JP3831418B2 - Imaging device - Google Patents

Description

ただし、この（１）式が成立するためには、
α＝Ｇ_Ye／（Ｇ＋Ｇ_Cy）＝Ｂ_Mg／Ｂ_Cy
が成立することが条件である。
【００２４】
Ｂ信号についても同様に、次の式により得られる。

ただし、この（２）式が成立するためには、
β＝Ｇ_Cy／（Ｇ＋Ｇ_Ye）＝Ｒ_Mg／Ｒ_Ye
が成立することが条件である。
【００２５】
Ｇ信号については、輝度信号Ｙと、（１）式、（２）式により求められたＲ_S 、Ｂ_S とから得られる。すなわち、

【００２６】
次に図４を参照してＲＧＢ信号の実際の抽出方法について説明する。
この図の画素配置において、第１および第２のＣＣＤ１６、１７をそれぞれパラメータＡ、Ｂで表し、水平方向をパラメータｉ、垂直方向をパラメータｊで表す。なおこの図において、重ね合わせて示された各画素のうち上方に位置するものが第１のＣＣＤ１６に対応し、下方に位置するものが第２のＣＣＤ１７に対応するものとする。各画素からの信号を、第１のＣＣＤ１６に関しては、
ＶA,i,j ＝Ｍｇ、ＶA,i+1,j ＝Ｇ
ＶA,i,j+１＝Ｙｅ、ＶA,i+1,j+1 ＝Ｃｙ
ＶA,i,j+2 ＝Ｇ 、ＶA,i+1,j+2 ＝Ｍｇ
ＶA,i,j+3 ＝Ｙｅ、ＶA,i+1,j+3 ＝Ｃｙ
となるように配置し、第２のＣＣＤ１７に関しては、
ＶB,i,j ＝Ｇ 、ＶB,i+1,j ＝Ｍｇ
ＶB,i,j+1 ＝Ｃｙ、ＶB,i+1,j+1 ＝Ｙｅ
ＶB,i,j+2 ＝Ｍｇ、ＶB,i+1,j+2 ＝Ｇ
ＶB,i,j+3 ＝Ｃｙ、ＶB,i+1,j+3 ＝Ｙｅ
となるように配置する。ここで、i=1,3,5,...;j=1,5,9,... の値をとるものとする。
【００２７】
一回目の走査で第１フィールドの信号すなわち、
ＶA,i,j ＝Ｍｇ、ＶA,i+1,j ＝Ｇ
ＶA,i,j+2 ＝Ｇ 、ＶA,i+1,j+2 ＝Ｍｇ
ＶB,i,j ＝Ｇ 、ＶB,i+1,j ＝Ｍｇ
ＶB,i,j+2 ＝Ｍｇ、ＶB,i+1,j+2 ＝Ｇ
が抽出され、二回目の走査で第２フィールドの信号すなわち、
ＶA,i,j+1 ＝Ｙｅ、ＶA,i+1,j+1 ＝Ｃｙ
ＶA,i,j+3 ＝Ｙｅ、ＶA,i+1,j+3 ＝Ｃｙ
ＶB,i,j+1 ＝Ｃｙ、ＶB,i+1,j+1 ＝Ｙｅ
ＶB,i,j+3 ＝Ｃｙ、ＶB,i+1,j+3 ＝Ｙｅ
が抽出される。
【００２８】
以上の全画素信号が画像メモリ３３、３４に記憶される。これらの画素信号は映像信号処理回路３６に読み出され、演算により奇数フィールドの奇偶数走査線のｉ番目の画素に対し、

のＲＧＢ信号が得られる。
【００２９】
同様にして、奇数フィールドの奇偶数走査線のｉ＋１番目の画素に対し、

のＲＧＢ信号が得られる。
ここで、p,q は（３）式を参照すれば１であっても良いが、Ｙ成分の値に応じ、適当に調整できる方が好ましい。
【００３０】
α、β、ｐ、ｑの定数は、システム制御回路１０において実行されるソフトウェアのパラメータを調整することによって定められる。
【００３１】
偶数フィールドについては、ｊ＋１番目とｊ＋２番目の画素を組み合わせることにより、上記（４）〜（１５）式と同様な式によりＲＧＢ信号が得られる。
なお、以上の式はガンマ補正を施していないリニアな演算方法であり、ガンマ補正された信号が画像メモリ３３、３４に記憶されているのであれば、一旦リニアに変換した後、それらの演算が行われ、その演算後、正規のガンマ補正が行われる。
【００３２】
次に図５〜図１１を参照して、第１実施例における撮影動作を説明する。図５と図６は測距・測光動作を行うプログラムのフローチャートであり、図７は映像信号のメモリカードへの記録動作を行うプログラムのフローチャートである。図８は撮影動作のタイミングチャートである。図９は自動焦点調節（ＡＦ）動作におけるフォーカスレンズの移動を示す図である。図１０は第２の読出モードにおける画素信号の読出動作を示す図である。図１１は第１の読出モードにおける画素信号の読出動作を示す図である。
【００３３】
図５と図６に示す測距・測光動作のプログラムの実行は、レリーズボタン４１を半押しする（符号Ａ１）ことにより開始する。ステップ１０１では、赤外線三角測距装置４２により赤外線三角測距が行われ（符号Ａ２）、本スチルビデオカメラから被写体までの距離が測定される。赤外線三角測距の精度は、図９に示す各赤外測距ゾーンＺ１、Ｚ２・・・ＺＮの大きさに対応しており、後述するＣＣＤを用いた測距の精度よりも粗い。この赤外線三角測距の結果、フォーカスレンズ１１は合焦のために、赤外測距ゾーンＺＮに位置すべきであると判断された場合、ステップ１０２において、フォーカスレンズ１１は現在位置（符号ＴＬ）から、その赤外測距ゾーンＺＮの中で最も現在位置ＴＬに近い端（Ｘ位置）まで移動する（符号Ａ３）。
【００３４】
ステップ１０３〜１０５では、絞り１３が開放位置に定められた状態で測光動作が行われる。この測光動作およびステップ１０７以下の測距動作におけるＣＣＤ１６、１７からの画素信号の読出動作は、第２の読出モードにより行われる。第２の読出モードとは、次に述べるように、水平方向に沿って隣接する行の画素信号を加算して読み出すモードである。
【００３５】
ここで図１０を参照して、第２の読出モードにより読み出された画素信号に基づいて輝度信号を求める方法を説明する。第２の読出モードでは、第１および第２の水平方向のラインＬ１、Ｌ２が加算され、また第３および第４の水平方向のラインＬ３、Ｌ４が加算されて読み出され、これらのラインにより第１フィールドが形成される。輝度信号Ｙは、次の（１６）式により表される。

【００３６】
（１６）式から理解されるように、図１０において例えば二点鎖線ＹＹにより囲まれるＭｇ、Ｙｅ、Ｇ、Ｃｙの４画素の信号を加算することにより、輝度信号が得られる。
【００３７】
なお第２の読出モードでは、図１に示すように、スイッチ２８、２９は増幅器２６、２７とは反対側に切り換えられており、ＣＤＳ回路２４、２５の出力信号は、増幅器２６、２７を通らずにＡ／Ｄ変換器３１、３２に入力される。したがって、この読出モードでは、ＣＤＳ回路２４、２５の出力信号は増幅されずにＡ／Ｄ変換器３１、３２に入力される。
【００３８】
さてステップ１０３では、第１および第２のＣＣＤ１６、１７が相互に異なる所定の電子シャッタスピードで露光される。すなわち、第１のＣＣＤ１６に対しては相対的に長い第１の電子シャッタスピードで露光が行われ（符号Ａ４）、第２のＣＣＤ１７に対しては相対的に短い第２の電子シャッタスピードで露光が行われる（符号Ａ５）。このように２つの異なる電子シャッタスピードでＣＣＤ１６、１７が露光されることにより、後述するように、ＣＣＤを１つだけ用いる場合と比較して、より広い測光範囲が得られる。
【００３９】
ステップ１０４では、第１および第２のＣＣＤ１６、１７により得られた撮像信号が第１および第２の画像メモリ３３、３４へ取り込まれる（符号Ａ６、Ａ７）。すなわち各画像メモリ３３、３４には、それぞれ１フィールドの画素信号が測光データとして格納される。ステップ１０５では、画像メモリ３３、３４に格納された測光データのうち所定のデータを用いて被写体輝度が求められる。すなわち、例えば画面中央の画素に対応する測光データであって、ＣＣＤ１６、１７のダイナミックレンジ内のデータを用い、（１６）式に基づいて１画素に対応する輝度値が求められる。さらに画面中央の各画素に対する輝度値を平均して、被写体輝度が求められる（符号Ａ８）。
【００４０】
ステップ１０６では、ステップ１０５において求められた被写体輝度とＣＣＤ１６、１７の感度に基づいて、適正露出が得られるような２つの電子シャッタスピードが求められる。すなわち、
(1)絞りが開放位置にある状態における電子シャッタスピード
(2)所定のプログラム線図に従った絞り値と電子シャッタスピード
が求められる（符号Ａ８）。
【００４１】
(1)の電子シャッタスピードは、ステップ１０７以下で実行される測距動作において用いられる。すなわち絞り１３が開放された状態で測距動作が行われ、合焦動作が行われる。 (2)の電子シャッタスピードは、図７に示す映像信号の記録動作において用いられる。
【００４２】
ステップ１０３〜１０５の測光動作では、第１および第２のＣＣＤ１６、１７が用いられたが、以下に述べる測距動作では、第１のＣＣＤ１６のみが用いられ、第２のＣＣＤ１７の画素信号は無視される。
【００４３】
ステップ１０７では、 (1)の電子シャッタスピードで第１のＣＣＤ１６が露光され（符号Ａ９）、ステップ１０８では、第１のＣＣＤ１６の撮像信号が第１の画像メモリ３３に取り込まれる（符号Ａ１０）。ステップ１０９では、第１の画像メモリ３３に格納されたデータのうち所定範囲のデータを用いてフォーカス評価値Ａが求められる（符号Ａ１１）。このフォーカス評価値Ａは例えば、（１６）式に基づく所定の画素に対応する輝度値と、この画素の周囲の画素に対応する輝度値との差分値（すなわち微分値）を求めることにより得られ、従来公知の種々の方法を用いることができる。
【００４４】
次いでステップ１１０では、図９に示すように、現在フォーカスレンズ１１が位置している赤外線三角測距ゾーンＺＮのほぼ中央（Ｙ位置）まで、フォーカスレンズ１１が移動する（符号Ａ１２）。
【００４５】
ステップ１１１〜１１４の作用は、ステップ１０７〜１１０と同様である。すなわちフォーカスレンズ１１がＹ位置に定められた状態で、ステップ１１１において、ＣＣＤ１６が露光され（符号Ａ１３）、ステップ１１２において、ＣＣＤ１６の撮像信号が画像メモリ３３に取り込まれる（符号Ａ１４）。ステップ１１３では、画像メモリ３３に格納されたデータからフォーカス評価値Ｂが求められる（符号Ａ１５）。ステップ１１４では、図９に示すように、フォーカスレンズ１１は赤外線三角測距ゾーンＺＮの後端（Ｚ位置）まで移動する（符号Ａ１６）。
【００４６】
そして上記と同様にして、フォーカスレンズ１１がＺ位置に定められた状態で、ステップ１１５では、ＣＣＤ１６が露光され（符号Ａ１７）、ステップ１１６では、ＣＣＤ１６の撮像信号が画像メモリ３３に取り込まれる（符号Ａ１８）。ステップ１１７では、画像メモリ３３に格納されたデータからフォーカス評価値Ｃが求められる（符号Ａ１９）。
【００４７】
ステップ１１８では、フォーカス評価値Ａ、Ｂ、Ｃの中で最も良い値、すなわち最も大きいフォーカス評価値を示す位置まで、フォーカスレンズ１１が移動し（符号Ａ２０）、ＡＦ動作は終了する。なお、図９の例では、フォーカスレンズ１１はＸ位置に移動している。
【００４８】
次いでレリーズボタン４１が全押しされると（符号Ａ２１）、図７のプログラムの実行が開始する。ステップ２０１では絞り１３が、レリーズボタン４１の半押し時、すなわち図５と図６のプログラムのステップ１０６において求められた
(2)の絞り値まで駆動される（符号Ａ２２）。
【００４９】
ステップ２０２では、このステップ１０６において求められた (2)の電子シャッタスピードで第１のＣＣＤ１６が露光され（符号Ａ２３）、ステップ２０３では、このＣＣＤ１６の撮像信号が第１の画像メモリ３３に取り込まれる（符号Ａ２４）。この露光は、上述したようにプログラム線図に従った絞り値と電子シャッタスピードにより行われるため、これにより適正な露光量が得られるはずであるが、上述した測光・測距動作は開放絞りで行われているため、その露光量には誤差が含まれている可能性がある。そこでステップ２０４では、第１の画像メモリ３３から読み出された所定範囲のデータを用いて、適正な露光量が得られるように、電子シャッタスピードの補正値が求められる（符号Ａ２５）。これにより絞りの誤差が補正され、最適電子シャッタスピードが得られる。
【００５０】
後述するステップ２０６、２０７では、第１の読出モードにより画素信号が読み出され、１回の読出動作ではＣＣＤ１６、１７においてそれぞれ半分のフォトダイオードの信号電荷が読み出される。これに対しステップ２０２では、第２の読出モードにより画素信号が読み出され、１回の読出動作ではＣＣＤ１６において全てのフォトダイオードの信号電荷が読み出される。したがって各ＣＣＤにおいて、信号電荷が蓄積されるフォトダイオードの数が異なることも考慮され、最適電子シャッタスピードはステップ２０２における電子シャッタスピードよりも短い。
【００５１】
ステップ２０５では、図１のスイッチ２８、２９が増幅器２６、２７側に切り換えられ、ＣＣＤからの画素信号の読出モードが第１の読出モードに定められる（符号Ａ２６）。この第１の読出モードは、ＣＣＤ１６、１７から画素信号が水平方向に沿って１行ずつ読み出されるモードである。この第１の読出モードでは、図１１に示すように、まず水平方向のラインＭ１、Ｍ３・・・を構成する画素信号から成る第１フィールドが１ライン毎に読み出され、次いで、水平方向のラインＭ２、Ｍ４・・・を構成する画素信号から成る第２フィールドが１ライン毎に読み出される。
【００５２】
また第１の読出モードでは、スイッチ２８、２９が増幅器２６、２７側に切り換えられているので、ＣＤＳ回路２４、２５の出力信号は、増幅器２６、２７を通ってＡ／Ｄ変換器３１、３２に入力される。すなわちＣＤＳ回路２４、２５の出力信号は増幅器２６、２７により所定の増幅率で増幅されて、Ａ／Ｄ変換器３１、３２に入力される。
【００５３】
ステップ２０６では、ステップ２０４において求められた最適電子シャッタスピードで、第１および第２のＣＣＤ１６、１７が露光される（符号Ａ２７）。これは本露光であり、第１および第２のＣＣＤ１６、１７に生成された撮像信号は、ステップ２０７において、これらのＣＣＤ１６、１７から読み出され、それぞれ第１および第２の画像メモリ３３、３４に取り込まれる（符号Ａ２８）。上述したように、この読出動作は第１の読出モードにより行われ、まず第１フィールドの画素信号が画像メモリ３３、３４への取り込まれる。
【００５４】
この画像メモリへの取り込みと並行して、残りの画素に対する露光が行われる（符号Ａ２９）。すなわち、画素信号を一度掃き出した後（図示せず）、最適電子シャッタスピードで再び露光が行われる。ステップ２０８では、第１および第２のＣＣＤ１６、１７の残りの画素に生成された撮像信号が、それぞれ第１および第２の画像メモリ３３、３４に取り込まれる（符号Ａ３０）。この時、取り込まれる画素信号は第２フィールドの信号であり、ステップ２０７と合わせると、それぞれの画像メモリ３３、３４には２フィールド分の画素信号が取り込まれたことになる。
【００５５】
なお、レリーズボタン４１の全押しのタイミングによって第２フィールドの画素信号を第１フィールドの画素信号よりも先にメモリ３３、３４に取り込むようにしてもよい。
【００５６】
次いでステップ２０９では、絞り１３が開放位置に定められ（符号Ａ３１）、ステップ２１０では、ＣＣＤからの画素信号の読出モードが第２の読出モードに切り換えられる（符号Ａ３２）。ステップ２１１では、第１および第２の画像メモリ３３、３４から画素信号が読み出されるとともに、映像信号処理回路３６においてＲ信号、Ｇ信号およびＢ信号に変換され、これらの信号はインターフェイス回路３７によりメモリカード３８に記録される（符号Ａ３３）。これにより、このプログラムは終了する。
【００５７】
次に図１２と図１３を参照して、図５のステップ１０３〜１０５において実行される測光動作を説明する。図１２はＣＣＤ１６、１７による測光範囲を示し、図１３は測光動作における各信号の出力タイミングを示している。
【００５８】
第１および第２のＣＣＤ１６、１７のダイナミックレンジＶ_DRは同じ大きさであり、実線Ｓ１で示すように第１のＣＣＤ１６による測光範囲は被写体輝度Ｅ₁ 〜Ｅ₂ 、また実線Ｓ２で示すように第２のＣＣＤ１７による測光範囲は被写体輝度Ｅ₂ 〜Ｅ₃ である。すなわち第１のＣＣＤ１６の電子シャッタスピードは第２のＣＣＤ１７のそれよりも長く、したがって、第１のＣＣＤ１６は相対的に暗い光を検出し、第２のＣＣＤ１７は相対的に明るい光を検出する。このように、２つのＣＣＤ１６、１７の電子シャッタスピードを変えたことにより、測光範囲（Ｅ₁ 〜Ｅ₃ ）はひとつのＣＣＤを用いた場合と比較して、対数で２倍になっている。
【００５９】
ＣＣＤ１６、１７からの信号電荷の読み出しは次のようにして行われる。まず、垂直同期信号ＶＤが出力された後、露光開始時点まで電荷掃き出しパルスＳＵＢ１、ＳＵＢ２が定期的に出力され、ＣＣＤ１６、１７の各フォトダイオードに残留している不要電荷がサブストレートに掃き出される。第１のＣＣＤ１６に対する電荷掃き出しパルスＳＵＢ１が停止した後、所定時間Ｔ_K が経過すると、第２のＣＣＤ１７に対する電荷掃き出しパルスＳＵＢ２が停止する。そして、電荷掃き出しパルスＳＵＢ１が停止してから時間Ｔ₁ が経過すると、２つの転送ゲート信号ＴＧ１とＴＧ２が同時に出力され、垂直転送ＣＣＤへ各画素の信号が転送される。これにより第１のＣＣＤ１６には時間Ｔ₁ の間、また第２のＣＣＤ１７には時間Ｔ₂ （＝Ｔ₁ −Ｔ_K ）の間、それぞれ電荷が蓄積されることとなる。すなわち、時間Ｔ₁ は第１のＣＣＤ１６の電子シャッタスピードに相当し、時間Ｔ₂ は第２のＣＣＤ１７の電子シャッタスピードに相当する。
【００６０】
また、２つの転送ゲートＴＧ１、ＴＧ２が同時に出力された時、これと共に読み出し転送パルス（図示せず）が出力される。これにより、ＣＣＤ１６、１７に蓄積されていた画素信号が第２の読出モードで読み出される。図１３において、符号Ｘ₁ は第１のＣＣＤ１６から読み出された画素信号、符号Ｘ₂ は第２のＣＣＤ１７から読み出された画素信号であり、これらの画素信号Ｘ₁ 、Ｘ₂ を用いて前記（１６）式により被写体輝度が求められる。
【００６１】
図１４〜図１６を参照して、測光・測距動作において実行される第２の読出モードにおける画素信号の読み出し動作を説明する。
【００６２】
図１４は、ＣＣＤ１６、１７のフォトダイオードに発生する２つの画素信号が垂直転送ＣＣＤ５１、５２において加算される様子を示している。なお、この図において、斜線ＳＨで示す部分はポテンシャルの井戸を示し、各フォトダイオードから転送されてきた画素信号はこのポテンシャルの井戸において混合されることにより加算される。また、「４」、「６」等の数字は、図１６に示す時間ｔに対応している。
【００６３】
第１フィールドにおける画素信号の読み出し動作を説明する。
フォトダイオードＦ１１、Ｆ１３に蓄積したＭｇ、Ｇ信号が垂直転送ＣＣＤ５１に転送され、またフォトダイオードＦ２１、Ｆ２３に蓄積したＧ信号、Ｍｇ信号が垂直転送ＣＣＤ５２に転送される（符号Ｊ１）。次いで、フォトダイオードＦ１２、Ｆ１４に蓄積したＹｅ信号が垂直転送ＣＣＤ５１に転送され、またフォトダイオードＦ２２、Ｆ２４に蓄積したＣｙ信号が垂直転送ＣＣＤ５２に転送される（符号Ｊ２）。
【００６４】
そして垂直転送ＣＣＤ５１では、フォトダイオードＦ１１のＭｇ信号とフォトダイオードＦ１２のＹｅ信号とが加算され、またフォトダイオードＦ１３のＧ信号とフォトダイオードＦ１４のＹｅ信号とが加算される。垂直転送ＣＣＤ５２では、フォトダイオードＦ２１のＧ信号とフォトダイオードＦ２２のＣｙ信号とが加算され、またフォトダイオードＦ２３のＭｇ信号とフォトダイオードＦ２４のＣｙ信号とが加算される（符号Ｊ３）。その後、各垂直転送ＣＣＤ５１、５２では垂直転送が行われ、加算された画素信号は水平転送ＣＣＤ（図示せず）側に転送される（符号Ｊ４）。１回の垂直転送において、信号は２画素分転送され、この度に、水平転送ＣＣＤでは１水平走査線分の画素信号が読み出される（符号Ｊ５）。
【００６５】
第２フィールドにおける画素信号の読み出し動作は第１フィールドと同様であるが、相互に加算される２つの画素信号の組合せが第１フィールドと異なる。すなわち垂直転送ＣＣＤ５１では、フォトダイオードＦ１１に蓄積したＭｇ信号は、図１４の上方に隣接するフォトダイオード（図示せず）に蓄積したＹｅ信号と加算され、フォトダイオードＦ１２に蓄積したＹｅ信号はフォトダイオードＦ１３に蓄積したＧ信号と加算される。フォトダイオードＦ１４に蓄積したＹｅ信号は、図１４の下方に隣接するフォトダイオード（図示せず）に蓄積したＭｇ信号と加算される。垂直転送ＣＣＤ５２についても同様である。
【００６６】
図１６は、画素信号の転送動作を行うために電極Ｖ１〜Ｖ４に供給される電圧信号の時間的変化と、垂直転送ＣＣＤにおけるポテンシャルの井戸の時間的変化とを示している。この図に示すように、時間ｔ＝４，６において画素読み出しパルス（転送ゲート信号）が出力され、これによりフォトダイオードから画素信号が垂直転送ＣＣＤ５１、５２に転送される。また時間ｔ＝８では、電極Ｖ１、Ｖ２、Ｖ３の電圧レベルが同じ大きさになり、これにより電極Ｖ１に対応した井戸と電極Ｖ３に対応した井戸とが合体して画素信号が加算される（符号Ｊ６）。
【００６７】
図１７〜図１９は、本露光において実行される第１の読出モードにおける画素信号の読み出し動作を示している。
【００６８】
図１７は、ＣＣＤ１６、１７のフォトダイオードに発生する画素信号が垂直転送ＣＣＤ５１、５２に転送される様子を示している。なお、この図において、「６」、「８」等の数字は、図１９に示す時間ｔに対応している。
【００６９】
第１フィールドにおける画素信号の読み出し動作を説明する。
フォトダイオードＦ１２、Ｆ１４、Ｆ２２、Ｆ２４に対しては、画素読み出しパルス（転送ゲート信号）は出力されない。したがって、フォトダイオードＦ１２、Ｆ１４に蓄積したＹｅ信号とフォトダイオードＦ２２、Ｆ２４に蓄積したＣｙ信号は垂直転送ＣＣＤ５１、５２に転送されず（符号Ｊ１１）、フォトダイオードＦ１１、Ｆ１３に蓄積したＭｇ信号、Ｇ信号とフォトダイオードＦ２１、Ｆ２３に蓄積したＧ、Ｍｇ信号だけが垂直転送ＣＣＤ５１、５２に転送される（符号Ｊ１２）。
【００７０】
この後、第２の読出モードと同様に、電極Ｖ１、Ｖ２、Ｖ３の電圧レベルが同じ大きさになり、垂直転送ＣＣＤ５１、５２においてポテンシャルの井戸ＳＨが大きくなるが、１つの井戸ＳＨには１つの画素信号しか転送されていないため、画素信号の加算は行われない（符号Ｊ１３）。次いで、各垂直転送ＣＣＤ５１、５２では垂直転送が行われ、画素信号は水平転送ＣＣＤ（図示せず）側に転送される（符号Ｊ１４）。１回の垂直転送において、信号は２画素分転送され、この度に、水平転送ＣＣＤでは１水平走査線分の画素信号が読み出される（符号Ｊ１５）。
【００７１】
第２フィールドにおける画素信号の読み出し動作は第１フィールドと同様である。すなわちフォトダイオードＦ１１、Ｆ１３、Ｆ２１、Ｆ２３に対しては、画素読み出しパルスは出力されず、したがって、これらのフォトダイオードに蓄積したＧ信号とＭｇ信号は垂直転送ＣＣＤ５１、５２に転送されない（符号Ｊ１７）。一方、フォトダイオードＦ１２、Ｆ１４に蓄積したＹｅ信号とフォトダイオードＦ２２、Ｆ２４に蓄積したＣｙ信号だけが垂直転送ＣＣＤ５１、５２に転送され（符号Ｊ１６）、垂直転送される（符号Ｊ１８）。
【００７２】
図１９は、第２の読出モードにおける図１６に対応している。この図に示すように、時間ｔ＝６では画素読出パルスが出力されず（符号Ｊ１９）、時間ｔ＝４において画素読み出しパルスが出力され、これによりフォトダイオードから画素信号が垂直転送ＣＣＤ５１、５２に転送される。また時間ｔ＝８では、電極Ｖ１、Ｖ２、Ｖ３の電圧レベルが同じ大きさになり、これにより電極Ｖ１に対応した井戸と電極Ｖ３に対応した井戸とが合体するが、電極Ｖ３に対応した井戸には画素信号が存在しないため、画素信号の加算は行われない（符号Ｊ２０）。
【００７３】
以上のように第１実施例は、ＣＣＤ１６、１７から１行ずつ画素信号を読み出す第１の読出モードでは、画素信号は増幅器２６、２７により増幅されてＡ／Ｄ変換器３１、３２に入力され、ＣＣＤ１６、１７から２行ずつ画素信号を読み出す第２の読出モードでは、画素信号は増幅器２６、２７を通らず、直接Ａ／Ｄ変換器３１、３２に入力されるように構成されている。すなわち第１の読出モードと第２の読出モードを比較すると、第１の読出モードではＣＣＤ１６、１７の出力信号のレベルが低いため、この信号は増幅されてＡ／Ｄ変換器３１、３２に入力され、第１および第２の読出モードにおいて、ほぼ同じダイナミックレンジで量子化される。
【００７４】
このように、読出モードが変化してもＡ／Ｄ変換器３１、３２に入力される信号のダイナミックレンジが変化しないので、画素信号のＡ／Ｄ変換の精度が高められ、これにより測光・測距および静止画像の記録の精度が向上する。また、各読出モードに対応して専用のＡ／Ｄ変換器を設ける必要がないので、Ａ／Ｄ変換器の数が最小限に抑えられ、スチルビデオカメラのコストを低減させることができる。
【００７５】
図２０は第２実施例の撮像装置を備えたスチルビデオカメラのブロック図である。第１実施例と異なる構成のみを説明する。
【００７６】
ＣＤＳ回路２４とスイッチ２８の間には遅延回路６１、加算器６２および減衰器６３が設けられ、ＣＤＳ回路２５とスイッチ２９の間には遅延回路６４、加算器６５および減衰器６６が設けられている。スイッチ２８、２９は、第１の読出モードでは減衰器６３、６６とは反対側に切り換えられ、第２の読出モードでは減衰器６３、６６側に切り換えられる。したがってＣＤＳ２４、２５の出力信号は、第１の読出モードでは直接Ａ／Ｄ変換器３１、３２に入力され、第２の読出モードでは、遅延回路６１、６４、加算器６２、６５および減衰器６３、６６を介してＡ／Ｄ変換器３１、３２に入力される。
【００７７】
ＣＤＳ２４、２５の出力信号は、遅延回路６１、６４において１画素分だけ遅延されて加算器６２、６５に入力され、また遅延回路６１、６４を通ることなく加算器６２、６５に入力される。すなわち加算器６２、６５では、１画素遅延された画素信号と遅延されない画素信号とが相互に加算される。この加算器６２、６５の出力信号は、減衰器６３、６６において所定の減衰率で減衰せしめられる。
【００７８】
その他の構成は、図１の第１実施例の構成と同じである。
【００７９】
第２の読出モードでは、図１０の符号ＹＹの部分を参照すると、例えばラインＬ１、Ｌ２のＭｇ信号とＹｅ信号が遅延回路６１、６４により１画素分遅延されて加算器６３、６６に入力され、Ｇ信号とＣｙ信号は遅延されずに加算器６３、６６に入力される。したがって、これらのＭｇ信号、Ｙｅ信号、Ｇ信号、Ｃｙ信号が加算され、（１６）式に示されるように輝度信号Ｙが求められる。そしてこの輝度信号Ｙは減衰器６３、６６において減衰され、Ａ／Ｄ変換器３１、３２に入力される。
【００８０】
これに対し、第１の読出モードでは、画素信号は減衰されることなくＡ／Ｄ変換器３１、３２に入力される。これは、第１実施例に関して上述したように、第１の読出モードではＣＣＤ１６、１７の出力信号のレベルが第２の読出モードよりも低いためである。
【００８１】
このように第２実施例においても、読出モードに対応して専用のＡ／Ｄ変換器を設けることなく、高精度にＡ／Ｄ変換を行うことができ、Ａ／Ｄ変換器の数を最小限に抑えることができる。
【００８２】
図２１は第３実施例の撮像装置を備えたスチルビデオカメラのブロック図である。第１実施例と異なる構成のみを説明する。
【００８３】
ＣＤＳ回路２４、２５とＡ／Ｄ変換器３１、３２の間には、増幅器あるいは減衰器等は設けられておらず、これらは直接接続されている。一方、Ａ／Ｄ変換器３１、３２には、スイッチ７３を介して第１および第２の基準電圧発生器７１、７２の一方が接続される。第１および第２の基準電圧発生器７１、７２は、Ａ／Ｄ変換における例えば上限値の基準電圧を発生するもので、Ａ／Ｄ変換器７１、７２では、この基準電圧を用いて、ＣＤＳ回路２４、２５から入力されるアナログの画素信号の量子化が行われる。第１の基準電圧発生器７１の基準電圧は相対的に低く、第２の基準電圧発生器７２の基準電圧は相対的に高い。なお、下限基準電圧は、Ａ／Ｄ変換器７１、７２ともに同じ値に固定されている。
【００８４】
スイッチ７３は、第１の読出モードでは第１の基準電圧発生器７１側に切り換えられ、第２の読出モードでは第２の基準電圧発生器７２側に切り換えられる。上述したように第１の読出モードでは、ＣＣＤ１６、１７の出力信号のレベルが第２の読出モードよりも低いため、この信号の量子化に用いる基準電圧を低くすることにより、第１および第２の読出モードにおけるＡ／Ｄ変換のダイナミックレンジをほぼ同じ大きさにすることができる。したがって第３実施例によっても、第１実施例と同様な効果が得られる。
【００８５】
なお第３実施例では、第１実施例と同様に、画像メモリ３３、３４から読み出された画素信号について、（１６）式を用いて輝度信号Ｙが求められる。
【００８６】
なお、図５のフローチャートにおいて、ＣＣＤ１６、１７のダイナミックレンジＶ_DRが充分に広い場合には、各ＣＣＤ１６、１７を相互に異なる電子シャッタスピードで露光する必要はない。
【００８７】
【発明の効果】
以上のように本発明によれば、イメージセンサからの画素信号の読出モードが変化する構成において、読出モードに対応させてＡ／Ｄ変換器の数を増加させることなく画素信号のＡ／Ｄ変換の精度を高めることができる、安価な撮像装置が得られる。
【図面の簡単な説明】
【図１】本発明の一実施例を適用したスチルビデオカメラの回路構成を示すブロック図である。
【図２】第１および第２のＣＣＤの受光面上に設けられたカラーフィルタの配列を示す図である。
【図３】第１および第２のＣＣＤの出力信号に関し、対応する画素同士を重ね合わせた状態を示す図である。
【図４】実施例における色信号の抽出方法を説明するための図である。
【図５】測距・測光動作を行うプログラムの前半部分を示すフローチャートである。
【図６】測距・測光動作を行うプログラムの後半部分を示すフローチャートである。
【図７】映像信号のメモリカードへの記録動作を行うプログラムのフローチャートである。
【図８】撮影動作のタイミングチャートである。
【図９】ＡＦ動作におけるフォーカスレンズの移動を示す図である。
【図１０】第２の読出モードにおける画素信号の読出動作を示す図である。
【図１１】第１の読出モードにおける画素信号の読出動作を示す図である。
【図１２】第１および第２のＣＣＤによる測光範囲を示す図である。
【図１３】測光動作における各信号の出力タイミングを示す図である。
【図１４】第２の読出モードにおいて、２つの画素信号が垂直転送ＣＣＤにおいて加算される動作を示す図である。
【図１５】第２の読出モードにおける画素信号の垂直転送ＣＣＤへの読み出し動作、垂直転送動作および水平転送動作を示す図である。
【図１６】第２の読出モードにおいて、垂直転送動作における電圧信号の時間的変化と、垂直転送ＣＣＤにおけるポテンシャルの井戸の時間的変化とを示す図である。
【図１７】第１の読出モードにおいて、画素信号が垂直転送ＣＣＤに転送される動作を示す図である。
【図１８】第１の読出モードにおける画素信号の垂直転送ＣＣＤへの読み出し動作、垂直転送動作および水平転送動作を示す図である。
【図１９】第１の読出モードにおいて、垂直転送動作における電圧信号の時間的変化と、垂直転送ＣＣＤにおけるポテンシャルの井戸の時間的変化とを示す図である。
【図２０】第２実施例の撮像装置を備えたスチルビデオカメラのブロック図である。
【図２１】第３実施例の撮像装置を備えたスチルビデオカメラのブロック図である。
【符号の説明】
１６、１７ ＣＣＤ（イメージセンサ）
２１、２２ フィルタ[0001]
[Industrial application fields]
The present invention relates to an apparatus for performing photometry / ranging operation and generating a video signal of a still image based on a pixel signal obtained by a solid-state imaging device such as a CCD.
[0002]
[Prior art]
2. Description of the Related Art Conventional imaging devices are known in which complementary color checkered color filters are provided on a light receiving surface of an image sensor, in which magenta, green, yellow, and cyan color filter elements are regularly arranged. In this imaging apparatus, when generating a frame mode video signal, the pixel signal of the odd-numbered row and the pixel signal of the row adjacent to the lower side of this row are added from the image sensor to read out the pixel signal of the odd-numbered field. In addition, the pixel signal of the even field is added to the pixel signal of the row adjacent to the lower side of this row to read out the pixel signal of the even field. That is, a pixel signal of one field is simultaneously read out from the image sensor every two rows and generated, and a video signal of one screen is obtained from the pixel signals of the odd field and the even field.
[0003]
Conventionally, when performing the photometry / ranging operation using the above-described imaging device, a luminance signal is generated based on the pixel signal of one field read out from the image sensor two rows at a time, and the distance measurement is performed based on the luminance signal. Data etc. are calculated.
[0004]
[Problems to be solved by the invention]
In the conventional imaging device having the complementary color checkered color filter described above, the resolution for color is low. Therefore, in Japanese Patent Application No. H4-262810, the present applicant provides two image sensors as a configuration for increasing the color resolution, reads out pixel signals from each image sensor one line at a time, and superimposes predetermined pixel signals, A configuration for obtaining a video signal (R signal, G signal and B signal) of a still image has been proposed.
[0005]
However, in this proposed apparatus, if control is performed to read out pixel signals from the image sensor two rows at a time and generate a luminance signal for photometry / ranging operation, the dynamic range of the A / D converter is one row. Since it is different from reading (when generating a video signal of a still image), it is necessary to provide two types of A / D converters in order to perform A / D conversion with high accuracy, and the manufacturing cost of the apparatus is reduced. The problem of becoming higher occurs.
[0006]
  The present inventionAn object of the present invention is to obtain an image pickup apparatus having a simple configuration in which an image pickup apparatus having a plurality of image pickup elements improves the image quality of a still image, expands a photometric range, and optimizes a dynamic range in quantization simultaneously.
[0007]
[Means for solving problems]
  An imaging device according to the present invention generates pixel signals of pixels arranged in a horizontal direction and a vertical direction.pluralPixels from the image sensor can be obtained from the image sensor and in a first readout mode in which pixel signals are read out row by row along the horizontal direction, or in a second readout mode in which pixel signals in adjacent rows along the horizontal direction are added and read out. Pixel signal reading means for reading a signal, and A / D conversion means for quantizing the pixel signal read by the pixel signal reading means in substantially the same dynamic range in the first and second reading modes;A luminance signal generating means for generating a luminance signal for photometry calculation or distance measurement calculation based on the pixel signal of one field read from each image sensor according to the second reading mode, and according to the first reading mode; Video signal generation means for generating a video signal of a still image based on the pixel signal read from the image sensor, and the luminance signal generation means is used when each image sensor is exposed at a different electronic shutter speed. The subject brightness is obtained based on the pixel signal read from each image sensor.It is characterized by that.
[0008]
【Example】
The present invention will be described below with reference to illustrated embodiments.
FIG. 1 is a block diagram of a still video camera provided with an image pickup apparatus according to the first embodiment of the present invention.
[0009]
The system control circuit 10 is a microcomputer and controls the entire still video camera.
[0010]
The focus lens 11 is controlled by a focus lens driving circuit 12 during a focusing operation. The aperture of the aperture 13 is adjusted by the aperture drive circuit 14 during exposure control. The focus lens driving circuit 12 and the aperture driving circuit 14 are controlled by the system control circuit 10.
[0011]
The light beam that has passed through the focus lens 11 and the diaphragm 13 is split by the half mirrors 15a and 15b. One light beam is guided to a finder (not shown), and the other two light beams are guided to first and second CCDs (image sensors) 16 and 17. These CCDs 16 and 17 are arranged so that an equivalent subject image is formed on each light receiving surface. The CCDs 16 and 17 are solid-state imaging devices, and have photodiodes corresponding to a large number of pixels arranged along the horizontal direction and the vertical direction of the reproduction screen, and pixel signals corresponding to the subject image are generated in these photodiodes. .
[0012]
The first and second CCDs 16 and 17 are provided with filters 21 and 22, respectively. These CCDs 16 and 17 are driven by a CCD drive circuit 23, whereby pixel signals corresponding to subject images formed on the CCDs 16 and 17 are supplied to correlated double sampling (CDS) circuits 24 and 25. . The CCD drive circuit 23 is controlled by the system control circuit 10.
[0013]
The pixel signals input to the CDS circuits 24 and 25 are subjected to predetermined processing such as reset noise removal. The signals output from the CDS circuits 24 and 25 are input to the A / D converters 31 and 32 through the amplifiers 26 and 27 or without passing through the amplifiers 26 and 27. As will be described later, there are first and second readout modes as the readout operation of the pixel signals from the CCDs 16 and 17, and the amplifiers 26 and 27 set the voltage levels of the pixel signals when the first readout mode is selected. Provided to amplify. The switches 28 and 29 are provided to connect the A / D converters 31 and 32 to the amplifiers 26 and 27 or the CDS circuits 24 and 25. The system control circuit 10 controls the switching of the switches 28 and 29. Is called.
[0014]
The pixel signals converted into digital signals by the A / D converters 31 and 32 are stored in the first and second image memories 33 and 34, respectively. Each of the image memories 33 and 34 has a storage capacity capable of storing pixel signals for two fields. Address control of the image memories 33 and 34 is performed by the system control circuit 10 via the image memory control circuit 35.
[0015]
The pixel signals read from the image memories 33 and 34 are input to the video signal processing circuit 36, subjected to predetermined processing, and converted into R signals, G signals, and B signals. These signals are input to the interface circuit 37 and converted into a format for recording on the memory card 38. The recording operation of the R signal, the G signal, and the B signal to the memory card 38 is performed by the system control circuit 10 via the memory card control circuit 39.
[0016]
A release button 41 is connected to the system control circuit 10. As will be described later, when the release button 41 is half-pressed, the photometry / ranging operation is performed, and when the release button 41 is fully pressed, the recording operation of the video signal to the memory card 38 is performed. An infrared triangular distance measuring device 42 is connected to the system control circuit 10. As is conventionally known, the distance measuring device 42 measures the distance to a subject by triangulation by irradiating the subject with infrared rays and receiving reflected light from the infrared subject.
[0017]
FIG. 2 shows an arrangement of the color filters 21 and 22 provided on the light receiving surfaces of the first and second CCDs 16 and 17. These color filters 21 and 22 are complementary color checkered color filters and have the same configuration. In these color filters 21 and 22, filter elements that transmit magenta (Mg), yellow (Ye), cyan (Ce), and green (G) are regularly arranged. In other words, in addition to green (G), magenta (Mg), yellow (Ye), and cyan (Ce) having different spectral characteristics of complementary colors are included in a total of four pixels that are arranged in two horizontal and vertical directions. Three pixels are provided.
[0018]
When the positional relationship of the second color filter 22 with respect to the CCD 17 is compared with the positional relationship of the first color filter 21 with respect to the CCD 16, the second color filter 22 is horizontal with respect to the CCD 17 by one pixel (left in FIG. 2). Direction). For example, when attention is paid to the pixel P in the upper left corner of the screen, the first color filter 21 is magenta, but the second color filter 22 is green.
[0019]
As described above, the pixel spectral characteristics of the CCDs 16 and 17 change regularly, respectively, and are of the complementary color difference line sequential type. Further, the pixel spectral characteristic of the second CCD 17 is shifted in the horizontal direction by one pixel with respect to the pixel spectral characteristic of the first CCD 16. Therefore, the four pixels of the two pixels arranged in the vertical direction of the first CCD 16 and the two pixels arranged in the vertical direction of the second CCD 17 at the optically same position of the two pixels have different spectral characteristics. ing. That is, for example, when one of the two pixels is Mg and Ye, the other two pixels are G and Cy.
[0020]
The output signal of the first CCD 16 and the output signal of the second CCD 17 are temporarily stored as digital signals in the image memories 33 and 34, but are read from these memories and processed in the video signal processing circuit 36. That is, corresponding pixels are overlapped with each other, and an R signal, a G signal, and a B signal corresponding to each pixel are extracted from the overlapped signal to obtain a video signal.
[0021]
FIG. 3 shows this superposition state. As understood from this figure, the magenta (Mg) of the filter 21 of the first CCD 16 and the green (G) of the filter 22 of the second CCD 17 are the green (G) of the filter 21 and the magenta (Mg of the filter 22 ), Yellow (Ye) of the filter 21 and cyan (Cy) of the filter 22 correspond to the same pixel, and cyan (Cy) of the filter 21 and yellow (Ye) of the filter 22 correspond to the same pixel. In FIG. 3, Px represents the interval (1 pitch) between the pixels in the horizontal direction, and Py represents the interval (1 pitch) between the pixels in the vertical direction.
[0022]
First, extraction of the R signal will be described.
R signal contained in magenta (Mg) is R_Mg, B signal to B_Mg, R signal included in yellow (Ye)_Ye, G signal to G_Ye, G signals included in cyan (Cy)_Cy, B signal to B_CyThen,
Mg = R_Mg+ B_Mg, Ye = R_Ye+ G_Ye, Cy = G_Cy+ B_Cy
It can be expressed as.
[0023]
The R signal is obtained from four pixels (pixels hatched in FIG. 3) of magenta (Mg) and yellow (Ye) aligned in the vertical direction, and green (G) and cyan (Cy) superimposed on them. It is obtained by the following formula.

However, in order for this equation (1) to hold,
α = G_Ye/ (G + G_Cy) = B_Mg/ B_Cy
Is a condition.
[0024]
Similarly, the B signal is obtained by the following equation.

However, in order for this equation (2) to hold,
β = G_Cy/ (G + G_Ye) = R_Mg/ R_Ye
Is a condition.
[0025]
For the G signal, the luminance signal Y and R obtained by the equations (1) and (2)_S, B_SAnd obtained from That is,

[0026]
Next, an actual RGB signal extraction method will be described with reference to FIG.
In the pixel arrangement of this figure, the first and second CCDs 16 and 17 are represented by parameters A and B, respectively, the horizontal direction is represented by parameter i, and the vertical direction is represented by parameter j. In this figure, it is assumed that among the pixels shown in an overlapping manner, the pixel located above corresponds to the first CCD 16 and the pixel located below corresponds to the second CCD 17. For the first CCD 16, the signal from each pixel is
VA, i, j = Mg, VA, i + 1, j = G
VA, i, j + 1 = Ye, VA, i + 1, j + 1 = Cy
VA, i, j + 2 = G, VA, i + 1, j + 2 = Mg
VA, i, j + 3 = Ye, VA, i + 1, j + 3 = Cy
With regard to the second CCD 17,
VB, i, j = G, VB, i + 1, j = Mg
VB, i, j + 1 = Cy, VB, i + 1, j + 1 = Ye
VB, i, j + 2 = Mg, VB, i + 1, j + 2 = G
VB, i, j + 3 = Cy, VB, i + 1, j + 3 = Ye
Arrange so that Here, it is assumed that i = 1, 3, 5,..., J = 1, 5, 9,.
[0027]
In the first scan, the first field signal,
VA, i, j = Mg, VA, i + 1, j = G
VA, i, j + 2 = G, VA, i + 1, j + 2 = Mg
VB, i, j = G, VB, i + 1, j = Mg
VB, i, j + 2 = Mg, VB, i + 1, j + 2 = G
Is extracted, and the second field signal in the second scan, ie,
VA, i, j + 1 = Ye, VA, i + 1, j + 1 = Cy
VA, i, j + 3 = Ye, VA, i + 1, j + 3 = Cy
VB, i, j + 1 = Cy, VB, i + 1, j + 1 = Ye
VB, i, j + 3 = Cy, VB, i + 1, j + 3 = Ye
Is extracted.
[0028]
All the above pixel signals are stored in the image memories 33 and 34. These pixel signals are read out to the video signal processing circuit 36, and the i-th pixel of the odd-even scanning line in the odd field is calculated.

RGB signals are obtained.
[0029]
Similarly, for the i + 1th pixel of the odd-even scan line in the odd field,

RGB signals are obtained.
Here, p and q may be 1 if the equation (3) is referred to, but it is preferable that p and q can be appropriately adjusted according to the value of the Y component.
[0030]
The constants α, β, p, and q are determined by adjusting software parameters executed in the system control circuit 10.
[0031]
For even fields, RGB signals can be obtained by combining the (j + 1) th and (j + 2) th pixels with equations similar to the above equations (4) to (15).
The above formula is a linear calculation method without performing gamma correction. If the gamma-corrected signal is stored in the image memories 33 and 34, the calculation is performed after linear conversion. After the calculation, normal gamma correction is performed.
[0032]
Next, the photographing operation in the first embodiment will be described with reference to FIGS. 5 and 6 are flowcharts of a program for performing distance measurement / photometry operations, and FIG. 7 is a flowchart of a program for recording video signals on a memory card. FIG. 8 is a timing chart of the photographing operation. FIG. 9 is a diagram illustrating movement of the focus lens in the automatic focus adjustment (AF) operation. FIG. 10 is a diagram illustrating a pixel signal reading operation in the second reading mode. FIG. 11 is a diagram showing a pixel signal reading operation in the first reading mode.
[0033]
The execution of the distance measurement / photometry program shown in FIGS. 5 and 6 is started by half-pressing the release button 41 (reference A1). In step 101, infrared triangulation is performed by the infrared triangulation device 42 (reference A2), and the distance from the still video camera to the subject is measured. The accuracy of the infrared triangulation corresponds to the size of each of the infrared ranging zones Z1, Z2,... ZN shown in FIG. 9, and is coarser than the accuracy of the distance measurement using a CCD described later. As a result of the infrared triangulation, when it is determined that the focus lens 11 should be positioned in the infrared ranging zone ZN for focusing, in step 102, the focus lens 11 is at the current position (reference TL). To the end (X position) closest to the current position TL in the infrared ranging zone ZN (reference A3).
[0034]
In steps 103 to 105, the photometric operation is performed in a state where the diaphragm 13 is set at the open position. The pixel signal readout operation from the CCDs 16 and 17 in this photometry operation and the distance measurement operation in step 107 and subsequent steps is performed in the second readout mode. The second readout mode is a mode in which pixel signals in adjacent rows along the horizontal direction are added and read out as described below.
[0035]
Here, with reference to FIG. 10, a method for obtaining a luminance signal based on the pixel signal read in the second reading mode will be described. In the second reading mode, the first and second horizontal lines L1 and L2 are added, and the third and fourth horizontal lines L3 and L4 are added and read. A first field is formed. The luminance signal Y is expressed by the following equation (16).

[0036]
As understood from the equation (16), the luminance signal is obtained by adding the signals of, for example, four pixels of Mg, Ye, G, and Cy surrounded by the two-dot chain line YY in FIG.
[0037]
In the second read mode, as shown in FIG. 1, the switches 28 and 29 are switched to the opposite side of the amplifiers 26 and 27, and the output signals of the CDS circuits 24 and 25 pass through the amplifiers 26 and 27. Without being input to the A / D converters 31 and 32. Therefore, in this read mode, the output signals of the CDS circuits 24 and 25 are input to the A / D converters 31 and 32 without being amplified.
[0038]
In step 103, the first and second CCDs 16 and 17 are exposed at different predetermined electronic shutter speeds. That is, the first CCD 16 is exposed at a relatively long first electronic shutter speed (reference A4), and the second CCD 17 is exposed at a relatively short second electronic shutter speed. Is performed (reference A5). By exposing the CCDs 16 and 17 at two different electronic shutter speeds as described above, a wider photometric range can be obtained as compared with the case where only one CCD is used, as will be described later.
[0039]
In step 104, the imaging signals obtained by the first and second CCDs 16 and 17 are taken into the first and second image memories 33 and 34 (reference numerals A6 and A7). That is, in each of the image memories 33 and 34, a pixel signal of one field is stored as photometric data. In step 105, the subject brightness is obtained using predetermined data among the photometric data stored in the image memories 33 and 34. That is, for example, the photometric data corresponding to the pixel at the center of the screen, and using the data within the dynamic range of the CCDs 16 and 17, the luminance value corresponding to one pixel is obtained based on the equation (16). Further, the luminance value for each pixel at the center of the screen is averaged to obtain the subject luminance (reference A8).
[0040]
In step 106, two electronic shutter speeds for obtaining proper exposure are obtained based on the subject brightness obtained in step 105 and the sensitivity of the CCDs 16 and 17. That is,
(1) Electronic shutter speed with the aperture in the open position
(2) Aperture value and electronic shutter speed according to a predetermined program diagram
Is obtained (reference A8).
[0041]
The electronic shutter speed (1) is used in the distance measuring operation executed in step 107 and subsequent steps. That is, the ranging operation is performed with the aperture 13 opened, and the focusing operation is performed. The electronic shutter speed (2) is used in the video signal recording operation shown in FIG.
[0042]
Although the first and second CCDs 16 and 17 are used in the photometric operation of steps 103 to 105, only the first CCD 16 is used in the distance measuring operation described below, and the pixel signal of the second CCD 17 is ignored. Is done.
[0043]
In step 107, the first CCD 16 is exposed at the electronic shutter speed of (1) (reference A9), and in step 108, the imaging signal of the first CCD 16 is taken into the first image memory 33 (reference A10). In step 109, a focus evaluation value A is obtained using a predetermined range of data stored in the first image memory 33 (reference A11). The focus evaluation value A is obtained, for example, by obtaining a difference value (that is, a differential value) between a luminance value corresponding to a predetermined pixel based on Expression (16) and a luminance value corresponding to pixels around this pixel. Various conventionally known methods can be used.
[0044]
Next, at step 110, as shown in FIG. 9, the focus lens 11 is moved to substantially the center (Y position) of the infrared triangular distance measuring zone ZN where the focus lens 11 is currently located (reference A12).
[0045]
The operation of steps 111 to 114 is the same as that of steps 107 to 110. That is, with the focus lens 11 set at the Y position, the CCD 16 is exposed in step 111 (reference A13), and in step 112, the image signal of the CCD 16 is taken into the image memory 33 (reference A14). In step 113, the focus evaluation value B is obtained from the data stored in the image memory 33 (reference A15). In step 114, as shown in FIG. 9, the focus lens 11 moves to the rear end (Z position) of the infrared triangular distance measuring zone ZN (reference A16).
[0046]
In the same manner as described above, with the focus lens 11 set at the Z position, the CCD 16 is exposed in step 115 (reference A17), and in step 116, the image pickup signal of the CCD 16 is taken into the image memory 33 (reference sign A17). A18). In step 117, the focus evaluation value C is obtained from the data stored in the image memory 33 (reference A19).
[0047]
In step 118, the focus lens 11 is moved to the position showing the best value among the focus evaluation values A, B, and C, that is, the largest focus evaluation value (reference A20), and the AF operation ends. In the example of FIG. 9, the focus lens 11 has moved to the X position.
[0048]
Next, when the release button 41 is fully pressed (reference A21), execution of the program of FIG. 7 starts. In step 201, the aperture 13 is obtained when the release button 41 is half-pressed, that is, in step 106 of the program shown in FIGS.
Driven to the aperture value of (2) (reference A22).
[0049]
In step 202, the first CCD 16 is exposed at the electronic shutter speed (2) obtained in step 106 (reference A23), and in step 203, the image pickup signal of the CCD 16 is taken into the first image memory 33. (Reference A24). Since this exposure is performed with the aperture value and electronic shutter speed according to the program diagram as described above, an appropriate exposure amount should be obtained by this, but the above-mentioned photometry / ranging operation is performed with an open aperture. Since the exposure is performed, there is a possibility that the exposure amount includes an error. Accordingly, in step 204, a correction value for the electronic shutter speed is obtained using the data in a predetermined range read from the first image memory 33 so that an appropriate exposure amount can be obtained (reference A25). Thereby, the aperture error is corrected and the optimum electronic shutter speed is obtained.
[0050]
In steps 206 and 207, which will be described later, pixel signals are read out in the first reading mode, and signal charges of half of the photodiodes are read out in the CCDs 16 and 17 in one reading operation, respectively. On the other hand, in step 202, the pixel signal is read out in the second reading mode, and the signal charges of all the photodiodes are read out in the CCD 16 in one reading operation. Therefore, in consideration of the fact that each CCD has a different number of photodiodes in which signal charges are stored, the optimum electronic shutter speed is shorter than the electronic shutter speed in step 202.
[0051]
In step 205, the switches 28 and 29 in FIG. 1 are switched to the amplifiers 26 and 27, and the reading mode of the pixel signals from the CCD is set to the first reading mode (reference A26). This first readout mode is a mode in which pixel signals are read out from the CCDs 16 and 17 line by line along the horizontal direction. In this first readout mode, as shown in FIG. 11, first, a first field consisting of pixel signals constituting horizontal lines M1, M3... Is read out line by line, and then in the horizontal direction. A second field composed of pixel signals constituting the lines M2, M4... Is read out for each line.
[0052]
In the first read mode, since the switches 28 and 29 are switched to the amplifiers 26 and 27 side, the output signals of the CDS circuits 24 and 25 pass through the amplifiers 26 and 27 and the A / D converters 31 and 32, respectively. Is input. That is, the output signals of the CDS circuits 24 and 25 are amplified by the amplifiers 26 and 27 at a predetermined amplification rate and input to the A / D converters 31 and 32.
[0053]
In step 206, the first and second CCDs 16 and 17 are exposed at the optimum electronic shutter speed obtained in step 204 (reference A27). This is the main exposure, and the imaging signals generated in the first and second CCDs 16 and 17 are read out from these CCDs 16 and 17 in step 207, and the first and second image memories 33 and 34, respectively. (Reference A28). As described above, this reading operation is performed in the first reading mode. First, the pixel signals of the first field are taken into the image memories 33 and 34.
[0054]
In parallel with the capture to the image memory, the remaining pixels are exposed (reference A29). That is, after sweeping out the pixel signal once (not shown), exposure is performed again at the optimum electronic shutter speed. In step 208, the imaging signals generated in the remaining pixels of the first and second CCDs 16 and 17 are taken into the first and second image memories 33 and 34, respectively (reference A30). At this time, the captured pixel signal is a signal of the second field, and when combined with step 207, the pixel signals for two fields are captured in the respective image memories 33 and 34.
[0055]
It should be noted that the pixel signal of the second field may be taken into the memories 33 and 34 before the pixel signal of the first field at the timing when the release button 41 is fully pressed.
[0056]
Next, at step 209, the aperture 13 is set to the open position (reference A31), and at step 210, the readout mode of the pixel signal from the CCD is switched to the second readout mode (reference A32). In step 211, pixel signals are read from the first and second image memories 33 and 34 and converted into R, G, and B signals by the video signal processing circuit 36. These signals are stored in the memory by the interface circuit 37. It is recorded on the card 38 (reference A33). This terminates this program.
[0057]
Next, with reference to FIG. 12 and FIG. 13, the photometry operation executed in steps 103 to 105 in FIG. 5 will be described. FIG. 12 shows the photometry range by the CCDs 16 and 17, and FIG. 13 shows the output timing of each signal in the photometry operation.
[0058]
Dynamic range V of the first and second CCDs 16 and 17_DRAre the same size, and as shown by the solid line S1, the photometric range of the first CCD 16 is subject luminance E.₁~ E₂In addition, as indicated by the solid line S2, the photometric range by the second CCD 17 is subject luminance E.₂~ E_ThreeIt is. That is, the electronic shutter speed of the first CCD 16 is longer than that of the second CCD 17, so that the first CCD 16 detects relatively dark light and the second CCD 17 detects relatively bright light. Thus, by changing the electronic shutter speed of the two CCDs 16 and 17, the photometric range (E₁~ E_Three) Is twice the logarithm as compared with the case of using one CCD.
[0059]
Reading signal charges from the CCDs 16 and 17 is performed as follows. First, after the vertical synchronization signal VD is output, the charge sweep-out pulses SUB1 and SUB2 are periodically output until the exposure start point, and unnecessary charges remaining in the photodiodes of the CCDs 16 and 17 are swept out to the substrate. . After the charge sweep-out pulse SUB1 for the first CCD 16 stops, a predetermined time T_KWhen elapses, the charge sweep-out pulse SUB2 for the second CCD 17 stops. Then, after the charge sweep-out pulse SUB1 stops, the time T₁When elapses, two transfer gate signals TG1 and TG2 are simultaneously output, and the signal of each pixel is transferred to the vertical transfer CCD. As a result, the first CCD 16 has time T₁And the second CCD 17 has a time T₂(= T₁-T_K) During this period, charges are accumulated. That is, time T₁Corresponds to the electronic shutter speed of the first CCD 16, and the time T₂Corresponds to the electronic shutter speed of the second CCD 17.
[0060]
Further, when the two transfer gates TG1 and TG2 are simultaneously output, a read transfer pulse (not shown) is output together therewith. Thereby, the pixel signals accumulated in the CCDs 16 and 17 are read out in the second readout mode. In FIG.₁Is the pixel signal read from the first CCD 16, the symbol X₂Is a pixel signal read from the second CCD 17, and these pixel signals X₁, X₂The subject brightness is obtained by the above equation (16) using.
[0061]
The pixel signal readout operation in the second readout mode executed in the photometry / ranging operation will be described with reference to FIGS.
[0062]
FIG. 14 shows how the two pixel signals generated in the photodiodes of the CCDs 16 and 17 are added in the vertical transfer CCDs 51 and 52. In this figure, the hatched portion SH indicates a potential well, and pixel signals transferred from each photodiode are added by being mixed in the potential well. Also, numbers such as “4” and “6” correspond to the time t shown in FIG.
[0063]
A pixel signal readout operation in the first field will be described.
The Mg and G signals accumulated in the photodiodes F11 and F13 are transferred to the vertical transfer CCD 51, and the G and Mg signals accumulated in the photodiodes F21 and F23 are transferred to the vertical transfer CCD 52 (reference J1). Next, the Ye signal accumulated in the photodiodes F12 and F14 is transferred to the vertical transfer CCD 51, and the Cy signal accumulated in the photodiodes F22 and F24 is transferred to the vertical transfer CCD 52 (reference J2).
[0064]
In the vertical transfer CCD 51, the Mg signal of the photodiode F11 and the Ye signal of the photodiode F12 are added, and the G signal of the photodiode F13 and the Ye signal of the photodiode F14 are added. In the vertical transfer CCD 52, the G signal of the photodiode F21 and the Cy signal of the photodiode F22 are added, and the Mg signal of the photodiode F23 and the Cy signal of the photodiode F24 are added (reference numeral J3). Thereafter, vertical transfer is performed in each of the vertical transfer CCDs 51 and 52, and the added pixel signal is transferred to the horizontal transfer CCD (not shown) side (reference numeral J4). In one vertical transfer, the signal is transferred for two pixels, and each time the horizontal transfer CCD reads a pixel signal for one horizontal scanning line (reference J5).
[0065]
The pixel signal readout operation in the second field is the same as that in the first field, but the combination of two pixel signals added to each other is different from that in the first field. That is, in the vertical transfer CCD 51, the Mg signal accumulated in the photodiode F11 is added to the Ye signal accumulated in the photodiode (not shown) adjacent to the upper side of FIG. 14, and the Ye signal accumulated in the photodiode F12 is added to the photodiode. It is added to the G signal stored in F13. The Ye signal accumulated in the photodiode F14 is added to the Mg signal accumulated in the photodiode (not shown) adjacent to the lower side of FIG. The same applies to the vertical transfer CCD 52.
[0066]
FIG. 16 shows a temporal change in the voltage signal supplied to the electrodes V1 to V4 in order to perform the pixel signal transfer operation, and a temporal change in the potential well in the vertical transfer CCD. As shown in this figure, a pixel readout pulse (transfer gate signal) is output at time t = 4, 6, whereby the pixel signal is transferred from the photodiode to the vertical transfer CCDs 51 and 52. At time t = 8, the voltage levels of the electrodes V1, V2, and V3 are the same, and the well corresponding to the electrode V1 and the well corresponding to the electrode V3 are merged to add a pixel signal ( Reference J6).
[0067]
17 to 19 show the pixel signal readout operation in the first readout mode executed in the main exposure.
[0068]
FIG. 17 shows how pixel signals generated in the photodiodes of the CCDs 16 and 17 are transferred to the vertical transfer CCDs 51 and 52. In this figure, numbers such as “6” and “8” correspond to the time t shown in FIG.
[0069]
A pixel signal readout operation in the first field will be described.
Pixel readout pulses (transfer gate signals) are not output to the photodiodes F12, F14, F22, and F24. Therefore, the Ye signal accumulated in the photodiodes F12 and F14 and the Cy signal accumulated in the photodiodes F22 and F24 are not transferred to the vertical transfer CCDs 51 and 52 (reference numeral J11), and the Mg signal accumulated in the photodiodes F11 and F13, G Only the signals and the G and Mg signals accumulated in the photodiodes F21 and F23 are transferred to the vertical transfer CCDs 51 and 52 (reference J12).
[0070]
Thereafter, as in the second read mode, the voltage levels of the electrodes V1, V2, and V3 are the same, and the potential well SH in the vertical transfer CCDs 51 and 52 is increased. Since only one pixel signal is transferred, the pixel signals are not added (reference numeral J13). Next, vertical transfer is performed in each of the vertical transfer CCDs 51 and 52, and the pixel signal is transferred to the horizontal transfer CCD (not shown) side (reference J14). In one vertical transfer, the signal is transferred for two pixels, and each time the horizontal transfer CCD reads the pixel signal for one horizontal scanning line (reference J15).
[0071]
The pixel signal readout operation in the second field is the same as that in the first field. That is, pixel readout pulses are not output to the photodiodes F11, F13, F21, and F23, and therefore the G and Mg signals accumulated in these photodiodes are not transferred to the vertical transfer CCDs 51 and 52 (reference numeral J17). . On the other hand, only the Ye signal accumulated in the photodiodes F12 and F14 and the Cy signal accumulated in the photodiodes F22 and F24 are transferred to the vertical transfer CCDs 51 and 52 (reference J16) and transferred vertically (reference J18).
[0072]
FIG. 19 corresponds to FIG. 16 in the second reading mode. As shown in this figure, the pixel readout pulse is not output at time t = 6 (reference numeral J19), and the pixel readout pulse is output at time t = 4, whereby the pixel signal from the photodiode is transferred to the vertical transfer CCDs 51 and 52. Transferred. At time t = 8, the voltage levels of the electrodes V1, V2, and V3 are the same, and the well corresponding to the electrode V1 and the well corresponding to the electrode V3 are merged, but the well corresponding to the electrode V3 is combined. Since there is no pixel signal, no pixel signal is added (reference numeral J20).
[0073]
As described above, in the first embodiment, in the first readout mode in which pixel signals are read out from the CCDs 16 and 17 one row at a time, the pixel signals are amplified by the amplifiers 26 and 27 and input to the A / D converters 31 and 32. In the second readout mode in which the pixel signals are read out from the CCDs 16 and 17 every two rows, the pixel signals are directly input to the A / D converters 31 and 32 without passing through the amplifiers 26 and 27. That is, when the first readout mode is compared with the second readout mode, the level of the output signal of the CCDs 16 and 17 is low in the first readout mode, so this signal is amplified and input to the A / D converters 31 and 32. In the first and second read modes, the quantization is performed with substantially the same dynamic range.
[0074]
As described above, since the dynamic range of the signals input to the A / D converters 31 and 32 does not change even when the readout mode is changed, the accuracy of A / D conversion of the pixel signal is improved, and thus photometry / measurement is performed. The accuracy of distance and still image recording is improved. Further, since it is not necessary to provide a dedicated A / D converter corresponding to each reading mode, the number of A / D converters can be minimized, and the cost of the still video camera can be reduced.
[0075]
FIG. 20 is a block diagram of a still video camera provided with the image pickup apparatus of the second embodiment. Only the configuration different from the first embodiment will be described.
[0076]
A delay circuit 61, an adder 62 and an attenuator 63 are provided between the CDS circuit 24 and the switch 28, and a delay circuit 64, an adder 65 and an attenuator 66 are provided between the CDS circuit 25 and the switch 29. Yes. The switches 28 and 29 are switched to the side opposite to the attenuators 63 and 66 in the first readout mode, and are switched to the attenuators 63 and 66 side in the second readout mode. Accordingly, the output signals of the CDSs 24 and 25 are directly input to the A / D converters 31 and 32 in the first reading mode, and in the second reading mode, the delay circuits 61 and 64, the adders 62 and 65, and the attenuator 63 are input. , 66 to the A / D converters 31 and 32.
[0077]
The output signals of the CDSs 24 and 25 are delayed by one pixel in the delay circuits 61 and 64 and input to the adders 62 and 65, and input to the adders 62 and 65 without passing through the delay circuits 61 and 64. That is, the adders 62 and 65 add the pixel signal delayed by one pixel and the pixel signal not delayed by each other. The output signals of the adders 62 and 65 are attenuated by the attenuators 63 and 66 at a predetermined attenuation rate.
[0078]
Other configurations are the same as those of the first embodiment of FIG.
[0079]
In the second readout mode, referring to the portion YY in FIG. 10, for example, the Mg signal and Ye signal on the lines L1 and L2 are delayed by one pixel by the delay circuits 61 and 64 and input to the adders 63 and 66, respectively. The G signal and the Cy signal are input to the adders 63 and 66 without being delayed. Therefore, the Mg signal, Ye signal, G signal, and Cy signal are added, and the luminance signal Y is obtained as shown in the equation (16). The luminance signal Y is attenuated by the attenuators 63 and 66 and input to the A / D converters 31 and 32.
[0080]
In contrast, in the first readout mode, the pixel signal is input to the A / D converters 31 and 32 without being attenuated. This is because the level of the output signals of the CCDs 16 and 17 is lower in the first readout mode than in the second readout mode, as described above with reference to the first embodiment.
[0081]
Thus, also in the second embodiment, A / D conversion can be performed with high accuracy without providing a dedicated A / D converter corresponding to the read mode, and the number of A / D converters can be minimized. To the limit.
[0082]
FIG. 21 is a block diagram of a still video camera provided with the image pickup apparatus of the third embodiment. Only the configuration different from the first embodiment will be described.
[0083]
No amplifier or attenuator is provided between the CDS circuits 24 and 25 and the A / D converters 31 and 32, and these are directly connected. On the other hand, one of the first and second reference voltage generators 71 and 72 is connected to the A / D converters 31 and 32 via a switch 73. The first and second reference voltage generators 71 and 72 generate, for example, an upper limit reference voltage in A / D conversion. The A / D converters 71 and 72 use this reference voltage to perform CDS. The analog pixel signals input from the circuits 24 and 25 are quantized. The reference voltage of the first reference voltage generator 71 is relatively low, and the reference voltage of the second reference voltage generator 72 is relatively high. The lower reference voltage is fixed to the same value for both A / D converters 71 and 72.
[0084]
The switch 73 is switched to the first reference voltage generator 71 side in the first read mode, and is switched to the second reference voltage generator 72 side in the second read mode. As described above, in the first readout mode, the levels of the output signals of the CCDs 16 and 17 are lower than those in the second readout mode. Therefore, by reducing the reference voltage used for quantizing these signals, the first and second The dynamic range of A / D conversion in the read mode can be made substantially the same. Therefore, the third embodiment can provide the same effect as the first embodiment.
[0085]
In the third embodiment, as in the first embodiment, the luminance signal Y is obtained using the equation (16) for the pixel signals read from the image memories 33 and 34.
[0086]
In the flowchart of FIG. 5, the dynamic range V of the CCDs 16 and 17_DRIs sufficiently wide, it is not necessary to expose the CCDs 16 and 17 at different electronic shutter speeds.
[0087]
【The invention's effect】
As described above, according to the present invention, in the configuration in which the readout mode of the pixel signal from the image sensor changes, the A / D conversion of the pixel signal is performed without increasing the number of A / D converters corresponding to the readout mode. Therefore, an inexpensive imaging device that can improve the accuracy of the above is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a circuit configuration of a still video camera to which an embodiment of the present invention is applied.
FIG. 2 is a diagram showing an arrangement of color filters provided on the light receiving surfaces of first and second CCDs.
FIG. 3 is a diagram showing a state in which corresponding pixels are superposed on the output signals of the first and second CCDs.
FIG. 4 is a diagram for explaining a color signal extraction method in the embodiment.
FIG. 5 is a flowchart showing a first half of a program for performing distance measurement / photometry operation;
FIG. 6 is a flowchart showing the latter half of a program for performing distance measurement / photometry operation;
FIG. 7 is a flowchart of a program for performing a recording operation of a video signal on a memory card.
FIG. 8 is a timing chart of a shooting operation.
FIG. 9 is a diagram illustrating movement of a focus lens in an AF operation.
FIG. 10 is a diagram illustrating a pixel signal readout operation in a second readout mode.
FIG. 11 is a diagram illustrating a pixel signal read operation in the first read mode;
FIG. 12 is a diagram showing a photometric range by the first and second CCDs.
FIG. 13 is a diagram showing the output timing of each signal in the photometric operation.
FIG. 14 is a diagram illustrating an operation in which two pixel signals are added in the vertical transfer CCD in the second readout mode.
FIG. 15 is a diagram illustrating a reading operation of a pixel signal to a vertical transfer CCD, a vertical transfer operation, and a horizontal transfer operation in a second read mode.
FIG. 16 is a diagram illustrating a temporal change of a voltage signal in a vertical transfer operation and a temporal change of a potential well in the vertical transfer CCD in the second read mode.
FIG. 17 is a diagram illustrating an operation in which a pixel signal is transferred to the vertical transfer CCD in the first readout mode.
FIG. 18 is a diagram illustrating a reading operation of a pixel signal to a vertical transfer CCD, a vertical transfer operation, and a horizontal transfer operation in a first read mode.
FIG. 19 is a diagram illustrating a temporal change of a voltage signal in a vertical transfer operation and a temporal change of a potential well in the vertical transfer CCD in the first read mode.
FIG. 20 is a block diagram of a still video camera provided with the image pickup apparatus of the second embodiment.
FIG. 21 is a block diagram of a still video camera provided with an imaging apparatus according to a third embodiment.
[Explanation of symbols]
16, 17 CCD (image sensor)
21, 22 Filter

Claims (8)

A plurality of image sensors that generate pixel signals of pixels arranged in a horizontal direction and a vertical direction;
Pixel signals from the respective image sensors in the first readout mode for reading out pixel signals row by row along the horizontal direction, or in the second readout mode of reading out pixel signals in adjacent rows along the horizontal direction. Pixel signal reading means for reading
A / D conversion means for quantizing a pixel signal read by the pixel signal reading means with substantially the same dynamic range in the first and second reading modes;
A luminance signal generating means for generating a luminance signal for photometric calculation or ranging calculation based on a pixel signal of one field read from each image sensor according to the second reading mode;
Video signal generating means for generating a video signal of a still image based on a pixel signal read from each of the image sensors according to the first readout mode;
The imaging apparatus according to claim 1, wherein the luminance signal generation means obtains subject luminance based on pixel signals read from the image sensors when the image sensors are exposed at different electronic shutter speeds.   2. The imaging apparatus according to claim 1, wherein a complementary color checkered color filter formed by regularly arranging magenta, yellow, cyan, and green color filter elements is provided on a light receiving surface of the image sensor.   The imaging apparatus according to claim 1, wherein the A / D conversion unit includes an amplifying unit that amplifies a pixel signal read from the image sensor in the first reading mode.   The imaging apparatus according to claim 1, wherein the A / D conversion unit includes an attenuation unit that attenuates a pixel signal read from the image sensor in the second readout mode.   5. The adder for adding a signal obtained by delaying a pixel signal read from the image sensor by one pixel and a signal not delayed between the image sensor and the attenuating unit. Imaging device.   The A / D conversion unit quantizes the pixel signal using a reference voltage in which the difference between the upper limit voltage and the lower limit voltage is relatively small in the first readout mode, and the upper limit voltage and the lower limit voltage in the second readout mode. By quantizing the pixel signal using a reference voltage having a relatively large difference, the dynamic range in the A / D conversion means becomes substantially the same in the first readout mode and the second readout mode. The imaging apparatus according to claim 1, wherein the imaging apparatus is set as follows.   The luminance signal generation means obtains a distance measuring electronic shutter speed based on the subject luminance, exposes the image sensor in a state where the aperture is opened according to the distance measuring electronic shutter speed, and is obtained from the image sensor by this exposure. The imaging apparatus according to claim 1, wherein a luminance signal for ranging calculation is generated based on the obtained pixel signal.   The luminance signal generation means obtains subject luminance based on the pixel signal read from the image sensor, obtains a distance measuring electronic shutter speed based on the subject luminance, and according to the distance measuring electronic shutter speed, The imaging apparatus according to claim 1, wherein the image sensor is exposed in a state where the aperture is open, and a luminance signal for ranging calculation is generated based on a pixel signal obtained from the image sensor by the exposure.

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