JP3810599B2

JP3810599B2 - Defect detection device

Info

Publication number: JP3810599B2
Application number: JP32047299A
Authority: JP
Inventors: 光弘友田
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1999-11-11
Filing date: 1999-11-11
Publication date: 2006-08-16
Anticipated expiration: 2019-11-11
Also published as: JP2001141659A

Description

【０００１】
【発明の属する技術分野】
この発明は、例えば積層型電子写真感光体や表面に透明層を設けたり色素を表面に塗布した各種製品の内部の欠陥と表面の欠陥を検出する欠陥検出装置、特に視感度を中心とした目視検査では輝度変化を検知しにくい不可視領域に存在する欠陥の検出に関するものである。
【０００２】
【従来の技術】
例えばアルミ基体のベースに内部層と透明表面層が積層された積層型電子写真感光体の製造ラインにおける塗膜欠陥の検査は、一般に製造ライン中に設けた検査ステーションで検査員による目視官能検査により行なわれていた。この目視官能検査においては、年々開発される異なる分光感度特性を持つ製品の外観欠陥を検査員が見出さなければならないが、近年、デジタル化に対応して開発された積層型電子写真感光体の吸光度のピーク波長領域が半導体レーザ発振波長である７８０ｎｍ近傍にシフトしてきており、検査員のほぼ５５０ｎｍの視感度ピークを中心とする可視領域の反射光では目視検査がしにくい製品も増えてきている。
【０００３】
このような難点を改善するために、被検査面の塗膜欠陥を撮像素子を用いたフライングイメージ方式で自動的に検出するようにした表面欠陥検査装置が、例えば特開平８−５５７７号公報や特開平６−１９４３１８号公報，特開平６−２０７９０９号公報等に開示されている。フライングイメージ方式は、被検査物の表面を撮像カメラ等の画像入力装置で読み取って画像データを取得し、フィルタリングや２値化等の画像処理をして被検査物の表面の情報から欠陥を検出する方法である。
【０００４】
特開平８−５５７７号公報に示された表面欠陥検査装置は、光沢面を有する表面層と拡散層という２種の光学的特異性を持つ層を積層し、拡散層には格子線を設け、表面層には疑似欠陥である特記を設けた標板を構成し、拡散層と表面層の欠陥受光状態に基づいてカメラの受光位置を補正して、感光体表面の欠陥を高いコントラストで撮像するようにしている。特開平６−１９４３１８号公報に示された表面欠陥検査装置は、取得した画像データを複数個のデジタルフィルタに異なる縮小率で入力して、各種サイズの表面欠陥を良好に検出するようにしている。
【０００５】
【発明が解決しようとする課題】
しかしながら可視領域の照明光を用いた照明方法や偏光特性を利用したこれらの表面欠陥装置では、可視領域に高吸光度である波長帯域を有するアナログ用積層型電子写真感光体の場合は高いコントラストで濃度ムラ欠陥を認識できるが、高吸光度の波長帯域が不可視領域、特に内部層の高吸光度の波長帯域が半導体レーザ光源の発振波長である近赤外線の不可視領域にあるデジタル対応の積層型電子写真感光体の場合は、内部層に存在する色ムラ欠陥等を高いＳ／Ｎ比で認識する事が困難であった。
【０００６】
また、このような低コントラストの感光体欠陥を視認するために、より光量の強い可視光を照射する方法が取られてきたが、光量の強い可視光を積層型電子写真感光体に照射すると、特に電荷移動層が前露光疲労を受け、電荷移動層のドナーが光ダメージを受けるという問題もあった。
【０００７】
この発明はかかる短所を改善し、半導体レーザ光源用の積層型電子写真感光体に対応した被検査面に存在する不可視画像を含む濃度ムラ欠陥等を高感度で、かつ光ダメージを与えないで撮像して検出する欠陥検出装置を提供することを目的とするものである。
【０００８】
【課題を解決するための手段】
この発明に係る欠陥検出装置は、不可視光光源と撮像手段と表示装置とからなる画像撮像装置及び画像処理手段とを有する欠陥検査装置であって、前記撮像手段は、光軸が積層型電子写真感光体の法線に対して僅かに傾けて配置され、前記不可視光光源は光軸が積層型電子写真感光体の表面において撮像手段の光軸と３０度〜６０度の角度で交差するように配置され、前記不可視光光源は近赤外線を積層型電子写真感光体の表面に照射し、撮像手段は積層型電子写真感光体の内部層で拡散反射した拡散反射成分のうち入射点における法線近傍の拡散反射近傍光と積層型電子写真感光体の透明表面層の表面からの散乱反射光を受光して光電変換して積層型電子写真感光体の内部層の不可視欠陥と透明表面層の凸凹欠陥を示す欠陥画像信号を前記画像処理手段に出力し、前記画像処理手段は、前記撮像手段から出力される欠陥画像信号の情報から欠陥の候補領域である特異領域を抽出し、特異領域の情報をフラクタル解析して画像の濃度変化から感光体内部層の濃淡ムラの不可視欠陥と透明表面層の凸凹欠陥を判定し、前記表示装置は前記画像処理手段で判定した欠陥画像を表示することを特徴とする。
【０００９】
前記不可視光照明手段から出射する光のピーク波長領域と、撮像手段の分光感度ピーク波長領域を積層型電子写真感光体の内部層における高吸光度である波長帯域と一致させることが望ましい。
【００１４】
【発明の実施の形態】
この発明の画像撮像装置は、アルミ基体のベースに内部層と透明表面層が積層されている積層型電子写真感光体の欠陥を撮像して表示するものであり、不可視光光源と撮像手段と表示装置とを有する。不可視光光源は視感度から外れた波長領域の不可視光、例えば近赤外線を感光体の表面に照射する。撮像手段は感光体から反射する拡散反射近傍光を受光して光電変換し視感度から外れた不可視欠陥画像信号を出力するものであり、１次元積算段数型ＣＣＤカメラを有する。表示装置５は撮像手段４から出力した欠陥画像信号により欠陥画像を表示する。
【００１５】
この画像撮像装置で感光体の欠陥を撮像して表示するときは、感光体を例えばステッピングモータ等を有する回転手段で軸心を中心にして回転しながら不可視光光源から感光体の表面に近赤外線の不可視光を照射する。感光体の透明表面層に入射した不可視光は透明表面層の表面で反射と屈折をする。透明表面層の表面で反射する光は、透明表面層の表面に欠陥がない場合には正反射光として反射し、透明表面層の表面に欠陥がある場合には散乱反射光として反射する。また、透明表面層で屈折した光は内部層で拡散反射し、透明表面層を透過し拡散反射光として出射する。このように不可視光光源から感光体の表面に不可視光として近赤外線を照射することにより、感光体のデジタル化に対応した吸光度のピーク波長領域の半導体レーザ発振波長である近赤外線領域シフトに対応でき、内部層で拡散反射した拡散反射光は、吸光度が高い色ムラ欠陥部分では欠陥部分が暗くなり、正常部とのコントラストが高くなる。この内部層で拡散反射した拡散反射近傍光を撮像手段で受光する。
【００１６】
【実施例】
図１はこの発明の一実施例の構成図である。図に示すように、被検査体、例えば積層型電子写真感光体（以下、感光体という）１の欠陥を撮像して表示する画像撮像装置２は不可視光光源３と撮像手段４と表示装置５とを有する。感光体１は、図２の断面図に示すように、アルミ基体のベース６に内部層７と透明表面層８が積層されている。不可視光光源３は視感度から外れた波長領域の不可視光、例えば近赤外線を感光体１の表面に照射する。ここで視感度とは波長を変えて同一明るさに見えるそれぞれの光の放射エネルギの逆数と定義されており、そのピーク波長領域はおおよそ５５０ｎｍである。撮像手段４は感光体１から反射する拡散反射近傍光を受光して光電変換し視感度から外れた不可視欠陥画像信号を出力するものであり、撮像手段４は感光体１からの拡散反射近傍光を受光する暗視野すなわち正常部が明るく欠陥部が暗くなる領域の光量変化を検出する反射光軸側に１次元積算段数型ＣＣＤカメラを有する。撮像手段４は感光体１からの拡散反射近傍光を受光するため、不可視光光源３と撮像手段４の光軸が感光体１の表面に対してなす角度αはほぼ３０度〜６０度になっている。表示装置５は撮像手段４から出力した欠陥画像信号により欠陥画像を表示する。
【００１７】
上記のように構成した画像撮像装置２で感光体１の欠陥を撮像して表示するときは、感光体１を例えばステッピングモータ等を有する回転手段で軸心を中心にして回転しながら不可視光光源３から感光体１の表面に近赤外線の不可視光を照射する。このとき、塵埃等による誤検出や過検出を防ぐため、回転する感光体１の円周位置にイオナイザやエアーブロー，超音波等の除塵機構を配置して塵埃等を除去する。感光体１の透明表面層８に入射した不可視光９は、図２に示すように、透明表面層８の表面で反射と屈折をする。透明表面層８の表面で反射する光は、透明表面層８の表面に欠陥がない場合には正反射光１０として反射し、透明表面層８の表面に欠陥がある場合には散乱反射光１１として反射する。また、透明表面層８で屈折した光は内部層７で拡散反射し、透明表面層８を透過し拡散反射光１２として出射する。
【００１８】
ここで不可視光光源３から感光体１の表面に不可視光９として近赤外線を照射することにより、感光体１のデジタル化に対応した吸光度のピーク波長領域の半導体レーザ発振波長である近赤外線領域シフトに対応できる。すなわち、感光体１において、正常面より色の濃くなる濃度ムラは内部層７に多く付着する有色材料に原因する場合が多い。この感光体１に光を照射したとき内部層７で拡散反射した拡散反射光は、吸光度が高い色ムラ欠陥部分では欠陥部分が暗くなり、正常部とのコントラストが高くなる。最も濃度ムラ欠陥の画像コントラストの高くなる条件は、内部層７の高吸光度である波長帯域と不可視光光源３から照射する光のピーク波長帯域が一致していることである。デジタル対応の感光体１の内部層７における吸光度のピーク波長領域は、図３の分光吸収特性に示すように、半導体レーザ発振波長である７８０ｎｍ近傍にある。この感光体１に従来から使用されている螢光燈やハロゲンライト等からの視感度ピークがほぼ５５０ｎｍの可視領域の光を照射しても濃度ムラ欠陥の画像コントラストは低下し、濃度ムラ欠陥を検出できなくなる。そこで不可視光光源３から感光体１の表面に半導体レーザ発振波長である７８０ｎｍ近傍にピーク波長領域を有する近赤外線を不可視光９として照射し、濃度ムラ欠陥の画像コントラストを高くする。また、不可視光９に紫外線成分が有った場合は、その過大な光エネルギのために感光体１に化学変化や燐光，蛍光発生といった光ダメージを与えてしまうが、近赤外線を用いることにより紫外線をカットすることができ、電荷移動層に含まれる電子供与体（ドナー）の光ダメージを抑えることができる。この不可視光光源３で近赤外線を出射する方法としては、分光を用いる方法やフィルタを用いる方法又は波長選択された発光光源を用いる方法の何れの方法でも良い。
【００１９】
撮像手段４は感光体１の内部層７で拡散反射した拡散反射光成分のうち入射点における法線近傍の拡散反射近傍光を受光し、受光した光に含まれる情報から不可視欠陥画像信号を出力する。この撮像手段４の１次元積算段数型ＣＣＤカメラのＣＣＤとしては、図４のＣＣＤの比感度特性に示すように、分光感度ピーク波長領域が特に近赤外線領域（７８０ｎｍ以上）にピークがあるものを選択して用い、分光感度ピーク波長領域を感光体１の内部層７の高吸光度である波長帯域と一致させて、濃度ムラ欠陥の画像コントラストが低下しないようにしておく。このようにして感光体１の内部層７の情報のＳ／Ｎを向上し、塗工ムラ等の電荷発生層における欠陥を認識することができる。また、撮像手段４に１次元積算段数型ＣＣＤセンサを用いることにより、従来型の１次元ＣＣＤセンサと比べて積算段数分の露光時間を多く素子に与えることができ、低コントラストの感光体１でも照射光量を大きくすることなく、必要最低限の照射エネルギで光ダメージを押さえながら濃度ムラ欠陥等を高感度で撮像できる。すなわち、従来型の１次元ＣＣＤセンサのように、ある一点を撮像するＣＣＤ素子が１画素のみで物体が通過する一瞬の電荷チャージで有るのに対して、１次元積算段数型ＣＣＤセンサは同じ点に対する電荷チャ−ジを感光体１の回転に同期して積算段数分引き渡しながら累積加算していく。また、撮像手段４として１次元積算段数型ＣＣＤセンサを用いることにより、電子走査により感光体１のドラム基体の長手方向である主走査方向を高速走査することができ、ドラム基体の全長方向に複数台の１次元積算段数型ＣＣＤセンサ、例えば低光量下での高速スキャンが可能な市販の２０４８画素の１次元積算段数型ＣＣＤセンサを２台を設置することにより、空間分解能を向上させることもできる。
【００２０】
また、撮像手段４は感光体１の内部層７で拡散反射した拡散反射光成分のうち入射点における法線近傍の拡散反射近傍光を受光するために、不可視光光源３と撮像手段４の光軸が感光体１の表面に対してなす角度αをほぼ３０度〜６０度にして不可視光光源３と撮像手段４を配置しておく。すなわち、感光体１の内部層７の高吸光度波長領域に依存しない表面散乱光１１や正反射成分１０を高い感度で撮る必要のない受光法（暗視野法）で内部層７の拡散反射光１２を多く受光するためには、幾何学的には不可視光光源３からある入射角で光を入射した感光体１の入射位置に対する法線方向に設けた撮像手段４で受光すれば良い。しかしながら感光体１の欠陥を検査する場合には、内部層７の欠陥だけでなく透明表面層８の凸凹形状を含む欠陥による散乱反射光１１も検出する必要がある。この感光体１の内部層７の濃度ムラと透明表面層８の凸凹欠陥を同時に検出するために様々な調査を行った結果、特に不可視光光源３と撮像手段４の光軸が感光体１の表面に対してなす角度αをほぼ３０度〜６０度にして撮像手段４１を感光体１の法線に対して僅かに傾けて拡散反射近傍光を受光することにより、感光体１の内部層７の高吸光度波長領域に依存する濃淡ムラ等の不可視欠陥をより高いコントラストで撮像できるとともに透明表面層８の凸凹欠陥を同時に検出することができる。
【００２１】
なお、撮像手段４を感光体１の入射位置に対する法線方向に設けて感光体１の内部層７の高吸光度波長領域に依存する濃淡ムラ等の不可視欠陥を撮像するとともに、感光体１の入射位置からの正反射光の光路に透明表面層８の凸凹欠陥を撮像する撮像手段を設けても良い。
【００２２】
次ぎに上記のように構成した画像撮像装置２で撮像した画像により感光体１の欠陥と欠陥の種類を検出する欠陥検出装置について説明する。欠陥検出装置２０は、図５のブロック図に示すように、画像撮像装置２と画像処理部２１を有する。画像処理部２１は、画像撮像装置２の撮像手段４がアナログカメラの場合であればＡ／Ｄ変換部２２と特異領域抽出部２３と特徴量算出部２４及び欠陥判定部２５を有する。撮像手段４としてアナログカメラを用いた際にＡ／Ｄ変換部２２は画像撮像装置２の撮像手段４で撮像した画像をＡ／Ｄ変換して多値画像を形成する。特異領域抽出部２３は形成された多値画像の特異領域を抽出する。特徴量算出部２４は抽出された特異領域の特徴量を算出する。欠陥判定部２５は算出された特徴量から欠陥の種類を判定する。ここで撮像手段４がデジタルカメラの場合は、デジタル８ビット等で出力が直接なされるため、Ａ／Ｄ変換部２２は不要である。
【００２３】
上記のように構成した欠陥検出装置２０で画像撮像装置２の不可視光照明装置３から感光体１に近赤外線を照射し、感光体１からの拡散反射近傍光を撮像手段４で受光し、受光した光に含まれる情報から不可視欠陥画像信号を表示装置５に出力して画像を表示するとともに画像処理部２１に出力する。画像処理部２１は送られた画像信号を撮像手段４としてアナログカメラを用いた場合はＡ／Ｄ変換して、例えば輝度情報をＺ軸とし、位置情報をＸ軸とＹ軸にした多値画像を形成し、表示装置５に表示するとともに特異領域抽出部２３に送る。特異領域抽出部２３は送られた多値画像の特異領域である欠陥の候補領域を抽出して、特異領域の情報を特徴量算出部２４に送る。特徴量算出部２４は送られた特異領域の情報から例えばフラクタル解析により特徴量を算出し、フラクタル次元で画像の濃度曲面の起伏等を表わす。欠陥検出部２５は算出された特異領域の特徴量から欠陥の種類を判定し、欠陥の種類とその位置を表示装置５に表示する。
【００２４】
このようにして感光体１の内部層７の高吸光度波長領域に依存する濃淡ムラ等の不可視欠陥や透明表面層８の凸凹欠陥を精度良く検出することができる。したがって複写機やプリンタ用に使用する感光体１の品質を高く維持することができ、良質な画像を形成することができる。
【００２５】
上記実施例はデジタル対応の感光体１の内部層７の濃淡ムラ等の不可視欠陥や透明表面層８の凸凹欠陥を検出する場合について説明したが、表面に透明層を設けたり色素を表面に塗布した各種製品の内部の疵や塗りムラ等の欠陥も同様にして検出することができる。
【００２６】
【発明の効果】
この発明は以上説明したように、被検査物の表面に視感度から外れた波長領域の光を照射し、被検査物からの拡散反射近傍光を受光して画像を撮像するようにしたから、被検査物の内部欠陥の画像と表面欠陥の画像を高感度で撮像することができる。
【００２７】
また、デジタル対応の積層型電子写真感光体の表面に視感度から外れた波長領域の光を照射し、感光体からの拡散反射近傍光を受光して画像を撮像するようにしたから、検査員の視認し難いデジタル対応の積層型電子写真感光体の内部有色層の濃度ムラ欠陥を高感度で撮像することができる。
【００２８】
さらに、不可視光として近赤外線を照射することにより、感光体のデジタル化に対応した吸光度のピーク波長領域の半導体レーザ発振波長である近赤外線領域シフトに対応でき、感光体の内部有色層の濃度ムラ欠陥の画像コントラストを高くすることができるとともに紫外線による感光体の電荷移動層に含まれる電子供与体（ドナー）の光ダメージを抑えることができる。
【００２９】
また、感光体に照射する不可視光のピーク波長領域と、感光体からの拡散反射近傍光を受光する撮像手段の分光感度ピーク波長領域を感光体の内部層における高吸光度である波長帯域と一致させることにより、濃度ムラ欠陥の画像コントラストをより高め、感光体の内部層の情報のＳ／Ｎを向上し、塗工ムラ等の電荷発生層における欠陥画像を高感度で撮像することができる。
【００３０】
また、撮像手段に１次元積算段数型ＣＣＤセンサを用いることにより、従来型の１次元ＣＣＤセンサと比べて積算段数分の露光時間を多く素子に与えることができ、低コントラストの感光体でも照射光量を大きくすることなく、必要最低限の照射エネルギで光ダメージを押さえながら濃度ムラ欠陥等を高感度で撮像できる。
【００３１】
さらに、画像撮像装置で撮像した画像を画像処理して欠陥の種類を判定することにより、デジタル対応の積層型電子写真感光体や表面に透明層を設けたり色素を表面に塗布した各種製品の内部の疵や塗りムラ等の欠陥を精度良く検出することができる。
【図面の簡単な説明】
【図１】この発明の実施例の画像撮像装置の構成図である。
【図２】感光体の構成と入射光と反射光及び拡散反射光を示す断面図である。
【図３】感光体の内部層の分光吸収特性図である。
【図４】撮像手段の比感度特性図である。
【図５】この発明の実施例の欠陥検出装置の構成を示すブロック図である。
【符号の説明】
１；感光体、２；画像撮像装置、３；不可視光光源、４；撮像手段、
５；表示装置、６；ベース、７；内部層、８；透明表面層、
２０；欠陥検出装置、２１；画像処理部、２２；Ａ／Ｄ変換部、
２３；特異領域抽出部、２４；特徴量算出部、２５；欠陥判定部。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a defect detection device for detecting internal defects and surface defects in, for example, a multilayer electrophotographic photosensitive member or a transparent layer provided on the surface or a pigment coated on the surface, and visual inspection centering on visual sensitivity. The inspection relates to detection of a defect existing in an invisible region where it is difficult to detect a change in luminance.
[0002]
[Prior art]
For example, inspection of coating film defects in a production line of a laminated electrophotographic photosensitive member in which an inner layer and a transparent surface layer are laminated on an aluminum base is generally performed by visual sensory inspection by an inspector at an inspection station provided in the production line. It was done. In this visual sensory inspection, inspectors must find appearance defects of products with different spectral sensitivity characteristics that are developed year by year, but in recent years, the absorbance of multilayer electrophotographic photoreceptors developed in response to digitization The peak wavelength region has shifted to around 780 nm, which is the semiconductor laser oscillation wavelength, and an increasing number of products are difficult to visually inspect with the reflected light in the visible region centered on the inspector's visibility peak at about 550 nm.
[0003]
In order to improve such a difficulty, a surface defect inspection apparatus that automatically detects a coating film defect on a surface to be inspected by a flying image method using an image sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-5577 or It is disclosed in JP-A-6-194318 and JP-A-6-207909. In the flying image method, the surface of the inspection object is read by an image input device such as an imaging camera to acquire image data, and image processing such as filtering and binarization is performed to detect defects from the information on the surface of the inspection object. It is a method to do.
[0004]
In the surface defect inspection apparatus disclosed in Japanese Patent Laid-Open No. 8-5577, a surface layer having a glossy surface and a layer having two optical specificities, a diffusion layer, are laminated, and a lattice line is provided in the diffusion layer. The surface layer is provided with a special plate with a special note that is a pseudo-defect, and the light receiving position of the camera is corrected based on the defect light receiving state of the diffusion layer and the surface layer, thereby imaging the defect on the surface of the photoreceptor with high contrast. I am doing so. In the surface defect inspection apparatus disclosed in Japanese Patent Laid-Open No. 6-194318, acquired image data is input to a plurality of digital filters at different reduction ratios so as to detect surface defects of various sizes satisfactorily. .
[0005]
[Problems to be solved by the invention]
However, in these surface defect devices using illumination methods using the illumination light in the visible region and polarization characteristics, in the case of analog type electrophotographic photoreceptors having a wavelength band with high absorbance in the visible region, the density is high and the contrast is high. Multi-layer electrophotographic photoconductor capable of recognizing mura defects, but with a high absorbance wavelength band in the invisible region, especially in the near infrared invisible region where the high absorbance wavelength band of the inner layer is the oscillation wavelength of the semiconductor laser light source In this case, it was difficult to recognize color unevenness defects and the like existing in the inner layer with a high S / N ratio.
[0006]
Further, in order to visually recognize such a low-contrast photoconductor defect, a method of irradiating visible light with a higher amount of light has been taken, but when irradiating a laminated electrophotographic photosensitive member with a higher amount of visible light, In particular, the charge transfer layer is subjected to pre-exposure fatigue, and the donor of the charge transfer layer is also damaged by light.
[0007]
The present invention improves such disadvantages and captures density unevenness defects including an invisible image existing on a surface to be inspected corresponding to a laminated electrophotographic photosensitive member for a semiconductor laser light source with high sensitivity and without causing optical damage. It is an object of the present invention to provide a defect detection device that detects the defect .
[0008]
[Means for Solving the Problems]
A defect detection apparatus according to the present invention is a defect inspection apparatus having an image imaging device and an image processing unit including an invisible light source, an imaging unit, and a display unit, and the imaging unit has an optical axis that is a laminated electrophotography. The invisible light source is arranged so as to be slightly inclined with respect to the normal line of the photoconductor, and the optical axis of the invisible light source intersects with the optical axis of the image pickup means at an angle of 30 to 60 degrees on the surface of the laminated electrophotographic photoconductor. The invisible light source irradiates near infrared rays on the surface of the multilayer electrophotographic photosensitive member, and the imaging means is near the normal at the incident point of the diffuse reflection component diffusely reflected by the inner layer of the multilayer electrophotographic photosensitive member. Invisible defects in the inner layer of the multilayer electrophotographic photosensitive member and irregularities in the transparent surface layer are received and photoelectrically converted by the diffuse reflection near light and the scattered reflected light from the surface of the transparent surface layer of the multilayer electrophotographic photosensitive member. wherein a defect image signal indicating the Output to the image processing means, the image processing means extracts a specific area that is a defect candidate area from the information of the defect image signal output from the imaging means, and performs fractal analysis on the information of the specific area to obtain the density of the image From the change, an invisible defect of shading unevenness of the inner layer of the photosensitive member and an uneven defect of the transparent surface layer are determined, and the display device displays the defect image determined by the image processing means .
[0009]
It is desirable that the peak wavelength region of the light emitted from the invisible light illuminating unit and the spectral sensitivity peak wavelength region of the imaging unit coincide with a wavelength band having high absorbance in the inner layer of the multilayer electrophotographic photosensitive member.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The image pickup apparatus of the present invention picks up and displays a defect of a laminated electrophotographic photosensitive member in which an inner layer and a transparent surface layer are laminated on a base of an aluminum substrate, and displays an invisible light source, an imaging means, and a display Device. The invisible light source irradiates the surface of the photosensitive member with invisible light in a wavelength region deviating from visibility, for example, near infrared rays. The imaging means receives diffuse reflection near light reflected from the photosensitive member, photoelectrically converts it, and outputs an invisible defect image signal deviating from visibility, and has a one-dimensional integration stage type CCD camera. The display device 5 displays the defect image based on the defect image signal output from the imaging unit 4.
[0015]
When imaging and displaying a defect of the photoreceptor with this image pickup device, the near-infrared light from the invisible light source to the surface of the photoreceptor is rotated while the photoreceptor is rotated about the axis by a rotating means having a stepping motor, for example. Of invisible light. Invisible light incident on the transparent surface layer of the photoreceptor is reflected and refracted on the surface of the transparent surface layer. The light reflected on the surface of the transparent surface layer is reflected as regular reflected light when there is no defect on the surface of the transparent surface layer, and is reflected as scattered reflected light when there is a defect on the surface of the transparent surface layer. Further, the light refracted by the transparent surface layer is diffusely reflected by the inner layer, passes through the transparent surface layer, and is emitted as diffusely reflected light. By irradiating the surface of the photoconductor with invisible light from an invisible light source in this way, it is possible to cope with the near infrared region shift, which is the semiconductor laser oscillation wavelength in the peak wavelength region of absorbance corresponding to the digitization of the photoconductor. In the diffuse reflection light diffusely reflected by the inner layer, the defective portion becomes dark at the color unevenness defect portion where the absorbance is high, and the contrast with the normal portion becomes high. The diffuse reflection near light diffusely reflected by the inner layer is received by the imaging means.
[0016]
【Example】
FIG. 1 is a block diagram of an embodiment of the present invention. As shown in the figure, an image pickup device 2 that picks up and displays a defect of an inspection object, for example, a laminated electrophotographic photosensitive member (hereinafter referred to as a photosensitive member) 1 is an invisible light source 3, an imaging means 4, and a display device 5. And have. As shown in the sectional view of FIG. 2, the photoreceptor 1 has an inner layer 7 and a transparent surface layer 8 laminated on a base 6 of an aluminum base. The invisible light source 3 irradiates the surface of the photoreceptor 1 with invisible light in a wavelength region deviating from visibility, for example, near infrared light. Here, the visibility is defined as the reciprocal of the radiant energy of each light that appears to have the same brightness by changing the wavelength, and its peak wavelength region is approximately 550 nm. The imaging unit 4 receives diffuse reflection near light reflected from the photosensitive member 1 and photoelectrically converts it to output an invisible defect image signal that is out of visibility. The imaging unit 4 emits diffuse reflection near light from the photosensitive member 1. A one-dimensional integrated stage type CCD camera is provided on the reflection optical axis side for detecting a change in the amount of light in a dark field where light is received, that is, in a region where the normal part is bright and the defective part is dark. Since the imaging unit 4 receives the diffuse reflection near light from the photoreceptor 1, the angle α formed by the optical axes of the invisible light source 3 and the imaging unit 4 with respect to the surface of the photoreceptor 1 is approximately 30 ° to 60 °. ing. The display device 5 displays the defect image based on the defect image signal output from the imaging unit 4.
[0017]
When the image pickup device 2 configured as described above picks up and displays a defect of the photosensitive member 1, the invisible light source is rotated while the photosensitive member 1 is rotated around the axis by a rotating unit having a stepping motor, for example. 3 irradiates the surface of the photoreceptor 1 with near-infrared invisible light. At this time, in order to prevent erroneous detection and excessive detection due to dust or the like, a dust removing mechanism such as an ionizer, air blow, or ultrasonic wave is disposed at the circumferential position of the rotating photosensitive member 1 to remove dust or the like. The invisible light 9 incident on the transparent surface layer 8 of the photoreceptor 1 is reflected and refracted on the surface of the transparent surface layer 8 as shown in FIG. The light reflected on the surface of the transparent surface layer 8 is reflected as regular reflected light 10 when there is no defect on the surface of the transparent surface layer 8, and the scattered reflected light 11 when there is a defect on the surface of the transparent surface layer 8. As reflective. The light refracted by the transparent surface layer 8 is diffusely reflected by the inner layer 7, passes through the transparent surface layer 8, and is emitted as diffusely reflected light 12.
[0018]
Here, by irradiating the surface of the photosensitive member 1 with near-infrared light as invisible light 9 from the invisible light source 3, the near-infrared region shift that is the semiconductor laser oscillation wavelength in the peak wavelength region of absorbance corresponding to the digitization of the photosensitive member 1 is performed. It can correspond to. That is, in the photoreceptor 1, the density unevenness in which the color is darker than the normal surface is often caused by the colored material adhering to the inner layer 7. The diffusely reflected light diffused and reflected by the inner layer 7 when the photosensitive member 1 is irradiated with light is dark at the defective color unevenness portion having a high absorbance and has a high contrast with the normal portion. The condition that the image contrast of the density unevenness defect is the highest is that the wavelength band, which is the high absorbance of the inner layer 7, matches the peak wavelength band of the light emitted from the invisible light source 3. The peak wavelength region of absorbance in the inner layer 7 of the digital photoconductor 1 is in the vicinity of 780 nm, which is the semiconductor laser oscillation wavelength, as shown in the spectral absorption characteristics of FIG. Even if this photoconductor 1 is irradiated with light in the visible region having a visibility peak of approximately 550 nm from a fluorescent lamp or halogen light conventionally used, the image contrast of the density unevenness defect is lowered, and the density unevenness defect is removed. Can no longer be detected. In view of this, near infrared light having a peak wavelength region near the semiconductor laser oscillation wavelength of 780 nm is irradiated as invisible light 9 from the invisible light source 3 to the surface of the photoconductor 1 to increase the image contrast of the density unevenness defect. Further, when the invisible light 9 has an ultraviolet component, the excessive light energy causes light damage such as chemical change, phosphorescence, and fluorescence generation to the photoconductor 1. The photodamage of the electron donor (donor) contained in the charge transfer layer can be suppressed. As a method of emitting near-infrared light with the invisible light source 3, any of a method using spectroscopy, a method using a filter, and a method using a light source having a wavelength selected may be used.
[0019]
The imaging unit 4 receives diffuse reflection near light near the normal line at the incident point among diffuse reflection components diffusely reflected by the inner layer 7 of the photoreceptor 1 and outputs an invisible defect image signal from information contained in the received light. To do. As the CCD of the one-dimensional integrated stage type CCD camera of the imaging means 4, as shown in the specific sensitivity characteristics of the CCD in FIG. 4, the spectral sensitivity peak wavelength region has a peak particularly in the near infrared region (780 nm or more). The spectral sensitivity peak wavelength region is selected and used so as to coincide with the wavelength band that is the high absorbance of the inner layer 7 of the photoreceptor 1 so that the image contrast of the density unevenness defect does not decrease. In this way, the S / N of information in the inner layer 7 of the photoreceptor 1 can be improved, and defects in the charge generation layer such as coating unevenness can be recognized. Further, by using a one-dimensional integrated stage number type CCD sensor for the image pickup means 4, it is possible to give the device a longer exposure time for the number of integrated stages compared to a conventional one-dimensional CCD sensor. Without increasing the amount of irradiation light, it is possible to image a density unevenness defect or the like with high sensitivity while suppressing light damage with the minimum necessary irradiation energy. That is, unlike a conventional one-dimensional CCD sensor, a CCD element that picks up an image of a certain point is an instant charge charge through which an object passes through only one pixel, whereas a one-dimensional integrated stage type CCD sensor has the same points. The charge charge is cumulatively added while being delivered by the number of integrated stages in synchronization with the rotation of the photosensitive member 1. Further, by using a one-dimensional integration stage type CCD sensor as the image pickup means 4, the main scanning direction which is the longitudinal direction of the drum base of the photosensitive member 1 can be scanned at high speed by electronic scanning, and a plurality of them can be provided in the entire length direction of the drum base. Spatial resolution can be improved by installing two one-dimensional integrated stage type CCD sensors, for example, two commercially available 2048 pixel one-dimensional integrated stage type CCD sensors capable of high-speed scanning under low light intensity. .
[0020]
Further, the imaging means 4 receives the light from the invisible light source 3 and the imaging means 4 in order to receive the diffuse reflection near light near the normal line at the incident point among the diffuse reflection light components diffusely reflected by the inner layer 7 of the photoreceptor 1. The invisible light source 3 and the image pickup means 4 are arranged such that the angle α formed by the axis with respect to the surface of the photoreceptor 1 is approximately 30 to 60 degrees. That is, the diffusely reflected light 12 of the inner layer 7 by the light receiving method (dark field method) that does not require taking the surface scattered light 11 and the specular reflection component 10 independent of the high absorbance wavelength region of the inner layer 7 of the photoreceptor 1 with high sensitivity. In order to receive a large amount of light, it may be received by the imaging means 4 provided in the normal direction with respect to the incident position of the photoreceptor 1 where light is incident from an invisible light source 3 at a certain incident angle. However, when inspecting the defect of the photoreceptor 1, it is necessary to detect not only the defect of the inner layer 7 but also the scattered reflected light 11 due to the defect including the uneven shape of the transparent surface layer 8. As a result of various investigations for simultaneously detecting the density unevenness of the inner layer 7 of the photosensitive member 1 and the unevenness of the transparent surface layer 8, the optical axes of the invisible light source 3 and the imaging means 4 are particularly different from those of the photosensitive member 1. The inner layer 7 of the photosensitive member 1 is received by receiving the light near the diffuse reflection by making the imaging device 41 slightly tilted with respect to the normal line of the photosensitive member 1 by setting the angle α formed with respect to the surface to approximately 30 ° to 60 °. Invisible defects such as shading unevenness depending on the high-absorbance wavelength region can be imaged with higher contrast, and irregularities in the transparent surface layer 8 can be detected simultaneously.
[0021]
The imaging means 4 is provided in the normal direction with respect to the incident position of the photosensitive member 1 to pick up invisible defects such as density unevenness depending on the high absorbance wavelength region of the inner layer 7 of the photosensitive member 1 and the incident of the photosensitive member 1. You may provide the imaging means which images the uneven defect of the transparent surface layer 8 in the optical path of the regular reflection light from a position.
[0022]
Next, a defect detection apparatus that detects the defect of the photoreceptor 1 and the type of defect from the image captured by the image capturing apparatus 2 configured as described above will be described. As shown in the block diagram of FIG. 5, the defect detection device 20 includes an image capturing device 2 and an image processing unit 21. The image processing unit 21 includes an A / D conversion unit 22, a specific region extraction unit 23, a feature amount calculation unit 24, and a defect determination unit 25 when the imaging unit 4 of the image imaging device 2 is an analog camera. When an analog camera is used as the imaging unit 4, the A / D conversion unit 22 performs A / D conversion on the image captured by the imaging unit 4 of the image imaging apparatus 2 to form a multi-value image. The singular region extraction unit 23 extracts a singular region of the formed multi-valued image. The feature amount calculation unit 24 calculates the feature amount of the extracted singular region. The defect determination unit 25 determines the type of defect from the calculated feature amount. Here, when the image pickup means 4 is a digital camera, output is directly performed by digital 8 bits or the like, so that the A / D converter 22 is unnecessary.
[0023]
The defect detection device 20 configured as described above irradiates the photosensitive member 1 with near-infrared light from the invisible light illuminating device 3 of the image pickup device 2, and receives light near the diffuse reflection from the photosensitive member 1 with the imaging means 4. The invisible defect image signal is output from the information included in the light to the display device 5 to display the image and to the image processing unit 21. The image processing unit 21 performs A / D conversion on the sent image signal when an analog camera is used as the imaging unit 4, for example, a multi-value image having luminance information on the Z axis and position information on the X and Y axes. It is formed, displayed on the display device 5 and sent to the singular region extraction unit 23. The singular region extraction unit 23 extracts a defect candidate region which is a singular region of the sent multi-valued image, and sends information on the singular region to the feature amount calculation unit 24. The feature amount calculation unit 24 calculates a feature amount from, for example, fractal analysis from the sent information on the singular region, and represents the undulation of the density curved surface of the image in the fractal dimension. The defect detection unit 25 determines the type of defect from the calculated characteristic amount of the specific area, and displays the type and position of the defect on the display device 5.
[0024]
In this way, invisible defects such as density unevenness depending on the high absorbance wavelength region of the inner layer 7 of the photoreceptor 1 and unevenness defects of the transparent surface layer 8 can be accurately detected. Therefore, the quality of the photoreceptor 1 used for a copying machine or a printer can be maintained high, and a high-quality image can be formed.
[0025]
In the above embodiment, the case of detecting invisible defects such as shading unevenness of the inner layer 7 of the digital-compatible photoreceptor 1 and unevenness of the transparent surface layer 8 is described. However, a transparent layer is provided on the surface or a dye is applied to the surface. Defects such as wrinkles and uneven coating inside various products can be detected in the same manner.
[0026]
【The invention's effect】
As described above, the present invention irradiates the surface of the inspection object with light in a wavelength region deviating from the visibility, and receives light near the diffuse reflection from the inspection object so as to capture an image. An image of an internal defect and an image of a surface defect of the inspection object can be taken with high sensitivity.
[0027]
In addition, the surface of the digital electrophotographic photosensitive member for digital use is irradiated with light in a wavelength region that is out of visibility, and light near the diffuse reflection from the photosensitive member is received to capture an image. Thus, it is possible to image with high sensitivity the density unevenness defect of the internal colored layer of the digital-compatible multilayer electrophotographic photoreceptor that is difficult to visually recognize.
[0028]
Furthermore, by irradiating near-infrared light as invisible light, it is possible to cope with the near-infrared region shift, which is the semiconductor laser oscillation wavelength in the peak wavelength region of absorbance corresponding to the digitization of the photoconductor, and density unevenness of the internal colored layer of the photoconductor. It is possible to increase the image contrast of the defect and to suppress light damage of the electron donor (donor) contained in the charge transfer layer of the photoreceptor due to ultraviolet rays.
[0029]
In addition, the peak wavelength region of the invisible light irradiated on the photoconductor and the spectral sensitivity peak wavelength region of the imaging means that receives light near the diffuse reflection from the photoconductor are matched with the wavelength band that is high absorbance in the inner layer of the photoconductor. As a result, the image contrast of the density unevenness defect can be further increased, the S / N of the information on the inner layer of the photoreceptor can be improved, and a defect image in the charge generation layer such as coating unevenness can be taken with high sensitivity.
[0030]
Further, by using a one-dimensional integrated stage type CCD sensor for the imaging means, it is possible to give the element a longer exposure time for the number of integrated stages than a conventional one-dimensional CCD sensor, and even with a low-contrast photoconductor Without increasing the value, it is possible to image a density unevenness defect or the like with high sensitivity while suppressing light damage with the minimum necessary irradiation energy.
[0031]
Furthermore, by processing the image captured by the image capturing device and determining the type of defect, the interior of various digital electrophotographic photoreceptors and various products with a transparent layer on the surface or coated with pigments on the surface It is possible to accurately detect defects such as wrinkles and uneven coating.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image pickup apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a configuration of a photosensitive member, incident light, reflected light, and diffuse reflected light.
FIG. 3 is a spectral absorption characteristic diagram of an inner layer of the photoreceptor.
FIG. 4 is a specific sensitivity characteristic diagram of an imaging unit.
FIG. 5 is a block diagram showing a configuration of a defect detection apparatus according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Photosensitive body, 2; Image pick-up device, 3; Invisible light source, 4: Imaging means,
5; display device, 6; base, 7; inner layer, 8; transparent surface layer,
20; Defect detection device, 21; Image processing unit, 22; A / D conversion unit,
23; a specific region extraction unit, 24; a feature amount calculation unit, 25; a defect determination unit.

Claims

A defect inspection apparatus having an image imaging device and an image processing means comprising an invisible light source, an imaging means, and a display device,
The imaging means is arranged with the optical axis slightly inclined with respect to the normal line of the multilayer electrophotographic photosensitive member, and the invisible light source has an optical axis that is the same as the optical axis of the imaging means on the surface of the multilayer electrophotographic photosensitive member. Arranged to intersect at an angle of 30-60 degrees,
The invisible light source irradiates near-infrared rays on the surface of the multilayer electrophotographic photosensitive member, and the imaging means diffuses and reflects near the normal line at the incident point among diffuse reflection components diffusely reflected on the inner layer of the multilayer electrophotographic photosensitive member. defect indicating an irregularity defect invisible defects and transparent surface layer of the inner layer of the by receiving scattered light reflected from the surface of the transparent surface layer of the neighboring light multilayer type electrophotographic photoreceptor photoelectrically converting multilayer type electrophotographic photoconductor Outputting an image signal to the image processing means;
The image processing means extracts a singular area that is a defect candidate area from the information of the defect image signal output from the imaging means, and performs fractal analysis on the singular area information to detect the inner layer of the photoconductor from the change in image density. Judge the invisible defect of shading unevenness and unevenness defect of the transparent surface layer
The defect detection device, wherein the display device displays a defect image determined by the image processing means .

2. The defect detection according to claim 1, wherein the peak wavelength region of the light emitted from the invisible light illuminating unit and the spectral sensitivity peak wavelength region of the imaging unit are made to coincide with a wavelength band having high absorbance in the inner layer of the multilayer electrophotographic photosensitive member. apparatus.