JP3675066B2 - Infrared imaging device and image correction method - Google Patents

Description

【００２４】
測定された輝度の標準偏差は標準偏差記憶器１４ｃ内の対応箇所に記憶される。感度ばらつき測定器１４に入力される画像データは、画像補正用シャッタＡ１２が閉じ、外界からの赤外光が遮断されている状態の画像なので、画像補正が全くずれていない場合、測定された各ゲート内の輝度のばらつきのデータは０になり、輝度の偏差は観測されない。つまり、仮にゲート内で偏差が観測されれば、それが画像補正ずれであるといえる。１画面分の各ゲート内の輝度の標準偏差の測定が完了した時点で、感度ばらつき測定器１４は標準偏差記憶器１４ｃ内の輝度の標準偏差の平均値を求める。この値が例えばあらかじめ記憶された前回のキャリブレーション直後の平均値の３倍（直後の平均値をσとすると３σになる）をこえたところで（あるいは、直後の平均値とあらかじめ設定した値との和をこえたところで）、感度ばらつき判定器１４ｄは補正ずれが発生していると判断し、画像補正用シャッタＡ１２を閉じた状態でキャリブレーションを行うよう画像補正指令信号１１を撮像制御器９に出力する。また、撮像制御器９は画像補正指令信号１１を受けて画像補正器７にキャリブレーション指令を送り、キャリブレーション終了直後、感度ばらつき判定器１４ｄは新たに輝度の標準偏差の平均値σを記憶保持し、画像補正用シャッタＡ１２が開く。
【００２５】
従来の装置では、撮像中に素子感度の補正ずれを測定する手段をもたなかったため、キャリブレーションは表示される画面を見ているオペレータの主観によって行われていた。この発明では素子感度の補正ずれの状態を撮像中に定量的に把握する手段を従来の装置に付加し、従来使用者が主観に基づき行っていたキャリブレーション指令を自動生成することで、自動でキャリブレーションを行えるようにし、結果として安定した映像品質の赤外線画像を出力できるようにしている。また、統計的手法を用いたデジタル計算処理を行う簡単な回路構成により、複雑な回路による構成要素を使わずに感度ばらつきを測定することができる。
【００２６】
実施の形態２．
図２はこの発明の実施の形態２を示すブロック図である。図において、１３ｃは画像補正器ＡＡ、１５は画像補正用シャッタＢ、１６はシェーディング量測定器である。それ以外で、１２から１４は実施の形態１と、他は従来の装置と同一である。
【００２７】
次に動作の説明をする。本実施の形態２においても通常の撮像動作は、従来の装置と同じである。本実施の形態における画像補正用シャッタＢ１５は、赤外レンズ１に入射される赤外光を遮断するために赤外レンズ１の手前におく。なお、反応速度は画像補正用シャッタＡと同じ程度のものを使用している。撮像制御器９は例えば１５秒に一度程度ずつ交互に画像補正用シャッタＡ１２と画像補正用シャッタＢ１５に１フレームの赤外光遮断の指令を出すとともに画像補正器ＡＡ１３ｃに赤外画像が遮断されることを伝える。画像補正器ＡＡ１３ｃは、画像補正器Ａ１３について、出力切換を３系統にかえた出力切換スイッチＡ１３ｄに変更したもので、画像補正用シャッタＡが閉じた場合は感度ばらつき測定器１４に、画像補正用シャッタＢが閉じたときはシェーディング量測定器１６に画像データを出力する。シェーディング量測定器１６は感度ばらつき測定器１４と同じような構成で、フレームメモリとシェーディング判定器を持っており、画面の部分ごとのシェーディング量を測定する。図１３はシェーディング量測定動作の概要を示す図である。シェーディング量測定器１６は入力された１画面分のデータを図１３のように例えば４８の領域に分割し、各々の領域の画像データの平均値を求める。シェーディング量測定器１６に入力される画像データは、画像補正用シャッタＢ１５が閉じ、外界からの赤外光が遮断されている状態の画面なので、シェーディングが無い場合、各々の領域の輝度の平均値の差はない。すなわちこの各々の領域の平均値に差があれば、それはシェーディングによるものといえる。図１４にシェーディング補正できている場合とできていない場合の各々の領域の輝度の平均値の分布を示している。図中、４２は補正できている場合の分布、４３は補正できていない場合の分布である。図１４に示すとおり、補正できている場合は、分布の幅は狭く、できていない場合は分布の幅は広くなる。シェーディング量測定器１６は各々の領域の輝度の平均値から最大値と最小値を求めることで、分布の幅を測定し、それが例えば前回のキャリブレーション直後の平均値βから３倍（３β）をこえたところで（あるいは直後の平均値とあらかじめ設定した値との和をこえたところで）シェーディング測定器１６のシェーディング判定器が画像補正用シャッタＢ１５を閉じた状態でキャリブレーション（例えばデフォーカスキャリブレーション）を行う画像補正指令信号１１を撮像制御部９に出力する。また感度ばらつき測定器１４は実施の形態１と同様の動作で感度ばらつきを検出した場合、画像補正用シャッタＡ１２を閉じた状態でキャリブレーションを行う画像補正指令信号１１を撮像制御部９に出力する。撮像制御部９は画像補正指令信号１１を受けて画像補正器７にキャリブレーション指令を送り、キャリブレーション終了直後、感度ばらつき測定器１４は新たに輝度の標準偏差の平均値αを記憶保持し、画像補正用シャッタＡ１２が開き、またはシェーディング量測定器１６は新たに輝度の平均値の分布の幅βを記憶保持し、画像補正用シャッタＢ１５が開く。
【００２８】
従来の装置では、撮像中にシェーディングの補正ずれを測定する手段をもたなかったため、キャリブレーションは表示される画面を見ているオペレータの主観によって行われていた。この発明では素子感度の補正ずれの状態を撮像中に定量的に把握する手段及びシェーディングの補正ずれの状態を撮像中に定量的に把握する手段を従来の装置に付加し、従来使用者が主観に基づき行っていたキャリブレーション指令を自動生成することで、レンズシェーディング補正を含めた自動でのキャリブレーションを行えるようにし、結果として安定した映像品質の赤外線画像を出力できるようにしている。
【００２９】
実施の形態３．
図３はこの発明の実施の形態３を示すブロック図である。図において、１７は補正状態判定器である。それ以外は、実施の形態２と同一である。
【００３０】
次に動作について説明する。本実施の形態３において、撮像動作及び感度ばらつき、シェーディングの量の測定動作は実施の形態２と全く同じである。本形態においては、補正状態判定器１７がキャリブレーション状態を判定し、内部にもつプログラムに基づき３種類のキャリブレーションをシーケンシャルに行えるようにしている。図１５にキャリブレーション制御の流れ図を示す。補正状態判定器１７は感度ばらつき測定器１４もしくはシェーディング量測定器１６からキャリブレーション要求を受けると、キャリブレーション実行状態となり、撮像制御器９に赤外レンズ１のピントをずらす指令（デフォーカス指令）を出させる。ピントが充分にずれて、かつ二つの画像補正シャッタが開いた状態で画像補正器ＡＡ１３ｃは第一のキャリブレーションを実施する（デフォーカスキャリブレーション）。デフォーカスキャリブレーションが終了した時点で、補正状態判定器１７よりデフォーカスキャリブレーション終了指令を受けて撮像制御器９は赤外レンズ１のピントを元に戻して画像補正用シャッタＢ１５を２フレーム分の時間閉じる。シャッタが閉じられたところで、画像補正器Ａ１３は感度ばらつき測定器１４及びシェーディング量測定器１６に出力を切り換え各々に１フレームずつの画像データを送る。感度ばらつき測定器１４及びシェーディング量測定器１６は感度ばらつき及びシェーディング量を測定し補正状態判定器１７に結果を送る。補正状態判定器１７は各々の結果が前回のキャリブレーション直後の測定値に対して許容範囲内であるか、あらかじめ設定されて内部のメモリに記憶されている値と比較し判定する。補正状態が許容範囲内であればデフォーカスキャリブレーションが正常に終了したとみなしキャリブレーション操作は終了する。補正状態が許容範囲外と判定された場合、補正状態判定器１７は撮像制御器９に画像補正用シャッタＢ１５のみを閉じた状態の第二のキャリブレーション（レンズシェーディングキャリブレーション）を要求する。レンズシェーディングキャリブレーションが終了した時点で、撮像制御器９は画像補正用シャッタＡ１２を１フレーム分の時間閉じる。シャッタが閉じられたところで、画像補正器ＡＡ１３ｃは感度ばらつき測定器１４のみに画像データを送る。感度ばらつき測定器１４は感度ばらつきを測定し、補正状態判定器１７に結果を送る。補正状態判定器１７は結果が前回のキャリブレーション直後のばらつきの測定値として許容範囲内であるか、あらかじめ設定されて内部のメモリに記憶されている値と比較し判定する。ここで補正状態が許容範囲内と判定された場合はキャリブレーションは終了し、感度ばらつきとシェーディングの測定値を記憶する。仮に許容範囲外と判定された場合は、画像補正用シャッタＡ１２を閉じた状態の第三の感度キャリブレーションを行いキャリブレーションを終了し、感度ばらつきとシェーディングの測定値を記憶する。また、キャリブレーション終了時点で補正状態判定器１７のキャリブレーション実行状態が解除される。
【００３１】
従来の装置では、どの運用状態でどのキャリブレーションを行うか使用者の主観で決定しており、またキャリブレーションの後にシェーディングの補正ずれや、感度のばらつきを測定する手段をもたなかったため、画面に補正むらを残したままで装置が運用されることがあった。例えば、航空機に搭載された本発明の赤外線撮像装置が空や海等の均一な温度背景を撮像している場合、デフォーカスキャリブレーションを行うのが最もよいキャリブレーションであるが、背景の中に雲や太陽が入ってくることにより、赤外レンズ１のピントをずらしても背景が均一にならず、レンズシェーディングキャリブレーションを行う方がよい場合がある。また、レンズシェーディングキャリブレーションを行う場合は、赤外レンズ１と画像補正用シャッタＢ１５との間に温度差があってレンズシェーディングキャリブレーションがうまく行かないことがあるので、この時は感度キャリブレーションを行う。このように使用者は状況に応じてキャリブレーション方法を選定する必要がある。本発明ではキャリブレーションの成否を判断する手段を付け加えることで、３種類のキャリブレーション指令をシーケンシャルに発生させることが可能となり、これにより運用状態における最も有効なキャリブレーションが自動的に選択されるようになるため、結果として安定した映像品質の赤外線画像を出力できる。
【００３２】
実施の形態４．
図４はこの発明の実施の形態４を示すブロック図である。図中、１８は感度ばらつき変化測定器である。それ以外で、１４と１３は実施の形態１と、他は従来の装置と同一である。
【００３３】
次に動作について説明する。通常の撮像動作に関しては従来の装置と同等であるが、本実施の形態では、環境の温度変化が小さく画面内の輝度に大きな影響を与えないような場合を想定している。また、本実施の形態においては、感度ばらつき測定器１４は常に画像補正器１３からデータを受け、実施の形態１と同様の操作で画面全体の各ゲート内の標準偏差を測定し、その平均値を感度ばらつき変化測定器１８に出力する。従来の装置では、正常にキャリブレーションが終了した後、温度環境等の変化状態にもよるが、３０分程度ごとにはキャリブレーションをやりなおしており、経験的にキャリブレーション直後１０分程度は出力される画像の状態は良好であるといえる。感度ばらつき変化測定器１８は、感度キャリブレーション実施後のあらかじめ設定された時間、例えば１０分間程度、感度ばらつき測定器１４から受けた標準偏差の平均値のデータを内部のメモリに蓄える。データが蓄積された時点で、感度ばらつき変化測定器１８は”数２”によりばらつきの時間的な変化量を求める。
【００３４】
【数２】

【００３５】
図１６は感度ばらつきの平均値と時間の関係を示したグラフである。図中、４４は測定された感度ばらつき平均値のライン、４５は求められるばらつきの時間的な変化のラインである。赤外線撮像装置がほぼ同じような画面を写し続けているとすると、感度キャリブレーション直後に見られる輝度のばらつきの大きさは、画面の持つ輝度のばらつきの固有値Ｃであると考えられる。当然、赤外線撮像装置の撮像対象が変化するにつれ画面の輝度のばらつきも変わるが、もし補正の劣化が起こらないのであれば、測定値は固有値Ｃを中心にＤの幅をもって観測される。ところが実際は時間の経過に伴い補正ずれが発生し徐々に大きくなるので、図１６に示すように輝度のばらつきの各ゲート内の標準偏差の平均値は増大する。感度ばらつき変化測定器１８は”数２”によって感度ばらつきの単位時間あたりの変化量を求め、その値に感度キャリブレーションしてからの経過時間をかけることで、例えば、感度キャリブレーション後１０分経過後の或時点での感度ばらつきの増加量を推測し、その値が感度キャリブレーションの直後の輝度ばらつきの各ゲート内の標準偏差の平均値の３倍（３σ）をこえた時点で、撮像制御器９に画像補正指令信号１１を出力する。
なお、本実施の形態における画像補正器は、従来の装置の画像補正器７と同様にフレームメモリを持たず、画像補正用シャッタ２が閉じている間に画像補正用シャッタ２の像を外部機器に出力するものであってもよい。
【００３６】
従来の装置では、感度キャリブレーションの後に継続して、画面の輝度のばらつきとその変化量を測定する手段をもたなかったため、感度キャリブレーションは表示される画面を見ているオペレータの主観によって行われていた。また、実施の形態１では外界から入射される赤外光を遮断するため、非常に短い時間ではあるが一定間隔で画像がとぎれてしまい、目標の検出や追尾を行う場合に複雑な信号処理が必要となる。本発明では画面の輝度ばらつきの状態とその変化を定量的に測定する手段を従来の装置に付加し、従来使用者が主観に基づき行っていたキャリブレーション指令を自動生成することで、自動で感度キャリブレーションを行えるようにするとともに、キャリブレーション後あらかじめ定められた時間経過後は、画像のとぎれをなくし、結果として安定した映像品質の赤外線画像を出力するとともに、後段で目標検出や追尾などをするために都合のよい画像を出力している。
【００３７】
実施の形態５．
図５はこの発明の実施の形態５を示すブロック図である。図において１９は画像補正用シャッタＣ、２０はシェーディング量変化測定器、１３ｃは実施の形態２と同一である。それ以外は実施の形態４と同一である。
【００３８】
次に動作について説明する。実施の形態５について、通常の撮像動作及び感度ばらつき変化測定器によるキャリブレーション要求までは実施の形態４と同じであり、環境の温度変化が小さい場合を想定している。画像補正用シャッタＣ１９は従来の装置に使用されている画像補正用シャッタ２と同程度の反応速度のもので、レンズシェーディングキャリブレーションの際に、外界の赤外光を遮断することのみを目標としている。この画像補正用シャッタＣ１９は、赤外線撮像装置に視軸駆動機構がついていて、撮像装置を格納する機能がある場合などは、それを持って代用することもある。シェーディング量測定器１６は常に画像補正器７からデータを受け、実施の形態２と同様に例えば４８に分割された各々の領域の輝度の平均値を測定する。シェーディング量変化測定器２０は感度ばらつき変化測定器１８と同様にキャリブレーション後あらかじめ設定された時間、例えば１０分間はシェーディング量測定器１６の測定した輝度の平均値を、画面の中心からの距離に応じて図１７のようにまとめ直し、この領域ごとの平均値として内部のメモリに蓄積する。また例えば１０分経過後は各々の領域について”数３”に基づき輝度平均値の時間変化量を求める。
【００３９】
【数３】

【００４０】
図１８は図１７で示した領域Ａと領域Ｅの輝度の平均値と時間の関係を示したグラフである。図中、４６は領域Ａで測定された輝度の平均値のライン、４７は領域Ｅで測定された輝度の平均値のライン、４８は領域Ａで求められる輝度平均値の時間的な変化のライン、４９は領域Ｅで求められる輝度平均値の時間的な変化のラインである。赤外線撮像装置がほぼ同じような画面を写し続けているとすると、キャリブレーション直後に見られる輝度の平均値の大きさは、画面の輝度の固有値Ｃであると考えられる。当然、赤外線撮像装置の撮像対象が変化するにつれ画面の輝度ばらつきも変わるが、もし補正の劣化が起こらないのであれば、測定値は固有値Ｃを中心にＤの幅をもって観測される。ところが実際は時間の経過に伴いシェーディング量が変化するため、図１８に示すように輝度の平均値は変化する。シェーディング量変化測定器２０は”数３”によって領域ごとの輝度の単位時間あたりの変化量を求め、その値にキャリブレーションしてからの経過時間をかけることで、現時点の領域ごとの輝度の変化量を推測し、その値の最大値と最小値の差が、例えば前回のキャリブレーション直後の各々の領域の輝度の平均値の３倍（３σ）を越えた時点で（あるいは、直後の平均値とあらかじめ設定した値との和を越えたところで）、撮像補正用シャッタＣを閉じた状態でレンズシェーディングキャリブレーションを行う画像補正指令信号１１を撮像制御器９に出力する。また、感度ばらつき変化測定器１８は実施の形態４と同様要領で画像補正用シャッタ２を閉じた状態で感度キャリブレーションを行う画像補正指令信号１１を撮像制御器９に出力する。
なお、本実施の形態における画像補正器は、従来の装置の画像補正器７と同様にフレームメモリを持たず、画像補正用シャッタ２が閉じている間に画像補正用シャッタ２の像を外部機器に出力するものであってもよい。
【００４１】
従来の装置では、キャリブレーションの後に継続して、画面のシェーディングとその変化量を測定する手段をもたなかったため、キャリブレーションは表示される画面を見ているオペレータの主観によって行われる。また、実施の形態２では外界から入射される赤外光を遮断するため、非常に短い時間ではあるが一定間隔で画像がとぎれてしまい、目標の検出や追尾を行う場合に複雑な信号処理が必要となる。本発明では画面の輝度ばらつきの状態とその変化を定量的に測定する手段及び画面のシェーディングの状態とその変化を定量的に測定する手段を従来の装置に付加し、従来使用者が主観に基づき行っていたキャリブレーション指令を自動生成することで、レンズシェーディング補正を含めた自動でのキャリブレーションを行えるようにするとともに、キャリブレーション後あらかじめ設定された時間経過後は、画像のとぎれをなくし、結果として安定した映像品質の赤外線画像を出力するとともに、後段で目標検出や追尾などをするために都合のよい画像を出力している。
【００４２】
実施の形態６．
図６はこの発明の実施の形態６を示すブロック図である。図において２１は画像補正器Ｂ、２２はシェーディング補正量設定器Ａである。それ以外は実施の形態５と同一である。
【００４３】
次に動作について説明する。実施の形態６について、赤外レンズ１からＡ／Ｄ変換器６までの動作と感度ばらつき変化測定器１８によるキャリブレーション要求は実施の形態４と同じである。画像補正器Ｂ２１は感度キャリブレーションにより事前に感度ばらつきが補正された画像データを感度ばらつき測定器１４に出力すると同時にシェーディング量測定器１６に出力する。感度ばらつき測定器１８は実施の形態５と同じ要領で画像補正用シャッタ２を閉じた状態で感度キャリブレーションを行う画像補正指令信号１１を撮像制御器９に出力する。しかしながら、画像補正用シャッタ２は赤外レンズ１の内側にあるため、レンズシェーディングまで含めた、キャリブレーションは行えない。そのため、本実施の形態６では、シェーディングの補正をするための回路として、シェーディング補正量設定器Ａ２２を付加している。今、画像補正器Ｂ２１によるキャリブレーション終了後、画像補正用シャッタ２を開いた状態で、例えば航空機に搭載された本発明の赤外線撮像装置において１フレーム間の画像の変化が小さい（ある一定領域の輝度の時間平均がほとんど変化しない）背景や目標を撮像している場合を考える。シェーディング補正量設定器Ａ２２はシェーディング量変化測定器２０から、図１７に示した５つの領域のキャリブレーション後からの輝度の変化量を受け、画面の中央からの距離に対応したシェーディングの補正量を定める。図１９はシェーディング補正量設定器Ａ２２の補正量設定の概念図である。図中５０から５４はシェーディング量変化測定器２０から得られる領域ＡからＥの輝度の平均値の傾きに一つ前のキャリブレーション終了時からの経過時間をかけて求めた輝度の平均値の増加量を示すプロットであり、５５は定められたシェーディングの補正量を示すシェーディングラインである。シェーディング補正量設定器Ａ２２は５つのプロットから適当な２次の曲線を求め、かつそれを輝度変化量０のラインについて反転させたラインをシェーディング補正量として画像補正器Ｂ２１に出力する。画像補正器Ｂ２１は感度ばらつきのみを補正した画面からシェーディング補正量を差し引いたデータをＤ／Ａ変換器８にリアルタイムで送る。実施の形態２や実施の形態５ではレンズシェーディングをキャリブレーションで補正するために、レンズの前面シャッタを置くという、機構的な構成となっている。それに対し、本実施の形態６では、従来の赤外線撮像装置の機構的な構成をできるだけかえず、かつ前述のシェーディングキャリブレーションのように補正用の均一温度面でデータを取り込むという操作をせずに、電気的な信号処理でリアルタイムにレンズシェーディング補正を達成する。
また、シェーディング量変化測定器２０から得られる輝度の変化量は画像補正用シャッタ２を開いた状態で得られるので、一定時間ごとに変化量を更新していけば補正の精度が高くなる。
【００４４】
従来の装置では、キャリブレーションの後に継続して、画面のシェーディングとその変化量を測定し、その値から補正するシェーディング量を決める手段とを持たなかったため、レンズシェーディングをキャリブレーションで補正するしかなく、そのためにレンズの前面にシャッタを置くという機構的な構成が必要だった。本実施の形態６では、従来の赤外線撮像装置の機構的な構成をできるだけかえずに、電気的な信号処理回路を付加することでリアルタイムのレンズシェーディング補正を達成しているとともに、画面の輝度ばらつきの状態とその変化を定量的に測定する手段を従来の装置に付加し、従来使用者が主観に基づき行っていたキャリブレーション指令を自動生成することで、自動でキャリブレーションを行い、安定した映像品質の赤外線画像を出力する。
【００４５】
実施の形態７．
図７はこの発明の実施の形態７を示すブロック図である。図において２３は赤外レンズＡ、２４は温度信号、２５は温度変化測定器、２６はシェーディング補正量設定器Ｂである。それ以外は実施の形態６と同一である。
【００４６】
次に動作について説明する。実施の形態７について、通常の撮像動作と感度ばらつき変化測定器１８によるキャリブレーション要求は実施の形態６と同じである。赤外レンズＡ２３はレンズの鏡筒部分の温度を測定する温度モニタ５８を持ち温度信号２４を温度変化測定器２５に送る。温度変化測定器２５は前回のキャリブレーションしてからの順次入力される温度信号２４から赤外レンズＡ２３の温度差を測定しシェーディング補正量設定器Ｂ２６に出力する。シェーディング補正量設定器Ｂ２６は内部のメモリに赤外レンズＡ２３の固有のレンズシェーディングの特性（例えば、温度差の４乗に比例して赤外線のエネルギー量が変化する。）を示すデータを保持している。図２０はシェーディング補正量設定器Ｂ２６の保持している上記データの１例を示す図である。図中、５６は赤外レンズＡ２３が温度差Ａのときに持っているシェーディングライン、５７は温度差Ｂのときに持っているシェーディングラインをそれぞれ示している。上記シェーディングラインは、輝度の増加量を使用する温度範囲内におけるレンズ鏡筒部分の温度差と画面中心からの距離の関数として表現したものである。上記内部のメモリ内には、例えばあらかじめシュミレーションや実験計測結果に基づいて離散化された上記シェーディングラインの節点が記憶されており、温度差に対応した所要のシェーディングラインを節点間を適度に補間することによって得ることができる。あるいは、上記内部のメモリ内に、上記シェーディングラインを多項式のような近似手段で表現した近似式の定数が記憶されており、温度差と画面中心からの距離から所要の輝度の増加量を出力することによってシェーディングラインを表現してもよい。シェーディング補正量設定器Ｂ２６は図２０に示すようなシェーディングラインから、画面中心からの位置ごとに温度変化に対応して、例えば温度差がＢのときは、温度Ｂのシェーディングライン５７を打ち消すように輝度の増加量を求め、シェーディングの補正量を決めて画像補正器Ｂ２１に出力する。画像補正器Ｂ２１は実施の形態６と同じ動作でＤ／Ａ変換器８にシェーディング補正されたデータをリアルタイムで送り、出力映像信号１０を出力する。実施の形態６では、画像データから各々の画素の補正量を定めていたため、画像を測定するための回路と、補正量を定める回路が必要であったが、本実施の形態７ではシェーディングが温度差に依存する性質を利用して温度を測定することにより、画像を測定する回路を無くすことができるため、少ない回路規模で同等の機能を達成できる。温度測定回路は熱電対と抵抗とトランジスタで構成できるのに対し、画像を測定する回路にはシェーディング量測定器１６内のフレームメモリのような画像を記憶するための膨大なメモリと高速の演算装置が必要である。また、上記固有のレンズシェーディングの特性データに要するメモリは、温度特性を離散的に表現する代表的な幾つかの点を記憶する程度でよく、上記画像を記憶するための膨大なメモリよりは充分小さくなり、小型、軽量化がはかれる。
【００４７】
従来の装置では、キャリブレーションの後に継続して光学系の温度とその変化量を測定し、その値から補正するシェーディング量を決める手段とを持たなかったため、レンズシェーディングをキャリブレーションで補正するしかなく、そのためにレンズの前面にシャッタを置く機構的な構成が必要であった。本実施の形態７では光学系の温度とその変化を定量的に測定する手段とレンズの特性データを保持している手段を付加することで、前述の実施の形態６よりも簡単な信号処理回路でリアルタイムのレンズシェーディング補正を達成している。また、画面の輝度ばらつきの状態とその変化を定量的に測定する手段を付加し、従来使用者が主観に基づき行っていたキャリブレーション指令を自動生成することで、自動でキャリブレーションを行い、安定した映像品質の赤外線画像を出力する。
【００４８】
実施の形態８．
この発明の実施の形態は、実施の形態１，２，４，５の感度ばらつき測定器において画像の補正ずれを定量的に検知した後、アラーム音や点滅光などの警告信号（または、目盛による警告表示）を発生するものである。これによって、使用者が画像の補正ずれを定量的に把握でき、画像補正器のキャリブレーションを手動で行うタイミングを得ることができる。
【００４９】
実施の形態９．
この発明の実施の形態は、実施の形態２，４，８のシェーディング量測定器において画像の補正ずれを定量的に検知した後、アラーム音や点滅光などの警告信号（または、目盛による警告表示）を発生するものである。これによって、使用者が画像の補正ずれを定量的に把握でき、画像補正器のキャリブレーションを手動で行うタイミングを得ることができる。
【００５０】
【発明の効果】
この第一の発明にかかる赤外線撮像装置は、素子感度の補正ずれの状態を撮像中に各画素ごとに求めた輝度の偏差の平均値を用いて定量的に把握する手段を従来の装置に付加したことで、従来使用者が主観に基づきおこなっていたキャリブレーション指令を生成して、キャリブレーションを行うことができる。これによって操作が簡単でありながら、素子感度の補正ずれやシェーディングの補正ずれによる性能劣化が少なく、使用者がキャリブレーション操作に煩わされることのない赤外線撮像装置を得ることができる。
【００５１】
また、第二の発明によれば、素子感度の補正ずれの状態を撮像中に定量的に把握する手段及びシェーディングの補正ずれの状態を撮像中に画面内に分割された幾つかの領域内の輝度の平均値から全領域の輝度分布を求めて定量的に把握する手段を従来の装置に付加したことで、従来使用者が主観に基づきおこなっていたキャリブレーション指令を生成し、レンズシェーディング補正を含めた自動でのキャリブレーションが行える。
【００５２】
また、第三の発明によれば、キャリブレーションの成否を判断する手段を付け加えることで、３種類のキャリブレーション指令をシェーディングに発生させることが可能となり、これにより運用状態における有効なキャリブレーションが自動的に選択され、実施される。これによって、最適なキャリブレーションをされた状態の画像を出力できる赤外線撮像装置を得ることができる。
【００５３】
また、第四の発明によれば、画面の輝度ばらつきの状態とその変化を定量的に測定する手段を従来の装置に付加したことで、従来使用者が主観に基づき行っていたキャリブレーション指令を生成し、自動でキャリブレーションが行える。また、第一の発明では短時間の画像のとぎれが発生するが、後段で目標検出や追尾などの信号処理する場合に都合のよい画像を出力できる。これによって信号処理にも適した画像を出力する赤外線撮像装置を得ることができる。
【００５４】
また、第五の発明によれば、画面の輝度ばらつきの状態とその変化を定量的に測定する手段及び画面のシェーディングの状態とその変化を定量的に測定する手段を従来の装置に付加したことで、従来使用者が主観に基づき行っていたキャリブレーション指令を生成し、レンズシェーディング補正を含めた自動でのキャリブレーションが行える。また、第二の発明で起きていた短時間の画像のとぎれをなくすことで、後段で目標検出や追尾などをする場合に都合のよい画像を出力できる。
【００５５】
また、第六の発明によれば、画面のシェーディングの状態とその変化を定量的に測定し、かつそれによって補正する量を定める手段を付加したことでリアルタイムのレンズシェーディング補正を達成している。また、画面の輝度ばらつきの状態とその変化を定量的に測定する手段を従来の装置に付加したことで、従来使用者が主観に基づき行っていたキャリブレーション指令を生成し、自動でキャリブレーションを行える。これによってレンズシェーディングがリアルタイムに補正されることによりシェーディングの補正ずれによる性能劣化が少なく、従来の装置ほど頻繁にキャリブレーションが行われない赤外線撮像装置を得ることができる。
【００５６】
さらにまた、第七の発明によれば、光学系の温度とその変化を定量的に測定する手段とレンズの特性データを保持している手段を付加したことで、第六の発明より簡単な回路でリアルタイムのレンズシェーディング補正を達成している。また、従来の装置ほど頻繁にキャリブレーションが行われない赤外線撮像装置をより小型軽量で得ることができる。
【図面の簡単な説明】
【図１】 この発明の実施の形態１の構成を示すブロック図である。
【図２】 この発明の実施の形態２の構成を示すブロック図である。
【図３】 この発明の実施の形態３の構成を示すブロック図である。
【図４】 この発明の実施の形態４の構成を示すブロック図である。
【図５】 この発明の実施の形態５の構成を示すブロック図である。
【図６】 この発明の実施の形態６の構成を示すブロック図である。
【図７】 この発明の実施の形態７の構成を示すブロック図である。
【図８】 従来の装置の構成を示すブロック図である。
【図９】 従来の装置のキャリブレーションの概要を示す図である。
【図１０】 目標の発生する光をレンズを通し集光する様子を示す図である。
【図１１】 シェーディング画像の一例を示すディスプレイ上の中間値画像である。
【図１２】 感度ばらつき測定動作の概要を示す図である。
【図１３】 シェーディング量測定動作の概要を示す図である。
【図１４】 シェーディング補正状態による領域の輝度平均値の分布を示す図である。
【図１５】 キャリブレーション制御の流れ図である。
【図１６】 感度ばらつきの平均値と時間の関係を示した図である。
【図１７】 輝度測定領域をまとめ直した様子を示す図である。
【図１８】 輝度の平均値と時間の関係を示す図である。
【図１９】 シェーディング補正量設定器Ａ２２のシェーディング補正量設定の概念図である。
【図２０】 シェーディング補正量設定器Ｂ２６のシェーディング補正量設定の概念図である。
【符号の説明】
１ 赤外レンズ、２ 画像補正用シャッタ、３ 赤外線検知器、４ アンプ、５ サンプルホールド回路、６ Ａ／Ｄ変換器、７ 画像補正器、８ Ｄ／Ａ変換器、９ 撮像制御器、１０ 出力映像信号、１１ 画像補正指令信号、１２ 画像補正用シャッタＡ、１３ 画像補正器Ａ、１３ａ 出力切換スイッチ、１３ｂ フレームメモリ、１３ｃ 画像補正器ＡＡ、１３ｄ 出力切換スイッチＡ、１４ 感度ばらつき測定器、１４ａ フレームメモリ、１４ｂ 標準偏差測定器、１４ｃ 標準偏差記憶器、１４ｄ 感度ばらつき判定器、１５ 画像補正用シャッタＢ、１６ シェーディング量測定器、１７ 補正状態判定器、１８ 感度ばらつき変化測定器、１９ 画像補正用シャッタＣ、２０ シェーディング量変化測定器、２１ 画像補正器Ｂ、２２ シェーディング補正量設定Ａ、２３ 赤外レンズＡ、２４ 温度信号、２５ 温度変換測定器、２６ シェーディング補正量設定Ｂ、２７ 出力特性ラインａ、２８ 出力特性ラインｂ、２９ 出力特性ラインａａ、３０ 出力特性ラインｂｂ、３１ 出力ラインｃ、３２ 目標Ａ、３３ 目標Ｂ、３４ レンズ、３５ 結像面、３６ 光束ＡＡ、３７ 光束ＢＢ、３８ 画像データ、３９ ばらつき測定ゲート、４０ 計測された感度ばらつき、４１ シェーディング測定領域、４２ 補正できている場合の輝度平均値の分布、４３ 補正できていない場合の輝度平均値の分布、４４ 測定された感度ばらつき平均値のライン、４５ ばらつきの時間的変化のライン、４６ 領域Ａの輝度平均値ライン、４７ 領域Ｅの輝度平均値ライン、４８ 領域Ａの輝度平均値の時間変化ライン、４９ 領域Ｅの輝度平均値の時間変化ライン、５０ 領域Ａのシェーディング変化量のプロット、５１ 領域Ｂのシェーディング変化量のプロット、５２ 領域Ｃのシェーディング変化量のプロット、５３ 領域Ｄのシェーディング変化量のプロット、５４ 領域Ｅのシェーディング変化量のプロット、５５ シェーディング補正量を示すライン、５６ 温度Ａの時の赤外レンズＡ２３のシェーディングライン、５７ 温度Ｂの時の赤外レンズＡ２３のシェーディングライン、５８ 温度モニタ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an infrared imaging device that collects infrared light emitted from an object, photoelectrically converts it, and then outputs it as a video signal.
[0002]
[Prior art]
In general, a conventional infrared imaging device is mounted on an aircraft, a vehicle, a ship, or the like and used for nighttime monitoring.
[0003]
FIG. 8 is a block diagram of an example of a conventional infrared imaging apparatus of this type, where 1 is an infrared lens, 2 is an image correction shutter, 3 is an infrared detector having a two-dimensional infrared detection element, 4 is an amplifier, Is a sample and hold circuit, 6 is an A / D converter, 7 is an image corrector, 8 is a D / A converter, 9 is an imaging controller, 10 is an output video signal, and 11 is an image correction command signal.
[0004]
Next, the operation will be described. As an imaging operation of the target object, the infrared lens 1 condenses infrared light emitted from the target object and its background, and forms an infrared image on the infrared detector 3. Detection pixels are two-dimensionally arranged in the infrared detector 3, and each detection pixel photoelectrically converts a part of the formed infrared image. The amplifier 4 amplifies the intermittent signal generated by each detection pixel, and the sample hold circuit 5 converts the intermittent signal output from the amplifier 4 into a continuous scanning signal. The signal is converted into a digital signal (hereinafter referred to as image data) by the A / D converter 6 so that the image correction processing is further facilitated, and then the luminance correction (hereinafter image correction) output for each pixel by the image corrector 7 is performed. Furthermore, it is converted into an output video signal 10 by the D / A converter 8 and outputted to the outside. The imaging control unit 9 controls the entire imaging apparatus by outputting a focus adjustment command to the infrared lens 1 and a pedestal level and gain adjustment command to the image corrector 7 based on a command from the outside. . The image correction shutter 2 is mechanically inserted into the infrared optical path between the infrared lens 1 and the infrared detector 3 when the image correction command signal 11 is input from the outside, so that the infrared lens 1 is At the same time as blocking infrared light that is collected, the image corrector 7 detects infrared light that is uniform so that correction data for image correction (hereinafter referred to as complementary image data) can be set (hereinafter referred to as calibration). Used to radiate on vessel 3.
[0005]
Next, the following two basic ideas regarding image correction will be described. First, the size of the output of a detection pixel of a two-dimensional infrared detection element normally used in the infrared detector 3 is an image of an object at the same temperature due to a subtle difference in the characteristics of each detection pixel. Even if it does, it will vary slightly. This variation is called sensitivity variation, and causes noise in the display image, and when tracking a target with a small image on the screen due to a long distance, it may be difficult to recognize the target due to the variation, It needs to be removed. FIG. 9 shows an operation for setting image correction data for sensitivity variations (hereinafter referred to as sensitivity calibration) and image correction for sensitivity variations after sensitivity calibration (hereinafter referred to as sensitivity correction). In the figure, 27 is an output characteristic line a of a pixel a, 28 is an output characteristic line b of another pixel b, 29 is an output characteristic line aa, 30 of a pixel a corrected by temperature, and 30 is a temperature. The output characteristic lines bb and 31 of the pixel b that has been corrected in (a) are the output lines c of the pixels that are aligned by the correction. Usually, the average of all the detection pixel output characteristics or the like is used for the line c31. The image corrector 7 stores in advance an inclination of each pixel output characteristic data such as the line a27 and the line b28 in the internal memory as a function of the temperature corresponding to the pixel for adjusting the output of each pixel to the inclination of the line c31. ing. For example, when the image corrector 7 performs correction by temperature a, the output of each pixel is matched with the output a of line a27 and the output c of line b28 so that the output of each pixel coincides with the line c31 at the corrected temperature. The line aa29 and the line bb30 are calculated by adding or subtracting a constant value that does not depend on the required temperature from the line a27 and the line b28 so that the average value of all the detected pixel outputs corresponding to the line c31 matches the value of line c31. Next, the line aa29 and the line bb30 are subjected to a function for each pixel held in the memory so that the output of each pixel is placed on the correction output line c31, and the above constant value is stored as image correction data in the memory. . At this time, if the input to each pixel is not at a constant temperature, the addition or subtraction for placing on the correction line c31 does not work well, and correction unevenness can occur. The image correction shutter 2 is used to keep the temperature detected by each pixel constant by blocking the infrared optical path and radiating the temperature of the image correction shutter 2 itself to the infrared detector 3 during sensitivity calibration. . The image corrector 7 can perform image correction without unevenness in a state where infrared rays having a uniform temperature are emitted to the infrared detector 3 by the image correction shutter 2. After the sensitivity calibration is completed, the image corrector 7 performs sensitivity correction by correcting the luminance output for each pixel by the image correction data stored in the memory and the function for each pixel. To go.
[0006]
The above is the basic concept of image correction by sensitivity correction of the two-dimensional infrared detection element. Secondly, in an actual infrared imaging device, a difference in energy collected between the center portion and the edge portion of the image may appear on the display image due to the imaging ability of the infrared lens 1. FIG. 10 is a diagram simply showing how the light emitted from the target is collected through the lens. 32 is a target A placed in front of the lens, 33 is a target B placed diagonally forward, 34 is a lens, 35 is an imaging plane, 36 is a light beam AA emitted from the target A, 37 is a light beam BB emitted from the target B It is. Now, it is assumed that the target A32 and the target B33 have the same size and the same temperature, and only the positional relationship with the lens 34 is different as shown in FIG. In this case, the light beam BB37 has a narrower incident width on the lens 34 than the light beam AA36, and the amount of energy on the imaging surface 35 is not uniform even though a certain temperature surface is imaged. FIG. 11 shows an example of an intermediate value image on a display showing what kind of image the energy non-uniformity actually looks. Now, since the target A32 has the same temperature as the target B33, it should be reflected in the same brightness if there is no nonuniform energy as described above. However, on the screen, the target A32 appears brighter and the target B33 appears darker due to energy nonuniformity. Other causes of such energy non-uniformity in an actual infrared imaging device include infrared light emitted from lenses and other optical system elements themselves, and all of them are generally called lens shading. (Hereafter referred to as shading). In a conventional infrared imaging device, when trying to correct such shading, the visual axis is directed to something that seems to have a relatively uniform temperature (for example, “sky”), the lens is in focus, and There is a method of performing calibration without closing the correction shutter. This is added or subtracted to put on the output line c31 by measuring the difference from the output line c31 including the non-uniformity of the output of the detection pixel due to the shading in a state where the focus is blurred during the sensitivity calibration. This is because the difference is included in the image correction data for sensitivity correction. The reason why the focus is shifted is that an infrared image formed on the infrared detector 3 causes uneven image correction in a focused state. The operation for setting the image correction data is called defocus calibration. In addition to this, there is a method in which a shutter is arranged in front of the lens as a calibration method for correcting shading. If there is a temperature difference between the two, this also causes correction unevenness. Therefore, defocus calibration performed while capturing the outside world is used as a calibration means that most accurately adjusts the output image. In addition, after the calibration is completed, the correction of the luminance output for each pixel is applied by the image correction data by the defocus calibration stored in the memory and the function for each pixel as in the sensitivity correction. Perform image correction.
[0007]
As described above, in the conventional infrared imaging device, the output image is adjusted by performing calibration. However, if the imaging is continued, a phenomenon that the image becomes gradually difficult to see occurs. This is because the pixel-corresponding function of the image corrector 7 used at the time of calibration is partially different from the actual pixel characteristics. This is because the amount of shading may change due to environmental temperature changes. In such a case, in the conventional apparatus, the correction state of the image is corrected by performing calibration in accordance with the temperature state during operation many times.
[0008]
[Problems to be solved by the invention]
As mentioned above, calibration is an indispensable function for an infrared imaging device that uses a two-dimensional infrared detector, but usually the screen that is displayed without being able to grasp the state of the image quantitatively. The calibration is performed according to a command from the user. For this reason, there has been a problem that the quality of the image output from the infrared imaging device is remarkably different depending on the skill level of the user.
[0009]
In addition, for example, an infrared imaging device mounted on an aircraft in which the environment of use of the device represented by temperature is drastically changed needs to be calibrated more frequently than that used in a stable temperature environment. However, depending on the situation, it is complicated to perform defocus calibration and calibration using the shutter, especially when the fighter pilot is a user, while operating other devices, Since it is necessary to judge the state of the image and issue a calibration command, there is a problem in that the calibration operation becomes a burden on the user.
[0010]
The present invention has been made to solve such a problem. The image quality to be output is stable regardless of the degree of use by the user, and the calibration operation is not burdened by the user. An object of the present invention is to obtain an infrared imaging apparatus that automatically generates calibration timing and performs calibration automatically.
[0011]
[Means for Solving the Problems]
An infrared imaging device according to the first invention includes a blocking unit that blocks infrared light collected by an infrared lens, and an infrared detector from an image signal while the infrared light is blocked by the blocking unit. Sensitivity variation measuring means for measuring the output variation of each pixel by calculating an average value of luminance deviations, and means for measuring the output variation by the sensitivity variation measuring means at predetermined time intervals And a control means comprising means for generating a command signal for performing calibration from the output variation measured by the sensitivity variation measuring means, so that the state of correction of the element sensitivity can be quantitatively measured during imaging. The timing for performing the calibration based on the above is generated, and the calibration can be automatically performed.
[0012]
The infrared imaging device according to the second aspect of the invention is a first blocking means for blocking infrared light before being collected by the infrared lens, and blocks infrared light collected by the infrared lens. Distribution of the output of the infrared detector generated by the infrared light emitted by the infrared lens from the digital image signal while the infrared light is blocked by the first blocking means. Part in the screen Variation of the output of the infrared detector from the image signal while the infrared light is blocked by the second blocking means, and a shading measuring means for determining and measuring the distribution of the average value of the luminance for each region consisting of Sensitivity variation measuring means for measuring by obtaining an average value of luminance deviations determined for each pixel, output signal distribution measurement by the shading measuring means, and output variation measurement by the sensitivity variation measuring means are alternately performed. Means, and a control means comprising means for generating a command signal for performing calibration from the output distribution measured by the shading measuring means and the output dispersion measured by the sensitivity variation measuring means, The device sensitivity correction deviation state and the shading correction deviation state are quantitatively grasped and captured during imaging. Generates a timing of performing calibration, is obtained so as to perform the calibration automatically.
[0013]
Further, the infrared imaging device according to the third invention is focused by the infrared lens and the first blocking means for blocking the infrared light before being focused by the infrared lens for one screen output unit time. A second blocking unit that blocks infrared light for one screen output unit time and an infrared light emitted from the infrared lens from a digital image signal while the infrared light is blocked by the first blocking unit. A shading measuring means for measuring the distribution of the output signal, a sensitivity variation measuring means for measuring a variation in the output of the infrared detector from the image signal while the infrared light is blocked by the second blocking means, and the shading measurement. Means for controlling the output signal distribution measurement by the means and the output variation measurement by the sensitivity variation measurement means alternately, and the output signal measured by the shading measurement means. And a control means for generating a command signal for recalibration from the output variation measured by the sensitivity variation measuring means, and the shading measurement when the control means generates the command signal. And a control means for controlling the execution of several calibrations step by step using the measurement results of the sensitivity variation measuring means and the sensitivity variation measuring means, thereby imaging the state of correction deviation of element sensitivity and the state of correction deviation of shading. The timing for performing calibration by quantitatively grasping the inside is generated, and the success or failure of the calibration is judged, so that stepwise calibration can be automatically performed.
[0014]
Further, the infrared imaging device according to the fourth aspect of the invention includes a blocking means for blocking infrared light collected by the infrared lens during calibration, and luminance within the screen from the image signal of the screen corrected by the correction circuit. A sensitivity variation measuring means for measuring an average value of the deviations, a means for measuring a slope of the average value of the brightness deviations with respect to time from an average value of the brightness deviations measured by the sensitivity variation measuring means, and a slope of the change Sensitivity variation change comprising means for generating a command signal for performing calibration by estimating the amount of increase in the average value of luminance deviation over the time elapsed since the previous calibration was performed By providing measurement means, the brightness variation state of the screen and its change are quantitatively measured, and the timing for calibration is generated from that value. To, in which so as to perform the calibration automatically.
[0015]
The infrared imaging device according to the fifth aspect of the invention is focused by the infrared lens and the first blocking means for blocking infrared light before being focused by the infrared lens during calibration. A second blocking unit that blocks infrared light during calibration, a sensitivity variation measuring unit that measures an average value of luminance deviation in the screen from the image signal of the screen corrected by the correction circuit, and the sensitivity variation measurement Sensitivity variation change measuring means for measuring the slope of the average value of the luminance deviation with respect to time from the average value of the luminance deviation measured by the means, and for each position in the screen from the image signal of the screen corrected by the correction circuit The above-mentioned shading measuring means for measuring the average luminance, and the inclination with respect to the time is measured from the average of the luminance at each position in the screen measured by the shading measuring means. Shading change measuring means, the slope of the average value of the deviation measured by the shading measuring means and the shading change measuring means, the average slope of the brightness for each position in the screen, and the time since the previous calibration was performed. And a control means for generating a command signal for recalibration from the measured time, quantitatively measure the state of brightness variation of the screen and its change and the state of shading of the screen and its change, A timing for performing calibration is generated from these values so that calibration can be automatically performed.
[0016]
Further, the infrared imaging device according to the sixth aspect of the invention includes a blocking means for blocking infrared light collected by the infrared lens during calibration, and luminance within the screen from the image signal of the screen corrected by the correction circuit. Sensitivity variation measuring means for measuring an average value of deviations of the sensitivity, sensitivity variation change measuring means for measuring temporal changes from the average value of deviations in luminance measured by the sensitivity variation measuring means, and a screen corrected by the correction circuit A shading measuring means for always measuring the average of the luminance for each part in the screen from the image signal of the image, and a shading change measuring means for measuring the inclination with respect to the time from the luminance for each position in the screen measured by the shading measuring means, , The time difference of the variation measured by the second measuring means and the time elapsed since the previous calibration. The control means for generating a command signal for performing the adjustment, the average slope of the brightness of each part in the screen measured by the shading change measurement means, and the time elapsed since the last image correction data was acquired By providing a correction amount setting means that determines the amount of brightness correction for each part of the screen, quantitatively measure the state of brightness variation on the screen and its change, and generate calibration timing from these values In addition to enabling automatic calibration, the amount of correction is determined by quantitatively measuring the state of shading on the screen and its change, and shading can be corrected without calibration It is.
[0017]
Further, the infrared imaging device according to the seventh aspect of the present invention always includes a blocking means for blocking infrared light collected by the infrared lens during calibration and an image signal of the screen corrected by the correction circuit. Sensitivity variation measuring means for measuring variations in brightness, sensitivity variation change measuring means for measuring changes in time from the luminance variations measured by the sensitivity variation measuring means, and variations time measured by the sensitivity variation measuring means. Control means for generating a command signal for recalibration from the change and the time elapsed since the previous calibration, temperature measuring means for measuring the temperature of the infrared lens, and temperature measured by the temperature measuring means Temperature difference measuring means to measure the temperature difference from the time elapsed since the last calibration was performed And a correction amount setting means for determining a luminance correction amount for each part in the screen from the temperature change amount measured by the temperature difference measuring means, thereby quantitatively measuring the state of brightness variation and its change. In addition to generating calibration timing from these values, it is possible to measure the temperature of the optical system and its changes quantitatively, and thereby determine the amount of shading correction, so that shading can be corrected without calibration. It is a thing.
[0018]
The infrared imaging device according to the eighth invention is the infrared imaging device according to the first, fourth, sixth, or seventh invention, the means for storing the image signal output from the correction circuit, and the first blocking means. And the storage output means for outputting the image signal of the previous frame from the storage means while the infrared light is cut off.
[0019]
Furthermore, the infrared imaging device according to the ninth invention is the infrared imaging device according to the second, third, or fifth invention, the means for storing the image signal output from the correction circuit, the first, second, While the infrared light is blocked by the blocking means, a storage output means comprising a means for outputting the image signal of the previous frame from the storage means is provided.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of an infrared imaging apparatus according to the first embodiment. In FIG. 1, 12 is an image correction shutter A, 13 is an image corrector A, and 14 is a sensitivity variation measuring device. Other than that, it is the same as the conventional apparatus.
[0021]
Next, the operation will be described. Usually, the target object incident from the infrared lens 1 and the infrared light from the background thereof are image-corrected by the image corrector 7 installed in the image corrector A13 by the same operation as before, and then D / A converted. The output video signal 10 is output to an external device. The output video signal 10 is a serial signal for 30 screens (frames) per second, and every 1 / 60th of a second screen, an odd-numbered horizontal line (odd field) and an even-numbered horizontal line are collected. By alternately outputting the same screen (even field), one screen is output. As the image correction shutter A12, a shutter having a quick response as used in a normal photographic camera is used (the conventional image correction shutter has a response speed as low as about a second). Infrared light condensed on the infrared detector 3 from the outside through the infrared lens 1 can be blocked for 1/30 second corresponding to one frame which is an output unit time. For example, the imaging controller 9 issues an instruction to block the infrared light of one frame to the image correction shutter A12 and transmits the instruction to block the infrared light to the image corrector A13, for example, about once every 30 seconds. The image corrector A13 has an image corrector 7, an output changeover switch 13a, and a frame memory 13b therein, and switches the output changeover switch 13a to the key side in response to an instruction to block infrared light. When the output selector switch 13a is switched to the key side, the data in the frame memory 13b is not updated, and as a result, the image data of the same frame as before is sent to the subsequent D / A converter 8. While the infrared light is blocked, the image data output from the image corrector 7 is sent to the sensitivity variation measuring instrument 14 through the key of the output changeover switch 13a. The sensitivity variation measuring device 14 has a frame memory 14a, a standard deviation measuring device 14b, and a standard deviation storage device 14c corresponding to each pixel, and measures sensitivity variations. Further, an instruction for canceling the cutoff of infrared light is output automatically after a preset time from the imaging controller 9, and the output switch 13 a is switched to the “O” side, and the image corrector 7 The output image data is output to the D / A converter 8.
[0022]
FIG. 12 is a diagram showing an outline of the sensitivity variation measuring operation. In the figure, 38 is image data input from the image corrector A13 and stored in the frame memory 14a, 39 is a gate for measuring variation set by the standard deviation measuring device 14b, and 40 is in the sensitivity variation measuring unit 14. The sensitivity variation measured and stored in the standard deviation memory 14c is shown. When the image data 38 is input to the sensitivity variation measuring instrument 14, the address of the frame memory 14a is designated by moving the variation measuring gate 39 in the X direction and the Y direction in order. The frame memory 14a outputs the data at the designated address to the standard deviation measuring device 14b, and the standard deviation measuring device 14b obtains the standard deviation of the luminance in the gate by digital calculation processing according to “Equation 1” and measures the sensitivity variation.
Note that the sensitivity variation may be measured by using an average of absolute values of luminance differences in the gate instead of the standard deviation of luminance.
[0023]
[Expression 1]

[0024]
The measured standard deviation of the brightness is stored in the corresponding location in the standard deviation storage 14c. The image data input to the sensitivity variation measuring device 14 is an image in a state where the image correction shutter A12 is closed and the infrared light from the outside is blocked. The luminance variation data in the gate is 0, and no luminance deviation is observed. That is, if a deviation is observed in the gate, it can be said that it is an image correction deviation. When the measurement of the luminance standard deviation in each gate for one screen is completed, the sensitivity variation measuring device 14 obtains the average value of the luminance standard deviation in the standard deviation storage device 14c. Where this value exceeds, for example, three times the average value immediately after the previous calibration stored in advance (3σ if the immediately following average value is σ) (or the average value immediately after and the preset value) After exceeding the sum), the sensitivity variation determination unit 14d determines that a correction deviation has occurred, and sends an image correction command signal 11 to the imaging controller 9 so that calibration is performed with the image correction shutter A12 closed. Output. The imaging controller 9 receives the image correction command signal 11 and sends a calibration command to the image corrector 7. Immediately after the calibration is finished, the sensitivity variation determination unit 14d newly stores and holds the average value σ of the standard deviation of luminance. Then, the image correction shutter A12 is opened.
[0025]
In the conventional apparatus, since there is no means for measuring the correction deviation of the element sensitivity during imaging, the calibration is performed by the subjectivity of the operator who is viewing the displayed screen. In this invention, a means for quantitatively grasping the state of correction of the element sensitivity during imaging is added to a conventional apparatus, and a calibration command that is conventionally performed by a user based on subjectivity is automatically generated. Calibration can be performed, and as a result, an infrared image with stable video quality can be output. In addition, with a simple circuit configuration that performs digital calculation processing using a statistical method, it is possible to measure sensitivity variations without using components of a complicated circuit.
[0026]
Embodiment 2. FIG.
FIG. 2 is a block diagram showing Embodiment 2 of the present invention. In the figure, 13c is an image corrector AA, 15 is an image correcting shutter B, and 16 is a shading amount measuring device. Other than that, 12 to 14 are the same as those of the first embodiment, and others are the same as the conventional apparatus.
[0027]
Next, the operation will be described. Also in the second embodiment, the normal imaging operation is the same as that of the conventional apparatus. The image correction shutter B15 in the present embodiment is placed in front of the infrared lens 1 in order to block infrared light incident on the infrared lens 1. Note that the same reaction speed as that of the image correction shutter A is used. For example, the imaging controller 9 alternately issues a command to block one frame of infrared light to the image correction shutter A12 and the image correction shutter B15 about once every 15 seconds, and the image correction unit AA13c blocks the infrared image. Tell them. The image corrector AA13c is the same as the image corrector A13 except that the output changeover is changed to an output changeover switch A13d with three systems, and when the image correction shutter A is closed, the sensitivity variation measuring device 14 When the shutter B is closed, the image data is output to the shading amount measuring device 16. The shading amount measuring device 16 has the same configuration as the sensitivity variation measuring device 14, has a frame memory and a shading determination device, and measures the shading amount for each portion of the screen. FIG. 13 is a diagram showing an outline of the shading amount measurement operation. The shading amount measuring device 16 divides the input data for one screen into, for example, 48 regions as shown in FIG. 13, and obtains the average value of the image data in each region. Since the image data input to the shading amount measuring device 16 is a screen in a state where the image correction shutter B15 is closed and the infrared light from the outside is blocked, if there is no shading, the average value of the luminance of each region There is no difference. That is, if there is a difference between the average values of these areas, it can be said that it is due to shading. FIG. 14 shows the distribution of the average value of luminance in each region when shading correction is possible and when it is not. In the figure, reference numeral 42 denotes a distribution when correction is possible, and 43 is a distribution when correction is not possible. As shown in FIG. 14, the width of the distribution is narrow when it is corrected, and the width of the distribution is widened when it is not. The shading amount measuring device 16 obtains the maximum value and the minimum value from the average value of the luminance of each region, thereby measuring the width of the distribution, which is, for example, three times (3β) from the average value β immediately after the previous calibration. (Or beyond the sum of the average value immediately after that and a preset value), the shading determination unit of the shading measuring device 16 performs calibration with the image correction shutter B15 closed (for example, defocus calibration). ) Is output to the imaging control unit 9. When the sensitivity variation measuring device 14 detects sensitivity variation by the same operation as in the first embodiment, it outputs an image correction command signal 11 for performing calibration with the image correction shutter A12 closed to the imaging control section 9. . The imaging control unit 9 receives the image correction command signal 11 and sends a calibration command to the image corrector 7. Immediately after the calibration is finished, the sensitivity variation measuring device 14 newly stores and holds the average value α of the standard deviation of luminance, The image correction shutter A12 opens, or the shading amount measuring device 16 newly stores and holds the width β of the average luminance distribution, and the image correction shutter B15 opens.
[0028]
In the conventional apparatus, since there is no means for measuring the shading correction deviation during imaging, the calibration is performed by the subjectivity of the operator looking at the displayed screen. In the present invention, means for quantitatively grasping the state of correction deviation of the element sensitivity during imaging and means for quantitatively grasping the state of correction deviation of shading during imaging are added to the conventional apparatus, and the conventional user is subjectively By automatically generating a calibration command based on the above, automatic calibration including lens shading correction can be performed, and as a result, an infrared image with stable video quality can be output.
[0029]
Embodiment 3 FIG.
FIG. 3 is a block diagram showing Embodiment 3 of the present invention. In the figure, reference numeral 17 denotes a correction state determiner. The rest is the same as in the second embodiment.
[0030]
Next, the operation will be described. In the third embodiment, the imaging operation, sensitivity variation, and shading amount measuring operation are exactly the same as in the second embodiment. In this embodiment, the correction state determination unit 17 determines the calibration state, and three types of calibration can be performed sequentially based on an internal program. FIG. 15 shows a flowchart of calibration control. When the correction state determination unit 17 receives a calibration request from the sensitivity variation measurement unit 14 or the shading amount measurement unit 16, the correction state determination unit 17 enters a calibration execution state, and instructs the imaging controller 9 to shift the focus of the infrared lens 1 (defocus command). To give out. The image corrector AA13c performs the first calibration (defocus calibration) with the focus sufficiently shifted and the two image correction shutters opened. When the defocus calibration is completed, upon receiving a defocus calibration end command from the correction state determiner 17, the imaging controller 9 returns the focus of the infrared lens 1 to the image correction shutter B15 for two frames. Close the time. When the shutter is closed, the image corrector A13 switches the output to the sensitivity variation measuring unit 14 and the shading amount measuring unit 16, and sends image data for each frame. The sensitivity variation measuring unit 14 and the shading amount measuring unit 16 measure the sensitivity variation and the shading amount and send the results to the correction state determination unit 17. The correction state determination unit 17 determines whether each result is within an allowable range with respect to the measurement value immediately after the previous calibration, or by comparing with a value set in advance and stored in the internal memory. If the correction state is within the allowable range, it is considered that the defocus calibration has ended normally, and the calibration operation ends. When it is determined that the correction state is outside the allowable range, the correction state determination unit 17 requests the imaging controller 9 to perform second calibration (lens shading calibration) in a state where only the image correction shutter B15 is closed. When the lens shading calibration is completed, the imaging controller 9 closes the image correction shutter A12 for one frame. When the shutter is closed, the image corrector AA 13 c sends image data only to the sensitivity variation measuring device 14. The sensitivity variation measuring unit 14 measures the sensitivity variation and sends the result to the correction state determination unit 17. The correction state determination unit 17 determines whether the result is within an allowable range as a measurement value of variation immediately after the previous calibration or by comparing with a value set in advance and stored in the internal memory. Here, when it is determined that the correction state is within the allowable range, the calibration is completed, and the sensitivity variation and the measured value of shading are stored. If it is determined that the image is out of the allowable range, the third sensitivity calibration is performed with the image correction shutter A12 closed, the calibration is terminated, and the sensitivity variation and the shading measurement value are stored. Further, the calibration execution state of the correction state determiner 17 is canceled at the end of calibration.
[0031]
In the conventional device, which calibration is performed in which operational state is determined by the user's subjectivity, and since there was no means for measuring shading correction deviation or sensitivity variation after calibration, the screen In some cases, the apparatus was operated with correction unevenness remaining. For example, when the infrared imaging device of the present invention mounted on an aircraft captures a uniform temperature background such as the sky or the sea, defocus calibration is the best calibration, but in the background Due to the entry of clouds and the sun, the background may not be uniform even if the focus of the infrared lens 1 is shifted, and it may be better to perform lens shading calibration. Further, when performing lens shading calibration, there is a temperature difference between the infrared lens 1 and the image correction shutter B15, and the lens shading calibration may not be performed well. At this time, sensitivity calibration is performed. Do. Thus, the user needs to select a calibration method according to the situation. In the present invention, by adding a means for determining the success or failure of the calibration, it is possible to generate three types of calibration commands sequentially, so that the most effective calibration in the operating state is automatically selected. As a result, an infrared image with stable video quality can be output.
[0032]
Embodiment 4 FIG.
FIG. 4 is a block diagram showing Embodiment 4 of the present invention. In the figure, 18 is a sensitivity variation change measuring device. Other than that, 14 and 13 are the same as those of the first embodiment, and the other is the same as the conventional apparatus.
[0033]
Next, the operation will be described. A normal imaging operation is the same as that of a conventional apparatus, but in this embodiment, it is assumed that the temperature change in the environment is small and the luminance in the screen is not greatly affected. In this embodiment, the sensitivity variation measuring instrument 14 always receives data from the image corrector 13, measures the standard deviation in each gate of the entire screen by the same operation as in the first embodiment, and averages the values. Is output to the sensitivity variation change measuring device 18. In the conventional apparatus, after the calibration is completed normally, the calibration is performed again every about 30 minutes, depending on the changing state of the temperature environment etc., and about 10 minutes immediately after calibration is empirically output. It can be said that the state of the image is good. The sensitivity variation change measuring device 18 stores the data of the average value of the standard deviation received from the sensitivity variation measuring device 14 in an internal memory for a preset time after the sensitivity calibration is performed, for example, about 10 minutes. At the time when the data is accumulated, the sensitivity variation change measuring device 18 obtains the variation amount of variation over time from “Equation 2”.
[0034]
[Expression 2]

[0035]
FIG. 16 is a graph showing the relationship between the average value of sensitivity variations and time. In the figure, 44 is a line of measured sensitivity variation average value, and 45 is a line of temporal variation of obtained variation. Assuming that the infrared imaging device continues to capture almost the same screen, it is considered that the magnitude of the luminance variation seen immediately after the sensitivity calibration is the eigenvalue C of the luminance variation of the screen. Naturally, as the imaging target of the infrared imaging device changes, the variation in luminance of the screen also changes. However, if the correction does not deteriorate, the measured value is observed with the width of D centering on the eigenvalue C. However, in actuality, correction deviation occurs with time and gradually increases, so that the average value of the standard deviations in each gate of luminance variation increases as shown in FIG. The sensitivity variation change measuring device 18 obtains the amount of change in sensitivity variation per unit time by “Equation 2”, and multiplies the elapsed time after sensitivity calibration by that value, for example, 10 minutes have passed since sensitivity calibration. The amount of increase in sensitivity variation at a later point in time is estimated, and when that value exceeds three times (3σ) the average value of the standard deviation in each gate of luminance variation immediately after sensitivity calibration, imaging control is performed. An image correction command signal 11 is output to the device 9.
Note that the image corrector in the present embodiment does not have a frame memory like the image corrector 7 of the conventional apparatus, and the image of the image correction shutter 2 is displayed while the image correction shutter 2 is closed. May be output.
[0036]
In the conventional apparatus, since there was no means for measuring the variation in screen brightness and the amount of change following the sensitivity calibration, sensitivity calibration is performed according to the subjectivity of the operator watching the displayed screen. It was broken. Further, in the first embodiment, since infrared light incident from the outside is blocked, the image is interrupted at a constant interval although it is a very short time, and complicated signal processing is performed when performing target detection and tracking. Necessary. In the present invention, a means for quantitatively measuring the state of brightness variation on the screen and a change thereof are added to a conventional apparatus, and a calibration command that is conventionally performed by a user based on subjectivity is automatically generated, thereby automatically generating sensitivity. Enables calibration, eliminates image breaks after a predetermined time after calibration, outputs a stable image quality infrared image, and performs target detection and tracking at a later stage. Therefore, a convenient image is output.
[0037]
Embodiment 5 FIG.
FIG. 5 is a block diagram showing Embodiment 5 of the present invention. In the figure, 19 is an image correction shutter C, 20 is a shading amount change measuring device, and 13c is the same as in the second embodiment. The rest is the same as in the fourth embodiment.
[0038]
Next, the operation will be described. The fifth embodiment is the same as the fourth embodiment until the normal imaging operation and the calibration request by the sensitivity variation measuring instrument, and it is assumed that the temperature change in the environment is small. The image correction shutter C19 has a reaction speed comparable to that of the image correction shutter 2 used in the conventional apparatus, and only aims to block external infrared light during lens shading calibration. Yes. The image correction shutter C19 may be substituted for the infrared imaging device having a visual axis drive mechanism and a function for storing the imaging device. The shading amount measuring device 16 always receives data from the image corrector 7 and measures the average value of the luminance of each region divided into 48, for example, as in the second embodiment. As with the sensitivity variation change measuring device 18, the shading amount change measuring device 20 sets the average brightness value measured by the shading amount measuring device 16 to a distance from the center of the screen for a preset time after calibration, for example, 10 minutes. Accordingly, they are rearranged as shown in FIG. 17 and stored in the internal memory as an average value for each area. Further, for example, after 10 minutes have elapsed, the temporal change amount of the luminance average value is obtained based on “Equation 3” for each region.
[0039]
[Equation 3]

[0040]
FIG. 18 is a graph showing the relationship between the average value of the brightness of region A and region E shown in FIG. 17 and time. In the figure, 46 is a line of average brightness values measured in the area A, 47 is a line of average brightness values measured in the area E, and 48 is a line of temporal change in brightness average value obtained in the area A. , 49 are lines of temporal change in luminance average value obtained in the region E. Assuming that the infrared imaging device continues to capture almost the same screen, it is considered that the average value of luminance seen immediately after calibration is the eigenvalue C of the luminance of the screen. Naturally, as the imaging target of the infrared imaging apparatus changes, the luminance variation of the screen also changes. However, if the correction does not deteriorate, the measured value is observed with the width of D centered on the eigenvalue C. However, since the shading amount actually changes with time, the average luminance value changes as shown in FIG. The shading amount change measuring device 20 obtains a change amount per unit time of luminance for each region by “Equation 3”, and applies the elapsed time after calibration to the value, thereby changing the current luminance for each region. When the amount is estimated and the difference between the maximum value and the minimum value exceeds, for example, three times (3σ) the average value of luminance in each area immediately after the previous calibration (or the average value immediately after And an image correction command signal 11 for performing lens shading calibration with the imaging correction shutter C closed, is output to the imaging controller 9. Further, the sensitivity variation change measuring device 18 outputs to the imaging controller 9 an image correction command signal 11 for performing sensitivity calibration with the image correction shutter 2 closed in the same manner as in the fourth embodiment.
Note that the image corrector in the present embodiment does not have a frame memory like the image corrector 7 of the conventional apparatus, and the image of the image correction shutter 2 is displayed while the image correction shutter 2 is closed. May be output.
[0041]
In the conventional apparatus, since there is no means for measuring the shading of the screen and its change amount after the calibration, the calibration is performed by the subjectivity of the operator who is viewing the displayed screen. Further, in the second embodiment, since infrared light incident from the outside is blocked, the image is interrupted at a constant interval although it is a very short time, and complicated signal processing is performed when performing target detection and tracking. Necessary. In the present invention, means for quantitatively measuring the state of brightness variation of the screen and its change and means for quantitatively measuring the state of shading of the screen and its change are added to the conventional apparatus, and the conventional user is based on the subjectivity. By automatically generating the calibration commands that have been performed, it is possible to perform automatic calibration including lens shading correction, and after the preset time has elapsed after calibration, there is no interruption in the image and the result In addition, an infrared image with stable video quality is output, and an image convenient for target detection and tracking is output later.
[0042]
Embodiment 6 FIG.
FIG. 6 is a block diagram showing Embodiment 6 of the present invention. In the figure, 21 is an image corrector B, and 22 is a shading correction amount setter A. The rest is the same as in the fifth embodiment.
[0043]
Next, the operation will be described. In the sixth embodiment, the operation from the infrared lens 1 to the A / D converter 6 and the calibration request by the sensitivity variation change measuring device 18 are the same as those in the fourth embodiment. The image corrector B21 outputs the image data whose sensitivity variation has been corrected in advance by sensitivity calibration to the sensitivity variation measuring device 14 and simultaneously outputs it to the shading amount measuring device 16. The sensitivity variation measuring device 18 outputs to the imaging controller 9 an image correction command signal 11 for performing sensitivity calibration in a state where the image correction shutter 2 is closed in the same manner as in the fifth embodiment. However, since the image correction shutter 2 is inside the infrared lens 1, calibration including lens shading cannot be performed. Therefore, in the sixth embodiment, a shading correction amount setting unit A22 is added as a circuit for correcting shading. Now, after the calibration by the image corrector B21 is completed, with the image correction shutter 2 opened, for example, in the infrared imaging device of the present invention mounted on an aircraft, the image change between one frame is small (in a certain region). Consider the case where the background and target are being imaged (the time average of luminance hardly changes). The shading correction amount setting unit A22 receives the amount of change in luminance after calibration of the five regions shown in FIG. 17 from the shading amount change measuring device 20, and calculates the amount of shading correction corresponding to the distance from the center of the screen. Determine. FIG. 19 is a conceptual diagram of correction amount setting of the shading correction amount setting unit A22. In the figure, reference numerals 50 to 54 denote increases in the average value of luminance obtained by multiplying the slope of the average value of the luminance values in the regions A to E obtained from the shading amount change measuring device 20 by the elapsed time from the end of the previous calibration. A plot showing the amount, and 55 is a shading line showing a predetermined shading correction amount. The shading correction amount setting unit A22 obtains an appropriate quadratic curve from the five plots, and outputs a line obtained by inverting it with respect to the line with the luminance change amount 0 as the shading correction amount to the image corrector B21. The image corrector B21 sends data obtained by subtracting the shading correction amount from the screen in which only the sensitivity variation is corrected to the D / A converter 8 in real time. The second and fifth embodiments have a mechanical configuration in which a lens front shutter is placed to correct lens shading by calibration. On the other hand, in the sixth embodiment, the mechanical configuration of the conventional infrared imaging device can be changed as much as possible, and the operation of capturing data on the uniform temperature surface for correction as in the above-described shading calibration is not performed. Achieve lens shading correction in real time with electrical signal processing.
Further, since the luminance change amount obtained from the shading amount change measuring device 20 is obtained with the image correction shutter 2 opened, the correction accuracy increases if the change amount is updated at regular intervals.
[0044]
In the conventional apparatus, since there was no means for measuring the shading of the screen and its amount of change continuously after the calibration and determining the shading amount to be corrected based on the measured value, there is no choice but to correct the lens shading by calibration. For this purpose, a mechanical structure is required in which a shutter is placed in front of the lens. In the sixth embodiment, the mechanical configuration of the conventional infrared imaging device is changed as much as possible, and real-time lens shading correction is achieved by adding an electric signal processing circuit, and the luminance variation of the screen By adding a means for quantitatively measuring the state of the image and its change to a conventional device, and automatically generating a calibration command that was previously performed by the user based on the subjectivity, automatic calibration is performed and a stable image is obtained. Output quality infrared image.
[0045]
Embodiment 7 FIG.
FIG. 7 is a block diagram showing Embodiment 7 of the present invention. In the figure, 23 is an infrared lens A, 24 is a temperature signal, 25 is a temperature change measuring device, and 26 is a shading correction amount setting device B. The rest is the same as in the sixth embodiment.
[0046]
Next, the operation will be described. Regarding the seventh embodiment, the normal imaging operation and the calibration request by the sensitivity variation measuring instrument 18 are the same as those in the sixth embodiment. The infrared lens A 23 has a temperature monitor 58 for measuring the temperature of the lens barrel portion of the lens, and sends a temperature signal 24 to the temperature change measuring device 25. The temperature change measuring device 25 measures the temperature difference of the infrared lens A23 from the temperature signal 24 sequentially input after the previous calibration, and outputs it to the shading correction amount setting device B26. The shading correction amount setting unit B26 holds data indicating the inherent lens shading characteristics of the infrared lens A23 (for example, the amount of infrared energy changes in proportion to the fourth power of the temperature difference) in the internal memory. Yes. FIG. 20 is a diagram showing an example of the data held by the shading correction amount setting unit B26. In the figure, reference numeral 56 denotes a shading line that the infrared lens A23 has when the temperature difference is A, and 57 denotes a shading line that the infrared lens A23 has when the temperature difference B is. The shading line is expressed as a function of the temperature difference of the lens barrel portion and the distance from the center of the screen within the temperature range in which the increase in luminance is used. In the internal memory, for example, the nodes of the shading line discretized in advance based on simulations and experimental measurement results are stored, and the required shading lines corresponding to the temperature difference are appropriately interpolated between the nodes. Can be obtained. Alternatively, the internal memory stores a constant of an approximate expression in which the shading line is expressed by an approximation means such as a polynomial, and outputs a required brightness increase amount from the temperature difference and the distance from the screen center. The shading line may be expressed as appropriate. The shading correction amount setting unit B26 corresponds to the temperature change from the shading line as shown in FIG. 20 for each position from the center of the screen. For example, when the temperature difference is B, the shading line 57 of the temperature B is canceled. The amount of increase in luminance is obtained, and the shading correction amount is determined and output to the image corrector B21. The image corrector B21 sends the data subjected to the shading correction to the D / A converter 8 in real time by the same operation as in the sixth embodiment, and outputs the output video signal 10. In the sixth embodiment, since the correction amount of each pixel is determined from the image data, a circuit for measuring the image and a circuit for determining the correction amount are necessary. In the seventh embodiment, the shading is performed at the temperature. By measuring the temperature by utilizing the property depending on the difference, the circuit for measuring the image can be eliminated, so that an equivalent function can be achieved with a small circuit scale. While the temperature measurement circuit can be composed of a thermocouple, a resistor, and a transistor, the circuit for measuring an image has a huge memory for storing an image such as a frame memory in the shading amount measuring device 16 and a high-speed computing device. is required. In addition, the memory required for the characteristic data of the lens shading described above is sufficient to store several representative points that discretely express the temperature characteristic, which is more sufficient than the enormous memory for storing the image. Smaller, smaller and lighter.
[0047]
The conventional apparatus has no means for measuring the temperature of the optical system and its variation continuously after calibration and determining a shading amount to be corrected based on the measured temperature, so the lens shading must be corrected by calibration. For this purpose, a mechanical configuration is required in which a shutter is placed in front of the lens. In the seventh embodiment, a signal processing circuit simpler than that of the sixth embodiment is added by adding a means for quantitatively measuring the temperature of the optical system and its change and a means for holding the lens characteristic data. Real-time lens shading correction is achieved. In addition, by adding a means of quantitatively measuring the state of brightness variation and changes in the screen, and automatically generating a calibration command that was previously performed by the user based on subjectivity, the calibration is automatically performed and stable. An infrared image with the specified video quality is output.
[0048]
Embodiment 8 FIG.
In the embodiment of the present invention, a warning signal such as an alarm sound or flashing light (or a scale) is used after quantitatively detecting a correction deviation of an image in the sensitivity variation measuring instrument of the first, second, fourth, and fifth embodiments. Warning display). Accordingly, the user can quantitatively grasp the correction deviation of the image, and the timing for manually calibrating the image corrector can be obtained.
[0049]
Embodiment 9 FIG.
In the embodiment of the present invention, after the correction correction of the image is quantitatively detected in the shading amount measuring device of the second, fourth, and eighth embodiments, a warning signal such as an alarm sound or flashing light (or a warning display by a scale) ). Accordingly, the user can quantitatively grasp the correction deviation of the image, and the timing for manually calibrating the image corrector can be obtained.
[0050]
【The invention's effect】
The infrared imaging apparatus according to the first aspect of the present invention adds a means for quantitatively grasping the state of correction of the element sensitivity by using the average value of the luminance deviation obtained for each pixel during imaging. As a result, calibration can be performed by generating a calibration command that is conventionally performed by the user based on the subjectivity. Accordingly, it is possible to obtain an infrared imaging device that is simple in operation but has little performance deterioration due to a deviation in correction of element sensitivity and a correction in shading, and that does not require the user to perform a calibration operation.
[0051]
Further, according to the second invention, the means for quantitatively grasping the state of the correction deviation of the element sensitivity during imaging and the state of the correction deviation of the shading in some areas divided in the screen during the imaging. By adding a means for obtaining the luminance distribution of the entire area quantitatively from the average value of luminance and adding it to the conventional device, a calibration command that was conventionally performed by the user based on the subjectivity was generated, and lens shading correction was performed. Automatic calibration can be performed.
[0052]
In addition, according to the third aspect of the invention, by adding a means for determining the success or failure of calibration, it is possible to generate three types of calibration commands for shading, thereby automatically performing effective calibration in the operating state. Selected and implemented. Thereby, an infrared imaging device capable of outputting an image in an optimally calibrated state can be obtained.
[0053]
In addition, according to the fourth aspect of the present invention, the calibration instruction that the user has conventionally performed based on the subjectivity is provided by adding to the conventional apparatus a means for quantitatively measuring the state of the brightness variation of the screen and the change thereof. Generate and automatically calibrate. In the first invention, short-time image breaks occur, but an image convenient for signal processing such as target detection and tracking can be output at a later stage. Thus, an infrared imaging device that outputs an image suitable for signal processing can be obtained.
[0054]
In addition, according to the fifth invention, a means for quantitatively measuring the state of luminance variation of the screen and its change and a means for quantitatively measuring the state of shading of the screen and its change are added to the conventional apparatus. Thus, it is possible to generate a calibration command that is conventionally performed by the user based on the subjectivity and perform automatic calibration including lens shading correction. Also, by eliminating the short-time image breaks that occurred in the second invention, it is possible to output an image that is convenient when performing target detection or tracking at a later stage.
[0055]
According to the sixth aspect of the invention, real-time lens shading correction is achieved by adding means for quantitatively measuring the state of the shading of the screen and its change and determining the amount to be corrected thereby. In addition, by adding a method for quantitatively measuring the state of brightness variation and changes in the screen to a conventional device, a calibration command that has been performed based on the subjectivity of conventional users is generated, and calibration is automatically performed. Yes. As a result, the lens shading is corrected in real time, so that there is little performance deterioration due to a shading correction shift, and an infrared imaging apparatus that is not frequently calibrated as in the conventional apparatus can be obtained.
[0056]
Furthermore, according to the seventh invention, by adding a means for quantitatively measuring the temperature of the optical system and its change and a means for holding the lens characteristic data, a circuit simpler than the sixth invention is provided. Real-time lens shading correction is achieved. In addition, an infrared imaging apparatus that is not frequently calibrated as in the conventional apparatus can be obtained in a smaller size and lighter.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a second embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of a third embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a fourth embodiment of the present invention.
FIG. 5 is a block diagram showing a configuration of a fifth embodiment of the present invention.
FIG. 6 is a block diagram showing a configuration of a sixth embodiment of the present invention.
FIG. 7 is a block diagram showing a configuration of a seventh embodiment of the present invention.
FIG. 8 is a block diagram showing a configuration of a conventional apparatus.
FIG. 9 is a diagram showing an outline of calibration of a conventional apparatus.
FIG. 10 is a diagram illustrating a state in which light generated by a target is collected through a lens.
FIG. 11 is an intermediate value image on a display showing an example of a shading image.
FIG. 12 is a diagram showing an outline of a sensitivity variation measuring operation.
FIG. 13 is a diagram showing an outline of a shading amount measurement operation.
FIG. 14 is a diagram illustrating a distribution of luminance average values in a region according to a shading correction state.
FIG. 15 is a flowchart of calibration control.
FIG. 16 is a diagram showing the relationship between the average value of sensitivity variations and time.
FIG. 17 is a diagram illustrating a state in which luminance measurement areas are regrouped.
FIG. 18 is a diagram illustrating a relationship between an average luminance value and time.
FIG. 19 is a conceptual diagram of shading correction amount setting performed by a shading correction amount setting unit A22.
FIG. 20 is a conceptual diagram of shading correction amount setting by a shading correction amount setting unit B26.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Infrared lens, 2 Image correction shutter, 3 Infrared detector, 4 amplifier, 5 Sample hold circuit, 6 A / D converter, 7 Image corrector, 8 D / A converter, 9 Imaging controller, 10 output Image signal, 11 Image correction command signal, 12 Image correction shutter A, 13 Image corrector A, 13a Output selector switch, 13b Frame memory, 13c Image corrector AA, 13d Output selector switch A, 14 Sensitivity variation measuring instrument, 14a Frame memory, 14b Standard deviation measurement device, 14c Standard deviation storage device, 14d Sensitivity variation determination device, 15 Image correction shutter B, 16 Shading amount measurement device, 17 Correction state determination device, 18 Sensitivity variation change measurement device, 19 Image correction Shutter C, 20 Shading amount change measuring device, 21 Image corrector B, 22 Shading correction amount setting , 23 Infrared lens A, 24 Temperature signal, 25 Temperature conversion measuring device, 26 Shading correction amount setting B, 27 Output characteristic line a, 28 Output characteristic line b, 29 Output characteristic line aa, 30 Output characteristic line bb, 31 output Line c, 32 Target A, 33 Target B, 34 Lens, 35 Imaging surface, 36 Light flux AA, 37 Light flux BB, 38 Image data, 39 Variation measurement gate, 40 Measured sensitivity variation, 41 Shading measurement area, 42 Correction Distribution of luminance average value when it is made, 43 Distribution of luminance average value when it is not corrected, 44 Line of measured sensitivity variation average value, 45 Line of variation variation with time, 46 Luminance average of region A Value line, 47 area E luminance average value line, 48 area A luminance average value time change line, 49 area E luminance Average time change line, 50 Region A shading change plot, 51 Region B shading change plot, 52 Region C shading change plot, 53 Region D shading change plot, 54 Region E A shading change amount plot of 55, a line indicating the shading correction amount, 56 a shading line of the infrared lens A23 when the temperature is A, a shading line of the infrared lens A23 when the temperature is 57, and a temperature monitor.

Claims (9)

An infrared lens for condensing and imaging infrared light emitted from a target object, an infrared detector for photoelectrically converting an infrared light image formed by the infrared lens by an infrared detection element; and Infrared light is cut off in an infrared imaging device including a conversion circuit that converts an output signal of an infrared detector into an image signal, and a correction circuit that performs signal processing on the image signal and corrects variations in the infrared detection elements. A shut-off means, a means for generating a first shut-off command in the shut-off means at a preset time interval, a calibration command is generated in the correction circuit after receiving a calibration request signal, and a second shut-off Each pixel from the image signal that has been signal-processed by the correction circuit while infrared light is blocked by the blocking means, and a control means having a means for generating a command to the blocking means A sensitivity variation measuring means for measuring the sensitivity variation by calculating an average value of the luminance deviation obtained in step (b) and an average value of the luminance deviation measured by the calibration performed previously. An infrared imaging apparatus, comprising: a sensitivity variation determination unit that generates a calibration request signal in the control unit when the average value is greater than a product of a preset value or a sum. An infrared lens for condensing and imaging infrared light emitted from a target object, an infrared detector for photoelectrically converting an infrared light image formed by the infrared lens by an infrared detection element; and An infrared imaging device comprising: a conversion circuit that converts an output signal of an infrared detector into an image signal; and a correction circuit that performs signal processing on the image signal and corrects variations in the output of the infrared detection element. The first blocking means for blocking the infrared light before being condensed by the infrared light, the second blocking means for blocking the infrared light collected by the infrared lens, and the first blocking means shading measuring means for measuring a shading amount seeking the distribution of the average value of the brightness of each part of the screen from the signal processed the image signal by the correction circuit while the external light is blocked, the shading measurement The width of the average brightness distribution measured at the stage is the product or sum of the width of the average brightness distribution measured in the previous calibration and the preset width. Shading determination means for generating a first calibration request signal when large, and for each pixel from the image signal signal-processed by the correction circuit while the infrared light is blocked by the second blocking means A sensitivity variation measuring unit that obtains an average value of the obtained luminance deviation and measures the sensitivity variation, and an average value of the luminance deviation measured by the sensitivity variation measuring unit is measured by the calibration performed one time before. A sensitivity variation determining means for generating a second calibration request signal when the product of the average value of the luminance deviation and a preset value is greater than the sum, or The first and second shut-off commands are alternately generated in the first shut-off means and the second shut-off means, and the infrared light shut-off time by the first shut-off means and the second shut-off means is designated. Receiving the first calibration request signal output from the shading determination means, generating a first calibration command to the correction circuit, and a third cutoff command to the first cutoff means A second calibration command is generated in the correction circuit in response to the second calibration request signal output from the sensitivity variation determination means, and the second blocking means receives a fourth signal. An infrared imaging apparatus comprising: control means comprising means for generating a shut-off command. An infrared lens that has the function of focusing and focusing infrared light emitted from the target object, and the infrared light image formed by the infrared lens is photoelectrically converted by the infrared detector. Infrared imaging comprising: an infrared detector that performs conversion; a conversion circuit that converts the output signal of the infrared detector into an image signal; and a correction circuit that performs signal processing on the image signal and corrects variations in the output of the infrared detection element In the image correction method of the apparatus, first blocking means for blocking infrared light before being collected by the infrared lens, and second blocking for blocking infrared light collected by the infrared lens And a shading measuring means for measuring a shading amount by obtaining a distribution of an average value of luminance for each portion in the screen from the image signal corrected by the correction circuit while infrared light is blocked, and Chez The product of the width of the distribution of the average value of brightness and the preset width measured by the calibration performed previously by the width of the distribution of the average value of brightness measured by the measuring means, or Shading determination means for generating a first calibration request signal when greater than the sum, and luminance deviation obtained for each pixel from the image signal corrected by the correction circuit while infrared light is blocked Sensitivity variation measuring means that obtains an average value and measures sensitivity variation, and the luminance deviation measured by the calibration performed previously by the average value of the luminance deviation measured by the sensitivity variation measuring means. Sensitivity variation determination means for generating a second calibration request signal when the product of the average value and a preset value is greater than the sum, or the first cutoff And a control means for outputting a first cutoff command, a second cutoff command, a calibration command and a defocus command to the second cutoff means, the correction circuit and the infrared lens. The image correction method (1) of the infrared imaging device for correcting an image according to the following procedure when the first and second calibration request signals are generated from the shading determination unit or the sensitivity variation determination unit Procedure for performing the first calibration of the correction circuit in a state where the first blocking means and the second blocking means are opened and the infrared lens is defocused (2) The first calibration After completion, the average width distribution of the luminance and the average deviation of the luminance are measured from the corrected image signal in a state where the first blocking means is blocked. Step (3) When the distribution width of the average luminance value measured in the step (2) is larger than a preset width, or when the average deviation value of the luminance is larger than a preset value. Procedure for performing second calibration in correction circuit (4) Procedure for measuring average value of luminance deviation from corrected image signal after completion of second calibration (5) Procedure (4) A procedure for performing a third calibration in the correction circuit when the average value of the deviations in luminance measured in step (b) is larger than a preset value.   Means for measuring the slope of change in the average value of the brightness deviation with respect to time from the average value of the brightness deviation measured by the sensitivity variation measuring means, and taking the elapsed time after calibration over the slope of the change. The amount of increase in the average value of the luminance deviation is estimated, and the amount of increase is greater than the product or sum of the average value of the luminance deviation and the preset value at the end of the previous calibration. 2. An infrared imaging apparatus according to claim 1, further comprising sensitivity variation change measuring means comprising means for generating said calibration request signal at said control means. Means for measuring the slope of the change in the average brightness distribution with respect to time from the width of the average brightness distribution measured by the shading measuring means, and calibrating to the slope of the change in the width of the distribution The amount of increase in the average value distribution of luminance is estimated over time, and the distribution of the average value of luminance at the end of the calibration in which the amount of increase in the width of the above distribution was performed one time before is estimated. When the product of the width and the preset width or larger than the sum, the shading change measuring means comprising means for generating the first calibration request signal to the control means and the sensitivity variation measuring means are set in advance. Means for measuring a slope of a change in the average value of the luminance deviation with respect to time from an average value of the luminance deviation measured at a predetermined time, the average value of the deviation The amount of increase in the average value of the deviation of the brightness is estimated by multiplying the slope of the change by the elapsed time after the calibration, and the increase amount of the average value of the deviation is And a sensitivity variation change measuring means comprising means for generating the calibration request signal to the control means when the product of the average value of deviation and a preset value is greater than the sum. The infrared imaging device according to claim 2. An infrared lens for condensing and imaging infrared light emitted from a target object, an infrared detector for photoelectrically converting an infrared light image formed by the infrared lens by an infrared detection element; and Infrared light is cut off in an infrared imaging device composed of a conversion circuit that converts an output signal of an infrared detector into an image signal and a correction circuit that performs signal processing on the image signal and corrects variations in the output of the infrared detection element. And obtaining an average value of luminance deviations determined for each pixel from the image signal signal-processed by the correction circuit while infrared light is blocked by the blocking unit, and measuring sensitivity variations. Sensitivity variation measuring means, means for measuring a slope of change in the average value of the luminance deviation with respect to time from an average value of the luminance deviation measured by the sensitivity variation measuring means, Estimate the increase in the average value of the luminance deviation over the elapsed time after calibration, and set in advance the average value of the above luminance deviation at the end of the calibration when the above increase was performed one time ago The image obtained by signal processing by the correction circuit in a state where the sensitivity variation change measuring means including means for generating a calibration request signal when it is greater than the product or sum of the measured values and the blocking means is opened A shading measuring means for obtaining an average value of luminance for each part in the screen from the signal and measuring a shading amount, and a change in the average value of the luminance with respect to time from the average value of the luminance measured by the shading measuring means. The shading change measuring means for measuring the slope and the slope of the average value of the luminance obtained from the shading change measuring means are carried. Approximate curve indicating the amount of increase in the average value of the luminance corresponding to the distance from the center of the screen in each region in the screen. Correction amount setting means for determining a correction amount of shading in the correction circuit so as to cancel out the increase amount of the average value of the luminance along the approximate curve, a means for generating the cutoff command to the cutoff means, and the sensitivity An infrared imaging apparatus comprising: a control unit having a unit that receives the calibration request signal output from the variation change measuring unit and generates a calibration command to the correction circuit. An infrared lens for condensing and imaging infrared light emitted from a target object, an infrared detector for photoelectrically converting an infrared light image formed by the infrared lens by an infrared detection element; and In an infrared imaging device including a correction circuit that performs signal processing on an output signal of an infrared detector and corrects variations in the output of an infrared detection element, blocking means for blocking infrared light and infrared light are blocked Sensitivity variation measuring means for measuring the sensitivity variation by obtaining an average value of the luminance deviation obtained for each pixel from the image signal signal-processed by the correction circuit, and the luminance measured by the sensitivity variation measuring means Means for measuring the slope of the change in the average value of the luminance deviation with respect to time from the average value of the deviation of the average value of the deviation in luminance over the elapsed time after calibration to the slope of the change in the deviation A request signal for calibration when the increase amount is estimated and the increase amount is greater than the product or the sum of the average value of the brightness deviation and the preset value at the end of the previous calibration. A sensitivity variation change measuring means comprising means for outputting the temperature, a temperature measuring means for measuring the temperature of the infrared lens, a temperature at the end of the previous calibration performed by the temperature measuring means and the current time A temperature change measuring means for calculating a temperature difference between the temperature and a shading correction amount corresponding to the temperature difference measured by the temperature change measuring means, and a luminance for a prestored temperature difference and a pixel position in the screen. Correction amount setting means for outputting based on data indicating the relationship of the increase amount, means for generating the shut-off command to the shut-off means, and the sensitivity variation Infrared imaging device receiving the calibration request signal output from the change measuring means can, characterized in that a control means and a means for outputting the calibration command to the correction circuit. Storage means for storing the image signal output from the correction circuit; and storage output means for outputting the image signal of the previous frame from the storage means while the infrared light is blocked by the first blocking means. The infrared imaging device according to any one of claims 1, 4, 6, and 7. Storage means for storing the image signal output from the correction circuit, and means for outputting the image signal of the previous frame from the storage means while the infrared light is blocked by the first and second blocking means. 6. The infrared imaging apparatus according to claim 2, further comprising a storage output unit.

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