JP4286077B2 - Camera with flash light control function - Google Patents

Description

に示す（式１）〜（式３）と、図９、図１０（ａ）、又は１０（ｂ）で示した各光量検出値によって算出することができる。
【００６３】
なお、ここでは、主に撮像素子１２の出力からストロボ発光時間を求める方法を説明したが、定常光成分除去積分によって得られた積分値Ｖ_ＩＮＴ１は、（式２）又は（式３）のＩ_Ｍ２−Ｉ_Ｍ１に対応するものである。したがって、Ｖ_ＩＮＴ１とこのＶ_ＩＮＴ１をＩ_Ｍ２−Ｉ_Ｍ１に変換するための変換係数Ｋを用いた
【数２】

を用いてストロボ発光時間ｔ_ＳＴを算出することができる。
【００６４】
また、単にストロボ部２１を用いて露出の不足分を補うだけでなく、図１０（ｂ）に示す、外光による露出量に対するストロボ光による露出量の比率（以下、ストロボ寄与率と称する）を考慮してストロボ制御を行ってもよい。このように、ストロボ寄与率を考慮してストロボ発光量を制御することにより、背景と主要被写体である人物との明るさのバランスを調整することができる。
【００６５】
一般にストロボ光は風景などの背景には届かないので、ストロボ寄与率を上げると人物の露出量に対して背景の露出量が相対的に小さくなっていく。逆にストロボ寄与率を低くすると、背景の露出量に対して人物の露出量が相対的に小さくなっていく。これらのことから、状況に応じてストロボの寄与率を切り換えて露出制御を行うことが好ましい。例えば、背景が空の場合などは、露出を多少アンダーにした方が空の青みが増し、また背景が雪景色などの場合では、露出をオーバーにしないと雪の白さが正しく撮影されない。
【００６６】
このようなストロボ寄与率の切り換えは、例えば図１１に示すようなフローチャートに従って行われる。
【００６７】
このフローチャートにおいて、演算制御回路１７は、ストロボ部２１を予備発光させた後、撮像素子１２を用いて主要被写体１１０を含む画面１１０ａ内の像信号を検出する（ステップＳ２１）。次に、演算制御回路１７は、画面１１０ａの中で、ストロボ光による反射信号光成分が検出できず、ストロボ光が露出に寄与しない領域を判別する（ステップＳ２２）。例えば、図１のようなシーンでは、図１２（ａ）に示す画面１１０ａの中から人物部１１０を除いた背景部１１０ｂが、ストロボ光が露出に寄与しない領域となる。
【００６８】
ストロボ光が露出に寄与しない背景部１１０ｂを判別した後、演算制御回路１７は、撮像素子１２を用いて背景部１１０ｂにおける像信号のコントラスト変化Ｃ_Ｂを検出する（ステップＳ２３）。ここでは、単に背景部１１０ｂの全領域における明暗の差を検出していくのではなく、例えば図１２（ｂ）において符号１１０ｃや符号１１０ｄで示したような代表部分のコントラスト変化を検出する。ここで「コントラスト変化の検出」とは、低輝度部分と高輝度部分の差（所謂コントラスト）がどのように分布しているのかを調べるものである。また、代表部分は、例えば図１２（ｃ）に示すような像信号において空間周波数が大きい領域、明るい領域、彩度が高い領域（これについては後で説明する）等である。また、図１２（ｂ）のように代表部分を複数検出できるようにしておき、それら全ての領域についてステップＳ２４以後の制御を行うようにしてもよいし、代表部分のコントラスト変化を全て加えた値を用いてステップＳ２４以後の制御を行うようにしてもよい。更には代表部分のコントラスト変化の平均値を用いてもよい。
【００６９】
また、コントラスト変化Ｃ_Ｂは、例えば図１２（ｃ）に示す像信号において、背景部の明暗変化ΔＢと背景部の周期Ｆとの積から求めてもよい。また、重要背景部の判別は、コントラストの変化から判別するだけでなく、背景部分における２次元的な像の形状を認識することで判別してもよい。
【００７０】
このように、背景の代表部分におけるコントラスト変化を検出するのは、背景の代表部分における細かなパターンが正しく再現されるような露出制御を行うためである。ここで、ステップＳ２３で検出したコントラスト変化が小さい場合には、背景はそれほど重要ではないと考える。
【００７１】
ここで、背景の明るさを基準にして露出制御を行う場合、背景が暗いときには露出時間が長くなってしまい、手ぶれなどが生じる可能性が高くなる。一方、背景が明るい場合には、主要被写体に対するストロボ寄与率を上げる、即ちストロボ発光量を上げる必要があるので、エネルギーのロスにつながる。
【００７２】
そこで、本第１の実施形態では、背景が重要な場合にのみ、背景の明るさを基準にして露出制御を行い、背景のコントラストが正しく再現されるようにする。
【００７３】
即ち、演算制御回路１７は、背景が重要であるかを判別するために、ステップＳ２３で検出したコントラスト変化Ｃ_Ｂが所定の大きさＣ_０よりも大きいか否かを判定する（ステップＳ２４）。この判定において、Ｃ_ＢがＣ_０よりも大きいと判定した場合には、そのコントラスト変化Ｃ_Ｂを出力する背景が重要であると判別する。そこで、演算制御回路１７は、この背景部分（例えば、図１２（ｂ）の背景部１１０ｃ）のコントラストが正しく再現されるような露出制御を行う。
【００７４】
即ち、演算制御回路１７は、この重要背景部１１０ｃの像信号が飽和しないような露出時間ｔ_Ｅを決定する。このために、演算制御回路１７は背景の平均的な輝度Ｂ_Ｂから、仮の露出時間ｔ_Ｅを決定する（ステップＳ２５）。更に、演算制御回路１７は、重要背景部１１０ｃにおける像信号の明暗の差ΔＢを考慮して、重要背景部１１０ｃにおける像信号の最大値Ｂ_Ｂ＋ΔＢ/２が、露出時間ｔ_Ｅの積分によって飽和してしまうか否かを判定する（ステップＳ２６）。このステップＳ２６の判定において、像信号の最大値が積分後に飽和してしまうと判定した場合に、演算制御回路７は、新たな露出時間ｔ_Ｅを、元のｔ_Ｅの１/２に設定する（ステップＳ２７）。なお、ここでは、露出時間ｔ_ＥをステップＳ２５で決定したｔ_Ｅの１/２に設定しているが、これに限るものではない。
【００７５】
一方、ステップＳ２６の判定において、重要背景部分１１０ｃにおける像信号の最大値が積分後に飽和しないと判定した場合に、演算制御回路１７は、ステップＳ２５で決定したｔ_Ｅを露出時間に設定する。
【００７６】
また、ステップＳ２４の判定において、コントラスト変化Ｃ_Ｂが所定の大きさＣ_０以下であると判定した場合に、演算制御回路１７は、背景部の色（彩度）などから重要背景部を判別する。
【００７７】
例えば、図１２（ｂ）の背景部１１０ｄのように、背景部が青空の場合等には、主要被写体１１０の明るさのみを考慮して露出制御を行うと、背景部１１０ｂが白く飛んでしまうことがある。このような場合にも、本第１の実施形態では、主要被写体に対するストロボ寄与率を上げて露出制御を行うことにより、主要被写体１１０と背景部１１０ｂの両方で正しい発色の画像が得られるようにする。
【００７８】
即ち、コントラスト変化Ｃ_Ｂが所定の大きさＣ_０以下であると判定した場合に、演算制御回路１７は、撮像素子１２の出力からＲＧＢの色信号を検出し、この色信号と輝度信号Ｙとから、色差（Ｒ−Ｙ）及び（Ｂ−Ｙ）を求め、これらのうちで大きいほうの値を彩度判定値Ｓ_Ｂとして選択する（ステップＳ２８）。この彩度判定値Ｓ_Ｂは、色が鮮やかになる、即ち彩度が高いほど大きくなる値である。そこで、演算制御回路１７は、Ｓ_Ｂが所定値Ｓ_０よりも大きいか否か、即ち背景の彩度が高いか否かを判定する（ステップＳ２９）。この判定において、即ちＳ_Ｂが所定値Ｓ_０よりも大きいと判定した場合には、この背景部を彩度の高い重要背景部１１０ｄと判別し、この背景部における撮像素子１２の出力から背景の明るさＹを、例えば
Ｙ＝０．２６３Ｒ＋０．６５５Ｇ＋０．０８１Ｂ （式５）
の式を用いて求める（ステップＳ３０）。なお、（式５）のＹはＣＩＥ表色系の例である。ここで、部品のできや色の考え方等によって（式５）のＲＧＢの各係数は異なるので、図１１では、
Ｙ＝ａＲ＋ｂＧ＋ｃＢ （式６）
のように一般化して表現している。このようにして、背景の明るさＹが得られた後、演算制御回路１７は、求めたＹより露出時間ｔ_Ｅを決定する（ステップＳ３１）。
【００７９】
また、ステップＳ２９の判定において、彩度が低い、即ちＳ_Ｂが所定値Ｓ_０以下であると判定した場合には、手ぶれが起きるまでの時間（手ぶれ秒時）から露出時間ｔ_Ｅを決定する（ステップＳ３２）。
【００８０】
ステップＳ３１又はＳ３２で露出時間ｔ_Ｅを決定した後、演算制御回路１７は、このｔ_Ｅより（式３）を用いてストロボ発光時間ｔ_ＳＴを算出し（ステップＳ３３）、その後、このフローチャートの制御を抜ける。
【００８１】
このように背景部分の色を判定し、この背景部分における撮像素子の色バランスが偏っている場合には、その特徴的な色が白く飛んでしまわないように主要被写体に対するストロボ寄与率を上げて露出時間を短くする。このよう露出時間を短くすることにより、例えば青空や夕焼け空等の背景が撮影時に白く飛んでしまうようなことがない。
【００８２】
ここで、ステップＳ２２のストロボ光が寄与しない領域を判別する手法の変形例を図１３（ａ）及び図１３（ｂ）を参照して説明する。図１３（ａ）の例は、被写体までの距離によって判別を行う例である。まず、演算制御回路１７は、測距部２３によって画面内における複数のポイントの距離を算出して、これら距離の分布を検出する（ステップＳ４１）。次に、検出した距離の分布において、例えば最も近い距離を主要被写体の距離Ｌ_Ｓとして決定する（ステップＳ４２）。その後、演算制御回路１７は、この決定したＬ_Ｓから充分に遠距離（ここでは、４倍の距離）を出力するポイントをストロボ光が露出に寄与しない領域と判別する（ステップＳ４３）。
【００８３】
また、図１３（ｂ）の例では、図８で説明した差分ΔＩ_Ｍや積分値Ｖ_ＩＮＴ１から判別を行う例である。即ち、演算制御回路１７は、差分ΔＩ_Ｍが所定値ΔＩ_０よりも小さい領域（ステップＳ５１）と積分値Ｖ_ＩＮＴ１が所定値Ｖ_０よりも小さい領域とをストロボ光が露出に寄与しない領域と判別する（ステップＳ５２）。
【００８４】
以上説明したように、本第１の実施形態によれば、ストロボ光と背景の明るさとのバランスを考慮した露出制御によってストロボ発光時間を制御しているので、色再現性を高くすることができる。また、敏感な定常光除去積分回路を利用すれば、予備発光時のストロボ発光量を微弱にでき、眩しさのない省エネ効果にすぐれた予備発光方式にすることができる。
【００８５】
［第２の実施形態］
図１４は、本発明の第２の実施形態のカメラにおける電気回路のブロック構成図である。なお、本カメラの一部の構成は、上述した第１の実施形態のカメラと同様である。したがって、同様の構成部材については同じ符号を附してその詳細な説明は省略する。この第２の実施形態は、ＴＴＬ（Trough The Lens）ダイレクト調光方式を用いた例である。
【００８６】
即ち、本第２の実施形態のカメラ１は、上記した第１の実施形態の構成に加えて、可動ミラー３０と、ファインダ光学系（スクリーン３１、ペンタゴナルダハプリズム（以下ペンタプリズムと略記する）３２、接眼レンズ３３等で構成される）と、ファインダ内測光センサ３４と、測光部３５と、サブミラー３６と、フィールドレンズ３７と、光路屈曲鏡３８と、再結像レンズ３９と、センサアレイ４０と、シャッタ幕４１と、測光光学系４２と、ボディ内測光センサ４３と、調光部４４と、表示制御部４５と、電子モニタ４６とを含む。
【００８７】
可動ミラー３０は、シャッタ幕４１と撮影光学系１１との間の空間において、撮影光学系１１の光路上から退避する位置（以下、退避位置３０ａと称する）と撮影光学系１１の光路上に配置される位置（以下、通常位置３０ｂと称する）との間で回動自在に構成されている。ここで、当該可動ミラー３０が通常位置３０ｂに配置されたときには、撮影光学系１１の光軸に対して角度略４５度だけ傾いた状態で固定される。この状態において、可動ミラー３０の反射面は、ファインダ光学系の側を向くように設定されている。
【００８８】
即ち、可動ミラー３０が通常位置３０ｂにある場合、撮影光学系１１を介して入射した光束は、可動ミラー３０で反射されてファインダ光学系に導かれる。ファインダ光学系では、入射した光束をスクリーン３１において光学像として結像させると共に結像された像をペンタプリズム３２に導く。ペンタプリズム３２は、スクリーン３１を透過した像を接眼レンズ３３方向（即ち、カメラ１の後方）へと導くと同時に、像の左右を反転させる。接眼レンズ３３は入射してきた像を拡大する。これにより、撮影者１１１は、被写体を観察することができる。
【００８９】
更に、ペンタプリズム３２の近傍には、ファインダ内測光センサ３４が設けられている。このファインダ内測光センサ３４は、ペンタプリズム３２に入射した光束の一部を受光して所定の電気信号を測光部３５に出力する。ここで、ファインダ内測光センサ３４は、図１５に示すように撮影画面内の所定の受光領域において測光動作を行い得るように形成されている。即ち、ファインダ内測光センサ３４は、略中央部近傍の所定の領域を測光する受光部３４ａと、略周縁部近傍の所定の領域を測光する受光部３４ｂとからなり、例えば逆光状態の検出も可能に構成されている。
【００９０】
測光部３５は、ファインダ内測光センサ３４から入力された電気信号に基づいて測光動作を行い、被写体の明るさを検出する。この測光部３５の検出結果に基づいて、演算制御回路１７は、ストロボ制御部２２を制御する。
【００９１】
また、可動ミラー３０の一部の領域、例えば略中央部近傍の領域は、撮影光学系１１からの光束の一部を透過させ得るように半透過鏡によって構成されている。そして、この半透過鏡で構成される領域に対向する部位には、サブミラー３６が配設されている。
【００９２】
即ち、サブミラー３６は、可動ミラー３０の背面側、即ち撮像素子１２に対向する側の面に対して、その一端部が所定方向に回動自在となるように軸支されており、これにより、サブミラー３６の反射面は、上述した可動ミラー３０の半透過鏡の領域に対向するよう配置される。即ち、サブミラー３６は、可動ミラー３０が通常位置３０ｂに配置されたときに、可動ミラー３０に対して図１４に示すような所定の角度をなすように配置されている。また、サブミラー３６は、可動ミラー３０が退避位置３０ａに配置されたときには、可動ミラー３０に対して略平行となる所定の位置に配置される。これにより、可動ミラー３０が退避位置３０ａに移動すると同時にサブミラー３６も撮影光学系１１の光路上から退避する。
【００９３】
即ち、可動ミラー３０及びサブミラー３６が通常位置にあるときには、撮影光学系１１を透過した入射光束の一部は、可動ミラー３０の半透過鏡領域を透過した後、サブミラー３６によって反射される。この反射された光束は、フィールドレンズ３７を透過し、更に光路屈曲鏡３８によってその光路が所定の方向へと折り曲げられた後、再結像レンズ３９を透過する。そして、センサアレイ４０の受光面上には１対の被写体像が結像する。センサアレイ４０は、受光した被写体像を電気信号に変換して演算制御回路１７に出力する。これを受けて演算制御回路１７は、所定の合焦処理を行う。
【００９４】
ここで、この合焦処理は、一般的に適用されているＴＴＬ位相差検出方式でよい。このＴＴＬ位相差検出方式について簡単に説明する。この方式において、演算制御回路１７は、レンズ駆動部１８を制御して撮影光学系１１をレンズ光軸方向に移動させながら、センサアレイ４０の出力を監視し、そして、センサアレイ４０から出力される一対の被写体像が所定の位置関係になったときに合焦状態であると判定して、その時点で撮影光学系１１の駆動を停止させる。
【００９５】
また、撮像素子１２の受光面側の近傍には、上述したようにシャッタ幕４１が配設されている。即ち、撮像素子１２は、当該シャッタ幕４１が開状態となっている期間のみ撮影光学系１１からの光束を受光し得るように構成されている。ここで、シャッタ幕自体の構成は、従来の一眼レフレックス方式のカメラにおいて一般的に利用されているものが適用されている。このシャッタ幕４１の構成について、図１６の概略図を用いて簡単に説明する。
【００９６】
図１６に示すようにシャッタ幕４１は、先幕４１ａ及び後幕４１ｂの二つの幕部材によって構成されている。通常状態においては先幕４１ａが撮像素子１２の受光面の前面に配置され、当該撮像素子１２の受光面は遮蔽された状態にある。
【００９７】
ここで、露出動作が実行されると、まず可動ミラー３０及びサブミラー３６が所定の退避位置３０ａに移動する。この状態で先幕４１ａが矢印Ｙ１方向に動き出す。続いて所定の時間を置いてから後幕４１ｂがＹ２方向（Ｙ１と同じ方向である）に動き出す。したがって、先幕４１ａと後幕４１ｂとの間には所定の隙間が生じることになる。この隙間寸法を調節する、即ち先幕４１ａ及び後幕４１ｂの動き出す時間を調節することにより撮像素子１２への露出時間（即ちシャッタ速度）を調節することができる。
【００９８】
また、先幕４１ａの表面には、この先幕４１ａの表面で反射する光束が標準反射率となるように所定のパターンが形成されている。即ち、先幕４１ａの表面で反射された光束は、測光光学系４２を介してボディ内測光センサ４３で受光される。ボディ内測光センサ４３は、この入射された光束を電気信号に変換して調光部４４に出力する。
【００９９】
ここで、ボディ内測光センサ４３は、図１７に示すように、その受光面全域を三つに分割した形態の三つの測光領域４３ａ、４３ｂ、及び４３ｃを有して構成されている。例えば、図１８に示すような構図枠（撮影画面１２１）を設定し、予備発光方式の調光制御を用いて撮影を行う場合においては、図１７に示すボディ内測光センサ４３の測光領域４３ｃのみを用いて測光を行う。これは、例えば、図１８に例示する構図のように太陽等の高輝度被写体が撮影画面１２１内に含まれているときに、その高輝度被写体を含めて測光を行うと測光値に誤差が生じてしまうのを避けるための措置である。
【０１００】
調光部４４は、ボディ内測光センサ４３から出力された電気信号に基づいて、被写体１１０からの入射光量の測定及び所定の調光制御を行う。
【０１０１】
ここで、従来の一般的なカメラにおけるＴＴＬ調光方式の調光制御では、例えば露出動作中にフイルム表面からの反射光束を受光するようにしているものもある。しかし、撮像素子１２の表面は、一般的に光の反射に正反射成分が多くなるので、本第２の実施形態のカメラ１においては、入射した光束を標準反射率で拡散反射させる先幕４１ａの表面からの反射光束により測光を行う。
【０１０２】
表示制御部４５は、演算制御回路１７に制御され、画像信号処理部１４から出力された画像データに基づいて、例えば液晶モニタ（ＬＣＤ）等の電子モニタ４６に画像表示を行う。この電子モニタ４６により、撮影終了後に撮影結果をすぐに確認することができる。また、この電子モニタ４６を上記したファインダ光学系の代わりに用いることもできる。これについては後に詳述する。
【０１０３】
ここで、上記した（式４）の関係によれば、適正露出量Ｉ_Ｍ４に対してストロボ光以外で露出される量を予測するための光量検出量（撮像素子１２の出力）Ｉ_Ｍ１と、ストロボ光が被写体からどれだけ反射してくるのかを示す値（積分結果）Ｖ_ＩＮＴ１とを別々に検出して計算してよいということがわかる。
【０１０４】
そこで、本第２の実施形態では、撮像素子１２に入射する光の光量を正確に測定するために、標準反射率の先幕４１ａで反射された光束の光量Ｉ_Ｍ１をボディ内測光センサ４３で検出する。これにより、取り付けられた撮影光学系に依存しない高精度の露出制御を行うことができる。
【０１０５】
また、露出におけるストロボ光の効果は、適宜、定常光成分除去積分機能付きの測光手段の出力を併用して予測する。これにより良好なストロボ撮影を行うことが可能である。ここで、測光手段の機能である定常光成分除去積分機能は、カメラ１のボディ内測光センサ４３に持たせるようにしてもよいが、上述したように、積分結果Ｖ_ＩＮＴ１を検出するのはボディ内測光センサ４３でなくともよい。そこで、本第２の実施形態では、定常光除去積分機能をファインダ内測光センサ３４に持たせる。即ち、本第２の実施形態では、上記した第１の実施形態における撮像素子１２を用いた測光をボディ内測光センサ４３により行い、センサアレイ２５ａ，２５ｂを用いた測光をファインダ内測光センサ３４により行う。
【０１０６】
このような場合には、例えば、図１５に示す受光部３４ａに設けられたセンサに定常光除去機能を持たせ、ここに入射する反射光を検出できるようにしておけば、撮影時に、この受光部３４ａに主要被写体を入れるようにストロボ予備発光及び露出を行うことで、ストロボ光がその受光部３４ａにおいてどれだけ寄与できるのかを予測することが可能である。なお、定常光成分除去積分機能は、ファインダ内センサ３４でなく、第１の実施形態と同様にセンサアレイ４０に持たせてもよい。
【０１０７】
図１９にこのような構成を有するカメラのストロボ撮影時のタイミングチャートを示し、図２０にこのストロボ撮影時の制御手順についてのフローチャートを示す。
【０１０８】
即ち、演算制御回路１７は、ストロボ部２１を予備発光させた後、ファインダ内測光センサ３４で測光を行い、積分結果Ｖ_ＩＮＴ１を取得する（ステップＳ６１）。このときは、可動ミラー３０を通常位置３０ｂに位置させておく。次に、可動ミラー３０を退避位置３０ａに退避させた後（ステップＳ６２）、ストロボを発光せずにボディ内測光センサ４３で測光を行い、そのときの露出量Ｉ_Ｍ１を取得する（ステップＳ６３）。次に演算制御回路１７は、ストロボ部２１を予備発光させて、ボディ内測光センサ４３で測光を行い、そのときの露出量Ｉ_Ｍ２を取得する（ステップＳ６４）。ここで、図１７で示したような３分割センサの場合には、ストロボ発光前後で最も光量差の大きかったセンサからの出力を露出量Ｉ_Ｍ１及びＩ_Ｍ２として採用する。ここで、シャッタ幕４１は標準反射率なので、ここから反射する光の量から所定シャッタ速度時（ｔ_Ｅ）の露出量を予測することができる。
【０１０９】
即ち、演算制御回路１７は、露出量Ｉ_Ｍ１とＩ_Ｍ２を比較して両者の差が少ないか否かを判定する（ステップＳ６５）。この判定において両者の差が少ないと判定した場合には、撮影シーンが明るく、ストロボ光による反射信号成分のみを抽出するのは、困難であるとして、ファインダ内測光センサ３４で検出した積分結果Ｖ_ＩＮＴ１と（式４）を用いてストロボ発光量（即ち、発光時間ｔ_ＳＴ）を決定する（ステップＳ６６）。
【０１１０】
一方、ステップＳ６５の判定において、Ｉ_Ｍ１とＩ_Ｍ２との差が大きいと判定した場合には、Ｉ_Ｍ１及びＩ_Ｍ２と（式３）を用いて発光時間ｔ_ＳＴを決定する（ステップＳ６７）。
【０１１１】
ストロボ部２１の発光時間ｔ_ＳＴを決定した後、演算制御回路１７は、シャッタ幕４１を開いて（ステップＳ６８）、露出を開始する。そして、演算制御回路１７は、シャッタ幕４１が全開した所でストロボ部２１を発光させ（ステップＳ６９）。所定時間ｔ_Ｅ経過後にシャッタ幕４１を閉じて（ステップＳ７０）、撮像素子１２に入る被写体からの光を遮断して露出制御を終了する。
【０１１２】
ここで、図１４のような所謂一眼レフレックスカメラでは、一般にストロボ制御が困難であり、閃光発光はシャッタ幕４１が全開のときにしか使用できない。このため、高速シャッタ時でも、比較的長時間にわたって同じ明るさでストロボ部２１を発光させる制御を行う必要がある。ここで、このような発光を、ここではフラット発光と称する。しかし、このようなフラット発光を用いたストロボ制御では、あまり遠距離まで光を照射することができない。
【０１１３】
また、一眼レフレックスカメラは、魚眼レンズのようなものを含む広角から望遠までの様々な画角を有するレンズに加え、マクロ機能に対応したマクロレンズなどの種々のレンズを選択して用いることができる。次に、このような種々のレンズのうち、マクロレンズを用いた場合のストロボ発光量の制御を適用した場合について説明する。
【０１１４】
図２１は、図１４を簡略化して図示したものである。例えば、図２１に示すように、主要被写体１１０として、例えば昆虫などをマクロで撮影する際には、ファインダ光学系を介して被写体１１０を確認して撮影を行うよりも、電子モニタ４６に、撮像素子１２で取得した画像をリアルタイムに表示させ、この電子モニタ４６上に表示させた画像により被写体１１０を確認して撮影を行うほうが、様々なアングルからの撮影が可能である。また、ファインダを覗き込みながら撮影を行う必要もないので撮影の自由度が高い。
【０１１５】
ここで、電子モニタ４６に画像をリアルタイムで表示させる際には、図２１に示すように可動ミラー３０及びサブミラー３６を撮影光学系１１の光路上から退避させ、シャッタ幕４１を開いておく必要がある。このようなマクロ撮影時の制御を図２２のフローチャートを参照して説明する。
【０１１６】
即ち、図示しないマクロモードボタンが撮影者によって操作されると、演算制御回路１７は、それを判定して図２１に示すように可動ミラー３０及びサブミラー３６を撮影光学系１１の光路上から退避させ（ステップＳ７１）、続いてシャッタ幕４１を開く（ステップＳ７２）。その後、演算制御回路１７は、撮像素子１２に撮像動作を開始させると同時に、演算制御回路１７は、画像信号処理部１４に撮像素子１２から像信号の読み出しを開始させ、画像信号処理部１４で処理された画像を、表示制御部４５を介して電子モニタ４６に表示させる（ステップＳ７３）。
【０１１７】
次に演算制御回路１７は、図示しないレリーズスイッチがＯＮされたか否かを判定することにより、撮影動作を開始するかを否かを判定し（ステップＳ７４）、レリーズスイッチがＯＮされるまで、像信号の読み出し及び画像表示を続ける。一方、ステップＳ７４の判定において、レリーズスイッチがＯＮされたと判定した場合に、演算制御回路１７は、撮影動作を開始する。
【０１１８】
ここで、マクロ撮影により撮影した写真にも、図２３（ａ）のように主要被写体と共に背景も正しく撮影されていることが重要な場合と、図２３（ｂ）のように主要被写体のみがクローズアップされていればよく、背景はそれほど重要でない場合とがある。そこで、以後は第１の実施形態と同様に背景が重要であるか否かを判定して、背景が重要である場合には、その重要背景部分の明るさを基準にして露出制御を行う。
【０１１９】
即ち、露出制御開始後、まず、演算制御回路１７は、ストロボ部２１を予備発光させ（ステップＳ７５）、被写体からの反射信号光が検出されない領域をストロボ光が寄与しない背景部１１０ｂの領域と判別する（ステップＳ７６）。次に、この背景部１１０ｂの領域において図１１（ａ）のステップＳ２８及びＳ２９で説明した彩度判定を行う。即ち、撮像素子１２の出力から色差（Ｒ−Ｙ）及び（Ｂ−Ｙ）を求め、これらのうちで大きいほうの値を彩度判定値Ｓ_Ｂとして選択する（ステップＳ７７）。そして、このＳ_Ｂが所定値Ｓ_０よりも大きいか否か、即ち彩度が所定値よりも高いか否かを判定し（ステップＳ７８）、彩度が高いと判定した場合に、演算制御回路１７は、背景が重要であると判別して、背景の明るさを基準にして露出時間ｔ_Ｅを決定する（ステップＳ７９）。一方、ステップＳ７８の判定において、彩度が低いと判定した場合には、背景が重要でないので、手ぶれ秒時に基づいて露出時間ｔ_Ｅを決定する（ステップＳ８０）。
【０１２０】
このようにして露出時間ｔ_Ｅを決定した後、演算制御回路１７は、このｔ_Ｅから（式３）を用いてストロボ発光時間ｔ_ＳＴを算出する（ステップＳ８１）。その後、ストロボ部２１を発光させて露出を開始して（ステップＳ８２）、露出時間ｔ_Ｅが経過してからシャッタ幕４１を閉じて露出を終了させる（ステップＳ８３）。そして、リアルタイムの画像表示を終了させた後、撮影結果を電子モニタ４６上に表示させて（ステップＳ８４）、このフローチャートの制御を終了する。
【０１２１】
なお、高速シャッタ時では、シャッタ幕４１が開の状態から閉の状態になるまでの時間も露出結果に影響してしまうので、この場合には、図示しない絞りを絞ることによって露出時間を長くして、シャッタ幕４１が閉じるまでの時間を無視できるようにしてもよい。
【０１２２】
以上説明したように、本第２の実施形態によれば、レンズ交換式の一眼レフカメラにおいても、撮像素子の出力を有効に利用して背景の美しさを引き出したストロボ撮影を行うことができる。
【０１２３】
以上実施形態に基づいて本発明を説明したが、本発明は上記した実施形態に限定されるものではなく、本発明の要旨の範囲内で種々の変形や応用が可能なことは勿論である。
【０１２４】
さらに、上記した実施形態には種々の段階の発明が含まれており、開示される複数の構成要件の適当な組合せにより種々の発明が抽出され得る。例えば、実施の形態に示される全構成要件からいくつかの構成要件が削除されても、発明が解決しようとする課題の欄で述べた課題が解決でき、発明の効果の欄で述べられている効果が得られる場合には、この構成要件が削除された構成も発明として抽出され得る。
【０１２５】
【発明の効果】
以上説明したように、本発明によれば、主要被写体に対して背景がどのようなシーンであるのかを考慮して適正なストロボ制御を行い、画面全体として調和が取れ、雰囲気が豊かであり、色再現性のよい写真を撮影することが可能なストロボ調光機能付きカメラを提供することができる。
【図面の簡単な説明】
【図１】 本発明の第１の実施形態に係るストロボ調光機能付きカメラにおける電気回路構成を示すブロック構成図である。
【図２】 定常光成分除去回路の電気回路図である。
【図３】 定常光成分除去回路の動作時のタイミングチャートである。
【図４】 定常光成分除去回路の非動作時のタイミングチャートである。
【図５】 ストロボ調光に関る重要機能を抜き出して記したブロック図である。
【図６】 撮像素子及びセンサアレイの検出範囲について説明するための図である。
【図７】 図７（ａ）は撮像素子の画素位置に応じた像信号の分布図であり、図７（ｂ）はセンサアレイの画素位置に応じた像信号の分布図である。
【図８】 本発明の第１の実施形態におけるストロボ撮影時の制御手順を示すフローチャートである。
【図９】 ストロボ発光を行わない場合の露出時間に対する露出量を示したグラフである。
【図１０】 図１０（ａ）はストロボ発光を行った場合の露出時間に対する露出量を示したグラフであり、図１０（ｂ）はストロボ寄与率について説明するためのグラフである。
【図１１】 ストロボ寄与率の切り換え制御について示したフローチャートである。
【図１２】 図１２（ａ）はストロボ光が寄与しない領域である背景部を説明するための図であり、図１２（ｂ）は重要な背景を含む撮影シーンの例を示す図であり、図１２（ｃ）は図１２（ｂ）のシーンにおける像信号の分布図である。
【図１３】 図１３（ａ）はストロボ光が寄与しない領域を判別するための制御を示すフローチャートにおける第１の変形例であり、図１３（ｂ）はストロボ光が寄与しない領域を判別するための制御を示すフローチャートにおける第２の変形例である。
【図１４】 本発明の第２の実施形態に係るストロボ調光機能付きカメラにおける電気回路構成を示すブロック構成図である。
【図１５】 ファインダ内測光センサの構成について説明するための図である。
【図１６】 シャッタ幕について説明するための図である。
【図１７】 ボディ内測光センサの測光領域について説明するための図である。
【図１８】 高輝度物体が存在するシーンの例を示す図である。
【図１９】 本発明の第２の実施形態におけるストロボ撮影時のタイミングチャートである。
【図２０】 本発明の第２の実施形態におけるストロボ撮影時の制御手順を示すフローチャートである。
【図２１】 第２の実施形態における重要機能を抜き出して記したブロック構成図である。
【図２２】 本発明の第２の実施形態におけるマクロモード時のストロボ制御について示したフローチャートである。
【図２３】 図２３（ａ）はマクロ撮影の画像の例であって背景が重要な場合の図であり、図２３（ｂ）はマクロ撮影の画像の例であって背景が重要でない場合の図である。
【符号の説明】
１…カメラ、１１…撮影光学系、１２…撮像素子、１３，２８…ＡＤ変換部、１４…画像信号処理部、１５…記録媒体部、１６…コントラスト検出部、１７…演算制御回路、１８…レンズ駆動部、１９…レンズ位置検出部、２０…操作スイッチ、２１…ストロボ部、２２…ストロボ制御部、２３…測距部、２４ａ，２４ｂ…受光レンズ、２５ａ，２５ｂ，４０…センサアレイ、２６…積分回路、２７…定常光成分除去回路、３０…可動ミラー、３１…スクリーン、３２…ペンタプリズム、３３…接眼レンズ、３４…ファインダ内測光センサ、３５…測光部、３６…サブミラー、３７…フィールドレンズ、３８…光路屈曲鏡、３９…再結像レンズ、４１…シャッタ幕、４２…測光光学系、４３…ボディ内測光センサ、４４…調光部、４５…表示制御部、４６…電子モニタ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a camera with a flash light control function, and more particularly to a camera with a flash light control function capable of performing flash photography by adjusting the exposure balance between a background and a main subject.
[0002]
[Prior art]
For example, Patent Documents 1 to 3 propose techniques for performing strobe light emission by adjusting the exposure balance between the background and the main subject during strobe shooting.
[0003]
In Patent Document 1, strobe light emission is performed by determining the ratio of the exposure amount by the strobe light to the exposure amount by the external light from the luminance of the subject. In Patent Document 2, the amount of strobe light emission is controlled by a histogram pattern indicating the ratio of pixels to the brightness obtained by an image sensor in a digital camera. Furthermore, in Patent Document 3, the exposure is determined from the photometric values of the main subject and the background.
[0004]
[Patent Document 1]
Japanese Patent No. 3177742
[0005]
[Patent Document 2]
JP 2001-296578 A
[0006]
[Patent Document 3]
Japanese Patent Laid-Open No. 2002-229094
[0007]
[Problems to be solved by the invention]
In the technologies proposed in Patent Documents 1 to 3, strobe control is performed based on the brightness of the main subject and the background, and the background of the main subject is fully considered. Strobe control is not performed.
[0008]
The present invention has been made in view of the above points, and performs an appropriate strobe control in consideration of what kind of scene the background is for the main subject, so that the entire screen is harmonized and has an atmosphere. An object of the present invention is to provide a camera with a stroboscopic light control function that is capable of taking pictures that are rich and have good color reproducibility.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a camera with a strobe light control function according to the first aspect of the present invention comprises a light emitting means for irradiating strobe light, and the strobe light from the light emitting means is exposed. Contributing area and An area discriminating unit that discriminates an area that does not contribute and an area discriminated by the area discriminating unit. The strobe light does not contribute to exposure Image signal detection means for detecting an image signal in the region; The contrast change or saturation of the area where the strobe light does not contribute to the exposure is detected from the image signal in the area where the strobe light does not contribute to the exposure, and the area where the detected contrast change or saturation is high is determined to have high importance. Then, the exposure control is performed based on the area determined to be high in importance, and the strobe light is controlled by the light emitting means according to the exposure result. Control means.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a block configuration diagram showing an electric circuit configuration of a camera with a flash light control function (hereinafter referred to as a camera) according to a first embodiment of the present invention.
[0023]
The camera according to the first embodiment photoelectrically converts a subject image formed by a photographing optical system using an imaging element such as a CCD, and an electric signal (image signal) obtained by the photoelectric conversion is converted. Recording in a predetermined form on a predetermined recording medium. Here, in the first embodiment, a so-called compact type electronic camera in which the configuration between the photographing optical system and the image sensor is relatively simple will be described as an example.
[0024]
That is, as shown in FIG. 1, the camera 1 of the first embodiment includes a photographing optical system 11, an image sensor (image signal detection means) 12, and an AD conversion unit 13 (referred to as an AD unit 13 in FIG. 1). An image signal processing unit (color signal detection unit) 14, a recording medium unit 15, a contrast detection unit 16, an arithmetic control circuit (region discrimination unit, control unit) 17, a lens driving unit 18, and a lens position detection. A unit 19, an operation switch 20, a strobe unit (light emitting unit) 21, a strobe control unit 22, and a distance measuring unit (distance distribution detecting unit) 23.
[0025]
The photographing optical system 11 is composed of a plurality of optical lenses and the like, and collects a reflected light beam from the subject to form a subject image on the image sensor 12. The image sensor 12 serving as an image signal detection unit generates an image signal by performing a photoelectric conversion process or the like on a subject image incident via the photographing optical system 11. The AD conversion unit 13 converts an analog image signal generated and output by the image sensor 12 into a digital image signal of a predetermined format and outputs the digital image signal to the image signal processing unit 14.
[0026]
The image signal processing unit 14 performs predetermined image processing on the digital image signal converted by the AD conversion unit 13, for example, color correction, gradation correction, and γ (gamma) correction of an image to be represented by the image data. After the adjustment and the like, the image data is further generated by performing compression in a format suitable for recording on the recording medium unit 15. The recording medium unit 15 includes various media that record image data in a predetermined form and the driving unit thereof, and records the image data generated by the image signal processing unit 14.
[0027]
The image signal processing unit 14 also outputs a digital image signal subjected to predetermined image processing to the contrast detection unit 16. The contrast detection unit 16 detects the contrast signal of the subject from the output of the image signal processing unit 14 and outputs it to the arithmetic control circuit 17.
[0028]
The arithmetic control circuit 17 having functions as a region discriminating unit and a control unit moves the photographing optical system 11 in the direction along the optical axis via the lens driving unit 18 while determining the contrast signal. In addition, the arithmetic control circuit 17 detects the position of the photographing optical system 11 by the lens position detection unit 19, and determines the camera from the relationship between the focus position of the photographing optical system 11 and the lens position detected by the lens position detection unit 19. A distance L from 1 to the subject 110 (hereinafter referred to as subject distance L) is calculated.
[0029]
Here, the arithmetic control circuit 17 is configured by, for example, a one-chip microcontroller such as a CPU (Central Processing Unit). The arithmetic control circuit 17 executes various control processes based on a signal from the operation switch 20 that is switched in conjunction with an operation member (not shown) operated by the operator of the camera 1. In addition, the arithmetic processing for calculating the subject distance L described above, the driving control of the lens driving unit 18, the signal processing of the image signal generated by the imaging element 12, and the recording control when recording the image data on the recording medium unit 15. And so on.
[0030]
Further, when the desired shooting environment including the subject 110 is dark, the arithmetic control circuit 17 controls the strobe control unit 22 to control the strobe unit 21 as a light emitting unit to emit auxiliary illumination light. In the first embodiment, the flash unit 21 is caused to emit a small amount of light (hereinafter referred to as preliminary light emission) before the flash unit 21 is caused to emit light during exposure (hereinafter referred to as main light emission). Based on the result obtained in step 1, the amount of strobe light emission at the time of main light emission is determined.
[0031]
Further, the camera 1 has a distance measuring unit 23 as a distance distribution detecting means. Based on a subject image incident through an optical system different from the photographing optical system 11, the camera 1 to the subject 110 are connected. The distance L can be obtained. That is, the distance measuring unit 23 includes a pair of light receiving lenses 24a and 24b, a pair of sensor arrays 25a and 25b, an integrating circuit 26, a steady light component removing circuit 27, and an AD converting unit 28. ing.
[0032]
The subject image incident through the pair of light receiving lenses 24a and 24b is formed on the sensor arrays 25a and 25b. The pair of sensor arrays 25 a and 25 b converts the formed subject image into a photocurrent corresponding to the brightness and outputs the photocurrent to the integration circuit 26. The integrating circuit 26 integrates the photocurrents output from the pair of sensor arrays 25a and 25b, respectively.
[0033]
The AD converter 28 digitizes the input integral value and outputs it to the arithmetic control circuit 17. The arithmetic control circuit 17 can detect the image signal of the subject 110 based on the signal input from the AD converter 28.
[0034]
Thereafter, the arithmetic control circuit 17 compares at which position of the sensor arrays 25a and 25b each image signal is detected. Then, from the relative position difference x of the detection position of the image signal, the lens parallax B, and the focal length f, the principle of triangulation, that is,
L = Bf / x
The subject distance L is calculated based on the above.
[0035]
Here, a stationary light component removal circuit 27 is provided between the sensor arrays 25 a and 25 b and the integration circuit 26. The stationary light component removal circuit 27 irradiates the subject when the strobe light is emitted from the strobe light 21 and the stray light component light current of the stationary light component which is generated constantly from the photocurrents input from the sensor arrays 25a and 25b. The photocurrent of the reflected signal light component reflected from 110 is separated and the steady light component is removed. In the first embodiment, ON / OFF switching of the operation of the stationary light component removal circuit 27 is controlled by the arithmetic control circuit 17.
[0036]
The switching control and the operation of the steady light component removing circuit will be described in more detail with reference to FIG. FIG. 2 is an electric circuit diagram showing a detailed configuration inside the integrating circuit 26 and the steady light component removing circuit 27. In FIG. 2, one sensor 25 included in the sensor arrays 25a and 25b will be described. The sensor 25 is constituted by a light detection element such as a photodiode.
[0037]
Although not shown in FIG. 2, the distance measuring unit 23 is connected to the calculation control circuit 17, and the calculation control circuit 17 switches the switches 161, 162, 165 of the integration circuit 26 and the steady light component removal circuit 27. , And 166 are controlled ON / OFF.
[0038]
That is, when the arithmetic control circuit 17 sets HOLD2 to H level and the switch 165 is turned on (switch 165 is closed), the component I that is constantly output out of the photocurrent output from the sensor 25. _P Does not flow to the amplifier 152 side but flows to GND via the transistor 150. Then, the signal component i that varies over time _P Only flows through the amplifier 152 to the base of the amplifying transistor 153. As a result, the amplified current flows through the diode 160 and the integrating circuit 26 through the current mirror circuit configured by the transistors 154, 155, and 156.
[0039]
Here, the potential of the diode 160 is compared with the potential of the diode 159 by the hold amplifier 157. That is, the hold amplifier 157 has a current I flowing from the constant current source 158 to the diode 159 while the switch 166 is ON. ₀ The base voltage of the transistor 150 is controlled so that the current flowing from the current mirror circuit to the diode 160 does not increase.
[0040]
As a result, the current amplified by the transistor 153 has a constant I regardless of the amount of light incident on the sensor 25. ₀ It becomes. Therefore, of the collector current of the transistor 156 by the current source 161, I ₀ Is extracted, the current input to the integrating circuit 26 becomes zero.
[0041]
Here, as shown in FIG. 3, the strobe control unit 22 is controlled by the arithmetic control circuit 17, and a strobe light of a minute amount is projected from the strobe unit 21 onto the subject 110. At the same time as this preliminary light emission, when HOLD1 is set to L level and the switch 166 is turned OFF (switch 166 is opened), the photocurrent output from the sensor 25 increases by the amount of strobe light. Flowing current I _P Does not change. For this reason, the photocurrent corresponding to the increase due to the strobe light is amplified by the transistor 153 and then flows to the integrating circuit 26 via the current mirror circuit.
[0042]
Here, if the switch 162 in the integration circuit is turned ON (switch 162 is closed), the integration operation is performed in the integration capacitor 163. As a result, the output voltage V of the integrating circuit 26 _INT Depends on the amount of reflected signal light incident on the sensor 25, V _INT1 Changes. This V _INT1 Is larger when the amount of reflected signal light incident on the sensor 25 during strobe light emission is larger, and smaller when the amount of reflected signal light is smaller. This V _INT1 Is digitized and read by the AD conversion unit 28, and the light amount of the reflected signal light reflected from the subject at the time of strobe light emission can be detected by the arithmetic control circuit 17.
[0043]
The output voltage V of the integrating circuit 26 is obtained by the action of the stationary light component removing circuit 27 described above. _INT1 , The stationary light component detected based on the brightness of the subject is removed, and only the reflected signal light component during strobe light emission is extracted.
[0044]
On the other hand, when the operation of the steady light component removing circuit 27 is turned off to detect the amount of light including the steady light component, as shown in FIG. 4, the HOLD 2 is set to L level and the switch 165 is turned off. In this case, all of the photocurrent output according to the amount of light incident on the sensor 25 flows to the amplifier circuit including the amplifier 152 and the transistor 153. Thereafter, the photocurrent is amplified by the amplifier circuit and then input to the integrating circuit 26 through the current mirror circuit. As a result, the output of the integrating circuit 26 is V V as shown in FIG. _INT2 become that way.
[0045]
As described above, if the stationary light component removing circuit 27 is provided between the sensor 25 and the integrating circuit 26, the reflected signal light component and the stationary light component are separated, and the reflected signal light component is amplified and then integrated. Therefore, a high signal detection capability can be obtained. For example, in a situation where the stationary light is 1000 times as large as the signal light, simply AD-converting the light incident on the sensor array may cause the signal component to be buried by AD conversion errors or noise components, The accuracy is significantly reduced. However, by separating and amplifying the steady light component, the amount of signal at the time of AD conversion can be increased, and since random noise is smoothed by the integration effect, it can be detected correctly. It becomes easy.
[0046]
Here, the amount of reflected signal can be detected for each pixel by incorporating a stationary light component removal circuit into each sensor of the sensor array. Also, if this function is used for autofocus, accurate distance measurement can be performed by the light distribution of reflected signal light from the subject 110 by strobe light, for example, even during backlighting.
[0047]
Further, when the flash light control is performed, even if the steady light is large in a bright scene, or even if the subject is far away and the amount of reflected signal light is small, correct reflected signal light can be detected and applied to accurate exposure control.
[0048]
FIG. 5 shows only the important functions at the time of strobe dimming of a camera having a sensor array with a function of removing a steady light component.
[0049]
That is, when the light from the flash unit 21 is projected onto the subject 110, the reflected signal light from the subject 110 enters the image pickup device 12 through the photographing optical system 11 and is sensored through the pair of light receiving lenses 24a and 24b. The light enters the arrays 25a and 25b. The output of each pixel of the image sensor 12 is input to the arithmetic control circuit 17 via the pixel output detection unit 14a in the image signal processing unit 14. On the other hand, the output of each pixel of the sensor arrays 25a and 25b is integrated after being removed from the steady light component by the steady light component removing / integrating unit 54a and then input to the arithmetic control circuit 17.
[0050]
Here, the features of strobe control using an image sensor or sensor array will be described.
Although the image sensor 12 does not have a steady light component removal function, the light distribution over the entire screen can be detected as indicated by reference numeral 111 in FIG. On the other hand, the sensor arrays 25a and 25b can detect only a limited region as indicated by reference numeral 112 in FIG. 6, but have a stationary light component removal function, so that the high signal detection capability as described above can be obtained. In addition, when the stationary light component removal function is attached to the image pickup device 12, the image pickup device 12 has a large number of pixels, so that the scale is increased, which is a major factor in increasing the cost.
[0051]
FIG. 7A shows an output of the image sensor 12 at the time of strobe light emission, that is, a distribution diagram of image signals. In FIG. 7A, the horizontal axis indicates the pixel position of the image sensor, and the vertical axis indicates the magnitude of the image signal. That is, in a bright scene, the amount of strobe light is very small compared to the amount of steady light, and it is difficult to detect changes in the image signal due to the presence or absence of strobe light emission.
[0052]
On the other hand, FIG. 7B shows a distribution diagram of the output of the sensor array during strobe light emission. In FIG. 7B, the horizontal axis indicates the pixel position of the sensor array, and the vertical axis indicates the magnitude of the image signal. That is, if a sensor array with a steady light component removal function is used, only the reflected signal light component from the subject 110 by strobe light can be detected as shown in FIG. 7B.
[0053]
FIG. 8 shows an example of a flowchart at the time of strobe control of the camera having such a configuration.
First, the arithmetic control circuit 17 outputs the output I of the image sensor 12 before the strobe preliminary light emission. _M1 Is acquired (step S1). After capturing the output of the image sensor 12, the arithmetic control circuit 17 causes the strobe unit 21 to perform preliminary light emission (step S2), and then removes the photocurrent due to the steady light component from the photocurrent output from the sensor arrays 25a and 25b. Then, integration is performed (step S3). After the integration is completed, the light emission of the flash unit 21 is terminated (step S4), and the output I of the image sensor 12 at this time _M2 Is acquired (step S5). At the same time, the integration result V _INT1 Is acquired (step S6).
[0054]
Next, the difference of the output of the image pick-up element 12 taken in step S1 and step S5 is taken (step S7). Here, since the imaging conditions for the output of the image sensor 12 acquired in steps S1 and S5 are all the same except for the presence or absence of strobe light emission, the output I of the image sensor 12 captured in step S5. _M2 And the output I of the image sensor 12 captured in step S1. _M1 ΔI which is the difference between _M Represents the amount of light increased by the strobe light, as shown in FIG. The arithmetic control circuit 17 determines the light emission amount of the flash unit 21 during the main light emission, using the numerical value obtained as described above.
[0055]
That is, the arithmetic control circuit 17 outputs the output I of the image sensor 12. _M1 Is the predetermined brightness I _M0 It is determined whether it is larger than (step S8). In this determination, the output I of the image sensor 12 even without strobe light emission. _M1 Is determined to be sufficiently large, the subject has high brightness. In this case, since it is difficult to detect the amount of light increased by the strobe light from the output of the image sensor 12 that does not have the steady light component removal function, the process branches to step S9. Then, the arithmetic control circuit 17 calculates the difference ΔI calculated in step S7. _M Is a predetermined amount ΔI _M1 It is determined whether it is larger than (step S9). In the determination of step S9, the difference ΔI _M Is a predetermined amount ΔI _M1 If it is determined as follows, the result V of the steady light component removal integration V _INT1 Is the predetermined amount V ₀ It is determined whether it is smaller than (step S10). In the determination of step S10, V _INT1 Is the predetermined amount V ₀ If it is determined that the reflected light is not sufficiently detected, the light emission amount of the flash unit 21 is determined to be a predetermined predetermined light amount, assuming that the subject is so far away that the reflected signal light cannot be sufficiently detected (step S11).
[0056]
In the determination of step S10, V _INT1 Is the predetermined amount V ₀ If it is determined that this is the case, V _INT1 Thus, the light emission amount of the flash unit 21 is determined (step S12).
[0057]
In step S8, I _M1 Is the predetermined brightness I _M0 If it is determined that the difference is ΔI or not in step S9 _M Is a predetermined amount ΔI _M1 If the calculation control circuit 17 determines that the reflected signal light by the strobe light can be sufficiently detected without using the steady light removal function, ΔI _M Thus, the light emission amount of the flash unit 21 is determined (step S13).
[0058]
After the strobe light emission amount is determined as described above, the strobe unit 21 is caused to perform main light emission based on this light emission amount to perform exposure (step S14).
[0059]
Next, the concept of such exposure control will be described with reference to FIG. 9, FIG. 10 (a), and FIG. 10 (b). Here, the horizontal axis in these drawings indicates the exposure time, and the vertical axis indicates the exposure amount.
[0060]
That is, as shown in FIG. 9, when exposure without a strobe is performed in a dark state of the subject, camera shake occurs (here, this time is set as the exposure time) t _E Appropriate exposure amount I _M4 I cannot get _M4 -I _M3 Only underexposure occurs.
[0061]
The flash unit 21 compensates for such underexposure. To determine the amount of light emitted from the flash unit 21, first, t ₁ The exposure is performed without a strobe for a very short time, and the exposure amount at that time (output of the image sensor 12) I _M1 Is detected, and then the flash unit 21 is preliminarily fired. ₁ The exposure is performed at a minute time, and the exposure amount I at that time _M2 Is detected. Thereafter, by calculating the difference between these exposure amounts, it is possible to obtain an appropriate exposure amount within the camera shake time as shown in FIG. Can predict whether or not
[0062]
The arithmetic control circuit 17 determines the flash emission amount to the flash time t of the flash unit 21. _ST Asking. Here, the emission time t _ST Is
[Expression 1]

(Equation 1) to (Equation 3) shown in FIG. 9 and each light quantity detection value shown in FIG. 9, FIG. 10 (a), or 10 (b).
[0063]
Here, the method of obtaining the strobe light emission time mainly from the output of the image sensor 12 has been described, but the integrated value V obtained by the steady light component removal integration is described. _INT1 Is I in (Formula 2) or (Formula 3). _M2 -I _M1 It corresponds to. Therefore, V _INT1 And this V _INT1 I _M2 -I _M1 Using conversion coefficient K for conversion to
[Expression 2]

The strobe firing time t _ST Can be calculated.
[0064]
In addition to compensating for the shortage of exposure using the strobe unit 21, the ratio of the exposure amount by the strobe light to the exposure amount by the external light (hereinafter referred to as the strobe contribution rate) shown in FIG. Strobe control may be performed in consideration. In this way, by controlling the strobe emission amount in consideration of the strobe contribution rate, the brightness balance between the background and the person who is the main subject can be adjusted.
[0065]
In general, strobe light does not reach the background of a landscape or the like, so when the strobe contribution ratio is increased, the exposure amount of the background becomes relatively smaller than the exposure amount of the person. Conversely, when the strobe contribution ratio is lowered, the exposure amount of the person becomes relatively smaller than the exposure amount of the background. For these reasons, it is preferable to perform exposure control by switching the strobe contribution rate according to the situation. For example, when the background is empty, the blueness of the sky increases when the exposure is slightly underexposed, and when the background is snowy, the snow white is not captured correctly unless the exposure is overexposed.
[0066]
The switching of the strobe contribution rate is performed according to a flowchart as shown in FIG. 11, for example.
[0067]
In this flowchart, the arithmetic control circuit 17 detects the image signal in the screen 110a including the main subject 110 using the image pickup device 12 after the strobe unit 21 is preliminarily emitted (step S21). Next, the arithmetic control circuit 17 determines a region in the screen 110a where the reflected signal light component due to the strobe light cannot be detected and the strobe light does not contribute to exposure (step S22). For example, in the scene as shown in FIG. 1, the background portion 110b excluding the person portion 110 from the screen 110a shown in FIG. 12A is an area where the strobe light does not contribute to exposure.
[0068]
After discriminating the background portion 110b where the strobe light does not contribute to the exposure, the arithmetic control circuit 17 uses the image sensor 12 to change the contrast change C of the image signal in the background portion 110b. _B Is detected (step S23). Here, instead of simply detecting the difference in brightness in the entire area of the background portion 110b, for example, the contrast change of the representative portion as indicated by reference numerals 110c and 110d in FIG. 12B is detected. Here, “contrast change detection” is an examination of how the difference between the low luminance portion and the high luminance portion (so-called contrast) is distributed. The representative portion is, for example, a region with a high spatial frequency, a bright region, a region with high saturation (this will be described later) in the image signal as shown in FIG. In addition, as shown in FIG. 12B, a plurality of representative portions may be detected, and the control after step S24 may be performed for all the regions, or a value obtained by adding all the contrast changes of the representative portions. You may make it perform control after step S24 using. Furthermore, the average value of the contrast change of the representative portion may be used.
[0069]
Also, contrast change C _B For example, in the image signal shown in FIG. 12C, it may be obtained from the product of the change in brightness ΔB of the background portion and the period F of the background portion. The important background portion may be determined not only from the change in contrast but also by recognizing the shape of a two-dimensional image in the background portion.
[0070]
Thus, the contrast change in the representative portion of the background is detected in order to perform exposure control so that a fine pattern in the representative portion of the background is correctly reproduced. Here, when the contrast change detected in step S23 is small, the background is considered not so important.
[0071]
Here, when exposure control is performed based on the brightness of the background, the exposure time becomes long when the background is dark, and there is a high possibility that camera shake will occur. On the other hand, when the background is bright, it is necessary to increase the strobe contribution rate to the main subject, that is, to increase the strobe emission amount, which leads to energy loss.
[0072]
Therefore, in the first embodiment, only when the background is important, exposure control is performed based on the brightness of the background so that the background contrast is correctly reproduced.
[0073]
That is, the arithmetic control circuit 17 determines the contrast change C detected in step S23 in order to determine whether the background is important. _B Is a predetermined size C ₀ It is determined whether it is larger than (step S24). In this determination, C _B Is C ₀ The contrast change C _B Is determined to be important. Therefore, the arithmetic control circuit 17 performs exposure control so that the contrast of the background portion (for example, the background portion 110c in FIG. 12B) is correctly reproduced.
[0074]
That is, the arithmetic control circuit 17 exposes the exposure time t such that the image signal of the important background portion 110c is not saturated. _E Decide. For this purpose, the arithmetic control circuit 17 determines the average brightness B of the background. _B To provisional exposure time t _E Is determined (step S25). Further, the arithmetic control circuit 17 considers the difference ΔB in the brightness of the image signal in the important background portion 110c, and the maximum value B of the image signal in the important background portion 110c. _B + ΔB / 2 is the exposure time t _E It is determined whether or not the saturation occurs due to integration (step S26). If it is determined in step S26 that the maximum value of the image signal is saturated after integration, the arithmetic control circuit 7 determines that the new exposure time t _E To the original t _E Is set to 1/2 (step S27). Here, exposure time t _E T determined in step S25 _E However, it is not limited to this.
[0075]
On the other hand, if it is determined in step S26 that the maximum value of the image signal in the important background portion 110c is not saturated after integration, the arithmetic control circuit 17 determines the t determined in step S25. _E Set to the exposure time.
[0076]
In step S24, the contrast change C _B Is a predetermined size C ₀ When it is determined that the following is true, the arithmetic control circuit 17 determines the important background portion from the color (saturation) of the background portion.
[0077]
For example, as in the background portion 110d of FIG. 12B, when the background portion is a blue sky or the like, if exposure control is performed considering only the brightness of the main subject 110, the background portion 110b will fly white. Sometimes. Even in such a case, in the first embodiment, by performing exposure control by increasing the strobe contribution ratio with respect to the main subject, a correct color image can be obtained on both the main subject 110 and the background portion 110b. To do.
[0078]
That is, contrast change C _B Is a predetermined size C ₀ When it is determined that it is below, the arithmetic control circuit 17 detects an RGB color signal from the output of the image sensor 12, and from this color signal and the luminance signal Y, the color difference (R−Y) and (B−Y) are detected. ), And the larger one of these values is used as the saturation judgment value S. _B Is selected (step S28). This saturation judgment value S _B Is a value that increases as the color becomes brighter, that is, as the saturation increases. Therefore, the arithmetic control circuit 17 is S _B Is the predetermined value S ₀ Or greater, that is, whether the background saturation is high (step S29). In this determination, that is, S _B Is the predetermined value S ₀ Is determined to be an important background portion 110d with high saturation, and the background brightness Y is determined from the output of the image sensor 12 in the background portion, for example,
Y = 0.263R + 0.655G + 0.081B (Formula 5)
(Step S30). Y in (Formula 5) is an example of the CIE color system. Here, since each RGB coefficient in (Equation 5) differs depending on the component creation, color concept, etc., in FIG.
Y = aR + bG + cB (Formula 6)
It is expressed in generalized as follows. After the background brightness Y is thus obtained, the arithmetic control circuit 17 determines the exposure time t from the obtained Y. _E Is determined (step S31).
[0079]
Further, in the determination of step S29, the saturation is low, that is, S _B Is the predetermined value S ₀ If it is determined that the exposure time t is less than the time until camera shake occurs (camera shake time), the exposure time t _E Is determined (step S32).
[0080]
Exposure time t in step S31 or S32 _E Is determined, the arithmetic control circuit 17 _E From (Equation 3), the flash emission time t _ST Is calculated (step S33), and then the control of this flowchart is exited.
[0081]
In this way, if the color of the background part is determined and the color balance of the image sensor in this background part is biased, increase the strobe contribution ratio for the main subject so that the characteristic color does not fly white. Reduce the exposure time. By shortening the exposure time in this way, a background such as a blue sky or a sunset sky does not fly white during photographing.
[0082]
Here, a modified example of the method for determining the region to which the strobe light does not contribute in step S22 will be described with reference to FIGS. 13 (a) and 13 (b). The example of FIG. 13A is an example in which discrimination is performed based on the distance to the subject. First, the arithmetic control circuit 17 calculates the distances of a plurality of points in the screen by the distance measuring unit 23, and detects the distribution of these distances (step S41). Next, in the distribution of detected distances, for example, the closest distance is set to the distance L of the main subject _S (Step S42). Thereafter, the arithmetic control circuit 17 determines the determined L _S Is determined to be a region where the strobe light does not contribute to exposure (step S43).
[0083]
In the example of FIG. 13B, the difference ΔI described in FIG. _M And integral value V _INT1 This is an example in which the determination is performed. That is, the arithmetic control circuit 17 uses the difference ΔI. _M Is a predetermined value ΔI ₀ Smaller area (step S51) and integral value V _INT1 Is the predetermined value V ₀ The smaller area is determined as the area where the strobe light does not contribute to the exposure (step S52).
[0084]
As described above, according to the first embodiment, since the strobe light emission time is controlled by the exposure control in consideration of the balance between the strobe light and the background brightness, the color reproducibility can be improved. . In addition, if a sensitive steady light removal integration circuit is used, the amount of strobe light emission during the preliminary light emission can be weakened, and a preliminary light emission system with excellent energy saving effect without glare can be achieved.
[0085]
[Second Embodiment]
FIG. 14 is a block configuration diagram of an electric circuit in the camera according to the second embodiment of the present invention. A part of the configuration of the camera is the same as that of the camera of the first embodiment described above. Therefore, the same components are denoted by the same reference numerals, and detailed description thereof is omitted. The second embodiment is an example using a TTL (Trough The Lens) direct dimming method.
[0086]
That is, the camera 1 of the second embodiment includes a movable mirror 30 and a viewfinder optical system (screen 31, pentagonal roof prism (hereinafter abbreviated as a pentaprism) 32 in addition to the configuration of the first embodiment described above. A viewfinder photometric sensor 34, a photometric unit 35, a sub mirror 36, a field lens 37, an optical path bending mirror 38, a re-imaging lens 39, and a sensor array 40. The shutter curtain 41, the photometric optical system 42, the in-body photometric sensor 43, the light control unit 44, the display control unit 45, and the electronic monitor 46 are included.
[0087]
The movable mirror 30 is disposed in a space between the shutter curtain 41 and the photographing optical system 11 so as to be retracted from the optical path of the photographing optical system 11 (hereinafter referred to as a retracted position 30a) and on the optical path of the photographing optical system 11. It is configured to be rotatable between a position to be moved (hereinafter referred to as a normal position 30b). Here, when the movable mirror 30 is disposed at the normal position 30b, the movable mirror 30 is fixed in an inclined state with respect to the optical axis of the photographing optical system 11 by about 45 degrees. In this state, the reflecting surface of the movable mirror 30 is set to face the viewfinder optical system.
[0088]
That is, when the movable mirror 30 is at the normal position 30b, the light beam incident through the photographing optical system 11 is reflected by the movable mirror 30 and guided to the finder optical system. In the finder optical system, the incident light beam is formed as an optical image on the screen 31 and the image formed is guided to the pentaprism 32. The pentaprism 32 guides the image transmitted through the screen 31 in the direction of the eyepiece 33 (ie, behind the camera 1), and at the same time, inverts the left and right of the image. The eyepiece 33 enlarges the incident image. As a result, the photographer 111 can observe the subject.
[0089]
Further, an in-finder photometric sensor 34 is provided in the vicinity of the pentaprism 32. The in-finder photometric sensor 34 receives a part of the light beam incident on the pentaprism 32 and outputs a predetermined electric signal to the photometric unit 35. Here, the finder photometric sensor 34 is formed so as to be able to perform a photometric operation in a predetermined light receiving area in the photographing screen as shown in FIG. That is, the finder photometric sensor 34 includes a light receiving unit 34a that measures a predetermined area near the center and a light receiving unit 34b that measures a predetermined area near the periphery, and can detect, for example, a backlight condition. It is configured.
[0090]
The photometric unit 35 performs a photometric operation based on the electrical signal input from the finder photometric sensor 34 to detect the brightness of the subject. Based on the detection result of the photometry unit 35, the arithmetic control circuit 17 controls the strobe control unit 22.
[0091]
In addition, a part of the movable mirror 30, for example, a region in the vicinity of the substantially central portion is configured by a semi-transmissive mirror so that a part of the light beam from the photographing optical system 11 can be transmitted. A sub-mirror 36 is disposed at a portion facing the region constituted by the semi-transmissive mirror.
[0092]
That is, the sub mirror 36 is pivotally supported so that one end portion thereof is rotatable in a predetermined direction with respect to the back side of the movable mirror 30, that is, the surface facing the image sensor 12. The reflection surface of the sub mirror 36 is disposed so as to face the region of the semi-transmissive mirror of the movable mirror 30 described above. In other words, the sub mirror 36 is arranged so as to form a predetermined angle as shown in FIG. 14 with respect to the movable mirror 30 when the movable mirror 30 is arranged at the normal position 30b. Further, the sub mirror 36 is disposed at a predetermined position that is substantially parallel to the movable mirror 30 when the movable mirror 30 is disposed at the retracted position 30a. As a result, the movable mirror 30 moves to the retracted position 30 a and at the same time the sub mirror 36 retracts from the optical path of the photographing optical system 11.
[0093]
That is, when the movable mirror 30 and the sub mirror 36 are in the normal position, a part of the incident light beam transmitted through the photographing optical system 11 is reflected by the sub mirror 36 after passing through the semi-transmissive mirror region of the movable mirror 30. The reflected light beam passes through the field lens 37, and further passes through the re-imaging lens 39 after the optical path is bent in a predetermined direction by the optical path bending mirror 38. Then, a pair of subject images is formed on the light receiving surface of the sensor array 40. The sensor array 40 converts the received subject image into an electrical signal and outputs it to the arithmetic control circuit 17. In response to this, the arithmetic control circuit 17 performs a predetermined focusing process.
[0094]
Here, this focusing process may be a TTL phase difference detection method that is generally applied. This TTL phase difference detection method will be briefly described. In this method, the arithmetic control circuit 17 controls the lens driving unit 18 to monitor the output of the sensor array 40 while moving the photographic optical system 11 in the lens optical axis direction, and outputs from the sensor array 40. When the pair of subject images are in a predetermined positional relationship, it is determined that the subject is in focus, and at that time, driving of the photographing optical system 11 is stopped.
[0095]
Further, as described above, the shutter curtain 41 is disposed in the vicinity of the light receiving surface side of the image sensor 12. That is, the image sensor 12 is configured to receive the light beam from the photographing optical system 11 only during the period when the shutter curtain 41 is in the open state. Here, as a configuration of the shutter curtain itself, a configuration generally used in a conventional single-lens reflex camera is applied. The configuration of the shutter curtain 41 will be briefly described with reference to the schematic diagram of FIG.
[0096]
As shown in FIG. 16, the shutter curtain 41 includes two curtain members, a front curtain 41a and a rear curtain 41b. In the normal state, the front curtain 41a is disposed in front of the light receiving surface of the image sensor 12, and the light receiving surface of the image sensor 12 is shielded.
[0097]
Here, when the exposure operation is executed, first, the movable mirror 30 and the sub mirror 36 are moved to a predetermined retracted position 30a. In this state, the front curtain 41a starts to move in the arrow Y1 direction. Subsequently, after a predetermined time, the trailing curtain 41b starts to move in the Y2 direction (the same direction as Y1). Therefore, a predetermined gap is generated between the front curtain 41a and the rear curtain 41b. By adjusting the size of the gap, that is, by adjusting the time when the front curtain 41a and the rear curtain 41b start to move, the exposure time (that is, the shutter speed) to the image sensor 12 can be adjusted.
[0098]
In addition, a predetermined pattern is formed on the surface of the front curtain 41a so that the light beam reflected on the surface of the front curtain 41a has a standard reflectance. That is, the light beam reflected by the surface of the front curtain 41 a is received by the in-body photometric sensor 43 through the photometric optical system 42. The in-body photometric sensor 43 converts the incident light beam into an electrical signal and outputs it to the light control unit 44.
[0099]
Here, as shown in FIG. 17, the in-body photometric sensor 43 includes three photometric areas 43a, 43b, and 43c in a form in which the entire light receiving surface is divided into three. For example, in the case where a composition frame (shooting screen 121) as shown in FIG. 18 is set and photographing is performed using the light control of the preliminary light emission method, only the photometric area 43c of the in-body photometric sensor 43 shown in FIG. Measure the light using. This is because, for example, when a high-luminance subject such as the sun is included in the shooting screen 121 as shown in the composition illustrated in FIG. This is a measure for avoiding this.
[0100]
The light control unit 44 measures the amount of incident light from the subject 110 and performs predetermined light control based on the electrical signal output from the in-body photometric sensor 43.
[0101]
Here, in a conventional TTL dimming control of a general camera, for example, a reflected light beam from a film surface is received during an exposure operation. However, since the surface of the image sensor 12 generally has more regular reflection components in the reflection of light, in the camera 1 of the second embodiment, the front curtain 41a that diffusely reflects the incident light flux with the standard reflectance. Photometry is performed using the reflected light beam from the surface of the lens.
[0102]
The display control unit 45 is controlled by the arithmetic control circuit 17 and displays an image on an electronic monitor 46 such as a liquid crystal monitor (LCD) based on the image data output from the image signal processing unit 14. With this electronic monitor 46, the photographing result can be confirmed immediately after the photographing is completed. Further, the electronic monitor 46 can be used in place of the finder optical system described above. This will be described in detail later.
[0103]
Here, according to the relationship of (Equation 4) described above, the appropriate exposure amount I _M4 A light amount detection amount (output of the image sensor 12) I for predicting the amount of exposure other than strobe light I _M1 And a value (integration result) V indicating how much strobe light is reflected from the subject. _INT1 It can be seen that and can be calculated separately.
[0104]
Therefore, in the second embodiment, in order to accurately measure the amount of light incident on the image sensor 12, the amount of light I reflected by the front curtain 41a having a standard reflectance is used. _M1 Is detected by the in-body photometric sensor 43. Thereby, it is possible to perform highly accurate exposure control that does not depend on the attached photographing optical system.
[0105]
In addition, the effect of the strobe light on the exposure is predicted as appropriate by using the output of the photometry means with the steady light component removal integration function. This makes it possible to perform good flash photography. Here, the steady light component removal integration function, which is a function of the photometry means, may be provided in the in-body photometry sensor 43 of the camera 1, but as described above, the integration result V _INT1 The in-body photometric sensor 43 may not be detected. Therefore, in the second embodiment, the in-finder photometric sensor 34 is provided with a steady light removal integration function. That is, in the second embodiment, photometry using the image sensor 12 in the first embodiment is performed by the in-body photometry sensor 43, and photometry using the sensor arrays 25a and 25b is performed by the in-finder photometry sensor 34. Do.
[0106]
In such a case, for example, if the sensor provided in the light receiving unit 34a shown in FIG. 15 has a function of removing steady light so that the reflected light incident thereon can be detected, this light reception can be performed at the time of photographing. By performing strobe preliminary light emission and exposure so as to put the main subject in the unit 34a, it is possible to predict how much the strobe light can contribute in the light receiving unit 34a. The steady light component removal integration function may be provided not in the finder sensor 34 but in the sensor array 40 as in the first embodiment.
[0107]
FIG. 19 shows a timing chart at the time of flash photography of the camera having such a configuration, and FIG. 20 shows a flowchart of the control procedure at the time of flash photography.
[0108]
That is, the arithmetic control circuit 17 performs preliminary photometry of the strobe unit 21, and then performs photometry with the photometric sensor 34 in the finder, and the integration result V _INT1 Is acquired (step S61). At this time, the movable mirror 30 is positioned at the normal position 30b. Next, after retracting the movable mirror 30 to the retracted position 30a (step S62), photometry is performed by the in-body photometric sensor 43 without emitting strobe light, and the exposure amount I at that time is measured. _M1 Is acquired (step S63). Next, the arithmetic control circuit 17 causes the strobe unit 21 to perform preliminary light emission and performs photometry with the in-body photometric sensor 43, and the exposure amount I at that time is measured. _M2 Is acquired (step S64). Here, in the case of the three-divided sensor as shown in FIG. 17, the output from the sensor having the largest light amount difference before and after the strobe emission is the exposure amount I. _M1 And I _M2 Adopt as. Here, since the shutter curtain 41 has a standard reflectance, the amount of light reflected from the shutter curtain 41 is determined at a predetermined shutter speed (t _E ) Exposure amount can be predicted.
[0109]
That is, the arithmetic control circuit 17 performs the exposure amount I _M1 And I _M2 Are compared to determine whether or not the difference between them is small (step S65). If it is determined that the difference between the two is small in this determination, it is difficult to extract only the reflected signal component by the strobe light because the shooting scene is bright, and the integration result V detected by the in-finder photometric sensor 34 is determined. _INT1 And (Equation 4), the amount of strobe light emission (ie, the light emission time t _ST ) Is determined (step S66).
[0110]
On the other hand, in the determination of step S65, I _M1 And I _M2 If it is determined that the difference between _M1 And I _M2 And (Equation 3), the emission time t _ST Is determined (step S67).
[0111]
Flash time t of the flash unit 21 _ST Is determined, the arithmetic control circuit 17 opens the shutter curtain 41 (step S68) and starts exposure. Then, the arithmetic control circuit 17 causes the flash unit 21 to emit light when the shutter curtain 41 is fully opened (step S69). Predetermined time t _E After the passage, the shutter curtain 41 is closed (step S70), the light from the subject entering the image sensor 12 is blocked, and the exposure control is finished.
[0112]
Here, in the so-called single-lens reflex camera as shown in FIG. 14, it is generally difficult to control the strobe, and the flash emission can be used only when the shutter curtain 41 is fully opened. For this reason, it is necessary to perform control for causing the flash unit 21 to emit light with the same brightness for a relatively long time even during a high-speed shutter. Here, such light emission is referred to herein as flat light emission. However, strobe control using such flat light emission cannot irradiate light to a far distance.
[0113]
A single-lens reflex camera can select and use various lenses such as a macro lens corresponding to a macro function in addition to lenses having various angles of view from a wide angle to a telephoto including a fish-eye lens. . Next, a description will be given of a case in which control of the strobe light emission amount when using a macro lens among such various lenses is applied.
[0114]
FIG. 21 is a simplified illustration of FIG. For example, as shown in FIG. 21, when a macro image of an insect or the like is taken as the main subject 110, for example, the image is captured on the electronic monitor 46 rather than the subject 110 being confirmed and photographed via the viewfinder optical system. It is possible to shoot from various angles by displaying the image acquired by the element 12 in real time and confirming the subject 110 with the image displayed on the electronic monitor 46 for shooting. In addition, since there is no need to take a picture while looking through the viewfinder, the degree of freedom of photography is high.
[0115]
Here, when displaying an image on the electronic monitor 46 in real time, it is necessary to retract the movable mirror 30 and the sub mirror 36 from the optical path of the photographing optical system 11 and open the shutter curtain 41 as shown in FIG. is there. Control during such macro shooting will be described with reference to the flowchart of FIG.
[0116]
That is, when a macro mode button (not shown) is operated by the photographer, the arithmetic control circuit 17 determines that and retracts the movable mirror 30 and the sub mirror 36 from the optical path of the photographing optical system 11 as shown in FIG. (Step S71), then, the shutter curtain 41 is opened (Step S72). Thereafter, the arithmetic control circuit 17 causes the image sensor 12 to start an imaging operation, and at the same time, the arithmetic control circuit 17 causes the image signal processor 14 to start reading the image signal from the image sensor 12, and the image signal processor 14 The processed image is displayed on the electronic monitor 46 via the display control unit 45 (step S73).
[0117]
Next, the arithmetic control circuit 17 determines whether or not to start a photographing operation by determining whether or not a release switch (not shown) is turned on (step S74), and until the release switch is turned on. Continue reading signals and displaying images. On the other hand, if it is determined in step S74 that the release switch has been turned ON, the arithmetic control circuit 17 starts the photographing operation.
[0118]
Here, also in a photograph taken by macro photography, it is important that the background is correctly photographed together with the main subject as shown in FIG. 23A, and only the main subject is closed as shown in FIG. The background may not be so important. Therefore, thereafter, similarly to the first embodiment, it is determined whether or not the background is important. If the background is important, exposure control is performed based on the brightness of the important background portion.
[0119]
That is, after the exposure control is started, the arithmetic control circuit 17 first causes the strobe unit 21 to perform preliminary light emission (step S75), and determines that the region where the reflected signal light from the subject is not detected is the region of the background portion 110b where the strobe light does not contribute. (Step S76). Next, the saturation determination described in steps S28 and S29 in FIG. 11A is performed in the region of the background portion 110b. That is, the color difference (R−Y) and (B−Y) are obtained from the output of the image sensor 12, and the larger value of these is determined as the saturation determination value S. _B (Step S77). And this S _B Is the predetermined value S ₀ Is determined, that is, whether the saturation is higher than a predetermined value (step S78). If it is determined that the saturation is high, the arithmetic control circuit 17 determines that the background is important. The exposure time t with reference to the brightness of the background _E Is determined (step S79). On the other hand, if it is determined in step S78 that the saturation is low, the background is not important, so the exposure time t is based on the camera shake time. _E Is determined (step S80).
[0120]
In this way, the exposure time t _E Is determined, the arithmetic control circuit 17 _E From (Equation 3), the flash emission time t _ST Is calculated (step S81). Thereafter, the flash unit 21 is caused to emit light to start exposure (step S82), and the exposure time t _E After the elapse of time, the shutter curtain 41 is closed to end the exposure (step S83). Then, after the real-time image display is finished, the photographing result is displayed on the electronic monitor 46 (step S84), and the control of this flowchart is finished.
[0121]
In the case of a high-speed shutter, the time until the shutter curtain 41 changes from the open state to the closed state also affects the exposure result. In this case, the exposure time is lengthened by narrowing the aperture (not shown). Thus, the time until the shutter curtain 41 is closed may be neglected.
[0122]
As described above, according to the second embodiment, even in an interchangeable lens single-lens reflex camera, it is possible to perform strobe shooting that draws out the beauty of the background by effectively using the output of the image sensor. .
[0123]
Although the present invention has been described based on the above embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.
[0124]
Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and is described in the column of the effect of the invention. When an effect is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.
[0125]
【The invention's effect】
As described above, according to the present invention, appropriate strobe control is performed in consideration of what the background is for the main subject, the entire screen is harmonized, and the atmosphere is rich. A camera with a stroboscopic light control function capable of taking a photograph with good color reproducibility can be provided.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram showing an electric circuit configuration in a camera with a flash light control function according to a first embodiment of the present invention.
FIG. 2 is an electric circuit diagram of a stationary light component removal circuit.
FIG. 3 is a timing chart during operation of the stationary light component removal circuit.
FIG. 4 is a timing chart when the stationary light component removing circuit is not operating;
FIG. 5 is a block diagram extracting and describing important functions related to strobe light control.
FIG. 6 is a diagram for explaining detection ranges of an image sensor and a sensor array.
FIG. 7A is a distribution diagram of image signals according to the pixel positions of the image sensor, and FIG. 7B is a distribution diagram of image signals according to the pixel positions of the sensor array.
FIG. 8 is a flowchart illustrating a control procedure during strobe shooting according to the first embodiment of the present invention.
FIG. 9 is a graph showing an exposure amount with respect to an exposure time when strobe light emission is not performed.
FIG. 10A is a graph showing an exposure amount with respect to an exposure time when strobe light is emitted, and FIG. 10B is a graph for explaining a strobe contribution rate.
FIG. 11 is a flowchart showing control for switching the strobe contribution rate.
FIG. 12A is a diagram for explaining a background portion that is an area where strobe light does not contribute, and FIG. 12B is a diagram illustrating an example of a shooting scene including an important background; FIG. 12C is a distribution diagram of image signals in the scene of FIG.
FIG. 13 (a) is a first modification in the flowchart showing the control for determining the region where the strobe light does not contribute, and FIG. 13 (b) is for determining the region where the strobe light does not contribute. It is the 2nd modification in the flowchart which shows this control.
FIG. 14 is a block configuration diagram showing an electric circuit configuration in a camera with a flash light control function according to a second embodiment of the present invention.
FIG. 15 is a diagram for explaining the configuration of a finder photometric sensor;
FIG. 16 is a diagram for explaining a shutter curtain.
FIG. 17 is a diagram for explaining a photometric area of the in-body photometric sensor.
FIG. 18 is a diagram illustrating an example of a scene where a high-luminance object exists.
FIG. 19 is a timing chart at the time of flash photography according to the second embodiment of the present invention.
FIG. 20 is a flowchart showing a control procedure during strobe shooting according to the second embodiment of the present invention.
FIG. 21 is a block configuration diagram extracting and describing important functions in the second embodiment.
FIG. 22 is a flowchart showing strobe control in the macro mode in the second embodiment of the present invention.
FIG. 23A is an example of a macro shot image when the background is important, and FIG. 23B is an example of a macro shot image when the background is not important. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Camera, 11 ... Imaging optical system, 12 ... Image pick-up element, 13, 28 ... AD conversion part, 14 ... Image signal processing part, 15 ... Recording medium part, 16 ... Contrast detection part, 17 ... Calculation control circuit, 18 ... Lens drive unit, 19 ... lens position detection unit, 20 ... operation switch, 21 ... strobe unit, 22 ... strobe control unit, 23 ... distance measuring unit, 24a, 24b ... light receiving lens, 25a, 25b, 40 ... sensor array, 26 ... Integral circuit, 27 ... Stationary light component removal circuit, 30 ... Moving mirror, 31 ... Screen, 32 ... Pental prism, 33 ... Eyepiece lens, 34 ... In-finder photometric sensor, 35 ... Photometry unit, 36 ... Sub-mirror, 37 ... Field Lens, 38 ... Optical path bending mirror, 39 ... Re-imaging lens, 41 ... Shutter curtain, 42 ... Photometric optical system, 43 ... In-body photometric sensor, 44 ... Light control unit, 45 ... Display Control unit, 46 ... electronic monitor

Claims (1)

A light emitting means for emitting strobe light;
Area discriminating means for discriminating an area where the strobe light from the light emitting means does not contribute to exposure; and
Image signal detection means for detecting an image signal in an area where the strobe light determined by the area determination means does not contribute to exposure ;
The contrast change or saturation of the area where the strobe light does not contribute to the exposure is detected from the image signal in the area where the strobe light does not contribute to the exposure, and the area where the detected contrast change or saturation is high is determined to have high importance. And a control means for performing exposure control based on the area determined to be high in importance, and controlling strobe light by the light emitting means according to the exposure result ,
A camera equipped with a flash light control function.

Images