JP3984357B2 - Electronic endoscope light source device for setting light shielding period - Google Patents

Description

となるので、遮光期間を設けたときの光量は通常の光量の９４％（６％の光量低下）となり、画像の輝度も６％低下する。
【００１２】
一方、絞り半開時で応答時間ｔa2が１ｍＳとなる場合は、このときの上記光量Ｃを２Ｖ、露光時間（ｔｂ）を1/60秒とすると、通常、ＣＣＤ１で蓄積される電荷量は、
ｔｂ×Ｃ＝１／６０[mS]×２[V]≒３３．３３[mVS]
となり、遮光期間を設ける場合の電荷量は、

となるので、遮光期間を設けたときの光量は通常の光量の９７％（３％の光量低下）となり、画像輝度も３％低下する。
【００１３】
このように、応答時間ｔa1，ｔa2が相違すると、撮影光量の低下の割合が異なり、この光量低下は応答時間ｔａが長い程大きくなることになり、この結果、画像の明るさが変化する。
【００１４】
本発明は上記問題点に鑑みてなされたものであり、その目的は、遮光期間を設けて全画素を読み出す電子内視鏡で、絞り開口量が相違する場合でも遮光機構の応答時間が一定となるようにし、光量低下のバラツキをなくすことができる遮光期間を設定する電子内視鏡光源装置を提供することにある。
【００１５】
【課題を解決するための手段】
上記目的を達成するために、請求項１記載の発明に係る遮光期間を設定する電子内視鏡光源装置は、光源光束を通過させる方形開口を有する遮光マスクと、この遮光マスクの方形開口の上下又は左右の二辺に沿って絞り部材を移動させ、出射光量を調整する絞り駆動手段と、この絞り駆動手段の上記絞り部材の移動方向に対し直交する二辺に沿って移動するように遮光シャッタを配置し、この遮光シャッタにより上記光源光束を完全に遮断することにより、撮像素子に蓄積された全画素の信号を読み出すための所定の遮光期間を設定する遮光手段と、を含んでなることを特徴とする。
請求項２記載の発明は、上記撮像素子に蓄積された画像信号を上下ライン間で混合して出力し、動画を形成する撮像素子出力時画素混合読出し方式と、１回の露光で上記撮像素子に蓄積された全画素の信号を上記遮光期間を利用して読み出し、静止画を形成する全画素読出し方式を備えた電子内視鏡に適用したことを特徴とする。
【００１６】
上記の構成によれば、例えば開口が長方形等とされた遮光マスクが配置され、この遮光マスク開口の左右の二辺に沿って絞り部材が移動し、この左右辺に直交する上下の二辺に沿って遮光シャッタが移動することになり、絞り部材が何れの絞り位置に配置されていても、遮光シャッタが光源光束を遮断する時間、即ち遮光シャッタの応答時間はほぼ一定となる。この結果、この応答（応答遅れ）時間で生じる光量不足も一定となり、遮光期間を設定する直前の露光時での光量低下のバラツキが解消される。
【００１７】
上記請求項２の構成によれば、上記の遮光期間を利用した全画素読出し方式で高画質の静止画が形成されることになる。この全画素読出し処理では、例えば所定（１番目とする）の1/60秒の期間（垂直同期期間）内での露光により蓄積された電荷について、２番目の期間（1/60秒）で撮像素子の奇数ラインが読み出され、３番目（次の露光時）の期間で残りの偶数ラインが読み出され、これらのデータは所定のメモリに記憶される。そして、この偶数ラインを読み出せるようにするために、上記２番目の期間が遮光期間として設定される。
【００１８】
即ち、上記奇数ラインの蓄積電荷を読み出す２番目の期間に、従来のように次の露光の電荷が蓄積されると、残りの偶数ラインの読出しができない。そのため、上記２番目の期間を遮光期間として、３番目の期間で偶数ラインの蓄積電荷を読み出す。これにより、１回の露光で得られた撮像素子の全画素分の信号を読み出せることになる。
【００１９】
次に、上記メモリに記憶された奇数ライン及び偶数ラインのビデオ信号は、位相合せがなされた後に、混合回路により、奇数ラインと偶数ラインとの間で画素混合処理が行われる。即ち、この画素混合処理は、結果としては撮像素子からの信号出力時に行われる撮像素子出力時画素混合読出し方式と同等の信号を形成するが、１回の露光で得られたデータに基づいて画素混合を行うという点で、上記の撮像素子出力時画素混合読出し方式と区別されるものとなる。
【００２０】
一方、通常の動画表示時では、撮像素子出力時画素混合読出し方式が選択されており、従来と同様に撮像素子から出力される時に２つの水平ラインの画素が混合されて読み出される。従って、動画の場合は、経時的な撮像により、逆に被写体の動き等を忠実に再現した画像を得ることができる。
【００２１】
【発明の実施の形態】
図１には、実施形態例の光源装置を適用した電子内視鏡装置の構成が示されており、この電子内視鏡装置はスコープ（電子内視鏡）１０を、画像処理回路を有するプロセッサ装置や光源装置に接続する構成となる。このスコープ１０には、その先端部に図７で説明したものと同様の色フィルタを備えたＣＣＤ１２が設けられると共に、光源ランプ１４の光を先端部まで導くためのライトガイド１５が配設される。また、スコープ１０の操作部には、静止画表示のためのフリーズスイッチ１６が設けられる。
【００２２】
上記ＣＣＤ１２には、これを駆動するためのＣＣＤ駆動回路１８が接続され、この駆動回路１８にはタイミングジュネレータ１９、各種の制御をするマイコン（マイクロコンピュータ）２０が接続され、このマイコン２０には上記フリーズスイッチ１６の動作信号が入力される。上記ＣＣＤ駆動回路１８は、マイコン２０の制御に基づきタイミング信号を入力し、動画のためのＣＣＤ出力時画素混合読出し方式と、静止画のための全画素読出し方式の駆動制御をする。
【００２３】
例えば、この全画素読出し方式の場合は、１回の露光でＣＣＤ１２に蓄積された全画素分の蓄積データを、奇数ラインと偶数ラインに分け時間的にもずらして読み出すための２種類のパルスを上記ＣＣＤ駆動回路１８から供給し、これに基づいてＣＣＤ１２から上記奇数ラインの信号と偶数ラインの信号を別々に順次読み出すための制御を行う。なお、ＣＣＤ出力時画素混合読出し方式では１種類の読出しパルスを各ラインに与える。
【００２４】
一方、上記ライトガイド１５に光を供給する光源部では、上記光源ランプ１４とライトガイド１５の入射端との間に、出射光量を調整するための絞り板２２、遮光マスク２３及び遮光期間を設定する遮光シャッタ（板）２４が配置される。上記の絞り板２２には、モータ２５及び絞り制御回路２６が接続され、上記遮光シャッタ２４にはモータ２７及び遮光シャッタ制御回路２８が接続される。なお、上記ランプ１４はランプ駆動回路２９によって点灯制御される。
【００２５】
そして、上記絞り制御回路２６は後述するＤＶＰ（３９）で得られる輝度信号に基づいて絞り板２２を駆動し、上記ランプ１４の出射光量を調整する。また、上記遮光シャッタ制御回路２８は、上記フリーズスイッチ１６が押された後の所定のタイミングで遮光シャッタ２４を駆動し、所定の1/60秒間の遮光期間につき光を完全に遮断する。
【００２６】
図２には、上記絞り板２２、遮光マスク２３及び遮光シャッタ２４の構成が示されている。図示されるように、遮光マスク２３では長方形（正方形でもよい）の開口２３Ａが形成されており、この長方形開口２３Ａの左右辺に沿って上下移動可能に絞り板２２が取り付けられ、この絞り板２２はモータ２５で上下に駆動される。また、上記開口２３Ａの上下辺に沿って左右移動可能に遮光シャッタ２４が配置され、この遮光シャッタ２４はモータ２７で左右に駆動される。
【００２７】
このようにして、遮光シャッタ２４と絞り板２２は、互いに直交する方向に移動することになり、開口２３Ａを上下動する絞り板２２がどのような絞り位置にあったとしても、実際の光束１０１を完全に遮光する遮光シャッタ２４は必ず開口２３Ａの左端から右端まで移動することになる。従って、遮光シャッタ２４の応答時間も常に同一となる。
【００２８】
図１において、上記ＣＣＤ１２の後段には、自動利得回路（ＡＧＣ）等からなる増幅器３１が設けられており、この増幅器３１では、上記の遮光シャッタ２４による遮光期間の設定で生じる光量不足分を増幅することもできる。この増幅器３１には、Ａ／Ｄ変換器３２を介して全画素読出しのために上記奇数ラインの画像データを記憶する第１メモリ３３、偶数ラインの画像データを記憶する第２メモリ３４、上記第１メモリ３３のデータをそのまま記憶し、読出しのタイミングを1/60秒だけ遅らせるための位相調整用の第３メモリ３５、静止画用混合回路３６が設けられる。
【００２９】
即ち、ＣＣＤ１２で得られた全画素信号は、奇数ラインのデータと偶数ラインのデータに分けられた状態で、それぞれのメモリ３３，３４に一旦格納されるが、第１メモリ３３の奇数ラインデータは1/60秒遅らせることにより、第２メモリ３４に格納された偶数ラインデータと同一位相となる。これにより、両方の画像データが同時に読み出せることになり、次段の混合回路３６では、第３メモリ３５の奇数ラインの画素データと第２メモリ３４の偶数ラインの画素データを加算混合（静止画用画素混合処理）することができる。従って、静止画の場合は、この混合回路３６で従来の色差線順次混合読出し方式と同等の画素混合信号が形成される。
【００３０】
図４には、上述したＣＣＤ１２から混合回路３６までの回路で処理される静止画データの内容が示されている。図（Ａ）に示されるように、ＣＣＤ１２では、走査線数に対応して、０ラインからＮラインまで水平ラインが設けられ、この水平ラインの画素データが転送ラインに転送して読み出される。そして、上記ＣＣＤ１２の奇数（ＯＤＤ）ライン（１，３，５…ライン）のデータが図（Ｂ）の第１メモリ３３（及び第３メモリ３５）に格納され、偶数（ＥＶＥＮ）ライン（２，４，６…ライン）のデータが図（Ｃ）の第２メモリ３４に格納される。
【００３１】
これらメモリ３５，３４のデータは、上記混合回路３６によって、図（Ｂ）と図（Ｃ）のライン同士で画素混合が行われ、図（Ｄ）に示されるように、０ライン＋１ライン，２ライン＋３ライン，４ライン＋５ライン…の加算演算データが奇数（Ｏｄｄ）フィールドデータとして出力される。また、図（Ｃ）の読出しラインを下側に１ラインずらした状態で（図示Ｃ1 の位置から読み出す）、図（Ｂ）とライン同士で画素混合が行われ、図（Ｅ）に示されるように、１ライン＋２ライン，３ライン＋４ライン，５ライン＋６ライン…の加算演算データが偶数（Ｅｖｅｎ）フィールドデータとして出力される。
【００３２】
図１において、上記混合回路３６の後段には、動画と静止画を切り替える画像切替え回路３８が設けられ、この画像切替え回路３８では、そのａ端子に動画形成のために上記Ａ／Ｄ変換器３２の出力がＬラインを介して供給され、他方のｂ端子に上記混合回路３６の出力が与えられており、上記フリーズスイッチ１６が押された時、ａ端子からｂ端子へ切り替えられる。この画像切替え回路３８には、ＤＶＰ（デジタルビデオプロセッサ）３９が接続されており、このＤＶＰ３９では、ガンマ補正を含む各種の処理が行われ、例えば色差信号や輝度信号が形成される。このＤＶＰ３９の後段には、奇数フィールド及び偶数フィールドのデータを記憶するメモリやＤ／Ａ変換器等が設けられ、ビデオ信号はこのＤ／Ａ変換器を介してモニタへ出力される。
【００３３】
実施形態例は以上の構成からなり、その作用を図３及び図４を参照しながら説明する。図３（Ａ）に示されるように、フィールドＯ（Ｏｄｄ）／Ｅ（Ｅｖｅｎ）信号として、従来と同様に、1/60秒で１フィールド画像を形成するタイミング信号が用いられる。通常状態では動画処理、即ちＣＣＤ出力時画素混合読出し方式を実行するように設定されており、上記図１の遮光シャッタ２４は光源光束を遮断しない位置に配置され、光源ランプ１４からの光はライトガイド１５を介して先端部から被観察体内へ照射される。
【００３４】
この光照射により、先端部のＣＣＤ１２では被観察体内からの像光に対応した電荷が蓄積される。この蓄積電荷は、ＣＣＤ駆動回路１８からの駆動パルスにより上下ライン間の画素が加算されて読み出され、従来と同様に、図７で説明した画素混合信号が出力される。そして、この動画信号は、Ａ／Ｄ変換器３２からスルーラインＬを介して画像切替え回路３８へ供給され、この画像切替え回路３８のａ端子を介してＤＶＰ３９へ供給される。このＤＶＰ３９から後の動作は従来と同様であり、奇数及び偶数フィールド信号に基づいて動画がモニタへ表示される。
【００３５】
ここで、上記ＤＶＰ３９で得られた輝度信号はマイコン２０に供給され、このマイコン２０及び上記絞り制御回路２６の制御により絞り板２２が駆動され、これによって画像の輝度が一定に維持される。
【００３６】
一方、図１のスコープ１０のフリーズスイッチ１６が押されると、マイコン２０により、上記画像切替え回路３８が端子ｂ側へ切り替えられ、画素混合読出し方式から静止画のための全画素読出し方式に切り替えられる。そうすると、例えば図３（Ｂ）に示されるように、Ｏ／Ｅ信号の立上り時（ｔ1 ）の少し手前から約1/60秒間だけ、上記遮光シャッタ２４が光束１０１を塞ぐことになり、その間、図３（Ｃ）のように、光源部からの出力光が遮断される。従って、全画素が読み出される画像データは、遮光期間より一つ前の1/60秒の期間の光出力ＬｔによりＣＣＤ１２で蓄積された電荷となる。
【００３７】
即ち、図３（Ｄ）が図４（Ｂ）で示した奇数ラインの読出しパルスＰ1 、図３（Ｅ）が図４（Ｃ）で示した偶数ラインの読出しパルスＰ2 であり、図示のようにｔ2 時のパルスをなくした読出しパルスＰ1 及びｔ1 時のパルスをなくした読出しパルスＰ2 により、ＣＣＤ１２から奇数（ＯＤＤ）ラインデータと偶数（ＥＶＥＮ）ラインデータが順に読み出される。従って、奇数ラインの読出しは、上記の遮光期間（ｔ1 〜ｔ2 ）に行われ、偶数ラインの読出しは次の期間（ｔ2 〜ｔ3 ）の間に行われる。
【００３８】
そして、図３（Ｇ）には電子シャッタの動作が示されており、ここではパルスの立上り期間の蓄積電荷が掃き出され、立上りでない期間の蓄積電荷が読み出される。従って、上記の静止画データ（蓄積電荷）は、電荷が掃き出された後の、露光時間ｔｂの露光ｇ1 で得られたものであり、この全画素の電荷がＣＣＤ駆動回路１８によって読み出される。なお、上記露光ｇ1 後の遮光期間（ｔ1 からｔ2 ）では掃出しが省略される。
【００３９】
ところで、上記の遮光期間では完全な遮光状態としてＣＣＤ１２に不要な電荷が蓄積されないようにする必要があり、そのために応答時間を考慮した制御が行われる。即ち、図３（Ｂ）の遮光シャッタ制御パルスでは、上記遮光シャッタ２４の駆動部（ギヤ等）の機械的な応答遅れ時間（応答時間）ｔａを考慮して、その時間ｔａだけ早く反転するパルスを形成する。そうして、この遮光シャッタ２４が駆動されると、光源部から出射される光は、図３（Ｃ）又は図９でも示したように、応答時間ｔａで二次曲線的に減衰し、その後完全な遮光状態へ移行する。従って、静止画のための光出力Ｌｔでは、光量Ｌａの損失分だけ光量不足となる。
【００４０】
そして、図９で説明したように、従来では、絞り開口量によって上記の応答時間ｔａが変化していたが、当該例では、遮光マスク２３に長方形開口２３Ａを設けると共に、遮光シャッタ２４を絞り板２２の移動方向に直交する状態で移動させるので、図２から分かるように、絞り板２２の位置に関係なく、遮光シャッタ２４の応答時間ｔａは同一となる。
【００４１】
図５には、当該例の上記開口２３Ａを通過する光束１０１の光量（Ｃ）と応答時間の関係が示されており、ここで、例えば絞り板２２が全開のときの不足光量Ｌa1、絞り板２２がある程度駆動されたときの不足光量Ｌa3を比較すると、絞り板２３により光量Ｃが変化したとしても、一定の応答時間により不足光量の全体の露光量に対する割合も一定となることが理解される。
【００４２】
まず、上記絞り板２２が全開のとき、単位時間当りの光量Ｃ＝４Ｖ、応答時間ｔａ＝ｔa1＝２ｍＳ（sec）、露光時間（ｔｂ）＝1/60秒とすると、図９の場合と同様に、ＣＣＤ１２で蓄積される動画の電荷量は６６．６７[mVS]となり、遮光期間を設けた静止画の電荷量が約６２．６７[mVS]となる。従って、静止画の光量は動画の光量の９４％で、不足光量Ｌa1は全体の６％となる。
【００４３】
一方、絞り板２２がある程度駆動されたとき、光量Ｃ＝１Ｖ、応答時間ｔａ＝２ｍＳ、露光時間ｔｂ＝1/60秒とすると、ＣＣＤ１で蓄積される動画の電荷量は、
ｔｂ×Ｃ＝１／６０[mS]×１[V]≒１６．６７[mVS]
となり、遮光期間を設けた静止画の電荷量は、上記応答時間ｔａの減衰線を直線とみなして、

となる。従って、この場合も静止画の光量は動画の光量の９４％で、不足光量Ｌa3は全体の６％となり、絞り開口量の相違があっても、静止画の不足光量の割合は同一となる。
【００４４】
この結果、遮光期間を設定する際に生じていた光量低下のバラツキが解消され、被観察体が遠点又は近点の何れにあっても、良好な明るさ（輝度）の静止画信号を得ることが可能となる。なお、上述したように、上記の６％の光量低下は、上記増幅器３１等で補うことが可能である。
【００４５】
そうして、このような光量制御でＣＣＤ１２で得られた静止画信号について、その奇数ラインデータが図１の第１メモリ３３へ書き込まれ、他方の偶数ラインデータが第２メモリ３４へ書き込まれ、上記の第１メモリ３３の奇数ラインデータは第３メモリ３５で1/60秒遅れて、上記第２メモリ３４の偶数ラインデータと位相が一致することになる。
【００４６】
次に、上記のメモリ３５，３４に格納された各データは、混合回路３６により画素混合され、この混合回路３６からは、図４（Ｄ）に示した、０ライン＋１ライン，２ライン＋３ライン…の加算データが奇数（Ｏｄｄ）フィールドデータとして出力され、また図４（Ｅ）に示した、１ライン＋２ライン，３ライン＋４ライン…の加算データが偶数（Ｅｖｅｎ）フィールドデータとして出力される。これらのフィールドデータに基づき、モニタには静止画が表示されるが、この静止画は、同一露光時に得られた全画素データで形成されるので、高画質となる。従って、1/60秒間に内視鏡自体のブレ、或いは被観察体に動きがあったとしても、その影響が小さい鮮明な静止画の観察が可能となる。
【００４７】
図６には、絞り機構の他の例が示されている。この例は、従来の図８と同様に、円形の光束（開口）１００を塞ぐように絞り羽根３が設けられたもので、この光束１００を遮蔽する遮光シャッタ４２を左右方向に移動可能に配置し、この遮光シャッタ４２をモータ４３で駆動する。この場合は、上記絞り羽根３が回転軸３Ａを中心に回動して上下方向に移動し、この移動方向に対して、上記遮光シャッタ４２がほぼ直交する形で左右移動することになる。
【００４８】
このような構成によっても、極めて小さく絞られた状態のときを除き、遮光シャッタ４２による応答時間をほぼ同一に維持することができ、この応答時間による不足光量の変化が抑制された安定した輝度の静止画を得ることが可能となる。
【００４９】
上記例では、動画につきＣＣＤ１２における出力時混合読み出し方式を採用して、逆に被写体の動き等を忠実に再現するようにしたが、この動画においてもブレのない鮮明な画像を追及する場合は、動画形成処理についても遮光期間を利用したた全画素読出し方式を採用することができる。
【００５０】
【発明の効果】
以上説明したように、本発明によれば、方形開口を有する遮光マスクを配置し、例えば絞り部材を上下方向に移動させ、この絞り部材の移動方向に直交する左右方向に遮光シャッタを移動させて、光源光束を完全に遮断するようにしたので、絞り開口量が相違する場合でも遮光シャッタの応答時間は一定となり、光量低下のバラツキをなくすことが可能となる。従って、遮光期間を利用して全画素読み出す方式でも、撮像距離等に関係なく安定した明るさの画像が得られる。
【００５１】
請求項２記載の発明によれば、明るさの安定した高画質の静止画が得られ、一方動画については動きを忠実に再現した滑らかな画像が形成できるという利点がある。
【図面の簡単な説明】
【図１】本発明の実施形態例に係る光源装置を適用した電子内視鏡装置の全体構成を示すブロック図である。
【図２】実施形態例の絞り部材、遮光板及び遮光シャッタの構成を示す図である。
【図３】実施形態例における静止画形成時の信号読出しの動作を示す波形図である。
【図４】図１のＣＣＤから混合回路までの間で読み出される画像データを示す図である。
【図５】実施形態例での遮光シャッタの応答時間と不足光量の関係を示す図である。
【図６】実施形態例における絞り機構の他の例の構成を示す図である。
【図７】従来のＣＣＤにおける色フィルタの構成及び画素混合読出しを説明する図である。
【図８】従来の光源装置における絞り羽根及び遮光シャッタの構成を示す図である。
【図９】図８の装置での遮光シャッタの応答時間と不足光量の関係を示す図である。
【符号の説明】
１，１２ … ＣＣＤ、
１４ … 光源ランプ、
１６ … フリーズスイッチ、
２０ … マイコン（制御手段）、
２２ … 絞り板、
２３ … 遮光マスク、
２４，４２ … 遮光シャッタ
２５，２７，４３ … モータ、
２６ … 絞り制御回路、
２８ … 遮光シャッタ制御回路、
３１ … 増幅器、
３８ … 混合回路。[0001]
BACKGROUND OF THE INVENTION
The present invention is an electronic endoscope light source device, particularly an electronic endoscope that reads a signal of all pixels stored in an image sensor by setting a light shielding period, and adjusts an exposure amount of an image signal to be read out of all pixels. It is related with the composition for doing.
[0002]
[Prior art]
In an electronic endoscope apparatus, for example, in a CCD (Charge Coupled Device) which is a solid-state imaging device, an image signal (video signal) is formed by reading out charges accumulated in units of pixels by a photoelectric conversion device. In the simultaneous electronic endoscope apparatus, a color filter is disposed on the upper surface of the CCD in units of pixels, thereby obtaining a color image.
[0003]
FIG. 7 shows an arrangement state of the above-described color filters. As shown in the drawing, on the imaging surface of the CCD 1, for example, Mg (magenta), Cy (cyan) pixels on even lines, and odd lines on odd lines. G (green) and Ye (yellow) pixels are arranged. In the CCD 1, accumulated charges (pixel signals) in pixel units are obtained through these color filters.
[0004]
Then, according to the conventional mixed readout method, the accumulated charges of the pixels on the upper and lower lines of the CCD 1 are added and mixed and read out. For example, as shown on the left side of FIG. 7, the mixed signal of 0 line and 1 line, 2 lines and 3 lines for the charge accumulated during the first 1/60 second exposure (vertical synchronization period) The odd-numbered (Odd) field video signal such as... Is read and the charge accumulated in the second 1/60 second exposure is shown on the right side of FIG. An even field video signal such as a mixed signal of 1 line and 2 lines, a mixed signal of 3 lines and 4 lines, etc. is read out.
[0005]
Accordingly, the two-line mixed signal of the CCD 1 becomes a signal of one line of the field image, and an odd-numbered field signal and an even-numbered field signal that are read out with a shift of one line are alternately output for each exposure within a 1/60 second period. . These odd-numbered and even-numbered field signals are interlaced to form an image of one frame, and this image is displayed on the monitor as a moving image or a still image.
[0006]
[Problems to be solved by the invention]
However, in the simultaneous electronic endoscope apparatus, as described above, there is a time lag of 1/60 seconds between the odd field signal and the even field signal for forming one frame image, If there is a blur of the endoscope itself or a movement of the observation object during this time, there is a problem that the image quality (resolution, color shift, etc.) of the still image is deteriorated.
[0007]
In view of this, the present applicant has provided a predetermined light-shielding period, and has adopted an all-pixel readout method that reads out data of all pixels obtained by the last one exposure using this light-shielding period. In driving the light shielding shutter for setting the light shielding period, a mechanical (gear, etc.) response delay occurs. That is, since a complete light shielding state is required in the light shielding period for data reading, the light shielding shutter is operated slightly before the light shielding period in consideration of the response time. The amount of light at the time of the previous exposure is reduced by the operation until the light is blocked. In addition, when the amount of light emitted from the light source is adjusted by the aperture mechanism, there is a problem that the response time of the light-shielding shutter varies depending on the aperture state of the aperture, and the insufficient amount of light varies.
[0008]
FIG. 8 shows the relationship between the diaphragm member of the diaphragm mechanism and the light shielding shutter for setting the light shielding period. For example, the diaphragm blade 3 and the light-shielding shutter 4 are arranged so that the light beam (aperture aperture) 100 from the light source can be shielded. One diaphragm blade 3 is centered on the rotation shaft 3A and the other light-shielding shutter 4 is the rotation shaft. It is attached so as to rotate and rotate in the clockwise direction around 4A. The diaphragm blade 3 is driven so that the luminance signal of the video signal is constant. For example, by increasing the amount of light at a far point and decreasing the amount of light at a near point, a good image can be obtained. Yes. The light-shielding shutter 4 completely shields the light flux 100 for a period of 1/60 seconds, for example, by making one rotation at a predetermined rotational speed.
[0009]
However, in such a configuration, since the diaphragm blade 3 and the light shielding shutter 4 rotate in the same direction, the timing at which the light shielding shutter 4 blocks the actual light beam 100P differs depending on the driving position of the diaphragm blade 3, and this light beam 100P is completely transmitted. The response time for shielding light will change. That is, in FIG. 8, in order to completely shield the actual light beam 100P, the rotation angle θ1 is when the diaphragm blade 3 is fully open, the rotation angle θ2 when the diaphragm blade 3 is at the position of the solid line, and the two-dot chain line. When the position is in the position, the light-shielding shutter 4 moves through the rotation angle θ3. As a result, the response time changes.
[0010]
FIG. 9 shows the relationship between the light amount (C) of the light beam 100 and the response time (the light amount is plotted on the vertical axis and the time is plotted on the horizontal axis). This figure shows the light beam 100 with the aperture blade 3 fully open. When the response time ta1 when shielding all of the light is 2 mS (sec), and when the diaphragm blade 3 is in a position blocking the half of the aperture 2 and the other half of the light flux 100 is shielded, the response time ta2 is 1 mS. This is a comparison of the times.
[0011]
Here, when the response time ta1 is 2 mS when the aperture is fully opened, the charge accumulated in the CCD 1 is normally set when the light amount C per unit time when the aperture is fully opened is 4 V and the exposure time (tb) is 1/60 seconds. The amount is
tb × C = 1/60 [mS] × 4 [V] ≈66.67 [mVS]
It becomes. On the other hand, the charge amount in the case of providing the light shielding period is as follows.

Therefore, the light amount when the light shielding period is provided is 94% of the normal light amount (6% light amount decrease), and the brightness of the image is also reduced by 6%.
[0012]
On the other hand, when the response time ta2 is 1 mS when the aperture is half-opened, if the light amount C at this time is 2 V and the exposure time (tb) is 1/60 second, the amount of charge accumulated in the CCD 1 is usually
tb × C = 1/60 [mS] × 2 [V] ≈33.33 [mVS]
The amount of charge when providing a light shielding period is

Therefore, the light amount when the light shielding period is provided is 97% of the normal light amount (3% light amount decrease), and the image luminance is also reduced by 3%.
[0013]
As described above, when the response times ta1 and ta2 are different, the rate of decrease in the amount of photographing light is different, and the decrease in the amount of light becomes larger as the response time ta is longer. As a result, the brightness of the image changes.
[0014]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an electronic endoscope that reads all pixels by providing a light shielding period, and the response time of the light shielding mechanism is constant even when the aperture opening amount is different. Thus, it is an object to provide an electronic endoscope light source device that sets a light-shielding period that can eliminate variations in light amount reduction.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, an electronic endoscope light source device for setting a light shielding period according to the first aspect of the present invention provides a light source luminous flux. A light-shielding mask having a square opening through which the light passes, and along the two sides of the square opening of the light-shielding mask above and below or left and right Diaphragm member Move The diaphragm driving means for adjusting the amount of emitted light and the direction of movement of the diaphragm member of the diaphragm driving means are orthogonal to each other. Along two sides A light shielding means for setting a predetermined light shielding period for reading out signals of all pixels accumulated in the image sensor by disposing a light shielding shutter so as to move and completely blocking the light source light flux by the light shielding shutter; It is characterized by comprising.
The invention according to claim 2 ,Up The image signal stored in the image sensor is mixed between the upper and lower lines and output to form a moving image, and the pixel mixture readout method at the time of output of the image sensor and the signal of all pixels stored in the image sensor in one exposure Is applied to an electronic endoscope equipped with an all-pixel readout method for forming a still image.
[0016]
According to the above configuration, for example, the light shielding mask whose opening is rectangular or the like is arranged, the diaphragm member moves along the left and right sides of the light shielding mask opening, and the upper and lower sides perpendicular to the left and right sides are moved. The light shielding shutter moves along the light blocking shutter, and the time when the light shielding shutter blocks the light source light beam, that is, the response time of the light shielding shutter is substantially constant regardless of the diaphragm position. As a result, the shortage of light quantity that occurs during this response (response delay) time is also constant, and variations in the light quantity at the time of exposure immediately before setting the light shielding period are eliminated.
[0017]
Claims above 2 According to the configuration, a high-quality still image is formed by the all-pixel reading method using the light shielding period. In this all-pixel readout process, for example, the charge accumulated by exposure within a predetermined (first) 1/60 second period (vertical synchronization period) is imaged in the second period (1/60 second). The odd lines of the element are read out, and the remaining even lines are read out in the third (during the next exposure) period, and these data are stored in a predetermined memory. The second period is set as a light shielding period so that the even lines can be read out.
[0018]
That is, if the charge of the next exposure is accumulated as in the prior art in the second period for reading out the accumulated charges in the odd lines, the remaining even lines cannot be read out. Therefore, the accumulated charge of the even lines is read out in the third period, with the second period as the light shielding period. As a result, signals for all pixels of the image sensor obtained by one exposure can be read out.
[0019]
Next, the odd line and even line video signals stored in the memory are phase-matched, and then a pixel mixing process is performed between the odd line and the even line by the mixing circuit. That is, as a result, this pixel mixing process forms a signal equivalent to the pixel mixing readout method at the time of image sensor output performed at the time of signal output from the image sensor, but the pixel based on the data obtained by one exposure. This is distinguished from the above-mentioned pixel mixture readout method at the time of image pickup device output in that mixing is performed.
[0020]
On the other hand, at the time of normal moving image display, the pixel mixture readout method at the time of image sensor output is selected, and when output from the image sensor as in the conventional case, the pixels of two horizontal lines are mixed and read out. Therefore, in the case of a moving image, it is possible to obtain an image that faithfully reproduces the movement of a subject or the like by imaging with time.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a configuration of an electronic endoscope apparatus to which the light source device of the embodiment is applied. This electronic endoscope apparatus includes a scope (electronic endoscope) 10 and a processor having an image processing circuit. It becomes the structure connected to an apparatus or a light source device. This scope 10 has a figure at its tip. 7 A CCD 12 having a color filter similar to that described above is provided, and a light guide 15 for guiding the light from the light source lamp 14 to the tip is provided. The operation unit of the scope 10 is provided with a freeze switch 16 for displaying a still image.
[0022]
A CCD drive circuit 18 for driving the CCD 12 is connected to the CCD 12, and a timing generator 19 and a microcomputer (microcomputer) 20 for various controls are connected to the drive circuit 18. An operation signal of the freeze switch 16 is input. The CCD drive circuit 18 receives a timing signal based on the control of the microcomputer 20 and performs drive control of a CCD mixed pixel reading method for moving images and an all pixel reading method for still images.
[0023]
For example, in the case of this all-pixel readout method, two types of pulses for reading out the accumulated data for all the pixels accumulated in the CCD 12 in one exposure into an odd line and an even line are also shifted in time. Based on the signal supplied from the CCD drive circuit 18, the control for reading out the odd line signal and the even line signal separately and sequentially from the CCD 12 is performed. In the pixel mixed readout method at the time of CCD output, one kind of readout pulse is given to each line.
[0024]
On the other hand, in the light source unit that supplies light to the light guide 15, a diaphragm plate 22, a light shielding mask 23, and a light shielding period for adjusting the amount of emitted light are set between the light source lamp 14 and the incident end of the light guide 15. A light shielding shutter (plate) 24 is disposed. A motor 25 and a diaphragm control circuit 26 are connected to the diaphragm plate 22, and a motor 27 and a light shielding shutter control circuit 28 are connected to the light shielding shutter 24. The lamp 14 is controlled to be turned on by a lamp driving circuit 29.
[0025]
The diaphragm control circuit 26 drives the diaphragm plate 22 based on a luminance signal obtained by a DVP (39), which will be described later, and adjusts the amount of light emitted from the lamp 14. The light-shielding shutter control circuit 28 drives the light-shielding shutter 24 at a predetermined timing after the freeze switch 16 is pressed to completely block light for a predetermined light-shielding period of 1/60 seconds.
[0026]
FIG. 2 shows the configuration of the diaphragm plate 22, the light shielding mask 23 and the light shielding shutter 24. As shown in the drawing, a rectangular (or square) opening 23A is formed in the light shielding mask 23, and a diaphragm plate 22 is attached to be movable up and down along the left and right sides of the rectangular opening 23A. Is driven up and down by a motor 25. Further, a light shielding shutter 24 is disposed so as to be movable left and right along the upper and lower sides of the opening 23A, and the light shielding shutter 24 is driven left and right by a motor 27.
[0027]
In this way, the light-shielding shutter 24 and the diaphragm plate 22 move in directions orthogonal to each other, and the actual light beam 101 no matter what diaphragm position the diaphragm plate 22 moving up and down through the opening 23A is located. The light-shielding shutter 24 that completely shields the light always moves from the left end to the right end of the opening 23A. Accordingly, the response time of the light shielding shutter 24 is always the same.
[0028]
In FIG. 1, an amplifier 31 composed of an automatic gain circuit (AGC) or the like is provided at the subsequent stage of the CCD 12, and this amplifier 31 amplifies an insufficient amount of light caused by setting the light shielding period by the light shielding shutter 24. You can also The amplifier 31 includes a first memory 33 for storing the odd-line image data for reading out all pixels via the A / D converter 32, a second memory 34 for storing the even-line image data, and the second memory 34. A third memory 35 for phase adjustment and a still image mixing circuit 36 are provided for storing data in one memory 33 as it is and delaying the read timing by 1/60 second.
[0029]
That is, all pixel signals obtained by the CCD 12 are temporarily stored in the memories 33 and 34 in a state of being divided into odd line data and even line data, but the odd line data in the first memory 33 is By delaying 1/60 second, the phase becomes the same as that of the even line data stored in the second memory 34. As a result, both image data can be read simultaneously, and the mixing circuit 36 in the next stage adds and mixes the pixel data of the odd lines in the third memory 35 and the pixel data of the even lines in the second memory 34 (still image). Pixel mixing processing). Therefore, in the case of a still image, the mixing circuit 36 forms a pixel mixed signal equivalent to the conventional color difference line sequential mixed readout method.
[0030]
FIG. 4 shows the contents of still image data processed by the circuits from the CCD 12 to the mixing circuit 36 described above. As shown in FIG. 1A, in the CCD 12, horizontal lines from 0 lines to N lines are provided corresponding to the number of scanning lines, and pixel data of the horizontal lines are transferred to a transfer line and read out. Then, data of odd (ODD) lines (1, 3, 5,...) Of the CCD 12 is stored in the first memory 33 (and the third memory 35) of FIG. 4, 6... Line) is stored in the second memory 34 in FIG.
[0031]
The data of these memories 35 and 34 is pixel-mixed between the lines of FIG. (B) and FIG. (C) by the mixing circuit 36, and as shown in FIG. (D), 0 line + 1 line, 2 The addition operation data of line +3 line, 4 line +5 line,... Is output as odd (Odd) field data. Also, with the readout line of FIG. (C) shifted downward by one line (reading from the position of C1 in the figure), pixel mixing is performed between the lines of FIG. (B) and as shown in FIG. In addition, the addition operation data of 1 line + 2 lines, 3 lines + 4 lines, 5 lines + 6 lines,... Is output as even field data.
[0032]
In FIG. 1, an image switching circuit 38 for switching between a moving image and a still image is provided at the subsequent stage of the mixing circuit 36. In the image switching circuit 38, the A / D converter 32 is formed at the a terminal for forming a moving image. Is supplied via the L line, and the output of the mixing circuit 36 is given to the other b terminal. When the freeze switch 16 is pressed, the a terminal is switched to the b terminal. A DVP (digital video processor) 39 is connected to the image switching circuit 38. In the DVP 39, various processes including gamma correction are performed, and for example, a color difference signal and a luminance signal are formed. At the subsequent stage of the DVP 39, a memory for storing odd-numbered field data and even-numbered field data, a D / A converter, and the like are provided, and a video signal is output to the monitor via the D / A converter.
[0033]
The embodiment is configured as described above, and its operation will be described with reference to FIGS. As shown in FIG. 3A, as the field O (Odd) / E (Even) signal, a timing signal for forming a one-field image in 1/60 seconds is used as in the conventional case. In the normal state, the moving image processing, that is, the pixel mixture readout method at the time of CCD output is set to be executed. The light-shielding shutter 24 in FIG. Irradiated from the tip portion into the body to be observed through the guide 15.
[0034]
By this light irradiation, the charge corresponding to the image light from the observed body is accumulated in the CCD 12 at the tip. This accumulated charge is read by adding pixels between the upper and lower lines by a drive pulse from the CCD drive circuit 18, and the pixel mixture signal described with reference to FIG. The moving image signal is supplied from the A / D converter 32 to the image switching circuit 38 via the through line L, and is supplied to the DVP 39 via the a terminal of the image switching circuit 38. The operation after this DVP 39 is the same as the conventional one, and a moving image is displayed on the monitor based on the odd and even field signals.
[0035]
Here, the luminance signal obtained by the DVP 39 is supplied to the microcomputer 20, and the diaphragm plate 22 is driven by the control of the microcomputer 20 and the diaphragm control circuit 26, whereby the luminance of the image is kept constant.
[0036]
On the other hand, when the freeze switch 16 of the scope 10 in FIG. 1 is pressed, the image switching circuit 38 is switched to the terminal b side by the microcomputer 20 to switch from the pixel mixture readout method to the all pixel readout method for still images. . Then, for example, as shown in FIG. 3B, the light-shielding shutter 24 blocks the light beam 101 for about 1/60 second from slightly before the rising edge (t1) of the O / E signal. As shown in FIG. 3C, the output light from the light source unit is blocked. Therefore, the image data from which all the pixels are read out is the electric charge accumulated in the CCD 12 by the light output Lt in the 1/60 second period immediately before the light shielding period.
[0037]
That is, FIG. 3D shows the odd-line read pulse P1 shown in FIG. 4B, and FIG. 3E shows the even-line read pulse P2 shown in FIG. 4C. Odd (ODD) line data and even (EVEN) line data are sequentially read out from the CCD 12 by a read pulse P1 in which the pulse at t2 is eliminated and a read pulse P2 in which the pulse at t1 is eliminated. Therefore, reading of odd lines is performed during the above-described light shielding period (t1 to t2), and reading of even lines is performed during the next period (t2 to t3).
[0038]
FIG. 3G shows the operation of the electronic shutter. Here, the accumulated charge during the rising period of the pulse is swept out, and the accumulated charge during the non-rising period is read out. Therefore, the still image data (accumulated charge) is obtained by the exposure g1 of the exposure time tb after the charge is swept out, and the charges of all the pixels are read out by the CCD driving circuit 18. Note that sweeping is omitted in the light shielding period (t1 to t2) after the exposure g1.
[0039]
By the way, in the above light shielding period, it is necessary to prevent unnecessary charges from being accumulated in the CCD 12 as a complete light shielding state. For this reason, control is performed in consideration of the response time. That is, in the light shielding shutter control pulse of FIG. 3B, a pulse that reverses earlier by the time ta in consideration of the mechanical response delay time (response time) ta of the drive unit (gear, etc.) of the light shielding shutter 24. Form. When the light-shielding shutter 24 is driven, the light emitted from the light source unit attenuates in a quadratic curve at the response time ta as shown in FIG. Transition to a completely light-shielded state. Accordingly, the light output Lt for the still image is insufficient for the light amount La.
[0040]
As described with reference to FIG. 9, the response time ta has conventionally changed depending on the aperture opening amount. In this example, the light shielding mask 23 is provided with a rectangular opening 23 </ b> A, and the light shielding shutter 24 is replaced with a diaphragm plate. As shown in FIG. 2, the response time ta of the light shielding shutter 24 is the same regardless of the position of the diaphragm plate 22.
[0041]
FIG. 5 shows the relationship between the light amount (C) of the light beam 101 passing through the opening 23A of the example and the response time. Here, for example, the insufficient light amount La1 when the diaphragm plate 22 is fully opened, the diaphragm plate Comparing the insufficient light amount La3 when 22 is driven to some extent, it is understood that even if the light amount C is changed by the diaphragm plate 23, the ratio of the insufficient light amount to the total exposure amount is constant with a certain response time. .
[0042]
First, when the aperture plate 22 is fully open, the light amount per unit time C = 4 V, the response time ta = ta1 = 2 mS (sec), and the exposure time (tb) = 1/60 seconds, the same as in FIG. In addition, the charge amount of the moving image accumulated in the CCD 12 is 66.67 [mVS], and the charge amount of the still image provided with the light shielding period is about 62.67 [mVS]. Therefore, the light amount of the still image is 94% of the light amount of the moving image, and the insufficient light amount La1 is 6% of the whole.
[0043]
On the other hand, when the diaphragm plate 22 is driven to some extent, assuming that the light amount C = 1V, the response time ta = 2 mS, and the exposure time tb = 1/60 seconds, the charge amount of the moving image accumulated in the CCD 1 is
tb × C = 1/60 [mS] × 1 [V] ≈16.67 [mVS]
The charge amount of a still image provided with a light-shielding period is considered that the attenuation line of the response time ta is a straight line,

It becomes. Therefore, in this case as well, the light quantity of the still image is 94% of the light quantity of the moving image, the insufficient light quantity La3 is 6% of the whole, and the ratio of the insufficient light quantity of the still image is the same even if there is a difference in aperture amount.
[0044]
As a result, the variation in light amount reduction that occurs when setting the light shielding period is eliminated, and a still image signal with good brightness (luminance) is obtained regardless of whether the object to be observed is at a far point or a near point. It becomes possible. As described above, the above 6% reduction in the amount of light can be compensated by the amplifier 31 or the like.
[0045]
Then, for the still image signal obtained by the CCD 12 by such light quantity control, the odd line data is written to the first memory 33 in FIG. 1, and the other even line data is written to the second memory 34. The odd line data in the first memory 33 is delayed by 1/60 second in the third memory 35, and the phase of the odd line data in the second memory 34 matches.
[0046]
Next, each data stored in the memories 35 and 34 is subjected to pixel mixing by the mixing circuit 36. From the mixing circuit 36, 0 lines + 1 lines, 2 lines + 3 lines shown in FIG. ... Is output as odd (Odd) field data, and the addition data of 1 line + 2 lines, 3 lines + 4 lines,... Shown in FIG. Based on these field data, a still image is displayed on the monitor, but this still image is formed of all pixel data obtained during the same exposure, so that the image quality is high. Therefore, even if the endoscope itself is shaken or the object to be observed moves in 1/60 second, it is possible to observe a clear still image with little influence.
[0047]
FIG. 6 shows another example of the diaphragm mechanism. In this example, similarly to the conventional FIG. 8, the diaphragm blades 3 are provided so as to block the circular light beam (aperture) 100, and the light shielding shutter 42 that shields the light beam 100 is arranged to be movable in the left-right direction. The light shielding shutter 42 is driven by a motor 43. In this case, the diaphragm blade 3 rotates about the rotation shaft 3A and moves in the vertical direction, and the light-shielding shutter 42 moves to the left and right in a direction substantially perpendicular to the moving direction.
[0048]
Even with such a configuration, the response time by the light-shielding shutter 42 can be maintained substantially the same except when the aperture is extremely small, and stable luminance with a change in insufficient light quantity due to the response time is suppressed. A still image can be obtained.
[0049]
In the above example, the mixed reading method at the time of output in the CCD 12 is adopted for the moving image, and the movement of the subject is faithfully reproduced. However, in the case of pursuing a clear image without blur in this moving image, For the moving image forming process, an all-pixel reading method using a light shielding period can be employed.
[0050]
【The invention's effect】
As explained above, according to the present invention, , A light-shielding mask having a shape opening, For example Since the diaphragm member is moved in the vertical direction and the light shielding shutter is moved in the left-right direction orthogonal to the movement direction of the diaphragm member, the light source light beam is completely blocked. The response time is constant, and it is possible to eliminate variations in the amount of light. Therefore, even with a method of reading all pixels using the light shielding period, an image with stable brightness can be obtained regardless of the imaging distance or the like.
[0051]
Claim 2 According to the described invention, there is an advantage that a high-quality still image with stable brightness can be obtained, while a smooth image with faithful reproduction of motion can be formed for moving images.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of an electronic endoscope apparatus to which a light source device according to an embodiment of the present invention is applied.
FIG. 2 is a diagram illustrating a configuration of a diaphragm member, a light shielding plate, and a light shielding shutter according to an exemplary embodiment.
FIG. 3 is a waveform diagram illustrating a signal reading operation during still image formation in the embodiment.
4 is a diagram showing image data read between the CCD and the mixing circuit in FIG. 1; FIG.
FIG. 5 is a diagram illustrating the relationship between the response time of the light shielding shutter and the insufficient light amount in the embodiment.
FIG. 6 is a diagram showing a configuration of another example of a diaphragm mechanism in the embodiment.
FIG. 7 is a diagram illustrating a configuration of a color filter and pixel mixture reading in a conventional CCD.
FIG. 8 is a diagram illustrating a configuration of a diaphragm blade and a light shielding shutter in a conventional light source device.
9 is a diagram showing the relationship between the response time of the light shielding shutter and the insufficient light quantity in the apparatus of FIG.
[Explanation of symbols]
1,12 ... CCD,
14 ... light source lamp,
16 ... Freeze switch,
20: Microcomputer (control means),
22 ... Aperture plate,
23 ... shading mask,
24, 42 ... Shading shutter
25, 27, 43 ... motor,
26 ... Aperture control circuit,
28 ... Light-shielding shutter control circuit,
31 ... amplifier,
38: Mixed circuit.

Claims (2)

A light- shielding mask having a square opening that allows the light source beam to pass through;
A diaphragm drive means for the up and down or left and right diaphragm member along the two sides of the square opening of the light shielding mask is moved, to adjust the amount of light emitted,
The light shielding shutter is disposed so as to move along two sides orthogonal to the moving direction of the diaphragm member of the diaphragm driving means, and the light source light flux is completely blocked by the light shielding shutter, thereby being accumulated in the image sensor. An electronic endoscope light source device for setting a light shielding period, comprising: a light shielding means for setting a predetermined light shielding period for reading out signals of all pixels. The image signal stored in the image sensor is mixed between the upper and lower lines and output to form a moving image, and the pixel mixture readout method at the time of output of the image sensor and the signals of all pixels stored in the image sensor in one exposure 2. An electronic endoscope light source device for setting a light shielding period according to claim 1, wherein the electronic endoscope light source apparatus is applied to an electronic endoscope having an all-pixel readout method for reading out using the light shielding period and forming a still image. .

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