JP3643201B2 - Digital camera - Google Patents

Description

【００９０】
なお、上記内分法では撮像画像の周辺に位置するブロックＢ(1,1)〜Ｂ(1,L)，Ｂ(2,L)〜Ｂ(K,L)，Ｂ(K,L-1)〜Ｂ(K,1)，Ｂ(K-1,1)〜Ｂ(2,1)において、各ブロックの中心位置より外側の部分のγ特性が補間されないが、この部分については外分法によりγ特性の線形補間を行なうようにすればよい。
【００９１】
また、各ブロックＢ(I,J)の中心位置を除く全ての位置についてγ特性を補間してもよいが、各ブロックＢ(I,J)の中心位置以外の部分を複数の画素データ（例えば４×４画素乃至６×６画素等）が含まれるブロックに分割し、このブロック単位でγ特性を線形補間するようにして補間演算の時間を短縮するようにしてもよい。
【００９２】
なお、上述の照度ムラ補正用のγ特性の補間処理は、各画素位置についてγ特性を設定しているので、各画素位置を中心とするブロックを設定し、そのブロックに含まれる画素データのレベル分布のヒストグラムを用いてγ特性を設定しても同様の結果が得られるが、この方法は、撮像画像Ｇに非常に沢山のブロックが設定されるため、γ特性の演算に長時間を要する欠点がある。また、隣接するブロック間では画素データの殆どが重複するため、作成されたヒストグラムに殆ど差異が見られないため、両ブロックについてそれぞれヒストグラムを作成する実益もないので、本実施の形態では、より高速演算が可能で、しかもメモリ容量の低減が可能なγ特性の線形補間処理を採用している。
【００９３】
図１２はカラー画像の画像処理を行なうためのＡ／Ｄ変換器３２１〜第１，第２γ補正部３２５，３２６までの構成を示すブロック構成図である。
【００９４】
画像メモリ３２２、第１γ特性設定部３２３、第１，第２γ補正部３２５，３２６及びスイッチ回路３２７はそれぞれＲ，Ｇ，Ｂの各色成分の画素データに対応して３個の同一構造の処理回路を有している。
【００９５】
例えばＲの色成分の画素信号はＡ／Ｄ変換器３２１Ａで画素データにＡ／Ｄ変換された後、画像メモリ３２２Ａに一時的に記録される。自然画モードにおいては、画像メモリ３２２Ａに記憶されたＲの色成分の画素データはスイッチ回路３２７を介して第１γ補正部３２５Ａに読み出され、所定の自然画用のγ特性を用いてガンマ補正が行なわれる。
【００９６】
一方、文字画モードにおいては、第１γ特性設定部３２３Ａによりブロック毎に各ブロックに含まれるＲの画素データのレベル分布のヒストグラムから照度ムラ補正用のγ特性が設定され、第２γ特性設定部３２４により黒色濃度調整スイッチ１７の調整値に基づき黒色調整用のγ特性が設定される。そして、画像メモリ３２２Ａに記憶されたＲの色成分の画素データはスイッチ回路３２７を介して第２γ補正部３２６Ａに読み出され、ブロック毎に照度ムラ補正用のγ特性を持ついてガンマ補正が行なわれた後、黒色濃度調整用のγ特性を用いてガンマ補正が行なわれる。
【００９７】
Ｇ，Ｂの各色成分の画素信号についても上述のＲの色成分の画素信号と同様に進行処理が行なわれる。
【００９８】
また、図１３は、Ｇの色成分に対する第１γ特性設定部３２３Ｂの内部構成を示すブロック図である。
同図において、ブロックサイズ設定部３２３ａは撮像画像を小画像のブロックＢ(I,J)に分割するためのブロックサイズを設定するものである。ブロックサイズ設定部３２３ａは、撮像画像をブロック分割するために、ＣＰＵ３０から入力される撮影画面中央の撮影倍率ｍと予め設定された基準サイズＳ０及び基準撮影倍率ｍ０とを用いてブロックサイズＳを設定する。
【００９９】
アドレス生成部３２３ｂはブロックサイズ設定部３２３ａで設定されたブロックサイズＳに基づいて各ブロックＢ(I,J)に含まれる画素データのアドレスを生成するものである。このアドレスデータはＣＣＤ２１からの画素信号に読出し及びＡ／Ｄ変換器３２１でのＡ／Ｄ変換に用いられるとともに、白色飽和レベル補間演算部３２３ｅにおける補間演算に用いられる。
【０１００】
ヒストグラム作成部３２３ｃは各ブロックＢ(I,J)毎にそのブロックに含まれる画素データのレベル分布のヒストグラム（図２２参照）を作成するものである。白色飽和レベル設定部３２３ｄはヒストグラム作成部３２３ｃで作成されたヒストグラムを用いて各ブロックＢ(I,j)の中心位置に対するγ特性の白色飽和レベルＷ（図２３参照）を設定するものである。白色飽和レベル補間演算部３２３ｅはブロックＢ(I,j)毎に設定されたγ特性の白色飽和レベルＷを用いて各ブロックＢ(I,j)の中心位置以外の部分に対するγ特性の白色飽和レベルＷを補間設定するものである。
【０１０１】
γ特性設定部３２３ｆは白色飽和レベル設定部３２３ｄ及び白色飽和レベル補間演算部３２３ｅにより設定された白色飽和レベルＷを用いて撮像画像の各画素データに対する照度ムラ補正用のγ特性を設定するものである。
【０１０２】
正反射検出部３２３ｇは、正反射警告スイッチ２０により正反射警告が指示されているとき、ブロック単位で撮影画像に主被写体で正反射された照明光の画像が含まれるか否かを判別し、正反射光の画像を含む撮影画像を検出するものである。正反射検出部３２３ｇはブロック毎に作成されたヒストグラムの形状に基づいて各ブロックＢ(I,J)内に正反射光の画像が含まれるか否かを判別する。
【０１０３】
すなわち、ホワイトボード２３に書かれた文字、図形等の文字情報が撮影された際、天井灯や窓外からの太陽光等の照明光がホワイトボード２３で正反射されていると、正反射光を受光した画素からは飽和レベルの画素データが出力されるので、正反射光の画像を含むブロックではホワイトボード２３の画像を構成する画素データの大部分は飽和レベルの画素データとなっている。このため、このブロックに対するヒストグラムの形状は、図２７に示すように、ホワイトボード２３に相当する山Ｕの最大頻度を有する階級ｗが最大階級ｐに略一致したものとなる。
【０１０４】
正反射検出部３２３ｇは、照度ムラ補正用のγ特性における白色飽和レベルＷの設定方法と同様の方法でヒストグラムのホワイトボード２３に相当する山Ｕの最大頻度を有する階級ｗを算出するとともに、この算出結果と最大階級ｐとを比較し、階級ｗが最大階級ｐと略一致する場合は、そのブロックに正反射光の画像が含まれていると判別する。そして、この判別結果をＣＰＵ３０に出力する。
【０１０５】
ＣＰＵ３０は正反射検出部３２３ｇの判別結果に応じてブザー１６を発音し、また、ＬＥＤ表示２４を点灯して正反射光を含む撮影画像であることの警告を行なう。
【０１０６】
なお、Ｒ，Ｂの色成分に対する第１γ特性設定部３２３Ａ，３２３Ｃは正反射検出部３２３ｇを除いてＧの色成分に対する第１γ特性設定部３２３Ｂと同一の内部構成を有している。
【０１０７】
図１１に戻り、カード駆動部３３は画像データを記録するべくハードディスクカード１３の駆動を制御するものである。発光制御部３４はフラッシュ７の発光を制御するものである。また、ＬＣＤ駆動部３５はＣＰＵ３０からの制御信号に基づき撮像画像のＬＣＤ表示部１９へのモニター表示を制御するものである。メモリ３６はＣＰＵ３０で演算された各種データを記憶するものである。
【０１０８】
レンズ駆動部３７はＣＰＵ３０から入力されるＡＦ制御値に基づき撮影レンズ２の合焦動作を制御するものである。また、ズーム駆動部３８はＣＰＵ３０から入力される駆動信号に基づき撮影レンズ２のズーム動作を制御するものである。絞り駆動部３９はＣＰＵ３０から入力される露出制御値の絞り値Ａｖに基づき絞り２２の開口量を制御するものである。
【０１０９】
測光部４０は測光窓３の後方位置に設けられたＳＰＣ等の受光素子からなり、被写体の輝度を測光するものである。測距部４１は被写体距離を検出するもので、投光窓４の後方位置に設けられ、赤外光を発光する投光部４１１と、受光窓５の後方位置に設けられ、被写体で反射した赤外光を受光する受光部４１２とからなる。
【０１１０】
ＣＰＵ３０はカメラの撮影動作を集中制御するものである。ＣＰＵ３０は撮影倍率演算部３０１を有し、測距部４１で検出された測距点（ＣＣＤ２１の撮像面の中央位置Ａ）における被写体距離Ｄ_A及びその測距点における撮影倍率ｍ_Aを演算する。また、ＣＰＵ３０は露出制御値演算部３０２を有し、測光部４０で検出された被写体の輝度情報に基づき露出制御値（絞り値Ａｖ、シャッタースピードＴｖ）を演算し、その演算結果をそれぞれ絞り駆動部３９とＣＣＤ駆動部３１とに出力する。また、ＣＰＵ３０はＡＦ制御値演算部３０３を有し、測距部４１で検出された被写体距離Ｄ_Aに基づき撮影レンズ２を合焦位置に設定するためのレンズ駆動量を演算し、その演算結果をＡＦ制御値としてレンズ駆動部３７に出力する。
【０１１１】
次に、上記カメラ１の撮影制御について、図２８〜図３１のフローチャートを用いて説明する。なお、撮影／再生スイッチ１２は撮影側に設定されているものとする。また、カメラ１が起動し、シャッタボタン１０によりＳ１スイッチがＯＮになると、ＣＣＤ２１により所定の周期で被写体像の取込み及び画像処理が行なわれ、Ｓ２スイッチがＯＮになると、この後に取り込まれた画像が所定の画像処理を経てハードディスクカード１３に記録される。
【０１１２】
メインスイッチ１４をオンにし、カメラ１を起動すると、撮影可能の状態となる。この状態でズームスイッチ１１が操作されると（＃２でＹＥＳ）、その操作方向及び操作量に応じて撮影レンズ２内のズームレンズが駆動され、ズーム比が変更される（＃４）。この後、シャッタボタン１０が半押しされ、Ｓ１スイッチがオンになると（＃６でＹＥＳ）、ステップ＃８に移行し、撮影準備のための処理が行なわれる。
【０１１３】
すなわち、まず、測距部４１により被写体距離Ｄ_Aが検出される（＃８）。測距部４１は投光部４１１から被写体に向けて測距用の赤外光を投光し、その赤外光の被写体からの反射光を受光部４１２で受光して測距用のデータを取り込み、このデータを用いて撮像画面中央における撮像面から被写体までの距離Ｄ_Aを算出する。続いて、算出された被写体距離Ｄ_Aに基づいて撮影レンズ２を合焦位置に設定するためのレンズ駆動量が演算される（＃１０）。
【０１１４】
続いて、正反射警告スイッチ２０により正反射警告が指示されているか否かが判別され（＃１２）、正反射警告が指示されていれば（＃１２でＹＥＳ）、ステップ＃１４〜＃２０で正反射警告処理が行なわれ、正反射警告が指示されていなければ（＃１２でＮＯ）、ステップ＃１４〜＃２０はスキップされ、正反射警告処理は行なわれない。
【０１１５】
正反射警告処理では、まず、被写体距離Ｄ_A及び撮影レンズ２の焦点距離ｆから撮影画面中央の撮影倍率ｍ_A（＝ａ・ｆ／Ｄ_A，ａ；比例係数）が算出され（＃１４）、続いて、図３１に示すサブルーチン「正反射光検出」のフローチャートに従って撮影画像内の正反射光の画像の検出が行なわれる（＃１６）。
【０１１６】
撮影画像内の正反射光の画像の検出は、まず、撮影倍率ｍ_Aと予め設定された基準の撮影倍率ｍ０及びブロックサイズＳ０とを用いて撮像画像をブロック分割するためのブロックサイズＳ（＝Ｓ０・ｍ_A／ｍ０）が算出され（＃７０）、更に、このブロックサイズＳと撮像面のサイズとから分割されるブロック数ｎが算出される（＃７２）。
【０１１７】
続いて、ブロック数をカウントするカウンタＭが「１」に設定される（＃７４）。なお、正反射光検出処理におけるブロックの順番は、図１６に示すブロック分割においてラスター方向に行なうようにしているので、Ｍ＝Ｌ・（Ｉ−１）＋Ｊとなり、ブロックＢ(I,J)はブロックＢ(L・(I-1)+J)に対応している。
【０１１８】
続いて、ブロックＢ(M)内に含まれる全画素データが全て読み出され（＃７６）、これらの画素データの内、ハイレベル側のＸ％を除いた画素データを用いて図２２もしくは図２７に示すようなヒストグラムが作成される（＃７８）。続いて、ヒストグラムの白地部分に対応する山Ｕのピーク値に対応する階級ｗが算出され（＃８０）、この階級ｗがヒストグラムの最大階級ｐ（＝２５５）に略一致しているか否かが判別される（＃８２）。
【０１１９】
階級ｗが最大階級ｐに略一致していれば（＃８２でＹＥＳ）、そのブロック内に正反射光の画像が含まれると判断し、フラグＦＬＡＧＨを「１」にセットして（＃９０）、リターンする。なお、フラグＦＬＡＧＨは正反射光の検出フラグで、「１」にセットされていれば、撮影画像内に正反射光の画像が含まれていることを示し、「０」にリセットされていれば、撮影画像内に正反射光の画像が含まれていないことを示す。
【０１２０】
ステップ＃８２で階級ｗが最大階級ｐに略一致していなければ、カウンタＭのカウント値が「１」だけインクリメントされた後（＃８４）、このカウント値Ｍが総ブロック数ｎより大きいか否かが判別され（＃８６）、Ｍ≦ｎであれば（＃８６でＮＯ）、ステップ＃７６に戻り、次のブロックＢ(M)について正反射光の画像が含まれているか否かの判別が行なわれる（＃７６〜＃８２）。
【０１２１】
そして、全てのブロックＢ(M)で正反射光の画像が検出されなければ（＃８６でＹＥＳ）、撮影画像には正反射光の画像が含まれていないと判断し、フラグＦＬＡＧＨを「０」にリセットして（＃８８）、リターンする。
【０１２２】
図２８に戻り、正反射光の検出処理が終了すると、フラグＦＬＡＧＨにより正反射光の画像の有無が判別され（＃１８）、フラグＦＬＡＧＨが「１」にセット（正反射光の画像有り）されていれば（＃１８でＹＥＳ）、ブザー１６及びＬＥＤ表示２４により正反射警告が行なわれる（＃２０）。一方、フラグＦＬＡＧＨが「０」にリセット（正反射光の画像無し）されていれば（＃１８でＮＯ）、ステップ＃２０はスキップされ、ブザー１６及びＬＥＤ表示２４による正反射警告は行なわれない。
【０１２３】
続いて、測光部４０により被写体の輝度のデータ（測光データ）が取り込まれ（＃２２）、この測光データに基づき露出制御値が演算される（＃２４）。更に照度ムラ補正スイッチ１７により照度ムラ補正が指示されているか否かが判別され（図２９，＃２６）、照度ムラ補正が指示されていれば（＃２４でＹＥＳ）、発光制御部３４に発光禁止の制御信号が出力されてフラッシュ７の発光が禁止され（＃２８）、照度ムラ補正が指示されていなければ（＃２４でＮＯ）、ステップ＃２８はスキップされ、フラッシュ７の発光禁止は行なわれない。これにより撮影準備処理は終了し、レリーズ待機状態となる。
【０１２４】
なお、照度ムラ補正が指示されているときにフラッシュ７の発光を禁止するようにしているのは、例えばホワイトボード２３に対して正面から撮影するシーンでフラッシュ７が自動発光される場合、フラッシュ光がホワイトボード２３で全反射されて撮像画像の文字が判読不能になるおそれがあるので、このような撮影ミスを防止するためである。
【０１２５】
レリーズ待機状態で、シャッタボタン１０が全押しされてＳ２スイッチがオンになると（＃３０でＹＥＳ）、ステップ＃３４に移行してレリーズ動作が行なわれる。一方、シャッタボタン１０の半押し状態が継続され、Ｓ１スイッチがオン状態であれば（＃３２でＹＥＳ）、ステップ＃８に戻り、上述の撮影準備処理が繰り返される（＃８〜＃３２のループ）。また、シャッタボタン１０の操作が解除され、Ｓ１スイッチがオフ状態になると（＃３２でＮＯ）、ステップ＃２に戻る。
【０１２６】
レリーズ動作に移行すると、まず、レンズ駆動量のデータがレンズ駆動部３７に出力され、撮影レンズ２の焦点調節が行なわれた後（＃３４）、露出制御値の絞り値Ａｖのデータが絞り駆動部３９に出力され、絞り２２の開口量が調節される（＃３６）。
【０１２７】
続いて、照度ムラ補正が指示されているか否かが判別され（＃３８）、照度ムラ補正が指示されていれば（＃３８でＹＥＳ）、画像を複数のブロックに分割する際のブロックサイズＳが演算される（＃４０）。この演算は正反射光検出処理におけるステップ＃７０と同様の方法で演算される。
【０１２８】
ブロックサイズの設定処理が終了すると、ステップ＃２４で算出されたシャッタスピードのデータがＣＣＤ駆動部３１に出力され、ＣＣＤ２１による撮像動作（積分動作）が開始される（＃４２）。ＣＣＤ２１はＣＣＤ駆動部３１からの駆動制御信号に基づき感光部の電荷をリセットした後、所定の時間だけ感光部に電荷を蓄積（電荷積分）することにより被写体を撮像する。
【０１２９】
ＣＣＤ２１による撮像動作が終了すると、感光部の各画素に蓄積された電荷（画素データ）の画像処理部３２への読出しが開始される（図３０，＃４４）。ＣＣＤ２１の画素データは、図３５に示すように、縦ライン毎に矢印方向に順次、読み出されて画像処理部３２に入力される。画像処理部３２に入力された画素信号はＡ／Ｄ変換器３２１で画素データに変換された後、画像メモリ３２２に記憶されるとともに、第１γ特性設定部３２３に入力される。
【０１３０】
続いて、照度ムラ補正が指示されているか否かが判別され（＃４６）、照度ムラ補正が指示されていれば（＃４６でＹＥＳ）、図３２に示すサブルーチン「γ特性設定」のフローチャートに従って第１γ特性設定部３２３により各ブロック毎の照度ムラ補正用のγ特性が設定される（＃４８）。
【０１３１】
各ブロックの照度ムラ補正用のγ特性の設定は、まず、ブロック数をカウントするカウンタＭが「１」に設定される（＃１００）。なお、γ特性設定処理におけるブロックの順番は上述の正反射光検出処理におけるブロックの順番と同一である。
【０１３２】
続いて、ブロックＢ(M)内に含まれる全画素データが全て読み出され（＃１０２）、これらの画素データの内、ハイレベル側のＸ％を除いた画素データを用いて図２２もしくは図２７に示すようなヒストグラムが作成される（＃１０４）。続いて、ヒストグラムの白地部分に対応する山Ｕのピーク値に対応する階級ｗが算出され（＃１０６）、この階級ｗがブロック(M)に対するγ特性の白色飽和レベルＷ(M)として記憶される（＃１０８）。
【０１３３】
続いて、カウンタＭのカウント値が「１」だけインクリメントされた後（＃１１０）、このカウント値Ｍが総ブロック数ｎより大きいか否かが判別され（＃１１２）、Ｍ≦ｎであれば（＃１１２でＮＯ）、ステップ＃１００に戻り、次のブロックＢ(M)について白色飽和レベルＷ(I)の設定が行なわれる（＃１０２〜＃１１０）。そして、Ｍ＞ｎになると（＃１０２でＹＥＳ）、全ブロックＢ(M)についてγ特性の白色飽和レベルＷ(M)の設定が終了したと判断して、リターンする。
【０１３４】
図３０のフローチャートに戻り、続いて、ブロックＢ(I)毎に設定された照度ムラ補正用のγ特性の白色飽和レベルＷ(I)の補間演算が行なわれ、各ブロックＢ(I)の中心位置以外の画素位置における照度ムラ補正用のγ特性が設定される（＃５０）。続いて、設定されたγ特性は第２γ補正部３２６に入力される一方、画像メモリ３２２からスイッチ回路３２７を介して第２γ補正部３２６に画素データが読み出され、この画素データはその画素位置に対応する照度ムラ補正用のγ特性を用いてガンマ補正が行なわれた後、更に黒色強調用のγ特性を用いてガンマ補正が行なわれる（＃５２）。
【０１３５】
一方、ステップ＃４６で照度ムラ補正が指示されていなれば（＃４６でＮＯ）、画像メモリ３２２からスイッチ回路３２７を介して第１γ補正部３２５に画素データが読み出され、この画素データは予め設定された自然画用のγ特性によりガンマ補正が行なわれる（＃５４）。続いて、ガンマ補正後の画素データはスイッチ回路３２８を介してハードディスクカード１３に書き込まれる（＃５６）。
【０１３６】
そして、ガンマ補正が行なわれた画素データは順次、スイッチ回路３２８を介してハードディスクカード１３に書き込まれ（＃４６〜＃５８のループ）、全画素データのハードディスクカード１３への書込みが完了とすると（＃５８でＹＥＳ）、ＣＣＤ駆動部３１に画素データの読出終了の制御信号が出力されるとともに、カード駆動部３３に画素データの書込終了の制御信号が出力されて１枚の撮影動作が終了し（＃６０）、次の撮影処理を行なうべくステップ＃２に戻る。
【０１３７】
上記のように、撮影準備処理において、取り込まれた画像を複数のブロックに分割し、ブロック単位で各ブロック毎に作成したヒストグラムを用いてそのブロック内に主被写体（ホワイトボード２３）で正反射された照明光の画像が含まれるか否かを判別することにより正反射光の検出を行なうようにしているので、スポット状の正反射光であっても確実に検出することができる。そして、この検出結果に応じて撮影者に正反射警告を行なうようにしているので、例えば被写体がホワイトボード２３に書かれた文字、図形等で、照明光のホワイトボード２３での正反射により文字、図形等の情報が不明瞭となる場合は、正反射警告によりこのような情報価値の低い画像の誤撮影を未然に防止することができる。
【０１３８】
なお、上記実施の形態では、正反射光が検出されると、正反射警告のみを行なうようにしていたが、照明光の正反射により文字情報が不明瞭となった画像は記録価値が低いので、ハードディスクカード１３のメモリ容量の有効活用を考慮し、正反射警告だけでなく、撮影画像のハードディスクカード１３への記録を禁止するようにしてもよい。この場合は、図３３に示すように、図２９のフローチャートにおいて、例えばステップ＃３０とステップ＃３４との間にフラグＦＬＡＧＨのセット状態の判別（ステップ＃１８に相当する正反射光の画像の有無の判別）を行なうステップ＃３１を挿入し、フラグＦＬＡＧＨが「１」にセットされていれば（＃３１でＹＥＳ）、ステップ＃８に戻って撮影準備処理を行ない、フラグＦＬＡＧＨが「０」にリセットされていれば（＃３１でＮＯ）、ステップ＃３４に移行する処理にするとよい。すなわち、フラグＦＬＡＧＨが「０」にリセットされない限り、Ｓ２スイッチがＯＮ状態になってもこれを無視して撮影準備処理を繰り返すような処理にするとよい。
【０１３９】
また、上記実施の形態では、シャッタボタン１０が全押しされると、正反射警告の有無に拘らず、取り込まれた画像に対して照度ムラ補正スイッチ１７による指示に応じた所定の画像処理（照度ムラ補正）を行なった後、ハードディスクカード１３に記録するようにしていたが、正反射警告が行なわれたときは、照度ムラ補正スイッチ１７の設定状態に拘らず、取り込まれた画像に対して通常の写真撮影に対する画像処理（すなわち、照度ムラ補正を行なわない。）を行なった後、ハードディスクカード１３に記録するようにしてもよい。
【０１４０】
この場合は、図３４に示すように、図２９，図３０のフローチャートにおいて、ステップ＃３６とステップ＃３８との間とステップ＃４４とステップ＃４６との間とにそれぞれフラグＦＬＡＧＨによる正反射光の画像の有無の判別を行なうステップ＃３７とステップ＃４５と挿入し、ステップ３７でフラグＦＬＡＧＨが「１」にセットされていれば（＃３７でＹＥＳ）、ステップ＃３８，＃４０をスキップし、ステップ＃４５で、フラグＦＬＡＧＨが「１」にセットされていれば（＃４５でＹＥＳ）、ステップ＃５４に移行する処理にするとよい。
【０１４１】
このように撮影画像に正反射光の画像が含まれるときは、照度ムラ補正が指示されていてもガンマ補正を通常の写真撮影に対するガンマ補正に切り換えて画像処理を行なうようにすると、正反射光により不明瞭となった文字情報が照度ムラ補正により更に不明瞭になり、画質及び情報価値の低下が増長されるという弊害を防止することができる。
【０１４２】
【発明の効果】
以上説明したように、本発明によれば、複数の光電変換素子からなる撮像手段により被写体光像を画素信号に光電変換して取り込み、その画素信号からなる画像を記録媒体に記録するデジタルカメラにおいて、取り込まれた画像を小画像に分割し、小画像毎に、作成したヒストグラムを用いて主被写体で正反射された照明光の有無を判別し、いずれかの小画像で正反射光が検出されると、警告等の特定の処理を行なうようにしたので、スポット状の正反射光であっても高精度で正反射光の警告が行なわれ、正反射光により不明瞭となった低画質の被写体像の誤撮影を防止することができる。
【０１４３】
また、いずれかの小画像で正反射光が検出されると、取り込まれた画像の記録媒体への記録を禁止するようにしたので、正反射光により不明瞭となった低画質の被写体像の誤撮影を確実に防止することができる。
【図面の簡単な説明】
【図１】本発明に係るデジタルカメラの外観を示す斜視図である。
【図２】本発明に係るデジタルカメラの背面図である。
【図３】本発明に係るデジタルカメラの光学系の概略構成図である。
【図４】ホワイトボードの照明光の照明方向の一例を示す図である。
【図５】撮像素子の出力分布を示すもので、（ａ）は縦方向の出力分布を示す図、（ｂ）は横方向の出力分布を示す図である。
【図６】撮像画像を複数のブロックに分割した状態を示す図である。
【図７】ブロック毎に設定される白地を強調するγ特性の一例を示す図である。
【図８】黒色部分を強調とするγ特性の一例を示す図である。
【図９】黒色濃度調整スイッチによる黒色調整と黒色部分を強調とするγ特性との関係を示す図である。
【図１０】ファインダー内の正反射光警告用のＬＥＤ表示を示す図である。
【図１１】本発明に係るデジタルカメラのブロック構成図である。
【図１２】カラー画像の画像処理を行なうためのＡ／Ｄ変換器〜第１，第２γ補正部までの構成を示すブロック構成図である。
【図１３】Ｇの色成分の第１γ特性設定部の内部構成を示すブロック図である。
【図１４】画像メモリの容量を説明するための図である。
【図１５】文字画像を構成する画素データのヒストグラムの一般的な形を示す図である。
【図１６】撮像画像を複数のブロックの小画像に分割した状態を示す図である。
【図１７】不適切なサイズのブロックで撮像画像を分割した状態を示すもので、（ａ）はブロックサイズが適正値より小さい場合を示す図、（ｂ）はブロックサイズが適正値より大きい場合を示す図である。
【図１８】ファインダー視野枠内にブロック枠を表示させた状態を示す図である。
【図１９】横方向に配列されたブロックで設定された照度ムラ補正用のγ特性を用いて他のブロックに対する照度ムラ補正用のγ特性を設定する方法を説明するための図である。
【図２０】縦方向に配列されたブロックで設定された照度ムラ補正用のγ特性を用いて他のブロックに対する照度ムラ補正用のγ特性を設定する方法を説明するための図である。
【図２１】照度ムラ補正を行なうための撮像画像の他のブロック分割の方法を示す図である。
【図２２】ブロックに分割された小画像を構成する画素データのヒストグラムの一例を示す図である。
【図２３】画素データのヒストグラムを用いて決定されるγ特性を示す図である。
【図２４】緑色成分の画素データを用いて設定されたγ特性の一例を示す図である。
【図２５】各色成分の画像毎に設定されたγ特性を示す図で、（ａ）は赤色成分の画像に対するγ特性、（ｂ）は緑色成分の画像に対するγ特性、（ｃ）は青色成分の画像に対するγ特性である。
【図２６】隣接する４個のブロックの中心位置で囲まれた領域内の画素データに対するγ特性の補間演算を説明するための図である。
【図２７】正反射光の画像を含むブロックの画素データのヒストグラムの形を示す図である。
【図２８】本発明に係るカメラの撮影制御を示すフローチャートである。
【図２９】本発明に係るカメラの撮影制御を示すフローチャートである。
【図３０】本発明に係るカメラの撮影制御を示すフローチャートである。
【図３１】サブルーチン「正反射光検出」のフローチャートである。
【図３２】サブルーチン「γ特性設定」のフローチャートである。
【図３３】正反射光検出時に取込画像のハードディスクカードへの記録禁止するためのフローチャートの修正案を示す図である。
【図３４】正反射光検出時の取込画像のガンマ補正を強制的に通常のガンマ補正に切り換えるためのフローチャートの修正案を示す図である。
【図３５】ＣＣＤの画素データの読出方向を示す図である。
【図３６】デジタル複写機における取込画像のブロック分割方法を示す図である。
【符号の説明】
１ カメラ（デジタルカメラ）
２ 撮影レンズ
３ 測光窓
４ 測距用投光窓
５ 測距用受光窓
６ ファインダー対物窓
７ フラッシュ
８ カード挿入口
９ カード取出ボタン
１０ シャッタボタン
１１ ズームスイッチ
１２ 撮影／再生スイッチ
１３ ハードディスクカード（記録媒体）
１４ メインスイッチ
１５ ファインダー接眼窓
１６ ブザー（警告手段）
１７ 照度ムラ補正スイッチ
１８ 黒色濃度調整スイッチ
１９ ＬＣＤ表示部
２０ 正反射警告スイッチ
２１ ＣＣＤエリアセンサ（撮像手段）
２２ 絞り
２３ ホワイトボード
２４ ＬＥＤ表示（警告手段）
３０ ＣＰＵ（特定処理手段）
３１ ＣＣＤ駆動部
３２ 画像処理部
３２１ Ａ／Ｄ変換器
３２２ 画像メモリ
３２３ 第１γ特性設定部
３２３ａ ブロックサイズ設定部（画像分割手段）
３２３ｂ アドレス生成部
３２３ｃ ヒストグラム作成部（ヒストグラム作成手段）
３２３ｄ 白色飽和レベル設定部
３２３ｅ 白色飽和レベル補間演算部
３２３ｆ γ特性設定部
３２３ｇ 正反射検出部（判別手段）
３２４ 第２γ特性設定部
３２５ 第１γ補正部
３２６ 第２γ補正部
３２７ スイッチ回路
３３ カード駆動部
３４ 発光制御部
３５ ＬＣＤ駆動部
３６ メモリ
３７ レンズ駆動部
３８ ズーム駆動部
３９ 絞り駆動部
４０ 測光部
４１ 測距部
４２ ファインダー視野枠
４３ ブロック枠[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera that photoelectrically converts a stationary subject light image into an electric signal.
[0002]
[Prior art]
Conventionally, in an image forming apparatus such as a digital copying machine, in order to increase the clarity of information such as characters and figures copied on a recording paper, a relatively γ value is obtained for an image captured by photoelectric conversion into an electric signal. Image processing (gamma correction processing) is performed using a large γ characteristic (γ characteristic having characteristics close to binarization processing). In this gamma correction processing, generally, in order to reduce the influence of illuminance unevenness, as shown in FIG. 36, the captured image G is converted into a plurality of strip-like blocks B (1), B (2) in the sub-scanning direction. ,... B (n) and γ characteristics γ (1), γ (2),... Γ () for each block based on a histogram showing the level distribution of pixel data contained in each block B (r). n) is set, and the pixel data in each block B (r) (r = 1, 2,... n) is subjected to gamma correction using the γ characteristic γ (r) for that block. .
[0003]
By this gamma correction, the white background part above the predetermined level is uniformly converted to a constant white color, and the character part below the predetermined level (the black part) is uniformly converted to a constant black color. Image quality.
[0004]
In Japanese Patent Laid-Open No. 6-113139, a captured image is divided into a plurality of partial image blocks, a selected partial image block (target partial image block) and a plurality of partial image blocks adjacent to the target partial image block. For each block, a histogram of the level distribution of the pixel data included in the block is created for each block, and the threshold value of the target partial image block is set by the neural network using the histogram data. An image binarization apparatus that performs binarization processing of pixel data in a partial image block is shown.
[0005]
Also, in an image forming apparatus such as a digital copying machine, when the illumination light is specularly reflected on the original, the density of characters and the like written on the original is significantly reduced by the specularly reflected light, and the original image is accurately captured. In order to prevent such problems, conventionally, a technique for detecting illumination light regularly reflected on a document is known.
[0006]
This detection technique creates a histogram of the level distribution of pixel signals captured by an image sensor such as a CCD (Charge Coupled Device) in units of sensor lines, and determines the presence or absence of specularly reflected light from the shape of this histogram. is there. More specifically, when regular reflected light is included, a pixel signal having a saturated level is output from a pixel that has received the regular reflected light, and thus, for example, the frequency at the saturation level of the histogram exceeds a predetermined threshold value. The presence or absence of regular reflection light is determined by determining whether or not the light is reflected.
[0007]
[Problems to be solved by the invention]
By the way, since a digital camera can freely control the image quality of an image taken by image processing, it can be converted into a normal silver salt film by appropriately processing the image quality of the taken image according to the purpose of photography and the type of subject. There is an advantage that it is possible to capture an image having a better image quality than a camera for photographing. For this reason, it is used not only for normal photography, but also as a device for copying information such as characters and figures written on a whiteboard in a conference hall, for example.
[0008]
When shooting a whiteboard with characters or figures written on it with a digital camera, the main purpose of the shooting is to record information such as letters and figures on the whiteboard. Similar to the digital copying machine, it is desirable to perform gamma correction to increase the clarity of the information portion (character or graphic portion) by skipping the white portion (whiteboard portion) white.
[0009]
In this case, the variation in character density and illuminance unevenness on the whiteboard is large, so the captured image is divided into a plurality of blocks two-dimensionally, and gamma correction is performed on a block basis to correct illuminance unevenness (shading correction). It is desirable to do so.
[0010]
That is, if the whiteboard is illuminated by the ceiling light in the room and sunlight outside the window, uneven illumination occurs due to non-uniform illumination light, and the incident light enters the entrance pupil of the photographing lens at an angle ω. Due to the synergistic effect of the incident light intensity distribution according to the so-called cosine fourth law and the above illuminance unevenness that the image of the object point outside the optical axis becomes darker in proportion to cos ⁴ ω, the output distribution of the image sensor such as a CCD is within the imaging plane. Greatly varies in the two-dimensional direction.
[0011]
For this reason, it is desirable to divide the captured image into a plurality of blocks in a two-dimensional manner and perform gamma correction according to the illuminance in the block for each block to perform illuminance unevenness correction. More preferably, when the γ characteristic set for each block greatly changes between adjacent blocks, in order to avoid the occurrence of a false line at the block boundary due to the sudden change of the γ characteristic, the block size It is preferable to set an appropriate γ characteristic for each block by making the value as small as possible.
[0012]
In this case, in a shooting position where illumination light such as ceiling light or sunlight is regularly reflected on the whiteboard, characters on the whiteboard fly white due to the regularly reflected illumination light, resulting in low information value. An image will be taken. In particular, when the above-described illuminance unevenness correction is performed in image processing, an accurate histogram cannot be created for a block including specular reflection light, and effective illuminance unevenness correction cannot be performed. The blocks that are not included are also adversely affected by the specularly reflected light, causing a problem that the image quality and the information value are significantly reduced.
[0013]
In a digital copying machine, since an original is illuminated with an artificial light source under a predetermined condition, specular reflection light can be sufficiently detected by detection processing in units of lines of a sensor. Illumination conditions are not constant, and in particular, external light such as sunlight is incident on the whiteboard in a spot shape and is regularly reflected, so detection processing is performed in units of lines as in the above-described conventional method of detecting regular reflected light in a digital copying machine If it is performed, it is difficult to reliably detect spot-like specularly reflected light, and sufficient detection accuracy cannot be obtained.
[0014]
On the other hand, the binarization processing technique described in Japanese Patent Laid-Open No. 6-113139 mainly relates to the binarization processing in a copy apparatus or a facsimile apparatus. There is no description of the problem of reflected light or any suggestion thereof.
[0015]
The present invention has been made in view of the above problems, and when photographing information such as characters written on a board under photographing conditions in which illumination light is regularly reflected on a whiteboard, the specularly reflected light is highly accurate. It is possible to provide a digital camera that can reliably prevent a shooting mistake of shooting a low-quality image.
[0016]
[Means for Solving the Problems]
The present invention is a digital camera that captures a light image of a subject by photoelectrically converting it into a pixel signal by an image capturing unit including a plurality of photoelectric conversion elements, and records the image including the pixel signal on a recording medium. An image dividing means for dividing an image into a plurality of small images, a histogram creating means for creating a histogram of level distribution of pixel signals constituting each small image for each small image, and a histogram created for each small image And determining means for determining whether or not the illumination light regularly reflected by the main subject is included in the small image, and illuminance unevenness correcting means for correcting the illuminance unevenness of the image captured by the imaging means, when any of the small image contains specular illumination light, it prohibits the correction of the uneven illuminance by the illuminance nonuniformity correcting means does not contain the specularly reflected illumination light Come, and is characterized in that to correct the uneven illuminance by the illuminance nonuniformity correction means (claim 1).
[0017]
According to the present invention, the digital camera includes a warning unit, and the warning unit warns that the illumination light is regularly reflected by the main subject.
[0018]
According to the above configuration, the image captured by the imaging unit is divided into a plurality of small images, and for each small image, a histogram of the level distribution of pixel signals constituting each small image is created. In addition, for each small image, it is determined whether or not illumination light regularly reflected by the main subject is included in the small image using the created histogram, and regular reflection light is included in any small image. and a tree, prohibits the correction of the illuminance unevenness due UI corrector, when there is not any specularly reflected light, the processing to correct the uneven illuminance by the illuminance nonuniformity correction means is performed. In addition, a process for giving a warning that the photographed image includes regular reflection light is performed.
[0019]
In addition, the present invention provides a digital camera that photoelectrically converts a subject light image into a pixel signal and captures it on a recording medium by an image capturing unit including a plurality of photoelectric conversion elements, and captures the image with the pixel signal on the recording medium. An image dividing means for dividing the image into a plurality of small images, a histogram creating means for creating a histogram of the level distribution of the pixel signals constituting each small image for each small image, and a histogram created for each small image When the small image contains illumination light regularly reflected in any one of the small images, the discrimination means for determining whether the illumination light regularly reflected by the main subject is included in the small image prohibits the recording to the recording medium of the captured image, when there is not any specularly reflected illumination light, the image captured is intended to be recorded on the recording medium (claim 3 .
[0020]
According to the above configuration, if any of the small images includes illumination light regularly reflected by the main subject, recording of the captured image on the recording unit is prohibited. That is, photographing of a subject including regular reflection light is prohibited.
[0021]
This ensures that the photographer mistakenly shoots a low-quality subject image that is partially obscured by specular reflection light (for example, an image in which characters written on the whiteboard are obscured by specular reflection light). Can be prevented.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view showing an appearance of a digital camera according to the present invention. FIG. 2 is a rear view of the digital camera.
[0023]
The camera 1 shown in the figure includes a CCD area sensor as an image pickup device, and image data picked up by the CCD area sensor is recorded on a PCMCIA-compliant hard disk card (not shown). In this embodiment, the case where an area sensor is used as the image sensor will be described. However, the subject optical image may be scanned by the line sensor to capture image data.
[0024]
The camera 1 illuminates the whiteboard with respect to a photographed image of information such as characters and figures written on the whiteboard (hereinafter this type of binary information is referred to as character information) (ceiling light or sun outside the window). A function of correcting unevenness in illuminance caused by unevenness in light and the like and variations in sensitivity of the CCD area sensor.
[0025]
That is, for example, as shown in FIG. 4, if the whiteboard 23 is illuminated by the ceiling light of the room and sunlight outside the window, uneven illumination occurs due to unevenness of the illumination light, and the photographing lens The CCD area sensor has a synergistic effect between the incident light distribution based on the so-called cosine fourth law and the uneven illuminance that the image of the off-axis object point incident on the entrance pupil of the lens at an angle ω becomes darker in proportion to cos ⁴ ω. As shown in FIGS. 5A and 5B, the output distribution of fluctuates greatly two-dimensionally within the imaging surface. In the camera 1, when shooting in a character image mode, which will be described later, an appropriate γ characteristic is set for each pixel data or a plurality of pixel data units, and each pixel data or each pixel data unit is set using the γ characteristics. By performing gamma correction, the output fluctuation of the CCD area sensor that occurs two-dimensionally is reduced as much as possible.
[0026]
In FIG. 5, the solid line shows the output distribution of the white background portion of the whiteboard 23 when nothing is written on the whiteboard 23, and the dotted line shows the character portion when the characters are written on the whiteboard 23. The output distribution is shown.
[0027]
Here, the illuminance unevenness correction will be briefly described.
The image of character information is mainly for the purpose of recording information, and image quality that is higher in legibility than information is required. Therefore, the contrast of the character information portion with respect to the white background portion of the whiteboard is increased. It is desirable to clarify the information and reduce the unevenness in illuminance to make it easy to see as a whole.
[0028]
In the present embodiment, as shown in FIG. 6, the captured image G is divided into a plurality of square blocks B (I) (I = 1, 2,... 18 in the figure) vertically and horizontally, and each block B (I 7), the γ characteristic γ (I) with respect to the center position O (I) of the block (I) is obtained from the white background level W calculated using the histogram of the level distribution of the pixel data included in the block (I). Further, using the set γ characteristics γ (I), the γ characteristics γ (P) of the pixel positions P other than the center position O (I) of each block B (I) are interpolated, and these γ characteristics Character information is clarified and illuminance unevenness correction is performed by performing gamma correction of pixel data at corresponding pixel positions O (I) and P using γ (I) and γ (P).
[0029]
FIG. 7 shows a case where the pixel data is A / D converted into 8-bit data, and the level value “255” of the input / output level indicates the maximum value. Further, in the γ characteristic shown in the figure, since all the pixel data of the input level W or higher are converted to pixel data saturated to the maximum level, the white background portion consisting of the pixel data of the input level W or higher is uniformly maximized in the captured image. The image quality is corrected to whiteness. Thereby, the contrast of the character information portion with respect to the white background portion is emphasized, and the character information is clarified.
[0030]
Further, as necessary, the character information portion is emphasized by performing gamma correction using the γ characteristic as shown in FIG. In other words, the image after the illuminance unevenness correction is corrected to an image quality in which the black background portion composed of pixel data of the input level B or less is uniformly black with the minimum brightness, whereby the density of characters, figures, etc. written on the whiteboard 23, Character portions are black-enhanced in accordance with the thickness and line density of the lines, so that the character information is clarified appropriately. Details of the gamma correction processing in the illuminance unevenness correction will be described later.
[0031]
Returning to FIG. 1, the camera 1 is provided with a photographing lens 2 including a zoom lens at a substantially central portion of the front surface, and a light projection window 4 and a light receiving window 5 for measuring a subject distance by an active distance measuring method are provided on the upper part. A photometric window 3 for measuring the luminance of the subject is provided between the windows. A finder objective window 6 is disposed on the left side of the light projection window 4, and a flash 7 is disposed on the right side of the light receiving window 5.
[0032]
As shown in FIG. 3, a horizontally long CCD area sensor 21 (hereinafter abbreviated as CCD 21) is disposed at the imaging position of the photographic lens 2 in the camera body. A diaphragm 22 is disposed between them.
[0033]
The light projecting window 4 is a window that irradiates the subject with infrared light, and the light receiving window 5 is a window that receives the reflected light from the subject of the infrared light. In this embodiment, the active distance measurement method is adopted as the distance measurement method, but a passive distance measurement method may be used.
[0034]
A card insertion slot 8 into which the hard disk card 13 is inserted and removed is provided on the side of the camera 1, and a card eject button 9 for ejecting the hard disk card 13 is provided above the card insertion slot 8. When printing out the photographing result, the hard disk card 13 can be removed from the camera 1 by pressing the card eject button 9 and the hard disk card 13 can be attached to a printer to which the hard disk card can be attached.
[0035]
The camera 1 may be provided with a SCSI cable interface, and the camera 1 and the printer may be connected with the SCSI cable to directly transfer the image data from the camera 1 to the printer to print out the photographed image.
[0036]
In this embodiment, a PCMCIA-compliant hard disk card is used as a recording medium for image data. However, as long as the photographing result can be stored as image data, another memory card, mini disk (MD), or the like can be used. It may be a recording medium.
[0037]
On the upper surface of the camera 1, a shutter button 10 is provided at the left end, and a zoom switch 11 and a photographing / playback switch 12 are provided at the right end. The shutter button 10 is an operation button that turns on an S1 switch that instructs to prepare for photographing such as focal length adjustment and exposure control value setting when pressed halfway and turns on an S2 switch that instructs release when fully pressed. The zoom switch 11 is composed of a three-contact switch that can slide to the left and right. When the zoom switch 11 is slid to the T (TELE) side, it is photographed to the telephoto side, and when it is slid to the W (WIDE) side, the wide angle side is photographed. The zoom ratio of the lens 2 can be continuously changed.
[0038]
The shooting / playback switch 12 is a switch for switching between shooting mode and playback mode. The shooting / playback switch 12 includes a two-contact selector switch that can slide to the left and right. When the shooting / playback switch 12 is set to the shooting (REC) side, shooting of a subject (recording of a captured image on the hard disk card 13) is performed. When the playback (PLAY) side is set, the captured image recorded on the hard disk card 13 can be displayed on the LCD display unit 19 (see FIG. 2).
[0039]
As shown in FIG. 2, a power switch main switch 14 and a viewfinder eyepiece window 15 are provided on the rear surface of the camera 1 at the upper left end and approximately the center, respectively, and a buzzer 16 is provided at the upper right corner. It has been. The buzzer 16 is used to warn the photographer that when the character information on the whiteboard 23 is photographed, the illumination light is regularly reflected by the whiteboard 23 and the character information becomes unclear. Hereinafter, this warning is referred to as “regular reflection warning”.
[0040]
Further, an illuminance unevenness correction switch 17 and a black density adjustment switch 18 are provided below the main switch 14, and a regular reflection warning switch 20 is provided on the right side of the black density adjustment switch 18. Further, an LCD display unit 19 is provided at the lower right corner on the back of the camera 1.
[0041]
The illuminance unevenness correction switch 17 is a switch for instructing the illuminance unevenness correction described above. The illuminance unevenness correction switch 17 is composed of an ON / OFF switch in which an operation button slides left and right. When illumination unevenness correction is instructed by the illumination unevenness correction switch 17, the captured image is divided into a plurality of blocks (small images), and each block is set using pixel data included in the block as shown in FIG. The gamma correction is performed according to the γ characteristic. On the other hand, when the illuminance unevenness correction switch 17 is OFF, a γ characteristic suitable for preset normal photography (highly descriptive image quality capable of reproducing the gradation of the subject as faithfully as possible). The gamma correction processing of the captured image is performed using the γ characteristics as obtained.
[0042]
Illuminance unevenness correction improves image quality deterioration due to illuminance unevenness when photographing character information written on a whiteboard, and is mainly applied when photographing such character information. Accordingly, when the image of information such as characters and figures is taken as a “character image” and the image taken of a landscape or a person is taken as a “natural image”, the illuminance unevenness correction switch 17 takes a picture. This is a switch for switching image processing (particularly gamma correction processing) of an image between a character image mode and a natural image mode.
[0043]
When the photographer shoots a character image, the illuminance unevenness correction switch 17 is set to “ON” so that the image quality is suitable for the character image (image quality in which information such as characters is appropriately emphasized by whitening the white background portion). When shooting a natural image, the illuminance unevenness correction switch 17 is set to “OFF” to obtain a captured image with an image quality suitable for a natural image (high image quality). Can do.
[0044]
The black density adjustment switch 18 is a switch for adjusting the black saturation level B (see FIG. 8) of the γ characteristic in the gamma correction with black enhancement for the image after the illuminance unevenness correction. The black density adjustment switch 18 is composed of a three-contact switch in which an operation button slides left and right. The black density adjustment switch 18 functions only when the illuminance unevenness correction switch 17 is set to “ON” (when the character image mode is set). In the character image mode, when the black density adjustment switch 18 is set to the OFF state, as shown in FIG. 9, the black saturation level of the γ characteristic is set to a predetermined level B0, and the black density adjustment switch When 18 is set to “dark”, the black saturation level of the γ characteristic is switched to a predetermined level B1 (> B0) higher than the predetermined level B0, and when set to “light”, the black saturation level of the γ characteristic is set. The level is switched and set to a predetermined level B2 (<B0) smaller than the predetermined level B0.
[0045]
In the image processing in the character image mode, the white saturation level of the γ characteristic is automatically adjusted so that the background portion is whitened. Further, the density of the character portion is changed by changing the black saturation level by the black density adjustment switch 18. The contrast with the ground (white background) can be adjusted.
[0046]
For example, comparing text written on a whiteboard with text written on a manuscript, the characters on the whiteboard are generally thicker and larger than the characters on the manuscript. When the gamma correction is performed, the contrast of the character with respect to the background is lowered as compared with the case of the whiteboard. Therefore, when shooting a document, the black density adjustment switch 18 is set to “dark” to emphasize the black color of the character portion and to suitably adjust the contrast of the character portion with respect to the background.
[0047]
In this embodiment, the black saturation level is set to be switched between two levels. However, a multi-stage switching method may be used, or the black saturation level may be switched continuously.
[0048]
The LCD display unit 19 displays the captured image on a monitor. When the shooting / playback switch 12 is set to the playback side, a captured image of a frame designated by a selection switch (not shown) is read from the hard disk card 13 and reproduced and displayed on the LCD display unit 19.
[0049]
The regular reflection warning switch 20 is a switch for instructing to perform the regular reflection warning described above. The regular reflection warning switch 20 is composed of an ON / OFF switch whose operation button slides to the left and right. When “with warning” is instructed by the regular reflection warning switch 20, the photographed image is divided into a plurality of blocks (small images), and each block is corrected using a histogram of the level distribution of the pixel data included in the block. When the presence or absence of reflected light is determined and regular reflected light is detected in any block, a warning sound is generated from the buzzer 16. Further, as shown in FIG. 10, the regular reflection warning LED display 24 provided in the finder field frame 42 is lit to warn that there is a possibility that the image quality of the photographed image may be deteriorated by the regular reflection light. On the other hand, when the regular reflection warning switch 20 is “OFF”, the detection of the regular reflection light and the regular reflection warning are not performed.
[0050]
Note that it is up to the photographer to decide whether or not to give a regular reflection warning as described above. The regular reflection light is a problem mainly in the shooting in the character image mode. On the contrary, in the natural image mode to be performed, specular reflection light may be effectively used as a photographing effect. Therefore, the specular reflection warning can be performed as necessary in consideration of the photographing purpose and the photographing scene. . Therefore, the regular reflection warning may be always performed without providing the regular reflection warning switch 20.
[0051]
FIG. 11 is a block diagram of the camera 1 according to the present invention.
In the figure, the same members as those described above are denoted by the same reference numerals. The CCD drive unit 31 controls the imaging operation of the CCD 21 based on the shutter speed of the exposure control value input from the CPU 30. The CCD 21 is composed of a color area sensor, performs an imaging operation (charge accumulation operation) based on a control signal input from the CCD driving unit 31, and converts pixel signals of R, G, and B color components into time-series signals to generate an image. The data is output to the processing unit 32.
[0052]
The image processing unit 32 performs predetermined signal processing on the pixel signal output from the CCD 21 and outputs it to the hard disk card 13. The image processing unit 32 includes an A / D converter 321, an image memory 322, a first γ characteristic setting unit 323, a second γ characteristic setting unit 324, a first γ correction unit 325, a second γ correction unit 326, and switch circuits 327 and 328. When illuminance unevenness correction is instructed, illuminance unevenness correction is performed. Illuminance unevenness correction is performed by setting γ characteristics for illuminance unevenness correction for each block and performing gamma correction using the γ characteristics. At this time, the γ characteristic for the portion between the center positions of the blocks is interpolated, and the image signal of this portion is gamma-corrected using the interpolated γ property, so that the discontinuity in image quality based on the difference in the γ property between the blocks is eliminated. Alleviated.
[0053]
The A / D converter 321 converts each pixel signal included in the image signal read from the CCD 21 into a digital signal (hereinafter referred to as pixel data).
[0054]
The image memory 322 stores the pixel data output from the A / D converter 321. The image memory 322 has a capacity capable of storing pixel data for one captured image, and can perform image processing of the captured image collectively.
[0055]
In addition, when dividing the captured image into a plurality of blocks with the maximum block size that can be set, the capacity of the image memory 322 of the memory so that image processing can be performed in units of rows of blocks when divided into blocks, It is possible to reduce the memory by setting the capacity to store pixel data included in blocks arranged in at least one row. That is, as shown in FIG. 14, for example, if the captured image G is divided into 3 × 3 blocks B (1) to B (9) with the maximum block size, the capacity of the image memory 322 is arranged in each row. The block B (1) to B (3), the block B (4) to B (6), and the block B (7) to B (9) may have a capacity capable of storing pixel data.
[0056]
The first γ characteristic setting unit 323 sets γ characteristics for correcting illuminance unevenness of a captured image. The first γ characteristic setting unit 323 divides the captured image into a plurality of blocks, and sets γ characteristics for illuminance unevenness correction using pixel data included in each block for each block. The second γ characteristic setting unit 324 sets a γ characteristic for emphasizing black density of an image after illuminance unevenness correction. The second γ characteristic setting unit 324 sets the γ characteristic for black density enhancement based on the operation information of the black density adjustment switch 18 input from the CPU 30.
[0057]
The first γ correction unit 325 is a circuit that performs gamma correction on a natural image, and the second γ correction unit 326 is a circuit that performs gamma correction on a character image. The first γ correction unit 325 performs gamma correction of the pixel data read from the image memory 322 using a preset γ characteristic suitable for a natural image. The second γ correction unit 326 divides the captured image of the character image into a plurality of blocks, and uses the γ characteristics for illuminance unevenness correction set by the first γ characteristic setting unit 323 for each block of the pixel data constituting the captured image. After performing the gamma correction, the gamma correction of the pixel data is performed using the γ characteristic for black density enhancement set by the second γ characteristic setting unit 324. Note that gamma correction for character images will be described later.
[0058]
The switch circuit 327 switches the connection between the image memory 322 and the first and second γ correction units 325 and 326, and the switch circuit 328 connects the first and second γ correction units 325 and 326 and the hard disk card 13. Is to switch. Switching control of the switch circuits 327 and 328 is performed by a control signal output from the CPU 30 corresponding to the setting state of the illuminance unevenness correction switch 17, and the illuminance unevenness correction switch 17 is set to “OFF” (natural image mode). Is set), the image memory 322, the first γ correction unit 325, the first γ correction unit 325, and the hard disk card 13 are connected, and the illuminance unevenness correction switch 17 is set to “ON” (character image). When the mode is set), the image memory 322, the second γ correction unit 326, the second γ correction unit 326, and the hard disk card 13 are connected to each other.
[0059]
Here, a method of gamma correction (illuminance unevenness correction and black enhancement correction) for a character image will be described.
[0060]
As described above, in the case of a character image, it is desirable to increase the clarity of the character portion relative to the white background portion. Therefore, in order to make the white background portion white, a predetermined input as shown in FIG. A γ characteristic in which the output level is saturated at level W is used.
[0061]
For the white saturation level W in this γ characteristic, for example, a histogram of the level distribution of the pixel data of the green component constituting the image of the character image is created, and a class having the maximum frequency within the range corresponding to the white background portion is set. That is, when a histogram of the level distribution of the pixel data of the green component is created for an image obtained by photographing the whiteboard 23 on which characters, figures, and the like are drawn, as shown in FIG. 15, it generally corresponds to a white background portion (board portion). A two-crest distribution having a mountain U and a mountain C corresponding to a black portion (character portion), and a level w corresponding to the peak of the mountain U corresponding to a white background portion is set as the white saturation level W of the γ characteristic.
[0062]
A γ characteristic in which the white saturation level W is determined from the histogram of the pixel data of the green component constituting the entire captured image may be set, and gamma correction of the entire captured image may be performed using this γ characteristic. What is handwritten in 23 has a large variation in character density (ratio of the character portion to the white background portion), and in the case of photography, the light source is not constant and the screen is different from the case of a copying machine equipped with an illumination device. Since the illuminance distribution changes greatly in the image, the illuminance unevenness in the imaging screen increases, so the captured image is preferably divided into a plurality of blocks, and gamma correction is performed in units of blocks according to the γ characteristics set for each block. Therefore, it is desirable to correct illuminance unevenness.
[0063]
In the camera 1 according to the present embodiment, in the normal shooting mode (that is, front shooting), as shown in FIG. 16, the captured image G is vertically and horizontally n (= K (vertical) × L (horizontal). ) Blocks B (I, J) (I = 1, 2,... K, J = 1, 2,... L), and for each block B (I, J), the block B (I, J ) Representing illuminance unevenness correction that is representative of) is set. In this case, the size (area) of the block B (I, J) is set to a size that can accommodate approximately 9 (= 3 × 3) characters. The size of the block B (I, J) is set relatively in relation to the number of characters in this way because the portion corresponding to the whiteboard 23 when the histogram is created using the pixel data in the block. This is because the peak U becomes a moderately steep peak and the peak position w of the peak U can be reliably detected.
[0064]
That is, as shown in FIG. 17A, when the block size is set to be relatively small with respect to the characters, the area occupied by the character portion in the block B (I, J) is large, and the histogram whiteboard 23 Since the peak U corresponding to is lower, there is a possibility that the peak position w of the peak U may be erroneously detected, and as shown in FIG. If set, the illuminance unevenness in the block B (I, J) is large, and the peak U corresponding to the whiteboard 23 of the histogram becomes gentle. In this case, the peak position w of the peak U is erroneously detected. Because there is a fear.
[0065]
In order to determine the block size, it is necessary to know the size of the character projected on the shooting screen. The size y ′ of the character projected on the shooting screen is the size y and the size of the character written on the whiteboard 23. It can be calculated from the photographing magnification m by y ′ = y · m, and the size y of the characters written on the whiteboard 23 is considered to be within a certain range even though there are individual differences. If the representative value y0 of the character size y written on the board 23 and the photographing magnification m0 are experimentally determined, the character size y ′ projected on the photographing screen is uniquely determined from the photographing magnification m. can do.
[0066]
In the present embodiment, a block size S0 serving as a reference is determined based on the size y0 of a character projected on the shooting screen at a certain shooting magnification m0, and the block size S at an arbitrary shooting magnification m is set as the shooting magnification. From m0 and block size S0, S = S0 · m / m0 is used to calculate. Therefore, assuming that a block having a block size S0 includes vertical and horizontal (i × j) pixel data, the vertical number i ′ of pixel data included in the block size S is i · m / m0, The number j ′ in the horizontal direction is j · m / m0.
[0067]
In this embodiment, the block size S is set so that the number of characters in the block is nine. However, this is an example, and the representative value of the character size y written on the whiteboard 23 If y0 is changed, the number of characters in the block also changes. Accordingly, the block size S is appropriately set so as to include an appropriate number of characters according to the setting of the representative value y0.
[0068]
In the present embodiment, the block size S is changed according to the shooting magnification m. However, the block size S0 is fixed, and the shooting magnification m is a predetermined value relative to the block size S0 when shooting a character image. You may make it adjust so that it may become the value m0. That is, as shown in FIG. 18, a block frame 43 corresponding to the block size S0 is displayed in the finder field frame 42, and the photographer enters nine characters written on the whiteboard 23 in the block frame 43. In addition, the zoom ratio or subject distance of the photographing lens 2 may be adjusted. The block frame 43 may be displayed at all times, but may be displayed only when the character image mode is set.
[0069]
Furthermore, in the above embodiment, a histogram is created for all the set blocks B (I, J), and the white saturation level W of the γ characteristic for illuminance unevenness correction is set from this histogram. When the illuminance unevenness is relatively small in the vertical direction and the illuminance unevenness is large only in the horizontal direction, the horizontal blocks B (3,1) and B (3 (3) passing through the center of the captured image G are shown in FIG. , 2),..., B (3, 9) is created, a white saturation level W of γ characteristics is set from the histogram, and the other blocks B (I, J) (I = 1, 2, 4, 5, J = 1, 2,... 9), the γ characteristic set in the block B (3, r) set in the column including the block may be applied. For example, for the blocks B (1,1), B (2,1), B (4,1), and B (5,1) included in the first column, γ set in the block B (3,1) Apply properties.
[0070]
On the contrary, when the illuminance unevenness is relatively small in the vertical direction and the illuminance unevenness is large only in the horizontal direction, the vertical blocks B (1,5), B passing through the center of the captured image G are shown in FIG. A histogram is created only for (2,5),... B (5,5), and the white saturation level W of the γ characteristic is set from the histogram, and other blocks B (I, J) (I = 1, 2, ..., 5, J = 1 to 4, 6 to 9), the γ characteristic set in the block B (r, 5) set in the row including the block may be applied. For example, the blocks B (1,1), B (1,2), B (1,3), B (1,4), B (1,6), B (1,7) included in the first row , B (1,8), B (1,9), the γ characteristic set in block B (1,5) is applied. In this way, it is possible to shorten the calculation time of the γ characteristic and reduce the capacity of the memory that stores the set γ characteristic.
[0071]
In the above embodiment, the entire captured image G is equally divided into a matrix and blocks B (I, J) are set continuously. However, as shown in FIG. A plurality of blocks B (I, J) may be set discretely. In this way, since the number of blocks is reduced, the calculation time for setting the γ characteristic can be shortened as in the above example, and the capacity of the memory for storing the calculated γ characteristic can be reduced. Can do.
[0072]
Next, a method for determining the γ characteristic for correcting illuminance unevenness from the histogram of the pixel data of the green component will be described.
[0073]
(I × j) pieces of pixel data g (1,1), g (1,2),... G (i−1, j), g (i, j) included in the block B (I, J) Among these, pixel data corresponding to X (%) set in advance is removed from the maximum level to the low level side, and a histogram of level distribution is created using the remaining pixel data. For example, if the total number of pixel data included in the block is 10,000 and X = 3%, the 300 pixel data obtained by sequentially integrating the pixel data of the maximum level q to the low level side is removed, and the rest A histogram is created using 9700 pixel data. The reason why X% pixel data on the high level side is removed is to avoid adverse effects such as noise.
[0074]
This histogram generally has a two-peak distribution as shown in FIG. 22, with the high-level mountain U corresponding to the background portion of the whiteboard 23 and the low-level mountain C corresponding to the character portion. In the figure, the class p is the maximum level of the pixel data included in the block B (I, J), and the class q (<p) is the maximum value of the histogram class.
[0075]
When the histogram is created, a class w having the highest frequency in the distribution included in the range d set in advance on the low level side from the maximum class p is calculated, and this class w is a white of γ characteristic for correcting illuminance unevenness. Saturation level W is set. In the above range d, since the block size is set to a predetermined size in relation to the number of characters, it is estimated that only the high-level mountain U is surely included if the block is shot with normal illuminance. It is a range. For example, when the pixel data is 8 bits and has a gradation of 0 to 255, the range d is set to about 48.
[0076]
Therefore, for example, if the maximum class q is 200, the class w having the maximum frequency within the class range 152 to 200 is calculated. If the class w is, for example, w = 180, the white saturation level W = 180 is set. Then, the γ characteristic as shown in FIG. 23 is determined.
[0077]
By the way, if the whiteboard 23 is not completely white and slightly colored, or if the white balance adjustment of the camera 1 is inappropriate, it is performed according to the γ characteristic for correcting uneven illuminance and the γ characteristic for black enhancement. Since the γ value of the equivalent γ characteristic of the gamma correction is relatively large, the γ characteristic for correcting the illuminance unevenness set using the green component pixel data is the gamma of the red component pixel data and the blue component pixel data. It cannot be applied to amendments.
[0078]
That is, the shooting data in a certain area of the whiteboard 23 is not completely white, and the pixel data levels D _R , D _G , D _{B of} the R, G, B color components are, for example, (D _R , D _G , D _B ) = (130, 140, 125), and an equivalent γ characteristic (both γ characteristics) of the γ characteristic for illuminance unevenness set using the pixel data of the green component and the γ characteristic for black enhancement. When the gamma correction of the red component pixel data and the blue component pixel data is performed using this γ characteristic, the output of each color component is as follows. As shown in the figure, (D _R , D _G , D _B ) = (185, 255, 140), and the image after gamma correction causes a large color shift to yellowish green.
[0079]
If the γ value of the γ characteristic shown in FIG. 24 is small (if the slope is gentle), the output difference of each color component after gamma correction is small, so color misregistration is not a problem, but is applied to the character image mode. Since the γ characteristic performs gamma correction similar to the binarization process, the γ value is set to be relatively large. Therefore, the γ characteristic set using the green component pixel data is changed to the red component pixel data and the blue component. It becomes difficult to apply this to gamma correction of component pixel data.
[0080]
As a method for avoiding the coloring phenomenon of the white portion as described above, the pixel data of each color component of R, G, B is converted into luminance data and color difference data, and after performing gamma correction only with the luminance data, again, A method of inverse conversion to pixel data of R, G, and B color components is conceivable. However, since color difference data is stored in this method, for example, a character written on a whiteboard is a light-colored character with ink. In the case of, the thin state of the character remains even after the gamma correction, and it becomes difficult to clearly reproduce the thin character.
[0081]
In this embodiment, the γ characteristic for correcting illuminance unevenness set by the pixel data of the green component is corrected, a dedicated γ characteristic is set for each color component, and gamma correction is performed with the dedicated γ characteristic for each color component. Therefore, even light characters can be clearly reproduced.
[0082]
The γ characteristic for each color component is, for example, that the margin value of the level is “5”, and the input level (D _R −5, D _G −5, D _B −5) is the white saturation level. It is set using pixel data. For example, in the example of the γ characteristic shown in FIG. 24, as shown in FIGS. 25A to 25C, the input levels (125, 135, 120) of the R, G, B color components become the white saturation level 255. As described above, the γ characteristics of the R, G, and B color components are set.
[0083]
In addition, since gamma correction is performed so that the colored white background portion becomes white, the colored portion will deviate from the original color, but in character images, information is more important than color reproducibility. Color misregistration is considered acceptable.
[0084]
In the above description, a histogram of the level distribution of the pixel data included in the block is created, and the white saturation level is determined using this histogram (that is, the γ characteristic is set). Instead, the γ characteristic may be set by calculating pixel data.
[0085]
By setting the γ characteristic for illuminance unevenness correction for each block B (I, J) by the above-described method, and performing gamma correction of the image in units of blocks using this γ characteristic, the illuminance unevenness correction is performed for each block. Therefore, the image quality changes suddenly at the boundary between the blocks, which may cause a boundary line (false line). That is, the white background level changes suddenly at the block boundary, and this white background level discontinuity may occur as a boundary line.
[0086]
Therefore, in this embodiment, the γ characteristic for correcting illuminance unevenness set for each block B (I, J) is used as the γ characteristic for the pixel data at the center position of the block B (I, J), and adjacent to the block B (I, J). The γ characteristic for illuminance unevenness correction for the pixel data between the block center positions is linearly interpolated using the γ characteristics for illuminance unevenness correction of both blocks, and the pixel data other than the center position is gamma-corrected using this linearly interpolated γ characteristic. By doing so, discontinuity in image quality based on the difference in γ characteristics between blocks is alleviated.
[0087]
That is, as shown in FIG. 26, the respective center positions of the blocks B (I, J), B (I, J + 1), B (I + 1, J), B (I + 1, J + 1) are determined. Assuming A, B, C, and D, the γ characteristics for correcting illuminance unevenness at an arbitrary position P in the area AR1 surrounded by ABCD are represented by blocks B (I, J), B (I, J + 1), Linear interpolation is performed using the γ characteristic for correcting illuminance unevenness set for each of B (I + 1, J) and B (I + 1, J + 1), and the pixel at the position P using this interpolated γ characteristic. Data gamma correction is performed.
[0088]
The interpolated illuminance unevenness correction γ characteristic with respect to the position P is represented by blocks B (I, J), B (I, J + 1), B (I + 1, J), B (I + 1, J + 1). ), The white saturation levels W _A , W _B , W _C , and W _D respectively calculated for) are treated as for the positions A, B, C, and D, so that these white saturation levels W _A , W _B , W _C , position from the W _D a, B, C, is set by calculating the value W _P which internally divides the position P by the following equation (1) with respect to D.
[0089]
[Expression 1]

[0090]
In the internal division method, blocks B (1,1) to B (1, L), B (2, L) to B (K, L), B (K, L-1) located around the captured image are used. ) To B (K, 1) and B (K-1,1) to B (2,1), the gamma characteristic of the portion outside the center position of each block is not interpolated. Thus, linear interpolation of the γ characteristic may be performed.
[0091]
Further, the γ characteristic may be interpolated for all positions except the center position of each block B (I, J), but a portion other than the center position of each block B (I, J) is replaced with a plurality of pixel data (for example, 4) to 4 × 4 pixels to 6 × 6 pixels), and the interpolation calculation time may be shortened by linearly interpolating the γ characteristics in units of blocks.
[0092]
In the above-described γ characteristic interpolation processing for illuminance unevenness correction, since the γ characteristic is set for each pixel position, a block centered on each pixel position is set, and the level of pixel data included in the block is set. Although the same result can be obtained even if the γ characteristic is set using the histogram of the distribution, this method requires a long time to calculate the γ characteristic because a large number of blocks are set in the captured image G. There is. In addition, since most of the pixel data overlaps between adjacent blocks, and almost no difference is seen in the created histograms, there is no practical advantage of creating histograms for both blocks. A linear interpolation process with a γ characteristic that can perform calculations and can reduce the memory capacity is employed.
[0093]
FIG. 12 is a block diagram showing the configuration from the A / D converter 321 to the first and second γ correction units 325 and 326 for performing image processing of a color image.
[0094]
The image memory 322, the first γ characteristic setting unit 323, the first and second γ correction units 325 and 326, and the switch circuit 327 are three processing circuits having the same structure corresponding to the pixel data of the R, G, and B color components, respectively. have.
[0095]
For example, the pixel signal of the R color component is A / D converted into pixel data by the A / D converter 321A, and then temporarily recorded in the image memory 322A. In the natural image mode, the pixel data of the R color component stored in the image memory 322A is read to the first γ correction unit 325A via the switch circuit 327, and gamma correction is performed using a predetermined γ characteristic for natural images. Is done.
[0096]
On the other hand, in the character image mode, the first γ characteristic setting unit 323A sets the γ characteristic for correcting unevenness of illuminance from the histogram of the level distribution of the R pixel data included in each block for each block, and the second γ characteristic setting unit 324 Thus, the γ characteristic for black adjustment is set based on the adjustment value of the black density adjustment switch 17. Then, the R color component pixel data stored in the image memory 322A is read out to the second γ correction unit 326A via the switch circuit 327, and each block has a γ characteristic for illuminance unevenness correction and performs gamma correction. After that, gamma correction is performed using the γ characteristic for black density adjustment.
[0097]
Progression processing is performed on the pixel signals of the G and B color components in the same manner as the pixel signal of the R color component.
[0098]
FIG. 13 is a block diagram illustrating an internal configuration of the first γ characteristic setting unit 323B for the G color component.
In the figure, a block size setting unit 323a sets a block size for dividing a captured image into small image blocks B (I, J). The block size setting unit 323a sets the block size S using the shooting magnification m at the center of the shooting screen input from the CPU 30, the preset reference size S0 and the reference shooting magnification m0, in order to divide the captured image into blocks. To do.
[0099]
The address generation unit 323b generates an address of pixel data included in each block B (I, J) based on the block size S set by the block size setting unit 323a. This address data is read out as a pixel signal from the CCD 21 and used for A / D conversion in the A / D converter 321 and also used for interpolation calculation in the white saturation level interpolation calculation unit 323e.
[0100]
The histogram creation unit 323c creates a histogram (see FIG. 22) of the level distribution of pixel data included in each block B (I, J). The white saturation level setting unit 323d sets the white saturation level W (see FIG. 23) of the γ characteristic with respect to the center position of each block B (I, j) using the histogram created by the histogram creation unit 323c. The white saturation level interpolation calculation unit 323e uses the white saturation level W of the γ characteristic set for each block B (I, j), and the white saturation of the γ characteristic for the portion other than the center position of each block B (I, j). Level W is set for interpolation.
[0101]
The γ characteristic setting unit 323f sets γ characteristics for correcting illuminance unevenness for each pixel data of a captured image using the white saturation level W set by the white saturation level setting unit 323d and the white saturation level interpolation calculation unit 323e. is there.
[0102]
When the regular reflection warning is instructed by the regular reflection warning switch 20, the regular reflection detection unit 323g determines whether or not the captured image includes illumination light image regularly reflected by the main subject in units of blocks, A captured image including an image of regular reflection light is detected. The regular reflection detection unit 323g determines whether or not an image of regular reflection light is included in each block B (I, J) based on the shape of the histogram created for each block.
[0103]
That is, when character information such as letters and figures written on the whiteboard 23 is photographed, if the illumination light such as sunlight from the ceiling lamp or the outside of the window is specularly reflected by the whiteboard 23, the specularly reflected light Since the pixel data at the saturation level is output from the pixel receiving the light, most of the pixel data constituting the image of the whiteboard 23 is the saturation level pixel data in the block including the image of the regular reflection light. For this reason, the shape of the histogram for this block is such that the class w having the maximum frequency of the mountain U corresponding to the whiteboard 23 substantially matches the maximum class p, as shown in FIG.
[0104]
The regular reflection detection unit 323g calculates the class w having the maximum frequency of the peak U corresponding to the whiteboard 23 of the histogram by the same method as the setting method of the white saturation level W in the γ characteristic for illuminance unevenness correction. The calculated result is compared with the maximum class p, and when the class w substantially matches the maximum class p, it is determined that the image of the regular reflection light is included in the block. Then, this determination result is output to the CPU 30.
[0105]
The CPU 30 sounds the buzzer 16 according to the determination result of the regular reflection detection unit 323g, and lights the LED display 24 to give a warning that the photographed image includes regular reflected light.
[0106]
The first γ characteristic setting units 323A and 323C for the R and B color components have the same internal configuration as the first γ characteristic setting unit 323B for the G color component except for the regular reflection detection unit 323g.
[0107]
Returning to FIG. 11, the card drive unit 33 controls the drive of the hard disk card 13 to record image data. The light emission control unit 34 controls the light emission of the flash 7. The LCD drive unit 35 controls the monitor display of the captured image on the LCD display unit 19 based on a control signal from the CPU 30. The memory 36 stores various data calculated by the CPU 30.
[0108]
The lens driving unit 37 controls the focusing operation of the taking lens 2 based on the AF control value input from the CPU 30. The zoom drive unit 38 controls the zoom operation of the photographic lens 2 based on the drive signal input from the CPU 30. The aperture drive unit 39 controls the aperture amount of the aperture 22 based on the aperture value Av of the exposure control value input from the CPU 30.
[0109]
The photometric unit 40 is composed of a light receiving element such as SPC provided at the rear position of the photometric window 3 and measures the luminance of the subject. The distance measuring unit 41 detects a subject distance, and is provided at a rear position of the light projecting window 4. The light projecting unit 411 that emits infrared light and a rear position of the light receiving window 5 are reflected by the subject. It comprises a light receiving portion 412 that receives infrared light.
[0110]
The CPU 30 centrally controls the shooting operation of the camera. The CPU 30 includes a photographing magnification calculation unit 301, and calculates a subject distance D _A at a distance measuring point (center position A on the imaging surface of the CCD 21) detected by the distance measuring unit 41 and a photographing magnification m _A at the distance measuring point. . Further, the CPU 30 has an exposure control value calculation unit 302, calculates an exposure control value (aperture value Av, shutter speed Tv) based on the luminance information of the subject detected by the photometry unit 40, and drives the calculation results to the respective apertures. To the unit 39 and the CCD drive unit 31. Further, the CPU 30 has an AF control value calculation unit 303, calculates a lens driving amount for setting the photographing lens 2 to the in-focus position based on the subject distance D _A detected by the distance measurement unit 41, and the calculation result Is output to the lens driving unit 37 as an AF control value.
[0111]
Next, shooting control of the camera 1 will be described with reference to the flowcharts of FIGS. It is assumed that the shooting / playback switch 12 is set on the shooting side. When the camera 1 is activated and the S1 switch is turned on by the shutter button 10, the subject image is captured and processed by the CCD 21 at a predetermined cycle. When the S2 switch is turned on, an image captured thereafter is captured. The image is recorded on the hard disk card 13 through predetermined image processing.
[0112]
When the main switch 14 is turned on and the camera 1 is activated, the camera 1 is ready for photographing. When the zoom switch 11 is operated in this state (YES in # 2), the zoom lens in the photographing lens 2 is driven according to the operation direction and the operation amount, and the zoom ratio is changed (# 4). Thereafter, when the shutter button 10 is pressed halfway and the S1 switch is turned on (YES in # 6), the process proceeds to step # 8, and processing for preparation for photographing is performed.
[0113]
That is, first, the subject distance D _A is detected by the distance measuring unit 41 (# 8). The distance measuring unit 41 projects infrared light for distance measurement from the light projecting unit 411 toward the subject, and the reflected light from the subject of the infrared light is received by the light receiving unit 412 to obtain data for distance measurement. The distance D _A from the imaging surface to the subject at the center of the imaging screen is calculated using this data. Subsequently, based on the calculated subject distance D _A , a lens driving amount for setting the photographing lens 2 to the in-focus position is calculated (# 10).
[0114]
Subsequently, it is determined whether or not the regular reflection warning is instructed by the regular reflection warning switch 20 (# 12). If the regular reflection warning is instructed (YES in # 12), steps # 14 to # 20 are performed. If the regular reflection warning process is performed and the regular reflection warning is not instructed (NO in # 12), steps # 14 to # 20 are skipped and the regular reflection warning process is not performed.
[0115]
In the regular reflection warning process, first, the photographing magnification m _A (= a · f / D _A , a: proportional coefficient) at the center of the photographing screen is calculated from the subject distance D _A and the focal length f of the photographing lens 2 (# 14). Subsequently, the image of the regular reflection light in the photographed image is detected according to the flowchart of the subroutine “Specular reflection detection” shown in FIG. 31 (# 16).
[0116]
First, the detection of the image of the specularly reflected light in the captured image is performed by first using a block size S (=) for dividing the captured image into blocks using the imaging magnification m _A and a preset reference imaging magnification m 0 and block size S 0. S0 · m _A / m0) is calculated (# 70), and the number of blocks n divided from the block size S and the size of the imaging surface is calculated (# 72).
[0117]
Subsequently, the counter M for counting the number of blocks is set to “1” (# 74). Note that the order of the blocks in the specular reflection detection process is M = L · (I−1) + J because the block division shown in FIG. 16 is performed in the raster direction, and the block B (I, J) is Corresponds to block B (L · (I-1) + J).
[0118]
Subsequently, all the pixel data included in the block B (M) are all read out (# 76), and the pixel data excluding X% on the high level side among these pixel data is used as shown in FIG. A histogram as shown in FIG. 27 is created (# 78). Subsequently, a class w corresponding to the peak value of the mountain U corresponding to the white background portion of the histogram is calculated (# 80), and whether or not this class w substantially matches the maximum class p (= 255) of the histogram. Discriminated (# 82).
[0119]
If class w substantially matches maximum class p (YES in # 82), it is determined that the image of the regular reflection light is included in the block, and flag FLAGH is set to “1” (# 90). To return. The flag FLAGH is a specular reflection light detection flag. If it is set to “1”, it indicates that the image of the specular reflection light is included in the captured image, and if it is reset to “0”. This indicates that the image of regular reflection light is not included in the captured image.
[0120]
If the class w does not substantially match the maximum class p in step # 82, the count value of the counter M is incremented by “1” (# 84), and then whether or not the count value M is greater than the total block number n. Is determined (# 86), and if M ≦ n (NO in # 86), the process returns to step # 76 to determine whether or not an image of regular reflection light is included in the next block B (M). Is performed (# 76 to # 82).
[0121]
If no image of regular reflection light is detected in all the blocks B (M) (YES in # 86), it is determined that the image of regular reflection light is not included in the captured image, and the flag FLAGH is set to “0”. ”(# 88) and return.
[0122]
Returning to FIG. 28, when the detection processing of the regular reflection light is completed, the presence or absence of the regular reflection light image is determined by the flag FLAGH (# 18), and the flag FLAGH is set to “1” (the regular reflection light image exists). If so (YES in # 18), a regular reflection warning is given by the buzzer 16 and the LED display 24 (# 20). On the other hand, if the flag FLAGH is reset to “0” (no image of specular reflection light) (NO in # 18), step # 20 is skipped, and the regular reflection warning by the buzzer 16 and the LED display 24 is not performed. .
[0123]
Subsequently, luminance data (photometric data) of the subject is captured by the photometric unit 40 (# 22), and an exposure control value is calculated based on the photometric data (# 24). Further, it is determined whether or not illuminance unevenness correction is instructed by the illuminance unevenness correction switch 17 (FIG. 29, # 26). If illuminance unevenness correction is instructed (YES in # 24), the light emission control unit 34 emits light. If the prohibit control signal is output and the flash 7 is inhibited from emitting light (# 28), and if uneven illumination correction is not instructed (NO in # 24), step # 28 is skipped and the flash 7 is inhibited from emitting light. I can't. As a result, the shooting preparation process ends, and the camera enters a release standby state.
[0124]
Note that the flash 7 is prohibited from being emitted when illumination unevenness correction is instructed, for example, when the flash 7 is automatically emitted in a scene where the whiteboard 23 is photographed from the front, the flash light This is for the purpose of preventing such a photographing error because there is a possibility that the characters of the captured image may become unreadable by being totally reflected by the whiteboard 23.
[0125]
When the shutter button 10 is fully pressed and the S2 switch is turned on in the release standby state (YES in # 30), the process proceeds to step # 34 and a release operation is performed. On the other hand, if the shutter button 10 is half-pressed and the S1 switch is on (YES in # 32), the process returns to step # 8 and the above-described shooting preparation process is repeated (loop of # 8 to # 32). ). When the operation of the shutter button 10 is released and the S1 switch is turned off (NO in # 32), the process returns to step # 2.
[0126]
When shifting to the release operation, first, lens driving amount data is output to the lens driving unit 37, and after the focus adjustment of the photographing lens 2 is performed (# 34), the aperture value Av data of the exposure control value is aperture driving. Is output to the unit 39, and the opening amount of the diaphragm 22 is adjusted (# 36).
[0127]
Subsequently, it is determined whether or not illuminance unevenness correction is instructed (# 38), and if illuminance unevenness correction is instructed (YES in # 38), the block size S for dividing the image into a plurality of blocks is determined. Is calculated (# 40). This calculation is performed by the same method as in step # 70 in the regular reflection light detection process.
[0128]
When the block size setting process is completed, the shutter speed data calculated in step # 24 is output to the CCD drive unit 31, and the imaging operation (integration operation) by the CCD 21 is started (# 42). The CCD 21 images the subject by accumulating the charge in the photosensitive portion for a predetermined time (charge integration) after resetting the charge of the photosensitive portion based on the drive control signal from the CCD drive portion 31.
[0129]
When the imaging operation by the CCD 21 is completed, reading of charges (pixel data) accumulated in each pixel of the photosensitive unit to the image processing unit 32 is started (FIG. 30, # 44). As shown in FIG. 35, the pixel data of the CCD 21 is sequentially read out in the direction of the arrow for each vertical line and input to the image processing unit 32. The pixel signal input to the image processing unit 32 is converted into pixel data by the A / D converter 321, stored in the image memory 322, and input to the first γ characteristic setting unit 323.
[0130]
Subsequently, it is determined whether or not illuminance unevenness correction is instructed (# 46), and if illuminance unevenness correction is instructed (YES in # 46), according to the flowchart of the subroutine “γ characteristic setting” shown in FIG. The first γ characteristic setting unit 323 sets γ characteristics for correcting illuminance unevenness for each block (# 48).
[0131]
In setting the γ characteristic for correcting illuminance unevenness of each block, first, a counter M for counting the number of blocks is set to “1” (# 100). The order of blocks in the γ characteristic setting process is the same as the order of blocks in the regular reflection light detection process described above.
[0132]
Subsequently, all the pixel data included in the block B (M) are all read out (# 102), and among these pixel data, pixel data excluding X% on the high level side is used as shown in FIG. A histogram as shown in FIG. 27 is created (# 104). Subsequently, the class w corresponding to the peak value of the mountain U corresponding to the white background portion of the histogram is calculated (# 106), and this class w is stored as the white saturation level W (M) of the γ characteristic for the block (M). (# 108).
[0133]
Subsequently, after the count value of the counter M is incremented by “1” (# 110), it is determined whether or not the count value M is larger than the total block number n (# 112). (NO in # 112), the process returns to step # 100, and the white saturation level W (I) is set for the next block B (M) (# 102 to # 110). If M> n (YES in # 102), it is determined that the setting of the white saturation level W (M) of the γ characteristic has been completed for all blocks B (M), and the process returns.
[0134]
Returning to the flowchart of FIG. 30, subsequently, the interpolation calculation of the white saturation level W (I) of the γ characteristic for correcting the illuminance unevenness set for each block B (I) is performed, and the center of each block B (I) is calculated. A γ characteristic for correcting illuminance unevenness at a pixel position other than the position is set (# 50). Subsequently, while the set γ characteristic is input to the second γ correction unit 326, pixel data is read from the image memory 322 to the second γ correction unit 326 via the switch circuit 327, and the pixel data is stored in the pixel position. After the gamma correction is performed using the γ characteristic for illuminance unevenness correction corresponding to γ, the gamma correction is further performed using the γ characteristic for black enhancement (# 52).
[0135]
On the other hand, if illuminance unevenness correction is not instructed in step # 46 (NO in # 46), pixel data is read from the image memory 322 to the first γ correction unit 325 via the switch circuit 327, and the pixel data is stored in advance. Gamma correction is performed by the set natural image γ characteristic (# 54). Subsequently, the pixel data after gamma correction is written to the hard disk card 13 via the switch circuit 328 (# 56).
[0136]
Then, the pixel data subjected to the gamma correction is sequentially written to the hard disk card 13 via the switch circuit 328 (loop of # 46 to # 58), and when the writing of all the pixel data to the hard disk card 13 is completed ( In step # 58, YES, the pixel data reading end control signal is output to the CCD driving unit 31, and the pixel data writing end control signal is output to the card driving unit 33, thereby completing one photographing operation. In step # 60, the process returns to step # 2 to perform the next photographing process.
[0137]
As described above, in the shooting preparation process, the captured image is divided into a plurality of blocks, and is regularly reflected by the main subject (whiteboard 23) in the block using a histogram created for each block in block units. Since the regular reflection light is detected by determining whether or not the image of the illumination light is included, even the spot-like regular reflection light can be reliably detected. Then, since the specular reflection warning is given to the photographer according to the detection result, for example, the subject is a character, a figure or the like written on the whiteboard 23, and the character is reflected by the regular reflection of the illumination light on the whiteboard 23. When the information such as the figure becomes unclear, it is possible to prevent such erroneous photographing of an image having a low information value by using a regular reflection warning.
[0138]
In the above embodiment, only the regular reflection warning is performed when the specular reflection light is detected. However, an image in which the character information is obscured by the regular reflection of the illumination light is low in recording value. Considering the effective utilization of the memory capacity of the hard disk card 13, not only the regular reflection warning but also recording of the photographed image on the hard disk card 13 may be prohibited. In this case, as shown in FIG. 33, in the flowchart of FIG. 29, for example, determination of the flag FLAGH set state between step # 30 and step # 34 (the presence or absence of an image of specular reflection light corresponding to step # 18) If the flag FLAGH is set to “1” (YES in # 31), the process returns to step # 8 to perform the shooting preparation process, and the flag FLAGH is set to “0”. If it has been reset (NO in # 31), the process may proceed to step # 34. That is, as long as the flag FLAGH is not reset to “0”, even if the S2 switch is turned on, it is preferable to ignore this and repeat the shooting preparation process.
[0139]
Further, in the above embodiment, when the shutter button 10 is fully pressed, predetermined image processing (illuminance) according to an instruction from the illuminance unevenness correction switch 17 is performed on the captured image regardless of whether there is a regular reflection warning. The recording is performed on the hard disk card 13 after performing (unevenness correction). However, when a regular reflection warning is issued, the captured image is usually recorded regardless of the setting state of the unevenness correction switch 17. The image processing (that is, the illuminance unevenness correction is not performed) may be recorded on the hard disk card 13.
[0140]
In this case, as shown in FIG. 34, in the flowcharts of FIGS. 29 and 30, the specularly reflected light by the flag FLAGH is provided between step # 36 and step # 38 and between step # 44 and step # 46, respectively. Step # 37 and Step # 45 for determining whether or not there is an image, and if the flag FLAGH is set to “1” in Step 37 (YES in # 37), Steps # 38 and # 40 are skipped. If the flag FLAGH is set to “1” in step # 45 (YES in # 45), the process may be shifted to step # 54.
[0141]
Thus, when an image of specular reflection light is included in the captured image, even if illuminance unevenness correction is instructed, if the gamma correction is switched to gamma correction for normal photography and image processing is performed, the specular reflection light Therefore, it is possible to prevent the adverse effect that the character information that is obscured by the above becomes further obscured by the illuminance unevenness correction and the deterioration of image quality and information value is increased.
[0142]
【The invention's effect】
As described above, according to the present invention, in a digital camera that captures a subject light image by photoelectrically converting it into a pixel signal by an imaging means composed of a plurality of photoelectric conversion elements, and records an image composed of the pixel signal on a recording medium. The captured image is divided into small images, and for each small image, the presence or absence of illumination light regularly reflected by the main subject is determined using the created histogram, and regular reflected light is detected in any of the small images. Then, since a specific process such as a warning is performed, even if it is a spot-like specular reflection light, a high-precision warning of the specular reflection light is performed, and the low image quality that is obscured by the specular reflection light is low. It is possible to prevent erroneous photographing of the subject image.
[0143]
In addition, when specular reflection light is detected in any small image, recording of the captured image on the recording medium is prohibited, so that the low-quality subject image that is obscured by the specular reflection light is not recorded. It is possible to reliably prevent erroneous photographing.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external appearance of a digital camera according to the present invention.
FIG. 2 is a rear view of the digital camera according to the present invention.
FIG. 3 is a schematic configuration diagram of an optical system of a digital camera according to the present invention.
FIG. 4 is a diagram illustrating an example of an illumination direction of illumination light from a whiteboard.
5A and 5B show output distributions of the image sensor, where FIG. 5A is a diagram showing output distribution in the vertical direction, and FIG. 5B is a diagram showing output distribution in the horizontal direction.
FIG. 6 is a diagram illustrating a state in which a captured image is divided into a plurality of blocks.
FIG. 7 is a diagram illustrating an example of a γ characteristic for emphasizing a white background set for each block.
FIG. 8 is a diagram illustrating an example of a γ characteristic in which a black portion is emphasized.
FIG. 9 is a diagram illustrating a relationship between black adjustment by a black density adjustment switch and a γ characteristic that emphasizes a black portion.
FIG. 10 is a view showing an LED display for warning of regular reflection light in the finder.
FIG. 11 is a block diagram of a digital camera according to the present invention.
FIG. 12 is a block configuration diagram illustrating a configuration from an A / D converter to first and second γ correction units for performing image processing of a color image;
FIG. 13 is a block diagram illustrating an internal configuration of a first γ characteristic setting unit for a G color component;
FIG. 14 is a diagram for explaining the capacity of an image memory;
FIG. 15 is a diagram showing a general shape of a histogram of pixel data constituting a character image.
FIG. 16 is a diagram illustrating a state in which a captured image is divided into small images of a plurality of blocks.
FIGS. 17A and 17B show a state in which a captured image is divided by an inappropriately sized block, where FIG. 17A shows a case where the block size is smaller than an appropriate value, and FIG. 17B shows a case where the block size is larger than an appropriate value; FIG.
FIG. 18 is a diagram illustrating a state in which a block frame is displayed in a finder field frame.
FIG. 19 is a diagram for explaining a method of setting γ characteristics for illuminance unevenness correction for other blocks using γ characteristics for illuminance unevenness correction set in blocks arranged in the horizontal direction.
FIG. 20 is a diagram for explaining a method of setting γ characteristics for illuminance unevenness correction for other blocks using γ characteristics for illuminance unevenness correction set in blocks arranged in the vertical direction.
FIG. 21 is a diagram illustrating another block division method of a captured image for correcting uneven illuminance.
FIG. 22 is a diagram illustrating an example of a histogram of pixel data constituting a small image divided into blocks.
FIG. 23 is a diagram illustrating γ characteristics determined using a histogram of pixel data.
FIG. 24 is a diagram illustrating an example of γ characteristics set using pixel data of a green component.
FIGS. 25A and 25B are diagrams illustrating γ characteristics set for each color component image, where FIG. 25A is a γ characteristic for a red component image, FIG. 25B is a γ characteristic for a green component image, and FIG. Γ characteristic for the image.
FIG. 26 is a diagram for explaining interpolation calculation of γ characteristics with respect to pixel data in a region surrounded by the center positions of four adjacent blocks.
FIG. 27 is a diagram showing a histogram shape of pixel data of a block including an image of regular reflection light.
FIG. 28 is a flowchart showing shooting control of the camera according to the present invention.
FIG. 29 is a flowchart showing shooting control of the camera according to the present invention.
FIG. 30 is a flowchart showing shooting control of the camera according to the present invention.
FIG. 31 is a flowchart of a subroutine “regular reflection detection”.
FIG. 32 is a flowchart of a subroutine “γ characteristic setting”;
FIG. 33 is a diagram showing a correction plan of a flowchart for prohibiting recording of a captured image on a hard disk card upon detection of specular reflection light.
FIG. 34 is a diagram showing a correction plan of a flowchart for forcibly switching the captured image gamma correction to the normal gamma correction when detecting regular reflection light.
FIG. 35 is a diagram showing a reading direction of pixel data of a CCD.
FIG. 36 is a diagram showing a block division method of a captured image in a digital copying machine.
[Explanation of symbols]
1 Camera (digital camera)
2 Shooting Lens 3 Photometric Window 4 Distance Projecting Window 5 Distance Light-Receiving Window 6 Viewfinder Objective Window 7 Flash 8 Card Slot 9 Card Eject Button 10 Shutter Button 11 Zoom Switch 12 Shooting / Playback Switch 13 Hard Disk Card (Recording Medium) )
14 Main switch 15 Viewfinder eyepiece window 16 Buzzer (Warning means)
17 Illuminance unevenness correction switch 18 Black density adjustment switch 19 LCD display unit 20 Regular reflection warning switch 21 CCD area sensor (imaging means)
22 Aperture 23 Whiteboard 24 LED display (warning)
30 CPU (specific processing means)
31 CCD drive unit 32 Image processing unit 321 A / D converter 322 Image memory 323 First γ characteristic setting unit 323a Block size setting unit (image dividing means)
323b Address generator 323c Histogram generator (histogram generator)
323d White saturation level setting unit 323e White saturation level interpolation calculation unit 323f γ characteristic setting unit 323g Regular reflection detection unit (discrimination means)
324 second γ characteristic setting unit 325 first γ correction unit 326 second γ correction unit 327 switch circuit 33 card drive unit 34 light emission control unit 35 LCD drive unit 36 memory 37 lens drive unit 38 zoom drive unit 39 aperture drive unit 40 photometry unit 41 measurement Distance unit 42 Viewfinder field frame 43 Block frame

Claims (3)

In a digital camera that photoelectrically converts a subject light image into a pixel signal and captures it by an image capturing unit composed of a plurality of photoelectric conversion elements, and records an image composed of the pixel signal on a recording medium, the image captured by the image capturing unit Image dividing means for dividing into small images, histogram creating means for creating a histogram of the level distribution of pixel signals constituting each small image for each small image, and the small image using the histogram created for each small image A determination unit that determines whether or not illumination light regularly reflected by the main subject is included, and an illuminance unevenness correction unit that corrects illuminance unevenness of an image captured by the imaging unit. when it contains specularly reflected illumination light to an image, to prohibit correction of the uneven illuminance by the illuminance nonuniformity correction means, when there is not any specularly reflected illumination light, the Digital camera, characterized in that to correct the illuminance unevenness due degrees unevenness correcting means. The digital camera according to claim 1, further comprising a warning means, the digital camera, wherein the benzalkonium warning by said warning means that the illumination light is regularly reflected light in the main object. In a digital camera that photoelectrically converts a subject light image into a pixel signal and captures it by an image capturing unit composed of a plurality of photoelectric conversion elements, and records an image composed of the pixel signal on a recording medium, the image captured by the image capturing unit Image dividing means for dividing into small images, histogram creating means for creating a histogram of the level distribution of pixel signals constituting each small image for each small image, and the small image using the histogram created for each small image Determining means for determining whether or not illumination light regularly reflected by the main subject is included, and when any of the small images contains illumination light that is regularly reflected, A digital camera that prohibits recording on the recording medium and records the captured image on the recording medium when specularly reflected illumination light is not included .

Images