JP4523744B2 - Imaging data correction method, beam measurement apparatus using the method, computer program, and storage medium - Google Patents

Description

【００７３】
図３は、ＣＣＤラインセンサ１の各光学素子１ａとレンズ２の光軸とがずれている状態を示す模式図である。
【００７４】
図２に示すグラフは理論値に基づくグラフであり、実際には、図３に示すように、ＣＣＤラインセンサ１の各光学素子１ａとレンズ２の光軸とが一致せず、主走査ライン上の主走査データがＣＣＤラインセンサ１の各光学素子１ａの中心からずれてしまう場合が多い。このため、このような光軸のずれを原因として、各種のパラメータが変動する。
【００７５】
まず、ＣＣＤラインセンサ１の各光学素子１ａにおける入射瞳Ｐまでの距離Ｌは、ＣＣＤラインセンサ１とレンズ２との間の取り付け誤差等に影響されて変動する。
【００７６】
次いで、主走査方向をｘ、入射瞳ＰからＣＣＤラインセンサ１を含む撮像面に垂直に降ろした軸の足をＡとし、Ａでの光量をＩ_０ とすると、レンズ２が軸対称であれば、シェーディングによる光量低下は同心円上に分布することとなる。これに対して、図３中に示す最小半径ｒの円は、Ｂ点でＣＣＤラインセンサ１ｂと一致することとなる円である。このＢ点での光量をＩ_１ として、Ｉ_１ を中心に角度ψを大きくしていった場合の光量はＩ_３ 、Ｉ_４ …となり、このようなＩ_３ 、Ｉ_４ は、同心円上Ｂから半径を大きくしていき同心円上ＣまでのＢ、Ｃを結ぶ光量低下と一致する。そこで、ＣＣＤラインセンサ１上の光量Ｉ_４ は、次の（２）式で表わすことができる。なお、（２）式中、ｘ_０ は、光軸の主走査方向の（Ａ，Ｂ，Ｃ等の）座標である。
【００７７】
【数２】

【００７８】
本実施の形態では、（２）式より、変動要因であるＩ_０ 、Ｌ、ｒ、ｘ_０ に適当な初期値を与え、実際にＣＣＤラインセンサ１によって得られる光量データｐと関数データＩ_４ との差ｄを、（３）式で示すように規定する。
【００７９】
【数３】

【００８０】
３．仮パラメータを変化させて撮像素子（ＣＣＤラインセンサ１）の出力データと関数データとを近似させるステップ
次いで、本実施の形態では、上記（３）式中、差ｄが小さくなるようにパラメータＩ_０ 、Ｌ、ｒ、ｘ_０ を変化させる。こうして、図４に示すように、ｄが最小となった時点での関数をシェーディングへの近似結果とする。関数の収束結果である近似解を導出する方法としては、準ニュートン法やLevenberg-Marqurdt法などを用いる。
【００８１】
４．撮像素子（ＣＣＤラインセンサ１）の出力データに近似させた後の関数データから光量に関するデータを除去したデータの逆数を補正データとして獲得するステップ
最適解として得られた近似関数のパラメータＩ_０ 、Ｌ、ｒ、ｘ_０ は、それぞれ、レンズ２の中心での光量、撮像面から入射瞳Ｐまでの距離、光軸からＣＣＤラインセンサ１までの最短距離、光軸の主走査方向の座標である。
【００８２】
これらの近似結果から得られたパラメータにより、各座標での補正データＲを規定することができる。（４）式は、このような補正データＲを規定する式である。
【００８３】
【数４】

【００８４】
５．補正データに基づいて撮像素子（ＣＣＤラインセンサ１）の出力データを補正するステップ
最後に、（４）式を用いて、補正した光量データが図５のように確認される。そこで、このような補正データを図示しないハードディスク等などに格納しておき、実際の撮像時に画像データにその補正データを乗じてシェーディング補正を実施することになる。
【００８５】
したがって、ＣＣＤラインセンサ１の各光学素子１ａにばらつきがあったり、撮像素子と結像素子との間の相対的な位置決めに厳密性がない場合であったりしても、そのような現状を変動パラメータとすることで、シェーディングを正しく補正することが可能となる。
【００８６】
撮像データ補正方法の第２の実施の形態を図６に基づいて説明する。
【００８７】
図６は、ＣＣＤラインセンサ１の主走査座標上でのシェーディング補正後の光量分布を示すグラフである。
【００８８】
本実施の形態は、概略的には、関数の近似により得られた補正データで補正後の全画像データにおける光量の平均値を算出し、この平均値より大きく離れた値を示す画素（図６中、５、６として示す）の座標を検出し、その画素５、６の周辺複数画素の光量値を平均し、この平均値を前述した画素５、６の光量値とするというものである。これにより、ＣＣＤラインセンサ１における各光学素子１ａ中の欠陥画素や画素毎の感度ばらつきを補正することができる。
【００８９】
具体的には、図６に示すように、シェーディング補正後の一様画像において、全体の平均値から任意のばらつきの割合を設定する。ビーム径を測定する場合などは、最大光量のばらつきがその１／ｅ^２ や１／ｅの割合の光量領域に影響するため、最大光量がばらついても、１／ｅ^２ や１／ｅの光量領域で光量データの変動が１画素以上ずれないように設定するなどの手法が考えられる。ここでは仮に±５％とすると、図６中の画素５、６等のばらつきが大きな画素の座標を図示しないハードディスク等の記憶手段に格納しておき、実際の撮像時に、取得した画像の光量値を隣接する複数画素の光量値平均と置き換える。
【００９０】
このような本実施の形態の発明は、次に示すステップによって実現される。
１．ＣＣＤラインセンサ１の出力データに含まれる光量の平均値を算出するステップ
２．その平均値を基準としてデータの上下限値を設定するステップ
３．補正後のＣＣＤラインセンサ１の出力データに含まれる光量値が設定された上下限値を外れた値となる画素位置を補正対象画素位置として獲得するステップ４．補正後のＣＣＤラインセンサ１の出力データに含まれる光量値のうち、補正対象画素位置の周辺複数画素における光量の平均値を算出し、補正対象画素の光量値をその平均値として扱うステップ
このような各ステップが実行された結果、ＣＣＤラインセンサ１における欠陥画素や各画素の感度ばらつきを補正することが可能となる。
【００９１】
撮像データ補正方法の第３の実施の形態を図７に基づいて説明する。
【００９２】
図７は、ＣＣＤラインセンサ１の主走査座標上での各種誤差補正後の光量分布を示すグラフである。
【００９３】
本実施の形態は、概略的には、関数近似による全体的な光量補正と、局所的な画素ばらつきの補正を繰り返すことにより、欠陥画素により影響される関数近似の誤差を修正しながら、画素ばらつきを補正する基準となる一様画像の平均値を修正することで、使用不可能な画素を除去するとともに、感度の一様性を向上してＣＣＤラインセンサ１の欠陥画素や画素毎の感度ばらつきを補正する、というものである。
【００９４】
具体的には、図７に示すように、７として示す画素のように、大きく感度が劣化しているか、あるいは欠陥画素の場合、第１の実施の形態での処理と同一の処理を実施してデータ補正し、次いで、後述する処理を実行することでその画素７における画素ばらつきを除去する、という処理を繰り返すものである。
【００９５】
このような本実施の形態の発明は、次に示す第１のステップ群と第２のステップ群とによって実現される。
【００９６】
〔第１のステップ群〕
１．レンズ２を介して照射された一様光をＣＣＤラインセンサ１に撮像させるステップ
２．その一様光を撮像して得たＣＣＤラインセンサ１の出力データを参照して、この出力データの各画素位置での光量と３次元オフセット量とを表わす仮パラメータを有する関数データを生成するステップ
３．仮パラメータを変化させてＣＣＤラインセンサ１の出力データと関数データとを近似させるステップ
４．ＣＣＤラインセンサ１の出力データに近似させた後の関数データから光量に関するデータを除去したデータの逆数を補正データとして獲得するステップ
５．補正データに基づいてＣＣＤラインセンサ１の出力データを補正するステップ
〔第２のステップ群〕
１．補正後のＣＣＤラインセンサ１の出力データに含まれる光量の平均値を算出するステップ
２．その平均値を基準としてデータの上下限値を設定するステップ
３．補正後のＣＣＤラインセンサ１の出力データに含まれる光量値が前記上下限値を最も外れた値となる画素位置を補正対象画素位置として獲得するステップ
４．補正後のＣＣＤラインセンサ１の出力データに含まれる光量値のうち、補正対象画素位置の周辺複数画素における光量の平均値を算出し、補正対象画素の光量値をその平均値として扱うステップ
〔第１のステップと第２のステップとの実行〕
補正後の前記撮像素子の出力データに含まれる全ての画素についての光量値が前記上下限値内に収まるまで第１のステップ群と第２のステップ群とを繰り返し実行する。
【００９７】
以上の処理によって、本実施の形態の発明が実行される。これにより、画素ばらつきの基準光量からの振り分けが均等になり、ＣＣＤラインセンサ１における欠陥画素や画素毎の感度ばらつきを補正することが可能となる。
【００９８】
撮像データ補正方法の第４の実施の形態を説明する。
【００９９】
本実施の形態は、概略的には、予め欠陥画素や感度の低い画素を補正するための座標データを把握して、レンズ２等の交換や変更があったときでも、ばらつきがある座標の画素における光量値を補正する、というものである。ここで、本実施の形態においては、座標データを把握するに際して、図１を参照すると、照明系３より照射された照明光を白色原稿４で反射させ、この反射光をレンズ２を通すことなく直接的にＣＣＤラインセンサ１に照射させている。
【０１００】
一例として、画素ばらつきを±５％に抑える場合、上限下限を全体の平均値の±５％とし、値がその上限下限を越える画素の座標を図示しないハードディスク等の記憶手段に格納しておき、実際の撮像時には、取得した画像データのその座標データからの画素の値を、近接複数画素の平均値として置き換える。
【０１０１】
このような本実施の形態の発明は、次に示すステップによって実現される。
１．照射された一様光をＣＣＤラインセンサ１に撮像させるステップ
２．ＣＣＤラインセンサ１の出力データに含まれる光量の平均値を算出するステップ
３．その平均値を基準としてデータの上下限値を設定するステップ
４．補正後のＣＣＤラインセンサ１の出力データに含まれる光量値が上下限値を外れた値となる画素位置を補正対象画素位置として獲得するステップ
５．補正後のＣＣＤラインセンサ１の出力データに含まれる光量値のうち、補正対象画素位置の周辺複数画素における光量の平均値を算出し、補正対象画素の光量値をその平均値として扱うステップ
このような各ステップが実行された結果、レンズ２等の光量に影響を与える光学素子の交換、変更等があった場合でも、シェーディング補正のための関数近似の精度を向上させることが可能となる。また、ＣＣＤラインセンサ１における欠陥画素や各画素の感度ばらつきを補正することが可能となる。
【０１０２】
撮像データ補正方法の第５の実施の形態を説明する。
【０１０３】
本実施の形態は、概略的には、基準光量データとなる画素全体の平均値より大きく離れた値を示す画素の座標を検出し、その画素の近接複数画素の値を平均してその画素の値とすることで、ＣＣＤラインセンサ１の欠陥画素や画素毎の感度ばらつきを補正する、というものである。
【０１０４】
例えば、画素全体の光量平均値から最も光量値が異なる画素の座標を図示しないハードディスク等の記憶手段に格納しておき、その画素の光量値を隣接複数画素の光量値で補正し、補正後に再度全体の平均値を導出して、最も光領値が異なる画素の座標を図示しないハードディスク等の記憶手段に格納しておき、その画素の光量値を隣接複数画素の光量値で補正する。このようなステップを繰り返すことにより、著しく感度が劣化している画素や欠陥画素による平均値の低下を低減することができる。
【０１０５】
このような本実施の形態の発明は、次に示す第１のステップ群と第２のステップ群とによって実現される。
【０１０６】
〔第１のステップ群〕
１．照射された一様光をＣＣＤラインセンサ１に撮像させるステップ
２．その一様光を撮像して得たＣＣＤラインセンサ１の出力データを参照して、この出力データの各画素位置での光量と３次元オフセット量とを表わす仮パラメータを有する関数データを生成するステップ
３．仮パラメータを変化させてＣＣＤラインセンサ１の出力データと関数データとを近似させるステップ
４．ＣＣＤラインセンサ１の出力データに近似させた後の関数データから光量に関するデータを除去したデータの逆数を補正データとして獲得するステップ
５．補正データに基づいてＣＣＤラインセンサ１の出力データを補正するステップ
〔第２のステップ群〕
１．補正後のＣＣＤラインセンサ１の出力データに含まれる光量の平均値を算出するステップ
２．その平均値を基準としてデータの上下限値を設定するステップ
３．補正後のＣＣＤラインセンサ１の出力データに含まれる光量値が上下限値を最も外れた値となる画素位置を補正対象画素位置として獲得するステップ
４．補正後のＣＣＤラインセンサ１の出力データに含まれる光量値のうち、補正対象画素位置の周辺複数画素における光量の平均値を算出し、補正対象画素の光量値をその平均値として扱うステップ
〔第１のステップと第２のステップとの実行〕
補正後のＣＣＤラインセンサ１の出力データに含まれる全ての画素についての光量値が上下限値内に収まるまで第１のステップ群と第２のステップ群とを繰り返し実行する。
【０１０７】
これによって、ＣＣＤラインセンサ１における欠陥画素や画素毎の感度ばらつきを補正することが可能となる。
【０１０８】
撮像データ補正方法の第６の実施の形態を説明する。
【０１０９】
本実施の形態は、概略的には、画素毎のばらつきを座標で把握しておき、撮像した光量データのばらつきを補正した後、関数の近似の精度を向上して、シェーディングも補正する、というものである。
【０１１０】
このような本実施の形態の発明は、次に示すステップによって実現される。
１．レンズ２を介して照射された一様光を１次元のＣＣＤラインセンサ１に撮像させるステップ
２．その一様光を撮像して得たＣＣＤラインセンサ１の出力データを、撮像データ補正方法の第５又は第６の実施の形態における撮像データ補正方法を実行して得られたＣＣＤラインセンサ１の出力データに基づいて補正し、補正後の出力データを参照して、この出力データの各画素位置での光量と３次元オフセット量とを表わす仮パラメータを有する関数データを生成するステップ
３．仮パラメータを変化させてＣＣＤラインセンサ１の出力データと関数データとを近似させるステップ
４．ＣＣＤラインセンサ１の出力データに近似させた後の関数データから光量に関するデータを除去したデータの逆数を補正データとして獲得するステップ
５．その補正データに基づいてＣＣＤラインセンサ１の出力データを補正するステップ
これによって、ＣＣＤラインセンサ１における欠陥画素や各画素の感度ばらつきを補正することが可能となる。
【０１１１】
撮像データ補正方法の第７の実施の形態を説明する。
【０１１２】
本実施の形態は、得られた補正データを画素感度が一様となるよう画像取得毎に光量データに乗じることにより、撮像した画像におけるＣＣＤラインセンサ１の画素毎の感度ばらつきによる光量ばらつきを補正する、というものである。
【０１１３】
例えば、ＣＣＤラインセンサ１を用いた各撮像について、その撮像された全画面データにシェーディング補正データを乗じて全体の光量を一様化し、かつ、画素ばらつきの座標データに基づいてその座標の画素を隣接複数画素の平均値に置き換える。
【０１１４】
これにより、撮像画像を一様感度の状態で取得すること可能となる。
【０１１５】
撮像データ補正方法の第８の実施の形態を図８ないし図１０に基づいて説明する。
【０１１６】
本実施の形態は、２次元の撮像素子を用いた点が前述した第１〜第７の実施の形態と異なる。以下、本実施の形態の撮像データ補正方法を、ステップ毎に説明する。
【０１１７】
１．結像素子（レンズ９）を介して照射された一様光を２次元の撮像素子（ＣＣＤエリアセンサ８）に撮像させるステップ
図８は、撮像データ補正方法を実施するためのビーム測定装置の模式図である。図８に示すように、本実施の形態では撮像素子としてＣＣＤエリアセンサ８が用いられている。このＣＣＤエリアセンサ８にレンズ９によって結像させられる画像データは、面発光タイプの面発光部材１０にファイバーライトガイド１１で導光されたコールドライトソース１２の照明光である。この照明光は、オパール拡散板１３，１３ａによって拡散されている。
【０１１８】
２．一様光を撮像して得た撮像素子（ＣＣＤエリアセンサ８）の出力データを参照して、この出力データの各画素位置での光量と３次元オフセット量とを表わす仮パラメータを有する３次元関数データを生成するステップ
そこで、このような拡散光を基準光量とする場合、図９に示すように、入射瞳Ｐまでの距離Ｌ、主走査方向をｘ、副走査方向をｙ、入射瞳ＰからＣＣＤエリアセンサ８ａを含む撮像面に垂直に降ろした軸の足をＡとし、Ａでの光量をＩ_０ とすると、レンズ９が軸対称であれば、シェーディングによる光量低下は同心円上に分布することとなり、ＣＣＤエリアセンサ８上の任意の位置での光量Ｉ_４ は、（５）式で表現される。ここで、ｘ_０ は、光軸の主走査方向の座標、ｙ_０ は、光軸の副走査方向の座標である。
【０１１９】
【数５】

【０１２０】
３．仮パラメータを変化させて撮像素子（ＣＣＤエリアセンサ８）の出力データと３次元関数データとを近似させるステップ
次に、（５）式より、変動要因であるＩ_０ 、Ｌ、ｘ_０ 、ｙ_０ に適当な初期値を与え、実際にＣＣＤエリアセンサによって得られる光量データｐと関数データＩ_４ の差ｄを(６)式で示すように規定する。
【０１２１】
【数６】

【０１２２】
そして、差ｄが小さくなるようにパラメータＩ_０ 、Ｌ、ｘ_０ 、ｙ_０ を変化させる。こうして、差ｄが最小となった時点での関数をシェーディングへの近似結果とする。関数の収束結果である近似解を導出する方法としては、準ニュートン法やLevenberg-Marqurdt法などを用いる。
【０１２３】
最適解として得られた近似関数のパラメータＩ_０ 、Ｌ、ｘ_０ 、ｙ_０ は、それぞれ、レンズ９の中心での光量、撮像面から入射瞳Ｐまでの距離、光軸の主副走査方向の座標である。
【０１２４】
４．撮像素子（ＣＣＤエリアセンサ８）の出力データに近似させた後の３次元関数データから光量に関するデータを除去したデータの逆数を補正データとして獲得するステップ
これら近似結果から得られたパラメータにより、各座標での補正データＲは次式（７）で規定される。
【０１２５】
【数７】

【０１２６】
５．補正データに基づいて撮像素子（ＣＣＤエリアセンサ８）の出力データを補正するステップ
次いで、（７）式を用いて、ＣＣＤエリアセンサ８の出力データを補正する。補正した光量データは、図１０に示すように確認される。ここで、図１０は、シェーディング補正前後のＣＣＤエリアセンサ８における光量分布を示す模式図である。
【０１２７】
この補正データを図示しないハードディスクなどに格納して、実際の撮像時に画像データに乗じてシェーディング補正を実施する。
【０１２８】
こうして、ＣＣＤエリアセンサ８の各素子にばらつきがあったり、ＣＣＤエリアセンサ８とレンズ９との間の相対的な位置決めに厳密性がない場合であったりしても、そのような現状を変動パラメータとすることで、シェーディングを正しく補正することが可能となる。
【０１２９】
以上説明した撮像データ補正方法の第８の実施の形態に対しては、前述した第２〜第７の実施の形態を適用することができる。この場合、撮像データ補正方法の第８の実施の形態においても、前述した第２〜第７の実施の形態での作用効果が得られる。なお、撮像データ補正方法の第２〜第７の実施の形態での処理自体は、撮像データ補正方法の第８の実施の形態に適用しても異なる点がないため、その説明は省略する。それらの第２〜第７の実施の形態での処理は、既に説明した該当箇所を参照することによって当業者が理解可能である。
【０１３０】
＜ビーム測定装置、ビーム測定用のコンピュータプログラム、及びこのようなコンピュータプログラムを記憶する記憶媒体＞
次いで、前述した撮像データ補正方法を実施することができるビーム測定装置、ビーム測定用のコンピュータプログラム、及びこのようなコンピュータプログラムを記憶する記憶媒体について説明する。
【０１３１】
ビーム測定装置の第１の実施の形態を図１１及び図１２に基づいて説明する。
【０１３２】
図１１は、ビーム測定装置の模式図である。
【０１３３】
図１１に示すように、本実施の形態のビーム測定装置は、回転するポリゴンミラー１４によって発光源としてのレーザダイオード（ＬＤ）ユニット１５から出射した光ビームを反射走査し、この反射走査光をｆθレンズ１６に透過させ、この透過光を２次元の撮像素子としてのＣＣＤエリアセンサ１７に結像素子としての対物レンズ１８を透過して受光させる。つまり、本実施の形態のビーム測定装置は、光源として、ポリゴンミラー１４、レーザダイオード（ＬＤ）ユニット１５及びｆθレンズ１６を有する。そして、ＣＣＤエリアセンサ１７から出力される光量データを図示しないＡ／Ｄコンバータでデジタルデータに変換した後、コンピュータ１９の図示しないハードディスク内に格納する。
【０１３４】
ビーム測定装置に設けられたコンピュータ１９は、ＣＰＵ、ＲＯＭ、ＲＡＭ等からなるマイクロプロセッサ（全て図示せず）を内蔵し、このマイクロプロセッサが備える記憶領域（ＲＯＭ、ＲＡＭ）に記憶されたコンピュータプログラムに従い、前述した第１〜第８の実施の形態における撮像データ補正方法を実行する。この際、コンピュータ１９は、マイクロプロセッサ等の各種のリソースを利用して、インストールされたコンピュータプログラムに従った処理を実行する。
【０１３５】
このような処理の一例として、コンピュータ１９の図示しないハードディスク内に格納した光量データを含む画像全体のデータにシェーディング補正を実施し、図１２の主走査方向での光量分布を示すグラフ中で、符号２０で示されるデータ曲線から符号２１で示されるデータ曲線となるような補正を実行する。次いで、図示しないハードディスク内に格納されている画素ばらつきの座標データより、該当する座標のデータを近接複数画素の画素データの平均値に置き換える。
【０１３６】
その他、コンピュータ１９は、マイクロプロセッサによる演算処理能力を利用して、前述した第１〜第８の実施の形態における撮像データ補正方法を必要に応じて実行する。
【０１３７】
なお、コンピュータ１９にインストールされたコンピュータプログラムは、各種の形態で流通し、コンピュータ１９にインストールされることができる。例えば、光学的又は磁気的に情報を保存可能な記憶媒体、例えば、ＣＤ−ＲＯＭ、ＣＤ−Ｒ、ＣＤ−ＲＷ、ＤＶＤ−ＲＯＭ、ＤＶＤ−ＲＡＭ、磁気テープ、フロッピーディスク等にコンピュータプログラムを記憶させておき、必要に応じてコンピュータ１９にインストールしたり、ネットワーク上でコンピュータ１９にダウンロードするような形態でインストールしたり等、各種の手法を実施することができる。
【０１３８】
なお、本実施の形態のビーム測定装置では、対物レンズ１８を必要に応じて除去してビーム測定を実行する。
【０１３９】
ビーム測定装置の第２の実施の形態を図１３に基づいて説明する。ビーム測定装置の第１の実施の形態と同一部分は同一符号で示し、説明も省略する。
【０１４０】
図１３は、ビーム測定装置の模式図である。このビーム測定装置は、撮像データ補正方法の第８の実施の形態の説明で用いた図８に示すビーム装置と類似の構成を有している。図１３は、このようなビーム測定装置を上方から観察した模式図を示している。
【０１４１】
図１３に示すように、面発光タイプの面発光部材１０にファイバーライトガイド１１でコールドライトソース１２の照明光を導光し、出射光をオパール拡散板１３，１３ａにより拡散させる。そして、その拡散光を基準光量とするため、それらのオパール拡散板１３，１３ａ及び面発光タイプの面発光部材１０を、ＣＣＤエリアセンサ１７と相対的に固定された対物レンズ１８の光軸上に出入できるようにスライダ２２上に固定し、ファイバーライトガイド１１によって外部からコールドライトソース１２の照明光を導光できるようにしている。
【０１４２】
このような本実施の形態のビーム測定装置では、光源として、面発光部材１０、ファイバーライトガイド１１、コールドライトソース１２及びオパール拡散板１３，１３ａを有している。
【０１４３】
このようなビーム測定装置も、図１１に例示したビーム測定装置と同様に、図示しないコンピュータを有し、このコンピュータは、内蔵する図示しないマイクロプロセッサによる演算処理能力を利用して、前述した第１〜第８の実施の形態における撮像データ補正方法を必要に応じて実行する。
【０１４４】
ビーム測定装置の第２の実施の形態の変形例としては、発光源であるコールドライトソース１２や光源である面発光部材１０、ファイバーライトガイド１１、コールドライトソース１２及びオパール拡散板１３，１３ａでの発光の一様性を検出する機能を備えさせることが実施可能である。具体的には、図１４に示すように、対物レンズ１８に隣接させて、受光面を対物レンズ１８の焦点位置と同一平面上になるよう一致させて配置された光量検出用である受光素子としてのＰＤ２３（フォトディテクタ）を設置し、このＰＤ２３を主走査方向及び副走査方向に移動させて一定領域内の光量を検出し、照明光である光源の発光一様性を検出する、というものである。これにより、ＣＣＤエリアセンサ１７の位置を、ＰＤ２３の走査によって光源の発光一様性を確認した範囲で撮像しうるように設定することで、基準光量となる一様画像を確実に撮像することができる。
【０１４５】
このようなビーム測定装置の第２の実施の形態の変形例の別の一例としては、図１５に示すように、ＰＤ２３の受光面に、ＣＣＤエリアセンサ１７などの撮像素子の解像度と略一致するサイズのピンホール２４を持つマスク２５を固定し、ＣＣＤエリアセンサ１７の撮像範囲と同等かそれよりも大きい領域で光走査して光量を検出するようにしても良い。こうして、光走査の間隔をＣＣＤエリアセンサ１７の画素ピッチと同等とすることで、ＣＣＤエリアセンサ１７の撮像解像度と同等である解像度で基準画像の光量一様性を検出することができる。
【０１４６】
【発明の効果】
請求項１記載の撮像データ補正方法の発明によれば、欠陥画素や感度が大きく劣化している画素によるばらつきが近似関数に影響して全体のシェーディング状態から多少ずれても、感度が大きくずれている画素の除去後、再度関数近似することで、シェーディング状態への関数近似の精度を向上させ、これによって、画素ばらつきの基準光量からの振り分けを均等にして、撮像素子における欠陥画素や画素毎の感度ばらつきを補正することができる。
【０１５０】
請求項２記載の撮像データ補正方法の発明によれば、欠画素や感度が大きく劣化している画素によるばらつきが近似関数に影響して全体のシェーディング状態から多少ずれても、感度が大きくずれている画素の除去後、再度関数近似することで、シェーディング状態への関数近似の精度を向上させることができ、これにより、画素ばらつきの基準光量からの振り分けを均等にして、撮像素子における欠陥画素や画素毎の感度ばらつきを補正することができる。
【０１５１】
請求項３記載の撮像データ補正方法の発明によれば、１次元の撮像素子の各素子にばらつきがあったり、撮像素子と結像素子との間の相対的な位置決めに厳密性がない場合であったりしても、感度が低下している画素や欠陥画素の座標等を予め把握しておくことができ、これにより、レンズ等の光量に影響を与える光学素子の交換、変更等があった場合でも、シェーディング補正のための関数近似の精度を向上させることができる。また、全体的なシェーディングの影響を除去してから、画素毎の基準となる光量を決定し、その基準光量からのばらつきが大きな画素の座標を補正する座標として予め設定しておくことで、その座標の光量データをその周辺複数画素の光量データの平均値に置き換え、これによって、撮像素子における欠陥画素や各画素の感度ばらつきを補正することができる。
【０１５５】
請求項４記載の撮像データ補正方法の発明によれば、欠陥画素や感度が大きく劣化している画素によるばらつきが近似関数に影響して全体のシェーディング状態から多少ずれても、感度が大きくずれている画素の除去後、再度関数近似することで、シェーディング状態への関数近似の精度を向上させ、これによって、画素ばらつきの基準光量からの振り分けを均等にして、撮像素子における欠陥画素や画素毎の感度ばらつきを補正することができる。
【０１５７】
請求項５記載の撮像データ補正方法の発明によれば、欠画素や感度が大きく劣化している画素によるばらつきが近似関数に影響して全体のシェーディング状態から多少ずれても、感度が大きくずれている画素の除去後、再度関数近似することで、シェーディング状態への関数近似の精度を向上させることができ、これにより、画素ばらつきの基準光量からの振り分けを均等にして、撮像素子における欠陥画素や画素毎の感度ばらつきを補正することができる。
【０１５８】
請求項６記載の撮像データ補正方法の発明によれば、２次元の撮像素子の各素子にばらつきがあったり、撮像素子と結像素子との間の相対的な位置決めに厳密性がない場合であったりしても、感度が低下している画素や欠陥画素の座標等を予め把握しておくことができ、これにより、レンズ等の光量に影響を与える光学素子の交換、変更等があった場合でも、シェーディング補正のための関数近似の精度を向上させることができる。また、全体的なシェーディングの影響を除去してから、画素毎の基準となる光量を決定し、その基準光量からのばらつきが大きな画素の座標を補正する座標として予め設定しておくことで、その座標の光量データをその周辺複数画素の光量データの平均値に置き換え、これによって、撮像素子における欠陥画素や各画素の感度ばらつきを補正することができる。
【０１５９】
請求項７記載の撮像データ補正方法の発明によれば、撮像画像を一様感度の状態で取得することができ、したがって、画像データの読み取り精度を向上させることができる。
【０１６０】
請求項８記載のビーム測定装置の発明によれば、請求項４又は６記載の撮像データ補正方法の効果を奏することができる。
【０１６１】
請求項９記載のビーム測定装置の発明によれば、発光源が発光する光を撮像素子に対面する面発光部材に導き、面発光部材からの光を撮像素子に撮像させることができる。
【０１６２】
請求項１０記載のビーム測定装置の発明によれば、受光素子の出力信号に基づいて光源からの光の一様性を検出することができる。
【０１６３】
請求項１１記載のビーム測定装置の発明によれば、撮像素子の画素ピッチで光量一様性を検出することができる。
【０１６４】
請求項１２記載のビーム測定装置の発明によれば、請求項５記載の撮像データ補正方法の効果を奏することができる。
【０１６５】
請求項１３記載のビーム測定装置の発明によれば、発光源が発光する光を撮像素子に対面する面発光部材に導き、面発光部材からの光を撮像素子に撮像させることができる。
【０１６６】
請求項１４記載のコンピュータプログラムの発明によれば、請求項４又は６記載の撮像データ補正方法の効果を奏することができる。
【０１６７】
請求項１５記載のコンピュータプログラムの発明によれば、請求項５記載の撮像データ補正方法の効果を奏することができる。
【０１６８】
請求項１６記載の記憶媒体の発明によれば、請求項１４又は１５記載のコンピュータプログラムを記憶媒体という形態で可搬性を持たせることができ、また、そのようなコンピュータプログラムをいつでも記憶媒体から出力することができる。
【図面の簡単な説明】
【図１】撮像データ補正方法の第１の実施の形態として、撮像データ補正方法を実現するため光学装置を示す斜視図である。
【図２】ＣＣＤラインセンサの主走査座標上での理論的な光量分布を示すグラフである。
【図３】ＣＣＤラインセンサの各光学素子とレンズの光軸とがずれている状態を示す模式図である。
【図４】ＣＣＤラインセンサの主走査座標上での各種誤差補正後の光量分布を示すグラフである。
【図５】ＣＣＤラインセンサの主走査座標上でのシェーディング補正後の光量分布を示すグラフである。
【図６】撮像データ補正方法の第２の実施の形態として、ＣＣＤラインセンサの主走査座標上でのシェーディング補正後の光量分布を示すグラフである。
【図７】撮像データ補正方法の第３の実施の形態として、ＣＣＤラインセンサの主走査座標上での各種誤差補正後の光量分布を示すグラフである。
【図８】撮像データ補正方法の第８の実施の形態として、撮像データ補正方法を実施するためのビーム測定装置を示す模式図である。
【図９】ＣＣＤエリアセンサの各光学素子とレンズの光軸とがずれている状態を示す模式図である。
【図１０】シェーディング補正前後のＣＣＤエリアセンサにおける光量分布を示す模式図である。
【図１１】ビーム測定装置の第１の実施の形態として、ビーム測定装置を示す模式図である。
【図１２】主走査座標上での光量分布を示すグラフである。
【図１３】ビーム測定装置の第２の実施の形態として、ビーム測定装置を示す模式図である。
【図１４】ビーム測定装置の第２の実施の形態の変形例として、ビーム測定装置を示す模式図である。
【図１５】ＰＤにピンホール付きのマスクが設けられている一例を示す斜視図である。
【符号の説明】
１、８、１７ 撮像素子（ＣＣＤラインセンサ、ＣＣＤエリアセンサ）
２、９ 結像素子（レンズ、対物レンズ）
３、１０、１１、１２、１３、１３ａ、１４、１５、１６ 光源（照明系、面発光部材、ファイバーライトガイド、コールドライトソース、オパール拡散板、ポリゴンミラー、レーザダイオード（ＬＤ）ユニット、ｆθレンズ）
１０ 面発光部材
１２、１５ 発光源
２３ 受光素子（ＰＤ）
２４ ピンホール
２５ マスク[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging data correction method for removing shading by an imaging element such as a lens and pixel variation of an imaging element, and a beam measurement apparatus and beam measurement for the same, when imaging an image using a one-dimensional or two-dimensional imaging element. And a storage medium for storing such a computer program.
[0002]
[Prior art]
In recent years, techniques for digitally reading image data have become widespread. As a method for digitally reading image data, for example, a one-dimensional or two-dimensional image sensor such as a CCD line sensor or a CMOS line sensor is used to capture an image, and image information is obtained from the output data of the image sensor. It is common to make it.
[0003]
In the technique of digitally reading such image information, it is necessary to obtain a two-dimensional distribution of light amount data including image data. For this reason, when the image sensor has a structure arranged in a one-dimensional array, two-dimensional data is acquired by relatively moving the image sensor and the image to be read, and the image sensor is two-dimensional. In the case of a structure arranged in an array, a two-dimensional light quantity distribution is taken in at a time.
[0004]
Here, in a scanner or the like using a one-dimensional or two-dimensional image sensor, it is common to perform shading correction or the like on the output data of the image sensor, which is an imaging result. As an example, the shading correction is performed by irradiating a white document giving a reference of light quantity with uniform light and capturing the reflected light, and obtaining a data ratio based on the height of the obtained light quantity data as correction data. Done.
[0005]
As for shading, for example, Japanese Patent Laid-Open No. 6-282793 discloses an invention in which shading is corrected by multiplying an input signal from a line sensor by correction data based on an inverse characteristic function of a cosine fourth power.
[0006]
Japanese Patent Laid-Open No. 8-79773 discloses an invention in which shading is corrected by applying a shading correction coefficient approximated by an Nth-order curved surface function to output data of an image sensor.
[0007]
[Problems to be solved by the invention]
However, one-dimensional or two-dimensional arrayed image sensors represented by CCD and CMOS generally have variations in pixel sensitivity. Further, in order to obtain image data, it is necessary to A / D convert the output data of the image sensor, and the conversion result also varies during such A / D conversion. For this reason, there is a problem that the image data that is actually acquired involves not only a decrease in the amount of peripheral light for which correction by shading correction is attempted, but also variations in various amounts of light.
[0008]
For this reason, as an example, when the reflected light from the document is acquired as the light amount data, there is a possibility that data that should not exist on the document due to pixel sensitivity variation or the like may be placed as noise. Inconvenience that the information to be obtained cannot be obtained.
[0009]
For such problems, the techniques disclosed in the above-mentioned Japanese Patent Application Laid-Open Nos. 6-282793 and 8-79773 do not provide any solution.
[0010]
An object of the present invention is to enable image data to be read correctly.
[0011]
[Means for Solving the Problems]
  The invention of the imaging data correction method according to claim 1As the first step group,With reference to the step of causing the one-dimensional image sensor to image uniform light irradiated through the imaging element, and the output data of the image sensor obtained by imaging the uniform light,The amount of light on the axis perpendicular to the imaging plane including the imaging element from the entrance pupil, the distance from the imaging plane to the entrance pupil, the shortest distance from the optical axis to the imaging element, and the main scanning direction of the optical axis Coordinate3D offset amount indicated byA formal parameter consisting ofRefer toSekiA few daysTGenerating, changing the temporary parameter to approximate the output data of the image sensor and the function data, and removing light quantity data from the function data after approximating the output data of the image sensor ShiTheStep of obtaining the reciprocal of data as correction dataAndEquippedThen, as a second step group, calculating an average value of the amount of light included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data; The light quantity value included in the output data of the image sensor after the correction is performed in the step of setting the upper and lower limit values of the data on the basis of the average value and the step of correcting the output data of the image sensor based on the correction data. Output data of the image sensor after correction in the step of acquiring the pixel position that is the most deviated from the upper and lower limit values as the correction target pixel position and the step of correcting the output data of the image sensor based on the correction data Among the light amount values included in the correction target pixel position, an average value of the light amounts in the plurality of peripheral pixels around the correction target pixel position is calculated, and the light amount value of the correction target pixel is calculated as the average value. A step of correcting the output data of the image sensor based on the correction data, and the light quantity values for all the pixels included in the output data of the image sensor after the correction is performed. The first step group and the second step group are repeatedly executed until the value falls within the lower limit value.
[0016]
Normally, the deterioration of the pixel tends to decrease in sensitivity and the transition to oversensitivity is rare. Therefore, the approximate function by shading correction is pulled toward the lower light amount. Therefore, even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, after removing pixels with greatly deviated sensitivity, by approximating the function again, The accuracy of function approximation to the shading state is improved. For this reason, the distribution of the pixel variation from the reference light amount becomes uniform, and it becomes possible to correct the defective pixel in the image sensor and the sensitivity variation for each pixel.
[0019]
  Claim2The imaging data correction method according to the present invention includes, as a first step group, a step of causing the one-dimensional imaging device to image the irradiated uniform light, and an output of the imaging device obtained by imaging the uniform light. Browse the dataThe amount of light on the axis perpendicular to the imaging plane including the imaging element from the entrance pupil, the distance from the imaging plane to the entrance pupil, the shortest distance from the optical axis to the imaging element, and the main scanning direction of the optical axis Coordinate3D offset amount indicated byA formal parameter consisting ofRefer toSekiA few daysTGenerating, changing the temporary parameter to approximate the output data of the image sensor and the function data, and removing light quantity data from the function data after approximating the output data of the image sensor ShiTheObtaining a reciprocal of data as correction data; and correcting output data of the image sensor based on the correction data, and as a second step group,Based on the correction dataCalculating an average value of the amount of light included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor, and setting upper and lower limits of data with reference to the average value; ,Based on the correction dataAcquiring as a correction target pixel position a pixel position at which a light amount value included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor is a value farthest from the upper and lower limit values; ,Based on the correction dataOf the light amount values included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor, an average value of the light amounts in a plurality of pixels around the correction target pixel position is calculated, and the correction target Treating the light quantity value of the pixel as its average value,Based on the correction dataThe first step group and the second step until the light amount values for all the pixels included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor are within the upper and lower limit values. Steps are repeatedly executed.
[0020]
Normally, the deterioration of the pixel tends to decrease in sensitivity and the transition to oversensitivity is rare. Therefore, the approximate function by shading correction is pulled toward the lower light amount. Therefore, even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, after removing pixels with greatly deviated sensitivity, by approximating the function again, The accuracy of function approximation to the shading state is improved. For this reason, the distribution of the pixel variation from the reference light amount becomes uniform, and it becomes possible to correct the defective pixel in the image sensor and the sensitivity variation for each pixel.
[0021]
  Claim3The invention of the imaging data correction method described includes the steps of causing the one-dimensional imaging device to image uniform light irradiated through the imaging element, and output data of the imaging device obtained by imaging the uniform light Claim2Correction based on the output data of the imaging element obtained by executing the imaging data correction method described,Based on the correction dataWith reference to the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor,The amount of light on the axis perpendicular to the imaging plane including the imaging element from the entrance pupil, the distance from the imaging plane to the entrance pupil, the shortest distance from the optical axis to the imaging element, and the main scanning direction of the optical axis Coordinate3D offset amount indicated byA formal parameter consisting ofRefer toSekiA few daysTGenerating, changing the temporary parameter to approximate the output data of the image sensor and the function data, and removing light quantity data from the function data after approximating the output data of the image sensor ShiTheObtaining the reciprocal of the data as correction data, and correcting the output data of the image sensor based on the correction data.
[0022]
Therefore, even if each element of the one-dimensional image sensor has variations or the relative positioning between the image sensor and the imaging element is not strict, the pixel whose sensitivity is lowered And coordinates of defective pixels can be grasped in advance. This makes it possible to improve the accuracy of function approximation for shading correction even when an optical element that affects the amount of light such as a lens is replaced or changed. In addition, after removing the influence of the overall shading, the reference light amount for each pixel is determined, and the coordinates of the pixels having a large variation from the reference light amount are set in advance as coordinates to be corrected. By replacing the light quantity data of the coordinates with the average value of the light quantity data of a plurality of peripheral pixels, it is possible to correct the defective pixels in the image sensor and the sensitivity variations of the respective pixels.
[0029]
  Claim4According to the imaging data correction method described above, the first step group is obtained by imaging the uniform light irradiated through the imaging element on a two-dimensional imaging element, and imaging the uniform light. With reference to the output data of the image sensor,The amount of light on the axis perpendicular to the imaging surface including the imaging element from the entrance pupil, the distance from the imaging surface to the entrance pupil, the coordinates of the optical axis in the main scanning direction, and the coordinates of the optical axis in the sub-scanning direction3D offset amount indicated byA formal parameter consisting ofSee3DFunction dataTA step of generating, approximating the output data of the image sensor and the three-dimensional function data by changing the temporary parameter, and a light amount from the three-dimensional function data after approximating the output data of the image sensor Remove data aboutTheObtaining a reciprocal of data as correction data; and correcting output data of the image sensor based on the correction data, and as a second step group,Based on the correction dataCalculating an average value of the amount of light included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor, and setting upper and lower limits of data with reference to the average value; ,Based on the correction dataAcquiring as a correction target pixel position a pixel position at which a light amount value included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor is a value farthest from the upper and lower limit values; ,Based on the correction dataOf the light amount values included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor, an average value of the light amounts in a plurality of pixels around the correction target pixel position is calculated, and the correction target Treating the light quantity value of the pixel as its average value,Based on the correction dataThe first step group and the second step until the light amount values for all the pixels included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor are within the upper and lower limit values. Steps are repeatedly executed.
[0030]
Normally, the deterioration of the pixel tends to decrease in sensitivity and the transition to oversensitivity is rare. Therefore, the approximate function by shading correction is pulled toward the lower light amount. Therefore, even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, after removing pixels with greatly deviated sensitivity, by approximating the function again, The accuracy of function approximation to the shading state is improved. For this reason, the distribution of the pixel variation from the reference light amount becomes uniform, and it becomes possible to correct the defective pixel in the image sensor and the sensitivity variation for each pixel.
[0033]
  Claim5According to the imaging data correction method described above, as a first step group, a step of causing the two-dimensional imaging device to image the irradiated uniform light, and an output of the imaging device obtained by imaging the uniform light Browse the dataThe amount of light on the axis perpendicular to the imaging surface including the imaging element from the entrance pupil, the distance from the imaging surface to the entrance pupil, the coordinates of the optical axis in the main scanning direction, and the coordinates of the optical axis in the sub-scanning direction3D offset amount indicated byA formal parameter consisting ofSee3DFunction dataTA step of generating, approximating the output data of the image sensor and the three-dimensional function data by changing the temporary parameter, and a light amount from the three-dimensional function data after approximating the output data of the image sensor Remove data aboutTheObtaining a reciprocal of data as correction data; and correcting output data of the image sensor based on the correction data, and as a second step group,Based on the correction dataCalculating an average value of the amount of light included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor, and setting upper and lower limits of data with reference to the average value; ,Based on the correction dataAcquiring as a correction target pixel position a pixel position at which a light amount value included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor is a value farthest from the upper and lower limit values; ,Based on the correction dataOf the light amount values included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor, an average value of the light amounts in a plurality of pixels around the correction target pixel position is calculated, and the correction target Treating the light quantity value of the pixel as its average value,Based on the correction dataThe first step group and the second step until the light amount values for all the pixels included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor are within the upper and lower limit values. Steps are repeatedly executed.
[0034]
Normally, the deterioration of the pixel tends to decrease in sensitivity and the transition to oversensitivity is rare. Therefore, the approximate function by shading correction is pulled toward the lower light amount. Therefore, even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, after removing pixels with greatly deviated sensitivity, by approximating the function again, The accuracy of function approximation to the shading state is improved. For this reason, the distribution of the pixel variation from the reference light amount becomes uniform, and it becomes possible to correct the defective pixel in the image sensor and the sensitivity variation for each pixel.
[0035]
  Claim6The invention of the imaging data correction method described includes the steps of causing the two-dimensional imaging element to image uniform light irradiated through the imaging element, and output data of the imaging element obtained by imaging the uniform light Claim5Correction based on the output data of the imaging element obtained by executing the imaging data correction method described,Based on the correction dataWith reference to the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor,The amount of light on the axis perpendicular to the imaging surface including the imaging element from the entrance pupil, the distance from the imaging surface to the entrance pupil, the coordinates of the optical axis in the main scanning direction, and the coordinates of the optical axis in the sub-scanning direction3D offset amount indicated byA formal parameter consisting ofSee3DFunction dataTA step of generating, approximating the output data of the image sensor and the three-dimensional function data by changing the temporary parameter, and a light amount from the three-dimensional function data after approximating the output data of the image sensor Remove data aboutTheObtaining the reciprocal of the data as correction data, and correcting the output data of the image sensor based on the correction data.
[0036]
Therefore, even if each element of the two-dimensional image sensor has variations or the relative positioning between the image sensor and the imaging element is not strict, the pixel whose sensitivity is lowered And coordinates of defective pixels can be grasped in advance. This makes it possible to improve the accuracy of function approximation for shading correction even when an optical element that affects the amount of light such as a lens is replaced or changed. In addition, after removing the influence of the overall shading, the reference light amount for each pixel is determined, and the coordinates of the pixels having a large variation from the reference light amount are set in advance as coordinates to be corrected. By replacing the light quantity data of the coordinates with the average value of the light quantity data of a plurality of peripheral pixels, it is possible to correct the defective pixels in the image sensor and the sensitivity variations of the respective pixels.
[0037]
  Claim7The invention of the imaging data correction method described in claim 1 is directed to the case where light including image data is enlarged or reduced by an imaging element and imaged by the imaging element.4Or6With reference to the output data of the image sensor corrected by one or more of the imaging data correction methods, the output data of the image sensor that images light including the image data is corrected.
[0038]
Therefore, the captured image can be acquired with a uniform sensitivity.
[0039]
  Claim8The invention of the described beam measuring device includes: a light source that emits uniform light; a two-dimensional image sensor; and an imaging element that forms an image on the image sensor with uniform light emitted from the light source.4Or6Means for executing the described imaging data correction method.
[0042]
  ThroughNormally, pixel deterioration tends to decrease in sensitivity and hardly shifts to oversensitivity, so the approximate function by shading correction is pulled toward the lower light amount. Therefore, even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, after removing pixels with greatly deviated sensitivity, by approximating the function again, The accuracy of function approximation to the shading state is improved. For this reason, the distribution of the pixel variation from the reference light amount becomes uniform, and it becomes possible to correct the defective pixel in the image sensor and the sensitivity variation for each pixel.4When executing the imaging data correction method described above).
[0043]
  Furthermore, even if each element of the two-dimensional image sensor has variations or the relative positioning between the image sensor and the imaging element is not strict, the pixel whose sensitivity is lowered And coordinates of defective pixels can be grasped in advance. This makes it possible to improve the accuracy of function approximation for shading correction even when an optical element that affects the amount of light such as a lens is replaced or changed. In addition, after removing the influence of the overall shading, the reference light amount for each pixel is determined, and the coordinates of the pixels having a large variation from the reference light amount are set in advance as coordinates to be corrected. By replacing the light quantity data of the coordinates with the average value of the light quantity data of the plurality of surrounding pixels, it becomes possible to correct defective pixels in the image sensor and variations in sensitivity of each pixel.6When executing the imaging data correction method described above).
[0044]
  Claim9The described invention is claimed.8In the described beam measuring apparatus, the light source guides light emitted from the light emitting source to a surface light emitting member facing the imaging element.
[0045]
Therefore, the light emitted from the light emitting source is guided to the surface light emitting member facing the image sensor, and the light from the surface light emitting member is imaged by the image sensor.
[0046]
  Claim10The described invention is claimed.8Or9In the beam measuring apparatus described above, a light receiving element that is disposed so as to coincide with a focal position of the imaging element and receives light from the light source is provided, and based on an output signal of the light receiving element, the light from the light source Uniformity was detected.
[0047]
Therefore, the uniformity of the light from the light source is detected based on the output signal of the light receiving element.
[0048]
  Claim11The described invention is claimed.10In the described beam measuring apparatus, the light receiving element is covered with a mask having a pinhole that matches the light receiving region of the light receiving element with the resolution of the imaging element.
[0049]
Therefore, the light quantity uniformity is detected at the pixel pitch of the image sensor.
[0050]
  Claim12The invention of the described beam measuring apparatus includes: a light source that emits uniform light; a two-dimensional image sensor that captures uniform light emitted from the light source;5Means for executing the described imaging data correction method.
[0052]
  ThroughNormally, pixel deterioration tends to decrease in sensitivity and hardly shifts to oversensitivity, so the approximate function by shading correction is pulled toward the lower light amount. Therefore, even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, after removing pixels with greatly deviated sensitivity, by approximating the function again, The accuracy of function approximation to the shading state is improved. For this reason, the distribution of the pixel variation from the reference light amount becomes uniform, and it becomes possible to correct the defective pixel in the image sensor and the sensitivity variation for each pixel.Ru.
[0053]
  Claim13The described invention is claimed.12In the described beam measuring apparatus, the light source guides light emitted from the light emitting source to a surface light emitting member facing the imaging element.
[0054]
Therefore, the light emitted from the light emitting source is guided to the surface light emitting member facing the image sensor, and the light from the surface light emitting member is imaged by the image sensor.
[0055]
  Claim14The invention described in the present invention is a computer program invention comprising a light source that emits uniform light, a two-dimensional image sensor, an imaging element that forms an image of uniform light emitted from the light source on the image sensor, A computer that executes various kinds of arithmetic processing based on output data of the image sensor, and is installed in the computer.4Or6The described imaging data correction method is executed.
[0058]
  ThroughNormally, pixel deterioration tends to decrease in sensitivity and hardly shifts to oversensitivity, so the approximate function by shading correction is pulled toward the lower light amount. Therefore, even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, after removing pixels with greatly deviated sensitivity, by approximating the function again, The accuracy of function approximation to the shading state is improved. For this reason, the distribution of the pixel variation from the reference light amount becomes uniform, and it becomes possible to correct the defective pixel in the image sensor and the sensitivity variation for each pixel.4When executing the imaging data correction method described above).
[0059]
  Furthermore, even if each element of the two-dimensional image sensor has variations or the relative positioning between the image sensor and the imaging element is not strict, the pixel whose sensitivity is lowered And coordinates of defective pixels can be grasped in advance. This makes it possible to improve the accuracy of function approximation for shading correction even when an optical element that affects the amount of light such as a lens is replaced or changed. In addition, after removing the influence of the overall shading, the reference light amount for each pixel is determined, and the coordinates of the pixels having a large variation from the reference light amount are set in advance as coordinates to be corrected. By replacing the light quantity data of the coordinates with the average value of the light quantity data of the plurality of surrounding pixels, it becomes possible to correct defective pixels in the image sensor and variations in sensitivity of each pixel.6When executing the imaging data correction method described above).
[0060]
  Claim15The invention of the computer program described includes a light source that emits uniform light, a two-dimensional image sensor that captures uniform light emitted from the light source, and various arithmetic processes based on output data of the image sensor. A computer that executes and is installed on the computer,5The described imaging data correction method is executed.
[0062]
  ThroughNormally, pixel deterioration tends to decrease in sensitivity and hardly shifts to oversensitivity, so the approximate function by shading correction is pulled toward the lower light amount. Therefore, even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, after removing pixels with greatly deviated sensitivity, by approximating the function again, The accuracy of function approximation to the shading state is improved. For this reason, the distribution of the pixel variation from the reference light amount becomes uniform, and it becomes possible to correct the defective pixel in the image sensor and the sensitivity variation for each pixel.Ru.
[0063]
  Claim16The invention of the storage medium described in the claims14Or15The described computer program is stored.
[0064]
  Therefore, the claims14Or15The described computer program can be output from a storage medium.
[0065]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described.
[0066]
The present embodiment relates to an imaging data correction method, a beam measurement device, software installed in a computer included in the beam measurement device, and a storage medium that stores such software.
[0067]
<Imaging data correction method>
A first embodiment of the imaging data correction method will be described with reference to FIGS.
[0068]
FIG. 1 is a perspective view of an optical device for realizing an imaging data correction method. The imaging data correction method of this embodiment using such an optical device will be described step by step.
[0069]
1. The step of causing the one-dimensional image sensor (CCD line sensor 1) to image uniform light irradiated through the imaging element (lens 2)
As shown in FIG. 1, in order to obtain a reference light amount of image data to be imaged by a lens 2 as an imaging element on a CCD line sensor 1 as an imaging element, in this embodiment, an illumination system 3 as a light source is used. The illuminated illumination light is reflected by the white original 4, and this reflected light is imaged on the CCD line sensor 1 by the lens 2.
[0070]
2. By referring to the output data of the imaging device (CCD line sensor 1) obtained by imaging the uniform light, function data having temporary parameters representing the light quantity and the three-dimensional offset amount at each pixel position of the output data is obtained. Step to generate
FIG. 2 is a graph showing the light amount distribution on the main scanning coordinates of the CCD line sensor 1.
[0071]
When the optical axes of the CCD line sensor 1 and the lens 2 coincide with each other, as shown in FIG. 2, the light quantity I obtained from the output signal of the CCD line sensor 1 is in accordance with the cosine fourth power law. From the relationship between the aperture efficiency η of the lens 2 and the tilt angle ω on each optical element 1 a of the sensor 1, it is obtained by the equation (1).
[0072]
[Expression 1]

[0073]
FIG. 3 is a schematic diagram showing a state in which the optical elements 1a of the CCD line sensor 1 and the optical axis of the lens 2 are shifted.
[0074]
The graph shown in FIG. 2 is a graph based on theoretical values. Actually, as shown in FIG. 3, each optical element 1a of the CCD line sensor 1 and the optical axis of the lens 2 do not coincide with each other on the main scanning line. In many cases, the main scanning data is shifted from the center of each optical element 1 a of the CCD line sensor 1. For this reason, various parameters fluctuate due to such deviation of the optical axis.
[0075]
First, the distance L to the entrance pupil P in each optical element 1a of the CCD line sensor 1 varies due to an attachment error between the CCD line sensor 1 and the lens 2 or the like.
[0076]
Next, let x be the main scanning direction, and A be the foot of the axis descending perpendicularly from the entrance pupil P to the imaging surface including the CCD line sensor 1, and let the amount of light at A be I₀ Then, if the lens 2 is axisymmetric, the light amount reduction due to shading is distributed on concentric circles. On the other hand, the circle with the minimum radius r shown in FIG. 3 is a circle that coincides with the CCD line sensor 1b at the point B. The amount of light at point B is I₁ As I₁ When the angle ψ is increased around₃ , I₄ ... and I like this₃ , I₄ Corresponds to a decrease in the amount of light connecting B and C from the concentric circle B to the concentric circle C by increasing the radius. Therefore, the light amount I on the CCD line sensor 1₄ Can be expressed by the following equation (2). In the formula (2), x₀ Are the coordinates (A, B, C, etc.) of the optical axis in the main scanning direction.
[0077]
[Expression 2]

[0078]
In the present embodiment, from equation (2), I which is a variation factor₀ , L, r, x₀ A suitable initial value is given to the light quantity data p and function data I actually obtained by the CCD line sensor 1.₄ Is defined as shown by the equation (3).
[0079]
[Equation 3]

[0080]
3. A step of approximating output data and function data of the image sensor (CCD line sensor 1) by changing temporary parameters
Next, in the present embodiment, in the above equation (3), the parameter I is set so that the difference d becomes small.₀ , L, r, x₀ To change. In this way, as shown in FIG. 4, the function at the time when d is minimized is set as an approximation result to shading. As a method for deriving an approximate solution that is a result of convergence of a function, a quasi-Newton method, a Levenberg-Marqurdt method, or the like is used.
[0081]
4). A step of acquiring, as correction data, a reciprocal number of data obtained by removing data related to light quantity from function data after being approximated to output data of the image sensor (CCD line sensor 1).
Parameter I of the approximate function obtained as an optimal solution₀ , L, r, x₀ Are the amount of light at the center of the lens 2, the distance from the imaging surface to the entrance pupil P, the shortest distance from the optical axis to the CCD line sensor 1, and the coordinates of the optical axis in the main scanning direction.
[0082]
The correction data R at each coordinate can be defined by parameters obtained from these approximation results. Equation (4) is an equation that defines such correction data R.
[0083]
[Expression 4]

[0084]
5. A step of correcting output data of the image sensor (CCD line sensor 1) based on the correction data
Finally, the corrected light quantity data is confirmed as shown in FIG. Therefore, such correction data is stored in a hard disk (not shown) or the like, and shading correction is performed by multiplying the image data by the correction data during actual imaging.
[0085]
Therefore, even if the optical elements 1a of the CCD line sensor 1 are varied or the relative positioning between the imaging element and the imaging element is not strict, such a current situation is fluctuated. By using parameters, it is possible to correct shading correctly.
[0086]
A second embodiment of the imaging data correction method will be described with reference to FIG.
[0087]
FIG. 6 is a graph showing the light amount distribution after shading correction on the main scanning coordinates of the CCD line sensor 1.
[0088]
In the present embodiment, roughly, an average value of light amounts in all image data after correction is calculated using correction data obtained by approximation of a function, and pixels indicating values far from the average value (FIG. 6). The coordinates of the pixels 5 and 6 are detected, the light intensity values of the peripheral pixels around the pixels 5 and 6 are averaged, and the average value is used as the light intensity value of the pixels 5 and 6 described above. Thereby, the defective pixel in each optical element 1a in the CCD line sensor 1 and the sensitivity variation for each pixel can be corrected.
[0089]
Specifically, as shown in FIG. 6, in the uniform image after shading correction, an arbitrary variation ratio is set from the overall average value. For example, when measuring the beam diameter, the variation in maximum light intensity is 1 / e.² Or 1 / e ratio, even if the maximum light intensity varies, 1 / e² For example, a method of setting the variation of the light amount data so that it does not deviate by one pixel or more in the 1 / e light amount region can be considered. Here, if ± 5% is assumed, the coordinates of pixels having large variations such as pixels 5 and 6 in FIG. 6 are stored in a storage means such as a hard disk (not shown), and the light amount value of the acquired image at the time of actual imaging. Is replaced with the average light quantity value of a plurality of adjacent pixels.
[0090]
Such an invention of the present embodiment is realized by the following steps.
1. A step of calculating an average value of the amount of light included in the output data of the CCD line sensor 1
2. Setting the upper and lower limits of the data based on the average value
3. 3. Obtain a pixel position where the light amount value included in the output data of the corrected CCD line sensor 1 is outside the set upper and lower limit values as a correction target pixel position. A step of calculating an average value of light amounts in a plurality of peripheral pixels around the correction target pixel position among light amount values included in the output data of the CCD line sensor 1 after correction, and handling the light amount value of the correction target pixel as the average value
As a result of the execution of these steps, it is possible to correct defective pixels in the CCD line sensor 1 and sensitivity variations among the pixels.
[0091]
A third embodiment of the imaging data correction method will be described with reference to FIG.
[0092]
FIG. 7 is a graph showing the light amount distribution after correcting various errors on the main scanning coordinates of the CCD line sensor 1.
[0093]
In the present embodiment, generally, it is possible to correct the pixel variation while correcting the error of the function approximation affected by the defective pixel by repeating the overall light amount correction by function approximation and the correction of local pixel variation. By correcting the average value of the uniform image serving as a reference for correcting the correction, the unusable pixels are removed and the uniformity of the sensitivity is improved to improve the uniformity of the sensitivity and the sensitivity variation for each pixel of the CCD line sensor 1 Is to correct.
[0094]
Specifically, as shown in FIG. 7, in the case where the sensitivity is greatly deteriorated or a defective pixel as in the pixel shown as 7, the same processing as the processing in the first embodiment is performed. Then, the process of correcting the data and then removing the pixel variation in the pixel 7 by executing the process described later is repeated.
[0095]
Such an invention of the present embodiment is realized by the following first step group and second step group.
[0096]
[First step group]
1. The step of causing the CCD line sensor 1 to image uniform light irradiated through the lens 2
2. A step of generating function data having temporary parameters representing the light quantity and the three-dimensional offset amount at each pixel position of the output data with reference to the output data of the CCD line sensor 1 obtained by imaging the uniform light.
3. Step of approximating output data and function data of the CCD line sensor 1 by changing a temporary parameter
4). A step of obtaining, as correction data, a reciprocal of data obtained by removing data relating to the light amount from the function data approximated to the output data of the CCD line sensor 1
5. Correcting the output data of the CCD line sensor 1 based on the correction data
[Second step group]
1. A step of calculating an average value of the amount of light included in the output data of the CCD line sensor 1 after correction
2. Setting the upper and lower limits of the data based on the average value
3. A step of acquiring a pixel position at which the light amount value included in the output data of the CCD line sensor 1 after correction is a value farthest from the upper and lower limit values as a correction target pixel position
4). A step of calculating an average value of light amounts in a plurality of peripheral pixels around the correction target pixel position among light amount values included in the output data of the CCD line sensor 1 after correction, and handling the light amount value of the correction target pixel as the average value
[Execution of first step and second step]
The first step group and the second step group are repeatedly executed until the light amount values for all the pixels included in the output data of the image sensor after correction fall within the upper and lower limit values.
[0097]
Through the above processing, the invention of the present embodiment is executed. Thereby, the distribution of the pixel variation from the reference light amount becomes uniform, and the defective pixel in the CCD line sensor 1 and the sensitivity variation for each pixel can be corrected.
[0098]
A fourth embodiment of the imaging data correction method will be described.
[0099]
In the present embodiment, roughly, coordinate data for correcting defective pixels and low-sensitivity pixels is grasped in advance, and even when the lens 2 or the like is replaced or changed, pixels with different coordinates are used. The light amount value at is corrected. Here, in the present embodiment, when grasping the coordinate data, referring to FIG. 1, the illumination light irradiated from the illumination system 3 is reflected by the white original 4, and this reflected light is passed through the lens 2. The CCD line sensor 1 is directly irradiated.
[0100]
As an example, when the pixel variation is suppressed to ± 5%, the upper and lower limits are set to ± 5% of the entire average value, and the coordinates of pixels whose values exceed the upper and lower limits are stored in a storage means such as a hard disk (not shown), At the time of actual imaging, the pixel value from the coordinate data of the acquired image data is replaced with the average value of the adjacent plural pixels.
[0101]
Such an invention of the present embodiment is realized by the following steps.
1. The step of causing the CCD line sensor 1 to image the irradiated uniform light
2. A step of calculating an average value of the amount of light included in the output data of the CCD line sensor 1
3. Setting the upper and lower limits of the data based on the average value
4). A step of acquiring, as a correction target pixel position, a pixel position at which the light amount value included in the corrected output data of the CCD line sensor 1 deviates from the upper and lower limit values.
5. A step of calculating an average value of light amounts in a plurality of peripheral pixels around the correction target pixel position among light amount values included in the output data of the CCD line sensor 1 after correction, and handling the light amount value of the correction target pixel as the average value
As a result of the execution of each step, it is possible to improve the accuracy of function approximation for shading correction even when the optical element such as the lens 2 is changed or changed. . In addition, it is possible to correct defective pixels in the CCD line sensor 1 and sensitivity variations among the pixels.
[0102]
A fifth embodiment of the imaging data correction method will be described.
[0103]
In the present embodiment, roughly, the coordinates of a pixel that shows a value farther than the average value of the entire pixel serving as the reference light amount data are detected, and the values of a plurality of adjacent pixels of the pixel are averaged to determine the pixel value. By setting a value, defective pixels of the CCD line sensor 1 and sensitivity variations for each pixel are corrected.
[0104]
For example, the coordinates of the pixel whose light amount value differs most from the average light amount value of the entire pixel is stored in a storage means such as a hard disk (not shown), and the light amount value of that pixel is corrected with the light amount values of adjacent pixels, and after the correction, The average value of the whole is derived, the coordinates of the pixel having the most different light area value are stored in a storage means such as a hard disk (not shown), and the light amount value of that pixel is corrected with the light amount value of the adjacent plural pixels. By repeating such steps, it is possible to reduce a decrease in the average value due to pixels with significantly deteriorated sensitivity or defective pixels.
[0105]
Such an invention of the present embodiment is realized by the following first step group and second step group.
[0106]
[First step group]
1. The step of causing the CCD line sensor 1 to image the irradiated uniform light
2. A step of generating function data having temporary parameters representing the light quantity and the three-dimensional offset amount at each pixel position of the output data with reference to the output data of the CCD line sensor 1 obtained by imaging the uniform light.
3. Step of approximating output data and function data of the CCD line sensor 1 by changing a temporary parameter
4). A step of obtaining, as correction data, a reciprocal of data obtained by removing data relating to the light amount from the function data approximated to the output data of the CCD line sensor 1
5. Correcting the output data of the CCD line sensor 1 based on the correction data
[Second step group]
1. A step of calculating an average value of the amount of light included in the output data of the CCD line sensor 1 after correction
2. Setting the upper and lower limits of the data based on the average value
3. A step of acquiring, as a correction target pixel position, a pixel position at which the light amount value included in the corrected output data of the CCD line sensor 1 is most deviated from the upper and lower limit values.
4). A step of calculating an average value of light amounts in a plurality of peripheral pixels around the correction target pixel position among light amount values included in the output data of the CCD line sensor 1 after correction, and handling the light amount value of the correction target pixel as the average value
[Execution of first step and second step]
The first step group and the second step group are repeatedly executed until the light amount values for all the pixels included in the corrected output data of the CCD line sensor 1 fall within the upper and lower limit values.
[0107]
This makes it possible to correct defective pixels in the CCD line sensor 1 and sensitivity variations for each pixel.
[0108]
A sixth embodiment of the imaging data correction method will be described.
[0109]
In the present embodiment, roughly speaking, the variation of each pixel is grasped by coordinates, and after correcting the variation of the captured light quantity data, the function approximation accuracy is improved and the shading is also corrected. Is.
[0110]
Such an invention of the present embodiment is realized by the following steps.
1. The step of causing the one-dimensional CCD line sensor 1 to image uniform light irradiated through the lens 2
2. The output data of the CCD line sensor 1 obtained by imaging the uniform light is output from the CCD line sensor 1 obtained by executing the imaging data correction method in the fifth or sixth embodiment of the imaging data correction method. A step of correcting based on the output data, and referring to the corrected output data, and generating function data having temporary parameters indicating the light quantity and the three-dimensional offset amount at each pixel position of the output data
3. Step of approximating output data and function data of the CCD line sensor 1 by changing a temporary parameter
4). A step of obtaining, as correction data, a reciprocal of data obtained by removing data relating to the light amount from the function data approximated to the output data of the CCD line sensor 1
5. Correcting the output data of the CCD line sensor 1 based on the correction data
This makes it possible to correct defective pixels in the CCD line sensor 1 and variations in sensitivity among the pixels.
[0111]
A seventh embodiment of the imaging data correction method will be described.
[0112]
In this embodiment, the obtained correction data is multiplied by the light amount data every time the image is acquired so that the pixel sensitivity is uniform, thereby correcting the light amount variation due to the sensitivity variation for each pixel of the CCD line sensor 1 in the captured image. Is to do.
[0113]
For example, for each imaging using the CCD line sensor 1, the entire screen data is multiplied by the shading correction data to make the entire light amount uniform, and the pixel of the coordinate is determined based on the pixel variation coordinate data. Replace with the average value of adjacent pixels.
[0114]
This makes it possible to acquire a captured image with a uniform sensitivity.
[0115]
An eighth embodiment of the imaging data correction method will be described with reference to FIGS.
[0116]
This embodiment is different from the first to seventh embodiments described above in that a two-dimensional image sensor is used. Hereinafter, the imaging data correction method of this embodiment will be described step by step.
[0117]
1. A step of causing the two-dimensional image sensor (CCD area sensor 8) to image uniform light irradiated through the imaging element (lens 9).
FIG. 8 is a schematic diagram of a beam measuring apparatus for carrying out the imaging data correction method. As shown in FIG. 8, in this embodiment, a CCD area sensor 8 is used as an image sensor. The image data formed on the CCD area sensor 8 by the lens 9 is illumination light of the cold light source 12 guided by the fiber light guide 11 to the surface emitting type surface emitting member 10. This illumination light is diffused by the opal diffusion plates 13 and 13a.
[0118]
2. A three-dimensional function having temporary parameters representing the amount of light and the three-dimensional offset amount at each pixel position of the output data with reference to output data of the image sensor (CCD area sensor 8) obtained by imaging uniform light Steps to generate data
Therefore, when such diffused light is used as the reference light amount, as shown in FIG. 9, the distance L to the entrance pupil P, the main scanning direction x, the sub-scanning direction y, and the entrance pupil P to the CCD area sensor 8a. Let A be the foot of the axis descending perpendicularly to the imaging surface including the amount of light at A₀ Then, if the lens 9 is axially symmetric, the light amount decrease due to shading is distributed concentrically, and the light amount I at an arbitrary position on the CCD area sensor 8.₄ Is expressed by equation (5). Where x₀ Is the coordinate in the main scanning direction of the optical axis, y₀ Are coordinates in the sub-scanning direction of the optical axis.
[0119]
[Equation 5]

[0120]
3. Step of approximating the output data of the image sensor (CCD area sensor 8) and the three-dimensional function data by changing the temporary parameter
Next, from equation (5), I which is a fluctuation factor₀ , L, x₀ , Y₀ A suitable initial value is given to the light quantity data p and function data I actually obtained by the CCD area sensor.₄ Is defined as shown by equation (6).
[0121]
[Formula 6]

[0122]
Then, the parameter I is set so that the difference d becomes small.₀ , L, x₀ , Y₀ To change. In this way, the function at the time when the difference d is minimized is used as an approximation result to shading. As a method for deriving an approximate solution that is a result of convergence of a function, a quasi-Newton method, a Levenberg-Marqurdt method, or the like is used.
[0123]
Parameter I of the approximate function obtained as an optimal solution₀ , L, x₀ , Y₀ Are the amount of light at the center of the lens 9, the distance from the imaging surface to the entrance pupil P, and the coordinates of the optical axis in the main and sub-scanning directions, respectively.
[0124]
4). A step of acquiring, as correction data, an inverse number of data obtained by removing data relating to light quantity from the three-dimensional function data approximated to output data of the image sensor (CCD area sensor 8)
Based on the parameters obtained from these approximation results, the correction data R at each coordinate is defined by the following equation (7).
[0125]
[Expression 7]

[0126]
5. A step of correcting output data of the image sensor (CCD area sensor 8) based on the correction data
Next, the output data of the CCD area sensor 8 is corrected using equation (7). The corrected light quantity data is confirmed as shown in FIG. Here, FIG. 10 is a schematic diagram showing a light amount distribution in the CCD area sensor 8 before and after the shading correction.
[0127]
The correction data is stored in a hard disk (not shown) and the shading correction is performed by multiplying the image data during actual imaging.
[0128]
Thus, even if there are variations in each element of the CCD area sensor 8 or the relative positioning between the CCD area sensor 8 and the lens 9 is not strict, such a present situation can be regarded as a variable parameter. By doing so, it becomes possible to correct shading correctly.
[0129]
The second to seventh embodiments described above can be applied to the eighth embodiment of the imaging data correction method described above. In this case, also in the eighth embodiment of the imaging data correction method, the operational effects of the second to seventh embodiments described above can be obtained. Note that the processing itself in the second to seventh embodiments of the imaging data correction method does not differ even when applied to the eighth embodiment of the imaging data correction method, and thus the description thereof is omitted. Those skilled in the art can understand the processes in the second to seventh embodiments by referring to the corresponding portions already described.
[0130]
<Beam measurement apparatus, beam measurement computer program, and storage medium storing such computer program>
Next, a description will be given of a beam measurement apparatus, a beam measurement computer program, and a storage medium storing such a computer program that can implement the above-described imaging data correction method.
[0131]
A first embodiment of the beam measuring apparatus will be described with reference to FIGS.
[0132]
FIG. 11 is a schematic diagram of a beam measuring apparatus.
[0133]
As shown in FIG. 11, the beam measuring apparatus according to the present embodiment reflects and scans a light beam emitted from a laser diode (LD) unit 15 as a light source by a rotating polygon mirror 14 and converts the reflected scanning light into fθ. The transmitted light is transmitted through the lens 16, and the transmitted light is transmitted through the objective lens 18 as the imaging element to the CCD area sensor 17 as the two-dimensional image sensor. That is, the beam measuring apparatus according to the present embodiment includes the polygon mirror 14, the laser diode (LD) unit 15, and the fθ lens 16 as light sources. The light amount data output from the CCD area sensor 17 is converted into digital data by an A / D converter (not shown) and then stored in a hard disk (not shown) of the computer 19.
[0134]
A computer 19 provided in the beam measuring apparatus incorporates a microprocessor (not shown) composed of a CPU, ROM, RAM, etc., and follows a computer program stored in a storage area (ROM, RAM) provided in the microprocessor. The imaging data correction method in the first to eighth embodiments described above is executed. At this time, the computer 19 executes processing according to the installed computer program by using various resources such as a microprocessor.
[0135]
As an example of such processing, shading correction is performed on the entire image data including the light amount data stored in the hard disk (not shown) of the computer 19, and the light amount distribution in the main scanning direction of FIG. The correction is performed so that the data curve indicated by reference numeral 20 becomes the data curve indicated by reference numeral 21. Next, based on coordinate data of pixel variation stored in a hard disk (not shown), the corresponding coordinate data is replaced with an average value of pixel data of a plurality of adjacent pixels.
[0136]
In addition, the computer 19 executes the imaging data correction methods in the first to eighth embodiments described above as necessary using the arithmetic processing capability of the microprocessor.
[0137]
The computer program installed on the computer 19 can be distributed in various forms and installed on the computer 19. For example, a computer program can be stored in a storage medium that can store information optically or magnetically, such as a CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, magnetic tape, floppy disk, etc. In addition, various methods such as installing in the computer 19 as necessary, or installing in a form of downloading to the computer 19 on the network can be implemented.
[0138]
In the beam measurement apparatus of the present embodiment, the objective lens 18 is removed as necessary to perform beam measurement.
[0139]
A second embodiment of the beam measuring apparatus will be described with reference to FIG. The same parts as those of the first embodiment of the beam measuring apparatus are denoted by the same reference numerals, and description thereof is also omitted.
[0140]
FIG. 13 is a schematic diagram of a beam measuring apparatus. This beam measuring apparatus has a configuration similar to that of the beam apparatus shown in FIG. 8 used in the description of the eighth embodiment of the imaging data correction method. FIG. 13 shows a schematic view of such a beam measuring apparatus observed from above.
[0141]
As shown in FIG. 13, the illumination light from the cold light source 12 is guided to the surface emitting member 10 of the surface emitting type by the fiber light guide 11, and the emitted light is diffused by the opal diffusers 13, 13a. In order to use the diffused light as a reference light quantity, the opal diffuser plates 13 and 13a and the surface emitting type surface emitting member 10 are placed on the optical axis of the objective lens 18 fixed relative to the CCD area sensor 17. It is fixed on the slider 22 so that it can enter and exit, and the illumination light of the cold light source 12 can be guided from the outside by the fiber light guide 11.
[0142]
Such a beam measuring apparatus according to the present embodiment includes the surface light emitting member 10, the fiber light guide 11, the cold light source 12, and the opal diffusers 13 and 13a as light sources.
[0143]
Similar to the beam measurement apparatus illustrated in FIG. 11, such a beam measurement apparatus also includes a computer (not shown), and this computer uses the arithmetic processing capability of a built-in microprocessor (not shown) to make the first described above. The imaging data correction method in the eighth embodiment is executed as necessary.
[0144]
As a modification of the second embodiment of the beam measuring apparatus, a cold light source 12 that is a light source, a surface light emitting member 10 that is a light source, a fiber light guide 11, a cold light source 12, and opal diffusers 13 and 13a are used. It is possible to provide a function of detecting the uniformity of light emission. Specifically, as shown in FIG. 14, as a light receiving element for detecting the amount of light, which is arranged adjacent to the objective lens 18 so that the light receiving surface coincides with the focal position of the objective lens 18. The PD 23 (photo detector) is installed, and the PD 23 is moved in the main scanning direction and the sub-scanning direction to detect the amount of light in a certain region, and the light emission uniformity of the light source as illumination light is detected. . Thus, by setting the position of the CCD area sensor 17 so that it can be imaged in a range in which the light emission uniformity of the light source is confirmed by scanning with the PD 23, it is possible to surely capture a uniform image as a reference light amount. it can.
[0145]
As another example of such a modification of the second embodiment of the beam measuring apparatus, as shown in FIG. 15, the light receiving surface of the PD 23 substantially matches the resolution of the image sensor such as the CCD area sensor 17. A mask 25 having a sized pinhole 24 may be fixed, and the amount of light may be detected by optical scanning in an area equal to or larger than the imaging range of the CCD area sensor 17. Thus, by making the optical scanning interval equal to the pixel pitch of the CCD area sensor 17, the light quantity uniformity of the reference image can be detected with a resolution equivalent to the imaging resolution of the CCD area sensor 17.
[0146]
【The invention's effect】
  According to the invention of the imaging data correction method according to claim 1,Even if variations due to defective pixels or pixels with greatly deteriorated sensitivity affect the approximate function and slightly deviate from the overall shading state, the shading state is obtained by performing function approximation again after removing pixels with greatly deviating sensitivity. This improves the accuracy of function approximation to the pixel, thereby evenly distributing the pixel variation from the reference light amount, thereby reducing defective pixels in the image sensor and variations in sensitivity from pixel to pixel.It can be corrected.
[0150]
  Claim2According to the imaging data correction method described above, even if a variation due to a missing pixel or a pixel whose sensitivity is greatly deteriorated affects the approximation function and slightly deviates from the overall shading state, After the removal, the function approximation can be performed again by performing the function approximation, thereby making it possible to evenly distribute the pixel variation from the reference light amount, and to detect the defective pixels in the image sensor or for each pixel. Sensitivity variation can be corrected.
[0151]
  Claim3According to the described imaging data correction method invention, each element of the one-dimensional imaging element may vary, or the relative positioning between the imaging element and the imaging element may not be accurate. However, it is possible to grasp in advance the coordinates of pixels with reduced sensitivity and defective pixels, etc., so that even when there is an exchange or change of an optical element that affects the amount of light such as a lens, The accuracy of function approximation for shading correction can be improved. In addition, after removing the influence of the overall shading, the reference light amount for each pixel is determined, and the coordinates of the pixels having a large variation from the reference light amount are set in advance as coordinates to be corrected. By replacing the light quantity data of the coordinates with the average value of the light quantity data of the plurality of peripheral pixels, it is possible to correct the defective pixels in the image sensor and variations in sensitivity of each pixel.
[0155]
  Claim4According to the imaging data correction method described above, even if a variation due to a defective pixel or a pixel whose sensitivity is greatly deteriorated affects the approximation function and slightly deviates from the overall shading state, After the removal, the function approximation is performed again to improve the accuracy of the function approximation to the shading state, thereby equalizing the distribution of the pixel variation from the reference light amount, thereby reducing the defective pixel in the image sensor and the sensitivity variation for each pixel. It can be corrected.
[0157]
  Claim5According to the imaging data correction method described above, even if a variation due to a missing pixel or a pixel whose sensitivity is greatly deteriorated affects the approximation function and slightly deviates from the overall shading state, After the removal, the function approximation can be performed again by performing the function approximation, thereby making it possible to equalize the distribution of the pixel variation from the reference light amount and to detect the defective pixels and the pixels for each pixel. Sensitivity variation can be corrected.
[0158]
  Claim6According to the invention of the imaging data correction method described above, there may be variations in each element of the two-dimensional imaging element, or the relative positioning between the imaging element and the imaging element is not strict. However, it is possible to grasp in advance the coordinates of pixels with reduced sensitivity and defective pixels, etc., so that even when there is an exchange or change of an optical element that affects the amount of light such as a lens, The accuracy of function approximation for shading correction can be improved. In addition, after removing the influence of the overall shading, the reference light amount for each pixel is determined, and the coordinates of the pixels having a large variation from the reference light amount are set in advance as coordinates to be corrected. By replacing the light quantity data of the coordinates with the average value of the light quantity data of the plurality of peripheral pixels, it is possible to correct the defective pixels in the image sensor and variations in sensitivity of each pixel.
[0159]
  Claim7According to the imaging data correction method described above, the captured image can be acquired with a uniform sensitivity, and therefore the reading accuracy of the image data can be improved.
[0160]
  Claim8According to the invention of a beam measuring device as claimed4Or6The effects of the described imaging data correction method can be achieved.
[0161]
  Claim9According to the described beam measuring apparatus, the light emitted from the light emitting source can be guided to the surface light emitting member facing the image sensor, and the light from the surface light emitting member can be imaged by the image sensor.
[0162]
  Claim10According to the described invention of the beam measuring apparatus, it is possible to detect the uniformity of light from the light source based on the output signal of the light receiving element.
[0163]
  Claim11According to the beam measuring apparatus described above, it is possible to detect the light quantity uniformity with the pixel pitch of the image sensor.
[0164]
  Claim12According to the invention of a beam measuring device as claimed5The effects of the described imaging data correction method can be achieved.
[0165]
  Claim13According to the described beam measuring apparatus, the light emitted from the light emitting source can be guided to the surface light emitting member facing the image sensor, and the light from the surface light emitting member can be imaged by the image sensor.
[0166]
  Claim14According to the described computer program invention, the claims4Or6The effects of the described imaging data correction method can be achieved.
[0167]
  Claim15According to the described computer program invention, the claims5The effects of the described imaging data correction method can be achieved.
[0168]
  Claim16According to the described storage medium invention, the claims14Or15The described computer program can be made portable in the form of a storage medium, and such a computer program can be output from the storage medium at any time.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an optical apparatus for realizing an imaging data correction method as a first embodiment of an imaging data correction method.
FIG. 2 is a graph showing a theoretical light amount distribution on main scanning coordinates of a CCD line sensor.
FIG. 3 is a schematic diagram showing a state where each optical element of the CCD line sensor and the optical axis of the lens are deviated.
FIG. 4 is a graph showing a light amount distribution after correcting various errors on a main scanning coordinate of a CCD line sensor.
FIG. 5 is a graph showing a light amount distribution after shading correction on a main scanning coordinate of a CCD line sensor;
FIG. 6 is a graph showing a light amount distribution after shading correction on a main scanning coordinate of a CCD line sensor as a second embodiment of the imaging data correction method;
FIG. 7 is a graph showing a light amount distribution after correcting various errors on a main scanning coordinate of a CCD line sensor as a third embodiment of an imaging data correction method;
FIG. 8 is a schematic diagram showing a beam measuring apparatus for carrying out an imaging data correction method as an eighth embodiment of the imaging data correction method.
FIG. 9 is a schematic diagram showing a state in which each optical element of the CCD area sensor is shifted from the optical axis of the lens.
FIG. 10 is a schematic diagram showing a light amount distribution in a CCD area sensor before and after shading correction.
FIG. 11 is a schematic diagram showing a beam measuring device as a first embodiment of the beam measuring device.
FIG. 12 is a graph showing a light amount distribution on main scanning coordinates.
FIG. 13 is a schematic diagram showing a beam measuring device as a second embodiment of the beam measuring device.
FIG. 14 is a schematic diagram showing a beam measuring device as a modification of the second embodiment of the beam measuring device.
FIG. 15 is a perspective view showing an example in which a mask with pinholes is provided on a PD.
[Explanation of symbols]
1, 8, 17 Image sensor (CCD line sensor, CCD area sensor)
2, 9 Imaging element (lens, objective lens)
3, 10, 11, 12, 13, 13a, 14, 15, 16 Light source (illumination system, surface emitting member, fiber light guide, cold light source, opal diffuser, polygon mirror, laser diode (LD) unit, fθ lens )
10 Surface light emitting member
12, 15 Light source
23 Light receiving element (PD)
24 pinhole
25 mask

Claims (16)

As a first step group, a step of causing the one-dimensional image sensor to image uniform light irradiated through the imaging element;
Referring to the output data of the image sensor obtained by imaging the uniform light, the amount of light on the axis perpendicular to the imaging surface including the imaging element from the entrance pupil, and the distance from the imaging surface to the entrance pupil When the shortest distance from the optical axis to the imaging element, a step of referring a three-dimensional offset amount indicated in the main scanning direction coordinate of the optical axis, the formal parameters consisting, for generating a function number data,
Changing the temporary parameter to approximate the output data of the image sensor and the function data;
A step of acquiring the reciprocal of the data obtained by removing the data relating to the amount of light from the function data after being approximated to the output data of the image pickup device as the correction data,
Correcting the output data of the imaging device based on the correction data,
As a second step group, calculating an average value of the amount of light included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the correction data ;
Setting upper and lower limit values of data on the basis of the average value;
The pixel position where the light amount value included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data is a value that is farthest from the upper and lower limit values is the pixel to be corrected A step of acquiring as a position;
Of the light amount values included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the correction data, an average value of the light amounts in a plurality of peripheral pixels around the correction target pixel position. Calculating and treating the light amount value of the correction target pixel as an average value thereof,
The first light intensity values for all the pixels included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data are within the upper and lower limit values. An imaging data correction method for repeatedly executing a step group and a second step group. As a first step group, a step of causing the one-dimensional image sensor to image the irradiated uniform light;
Referring to the output data of the image sensor obtained by imaging the uniform light, the amount of light on the axis perpendicular to the imaging surface including the imaging element from the entrance pupil, and the distance from the imaging surface to the entrance pupil When the shortest distance from the optical axis to the imaging element, a step of referring a three-dimensional offset amount indicated in the main scanning direction coordinate of the optical axis, the formal parameters consisting, for generating a function number data,
Changing the temporary parameter to approximate the output data of the image sensor and the function data;
A step of acquiring the reciprocal of the data obtained by removing the data relating to the amount of light from the function data after being approximated to the output data of the image pickup device as the correction data,
Correcting the output data of the imaging device based on the correction data,
As a second step group, calculating an average value of the amount of light included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the correction data ;
Setting upper and lower limit values of data on the basis of the average value;
The pixel position where the light amount value included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data is a value that is farthest from the upper and lower limit values is the pixel to be corrected A step of acquiring as a position;
Of the light amount values included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the correction data, an average value of the light amounts in a plurality of peripheral pixels around the correction target pixel position. Calculating and treating the light amount value of the correction target pixel as an average value thereof,
The first light intensity values for all the pixels included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data are within the upper and lower limit values. An imaging data correction method for repeatedly executing a step group and a second step group. Causing the one-dimensional image sensor to image uniform light irradiated through the imaging element;
The output data of the imaging device obtained by imaging the uniform light is corrected based on the output data of the imaging device obtained by executing the imaging data correction method according to claim 2 , and the correction data Based on the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the amount of light on the axis dropped from the entrance pupil perpendicular to the imaging surface including the imaging element, and imaging the distance from the surface to the entrance pupil, and the shortest distance from the optical axis to the image forming element, with reference the three-dimensional offset amount indicated in the main scanning direction coordinate of the optical axis, the formal parameters consisting, functions Day the method comprising the steps of: generating the data,
Changing the temporary parameter to approximate the output data of the image sensor and the function data;
A step of acquiring the reciprocal of the data obtained by removing the data relating to the amount of light from the function data after being approximated to the output data of the image pickup device as the correction data,
Correcting the output data of the image sensor based on the correction data. As a first step group, the step of causing the two-dimensional image sensor to image uniform light irradiated through the imaging element;
Referring to the output data of the image sensor obtained by imaging the uniform light, the amount of light on the axis perpendicular to the imaging surface including the imaging element from the entrance pupil, and the distance from the imaging surface to the entrance pupil When the steps of the main scanning direction coordinate of the optical axis, with reference the three-dimensional offset amount represented by the sub-scanning direction coordinate of the optical axis, the formal parameters consisting, to generate a three-dimensional function data,
Changing the temporary parameter to approximate the output data of the image sensor and the three-dimensional function data;
Obtaining a reciprocal of the data obtained by removing the data relating to the light amount from the three-dimensional function data after being approximated to the output data of the image sensor as correction data;
Correcting the output data of the imaging device based on the correction data,
As a second step group, calculating an average value of the amount of light included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the correction data ;
Setting upper and lower limit values of data on the basis of the average value;
The pixel position where the light amount value included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data is a value that is farthest from the upper and lower limit values is the pixel to be corrected A step of acquiring as a position;
Of the light amount values included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the correction data, an average value of the light amounts in a plurality of peripheral pixels around the correction target pixel position. Calculating and treating the light amount value of the correction target pixel as an average value thereof,
The first light intensity values for all the pixels included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data are within the upper and lower limit values. An imaging data correction method for repeatedly executing a step group and a second step group. As a first step group, a step of causing the two-dimensional image sensor to image the irradiated uniform light;
Referring to the output data of the image sensor obtained by imaging the uniform light, the amount of light on the axis perpendicular to the imaging surface including the imaging element from the entrance pupil, and the distance from the imaging surface to the entrance pupil When the steps of the main scanning direction coordinate of the optical axis, with reference the three-dimensional offset amount represented by the sub-scanning direction coordinate of the optical axis, the formal parameters consisting, to generate a three-dimensional function data,
Changing the temporary parameter to approximate the output data of the image sensor and the three-dimensional function data;
Obtaining a reciprocal of the data obtained by removing the data relating to the light amount from the three-dimensional function data after being approximated to the output data of the image sensor as correction data;
Correcting the output data of the imaging device based on the correction data,
As a second step group, calculating an average value of the amount of light included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the correction data ;
Setting upper and lower limit values of data on the basis of the average value;
The pixel position where the light amount value included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data is a value that is farthest from the upper and lower limit values is the pixel to be corrected A step of acquiring as a position;
Of the light amount values included in the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the correction data, an average value of the light amounts in a plurality of peripheral pixels around the correction target pixel position. Calculating and treating the light amount value of the correction target pixel as an average value thereof,
The first light intensity values for all the pixels included in the output data of the image sensor after correction in the step of correcting the output data of the image sensor based on the correction data are within the upper and lower limit values. An imaging data correction method for repeatedly executing a step group and a second step group. Causing the two-dimensional image sensor to image the uniform light irradiated through the imaging element;
The output data of the imaging device obtained by imaging the uniform light is corrected based on the output data of the imaging device obtained by executing the imaging data correction method according to claim 5 , and the correction data Based on the output data of the image sensor after being corrected in the step of correcting the output data of the image sensor based on the amount of light on the axis dropped from the entrance pupil perpendicular to the imaging surface including the imaging element, and imaging the distance from the surface to the entrance pupil, the main scanning direction coordinate of the optical axis, with reference the three-dimensional offset amount represented by the sub-scanning direction coordinate of the optical axis, the formal parameters consisting of the three-dimensional function data A step of generating
Changing the temporary parameter to approximate the output data of the image sensor and the three-dimensional function data;
Obtaining a reciprocal of the data obtained by removing the data relating to the light amount from the three-dimensional function data after being approximated to the output data of the image sensor as correction data;
Correcting the output data of the image sensor based on the correction data. 7. Refer to the output data of the imaging device corrected by the imaging data correction method according to any one of claims 4 to 6 when the imaging device enlarges or reduces light including image data by the imaging device and images the imaging device. And the imaging data correction method which correct | amended the output data of the said image pick-up element which imaged the light containing the said image data. A light source that emits uniform light, a two-dimensional image sensor, an imaging element that forms an image of the uniform light emitted from the light source on the image sensor, and an imaging data correction method according to claim 4 or 6. Means for performing the beam measurement. The beam measuring apparatus according to claim 8 , wherein the light source guides light emitted from the light source to a surface light emitting member facing the image sensor. A light receiving element that is disposed so as to coincide with the focal position of the imaging element and receives light from the light source is provided, and uniformity of light from the light source is detected based on an output signal of the light receiving element. The beam measuring device according to claim 8 or 9 . The beam measuring apparatus according to claim 10 , wherein the light receiving element is covered with a mask having a pinhole that matches a light receiving region of the light receiving element with a resolution of the image pickup element. 6. A beam measuring apparatus comprising: a light source that emits uniform light; a two-dimensional image sensor that images uniform light emitted from the light source; and means for executing the imaging data correction method according to claim 5 . The beam measuring apparatus according to claim 12 , wherein the light source guides light emitted from a light emitting source to a surface light emitting member facing the imaging element. A light source that emits uniform light, a two-dimensional image sensor, an imaging element that forms an image of uniform light emitted from the light source on the image sensor, and various calculations based on output data of the image sensor A computer program comprising: a computer for executing processing; and being installed in the computer, causing the computer to execute the imaging data correction method according to claim 4 or 6 . A light source that emits uniform light; a two-dimensional image sensor that captures uniform light emitted from the light source; and a computer that executes various arithmetic processes based on output data of the image sensor. A computer program that is installed in the computer and causes the computer to execute the imaging data correction method according to claim 5 . A storage medium for storing the computer program according to claim 14 or 15 .

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