JP4093790B2 - Imaging device - Google Patents

Description

【００５５】
また、図６に示す分布の標準偏差σは次の式（２）で表す。
【００５６】
【数２】

【００５７】
統計処理部３３は、式（１）によって撮像範囲の文字列が最も通過した位置であるピーク値Ｘｐｅａｋを算出し、式（２）によって分布の標準偏差σを算出する。
【００５８】
パン可変部３４は、統計処理部３３が算出したピーク値が、撮像範囲の中央の値となるようにパン変更値を算出する。なお、ピーク値は、文字列の通過状況に応じて変動し、ピーク値の変動に応じた撮像カメラ３０の過剰なまでのパン変更による認識率低下を防ぐため、パン可変部３４は、撮像範囲の中央の値とピーク値との値の幅に閾値を設定、保持し、撮像範囲の中央の値とピーク値との値の幅が閾値を超えたときのみ、パン変更値を算出する。
【００５９】
図７は、パン変更値算出を説明する図である。図に示す撮像範囲４０に示す縦線は、撮像カメラ３０へ向かって移動する物体の文字列が、撮像範囲４０に入ってから撮像範囲を抜け出るまでの軌跡を示す。軌跡の方向は撮像範囲の上から下へと向かう。軌跡の密度が高いほど、多くの文字列が通過したことを示す。分布４１は、撮像範囲４０の各通過位置での文字列の通過数を示す分布である。パン可変部３４は、分布４１におけるピーク値Ｘｐｅａｋを撮像範囲４０の中央の値となるように撮像カメラ３０のパンを可変するパン変更値を算出する。
【００６０】
ズーム比率可変部３５は、標準偏差σから、撮像範囲外を通過する文字列の通過位置を予測し、撮像範囲外を通過する文字列も撮像範囲内に入るようにするためのズーム値を算出する。
【００６１】
図８は、ズーム値算出を説明する図である。図に示す撮像範囲４２に示す縦線は、撮像カメラ３０へ向かって移動する物体の文字列が、撮像範囲４２に入ってから撮像範囲を抜け出るまでの軌跡を示す。分布４３は、撮像範囲４２の水平方向における各通過位置での文字列の通過数を示す。分布４４ａ，４４ｂは、撮像範囲４２の外側を通過する文字列の予想分布を示している。分布４４ａ，４４ｂに示す文字列は、撮像範囲４２の範囲外であり、認識処理されることがない。そこで、ズーム比率可変部３５は、標準偏差σから、分布４３の予想広がりＤ（分布４３に分布４４ａ，４４ｂが合わされた分布）を算出する。予想広がりＤは次の式（３）で表す。
【００６２】
【数３】

【００６３】
一般に式（３）のｍを３とすると、予想広がりＤに対して約９９％の予想広がりが求まる。以下では、ｍを３として説明する。
ズーム比率可変部３５は、式（３）から求まる予想広がりＤの値と、撮像範囲４２の水平方向における幅の値の比が１となるようなズーム値を算出する。図８の例では、予想広がりＤの値と、撮像範囲４２の水平方向における幅の値の比が１となるためには、撮像カメラ３０のズームを引くズーム値が算出されることになる。図９は、ズームを引いたときの図８の分布の様子を示した図である。図９に示すように、撮像範囲４２の範囲内に、文字列が通過することが予想される分布４４ａ，４４ｂが含まれる。これによって、撮像範囲４２の範囲外を通過していた文字列も認識できるようになる。なお、標準偏差σは、文字列の通過状況に応じて変動し、標準偏差σの変動に応じた撮像カメラ３０の過剰なまでのズーム変更による認識率低下を防ぐため、ズーム比率可変部３５は、予想広がりＤと撮像範囲の幅の比に閾値を設定、保持し、この閾値を超えたときのみ、ズーム値を算出する。
【００６４】
文字列認識処理部３６は、文字列領域抽出部３２によって抽出される文字列の認識処理をする。文字列認識処理部３６は、文字列の文字を辞書ＤＢ３６ａに登録されている文字を参照、比較し、最も一致した文字を物体に記された文字として認識する。
【００６５】
制御コマンド送信部３７は、パン可変部３４が算出したパン変更値、及びズーム比率可変部３５が算出したズーム値を撮像カメラ３０へ送信する。また、制御コマンド送信部３７は、パン変更値、及びズーム値に関して、文字列を認識するための、最低限の性能を確保できる限界値を保持している。制御コマンド送信部３７は、限界値を超えたパン変更値、ズーム値を受け付けた場合、限界値をパン変更値、ズーム値として、撮像カメラ３０へ送信する。ここで、文字列を認識するための最低限の性能とは、例えば、ズーム比率可変部３５が、予想広がりＤの値と撮像範囲４２の水平方向における幅の値との比が１となるようにズームを引いても、文字列を認識できる範囲内でズームを引くということである。また、文字列が認識できる範囲内でパンを変更するということである。
【００６６】
以下、図５の機能ブロック図の処理の一例をフローチャートを用いて説明する。
図１０、１１は、図５の機能ブロック図の処理の一例を示すフローチャートである。
【００６７】
［ステップＳ２１］画像取り込み部３１は、撮像カメラ３０が撮像する物体を画像データとして取り込む。
［ステップＳ２２］文字列領域抽出部３２は、画像取り込み部３１が取り込んだ物体の画像データから、物体に記される文字列を抽出する。そして、抽出した文字列の、撮像カメラ３０の撮像範囲の水平方向における通過位置を取得する。
【００６８】
［ステップＳ２３］文字列認識処理部３６は、文字列領域抽出部３２が抽出した文字列を、辞書ＤＢ３６ａを参照して認識する。
［ステップＳ２４］統計処理部３３は、文字列領域抽出部３２が取得した文字列の通過位置と、その通過位置における文字列の通過数の統計を採る。
【００６９】
［ステップＳ２５］統計処理部３３は、一定時間経過しているか否かを判断する。一定時間経過していると、ステップＳ２６へ進む。一定時間経過していなければ、ステップＳ２１へ進む。
【００７０】
［ステップＳ２６］統計処理部３３は、文字列の通過数の最も多い通過位置であるピーク値と、文字列の通過位置とその通過位置における通過数の分布の標準偏差を算出する。
【００７１】
［ステップＳ２７］パン可変部３４は、統計処理部３３が算出したピーク値が、撮像範囲の中央の値となるためのパン変更値を算出する。そして、撮像範囲の中央の値とピーク値との値の幅が、閾値以上であるか否かを判断する。閾値以上であればステップＳ２８へ進み、閾値未満であればステップＳ３１へ進む。
【００７２】
［ステップＳ２８］制御コマンド送信部３７は、パン可変部３４が算出したパン変更値が、文字列を認識するための、最低限の性能を確保できる限界値以上か否かを判断する。限界値以上であれば、ステップＳ２９へ進み、限界値未満であれば、ステップＳ３０へ進む。
【００７３】
［ステップＳ２９］制御コマンド送信部３７は、限界値をパン変更値として撮像カメラ３０へ送信する。撮像カメラ３０は、受信した限界値で、パンを可変する。
【００７４】
［ステップＳ３０］制御コマンド送信部３７は、パン可変部３４が算出したパン変更値を撮像カメラ３０へ送信する。撮像カメラ３０は、受信したパン変更値に応じて、パンを可変する。これにより、撮像カメラ３０が撮像する文字列の最も通過数の多い通過位置が、撮像範囲の中央へ位置する。
【００７５】
［ステップＳ３１］ズーム比率可変部３５は、統計処理部３３が算出した標準偏差から、分布の予想広がりを算出する。そして、予想広がりと撮像範囲の幅の比が閾値以上であるか否かを判断する。閾値以上であればステップＳ３２へ進み、閾値未満であれば処理を終了する。
【００７６】
［ステップＳ３２］ズーム比率可変部３５は、予想広がりと撮像範囲の幅の比が１となるためのズーム値を算出する。制御コマンド送信部３７は、算出されたズーム値が、文字列を認識するための、最低限の性能を確保できる限界値以上であるか否かを判断する。限界値以上であれば、ステップＳ３３へ進み、限界値未満であれば、ステップＳ３４へ進む。
【００７７】
［ステップＳ３３］制御コマンド送信部３７は、限界値をズーム値として撮像カメラ３０へ送信する。撮像カメラ３０は、受信した限界値で、ズーム比率を可変する。
【００７８】
［ステップＳ３４］制御コマンド送信部３７は、ズーム比率可変部３５が算出したズーム値を撮像カメラ３０へ送信する。撮像カメラ３０は、受信したズーム値に応じて、ズーム比率を可変する。これにより、撮像カメラ３０の撮像範囲外を移動する物体の文字列を認識することができる。
【００７９】
このように、物体の通過位置とその通過数の分布統計を採り、分布の統計から最も通過数の多い通過位置を算出し、この通過位置が撮像範囲の中央に位置するようにパンを変更する。また、認証処理を適切に実行できる大きさにズーム比率を変更するので、常に高い認識率を維持して、移動する物体の文字列を認識することができる。
【００８０】
次に、本発明の第３の実施の形態について説明する。
図１２は、本発明の第３の実施の形態に係る撮像装置の機能ブロック図である。図に示すように、移動する物体に記される文字列を撮像して認識する撮像装置は、撮像カメラ５０、画像取り込み部５１、文字列領域抽出部５２、撮像カメラ制御部５３、統計処理部５４、統計的撮像カメラ制御部５５、制御コマンド送信部５６、文字列認識処理部５７、及び辞書ＤＢ５７ａを有している。
【００８１】
撮像カメラ５０は、パン、及びズーム比率が変更可能な撮像カメラである。
画像取り込み部５１は、撮像カメラ５０が撮像している物体を画像データとして取り込む。
【００８２】
文字列領域抽出部５２は、所定時間、撮像カメラ５０の撮像範囲に物体が通過した通過数をカウントし、予め設定される通過数の閾値以上であるか否かを判断する。通過数が閾値以上である場合には、画像取り込み部５１が取り込んだ画像データを解析して物体に記される文字列を抽出し、文字列の通過位置を統計処理部５４へ通知する。閾値未満である場合には、文字列の大きさと通過位置を撮像カメラ制御部５３へ通知する。
【００８３】
撮像カメラ制御部５３は、第１の実施の形態で説明した図２の機能ブロック図のパン可変部１３、ズーム比率可変部１４と同じ機能を有する。すなわち、撮像カメラ制御部５３は、文字列領域抽出部５２が取得した文字列の通過位置を、撮像範囲の中央に位置するように、撮像カメラ５０のパンを可変するためのパン変更値を算出する。また、文字列領域抽出部５２が取得した文字列の大きさを、予め登録されている、認識処理に適した大きさとなるように撮像カメラ５０のズーム比率を可変するためのズーム値を算出する。
【００８４】
統計処理部５４は、第２の実施の形態で説明した図２の機能ブロック図の統計処理部３３と同じ機能を有する。すなわち、式（１）によって撮像範囲の文字列が最も通過した位置であるピーク値Ｘｐｅａｋを算出し、式（２）によって分布の標準偏差σを算出する。
【００８５】
統計的撮像カメラ制御部５５は、第２の実施の形態で説明した図２の機能ブロック図のパン可変部３４とズーム比率可変部３５とを含む機能を有する。すなわち、統計処理部５４が算出したピーク値が、撮像範囲の中央の値となるようにパン変更値を算出する。また、統計処理部５４が算出した標準偏差値から、撮像範囲外を通過する文字列の通過位置の予想広がりを算出し、この予想広がりの幅と撮像範囲の幅との比が１となるようにズーム値を算出する。
【００８６】
制御コマンド送信部５６は、撮像カメラ制御部５３が算出するパン変更値、ズーム値を撮像カメラ５０に送信する。また、統計的撮像カメラ制御部５５が算出するパン変更値、ズーム値を撮像カメラ５０に送信する。
【００８７】
文字列認識処理部５７は、文字列が撮像カメラ制御部５３によって処理される場合、撮像カメラ５０のパン、又はズーム比率が変更された後の、文字列領域抽出部５２によって抽出される文字列の認識処理をする。また、文字列が統計的撮像カメラ制御部５５によって処理される場合、文字列領域抽出部５２によって毎回抽出される文字列の認識処理をする。なお、文字列認識処理部５７は、文字列の文字を、辞書ＤＢ５７ａに登録されている文字を参照して、認識する。
【００８８】
以下、図１２の機能ブロック図の処理の一例をフローチャートを用いて説明する。
図１３、１４、及び図１５は、図１２の機能ブロック図の処理の一例を示すフローチャートである。
【００８９】
［ステップＳ４１］画像取り込み部５１は、撮像カメラ５０が撮像する物体を画像データとして取り込む。
［ステップＳ４２］文字列領域抽出部５２は、所定時間内における、文字列の撮像範囲の通過数が閾値以上であるか否かを判断する。閾値以上である場合は、ステップＳ４３へ進み、閾値未満である場合は、ステップＳ６１へ進む。
【００９０】
［ステップＳ４３］文字列領域抽出部５２は、画像取り込み部５１が取り込んだ物体の画像データから、物体に記される文字列を抽出する。そして、抽出した文字列の、撮像カメラ５０の撮像範囲を通過している通過位置を取得する。
【００９１】
［ステップＳ４４］文字列認識処理部５７は、文字列領域抽出部５２が抽出した文字列を、辞書ＤＢ５７ａを参照して認識する。
［ステップＳ４５］統計処理部５４は、文字列領域抽出部５２が取得した文字列の通過位置と、その通過位置における文字列の通過数の統計を採る。
【００９２】
［ステップＳ４６］統計処理部５４は、一定時間経過しているか否かを判断する。一定時間経過していると、ステップＳ４７へ進む。一定時間経過していなければ、ステップＳ４１へ進む。
【００９３】
［ステップＳ４７］統計処理部５４は、文字列の通過数の最も多い通過位置であるピーク値と、文字列の通過位置とその通過位置における通過数の分布の標準偏差を算出する。
【００９４】
［ステップＳ４８］統計的撮像カメラ制御部５５は、統計処理部５４が算出したピーク値が、撮像範囲の中央の値となるようにパン変更値を算出する。そして、撮像範囲の中央の値とピーク値との値の幅が、閾値以上であるか否かを判断する。閾値以上であればステップＳ４９へ進み、閾値未満であればステップＳ５２へ進む。
【００９５】
［ステップＳ４９］制御コマンド送信部５６は、統計的撮像カメラ制御部５５が算出したパン変更値が、文字列を認識するための、最低限の性能を確保できる限界値以上であるか否かを判断する。限界値以上であれば、ステップＳ５０へ進み、限界値未満であれば、ステップＳ５１へ進む。
【００９６】
［ステップＳ５０］制御コマンド送信部５６は、限界値をパン変更値として撮像カメラ５０へ送信する。撮像カメラ５０は、受信した限界値で、パンを可変する。
【００９７】
［ステップＳ５１］制御コマンド送信部５６は、統計的撮像カメラ制御部５５が算出したパン変更値を撮像カメラ５０へ送信する。撮像カメラ５０は、受信したパン変更値に応じて、パンを可変する。これにより、撮像カメラ５０が撮像する文字列の最も通過数の多い通過位置が、撮像範囲の中央へ位置する。
【００９８】
［ステップＳ５２］統計的撮像カメラ制御部５５は、統計処理部５４が算出した標準偏差から、分布の予想広がりを算出する。そして、予想広がりと撮像範囲の幅の比が閾値以上であるか否かを判断する。閾値以上であればステップＳ５３へ進み、閾値未満であれば処理を終了する。
【００９９】
［ステップＳ５３］統計的撮像カメラ制御部５５は、予想広がりと撮像範囲の幅の比が１となるためのズーム値を算出する。制御コマンド送信部５６は、算出されたズーム値が、文字列を認識するための、最低限の性能を確保できる限界値以上であるか否かを判断する。限界値以上であれば、ステップＳ５４へ進み、限界値未満であれば、ステップＳ５５へ進む。
【０１００】
［ステップＳ５４］制御コマンド送信部５６は、限界値をズーム値として撮像カメラ５０へ送信する。撮像カメラ５０は、受信した限界値で、ズーム比率を可変する。
【０１０１】
［ステップＳ５５］制御コマンド送信部５６は、統計的撮像カメラ制御部５５が算出したズーム値を撮像カメラ５０へ送信する。撮像カメラ５０は、受信したズーム値に応じて、ズーム比率を可変する。これにより、撮像カメラ５０の撮像範囲外を移動する物体の文字列を認識することができる。
【０１０２】
［ステップＳ６１］文字列領域抽出部５２は、画像取り込み部５１が取り込んだ物体の画像データから、物体に記される文字列を抽出する。そして、文字列領域抽出部５２は、抽出した文字列の大きさと、文字列が撮像カメラ５０の撮像範囲を通過する通過位置を取得する。
【０１０３】
［ステップＳ６２］撮像カメラ制御部５３は、文字列領域抽出部５２が取得した文字列の通過位置が、撮像範囲の中央に位置するためのパン変更値を算出する。
【０１０４】
［ステップＳ６３］制御コマンド送信部５６は、撮像カメラ制御部５３が算出したパン変更値が、文字列を認識するための、最低限の性能を確保できる限界値以上であるか否かを判断する。限界値以上であれば、ステップＳ６４へ進み、限界値未満であれば、ステップＳ６５へ進む。
【０１０５】
［ステップＳ６４］制御コマンド送信部５６は、限界値をパン変更値として撮像カメラ５０へ送信する。撮像カメラ５０は、受信した限界値に応じて、パンを可変する。
【０１０６】
［ステップＳ６５］制御コマンド送信部５６は、撮像カメラ制御部５３が算出したパン変更値を撮像カメラ５０へ送信する。撮像カメラ５０は、受信したパン変更値に応じて、パンを可変する。これにより、撮像カメラ５０が撮像する物体の文字列は、撮像範囲の中央へ位置する。
【０１０７】
［ステップＳ６６］撮像カメラ制御部５３は、ステップＳ６１において文字列領域抽出部５２が取得した文字列の大きさが、予め登録されている、認識処理に適した大きさとなるためのズーム値を算出する。
【０１０８】
［ステップＳ６７］制御コマンド送信部５６は、撮像カメラ制御部５３が算出したズーム値が、限界値以上か否かを判断する。限界値以上であれば、ステップＳ６８へ進み、限界値未満であれば、ステップＳ６９へ進む。
【０１０９】
［ステップＳ６８］制御コマンド送信部５６は、限界値をズーム値として撮像カメラ５０へ送信する。撮像カメラ５０は、受信した限界値で、ズーム比率を可変する。
【０１１０】
［ステップＳ６９］制御コマンド送信部５６は、撮像カメラ制御部５３が算出したズーム値を撮像カメラ５０へ送信する。撮像カメラ５０は、受信したズーム値に応じて、ズーム比率を可変する。これにより、撮像カメラ５０が撮像する物体の文字列の大きさは、認識処理に適した大きさとなる。
【０１１１】
［ステップＳ７０］画像取り込み部５１は、撮像カメラ５０が撮像する物体を再度画像データとして取り込む。このとき、物体の文字列は、撮像範囲の中央で、認識処理に適切な大きさで取り込まれる。
【０１１２】
［ステップＳ７１］文字列認識処理部５７は、文字列領域抽出部５２が再び抽出する文字列の文字を、辞書ＤＢ５７ａに登録されている文字を参照して、認識する。
【０１１３】
このように、所定時間内における、撮像カメラ５０の撮像範囲を通過する物体の通過数に応じて処理を切替えることにより、認識対象となる文字列の通過数が少ない時間帯には、物体ごとにパン、ズーム比率を可変して認識処理させ、通過数が多い時間帯には、一定時間の通過数分布の統計からパン、ズーム比率を可変させて、状況に応じた最適な認識処理を行うことができ、常に高い認識率を維持して文字列を認識することができる。
【０１１４】
（付記１） 移動物体の文字列を認識する撮像装置において、
パン及びズーム比率が変更可能な撮像カメラと、
前記撮像カメラが撮像する移動物体の文字列を抽出し、前記文字列の大きさ及び前記撮像カメラの撮像範囲を通過する前記文字列の通過位置を取得する文字列抽出手段と、
前記文字列の通過位置を前記撮像範囲の中央に位置するように前記撮像カメラのパンを可変するパン可変手段と、
前記文字列の大きさを予め登録されている文字列認識処理に適した大きさとなるように前記撮像カメラのズーム比率を可変するズーム比率可変手段と、
前記ズーム比率又はパンが変更された前記撮像カメラによって撮像される前記文字列を認識処理する文字列認識手段と、
を有することを特徴とする撮像装置。
【０１１５】
（付記２） 一定時間、前記文字列抽出手段により取得された前記文字列の通過位置とその通過位置における通過数との統計を採り、前記文字列が前記撮像範囲を最も通過した最大通過位置と前記統計の標準偏差とを算出する統計手段と、
前記最大通過位置を前記撮像範囲の中央に位置するように前記撮像カメラのパンを可変する統計パン可変手段と、
前記標準偏差から前記撮像カメラの撮像範囲外を通過した文字列の予想通過位置を算出し、前記予想通過位置を前記撮像範囲の範囲内に納まるように前記撮像カメラのズーム比率を可変する統計ズーム比率可変手段と、
を有することを特徴とする付記１記載の撮像装置。
【０１１６】
（付記３） 前記文字列抽出手段は、所定時間内に前記物体が一定数以上前記撮像範囲を通過する場合に、前記統計ズーム比率可変手段と統計パン可変手段とに前記撮像カメラのズーム比率とパンの可変処理をさせることを特徴とする付記２記載の撮像装置。
【０１１７】
（付記４） 前記ズーム比率可変手段は、前記文字列認識手段が前記物体の文字列を認識した後に、前記撮像カメラの画角を広角にすることを特徴とする付記１記載の撮像装置。
【０１１８】
（付記５） 移動物体の文字列を認識する撮像装置において、
ズーム比率及びパンが変更可能な撮像カメラと、
前記撮像カメラが撮像する移動物体の文字列を抽出し、前記撮像カメラの撮像範囲を通過する前記文字列の通過位置を取得する文字列抽出手段と、
一定時間、前記文字列抽出手段が取得した前記文字列の通過位置とその通過位置における通過数との統計を採り、前記文字列が前記撮像範囲を最も通過した最大通過位置と前記統計の標準偏差とを算出する統計手段と、
前記最大通過位置を前記撮像範囲の中央に位置するように前記撮像カメラのパンを可変するパン可変手段と、
前記標準偏差から前記撮像カメラの撮像範囲外を通過した文字列の予想通過位置を算出し、前記予想通過位置を前記撮像範囲の範囲内に納まるように前記撮像カメラのズーム比率を可変するズーム比率可変手段と、
前記撮像カメラによって撮像される前記物体の文字列を認識処理する文字列認識手段と、
を有することを特徴とする撮像装置。
【０１１９】
（付記６） 前記パン可変手段は、前記文字列認識手段が前記文字列を認識できる範囲内でパンを可変することを特徴とする付記５記載の撮像装置。
（付記７） 前記ズーム比率可変手段は、前記文字列認識手段が前記文字列を認識できる範囲内でズーム比率を可変することを特徴とする付記５記載の撮像装置。
【０１２０】
（付記８） 前記パン可変手段は、前記最大通過位置が前記撮像範囲の中央から所定以上離れている場合に前記撮像カメラのパンを可変することを特徴とする付記５記載の撮像装置。
【０１２１】
（付記９） 前記ズーム比率可変手段は、前記予想通過位置の幅と前記撮像範囲の幅とが所定以上異なる場合に前記撮像カメラのズーム比率を可変することを特徴とする付記５記載の撮像装置。
【０１２２】
【発明の効果】
以上説明したように本発明では、文字列の大きさと撮像範囲を通過する文字列の通過位置とを取得して、文字列の通過位置が撮像範囲の中央に位置するように撮像カメラのパンを可変し、文字列の大きさが文字列認識処理に適した大きさとなるように撮像カメラのズーム比率を可変するようにした。また、文字列が撮像範囲を最も通過した最大通過位置と文字列が撮像範囲外を通過した予想通過位置とを算出して、文字列の最大通過位置が撮像範囲の中央に位置するように撮像カメラのパンを可変し、文字列の予想通過位置が撮像範囲に納まるように撮像カメラのズーム比率を可変するようにした。これにより、常に高い認識率を維持して、移動する物体の文字列を認識することができる。
【０１２３】
また、本発明では、文字列が撮像範囲を最も通過した最大通過位置と文字列が撮像範囲外を通過した予想通過位置とを算出して、文字列の最大通過位置が撮像範囲の中央に位置するように撮像カメラのパンを可変し、文字列の予想通過位置が撮像範囲に納まるように撮像カメラのズーム比率を可変するようにした。これにより、常に高い認識率を維持して、移動する物体の文字列を認識することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態に係る撮像装置の原理を説明する原理図である。
【図２】本発明の第１の実施の形態に係る撮像装置の機能ブロック図である。
【図３】図２の機能ブロック図の処理の一例を示すフローチャートである。
【図４】本発明の第２の実施の形態に係る撮像装置の原理を説明する原理図である。
【図５】本発明の第２の実施の形態に係る撮像装置の機能ブロック図である。
【図６】文字列の通過位置と通過数の分布の一例を示す図である。
【図７】パン変更値算出を説明する図である。
【図８】ズーム値算出を説明する図である。
【図９】ズームを引いたときの図８の分布の様子を示した図である。
【図１０】図５の機能ブロック図の処理の一例を示す第１のフローチャートである。
【図１１】図５の機能ブロック図の処理の一例を示す第２のフローチャートである。
【図１２】本発明の第３の実施の形態に係る撮像装置の機能ブロック図である。
【図１３】図１２の機能ブロック図の処理の一例を示す第１のフローチャートである。
【図１４】図１２の機能ブロック図の処理の一例を示す第２のフローチャートである。
【図１５】図１２の機能ブロック図の処理の一例を示す第３のフローチャートである。
【図１６】撮像装置の画角の大きさと認識率の一般的な関係を示した図である。
【図１７】文字列通過分布の一例を示した図である。
【符号の説明】
１，１０，２０，３０，５０ 撮像カメラ
２，２１ 文字列抽出手段
３，２３ パン可変手段
４，２４ ズーム比率可変手段
５，２５ 文字列認識手段
６，２６ａ，２６ｂ，２６ｃ 自動車
６ａ，２６ａａ，２６ｂａ，２６ｃａ 英数字文字列
１１，３１，５１ 画像取り込み部
１２，３２，５２ 文字列領域抽出部
１３，３４ パン可変部
１４，３５ ズーム比率可変部
１５，３６，５７ 文字列認識処理部
１５ａ，３６ａ，５７ａ 辞書ＤＢ
１６，３７，５６ 制御コマンド送信部
２２ 統計手段
３３，５４ 統計処理部
５３ 撮像カメラ制御部
５５ 統計的撮像カメラ制御部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus that recognizes a character string written on a moving object.
[0002]
[Prior art]
2. Description of the Related Art In recent years, an imaging apparatus has been developed that extracts and recognizes a character string written on a moving object, due to advances in image processing technology. For example, an apparatus for extracting and recognizing an alphanumeric character string written on a running car has been developed.
[0003]
In such an imaging apparatus, since the character string of the object existing within the imaging range of the imaging camera is extracted and the recognition process is performed, it is recognized that the character string to be recognized passes through the imaging range. Will be related to.
[0004]
FIG. 16 is a diagram illustrating a general relationship between the size of the angle of view of the imaging apparatus and the recognition rate. As shown in the figure, when the angle of view with respect to the character string to be recognized is increased, the imaging range becomes wider, but the character string to be recognized becomes smaller and the recognition rate decreases. Conversely, when the angle of view is reduced, the imaging range is narrowed, but the character string to be recognized increases and the recognition rate of the character string increases. Therefore, in order to ensure a stable recognition rate of the character string, it is necessary to capture an image with an optimum angle of view.
[0005]
FIG. 17 is a diagram illustrating an example of the character string passage distribution. The distribution 60 indicates the number of passages of the character string at the horizontal direction passing position when the character string to be recognized passes through the imaging range of the imaging camera 61 from top to bottom. Let α be the recognition rate of the character string with the total number of characters passing in the imaging range V1 as a parameter, and β be the recognition rate of the character string with the number of characters passing in the imaging range V2 as a parameter. In general, the recognition rate increases as the character string to be recognized passes through the centers of the imaging range V1 and the imaging range V2, and the relationship of α <β is established. However, in the case of the imaging range V2, the character string that has passed through the imaging ranges R1 and R2 that are outside the imaging range is not recognized and leads to a reduction in the recognition performance of the imaging apparatus. Therefore, when the character string roughly passes the imaging range V2, the imaging range needs to be the imaging range V2, and when the character string also passes the imaging ranges R1 and R2, the imaging range needs to be the imaging range V1.
[0006]
[Problems to be solved by the invention]
However, in the conventional imaging device, since the imaging range is fixed, the imaging range can be adjusted with respect to changes in the installation location and conditions of the imaging device, the passage position of a character string that occurs accidentally, and the like. There is a problem that the recognition rate of the character string may be lowered depending on the situation.
[0007]
The present invention has been made in view of these points, and an object of the present invention is to provide an imaging device that can always recognize a character string of a moving object while maintaining a high recognition rate.
[0008]
[Means for Solving the Problems]
  In the present invention, in order to solve the above problems, in an imaging apparatus that recognizes a character string of a moving object, an imaging camera capable of changing a pan and zoom ratio, and a character string of a moving object captured by the imaging camera are extracted. Character string extraction means for acquiring the size of the character string and the passage position of the character string passing through the imaging range of the imaging camera, and the imaging so that the passage position of the character string is located at the center of the imaging range Pan variable means for varying the pan of the camera, zoom ratio variable means for varying the zoom ratio of the imaging camera so that the size of the character string is suitable for a character string recognition process registered in advance, The zoom ratio orSaidCharacter string recognition means for recognizing the character string imaged by the imaging camera whose pan has been changed,The statistics of the passage position of the character string acquired by the character string extraction means and the number of passages at the passage position are taken for a certain period of time, the maximum passage position where the character string has passed the imaging range most and the standard of the statistics Statistical means for calculating a deviation, statistical pan variable means for varying the pan of the imaging camera so that the maximum passage position is located at the center of the imaging range, and outside the imaging range of the imaging camera from the standard deviation Statistical zoom ratio variable means for calculating an expected passage position of the passed character string and varying the zoom ratio of the imaging camera so that the expected passage position falls within the imaging range;There is provided an imaging device characterized by comprising:
[0009]
  In such an imaging apparatus, the size of the character string and the passage position of the character string passing through the imaging range are acquired, and the pan of the imaging camera is varied so that the passage position of the character string is located at the center of the imaging range. The zoom ratio of the imaging camera is varied so that the character string has a size suitable for the character string recognition process. Also, the maximum passage position where the character string has passed most of the imaging range and the expected passage position where the character string has passed outside the imaging range are calculated, and imaging is performed so that the maximum passage position of the character string is located at the center of the imaging range. The camera pan is varied, and the zoom ratio of the imaging camera is varied so that the expected passage position of the character string is within the imaging range. As a result, the character string of the moving object is recognized while always maintaining a high recognition rate.
[0010]
According to the present invention, in an imaging apparatus that recognizes a character string of a moving object, an imaging camera capable of changing a zoom ratio and pan, a character string of a moving object captured by the imaging camera is extracted, and an imaging range of the imaging camera A character string extracting means for acquiring a passage position of the character string passing through the character string, and taking statistics of the passage position of the character string obtained by the character string extraction means and the number of passages at the passage position for a certain period of time, Statistical means for calculating a maximum passage position through which the column has passed most of the imaging range and a standard deviation of the statistics, and a pan for varying the pan of the imaging camera so that the maximum passage position is located at the center of the imaging range The variable means calculates the expected passage position of the character string that has passed outside the imaging range of the imaging camera from the standard deviation, and the previous passage position is within the imaging range so as to be within the range of the imaging range. A zoom ratio varying means for varying the zoom ratio of the imaging camera, a character string recognizing means for recognizing handle strings of the object to be imaged by the imaging camera, an imaging apparatus characterized by having a are provided.
[0011]
In such an imaging device, the maximum passage position where the character string has passed most of the imaging range and the expected passage position where the character string has passed outside the imaging range are calculated, and the maximum passage position of the character string is at the center of the imaging range. The pan of the imaging camera is varied so as to be positioned, and the zoom ratio of the imaging camera is varied so that the expected passage position of the character string is within the imaging range. As a result, the character string of the moving object is recognized while always maintaining a high recognition rate.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a principle diagram for explaining the principle of the imaging apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the imaging apparatus includes an imaging camera 1, a character string extraction unit 2, a pan variable unit 3, a zoom ratio variable unit 4, and a character string recognition unit 5. It is assumed that the imaging device images the automobile 6 as a moving object and recognizes an alphanumeric character string 6a written on the automobile 6 as a character string written on the object. The imaging ranges 7a to 7c indicate ranges in which an object of the imaging camera 1 can be imaged.
[0013]
The imaging camera 1 is an imaging camera that can change the zoom ratio and pan.
The character string extraction means 2 extracts an alphanumeric character string 6a recorded on the automobile 6 that is imaged by the imaging camera 1, and the size of the alphanumeric character string 6a and the imaging range of the imaging camera 1 of the alphanumeric character string 6a. And the passing position passing through.
[0014]
The pan variable means 3 changes the pan of the imaging camera 1 so that the passage position of the alphanumeric character string 6a acquired by the character string extraction means 2 is positioned at the center of the imaging range.
The zoom ratio variable means 4 is an imaging camera so that the size of the alphanumeric character string 6a acquired by the character string extraction means 2 becomes a size suitable for the recognition processing of the alphanumeric character string 6a registered in advance. The zoom ratio of 1 is varied.
[0015]
The character string recognizing means 5 recognizes an alphanumeric character string 6a that is picked up again by the imaging camera 1 whose zoom ratio or pan is changed by the pan variable means 3 and zoom ratio variable means 4.
[0016]
The operation of the principle diagram will be described below.
First, the imaging camera 1 images the automobile 6. The character string extraction means 2 extracts the alphanumeric character string 6a of the automobile 6 imaged by the imaging camera 1, and passes through the size of the alphanumeric character string 6a and the imaging range of the imaging camera 1 of the alphanumeric character string 6a. Get position and. Here, as shown in the imaging range 7a, the passage position of the alphanumeric character string 6a in the imaging range passes to the right from the center.
[0017]
The pan variable means 3 changes the pan of the imaging camera 1 so that the passage position of the alphanumeric character string 6a acquired by the character string extraction means 2 is positioned at the center of the imaging range as shown in the imaging range 7b. .
[0018]
The zoom ratio varying unit 4 appropriately recognizes the alphanumeric character string 6a registered in advance so that the size of the alphanumeric character string 6a acquired by the character string extracting unit 2 is indicated by the imaging range 7c. The zoom ratio is varied so as to be the size.
[0019]
The character string recognizing means 5 recognizes the alphanumeric character string 6a captured again by the imaging camera 1 whose zoom ratio and pan are changed as shown in the imaging range 7c.
Thereby, for example, even when an automobile travels by changing a plurality of lanes or when changing lanes to avoid obstacles on the road, the imaging device changes the pan and zoom ratio of the imaging camera. Then, the alphanumeric character string 6a of the automobile 6 is recognized in an appropriate state. Therefore, it is possible to always recognize the alphanumeric character string 6a written on the automobile while maintaining a high recognition rate.
[0020]
FIG. 2 is a functional block diagram of the imaging apparatus according to the first embodiment of the present invention. As shown in the figure, an imaging device that captures a character string recorded on a moving object in an appropriate state includes an imaging camera 10, an image capturing unit 11, a character string region extracting unit 12, a pan variable unit 13, and a zoom ratio. A variable unit 14, a character string recognition processing unit 15, a dictionary DB (DB) 15 a, and a control command transmission unit 16 are included.
[0021]
The imaging camera 10 is an imaging camera that can change the pan and zoom ratio.
The image capturing unit 11 captures an object imaged by the imaging camera 10 as image data.
[0022]
The character string region extraction unit 12 analyzes the image data captured by the image capturing unit 11 to extract a character string written on the object, and acquires the size of the character string. Further, the object acquires the passing position in the horizontal direction of the imaging range of the imaging camera 10. Here, it is assumed that the position of the character string written on the object is roughly determined for any object, and the position of the character string of the object can be predicted and extracted from the captured image data of the object.
[0023]
The pan variable unit 13 calculates a pan change value for varying the pan of the imaging camera 10 so that the passage position of the character string acquired by the character string region extraction unit 12 is positioned at the center in the horizontal direction of the imaging range. To do.
[0024]
The zoom ratio variable unit 14 varies the zoom ratio of the imaging camera 10 so that the size of the character string acquired by the character string region extraction unit 12 becomes a size that is registered in advance and is suitable for character string recognition processing. The zoom value for calculating the image is calculated.
[0025]
The character string recognition processing unit 15 performs character string recognition processing of an object that is imaged again by the imaging camera 10 after the pan or zoom ratio is changed. The character string recognition processing unit 15 refers to and compares characters in the character string with characters registered in the dictionary DB 15a, and recognizes the most matched character as the character written on the object.
[0026]
The control command transmission unit 16 transmits the pan change value calculated by the pan variable unit 13 and the zoom value calculated by the zoom ratio variable unit 14 to the imaging camera 10. Further, the control command transmission unit 16 holds a limit value that can ensure a minimum performance for recognizing a character string regarding the pan change value and the zoom value. When receiving the pan change value and zoom value exceeding the limit value, the control command transmission unit 16 transmits the held limit value to the imaging camera 10 as the pan change value and zoom value. Here, the minimum performance for recognizing the character string is, for example, when imaging a car, it is only necessary to change the pan and zoom ratio within the range of the road width through which the car passes. This means that the ability to change the zoom is unnecessary.
[0027]
Hereinafter, an example of the processing of the functional block diagram of FIG. 2 will be described using a flowchart.
FIG. 3 is a flowchart illustrating an example of processing of the functional block diagram of FIG.
[0028]
[Step S1] The image capturing unit 11 captures an object imaged by the imaging camera 10 as image data.
[Step S2] The character string region extraction unit 12 extracts a character string written on the object from the image data of the object captured by the image capturing unit 11. Then, the character string area extraction unit 12 acquires the size of the extracted character string and the passing position in the horizontal direction of the imaging range of the imaging camera 10 of the character string.
[0029]
[Step S3] The pan variable unit 13 calculates a pan change value for the passage position of the character string acquired by the character string region extraction unit 12 to be located at the center in the horizontal direction of the imaging range.
[0030]
[Step S4] The control command transmission unit 16 determines whether or not the pan change value calculated by the pan variable unit 13 is equal to or greater than a limit value that can ensure a minimum performance for recognizing the character string. If it is not less than the limit value, the process proceeds to step S5, and if it is less than the limit value, the process proceeds to step S6.
[0031]
[Step S5] The control command transmitter 16 transmits the limit value to the imaging camera 10 as a pan change value. The imaging camera 10 varies the pan according to the received limit value.
[Step S <b> 6] The control command transmission unit 16 transmits the pan change value calculated by the pan variable unit 13 to the imaging camera 10. The imaging camera 10 varies the pan in accordance with the received pan change value. Thereby, the character string of the object imaged by the imaging camera 10 is located at the center of the imaging range.
[0032]
[Step S7] The zoom ratio variable unit 14 sets the size of the character string acquired by the character string region extraction unit 12 in step S2 to a pre-registered zoom value suitable for the character string recognition process. Is calculated.
[0033]
[Step S8] The control command transmission unit 16 determines whether or not the zoom value calculated by the zoom ratio variable unit 14 is equal to or greater than a limit value that can ensure a minimum performance for recognizing a character string. If it is equal to or greater than the limit value, the process proceeds to step S9, and if it is less than the limit value, the process proceeds to step S10.
[0034]
[Step S9] The control command transmitter 16 transmits the limit value to the imaging camera 10 as a zoom value. The imaging camera 10 varies the zoom ratio according to the received limit value.
[0035]
[Step S <b> 10] The control command transmission unit 16 transmits the zoom value calculated by the zoom ratio variable unit 14 to the imaging camera 10. The imaging camera 10 varies the zoom ratio according to the received zoom value. Thereby, the size of the character string of the object imaged by the imaging camera 10 becomes a size suitable for recognition processing.
[0036]
[Step S11] The image capture unit 11 captures an object captured by the imaging camera 10 as image data again. At this time, the character string of the object is captured at an appropriate size for the recognition process at the center of the imaging range.
[0037]
[Step S12] The character string recognition processing unit 15 recognizes characters of the character string extracted again by the character string region extraction unit 12 with reference to the characters registered in the dictionary DB 15a.
[0038]
In this way, the object is tracked one by one, the pan is changed so that the character string of the object is located in the center of the imaging range, and the zoom ratio is changed to a size that can appropriately execute the recognition process. A character string of a moving object can be recognized while always maintaining a high recognition rate.
[0039]
Note that the zoom ratio variable unit 14 may subtract the zoom ratio of the imaging camera 10 (make the angle of view wide) after the character string recognition processing of the character string recognition processing unit 15 is completed. Thereby, the angle of view of the imaging camera 10 is widened, and it becomes easy to capture the image data of the object before the pan / zoom ratio is changed.
[0040]
Next, a second embodiment of the present invention will be described.
FIG. 4 is a principle diagram for explaining the principle of the imaging apparatus according to the second embodiment of the present invention. As shown in FIG. 4, the imaging apparatus includes an imaging camera 20, a character string extraction unit 21, a statistical unit 22, a pan variable unit 23, a zoom ratio variable unit 24, and a character string recognition unit 25. The imaging device images automobiles 26a, 26b, 26c,... As moving objects, and alphanumeric character strings 26aa, 26ba, 26ca,. It is assumed that specific alphanumeric characters are omitted in the figure. Distributions 27a to 27c indicate the passage positions of the alphanumeric character strings in the horizontal direction of the imaging range of the imaging camera 20 and the number of passages of the alphanumeric character strings at the passage positions.
[0041]
The imaging camera 20 is an imaging camera that can change the zoom ratio and pan.
The character string extraction unit 21 extracts an alphanumeric character string of the automobile imaged by the imaging camera 20, and acquires a passing position of the alphanumeric character string in the horizontal direction of the imaging range.
[0042]
The statistical means 22 takes statistics of the passage position of the alphanumeric character string in the horizontal direction of the imaging range and the number of passages at the passage position for a certain time.
The pan variable means 23 calculates the maximum passage position through which the alphanumeric character string has passed most from the statistics taken by the statistics means 22, and pans the imaging camera 20 so that the maximum passage position is located at the center of the imaging range. Variable.
[0043]
The zoom ratio variable unit 24 calculates the predicted passing position of the alphanumeric character string that has passed outside the imaging range of the imaging camera 20 from the standard deviation of the statistics taken by the statistical unit 22, and the expected passing position falls within the imaging range. As described above, the zoom ratio of the imaging camera 20 is varied.
[0044]
The character string recognizing means 25 recognizes the alphanumeric character string extracted by the character string extracting means 21 when the imaging camera 20 images the automobile.
The operation of the principle diagram will be described below.
[0045]
The character string extraction unit 21 extracts an alphanumeric character string of the automobile imaged by the imaging camera 20 and acquires a passing position of the alphanumeric character string in the horizontal direction of the imaging range of the imaging camera 20.
[0046]
The statistical means 22 takes statistics of the passage position of the alphanumeric character string passing through the horizontal direction of the imaging range and the number of passages at the passage position for a certain period of time. Accordingly, it is assumed that the passage positions and the passage numbers of the alphanumeric character strings are distributed as shown in the distribution 27a. From the distribution 27a, it can be seen that the alphanumeric character string passes more to the right than the center of the imaging range.
[0047]
The pan variable means 23 calculates the maximum passing position through which the alphanumeric character string has passed most from the distribution 27a, and the imaging camera 20 so that the maximum passing position is located at the center of the imaging range as shown in the distribution 27b. Variable bread.
[0048]
The zoom ratio variable unit 24 calculates the predicted passage position of the alphanumeric character string that has passed outside the imaging range 27b from the standard deviation of the statistics taken by the statistical unit 22, so that the expected passage position falls within the imaging range. In addition, the zoom ratio of the imaging camera 20 is varied. In the example of FIG. 4, both ends (predicted passage positions) of the distribution 27b are predicted from the standard deviation, and as shown in the distribution 27c, the zoom is pulled so that the entire distribution including the predicted passage positions falls within the imaging range. .
[0049]
The character string recognizing means 25 recognizes an alphanumeric character string of the automobile imaged by the imaging camera 20.
In this way, from the passing position of the alphanumeric character string of the car and the distribution of the number of passing at that passing position, the passing situation and change of the car for every fixed time are determined, the pan and zoom ratio of the imaging camera is changed, and the appropriate Recognize alphanumeric strings in the correct state. Therefore, it is possible to always recognize the alphanumeric character string of the automobile while maintaining a high recognition rate.
[0050]
FIG. 5 is a functional block diagram of an imaging apparatus according to the second embodiment of the present invention. As shown in the figure, an imaging device that captures a character string recorded on a moving object in an appropriate state includes an imaging camera 30, an image capturing unit 31, a character string region extracting unit 32, a statistical processing unit 33, and a variable pan. Section 34, zoom ratio variable section 35, character string recognition processing section 36, dictionary DB 36a, and control command transmission section 37.
[0051]
The imaging camera 30 is an imaging camera that can change the pan and zoom ratio.
The image capturing unit 31 captures an object imaged by the imaging camera 30 as image data.
[0052]
The character string region extracting unit 32 analyzes the image data captured by the image capturing unit 31 to extract a character string recorded on the object, and the passage position of the character string passing through the imaging range of the imaging camera 30 To get.
[0053]
The statistical processing unit 33 takes statistics of the passage position of the character string acquired by the character string region extraction unit 32 during a certain period of time and the number of passages of the character string at the passage position. Then, the maximum passage position with the largest number of passages of the character string and the standard deviation of the distribution are calculated. FIG. 6 is a diagram illustrating an example of the distribution of the passage position and the passage number of the character string. The horizontal axis represents the passage position of the character string in the horizontal direction of the imaging range of the imaging camera 30, and the vertical axis represents the number of passages of the character string at the passage position. The function represented by the distribution in FIG. 6 is h (X), and the position where the character string to be recognized passes most in the imaging range is the peak value Xpeak. The peak value Xpeak is expressed by the following formula (1).
[0054]
[Expression 1]

[0055]
Further, the standard deviation σ of the distribution shown in FIG. 6 is expressed by the following formula (2).
[0056]
[Expression 2]

[0057]
The statistical processing unit 33 calculates the peak value Xpeak, which is the position through which the character string in the imaging range passes most, using Equation (1), and calculates the standard deviation σ of the distribution using Equation (2).
[0058]
The pan variable unit 34 calculates the pan change value so that the peak value calculated by the statistical processing unit 33 becomes the center value of the imaging range. Note that the peak value fluctuates according to the passage state of the character string, and in order to prevent a recognition rate from being lowered due to an excessive pan change of the imaging camera 30 according to the fluctuation of the peak value, the pan variable unit 34 A threshold value is set and held in the width of the center value and the peak value of the image, and the pan change value is calculated only when the width of the value of the center value and the peak value of the imaging range exceeds the threshold value.
[0059]
FIG. 7 is a diagram for explaining pan change value calculation. The vertical line shown in the imaging range 40 shown in the drawing indicates the trajectory from when the character string of the object moving toward the imaging camera 30 enters the imaging range 40 until it exits the imaging range. The direction of the locus is from the top to the bottom of the imaging range. It shows that many character strings passed, so that the density of a locus | trajectory is high. The distribution 41 is a distribution indicating the number of passages of the character string at each passage position in the imaging range 40. The pan variable unit 34 calculates a pan change value that varies the pan of the imaging camera 30 so that the peak value Xpeak in the distribution 41 becomes the center value of the imaging range 40.
[0060]
The zoom ratio variable unit 35 predicts the passage position of the character string that passes outside the imaging range from the standard deviation σ, and calculates a zoom value for allowing the character string that passes outside the imaging range to also enter the imaging range. To do.
[0061]
FIG. 8 is a diagram for explaining the calculation of the zoom value. The vertical line shown in the imaging range 42 shown in the figure indicates the trajectory from when the character string of the object moving toward the imaging camera 30 enters the imaging range 42 until it exits the imaging range. A distribution 43 indicates the number of passages of the character string at each passing position in the horizontal direction of the imaging range 42. Distributions 44 a and 44 b indicate the expected distribution of character strings that pass outside the imaging range 42. The character strings shown in the distributions 44a and 44b are outside the imaging range 42 and are not recognized. Therefore, the zoom ratio variable unit 35 calculates an expected spread D of the distribution 43 (a distribution obtained by adding the distributions 44a and 44b to the distribution 43) from the standard deviation σ. The expected spread D is expressed by the following equation (3).
[0062]
[Equation 3]

[0063]
In general, when m in the expression (3) is 3, an expected spread of about 99% with respect to the expected spread D is obtained. In the following description, m is assumed to be 3.
The zoom ratio variable unit 35 calculates a zoom value such that the ratio between the value of the expected spread D obtained from Expression (3) and the value of the width in the horizontal direction of the imaging range 42 is 1. In the example of FIG. 8, in order for the ratio between the value of the expected spread D and the value of the width of the imaging range 42 in the horizontal direction to be 1, a zoom value for subtracting the zoom of the imaging camera 30 is calculated. FIG. 9 is a diagram showing the distribution of FIG. 8 when the zoom is pulled. As shown in FIG. 9, distributions 44 a and 44 b in which a character string is expected to pass are included in the range of the imaging range 42. As a result, a character string that has passed outside the imaging range 42 can also be recognized. The standard deviation σ varies according to the passage state of the character string, and the zoom ratio variable unit 35 is configured to prevent a recognition rate from being lowered due to an excessive zoom change of the imaging camera 30 according to the variation of the standard deviation σ. A threshold value is set and held in the ratio between the expected spread D and the width of the imaging range, and the zoom value is calculated only when the threshold value is exceeded.
[0064]
The character string recognition processing unit 36 performs recognition processing for the character string extracted by the character string region extraction unit 32. The character string recognition processing unit 36 refers to and compares characters in the character string with characters registered in the dictionary DB 36a, and recognizes the most matched character as the character written on the object.
[0065]
The control command transmission unit 37 transmits the pan change value calculated by the pan variable unit 34 and the zoom value calculated by the zoom ratio variable unit 35 to the imaging camera 30. In addition, the control command transmission unit 37 holds a limit value that can ensure a minimum performance for recognizing a character string regarding the pan change value and the zoom value. When receiving the pan change value and zoom value that exceed the limit value, the control command transmission unit 37 transmits the limit value as the pan change value and zoom value to the imaging camera 30. Here, the minimum performance for recognizing the character string is such that, for example, the ratio of the expected spread D and the horizontal width of the imaging range 42 is 1 in the zoom ratio variable unit 35. Even if the zoom is pulled, the zoom is pulled within the range where the character string can be recognized. In addition, panning is changed within a range where the character string can be recognized.
[0066]
Hereinafter, an example of the process of the functional block diagram of FIG. 5 will be described using a flowchart.
10 and 11 are flowcharts showing an example of the processing of the functional block diagram of FIG.
[0067]
[Step S21] The image capturing unit 31 captures an object captured by the imaging camera 30 as image data.
[Step S22] The character string region extraction unit 32 extracts a character string written in the object from the image data of the object captured by the image capturing unit 31. Then, the passage position of the extracted character string in the horizontal direction of the imaging range of the imaging camera 30 is acquired.
[0068]
[Step S23] The character string recognition processing unit 36 recognizes the character string extracted by the character string region extraction unit 32 with reference to the dictionary DB 36a.
[Step S24] The statistical processing unit 33 takes statistics of the passage position of the character string acquired by the character string region extraction unit 32 and the number of passages of the character string at the passage position.
[0069]
[Step S25] The statistical processing unit 33 determines whether or not a predetermined time has elapsed. If the predetermined time has elapsed, the process proceeds to step S26. If the fixed time has not elapsed, the process proceeds to step S21.
[0070]
[Step S26] The statistical processing unit 33 calculates the peak value, which is the passage position with the largest number of passages of the character string, and the standard deviation of the passage position of the character string and the distribution of the passage number at the passage position.
[0071]
[Step S27] The pan variable unit 34 calculates a pan change value for the peak value calculated by the statistical processing unit 33 to be the center value of the imaging range. Then, it is determined whether or not the width of the center value and the peak value of the imaging range is equal to or greater than a threshold value. If it is equal to or greater than the threshold, the process proceeds to step S28, and if it is less than the threshold, the process proceeds to step S31.
[0072]
[Step S28] The control command transmission unit 37 determines whether or not the pan change value calculated by the pan variable unit 34 is equal to or greater than a limit value that can ensure the minimum performance for recognizing the character string. If it is equal to or greater than the limit value, the process proceeds to step S29, and if it is less than the limit value, the process proceeds to step S30.
[0073]
[Step S29] The control command transmission unit 37 transmits the limit value to the imaging camera 30 as the pan change value. The imaging camera 30 varies the pan with the received limit value.
[0074]
[Step S <b> 30] The control command transmission unit 37 transmits the pan change value calculated by the pan variable unit 34 to the imaging camera 30. The imaging camera 30 varies the pan in accordance with the received pan change value. Thereby, the passage position with the largest number of passages of the character string imaged by the imaging camera 30 is located at the center of the imaging range.
[0075]
[Step S31] The zoom ratio variable unit 35 calculates the expected spread of the distribution from the standard deviation calculated by the statistical processing unit 33. Then, it is determined whether or not the ratio between the expected spread and the width of the imaging range is equal to or greater than a threshold value. If it is equal to or greater than the threshold value, the process proceeds to step S32, and if it is less than the threshold value, the process ends.
[0076]
[Step S32] The zoom ratio variable unit 35 calculates a zoom value for the ratio of the expected spread and the width of the imaging range to be 1. The control command transmission unit 37 determines whether or not the calculated zoom value is equal to or greater than a limit value that can ensure the minimum performance for recognizing the character string. If it is not less than the limit value, the process proceeds to step S33, and if it is less than the limit value, the process proceeds to step S34.
[0077]
[Step S33] The control command transmission unit 37 transmits the limit value to the imaging camera 30 as a zoom value. The imaging camera 30 varies the zoom ratio with the received limit value.
[0078]
[Step S <b> 34] The control command transmission unit 37 transmits the zoom value calculated by the zoom ratio variable unit 35 to the imaging camera 30. The imaging camera 30 varies the zoom ratio according to the received zoom value. Thereby, the character string of the object moving outside the imaging range of the imaging camera 30 can be recognized.
[0079]
In this way, the distribution statistics of the passage position and the number of passages of the object are taken, the passage position with the largest number of passages is calculated from the distribution statistics, and the pan is changed so that the passage position is located at the center of the imaging range. . In addition, since the zoom ratio is changed to a size that allows the authentication process to be appropriately executed, it is possible to always recognize a character string of a moving object while maintaining a high recognition rate.
[0080]
Next, a third embodiment of the present invention will be described.
FIG. 12 is a functional block diagram of an imaging apparatus according to the third embodiment of the present invention. As shown in the figure, an imaging device that captures and recognizes a character string recorded on a moving object includes an imaging camera 50, an image capturing unit 51, a character string region extraction unit 52, an imaging camera control unit 53, and a statistical processing unit. 54, a statistical imaging camera control unit 55, a control command transmission unit 56, a character string recognition processing unit 57, and a dictionary DB 57a.
[0081]
The imaging camera 50 is an imaging camera that can change the pan and zoom ratio.
The image capturing unit 51 captures an object imaged by the imaging camera 50 as image data.
[0082]
The character string region extraction unit 52 counts the number of passages that the object has passed through the imaging range of the imaging camera 50 for a predetermined time, and determines whether or not it is equal to or greater than a preset threshold value for the number of passages. When the number of passages is equal to or greater than the threshold value, the image capturing unit 51 analyzes the captured image data to extract a character string written on the object, and notifies the statistical processing unit 54 of the passage position of the character string. If it is less than the threshold, the imaging camera control unit 53 is notified of the size and passage position of the character string.
[0083]
The imaging camera control unit 53 has the same functions as the pan variable unit 13 and the zoom ratio variable unit 14 in the functional block diagram of FIG. 2 described in the first embodiment. That is, the imaging camera control unit 53 calculates a pan change value for changing the pan of the imaging camera 50 so that the passage position of the character string acquired by the character string region extraction unit 52 is located at the center of the imaging range. To do. In addition, a zoom value for varying the zoom ratio of the imaging camera 50 is calculated so that the size of the character string acquired by the character string region extraction unit 52 becomes a size that is registered in advance and is suitable for the recognition process. .
[0084]
The statistical processing unit 54 has the same function as the statistical processing unit 33 in the functional block diagram of FIG. 2 described in the second embodiment. That is, the peak value Xpeak, which is the position through which the character string in the imaging range has passed most, is calculated according to equation (1), and the standard deviation σ of the distribution is calculated according to equation (2).
[0085]
The statistical imaging camera control unit 55 has a function including the pan variable unit 34 and the zoom ratio variable unit 35 in the functional block diagram of FIG. 2 described in the second embodiment. That is, the pan change value is calculated so that the peak value calculated by the statistical processing unit 54 becomes the center value of the imaging range. Further, the expected spread of the passage position of the character string passing outside the imaging range is calculated from the standard deviation value calculated by the statistical processing unit 54, and the ratio between the expected spread width and the imaging range width is 1. Calculate the zoom value.
[0086]
The control command transmission unit 56 transmits the pan change value and the zoom value calculated by the imaging camera control unit 53 to the imaging camera 50. Further, the pan change value and the zoom value calculated by the statistical imaging camera control unit 55 are transmitted to the imaging camera 50.
[0087]
When the character string is processed by the imaging camera control unit 53, the character string recognition processing unit 57 extracts the character string extracted by the character string region extraction unit 52 after the pan or zoom ratio of the imaging camera 50 is changed. Perform recognition processing. When the character string is processed by the statistical imaging camera control unit 55, the character string extracted by the character string region extraction unit 52 is recognized each time. The character string recognition processing unit 57 recognizes characters in the character string with reference to characters registered in the dictionary DB 57a.
[0088]
Hereinafter, an example of the process of the functional block diagram of FIG. 12 will be described using a flowchart.
FIGS. 13, 14 and 15 are flowcharts showing an example of the processing of the functional block diagram of FIG.
[0089]
[Step S41] The image capturing unit 51 captures an object imaged by the imaging camera 50 as image data.
[Step S42] The character string region extraction unit 52 determines whether or not the number of passages of the character string imaging range within a predetermined time is equal to or greater than a threshold value. If it is equal to or greater than the threshold, the process proceeds to step S43, and if it is less than the threshold, the process proceeds to step S61.
[0090]
[Step S43] The character string region extraction unit 52 extracts a character string written in the object from the image data of the object captured by the image capturing unit 51. Then, the passage position of the extracted character string passing through the imaging range of the imaging camera 50 is acquired.
[0091]
[Step S44] The character string recognition processing unit 57 recognizes the character string extracted by the character string region extraction unit 52 with reference to the dictionary DB 57a.
[Step S45] The statistical processing unit 54 takes statistics of the passage position of the character string acquired by the character string region extraction unit 52 and the number of passages of the character string at the passage position.
[0092]
[Step S46] The statistical processing unit 54 determines whether or not a predetermined time has elapsed. If the predetermined time has elapsed, the process proceeds to step S47. If the predetermined time has not elapsed, the process proceeds to step S41.
[0093]
[Step S47] The statistical processing unit 54 calculates a peak value that is the passage position with the largest number of passages of the character string, and a standard deviation of the passage position of the character string and the distribution of the passage number at the passage position.
[0094]
[Step S48] The statistical imaging camera control unit 55 calculates the pan change value so that the peak value calculated by the statistical processing unit 54 becomes the center value of the imaging range. Then, it is determined whether or not the width of the center value and the peak value of the imaging range is equal to or greater than a threshold value. If it is greater than or equal to the threshold, the process proceeds to step S49, and if less than the threshold, the process proceeds to step S52.
[0095]
[Step S49] The control command transmission unit 56 determines whether or not the pan change value calculated by the statistical imaging camera control unit 55 is equal to or greater than a limit value that can ensure a minimum performance for recognizing the character string. to decide. If it is not less than the limit value, the process proceeds to step S50, and if it is less than the limit value, the process proceeds to step S51.
[0096]
[Step S50] The control command transmission unit 56 transmits the limit value to the imaging camera 50 as a pan change value. The imaging camera 50 varies the pan with the received limit value.
[0097]
[Step S51] The control command transmission unit 56 transmits the pan change value calculated by the statistical imaging camera control unit 55 to the imaging camera 50. The imaging camera 50 varies the pan in accordance with the received pan change value. Thereby, the passage position with the largest number of passages of the character string imaged by the imaging camera 50 is located at the center of the imaging range.
[0098]
[Step S52] The statistical imaging camera control unit 55 calculates the expected spread of the distribution from the standard deviation calculated by the statistical processing unit 54. Then, it is determined whether or not the ratio between the expected spread and the width of the imaging range is equal to or greater than a threshold value. If it is equal to or greater than the threshold value, the process proceeds to step S53, and if it is less than the threshold value, the process ends.
[0099]
[Step S53] The statistical imaging camera control unit 55 calculates a zoom value for the ratio of the expected spread to the width of the imaging range to be 1. The control command transmission unit 56 determines whether or not the calculated zoom value is equal to or greater than a limit value that can ensure the minimum performance for recognizing the character string. If it is equal to or greater than the limit value, the process proceeds to step S54, and if it is less than the limit value, the process proceeds to step S55.
[0100]
[Step S54] The control command transmitter 56 transmits the limit value to the imaging camera 50 as a zoom value. The imaging camera 50 varies the zoom ratio with the received limit value.
[0101]
[Step S55] The control command transmission unit 56 transmits the zoom value calculated by the statistical imaging camera control unit 55 to the imaging camera 50. The imaging camera 50 varies the zoom ratio according to the received zoom value. Thereby, the character string of the object moving outside the imaging range of the imaging camera 50 can be recognized.
[0102]
[Step S61] The character string region extraction unit 52 extracts a character string written on the object from the image data of the object captured by the image capturing unit 51. Then, the character string area extraction unit 52 acquires the size of the extracted character string and the passage position where the character string passes through the imaging range of the imaging camera 50.
[0103]
[Step S62] The imaging camera control unit 53 calculates a pan change value for the passage position of the character string acquired by the character string region extraction unit 52 to be located at the center of the imaging range.
[0104]
[Step S63] The control command transmission unit 56 determines whether or not the pan change value calculated by the imaging camera control unit 53 is equal to or greater than a limit value that can ensure a minimum performance for recognizing the character string. . If it is equal to or greater than the limit value, the process proceeds to step S64, and if it is less than the limit value, the process proceeds to step S65.
[0105]
[Step S64] The control command transmitter 56 transmits the limit value to the imaging camera 50 as a pan change value. The imaging camera 50 varies the pan according to the received limit value.
[0106]
[Step S <b> 65] The control command transmission unit 56 transmits the pan change value calculated by the imaging camera control unit 53 to the imaging camera 50. The imaging camera 50 varies the pan in accordance with the received pan change value. Thereby, the character string of the object imaged by the imaging camera 50 is located at the center of the imaging range.
[0107]
[Step S66] The imaging camera control unit 53 calculates a zoom value so that the size of the character string acquired by the character string region extraction unit 52 in step S61 is registered in advance and becomes a size suitable for recognition processing. To do.
[0108]
[Step S67] The control command transmission unit 56 determines whether or not the zoom value calculated by the imaging camera control unit 53 is greater than or equal to a limit value. If it is equal to or greater than the limit value, the process proceeds to step S68, and if it is less than the limit value, the process proceeds to step S69.
[0109]
[Step S68] The control command transmitter 56 transmits the limit value to the imaging camera 50 as a zoom value. The imaging camera 50 varies the zoom ratio with the received limit value.
[0110]
[Step S <b> 69] The control command transmission unit 56 transmits the zoom value calculated by the imaging camera control unit 53 to the imaging camera 50. The imaging camera 50 varies the zoom ratio according to the received zoom value. Thereby, the size of the character string of the object imaged by the imaging camera 50 becomes a size suitable for recognition processing.
[0111]
[Step S <b> 70] The image capturing unit 51 captures again an object imaged by the imaging camera 50 as image data. At this time, the character string of the object is captured at an appropriate size for the recognition process at the center of the imaging range.
[0112]
[Step S71] The character string recognition processing unit 57 recognizes the characters of the character string extracted again by the character string region extraction unit 52 with reference to the characters registered in the dictionary DB 57a.
[0113]
In this way, by switching the processing according to the number of passages of the object passing through the imaging range of the imaging camera 50 within a predetermined time, for each object in a time zone where the number of passages of the character string to be recognized is small, Perform recognition processing with variable pan and zoom ratios, and perform optimal recognition processing according to the situation by varying the pan and zoom ratios based on statistics of the distribution of the number of passages over a certain period of time during times when there are many passes. And can always recognize a character string while maintaining a high recognition rate.
[0114]
(Supplementary Note 1) In an imaging device that recognizes a character string of a moving object,
An imaging camera capable of changing the pan and zoom ratio;
A character string extracting means for extracting a character string of a moving object imaged by the imaging camera and obtaining a size of the character string and a passing position of the character string passing through an imaging range of the imaging camera;
Pan variable means for varying the pan of the imaging camera so that the passage position of the character string is located at the center of the imaging range;
Zoom ratio varying means for varying the zoom ratio of the imaging camera so that the size of the character string becomes a size suitable for a character string recognition process registered in advance;
Character string recognition means for recognizing the character string captured by the imaging camera in which the zoom ratio or pan is changed;
An imaging device comprising:
[0115]
(Additional remark 2) The statistics of the passage position of the said character string acquired by the said character string extraction means and the passage number in the passage position for a fixed time are taken, and the largest passage position where the said character string passed the said imaging range most A statistical means for calculating a standard deviation of the statistics;
Statistical pan varying means for varying the pan of the imaging camera so that the maximum passing position is located in the center of the imaging range;
A statistical zoom that calculates an expected passage position of a character string that has passed outside the imaging range of the imaging camera from the standard deviation, and varies a zoom ratio of the imaging camera so that the expected passage position is within the imaging range. A variable ratio means;
The imaging apparatus according to appendix 1, characterized by comprising:
[0116]
(Supplementary Note 3) When the object passes through the imaging range for a predetermined number of times within a predetermined time, the character string extraction unit includes the zoom ratio of the imaging camera in the statistical zoom ratio variable unit and the statistical pan variable unit. The imaging apparatus according to appendix 2, wherein variable processing of pan is performed.
[0117]
(Additional remark 4) The said zoom ratio variable means makes the angle of view of the said imaging camera a wide angle after the said character string recognition means recognizes the character string of the said object, The imaging device of Additional remark 1 characterized by the above-mentioned.
[0118]
(Additional remark 5) In the imaging device which recognizes the character string of a moving object,
An imaging camera capable of changing the zoom ratio and pan; and
A character string extracting means for extracting a character string of a moving object imaged by the imaging camera and acquiring a passing position of the character string passing through an imaging range of the imaging camera;
Taking a statistic of the passage position of the character string acquired by the character string extraction means and the number of passages at the passage position for a certain period of time, the maximum passage position where the character string has passed most of the imaging range and the standard deviation of the statistic A statistical means for calculating
Pan variable means for varying the pan of the imaging camera so that the maximum passage position is located in the center of the imaging range;
A zoom ratio that calculates an expected passing position of a character string that has passed outside the imaging range of the imaging camera from the standard deviation, and varies a zoom ratio of the imaging camera so that the expected passing position falls within the imaging range. Variable means;
Character string recognition means for recognizing a character string of the object imaged by the imaging camera;
An imaging device comprising:
[0119]
(Supplementary note 6) The imaging apparatus according to supplementary note 5, wherein the pan varying unit varies the pan within a range in which the character string recognizing unit can recognize the character string.
(Supplementary note 7) The imaging apparatus according to supplementary note 5, wherein the zoom ratio varying unit varies the zoom ratio within a range in which the character string recognizing unit can recognize the character string.
[0120]
(Supplementary note 8) The imaging apparatus according to supplementary note 5, wherein the pan varying unit varies the pan of the imaging camera when the maximum passage position is a predetermined distance or more away from the center of the imaging range.
[0121]
(Supplementary note 9) The imaging apparatus according to supplementary note 5, wherein the zoom ratio varying unit varies the zoom ratio of the imaging camera when a width of the predicted passing position and a width of the imaging range are different from each other by a predetermined amount or more. .
[0122]
【The invention's effect】
  As described above, in the present invention, the size of the character string and the passage position of the character string passing through the imaging range are acquired, and the panning of the imaging camera is performed so that the passage position of the character string is located at the center of the imaging range. The zoom ratio of the imaging camera is varied so that the character string size is suitable for the character string recognition process.Also, the maximum passage position where the character string has passed most of the imaging range and the expected passage position where the character string has passed outside the imaging range are calculated, and imaging is performed so that the maximum passage position of the character string is located at the center of the imaging range. The camera pan was varied, and the zoom ratio of the imaging camera was varied so that the expected passage position of the character string was within the imaging range.As a result, it is possible to always recognize a character string of a moving object while maintaining a high recognition rate.
[0123]
In the present invention, the maximum passage position where the character string has passed most of the imaging range and the expected passage position where the character string has passed outside the imaging range are calculated, and the maximum passage position of the character string is positioned at the center of the imaging range. Thus, the pan of the imaging camera is varied, and the zoom ratio of the imaging camera is varied so that the expected passage position of the character string is within the imaging range. As a result, it is possible to always recognize a character string of a moving object while maintaining a high recognition rate.
[Brief description of the drawings]
FIG. 1 is a principle diagram illustrating the principle of an imaging apparatus according to a first embodiment of the present invention.
FIG. 2 is a functional block diagram of the imaging apparatus according to the first embodiment of the present invention.
FIG. 3 is a flowchart showing an example of processing of the functional block diagram of FIG. 2;
FIG. 4 is a principle diagram illustrating the principle of an imaging apparatus according to a second embodiment of the present invention.
FIG. 5 is a functional block diagram of an imaging apparatus according to a second embodiment of the present invention.
FIG. 6 is a diagram illustrating an example of distributions of passage positions and passage numbers of character strings.
FIG. 7 is a diagram for explaining pan change value calculation;
FIG. 8 is a diagram illustrating zoom value calculation.
FIG. 9 is a diagram illustrating the distribution in FIG. 8 when zooming is performed.
FIG. 10 is a first flowchart illustrating an example of processing of the functional block diagram of FIG. 5;
FIG. 11 is a second flowchart showing an example of processing of the functional block diagram of FIG. 5;
FIG. 12 is a functional block diagram of an imaging apparatus according to a third embodiment of the present invention.
13 is a first flowchart showing an example of processing of the functional block diagram of FIG. 12;
14 is a second flowchart showing an example of processing of the functional block diagram of FIG.
15 is a third flowchart illustrating an example of the process of the functional block diagram of FIG.
FIG. 16 is a diagram illustrating a general relationship between the size of the angle of view of the imaging apparatus and the recognition rate.
FIG. 17 is a diagram illustrating an example of a character string passage distribution.
[Explanation of symbols]
1,10,20,30,50 Imaging camera
2,21 Character string extraction means
3,23 Pan variable means
4,24 Zoom ratio variable means
5,25 Character string recognition means
6, 26a, 26b, 26c Car
6a, 26aa, 26ba, 26ca alphanumeric character string
11, 31, 51 Image capture unit
12, 32, 52 Character string area extraction unit
13, 34 Pan variable part
14, 35 Zoom ratio variable part
15, 36, 57 Character string recognition processor
15a, 36a, 57a Dictionary DB
16, 37, 56 Control command transmitter
22 Statistical means
33, 54 Statistical processing section
53 Imaging Camera Control Unit
55 Statistical imaging camera controller

Claims (4)

In an imaging device that recognizes a character string of a moving object,
An imaging camera capable of changing the pan and zoom ratio;
A character string extracting unit that extracts a character string of a moving object imaged by the imaging camera, and acquires a size of the character string and a passing position of the character string passing through an imaging range of the imaging camera;
Pan variable means for varying the pan of the imaging camera so that the passage position of the character string is located at the center of the imaging range;
Zoom ratio varying means for varying the zoom ratio of the imaging camera so that the size of the character string becomes a size suitable for pre-registered character string recognition processing;
A character string recognition unit for recognizing processing the character string to be imaged by the zoom ratio or said imaging camera panning has been changed,
The statistics of the passage position of the character string acquired by the character string extraction means and the number of passages at the passage position are taken for a certain period of time, the maximum passage position where the character string has passed the imaging range most and the standard of the statistics A statistical means for calculating the deviation,
Statistical pan varying means for varying the pan of the imaging camera so that the maximum passing position is located in the center of the imaging range;
Statistical zoom that calculates an expected passing position of a character string that has passed outside the imaging range of the imaging camera from the standard deviation, and varies a zoom ratio of the imaging camera so that the expected passing position falls within the imaging range. A variable ratio means;
An imaging device comprising: The character string extraction unit may include the zoom ratio of the imaging camera and the panning pan in the statistical zoom ratio varying unit and the statistical pan varying unit when the moving object passes through the imaging range more than a certain number within a predetermined time. The imaging apparatus according to claim 1, wherein variable processing is performed. The imaging apparatus according to claim 1, wherein the zoom ratio varying unit widens the angle of view of the imaging camera after the character string recognizing unit recognizes the character string of the moving object. In an imaging device that recognizes a character string of a moving object,
  An imaging camera capable of changing the zoom ratio and pan; and
  A character string extracting means for extracting a character string of a moving object imaged by the imaging camera and acquiring a passing position of the character string passing through an imaging range of the imaging camera;
  Taking a statistic of the passage position of the character string acquired by the character string extraction means and the number of passages at the passage position for a certain period of time, the maximum passage position where the character string has passed most of the imaging range and the standard deviation of the statistic A statistical means for calculating
  Pan variable means for varying the pan of the imaging camera so that the maximum passage position is located in the center of the imaging range;
  A zoom ratio that calculates an expected passing position of a character string that has passed outside the imaging range of the imaging camera from the standard deviation, and varies a zoom ratio of the imaging camera so that the expected passing position falls within the imaging range. Variable means;
  Character string recognition means for recognizing the character string of the moving object imaged by the imaging camera;
  An imaging device comprising:

Images