JP4020481B2 - Automatic focus adjustment device - Google Patents

Description

この（４）式から、回転角△θＦは次のように求められる。

測距動作によりデフォーカス量が検出され、更に合焦状態になるレンズ移動量△Ｌが算出されて、上記式（５）によりフォーカスリング９３の回転角△θＦが求められ、ＡＦモータ３１の駆動量制御が行われる。
【００８３】
フォーカスリング９３の摺動ピン９３ｄは、カム環９５のフォーカスカム溝９５ｂに嵌合されることはすでに述べたが、一般的には摺動ピン９３ｄとカム溝９５ｂの間には嵌合ガタが存在する。
【００８４】
図１３はその嵌合状態を示し、フォーカスリング３を時計回り（近距離側から遠距離側）に駆動した後の状態から反時計回り（遠距離側から近距離側）へ駆動した時の様子を示している。
【００８５】
図１３に示されるように、嵌合ガタ△ｇのため、ガタ回転角△θｇ₀ 、△θｇ₁ 、すなわち、フォーカスリング９３の回転に対してカム環９５が回転しない角度が生じる。しかも、このガタ回転角とカム環９５の回転角の和の回転角が大きくなるほど、△θｇは小さくなる。
【００８６】
この第２の実施の形態の鏡筒に於ける代表的なガタ回転角△θｇと回転角θとの関係は、図１４に示される。
【００８７】
図１４の曲線は、原理的にはカム溝９５ｂの曲線形状によって決定されるはずであるが、実際には一致しない。これはカム溝９５ｂの溝幅の精度やカム環９５の駆動トルクがカム溝９５ｂの位置によって変化するためである。
【００８８】
次に、測距動作により検出されたデフォーカス量よりレンズ駆動量を求める方法について説明する。
【００８９】
デフォーカス量△ＤＦより、光軸方向レンズ移動量△Ｌは、次式により計算される。
【００９０】
ΔＬ＝ｂ−（ａ・ｂ）／（ａ・△ＤＦ）＋ｃ・△ＤＦ… （６）
ここで、ａ、ｂ、ｃは焦点距離毎に記憶された定数である。尚、この光軸方向レンズ移動量△Ｌは、図７に於けるフォーカス群である第１、２群の等価的な光学位置の移動量であって、このフォーカスレンズ群の駆動量とは異なる。
【００９１】
このフォーカスレンズ群は、上記カム構造により駆動が行われるので、光軸方向レンズ移動量△Ｌよりフォーカスリングの回転角△θを求める式は、上述した（５）式と同様に、下記（７）式により求められる。

ここでＡ、Ｂはカム形状によって決定される定数であり、θｆは焦点距離毎に記憶されたズーム回転角である。
【００９２】
また、θＦは焦点調節時のフォーカスリング９３の回転角で、ＡＦモータ３１の繰り出しパルス、すなわちＡＦフォトインタラプタ３３の発生パルスの積算カウンタ値から求められる。ズームエンコーダ２３の分割領域が略等回転角になっている場合は、θｆをズームエンコーダ２３の出力値によって求めてもよい。例えば、基準位置からｎ番目のエンコーダの出力値によると、θｆ＝θｆ・ｎとなる。
【００９３】
また、上記回転角△θにＡＦフォトインタラプタ３３の回転角当たりの発生パルス数を乗ずれば、合焦までのＡＦモータ３１の駆動制御パルス数が求められる。
【００９４】
尚、上記（７）式のデフォーカス量△ＤＦは符号付きの数値であり、正の場合はフィルムの後ろ側に結像する、いわゆる後ピン状態であり、合焦させるためにフォーカスレンズを繰り出す方向にピントがずれていることを表す。一方、上記数値が負の場合は、合焦させるためにフォーカスレンズを繰り込む方向にピントがずれている、いわゆる前ピン状態であることを表している。
【００９５】
次に、図１５のフローチャートを参照して、第２の実施の形態のカメラの動作について説明する。
【００９６】
この図１５のフローチャートは、図２に示されるコントローラ１１の動作制御手順を示すメインルーチンである。
【００９７】
先ず、コントローラ１１が動作を開始すると、図１５のメインルーチンが実行され、最初にステップＳ１にて、ＥＥＰＲＯＭ１６に予め記憶されている各種補正データが読み込まれてＲＡＭ１４に展開される。
【００９８】
続いて、ステップＳ２に於いて、ファーストレリーズスイッチ２８がオンされているか否かが判断される。ここで、オンでなければステップＳ１０に分岐する。一方、オンであれば、ステップＳ３に移行して、測光部２５が動作されて可視光に基づく被写体輝度が測定される測光動作が行われる。これにより、測光値が検出されてＲＡＭ１４に格納される。
【００９９】
そして、ステップＳ４にて、サブルーチン「ＡＦ」が実行されて被写体の焦点検出が行われる。この焦点検出に基づいて、フォーカシングレンズが合焦位置へ駆動されて、被写体にピントが合わせられる。
【０１００】
このＡＦ動作の結果、ステップＳ５に於いて、合焦したか否かが判断される。ここで、合焦していなければステップＳ９に進移行し、合焦している場合は、続くステップＳ６に於いてセカンドレリーズスイッチ２９がオンされているか否かが判断される。
【０１０１】
このステップＳ６で、セカンドレリーズスイッチ２９がオンされていなければ上記ステップＳ２に戻る。一方、オンされている場合は、上記ステップＳ３で求められた測光値に基づいて決定された絞り値及びシャッタスピード値に応じ、ステップＳ７にて絞り及びシャッタが制御されて露出動作が行われる。
【０１０２】
この露出動作が終了すると、ステップＳ８にて撮影されたフィルムが巻き上げられて次の駒の位置に給送され、一連の撮影動作が終了する。そして、ステップＳ９にて、図示されない表示装置ＬＣＤ、ＬＥＤの表示動作が制御される。
【０１０３】
また、上記ステップＳ１０では、ファーストレリーズスイッチ２８やセカンドレリーズスイッチ２９以外のスイッチのどれかが操作された場合に対応して他のスイッチの状態が検出され、オンされていなければ上記ステップＳ９に移行する。一方、ステップＳ１０でオンされているスイッチがある場合は、ステップＳ１１にて、そのオンされたスイッチに応じた処理が実行された後、ステップＳ９に移行する。
【０１０４】
次に、図１６のフローチャートを参照して、図１５のメインルーチンに於けるサブルーチン「ＡＦ」の動作を説明する。
【０１０５】
最初に、ステップＳ２１で、測距が行われてデフォーカス量ＤＦ₀ が得られる。尚、測距動作は、ＡＦセンサ２４から出力されるセンサデータに基づいて、コントローラ１１内で焦点検出演算がなされ、デフォーカス量とデフォーカス方向が算出される。演算方法等は公知であるので詳しい説明は省略する。
【０１０６】
続くステップＳ２２では、測距結果が合焦か否かが、デフォーカス量ＤＦ₀ と所定の合焦判定値とが比較されて判定される。ここで、デフォーカス量が合焦判定値以内の場合は合焦していると判定され、リターンされてＡＦ処理が終了する。一方、合焦ではない場合は、ステップＳ２３に移行して、前回のレンズ駆動方向と、今回の測距結果に基づくレンズ駆動方向が反対か否かが判定される。
【０１０７】
このステップＳ２３にてレンズ駆動方向が反転しない場合は、ステップＳ２４に移行して、上記ステップＳ２１で検出されたデフォーカス量ＤＦ₀ に基づくレンズ駆動が行われる。この後、上記ステップＳ２１に戻って再度測距が行われる。また、上記ステップＳ２３でレンズ駆動方向が反転する場合は、ステップＳ２５に移行してＥＥＰＲＯＭ１６に記憶されているガタデータに基づいてガタ量△θG が計算される。
【０１０８】
ここで、ガタ量△θＧの計算方法について説明する。
【０１０９】
この第２の実施の形態に於いては、ガタ量△θＧは、上記フォーカスリングの摺動ピン９３ｄとカム溝９５ｂの間に発生するガタ△θｇと、ＡＦモータ３１のギア列１０１ｂのバックラッシュと、ギア列とフォーカスリング９３の内歯ギアとの間に発生するガタ、及びフォーカスレンズの保持枠とカム環９５の嵌合ガタを加算したガタ△θＩと、係数αにより（８）式に示される。
ΔθＧ＝（△θｇ＋△θＩ）＊α …（８）
ここで、△θｇは図１４のガタ回転角として示される。またαは、後述するガタの近似誤差や経時変化、カメラ姿勢差、電源電圧等で変化するガタの最大量を予測する係数で、１．２程度の値となる。すなわち、基準状態に対して２０％のガタは起こり得るものとする。
【０１１０】
図１７は、第２の実施の形態に於けるガタ量△θＧとフォーカスリング９３、カム環９５の相対回転角θの関係を示した図である。焦点距離毎に近似することも可能であるが、本実施の形態に於いては、図１７に破線で示されるように、１つの関係式により近似させ、演算量の低減や後述する製品個々の測定工数が低減される。
【０１１１】
このように近似したガタ量△θＧは、（９）式のようになる。

但し、θ＝θｆ＋θＦである。
【０１１２】
θｆはフォーカスリング９３の回転角で、無限側の当接位置からのＡＦモータ３１の繰り出しパルス積算値より求められる。θｆはカム環９５の回転角で、ズームエンコーダ２３により検出された焦点距離毎に記憶されている。
【０１１３】
回転角θＷでのガタ△θＧＷと、回転角θＴでのガタ△θＧＴは、製品個々に測定されてＥＥＰＲＯＭ１６に記憶されている。本実実施の形態の鏡筒構造ではフォーカスリング９３の回転角とカム環９５の回転角によってガタ量を求めているが、これは鏡筒構造により決定されるものであり、計算方法はこの限りではない。
【０１１４】
図１６のサブルーチン「ＡＦ」に戻って、ステップＳ２６では上記計算されたガタ量分だけレンズ駆動が行われてガタが除去される。次いで、ステップＳ２７では測距が行われ、デフォーカス量ＤＦ１が得られ、ステップＳ２８で合焦か否かが、上記ステップＳ２２と同じ合焦判定値が用いられて判定される。
【０１１５】
次に、ステップＳ２９に於いて、ガタ量駆動の前後でレンズ駆動方向が反転したか否かが、上記ステップＳ２６のガタ量駆動の時のレンズ駆動方向とデフォーカス量ＤＦ１に基づくレンズ駆動方向とから判定される。
【０１１６】
ここで、駆動方向が反転された場合は、駆動過多になっており、合焦点をオーバーランしていることから、上記ガタ量△θＧが実際のガタ量よりも大きいということが判定される。このような場合、ガタ除去後に再度測距すると再び駆動方向が反転するので、再びガタ量駆動を繰り返すことになる。つまり、合焦点近傍で往復運動を繰り返して合焦できない、いわゆるハンチング状態になるという不具合となる。
【０１１７】
これを防止するため、ステップＳ３０では、上記ガタ量△θＧが補正されて、実際のガタ量に等しい新ガタ量△θＧｎが求められる。

（θＦ：フォーカスリング回転角、θｆ：ズーム回転角、Ａ、Ｂ：カム形状による係数）
デフォーカス量からレンズ駆動量に換算する方法は、レンズ鏡筒のフォーカス方式により異なるので、上記（１０）式を一般式として記述すると、下記（１１）式のようになる。
【０１１８】
△θＧｎ＝△θＧ−ｆ（ＤＦ１−ＤＦ０） …（１１）
（ｆ（ＤＦ）デフォーカス量をレンズ駆動量に変換する関数式）
そして、ステップＳ３１では、補正された新たなガタ量△θＧｎが、レンズ駆動されることにより正確に除去される。次いで、ステップＳ３２では再度測距が行われ、ステップＳ３３で上記測距データに基づいてレンズ駆動が行われる。
【０１１９】
上記ステップＳ３２、Ｓ３３は、ガタが除去された状態でなされるので焦点調節精度は充分高く、続くステップＳ２１の測距、ステップＳ２２の合焦判定で合焦となり、ＡＦ動作が終了する。
【０１２０】
これに対し、上記ステップＳ２９で駆動方向が反転しない場合は、ステップＳ３２に移行して測距、そしてステップＳ３３で上記測距に基づくレンズ駆動が行われた後、ステップＳ２１に戻り、ＡＦ動作が続けられる。
【０１２１】
図１８は、この第２の実施の形態の動作を説明するためのデフォーカス量とフォーカスレンズ位置の関係の一例を示すグラフである。同図に於いて、縦軸はデフォーカス量、すなわちフォーカスレンズの光学的位置であり、横軸は制御上のフォーカスレンズ位置（フォーカスリング３の回転角）を示している。
【０１２２】
ここで、経時変化やカメラの姿勢、電源電圧等により実際のガタ量＜記憶ガタ量という条件下での動作を説明する。
【０１２３】
最初に、フォーカスレンズは繰り出し方向に駆動された状態にあり、測距結果に基づく次のフォーカスレンズ駆動方向は繰り込み方向であるとする（Ｐ１）と、駆動方向が反転されるので記憶ガタ量が駆動される（上記ステップＳ２６）。記憶ガタ量が駆動されると、実際のガタ量より多く駆動するのでＰ２に移行する。ここで、再度測距が行われると（上記ステップＳ２７）、フォーカスレンズ駆動方向が反転され（上記ステップＳ２９）、上記（１０）式によりガタ量が補正される（上記ステップＳ３０）。
【０１２４】
続いて、補正ガタ量が駆動されると（上記ステップＳ３１）、Ｐ３に移行して正確にガタが除去される。そして、次の測距、レンズ駆動（上記ステップＳ３２、Ｓ３３）により合焦点Ｐ４に移行する。
【０１２５】
以上述べたように、第２の実施の形態に於いては、フォーカスレンズの駆動方向反転時にガタ除去駆動を行い、その前後の検出デフォーカス量に基づいて現在のガタデータが適切か否か判定している。そして、現在のガタデータが不適切な場合は上記検出デフォーカス量を用いて補正するようにしたので、常に正確なガタ量を求めることができ、正確な焦点調節を行うことが可能となる。
【０１２６】
図１９及び図２０は、この発明の第３の実施の形態であるサブルーチン「ＡＦ」のフローチャートである。この第３の実施の形態の他の部分は、上述した第２の実施の形態と同一であるので説明を省略する。
【０１２７】
図１９に於いて、ステップＳ４１〜Ｓ４３では、精度の高いデフォーカス量を得るために複数回の測距が行われ、複数の検出デフォーカス量の平均値デフォーカス量ＤＦ０が得られる。続くステップＳ４４では、デフォーカス量ＤＦ０と第１合焦判定値とが比較されて、合焦か否かが判定される。
【０１２８】
ここで、デフォーカス量ＤＦ０が第１合焦判定値以内の場合は合焦していると判定され、リターンしてＡＦ処理が終了する。一方、合焦ではない場合は、ステップＳ４５に移行して、前回のレンズ駆動方向と、今回の測距結果に基づくレンズ駆動方向が反対か否かが判定される。
【０１２９】
このステップＳ４５でレンズ駆動方向が反転していない場合は、ステップＳ４６に移行して上記ステップＳ４３で検出されたデフォーカス量ＤＦ０に基づくレンズ駆動が行われる。その後、上記ステップＳ４１に戻って再度測距が行われる。
【０１３０】
一方、上記ステップＳ４５にてレンズ駆動方向が反転する場合は、ステップＳ４７に移行して、ＥＥＰＲＯＭ１６に記憶されているガタデータに基づいて、上述した第２の実施の形態と同様の方法により、ガタ量△θＧが計算される。そして、ステップＳ４８にて、上記計算されたガタ量△θＧ分だけレンズ駆動が行われてガタが除去される。
【０１３１】
次のステップＳ４９〜Ｓ５１では再度複数回測距が行われて、平均デフォーカス量ＤＦ１が得られる。そして、ステップＳ５２に於いて、第１合焦判定値より広い許容範囲を有する第２合焦判定値が用いられて合焦判定される。この第２合焦判定値は、レンズ位置が合焦近傍にある場合で、ガタ量に比較してデフォーカス量に基づくレンズ駆動量が充分小さい場合に、レンズ駆動のばらつき等で実質的に合焦範囲に入ってしまうことを考慮して、処理の簡略化やタイムラグ短縮のために用いられる。
【０１３２】
ステップＳ５２で非合焦の場合はステップＳ５３に移行し、ガタ量駆動の前後でレンズ駆動方向が反転したか否かが、ガタ量駆動（上記ステップＳ４８）の時のレンズ駆動方向とデフォーカス量ＤＦ１に基づく今回のレンズ駆動方向とから判定される。
【０１３３】
そして、ステップＳ５３で駆動方向が反転した場合であれば、駆動過多で合焦点をオーバーランしていることから、上記ガタ量△θＧが実際のガタ量よりも大きいということが判定される。ステップＳ５４では、上記ガタ量△θＧが補正されて、実際のガタ量に等しい新ガタ量△θＧｎが、上記（１０）式により求められる。
【０１３４】
次いで、ステップＳ５４では再度測距が行われ、更にステップＳ５６では測距により求められたデフォーカス量ＤＦ２と、補正された新ガタ量△θＧｎの加算分がレンズ駆動される。ここでは、合焦までの残りレンズ駆動量と正確なガタ量とが同時にレンズ駆動されるので、焦点調節精度が充分高く、続くステップＳ４１〜Ｓ４３の測距、ステップＳ４４の合焦判定で合焦となり、ＡＦ動作が終了する。
【０１３５】
一方、上記ステップＳ５３で駆動方向が反転しない場合は、ステップＳ５７に移行して測距、そしてステップＳ５８で上記測距に基づくレンズ駆動が行われた後、ステップＳ４１に戻り、ＡＦ動作が続けられる。
【０１３６】
以上述べたように、この第３の実施の形態に於いては、検出デフォーカス量の平均処理をすることによって、ガタ量の補正をより高精度に行うことができ、更なる焦点調節精度の向上が可能となる。
【０１３７】
また、正確なガタ量を求めた上で検出デフォーカス量とガタ量の加算分をレンズ駆動しているので、焦点調節の応答性と精度を確保することが可能となる。
【０１３８】
更に、ガタ量駆動後の合焦判定値の通常の合焦判定値より広くして、応答性を向上させカメラの使い勝手を改善することができる。
【０１３９】
尚、この発明の上記実施態様によれば、以下の如き構成を得ることができる。
【０１４０】
すなわち、
（１） 移動可能なレンズと、このレンズの移動手段と、上記レンズの移動ガタ量を加味して上記移動手段を制御する制御手段とを有する焦点調節装置に於いて、
上記移動ガタ量を補正する補正手段を有する自動焦点調節装置。
【０１４１】
（２） 移動可能なレンズと、このレンズの移動手段と、上記レンズの移動に応じて生じるガタを、予め記憶手段に記憶させておいた移動ガタ量に基づいて補正しつつ上記移動手段を制御する制御手段とを有する焦点調節装置に於いて、
上記移動ガタ量を補正する補正手段を有することを特徴とする自動焦点調節装置。
【０１４２】
（３） 合焦状態を検出して撮影レンズの駆動量及び駆動方向を求める測距手段と、
上記駆動量及び駆動方向に基づいて上記撮影レンズを駆動するレンズ駆動手段と、
上記測距手段により求めた駆動方向が、前回の撮影レンズの駆動方向に対して反転か否かを検出する反転検出手段と、
この反転検出手段の出力と予め記憶したデータとに基づき、上記撮影レンズのガタ量を出力するガタ量出力手段と、
上記ガタ量が適切か否かを判定する判定手段と、
この判定結果に基づいて上記ガタ量を補正する補正手段と
を具備することを特徴とする自動焦点調節装置。
【０１４３】
（４） 撮影レンズの合焦位置からのずれ量及びずれ方向を求め、上記ずれ量及びずれ方向に基づいて撮影レンズの駆動量及び駆動方向を求める測距手段と、
上記駆動量及び駆動方向に基づいて撮影レンズのフォーカスレンズ群を駆動するレンズ駆動手段と、
前回のフォーカスレンズ群の駆動方向に対して、今回の駆動方向が反転か否かを検出する反転検出手段と、
今回のフォーカスレンズ群の駆動方向が判定する場合、記憶したデータに基づき、ガタ量を出力するガタ量出力手段と、
このガタ量出力手段の出力である上記ガタ量が適切か否かを判定する判定手段と、
この判定手段が適切ではないと判定した場合に、上記ガタ量を補正する補正手段と
を具備することを特徴とする自動焦点調節装置。
【０１４４】
（５） 上記レンズ駆動手段は上記ガタ量出力手段の出力するガタ量だけフォーカスレンズ群の駆動を行い、上記判定手段はその後の上記測距手段の検出ずれ量に基づいて上記ガタ量が適切か否かを判定することを特徴とする上記（４）に記載の自動焦点調節装置。
【０１４５】
（６） 上記レンズ駆動手段は、上記ガタ量出力手段の出力するガタ量だけフォーカスレンズ群の駆動を行い、上記補正手段はその後の上記測距手段の検出ずれ量に基づいて上記ガタ量を補正することを特徴とする上記（４）に記載の自動焦点調節装置。
【０１４６】
【発明の効果】
以上のようにこの発明によれば、経時変化や使用状況に応じたカメラの姿勢、電源電圧等で変化するレンズ駆動に関するガタを確実に除去して、高精度なＡＦと使用感の改善を低コストで実現することができる。
【図面の簡単な説明】
【図１】この発明の第１の実施の形態で、自動焦点調節装置の概念を示したブロック図である。
【図２】この発明の自動焦点調節装置が適用されたカメラの電気制御系の構成を示したブロック図である。
【図３】この第２の実施の形態に於けるカメラの光路系の構成を示した図である。
【図４】第２の実施の形態のカメラに用いられるズームレンズ鏡筒について説明するもので、ズームレンズ鏡筒の分解斜視図である。
【図５】第２の実施の形態のカメラに用いられるズームレンズ鏡筒について説明するもので、ズームレンズ鏡筒の分解斜視図である。
【図６】第２の実施の形態のカメラに用いられるズームレンズ鏡筒について説明するもので、ズームレンズ鏡筒の分解斜視図である。
【図７】第２の実施の形態のカメラに用いられるズームレンズ鏡筒について説明するもので、沈胴状態での縦断図である。
【図８】フォーカスリング９３の動作について説明する図である。
【図９】フォーカスリング９３の動作について説明する図である。
【図１０】フォーカスリング９３の動作について説明する図である。
【図１１】フォーカスリング９３の動作について説明する図である。
【図１２】フォーカスリング９３とカム環９５との相対回転角θと、カム環９５の移動量Ｌとの関係を表した図である。
【図１３】フォーカスリング９３の摺動ピン９３ｄとカム環９５のフォーカスカム溝９５ｂの嵌合状態を示した図である。
【図１４】第２の実施の形態の鏡筒に於ける代表的なガタ回転角△θｇと回転角θとの関係を示した図である。
【図１５】第２の実施の形態のカメラの動作について説明するフローチャートである。
【図１６】図１５のメインルーチンに於けるサブルーチン「ＡＦ」の動作を説明するフローチャートである。
【図１７】第２の実施の形態に於けるガタ量△θＧとフォーカスリング９３、カム環９５の相対回転角θの関係を示した図である。
【図１８】この第２の実施の形態の動作を説明するためのデフォーカス量とフォーカスレンズ位置の関係の一例を示すグラフである。
【図１９】この発明の第３の実施の形態であるサブルーチン「ＡＦ」のフローチャートである。
【図２０】この発明の第３の実施の形態であるサブルーチン「ＡＦ」のフローチャートである。
【符号の説明】
１ 測距部、
２ レンズ駆動部、
３ 反転検出部、
４ ガタ量出力部、
５ 判定部、
６ 補正部、
１１ コントローラ、
１２ ＣＰＵ（中央処理装置）、
１３ ＲＯＭ、
１４ ＲＡＭ、
１５ アナログ−デジタル（Ａ／Ｄ）コンバータ（ＡＤＣ）、
１６ ＥＥＰＲＯＭ、
１９ フィルム駆動部、
２０ レンズ駆動部、
２１ ＡＦエンコーダ、
２２ ズーム駆動部、
２３ ズームエンコーダ、
２４ ＡＦセンサ、
２５ 測光部、
２６ シャッタ駆動部、
２７ 絞り駆動部、
２８ ファーストレリーズスイッチ（１ＲＳＷ）、
２９ セカンドレリーズスイッチ（２ＲＳＷ）、
３１ ＡＦモータ、
３２ ズームモータ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic focus adjustment device used for a camera or the like, for example.
[0002]
[Prior art]
Conventionally, in an automatic focusing device such as a camera, a defocus amount and a defocus direction of a photographing lens are detected, and based on this, a lens driving amount and a driving direction are obtained, and the photographing lens is driven to focus. Many devices have been proposed.
[0003]
When the photographic lens drive direction is reversed, the photographic lens drive system has a backlash that causes the photographic lens not to move despite the photographic lens drive motor being operated. The cause is as follows.
[0004]
In order to transmit the driving force from the driving motor to the driving lens, the rotation of the gear train is reduced and the torque is increased. However, position shift occurs due to backlash caused by the meshing of the gear train.
[0005]
Many photographing lenses have a cam structure for moving the photographing lens straight in the optical axis direction with respect to a ring member rotated by a drive motor. Backlash occurs due to the backlash of the cam.
[0006]
If the movement of the photographic lens is directly detected to control the driving amount of the lens, there is no need to consider these backlashes. However, in the current automatic focusing apparatus, a method of monitoring and detecting the moving amount of the photographing lens by a photo interrupter disposed in the vicinity of the lens driving motor has become mainstream. For this reason, the above-described play between the drive motor and the photographic lens is inevitable.
[0007]
Therefore, when driving the lens based on the defocus direction and the defocus amount obtained by the focus detection means, if the lens drive direction is reversed, even if the lens drive amount obtained based on the defocus amount is driven, as described above. Since the lens does not move by the amount of play, the amount of drive is insufficient and focusing cannot be performed accurately.
[0008]
In order to solve these problems, several proposals have been made in the past.
[0009]
For example, an apparatus disclosed in Japanese Patent Application Laid-Open No. 60-52812 stores a backlash amount unique to a lens and corrects the drive amount when the drive direction is reversed.
[0010]
In Japanese Patent Laid-Open No. 4-306608, when the driving direction is reversed, the amount of play of the lens is obtained based on the stored data, the lens is first driven by the amount of play, and then the distance is measured again. Focusing accuracy and speed are obtained by driving the lens for the obtained lens driving amount.
[0011]
In addition, there is a problem that the occurrence of play varies depending on the tilt of the camera. When the tilt of the camera increases, the backlash of the transmission system is shifted in one direction due to the weight of the focus lens. Therefore, the position of the focus lens is determined only by the falling direction of the weight of the focus lens regardless of the driving direction.
[0012]
Therefore, for example, if the camera is driven downward in the retracting direction (the focus lens is shifted to the extending side and stopped) and then driven in the retracting direction, it is driven in the opposite direction to the previous, but the backlash correction It will be overdrive by that amount. For this reason, the focus lens repeats reciprocation in the vicinity of the in-focus point, so-called hunting occurs, and there is a problem that in-focus cannot be achieved forever.
[0013]
In order to solve such problems, Japanese Patent Laid-Open No. 9-33786 provides posture detection means for detecting the posture of a lens, and corrects play by changing the control method using the detection result of the posture detection means. Technology is disclosed.
[0014]
[Problems to be solved by the invention]
However, in the case of the devices disclosed in the above-mentioned Japanese Patent Application Laid-Open Nos. 60-52812 and 4-306608, only the amount of play stored at the initial stage of manufacture is targeted. However, the amount of play varies depending on the camera posture, the power supply voltage, etc. according to changes over time and usage conditions. In the techniques described in the above Japanese Patent Application Laid-Open Nos. 60-52812 and 4-306608, such a change amount is not taken into consideration, so that it is not possible to remove the correct play, and the AF accuracy is lowered or near the focal point. There is a problem that the focus lens repeats reciprocation, that is, so-called hunting occurs and the usability is poor.
[0015]
In Japanese Patent Application Laid-Open No. 9-33786, the tilt angle of the lens is detected and the amount of play varies depending on the posture. However, posture detection devices (such as mercury switches) are generally expensive, and there is a problem that this method cannot be used with cameras of a popular machine class.
[0016]
The present invention has been made in view of the above-described problems, and is an automatic focus that can realize high-precision AF and improved usability by reliably removing lens backlash with a low-cost and simple configuration. An object is to provide an adjusting device.
[0017]
[Means for Solving the Problems]
  That is, the present invention obtains a deviation amount and a deviation direction from the in-focus position of the photographing lens, and a distance measuring means for obtaining a driving amount and a driving direction of the photographing lens based on the deviation amount and the deviation direction, and the driving amount and driving The lens driving means for driving the photographic lens based on the direction, and the driving direction of the previous photographic lens,Based on the output of the distance measuring meansA reversal detecting means for detecting whether or not the current driving direction is reversed; and a backlash amount outputting means for outputting a backlash amount based on the stored data when the current driving direction of the photographing lens is reversed;When the inversion detection means detects inversion,Output of the backlash output meansDoAmount of playAfter the lens drive is executed by the lens driving unit based on the above, the shift amount is detected by the distance measuring unit, and the inversion is detected again by the inversion detection unit.Determination means for determining whether or not,The determination means is reversed againA correction means for correcting the amount of looseness.Then, based on the backlash amount corrected by the correction unit, the lens driving unit performs lens driving.It is characterized by that.
[0018]
  In the present invention, the distance measurement means obtains the deviation amount and deviation direction of the photographing lens from the in-focus position, and obtains the photographing lens driving amount and driving direction based on the deviation amount and deviation direction. Then, the photographing lens is driven by the lens driving means based on the driving amount and the driving direction. Also, with respect to the previous driving direction of the taking lens,Based on the output of the distance measuring meansWhether the current driving direction is reversed or not is detected by the inversion detection means. Here, when the driving direction of the photographing lens is reversed, the backlash amount is output from the backlash output means based on the stored data.The Further, when the inversion detection is detected by the inversion detection means, the lens driving means executes lens driving based on the backlash amount output from the backlash amount output means, and then the shift amount is detected by the distance measuring means. Whether it is detected and reversed again by the inversion detection means.It is determined by the determination means. AndThe determination means is reversed againIf it is determined, the amount of play is corrected by the correcting means.Further, lens driving is performed by the lens driving unit based on the amount of play corrected by the correcting unit.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0020]
FIG. 1 is a block diagram showing the concept of an automatic focusing apparatus according to the first embodiment of the present invention.
[0021]
In FIG. 1, this automatic focus adjustment device obtains a deviation amount and a deviation direction from the in-focus position of the photographing lens, and distance measurement obtains a driving amount and a driving direction of the photographing lens based on the deviation amount and the deviation direction. Unit 1, lens driving unit 2 for driving the focus lens group of the photographing lens based on the driving amount and the driving direction, and whether or not the current driving direction is reversed with respect to the previous driving direction of the focus lens group. The reversal detection unit 3 to detect, when the reversal detection unit 3 detects that the driving direction of the current focus lens group is reversed, the backlash amount output unit 4 that outputs a backlash amount based on the stored data, A determination unit 5 that determines whether or not the play amount that is the output of the play amount output unit 4 is appropriate, and a correction that corrects the play amount when the determination unit 5 determines that the play amount is not appropriate. Consists of part 6 It has been.
[0022]
In such a configuration, the distance measuring unit 1 obtains the shift amount and the shift direction from the in-focus position of the photographic lens, and the driving amount and drive of the photographic lens based on the shift amount and the shift direction. A direction is required. In the lens driving unit 2, the focus lens group of the photographing lens is driven based on the driving amount and the driving direction. The inversion detection unit 3 detects whether or not the current driving direction is reversed with respect to the previous driving direction of the focus lens group based on the output of the distance measuring unit 1 and the output of the lens driving unit 2.
[0023]
Here, when it is detected that the reversal detection unit 3 performs reversal, the backlash amount is output from the backlash amount output unit 4 to the determination unit 5 based on the stored data, and the determination unit 5 determines whether the backlash amount is appropriate. Is determined. When it is determined that the amount of play is inappropriate, the amount of play is corrected by the correction unit 6. Thereby, an accurate backlash amount is obtained. In the subsequent focus adjustment operation, high-precision focus adjustment can be performed by using the correction play amount.
[0024]
Next explained is the second embodiment of the invention.
[0025]
FIG. 2 is a block diagram showing the configuration of the electric control system of the camera to which the automatic focusing apparatus of the present invention is applied.
[0026]
In FIG. 2, a controller 11 that is a camera control device includes, for example, a CPU (central processing unit) 12, a ROM 13, a RAM 14, and an analog-digital (A / D) converter (ADC) 15. This camera performs a series of camera operations according to the camera sequence program stored in the ROM 13 of the controller 11. Further, the controller 11 has an EEPROM 16 therein, and can store correction data relating to AF control, photometry, etc. for each body.
[0027]
The controller 11 includes a film driving unit 19, a lens driving unit 20, an AF encoder 21, a zoom driving unit 22, a zoom encoder 23, an AF sensor 24, a photometry unit 25, a shutter driving unit 26, A diaphragm driver 27 is connected to a first release switch (1RSW) 28 and a second release switch (2RSW) 29.
[0028]
The film driving unit 19 controls film winding and rewinding (not shown) based on commands from the controller 11.
[0029]
The lens driving unit 20 is controlled by the controller 11, and drives a focus lens group of a photographing lens 41 described later by an AF motor 31. The control position of the focus lens group is detected by an AF encoder 21 including an AF photo interrupter and input to the controller 11.
[0030]
The zoom drive unit 22 is controlled by the controller 11 and drives the zoom lens group of the photographing lens 41 by the zoom motor 32. The zoom encoder 23 inputs the zoom control position to the controller 11.
[0031]
The AF sensor 24 includes photodiode arrays 24 </ b> L and 24 </ b> R that are photoelectric conversion element arrays, and its operation is controlled by a control signal from the controller 11.
[0032]
The photometry unit 25 generates an output corresponding to the luminance of the subject. The controller 11 A / D converts the generated photometric output by the A / D converter 15 and stores it in the RAM 14 as a photometric value.
[0033]
The shutter drive unit 26 and the aperture drive unit 27 perform shutter control and aperture control, respectively, based on commands from the controller 11.
[0034]
Furthermore, the first release switch 28 and the second release switch 29 are switches linked to a release button (not shown). The first release switch 28 is turned on when the release button is pushed down in the first stage, and the second release switch 29 is turned on when the release button is pushed down in the second stage. The controller 11 performs photometry and AF when the first release switch 28 is turned on, and performs an exposure operation and film winding when the second release switch 29 is turned on.
[0035]
FIG. 3 is a diagram showing the configuration of the optical path system of the camera in the second embodiment.
[0036]
In FIG. 3, the light beam from the subject passes through the photographing lens 41 having a five-group structure and enters the main mirror 42. The photographic lens 41 is composed of a first lens group 51, a second lens group 52, a third lens group 53, a fourth lens group 54, and a fifth lens group 55. The first group lens 51 and the second group lens 52 perform focusing, and the third group lens 53 and the fourth group lens 54 perform zooming. During zooming, the third lens group 53 and the fourth lens group 54 are moved, and at the same time, the first lens group 51 and the second lens group 52 are driven with a cam structure, thereby preventing focus movement during zooming. .
[0037]
The main mirror 42 is a half mirror, and 70% of the amount of incident light is reflected toward the viewfinder optical system 43. On the other hand, the remaining 30% of the incident light quantity is transmitted through the main mirror 42, reflected by the sub mirror 44, and then guided to the focus detection optical system 45.
[0038]
The finder optical system 43 includes a screen 61, a condenser lens 62, a prism 63, a mold roof mirror 64, and an eyepiece lens 65. Light incident on the finder optical system 43 is the screen 61, condenser lens. 62, the prism 63, the mold roof mirror 64, and the eyepiece 65 are observed by the photographer.
[0039]
The main mirror 42 and the sub mirror 44 are retracted to the positions indicated by broken lines in the drawing during film exposure. The subject luminous flux that has passed through the photographing lens 41 is exposed to the film 72 while the shutter 71 is open.
[0040]
Further, the focus detection optical system 45 includes a field stop 81, an infrared cut filter 82, a condenser lens 83, a mirror 84, a re-imaging stop 85, and a re-imaging lens 86, and focuses on the AF sensor 24. A detection light beam is guided.
[0041]
Next, a zoom lens barrel used in the camera of the second embodiment will be described with reference to FIGS. 4 to 6 are exploded perspective views of the zoom lens barrel, and FIG. 7 is a longitudinal sectional view in the retracted state.
[0042]
The main components of the zoom lens barrel are a fixed frame 91, a fixed lens frame 92, a focus ring 93, an inner zoom ring 94, a cam ring 95 which is an outer zoom ring, first to fifth group lenses 51 to 55, and the above. The first group to the fifth group frames 96 to 100 that respectively hold the first group to the fifth group lenses 51 to 55, the focus driving unit 101, the zoom driving unit 102, and the zoom encoder 23 are configured.
[0043]
The fixed frame 91 is fixed to the mirror box of the camera via spacers 105 and 106. The fixed frame 91 has an opening 91a that supports the fifth group frame 100 at the center, and a fitting portion 91d into which the fixed lens frame 92 is fitted. Further, the fixed frame 91 has a cylindrical portion 91e that supports the inner zoom ring 94 so as to be rotatable about the optical axis O, and a sliding pin 91g for restricting the movement of the inner zoom ring 94 in the optical axis direction. Is fixed on the cylindrical portion 91e by a screw 91f.
[0044]
The fixed frame 91 is provided with a fitting hole 91b and a fitting long hole 91c for supporting the second group main rod 97e and the sub rod 97f slidably in the optical axis direction. A focus drive unit 101 and a zoom drive unit 102 are attached to the fixed frame 91.
[0045]
The fixed lens frame 92 is fixed to the fitting portion 91d of the fixed frame 91 in a state where the inner peripheral portion 92a is fitted. The circumferential portion includes guide straight grooves 92b and 92c of the first group frame 96 and the second group frame 97 along the optical axis O, and the focus ring 93 along the circumferential direction of the inner periphery on the fixed frame 91 side. An inner circumferential groove 92g for restricting the axial position is provided.
[0046]
The outer periphery of the focus ring 93 is fitted with the inner peripheral portion 92a of the fixed lens frame 92. The inner peripheral portion 92a is provided with an internal gear 93e that meshes with the output gear 101a of the focus drive unit 101. ing. Reference numeral 101b denotes a gear train that meshes with the output gear 101a. Further, a slide pin 93d is fixed to the outer peripheral portion by a screw 93a, and the slide pin 93b is slidably fitted in the inner peripheral groove 92g of the fixed lens frame 92, so that the focus ring 93 in the optical axis O direction is fitted. Movement is prohibited.
[0047]
A sliding pin 93d for moving the cam ring 95 in the optical axis direction is fixed to the pin fixing portion 93g of the cam ring 95 with a screw 93c. The sliding pin 93d is slidably fitted into the focus cam groove 95b of the cam ring 95. As shown in FIGS. 8 to 11, the position where the notch 93 h of the focus ring 93 abuts on the stopper pin 91 i fixed to the fixed frame 91 by the rotation in the circumferential direction is the optical axis direction of the cam ring 95. This is the mechanical end of the retraction side.
[0048]
The inner zoom ring 94 has an inner peripheral portion that is rotatably fitted to a circumferential portion 91e of the fixed frame 91, and a slide of the fixed frame 91 in an inner circumferential groove 94d provided in the circumferential portion. The moving pin 91g is inserted, and the movement of the inner zoom ring 94 in the optical axis direction is prohibited. An inner gear 94 c that meshes with the output gear 102 a of the zoom drive unit 102 is provided on the inner periphery of the inner zoom ring 94.
[0049]
The inner zoom ring 94 is provided with cam grooves 94a and 94b for driving the third and fourth group frames 98 and 99 to zoom. Sliding pins 98j and 99f to which the third and fourth group frames 98 and 99 are fixed are fitted in the cam grooves 94a and 94b, respectively, but their cam shapes have no displacement in the optical axis direction. The cam groove portion in the retracted region corresponding to the retracted state and the cam groove in the zoom region having a zoom displacement in the optical axis direction are formed. In addition, a roller 94f fitted in the rectilinear groove 95a of the cam ring 95 is rotatably supported by a pin 94e on the outer periphery thereof.
[0050]
The outer periphery and the inner periphery of the cam ring 95 are fitted into the fixed lens frame 92 and the first group frame 96 so as to be rotatable or slidable, respectively. A rectilinear groove 95a is provided along the optical axis O direction, and the inner zoom ring 94 is driven to rotate according to the zoom amount via a roller 94f fitted in the groove.
[0051]
Further, the cam ring 95 is provided with a focus cam groove 95b corresponding to the focusing feed amount, and the sliding pin 93d of the focus ring 93 is fitted, so that the cam ring 95 is moved in the optical axis direction by the focusing amount. The
[0052]
The cam ring 95 is provided with cam grooves 95c and 95d. The cam grooves 95c and 95d have first and second group rollers 96b and 97j supported by the first group frame 96 and the second group frame 97, respectively. Is inserted. Therefore, the first group frame 96 and the second group frame 97 are displaced in the direction of the optical axis O in accordance with the rotation value by the zoom of the cam ring 95 or the axial movement by focusing.
[0053]
The cam grooves 95c and 95d are respectively a zoom region cam portion that provides a driving position during zooming and focusing, and a collapsible for moving the first group frame 96 and the second group frame 97 to the collapsed position when the camera is not used. And a cam portion of the region.
[0054]
A first group lens holding frame 96 c that holds the first group lens 51 is fixed to the first group frame 96. The outer peripheral portion is slidably fitted into the cam ring 95. The first group roller 96b is rotatably attached to the corresponding portion 96f of the outer cam groove 95c by a pin 96a. The first group roller 96b is also fitted into the cam groove 95c and the rectilinear groove 92b of the fixed lens frame 92. The first group frame 96 is guided by the rectilinear groove 92 in the direction of the optical axis O while being guided by the cam ring 95. It moves according to the rotation and straight movement.
[0055]
The second group frame 97 holds a second group lens frame 97a to which the second group lens 52 is attached. One end of the second group main rod 97e and the sub rod 97f is inserted into the notch 97b, and is fixed in pressure contact with a fixing piece 97d and a screw 97g.
[0056]
The other ends of the rods 97e and 97f are slidably fitted into the fitting hole 91b and the fitting long hole 91c of the fixed frame 91. Accordingly, the second group frame 97 can slide back and forth along the optical axis O without rotating. A third group frame 98 that is slidably supported and guided is inserted in an intermediate portion between the rods 97e and 97f.
[0057]
Further, a second group drive plate 97h is fixed to the second group frame 97, and a roller 97j is rotatably attached to the tip of the drive plate 97h via a pin 97i. As described above, the roller 97j is fitted into the cam groove 95c of the cam ring 95 and the linear groove 92c of the fixed lens frame 92. Therefore, as the cam ring 95 rotates and moves in the axial direction, the second group lens holding frame 97 moves in the optical axis direction via the second group drive plate 97h.
[0058]
The third group frame 98 holds the third group lens 53. Then, the second group main rod 97 e fixed to the second group frame 97 is fitted into the notch 98 c of the third group frame 98. The sub rod 97f supports the third group frame 98 so as to be slidable in the optical axis direction via the sleep 98a.
[0059]
A fourth group frame 99 is attached to the third group rod 98h and the sub rod 98k so as to be slidably supported in the direction of the optical axis O. A sliding pin 98j fitted into the cam groove 94a of the inner zoom ring 94 is fixed to the pin mounting portion 98s with a screw 98i. Accordingly, the third group frame 98 is moved back and forth in the direction of the optical axis O by the rotation of the inner zoom ring 94.
[0060]
The third group frame 98 is provided with an aperture drive unit (not shown).
[0061]
The fourth group frame 99 holds the fourth group lens 54, and is supported by the third group rod 98h and the sub rod 98k so as to be slidable in the optical axis direction. A sliding pin 99f fitted into a cam groove 94b provided in the inner zoom ring 94 is fixed to the sliding arm 99a with a screw 99e. Accordingly, the fourth group frame 99 is moved back and forth in the direction of the optical axis O by the rotation of the inner zoom ring 94.
[0062]
The fifth group frame 100 holds the fifth group lens 55 and is attached to the fixed frame 91.
[0063]
Next, zooming and focusing operations of the zoom lens barrel in the second embodiment configured as described above will be described. In the following description, the rotation direction is indicated by the rotation direction viewed from the subject side.
[0064]
FIG. 7 shows a lens barrel retracted state of the lens barrel, in which the first group frame 96 and the second group frame 97 are retracted, and the second group main rod 97e protrudes to the rear of the fixed frame. It has become. First, the zooming operation from this state to the long focal point will be described.
[0065]
Based on the zoom drive instruction from the controller 11, the first to fourth group lenses 51 to 54 are moved to the extended position by driving the zoom motor 32 of the zoom drive unit 102. That is, the inner zoom ring 94 is rotated clockwise through the output gear 102a of the drive unit 102. Along with the rotation, the sliding pins 98j and 99f are positioned from the retracted region groove to the zoom region groove in the cam grooves 94a and 94b.
[0066]
Then, the third and fourth group frames 98 and 99 to which the pins are fixed are moved, and the third and fourth group lenses 53 and 54 are extended to the zoom positions. On the other hand, the cam ring 95 is also rotated in the same direction via a roller 94 f supported by the inner zoom ring 94.
[0067]
By this rotation, the rollers 96b and 97j are positioned from the groove portion in the retracted region to the groove portion in the zoom region in the cam grooves 95c and 95d. At the same time, since the rollers 96b and 97j are fitted in the rectilinear grooves 92b and 92c of the fixed lens frame 92, the rollers 96b and 97j are moved straight in the direction of the subject.
[0068]
Incidentally, in the rectilinear groove 92c, the groove in the retracted area is shifted to the rectilinear groove in the zoom area.
[0069]
Further, during zoom driving, the slide pin 93d, which is stationary, is fitted in the focus cam groove 95b of the cam ring 95, and this cam action causes the cam ring 95 itself to move toward the subject side by the focus correction amount. Is done.
[0070]
Therefore, the amount of movement of the first group frame 96 or the second group frame 97 to which the rollers 96b and 97j are fixed directly or indirectly by zooming is driven by the cam grooves 95c and 95d of the cam ring 95. And the focus correction amount driven by the focus cam groove 95d.
[0071]
The above zoom movement amount is described in the case of zoom driving to the long focal side, and zoom driving to the short focal side can be performed by driving the inner zoom ring counterclockwise. The operation is the reverse of the zoom drive described above.
[0072]
Regarding the detection of the zoom state accompanying the zoom drive, the rotation of the cam ring 95 is detected by the zoom encoder 23. In the encoder 23, the conductive pattern on the encoder board 104 attached to the fixed lens frame 92 is brought into sliding contact with the contact piece 103a supported by the contact piece base 103 attached to the cam ring 95, so that the code relating to the zoom position is obtained. Is used to extract the signal.
[0073]
Next, the operation of the focus ring 93 will be described with reference to FIGS. 8 to 11 show how the focus ring 93 and its sliding pin 93d slide in the focus cam groove 95d of the cam ring 95. FIG.
[0074]
FIG. 8 shows the focal length f₀The cam ring 95 corresponding to the rotation angle θf₀The state in which the focus state is in contact with the infinite mechanical stopper, that is, the state in which the notch portion 93h of the focus ring 93 is in contact with the stopper ring 91i of the fixed frame 91 is shown.
[0075]
From the state of FIG. 8, the AF motor 31 of the focus drive unit 101 is driven based on the focus drive instruction from the controller 11, and the focus ring 93 rotates counterclockwise by ΔθF via the unit output gear 101a. Is done. Along with this rotation, the focus cam groove 95d is slid with the slide pin 93d, so that the cam ring 95 is moved to the subject side. In this case, since the inner zoom ring 94 is in the correct state, as shown in FIG. 9, the cam ring 95 is linearly moved by the movement amount ΔL1.
[0076]
Then, the first group frame 96 and the second group frame 97 are moved via the rollers 96b and 97j, and the first lens 51 and the second lens group 52, which are focus lens groups, are extended toward the subject.
[0077]
FIG. 10 illustrates the focal length f from the state of FIG. 8 by the zooming operation described above.₁Rotation angle θf corresponding to₁Only the cam ring 95 is rotated counterclockwise. By this rotation, the cam ring 95 is linearly moved by a movement amount ΔL2.
[0078]
FIG. 11 shows a state in which the focus ring 93 is rotated counterclockwise by the rotation angle θF by the focusing operation from the state of FIG. As described above, the cam ring 95 is linearly moved by the movement amount ΔL3. However, since the cam groove 95b has a large inclination, the movement amount ΔL3 is equal to the focal length f.₀In this case, the value is larger than the movement amount ΔL1.
[0079]
The focal length f₀, F₁Is calculated from the rotational position of the cam ring 95 detected by the zoom encoder 23. Further, the focusing operation from the short distance side to the long distance side of the subject is performed by driving the focus ring 93 in the direction opposite to the above.
[0080]
FIG. 12 is a diagram showing the relationship between the relative rotation angle θ between the focus ring 93 and the cam ring 95 and the movement amount L of the cam ring 95. The cam ring 95 and the movement amount L have the following relationship.
L = B / (A−θ) −C (1)
As described above, the relative rotation angle θ is the sum of the rotation angle θf of the cam ring 95 and the rotation angle θF of the focus ring 93 in a state where the focus ring 93 is in contact with the stopper on the infinity side. The quantity L is given by
L = B / (A− (θf + θF)) − C (2)
Now, when θf and θF are 0 at the reference position, assuming that L is 0, the above equation (2) is as follows.
[0081]
L = B / (A− (θf + θF)) − B / A (3)
Normally, the reference amount (θf = 0) is set to the short focus side end (wide end) of the normal imaging region, thereby controlling the amount of extension of the focus lens. In this case, the rotation angle θf is obtained from the focal length of the zoom lens, that is, the output value of the zoom encoder 23, and the rotation angle θF is obtained from the number of extended pulses detected by the AF photo interrupter 33 from the infinite mechanical stopper.
[0082]
Now, the rotation angle ΔθF of the focus ring 93 for extending the focus lens from the position of any rotation angle θf ′, θF ′ by the movement amount ΔL is obtained as follows.

From this equation (4), the rotation angle ΔθF is obtained as follows.

The defocus amount is detected by the distance measuring operation, and the lens movement amount ΔL that achieves the in-focus state is calculated, and the rotation angle ΔθF of the focus ring 93 is obtained by the above equation (5), and the AF motor 31 is driven. Quantity control is performed.
[0083]
Although it has already been described that the slide pin 93d of the focus ring 93 is fitted into the focus cam groove 95b of the cam ring 95, generally there is a fitting play between the slide pin 93d and the cam groove 95b. Exists.
[0084]
FIG. 13 shows the fitting state, when the focus ring 3 is driven clockwise (from the short distance side to the long distance side) and then driven counterclockwise (from the long distance side to the short distance side). Is shown.
[0085]
As shown in FIG. 13, because of the fitting backlash Δg, the backlash rotation angle Δθg₀, △ θg₁That is, an angle at which the cam ring 95 does not rotate with respect to the rotation of the focus ring 93 is generated. Moreover, Δθg decreases as the rotation angle of the sum of the backlash angle and the rotation angle of the cam ring 95 increases.
[0086]
FIG. 14 shows the relationship between the representative backlash angle Δθg and the rotation angle θ in the lens barrel of the second embodiment.
[0087]
The curve in FIG. 14 should in principle be determined by the curve shape of the cam groove 95b, but does not actually match. This is because the accuracy of the groove width of the cam groove 95b and the driving torque of the cam ring 95 vary depending on the position of the cam groove 95b.
[0088]
Next, a method for obtaining the lens driving amount from the defocus amount detected by the distance measuring operation will be described.
[0089]
From the defocus amount ΔDF, the lens movement amount ΔL in the optical axis direction is calculated by the following equation.
[0090]
ΔL = b− (a · b) / (a · ΔDF) + c · ΔDF (6)
Here, a, b, and c are constants stored for each focal length. This lens movement amount ΔL in the optical axis direction is the movement amount of the equivalent optical position of the first and second groups, which are the focus groups in FIG. 7, and is different from the drive amount of the focus lens group. .
[0091]
Since this focus lens group is driven by the cam structure, the equation for obtaining the rotation angle Δθ of the focus ring from the lens movement amount ΔL in the optical axis direction is the following (7) as in the above equation (5). ).

Here, A and B are constants determined by the cam shape, and θf is a zoom rotation angle stored for each focal length.
[0092]
Further, θF is a rotation angle of the focus ring 93 at the time of focus adjustment, and is obtained from an integrated counter value of a feed pulse of the AF motor 31, that is, a pulse generated by the AF photo interrupter 33. When the divided area of the zoom encoder 23 has a substantially equal rotation angle, θf may be obtained from the output value of the zoom encoder 23. For example, according to the output value of the nth encoder from the reference position, θf = θf · n.
[0093]
Further, if the rotation angle Δθ is multiplied by the number of pulses generated per rotation angle of the AF photo interrupter 33, the number of drive control pulses of the AF motor 31 until focusing is obtained.
[0094]
Note that the defocus amount ΔDF in the above equation (7) is a numerical value with a sign, and when it is positive, the image is formed on the back side of the film, which is a so-called rear pin state, and the focus lens is extended for focusing. Indicates that the camera is out of focus in the direction. On the other hand, when the numerical value is negative, it indicates a so-called front focus state in which the focus lens is defocused in the direction in which the focus lens is retracted for focusing.
[0095]
Next, the operation of the camera of the second embodiment will be described with reference to the flowchart of FIG.
[0096]
The flowchart of FIG. 15 is a main routine showing the operation control procedure of the controller 11 shown in FIG.
[0097]
First, when the controller 11 starts operating, the main routine of FIG. 15 is executed. First, in step S1, various correction data stored in advance in the EEPROM 16 are read and developed in the RAM.
[0098]
Subsequently, in step S2, it is determined whether or not the first release switch 28 is turned on. If it is not ON, the process branches to step S10. On the other hand, if it is ON, the process proceeds to step S3, where the photometric unit 25 is operated to perform a photometric operation in which the subject luminance based on visible light is measured. Thereby, a photometric value is detected and stored in the RAM 14.
[0099]
In step S4, the subroutine “AF” is executed to detect the focus of the subject. Based on this focus detection, the focusing lens is driven to the in-focus position, and the subject is brought into focus.
[0100]
As a result of the AF operation, in step S5, it is determined whether or not the subject is in focus. If it is not in focus, the process proceeds to step S9. If it is in focus, it is determined in subsequent step S6 whether or not the second release switch 29 is turned on.
[0101]
If the second release switch 29 is not turned on in step S6, the process returns to step S2. On the other hand, if it is turned on, the aperture and shutter are controlled in step S7 according to the aperture value and shutter speed value determined based on the photometric value obtained in step S3, and the exposure operation is performed.
[0102]
When this exposure operation is finished, the film photographed in step S8 is wound up and fed to the position of the next frame, and a series of photographing operations is finished. In step S9, display operations of the display device LCD and LED (not shown) are controlled.
[0103]
In step S10, the state of other switches is detected in response to the operation of any switch other than the first release switch 28 and the second release switch 29. If not, the process proceeds to step S9. To do. On the other hand, if there is a switch turned on in step S10, processing corresponding to the turned on switch is executed in step S11, and then the process proceeds to step S9.
[0104]
Next, the operation of the subroutine “AF” in the main routine of FIG. 15 will be described with reference to the flowchart of FIG.
[0105]
First, in step S21, distance measurement is performed and the defocus amount DF₀Is obtained. In the distance measuring operation, the focus detection calculation is performed in the controller 11 based on the sensor data output from the AF sensor 24, and the defocus amount and the defocus direction are calculated. Since the calculation method and the like are well known, detailed description thereof is omitted.
[0106]
In subsequent step S22, whether or not the distance measurement result is in focus is determined by the defocus amount DF.₀And a predetermined focus determination value are compared and determined. Here, if the defocus amount is within the in-focus determination value, it is determined that the in-focus state is obtained, and the process returns to complete the AF process. On the other hand, if not in focus, the process proceeds to step S23, where it is determined whether or not the previous lens driving direction is opposite to the lens driving direction based on the current distance measurement result.
[0107]
If the lens driving direction is not reversed in step S23, the process proceeds to step S24, where the defocus amount DF detected in step S21 is detected.₀Based on the lens drive. Thereafter, the process returns to step S21 and distance measurement is performed again. If the lens driving direction is reversed in step S23, the process proceeds to step S25, and the backlash amount ΔθG is calculated based on the backlash data stored in the EEPROM 16.
[0108]
Here, a method of calculating the backlash amount ΔθG will be described.
[0109]
In this second embodiment, the amount of play ΔθG is the amount of play Δθg generated between the slide pin 93d of the focus ring and the cam groove 95b, and the backlash of the gear train 101b of the AF motor 31. And a backlash generated between the gear train and the internal gear of the focus ring 93, a backlash ΔθI obtained by adding a backlash of the focus lens holding frame and the cam ring 95, and a coefficient α to formula (8). Indicated.
ΔθG = (Δθg + ΔθI) * α (8)
Here, Δθg is shown as the backlash angle in FIG. Further, α is a coefficient for predicting the maximum amount of backlash that changes due to an approximate error of a backlash, a change with time, a camera attitude difference, a power supply voltage, and the like, which will be described later, and has a value of about 1.2. That is, it is assumed that a backlash of 20% can occur with respect to the reference state.
[0110]
FIG. 17 is a diagram showing the relationship between the amount of play ΔθG and the relative rotation angle θ of the focus ring 93 and the cam ring 95 in the second embodiment. Although it can be approximated for each focal length, in the present embodiment, as shown by a broken line in FIG. 17, it is approximated by one relational expression to reduce the amount of calculation and individual products described later. Measurement man-hours are reduced.
[0111]
The approximate backlash amount ΔθG is expressed by equation (9).

However, θ = θf + θF.
[0112]
θf is the rotation angle of the focus ring 93, and is obtained from the integrated value of the extended pulses of the AF motor 31 from the infinite contact position. θf is the rotation angle of the cam ring 95 and is stored for each focal length detected by the zoom encoder 23.
[0113]
The play ΔθGW at the rotation angle θW and the play ΔθGT at the rotation angle θT are measured for each product and stored in the EEPROM 16. In the lens barrel structure of the present embodiment, the amount of play is determined by the rotation angle of the focus ring 93 and the rotation angle of the cam ring 95, but this is determined by the lens barrel structure, and the calculation method is limited to this. is not.
[0114]
Returning to the subroutine “AF” in FIG. 16, in step S26, the lens is driven by the calculated amount of play, and the play is removed. Next, in step S27, distance measurement is performed to obtain a defocus amount DF1, and in step S28, it is determined using the same focus determination value as in step S22.
[0115]
Next, in step S29, whether or not the lens driving direction is reversed before and after the backlash driving is determined based on the lens driving direction in the backlash driving in step S26 and the lens driving direction based on the defocus amount DF1. It is determined from.
[0116]
Here, when the driving direction is reversed, it is determined that the amount of play ΔθG is larger than the actual amount of play because the driving is excessive and the focal point is overrun. In such a case, if the distance is measured again after the play is removed, the drive direction is reversed again, so that the play of the play is repeated again. That is, there is a problem that a so-called hunting state in which reciprocating motion is repeated in the vicinity of the in-focus point and the in-focus state cannot be achieved.
[0117]
In order to prevent this, in step S30, the backlash amount ΔθG is corrected, and a new backlash amount ΔθGn equal to the actual backlash amount is obtained.

(ΘF: focus ring rotation angle, θf: zoom rotation angle, A, B: coefficient depending on cam shape)
Since the method for converting the defocus amount into the lens drive amount differs depending on the lens barrel focus method, the above equation (10) can be expressed as the following equation (11).
[0118]
ΔθGn = ΔθG−f (DF1-DF0) (11)
(Functional expression for converting f (DF) defocus amount into lens drive amount)
In step S31, the corrected new play amount ΔθGn is accurately removed by driving the lens. Next, distance measurement is performed again in step S32, and lens driving is performed based on the distance measurement data in step S33.
[0119]
Since the steps S32 and S33 are performed with the backlash removed, the focus adjustment accuracy is sufficiently high. The focus is determined by the distance measurement in step S21 and the focus determination in step S22, and the AF operation ends.
[0120]
On the other hand, if the driving direction is not reversed in step S29, the process proceeds to step S32 to perform distance measurement, and lens driving based on the distance measurement is performed in step S33, and then the process returns to step S21 to perform the AF operation. You can continue.
[0121]
FIG. 18 is a graph showing an example of the relationship between the defocus amount and the focus lens position for explaining the operation of the second embodiment. In the figure, the vertical axis represents the defocus amount, that is, the optical position of the focus lens, and the horizontal axis represents the focus lens position for control (the rotation angle of the focus ring 3).
[0122]
Here, the operation under the condition that the actual play amount is smaller than the stored play amount due to changes with time, camera posture, power supply voltage, and the like will be described.
[0123]
First, if the focus lens is driven in the extending direction, and the next focus lens driving direction based on the distance measurement result is the retracting direction (P1), the driving direction is reversed, so the amount of stored play is reduced. Driven (step S26). When the stored play amount is driven, the drive amount is larger than the actual play amount, so that the process proceeds to P2. Here, when distance measurement is performed again (step S27), the focus lens driving direction is reversed (step S29), and the amount of play is corrected by the above equation (10) (step S30).
[0124]
Subsequently, when the correction backlash amount is driven (step S31), the process proceeds to P3 and the backlash is accurately removed. Then, the focus shifts to P4 by the next distance measurement and lens driving (steps S32 and S33).
[0125]
As described above, in the second embodiment, when the driving direction of the focus lens is reversed, the backlash removal driving is performed, and it is determined whether or not the current backlash data is appropriate based on the detected defocus amounts before and after that. ing. When the current backlash data is inappropriate, correction is made using the detected defocus amount, so that an accurate backlash amount can always be obtained and accurate focus adjustment can be performed.
[0126]
FIGS. 19 and 20 are flowcharts of a subroutine “AF” according to the third embodiment of the present invention. Since other parts of the third embodiment are the same as those of the second embodiment described above, description thereof is omitted.
[0127]
In FIG. 19, in steps S41 to S43, a plurality of distance measurements are performed to obtain a highly accurate defocus amount, and an average defocus amount DF0 of the plurality of detected defocus amounts is obtained. In the subsequent step S44, the defocus amount DF0 is compared with the first focus determination value to determine whether or not the focus is achieved.
[0128]
Here, when the defocus amount DF0 is within the first focus determination value, it is determined that the focus is achieved, and the process returns and the AF process is terminated. On the other hand, if not in focus, the process proceeds to step S45, where it is determined whether or not the previous lens driving direction is opposite to the lens driving direction based on the current distance measurement result.
[0129]
If the lens driving direction is not reversed in step S45, the process moves to step S46, and lens driving based on the defocus amount DF0 detected in step S43 is performed. Thereafter, the process returns to step S41 and distance measurement is performed again.
[0130]
On the other hand, when the lens driving direction is reversed in step S45, the process proceeds to step S47, and the amount of play is determined by the same method as in the second embodiment described above based on the backlash data stored in the EEPROM 16. ΔθG is calculated. In step S48, the lens is driven by the calculated amount of play ΔθG to remove the play.
[0131]
In the next steps S49 to S51, the distance measurement is performed a plurality of times again to obtain the average defocus amount DF1. In step S52, the focus determination is performed using the second focus determination value having a wider allowable range than the first focus determination value. This second in-focus determination value is obtained when the lens position is close to the in-focus position, and when the lens drive amount based on the defocus amount is sufficiently small compared to the backlash amount, the second focus determination value is substantially adjusted due to variations in lens drive. In consideration of entering the focal range, it is used for simplification of processing and shortening of the time lag.
[0132]
If the in-focus state is not in step S52, the process proceeds to step S53, and whether or not the lens driving direction is reversed before and after the backlash driving is determined based on the lens driving direction and the defocusing amount in the backlash driving (step S48). It is determined from the current lens driving direction based on DF1.
[0133]
If the driving direction is reversed in step S53, it is determined that the backlash amount ΔθG is larger than the actual backlash amount because the focus is overrun due to excessive driving. In step S54, the backlash amount ΔθG is corrected, and a new backlash amount ΔθGn equal to the actual backlash amount is obtained by the above equation (10).
[0134]
Next, in step S54, the distance is measured again, and in step S56, the lens is driven by the addition of the defocus amount DF2 obtained by the distance measurement and the corrected new play amount ΔθGn. Here, since the remaining lens drive amount until the in-focus and the accurate backlash amount are driven simultaneously, the focus adjustment accuracy is sufficiently high, and the focus is determined by the distance measurement in steps S41 to S43 and the focus determination in step S44. Thus, the AF operation ends.
[0135]
On the other hand, if the driving direction is not reversed in step S53, the process proceeds to step S57 to perform distance measurement, and lens driving based on the distance measurement is performed in step S58, and then the process returns to step S41 to continue the AF operation. .
[0136]
As described above, in the third embodiment, by performing the average processing of the detected defocus amount, the backlash amount can be corrected with higher accuracy, and further focus adjustment accuracy can be improved. Improvement is possible.
[0137]
In addition, since the lens is driven by adding the detected defocus amount and the backlash amount after obtaining the accurate backlash amount, it is possible to ensure the responsiveness and accuracy of the focus adjustment.
[0138]
Furthermore, the focus determination value after driving the play amount can be made wider than the normal focus determination value, so that the responsiveness can be improved and the usability of the camera can be improved.
[0139]
In addition, according to the said embodiment of this invention, the following structures can be obtained.
[0140]
That is,
(1) In a focus adjustment apparatus having a movable lens, a moving means for the lens, and a control means for controlling the moving means in consideration of the moving play amount of the lens.
An automatic focus adjustment apparatus having correction means for correcting the amount of movement play.
[0141]
(2) Control of the moving means while correcting the movable lens, the moving means of the lens, and the backlash generated in accordance with the movement of the lens based on the moving play amount stored in the storage means in advance. And a focusing device having control means for
An automatic focus adjustment device comprising correction means for correcting the amount of movement play.
[0142]
(3) distance measuring means for detecting the in-focus state to determine the driving amount and driving direction of the photographing lens;
Lens driving means for driving the photographing lens based on the driving amount and driving direction;
A reversal detecting means for detecting whether or not the driving direction obtained by the distance measuring means is reversed with respect to the previous driving direction of the photographing lens;
Based on the output of the inversion detection means and the data stored in advance, the play amount output means for outputting the play amount of the photographing lens,
Determining means for determining whether or not the amount of play is appropriate;
Correction means for correcting the amount of play based on the determination result;
An automatic focusing device comprising:
[0143]
(4) A distance measuring unit that obtains a deviation amount and a deviation direction from the in-focus position of the photographing lens and obtains a driving amount and a driving direction of the photographing lens based on the deviation amount and the deviation direction;
Lens driving means for driving the focus lens group of the photographing lens based on the driving amount and the driving direction;
Reversal detection means for detecting whether or not the current drive direction is reversed with respect to the previous drive direction of the focus lens group;
When determining the current driving direction of the focus lens group, based on the stored data, a backlash output means for outputting a backlash,
Determination means for determining whether or not the backlash amount, which is an output of the backlash amount output means, is appropriate;
Correction means for correcting the amount of play when it is determined that the determination means is not appropriate;
An automatic focusing device comprising:
[0144]
(5) The lens driving means drives the focus lens group by the backlash amount output from the backlash output means, and the determination means determines whether the backlash amount is appropriate based on the detection deviation amount of the distance measuring means thereafter. The automatic focusing apparatus according to (4), wherein it is determined whether or not.
[0145]
(6) The lens driving unit drives the focus lens group by the backlash amount output from the backlash amount output unit, and the correction unit corrects the backlash amount based on the detection deviation amount of the distance measuring unit thereafter. The automatic focusing apparatus according to (4), characterized in that:
[0146]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably remove the rattling related to lens driving that changes depending on the time-dependent change and usage conditions of the camera, the power supply voltage, etc. Can be realized at a cost.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a concept of an automatic focus adjustment apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an electric control system of a camera to which the automatic focusing apparatus of the present invention is applied.
FIG. 3 is a diagram showing a configuration of an optical path system of a camera in the second embodiment.
FIG. 4 is an exploded perspective view of a zoom lens barrel for explaining a zoom lens barrel used in a camera according to a second embodiment.
FIG. 5 is an exploded perspective view of a zoom lens barrel for explaining a zoom lens barrel used in a camera according to a second embodiment;
FIG. 6 is an exploded perspective view of a zoom lens barrel for explaining a zoom lens barrel used in the camera of the second embodiment.
FIG. 7 is a longitudinal sectional view in a retracted state for explaining a zoom lens barrel used in the camera of the second embodiment.
FIG. 8 is a diagram for explaining the operation of the focus ring 93;
9 is a diagram for explaining the operation of the focus ring 93. FIG.
10 is a diagram for explaining the operation of a focus ring 93. FIG.
FIG. 11 is a diagram for explaining the operation of the focus ring 93;
12 is a diagram showing the relationship between the relative rotation angle θ between the focus ring 93 and the cam ring 95 and the movement amount L of the cam ring 95. FIG.
13 is a view showing a fitting state of a sliding pin 93d of the focus ring 93 and a focus cam groove 95b of the cam ring 95. FIG.
FIG. 14 is a diagram showing a relationship between a typical backlash angle Δθg and a rotation angle θ in the lens barrel of the second embodiment.
FIG. 15 is a flowchart for explaining the operation of the camera of the second embodiment;
FIG. 16 is a flowchart for explaining the operation of a subroutine “AF” in the main routine of FIG. 15;
17 is a diagram showing the relationship between the amount of play ΔθG and the relative rotation angle θ of the focus ring 93 and the cam ring 95 in the second embodiment. FIG.
FIG. 18 is a graph showing an example of the relationship between the defocus amount and the focus lens position for explaining the operation of the second embodiment.
FIG. 19 is a flowchart of a subroutine “AF” according to the third embodiment of the present invention;
FIG. 20 is a flowchart of a subroutine “AF” according to the third embodiment of the present invention;
[Explanation of symbols]
1 ranging unit,
2 Lens drive unit,
3 Inversion detection unit,
4 Backlash output section,
5 judgment part,
6 Correction part,
11 controller,
12 CPU (Central Processing Unit),
13 ROM,
14 RAM,
15 analog-to-digital (A / D) converter (ADC),
16 EEPROM,
19 Film drive unit,
20 Lens drive unit,
21 AF encoder,
22 Zoom drive unit,
23 Zoom encoder,
24 AF sensor,
25 Metering section,
26 shutter drive unit,
27 Aperture drive unit,
28 First release switch (1RSW),
29 Second release switch (2RSW),
31 AF motor,
32 Zoom motor.

Claims (2)

Distance measuring means for obtaining a deviation amount and a deviation direction from the in-focus position of the photographing lens and obtaining a driving amount and a driving direction of the photographing lens based on the deviation amount and the deviation direction;
Lens driving means for driving the photographing lens based on the driving amount and the driving direction;
Reversal detecting means for detecting whether or not the current driving direction is reversed based on the output of the distance measuring means with respect to the previous driving direction of the photographing lens;
When the driving direction of the current photographing lens is reversed, a backlash amount output means for outputting a backlash amount based on the stored data,
When the inversion detection means detects the inversion, after to execute the lens driven by the lens driving means on the basis of the output amount of play for the play amount output unit, by detecting the shift amount by the distance measurement means described above Determination means for determining whether or not the reversal is reversed again by the reversal detection means ;
When it is determined that the determination unit is reversed again, a correction unit that corrects the play amount;
Equipped with,
The automatic focus adjustment apparatus , wherein the lens driving means performs lens driving based on the amount of play corrected by the correcting means . The correcting means causes the distance measuring means to detect a shift amount before and after driving the lens based on the play amount, and corrects the play amount based on the shift amount detected before and after the lens drive. The automatic focusing apparatus according to claim 1, wherein

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