JP4654482B2 - Variable focal length lens system - Google Patents

Variable focal length lens system Download PDF

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Publication number
JP4654482B2
JP4654482B2 JP2000103832A JP2000103832A JP4654482B2 JP 4654482 B2 JP4654482 B2 JP 4654482B2 JP 2000103832 A JP2000103832 A JP 2000103832A JP 2000103832 A JP2000103832 A JP 2000103832A JP 4654482 B2 JP4654482 B2 JP 4654482B2
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lens
lens group
focal length
positive
object side
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JP2001290077A (en
JP2001290077A5 (en
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基之 大竹
昭彦 小濱
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Nikon Corp
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B15/00—Optical objectives with means for varying the magnification
    • G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
    • G02B15/16—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group
    • G02B15/177—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group having a negative front lens or group of lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B15/00—Optical objectives with means for varying the magnification
    • G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
    • G02B15/143—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having three groups only
    • G02B15/1435—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having three groups only the first group being negative
    • G02B15/143503—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having three groups only the first group being negative arranged -+-

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Nonlinear Science (AREA)
  • Lenses (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、広角端状態における画角が８０度を超え、口径比３．５程度の可変焦点距離レンズ系に関し、特に近距離合焦時にも高い光学性能を有する可変焦点距離レンズ系に関する。
【０００２】
【従来の技術】
レンズシャッター式カメラの特徴は携帯性に優れることである。この携帯性は小型であること、軽量であることに分類される。撮影レンズの長さがカメラ本体の厚みに影響し、レンズ径がカメラ本体の高さと横幅に影響するので、撮影レンズ系の小型化がカメラの小型化に直接影響を与えてきた。
【０００３】
ズームレンズは被写体により近づいた撮影が可能であり、撮影者に自由度を与えるため、ズームレンズ付カメラが主流になってきた。そして、望遠端状態の焦点距離が大きいほど被写体に近付いた撮影が可能になるので、望遠端状態での焦点距離が長くなるように変倍比が高まる傾向であった。
【０００４】
ところで、レンズシャッター式カメラは携帯性に優れる点から旅行等に出掛ける際に使われる機会が多いが、一眼レフカメラのユーザー層がレンズシャッター式カメラを携行する場合、口径比の明るい単焦点レンズ付カメラを携行する場合が多い。
【０００５】
そして、一眼レフカメラのユーザー層が旅行時に携行する場合、口径比が大きく、画角が広い撮影系が好まれる。前者はストロボなしで自然な発色での撮影ができるからであり、後者は撮影者と被写体との距離が近い状態でも画角が広いため撮影できるからである。
【０００６】
【発明が解決しようとする課題】
しかしながら、従来のレンズシャッター式カメラ用ズームレンズは、旅行に携行するのに不向きな面があった。それは、望遠端状態での焦点距離が長くなるに従って、望遠端状態での開放Ｆナンバーが大きくなる傾向で、遠近感に乏しい写真に仕上がってしまうこと、また、ストロボ撮影が多いこと等である。
【０００７】
旅行に携行するカメラは上述の通り、画角が広く、口径比が大きなレンズ系が好まれるが、画角が広がるとレンズ径が大きくなりがちなこと、さらに軸外光束がフォーカシング群に入射する入射角度が大きく、近距離合焦時にフォーカシング群が移動すると、通過する高さが大きく変化して軸外収差変動が大きくなること等の問題があった。
【０００８】
本発明は上記問題に鑑みてなされたものであり、広角端状態での画角が８０度を超え、明るく小型で、且つ近距離合焦時にも高い光学性能が得られる可変焦点距離レンズ系を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記目的を達成するために本発明は、物体側より順に、負屈折力を有する第１レンズ群と、正屈折力を有する第２レンズ群と、負屈折力を有する第３レンズ群とを有し、広角端状態から望遠端状態までレンズ位置状態が変化する際に、前記第１レンズ群と前記第２レンズ群との間隔が減少し、前記第２レンズ群と前記第３レンズ群との間隔が減少するように、少なくとも前記第２レンズ群と前記第３レンズ群がぞれぞれ物体側へ移動して、前記第２レンズ群は少なくとも２枚の正レンズ成分と、該２枚の正レンズ成分の間に配置される少なくとも１枚の負レンズ成分を有し、前記２枚の正レンズ成分の間に開口絞りが配置され、近距離合焦時に前記第２レンズ群が物体側へ移動して、以下の条件式（１）、（２）、（４）、及び（５）を満足する可変焦点距離レンズ系を提供する。
（１） ０．１＜（ｆ３＋ｆ２）／（ｆ１＋ｆ２）＜０．５
（ｆ１＜０，ｆ２＞０，ｆ３＜０）
（２） ０．４＜ΣＤ２／ｆｗ＜０．６
（４） １．２＜ｆ21／ｆ22＜３．０
（５） １．０＜│ｆ2N│／ｆ２＜１．４ （ｆ２＜０）
但し、
ｆ１：前記第１レンズ群の焦点距離，
ｆ２：前記第２レンズ群の焦点距離，
ｆ３：前記第３レンズ群の焦点距離，
ΣＤ２：前記第２レンズ群のレンズ厚，
ｆ2N：前記第２レンズ群中の前記負レンズ成分の焦点距離．
ｆ21：前記第２レンズ群中で、前記開口絞りよりも物体側に配置される前記正レンズ成分の焦点距離，
ｆ22：前記第２レンズ群中で、前記開口絞りよりも像側に配置される前記正レンズ成分の焦点距離．
【００１０】
【発明の実施の形態】
従来より可変焦点距離レンズ系は、レンズ系のもっとも物体側に正屈折力を有するレンズ群を配置する正先行型と負屈折力を有するレンズ群を配置する負先行型とに大別される。
【００１１】
正先行型は主に画面対角長よりも焦点距離が長いレンズ系に用いられ、レンズ全長の短縮に適している。また、負先行型は主に画角が広いレンズ系に用いられている。
【００１２】
負先行型は広角端状態で（もっとも物体側に配置される）第１レンズ群を通過する軸外光束が正先行型に比べて光軸に近い位置を通過するのでレンズ径の小型化が図れる。しかし、変倍比を高めると望遠端状態において、（第１レンズ群の像側に配置される）第２レンズ群を軸上光束が広がって通過するので、画面中心部で所定の光学性能を確保するのが困難である。
【００１３】
また、レンズシャッター式カメラに用いられるレンズ系は、レンズ系のもっとも像側に負レンズ群を配置することで、レンズ全長の短縮化とレンズ径の小型化を実現している。
【００１４】
本発明においては、ズーム比よりも大口径比と広い画角を優先し、レンズ系のもっとも物体側に負屈折力を有する第１レンズ群、その像側に正屈折力を有する第２レンズ群、さらにその像側に負屈折力を有する第３レンズ群を配置している。そして、広角端状態では第１レンズ群と第２レンズ群との間隔、第２レンズ群と第３レンズ群との間隔がそれぞれ広がった状態に配置して、望遠端状態に向かってレンズ位置状態が変化するに従って、各レンズ群同士の間隔が狭まるように、少なくとも第２レンズ群、第３レンズ群とを物体側へ移動させている。これにより、第１レンズ群と第３レンズ群を通過する軸外光束が光軸から大きく離れないようにしてレンズ径を小型化している。
【００１５】
また、画角の広い光学系では、開口絞りを配置する位置が重要であり、本発明では、第２レンズ群の内部に開口絞りを配置している。
【００１６】
このように開口絞りを配置して、広角端状態では各レンズ群同士の間隔を充分広げることで、第１レンズ群及び第３レンズ群を通過する軸外光束が光軸からやや離れるので、軸外収差の補正が充分良好に行うことができる。また、望遠端状態へ向かってレンズ位置状態が変化するに従って、各レンズ群同士の間隔を狭めることで、第１レンズ群と第３レンズ群を通過する軸外光束の高さを積極的に変化させて、レンズ位置状態の変化に伴って発生する軸外収差の変動を良好に補正することができる。
【００１７】
また、本発明では第２レンズ群の物体側と像側に負屈折力の第１レンズ群と第３レンズ群をそれぞれ配置することにより、光学系全体での屈折力配置を対称型に近づけて、歪曲収差及び倍率色収差を良好に補正できる。
【００１８】
そして、第２レンズ群が主に軸上収差の補正を担っている。この第２レンズ群を物体側から順に、正レンズ成分、負レンズ成分、正レンズ成分の３レンズ成分を配置することで、軸上収差を特に良好に補正し、軸外収差の発生も抑えることができる。
【００１９】
以上の構成により、本発明では各レンズ群で発生する諸収差をある程度補正しながら、第１レンズ群と第３レンズ群が主に軸外収差を補正する機能、そして第２レンズ群が主に軸上収差を補正する機能をそれぞれ有するように、収差補正上の機能を明確にすることで小型化と高性能化とを適切に図ることができる。
【００２０】
ところで、可変焦点距離レンズ系の近距離合焦方法としては、レンズ系を構成するレンズ群のうち１つのレンズ群を光軸方向に移動させるのが一般的である。そして、近距離合焦方法は以下の３通りに大別される。
（Ａ）１群繰出し方式，
（Ｂ）リアーフォーカス方式，
（Ｃ）インナーフォーカス方式．
１群繰出し方式はもっとも物体側に配置される第１レンズ群を移動させる方式、リアーフォーカス方式はもっとも像側に配置される最終レンズ群を移動させる方式、インナーフォーカス方式は第１レンズ群より像側で、最終レンズ群より物体側に配置されるレンズ群を移動させる方式である。
【００２１】
画角の大きなレンズ系では開口絞りから離れて配置されるレンズ群を通過する軸外光束が光軸から離れるため、レンズ径が大きく、フォーカシング時の仕事量が大きくなってしまう。このため、フォーカシング動作の高速化が難しく、撮影者が写したいと思った瞬間から、実際に撮影が行われるまでのタイムラグが大きく、違和感を与えてしまう。従って、（Ａ）や（Ｂ）の方式は不向きである。
【００２２】
（Ｃ）の方式で近距離合焦を行う場合、第１レンズ群で光束が広げられて第２レンズ群に入射するので、近距離合焦時に発生する軸上収差の変動が大きくなってしまう。
【００２３】
本発明においては、上述のように第２レンズ群中に開口絞りを配置して、第１レンズ群の屈折力を弱めることで、第１レンズ群を通過する軸外光束が光軸から大きく離れないようにして、且つ、第２レンズ群に入射する軸上光束が広がらないようにした。
【００２４】
また、近距離合焦時に第２レンズ群を移動させることで、近距離合焦時に第１レンズ群を通過する軸外光束が光軸に近づき、逆に第３レンズ群を通過する軸外光束が光軸から離れるので、結果的に両方で引き起こされる軸外収差変動が打ち消しあう。このため、無限遠合焦状態から近距離合焦状態まで良好なる性能を維持することができる。
【００２５】
従来より、物体側より順に、負屈折力を有する第１レンズ群、正屈折力を有する第２レンズ群、負屈折力を有する第３レンズ群を配置した負正負３群型のズームレンズが知られている。例えば、特開昭６４−７２１１４号公報では広角端状態で７２度程度の画角のズームレンズを提案しているが、第２レンズ群の像側に開口絞りが配置されたため、８０度を超える画角を包括すると、第１レンズ群のレンズ径が非常に大きくなってしまっている。
【００２６】
本発明では、以上のことから、広角端状態での画角が８０度を超える広い画角と、Ｆ３．５程度の大口径比化を実現しながら、近距離合焦時にも高い光学性能が達成できている。
【００２７】
以下、各条件式について説明する。
【００２８】
条件式（１）は第１レンズ群と第３レンズ群との屈折力のバランス化を図る条件式である。上述の通り、本発明では第２レンズ群を近距離合焦時に移動させる場合、軸上収差の変動を抑えるために第１レンズ群と第３レンズ群との屈折力を適切に設定することが肝要である。
【００２９】
条件式（１）の上限値を上回った場合、つまり、第１レンズ群の屈折力が負に強まり、第３レンズ群の屈折力が負に弱まる場合、近距離合焦時に発生する軸上収差の変動が大きくなってしまうため、良好なる光学性能が得られなくなってしまう。
【００３０】
逆に、条件式（１）の下限値を下回った場合、つまり、第１レンズ群の屈折力が負に弱まり、第３レンズ群の屈折力が負に強まる場合、第１レンズ群のレンズ径が大きくなって、ゴーストが目立ちやすくなる。これは、画角が大きなレンズ系では、第１レンズ群が画角の大きな光線がスムーズに入射する形状になっていることに起因する。撮影範囲外に強い光源があった場合にも、第１レンズ群内のレンズ面で反射した光束がフィルム上に到達して、ゴーストになるが、レンズ径が大きいほど、より多くの光束が入射できるため、ゴーストが起こりやすく、良好なる結像性能を阻害してしまう。
【００３１】
条件式（２）は第２レンズ群のレンズ厚を規定する条件式である。第２レンズ群は２つの正レンズの間に開口絞りを配置する構造であるため、開口絞り位置を通過する軸外光束が光軸に対して大きな角度をなす。このため、レンズ厚が大きくなると開口絞りから離れたレンズを通過する軸外光束が光軸から離れてしまうので、広角端状態で画面周辺部におけるコマ収差が多大に発生してしまう。
【００３２】
条件式（２）の上限値を上回った場合、広角端状態で画面周辺部におけるコマ収差が多大に発生して所定の性能を満足できなくなってしまう。本発明では、上記２つの正レンズだけでは第２レンズ群単独で発生する負の球面収差を良好に補正することができない。従って、これら正レンズの他に少なくとも１枚の負レンズが必要である。
【００３３】
逆に、条件式（２）の下限値を下回った場合、レンズ厚を考慮すると、開口絞りを配置する充分なスペースが確保できなくなってしまう。
【００３４】
また、本発明においては、良好なる結像性能を得ながらも、第１レンズ群のレンズ径を小型化するために、
第１レンズ群が像側に凹面を向けた負レンズとその像側に配置され、物体側に凸面を向けた正レンズで構成され、以下の条件式（３）を満足するように構成することが望ましい。
（３）１．３＜ｆ1P／ｆｗ＜３．０
但し、
ｆ1P：前記第１レンズ群中の正レンズの焦点距離，
ｆｗ：広角端状態における前記可変焦点距離レンズ系の焦点距離．
条件式（３）は第１レンズ群中の正レンズの焦点距離を規定する条件式である。条件式（３）の下限値を下回った場合、第１レンズ群を構成する負レンズと正レンズの屈折力がそれぞれ強まって、微小量の相互偏心でも周辺画像が劣化しまうので、製造時に安定した品質を確保できなくなってしまう。
【００３５】
逆に、条件式（３）の上限値を上回った場合、第１レンズ群に入射する軸外光束が光軸から大きく離れて、広角端状態で画面周辺部におけるコマ収差が多大に発生してしまう。
【００３６】
また、本発明においては、第２レンズ群中に開口絞りを挟んで物体側と像側にそれぞれ１枚以上の正レンズ成分を配置しているが、レンズ全長を短縮し、且つより良好なる結像性能を得るには以下の条件式（４）を満足することが望ましい。
（４）１．２＜ｆ21／ｆ22＜３．０
但し、
ｆ21：前記第２レンズ群中で、前記開口絞りよりも物体側に配置される前記正レンズ成分の焦点距離，
ｆ22：前記第２レンズ群中で、前記開口絞りよりも像側に配置される前記正レンズの焦点距離．
条件式（４）の上限値を上回った場合、レンズ全長が大きくなってしまうので、カメラ本体の携帯性を損ねてしまう。逆に、条件式（４）の下限値を下回った場合、開口絞りの物体側に配置される正レンズを通過する軸外光束が光軸から離れるので、広角端状態において、画角によるコマ収差の変動が大きくなってしまう。
【００３７】
また、本発明においては、第２レンズ群が物体側より順に、正レンズ成分、負レンズ成分、正レンズ成分の３つのレンズ成分で構成されるとき、充分高い光学性能とレンズ系の小型化とが両立できる。そして、製造時に安定した光学品質を確保するために、以下の条件式（５）を満足することが望ましい。
（５）１．０＜│ｆ2N│／ｆ２＜１．４ （ｆ２＜０）
但し、
ｆ2N：前記第２レンズ群中の前記負レンズの焦点距離
本発明においては、各レンズ群それぞれで発生する諸収差を補正することが、より良い光学性能を得る上で重要である。第１レンズ群と第２レンズ群を上述のように構成することで、良好なる光学性能が得られる。さらに、第３レンズ群が像側に凸面を向けた正レンズとその像側に配置され、物体側に凹面を向けた負レンズで構成するのが、小型化と高い光学品質とのバランス化に適している。
【００３８】
以下の各実施例では、第１レンズ群に非球面レンズを配置しているが、例えばさらに第３レンズ群中に非球面レンズを配置することで更なる高性能化が実現できるのは言うまでもない。
【００３９】
また、第３実施例及び第４実施例では、第２レンズ群を構成する正レンズ成分の１つを接合レンズとしているように、単レンズを接合レンズとすることでより高性能化が図れ、更に、他のレンズ成分を接合化することでより高性能化が達成できるのは言うまでもない。
【００４０】
さらに、以下の各実施例は３つのレンズ群で構成されるが、第３レンズ群の像側に屈折力が弱い他のレンズ群を付加することも容易である。
【００４１】
本発明においては、別の観点によれば、撮影を行う際に、発生しがちな手ブレ等が原因の像ブレによる失敗を防ぐために、ブレを検出するブレ検出系と駆動手段とをレンズ系に組み合わせ、レンズ系を構成するレンズ群のうち、１つのレンズ群を全体か、あるいはその一部を偏心レンズ群として偏心させることにより、ブレをブレ検出系により検出し、検出されたブレを補正するように駆動手段により偏心レンズ群を偏心させ像をシフトさせて、像ブレを補正することで防振光学系とすることが可能である。
【００４２】
【実施例】
以下、添付図面に基いて数値実施例について説明する。
【００４３】
なお、各実施例において、非球面は以下の式で表される。
【００４４】
【数１】
ｘ＝ｃｙ2／｛１＋（１−κｃ2ｙ2）1/2｝＋Ｃ4ｙ4＋Ｃ6ｙ6＋…
【００４５】
ここで、ｙは光軸からの高さ、ｘはサグ量、ｃは曲率、κは円錐定数、Ｃ4，Ｃ6，…は非球面係数である。
【００４６】
図１は、本発明の各実施例にかかる可変焦点距離レンズ系の屈折力配分を示す図である。物体側より順に、負屈折力を有する第１レンズ群Ｇ１、正屈折力を有する第２レンズ群Ｇ２、負屈折力を有する第３レンズ群Ｇ３で構成され、広角端状態より望遠端状態まで焦点距離が変化する際に、第１レンズ群Ｇ１と第２レンズ群Ｇ２との間隔が減少し、第２レンズ群Ｇ２と第３レンズ群Ｇ３との間隔が減少するように、少なくとも第２レンズ群Ｇ２と第３レンズ群Ｇ３が物体側へ移動する。
【００４７】
（第１実施例）
図２は、本発明の第１実施例にかかる可変焦点距離レンズ系のレンズ構成を示す図である。第１レンズ群Ｇ１は両凹レンズＬ１１と物体側に凸面を向けた正メニスカスレンズＬ１２とで構成され、第２レンズ群Ｇ２は物体側より順に、両凸レンズＬ２１と、物体側に凹面を向けたメニスカス形状のＬ２２と、両凸レンズＬ２３とで構成され、第３レンズ群Ｇ３は像側に凸面を向けたメニスカス形状の正レンズＬ３１と、物体側に凹面を向けたメニスカス形状の負レンズＬ３２とで構成される。
【００４８】
本実施例では、開口絞りＳが両凸レンズＬ２１と負レンズＬ２２との間に配置され、レンズ位置状態が変化する際に、第２レンズ群Ｇ２と一緒に移動する。
【００４９】
以下の表１に、本実施例の諸元の値を掲げる。諸元表中のｆは焦点距離、ＦNOはＦナンバー、２ωは画角をそれぞれ表し、屈折率はｄ線（λ=587.6nm）に対する値である。なお、表１中で曲率半径０とは平面を示す。また、以下全ての実施例の諸元値において本実施例の諸元値と同様の符号を用いる。
【００５０】
（表１）
（全体諸元）
ｆ 25.20 〜 28.00 〜 34.00
ＦNO 3.70 〜 3.70 〜 3.70
２ω 83.51 〜 77.45 〜 65.93°
（レンズデータ）
面 曲率半径 間 隔 屈折率 アッベ数
1 -68.0802 1.2000 1.74430 49.23
2 19.2543 2.2092 1.0
3 28.5714 2.7295 1.77250 49.61
4 -1406.0063 (D4) 1.0
5 18.6706 2.5833 1.62041 60.35
6 -256.5988 6.3790 1.0
7 0.0000 1.3335 1.0 開口絞り
8 -10.7645 0.8000 1.80518 25.46
9 -24.8063 0.7261 1.0
10 73.9918 2.8329 1.69680 55.48
11 -12.2915 (D11) 1.0
12 -19.0494 2.1406 1.69680 55.48
13 -14.2857 4.3377 1.0
14 -11.5265 1.0000 1.58913 61.24
15 -111.8463 (Bf) 1.0
（非球面係数）
第３面，第１１面の各レンズ面は非球面であり、非球面係数は以下に示す通りである。
［第３面］
κ＝ 1.000 Ｃ4 ＝-1.1331×10-6 Ｃ6 ＝+8.6403×10-8
Ｃ8 ＝-3.6633×10-10 Ｃ10＝+9.6406×10-13
［第１１面］
κ＝ 1.000 Ｃ4 ＝+8.1237×10-5 Ｃ6 ＝+1.0121×10-6
Ｃ8 ＝-2.2792×10-8 Ｃ10＝+2.9493×10-10
（可変間隔データ）
ｆ 25.2000 28.0000 34.0000
D4 3.3766 3.6103 1.5982
D11 6.8515 4.1928 1.2000
BF 9.5000 14.4237 22.4298
（フォーカシング時の第２レンズ群の移動量Δ２）
ただし、撮影倍率-1/30倍状態に合焦する場合である。
ｆ 25.2000 28.0000 34.0000
Δ２ 0.5863 0.5216 0.4690
なお、物体側への移動を正とする。
（条件式対応値）
ｆ１＝-52.726
ｆ２＝+19.790
ｆ３＝-32.766
ｆ1P＝+35.279
ｆ21＝+28.154
ｆ22＝+15.334
ｆ2N＝-24.234
（１）（ｆ３＋ｆ２）／（ｆ１＋ｆ２）＝０．３９４
（２）ΣＤ２／ｆｗ＝０．５８２
（３）ｆ1P／ｆｗ＝１．４００
（４）ｆ21／ｆ22＝１．８３６
（５）│ｆ2N│／ｆ２＝１．２２５
【００５１】
図３（ａ）より図３（ｃ）は本実施例の無限遠合焦状態での諸収差図をそれぞれ示し、それぞれ広角端状態（ｆ＝25.20）、中間焦点距離状態（ｆ＝28.00）、望遠端状態（ｆ＝34.00）における諸収差図を示す。
【００５２】
図４（ａ）より図４（ｃ）は本実施例の近距離合焦状態（撮影倍率-1/30倍）での諸収差図をそれぞれ示し、それぞれ広角端状態（ｆ＝25.20）、中間焦点距離状態（ｆ＝28.00）、望遠端状態（ｆ＝34.00）における諸収差図を示す。
【００５３】
各収差図において、球面収差図中の実線は球面収差、点線はサイン・コンディション、ｙは像高をそれぞれ示している。また、非点収差図中の実線はサジタル像面、破線はメリディオナル像面を示す。さらに、コマ収差図は、像高ｙ＝０，１０．８，１５．１２，１８．３４，２１．６でのコマ収差を表し、Ａは画角、Ｈは物体高をそれぞれ示す。なお、以下全ての実施例の収差図において、本実施例と同様の符号を用いる。
【００５４】
各収差図から、本実施例は諸収差が良好に補正され、優れた結像性能を有していることは明らかである。
【００５５】
（第２実施例）
図５は、本発明の第２実施例にかかる可変焦点距離レンズ系のレンズ構成を示す図である。第１レンズ群Ｇ１は両凹レンズＬ１１と物体側に凸面を向けた正メニスカスレンズＬ１２とで構成され、第２レンズ群Ｇ２は物体側より順に、物体側に凸面を向けたメニスカス形状の正レンズＬ２１と、物体側に凹面を向けたメニスカス形状のＬ２２と、両凸レンズＬ２３とで構成され、第３レンズ群Ｇ３は像側に凸面を向けたメニスカス形状の正レンズＬ３１と物体側に凹面を向けたメニスカス形状の負レンズＬ３２とで構成される。
【００５６】
本実施例では、開口絞りＳが正レンズＬ２１と負レンズＬ２２との間に配置され、レンズ位置状態が変化する際に、第２レンズ群Ｇ２と一緒に移動する。
【００５７】
以下の表２に、本実施例の諸元の値を掲げる。
【００５８】
（表２）
（全体諸元）
ｆ 25.20 〜 28.00 〜 34.00
ＦNO 3.70 〜 3.70 〜 3.70
２ω 83.04 〜 76.65 〜 64.91°
（レンズデータ）
面 曲率半径 間 隔 屈折率 アッベ数
1 -65.4521 1.2000 1.65844 50.84
2 25.7844 1.5000 1.0
3 25.0000 2.2500 1.79450 45.50
4 78.5031 (D4) 1.0
5 17.1172 2.1500 1.62041 60.35
6 2729.9303 2.5000 1.0
7 0.0000 2.2000 1.0 開口絞り
8 -12.1697 0.8000 1.80518 25.46
9 -34.8530 1.4500 1.0
10 50.3454 2.7000 1.69680 55.48
11 -14.1272 (D11) 1.0
12 -22.2222 2.0500 1.69680 55.48
13 -15.6344 5.0000 1.0
14 -11.1111 1.0000 1.58913 61.24
15 -156.1951 (Bf) 1.0
（非球面係数）
第３面，第１１面の各レンズ面は非球面であり、非球面係数は以下に示す通りである。
［第３面］
κ＝ 1.000 Ｃ4 ＝-6.0968×10-6 Ｃ6 ＝+1.5234×10-7
Ｃ8 ＝-1.4934×10-9 Ｃ10＝+6.1161×10-12
［第１１面］
κ＝ 1.000 Ｃ4 ＝+7.4274×10-5 Ｃ6 ＝+7.0858×10-7
Ｃ8 ＝-1.3234×10-8 Ｃ10＝+1.2553×10-10
（可変間隔データ）
ｆ 25.2000 28.0000 34.0000
D4 6.2994 4.9183 1.6168
D11 6.1006 4.1673 1.3155
BF 8.8000 12.3728 19.2679
（フォーカシング時の第２レンズ群の移動量Δ２）
ただし、撮影倍率-1/30倍状態に合焦する場合である。
ｆ 25.2000 28.0000 34.0000
Δ２ 0.5596 0.5233 0.4742
なお、物体側への移動を正とする。
（条件式対応値）
ｆ１＝-77.950
ｆ２＝+19.575
ｆ３＝-30.807
ｆ1P＝+45.325
ｆ21＝+27.756
ｆ22＝+16.109
ｆ2N＝-23.594
（１）（ｆ３＋ｆ２）／（ｆ１＋ｆ２）＝０．１９２
（２）ΣＤ２／ｆｗ＝０．４６８
（３）ｆ1P／ｆｗ＝１．８００
（４）ｆ21／ｆ22＝１．７２３
（５）│ｆ2N│／ｆ２＝１．２０５
【００５９】
図６（ａ）より図６（ｃ）は本実施例の無限遠合焦状態での諸収差図をそれぞれ示し、それぞれ広角端状態（ｆ＝25.20）、中間焦点距離状態（ｆ＝28.00）、望遠端状態（ｆ＝34.00）における諸収差図を示す。
【００６０】
図７（ａ）より図７（ｃ）は本実施例の近距離合焦状態（撮影倍率-1/30倍）での諸収差図をそれぞれ示し、それぞれ広角端状態（ｆ＝25.20）、中間焦点距離状態（ｆ＝28.00）、望遠端状態（ｆ＝34.00）における諸収差図を示す。
【００６１】
各収差図から、本実施例は諸収差が良好に補正され、優れた結像性能を有していることは明らかである。
【００６２】
（第３実施例）
図８は、本発明の第３実施例にかかる可変焦点距離レンズ系のレンズ構成を示す図である。第１レンズ群Ｇ１は両凹レンズＬ１１と物体側に凸面を向けた正メニスカスレンズＬ１２とで構成され、第２レンズ群Ｇ２は物体側より順に、両凸レンズと物体側に凹面を向けた負メニスカスレンズとの接合正レンズＬ２１と、物体側に凹面を向けたメニスカス形状のＬ２２と、両凸レンズＬ２３とで構成され、第３レンズ群Ｇ３は像側に凸面を向けたメニスカス形状の正レンズＬ３１と物体側に凹面を向けたメニスカス形状の負レンズＬ３２とで構成される。
【００６３】
本実施例では、開口絞りＳが接合正レンズＬ２１と負レンズＬ２２との間に配置され、レンズ位置状態が変化する際に、第２レンズ群Ｇ２と一緒に移動する。
【００６４】
以下の表３に、本実施例の諸元の値を掲げる。
【００６５】
（表３）
（全体諸元）
ｆ 25.20 〜 28.00 〜 34.00
ＦNO 3.70 〜 3.70 〜 3.70
２ω 83.06 〜 76.12 〜 64.38°
（レンズデータ）
面 曲率半径 間 隔 屈折率 アッベ数
1 -60.2717 1.2000 1.62041 60.35
2 28.1025 1.5000 1.0
3 25.0000 2.0500 1.83500 42.97
4 49.3557 (D4) 1.0
5 17.4148 2.8500 1.71300 53.93
6 -37.8130 0.8000 1.78472 25.70
7 -417.6123 2.8500 1.0
8 0.0000 2.3500 1.0 開口絞り
9 -11.6583 0.8000 1.80518 25.46
10 -35.2519 0.8000 1.0
11 85.4876 2.5000 1.74400 44.90
12 -13.4807 (D12) 1.0
13 -22.2268 2.2000 1.69680 55.48
14 -14.7519 3.9500 1.0
15 -11.1111 1.0000 1.62041 60.35
16 -102.6898 (Bf) 1.0
（非球面係数）
第３面，第１２面の各レンズ面は非球面であり、非球面係数は以下に示す通りである。
［第３面］
κ＝ 1.000 Ｃ4 ＝-8.9883×10-6 Ｃ6 ＝+1.0862×10-7
Ｃ8 ＝-1.0524×10-9 Ｃ10＝+3.8757×10-12
［第１２面］
κ＝ 1.000 Ｃ4 ＝+6.8930×10-5 Ｃ6 ＝+1.0220×10-6
Ｃ8 ＝-2.5729×10-8 Ｃ10＝+3.0895×10-10
（可変間隔データ）
ｆ 25.2000 28.0000 34.0000
D4 6.3573 4.7616 1.7264
D11 5.9927 4.1320 1.2000
BF 8.8000 12.5665 19.2238
（フォーカシング時の第２レンズ群の移動量Δ２）
ただし、撮影倍率-1/30倍状態に合焦する場合である。
ｆ 25.2000 28.0000 34.0000
Δ２ 0.5879 0.5594 0.5148
なお、物体側への移動を正とする。
（条件式対応値）
ｆ１＝-66.337
ｆ２＝+19.235
ｆ３＝-32.920
ｆ1P＝+58.434
ｆ21＝+24.454
ｆ22＝+15.822
ｆ2N＝-21.966
（１）（ｆ３＋ｆ２）／（ｆ１＋ｆ２）＝０．２９１
（２）ΣＤ２／ｆｗ＝０．５１４
（３）ｆ1P／ｆｗ＝２．３１９
（４）ｆ21／ｆ22＝１．５４６
（５）│ｆ2N│／ｆ２＝１．１４２
【００６６】
図９（ａ）より図９（ｃ）は本実施例の無限遠合焦状態での諸収差図をそれぞれ示し、それぞれ広角端状態（ｆ＝25.20）、中間焦点距離状態（ｆ＝28.00）、望遠端状態（ｆ＝34.00）における諸収差図を示す。
【００６７】
図１０（ａ）より図１０（ｃ）は本実施例の近距離合焦状態（撮影倍率-1/30倍）での諸収差図をそれぞれ示し、それぞれ広角端状態（ｆ＝25.20）、中間焦点距離状態（ｆ＝28.00）、望遠端状態（ｆ＝34.00）における諸収差図を示す。
【００６８】
各収差図から、本実施例は諸収差が良好に補正され、優れた結像性能を有していることは明らかである。
【００６９】
（第４実施例）
図１１は、本発明の第４実施例にかかる可変焦点距離レンズ系のレンズ構成を示す図である。第１レンズ群Ｇ１は両凹レンズＬ１１と物体側に凸面を向けた正メニスカスレンズＬ１２とで構成され、第２レンズ群Ｇ２は物体側より順に、両凸レンズと物体側に凹面を向けた負メニスカスレンズとの接合正レンズＬ２１と、物体側に凹面を向けたメニスカス形状のＬ２２と、両凸レンズＬ２３とで構成され、第３レンズ群Ｇ３は像側に凸面を向けたメニスカス形状の正レンズＬ３１と物体側に凹面を向けたメニスカス形状の負レンズＬ３２とで構成される。
【００７０】
本実施例では、開口絞りＳが接合正レンズＬ２１と負レンズＬ２２との間に配置され、レンズ位置状態が変化する際に、第２レンズ群Ｇ２と一緒に移動する。
【００７１】
以下の表４に、本実施例の諸元の値を掲げる。
【００７２】
（表４）
（全体諸元）
ｆ 24.70 〜 28.00 〜 34.00
ＦNO 3.70 〜 3.70 〜 3.70
２ω 84.19 〜 76.23 〜 65.06°
（レンズデータ）
面 曲率半径 間 隔 屈折率 アッベ数
1 -57.4077 1.0000 1.62041 60.35
2 29.2764 1.5000 1.0
3 25.0000 2.0000 1.83500 42.97
4 47.8820 (D4) 1.0
5 18.1004 2.7500 1.72000 50.35
6 -38.9036 0.8000 1.80518 25.46
7 -240.6798 2.8500 1.0
8 0.0000 1.8500 1.0 開口絞り
9 -11.6649 0.8000 1.84666 23.83
10 -33.2916 1.0000 1.0
11 82.8214 2.4500 1.74400 44.90
12 -13.3522 (D12) 1.0
13 -22.2222 2.2500 1.69350 53.31
14 -14.9416 4.1000 1.0
15 -11.1111 1.0000 1.62041 60.35
16 -91.4973 (Bf) 1.0
（非球面係数）
第３面，第１２面の各レンズ面は非球面であり、非球面係数は以下に示す通りである。
［第３面］
κ＝ 1.000 Ｃ4 ＝-9.2627×10-6 Ｃ6 ＝+1.3781×10-7
Ｃ8 ＝-1.2223×10-9 Ｃ10＝+4.3623×10-12
［第１２面］
κ＝ 1.000 Ｃ4 ＝+6.5534×10-5 Ｃ6 ＝+1.2767×10-6
Ｃ8 ＝-3.7166×10-8 Ｃ10＝+4.7557×10-10
（可変間隔データ）
ｆ 24.7000 28.0000 34.0000
D4 5.6746 3.9449 1.6987
D11 6.7754 4.4708 1.2000
BF 8.0000 12.1648 19.7718
（フォーカシング時の第２レンズ群の移動量Δ２）
ただし、撮影倍率-1/30倍状態に合焦する場合である。
ｆ 24.7000 28.0000 34.0000
Δ２ 0.5994 0.5624 0.5034
なお、物体側への移動を正とする。
（条件式対応値）
ｆ１＝-65.600
ｆ２＝+19.013
ｆ３＝-32.940
ｆ1P＝+60.255
ｆ21＝+24.507
ｆ22＝+15.625
ｆ2N＝-21.575
（１）（ｆ３＋ｆ２）／（ｆ１＋ｆ２）＝０．２９９
（２）ΣＤ２／ｆｗ＝０．５０６
（３）ｆ1P／ｆｗ＝２．４３９
（４）ｆ21／ｆ22＝１．５６９
（５）│ｆ2N│／ｆ２＝１．１３５
【００７３】
図１２（ａ）より図１２（ｃ）は本実施例の無限遠合焦状態での諸収差図をそれぞれ示し、それぞれ広角端状態（ｆ＝24.70）、中間焦点距離状態（ｆ＝28.00）、望遠端状態（ｆ＝34.00）における諸収差図を示す。
【００７４】
図１３（ａ）より図１３（ｃ）は本実施例の近距離合焦状態（撮影倍率-1/30倍）での諸収差図をそれぞれ示し、それぞれ広角端状態（ｆ＝24.70）、中間焦点距離状態（ｆ＝28.00）、望遠端状態（ｆ＝34.00）における諸収差図を示す。
【００７５】
各収差図から、本実施例は諸収差が良好に補正され、優れた結像性能を有していることは明らかである。
【００７６】
【発明の効果】
本発明によれば、広角端状態での画角が８０度を超え、Ｆ３．５程度の明るく、小型の可変焦点距離レンズ系が達成できる。
【図面の簡単な説明】
【図１】本発明による可変焦点距離レンズ系の屈折力配置図
【図２】第１実施例にかかる可変焦点距離レンズ系の構成を示す断面図
【図３】第１実施例の、（ａ）は広角端状態における収差図（無限遠合焦状態）、（ｂ）は中間焦点距離状態における収差図（無限遠合焦状態）、（ｃ）は望遠端状態における収差図（無限遠合焦状態）
【図４】第１実施例の、（ａ）は広角端状態における収差図（近距離合焦状態）、（ｂ）は中間焦点距離状態における収差図（近距離合焦状態）、（ｃ）は望遠端状態における収差図（近距離合焦状態）
【図５】第２実施例にかかる可変焦点距離レンズ系の構成を示す断面図
【図６】第２実施例の、（ａ）は広角端状態における収差図（無限遠合焦状態）、（ｂ）は中間焦点距離状態における収差図（無限遠合焦状態）、（ｃ）は望遠端状態における収差図（無限遠合焦状態）
【図７】第２実施例の、（ａ）は広角端状態における収差図（近距離合焦状態）、（ｂ）は中間焦点距離状態における収差図（近距離合焦状態）、（ｃ）は望遠端状態における収差図（近距離合焦状態）
【図８】第３実施例にかかる可変焦点距離レンズ系の構成を示す断面図
【図９】第３実施例の、（ａ）は広角端状態における収差図（無限遠合焦状態）、（ｂ）は中間焦点距離状態における収差図（無限遠合焦状態）、（ｃ）は望遠端状態における収差図（無限遠合焦状態）
【図１０】第３実施例の、（ａ）は広角端状態における収差図（近距離合焦状態）、（ｂ）は中間焦点距離状態における収差図（近距離合焦状態）、（ｃ）は望遠端状態における収差図（近距離合焦状態）
【図１１】第４実施例にかかる可変焦点距離レンズ系の構成を示す断面図
【図１２】第４実施例の、（ａ）は広角端状態における収差図（無限遠合焦状態）、（ｂ）は中間焦点距離状態における収差図（無限遠合焦状態）、（ｃ）は望遠端状態における収差図（無限遠合焦状態）
【図１３】第４実施例の、（ａ）は広角端状態における収差図（近距離合焦状態）、（ｂ）は中間焦点距離状態における収差図（近距離合焦状態）、（ｃ）は望遠端状態における収差図（近距離合焦状態）
【符号の説明】
Ｇ１：第１レンズ群
Ｇ２：第２レンズ群
Ｇ３：第３レンズ群
Ｓ：開口絞り
Ｌ１１〜Ｌ３２ 各レンズ成分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable focal length lens system having an angle of view exceeding 80 degrees at a wide angle end state and an aperture ratio of about 3.5, and more particularly to a variable focal length lens system having high optical performance even when focusing at close range.
[0002]
[Prior art]
The feature of the lens shutter type camera is that it is excellent in portability. This portability is classified as being small and lightweight. Since the length of the photographic lens affects the thickness of the camera body, and the lens diameter affects the height and width of the camera body, downsizing of the photographic lens system has directly affected the miniaturization of the camera.
[0003]
Zoom lenses can be taken closer to the subject, and cameras with zoom lenses have become mainstream in order to give the photographer freedom. And as the focal length in the telephoto end state is larger, shooting closer to the subject becomes possible, so the zoom ratio tends to increase so that the focal length in the telephoto end state becomes longer.
[0004]
By the way, lens shutter cameras are often used when going on a trip because of their excellent portability. However, when single-lens reflex camera users carry lens shutter cameras, they have a single aperture lens with a bright aperture ratio. I often carry my camera with me.
[0005]
And when the user group of a single-lens reflex camera carries at the time of a travel, the imaging system with a large aperture ratio and a wide angle of view is preferred. This is because the former allows shooting with natural color without a strobe, and the latter allows shooting with a wide angle of view even when the distance between the photographer and the subject is short.
[0006]
[Problems to be solved by the invention]
However, the conventional lens shutter type camera zoom lens has an unsuitable surface for traveling. That is, as the focal length in the telephoto end state increases, the open F number in the telephoto end state tends to increase, resulting in a photograph with poor perspective, and more flash photography.
[0007]
As described above, a camera system for traveling is preferred to a lens system having a wide angle of view and a large aperture ratio. However, as the angle of view widens, the lens diameter tends to increase, and off-axis light flux enters the focusing group. When the focusing group is moved when the incident angle is large and focusing at a short distance, there is a problem that the passing height is greatly changed to increase the off-axis aberration fluctuation.
[0008]
The present invention has been made in view of the above problems, and provides a variable focal length lens system in which the angle of view in the wide-angle end state exceeds 80 degrees, is bright and compact, and provides high optical performance even when focusing at close range. The purpose is to provide.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention includes, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power. When the lens position changes from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, and the second lens group and the third lens group At least the second lens group and the third lens group are moved toward the object side so that the interval is reduced, and the second lens group includes at least two positive lens components and the two lens elements. It has at least one negative lens component arranged between the positive lens components, an aperture stop is arranged between the two positive lens components, and the second lens group moves toward the object side when focusing at a short distance. Move to the following conditional expressions (1), (2),(4),And a variable focal length lens system that satisfies (5).
(1) 0.1 <(f3 + f2) / (f1 + f2) <0.5
                (F1 <0, f2> 0, f3 <0)
(2) 0.4 <ΣD2 / fw <0.6
(4) 1.2 <f21 / f22 <3.0
(5) 1.0 <| f2N | / f2 <1.4 (f2 <0)
  However,
f1: the focal length of the first lens group,
f2: focal length of the second lens group,
f3: focal length of the third lens group,
ΣD2: lens thickness of the second lens group,
f2N: focal length of the negative lens component in the second lens group.
f21: a focal length of the positive lens component arranged on the object side of the aperture stop in the second lens group,
f22: Focal length of the positive lens component arranged on the image side of the aperture stop in the second lens group.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Conventionally, the variable focal length lens system is roughly classified into a positive leading type in which a lens group having positive refractive power is arranged on the most object side of the lens system and a negative leading type in which a lens group having negative refractive power is arranged.
[0011]
The positive leading type is mainly used for a lens system having a focal length longer than the diagonal length of the screen, and is suitable for shortening the total lens length. The negative leading type is mainly used for a lens system having a wide angle of view.
[0012]
In the negative leading type, the off-axis light beam passing through the first lens group in the wide-angle end state (arranged closest to the object side) passes through a position closer to the optical axis than in the positive leading type, so that the lens diameter can be reduced. . However, when the zoom ratio is increased, in the telephoto end state, the axial light beam spreads and passes through the second lens group (arranged on the image side of the first lens group), so that a predetermined optical performance is obtained at the center of the screen. It is difficult to secure.
[0013]
In addition, the lens system used in the lens shutter type camera realizes a reduction in the overall lens length and a reduction in the lens diameter by disposing the negative lens group on the most image side of the lens system.
[0014]
In the present invention, the first lens group having negative refractive power on the most object side of the lens system and the second lens group having positive refractive power on the image side thereof are given priority over a large aperture ratio and a wide angle of view over the zoom ratio. Further, a third lens group having negative refractive power is disposed on the image side. In the wide-angle end state, the distance between the first lens group and the second lens group, and the distance between the second lens group and the third lens group are widened, and the lens position state toward the telephoto end state. As the distance changes, at least the second lens group and the third lens group are moved toward the object side so that the distance between the lens groups is narrowed. Thereby, the lens diameter is reduced so that the off-axis light beam passing through the first lens group and the third lens group is not greatly separated from the optical axis.
[0015]
Further, in an optical system having a wide angle of view, the position where the aperture stop is disposed is important. In the present invention, the aperture stop is disposed inside the second lens group.
[0016]
By arranging the aperture stop in this manner and sufficiently widening the distance between the lens groups in the wide-angle end state, the off-axis light beam passing through the first lens group and the third lens group is slightly separated from the optical axis. External aberrations can be corrected sufficiently satisfactorily. In addition, as the lens position state changes toward the telephoto end state, the height of the off-axis light beam passing through the first lens group and the third lens group is positively changed by narrowing the distance between the lens groups. Thus, it is possible to satisfactorily correct the fluctuation of the off-axis aberration that occurs with the change in the lens position state.
[0017]
In the present invention, the first lens group and the third lens group having negative refractive power are arranged on the object side and the image side of the second lens group, respectively, so that the refractive power arrangement in the entire optical system is made closer to a symmetrical type. In addition, distortion and lateral chromatic aberration can be satisfactorily corrected.
[0018]
The second lens group is mainly responsible for correcting the axial aberration. By arranging the second lens group in order from the object side, three lens components including a positive lens component, a negative lens component, and a positive lens component, axial aberrations are corrected particularly well, and occurrence of off-axis aberrations is also suppressed. Can do.
[0019]
With the above configuration, in the present invention, the first lens group and the third lens group mainly correct off-axis aberrations while correcting various aberrations generated in each lens group to some extent, and the second lens group mainly By clarifying the aberration correction function so as to have the function of correcting the axial aberration, it is possible to appropriately achieve downsizing and high performance.
[0020]
By the way, as a short-distance focusing method of the variable focal length lens system, it is general to move one lens group in the optical axis direction among the lens groups constituting the lens system. And the short distance focusing method is roughly divided into the following three types.
(A) 1 group feeding system,
(B) Rear focus method,
(C) Inner focus method.
The first group feeding method is a method of moving the first lens group arranged closest to the object side, the rear focus method is a method of moving the final lens group arranged closest to the image side, and the inner focus method is an image from the first lens group. This is a method of moving the lens group arranged on the object side from the final lens group.
[0021]
In a lens system having a large angle of view, the off-axis light beam that passes through a lens group arranged away from the aperture stop is separated from the optical axis, so that the lens diameter is large and the amount of work during focusing is large. For this reason, it is difficult to increase the speed of the focusing operation, and the time lag from the moment when the photographer wants to take a picture to when the picture is actually taken is great, which gives a sense of incongruity. Therefore, the methods (A) and (B) are not suitable.
[0022]
When focusing at a short distance by the method (C), the luminous flux is expanded by the first lens group and is incident on the second lens group, so that the fluctuation of the on-axis aberration generated at the time of focusing at the short distance becomes large. .
[0023]
In the present invention, as described above, the aperture stop is disposed in the second lens group, and the refractive power of the first lens group is weakened so that the off-axis light beam passing through the first lens group is greatly separated from the optical axis. The axial light beam incident on the second lens group is prevented from spreading.
[0024]
Further, by moving the second lens group at the time of focusing at a short distance, the off-axis light beam that passes through the first lens group at the time of focusing at a short distance approaches the optical axis, and conversely, the off-axis light beam that passes through the third lens group. Since the distance from the optical axis, off-axis aberration fluctuations caused by both cancel each other. For this reason, it is possible to maintain good performance from the infinitely focused state to the short-range focused state.
[0025]
Conventionally, in order from the object side, there is known a negative positive / negative three group type zoom lens in which a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power are arranged. It has been. For example, Japanese Patent Laid-Open No. 64-72114 proposes a zoom lens having an angle of view of about 72 degrees in the wide-angle end state. However, since an aperture stop is disposed on the image side of the second lens group, it exceeds 80 degrees. Including the angle of view, the lens diameter of the first lens group has become very large.
[0026]
In the present invention, from the above, a wide angle of view exceeding 80 degrees at the wide-angle end state and a large aperture ratio of about F3.5, while achieving high optical performance even at close focus. It has been achieved.
[0027]
Hereinafter, each conditional expression will be described.
[0028]
Conditional expression (1) is a conditional expression for balancing the refractive powers of the first lens group and the third lens group. As described above, in the present invention, when the second lens group is moved when focusing at a short distance, the refractive powers of the first lens group and the third lens group can be appropriately set in order to suppress the fluctuation of the axial aberration. It is essential.
[0029]
When the upper limit value of conditional expression (1) is exceeded, that is, when the refractive power of the first lens group becomes negative and the refractive power of the third lens group becomes negatively negative, on-axis aberrations that occur during focusing at short distances As a result, the optical performance will not be satisfactory.
[0030]
Conversely, when the lower limit value of conditional expression (1) is not reached, that is, when the refractive power of the first lens group becomes negatively negative and the refractive power of the third lens group becomes negatively negative, the lens diameter of the first lens group Becomes larger and the ghost is more noticeable. This is because, in a lens system having a large angle of view, the first lens group has a shape in which a light beam having a large angle of view smoothly enters. Even if there is a strong light source outside the shooting range, the light beam reflected by the lens surface in the first lens group reaches the film and becomes a ghost. However, the larger the lens diameter, the more light beam is incident. Therefore, a ghost is likely to occur, and good imaging performance is hindered.
[0031]
Conditional expression (2) is a conditional expression that defines the lens thickness of the second lens group. Since the second lens group has a structure in which an aperture stop is disposed between two positive lenses, an off-axis light beam passing through the aperture stop position forms a large angle with respect to the optical axis. For this reason, when the lens thickness is increased, the off-axis light beam passing through the lens away from the aperture stop is separated from the optical axis, so that a large amount of coma aberration occurs at the periphery of the screen in the wide-angle end state.
[0032]
If the upper limit value of conditional expression (2) is exceeded, a large amount of coma aberration occurs at the periphery of the screen in the wide-angle end state, and the predetermined performance cannot be satisfied. In the present invention, it is not possible to satisfactorily correct negative spherical aberration that occurs in the second lens group alone by using only the two positive lenses. Therefore, at least one negative lens is required in addition to these positive lenses.
[0033]
On the other hand, if the lower limit of conditional expression (2) is not reached, considering the lens thickness, a sufficient space for arranging the aperture stop cannot be secured.
[0034]
In the present invention, in order to reduce the lens diameter of the first lens group while obtaining good imaging performance,
The first lens group is composed of a negative lens having a concave surface facing the image side and a positive lens having the convex surface facing the object side, and is configured to satisfy the following conditional expression (3): Is desirable.
(3) 1.3 <f1P / fw <3.0
However,
f1P: the focal length of the positive lens in the first lens group,
fw: focal length of the variable focal length lens system in the wide-angle end state.
Conditional expression (3) is a conditional expression that defines the focal length of the positive lens in the first lens group. If the lower limit of conditional expression (3) is not reached, the refractive power of the negative lens and the positive lens constituting the first lens group will increase, and the surrounding image will deteriorate even with a minute amount of mutual decentering. Quality cannot be secured.
[0035]
Conversely, when the upper limit value of conditional expression (3) is exceeded, the off-axis light beam incident on the first lens group is far away from the optical axis, resulting in a large amount of coma at the periphery of the screen at the wide-angle end state. End up.
[0036]
In the present invention, one or more positive lens components are disposed on the object side and the image side, respectively, with an aperture stop in the second lens group. However, the overall length of the lens is shortened and a better result is obtained. In order to obtain image performance, it is desirable to satisfy the following conditional expression (4).
(4) 1.2 <f21 / f22 <3.0
However,
f21: a focal length of the positive lens component arranged on the object side of the aperture stop in the second lens group,
f22: Focal length of the positive lens disposed in the second lens group on the image side of the aperture stop.
If the upper limit value of conditional expression (4) is exceeded, the total lens length becomes large, and the portability of the camera body is impaired. Conversely, when the lower limit value of conditional expression (4) is not reached, the off-axis light beam that passes through the positive lens disposed on the object side of the aperture stop is separated from the optical axis. The fluctuation of becomes large.
[0037]
In the present invention, when the second lens group is composed of three lens components in order from the object side, a positive lens component, a negative lens component, and a positive lens component, sufficiently high optical performance and downsizing of the lens system are achieved. Can be compatible. And in order to ensure the stable optical quality at the time of manufacture, it is desirable to satisfy the following conditional expressions (5).
(5) 1.0 <| f2N | / f2 <1.4 (f2 <0)
However,
f2N: focal length of the negative lens in the second lens group
In the present invention, it is important to correct various aberrations generated in each lens group in order to obtain better optical performance. By configuring the first lens group and the second lens group as described above, good optical performance can be obtained. Furthermore, the third lens group is composed of a positive lens with a convex surface facing the image side and a negative lens with the convex surface facing the image side, and a concave lens facing the object side, to achieve a balance between miniaturization and high optical quality. Is suitable.
[0038]
In each of the following embodiments, an aspheric lens is arranged in the first lens group. Needless to say, further performance improvement can be realized by further arranging an aspheric lens in the third lens group, for example. .
[0039]
In the third and fourth embodiments, a single lens can be a cemented lens so that one of the positive lens components constituting the second lens group is a cemented lens. Furthermore, it goes without saying that higher performance can be achieved by bonding other lens components.
[0040]
Furthermore, each of the following examples is composed of three lens groups.Of the third lens groupimageOn the sideIt is easy to add another lens group having a weak refractive power.
[0041]
According to another aspect of the present invention, in order to prevent a failure due to an image blur caused by a camera shake or the like that is likely to occur when taking a picture, a blur detection system that detects a blur and a driving unit are provided in the lens system. In combination with the lens group, one lens group is made entirely or partly decentered as an eccentric lens group, and blur is detected by the blur detection system, and the detected blur is corrected. As described above, it is possible to obtain an image stabilizing optical system by correcting the image blur by decentering the decentering lens group by the driving means and shifting the image.
[0042]
【Example】
Hereinafter, numerical examples will be described with reference to the accompanying drawings.
[0043]
In each embodiment, the aspherical surface is expressed by the following equation.
[0044]
[Expression 1]
x = cy2/ {1+ (1-κc2y2)1/2} + CFouryFour+ C6y6+ ...
[0045]
Here, y is the height from the optical axis, x is the sag amount, c is the curvature, κ is the conic constant, CFour, C6, ... are aspheric coefficients.
[0046]
FIG. 1 is a diagram showing the refractive power distribution of the variable focal length lens system according to each embodiment of the present invention. In order from the object side, the first lens group G1 having negative refracting power, the second lens group G2 having positive refracting power, and the third lens group G3 having negative refracting power are focused from the wide-angle end state to the telephoto end state. At least the second lens group so that the distance between the first lens group G1 and the second lens group G2 decreases and the distance between the second lens group G2 and the third lens group G3 decreases when the distance changes. G2 and the third lens group G3 move to the object side.
[0047]
  (First embodiment)
  FIG. 2 is a diagram showing a lens configuration of the variable focal length lens system according to the first embodiment of the present invention. The first lens group G1 is composed of a biconcave lens L11 and a positive meniscus lens L12 having a convex surface facing the object side, and the second lens group G2 is, in order from the object side, a biconvex lens L21 and a meniscus having a concave surface facing the object side. The third lens group G3 includes a meniscus positive lens L31 having a convex surface facing the image side, and a meniscus negative lens L having a concave surface facing the object side.32It consists of.
[0048]
In this embodiment, the aperture stop S is disposed between the biconvex lens L21 and the negative lens L22, and moves together with the second lens group G2 when the lens position state changes.
[0049]
Table 1 below lists values of specifications of the present example. In the specification table, f represents the focal length, FNO represents the F number, 2ω represents the angle of view, and the refractive index is a value for the d-line (λ = 587.6 nm). In Table 1, a curvature radius of 0 indicates a plane. In addition, the same signs as the specification values of the present embodiment are used in the specification values of all the embodiments below.
[0050]
  (Table 1)
(Overall specifications)
  f 25.20-28.00-34.00
  FNO 3.70-3.70-3.70
  2ω 83.51 to 77.45 to 65.93 °
(Lens data)
  Surface Curvature Radius Separation Refractive Index Abbe Number
  1 -68.0802 1.2000 1.74430 49.23
  2 19.2543 2.2092 1.0
  3 28.5714 2.7295 1.77250 49.61
  4 -1406.0063 (D4) 1.0
  5 18.6706 2.5833 1.62041 60.35
  6 -256.5988 6.3790 1.0
  7 0.0000 1.3335 1.0 Aperture stop
  8 -10.7645 0.8000 1.80518 25.46
  9 -24.8063 0.7261 1.0
10 73.9918 2.8329 1.69680 55.48
11 -12.2915 (D11) 1.0
12 -19.0494 2.1406 1.69680 55.48
13 -14.2857 4.3377 1.0
14 -11.5265 1.0000 1.58913 61.24
15 -111.8463 (Bf) 1.0
(Aspheric coefficient)
The lens surfaces of the third surface and the eleventh surface are aspheric surfaces, and the aspheric coefficient isLess thanAs shown in
[Third side]
    κ = 1.000 CFour= -1.1331 × 10-6  C6= + 8.6403 × 10-8
                 C8= -3.6633 × 10-Ten   CTen= + 9.6406 × 10-13
[Eleventh side]
    κ = 1.000 CFour= + 8.1237 × 10-Five  C6= + 1.0121 × 10-6
                 C8= -2.2792 × 10-8   CTen= + 2.9493 × 10-Ten
(Variable interval data)
   f 25.2000 28.000034.0000
  D4 3.3766 3.6103 1.5982
D11 6.8515 4.1928 1.2000
  BF 9.5000 14.4237 22.4298
(Moving amount Δ2 of the second lens group during focusing)
However, this is a case of focusing on the photographing magnification of -1/30.
f 25.2000 28.0000 34.0000
Δ2 0.5863 0.5216 0.4690
Note that the movement toward the object side is positive.
(Values for conditional expressions)
f1 = -52.726
f2 = + 19.790
f3 = -32.766
f1P = + 35.279
f21 = + 28.154
f22 = + 15.334
f2N = -24.234
(1) (f3 + f2) / (f1 + f2) = 0.394
(2) ΣD2 / fw = 0.582
(3) f1P / fw =1.400
(4) f21 / f22 = 1.835
(5) | f2N | /f2=1.225
[0051]
3 (a) to 3 (c) show various aberration diagrams in the infinitely focused state according to the present embodiment, respectively, and the wide-angle end state (f = 25.20), the intermediate focal length state (f = 28.00), respectively. The aberration diagrams in the telephoto end state (f = 34.00) are shown.
[0052]
4 (a) to 4 (c) show various aberration diagrams in the short-distance in-focus state (shooting magnification -1/30 times) of the present embodiment, respectively, in the wide-angle end state (f = 25.20) and in the middle. The aberration diagrams in the focal length state (f = 28.00) and the telephoto end state (f = 34.00) are shown.
[0053]
In each aberration diagram, the solid line in the spherical aberration diagram indicates the spherical aberration, the dotted line indicates the sine condition, and y indicates the image height. In the graph showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, the coma aberration diagram shows coma aberration at image heights y = 0, 10.8, 15.12, 18.34, and 21.6, A indicates an angle of view, and H indicates an object height. In the following aberration diagrams of all the examples, the same reference numerals as those in this example are used.
[0054]
From each aberration diagram, it is clear that the present example has excellent image forming performance with various aberrations corrected well.
[0055]
  (Second embodiment)
  FIG. 5 is a diagram showing a lens configuration of a variable focal length lens system according to the second embodiment of the present invention. The first lens group G1 includes a biconcave lens L11 and a positive meniscus lens L12 having a convex surface facing the object side. The second lens group G2 is a meniscus positive lens L21 having a convex surface facing the object side in order from the object side. A meniscus L22 having a concave surface facing the object side, and a biconvex lens L23. The third lens group G3 has a meniscus positive lens L31 having a convex surface facing the image side and a concave surface facing the object side. Meniscus negative lens L32It consists of.
[0056]
In this embodiment, the aperture stop S is disposed between the positive lens L21 and the negative lens L22, and moves together with the second lens group G2 when the lens position state changes.
[0057]
Table 2 below lists values of specifications of this example.
[0058]
  (Table 2)
(Overall specifications)
   f 25.20-28.00-34.00
FNO 3.70-3.70-3.70
  2ω 83.04 to 76.65 to 64.91 °
(Lens data)
  Surface Curvature Radius Separation Refractive Index Abbe Number
  1 -65.4521 1.2000 1.65844 50.84
  2 25.7844 1.5000 1.0
  3 25.0000 2.2500 1.79450 45.50
  4 78.5031 (D4) 1.0
  5 17.1172 2.1500 1.62041 60.35
  6 2729.9303 2.5000 1.0
  7 0.0000 2.2000 1.0 Aperture stop
  8 -12.1697 0.8000 1.80518 25.46
  9 -34.8530 1.4500 1.0
10 50.3454 2.7000 1.69680 55.48
11 -14.1272 (D11) 1.0
12 -22.2222 2.0500 1.69680 55.48
13 -15.6344 5.0000 1.0
14 -11.1111 1.0000 1.58913 61.24
15 -156.1951 (Bf) 1.0
(Aspheric coefficient)
The lens surfaces of the third surface and the eleventh surface are aspheric surfaces, and the aspheric coefficient isLess thanAs shown in
[Third side]
    κ = 1.000 CFour= -6.0968 × 10-6     C6= + 1.5234 × 10-7
                   C8= -1.4934 × 10-9     CTen= + 6.1161 × 10-12
[Eleventh side]
    κ = 1.000 CFour= + 7.4274 × 10-Five     C6= + 7.0858 × 10-7
                   C8= -1.3234 × 10-8     CTen= + 1.2553 × 10-Ten
(Variable interval data)
  f 25.2000 28.0000 34.0000
D4 6.2994 4.9183 1.6168
D11 6.1006 4.1673 1.3155
  BF 8.8000 12.3728 19.2679
(Moving amount Δ2 of the second lens group during focusing)
  However, this is a case of focusing on the photographing magnification of -1/30.
  f 25.2000 28.0000 34.0000
Δ2 0.5596 0.5233 0.4742
  Note that the movement toward the object side is positive.
(Values for conditional expressions)
f1 = -77.950
f2 = + 19.575
f3 = -30.807
f1P = + 45.325
f21 = + 27.756
f22 = + 16.109
f2N = -23.594
(1) (f3 + f2) / (f1 + f2) = 0.192
(2) ΣD2 / fw = 0.468
(3) f1P / fw = 1.800
(4) f21 / f22 = 1.723
(5) | f2N | /f2=1.205
[0059]
6 (a) to 6 (c) show various aberration diagrams in the infinitely focused state according to the present embodiment, respectively, and the wide-angle end state (f = 25.20), the intermediate focal length state (f = 28.00), respectively. The aberration diagrams in the telephoto end state (f = 34.00) are shown.
[0060]
FIG. 7 (a) to FIG. 7 (c) show various aberration diagrams in the short-distance in-focus state (imaging magnification-1 / 30 times) of the present embodiment, respectively, in the wide-angle end state (f = 25.20) and in the middle. The aberration diagrams in the focal length state (f = 28.00) and the telephoto end state (f = 34.00) are shown.
[0061]
From each aberration diagram, it is clear that the present example has excellent image forming performance with various aberrations corrected well.
[0062]
  (Third embodiment)
  FIG. 8 is a diagram showing the lens configuration of the variable focal length lens system according to the third example of the present invention. The first lens group G1 includes a biconcave lens L11 and a positive meniscus lens L12 having a convex surface facing the object side. The second lens group G2 is a negative meniscus lens having a biconvex lens and a concave surface facing the object side in order from the object side. Positive lens L21 having a concave surface facing the object side, a biconvex lens L23, and a third lens group G3 having a meniscus positive lens L31 having a convex surface facing the image side and the object Meniscus negative lens L with concave surface facing32It consists of.
[0063]
In the present embodiment, the aperture stop S is disposed between the cemented positive lens L21 and the negative lens L22, and moves together with the second lens group G2 when the lens position state changes.
[0064]
Table 3 below lists values of specifications of the present example.
[0065]
  (Table 3)
(Overall specifications)
   f 25.20-28.00-34.00
FNO 3.70-3.70-3.70
  2ω 83.06 to 76.12 to 64.38 °
(Lens data)
  Surface Curvature Radius Separation Refractive Index Abbe Number
  1 -60.2717 1.2000 1.62041 60.35
  2 28.1025 1.5000 1.0
  3 25.0000 2.0500 1.83500 42.97
  4 49.3557 (D4) 1.0
  5 17.4148 2.8500 1.71300 53.93
  6 -37.8130 0.8000 1.78472 25.70
  7 -417.6123 2.8500 1.0
  8 0.0000 2.3500 1.0 Aperture stop
  9 -11.6583 0.8000 1.80518 25.46
10 -35.2519 0.8000 1.0
11 85.4876 2.5000 1.74400 44.90
12 -13.4807 (D12) 1.0
13 -22.2268 2.2000 1.69680 55.48
14 -14.7519 3.9500 1.0
15 -11.1111 1.0000 1.62041 60.35
16 -102.6898 (Bf) 1.0
(Aspheric coefficient)
  The lens surfaces of the third surface and the twelfth surface are aspheric, and the aspheric coefficient isLess thanAs shown in
[Third side]
    κ = 1.000 CFour= -8.9883 × 10-6    C6= + 1.0862 × 10-7
                  C8= -1.0524 × 10-9    CTen= + 3.8757 × 10-12
[Twelfth surface]
    κ = 1.000 CFour= + 6.8930 × 10-Five    C6= + 1.0220 × 10-6
                  C8= -2.5729 × 10-8    CTen= + 3.0895 × 10-Ten
(Variable interval data)
  f 25.2000 28.0000 34.0000
D4 6.3573 4.7616 1.7264
D11 5.9927 4.1320 1.2000
  BF 8.8000 12.5665 19.2238
(Moving amount Δ2 of the second lens group during focusing)
  However, this is a case of focusing on the photographing magnification of -1/30.
  f 25.2000 28.0000 34.0000
Δ2 0.5879 0.5594 0.5148
  Note that the movement toward the object side is positive.
(Values for conditional expressions)
f1 = -66.337
f2 = + 19.235
f3 = -32.920
f1P = + 58.434
f21 = + 24.454
f22 = + 15.822
f2N = -21.966
(1) (f3 + f2) / (f1 + f2) = 0.291
(2) ΣD2 / fw = 0.514
(3) f1P / fw = 2.319
(4) f21 / f22 = 1.546
(5) | f2N | /f2=1.142
[0066]
9 (a) to 9 (c) show various aberration diagrams in the infinitely focused state according to the present embodiment, respectively. The wide-angle end state (f = 25.20), the intermediate focal length state (f = 28.00), respectively. The aberration diagrams in the telephoto end state (f = 34.00) are shown.
[0067]
10 (a) to 10 (c) show various aberration diagrams in the short-distance in-focus state (imaging magnification-1 / 30 times) of the present embodiment, respectively, in the wide-angle end state (f = 25.20) and in the middle. The aberration diagrams in the focal length state (f = 28.00) and the telephoto end state (f = 34.00) are shown.
[0068]
From each aberration diagram, it is clear that the present example has excellent image forming performance with various aberrations corrected well.
[0069]
  (Fourth embodiment)
  FIG. 11 is a diagram showing a lens configuration of a variable focal length lens system according to the fourth example of the present invention. The first lens group G1 includes a biconcave lens L11 and a positive meniscus lens L12 having a convex surface facing the object side. The second lens group G2 is a negative meniscus lens having a biconvex lens and a concave surface facing the object side in order from the object side. Positive lens L21 having a concave surface facing the object side, a biconvex lens L23, and a third lens group G3 having a meniscus positive lens L31 having a convex surface facing the image side and the object Meniscus negative lens L with concave surface facing32It consists of.
[0070]
In the present embodiment, the aperture stop S is disposed between the cemented positive lens L21 and the negative lens L22, and moves together with the second lens group G2 when the lens position state changes.
[0071]
Table 4 below lists values of specifications of the present example.
[0072]
  (Table 4)
(Overall specifications)
   f 24.70-28.00-34.00
FNO 3.70-3.70-3.70
2ω 84.19 〜 76.23 〜 65.06 °
(Lens data)
  Surface Curvature Radius Separation Refractive Index Abbe Number
  1 -57.4077 1.0000 1.62041 60.35
  2 29.2764 1.5000 1.0
  3 25.0000 2.0000 1.83500 42.97
  4 47.8820 (D4) 1.0
  5 18.1004 2.7500 1.72000 50.35
  6 -38.9036 0.8000 1.80518 25.46
  7 -240.6798 2.8500 1.0
  8 0.0000 1.8500 1.0 Aperture stop
  9 -11.6649 0.8000 1.84666 23.83
10 -33.2916 1.0000 1.0
11 82.8214 2.4500 1.74400 44.90
12 -13.3522 (D12) 1.0
13 -22.2222 2.2500 1.69350 53.31
14 -14.9416 4.1000 1.0
15 -11.1111 1.0000 1.62041 60.35
16 -91.4973 (Bf) 1.0
(Aspheric coefficient)
  The lens surfaces of the third surface and the twelfth surface are aspheric, and the aspheric coefficient isLess thanAs shown in
[Third side]
    κ = 1.000 CFour= -9.2627 × 10-6    C6= + 1.3781 × 10-7
                 C8= -1.2223 × 10-9    CTen= + 4.3623 × 10-12
[Twelfth surface]
    κ = 1.000 CFour= + 6.5534 × 10-Five    C6= + 1.2767 × 10-6
                  C8= -3.7166 × 10-8    CTen= + 4.7557 × 10-Ten
(Variable interval data)
  f 24.7000 28.0000 34.0000
  D4 5.6746 3.9449 1.6987
D11 6.7754 4.4708 1.2000
  BF 8.0000 12.1648 19.7718
(Moving amount Δ2 of the second lens group during focusing)
  However, this is a case of focusing on the photographing magnification of -1/30.
  f 24.7000 28.0000 34.0000
Δ2 0.5994 0.5624 0.5034
  Note that the movement toward the object side is positive.
(Values for conditional expressions)
f1 = -65.600
f2 = + 19.013
f3 = −32.940
f1P = + 60.255
f21 = + 24.507
f22 = + 15.625
f2N = -21.575
(1) (f3 + f2) / (f1 + f2) = 0.299
(2) ΣD2 / fw = 0.506
(3) f1P / fw = 2.439
(4) f21 / f22 = 1.568
(5) | f2N | /f2=1.135
[0073]
  12 (a) to 12 (c) show various aberration diagrams in the infinitely focused state according to the present embodiment, respectively, and are respectively in the wide-angle end state (f =24.70), Various aberration diagrams in the intermediate focal length state (f = 28.00) and the telephoto end state (f = 34.00).
[0074]
  From FIG. 13 (a) to FIG. 13 (c), various aberration diagrams in the short-distance focusing state (imaging magnification: −1/30 times) of the present example are shown, respectively, and the wide-angle end state (f =24.70), Various aberration diagrams in the intermediate focal length state (f = 28.00) and the telephoto end state (f = 34.00).
[0075]
From each aberration diagram, it is clear that the present example has excellent image forming performance with various aberrations corrected well.
[0076]
【The invention's effect】
According to the present invention, it is possible to achieve a bright and compact variable focal length lens system in which the angle of view in the wide-angle end state exceeds 80 degrees and is approximately F3.5.
[Brief description of the drawings]
FIG. 1 is a refractive power arrangement diagram of a variable focal length lens system according to the present invention.
FIG. 2 is a cross-sectional view showing a configuration of a variable focal length lens system according to a first embodiment.
3A is an aberration diagram in the wide-angle end state (infinite focus state), FIG. 3B is an aberration diagram in the intermediate focal length state (infinite focus state), and FIG. Is the aberration diagram in the telephoto end state (focused state at infinity)
4A is an aberration diagram in the wide-angle end state (near focus state), FIG. 4B is an aberration diagram in the intermediate focal length state (short focus state), and FIG. 4C. Is an aberration diagram in the telephoto end state (close-range in-focus state)
FIG. 5 is a sectional view showing a configuration of a variable focal length lens system according to a second embodiment.
6A is an aberration diagram in the wide-angle end state (infinite focus state), FIG. 6B is an aberration diagram in the intermediate focal length state (infinite focus state), and FIG. Is the aberration diagram in the telephoto end state (focused state at infinity)
7A is an aberration diagram in the wide-angle end state (near focus state), FIG. 7B is an aberration diagram in the intermediate focal length state (short focus state), and FIG. 7C. Is an aberration diagram in the telephoto end state (close-range in-focus state)
FIG. 8 is a sectional view showing a configuration of a variable focal length lens system according to a third embodiment;
9A is an aberration diagram in the wide-angle end state (infinite focus state), FIG. 9B is an aberration diagram in the intermediate focal length state (infinite focus state), and FIG. Is the aberration diagram in the telephoto end state (focused state at infinity)
10A is an aberration diagram in the wide-angle end state (near focus state), FIG. 10B is an aberration diagram in the intermediate focal length state (short focus state), and FIG. 10C. Is an aberration diagram in the telephoto end state (close-range in-focus state)
FIG. 11 is a sectional view showing a configuration of a variable focal length lens system according to a fourth embodiment;
12A is an aberration diagram in the wide-angle end state (infinite focus state), FIG. 12B is an aberration diagram in the intermediate focal length state (infinite focus state), and FIG. Is the aberration diagram in the telephoto end state (focused state at infinity)
13A is an aberration diagram in the wide-angle end state (near focus state), FIG. 13B is an aberration diagram in the intermediate focal length state (short focus state), and FIG. 13C. Is an aberration diagram in the telephoto end state (close-range in-focus state)
[Explanation of symbols]
G1: First lens group
G2: Second lens group
G3: Third lens group
S: Aperture stop
L11 to L32 Each lens component

Claims (4)

物体側より順に、負屈折力を有する第１レンズ群と、正屈折力を有する第２レンズ群と、負屈折力を有する第３レンズ群とを有し、
広角端状態から望遠端状態までレンズ位置状態が変化する際に、前記第１レンズ群と前記第２レンズ群との間隔が減少し、前記第２レンズ群と前記第３レンズ群との間隔が減少するように、少なくとも前記第２レンズ群と前記第３レンズ群がぞれぞれ物体側へ移動して、
前記第２レンズ群は、少なくとも２枚の正レンズ成分と、該２枚の正レンズ成分の間に配置される少なくとも１枚の負レンズ成分とを有し、
前記２枚の正レンズ成分の間に開口絞りが配置され、近距離合焦時に前記第２レンズ群が物体側へ移動し、以下の条件式（１）、（２）、（４）、及び（５）を満足することを特徴とする可変焦点距離レンズ系。
（１） ０．１＜（ｆ３＋ｆ２）／（ｆ１＋ｆ２）＜０．５
（ｆ１＜０，ｆ２＞０，ｆ３＜０）
（２） ０．４＜ΣＤ２／ｆｗ＜０．６
（４） １．２＜ｆ21／ｆ22＜３．０
（５） １．０＜│ｆ2N│／ｆ２＜１．４ （ｆ２＜０）
但し、
ｆ１：前記第１レンズ群の焦点距離，
ｆ２：前記第２レンズ群の焦点距離，
ｆ３：前記第３レンズ群の焦点距離，
ΣＤ２：前記第２レンズ群のレンズ厚，
ｆ2N：前記第２レンズ群中の前記負レンズ成分の焦点距離，
ｆ21：前記第２レンズ群中で、前記開口絞りよりも物体側に配置される前記正レンズ成分の焦点距離，
ｆ22：前記第２レンズ群中で、前記開口絞りよりも像側に配置される前記正レンズ成分の焦点距離． In order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power,
When the lens position changes from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, and the distance between the second lens group and the third lens group decreases. So that at least the second lens group and the third lens group move toward the object side, respectively, so as to decrease,
The second lens group includes at least two positive lens components and at least one negative lens component disposed between the two positive lens components,
An aperture stop is disposed between the two positive lens components, and the second lens group moves toward the object side when focusing at a short distance, and the following conditional expressions (1), (2), (4), and A variable focal length lens system satisfying (5).
(1) 0.1 <(f3 + f2) / (f1 + f2) <0.5
(F1 <0, f2> 0, f3 <0)
(2) 0.4 <ΣD2 / fw <0.6
(4) 1.2 <f21 / f22 <3.0
(5) 1.0 <| f2N | / f2 <1.4 (f2 <0)
However,
f1: the focal length of the first lens group,
f2: focal length of the second lens group,
f3: focal length of the third lens group,
ΣD2: lens thickness of the second lens group,
f2N: focal length of the negative lens component in the second lens group,
f21: a focal length of the positive lens component arranged on the object side of the aperture stop in the second lens group,
f22: Focal length of the positive lens component arranged on the image side of the aperture stop in the second lens group. 前記第１レンズ群は、像側に凹面を向けた負レンズとその像側に配置され、物体側に凸面を向けた正レンズとで構成され、以下の条件式（３）を満足することを特徴とする請求項１に記載の可変焦点距離レンズ系。
（３） １．３＜ｆ1P／ｆｗ＜３．０
但し、
ｆ1P：前記第１レンズ群中の正レンズの焦点距離，
ｆｗ：広角端状態における前記可変焦点距離レンズ系の焦点距離．The first lens group includes a negative lens having a concave surface facing the image side and a positive lens disposed on the image side and having a convex surface facing the object side, and satisfies the following conditional expression (3): The variable focal length lens system according to claim 1, wherein:
(3) 1.3 <f1P / fw <3.0
However,
f1P: the focal length of the positive lens in the first lens group,
fw: focal length of the variable focal length lens system in the wide-angle end state. 前記第１レンズ群は、非球面を有することを特徴とする請求項１または２に記載の可変焦点距離レンズ系。 3. The variable focal length lens system according to claim 1, wherein the first lens group has an aspherical surface. 前記第２レンズ群は、非球面を有することを特徴とする請求項１から３のいずれか一項に記載の可変焦点距離レンズ系。The second lens group, the variable focal length lens system according to any one of claims 1 to 3, characterized in that it has an aspherical surface.
JP2000103832A 2000-04-05 2000-04-05 Variable focal length lens system Expired - Lifetime JP4654482B2 (en)

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JP2004252099A (en) * 2003-02-19 2004-09-09 Nikon Corp Zoom lens equipped with vibration-proofing function
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JPH02136811A (en) * 1988-11-18 1990-05-25 Canon Inc Small-sized zoom lens
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JPH07253541A (en) * 1994-03-14 1995-10-03 Canon Inc Zoom lens

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JPH01163715A (en) * 1987-12-19 1989-06-28 Minolta Camera Co Ltd Zoom lens system for projecting microfilm with small distortion aberration
JPH02136811A (en) * 1988-11-18 1990-05-25 Canon Inc Small-sized zoom lens
JPH06160716A (en) * 1992-11-20 1994-06-07 Olympus Optical Co Ltd Zoom lens for scarcely causing short distance aberration fluctuation
JPH06175027A (en) * 1992-12-10 1994-06-24 Olympus Optical Co Ltd Small zoom lens of rear-focusing type
JPH07151974A (en) * 1993-11-29 1995-06-16 Canon Inc Zoom lens
JPH07253541A (en) * 1994-03-14 1995-10-03 Canon Inc Zoom lens

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