JP3843924B2 - Imaging device - Google Patents

Description

【０１０８】
ここでは、式（１）〜（４）がそれぞれ、第１フィールド２１に属する画素についてのＲ、Ｇｒ、Ｇｂ、Ｂの画素値を示す場合は、第１項が第１フィールド画像データ２１０における画素値、第２項が第２補間画像データにおける画素値、第３項が第３補間画像データにおける画素値をそれぞれ示す。また、式（１）〜（４）がそれぞれ、第２フィールド２２に属する画素についてのＲ、Ｇｒ、Ｇｂ、Ｂの画素値を示す場合は、第１項が第２フィールド画像データ２２０における画素値、第２項が第３補間画像データにおける画素値、第３項が第１補間画像データにおける画素値をそれぞれ示す。さらに、式（１）〜（４）がそれぞれ、第３フィールド２３に属する画素についてのＲ、Ｇｒ、Ｇｂ、Ｂの画素値を示す場合は、第１項が第３フィールド画像データ２３０における画素値、第２項が第１補間画像データにおける画素値、第３項が第２補間画像データにおける画素値をそれぞれ示す。
【０１０９】
なお、上述した補間処理の一例では、垂直方向（Ｊ方向）の画素値のみを考慮した補間処理を行っているが、その他、水平方向（Ｉ方向）の画素値を考慮した補間処理を行っても良い。
【０１１０】
図８のフローチャートに戻って説明を続ける。
【０１１１】
ステップＳ３３では、上述したように第１〜第３補間画像データを合成することによって１フレーム分の画像データを生成し、ステップＳ３４に進む。なお、各補間画像データは、例えば、１０ビットのデジタルデータであり、合成後の１フレーム分の画像データも１０ピットのデジタルデータとなっている。
【０１１２】
ステップＳ３４では、画像処理部４３において、ステップＳ３３で生成した１フレーム分の画像データについて、カラー化、γ補正、各種の画像処理、およびＡＥ・ＷＢ補正を行う。そして、得られた１フレーム分の画像データに基づいて、圧縮／伸張部４５で、圧縮処理を施してメモリカード９に保存するとともに、ＬＣＤ１８に表示し、撮影が終了する。その後、再び撮像装置１Ａは、撮影待機状態となる。
【０１１３】
このように、例えば、３つの露出条件（ＥＶ＝ＥＶ₀−１，ＥＶ₀，ＥＶ₀＋１）において得られた第１〜第３フィールド画像データ２１０〜２３０に基づいて１フレーム分の画像データを取得する。この取得された画像データは、式（１）〜（４）に示すように、一般的なデジタル撮像装置において露出量が適正露出の３．５倍となるような発光量でフラッシュ撮影して得られた画像データと等価な画素値を有することとなる。したがって、高感度モードにおける撮影においては、高感度の撮影画像を取得することができる。
【０１１４】
ところで、露出量が適正露出となるような発光量で得られた画素値を３．５倍に増幅することによっても、露出量が適正露出の３．５倍となるような発光量でフラッシュ撮影して得られた画像データとほぼ等価な画素値を得ることができる。しかし、この方法では、画像データにおけるノイズ成分までも３．５倍に増幅してしまうため、撮影画像の画質が劣化する。これに対して、本実施形態に係る高感度モードにおける撮影においては、３つの異なる画像データを合成するため、画像データ中のノイズ成分がランダム化されるため、撮影画像の画質劣化を抑制することができる。
【０１１５】
また、一般的なデジタル撮像装置においては、例えば、シャッタースピードを一定として、露出量が適正露出の３．５倍となるような発光量で撮影して画像データを得るためには、適正露出で撮影する場合を基準にして約３．５倍のエネルギーを内蔵フラッシュが消費することとなる。さらに、３回の撮影に分けて、３つの露出条件（ＥＶ＝ＥＶ₀−１，ＥＶ₀，ＥＶ₀＋１）で露光を行う場合にも、適正露出で撮影する場合を基準にして３．５倍のエネルギーを内蔵フラッシュが消費する。
【０１１６】
これに対して、本実施形態に係る高感度モードにおける撮影では、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、得られる露光条件の異なる複数の画像データについての画素値を加算する。その結果、適正露出で撮影する場合を基準にして約２倍のエネルギーしか内蔵フラッシュ７が消費しないため、消費電力の増加を抑制しつつ、フラッシュ撮影時に高感度の撮影画像を取得することができる。また、内蔵フラッシュ７が小型のキセノン管などで構成され、１回あたりの最大発光量が小さな場合でも、１回の短いフラッシュ撮影において、露光中に複数回の発光を行うことによって、ある程度の露光量を確保することができる。したがって、少ない光量でより遠くの被写体に露出を合わせること等ができ、装置の大型化を抑制しつつ、フラッシュ撮影時に高感度の撮影画像を取得することができる。
【０１１７】
また、最近のデジタルカメラ用の高画素ＣＣＤ撮像素子が用いられている一般的なデジタル撮像装置においては、例えば、撮像素子の全画素のデータを読み出すために必要な時間（必要読み出し時間）が約２５０ｍｓ〜３００ｍｓとなる。そして、３つの露出条件（ＥＶ＝ＥＶ₀−１，ＥＶ₀，ＥＶ₀＋１）で３回の撮影を行うためには、１回目の露光開始から３回目の露光終了までに、最低限、必要読み出し時間の２倍以上の時間が必要となる。したがって、後に３つの画像を合成して生成される画像にボケが発生しないようにするためには、被写体は完全に静止しているような物体に限られてしまう。
【０１１８】
これに対して、本実施形態に係る高感度モードにおける撮影では、３つの露出条件（ＥＶ＝ＥＶ₀−１，ＥＶ₀，ＥＶ₀＋１）における撮影の露出開始から露出終了までに要する時間は、例えば、必要読み出し時間と同程度の２５０〜３００ｍｓと短時間となる。したがって、ある程度動きのある被写体にも適用することができる。即ち、フラッシュ撮影時に被写体に応じた適正な撮影画像を取得することができる。
【０１１９】
＜(1-3-2)フラッシュブラケットモードにおける撮影動作について＞
上述した、高感度モードにおける撮影では、例えば、第１〜第３補間画像データを合成して１フレーム分の画像データを得たが、フラッシュブラケットモードにおける撮影では第１〜第３補間画像データを合成することなく、第１〜第３補間画像データについて、それぞれ、カラー化、γ補正、各種の画像処理、およびＡＥ・ＷＢ補正を行い、３フレーム分の画像データを得る。そして、得られた３フレーム分の画像データそれぞれについて、圧縮／伸張部４５で、圧縮処理を施してメモリカード９に保存するとともに、ＬＣＤ１８に表示し、撮影動作が終了する。したがって、フラッシュブラケットモードにおける撮影動作のフローは図８に示すステップＳ３３の処理が異なるのみで、その他の撮影動作のフローは、高感度モードにおける撮影動作と全く同様となる。
【０１２０】
このように、本実施形態に係るフラッシュブラケットモードにおける撮影では、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、得られる露光条件の異なる複数の画像データに基づいて、最終的に露出条件の異なる複数フレーム分の画像データを取得する。その結果、高感度モードにおける撮影についての説明で述べたように、一般的なデジタル撮像装置において、複数回の撮影に分けて同様な複数の画像データを取得する場合よりも電力消費の増加などを抑制することができる。
【０１２１】
また、本実施形態に係るフラッシュブラケットモードにおける撮影では、高感度モードにおける撮影についての説明で述べたように、一般的なデジタル撮像装置よりも短時間で露出条件の異なる複数の撮影画像を得ることができる。したがって、ある程度動きのある被写体であっても、ほぼ同じような構図で露出条件の異なる複数フレーム分の画像データを得ることができる。即ち、フラッシュ撮影時に被写体に応じた適正な撮影画像を取得することができる。
【０１２２】
さらに、本実施形態に係るフラッシュブラケットモードにおける撮影では、受光部２ａのカラーフィルタ配列に対応する全色成分を含み、かつ露光条件の異なる複数のフィールド画像データを得ることができるため、露光条件の異なる複数のフルカラーの撮影画像を短時間で効率良く取得することができる。
【０１２３】
＜(1-3-3)適正階調モードにおける撮影動作について＞
上述した、高感度モードにおける撮影では、例えば、第１〜第３フィールド画像データ２１０〜２３０が１０ビットのデジタルデータであると、合成後の１フレーム分の画像データも同様の１０ビットのデジタルデータとなった。しかし、適正階調モードにおける撮影動作では、例えば、合成後の１フレーム分の画像データを１１ビットのデジタルデータとして扱う。したがって、適正階調モードの撮影動作のフローは図８に示すステップＳ３３の処理が異なるのみで、その他の撮影動作のフローは、高感度モードにおける撮影動作と全く同様となる。
【０１２４】
適正階調モードにおける撮影動作において高感度モードにおける撮影動作と異なる点について、以下説明する。
【０１２５】
例えば、高感度モードにおける撮影動作において説明したように、第１〜第３補間画像データを加算処理すると、式（１）〜（４）に基づいて、合成後の１フレーム分の画像データにおけるＲ、Ｇｒ、Ｇｂ、Ｂの各画素についての画素値が求まる。このとき、適正階調モードでは、加算処理を行うとともに、各画素値が２／３倍となるような階調変換処理を行い、その画素値を１１ビットのデジタルデータとして扱う。即ち、第１〜第３補間画像データにおける画素値について、階調数などの階調特性を変換しつつ加算処理することによって、１フレーム分の画像データを生成する。
【０１２６】
この処理における２／３倍という数値の意味は以下の通りである。すなわち、それぞれの画像データの画素値は１０ビットで表現されているため、３つの画像データの画素値を単純に加算した場合の最大値は、２¹⁰×３＝２¹¹×（３／２）となり、１０ビットのデータでは取り扱えない数値が出てくる。また、１２ビットのデータによって表される階調を全て使い切っていない。そこで、３つの画像データのそれぞれの最大値につきそれぞれの画素値を２／３倍すれば、２¹⁰×（２／３）となるため、３つの画像データの加算値は、２¹⁰×（２／３）×３＝２¹¹（１１ビット）のように、１１ビットのデータによって表される階調を全て使い切ることができる。合成後の値を２／３倍しても同様である。このように、階調表現数Ｎビット（但し、Ｎは自然数）のデータによって表される階調を全て使い切ることによって、コントラストを明瞭に表現することができる。
【０１２７】
なお、本実施形態においては、２／３倍という数値を乗算したが、例えば、４／３倍という数値を乗算して、２¹⁰×（４／３）×３＝２¹²（１２ビット）のように、１２ビットのデータによって表される階調を全て使い切るようにしても良い。また、１／３倍という数値を乗算して、２¹⁰×（１／３）×３＝２¹⁰（１０ビット）のように、１０ビットのデータによって表される階調を全て使い切ることもできる。
【０１２８】
よって、一般には、合成する画像データがＭ個ある場合（但し、Ｍ≧２）で考えると、ｒ＝２ⁿ／Ｍ（但し、ｎは自然数）を満足する値ｒを加算前の各補間画像データにおける各画素値、または加算前の各画素値に乗算することによって、Ｎビット（但し、Ｎは自然数）のデータによって表される階調を全て使い切ることによって、コントラストを明瞭に表現することができる。しかし、ｒがあまりにも小さな値となると、階調表現数が減少してしまい、画質の劣化を招くこととなる。よって、元の画像データの階調表現数（Ｎビット）よりは大きくする方が画質の面からは好ましい。また、逆にｒが大きすぎると、階調表現数（データ長ないしはビット数）が大きくなり、処理速度の低下や記憶媒体の容量の不足を招くため、ｒの値は２以下であることが好ましい。
【０１２９】
この実施形態での具体的な処理では、合成前のある画素について、第１補間画像データにおける画素値が５１９／１０２３階調、第２補間画像データにおける画素値が最大輝度である１０２３／１０２３階調、第３補間画像データの画素値が最大輝度である１０２３／１０２３階調の場合は、合成後の画素値を２／３倍する変換処理を施して、この画素値を１１ビットのデジタルデータとして扱うことによって、合成および変換後の画素値は１７１０／２０４７階調となる。同様にして、種々の画素値の組合せに対して、上述のごとく合成、変換処理を行い、１フレーム分の画像データを１１ビットのデジタルデータとして扱う。
【０１３０】
ところで、一般的なデジタル撮像装置では、フラッシュ撮影時に、露出条件（ＥＶ＝ＥＶ₀）のみで撮影した場合、非常に明るい部分と非常に暗い部分とが混在した被写体については黒潰れや白潰れが発生する傾向にある。
【０１３１】
これに対して、本実施形態に係る適正階調モードにおける撮影では、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、得られる露光条件の異なる複数の画像データ（第１〜第３の補間画像データ）における画素値について、階調特性を変換しつつ加算することによって、非常に明るい部分と非常に暗い部分とが混在した被写体について取得される撮影画像においても、黒潰れや白潰れの発生を抑制することができる。
【０１３２】
例えば、非常に暗い部分については、特に、第３補間画像データにおける画素値の変化によって階調差を出すことによって、黒潰れの発生を防ぐことができる。また、非常に明るい部分については、特に、第１補間画像データにおける画素値の変化によって階調差を出すことによって、白潰れの発生を防ぐことができる。その結果、適正階調モードにおける撮影においては、輝度差の大きな被写体を撮影する場合にも、最終的に得られる１フレーム分の画像データは輝度差が圧縮されて表現されるため、全体的に露出の良好な画像を得ることができる。即ち、フラッシュ撮影時に被写体からの光の反射が多い部分と、光の反射が少ない部分とをそれぞれ補完することにより、ダイナミックレンジの大きな画像を得ることができる。
【０１３３】
また、本実施形態に係る適正階調モードにおける撮影では、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、得られる露光条件の異なる複数の画像データ（第１〜第３の補間画像データ）における画素値について、階調特性を変換しつつ加算する。その結果、高感度モードにおける撮影についての説明で述べたように、一般的なデジタル撮像装置よりも短時間で露出条件の異なる複数の撮影画像を得ることができる。したがって、ある程度動きのある被写体であっても、ほぼ同じような構図で露出条件の異なる複数のフィールド画像データを取得することによって、フラッシュ撮影時に、画像のボケの発生などを抑制しつつ、被写体の輝度に応じた適正な撮影画像を取得することができる。さらに、高感度モードにおける撮影についての説明で述べたように、一般的なデジタル撮像装置において、複数回の撮影に分けて同様な複数のフィールド画像データを取得する場合よりも電力消費の増加などを抑制することができる。
【０１３４】
以上のように、本実施形態に係る撮像装置１Ａでは、特殊撮影モードの設定に応じて、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、得られる露光状態の異なる複数の画像データに基づいて、種々の画像を生成する。その結果、フラッシュ撮影時に被写体に応じた種々の撮影画像や適正な撮影画像などを容易に取得可能な撮像装置を提供することができる。
【０１３５】
＜(2)変形例＞
以上、この発明の実施形態について説明したが、この発明は上記説明した内容のものに限定されるものではない。
【０１３６】
◎例えば、ＣＣＤ２の構造を改良し、いわゆる”加算読み出し”ができるようにしても良い。
【０１３７】
ここで言う”加算読み出し”とは、一般的なデジタルカメラ用のＣＣＤ撮像素子の被写体モニターモードで採用されている読み出し方法であり、高感度化、偽色対策のために用いられる。具体例としては、垂直ＣＣＤから水平ＣＣＤに電荷が転送される際に、水平方向の１ラインごとに電荷を転送するのではなく、垂直ＣＣＤが水平方向の複数ラインの電荷を水平ＣＣＤに転送した後に、水平ＣＣＤによる電荷の転送動作を行い、水平方向の複数ライン分の電荷が重畳して画素値として出力される読み出し方法などがある。
【０１３８】
図１０は、本発明の変形例に係る撮像装置１Ｂの動作を説明するための図である。なお、図１０では、ＣＣＤ２に”加算読み出し”可能な撮像素子を用いた場合について例示している。
【０１３９】
図１０に示すように、図９に示す撮像装置１Ａの動作と異なる点は、第１フィールド２１の電荷蓄積状態である。図１０に示す動作では、ＣＣＤ２からの第１および第２フィールド画像データ２１０，２２０の読み出しは、図９に示す動作と全く同じであるが、ＣＣＤ２から第３フィールド画像データ２３０を読み出す際に、第１フィールド２１に蓄積された電荷が加算される。
【０１４０】
ここでは、ＣＣＤ２から第１フィールド画像データ２１０が読み出された後も、シャッター１２は開放されているため、ＣＣＤ２の第１フィールド２１には、２回目および３回目の発光Ｆ２，Ｆ３の際などにも電荷が蓄積される。そして、例えば、図５に示すような画素配列を有している場合は、ＣＣＤ２から第３フィールド画像データ２３０を読み出す際に、第３フィールド２３のＲの画素Ｒａ（不図示）に蓄積された電荷が垂直ＣＣＤによって転送されている途中に、画素Ｒａから垂直ＣＣＤの転送方向に４つずれた画素位置にあたる第１フィールド２１のＲの画素Ｒｂ（不図示）に蓄積された電荷が重畳される。そして、重畳された電荷に基づく信号を第３フィールド画像データ２３０として読み出す。
【０１４１】
このような場合には、第３フィールド画像データ２３０が、第３フィールド２３に蓄積された電荷のみに基づく画像データよりも画素値が大きくなる。その結果、第３フィールド画像データ２３０に基づいて生成される画像データの画素値が増加する傾向となるため、さらに高感度の撮影画像を容易に取得することができる。また、内蔵フラッシュ７の３回目の発光量を減少させても所望の第３フィールド画像データ２３０を取得することができるため、内蔵フラッシュ７の電力消費量をより低減することができる。
【０１４２】
◎また、上述した実施形態では、図９に示すように、第２フィールド２２から電荷信号を読み出す際に、内蔵フラッシュ７が３回目の発光Ｆ３を行ったが、この動作に限られるものではなく、例えば、第２フィールド２２からの電荷信号の読み出しが開始した際に、シャッター１２を閉じて、３回目の発光Ｆ３を行わないようにしても良い。
【０１４３】
このとき、第２および第３フィールド画像データ２２０，２３０は同一の露出条件（ＥＶ＝ＥＶ₀）において得られるため、両画像データ２２０，２３０を合わせて１つの露出条件（ＥＶ＝ＥＶ₀）において得られた画像データとすることができる。よって、露出条件の異なる画像データの数は減少するが、ここで露出条件（ＥＶ＝ＥＶ₀）において得られる画像データについては、上述した実施形態における第２および第３フィールド画像データ２２０，２３０のそれぞれと比較して、空画素が半分となる。その結果、画像処理部４３における補間処理の精度が向上することとなるため、画像処理部４３において最終的に得られる画像データの画質を向上させることができる。
【０１４４】
◎また、上述した実施形態では、３つの露出条件（ＥＶ＝ＥＶ₀−１，ＥＶ₀，ＥＶ₀＋１）において第１〜第３フィールド画像データ２１０〜２３０を取得したが、露出条件は上記のものに限られず、例えば、ユーザーの設定などによって、露出量が適正露出の１／４倍、１倍、３倍となるように１〜３回目の発光量をそれぞれ設定して、３つの露出条件（ＥＶ＝ＥＶ₀−２，ＥＶ₀，ＥＶ₀＋２）において第１〜第３フィールド画像データ２１０〜２３０を取得しても良い。即ち、１回目の発光における発光量と、２回目の発光における発光量とが異なるようにしても良い。
【０１４５】
このように、１回の短いフラッシュ撮影における露光中の複数回の発光について、発光量を変更することによって、例えば、露光状態が種々異なる複数の画像を短時間で効率良く取得することができる。即ち、ユーザーの意図や被写体の状態などに応じて、さらに適正な撮影画像を取得することができる。
【０１４６】
◎また、上述した実施形態では、第１〜第３フィールド２１〜２３から電荷信号を各フィールドごとに読み出したが、これに限られるものではなく、各フィールド２１〜２３をそれぞれ、複数の領域に分けて、その領域ごとに時間的に連続して電荷信号を読み出して、複数の領域からの電荷信号に基づいた複数の画像データを合わせて第１〜第３フィールド画像データ２１０，２２０，２３０としても良い。
【０１４７】
具体的には、例えば、第１フィールド２１をさらに複数の領域に分けて、その領域ごとに時間的に連続して電荷信号を読み出して、複数の領域からの電荷信号に基づいた複数の画像データを合わせて第１フィールド画像データ２１０とするようにしても良い。なお、このとき、第１フィールド２１を複数に分けた領域の露光条件を略一致させることが望ましい。
【０１４８】
◎また、上述した実施形態では、受光部２ａを３つのフィールド２１〜２３に分けて、電荷信号を読み出したが、これに限られるものではなく、受光部２ａを４つのフィールド以上の複数のフィールドに分けて、フィールドごとにカラーフィルタ配列の全色成分にあたる電荷信号を読み出すようにしても良い。また、フィールドごとにカラーフィルタ配列の全色成分を読み出すことができるのであれば、受光部２ａを２つのフィールドに分けて、電荷信号を読み出すようにしても良い。
【０１４９】
◎また、上述した実施形態では、ＣＣＤ２はカラーフィルタ配列を有するが、これに限られるものではなく、例えば、カラーフィルタを設けていない、いわゆるモノクロ用のＣＣＤであっても良い。この場合は、得られる画像データはモノクロ画像データであるが、特殊撮影モードの各設定に応じた種々の効果を得ることができる。なお、この場合は、受光部２ａを２つのフィールドに分けて、電荷信号を読み出すようにしても良い。
【０１５０】
◎また、上述した実施形態では、フラッシュブラケットモードにおける撮影において、各フィールド画像データについて補完処理を施して、補完画像データを生成したが、補完処理を施さずに、各フィールド画像データそれぞれから垂直および水平方向に間引かれた画像（間引き画像）を生成しても良い。このとき、各間引き画像は画像サイズが小さくなるものの、画像データの量が少なくなるため、撮影開始から記録および表示までに要する処理時間を短縮することができる。
【０１５１】
◎また、上述した実施形態では、フラッシュ撮影において、連続して取得されるフィールド画像データの全てに基づいて、最終的に種々の画像を生成したが、これに限られるものではなく、例えば、３つのフィールド画像データのうちの２つのフィールド画像データから２つの補間画像データを生成して、その２つの補間画像データに基づいて、最終的に種々の画像を生成するようにしても良い。
【０１５２】
◎また、上述した実施形態では、発光する部位が内蔵フラッシュ７であったが、これに限られるものではなく、例えば、撮像装置１Ａに対して外側から装着する外付けタイプのフラッシュ装置などであっても良い。
【０１５３】
【発明の効果】
以上説明したように、請求項１ないし請求項５の発明によれば、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、得られる露光条件の異なる複数の画像データに基づいて、種々の画像データを生成することにより、フラッシュ撮影時に被写体に応じた種々の撮影画像や適正な撮影画像を容易に取得可能な撮像装置を提供することができる。
【０１５４】
特に、請求項２の発明においては、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、受光部のカラーフィルタ配列に対応する全色成分を含み、かつ露光条件の異なる複数の画像データを得ることができるため、フラッシュ撮影時に被写体に応じた適正なフルカラーの撮影画像を容易に取得することができる。例えば、露光条件の異なる複数のフルカラーの撮影画像を短時間で効率良く取得することができる。
【０１５５】
また、請求項３の発明においては、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、得られる露光条件の異なる複数の画像データについての画素値を加算することによって、装置の大型化や消費電力などを抑制しつつ、フラッシュ撮影時に高感度の撮影画像を取得することができる。
【０１５６】
また、請求項４の発明においては、短時間に複数回の発光を行って１回のフラッシュ撮影を行い、得られる露光条件の異なる複数の画像データについての画素値について、階調特性を変換しつつ加算することによって、フラッシュ撮影時に、画像のボケの発生や消費電力などを抑制しつつ、被写体の輝度に応じた適正な撮影画像を取得することができる。
【０１５７】
また、請求項５の発明においては、短時間に複数回の発光を行って１回のフラッシュ撮影を行う際に、露光中の複数回の発光について、発光量を変更することによって、フラッシュ撮影時に、ユーザーの意図や被写体の状態などに応じて、さらに適正な撮影画像を取得することができる。例えば、露光条件が種々異なる複数の画像を容易に取得することができる。
【図面の簡単な説明】
【図１】 本発明の実施形態に係る撮像装置１Ａを示す斜視図である。
【図２】 撮像装置１Ａの背面図である。
【図３】 撮像装置１Ａの機能ブロックを示す図である。
【図４】 撮像装置１Ａにおける画像信号等の流れを説明するための図である。
【図５】 ＣＣＤ２の電荷読み出し方法を説明するための図である。
【図６】 ＣＣＤ２の高速読み出しモードを説明するための図である。
【図７】 撮像装置１Ａの撮影動作を説明するためのフローチャートである。
【図８】 撮像装置１Ａの撮影動作を説明するためのフローチャートである。
【図９】 撮像装置１Ａの撮影動作を説明するための図である。
【図１０】 本発明の変形例に係る撮像装置１Ｂの撮影動作を説明するための図である。
【図１１】 従来技術に係るＣＣＤの電荷読み出し方法を説明するための図である。
【図１２】 従来技術に係るＣＣＤの電荷読み出し方法を説明するための図である。
【符号の説明】
１Ａ，１Ｂ 撮像装置
２ ＣＣＤ（撮像手段）
２ａ 受光部
５ カメラマイコン
７ 内蔵フラッシュ（発光部）
２１ 第１フィールド
２２ 第２フィールド
２３ 第３フィールド
４３ 画像処理部（画像生成手段）
６６ フラッシュ制御回路（発光制御手段）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an all-pixel readout type imaging apparatus that reads out image signals of all pixels of a light receiving unit into a plurality of fields and reads out each field.
[0002]
[Prior art]
In recent years, the number of pixels in the light receiving portion of a digital camera has been dramatically increased. On the other hand, since the overall size of the light receiving unit does not increase in accordance with the number of pixels, the light receiving area of each unit light receiving element (unit CCD cell) is reduced due to the increase in pixel density in the light receiving unit, and as a result, imaging is performed. Sensitivity will decrease. In order to prevent such a decrease in sensitivity, a technique for reducing the area of the charge transfer path of the light receiving unit as a region that does not contribute to the photoelectric conversion function is known. However, if the area of the charge transfer path is reduced, it becomes difficult to read out the charge signals of all the lines of the light receiving unit at the same time in parallel. To solve this problem, the charge signals of all the pixels A method is adopted in which is divided into a plurality of fields and read sequentially for each field.
[0003]
As described above, in a digital imaging apparatus typified by a digital camera, a method of reading out image signals of all pixels for each field divided into a plurality of fields (hereinafter referred to as “field-sequential all-pixel reading method”) is adopted. At present, a type in which one frame is divided into two fields and all pixels are read out is generally used. However, it is speculated that the method of reading all pixels by dividing one frame into more fields will be expanded, such as a type of reading all pixels by dividing one frame into 3 fields or 4 fields.
[0004]
In a general two-field readout type image pickup device, adjacent pixel lines cannot be read out as an image signal in the same field. Therefore, in a color filter employing a Bayer array or the like, as shown in FIGS. It is impossible to acquire color information of all colors using only the first field image or only the second field image. Therefore, when performing normal shooting, in order to acquire color information of all colors, it is necessary to acquire all color information from the image data after reading out the image data of all fields.
[0005]
By the way, in an imaging device using such an image sensor, when performing flash photography with flash photography, the flash emission amount is changed, and multiple photography is performed continuously under multiple exposure conditions. Bracket photography (hereinafter referred to as “flash bracket photography”) is performed (for example, Patent Documents 1 and 2).
[0006]
Also, during flash photography, the main subject (main subject) has a high optical reflectance, but often encounters photographing conditions where it is difficult to obtain an appropriate exposure, such as a low background optical reflectance. When shooting with normal flash under such shooting conditions, the main subject's reflectivity is taken into consideration, so the main subject's exposure is appropriate, but the background becomes dark and details such as the background Tends to cause the so-called “black crushing”. Furthermore, if there is a very bright part other than the main subject, the part tends to be whitish, so-called “white crushing” tends to occur. And since the dynamic range which an image pick-up element has is often narrower than a silver salt film, in the digital image pick-up device, the occurrence frequency of the above-described black crushing and white crushing tends to become remarkable.
[0007]
As a measure for solving such problems, conventionally, a plurality of images with different exposure conditions are combined with good consistency, thereby generating an image in which the gradation of a portion where white crushing and black crushing has occurred is adjusted. There has been proposed an imaging apparatus that can perform such processing (for example, Patent Documents 3 and 4).
[0008]
Prior art documents relating to such technology include the following.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-196985
[Patent Document 2]
JP 2000-75371 A
[Patent Document 3]
JP 2000-69355 A
[Patent Document 4]
JP 2002-84449 A
[Patent Document 5]
JP 9-46582 A
[0010]
[Problems to be solved by the invention]
However, with the above-described flash bracket shooting and shooting that generates a well-graded image, when an image sensor with a large number of pixels is used, it takes a considerable amount of time to acquire a plurality of images with different exposure conditions. Therefore, it has been difficult to apply to shooting conditions in which the position of the subject, the surrounding environment, and the like change every moment.
[0011]
In particular, for shooting to generate an image in which the gradation of the portion where white and black crushing has occurred is adjusted, a plurality of images are combined, so even when shooting a subject that is almost stationary, There is a problem that the generated image tends to be blurred due to the camera shake of the photographer.
[0012]
In addition, in order to change the exposure conditions in flash photography, the flash must be emitted a plurality of times, which has the disadvantage of increasing energy consumption.
[0013]
Further, a general compact camera has a certain limit in the amount of flash emission in order to add a flash function without increasing the size of the camera. Therefore, there is a problem that it is difficult to obtain a photographed image having sufficient sensitivity when the flash light arrival distance during flash photography is short and the distance to the subject is long.
[0014]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an imaging apparatus that can easily acquire various captured images and appropriate captured images according to the subject during flash shooting.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the invention of claim 1 is an imaging device having a light emitting unit, and (a) the charge signal accumulated in the light receiving unit at the time of photographing is represented by the pixel arrangement of the light receiving unit. (B) the light emitting unit emits a first light, and after the first light emission, a charge signal is output from the first field of the plurality of fields. A light emission control means for controlling the light emitting section to perform second light emission when reading, and (c) reading out a charge signal accumulated in the light receiving section before the second light emission from the first field. 1st image data obtained by this, and 2nd image data obtained by reading the electric charge signal accumulated in the photo acceptance unit before and after the 2nd light emission from the 2nd field of the plurality of fields, Based on Te, characterized in that it comprises an image generating means for generating a predetermined image data.
[0016]
The invention according to claim 2 is the imaging apparatus according to claim 1, wherein the pixel array of the light receiving unit has a color filter array, and each of the first and second fields is the color. All the color components of the filter array are included.
[0017]
The invention according to claim 3 is the imaging apparatus according to claim 1 or 2, wherein the image generation means includes a pixel value in the first image data and a pixel in the second image data. The predetermined image data is generated by adding the values.
[0018]
According to a fourth aspect of the present invention, there is provided the imaging apparatus according to the first or second aspect, wherein the image generation means includes a pixel value in the first image data and a pixel in the second image data. The predetermined image data is generated by performing addition processing on the values while converting the gradation characteristics.
[0019]
The invention according to claim 5 is the imaging apparatus according to any one of claims 1 to 4, wherein a light emission amount in the first light emission is different from a light emission amount in the second light emission. It is characterized by.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
<(1) First Embodiment>
<(1-1) Configuration of main part of imaging device>
FIG. 1 is a perspective view showing an imaging apparatus 1A according to the first embodiment of the present invention. FIG. 2 is a rear view of the image pickup apparatus 1A. 1 and 2 show three axes X, Y, and Z orthogonal to each other in order to clarify the azimuth relationship.
[0022]
On the front side of the image pickup apparatus 1A, a photographing lens 11, a finder window 13, and a built-in flash 7, which is a part that emits light, are provided. A CCD (Charge Coupled Device) 2, which is an image sensor that photoelectrically converts a subject image incident through the photographing lens 11 and generates an image signal, is provided inside the photographing lens 11.
[0023]
The photographic lens 11 includes a lens system that can be driven along the optical axis direction. By driving the lens system in the optical axis direction, a focused state of the subject image formed on the CCD 2 is realized. It is configured to be able to.
[0024]
A shutter button 14 and a mode switching button 15 are arranged on the upper surface side of the imaging apparatus 1A. The shutter button 14 is a button for giving a shooting instruction to the image pickup apparatus 1A by being pressed by a user when shooting a subject.
[0025]
The mode switching button 15 is a button for switching modes such as a “photographing mode” for photographing a subject and a “reproduction mode” for reproducing and displaying a photographed image on the LCD 18. Note that when the camera is switched to the shooting mode with the power turned on, the camera enters a shooting standby state in which shooting is possible.
[0026]
On the side surface of the image pickup apparatus 1A, a wearing part 16 is formed for wearing a memory card 9 for storing image data obtained by a main photographing operation in accordance with a pressing operation of the shutter button 14 by the user. Further, a card eject button 17 that is pressed when the memory card 9 is removed from the attachment unit 16 is disposed, and the memory card 9 can be extracted from the attachment unit 16.
[0027]
On the back surface of the imaging apparatus 1A, a live view display that displays a subject in a moving image mode before the main shooting, a liquid crystal display (LCD) 18 for displaying a shot image and the like, and an imaging apparatus 1A such as a shutter speed. Are provided with an operation button 19 for changing various setting states and a finder window 13.
[0028]
Here, a mode in which the user operates the operation buttons 19 to control the light emission of the built-in flash 7 at the time of shooting (hereinafter referred to as “flash control mode”), and a flash for shooting with the built-in flash 7 emitting light. A “special shooting mode” or the like for performing special shooting can be set.
[0029]
In the flash control mode, the “forced flash mode” in which the built-in flash 7 always emits light during shooting, the “flash prohibit mode” in which the built-in flash 7 does not emit light during shooting, and the light emission of the built-in flash 7 are left to the judgment of the imaging apparatus 1A. There is an “auto flash mode”. The light emission control of the built-in flash 7 will be further described later.
[0030]
The special shooting mode includes a “high sensitivity mode” for acquiring high-sensitivity shot images during flash shooting, a “flash bracket mode” for acquiring multiple images with different exposure conditions in a short time during flash shooting, and a subject. There is an “appropriate gradation mode” for preventing the occurrence of black crushing or white crushing when the luminance difference between the two is large. Note that in order to perform flash shooting in the special shooting mode described here, it is necessary to make the built-in flash 7 emit light. Therefore, in order to perform shooting operation in the special shooting mode, the flash control mode is forced light emission. Mode or auto-issue mode must be set.
[0031]
The flash shooting in the special shooting mode, which is a feature of the present invention, will be described in detail later.
[0032]
FIG. 3 is a diagram illustrating functional blocks of the imaging apparatus 1A. FIG. 4 is a diagram for explaining the flow of image signals and the like in the imaging apparatus 1A.
[0033]
The imaging apparatus 1A includes an AFE (analog front end) 3 that is connected to the CCD 2 so as to be able to transmit data, an image processing block 4 that is connected so as to be able to transmit data to the AEF 3, and a camera microcomputer 5 that performs overall control of these units.
[0034]
The CCD 2 is provided with a light receiving portion 2a on the surface facing the photographing lens 11, and a plurality of pixels are arranged on the light receiving portion 2a. The pixel array constituting the light receiving portion 2a is divided into three fields, and the CCD 2 can sequentially read out charge signals (image signals) accumulated in the respective pixels at the time of actual photographing for each field. It has a configuration. In addition, the CCD 2 is a mode (hereinafter referred to as a high-speed reading mode) for reading a signal (hereinafter referred to as “live view photographing”) for generating a live view image for previewing in a photographing standby state before the actual photographing. , Referred to as “high-speed reading mode”).
[0035]
Here, a method for reading the charge signal in the CCD 2 will be described.
[0036]
FIG. 5 is a diagram for explaining a method of reading the charge signal of the CCD 2 in the main photographing, and FIG. 6 is a diagram for explaining a high-speed readout mode of the CCD 2. Actually, millions of pixels or more are arranged, but only a part of them is shown for convenience of illustration. 5 and 6 have two axes I and J orthogonal to each other in order to clearly represent the pixel positions in the vertical direction and the horizontal direction in the light receiving unit 2a.
[0037]
As shown in FIGS. 5 and 6, the light receiving unit 2a is provided with a color filter array corresponding to the pixel array. That is, the light receiving unit 2a has a color filter array. This color filter array is composed of periodically distributed red (R), green (Gr, Gb) and blue (B) color filters, that is, three types of color filters having different colors.
[0038]
When reading the charge signal stored in each cell of the CCD 2, first, as shown in FIG. 5 (a), the lines 1, 4, 7,. That is, with the 3n + 1 line (n is an integer) as the first field 21, the charge signal is read from the first field 21, and the first field image data 210 is configured. Next, as shown in FIG. 5B, in the light receiving portion 2a, the 2, 5, 8,... Lines arranged in order in the J direction, that is, the 3n + 2 lines are used as the second field 22, and the second field. A charge signal is read from the second field image data 220 to form second field image data 220. Finally, as shown in FIG. 5 (c), from the third field 23, the 3, 6, 9,... The charge signal is read to form third field image data 230. With such a charge readout method, each of the first to third fields 21 to 23 includes all color components of the color filter array, that is, pixels of all RGB colors provided with all types of RGB color filters. It becomes.
[0039]
On the other hand, in the high-speed reading mode, for example, as shown in FIG. 6, the light signals of the respective lines 2, 7, 10,... Are read out by the light receiving unit 2a to obtain image data (high-speed reading image data). . That is, the horizontal line is read out with 1/4 thinned out. As shown in FIG. 6, the high-speed read image data includes all color components in the color filter array, that is, data on all RGB color pixels provided with all RGB color filters.
[0040]
Returning to FIG. 3 and FIG. 4, the description will be continued.
[0041]
The AFE 3 is configured as an LSI (Large Scale Integrated Circuit) including a signal processing unit 31 and a TG (timing generator) 32 that sends a timing signal to the signal processing unit 31. The TG 32 sends a CCD drive signal to the CCD 2, and a charge signal is output from the CCD 2 in synchronization with the drive signal.
[0042]
The signal processing unit 31 includes a CDS (correlated double sampler) 311, a PGA (Programmable-Gain-Amplifier) 312 that functions as an amplifier unit, and an ADC (A / D converter) 313. The output signal of each field output from the CCD 2 is sampled by the CDS 311 based on the sampling signal from the TG 32, and desired amplification is performed by the PGA 312. The PGA 312 can change the amplification factor with numerical data via serial communication from the camera microcomputer 5 and can correct the image signal based on the AE / WB control value sent from the selector 46. ing. The analog signal amplified by the PGA 312 is converted into, for example, a 10-bit digital signal by the ADC 313 and then sent to the image processing block 4.
[0043]
The image processing block 4 includes an image memory 41, an AE / WB calculator 42 and an image processing unit 43 that are connected to the image memory 41 so as to be able to transmit, and a compression / decompression unit 45.
[0044]
The image memory 41 is constituted by a semiconductor memory, for example, and is a part that temporarily stores the field image data 210 to 230 digitally converted by the ADC 313. Then, after the image data of all fields are stored in the image memory 41, the image data is sent to the image processing unit 43 in order to generate a single all-pixel image.
[0045]
The image memory 41 also temporarily stores high-speed read image data digitally converted by the ADC 313 and sends it to the image processing unit 43 to generate a live view image. Further, the high-speed read image data stored in the image memory 41 is also sent to the AE / WB calculator 42.
[0046]
The AE / WB calculator 42 is a value (AE control value and WB control value) for performing automatic exposure correction (AE) and white balance (WB) correction based on the high-speed read image data sent from the image memory 41. ) Is calculated.
[0047]
For example, first, the high-speed read image data is divided into a plurality of blocks, and multi-division photometry for calculating photometry data for each block is performed to detect subject luminance. As a specific process of subject luminance detection, each color component value (luminance value for each color component) for each pixel defined by the image data given by R, G, and B is averaged over the entire image. , The subject luminance value is calculated in correspondence with integer values from 0 to 1023. For AE, based on the calculated subject luminance value, the aperture value and shutter speed of the photographic lens 11 are determined so as to achieve proper exposure. If an appropriate exposure amount cannot be set when the subject brightness is low, a gain value is obtained so that improper exposure due to underexposure is corrected by adjusting the level of the image signal in the PGA 312. That is, here, the aperture value, shutter speed, gain value, and the like correspond to the AE control value. For WB correction, a WB control value is determined based on the calculated luminance value for each color component so that the white balance is appropriate.
[0048]
Further, for example, when the calculated subject brightness is equal to or lower than a predetermined threshold, the AE / WB calculator 42 determines to make the built-in flash 7 emit light, and transmits that fact to the camera microcomputer 5. It should be noted that a preset WB control value for flash photography is employed when performing flash photography in which the built-in flash 7 is used for photography. Further, AE in flash photography will be further described later.
[0049]
The AE / WB control value calculated by the AE / WB calculator 42 is sent to the selector 46. The selector 46 sends the AE / WB control value to the signal processing unit 31 or the image processing unit 43 in accordance with the high-speed readout image data or the readout situation of the field of the CCD 2.
[0050]
The image processing unit 43 is means for generating various frame image data from the first to third field image data 210 to 230 based on the setting of the special photographing mode. For example, when the “high sensitivity mode” is set as the special photographing mode, the interpolation processing is performed on the first to third field image data 210 to 230, and then the respective pixel values are added. Image data for one frame is generated. When the “flash bracket mode” is set, interpolation processing is performed on each of the first to third field image data 210 to 230 to generate three image data. When “appropriate gradation mode” is set, interpolation is performed on each of the first to third field image data 210 to 230, and then the gradation characteristics of the respective pixel values are added while being converted. Processing is performed to generate image data for one frame. The generation of various image data according to each mode setting of the special photographing mode in the image processing unit 43 will be described in detail later. When the special shooting mode is not set, the first to third field image data 210 to 230 are simply combined to generate image data for one frame.
[0051]
The image processing unit 43 performs interpolation processing based on the color filter characteristics of the CCD 2 on various image data generated according to each mode setting of the special photographing mode and high-speed read image data sent from the image memory 41. Colorize.
[0052]
Further, the image processing unit 43 performs various types of image processing such as γ correction for obtaining natural gradation, filter processing for performing contour enhancement and saturation adjustment on the colorized image data. Further, the image processing unit 43 performs AE / WB correction for adjusting the brightness and color balance of the image based on the AE / WB control value sent from the selector 46.
[0053]
The display unit 44 includes an LCD 18 and can display an image based on image data acquired by the CCD 2.
[0054]
The compression / decompression unit 45 compresses the image processed by the image processing unit 43 at the time of actual photographing, for example, using the JPEG method, and stores the compressed image in the memory card 9 as a storage medium. The compression / decompression unit 45 decompresses image data stored in the memory card 9 for reproduction and display on the display unit 44.
[0055]
The imaging apparatus 1 </ b> A includes a lens driving unit 61 and a shutter control unit 62 connected to the camera microcomputer 5, and includes a photometric unit 63, an operation unit 64, and a power supply unit 65. Furthermore, the imaging apparatus 1 </ b> A includes a flash control circuit 66 connected to the camera microcomputer 5 and a built-in flash 7.
[0056]
The lens driving unit 61 is for changing the position of each lens of the photographing lens 11, and the lens driving unit 61 can perform autofocus (AF) and zoom. The AF is controlled by the camera microcomputer 5, and for example, in the shooting standby state, the position of each lens of the shooting lens 11 is changed so as to focus on the closest subject or the like, or the distance to the main subject is calculated. be able to.
[0057]
The shutter control unit 62 is a part for opening and closing a mechanical shutter (hereinafter simply referred to as “shutter”) 12.
[0058]
The photometric unit 63 has a photometric sensor and performs photometry on the subject.
[0059]
The flash control circuit 66 is means for controlling the light emission of the built-in flash 7 under the control of the camera microcomputer 5. When the special photographing mode is set, the built-in flash 7 is controlled so as to divide light emission (hereinafter referred to as “main light emission”) performed during the exposure of the main photographing. That is, the flash control circuit 66 performs control so that light emission obtained by dividing the main light emission (hereinafter referred to as “divided main light emission”) is performed a plurality of times.
[0060]
The operation unit 64 includes various operation members such as the shutter button 14, the mode switching button 15, and the operation button 19.
[0061]
The power supply unit 65 includes a battery and supplies power to each unit of the imaging device 1A.
[0062]
The camera microcomputer 5 has a CPU and a memory, and is a part that performs overall control of each part of the imaging apparatus 1A.
[0063]
<(1-2) AE in flash photography>
Here, a case where the automatic control mode is set as the flash control mode will be described as an example.
[0064]
If the AE / WB calculator 42 sends a message to the camera microcomputer 5 that the built-in flash 7 has been determined to emit light when the shutter button 14 is pressed, the camera microcomputer 5 sends a flash control circuit 66. A flash emission signal is sent to the built-in flash 7. Here, the built-in flash 7 is based on various conditions such as exposure control values such as exposure time and aperture, subject brightness calculated by the AE / WB calculator 42, and distance to the main subject calculated by the AF operation. Is adjusted so that the subject is properly exposed. It should be noted that an appropriate amount of light emission can be adjusted by measuring the reflected light from the subject in the photometry unit 63.
[0065]
Here, an example of a method of determining the appropriate light emission amount of the built-in flash 7 in the camera microcomputer 5 or the like will be briefly described below.
[0066]
As described above, in the AE / WB computing unit 42, for example, when the subject brightness is equal to or lower than a predetermined threshold, the internal flash 7 is determined to emit light, and the fact is transmitted to the camera microcomputer 5. Then, in the camera microcomputer 5, an approximate light emission amount necessary for proper exposure (hereinafter referred to as “pseudo required light emission amount”) based on the subject brightness, the distance to the main subject, the focal length of the photographing lens 11, and the like. Calculated). Thereafter, a light emission amount (hereinafter referred to as “pre-light emission amount”) in pre-light emission that causes the built-in flash 7 to emit light before the main photographing is calculated based on the pseudo required light emission amount.
[0067]
In a normal case, if the pre-emission amount becomes too large, a large amount of electric charge stored in the capacitor for causing the built-in flash 7 to emit light is consumed. There is a risk that the amount cannot be obtained. Therefore, for example, the pre-emission amount is set to be about 1 / several to several tenths of the pseudo required emission amount.
[0068]
At this time, the AE / WB calculator 42 transmits the subject luminance (hereinafter referred to as “luminance before light emission”) before the pre-light emission to the camera microcomputer 5. The luminance before light emission includes, for example, subject luminance used to calculate the pre-light emission amount.
[0069]
When the pre-emission amount is determined in the camera microcomputer 5, a flash emission signal is sent from the camera microcomputer 5 to the flash control circuit 66, and the built-in flash 7 performs pre-emission so that the determined pre-emission amount is obtained. At this time, the charge signal accumulated in the CCD 2 during pre-emission is read out in the high-speed readout mode, and the high-speed readout image data (pre-emission image data) is stored in the image memory 41. Then, the AE / WB calculator 42 calculates subject luminance at the time of pre-emission (hereinafter referred to as “pre-emission luminance”) based on the pre-emission image data, and transmits it to the camera microcomputer 5. The camera microcomputer 5 determines the appropriate light emission amount (hereinafter referred to as “appropriate main light emission amount) of the built-in flash 7 at the time of actual photographing from the pre-emission luminance, pre-emission luminance, pre-emission amount, and exposure control values (sensitivity, aperture, shutter speed). "). At this time, if the built-in flash 7 emits light at an appropriate main flash amount during main shooting, the exposure EV is EV. ₀ It shall be
[0070]
Even when the forced light emission mode is set as the flash control mode, the proper main light emission amount can be determined in the same manner.
[0071]
When the special photographing mode is set, the camera microcomputer 5 can calculate each light emission amount of the divided main light emission based on the proper main light emission amount. Each light emission amount of the divided main light emission is variously calculated and determined by changing the special shooting mode setting and the detailed setting by the user operating the operation buttons 19 variously.
[0072]
<(1-3) Shooting operation in special shooting mode>
As described above, depending on the setting of the special shooting mode, there are differences in the respective main flash emission amounts at the time of main shooting and the generation of image data in the image processing unit 43. The shooting operation in will be described below.
[0073]
<(1-3-1) Shooting operation in high sensitivity mode>
7 and 8 are flowcharts for explaining a basic photographing operation according to the high sensitivity mode of the imaging apparatus 1A. This operation is executed under the control of the camera microcomputer 5. FIG. 9 is a diagram for explaining the photographing operation in the high sensitivity mode of the image pickup apparatus 1A. The vertical synchronization signal VD, the shutter 12, the light emission of the built-in flash 7, the first to third fields 21 to 23 in the CCD 2. It is a timing chart showing the charge accumulation state and the output of the CCD 2. Hereinafter, the flowcharts of FIGS. 7 and 8 will be described with reference to FIG.
[0074]
First, live view shooting is performed with the shutter 12 opened, and a live view image acquired by the CCD 2 is displayed on the display unit 44. Then, when the user presses the shutter button 14, shooting is started (step S1).
[0075]
When shooting is started, as described above, the pre-emission amount is calculated by the camera microcomputer 5, the emission signal is transmitted from the camera microcomputer 5 to the flash control circuit 66, and the built-in flash 7 performs the pre-emission PF (step). S2).
[0076]
In step S3, as described above, the camera microcomputer 5 calculates the proper main light emission amount. For example, the exposure amount from the start of the main photographing exposure to the start of reading the first field image data 210 from the CCD 2 is half of the proper exposure. EV = EV ₀ The first emission amount is calculated so as to be −1 (step S3).
[0077]
In step S4, exposure of the CCD 2 in the actual photographing is started, and the built-in flash 7 performs the first light emission F1 according to the light emission amount calculated in step S3.
[0078]
In step S5, reading of the first field image data 210 from the CCD 2 is started while the shutter 12 is kept open and exposure of the CCD 2 is continued.
[0079]
In step S6, EV = EV which is appropriate exposure ₀ Based on the above, the second emission amount is calculated. For example, EV = EV in which the exposure amount from the start of reading the first field image data 210 to the start of reading the second field image data 220 is half of the appropriate exposure. ₀ The second light emission amount is calculated so as to be -1.
[0080]
In step S7, the built-in flash 7 performs the second light emission F2 according to the light emission amount calculated in step S6.
[0081]
In step S8, the reading of the first field image data 210 started in step S5 is continued while the shutter 12 is kept open.
[0082]
In step S 9, the read first field image data 210 is stored in the image memory 41.
[0083]
Here, EV = EV where the exposure amount from the start of exposure of the main photographing to the start of reading of the first field image data 210 from the CCD 2 is half of the appropriate exposure. ₀ When the first light emission amount is set to be −1, the first field image data 210 has an exposure amount that is half of the appropriate exposure EV = EV ₀ This is image data obtained when -1.
[0084]
In step S10, it is determined whether reading of the first field image data 210 has been completed. Here, when the reading is completed, the process proceeds to step S21 in FIG. 8, and when the reading is not completed, the process returns to step S8.
[0085]
In step S21, reading of the second field image data 220 from the CCD 2 is started while the shutter 12 is kept open and exposure of the CCD 2 is continued.
[0086]
In step S22, EV = EV which is appropriate exposure ₀ Based on the above, the third emission amount is calculated. For example, EV = EV in which the exposure amount from the start of reading of the second field image data 220 to the start of reading of the third field image data 230 is an appropriate exposure. ₀ The third emission amount is calculated so that
[0087]
In step S23, the built-in flash 7 performs the third light emission F3 according to the light emission amount calculated in step S22.
[0088]
In step S24, the reading of the second field image data 220 started in step S21 is continued while the shutter 12 is kept open.
[0089]
In step S25, the read second field image data 220 is stored in the image memory 41.
[0090]
Here, for example, the exposure amount from the start of reading of the first field image data 210 to the start of reading of the second field image data 220 is EV = EV which is half of the appropriate exposure. ₀ When the second light emission amount is set to be −1, the second field image data 220 is obtained by adding the charges accumulated until the first field image data 210 is read and the charges accumulated thereafter. Based on charge. Therefore, in the second field image data 220, EV = EV where the exposure amount is appropriate exposure. ₀ In this case, the image data is obtained.
[0091]
In step S26, it is determined whether the reading of the second field image data 220 has been completed. If the reading has been completed, the process proceeds to step S27. If the reading has not been completed, the process returns to step S24.
[0092]
In step S27, the shutter 12 is closed, the exposure of the CCD 2 is completed, and the process proceeds to step S28.
[0093]
Here, the exposure of the CCD 2 in one shooting is completed. As shown in FIG. 9, the built-in flash 7 emits the first light emission F1 from the start of exposure to the end of exposure under the control of the flash control circuit 66 as shown in FIG. When the charge signal is read from the first field 21 after the first light emission F1, the built-in flash 7 performs the second light emission F2. Similarly, the built-in flash 7 performs the second light emission F2 and, after the second light emission F2, when the charge signal is read from the second field 22, the built-in flash 7 performs the third light emission F3. Here, the first and second light emission F1 and F2 are also referred to as first and second light emission, respectively.
[0094]
In step S28, reading of the third field image data 230 from the CCD 2 is started.
[0095]
In step S29, the reading of the third field image data 230 started in step S28 is continued.
[0096]
In step S30, the read third field image data 230 is stored in the image memory 41.
[0097]
Here, for example, EV = EV where the exposure amount from the start of reading of the second field image data 220 to the start of reading of the third field image data 230 is an appropriate exposure. ₀ If the third light emission amount is set so that the second field image data 220 is read, the third field image data 230 is a sum of the charges accumulated until the start of reading the second field image data 220 and the charges accumulated thereafter. Based. Therefore, the third field image data 230 has an exposure amount that is twice the appropriate exposure EV = EV ₀ The image data obtained when +1 is obtained.
[0098]
In step S31, it is determined whether reading of the image data of the third field is completed. If the reading has been completed, the process proceeds to step S32. If the reading has not been completed, the process returns to step S29.
[0099]
In step S <b> 32, the first to third field image data 210 to 230 stored in the image memory 41 are read and output to the image processing unit 43.
[0100]
In step S <b> 33, the image processing unit 43 combines the first to third field image data 210 to 230 to generate one frame of image data.
[0101]
Here, for example, three exposure conditions (EV = EV ₀ -1, EV ₀ , EV ₀ In each of the first to third field image data 210 to 230 obtained in +1), the other two fields of pixel data (pixel values) do not exist. Therefore, for each of the first to third field image data 210 to 230, pixel values of nonexistent pixels (hereinafter referred to as “empty pixels”) are obtained by interpolation processing, and three images (hereinafter referred to as interpolation processing) are performed. , Referred to as “first to third interpolated image data”). Then, image data for one frame is generated by combining the first to third interpolation image data.
[0102]
In the interpolation processing for each field image data referred to here, for example, with respect to a sky pixel for a predetermined color, a pixel of a sky pixel is used by using pixel data of a predetermined color that is closest in the J direction and −J direction that are vertical directions. The value can be determined. This will be specifically described below.
[0103]
For example, assuming that the light receiving unit 2a of the CCD 2 as shown in FIG. 5 is arranged so that R pixels come at positions (even and even) in the I and J directions. When both are even numbers of 0 or more, the positions of R, Gr, Gb, and B pixels are (i, j), (i + 1, j), (i, j + 1), and (i + 1, j + 1), respectively. .
[0104]
As for the R pixel, if the position (i, j) belongs to the first field 21, the position (i, j) of the second field image data 220 is an empty pixel. Therefore, for the second field image data 220, the pixel values of the position (i, j-2) and the position (i, j + 4), which are the R pixels closest to the position (i, j) in the J direction and the -J direction. From this, the pixel value at the position (i, j) is calculated. Similarly, pixel values are calculated for the empty pixels of the first and third field image data 210 and 230. For the Gr, Gb, and B pixels, the pixel value of the empty pixel is calculated in the same manner as the R pixel. In this way, the first to third field image data 210 to 230 can be interpolated to generate the first to third interpolation image data, respectively.
[0105]
That is, the first field image data 210 is acquired by reading out the charge signal accumulated in the light receiving unit 2a before the second light emission F2 from the first field 21, and further subjected to interpolation processing to obtain the first interpolation image data. Obtainable. Further, the second field image data 220 is obtained by reading out the charge signal accumulated in the light receiving section 2a before and after the second light emission F2 from the second field 22, and further subjected to interpolation processing to obtain the second interpolation image. Data can be obtained. Here, the first and second interpolated image data are also referred to as first and second images.
[0106]
Then, by adding each pixel value of the first to third interpolation image data, the first to third interpolation image data is synthesized to generate one frame of image data. That is, the image processing unit 43 generates predetermined image data based on the first to third interpolation image data. Expressions (1) to (4) shown below are expressions indicating pixel values for R, Gr, Gb, and B pixels in the image data for one frame after synthesis. In the expressions (1) to (4), the lowercase letters on the right side of R, Gr, Gb, and B indicate the positions of the respective pixels in the I direction and the J direction.
[0107]
[Expression 1]

[0108]
Here, when the expressions (1) to (4) indicate the pixel values of R, Gr, Gb, and B for the pixels belonging to the first field 21, the first term is a pixel in the first field image data 210. The second term represents the pixel value in the second interpolated image data, and the third term represents the pixel value in the third interpolated image data. Further, when the expressions (1) to (4) indicate the pixel values of R, Gr, Gb, and B for the pixels belonging to the second field 22, the first term is the pixel value in the second field image data 220. The second term represents the pixel value in the third interpolation image data, and the third term represents the pixel value in the first interpolation image data. Furthermore, when the expressions (1) to (4) indicate the pixel values of R, Gr, Gb, and B for the pixels belonging to the third field 23, the first term is the pixel value in the third field image data 230. The second term represents the pixel value in the first interpolated image data, and the third term represents the pixel value in the second interpolated image data.
[0109]
In the example of the interpolation processing described above, interpolation processing considering only pixel values in the vertical direction (J direction) is performed, but other interpolation processing considering pixel values in the horizontal direction (I direction) is performed. Also good.
[0110]
Returning to the flowchart of FIG.
[0111]
In step S33, as described above, image data for one frame is generated by combining the first to third interpolation image data, and the process proceeds to step S34. Each interpolated image data is, for example, 10-bit digital data, and the image data for one frame after synthesis is also 10-pit digital data.
[0112]
In step S34, the image processing unit 43 performs colorization, γ correction, various image processing, and AE / WB correction on the image data for one frame generated in step S33. Then, based on the obtained image data for one frame, the compression / decompression unit 45 performs compression processing and stores it in the memory card 9 and displays it on the LCD 18, and the photographing is finished. Thereafter, the imaging apparatus 1A again enters a shooting standby state.
[0113]
Thus, for example, three exposure conditions (EV = EV ₀ -1, EV ₀ , EV ₀ Image data for one frame is acquired based on the first to third field image data 210 to 230 obtained in +1). The acquired image data is obtained by flash photography with a light emission amount such that the exposure amount is 3.5 times the appropriate exposure in a general digital imaging device, as shown in equations (1) to (4). It has a pixel value equivalent to the obtained image data. Therefore, a highly sensitive photographed image can be acquired in photographing in the high sensitivity mode.
[0114]
By the way, even by amplifying the pixel value obtained with the light emission amount so that the exposure amount becomes the appropriate exposure to 3.5 times, the flash photography is performed with the light emission amount so that the exposure amount becomes 3.5 times the appropriate exposure. A pixel value substantially equivalent to the image data obtained in this way can be obtained. However, with this method, even the noise component in the image data is amplified by a factor of 3.5, so the quality of the captured image is degraded. In contrast, in shooting in the high sensitivity mode according to the present embodiment, since three different image data are synthesized, noise components in the image data are randomized, so that deterioration of the image quality of the shot image is suppressed. Can do.
[0115]
Also, in a general digital imaging device, for example, in order to obtain image data by photographing with a light emission amount such that the shutter speed is constant and the exposure amount is 3.5 times the appropriate exposure, the appropriate exposure is required. The built-in flash consumes about 3.5 times as much energy as the case of shooting. In addition, three exposure conditions (EV = EV) ₀ -1, EV ₀ , EV ₀ Even in the case of performing the exposure in +1), the built-in flash consumes 3.5 times as much energy as the standard when shooting with proper exposure.
[0116]
On the other hand, in the shooting in the high sensitivity mode according to the present embodiment, a single flash shooting is performed by emitting a plurality of times in a short time, and pixel values for a plurality of image data obtained with different exposure conditions are obtained. to add. As a result, since the built-in flash 7 consumes only about twice as much energy as the standard when shooting with proper exposure, it is possible to acquire a high-sensitivity shot image during flash shooting while suppressing an increase in power consumption. . Further, even when the built-in flash 7 is composed of a small xenon tube or the like and the maximum light emission amount per time is small, a certain amount of exposure is obtained by performing light emission a plurality of times during exposure in one short flash photography. The amount can be secured. Therefore, it is possible to adjust the exposure to a farther subject with a small amount of light, and it is possible to acquire a high-sensitivity photographed image at the time of flash photography while suppressing an increase in the size of the apparatus.
[0117]
Further, in a general digital imaging apparatus in which a high-pixel CCD imaging device for a recent digital camera is used, for example, a time required for reading out data of all pixels of the imaging device (required reading time) is about 250 ms to 300 ms. And three exposure conditions (EV = EV ₀ -1, EV ₀ , EV ₀ In order to perform photographing three times at +1), at least twice the required readout time is required from the start of the first exposure to the end of the third exposure. Therefore, in order to prevent blur from occurring in an image generated by combining three images later, the subject is limited to an object that is completely stationary.
[0118]
On the other hand, in the shooting in the high sensitivity mode according to the present embodiment, three exposure conditions (EV = EV ₀ -1, EV ₀ , EV ₀ The time required from the start of exposure to the end of exposure in +1) is, for example, 250 to 300 ms, which is about the same as the required readout time. Therefore, the present invention can be applied to a subject that moves to some extent. That is, it is possible to acquire an appropriate captured image corresponding to the subject during flash shooting.
[0119]
<(1-3-2) Shooting operation in flash bracket mode>
In the above-described shooting in the high sensitivity mode, for example, the first to third interpolation image data are combined to obtain one frame of image data. However, in the shooting in the flash bracket mode, the first to third interpolation image data are used. Coloring, γ correction, various image processing, and AE / WB correction are performed on the first to third interpolated image data without combining, and image data for three frames is obtained. Then, each of the obtained image data for three frames is subjected to compression processing by the compression / decompression unit 45 and stored in the memory card 9 and displayed on the LCD 18, and the photographing operation is completed. Therefore, the flow of the shooting operation in the flash bracket mode is different only in the process of step S33 shown in FIG. 8, and the flow of the other shooting operations is exactly the same as the shooting operation in the high sensitivity mode.
[0120]
As described above, in the shooting in the flash bracket mode according to the present embodiment, the flash shooting is performed a plurality of times in a short time to perform one flash shooting, and finally, based on a plurality of image data obtained with different exposure conditions. The image data for a plurality of frames having different exposure conditions is acquired. As a result, as described in the description of the shooting in the high sensitivity mode, in a general digital imaging device, an increase in power consumption or the like is obtained in comparison with a case where a plurality of similar image data is acquired by dividing into a plurality of shootings. Can be suppressed.
[0121]
Further, in the shooting in the flash bracket mode according to the present embodiment, as described in the description of the shooting in the high sensitivity mode, a plurality of captured images having different exposure conditions can be obtained in a shorter time than a general digital imaging device. Can do. Therefore, even for a subject that moves to some extent, image data for a plurality of frames with different exposure conditions can be obtained with substantially the same composition. That is, it is possible to acquire an appropriate captured image corresponding to the subject during flash shooting.
[0122]
Furthermore, in the shooting in the flash bracket mode according to the present embodiment, a plurality of field image data including all color components corresponding to the color filter array of the light receiving unit 2a and having different exposure conditions can be obtained. A plurality of different full-color captured images can be efficiently acquired in a short time.
[0123]
<(1-3-3) Shooting operation in proper gradation mode>
In the above-described shooting in the high sensitivity mode, for example, if the first to third field image data 210 to 230 are 10-bit digital data, the image data for one frame after synthesis is also the same 10-bit digital data. It became. However, in the photographing operation in the appropriate gradation mode, for example, the image data for one frame after synthesis is handled as 11-bit digital data. Therefore, the flow of the shooting operation in the appropriate gradation mode is different only in the process of step S33 shown in FIG. 8, and the flow of the other shooting operations is exactly the same as the shooting operation in the high sensitivity mode.
[0124]
The difference between the shooting operation in the proper gradation mode and the shooting operation in the high sensitivity mode will be described below.
[0125]
For example, as described in the photographing operation in the high sensitivity mode, when the first to third interpolated image data are added, R in the image data for one frame after the synthesis is calculated based on the equations (1) to (4). , Gr, Gb, and B pixels are obtained. At this time, in the appropriate gradation mode, addition processing is performed, gradation conversion processing is performed so that each pixel value is 2/3 times, and the pixel value is handled as 11-bit digital data. That is, the image data for one frame is generated by adding the pixel values in the first to third interpolation image data while converting the gradation characteristics such as the number of gradations.
[0126]
The meaning of the numerical value 2/3 times in this processing is as follows. That is, since the pixel value of each image data is expressed by 10 bits, the maximum value when the pixel values of the three image data are simply added is 2 ^Ten × 3 = 2 ¹¹ × (3/2), and a numerical value that cannot be handled with 10-bit data appears. In addition, all gradations represented by 12-bit data are not used up. Therefore, if each pixel value is multiplied by 2/3 for each maximum value of the three image data, 2 ^Ten Since x (2/3), the sum of the three image data is 2 ^Ten × (2/3) × 3 = 2 ¹¹ As in (11 bits), all gradations represented by 11-bit data can be used up. It is the same even if the value after synthesis is multiplied by 2/3. In this way, the contrast can be clearly expressed by using up all the gradations represented by the data of the gradation expression number N bits (where N is a natural number).
[0127]
In the present embodiment, the numerical value of 2/3 times is multiplied, but for example, the numerical value of 4/3 times is multiplied by 2 ^Ten × (4/3) × 3 = 2 ¹² As in (12 bits), all gradations represented by 12-bit data may be used up. Also, multiply by a value of 1/3 times 2 ^Ten × (1/3) × 3 = 2 ^Ten As in (10 bits), all gradations represented by 10-bit data can be used up.
[0128]
Therefore, in general, when there are M pieces of image data to be combined (provided that M ≧ 2), r = 2 ⁿ Multiplying each pixel value in each interpolated image data before addition or each pixel value before addition by a value r satisfying / M (where n is a natural number), N bits (where N is a natural number) By using up all the gradations represented by the data, the contrast can be expressed clearly. However, if r is too small, the number of gradation representations decreases, leading to degradation of image quality. Therefore, it is preferable from the viewpoint of image quality to make it larger than the number of gradation representations (N bits) of the original image data. On the other hand, if r is too large, the number of gradation representations (data length or number of bits) increases, leading to a decrease in processing speed and a lack of storage medium capacity. Therefore, the value of r may be 2 or less. preferable.
[0129]
In the specific processing in this embodiment, for a certain pixel before synthesis, the pixel value in the first interpolation image data is 519/1023 gradation, and the pixel value in the second interpolation image data is the maximum luminance. When the pixel value of the tone and the third interpolation image data is 1023/1023 gradation, which is the maximum luminance, a conversion process for multiplying the combined pixel value by 2/3 is performed, and this pixel value is converted into 11-bit digital data. As a result, the combined and converted pixel value becomes 1710/2047 gradation. Similarly, a combination and conversion process is performed on various combinations of pixel values as described above, and image data for one frame is handled as 11-bit digital data.
[0130]
By the way, in a general digital imaging device, exposure conditions (EV = EV = ₀ ) Only, the subject in which a very bright portion and a very dark portion are mixed tends to be blacked out or whited out.
[0131]
On the other hand, in shooting in the proper gradation mode according to the present embodiment, a plurality of image data (first to first images) having different exposure conditions are obtained by performing flash emission once in a plurality of times in a short time. The pixel values in the third interpolated image data) are added while converting the gradation characteristics, so that even in a photographed image acquired for a subject in which a very bright part and a very dark part are mixed, The occurrence of white crushing can be suppressed.
[0132]
For example, with respect to a very dark portion, it is possible to prevent the occurrence of black crushing, particularly by producing a gradation difference due to a change in pixel value in the third interpolation image data. Further, with respect to a very bright portion, it is possible to prevent occurrence of white crushing, particularly by producing a gradation difference due to a change in pixel value in the first interpolation image data. As a result, in shooting in the proper gradation mode, even when shooting a subject with a large luminance difference, the image data for one frame that is finally obtained is expressed with the luminance difference compressed. An image with good exposure can be obtained. That is, an image having a large dynamic range can be obtained by complementing a portion where light reflection from a subject is large and a portion where light reflection is low during flash photography.
[0133]
In the shooting in the appropriate gradation mode according to the present embodiment, a plurality of image data (first to third images) having different exposure conditions are obtained by performing a single flash shooting by emitting light a plurality of times in a short time. The pixel values in the interpolation image data) are added while converting the gradation characteristics. As a result, as described in the description of photographing in the high sensitivity mode, a plurality of photographed images with different exposure conditions can be obtained in a shorter time than a general digital imaging device. Therefore, even with a subject that moves to some extent, by acquiring multiple field image data with almost the same composition and different exposure conditions, it is possible to suppress the occurrence of blurring of the subject during flash photography. Appropriate captured images corresponding to the luminance can be acquired. Furthermore, as described in the description of the shooting in the high sensitivity mode, in a general digital imaging device, the power consumption is increased as compared with the case where a plurality of similar field image data is acquired by dividing into a plurality of shootings. Can be suppressed.
[0134]
As described above, in the imaging apparatus 1A according to the present embodiment, in accordance with the setting of the special shooting mode, a plurality of flashes are emitted in a short time to perform one flash shooting, and a plurality of different exposure states are obtained. Various images are generated based on the image data. As a result, it is possible to provide an imaging device that can easily acquire various captured images and appropriate captured images according to the subject during flash shooting.
[0135]
<(2) Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the contents described above.
[0136]
For example, the structure of the CCD 2 may be improved so that so-called “addition readout” can be performed.
[0137]
The “addition readout” here is a readout method employed in a subject monitor mode of a CCD image sensor for a general digital camera, and is used for high sensitivity and countermeasures against false colors. As a specific example, when a charge is transferred from a vertical CCD to a horizontal CCD, the vertical CCD transfers the charges of a plurality of lines in the horizontal direction to the horizontal CCD instead of transferring the charges for each line in the horizontal direction. Later, there is a readout method in which a charge transfer operation by a horizontal CCD is performed, and charges for a plurality of horizontal lines are superimposed and output as pixel values.
[0138]
FIG. 10 is a diagram for explaining the operation of the imaging apparatus 1B according to the modification of the present invention. Note that FIG. 10 illustrates the case where an image sensor capable of “addition reading” is used for the CCD 2.
[0139]
As shown in FIG. 10, the difference from the operation of the imaging apparatus 1 </ b> A shown in FIG. 9 is the charge accumulation state of the first field 21. In the operation shown in FIG. 10, the reading of the first and second field image data 210 and 220 from the CCD 2 is exactly the same as the operation shown in FIG. 9, but when reading the third field image data 230 from the CCD 2, The charges accumulated in the first field 21 are added.
[0140]
Here, since the shutter 12 is opened even after the first field image data 210 is read from the CCD 2, the first field 21 of the CCD 2 has the second and third light emission F2 and F3. Charge is also accumulated. For example, in the case where the pixel arrangement as shown in FIG. 5 is provided, when the third field image data 230 is read from the CCD 2, it is accumulated in the R pixel Ra (not shown) of the third field 23. While the charges are being transferred by the vertical CCD, the charges accumulated in the R pixel Rb (not shown) in the first field 21 corresponding to the pixel position shifted from the pixel Ra by four in the transfer direction of the vertical CCD are superimposed. . Then, a signal based on the superimposed charge is read as third field image data 230.
[0141]
In such a case, the pixel value of the third field image data 230 is larger than that of the image data based only on the charges accumulated in the third field 23. As a result, since the pixel value of the image data generated based on the third field image data 230 tends to increase, it is possible to easily obtain a captured image with higher sensitivity. In addition, since the desired third field image data 230 can be obtained even if the amount of light emitted from the built-in flash 7 for the third time is reduced, the power consumption of the built-in flash 7 can be further reduced.
[0142]
In the above-described embodiment, as shown in FIG. 9, when the charge signal is read from the second field 22, the built-in flash 7 performs the third light emission F3. However, the present invention is not limited to this operation. For example, when reading of the charge signal from the second field 22 is started, the shutter 12 may be closed so that the third light emission F3 is not performed.
[0143]
At this time, the second and third field image data 220 and 230 have the same exposure condition (EV = EV ₀ ), The two image data 220 and 230 are combined to form one exposure condition (EV = EV ₀ ) Can be obtained as image data. Therefore, the number of image data with different exposure conditions decreases, but here the exposure condition (EV = EV ₀ As for the image data obtained in (), the number of empty pixels is halved as compared with each of the second and third field image data 220 and 230 in the above-described embodiment. As a result, since the accuracy of the interpolation processing in the image processing unit 43 is improved, the image quality of the image data finally obtained in the image processing unit 43 can be improved.
[0144]
In the above-described embodiment, three exposure conditions (EV = EV ₀ -1, EV ₀ , EV ₀ +1), the first to third field image data 210 to 230 are acquired. However, the exposure conditions are not limited to those described above. For example, depending on the setting of the user, the exposure amount is 1/4 times or 1 time the appropriate exposure. Three to three times of exposure conditions (EV = EV) ₀ -2, EV ₀ , EV ₀ In +2), the first to third field image data 210 to 230 may be acquired. That is, the light emission amount in the first light emission may be different from the light emission amount in the second light emission.
[0145]
As described above, by changing the light emission amount for a plurality of times of light emission during exposure in one short flash photography, for example, a plurality of images with different exposure states can be efficiently acquired in a short time. That is, it is possible to acquire a more appropriate captured image according to the user's intention and the state of the subject.
[0146]
In the above-described embodiment, the charge signals are read from the first to third fields 21 to 23 for each field. However, the present invention is not limited to this, and each field 21 to 23 is divided into a plurality of regions. Separately, a charge signal is read out continuously in time for each region, and a plurality of image data based on the charge signals from a plurality of regions are combined to form first to third field image data 210, 220, 230. Also good.
[0147]
Specifically, for example, the first field 21 is further divided into a plurality of regions, and a charge signal is read out continuously in time for each region, and a plurality of image data based on the charge signals from the plurality of regions. The first field image data 210 may be combined. At this time, it is desirable to substantially match the exposure conditions of the region where the first field 21 is divided into a plurality.
[0148]
In the above-described embodiment, the light receiving unit 2a is divided into the three fields 21 to 23 and the charge signal is read out. However, the present invention is not limited to this, and the light receiving unit 2a includes a plurality of fields including four or more fields. The charge signals corresponding to all the color components of the color filter array may be read out for each field. If all the color components of the color filter array can be read for each field, the light receiving unit 2a may be divided into two fields to read the charge signal.
[0149]
In the above-described embodiment, the CCD 2 has a color filter array, but is not limited to this. For example, a so-called monochrome CCD without a color filter may be used. In this case, the obtained image data is monochrome image data, but various effects according to the settings of the special photographing mode can be obtained. In this case, the light receiving unit 2a may be divided into two fields to read out a charge signal.
[0150]
Also, in the above-described embodiment, in the shooting in the flash bracket mode, the complementary processing is performed on each field image data to generate the complementary image data. An image (thinned image) thinned out in the horizontal direction may be generated. At this time, although the image size of each thinned image is reduced, the amount of image data is reduced, so that the processing time required from the start of recording to recording and display can be shortened.
[0151]
In the above-described embodiment, in flash photography, various images are finally generated based on all the field image data acquired continuously. However, the present invention is not limited to this. For example, 3 Two interpolated image data may be generated from two field image data of the two field image data, and finally various images may be generated based on the two interpolated image data.
[0152]
In the above-described embodiment, the portion that emits light is the built-in flash 7. However, the present invention is not limited to this. For example, an external flash device that is attached to the image pickup apparatus 1A from the outside. May be.
[0153]
【The invention's effect】
As described above, according to the first to fifth aspects of the present invention, a plurality of flashes are emitted in a short period of time to perform one flash photography, and based on a plurality of image data obtained under different exposure conditions. By generating various image data, it is possible to provide an imaging apparatus that can easily acquire various captured images and appropriate captured images according to the subject during flash shooting.
[0154]
In particular, in the second aspect of the present invention, a plurality of light emission is performed in a short time to perform one flash photographing, a plurality of color components corresponding to the color filter array of the light receiving unit, and a plurality of different exposure conditions. Since image data can be obtained, it is possible to easily acquire an appropriate full-color captured image corresponding to the subject during flash shooting. For example, a plurality of full-color captured images with different exposure conditions can be efficiently acquired in a short time.
[0155]
According to a third aspect of the present invention, a plurality of times of light emission is performed in a short time to perform one flash photographing, and pixel values for a plurality of image data obtained under different exposure conditions are added, thereby High-sensitivity captured images can be acquired during flash photography while suppressing enlargement and power consumption.
[0156]
According to a fourth aspect of the present invention, light emission is performed a plurality of times in a short time to perform one flash photographing, and gradation characteristics are converted for pixel values of a plurality of image data obtained under different exposure conditions. By adding them, it is possible to acquire an appropriate captured image according to the brightness of the subject while suppressing blurring of the image and power consumption during flash shooting.
[0157]
Further, in the invention of claim 5, when performing flash shooting once by performing multiple flashes in a short time, by changing the flash amount for multiple flashes during exposure, Further, it is possible to obtain a more appropriate captured image according to the user's intention, the state of the subject, and the like. For example, a plurality of images with different exposure conditions can be easily acquired.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an imaging apparatus 1A according to an embodiment of the present invention.
FIG. 2 is a rear view of the imaging apparatus 1A.
FIG. 3 is a diagram illustrating functional blocks of the imaging apparatus 1A.
FIG. 4 is a diagram for explaining a flow of image signals and the like in the imaging apparatus 1A.
FIG. 5 is a diagram for explaining a charge reading method of the CCD 2;
FIG. 6 is a diagram for explaining a high-speed reading mode of the CCD 2;
FIG. 7 is a flowchart for explaining a photographing operation of the imaging apparatus 1A.
FIG. 8 is a flowchart for explaining a photographing operation of the imaging apparatus 1A.
FIG. 9 is a diagram for describing a photographing operation of the imaging apparatus 1A.
FIG. 10 is a diagram for describing a shooting operation of an imaging apparatus 1B according to a modification of the present invention.
FIG. 11 is a diagram for explaining a charge reading method of a CCD according to a conventional technique.
FIG. 12 is a diagram for explaining a charge reading method of a CCD according to a conventional technique.
[Explanation of symbols]
1A, 1B imaging device
2 CCD (imaging means)
2a Light receiver
5 Camera microcomputer
7 Built-in flash (light emitting part)
21 First field
22 Second field
23 Third field
43 Image processing unit (image generating means)
66 Flash control circuit (light emission control means)

Claims (5)

An imaging device having a light emitting unit,
(a) an image pickup means capable of reading out a charge signal accumulated in a light receiving portion at the time of photographing by dividing a pixel array of the light receiving portion into a plurality of fields;
(b) The light emitting unit emits the first light, and after the first light emission, the light emitting unit emits the second light when the charge signal is read from the first field of the plurality of fields. Light emission control means for controlling to perform,
(c) first image data obtained by reading from the first field a charge signal accumulated in the light receiving unit before the second light emission, and accumulation in the light receiving unit before and after the second light emission. Image generating means for generating predetermined image data based on second image data obtained by reading out a charge signal to be read from a second field of the plurality of fields;
An imaging apparatus comprising: The imaging apparatus according to claim 1,
The pixel array of the light receiving unit is
A color filter array;
Each of the first and second fields is
An imaging apparatus comprising all the color components of the color filter array. The imaging apparatus according to claim 1 or 2,
The image generating means
An image pickup apparatus that generates the predetermined image data by adding a pixel value in the first image data and a pixel value in the second image data. The imaging apparatus according to claim 1 or 2,
The image generating means
The predetermined image data is generated by adding the pixel values in the first image data and the pixel values in the second image data while converting gradation characteristics. apparatus. The imaging device according to any one of claims 1 to 4,
An imaging apparatus, wherein a light emission amount in the first light emission is different from a light emission amount in the second light emission.

Images