JP4349689B2 - Electronic endoscope - Google Patents

Description

【００４１】
ここで、Ｌ_n は各輝度レベル（０から255)に対応した輝度値を示し、例えばその輝度値として輝度レベルの数値を用いてもよい。即ち、輝度レベル０ないし255 に対応した輝度値のそれぞれを０ないし225 とすることができる。また、ｓ_n は各輝度レベル（０から255)に振り分けられたデジタル輝度画素信号の度数（個数）を示し、ｆ_o は一フレーム分のデジタル輝度画素信号の総和を示す。
【００４２】
システムコントローラ３０では、算出された平均輝度値Ｙ_a と輝度参照値Ｙ_r とが一致するように絞り２０の開度が調節される。即ち、平均輝度値Ｙ_a が輝度参照値Ｙ_r よりも大きければ、絞り２０の開度が小さくなるように駆動モータ５８が駆動され、これとは反対に平均輝度値Ｙ_a が輝度参照値Ｙ_r よりも小さければ、絞り２０の開度が大きくなるように駆動モータ５８が駆動される。輝度参照値Ｙ_r については上述したようにＵＰボタンスイッチ７４及びＤＯＷＮボタンスイッチ７６の操作によって段階的に変えることが可能であり、これによりＴＶモニタ装置４０の映像再現画面の全体の輝度を適宜調節することができる。
【００４３】
先にも述べたように、光学的被写体の比較的小さな領域がスコープ１０の対物レンズに接近し、その他の大部分の領域が該対物レンズから遠く離れているような場合には、絞り２０の開度が広げられる傾向にある。というのは、光学的被写体の大部分の領域がスコープ１０の対物レンズから遠く離れている場合には、平均輝度値Ｙ_a は小さなものとなるので、その平均輝度値Ｙ_a を輝度参照値Ｙ_r に一致させるためには絞り２０の開度を大きくしなければならないからである。かくして、そのような場合には、スコープ１０の対物レンズに接近した光学的被写体の比較的小さな領域の箇所でハレーションが発生し得ることになる。このような局部的なハレーションの発生時には、そのヒストグラムには共通した特徴的な傾向が見られ、その特徴的な傾向を検出することにより、局部的なハレーションの発生の有無を判断することができる。
【００４４】
詳述すると、局部的なハレーションの発生時のヒストグラムには、図８に示すように、最高輝度レベル255 とそこに接近した特定輝度レベルＶ_h との間の度数の総和ｆ_H が大きな値となる。例えば、一フレーム分の全デジタル輝度画素信号の総和をｆ_o とした場合、ｆ_o に対するｆ_H の比ｔ_r を求め、この比ｔ_r を適当な閾値Ｆ_r と比較することにより、局部的なハレーションの発生の有無を判断することが可能である。即ち、比ｔ_r が閾値Ｆ_r を越えたとき、局部的なハレーションが発生していると判断され、比ｔ_r が閾値Ｆ_r 以下のときは、局部的なハレーションの発生は無いと判断される。本発明によれば、局部的なハレーションの発生時には、輝度参照値Ｙ_r が強制的に低下させられ、これにより絞り２０の開度が小さくされてＴＶモニタ装置４０の映像再現画面の全体の輝度が低下させられ、これにより局部的ハレーションの発生が抑えられる。
【００４５】
特定輝度レベルＶ_h については、例えば輝度レベル200 と輝度レベル230 との間で適宜設定され得るが、好ましくは、スコープ１０の種別（あるいは、そこに組み込まれる撮像センサ１４のタイプ）に応じて個々に設定される。また、閾値Ｆ_r については、適宜設定することができるが、この場合にもスコープ１０の種別に応じて個々に設定することが好ましい。
【００４６】
現在、画像信号処理ユニット１２に対して接続可能なスコープ１０の種類としては、20以上知られているが、これらスコープ１０は３つのグループに大別することができる。例えば、気管支スコープで代表されるようなスコープでは、Ｖ_h ＝210 及びＦ_r ＝0.13とされ、大腸スコープで代表されるようなスコープでは、Ｖ_h ＝210 及びＦ_r ＝0.20とされ、胃スコープで代表されるスコープでは、Ｖ_h ＝225 及びＦ_r ＝0.13とされる。
【００４７】
図９を参照すると、システムコントローラ３０で実行されるスコープ判別／設定ルーチンのフローチャートが示される。このスコープ判別／設定ルーチンは電子内視鏡のメイン作動ルーチンのサブルーチンとして機能するものであり、その実行は主電源スイッチ７０のオンによって開始される。
【００４８】
ステップ９０１では、画像信号処理ユニット１２にスコープ１０が接続されたか否かが判断される。即ち、ステップ９０１では、スコープ１０の接続が監視され、この監視については、例えば画像信号処理ユニット１２側の接続部に適当なスイッチ回路（図示されない）を組み込み、このスイッチ回路のオン／オフ状態をシステムコントローラ３０で監視することにより行われる。なお、本ルーチンは例えば20ms毎に実行されるが、画像信号処理ユニット１２にスコープ１０が接続されない限り、何等の進展もない。
【００４９】
ステップ９０１で画像信号処理ユニット１２に対するスコープ１０の接続が確認されると、ステップ９０２に進み、そこでスコープ１０のＥＥＰＲＯＭ６６から情報データが読み出され、その読出し情報データはシステムコントローラ３０のＲＡＭ３０Ｃ（図６）内に格納される。
【００５０】
ステップ９０３では、かかる情報データのうちのスコープ種別データを参照して、接続スコープ１０が気管支スコープで代表されるスコープであるか否かが判断される。接続スコープ１０が気管支スコープで代表されるようなスコープであるならば、ステップ９０４に進み、そこで特定輝度レベルＶ_h として210 が与えられ、また閾値Ｆ_r として0.13が与えられる。
【００５１】
ステップ９０３で接続スコープ１０が気管支スコープで代表されるようなスコープでないときには、ステップ９０５に進み、そこで接続スコープ１０が大腸スコープで代表されるスコープであるか否かが判断される。接続スコープ１０が大腸スコープで代表されるようなスコープであると確認された場合には、ステップ９０６に進み、そこで特定輝度レベルＶ_h として210 が与えられ、また閾値Ｆ_r として0.20が与えられる。
【００５２】
ステップ９０５で接続スコープ１０が大腸スコープで代表されるようなスコープでないときには、接続スコープ１０は胃スコープで代表されるスコープとなり、このときはステップ９０７に進み、そこで特定輝度レベルＶ_h として225 が与えられ、また閾値Ｆ_r として0.13が与えられる。
【００５３】
なお、スコープ１０が画像信号処理ユニット１２から外され、別のスコープ１０が接続されたときも、その別のスコープ１０に対して特定輝度レベルＶ_h 及び閾値Ｆ_r に対して再設定が行われる。
【００５４】
図１０及び図１１を参照すると、システムコントローラ３０で実行される絞り制御ルーチンのフローチャートが示される。この絞り制御ルーチンは時間割込みルーチンとして機能するものであって、例えば映像再現方式としてＮＴＳＣ方式が採用されている場合には1/30sec 毎に実行される時間割込みルーチンとされる。
【００５５】
先ず、ステップ１００１では、ヒストグラムの全データ（０≦Ｘ≦255)の度数の総和ｆ_o （即ち、一フレーム分のデジタル輝度画素信号の総画素数）が算出される。
【００５６】
ステップ１００２では、ビデオプロセス回路３８から得られた一フレーム分のデジタル輝度画素信号に基づいてヒストグラム抽出回路６４で展開されたヒストグラムの全データ（０≦Ｘ≦255)から平均輝度値Ｙ_a が上記演算式によって算出される。なお、ここでは、各輝度レベル（０から255)に対応した輝度値Ｌ_n については輝度レベル自体の数値（０ないし255)とされる。
【００５７】
ステップ１００３では、ヒストグラムの全データ（０≦Ｘ≦255)のうち特定輝度レベルＶ_h と最高輝度レベル255 との間（Ｖ_h ≦Ｘ≦255)の度数の総和ｆ_H が算出される。次いで、ステップ１００４では、以下の演算が実行される。
ｔ_r ←ｆ_H ／ｆ_o
即ち、一フレーム分のデジタル輝度画素信号の総画素数に対する特定輝度レベルＶ_h と最高輝度レベル255 との間の総画素数ｆ_H の比率ｔ_r が求められ、このデータはシステムコントローラ３０のＲＡＭ３０Ｃ（図６）に格納される。
【００５８】
ステップ１００５では、フラグＦ１が“０”であるか“１”であるかが判断される。フラグＦ１は局部的ハレーションの発生の有無を判別するもであり、局部的ハレーションの発生が認められるときにはフラグＦ１は“１”とされ、局部的ハレーションの発生が認められてないときにはＦ１は“０”とされる。
【００５９】
初期段階では、Ｆ１＝０と設定してあるので、ステップ１００５からステップ１００６に進み、そこで以下の演算が実行される。
【００６０】
【数２】

【００６１】
即ち、平均輝度値Ｙ_a と輝度参照値Ｙ_r との差ΔＹ_d1が求められる。
【００６２】
本実施形態では、輝度参照値Ｙ_r は例えば輝度レベル80と輝度レベル180 との間で適宜設定される値であって、上述したようにＵＰボタンスイッチ７４及びＤＯＷＮボタンスイッチ７６の操作によって段階的に変え得るものである。即ち、例えば、輝度レベル表示器７８の11個の表示窓のうちの中央の表示窓（ＬＥＤ８０₀ ）が点灯されているとき、輝度参照値Ｙ_r は輝度レベル130 に対応したものとされ、ＵＰボタンスイッチ７４或いはＤＯＷＮボタンスイッチ７６の操作により10輝度レベルずつ段階的に変化させられる。輝度参照値Ｙ_r は最大値で輝度レベル180 に対応したものとなり（ＬＥＤ８０₊₅）、最小値で輝度レベル80に対応したものとなる（ＬＥＤ８０_-5）。
【００６３】
ステップ１００７では、平均輝度値Ｙ_a と輝度参照値Ｙ_r との差ΔＹ_d1が許容値Ｙ_t と比較される。本実施形態では、許容値Ｙ_t は例えば２とされ、差ΔＹ_d1が２を越えた場合に、ＴＶモニタ装置４０の映像再現画面の全体の輝度が設定輝度参照値Ｙ_r に一致してないと判断され、絞り２０の開度が調整されることになる。
【００６４】
詳しく述べると、もし差ΔＹ_d1が許容値Ｙ_t を越えている場合には、ステップ１００８に進み、そこで平均輝度値Ｙ_a と設定輝度参照値Ｙ_r との大小が判断される。Ｙ_a ≧Ｙ_r のとき（これはＴＶモニタ装置４０の映像再現画面の全体の輝度が設定輝度参照値Ｙ_r に比べて大きいことを意味する）、ステップ１００９に進み、そこでフラグＦ２が“１”とされる。これとは反対に、Ｙ_a ＜Ｙ_r のとき（これはＴＶモニタ装置４０の映像再現画面の全体の輝度が設定輝度参照値Ｙ_r に比べて小さいことを意味する）、ステップ１０１０に進み、そこでフラグＦ２が“０”とされる。フラグＦ２は駆動モータ５８の回転方向を指示するためのものであり、Ｆ２＝１のとき、駆動モータ５８は絞り２０を閉じる方向に回転駆動させられることになる。一方、Ｆ２＝０のとき、駆動モータ５８は絞り２０を広げるように回転駆動させられることになる。
【００６５】
ステップ１０１１では、差ΔＹ_d1の大きさに応じて、駆動回路６０から駆動モータ５８に出力されるべき駆動パルスの数Ｐ_V が設定される。駆動パルス数Ｐ_V の設定については、例えば以下の表１に従って行われる。
【００６６】
【表１】

【００６７】
即ち、差ΔＹ_d1が大きければ大きい程、駆動パルス数Ｐ_V には大きな設定値が与えられる。例えば、差ΔＹ_d1が９ないし17であれば、駆動パルス数Ｐ_V には２が与えられ、差ΔＹ_d1が36ないし62であれば、駆動パルス数Ｐ_V には10が与えられる。なお、表１に対応する一次元マップがシステムコントローラ３０のＲＯＭ３０Ｂに展開されており、差ΔＹ_d1の大きさに応じて駆動パルス数Ｐ_V の設定値が該一次元マップから出力される。
【００６８】
次いで、ステップ１０１２では、駆動モータ５８がフラグＦ２で指示された回転方向でかつ上述の設定駆動パルス数Ｐ_V に基づいて回転駆動され、これにより絞り２０の開度が調整される。その後、本ルーチンは一旦終了する。
【００６９】
1/30sec 後に再び本ルーチンが実行されるとき、Ｙ_a 、ｆ₀ 及びｆ_H はビデオプロセス回路３８から得られる次の一フレーム分のデジタル輝度画素信号に基づいて展開されたヒストグラムから算出され、同様なルーチンが繰り返され、かくして平均輝度値Ｙ_a と輝度参照値Ｙ_r とが許容値Ｙ_t （＝２）の範囲内で一致させられる。即ち、ＴＶモニタ装置４０の映像再現画面の全体の輝度が設定輝度参照値Ｙ_r に常に一致するように絞り２０の開度調節（即ち、自動調光）が行われる。なお、ここで注目すべきことは、差ΔＹ_d1が大きければ大きい程、駆動パルス数Ｐ_V も大きく設定されるので、平均輝度値Ｙ_a を輝度参照値Ｙ_r に速やかに一致させ得るということである。
【００７０】
ステップ１００７でΔＹ_d1が許容値Ｙ_t 以下となったとき、即ち、平均輝度値Ｙ_a と輝度参照値Ｙ_r とが許容値Ｙ_t （＝２）の範囲内で一致したとき、ステップ１００７からステップ１０１３に進み、そこで比率ｔ_r が閾値Ｆ_r を越えているか否かが判断される。もしｔ_r ≦Ｆ_r であれば、局部的なハレーションの発生は無いとされるので、ステップ１０１３からステップ１０１１に進むことになるが、このときΔＹ_d1は許容値Ｙ_t （＝２）以下となっており、このため駆動パルス数Ｐ_V の設定は“０”とされるので（表１）、駆動モータ５８自体は駆動されずに本ルーチンは一旦終了する。
【００７１】
要するに、ｔ_r ≦Ｆ_r である限り、即ち局部的なハレーションの発生が無い限り、ＴＶモニタ装置４０の再現映像画面の全体の輝度は設定輝度参照値Ｙ_r に一致するように絞り２０の開度が調節される。
【００７２】
ステップ１０１３でｔ_r ＞Ｆ_r と判断されたとき、即ち局部的なハレーションの発生が認められたとき、ステップ１０１４に進み、そこでフラグＦ１が“１”とされ、次いでステップ１０１５でカウンタＣが“０”にリセットされる。なお、カウンタＣの機能については後で説明される。次に、ステップ１０１６ではフラグＦ２が“１”とされ、ステップ１０１７では駆動パルス数Ｐ_V として適当な値例えば“６”が設定される。続いて、ステップ１０１２に進み、そこで駆動モータ５８が絞り２０を閉じる方向に駆動パルス数Ｐ_V ＝６だけ回転駆動させられる（Ｆ２＝１）。即ち、局部的なハレーションの発生が認められると、直ちに絞り２０の開度がステップ１０１７での駆動パルス数Ｐ_V （＝６）の設定値分だけ狭められる。
【００７３】
1/30sec 経過後に再び本ルーチンが実行されると、ステップ１００５からステップ１０１８に進み（Ｆ１＝１）、そこで以下の演算が行われる。
【００７４】
【数３】

【００７５】
即ち、輝度参照値Ｙ_r が適当な値Ｙ_c （例えばＹ_c には初期設定値として10が与えられる）だけ減少させられ、その減少輝度参照値（Ｙ_r −Ｙ_c ）と平均輝度値Ｙ_a との差ΔＹ_d2が求められる。
【００７６】
ステップ１０１９では、平均輝度値Ｙ_a と減少輝度参照値（Ｙ_r −Ｙ_c ）との差ΔＹ_d2が許容値Ｙ_t （＝２）と比較される。差ΔＹ_d2が許容値Ｙ_t を越えている場合には、ステップ１０２０に進み、そこで平均輝度値Ｙ_a と減少輝度参照値（Ｙ_r −Ｙ_c ）との大小が判断される。Ｙ_a ≧（Ｙ_r −Ｙ_c ）のとき、ステップ１０２１に進み、そこでフラグＦ２が“１”とされる。これとは反対に、Ｙ_a ＜（Ｙ_r −Ｙ_c ）のとき、ステップ１０２２に進み、そこでフラグＦ２が“０”とされる。上述したように、フラグＦ２は駆動モータ５８の回転方向を指示するためのものであり、Ｆ２＝１のとき、駆動モータ５８は絞り２０を閉じる方向に回転駆動させられることになる。一方、Ｆ２＝０のとき、駆動モータ５８は絞り２０を広げるように回転駆動させられることになる。
【００７７】
ステップ１０２３では、以下の演算が実行される。
【００７８】
【数２】

【００７９】
即ち、ステップ１００６の場合と同様に、平均輝度値Ｙ_a と輝度参照値Ｙ_r との差ΔＹ_d1が求められる。
【００８０】
次に、ステップ１０２４では、平均輝度値Ｙ_a と輝度参照値Ｙ_r との差ΔＹ_d1が比較的大きな値を持つ閾値Ｄ_y （本実施形態では、Ｄ_y ＝25）と比較される。もし差ΔＹ_d1が閾値Ｄ_y よりも大きければ、ステップ１０２５に進み、そこでカウンタＣのカウント値が“１”だけカウントアップされる。次いで、ステップ１０２６では、カウンタＣのカウント値が前もって決められた所定値Ｃ_t （本実施形態では、Ｃ_t ＝５）に到達したか否かが判断される。もしＣ＜Ｃ_t であれば、ステップ１０２７をスキップしてステップ１０２８に進み、そこで差ΔＹ_d2の大きさに応じて、駆動回路６０から駆動モータ５８に出力されるべき駆動パルスの数Ｐ_V が設定される。なお、駆動パルス数Ｐ_V の設定については、上記の表１に従って行われる。
【００８１】
ステップ１０２９では、駆動モータ５８がフラグＦ２で指示された回転方向で（ステップ１０２１又は１０２２）かつ上述の設定駆動パルス数Ｐ_V （ステップ１０２８）に基づいて回転駆動され、これにより絞り２０の開度が調整される。その後、本ルーチンは一旦終了する。その後、1/30sec 経過毎に本ルーチンが実行されるが、ステップ１０１９で差ΔＹ_d2が許容値Ｙ_t を越えている限り、絞り２０の開度の調節が上述の場合と同様な態様で繰り返される。要するに、平均輝度値Ｙ_a が減少参照値（Ｙ_r −Ｙ_c ）に実質的に等しくなるように自動調光が行われる。
【００８２】
ところで、ステップ１０２４では、スコープ１０の比較的大きな移動によって光学的被写体が変化したか否かが監視される。というのは、局部的なハレーションの発生後にスコープ１０に比較的大きな動きがあった場合には、局部的なハレーション発生時に得られた平均輝度値Ｙ_a とその後に得られた平均輝度値Ｙ_a との間には大きな差が生じ得ることになり、それに伴って後者の平均輝度値Ｙ_a と輝度参照値Ｙ_r との差ΔＹ_d1も大きなものとなり得る。一方、局部的なハレーションの発生後にスコープ１０に比較的大きな動きがあったとき、その局部的なハレーションの発生条件が回避され得ることもある。
【００８３】
従って、差ΔＹ_d1が比較的大きな値の閾値Ｄ_y （＝２５）を越えた回数がステップ１０２５でカウンタＣによってカウントされ、そのカウント数が所定値Ｃ_t （例えば５）に到達した場合には、局部的なハレーション発生条件が回避されたとして、ステップ１０２６からステップ１０２７に進み、そこでＦ１が“１”から“０”に書き直され、また輝度参照値Ｙ_r を減少させる値Ｙ_c には初期設定値“10”が与えられる。その後の本ルーチンの実行時には、Ｆ１＝０となっているので、ステップ１００５からステップ１００６に進んで、上述したような自動調光、即ち輝度参照値Ｙ_r に対する自動調光が再び行われる。
【００８４】
一方、差ΔＹ_d1が比較的大きな値の閾値Ｄ_y （＝２５）を越えた回数のカウンタ数が所定値Ｃ_t （＝５）に到達するまでの間にもし差ΔＹ_d1が比較的大きな値の閾値Ｄ_y 以下となった場合には、局部的なハレーション発生条件が回避されていないと判断され、ステップ１０２４からステップ１０３０に進み、そこでカウンタＣが“０”にリセットされる。その後、1/30sec 経過毎に本ルーチンが実行されるが、ステップ１０１９で差ΔＹ_d2が許容値Ｙ_t を越えている限り、絞り２０の開度の調節が上述の場合と同様な態様で繰り返される。
【００８５】
ステップ１０１９で差ΔＹ_d2が許容値Ｙ_t 以下となったとき、即ち、減少輝度参照値（Ｙ_r −Ｙ_c ）に対して自動調光が行われた後に平均輝度値Ｙ_a と減少輝度参照値（Ｙ_r −Ｙ_c ）とが許容値Ｙ_t （＝２）の範囲内で一致したとき、ステップ１０１９からステップ１０３１に進み、そこで局部的ハレーションの発生の有無が再度判断される。減少輝度参照値（Ｙ_r −Ｙ_c ）に対する自動調光が完了したにも拘らず（差ΔＹ_d2が許容値Ｙ_t 以下）、ステップ１０３１で局部的ハレーションの発生が認められるときには、ステップ１０３１からステップ１０３２に進み、そこで以下の演算が行われる。
Ｙ_c ←Ｙ_c ＋Ｋ_c
即ち、値Ｙ_c に対して定数Ｋ_c （例えば許容値Ｙ_t ＝２よりも大きな値４が与えられる）が加えられる。その後、本ルーチンは一旦終了する。
【００８６】
次の割込み処理で本ルーチンが再び実行されると、ステップ１００５からステップ１０１８に進み（Ｆ１＝１）、そこで以下の演算が行われる。
【００８７】
【数３】

【００８８】
即ち、上述の場合と同様、輝度参照値Ｙ_r が値Ｙ_c だけ減少させられ、その減少輝度参照値（Ｙ_r −Ｙ_c ）と平均輝度値Ｙ_a との差ΔＹ_d2が求められるが、しかし該減少輝度参照値（Ｙ_r −Ｙ_c ）は先の場合に比べて更に減少されたものとなる。というのは、値Ｙ_c には初期設定値10よりも大きな値14が与えられているからである。
【００８９】
その後に行われる処理は同様である。即ち、減少輝度参照値（Ｙ_r −Ｙ_c ）に対する自動調光が行われ（Ｙ_c ＝14）、その自動調光完了後に未だ局部的なハレーションの発生が認められる場合には、値Ｙ_c に更に４が加算され（ステップ１０３２）、同様な処理が繰り返される。
【００９０】
一方、ステップ１０３１で局部的なハレーションの発生が認められない場合には、本ルーチンは一旦終了する。その後、1/30sec 経過毎に本ルーチンが実行されるが、Ｆ１＝１である限り、減少輝度参照値（Ｙ_r −Ｙ_c ）に対する自動調光が持続される。
【００９１】
スコープ１０の移動によって光学的被写体が変化すると、スコープ１０の移動前に得られた平均輝度値Ｙ_a とスコープ１０の移動後に得られた平均輝度値Ｙ_a との間には大きな差が生じ得ることになり、それに伴ってスコープ１０の移動後の平均輝度値Ｙ_a と輝度参照値Ｙ_r との差ΔＹ_d1の絶対値も大きなものとなる（ステップ１０２３）。このため差ΔＹ_d1が閾値Ｄ_y （＝２５）を越えることとなり、その回数がステップ１０２５でカウンタＣによってカウントされ、そのカウント数が所定値Ｃ_t （＝５）に到達したとき、ステップ１０２６からステップ１０２７に進み、そこでＦ１が“１”から“０”に書き直され、また値Ｙ_c には初期設定値“10”が与えられる。その後の本ルーチンの実行時には、Ｆ１＝０となっているので、ステップ１００５からステップ１００６に進んで、上述したような自動調光、即ち輝度参照値Ｙ_r に対する自動調光が再び行われる。
【００９２】
図１２及び図１３を参照すると、図１０及び図１１に示した絞り制御ルーチンの変形例のフローチャートが示される。図１０及び図１１に示した絞り制御ルーチンにあっては、一フレーム分のデジタル輝度画素信号の総画素数に対する特定輝度レベルＶ_h と最高輝度レベル255 との間の総画素数ｆ_H の比率ｔ_r が求められ、その比率ｔ_r が閾値Ｆ_r を越えた際に、局部的なハレーションが発生していると判断されているが、図１２及び図１３に示す絞り制御ルーチンにあっては、ヒストグラムの全データ（０≦Ｘ≦255)のうち特定輝度レベルＶ_h と最高輝度レベル255 との間（Ｖ_h ≦Ｘ≦255)の度数の総和ｆ_H が算出され、この総和ｆ_H が所定の閾値Ｆ_m を越えた際に、局部的なハレーションが発生していると判断される。
【００９３】
先ず、ステップ１２０１では、ヒストグラムの全データ（０≦Ｘ≦255)のうち特定輝度レベルＶ_h と最高輝度レベル255 との間（Ｖ_h ≦Ｘ≦255)の度数の総和ｆ_H が算出される。
【００９４】
ステップ１２０２では、ビデオプロセス回路３８から得られた一フレーム分のデジタル輝度画素信号に基づいてヒストグラム抽出回路６４で展開されたヒストグラムの全データ（０≦Ｘ≦255)から平均輝度値Ｙ_a が上記演算式によって算出される。なお、ここでも、各輝度レベル（０から255)に対応した輝度値Ｌ_n については輝度レベル自体の数値（０ないし255)とされる。
【００９５】
ステップ１２０３ないし１２３０はそれぞれ図１０及び図１１に示すステップ１００５ないし１０３２に対応し、かつ次の点を除けば同じルーチンが実行される。即ち、ステップ１２１１及びステップ１２２９では、上述したように、総和ｆ_H が所定の閾値Ｆ_m を越えた際に局部的なハレーションが発生していると判断され、この点が異なるだけで、ステップ１２０３ないし１２３０から成るルーチンは図１０及び図１１に示すステップ１００５ないし１０３２から成るルーチンと実質的に同じものである。なお、閾値Ｆ_m については、例えば一フレーム分の総画素数が65,000のとき、7,000 と設定され得る。
【００９６】
図１４ないし図１６を参照すると、システムコントローラ３０で実行される別の絞り制御ルーチンのフローチャートが示される。この絞り制御ルーチンも時間割込みルーチンとして機能するものであって、例えば映像再現方式としてＮＴＳＣ方式が採用されている場合には1/30sec 毎に実行される。
【００９７】
先ず、ステップ１４０１では、ヒストグラムの全データ（０≦Ｘ≦255)の度数の総和ｆ_o （即ち、一フレーム分のデジタル輝度画素信号の総画素数）が算出される。
【００９８】
ステップ１４０２では、ビデオプロセス回路３８から得られた一フレーム分のデジタル輝度画素信号に基づいてヒストグラム抽出回路６４で展開されたヒストグラムの全データ（０≦Ｘ≦255)から平均輝度値Ｙ_a が上記演算式によって算出される。なお、ここでも、各輝度レベル（０から255)に対応した輝度値Ｌ_n については輝度レベル自体の数値（０ないし255)とされる。
【００９９】
ステップ１４０３では、ヒストグラムの全データ（０≦Ｘ≦255)のうち第１の特定輝度レベルＶ_h1と最高輝度レベル255 との間（Ｖ_h1≦Ｘ≦255)の度数の総和ｆ_H1が算出される。次いで、ステップ１４０４では、以下のような演算が実行される。
ｔ_r1←ｆ_H1／ｆ_o
即ち、一フレーム分のデジタル輝度画素信号の総画素数に対する第１の特定輝度レベルＶ_h1と最高輝度レベル255 との間の総画素数ｆ_H1の比率ｔ_r1が求められ、このデータはシステムコントローラ３０のＲＡＭに格納される。
【０１００】
ステップ１４０５では、ヒストグラムの全データ（０≦Ｘ≦255)のうち第２の特定輝度レベルＶ_h2と最高輝度レベル255 との間（Ｖ_h2≦Ｘ≦255)の度数の総和ｆ_H2が算出される。次いで、ステップ１４０６では、以下のような演算が実行される。
ｔ_r2←ｆ_H2／ｆ_o
即ち、一フレーム分のデジタル輝度画素信号の総画素数に対する第２の特定輝度レベルＶ_h2と最高輝度レベル255 との間の総画素数ｆ_H2の比率ｔ_r2が求められ、このデータはシステムコントローラ３０のＲＡＭに格納される。
【０１０１】
なお、図１７に示すように、第２の特定輝度レベルＶ_h2は第１の特定輝度レベルＶ_h1よりも高く、これら第１及び第２の特定輝度レベルＶ_h1及びＶ_h2の具体的な値については、本ルーチンの実行前にスコープ１０の種別に応じてあるいはキーボード６７を介して入力設定し得る。本実施形態では、第１の輝度レベルＶ_h1については、例えば210 とされ、また第２の輝度レベルＶ_h2については、例えば225 とされる。
【０１０２】
ステップ１４０７では、比率ｔ_r1及びｔ_r2のそれぞれの値に基づいて変数ｔ_m1及びｔ_m2の値が表２に従って設定される。
【０１０３】
【表２】

【０１０４】
即ち、０％≦ｔ_r1＜12％であるとき、変数ｔ_m1の値は“０”に設定され、12％≦ｔ_r1＜18％のとき、変数ｔ_m1の値は“１”に設定され、18％≦ｔ_r1＜24％のとき、変数ｔ_m1の値は“２”に設定され、24％≦ｔ_r1とき、変数ｔ_m1の値は“３”に設定される。また、０％≦ｔ_r2＜６％のとき、変数ｔ_m2の値は“０”に設定され、６％≦ｔ_r2＜12％のとき、変数ｔ_m2の値は“１”に設定され、12％≦ｔ_r2＜18％のとき、変数ｔ_m2の値は“２”に設定され、18％≦ｔ_r2＜24％のとき、変数ｔ_m2の値は“３”に設定され、24％≦ｔ_r2とき、変数ｔ_m2の値は“４”に設定される。なお、上記表１の場合と同様、表２に対応する一次元マップがシステムコントローラ３０のＲＯＭ３０Ｂに展開され、比率ｔ_r1及びｔ_r2のそれぞれの値の大きさに応じて変数ｔ_m1及びｔ_m2の設定値が該一次元マップから出力される。
【０１０５】
ステップ１４０８では、変数ｔ_m1及びｔ_m2の設定値の大きさが比べられ、大きい方の設定値が変数ｔ_m の値として設定される。勿論、変数ｔ_m1及びｔ_m2が互いに同じ設定値を持つ場合には、その設定値がｔ_m の値として設定される。本実施形態にあっては、ｔ_m ＝０のとき、局部的なハレーションの発生は無いとされ、ｔ_m ≧１のとき、局部的なハレーションの発生があると判断される。また、ｔ_m ≧１のとき、その値が大きければ大きい程、局部的ハレーションの程度が大きいものとなる。
【０１０６】
なお、本実施形態では、２つの変数ｔ_m1及びｔ_m2から変数ｔ_m が決められているが、２つの変数ｔ_m1及びｔ_m2のうちのいずれか一方だけを求めて、その一方の値だけを用いて変数ｔ_m としてもよい。
【０１０７】
ステップ１４０９ないし１４１６は図１０及び図１１に示す絞り制御ルーチンのステップ１００５ないし１０１２にそれぞれ対応するものであり、ＴＶモニタ装置４０の映像再現画面の全体の輝度が設定輝度参照値Ｙ_r に常に一致するように絞り２０の開度調節（即ち、自動調光）が行われる。なお、駆動パルス数Ｐ_V の設定についても、例えば上述の表１に従って行われる。
【０１０８】
ステップ１４１１でΔＹ_d1が許容値Ｙ_t （＝２）以下となったとき、即ち平均輝度値Ｙ_a と輝度参照値Ｙ_r とが許容値Ｙ_t の範囲内で一致したとき、ステップ１４１１からステップ１４１７に進み、そこで変数ｔ_m ≠０であるか否かが判断される。即ち、局部的なハレーションの発生の有無が判断される。もしｔ_m ＝０のとき、即ち局部的なハレーションの発生は無いとき、ステップ１４１７からステップ１４１５に進むことになるが、このときΔＹ_d1は許容値Ｙ_t 以下となっており、このため駆動パルス数Ｐ_V の設定は“０”とされるので（表１）、駆動モータ５８自体は駆動されずに本ルーチンは一旦終了する。
【０１０９】
要するに、ｔ_m ＝０である限り、即ち局部的なハレーションの発生が無い限り、ＴＶモニタ装置４０の再現映像画面の全体の輝度は設定輝度参照値Ｙ_r に一致するように絞り２０の開度が調節されるだけである。
【０１１０】
ステップ１４１７でｔ_m ≠０と判断されたとき、即ち局部的なハレーションの発生が認められたとき、ステップ１４１８に進み、そこでフラグＦ１が“１”とされ、次いでステップ１４１９でカウンタＣが“０”にリセットされる。なお、カウンタＣの機能については図１０及び図１１に示した絞り制御ルーチンの場合と同様である。次に、ステップ１４２０ではフラグＦ２が“１”とされる。なお、フラグＦ２の機能についても図１０及び図１１に示した絞り制御ルーチンの場合と同様であり、ステップ１４２０では、駆動モータ５８の回転駆動方向が絞り２０を閉じる方向に設定される（Ｆ２＝１）。
【０１１１】
ステップ１４２１では、駆動パルス数Ｐ_V の設定値が以下の演算によって求められる。即ち、
Ｐ_V ＝ＣＮ₁ ＊ｔ_m
ここで、ＣＮ₁ は適当な定数であり、例えば３とされる。要するに、変数ｔ_m の設定値が大きければ大きい程、即ち局部的なハレーションの程度が大きければ大きい程、駆動パルス数Ｐ_V の設定値として大きな値が与えられる。
【０１１２】
ステップ１４２２では、局部的なハレーションの発生時に輝度参照値Ｙ_r から減算すべき値Ｙ_c が以下の演算によって求められる。
Ｙ_c ＝ＣＮ₂ ＊ｔ_m
ここで、ＣＮ₂ は適当な定数であり、例えば４とされる。要するに、変数ｔ_m の設定値が大きければ大きい程、即ち局部的なハレーションの程度が大きければ大きい程、かかる値Ｙ_c として大きな値が与えられる。
【０１１３】
続いて、ステップ１４１６に進み、そこで駆動モータ５８が絞り２０を閉じる方向に駆動パルス数Ｐ_V ＝ＣＮ₁ ＊ｔ_m だけ回転駆動させられる（Ｆ２＝１）。即ち、局部的なハレーションの発生が認められると、その程度に応じて直ちに絞り２０の開度が駆動パルス数Ｐ_V ＝ＣＮ₁ ＊ｔ_m だけ狭められる。
【０１１４】
1/30sec 経過後に再び本ルーチンが実行されると、ステップ１４０９からステップ１４２３に進むことになるが（Ｆ１＝１）、ステップ１４２３ないし１４３７は図１０及び図１１に示す絞り制御ルーチンのステップ１０１８ないし１０３２にそれぞれ対応するものであり、図１０及び図１１に示す絞り制御ルーチンと同様な絞り制御が行われるが、しかし値Ｙ_c には局部的なハレーションの程度に応じた値（ステップ１４２２）が設定される点で本絞り制御ルーチンは図１０及び図１１に示す絞り制御ルーチンとは異なる。
【０１１５】
要するに、図１４ないし図１６に示す絞り制御ルーチンでは、局部的なハレーションの発生時にそのハレーションの程度が数値化され、該ハレーションの程度が大きければ大きい程、ハレーションの発生が一層速やかに解消するようになっている。
【０１１６】
図１８及び図１９を参照すると、システムコントローラ３０で実行される更に別の絞り制御ルーチンのフローチャートが示される。この絞り制御ルーチンも時間割込みルーチンとして機能するものであって、例えば映像再現方式としてＮＴＳＣ方式が採用されている場合には1/30sec 毎に実行される。
【０１１７】
図１８及び図１９に示す絞り制御ルーチンでは、局部的なハレーションの発生の有無の判断については、キーボード６７を操作するオペレータがＴＶモニタ装置４０の映像再現画面を実際に監視することによって判断される。
【０１１８】
ステップ１８０１では、ビデオプロセス回路３８から得られた一フレーム分のデジタル輝度画素信号に基づいてヒストグラム抽出回路６４で展開されたヒストグラムの全データ（０≦Ｘ≦255)から平均輝度値Ｙ_a が上述の数式１によって算出される。なお、ここでも、各輝度レベル（０から255)に対応した輝度値Ｌ_n については輝度レベル自体の数値（０ないし255)とされる。
【０１１９】
ステップ１８０２では、フラグＦ１が“０”であるか“１”であるかが判断される。フラグＦ１の書替えについてはキーボード６７のオペレータによって行われる。詳述すると、オペレータがＴＶモニタ装置４０の映像再現画面を実際に監視し、局部的なハレーションの発生が確認されたとき、キーボード６７上の所定の機能キーを押下することにより、フラグＦ１の書替えが行われる。要するに、オペレータが局部的なハレーションの発生を認めた際にキーボード６７上の特定のキーを押下すると、フラグＦ１は“０”から“１”にされる。
【０１２０】
Ｆ１＝０のとき、即ちオペレータによって局部的なハレーションの発生が認められないとき、ステップ１８０２からステップ１８０３に進み、そこでフラグＦ１と連動する連動フラグＦＬが“０”とされる。
【０１２１】
ステップ１８０４ないしステップ１８１０は図１０及び図１１に示す絞り制御ルーチンのステップ１００６ないし１０１２にそれぞれ対応するものであり、ＴＶモニタ装置４０の映像再現画面の全体の輝度が設定輝度参照値Ｙ_r に常に一致するように絞り２０の開度調節（即ち、自動調光）が行われる。なお、駆動パルス数Ｐ_V の設定についても、例えば上述の表１に従って行われ、またステップ１８０５でΔＹ_d1が許容値Ｙ_t （＝２）以下となったとき、即ち平均輝度値Ｙ_a と輝度参照値Ｙ_r とが許容値Ｙ_t の範囲内で一致したとき、ステップ１８０５からステップ１８０９に進むが、このときΔＹ_d1は許容値Ｙ_t 以下となっており、このため駆動パルス数Ｐ_V の設定は“０”とされるので（表１）、駆動モータ５８自体は駆動されずに本ルーチンは一旦終了する。
【０１２２】
要するに、オペレータによって局部的なハレーションの発生が認められてＦ１が“１”とされない限り、ＴＶモニタ装置４０の再現映像画面の全体の輝度は設定輝度参照値Ｙ_r に一致するように絞り２０の開度が調節されるだけである。
【０１２３】
オペレータによって局部的なハレーションの発生が認められて、Ｆ１が“０”から“１”に書き替えられると、ステップ１８０２からステップ１８１１に進み、そこで連動フラグＦＬが“０”であるか“１”であるかが判断される。この時点では、ＦＬ＝０であるが、ステップ１８１２に進み、そこで連動フラグＦＬはＦ１＝１に連動して“０”から“１”に書き替えられる。次に、ステップ１８１３でカウンタＣが“０”にリセットされ、ステップ１８１４でフラグＦ２が“１”とされる。なお、カウンタＣの機能及びフラグＦ２の機能については図１０及び図１１に示した絞り制御ルーチンの場合と同様である。ステップ１８１４では、駆動モータ５８の回転駆動方向が絞り２０を閉じる方向に設定され、ステップ１８１５では、駆動パスル数Ｐ_V として適当な値例えば“６”が設定される。その後、ステップ１８１０に進み、そこで駆動モータ５８が絞り２０を閉じる方向に駆動パルス数Ｐ_V ＝６だけ回転駆動させられる（Ｆ２＝１）。即ち、局部的なハレーションの発生が認められた直後に絞り２０の開度がステップ１８１５での駆動パルス数Ｐ_V （＝６）の設定値分だけ狭められる。
【０１２４】
1/30sec 経過後に再び本ルーチンが実行されると、ステップ１８０２及びステップ１８１１を経た後（Ｆ１＝１；ＦＬ＝１）、ステップ１８１６に進むことになるが、ステップ１８１６ないし１８３０は図１０及び図１１に示す絞り制御ルーチンのステップ１０１８ないし１０３２にそれぞれ対応するものであり、図１０及び図１１に示す絞り制御ルーチンと同様な絞り制御が行われる。
【０１２５】
【発明の効果】
以上の記載から明らかなように、本発明による電子内視鏡にあっては、自動調光時での局部的なハレーションが発生したとしても、そのハレーションの発生を速やかに解消することができるので、ハレーションの発生による診断、治療等への悪影響が直ちに排除され得る。
【図面の簡単な説明】
【図１】本発明による電子内視鏡の概略ブロック図である。
【図２】図１に示す回転式ＲＧＢカラーフィルタの正面図である。
【図３】図１に示す回転式ＲＧＢカラーフィルタをその駆動モータと共に示す側面図である。
【図４】図１に示す絞りをその駆動機構と共に示す概略正面図である。
【図５】本発明による電子内視鏡の画像信号処理ユニットに設けられた操作パネルの正面図である。
【図６】図５の操作パネル上の設けられた種々のスイッチ等とシステムコントローラの関係を示すブロック図である。
【図７】図１に示すヒストグラム抽出回路で展開されるヒストグラムの一例を概念的に示すグラフである。
【図８】局部的なハレーションの発生とヒストグラムの特性との関係を示すグラフである。
【図９】図１のシステムコントローラで実行されるスコープ判別／設定ルーチンルーチンを説明するためのフローチャートである。
【図１０】図１のシステムコントローラで実行される絞り制御ルーチンを説明するためのフローチャートの一部分である。
【図１１】図１のシステムコントローラで実行される絞り制御ルーチンを説明するためのフローチャートの残りの部分である。
【図１２】図１０及び図１１に示した絞り制御ルーチンの変形例を説明するためのフローチャートの一部分である。
【図１３】図１０及び図１１に示した絞り制御ルーチンの変形例を説明するためのフローチャートの残りの部分である。
【図１４】図１のシステムコントローラで実行される別の絞り制御ルーチンを説明するためのフローチャートの一部分である。
【図１５】図１のシステムコントローラで実行される別の絞り制御ルーチンを説明するためのフローチャートの一部分である。
【図１６】図１のシステムコントローラで実行される別の絞り制御ルーチンを説明するためのフローチャートの残りの部分である。
【図１７】図８に示すグラフと同様なグラフであって、図１４ないし図１６に示すフローチャートの説明に用いられるグラフである。
【図１８】図１のシステムコントローラで実行される更に別の絞り制御ルーチンを説明するためのフローチャートの一部分である。
【図１９】図１のシステムコントローラで実行される更に別の絞り制御ルーチンを説明するためのフローチャートの残りの部分である。
【符号の説明】
１０ スコープ
１２ 画像信号処理ユニット
１４ 撮像センサ
１６ 光ガイド
１８ 白色光源
２０ 絞り
２２ 集光レンズ
２４ 回転式ＲＧＢカラーフィルタ
２８ ＣＣＤドライバ
３０ システムコントローラ
３２ ＣＣＤプロセス回路
３４ アナログ／デジタル（Ａ／Ｄ）変換器
３６ フレームメモリ
３８ ビデオプロセス回路
４０ ＴＶモニタ装置
６４ ヒストグラム抽出回路
６６ ＥＥＰＲＯＭ
６７ キーボード
６８ 操作パネル
７０ 電源スイッチ
７２ ランプ電源ＯＮ／ＯＦＦスイッチ
７４ ＵＰボタンスイッチ
７６ ＤＯＷＮボタンスイッチ
８２ ＬＥＤ電源回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic endoscope including a scope made of a flexible conduit and an image signal processing unit for detachably connecting the scope.
[0002]
[Prior art]
In an electronic endoscope of the type described above, a solid-state imaging device, for example, a CCD (charge coupled device) image sensor is provided at the distal end of the scope, and this CCD image sensor is combined with an objective lens system. In addition, an illumination light guide composed of an optical fiber bundle is inserted into the scope, and the end surface of the distal end thereof is combined with the illumination lens.
[0003]
A white light source for illumination such as a halogen lamp or a xenon lamp is provided in the image signal processing unit, and the proximal end of the light guide for illumination is optically connected to the white light source for illumination when the scope and the image signal processing unit are connected. The Thus, when the scope is inserted into the body cavity of the patient, the front of the objective lens system at the distal end is illuminated with the illumination light emitted from the end face of the illumination light guide of the scope, whereby the optical object is illuminated. Is imaged on the light receiving surface of the CCD image sensor, where it is photoelectrically converted as a pixel signal. The pixel signal obtained by the CCD image sensor is sent to an image signal processing unit, where a video signal is created based on the pixel signal. The video signal is then output from the image signal processing unit to the TV monitor device, where an optical subject image is reproduced on the TV monitor device.
[0004]
By the way, generally, the depth of focus of the objective lens system of the scope of the electronic endoscope is relatively deep. This is because it is necessary not only to observe the distal end of the scope close to the affected area such as a lesion, but also to find the affected area such as a lesion, to observe the entire wide area including the affected area. is there. In this case, in order to always reproduce the optical subject image with appropriate luminance, it is necessary to appropriately adjust the amount of light emitted from the distal end of the illumination light guide. That is, when observing with the distal end of the scope closest to the affected part such as a lesion, the amount of light is reduced to the lowest level, and the distal end of the scope gradually moves away from the affected part to gradually increase the amount of light. is necessary.
[0005]
The light amount adjustment as described above is called automatic dimming. In general, for this automatic dimming, the aperture of the diaphragm incorporated in the light source is controlled based on the average luminance level of the pixel signal for one frame. Is done. More specifically, the histogram extraction circuit develops a histogram for the pixel signal for one frame, the average luminance level of the pixel signal for one frame is calculated from this histogram, and the aperture is controlled based on the calculation result. Thus, the brightness of the reproduced image is properly maintained. For example, when the entire optical object is relatively far away from the scope objective lens, in order to maintain the brightness of the reproduced image properly, the amount of illumination light must be increased by widening the aperture. On the contrary, when the entire optical object approaches the objective lens of the scope, in order to maintain the brightness of the reproduced image properly, the aperture amount must be reduced to reduce the amount of illumination light.
[0006]
[Problems to be solved by the invention]
By the way, in the automatic light control as described above, local halation often occurs on the video reproduction screen of the TV monitor device. Here, the halation means that the luminance of the video reproduction screen of the TV monitor device becomes abnormally high and whitens. For example, when a relatively small area of an optical object is close to the objective lens of the scope and most of the other area is away from the objective lens, the aperture opening tends to be widened. Therefore, halation may occur at a relatively small area of the optical subject. Of course, when halation occurs, it becomes difficult to observe the reproduced image of the TV monitor device, which adversely affects diagnosis, treatment, etc. using an electronic endoscope.
[0007]
Accordingly, an object of the present invention is to provide an electronic endoscope of the type described above, which is configured to prevent the occurrence of local halation during automatic light control. That is.
[0008]
[Means for Solving the Problems]
An electronic endoscope according to the present invention includes a scope and an image signal processing unit in which the scope is detachably connected. A light source is provided in the image signal processing unit, and light emitted from the light source is guided to the scope to illuminate the front thereof, and a solid-state imaging means is provided on the distal end side of the scope. An electronic endoscope according to the present invention is based on a histogram extracting means for developing a histogram based on luminance pixel signals for one frame or one field obtained from a solid-state imaging means, and on the histogram developed by the histogram extracting means. Light amount adjusting means for adjusting the amount of light guided from the light source to the scope. Preferably, the average luminance value is obtained from the histogram, and the light amount adjustment by the light amount adjusting means is performed so that the average luminance value substantially coincides with a predetermined luminance reference value. In this case, it is determined that the occurrence of local halation has been avoided when it is determined that the difference between the average luminance value and the luminance reference value is larger than a relatively large threshold value over a predetermined period after the occurrence of local halation. Can do. Preferably, manual setting means for changing the luminance reference value stepwise is provided.
[0009]
According to the first aspect of the present invention, the determination means for determining the presence or absence of local halation from the histogram characteristics developed by the histogram extraction means, and the determination means for determining the occurrence of local halation. When this is done, local halation elimination means for forcibly reducing the light quantity adjustment by the light quantity adjustment means to eliminate the occurrence of local halation is provided.
[0010]
In the first aspect of the present invention, calculation means for calculating a ratio of the sum of the frequencies of a predetermined area of the high luminance level of the histogram to the sum of all frequencies of the histogram, and the ratio calculated by the calculation means are set to a predetermined value. Comparing means for comparing with the threshold value may be provided. In this case, when the ratio exceeds a predetermined threshold value, it is determined by the determining means that local halation has occurred.
[0011]
Further, in the second aspect of the present invention, there is an arithmetic means for calculating the sum of the frequencies of the predetermined area of the high luminance level of the histogram, and a comparing means for comparing the total calculated by the arithmetic means with a predetermined threshold value. Can be provided. In this case, when the sum exceeds a predetermined threshold value, it is determined by the determining means that local halation has occurred. Such a threshold value can be appropriately set according to the type of scope, and can be set via an appropriate input means such as a keyboard.
[0012]
According to the second aspect of the present invention, the first discriminating means for discriminating whether or not local halation has occurred from the histogram characteristics developed by the histogram extracting means, and the local halation by the first discriminating means. A second discriminating means for discriminating the degree of local halation when it is discriminated that there is an occurrence of light, and forcibly adjusting the light quantity by the light quantity adjusting means according to the degree discriminated by the second discriminating means Local halation elimination means for reducing the occurrence of local halation by reducing the occurrence of local halation.
[0013]
In the second aspect of the present invention, computing means for calculating the ratio of the sum of the frequencies of the predetermined area of the high luminance level of the histogram to the sum of all the frequencies of the histogram, and the magnitude of the ratio calculated by the computing means According to the method, a digitizing means for digitizing stepwise may be provided. In this case, when the numerical value digitized by the digitizing means is the minimum value, the first discriminating means determines that no local halation has occurred. On the other hand, when the numerical value digitized by the numerical digitizing means is other than the minimum value, the occurrence of local halation is judged by the first discriminating means and the light quantity adjusting means according to the magnitude of the numerical value. The degree to which the light amount adjustment should be forcibly reduced is determined by the second determining means.
[0014]
According to the third aspect of the present invention, flag means for instructing whether or not local halation has occurred, and light quantity adjustment by the light quantity adjusting means when instructed by the flag means that local halation has occurred Local halation elimination means for forcibly reducing the occurrence of local halation is provided.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of an electronic endoscope according to the present invention will be described with reference to the accompanying drawings.
[0016]
Referring to FIG. 1, an embodiment of an electronic endoscope according to the present invention is illustrated as a block diagram. The electronic endoscope includes a scope 10 made of a flexible conduit, and the scope 10 is detachably connected to an image signal processing unit 12 called a processor. An imaging sensor 14 including a solid-state imaging device, for example, a CCD (charge-coupled device) imaging device is provided at the distal end or distal end of the scope 10, and the imaging sensor 14 includes an objective lens system combined with the CCD imaging device. To do.
[0017]
An illumination light guide 16 composed of an optical fiber bundle is inserted into the scope 10, and the distal end of the illumination light guide 16 extends to the distal end of the scope 10. An illumination lens (not shown) is combined with the end face. The proximal end of the illumination light guide 16 is optically connected to a white light source 18 such as a xenon lamp or a halogen lamp provided in the image signal processing unit 12 when the scope 10 is connected to the image signal processing unit 12. . A diaphragm 20 and a condenser lens 22 are sequentially provided on the light emission side of the white light source 18, and the diaphragm 20 is used as a light amount adjusting means for appropriately adjusting a light amount from the white light source 18, and the condenser lens 22 is a diaphragm. It is used for condensing the light having passed through 20 on the end face of the proximal end of the illumination light guide 16.
[0018]
In the present embodiment, since a frame sequential method is adopted to reproduce a color image, a rotary RGB color filter is used as a rotary tri-primary color filter between the proximal end face of the illumination light guide 16 and the condenser lens 22. A color filter 24 is interposed. As shown in FIG. 2, the rotary RGB color filter 24 is composed of a disk element, and the disk element is provided with a red filter 24R, a green filter 24G, and a blue filter 24B. It is said. The color filters 24R, 24G, and 24B are arranged along the circumferential direction of the disk element so that the respective radial centers are at an angular interval of 120 °, and an area between adjacent color filters is a light shielding area. Is done.
[0019]
As shown in FIG. 3, the rotary three primary color filter 24 is rotated by a drive motor 26 such as a servo motor or a step motor. The rotation frequency of the rotary RGB color filter 24 is determined according to the TV image reproduction method adopted in the electronic endoscope. For example, when the PAL method is adopted, the rotation frequency of the rotary RGB color filter 24 is 25 Hz, and when the NTSC method is adopted, the rotation frequency is 30 Hz.
[0020]
For example, if the rotary RGB color filter 24 is rotated at a rotation frequency of 30 Hz (NTSC method), the time required for one rotation is approximately 33 ms (1/30 sec), and the illumination time by each color filter is approximately 33/6 ms. Become. From the end face of the distal end of the light guide 16, red light, green light and blue light are sequentially emitted every 33 ms (1/30 sec) for approximately 33/6 ms, and the optical object is red light, green light and Illumination is sequentially performed with blue light, and optical subjects of the respective colors are sequentially formed on the light receiving surface of the CCD image sensor by the objective lens system of the image sensor 14. The image sensor 14 photoelectrically converts each color optical subject image formed on the light receiving surface of the CCD image sensor into an analog pixel signal for one frame, and the analog pixel signal for one frame of each color is an illumination time of each color. The readout is sequentially performed from the imaging sensor 14 over the next shading time (33/6 ms) following (33/6 ms), and the readout of the analog pixel signal from the imaging sensor 14 is provided in the scope 10. This is performed by the CCD driver 28.
[0021]
Strictly speaking, since the output power of each color from the color filters 24R, 24G, and 24B and the spectral sensitivity characteristics of the CCD image sensor 14 are different, the illumination times of the red light, the green light, and the blue light are slightly different. Although different, the readout of the analog pixel signal for one frame of each color from the CCD image sensor 14 is performed within the light shielding time in the same manner.
[0022]
As is apparent from FIG. 1, the image signal processing unit 12 is provided with a system controller 30, and the system controller 30 is constituted by a microcomputer. That is, the system controller 30 is a central processing unit (CPU), a program for executing various routines, a read only memory (ROM) for storing constants, and a write / readable memory (temporarily storing data). RAM) and input / output interface (I / O), and controls the overall operation of the electronic endoscope.
[0023]
When the scope 10 is connected to the image signal processing unit 12, the imaging sensor 14 is connected to the CCD process circuit 32 in the image signal processing unit 12 via the CCD driver 28. The analog pixel signal for one frame of each color read from the image sensor 14 by the CCD driver 28 is sent to the CCD process circuit 32, where predetermined image processing such as white balance correction processing, gamma correction processing, contour enhancement processing, etc. is performed. receive. In FIG. 1, the connection relationship of the system controller 30 to the CCD driver 28 and the CCD process circuit 32 is not particularly shown in order to avoid complication, but the pixel signal readout by the CCD driver 28 and the CCD process circuit are not shown. The image processing at 32 is performed under the control of the system controller 30.
[0024]
The analog pixel signals for one frame of each color processed by the CCD process circuit 32 are sequentially sent to an analog / digital (A / D) converter 34 where they are converted into digital pixel signals, and then digital for one frame of each color. The pixel signal is once written and stored in the frame memory 36. The frame memory 36 is provided with three storage areas for storing digital pixel signals for one frame of each color. From the frame memory 36, digital image signals of three primary colors for one frame are sequentially read out simultaneously. At this time, a horizontal synchronization signal, a vertical synchronization signal, and the like are added to the read digital image signal of each color. That is, digital image signals of three primary colors for one frame are sequentially output from the frame memory 36 as color digital video signals (R, G, B) and sent to the video process circuit 38.
[0025]
The video process circuit 38 is provided with a digital / analog (D / A) and low-pass filter corresponding to the color digital video signal of each color, and the color digital video signal for one frame of each color is color analog video for one frame. The signal is converted into a signal, and then, after passing through a low-pass filter, is appropriately amplified and sent to the color TV monitor device 40, where an optical subject image is reproduced as a color image. The video process circuit 38 generates a component video signal based on the color digital video signals (R, G, B), and the component video signal is a separate TV monitor device, video tape recorder, image processing computer, or the like. Are output from the video process circuit 38 to the outside.
[0026]
Referring to FIG. 4, the diaphragm 20 is illustrated along with its drive mechanism. The diaphragm 20 includes a pair of blade elements 42 and 44, and arm portions 42 </ b> A and 44 </ b> A extend integrally from the blade elements 42 and 44. The blade elements 42 and 44 are pivotally supported by a pivot pin 46 in such a manner that they intersect with each other, and the amount of white light emitted from the white light source 18 is appropriately determined according to the opening degree of the blade elements 42 and 44. Adjusted. The drive mechanism of the diaphragm 20 includes a tension coil spring 48 that is acted between the ends of the arm portions 42A and 44A, and the coil spring 48 causes the blade elements 42 and 44 to be elastically biased so as to reduce the opening thereof. Always receive. The pivot pin 46 is appropriately held with respect to the housing of the image signal processing unit 12.
[0027]
The drive mechanism of the diaphragm 20 further includes a cam pin 50 engaged between the arm portions 42A and 44A in order to adjust the opening degree of the pair of blade elements 42 and 44. The cam pin 50 is a lower end portion of the drive plate 52. It is fixed and held on. A rack 54 is formed on one side of the drive plate 52, and a pinion 56 is engaged with the rack 54. The pinion 56 is fixed on an output shaft 58A of an appropriate drive motor 58 such as a servo motor or a step motor. The drive motor 58 is appropriately held with respect to the housing of the image signal processing unit 12, and the rack 54 is appropriately held slidably by appropriate guide means (not shown). When the drive motor 58 is rotated, the drive plate 52 is moved along the longitudinal direction (that is, the vertical direction in FIG. 4) together with the cam pin 50, and the movement direction depends on the rotation direction of the drive motor 58. In short, according to the rotational direction of the drive motor 58, the opening degree of the blade elements 42 and 44, that is, the throttle opening degree is adjusted.
[0028]
As shown in FIG. 1, the drive motor 58 is driven by a drive circuit 60, and the drive circuit 60 is controlled by the system controller 30. In other words, a drive pulse is output from the drive circuit 60 to the drive motor 58. By appropriately controlling the number of output drive pulses, the amount of rotation of the drive motor 58 is adjusted, and the phase of the output drive pulse is reversed. By doing so, the rotation direction of the drive motor 58 is reversed, and thereby the opening degree of the diaphragm 20 is adjusted. Of course, the control of the number of drive pulses output from the drive circuit 60 and the reverse control of the phase are performed by the system controller 30.
[0029]
As shown in FIG. 1, the image signal processing unit 12 is provided with a lamp power circuit 62, and power is supplied to the white light source 18 by the lamp power circuit 62. The lamp power supply circuit 62 is connected to a commercial power supply via a plug (not shown) and is appropriately controlled by the system controller 30.
[0030]
As shown in FIG. 1, the image signal processing unit 12 is provided with a histogram extraction circuit 64. The histogram extraction circuit 64 is connected to the video process circuit 38, and the video process circuit 38 receives luminance from the component video signal. A pixel signal is output to the histogram extraction circuit 64.
[0031]
As shown in FIG. 1, a suitable non-volatile memory such as a rewritable read-only memory (EEPROM) 66 is provided on the scope 10 side, and various information of the scope 10 itself is written in the EEPROM 66. For example, the EEPROM 66 stores type data of the scope, for example, type data such as a stomach scope, a bronchial scope, or a large intestine scope, and the pixel number data of the CCD image sensor 14 used therefor, read by the CCD driver 28. The frequency information of the clock pulse when the outputted analog image signal is processed is stored. When the scope 10 is connected to the image signal processing unit 12, the EEPROM 66 is connected to the system controller 30. At this time, the system controller 30 reads information data in the EEPROM 66 and stores the information data in a RAM in the system controller 30. Retained.
[0032]
As shown in FIG. 1, a keyboard 67 is further connected to the system controller 30, and various command signals and various data are input through the keyboard 67. The input of the command signal and data related to the present invention will be clarified in the later description.
[0033]
As shown in FIG. 5, an operation panel 68 is attached to the outer wall surface of the casing of the image signal processing unit 12, and various switches and the like are provided on the operation panel 68. Referring to FIG. 6, various switches and the like on the operation panel 68 are shown as a block diagram in relation to the system controller 30. In FIG. 6, the CPU, ROM, RAM, and I / O of the system controller 30 are denoted by reference numerals 30A, 30B, 30C, and 30D, respectively, and these components are connected to each other by a bus.
[0034]
In FIG. 5, reference numeral 70 indicates a main power ON / OFF switch of a main power supply circuit (not shown). With this main power ON / OFF switch 70, the power supply from the commercial power supply to the image signal processing unit 12 is turned ON / OFF. Is done. In short, when the main power ON / OFF switch 70 is turned on, the image signal processing unit 12 becomes operable. 5 and 6, reference numeral 72 indicates an ON / OFF switch of the lamp power supply circuit 62, and an ON / OFF signal is output from the lamp power ON / OFF switch 72 to the system controller 30. That is, when the lamp power ON / OFF switch 72 is turned on, the white light source 18 is supplied with power from the lamp power source 62 and is lit.
[0035]
Further, an UP button switch 74 and a DOWN button switch 76 are provided on the operation panel 68 in order to adjust the overall luminance of the video reproduction screen of the TV monitor device 40. The UP button switch 74 forms part of a luminance increase pulse signal generation circuit (not shown), and the luminance increase pulse signal generation circuit generates a luminance increase pulse signal every time the UP button switch 74 is pressed. The luminance reference value (Y described later) is output every time the luminance increase pulse signal is output._r) Is increased step by step by a predetermined amount. The DOWN button switch 76 forms part of a luminance reduction pulse signal generation circuit (not shown), and the luminance reference value (Y) that is applied each time the DOWN button switch 76 is pressed from the luminance reduction pulse signal generation circuit._r) Is decreased step by step by a predetermined amount.
[0036]
As described above, the overall luminance of the video reproduction screen of the TV monitor device 40 is adjusted by pressing the UP button switch 74 and the DOWN button switch 76. For the operator of the electronic endoscope, which level of light quantity is selected. It must be recognized as a degree. For this purpose, a brightness level indicator 78 is provided on the operation panel 68, and the brightness level indicator 78 has 11 display windows aligned vertically on the operation panel 68 as shown in FIG. Each display window is formed of a translucent light diffusing plate. The 11 display windows are numbered “-5” to “+5” adjacent to each other, the display window located in the center is larger than the others, and the number “0” is appended to it. Is done.
[0037]
The brightness level indicator 78 further includes an electrical light emitter, such as a light emitting diode (LED) 80, disposed inside each display window._-Five, 80_-Four... 80₀... 80₊₄And 80₊₅These LEDs are shown in FIG. 6 as small blocks aligned with each other, and the numbers corresponding to the display windows described above are attached to the individual small blocks. Individual LEDs 80_-Five, 80_-Four... 80₀... 80₊₄And 80₊₅Is supplied with power from the LED power supply circuit 82 and is turned on, and which LED is turned on is controlled by controlling the LED power supply circuit 82 with the system controller 30.
[0038]
Referring to FIG. 7, there is shown an example of a histogram developed by the histogram extraction circuit 64 based on the digital luminance pixel signal for one frame obtained from the video process circuit 38. As shown in FIG. 7, in the present embodiment, the histogram extraction circuit 64 distributes the digital luminance pixel signal for one frame into 256 luminance levels. In short, the histogram shown in FIG. 7 shows 256 luminance levels along the horizontal axis X, and the vertical axis Y shows the number of digital luminance pixel signals corresponding to each luminance level, that is, the frequency. The luminance level 0 corresponds to the pedestal level, and the luminance level 255 corresponds to the maximum luminance level.
[0039]
In the present invention, the average luminance level Y is determined from the histogram obtained from the digital luminance pixel signal for each frame._aIs obtained by the following calculation.
[0040]
[Expression 1]

[0041]
Where L_nIndicates a luminance value corresponding to each luminance level (0 to 255). For example, a numerical value of the luminance level may be used as the luminance value. That is, the luminance values corresponding to the luminance levels 0 to 255 can be set to 0 to 225, respectively. Also, s_nIndicates the frequency (number) of digital luminance pixel signals assigned to each luminance level (0 to 255), and f_oIndicates the sum of digital luminance pixel signals for one frame.
[0042]
In the system controller 30, the calculated average luminance value Y_aAnd luminance reference value Y_rThe opening degree of the diaphragm 20 is adjusted so that. That is, the average luminance value Y_aIs the luminance reference value Y_rIf larger, the drive motor 58 is driven so that the opening degree of the diaphragm 20 becomes smaller, and on the contrary, the average luminance value Y_aIs the luminance reference value Y_rIf smaller, the drive motor 58 is driven so that the opening degree of the diaphragm 20 is increased. Luminance reference value Y_rAs described above, it is possible to change the brightness stepwise by operating the UP button switch 74 and the DOWN button switch 76, whereby the overall luminance of the video reproduction screen of the TV monitor device 40 can be appropriately adjusted.
[0043]
As described above, when a relatively small area of the optical object is close to the objective lens of the scope 10 and most other areas are far from the objective lens, the aperture 20 The opening tends to be widened. This is because when the most area of the optical subject is far from the objective lens of the scope 10, the average luminance value Y_aIs small, and its average luminance value Y_aBrightness reference value Y_rThis is because the aperture of the diaphragm 20 must be increased in order to match the above. Thus, in such a case, halation can occur at a relatively small region of the optical subject close to the objective lens of the scope 10. When such local halation occurs, a common characteristic tendency is seen in the histogram, and it is possible to determine whether or not local halation has occurred by detecting the characteristic tendency. .
[0044]
More specifically, as shown in FIG. 8, the histogram at the time of occurrence of local halation has a maximum luminance level 255 and a specific luminance level V close thereto._hSum of frequencies between and f_HIs a large value. For example, the sum of all digital luminance pixel signals for one frame is expressed as f_oF_oF for_HRatio t_rAnd this ratio t_rTo an appropriate threshold F_rIt is possible to determine whether or not local halation has occurred. That is, the ratio t_rIs the threshold F_rIs exceeded, it is determined that local halation has occurred, and the ratio t_rIs the threshold F_rIn the following cases, it is determined that local halation does not occur. According to the present invention, when local halation occurs, the luminance reference value Y_rIs forcibly reduced, thereby reducing the aperture of the diaphragm 20 and lowering the overall luminance of the video reproduction screen of the TV monitor device 40, thereby suppressing the occurrence of local halation.
[0045]
Specific brightness level V_hCan be appropriately set between the luminance level 200 and the luminance level 230, for example, but is preferably set individually according to the type of the scope 10 (or the type of the imaging sensor 14 incorporated therein). Also, the threshold value F_rCan be set as appropriate, but in this case as well, it is preferably set individually according to the type of the scope 10.
[0046]
Currently, 20 or more types of scopes 10 that can be connected to the image signal processing unit 12 are known, but these scopes 10 can be roughly divided into three groups. For example, in a scope represented by a bronchoscope, V_h= 210 and F_r= 0.13, and in a scope represented by a large intestine scope, V_h= 210 and F_r= 0.20, and in the scope represented by the stomach scope, V_h= 225 and F_r= 0.13.
[0047]
Referring to FIG. 9, a flowchart of a scope determination / setting routine executed by the system controller 30 is shown. This scope discrimination / setting routine functions as a subroutine of the main operation routine of the electronic endoscope, and its execution is started when the main power switch 70 is turned on.
[0048]
In step 901, it is determined whether or not the scope 10 is connected to the image signal processing unit 12. That is, in step 901, the connection of the scope 10 is monitored. For this monitoring, for example, an appropriate switch circuit (not shown) is incorporated in the connection portion on the image signal processing unit 12 side, and the on / off state of this switch circuit is set. This is performed by monitoring with the system controller 30. This routine is executed every 20 ms, for example, but no progress is made unless the scope 10 is connected to the image signal processing unit 12.
[0049]
When the connection of the scope 10 to the image signal processing unit 12 is confirmed in step 901, the process proceeds to step 902, where information data is read from the EEPROM 66 of the scope 10, and the read information data is stored in the RAM 30C (FIG. 6) of the system controller 30. ).
[0050]
In step 903, it is determined whether or not the connection scope 10 is a scope represented by a bronchial scope with reference to the scope type data in the information data. If the connection scope 10 is a scope represented by a bronchoscope, the process proceeds to step 904, where the specific brightness level V is reached._hAs 210 and the threshold F_rIs given as 0.13.
[0051]
In step 903, when the connection scope 10 is not a scope represented by a bronchial scope, the process proceeds to step 905, where it is determined whether or not the connection scope 10 is a scope represented by a colonic scope. When it is confirmed that the connection scope 10 is a scope represented by a large intestine scope, the process proceeds to step 906 where the specific brightness level V is determined._hAs 210 and the threshold F_rIs given as 0.20.
[0052]
In step 905, when the connection scope 10 is not a scope represented by a large intestine scope, the connection scope 10 becomes a scope represented by a stomach scope. In this case, the process proceeds to step 907, where a specific luminance level V is obtained._hAs 225 and threshold F_rIs given as 0.13.
[0053]
Even when the scope 10 is removed from the image signal processing unit 12 and another scope 10 is connected, the specific brightness level V with respect to the other scope 10 is also determined._hAnd threshold F_rIs reset.
[0054]
Referring to FIGS. 10 and 11, a flowchart of an aperture control routine executed by the system controller 30 is shown. This aperture control routine functions as a time interrupt routine. For example, when the NTSC system is adopted as the video reproduction system, the aperture control routine is a time interrupt routine executed every 1/30 sec.
[0055]
First, in step 1001, the total frequency f of all histogram data (0 ≦ X ≦ 255) f_o(That is, the total number of pixels of the digital luminance pixel signal for one frame) is calculated.
[0056]
In step 1002, the average luminance value Y is calculated from all the histogram data (0 ≦ X ≦ 255) developed by the histogram extraction circuit 64 based on the digital luminance pixel signal for one frame obtained from the video process circuit 38._aIs calculated by the above equation. Here, the luminance value L corresponding to each luminance level (0 to 255) is used._nIs the numerical value of the luminance level itself (0 to 255).
[0057]
In step 1003, the specific luminance level V out of all the histogram data (0 ≦ X ≦ 255)._hAnd the maximum brightness level of 255 (V_h≦ X ≦ 255)_HIs calculated. Next, in step 1004, the following calculation is executed.
t_r← f_H/ F_o
That is, the specific luminance level V with respect to the total number of pixels of the digital luminance pixel signal for one frame._hAnd the total number of pixels f between the maximum luminance level 255_HRatio t_rThis data is stored in the RAM 30C (FIG. 6) of the system controller 30.
[0058]
In step 1005, it is determined whether the flag F1 is “0” or “1”. The flag F1 determines whether or not local halation has occurred. When the occurrence of local halation is recognized, the flag F1 is set to “1”. When the occurrence of local halation is not recognized, F1 is set to “0”. "
[0059]
Since F1 = 0 is set in the initial stage, the process proceeds from step 1005 to step 1006, where the following calculation is executed.
[0060]
[Expression 2]

[0061]
That is, the average luminance value Y_aAnd luminance reference value Y_rDifference from Y_d1Is required.
[0062]
In the present embodiment, the luminance reference value Y_rIs a value set as appropriate between the luminance level 80 and the luminance level 180, for example, and can be changed in stages by operating the UP button switch 74 and the DOWN button switch 76 as described above. That is, for example, among the 11 display windows of the luminance level indicator 78, the central display window (LED 80).₀) Is lit, luminance reference value Y_rCorresponds to the luminance level 130, and is changed stepwise by 10 luminance levels by operating the UP button switch 74 or the DOWN button switch 76. Luminance reference value Y_rCorresponds to the maximum brightness level 180 (LED80₊₅), The minimum value corresponds to the luminance level 80 (LED 80)._-Five).
[0063]
In step 1007, the average luminance value Y_aAnd luminance reference value Y_rDifference from Y_d1Is allowable value Y_tCompared with In the present embodiment, the allowable value Y_tIs, for example, 2 and the difference ΔY_d1When the value exceeds 2, the overall luminance of the video reproduction screen of the TV monitor device 40 becomes the set luminance reference value Y._rTherefore, the opening of the diaphragm 20 is adjusted.
[0064]
More specifically, if the difference ΔY_d1Is allowable value Y_tIf it exceeds, the process proceeds to step 1008 where the average luminance value Y_aAnd set brightness reference value Y_rIs determined. Y_a≧ Y_r(This is because the overall brightness of the video reproduction screen of the TV monitor device 40 is the set brightness reference value Y._rThe process proceeds to step 1009, where the flag F2 is set to “1”. On the contrary, Y_a<Y_r(This is because the overall brightness of the video reproduction screen of the TV monitor device 40 is the set brightness reference value Y._rThe process proceeds to step 1010 where the flag F2 is set to “0”. The flag F2 is for indicating the rotation direction of the drive motor 58. When F2 = 1, the drive motor 58 is driven to rotate in a direction to close the diaphragm 20. On the other hand, when F2 = 0, the drive motor 58 is rotationally driven to widen the diaphragm 20.
[0065]
In step 1011, the difference ΔY_d1The number of drive pulses P to be output from the drive circuit 60 to the drive motor 58 according to the magnitude of_VIs set. Number of drive pulses P_VThe setting is performed according to the following Table 1, for example.
[0066]
[Table 1]

[0067]
That is, the difference ΔY_d1Is larger, the number of drive pulses P_VA large setting value is given to. For example, the difference ΔY_d1Is 9 to 17, the number of drive pulses P_VIs given 2 and the difference ΔY_d1Is 36 to 62, the number of drive pulses P_VIs given 10 A one-dimensional map corresponding to Table 1 is developed in the ROM 30B of the system controller 30, and the difference ΔY_d1The number of drive pulses P according to the size of_VAre set from the one-dimensional map.
[0068]
Next, at step 1012, the drive motor 58 is in the rotational direction indicated by the flag F2 and the set drive pulse number P described above._VAnd the opening degree of the diaphragm 20 is adjusted. Thereafter, this routine is temporarily terminated.
[0069]
When this routine is executed again after 1/30 sec, Y_a, F₀And f_HIs calculated from a histogram developed based on the digital luminance pixel signal for the next one frame obtained from the video process circuit 38, and a similar routine is repeated, thus the average luminance value Y_aAnd luminance reference value Y_rIs the allowable value Y_tMatching is made within the range of (= 2). That is, the overall luminance of the video reproduction screen of the TV monitor device 40 is the set luminance reference value Y._rThus, the opening degree of the diaphragm 20 is adjusted (that is, automatic dimming) so as to always match. It should be noted that the difference ΔY_d1Is larger, the number of drive pulses P_VIs set to a large value, the average luminance value Y_aBrightness reference value Y_rIt can be matched quickly.
[0070]
ΔY in step 1007_d1Is allowable value Y_tThat is, the average luminance value Y_aAnd luminance reference value Y_rIs the allowable value Y_tWhen they match within the range of (= 2), the process proceeds from step 1007 to step 1013, where the ratio t_rIs the threshold F_rIt is determined whether or not the value exceeds. If t_r≦ F_rIf this is the case, there is no occurrence of local halation, so the process proceeds from step 1013 to step 1011. At this time, ΔY_d1Is the tolerance Y_t(= 2) or less, so the number of drive pulses P_VIs set to “0” (Table 1), the drive motor 58 itself is not driven and this routine is temporarily terminated.
[0071]
In short, t_r≦ F_rAs long as there is no occurrence of local halation, the overall brightness of the reproduced video screen of the TV monitor device 40 is the set brightness reference value Y._rThe opening degree of the diaphragm 20 is adjusted so as to coincide with.
[0072]
T in step 1013_r> F_rIs determined, that is, when occurrence of local halation is recognized, the process proceeds to step 1014, where the flag F1 is set to "1", and then in step 1015, the counter C is reset to "0". The function of the counter C will be described later. Next, in step 1016, the flag F2 is set to “1”, and in step 1017, the number of drive pulses P_VAn appropriate value such as “6” is set. Subsequently, the routine proceeds to step 1012, where the drive motor 58 in the direction in which the drive motor 58 closes the diaphragm 20_V= 6 (F2 = 1). That is, when the occurrence of local halation is recognized, the opening degree of the diaphragm 20 immediately becomes the number of drive pulses P in step 1017._VIt is narrowed by the set value of (= 6).
[0073]
When this routine is executed again after 1/30 sec has elapsed, the routine proceeds from step 1005 to step 1018 (F1 = 1), where the following calculation is performed.
[0074]
[Equation 3]

[0075]
That is, the luminance reference value Y_rIs an appropriate value Y_c(For example, Y_cIs reduced by an initial setting value of 10), and the reduced luminance reference value (Y_r-Y_c) And average luminance value Y_aDifference from Y_d2Is required.
[0076]
In step 1019, the average luminance value Y_aAnd reduced luminance reference value (Y_r-Y_cΔY_d2Is allowable value Y_tCompared with (= 2). Difference ΔY_d2Is allowable value Y_tIf it exceeds, the process proceeds to step 1020, where the average luminance value Y_aAnd reduced luminance reference value (Y_r-Y_c) Is judged. Y_a≧ (Y_r-Y_c), The process proceeds to step 1021, where the flag F2 is set to “1”. On the contrary, Y_a<(Y_r-Y_c), The process proceeds to step 1022, where the flag F2 is set to “0”. As described above, the flag F2 is for instructing the rotation direction of the drive motor 58. When F2 = 1, the drive motor 58 is driven to rotate in the direction in which the diaphragm 20 is closed. On the other hand, when F2 = 0, the drive motor 58 is rotationally driven to widen the diaphragm 20.
[0077]
In step 1023, the following calculation is executed.
[0078]
[Expression 2]

[0079]
That is, as in step 1006, the average luminance value Y_aAnd luminance reference value Y_rDifference from Y_d1Is required.
[0080]
Next, in step 1024, the average luminance value Y_aAnd luminance reference value Y_rDifference from Y_d1Threshold D having a relatively large value_y(In this embodiment, D_y= 25). If the difference ΔY_d1Is threshold D_yIf larger, the process proceeds to Step 1025, where the count value of the counter C is incremented by "1". Next, at step 1026, the count value of the counter C is a predetermined value C determined in advance._t(In this embodiment, C_t= 5) is determined. If C <C_tIf so, skip step 1027 and go to step 1028 where the difference ΔY_d2The number of drive pulses P to be output from the drive circuit 60 to the drive motor 58 according to the magnitude of_VIs set. Drive pulse number P_VIs set according to Table 1 above.
[0081]
In step 1029, the drive motor 58 rotates in the direction indicated by the flag F2 (step 1021 or 1022) and the set drive pulse number P described above._VBased on (Step 1028), it is rotationally driven, whereby the opening degree of the diaphragm 20 is adjusted. Thereafter, this routine is temporarily terminated. Thereafter, this routine is executed every 1/30 sec. However, in step 1019, the difference ΔY_d2Is allowable value Y_tAs long as the value exceeds the range, the adjustment of the opening degree of the diaphragm 20 is repeated in the same manner as in the above case. In short, the average luminance value Y_aDecrease reference value (Y_r-Y_c) Is automatically adjusted so as to be substantially equal to.
[0082]
Incidentally, in step 1024, it is monitored whether or not the optical subject has changed due to a relatively large movement of the scope 10. This is because if the scope 10 has relatively large movement after the occurrence of local halation, the average luminance value Y obtained at the time of occurrence of local halation._aAnd the average luminance value Y obtained thereafter_aA large difference between the average luminance value Y and the latter._aAnd luminance reference value Y_rDifference from Y_d1Can also be big. On the other hand, when there is a relatively large movement of the scope 10 after the occurrence of local halation, the local halation occurrence condition may be avoided.
[0083]
Therefore, the difference ΔY_d1Is a relatively large threshold D_yThe number of times exceeding (= 25) is counted by the counter C in step 1025, and the counted number is a predetermined value C._tIf (for example, 5) is reached, it is determined that the local halation occurrence condition has been avoided, and the process proceeds from step 1026 to step 1027, where F1 is rewritten from “1” to “0”, and the luminance reference value Y_rY to decrease_cIs given an initial set value of “10”. At the subsequent execution of this routine, since F1 = 0, the routine proceeds from step 1005 to step 1006, where automatic dimming as described above, that is, the luminance reference value Y_rThe automatic dimming is performed again.
[0084]
On the other hand, the difference ΔY_d1Is a relatively large threshold D_yThe number of counters exceeding (= 25) is a predetermined value C_tIf the difference is reached until (= 5)_d1Is a relatively large threshold D_yIn the following case, it is determined that the local halation occurrence condition is not avoided, and the process proceeds from step 1024 to step 1030, where the counter C is reset to “0”. Thereafter, this routine is executed every 1/30 sec. However, in step 1019, the difference ΔY_d2Is allowable value Y_tAs long as the value exceeds the range, the adjustment of the opening degree of the diaphragm 20 is repeated in the same manner as in the above case.
[0085]
In step 1019, the difference ΔY_d2Is allowable value Y_tWhen it is below, that is, the reduced luminance reference value (Y_r-Y_c) After the automatic light control is performed, the average luminance value Y_aAnd reduced luminance reference value (Y_r-Y_c) Is the allowable value Y_tWhen they match within the range of (= 2), the process proceeds from step 1019 to step 1031 where it is determined again whether or not local halation has occurred. Decrease luminance reference value (Y_r-Y_c) (Difference ΔY)_d2Is allowable value Y_tHereinafter, when occurrence of local halation is recognized in step 1031, the process proceeds from step 1031 to step 1032, where the following calculation is performed.
Y_c← Y_c+ K_c
That is, the value Y_cFor constant K_c(For example, allowable value Y_tIs given a value 4 greater than = 2). Thereafter, this routine is temporarily terminated.
[0086]
When this routine is executed again in the next interrupt process, the process proceeds from step 1005 to step 1018 (F1 = 1), where the following calculation is performed.
[0087]
[Equation 3]

[0088]
That is, as in the case described above, the luminance reference value Y_rIs the value Y_cReduced brightness reference value (Y_r-Y_c) And average luminance value Y_aDifference from Y_d2However, the reduced luminance reference value (Y_r-Y_c) Is further reduced compared to the previous case. Because the value Y_cThis is because a value 14 larger than the initial setting value 10 is given to.
[0089]
The processing performed thereafter is the same. That is, the reduced luminance reference value (Y_r-Y_c) Is automatically adjusted (Y_c= 14) If the occurrence of local halation is still recognized after completion of the automatic dimming, the value Y_c4 is added to (step 1032), and the same processing is repeated.
[0090]
On the other hand, if the occurrence of local halation is not recognized in step 1031, this routine is temporarily terminated. Thereafter, this routine is executed every 1/30 sec. As long as F1 = 1, the reduced luminance reference value (Y_r-Y_cAuto dimming is maintained.
[0091]
When the optical subject changes due to the movement of the scope 10, the average luminance value Y obtained before the movement of the scope 10._aAnd the average luminance value Y obtained after moving the scope 10_aA large difference can occur between the average brightness value Y after the movement of the scope 10._aAnd luminance reference value Y_rDifference from Y_d1The absolute value of is also large (step 1023). For this reason, the difference ΔY_d1Is threshold D_y(= 25) is exceeded, and the number of times is counted by the counter C in step 1025._tWhen (= 5) is reached, the process proceeds from step 1026 to step 1027 where F1 is rewritten from “1” to “0” and the value Y_cIs given an initial set value of “10”. At the subsequent execution of this routine, since F1 = 0, the routine proceeds from step 1005 to step 1006, where automatic dimming as described above, that is, the luminance reference value Y_rThe automatic dimming is performed again.
[0092]
Referring to FIGS. 12 and 13, flowcharts of modified examples of the aperture control routine shown in FIGS. 10 and 11 are shown. In the aperture control routine shown in FIGS. 10 and 11, the specific luminance level V with respect to the total number of pixels of the digital luminance pixel signal for one frame._hAnd the total number of pixels f between the maximum luminance level 255_HRatio t_rIs obtained and its ratio t_rIs the threshold F_rIt is determined that local halation has occurred when the value exceeds the upper limit, but in the aperture control routine shown in FIGS. 12 and 13, out of all the histogram data (0 ≦ X ≦ 255) Specific brightness level V_hAnd the maximum brightness level of 255 (V_h≦ X ≦ 255)_HIs calculated, and this sum f_HIs a predetermined threshold F_mIt is determined that local halation has occurred.
[0093]
First, in step 1201, the specific brightness level V out of all the histogram data (0 ≦ X ≦ 255)._hAnd the maximum brightness level of 255 (V_h≦ X ≦ 255)_HIs calculated.
[0094]
In step 1202, the average luminance value Y is calculated from all the histogram data (0 ≦ X ≦ 255) developed by the histogram extraction circuit 64 based on the digital luminance pixel signal for one frame obtained from the video process circuit 38._aIs calculated by the above equation. Here again, the luminance value L corresponding to each luminance level (0 to 255)._nIs the numerical value of the luminance level itself (0 to 255).
[0095]
Steps 1203 to 1230 correspond to steps 1005 to 1032 shown in FIGS. 10 and 11, respectively, and the same routine is executed except for the following points. That is, in step 1211 and step 1229, as described above, the sum f_HIs a predetermined threshold F_mThe routine consisting of steps 1203 to 1230 is substantially different from the routine consisting of steps 1005 to 1032 shown in FIG. 10 and FIG. Is the same. Note that the threshold value F_mFor example, when the total number of pixels for one frame is 65,000, 7,000 can be set.
[0096]
Referring to FIGS. 14 to 16, a flowchart of another aperture control routine executed by the system controller 30 is shown. This aperture control routine also functions as a time interruption routine. For example, when the NTSC system is adopted as the video reproduction system, it is executed every 1/30 sec.
[0097]
First, in step 1401, the total frequency f of all histogram data (0 ≦ X ≦ 255) f_o(That is, the total number of pixels of the digital luminance pixel signal for one frame) is calculated.
[0098]
In step 1402, the average luminance value Y is calculated from all the histogram data (0 ≦ X ≦ 255) developed by the histogram extraction circuit 64 based on the digital luminance pixel signal for one frame obtained from the video process circuit 38._aIs calculated by the above equation. Here again, the luminance value L corresponding to each luminance level (0 to 255)._nIs the numerical value of the luminance level itself (0 to 255).
[0099]
In step 1403, the first specific brightness level V out of all the histogram data (0 ≦ X ≦ 255)._h1And the maximum brightness level of 255 (V_h1≦ X ≦ 255)_H1Is calculated. Next, in step 1404, the following calculation is executed.
t_r1← f_H1/ F_o
That is, the first specific luminance level V with respect to the total number of pixels of the digital luminance pixel signal for one frame._h1And the total number of pixels f between the maximum luminance level 255_H1Ratio t_r1This data is stored in the RAM of the system controller 30.
[0100]
In step 1405, the second specific brightness level V out of all the histogram data (0 ≦ X ≦ 255)._h2And the maximum brightness level of 255 (V_h2≦ X ≦ 255)_H2Is calculated. Next, in step 1406, the following calculation is executed.
t_r2← f_H2/ F_o
That is, the second specific luminance level V with respect to the total number of pixels of the digital luminance pixel signal for one frame._h2And the total number of pixels f between the maximum luminance level 255_H2Ratio t_r2This data is stored in the RAM of the system controller 30.
[0101]
As shown in FIG. 17, the second specific luminance level V_h2Is the first specific luminance level V_h1Higher than these first and second specific luminance levels V_h1And V_h2The specific value of can be input and set according to the type of the scope 10 or via the keyboard 67 before execution of this routine. In the present embodiment, the first luminance level V_h1For example, 210 and the second luminance level V_h2For example, 225 is set.
[0102]
In step 1407, the ratio t_r1And t_r2Variable t based on each value of_m1And t_m2Is set according to Table 2.
[0103]
[Table 2]

[0104]
That is, 0% ≦ t_r1When <12%, the variable t_m1Value is set to “0”, 12% ≦ t_r1<18%, variable t_m1Is set to “1” and 18% ≦ t_r1<24%, variable t_m1Is set to “2” and 24% ≦ t_r1Variable t_m1The value of is set to “3”. In addition, 0% ≦ t_r2<6%, variable t_m2Is set to “0” and 6% ≦ t_r2<12%, variable t_m2Is set to “1” and 12% ≦ t_r2<18%, variable t_m2Is set to “2” and 18% ≦ t_r2<24%, variable t_m2Is set to “3” and 24% ≦ t_r2Variable t_m2The value of is set to “4”. As in the case of Table 1 above, a one-dimensional map corresponding to Table 2 is developed in the ROM 30B of the system controller 30, and the ratio t_r1And t_r2Depending on the magnitude of each value of t_m1And t_m2Are set from the one-dimensional map.
[0105]
In step 1408, the variable t_m1And t_m2Are compared, and the larger setting value is the variable t_mIs set as the value of. Of course, the variable t_m1And t_m2If they have the same set value, the set value is t_mIs set as the value of. In this embodiment, t_mWhen = 0, no local halation occurs and t_mWhen ≧ 1, it is determined that local halation has occurred. T_mWhen ≧ 1, the greater the value, the greater the degree of local halation.
[0106]
In the present embodiment, two variables t_m1And t_m2To variable t_mIs determined, but two variables t_m1And t_m2Only one of them is obtained, and the variable t is used by using only one of the values._mIt is good.
[0107]
Steps 1409 to 1416 correspond to steps 1005 to 1012 of the aperture control routine shown in FIGS. 10 and 11, respectively, and the overall luminance of the video reproduction screen of the TV monitor device 40 is the set luminance reference value Y._rThus, the opening degree of the diaphragm 20 is adjusted (that is, automatic dimming) so as to always match. Drive pulse number P_VThis setting is also performed according to Table 1 described above, for example.
[0108]
In step 1411 ΔY_d1Is allowable value Y_tWhen (= 2) or less, that is, the average luminance value Y_aAnd luminance reference value Y_rIs the allowable value Y_t, The process proceeds from step 1411 to step 1417, where the variable t_mIt is determined whether or not ≠ 0. That is, whether or not local halation has occurred is determined. If t_mWhen = 0, that is, when there is no local halation, the process proceeds from step 1417 to step 1415. At this time, ΔY_d1Is the tolerance Y_tFor this reason, the number of drive pulses P_VIs set to “0” (Table 1), the drive motor 58 itself is not driven and this routine is temporarily terminated.
[0109]
In short, t_mAs long as = 0, that is, as long as local halation does not occur, the overall luminance of the reproduced video screen of the TV monitor device 40 is the set luminance reference value Y._rThe aperture of the diaphragm 20 is only adjusted so as to match
[0110]
T in step 1417_mWhen it is determined that ≠ 0, that is, when occurrence of local halation is recognized, the routine proceeds to step 1418, where the flag F1 is set to “1”, and then the counter C is reset to “0” at step 1419. . The function of the counter C is the same as that of the aperture control routine shown in FIGS. Next, in step 1420, the flag F2 is set to “1”. The function of the flag F2 is the same as in the case of the aperture control routine shown in FIGS. 10 and 11, and in step 1420, the rotational drive direction of the drive motor 58 is set to the direction to close the aperture 20 (F2 = 1).
[0111]
In step 1421, the number of drive pulses P_VIs set by the following calculation. That is,
P_V= CN₁* T_m
Where CN₁Is an appropriate constant, for example, 3. In short, the variable t_mThe larger the set value of, that is, the greater the degree of local halation, the greater the number of drive pulses P_VA large value is given as the set value.
[0112]
In step 1422, the luminance reference value Y is generated when local halation occurs._rY to be subtracted from_cIs obtained by the following calculation.
Y_c= CN₂* T_m
Where CN₂Is an appropriate constant, for example, 4. In short, the variable t_mThe larger the set value of, that is, the greater the degree of local halation, the greater the value Y_cAs a large value is given.
[0113]
Subsequently, the process proceeds to step 1416, where the drive motor 58 has a drive pulse number P in the direction in which the drive motor 58 closes the diaphragm 20._V= CN₁* T_mOnly by a rotational drive (F2 = 1). That is, when the occurrence of local halation is recognized, the opening degree of the diaphragm 20 immediately depends on the degree of the drive pulse number P._V= CN₁* T_mOnly narrowed.
[0114]
When this routine is executed again after 1/30 sec elapses, the process proceeds from step 1409 to step 1423 (F1 = 1), but steps 1423 to 1437 are performed in steps 1018 to 1018 of the aperture control routine shown in FIGS. 1032 respectively, and aperture control similar to the aperture control routine shown in FIGS. 10 and 11 is performed, but the value Y_cThis aperture control routine differs from the aperture control routine shown in FIGS. 10 and 11 in that a value (step 1422) according to the degree of local halation is set.
[0115]
In short, in the aperture control routine shown in FIGS. 14 to 16, the degree of halation is quantified when local halation occurs, and the larger the degree of halation, the faster the occurrence of halation is resolved. It has become.
[0116]
Referring to FIGS. 18 and 19, a flowchart of still another aperture control routine executed by the system controller 30 is shown. This aperture control routine also functions as a time interruption routine. For example, when the NTSC system is adopted as the video reproduction system, it is executed every 1/30 sec.
[0117]
In the aperture control routine shown in FIGS. 18 and 19, whether or not local halation has occurred is determined by the operator who operates the keyboard 67 actually monitoring the video reproduction screen of the TV monitor device 40. .
[0118]
In step 1801, the average luminance value Y is calculated from all the histogram data (0 ≦ X ≦ 255) developed by the histogram extraction circuit 64 based on the digital luminance pixel signal for one frame obtained from the video process circuit 38._aIs calculated by Equation 1 described above. Here again, the luminance value L corresponding to each luminance level (0 to 255)._nIs the numerical value of the luminance level itself (0 to 255).
[0119]
In step 1802, it is determined whether the flag F1 is “0” or “1”. The rewriting of the flag F1 is performed by the operator of the keyboard 67. Specifically, the operator actually monitors the video reproduction screen of the TV monitor device 40, and when the occurrence of local halation is confirmed, the operator rewrites the flag F1 by pressing a predetermined function key on the keyboard 67. Is done. In short, when the operator recognizes the occurrence of local halation and presses a specific key on the keyboard 67, the flag F1 is changed from "0" to "1".
[0120]
When F1 = 0, that is, when the occurrence of local halation is not recognized by the operator, the process proceeds from step 1802 to step 1803, where the interlock flag FL interlocked with the flag F1 is set to “0”.
[0121]
Steps 1804 to 1810 correspond to steps 1006 to 1012 of the aperture control routine shown in FIGS. 10 and 11, respectively, and the overall luminance of the video reproduction screen of the TV monitor device 40 is the set luminance reference value Y._rThus, the opening degree of the diaphragm 20 is adjusted (that is, automatic dimming) so as to always match. Drive pulse number P_VIs set according to, for example, the above-mentioned Table 1, and ΔY is set in Step 1805._d1Is allowable value Y_tWhen (= 2) or less, that is, the average luminance value Y_aAnd luminance reference value Y_rIs the allowable value Y_tWhen the values match within the range, the process proceeds from step 1805 to step 1809. At this time, ΔY_d1Is the tolerance Y_tFor this reason, the number of drive pulses P_VIs set to “0” (Table 1), the drive motor 58 itself is not driven and this routine is temporarily terminated.
[0122]
In short, unless the operator recognizes the occurrence of local halation and F1 is set to “1”, the overall luminance of the reproduced video screen of the TV monitor device 40 is the set luminance reference value Y._rThe aperture of the diaphragm 20 is only adjusted so as to match
[0123]
When the occurrence of local halation is recognized by the operator and F1 is rewritten from “0” to “1”, the process proceeds from step 1802 to step 1811, where the interlock flag FL is “0” or “1”. Is determined. At this time, FL = 0, but the process proceeds to step 1812, where the interlock flag FL is rewritten from “0” to “1” in conjunction with F1 = 1. Next, in step 1813, the counter C is reset to “0”, and in step 1814, the flag F2 is set to “1”. The function of the counter C and the function of the flag F2 are the same as those in the aperture control routine shown in FIGS. In step 1814, the rotational drive direction of the drive motor 58 is set to the direction to close the diaphragm 20, and in step 1815, the number of drive pulses P_VAn appropriate value such as “6” is set. Thereafter, the process proceeds to step 1810, where the drive motor 58 is driven in the direction in which the drive motor 58 closes the diaphragm 20._V= 6 (F2 = 1). That is, immediately after the occurrence of local halation is recognized, the opening of the diaphragm 20 is changed to the number of drive pulses P in step 1815._VIt is narrowed by the set value of (= 6).
[0124]
When this routine is executed again after 1/30 sec elapses, after step 1802 and step 1811 (F1 = 1; FL = 1), the process proceeds to step 1816, but steps 1816 to 1830 are shown in FIGS. 11 corresponds to steps 1018 to 1032 of the aperture control routine shown in FIG. 11, and the aperture control similar to the aperture control routine shown in FIGS. 10 and 11 is performed.
[0125]
【The invention's effect】
As is clear from the above description, in the electronic endoscope according to the present invention, even if local halation occurs during automatic light control, the occurrence of the halation can be quickly eliminated. The adverse effects on diagnosis, treatment, etc. due to the occurrence of halation can be eliminated immediately.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of an electronic endoscope according to the present invention.
FIG. 2 is a front view of the rotary RGB color filter shown in FIG.
FIG. 3 is a side view showing the rotary RGB color filter shown in FIG. 1 together with its drive motor.
4 is a schematic front view showing the diaphragm shown in FIG. 1 together with its drive mechanism. FIG.
FIG. 5 is a front view of an operation panel provided in an image signal processing unit of an electronic endoscope according to the present invention.
6 is a block diagram showing the relationship between various switches and the like provided on the operation panel of FIG. 5 and the system controller.
7 is a graph conceptually showing an example of a histogram developed by the histogram extraction circuit shown in FIG. 1. FIG.
FIG. 8 is a graph showing the relationship between the occurrence of local halation and the characteristics of a histogram.
FIG. 9 is a flowchart for explaining a scope determination / setting routine executed by the system controller of FIG. 1;
10 is a part of a flowchart for explaining an aperture control routine executed by the system controller of FIG. 1. FIG.
11 is the remaining part of the flowchart for explaining the aperture control routine executed by the system controller of FIG. 1;
12 is a part of a flowchart for explaining a modification of the aperture control routine shown in FIGS. 10 and 11. FIG.
13 is a remaining portion of a flowchart for explaining a modification of the aperture control routine shown in FIGS. 10 and 11. FIG.
14 is a part of a flowchart for explaining another aperture control routine executed by the system controller of FIG. 1; FIG.
15 is a part of a flowchart for explaining another aperture control routine executed by the system controller of FIG. 1; FIG.
FIG. 16 is a remaining portion of a flowchart for explaining another aperture control routine executed by the system controller of FIG. 1;
17 is a graph similar to the graph shown in FIG. 8, and is used for explaining the flowcharts shown in FIGS. 14 to 16. FIG.
FIG. 18 is a part of a flowchart for explaining still another aperture control routine executed by the system controller of FIG. 1;
FIG. 19 is a remaining portion of a flowchart for explaining still another aperture control routine executed by the system controller of FIG. 1;
[Explanation of symbols]
10 Scope
12 Image signal processing unit
14 Imaging sensor
16 Light guide
18 White light source
20 aperture
22 Condensing lens
24 Rotating RGB color filter
28 CCD driver
30 System controller
32 CCD process circuit
34 Analog / digital (A / D) converter
36 frame memory
38 Video process circuit
40 TV monitor device
64 Histogram extraction circuit
66 EEPROM
67 keyboard
68 Operation panel
70 Power switch
72 Lamp power ON / OFF switch
74 UP button switch
76 DOWN button switch
82 LED power circuit

Claims (13)

An electronic endoscope comprising a scope and an image signal processing unit adapted to be detachably connected to the scope,
A light source provided in the image signal processing unit is provided, and light emitted from the light source is guided to the scope to illuminate the front thereof, and further provided on the distal end side of the scope. Solid-state imaging means, histogram extraction means for developing a histogram based on luminance pixel signals for one frame or one field obtained from the solid-state imaging means, and from the light source based on the histogram developed by the histogram extraction means In an electronic endoscope comprising a light amount adjusting means for adjusting the amount of light guided to the scope,
Discriminating means for discriminating whether or not local halation occurs from the histogram characteristics developed by the histogram extracting means;
When it is determined by the determining means that the occurrence of local halation has occurred, the light amount adjusting means forcibly reduces the amount of light to eliminate the occurrence of local halation, and the local halation eliminating means is provided.
The local halation elimination means automatically detects the degree of local halation occurring in the reproduced image displayed on the screen , and the degree of determination is such that the amount of light to be reduced increases as the degree of halation increases. An electronic endoscope characterized by forcibly reducing the amount of light accordingly.   2. The electronic endoscope according to claim 1, wherein an average luminance value is obtained from the histogram, and light amount adjustment is performed by the light amount adjusting means so that the average luminance value substantially coincides with a predetermined luminance reference value. An electronic endoscope characterized by that.   3. The electronic endoscope according to claim 2, wherein when it is determined that a difference between the average luminance value and the luminance reference value is larger than a relatively large threshold value over a predetermined period after occurrence of local halation. An electronic endoscope characterized in that it is determined that the occurrence of a halation is avoided.   4. The electronic endoscope according to claim 2, further comprising a manual setting unit that changes the luminance reference value in a stepwise manner.   5. The electronic endoscope according to claim 1, further comprising: a calculating unit that calculates a ratio of a sum of frequencies of a predetermined region at a high luminance level of the histogram to a sum of all frequencies of the histogram. And a comparing means for comparing the ratio calculated by the calculating means with a predetermined threshold, and when the ratio exceeds the predetermined threshold, it is determined by the determining means that local halation has occurred. An electronic endoscope characterized by that.   5. The electronic endoscope according to claim 1, further comprising: a calculation unit that calculates a sum of frequencies of a predetermined area of a high luminance level of the histogram; and a total calculated by the calculation unit. The electronic endoscope is characterized in that a comparison means for comparing the threshold value with a predetermined threshold value is provided, and when the total exceeds the threshold value, it is determined by the determination means that a local halation has occurred. An electronic endoscope comprising a scope and an image signal processing unit adapted to be detachably connected to the scope,
A light source provided in the image signal processing unit is provided, and light emitted from the light source is guided to the scope to illuminate the front thereof, and further provided on the distal end side of the scope. Solid-state imaging means, histogram extraction means for developing a histogram based on luminance pixel signals for one frame or one field obtained from the solid-state imaging means, and from the light source based on the histogram developed by the histogram extraction means In an electronic endoscope comprising a light amount adjusting means for adjusting the amount of light guided to the scope,
First determination means for determining the presence or absence of local halation from the histogram characteristics developed by the histogram extraction means;
Second discriminating means for automatically discriminating the degree of local halation occurring in the reproduced video displayed on the screen when it is discriminated that the occurrence of local halation has occurred by the first discriminating means;
A local halation eliminating means for forcibly reducing the amount of light by the light amount adjusting means according to the degree determined by the second determining means to eliminate the occurrence of local halation ;
An electronic endoscope characterized in that the local halation elimination means increases the amount of light to be reduced as the degree of halation increases .   8. The electronic endoscope according to claim 7, wherein an average luminance value is obtained from the histogram, and light amount adjustment is performed by the light amount adjusting means so that the average luminance value substantially coincides with a predetermined luminance reference value. An electronic endoscope characterized by that.   9. The electronic endoscope according to claim 8, wherein when it is determined that a difference between the average luminance value and the luminance reference value is larger than a relatively large threshold value over a predetermined period after occurrence of local halation. An electronic endoscope characterized in that it is determined that the occurrence of a halation is avoided.   The electronic endoscope according to claim 9, wherein the threshold value is set according to a type of a scope.   11. The electronic endoscope according to claim 9, wherein the threshold value is set via an appropriate input unit.   12. The electronic endoscope according to claim 8, further comprising manual setting means for changing the luminance reference value in a stepwise manner.   The electronic endoscope according to any one of claims 7 to 12, wherein a calculation unit that calculates a ratio of a sum of frequencies of a predetermined region of a high luminance level of the histogram to a sum of all frequencies of the histogram; There is provided a digitizing means for digitizing stepwise according to the ratio calculated by the computing means, and when the numerical value digitized by the numerical means is the minimum value, local halation When there is no occurrence, it is determined by the first determining means. When the numerical value expressed by the numerical converting means is other than the minimum value, it is determined by the first determining means that local halation has occurred. And the second determining means determines the degree to which the light amount adjustment by the light amount adjusting means should be forcibly reduced according to the numerical value. Daughter endoscope.

Images