が検出できない、あるいは、検出感度が低くなってしまうことがある。
【００５９】
この実施の形態の例では、帯状検査領域２２Ａの両側に、２本の光Ｌａ、Ｌｂによる光源像領域１８Ａ、１８Ｂを設定していて、２つの光源像領域１８Ａ、１８Ｂの間が両者の外側の光源像外側領域１８Ｄとなっているので、凹部３２が帯状検査領域２２Ａにあるとき、その両側から斜めに照射されることになる。
【００６０】
従って、上記のような傾き方向の異なる傾斜面３２Ａ、３２Ｂでは、いずれの場合も散乱光がＣＣＤラインカメラ２２に入射して欠陥を検出することができる。図７（Ａ）の場合は、光Ｌａ、図７（Ｂ）の場合は光Ｌｂによる散乱光が得られる。
【００６１】
又、図８に示されるように、磁気テープ１２の表面に塗布時の欠陥、付着物等の高さが高く、且つ大きい凸部３４があるときは、該凸部３４の側面３４Ａからの比較的大きい散乱光量を得ることができる。
【００６２】
凸部３４のような欠陥の場合は、右上りと左上りのどちらの傾斜面（側面）からも十分な反射光が得られるので、光は１本でもよい。図８の符号γ、γ´は、前記光Ｌａ、Ｌｂが側面３４Ａにより反射されてＣＣＤラインカメラ２２に入射する場合の、側面３４Ａの法線に対する入射光の角度及び散乱光の角度を示す。
【００６３】
従って、前述と同様に、高ＳＮ比を得るためには傾斜角αをできるだけ０°に接近させるのが好ましいが、磁気テープの走行ばたつき等により検査領域が正反射領域に入り込んでしまう危険性があるので、検査の安定性を優先して、傾斜角αは５°以上のやや大きい範囲に設定すると良い。
【００６４】
更に最も検査の安定性を優先する場合から、高ＳＮ比を優先する場合までを３段階に分けて、１５°≦α＜２５°、１０°≦α＜１５°、５°≦α＜１０°の３段階の範囲でいずれかを選択して設定すると良い。
【００６５】
βについては、β＝０°では検査環境周囲からの外乱光によるノイズが集まりやすく、β＞１０°では、表面欠陥を斜め方向から見る度合いが大きくなるため欠陥が小さく観察されることになり検出感度が低くなってしまうので０＜β≦１０°が適切である。
【００６６】
なお上記実施の形態の例は、磁気テープ１２の表面欠陥を検出する装置に関するものであるが、本発明はこれに限定されるものでなく、ガラス基板の表面、メッキ表面、研磨した金属表面、等の反射率が高い材料の表面における欠陥を検出する際に適用することができる。
【００６７】
又、上記実施の形態の例では、光Ｌａ、Ｌｂを用いているが、この光は、その照射光軸上の一定領域の外側にも照射領域を有するものであればよく、平行光線束、収束光線束、発散光線束のいずれでもよい。
【００６８】
更に、上記表面欠陥検出装置１０は、検査対象物である磁気テープ１２表面に帯状光源像領域１８Ａ、１８Ｂを形成し、これに対してＣＣＤラインカメラ２２も、帯状検査領域２２Ａを有するものであるが、本発明はこれに限定されるものでなく、光源像領域及び検査領域がスポット状であってもよい。この場合、光源の数は３つ以上の多灯でもよい。又、被検査面の法線を基準として傾斜角α及びβを設定する。又、光源像スポットと検査スポットとのオフセット量Ｄも前述のＷ／２＜Ｄ≦３Ｗ／２の範囲で設定する。ここで、光源像スポットの幅Ｗは、検査スポットからみた光源像スポットの中心方向の外径となる。更に、光源をリング状とし、検査スポットを囲むような光源像領域の配置としてもよい。
【００６９】
なお、前記検査光照射装置２０は、光源種についてはハロゲンランプ、ＬＥＤ、ナトリウムランプ、レーザダイオード等の種々のものが考えられるが、絶対光量が大きく調光が容易という点から、ハロゲンランプが特に優れている。
【００７０】
更に、前記帯状検査領域２２Ａは、磁気テープ１２の表面を、送り方向に対して直角に横切るように設定されているが、本発明はこれに限定されるものでなく、これはテープの幅方向に対して±４０度以内、好ましくは±２０度以内で傾けてもよい。
【００７１】
【実施例】
この実施例は１／２インチ幅のビデオ用磁気テープ（塗布型の磁性層及びバックコート層を備える）を測定対象物とし、検査光照射装置の光源種としてはハロゲンランプを用いた。光は１本のみとした。
【００７２】
又、ＣＣＤラインカメラは、市販のライカサイズ１眼レフカメラ用のレンズ、を備え、ＣＣＤアレイはテープ幅方向の画素数が１０２４で、磁気テープは送り速度がＶ＝５ｍ／ｓｅｃという条件とすることにより、テープ幅方向分解能が１２μｍ、テープ走行方向のサイズを１２８μｍとした。
【００７３】
磁性層側の検出結果を、図９（Ａ）に示し、これに対応して、図９（Ｂ）に、同じ欠陥を、帯状光源像領域と検査領域とを一致させた従来の表面結果検出装置により測定した結果を示す。なお、図９（Ａ）、図９（Ｂ）は欠陥種が付着物の場合をそれぞれ示す。
【００７４】
これらの図から分かるように、図９（Ｂ）では、符号Ｘｂで示される欠陥部において輝度信号が大きく立ち下がっているが、他の部分でも輝度信号が立ち下がっていて、欠陥による立ち下がりか否かを弁別することが困難である。
【００７５】
これに対して、本発明の実施例では、図９（Ａ）において符号Ｘａで示されるように、欠陥部では輝度信号が大きく立ち上がり、他の部分にこれと紛らわしい信号が見られない。従って、表面欠陥を高ＳＮＲで検出できることが分かる。
【００７６】
次に、欠陥が凸部である場合と凹部である場合のそれぞれについての前記傾斜角α、及びβと、ＳＮ比（ＳＮＲ）との関係について実験により得られた結果を示す。
【００７７】
表１及び図１０は、前記と同様の磁気テープの磁性層側について測定したものであり、欠陥として付着物により凸部が形成された場合の、傾斜角α、βとＳＮＲとの関係を示している。
【００７８】
なお、ＳＮＲの値は次のようにして求めた。欠陥部からの輝度信号強度をａ、ローレベルの輝度信号強度をｂとしたとき、ＳＮＲ＝ａ／ｂとした。但し、図９（Ｂ）等のようにａがｂよりも小さい場合は、ＳＮＲ＝−（１−ａ／ｂ）とした。又、αは、図２に例示したように、設定直線１９Ｂがカメラ対称光軸２３に対して法線１６から離れる方向に傾いている場合をプラスの値とし、反対方向に傾いている場合をマイナスの値で表記した。このマイナスの表記は方向を示すためだけのものであり、絶対値をとったものが本発明の傾きαとなる。
【００７９】
【表１】

【００８０】
表１において、○印は得られたＳＮＲが好ましい範囲である場合、×印は設定した傾斜角度が利用できる範囲外の場合、△印は利用できる範囲をそれぞれ示す。又、無印も利用範囲外を示す。
【００８１】
表１及び図１０から、欠陥が付着物等の凸部の場合は、傾斜角βが０＜β＜１０°の範囲で、傾斜角αが５°≦α＜１０°が最も好ましく、以下、１０°≦α＜１５°、１５°≦α＜２５゛の順で良好なＳＮＲを得ることができることが分かる。
【００８２】
なお、βが１５°と２０°のデータについては、ＳＮＲの値そのものは良好な場合もあるが、前記のような理由により、本発明において利用できる範囲外という意味で１５°と２０°の欄にＸ印を付した。
【００８３】
次に、表２及び図１１に、前記と同様の磁気テープのバックコート側表面における欠陥が押し疵であり、且つテープ送り方向に非対称な凹部（大きさ１０μｍ程度の微小なもの）の場合について傾斜角α、βとＳＮＲとの関係を、前記と同様に確認したものを示す。
【００８４】
【表２】

【００８５】
表２における「光源１灯」の欄において、○印、×印は表１におけると同一の範囲を示す。表２からは、０＜β≦１０°の領域で、傾斜角αが、５°より小さく且つ限りなく０°に近いときに良好な検出結果を得られることが分かる。なお、用いた磁気テープのバックコート側表面における凹部欠陥のサイズは非常に微細であるため、欠陥部からの散乱光量が少なく、得られるＳＮＲの値も低くなっているが、磁気テープの走行系の調整（具体的には走行スピードを低く設定し、検査部１２Ａの平面性を高くする）をすることにより、ＳＮＲを向上して検出可能となるように設定したものである。
【００８６】
次に、光を、図１、図２に示されるような２本とした場合の効果を検証した。
【００８７】
上記のように、表２において、光を１本のみとした場合で、傾斜角度αおよび傾斜角度βをそれぞれ変化させて実験したところ、目的とする欠陥が非常に小さい場合でも、傾斜角度βをテープ表面の法線に近い５°とし、且つ、光の傾斜角度α＝３°まで条件を詰めると、検出信号は必要な波高値を得られることが判明した。
【００８８】
ただし、この条件においても、試料であるテープを逆向きにすると、表２における「試料逆向」の欄のように、検出値は１．３５から０．００になった。そこで、２本の光を±３度から照射すると、感度の高い側に近似した波高値（１．３０）が得られた（表２最右欄）。なお、表１、２の実施例は、静特性確認なので最も高い波高値の情報のみ得られたが、動特性においては感度の低い側の波高値もＣＣＤカメラへの光エネルギーとして蓄積されるので、感度向上効果が期待できる。又、表１に示される凸状の欠陥であっても、テープ送り方向に非対称なものの場合には本発明の２本の光照射による検出向上効果が得られる。
【００８９】
【発明の効果】
本発明は上記のように構成したので、磁気テープ等の表面欠陥を高ＳＮＲで検出することができるという優れた効果を有する。
【図面の簡単な説明】
【図１】本発明の実施の形態の例に係る表面欠陥検出装置を示す一部ブロック図を含む斜視図
【図２】同表面欠陥検出装置における光の照射光軸（面）とＣＣＤラインカメラのカメラ光軸（面）との関係を示す模式図
【図３】同表面欠陥検出装置において磁気テープを支持するための支持装置を示す斜視図
【図４】光による磁気テープ表面での照射領域、検査領域、光源像領域、光源像外領域の関係を拡大して示す模式図
【図５】光の照射光軸とカメラ光軸との関係をテープ送り方向から見た模式図
【図６】磁気テープ表面の欠陥部が凹部である場合の光と散乱光との関係を示す模式図
【図７】同凹部での傾斜面の傾斜方向及び光と散乱光との関係を示す模式図
【図８】磁気テープ表面の欠陥部が凸部である場合の光と散乱光との関係を示す模式図
【図９】表面欠陥検出装置の実施例によって磁気テープ表面の付着物欠陥を検出した場合の検出信号の波形を、従来例と比較して示す線図
【図１０】磁気テープ表面の欠陥部が凸部である場合の傾斜角β及びαと検出値のＳＮＲとの関係を示す線図
【図１１】磁気テープ表面の欠陥部が凹部である場合の図１０と同様の線図
【符号の説明】
Ｌａ、Ｌｂ…光
１０…表面欠陥検出装置
１２…磁気テープ
１２Ａ…検査部
１４…支持装置
１６…第１の仮想平面
１６Ａ…法線
２５Ａ、２５Ｂ…光出射口
１８Ａ、１８Ｂ…光源像領域
１８Ｃ…幅方向中心線
１８Ｄ…光源像外側領域
１９Ａ、１９Ｂ…照射光軸
１９Ｃ…照射光軸面
２９Ａ、２９Ｂ…設定直線
２０…検査光照射装置
２１…カメラ光軸
２１Ａ…カメラ光軸面
２２…ＣＣＤラインカメラ
２２Ａ…帯状検査領域
２２Ｂ…幅方向中心線
２２Ｍ…仮想位置
２３…カメラ対称光軸
２４…判定装置
３０…凹部
３２…凸部
３２Ａ…側面[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a glossy material such as a magnetic layer surface or a back coat layer surface of a magnetic recording medium such as a magnetic tape, a rolled material, a surface of a polished metal, a resin surface having a high light reflectance, a glass surface, etc. The present invention relates to a method and apparatus for detecting a surface defect such as a very fine defect on the surface of various materials during application, such as a defect, an adhering substance, and a pressing scratch.
[0002]
[Prior art]
Inspection methods for conventional magnetic recording media, for example, magnetic tapes, generally use a magnetic head to record and reproduce signals on a magnetic tape, and determine the presence or absence of a defect in the magnetic tape from the reproduction level. .
[0003]
Such an inspection method has been regarded as the most reliable inspection method because the correlation between the scratches on the magnetic recording medium and the actual harm appearing in the reproduced signal is large.
[0004]
Specifically, this conventional method for inspecting a magnetic recording medium performs high-speed and high-efficiency inspection by running a magnetic recording medium at high speed and using a multi-channel fixed magnetic head as a signal reproducing head. I was
[0005]
In the field of defect inspection of such magnetic recording media, in order to respond to the recent increase in the density of recorded information on magnetic recording media, high resolution that can detect even finer and finer defects than before is required. Have been.
[0006]
However, in the method of inspecting the surface of a magnetic recording medium using a multi-channel fixed magnetic head as described above, it is not easy to increase the detection resolution due to limitations in the manufacturing technology of the magnetic head. The limit of practical use is about 50 μm in the width direction of the recording medium, and the limit is about 20 μm even if an expert inspects it by adjusting the conditions of the apparatus. In addition, as the number of channels increases, the size of the apparatus increases, causing an increase in cost.
[0007]
Further, as a magnetic recording medium inspection method capable of obtaining an inspection resolution higher than when the above-described multi-channel fixed magnetic head is used, an optical magnetic recording method disclosed in Patent Document 1 or Patent Document 2 is known. There is a method for inspecting a surface defect of a medium.
[0008]
In the magnetic tape inspection method of Patent Document 1, light emitted from a red LED (light emitting diode) light source is reflected on the surface of the magnetic tape, and when the light is received and detected by the sensor head, the light receiving axis direction of the sensor head is set to the direction of the magnetic tape. By inclining at a certain angle with respect to the normal direction of the main surface, a signal of a defective portion can be detected at a high SN.
[0009]
In addition, the surface inspection method of the magnetic recording medium disclosed in Patent Document 2 illuminates the surface of the magnetic layer with halogen light, and when the reflected light is received and detected by a CCD camera, the light projection / reception angle is set to a specific range. By shifting the optical axis position from the reflection point, the signal output level is maximized and the system noise is minimized.
[0010]
Further, in the optical inspection method for a magnetic disk disclosed in Patent Document 3, a light beam is incident from a direction having an inclination angle with respect to a perpendicular line of the magnetic disk surface, and the light scattered above the disk surface is imaged to form a dark image. While obtaining a field image, the dark field image is received by a line sensor having light receiving elements arranged in a row, and the scattered light intensity is measured. When one or a plurality of elements acquire a signal having an intensity equal to or higher than a predetermined level for a predetermined time or more, it is detected as a defective portion.
[0011]
In particular, in magnetic recording media devices and the like that make full use of recent high-density recording technology, for example, defects such as defects during application of a magnetic layer, deposits, and defects such as press scratches have a low height and a smooth shape as a whole. For this reason, although the influence on the reproduction signal is relatively moderate, the error rate increases when many defects are concentrated. When the size is 10 to 20 μm, an increase in the error rate of the reproduced signal is recognized. A method and an apparatus capable of stably and easily detecting such a defect having a size of about 10 to 20 μm are desired.
[0012]
[Patent Document 1]
JP-A-8-201309
[Patent Document 2]
JP-A-8-233560
[Patent Document 3]
JP-A-10-143801
[0013]
[Problems to be solved by the invention]
However, the method disclosed in Patent Document 1 is capable of detecting a large foreign object or the like because the amount of light from the LED light source is small and the total reflection method is used, but it is possible to stabilize defects having a size of 10 to 20 μm. And it was difficult to detect.
[0014]
Also, the surface inspection method of the magnetic recording medium disclosed in Patent Document 2 has a problem that it is difficult to stably detect a defect having a size of 10 to 20 μm because the method is a total reflection type detection. .
[0015]
Further, in the optical inspection method for a magnetic disk disclosed in Patent Document 3, a dark field image is obtained by imaging scattered light from a direct irradiation area by irradiation light. There is a problem that the strong wave light value of the scattered light from the light source is at a low level and the SN ratio is low.
[0016]
In addition, the surface defect inspection method disclosed in each of the above-mentioned patent documents is applied to a field other than the surface of a magnetic recording medium, for example, a defect inspection of a strip surface in a rolling process, a defect inspection of a plating surface, a glass product such as a glass substrate. Surface defect inspection, the inspection of the polished metal surface in the machining process, etc., but in any case, the ratio of the scattered light at the defective portion to the background light is small, so detection is difficult. There were many things.
[0017]
The present invention has been made in view of the above-described conventional problems, and provides an optical surface defect detection method and apparatus capable of reliably detecting even a small defect with a high SN ratio. With the goal.
[0018]
[Means for Solving the Problems]
The present inventor has conducted intensive studies on a method of inspecting the surface of a magnetic tape or the like, and has performed an inspection area by a camera having a camera optical axis inclined at a certain angle with respect to a perpendicular to the surface of the inspection object, and a slight shift from this area. A light source image area where a mirror image of the light exit is located is set, and scattered light from a surface defect is received by a camera in an area darker than the area, that is, in an area where the amount of background light is small, and a high SN ratio is obtained. It was found that surface defects could be detected by the method. Also, at this time, depending on the type of surface defect, the detection sensitivity differs depending on the running direction of the magnetic tape, and the detection may not be possible. This problem can be solved by irradiating both sides of the inspection area with light from two light emission ports. I know what I can do.
[0019]
That is, the above object can be achieved by the present invention described below.
[0020]
(1) An inspection area by a camera is set on the surface of the inspection object, and irradiation with the light including the inspection area when light from a plurality of light emission ports is incident on the surface of the inspection object. In the area, adjacent to the outside of the inspection area, and at least two positions between the inspection area, so that the mirror images of the plurality of light emission ports are located, Setting, the scattered light from the inspection area is received by the camera and converted into a light reception signal, and when the light reception signal is larger than the intensity of the light reception signal from the defect-free portion of the inspection area by a certain value or more, A method for detecting a surface defect, which is detected as a surface defect of an inspection object.
[0021]
(2) An inspection area by a camera is set on the surface of the inspection object, and the camera optical axis passing through the center of the inspection area is inclined at an angle β <0 ≦ β ≦ 10 ° with respect to a normal to the surface of the inspection object. When the light is incident on the surface of the inspection object from two light exit ports, the inspection area is included by the light. M In the irradiation area, two light exits are set such that mirror images of the two exits are located at positions adjacent to both outer sides of the inspection area, and the light exits of these light exits are set. Setting a straight line passing through the center and the center of the inspection area on both sides from a camera symmetric optical axis of the camera optical axis about the normal line, and setting an inclination angle α to 0 <α <25 °, The scattered light from the inspection area is received by the camera and converted into a light reception signal, and when the light reception signal is larger than the intensity of the light reception signal from the defect-free portion of the inspection area by a certain value or more, A method for detecting a surface defect, which is detected as a surface defect.
[0022]
(3) The inspection method for surface defects according to (2), wherein the inclination angle α is set to 0 <α <5 °.
[0023]
(4) The inclination angle α is set to any one of 5 ° ≦ α <10 °, 10 ° ≦ α <15 °, or 15 ° ≦ α <25 °. Inspection method for surface defects.
[0024]
(5) Assuming that the total length of two light source image areas on the surface of the inspection object where the mirror image of the light exit port is located in the adjacent direction from the inspection area is W, the adjacent direction of the light source image area is The method for detecting a surface defect according to any one of (2) to (4), wherein a distance D from a center position to the inspection area is W / 2 <D ≦ 3W / 2.
[0025]
(6) The light source is configured such that the light source image area where the mirror image of the light exit opening is located by the camera has a linear band shape, and the irradiation optical axis is in a plane parallel to the width direction center line of the light source image area. Set to be, and the inspection area has a linear band shape parallel to the linear light source image area, and the camera optical axis passes through the light exit port with respect to the normal. Any one of (2) to (5), characterized by being set so as to be inclined at an inclination angle β to the opposite side to the set straight line and to lie within a plane including the center line in the width direction in the inspection area of the straight band shape. 3. The method for detecting a surface defect according to 1.
[0026]
(7) With respect to a first virtual plane parallel to the center line in the width direction of each of the light source image area and the inspection area and perpendicular to the surface of the inspection object, the first virtual plane and the inspection object surface In a second vertical virtual plane, the irradiation optical axes of the two lights are inclined at an inclination angle α on both sides with respect to the camera symmetric optical axis, respectively, and the camera optical axis is set to the irradiation optical axis. (6) The method for detecting a surface defect according to (6), wherein the surface is set at a tilt angle β with respect to the first virtual plane on the opposite side to the first virtual plane.
A method for detecting a surface defect, wherein the surface is set at an inclination angle β.
[0027]
(8) When the object to be inspected is a strip, the light source image area and the inspection area are set to a linear strip shape crossing the strip in the width direction, and the surface is moved while the strip is running in the longitudinal direction. The method for detecting a surface defect according to (6) or (7), wherein the defect is detected.
[0028]
(9) The camera is a CCD line camera, and an incident optical axis plane including a plurality of incident optical axes of the CCD line camera is set to coincide with a plane including a center line in a width direction of the inspection area. (6) The method for detecting a surface defect according to (7) or (8).
[0029]
(10) A support device for supporting the inspection target such that at least a part of the surface passes through the inspection position at the fixed position in the thickness direction or stops at the inspection position, and an inspection region is formed on the surface at the inspection position. A light receiving signal having an intensity proportional to the incident light intensity, wherein the optical axis of the camera is set so that the camera optical axis is inclined with respect to the normal to the surface so that the inclination angle β is 0 <β ≦ 10 °. And a camera that outputs the light, when the surface of the inspection object is irradiated with light from two light emission ports, in the irradiation region including the inspection region by the light, and on both outer sides of the inspection region. At adjacent positions, two light source image areas in which mirror images of the two light exits are located are formed, and a straight line passing through the center of the light exits and the center of the inspection area is the camera optical axis. On both sides from the camera symmetric optical axis about the normal, An inspection light irradiation device in which the inclination angle α is set to 0 ° <α <25 °, and the intensity of the light reception signal from the camera is the intensity of the light reception signal due to the incident light from the defect-free portion in the inspection area. And a determination device that outputs a defect detection signal when the value is greater than or equal to a predetermined value.
[0030]
(11) The inspection device for surface defects according to (10), wherein the inclination angle α in the inspection light irradiation device is set to 0 <α <5 °.
[0031]
(12) The inclination angle α in the inspection light irradiation device is set to any one of 5 ° ≦ α <10 °, 10 ° ≦ α <15 °, or 15 ° ≦ α <25 °. A surface defect inspection apparatus according to (10).
[0032]
(13) When the total length of the light source image region in the direction toward the center of the light source image region as viewed from the inspection region is W, the camera is arranged from a center position of the light source image region in the direction to the inspection region. Wherein the distance D is set to satisfy W / 2 <D ≦ 3W / 2. The surface defect detection device according to any one of (10) to (12),
[0033]
(14) The inspection light irradiation device is configured such that the light source image region has a linear band shape, and the irradiation optical axis of the light is in a plane parallel to a center line in the width direction of the light source image region. And, in the camera, the inspection region has a linear band shape parallel to the linear band light source image region, and the camera optical axis passes through the light exit port with respect to the normal line. Any one of (10) to (13), characterized in that it is inclined at an inclination angle β to the opposite side to the set straight line and is set within a plane including the width direction center line in the inspection area of the straight band shape. A surface defect detection device according to any one of the above.
[0034]
(15) The inspection light irradiating device may be configured such that the first virtual plane is parallel to a center line in the width direction of each of the light source image area and the inspection area and perpendicular to a surface of the inspection object. And in a second virtual plane perpendicular to the surface of the inspection object, the set straight line passing through the two light emission ports is provided at an inclination angle α, and the camera has an optical axis of the camera. A surface defect detecting device, which is provided at a tilt angle β on the opposite side to the set straight line.
[0035]
(16) The inspection object is a strip, the support device is configured to move the strip in the longitudinal direction, and the inspection light irradiation device and the camera are configured such that the light source image area and the inspection area are The surface defect detection device according to (14) or (15), wherein the surface defect detection device is set to have a linear band shape crossing the band-shaped member in the width direction.
[0036]
(17) The camera is a CCD line camera, and an incident optical axis surface including a plurality of incident optical axes of the CCD line camera is set to coincide with a plane including a center line in a width direction of the inspection area. The surface defect detection device according to (14), (15) or (16), which is characterized in that:
[0037]
As described above, when the irradiation optical axis of the inspection light, the inspection area of the camera, and the optical axis of the camera are set, a light reception signal based on the scattered light from the defective portion can be obtained with a high SN ratio.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the example of this embodiment, the inspection object is a magnetic recording medium.
[0039]
As shown in FIG. 1, a surface defect detection device 10 according to an example of this embodiment includes a support device 14 that supports an inspection unit 12A of a magnetic tape 12 as a magnetic recording medium in a straight plane, and a support device 14 that supports the inspection unit 12A. A first virtual plane 16 (see FIG. 2) that includes a normal 16A (see FIG. 2) to the surface of the magnetic tape 12 supported in a straight plane and crosses the magnetic tape 12 in the width direction. ) And the surface of the magnetic tape 12, the camera optical axis 21 passing through the center line 22 B (see FIG. 4) in the width direction of the band-shaped inspection area 22 A is inclined with respect to the first virtual plane 16. Two light La from two

light irradiation ports

25A and 25B are provided to a CCD line camera 22 arranged at an angle so that β is 0 <β ≦ 10 ° and an irradiation area 30 including the band-shaped inspection area 22A. , Lb, and within the irradiation area 30, The two strip-shaped light source image areas (lights La, La) that traverse the magnetic tape 12 in the width direction are located at positions close to and adjacent to both outer sides in the width direction (left and right sides in FIG. 2) as viewed from the shape inspection area 22A. The area where the mirror images of the

light emission ports

25A and 25B of Lb are located) The inspection light irradiating device 20 that forms 18A and 18B, and the intensity of the light reception signal from the CCD line camera 22 is the defect-free portion in the strip inspection area 22A. And a determination device 24 that outputs a defect signal when the intensity of the light reception signal due to the incident light from the light source is larger than a predetermined value.
[0040]
The inclination angle β is an angle in a second virtual plane 17 that includes the normal 16A and is perpendicular to the first virtual plane 16 and the surface of the inspection unit 12A.
[0041]
A camera symmetric optical axis 23 of the camera optical axis 21 having the first virtual plane 16 as a plane of symmetry is located within a second virtual plane 17 with respect to the first virtual plane 16. The angle β is inclined to the opposite side. The two irradiation optical axes 19A and 19B passing through the light exits 25A and 25B are provided with a virtual position 22M for observing a mirror image of the CCD line camera 22 having a surface of the inspection unit 12A as a plane of symmetry, and a light exit 25A. , 25B, and the

light exit ports

25A, 25B of the inspection light irradiation device 20 are provided with two setting straight lines 29A passing through the center thereof and the center line 22B in the width direction of the band-shaped inspection region 22A. 29B is set so as to intersect the camera symmetric optical axis 23 from both sides at an inclination angle α.
[0042]
As shown in FIG. 3, the support device 14 includes a pair of cylindrical guide members 26A and 26B arranged in parallel, and the cylindrical guide members 26A and 26B are provided in a range where the magnetic tape 12 is wound. A large number of air outlet pores 27 are formed, and the magnetic tape 12 wound around the cylindrical guide members 26A and 26B by blowing compressed air from the air outlet pores 27 is brought into contact with the guide member surface in a non-contact state. 12 is run while maintaining a straight plane. Note that the portion of the magnetic tape 12 maintained in a straight plane is the detection unit 12A.
[0043]
The support device 14 may be any device as long as it can run while maintaining the magnetic tape 12 in a straight plane, and is not limited to a device that is not in contact with the magnetic tape.
[0044]
The setting straight lines 29A, 29B passing through the centers of the

light exit ports

25A, 25B and the width direction center of the band-shaped inspection region 22A are camera symmetrical including the camera symmetric optical axis 23 and the width direction center line of the band-shaped inspection region 22A. The CCD line camera 22 is arranged at an angle of α with respect to the optical axis 23A on the camera optical axis 21 side of the CCD line camera 22 and on the opposite side. The inclination angle α is set in the range of 0 <α <25 ° as described later.
[0045]
The irradiation optical axes 19A and 19B and the camera optical axis 21 are both continuous in the width direction of the magnetic tape 12, and as shown in FIG. 21A are formed. The camera optical axis plane 21A is inclined at an inclination angle β with respect to the virtual plane 16, and the irradiation optical axis plane 19C is formed through the center line 18C in the width direction of the light

source image areas

18A and 18B.
[0046]
As shown in FIG. 5, the light La, Lb and the camera optical axis 21 are set so as to be perpendicular to and overlap the magnetic tape 12 when viewed from the running direction of the magnetic tape 12.
[0047]
As shown in FIG. 1, the inspection light irradiation device 20 includes a halogen lamp 28, and optical fiber bundles 28A and 28B for guiding the light as two lights La and Lb. 14 irradiates the surface of the magnetic tape 12 supported in a straight plane by the irradiation area 14 and includes, as described above, the two band-shaped light

source image areas

18A and 18B crossing the magnetic tape 12 in the width direction. 30 (see FIG. 4). The irradiation area 30 includes the two light

source image areas

18A and 18B, and light source image outside areas 18D (see FIG. 4, which will be described later in detail), on both sides of which light source images are not observed but light La and Lb are irradiated. Consists of The strip inspection area 22A is located in the light source image outer area 18D attached to both of the two strip light

source image areas

18A and 18B.
[0048]
Here, the distance D of the band-shaped inspection region 22A with respect to the center line 18C in the width direction of the band-shaped light

source image regions

18A and 18B is, as shown in FIG. 2, when the width of the light

source image regions

18A and 18B is W. , W / 2 <D ≦ 3W / 2. When D ≦ W / 2, strong irradiation light may enter as disturbance light. When D> 3W / 2, the band-shaped inspection region 22A is located at a position apart from the light

source image regions

18A and 18B in the light source image outer region 18D, so that the irradiation light is weak, and therefore, the scattered light obtained from this region is small. become weak.
[0049]
The determination device 24 enters the CCD line camera 22 from the CCD line camera 22 at a constant interval in the longitudinal direction of the magnetic tape 12, that is, at a position corresponding to the resolution in the tape width direction at a predetermined line scanning cycle. A luminance signal corresponding to the light energy to be received is received, and the luminance signal is compared with the level (low level) of the luminance signal at the defect-free portion in the band-shaped inspection region 22A, and there is a difference of a certain value or more. At this time, a defect signal is output.
[0050]
In detail, the integrated value obtained by accumulating the incident light energy is output from the CCD line camera 22 as a luminance signal, and in the determination device 24, the luminance signal is preset by a comparator 24A. A defect signal is output when the input luminance signal is larger than the comparison value, as compared with a luminance signal obtained by adding a predetermined value to the low-level luminance (comparison value).
[0051]
When a surface defect of the magnetic tape 12 is detected by the surface defect detection device 10 as described above, the band-like inspection region 22A is positioned between the light

source image regions

18A and 18B by the two lights La and Lb. In the area where there is no defect on the surface of the magnetic tape 12, the luminance signal obtained by the CCD line camera 22 is almost close to the black level, and is due to the flatness of the magnetic tape 12 and the optical system. And the degree of increase in luminance is small.
[0052]
More specifically, as shown in FIG. 4, the band-shaped inspection region 22A is included in a light source image outer region 18D adjacent between the light

source image regions

18A and 18B due to the two lights La and Lb, and As described above, since the

light emission ports

25A and 25B are on the setting straight lines 29A and 29B having the inclination angle α with respect to the camera symmetric optical axis 23 of the camera optical axis 21, the light source image area 18A of the light La and Lb is provided. , 18B do not enter the CCD line camera 22.
[0053]
On the other hand, when there is any defect on the surface of the magnetic tape 12, the irradiation light is scattered in the belt-shaped inspection area 22 A, and a part of the scattered light enters the CCD line camera 22.
[0054]
As described above, since the luminance of the magnetic tape 12 in the light source image outer region 18D is almost close to the black level, the scattered light from the defective portion has a higher luminance than this black level, and as a result, the SNR of the detection signal is greatly increased. To be improved. On the other hand, when the band-shaped light source image area and the inspection area are made to coincide with each other as in the related art, the luminance of the defect-free portion is high and the luminance of the defective portion falls, and a certain luminance difference is obtained. Is low, the high SNR as in the present invention cannot be obtained.
[0055]
Here, the relationship between the setting of the inclination angle α, the type of defect on the surface of the magnetic tape 12 and the two lights La and Lb will be described.
[0056]
As shown in FIG. 6, when the concave portion 32 such as a pressing flaw is on the surface of the magnetic tape 12, the amount of scattered light from the concave portion 32 is small, the SN ratio level is considerably small, and the amount of scattered light is specifically large. The angle is close to the normal 16 A of the surface of the magnetic tape 12 or the first virtual plane 16. Therefore, in order to increase the SN ratio level, the inclination angle α is set to 5 ° or less and as close to 0 ° as possible.
[0057]
When the inclination angle α is close to 0, the irradiation optical axes 19A and 19B of the light La and Lb and the camera symmetric optical axis 23 are parallel and close to each other, so that an erroneous detection occurs when the magnetic tape 12 flaps during traveling. Therefore, in order to maintain the flatness of the magnetic tape 12 at the time of inspection, it is preferable to adjust the running tension, speed fluctuation, tape guide shape, and the like.
[0058]
Even with such adjustment, when the shape of the concave portion 32 is asymmetrical in the tape running direction, for example, the scattered light is generated on the inclined surface 32A on the upper right and the inclined surface 32B on the left as shown in FIG. Since the reflection directions of the two are different, depending on the running direction of the tape, one may be detected but the other may not be detected, or the detection sensitivity may be reduced.
[0059]
In the example of this embodiment, the light

source image regions

18A and 18B by two light beams La and Lb are set on both sides of the belt-shaped inspection region 22A, and the space between the two light

source image regions

18A and 18B is outside the both. Therefore, when the concave portion 32 is in the band-shaped inspection region 22A, the light is radiated obliquely from both sides.
[0060]
Therefore, in any of the inclined surfaces 32A and 32B having different inclination directions as described above, scattered light enters the CCD line camera 22 to detect a defect. In the case of FIG. 7A, light La is obtained, and in the case of FIG. 7B, light scattered by light Lb is obtained.
[0061]
As shown in FIG. 8, when the surface of the magnetic tape 12 has a large height of a defect or a deposit at the time of application and a large convex portion 34, a comparison is made from the side surface 34 A of the convex portion 34. An extremely large amount of scattered light can be obtained.
[0062]
In the case of a defect such as the convex portion 34, a sufficient amount of reflected light can be obtained from any of the inclined surfaces (side surfaces) of the upper right and the upper left, so that only one light may be used. 8 indicate the angles of the incident light and the scattered light with respect to the normal to the side surface 34A when the light La and Lb are reflected by the side surface 34A and enter the CCD line camera 22.
[0063]
Therefore, as described above, in order to obtain a high SN ratio, it is preferable to make the inclination angle α as close to 0 ° as possible. However, there is a risk that the inspection area may enter the specular reflection area due to running fluctuation of the magnetic tape or the like. Therefore, the inclination angle α is preferably set to a slightly large range of 5 ° or more in consideration of the stability of the inspection.
[0064]
Furthermore, from the highest priority on the stability of the inspection to the highest priority on the high SN ratio, it is divided into three stages, 15 ° ≦ α <25 °, 10 ° ≦ α <15 °, 5 ° ≦ α <10 ° It is preferable to select and set one of the three levels.
[0065]
As for β, when β = 0 °, noise due to disturbance light from around the inspection environment is likely to be collected, and when β> 10 °, the degree of observing the surface defect from an oblique direction becomes large, so that the defect is observed small and detected. 0 <β ≦ 10 ° is appropriate because the sensitivity is lowered.
[0066]
Although the example of the above embodiment relates to an apparatus for detecting a surface defect of the magnetic tape 12, the present invention is not limited to this, and a surface of a glass substrate, a plated surface, a polished metal surface, And the like when detecting a defect on the surface of a material having a high reflectance.
[0067]
Further, in the example of the above-described embodiment, the lights La and Lb are used. However, the light may have an irradiation area outside a certain area on the irradiation optical axis. Either a convergent light beam or a divergent light beam may be used.
[0068]
Further, the surface defect detecting device 10 forms band light

source image regions

18A and 18B on the surface of the magnetic tape 12 to be inspected, and the CCD line camera 22 also has a band inspection region 22A. However, the present invention is not limited to this, and the light source image area and the inspection area may be spot-shaped. In this case, the number of light sources may be three or more. Further, the inclination angles α and β are set with reference to the normal line of the surface to be inspected. Further, the offset amount D between the light source image spot and the inspection spot is also set in the range of W / 2 <D ≦ 3W / 2. Here, the width W of the light source image spot is the outer diameter in the center direction of the light source image spot viewed from the inspection spot. Further, the light source may have a ring shape and the light source image area may be arranged so as to surround the inspection spot.
[0069]
The inspection light irradiating device 20 may employ various types of light sources, such as a halogen lamp, an LED, a sodium lamp, and a laser diode. Are better.
[0070]
Further, the belt-shaped inspection area 22A is set so as to cross the surface of the magnetic tape 12 at right angles to the feeding direction, but the present invention is not limited to this, May be inclined within ± 40 degrees, preferably ± 20 degrees.
[0071]
【Example】
In this example, a 1/2 inch wide video magnetic tape (provided with a coating type magnetic layer and a back coat layer) was used as an object to be measured, and a halogen lamp was used as a light source type of an inspection light irradiation device. There was only one light.
[0072]
The CCD line camera has a lens for a commercially available Leica size single lens reflex camera, the CCD array has 1024 pixels in the tape width direction, and the magnetic tape has a feed speed of V = 5 m / sec. Thereby, the resolution in the tape width direction was 12 μm, and the size in the tape running direction was 128 μm.
[0073]
FIG. 9 (A) shows the detection result on the magnetic layer side, and FIG. 9 (B) correspondingly shows a conventional surface result detection in which the same defect is matched between the band-shaped light source image area and the inspection area. The result measured by the apparatus is shown. Note that FIGS. 9A and 9B show the case where the defect type is a deposit.
[0074]
As can be seen from these figures, in FIG. 9B, the luminance signal largely falls at the defective portion indicated by the symbol Xb. It is difficult to discriminate whether or not.
[0075]
On the other hand, in the embodiment of the present invention, as indicated by reference numeral Xa in FIG. 9A, the luminance signal largely rises at the defective portion, and no confusing signal is seen in other portions. Therefore, it can be seen that surface defects can be detected with a high SNR.
[0076]
Next, results obtained by experiments are shown on the relationship between the inclination angles α and β and the SN ratio (SNR) for the case where the defect is a convex portion and the case where the defect is a concave portion.
[0077]
Table 1 and FIG. 10 show the relationship between the inclination angles α and β and the SNR in the case where a protrusion is formed by a deposit as a defect, as measured on the magnetic layer side of the same magnetic tape as described above. ing.
[0078]
The SNR value was obtained as follows. Assuming that the luminance signal intensity from the defective portion is a and the low-level luminance signal intensity is b, SNR = a / b. However, when a is smaller than b as in FIG. 9B, SNR = − (1−a / b). Α has a positive value when the setting straight line 19B is inclined in a direction away from the normal 16 with respect to the camera symmetric optical axis 23 as illustrated in FIG. Expressed as a negative value. This negative notation is only for indicating the direction, and the one having an absolute value is the inclination α of the present invention.
[0079]
[Table 1]

[0080]
In Table 1, a circle indicates a case where the obtained SNR is in a preferable range, a cross indicates a case where the set tilt angle is out of a usable range, and a triangle indicates a usable range. In addition, a blank mark indicates that the area is out of the usable range.
[0081]
From Table 1 and FIG. 10, when the defect is a protrusion such as a deposit, the inclination angle β is most preferably in the range of 0 <β <10 °, and the inclination angle α is most preferably 5 ° ≦ α <10 °. It can be seen that good SNR can be obtained in the order of 10 ° ≦ α <15 ° and 15 ° ≦ α <25 °.
[0082]
It should be noted that, for the data where β is 15 ° and 20 °, the SNR value itself may be good in some cases. However, for the reasons described above, the columns of 15 ° and 20 ° mean that they are outside the range usable in the present invention. Was marked with X.
[0083]
Next, Table 2 and FIG. 11 show the case where the same defect on the back coat side surface of the magnetic tape as described above is a pressing flaw, and the concave portion (a minute one having a size of about 10 μm) is asymmetric in the tape feeding direction. The relationship between the inclination angles α and β and the SNR was confirmed in the same manner as described above.
[0084]
[Table 2]

[0085]
In the column of “one light source” in Table 2, a circle and a cross indicate the same range as in Table 1. From Table 2, it can be seen that in the range of 0 <β ≦ 10 °, a good detection result can be obtained when the inclination angle α is smaller than 5 ° and as close to 0 ° as possible. Since the size of the concave defect on the back coat side surface of the magnetic tape used is very fine, the amount of scattered light from the defective portion is small and the obtained SNR value is low. (Specifically, the traveling speed is set low, and the flatness of the inspection unit 12A is increased), so that the SNR is improved and the detection can be performed.
[0086]
Next, the effect of using two light beams as shown in FIGS. 1 and 2 was verified.
[0087]
As described above, in Table 2, when only one light beam was used, and experiments were performed while changing the inclination angle α and the inclination angle β, the inclination angle β was set to be small even when the target defect was very small. It was found that when the condition was set to 5 ° close to the normal to the tape surface and the condition was reduced to the light inclination angle α = 3 °, the required peak value of the detection signal could be obtained.
[0088]
However, even under these conditions, when the tape as the sample was reversed, the detection value was changed from 1.35 to 0.00 as shown in the column of “Sample Reverse” in Table 2. Therefore, when the two lights were irradiated from ± 3 degrees, a peak value (1.30) approximated to the higher sensitivity side was obtained (the rightmost column in Table 2). In the examples of Tables 1 and 2, only the information of the highest peak value was obtained because the static characteristics were confirmed. However, in the dynamic characteristics, the peak value of the lower sensitivity side is also accumulated as light energy to the CCD camera. The effect of improving the sensitivity can be expected. In addition, even if the convex defects shown in Table 1 are asymmetric in the tape feeding direction, the effect of improving detection by two light irradiations of the present invention can be obtained.
[0089]
【The invention's effect】
Since the present invention is configured as described above, it has an excellent effect that a surface defect such as a magnetic tape can be detected with a high SNR.
[Brief description of the drawings]
FIG. 1 is a perspective view including a partial block diagram showing a surface defect detection device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram showing a relationship between an optical axis (plane) of light irradiation and a camera optical axis (plane) of a CCD line camera in the surface defect detection device.
FIG. 3 is a perspective view showing a support device for supporting a magnetic tape in the surface defect detection device.
FIG. 4 is an enlarged schematic view showing the relationship among an irradiation area, an inspection area, a light source image area, and a light source non-image area on the surface of the magnetic tape by light.
FIG. 5 is a schematic view of a relationship between a light irradiation optical axis and a camera optical axis as viewed from a tape feeding direction.
FIG. 6 is a schematic diagram showing a relationship between light and scattered light when a defective portion on the surface of the magnetic tape is a concave portion.
FIG. 7 is a schematic diagram showing the inclination direction of the inclined surface in the recess and the relationship between light and scattered light.
FIG. 8 is a schematic diagram showing a relationship between light and scattered light when a defective portion on the surface of the magnetic tape is a convex portion;
FIG. 9 is a diagram showing a waveform of a detection signal when a deposit defect on the surface of a magnetic tape is detected by the embodiment of the surface defect detection device in comparison with a conventional example.
FIG. 10 is a diagram showing the relationship between the inclination angles β and α and the SNR of the detected value when the defective portion on the surface of the magnetic tape is a convex portion;
FIG. 11 is a diagram similar to FIG. 10 when a defective portion on the surface of the magnetic tape is a concave portion;
[Explanation of symbols]
La, Lb ... light
10. Surface defect detection device
12 ... Magnetic tape
12A… Inspection unit
14 ... Support device
16: first virtual plane
16A ... normal
25A, 25B ... light exit
18A, 18B: Light source image area
18C: Width center line
18D: Light source image outside area
19A, 19B ... irradiation optical axis
19C: Irradiation optical axis plane
29A, 29B ... Setting straight line
20 ... Inspection light irradiation device
21: Camera optical axis
21A: Camera optical axis plane
22 ... CCD line camera
22A ... Strip inspection area
22B ... width direction center line
22M ... virtual position
23: Camera symmetric optical axis
24 ... judgment device
30 ... recess
32 ... convex part
32A ... side

Claims

On the surface of the inspection object, set an inspection region by a camera, and, when light from a plurality of light exit ports is incident on the surface of the inspection object, in the irradiation region by the light including the inspection region. There, adjacent to the outside of the inspection area, and at least two positions between the inspection area, so that the mirror image of the plurality of light emission ports are located, set the light exit, The scattered light from the inspection area is received by the camera and converted into a light reception signal. When the light reception signal is larger than the intensity of the light reception signal from the defect-free portion of the inspection area by a certain value or more, the inspection object A method for detecting a surface defect, comprising detecting the surface defect as a surface defect.

An inspection area by a camera is set on the surface of the inspection object, and a camera optical axis passing through the center of the inspection area is set such that an inclination angle β with respect to a normal to the surface of the inspection object is 0 <β ≦ 10 °. and tilted set to the surface of the test object, when the incident light from the two light outlet, by light, the inspection area even during including irradiation area, both outer sides of the examination region The two light exits are set such that the mirror images of the two light exits are located at positions adjacent to each other, and a set straight line passing through the center of these light exits and the center of the inspection area is defined by: The tilt angle α is set to 0 <α <25 ° on both sides from the camera symmetric optical axis of the camera optical axis about the normal line, and scattered light from the inspection area is received by the camera. , Is converted into a light receiving signal. When larger by a predetermined value than the intensity of the received signal, the detection method of surface defects and detecting a surface defect of the inspection object.

3. The method according to claim 2, wherein the inclination angle α is 0 <α <5 °.

3. The surface defect according to claim 2, wherein the inclination angle α is set to any one of 5 ° ≦ α <10 °, 10 ° ≦ α <15 °, or 15 ° ≦ α <25 °. Inspection methods.

In any one of claims 2 to 4, wherein the total length of the two light source image areas where the mirror image of the light emission port is located on the surface of the inspection object is W in the direction adjacent to the inspection area. A method of detecting a surface defect, wherein a distance D from the center position of the light source image area in the adjacent direction to the inspection area is W / 2 <D ≦ 3W / 2.

6. The light source according to claim 2, wherein a light source image region in which a mirror image of the light exit port is positioned by the camera has a linear band shape, and an irradiation optical axis is centered in a width direction of the light source image region. Set to be in a plane parallel to the line, and, the inspection area is a linear band parallel to the linear light source image area, and the camera optical axis, with respect to the normal, The surface defect is characterized in that it is inclined at an inclination angle β to the opposite side to the set straight line passing through the light emission port, and is set to be in a plane including the width direction center line in the inspection area of the straight band shape. Detection method.

7. The first virtual plane and the inspection object according to claim 6, wherein the first virtual plane is parallel to the center line in the width direction of each of the light source image area and the inspection area, and is perpendicular to the inspection object surface. In a second virtual plane perpendicular to the surface, the two light irradiation optical axes are inclined at an inclination angle α on both sides with respect to the camera symmetric optical axis, respectively, and the camera optical axis is set to the irradiation optical axis. A surface defect detection method characterized by being set on the opposite side to the first virtual plane at an inclination angle β with respect to the first virtual plane.

In claim 6 or 7, when the inspection object is a strip, the light source image area and the inspection area are set in a linear strip shape crossing the strip in the width direction, and the strip is set in the longitudinal direction. A method of detecting a surface defect, comprising detecting a surface defect while running.

9. The camera according to claim 6, 7 or 8, wherein the camera is a CCD line camera, and an incident optical axis surface of the CCD line camera including a plurality of incident optical axes coincides with a plane including a width direction center line of the inspection area. A method for detecting a surface defect, wherein the method is set.

A support device that supports the inspection object so that at least a part of the surface passes through the inspection position or stops at the inspection position at a fixed position in the thickness direction, and an inspection area is set on the surface at the inspection position. Further, the camera optical axis is arranged so as to be inclined with respect to the normal to the surface so that the inclination angle β satisfies 0 <β ≦ 10 °, and outputs a light receiving signal having an intensity proportional to the incident light intensity. A camera and a position adjacent to both outer sides of the inspection area in an irradiation area including the inspection area by the light when the surface of the inspection object is irradiated with light from two light emission ports. Forming two light source image areas where the mirror images of the two light exits are located, and a straight line passing through the center of the light exits and the center of the inspection area, the line of the camera optical axis, On both sides from the camera symmetric optical axis about the normal, respectively An inspection light irradiator in which the oblique angle α is set to 0 ° <α <25 °, wherein the intensity of the light reception signal from the camera is more constant than the intensity of the light reception signal due to incident light from a defect-free portion in the inspection area. And a determination device that outputs a defect detection signal when the value is greater than or equal to the value.

11. The surface defect inspection apparatus according to claim 10, wherein the inclination angle α in the inspection light irradiation apparatus is set to 0 <α <5 °.

11. The method according to claim 10, wherein the inclination angle α in the inspection light irradiation device is set to any of 5 ° ≦ α <10 °, 10 ° ≦ α <15 °, or 15 ° ≦ α <25 °. Inspecting device for surface defects.

The camera according to any one of claims 10 to 12, wherein, when the total length of the light source image region in a direction toward the center of the light source image region when viewed from the inspection region is W, the direction of the light source image region is the same. A surface defect detection device, wherein a distance D from a center position to the inspection area is set to satisfy W / 2 <D ≦ 3W / 2.

14. The inspection light irradiation device according to claim 10, wherein the light source image region has a linear band shape, and the light irradiation optical axis of the light is parallel to a width direction center line of the light source image region. And the camera is configured such that the inspection region has a linear band shape parallel to the linear band light source image region, and the camera optical axis is relative to the normal line. A surface defect which is inclined at an inclination angle β to a side opposite to the set straight line passing through the light emission port, and is set so as to lie within a plane including a width direction center line in the straight band-shaped inspection region. Detection device.

The inspection light irradiation device according to claim 14, wherein the first virtual plane parallel to a center line in the width direction of each of the light source image area and the inspection area, and perpendicular to a surface of the inspection object, In a virtual plane and a second virtual plane perpendicular to the surface of the inspection object, the set straight line passing through the two light emission ports is provided to be inclined at an inclination angle α, and the camera emits the camera light. A surface defect detection device characterized in that an axis is inclined at an inclination angle β on a side opposite to the set straight line.

The inspection object according to claim 14 or 15, wherein the inspection target is a band-shaped material, the support device is configured to move the band-shaped material in a longitudinal direction, and the inspection light irradiation device and the camera include the light source image region and A surface defect detection device, wherein an inspection area is set to have a linear band shape crossing the band material in a width direction.

17. The camera according to claim 14, 15 or 16, wherein the camera is a CCD line camera, and an incident optical axis plane including a plurality of incident optical axes of the CCD line camera coincides with a plane including a width direction center line of the inspection area. A surface defect detection device characterized by being set in the following manner.