JP4829445B2 - Zoom lens and optical apparatus having the same - Google Patents

Description

【００２６】
なる条件式を満足することを特徴としている。
【００２７】
請求項７の発明は請求項１から６のいずれか１項の発明において前記第１レンズ群中の１つの負レンズの物体側の面の曲率半径をＲ１１ａ、像側の面の曲率半径をＲ１１ｂとするとき、
−３．８＜（Ｒ１１ｂ＋Ｒ１１ａ）／（Ｒ１１ｂ−Ｒ１１ａ）＜ −２．０
なる条件式を満足することを特徴としている。
【００２８】
請求項８の発明は請求項１から７のいずれか１項の発明において、前記第１レンズ群の最も物体側に位置する正レンズの物体側の面の曲率半径をＲ１２ａ、像側の面の曲率半径をＲ１２ｂとするとき、
０．５５＜（Ｒ１２ｂ＋Ｒ１２ａ）／（Ｒ１２ｂ−Ｒ１２ａ）＜ １．１
なる条件式を満足することを特徴としている。
【００２９】
請求項９の発明は請求項１から８のいずれか１項の発明において、前記第３レンズ群全体を光軸に対し垂直方向の成分を持つように変位させて光軸に対し垂直方向の像位置の補正を行うことを特徴としている。
【００３０】
請求項１０の発明は請求項１から９のいずれか１項の発明において、前記第３レンズ群は物体側より順に、物体側に凸面を向けた正レンズＧ３１と、像面側に凹面を向けたメニスカス形状の負レンズＧ３２を有し、前記正レンズＧ３１の物体側の面の曲率半径をＲ３１ａ、像側の面の曲率半径をＲ３１ｂ、前記負レンズＧ３２の物体側の面の曲率半径をＲ３２ａ、像側の面の曲率半径をＲ３２ｂとするとき、
１．３＜（Ｒ３１ｂ＋Ｒ３１ａ）／（Ｒ３１ｂ−Ｒ３１ａ）＜２．３
−４．０＜（Ｒ３２ｂ＋Ｒ３２ａ）／（Ｒ３２ｂ−Ｒ３２ａ）＜−１．５
なる条件式を満足することを特徴としている。
【００３１】
請求項１１の発明は請求項１から１０のいずれか１項の発明において、撮像素子上に像を形成する為の光学系であることを特徴としている。
【００３２】
請求項１２の発明の光学機器は、請求項１〜１１のいずれか１項に記載のズームレンズと、該ズームレンズによって形成された像を受光する撮像素子を有することを特徴としている。
【００３４】
【発明の実施の形態】
以下、本発明のズームレンズ及びそれを有する光学機器の実施形態について説明する。
【００３５】
図１は本発明の実施形態１の広角端におけるレンズ断面図、図２、図３、図４は本発明の実施形態１の広角端、中間のズーム位置、望遠端における収差図である。
【００３６】
図５は本発明の実施形態２の広角端におけるレンズ断面図、図６、図７、図８は本発明の実施形態２の広角端、中間のズーム位置、望遠端における収差図である。
【００３７】
図９は本発明の実施形態３の広角端におけるレンズ断面図、図１０、図１１、図１２は本発明の実施形態３の広角端、中間のズーム位置、望遠端における収差図である。
【００３８】
図１３は本発明のズームレンズの近軸屈折力配置の要部概略図である。
【００３９】
図１４は本発明において、光学系が振動したときに生ずる画像ぶれを補正する光学的原理の説明図である。
【００４０】
各実施形態のズームレンズのレンズ断面図と図１３において、Ｌ１は正の屈折力の第１レンズ群、Ｌ２は負の屈折力の第２レンズ群、Ｌ３は正の屈折力の第３レンズ群、Ｌ４は正の屈折力の第４レンズ群である。ＳＰは開口絞りであり、第３レンズ群Ｌ３の前方に位置している。
【００４１】
Ｇは光学フィルター、フェースプレート等に相当する光学ブロックである。ＩＰは像面であり、撮像手段の撮像面が位置している。ＦＰはフレアーカット絞りであり、不要光をカットしている。
【００４２】
各実施形態では、第３レンズ群Ｌ３の全部を光軸に垂直方向の成分を持つように移動（変移）させることにより、光学系全体が振動（傾動）したときの撮影画像のぶれを補正している。尚、第３レンズ群Ｌ３の一部を光軸と垂直方向の成分を持つように移動させて撮影画像のぶれを補正しても良い。
【００４３】
各実施形態では、広角端から望遠端への変倍(ズーミング)に際して矢印のように、変倍機能を有する第２レンズ群Ｌ２を像面側へ移動させると共に、変倍に伴う像面変動を第４レンズ群Ｌ４を移動させて補正している。また、第４レンズ群Ｌ４を光軸上移動させてフォーカシング（合焦）を行うリヤーフォーカス式を採用している。第４レンズ群Ｌ４に関する実線の曲線４ａと点線の曲線４ｂは、各々無限遠物体と近距離物体にフォーカスしているときの広角端から望遠端への変倍に伴う像面変動を補正するための移動軌跡を示している。尚、第１レンズ群Ｌ１と第３レンズ群Ｌ３は、変倍及びフォーカスの為には光軸方向に不動である。
【００４４】
各実施形態においては、第４レンズ群Ｌ４を移動させて変倍に伴う像面変動の補正を行う（像面の補正機能）と共に、第４レンズ群Ｌ４を移動させてフォーカスを行う（合焦機能を有する）ようにしている。特に、曲線４ａ、４ｂに示すように、広角端から望遠端への変倍に際して物体側へ凸状の軌跡を有するように移動させている。これにより第３レンズ群Ｌ３と第４レンズ群Ｌ４との空間の有効利用を図り、レンズ全長の短縮化を効果的に達成している。各実施形態において例えば、望遠端において無限遠物体から近距離物体へフォーカスを行う場合には、矢印４ｃに示すように第４レンズ群Ｌ４を前方に繰り出すことで行っている。
【００４５】
各実施形態においては、第３レンズ群Ｌ３を光軸と垂直方向の成分を持つように移動（変移）させて光学系全体が振動したときの像ぶれを補正するようにしている。これにより、可変頂角プリズム等の光学部材や防振のためのレンズ群を新たに付加することなく防振を行うようにし、光学系全体が大型化するのを防止している。
【００４６】
次にレンズ群を光軸と垂直方向の成分を持つように移動させて撮影画像のぶれを補正する防振系の光学的原理を図１４を用いて説明する。
【００４７】
図１４（Ａ）に示すように、光学系が物点Ｐ側より順に、固定群（固定レンズ群）Ｙ１、偏心群(偏心レンズ群、シフト群)Ｙ２そして固定群（固定レンズ群）Ｙ３の３つのレンズ群から成り立っており、光学系から十分に離れた光軸Ｌａ上の物点Ｐが撮像面ＩＰの中心に像点ｐとして結像しているものとする。今、撮像面ＩＰを含めた光学系全体が、図１４（Ｂ）のように手ぶれにより瞬間的に傾いたとすると、物点Ｐは像点Ｐ'にやはり瞬間的に移動し、ぶれた画像となる。一方、偏心群Ｙ２を光軸Ｌａと垂直方向に移動させると、図１４（Ｃ）のように、像点ｐは点ｐ"に移動し、その移動量と方向は光学系の屈折力配置に依存し、そのレンズ群の偏心敏感度として表される。そこで図１４（Ｂ）で、手振れによってずれた像点ｐ'を偏心群Ｙ２を適切な量だけ光軸と垂直方向に移動させることによって、もとの結像位置ｐに戻すことで図１４（Ｄ）に示すとおり、手振れ補正つまり防振を行っている。
【００４８】
今、光軸をθ°補正するために必要な偏心群Ｙ２の移動量（シフト量）をΔ、光学系全体の焦点距離をｆ，偏心群Ｙ２の偏心敏感度をＴＳとするとΔは以下の式で与えられる。
【００４９】
Δ＝ｆ・tan（θ） ／ ＴＳ
今、偏心群Ｙ２の偏心敏感度ＴＳが大きすぎると、移動量Δは小さな値となり防振に必要なシフト群Ｙ２の移動量は小さく出来るが、適切に防振を行うための制御が困難になり、補正残りが生じてしまう。特に、ビデオカメラやデジタルスチルカメラでは、ＣＣＤなどの撮像素子のイメージサイズが銀塩フィルムと比べて小さく、同一画角に対する焦点距離が短いため、同一角度を補正するための偏心群Ｙ２のシフト量Δが小さくなる。従って、メカの精度が同程度だと画面上での補正残りが相対的に大きくなることになってしまう。
【００５０】
一方偏心敏感度ＴＳが小さすぎると制御のために必要な偏心群Ｙ２の移動量が大きくなってしまい、偏心群Ｙ２を駆動するためのアクチュエーターなどの駆動手段も大きくなってしまう。
【００５１】
各実施形態では、各レンズ群の屈折力配置を適切な値に設定することで、第３レンズ群Ｌ３の偏心敏感度ＴＳを適正な値とし、メカの制御誤差による防振の補正残りが少なく、アクチュエーターなどの駆動手段の負荷も少ないズームレンズを達成している。
【００５２】
次に各実施形態のレンズ構成の特徴について説明する。
【００５３】
（ア−１） 第１レンズ群Ｌ１を、物体側より順に、物体側に比べ、像側に屈折力の絶対値に大きい凹面を向けた負レンズＧ１１、正レンズＧ１２、物体側に凸面を向けた２枚のメニスカス形状の正レンズＧ１３、Ｇ１４で構成している。負レンズＧ１１と正レンズＧ１２は独立又は接合されている。
【００５４】
実施形態１では正レンズＧ１２と正レンズＧ１４、実施形態２では正レンズＧ１２、実施形態３では正レンズＧ１２、正レンズＧ１３、正レンズＧ１４に異常分散性の硝材を使用することで第１レンズＬ１群で発生する色収差、特に焦点距離が長くなったときに補正が困難になる２次スペクトルを良好に補正している。
【００５５】
特に実施形態２では正レンズＧ１２にアッベ数νｄが９０以上の異常分散性の硝材を用いて、２次スペクトルを良好に補正している。
【００５６】
又、２次スペクトルを抑制する為に第１レンズ群Ｌ１中の負レンズＧ１１の材料のアッベ数をν−、部分分散比をＰｇｆとするとき、
３０ ＜ ν− ＜ ４０ ・・・（１）
Ｐｇｆ− ＜ ０．６ ・・・（２）
なる条件式を満足している。
但し Ｐｇｆ＝ （Ｎｇ−Ｎｆ）／（Ｎｆ−Ｎｃ）
Ｎｇ，Ｎｃ，Ｎｆは各々ｇ線、ｃ線、ｆ線に対する材料の屈折率である。
【００５７】
条件式（１）の下限を超えると負レンズＧ１１と正レンズＧ１２材料の分散の差が大きくなって、２波長での色消しを行う際に、各レンズの屈折力が弱くなって望遠端での球面収差の補正等には有利となるが、２次スペクトルを補正するための適切な硝材の選択が出来なくなってしまう。逆に上限を超えると各レンズの屈折力が強くなりすぎて望遠端での球面収差等が困難になるので良くない。
また条件式（２）の上限を超えると正レンズＧ１２と負レンズＧ１１の材料の部分分散比の差が大きくなって２次スペクトルの補正が難しくなってくる。
【００５８】
更に好ましくは、条件式（１）、（２）の数値範囲を
３２ ＜ ν− ＜ ３８ ・・・（１ａ）
Ｐｇｆ− ＜ ０．５９ ・・・（２ａ）
とするのが良い。
【００５９】
（ア−２） 第１レンズ群Ｌ１を構成する複数（２枚以上）の正レンズの材料の平均アッベ数をν＋とするとき、
ν＋ ＞ ７５ ・・・（３）
なる条件を満足している。条件式（３）の下限を超えると条件式（１）の条件下で色収差の補正を行おうとすると各レンズの屈折力が大きくなり過ぎて他の諸収差、特に望遠端における球面収差やコマ収差の補正が困難になるので良くない。
【００６０】
更に好ましくは条件式（３）の数値範囲を
ν＋ ＞ ７６ ・・・（３ａ）
とするのが良い。
【００６１】
（ア−３） 第１レンズ群Ｌ１の最も物体側に負レンズを配置している。これによって第１レンズ群と第２レンズ群間の主点間隔を小さくして前玉有効径が小さくなるようにしている
（ア−４） 通常、民生用の４つのレンズ群より成るズームレンズでは第１レンズ群は１枚の負レンズと２枚の正レンズで構成されているが、低分散硝材は屈折率も低いため、これをそのまま第１レンズ群中に使用すると各レンズの曲率が大きくなって望遠端における球面収差の補正が困難になる。
【００６２】
そこで各実施形態では第１レンズ群Ｌ１を１枚の負レンズと３枚の正レンズより構成することで正レンズの各レンズ面の曲率を適切な範囲とすることが出来、望遠端での球面収差を良好に補正している。
【００６３】
（ア−５） 第１レンズ群Ｌ１の焦点距離をｆ１、第１レンズ群Ｌ１中の負レンズＧ１２の焦点距離をｆ１Ｎとするとき
１．２ ＜ ｜ｆ１Ｎ｜／ｆ１ ＜ ２．２ ・・・（４）
なる条件式を満足している。
【００６４】
条件式（４）の下限を超えると広角端での歪曲の補正が困難になるので良くない。
【００６５】
また上限を超えると第１レンズ群Ｌ１内での色収差の補正が十分に行えないので良くない。
【００６６】
更に好ましくは条件式（４）の数値範囲を
１．４ ＜ ｜ｆ１Ｎ｜ｆ１ ＜ ２．０ ・・・（４ａ）
とするのが良い。
【００６７】
（ア−６） 実施形態１、３では十分な色収差補正効果を得る為に第１レンズ群Ｌ１中に材料のアッベ数をν＋とするとき、
ν１＋ ＞ ８０ ・・・（５）
なる条件式を満足する複数の正レンズを有している。
【００６８】
（ア−７） 良好な光学性能を維持しつつ、ズームレンズ全系の小型化を図る為に、第２レンズ群Ｌ２の焦点距離をｆ２、広角端での全系の焦点距離をｆｗ、望遠端での全系の焦点距離をｆｔとするとき
【００６９】
【数３】

【００７０】
なる条件式を満足している。
【００７１】
条件式（６）は、第１レンズ群Ｌ１の屈折力を規定する式である。条件式（６）の下限を超えて第１レンズ群Ｌ１の屈折力が強くなると、条件式（１）、（２）を満たしていても二次スペクトルの発生量が大きくなってくるので好ましくない。また、広角側で発生する倍率色収差が大きくなり補正困難となるためよくない。逆に上限を超えて第１レンズ群Ｌ１の屈折力が弱まると、レンズ全長が長くなり全系の小型化が難しくなる。
【００７２】
条件式（７）は、第２レンズ群Ｌ２の屈折力を規定する式である。条件式（７）の下限を超えて第２レンズ群Ｌ２の屈折力が強くなると、変倍時の第２レンズ群Ｌ２の移動量は小さくなるが、ペッツバール和が全体に負の方向に大きくなり像面湾曲の補正が困難になるので良くない。逆に条件式（７）の上限を超えると、第２レンズ群Ｌ２の変倍時の移動量が大きくなり、レンズ系全体が小型にならないので良くない。
【００７３】
更に好ましくは条件式（６）、（７）の数値範囲を
【００７４】
【数４】

【００７５】
とするのが良い。
【００７６】
（ア−８） デジタルスチルカメラ用のズームレンズでは高解像力が要望されており、特に変倍に伴なう倍率色収差を通常のビデオカメラ用のズームレンズに比べて、より良好に補正することが要望されている。そのため、第２レンズ群Ｌ２を、３枚以上の負レンズと１枚以上の正レンズより構成している。負レンズが２枚だけでは、全長短縮のために第２レンズ群Ｌ２の屈折力を大きくして変倍における移動量を小さくしようとすると、倍率色収差の補正が困難になる。この為第２レンズ群Ｌ２を物体側より順に、物体側に比べ像側に屈折力の絶対値が大きい凹面を向けたメニスカス形状の負レンズ、負レンズ、物体側に凸面を向けた正レンズ、負レンズを有するように構成することで第２レンズ群Ｌ２の主点の色消しを効果的に行って変倍に伴う倍率色収差の変動を良好に補正している。
【００７７】
（ア−９） 球面収差や歪曲などの諸収差を良好に補正するために、第１レンズ群Ｌ１中の負レンズＧ１１の物体側の面の曲率半径をＲ１１ａ、像側の面の曲率半径をＲ１１ｂとするとき
−３．８ ＜（Ｒ１１ｂ＋Ｒ１１ａ）／（Ｒ１１ｂ−Ｒ１１ａ）＜−２．０・・・（８）
なる条件式を満足している。
【００７８】
条件式（８）の下限を超えると、望遠端で球面収差の補正が困難になるので良くない。逆に上限を超えると広角端での歪曲収差の補正が困難になるので良くない。
【００７９】
更に好ましくは、条件式（８）の数値範囲を
−３．０＜（Ｒ１１ｂ＋Ｒ１１ａ）／（Ｒ１１ｂ−Ｒ１１ａ）＜−２．２・・・（８ａ）
とするのが良い。
【００８０】
（ア−１０） 第１レンズ群Ｌ１のもっとも物体側の正レンズＧ１２の物体側の面の曲率半径をＲ１２ａ、像側の面の曲率半径をＲ１２ｂとするとき
０．５５＜（Ｒ１２ｂ＋Ｒ１２ａ）／（Ｒ１２ｂ−Ｒ１２ａ）＜１．１・・・（９）
なる条件式を満足している。
【００８１】
条件式（９）の下限を超えると望遠端での球面収差の補正が困難になるので良くない。逆に上限を超えると望遠端での歪曲の補正が困難になる。
【００８２】
更に好ましくは条件式（９）の数値範囲を
０．６０＜（Ｒ１２ｂ＋Ｒ１２ａ）／（Ｒ１２ｂ−Ｒ１２ａ）＜１．０・・（９ａ）
とするのが良い。
【００８３】
（ア−１１） 第３レンズ群をＬ３の一部又は全部を光軸に垂直方向の成分を持つようにシフトすることで防振を行っている。各実施形態では第３レンズＬ３全体をシフトさせている。
【００８４】
光学性能、特に防振時の光学性能を良好に維持しつつ光学全長の小型化を達成する為に、第３レンズ群Ｌ３を２枚以上の正レンズと１枚以上の負レンズより構成している。特に、第３レンズ群Ｌ３を物体側から順に、物体側に凸面を向けた正レンズと物体側に比べ像面側に屈折力の絶対値が大きい凹面を有するメニスカス形状の負レンズを配置することで収差補正と全長短縮を両立を図っている。
【００８５】
更により良い光学性能を達成する為に、第３レンズ群Ｌ３の最も物体側に位置している正レンズＧ３１の物体側の面の曲率半径をＲ３１ａ、像側の面の曲率半径をＲ３１ｂ、第３レンズ群Ｌ３の負レンズＧ３２の物体側の面の曲率半径をＲ３２ａ、像側の面の曲率半径をＲ３２ｂとするとき、
１．３＜（Ｒ３１ｂ＋Ｒ３１ａ）／（Ｒ３１ｂ−Ｒ３１ａ）＜２．３・・・（１０）
−４．０＜（Ｒ３２ｂ＋Ｒ３２ａ）／（Ｒ３２ｂ−Ｒ３２ａ）＜−１．５
・・・（１１）
の条件式を満足している。
【００８６】
条件式（１０）は、第３レンズ群Ｌ３の最も物体側の正レンズの形状因子を規定する式である。条件式（１０）の上限を超えて、メニスカスの度合いが強まると各レンズ面で発生するコマ収差が大きくなり、高次のコマ収差が発生する。特に、防振時の偏芯コマ収差の発生が顕著になり、防振時の性能劣化となるためよくない。また下限を超えて両凸形状となると、物体側の面で発生する倍率色収差を像側面で補正する作用が弱まるためよくない。
【００８７】
条件式（１１）は、第３レンズ群Ｌ３の負レンズの形状因子を規定する式である。条件式（１１）の下限を超えてメニスカスの度合いが強まると、像側のレンズ面において一次の軸上色収差が補正過剰に作用し、ｇ線がｄ線に対してオーバーとなりすぎるためよくない。また上限を超えてメニスカスの度合いが弱まると、第３レンズ群Ｌ３をテレフォト構成とする作用が弱まり、レンズ全長が長くなるためよくない。
【００８８】
このような負レンズを設けた場合、そのレンズ面で正の歪曲収差が発生する。
これが防振時における偏心歪曲が大きくなる原因となる。
【００８９】
この減少を低減させるには、第３レンズ群Ｌ３全体で発生する歪曲収差を少なくしてやればよい。
【００９０】
各実施形態では、負レンズの像面側に正レンズを配置することによってある程度のテレフォト構成を維持しつつ、第３レンズ群Ｌ３内で歪曲収差を補正し、第３レンズ群Ｌ３をシフトして防振を行う際に、発生する偏心歪曲収差の発生を低減している。
【００９１】
更に好ましくは条件式（１０）、（１１）の数値範囲を
１．５＜（Ｒ３１ｂ＋Ｒ３１ａ）／（Ｒ３１ｂ−Ｒ３１ａ）＜２．０・・・（１０ａ）
−３．５＜（Ｒ３２ｂ＋Ｒ３２ａ）／（Ｒ３２ｂ−Ｒ３２ａ）＜−２．０・・・（１１ａ）
とするのが良い。
【００９２】
（ア−１２） 第４レンズ群Ｌ４を２枚の正レンズと１枚の負レンズで構成して、変倍時やフォーカス時に第４レンズ群Ｌ４が移動する事により発生する球面収差や像面湾曲の変動を低減している。
【００９３】
更に第４レンズ群Ｌ４の少なくとも１枚の正レンズは非球面を有している。
【００９４】
（ア−１３） 防振時の光量変化の低減を達成するためには変倍時に絞り開口径を望遠側で小さくして中心光束を制限することで相対的に周辺光量を増加するようにしている。
【００９５】
第３レンズ群Ｌ３は防振のために主軸と垂直方向の成分を持つように移動する分、レンズ径をそれだけ大きくしてやる必要がある。従って、Ｆナンバーで規制する以外の余計な軸上光束が入り過ぎないようにする為に、第３レンズ群Ｌ３の物体側あるいは像面側に固定の絞りを配置している。各実施形態では、第３レンズ群Ｌ３と第４レンズ群Ｌ４の間に固定絞りＦＰを配置することでスペースを有効に利用しつつ、不要な光束が通過しないようにしている。
【００９６】
次に本発明のズームレンズを撮影光学系として用いたデジタルスチルカメラ（光学機器）の実施形態を図１５を用いて説明する。
【００９７】
図１５において、１０はカメラ本体、１１は本発明のズームレンズによって構成された撮影光学系、１２は被写体像を観察するためのファインダーである。
【００９８】
１３はストロボ装置、１４は測定窓、１５はカメラの動作を知らせる液晶表示窓、１６はレリーズボタン、１７は各種のモードを切り替える操作スイッチである。このように本発明のズームレンズを光学機器に適用することにより小型で高い光学性能を有する光学機器を達成している。
【００９９】
以上のように、構成することにより各実施形態によれば望遠端の色収差を良好に補正し、かつズーム全域に渡って良好な光学性能を有するズームレンズを実現している。
【０１００】
特に、変倍比８以上の大きな変倍比を持ちながら、従来のビデオカメラ用のズームレンズと比較して望遠側の二次スペクトルが良好に補正され高い光学性能を有し、１００万画素以上の画素を有し、形成された像を受光する撮影素子を有するデジタルカメラにも十分対応できる光学性能を有したズームレンズ及びそれを有する各種の光学機器を実現することが出来る。
【０１０１】
次に、本発明の実施形態１〜３に各々対応する数値実施例１〜３を示す。各数値実施例においてｉは物体側からの光学面の順序を示し、Ｒｉは第ｉ番目の光学面（第ｉ面）の曲率半径、Ｄｉは第ｉ面と第ｉ＋１面との間の間隔、Ｎｉとνｉはそれぞれｄ線に対する第ｉ番目の光学部材の材料の屈折率、アッベ数を示す。またｋを離心率、Ｂ、Ｃ、Ｄ、Ｅ、Ｆ・・・を非球面係数、光軸からの高さｈの位置での光軸方向の変位を面頂点を基準にしてｘとするとき、非球面形状は、
ｘ＝（ｈ²／Ｒ）／[１＋[１−（１＋ｋ）（ｈ／Ｒ）²]^1/2]＋Ｂｈ⁴＋Ｃｈ⁶＋Ｄｈ⁸＋Ｅｈ¹⁰＋Ｆｈ¹²＋Ｇｈ¹⁴＋Ｈｈ¹⁶
で表示される。但しＲは曲率半径である。また例えば「ｅ−Ｚ」の表示は「１０^-Z」を意味する。また、各数値実施例における上述した条件式との対応を表１に示す。
【０１０２】
ｆは焦点距離、ＦｎｏはＦナンバーωは半画角を示す。
【０１０３】
【外１】

【０１０４】
【外２】

【０１０５】
【外３】

【０１０６】
【表１】

【０１０７】
【発明の効果】
本発明によれば高変倍比で多くの画素よりなる固体撮像素子を用いたときにも、十分対応できる高い光学性能を有したズームレンズ及びそれを有する光学機器を達成することができる。
【０１０８】
この他本発明によれば光学系の一部を構成する比較的小型軽量のレンズ群を光軸と垂直方向の成分を持つように移動させて、該光学系が振動（傾動）したときの画像のぶれを補正するように構成するとともに、画素のぶれを補正するためのレンズ群の構成を適切なものとすることにより、装置全体の小型化、機構上の簡素化及び駆動手段の負荷の軽減化を図りつつ、該レンズ群を偏心させた時の偏心収差を良好に補正した防振機能を有し、かつ望遠側の二次スペクトルを良好に補正し、１００万画素以上の画素を有する撮像素子を用いたカメラであっても、十分対応することができるズームレンズ及びそれを有する光学機器を達成することができる。
【図面の簡単な説明】
【図１】 本発明の数値実施例１のレンズ断面図
【図２】 本発明の数値実施例１の広角端の収差図
【図３】 本発明の数値実施例１の中間のズーム位置の収差図
【図４】 本発明の数値実施例１の望遠端の収差図
【図５】 本発明の数値実施例２のレンズ断面図
【図６】 本発明の数値実施例２の広角端の収差図
【図７】 本発明の数値実施例２の中間のズーム位置の収差図
【図８】 本発明の数値実施例２の望遠端の収差図
【図９】 本発明の数値実施例３のレンズ断面図
【図１０】 本発明の数値実施例３の広角端の収差図
【図１１】 本発明の数値実施例３の中間のズーム位置の収差図
【図１２】 本発明の数値実施例３の望遠端の収差図
【図１３】 本発明のズームレンズの近軸屈折力配置の概略図
【図１４】 本発明における防振の光学的原理の説明図
【図１５】 本発明の光学機器の要部概略図
【符号の説明】
Ｌ１ 第１レンズ群
Ｌ２ 第２レンズ群
Ｌ３ 第３レンズ群
Ｌ４ 第４レンズ群
ｄ ｄ線
ｇ ｇ線
ΔＭ メリディオナル像面
ΔＳ サジタル像面
ＳＰ 絞り
ＦＰ フレアーカット絞り
ＩＰ 結像面
Ｇ ＣＣＤのフォースプレートやローパスフィルター等のガラスブロック
ω 半画角
ｆｎｏ Ｆナンバー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens suitable for a still camera, a video camera, a silver salt photography camera, a digital still camera, and the like, and an optical apparatus having the same.
[0002]
In addition to this, the present invention moves a part of the lens group of the optical system so as to have a component in a direction perpendicular to the optical axis, thereby blurring a captured image (image) when the optical system vibrates (tilts). The present invention relates to a zoom lens having an anti-vibration function suitable for a video camera, a silver halide photography camera, a digital camera, and the like, which are optically corrected to obtain a still image and to stabilize a captured image, and an optical apparatus having the same. Is.
[0003]
[Prior art]
If an attempt is made to shoot from a moving object such as an ongoing car or aircraft, vibrations are transmitted to the photographic system, causing camera shake and blurring of the captured image. Conventionally, various anti-vibration optical systems (zoom lenses) having a function (anti-vibration function) for preventing blurring of captured images have been proposed.
[0004]
For example, in Japanese Patent Laid-Open No. 56-21133, an optical device is provided with detection means for detecting a vibration state, and some optical members in the optical device are imaged by vibration according to an output signal from the detection means. In order to stabilize the image, image blur is corrected (vibration-proof) by moving in a direction that cancels the vibrational displacement of the image. In JP-A-61-223819, in an imaging system in which a variable apex angle prism is arranged closest to the object side, image blurring is caused by changing the prism apex angle of the variable apex angle prism in response to vibration of the imaging system. The image is corrected to stabilize the image. In Japanese Patent Application Laid-Open Nos. 1-116619 and 2-124521, an acceleration sensor is used to detect vibration of the photographing system, and a part of the lens group of the photographing system is moved to the optical axis according to a signal obtained at this time. A still image is obtained by vibrating in the vertical direction.
[0005]
Japanese Patent Laid-Open No. 7-128619 discloses a third lens unit in a variable power optical system having a four-group configuration including first, second, third, and fourth lens units having positive, negative, positive, and positive refractive powers. The lens unit is composed of two lens units having positive and negative refractive powers, and image blurring is corrected by vibrating the lens unit having positive refractive power. In Japanese Patent Application Laid-Open No. 7-199124, in a variable power optical system having a four-group configuration including first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers, the entire third lens group Is used to correct image blur. On the other hand, in Japanese Patent Laid-Open No. 5-60974, in a zoom lens having a four-group structure including first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers, The telephoto type is composed of a positive lens and a meniscus negative lens to shorten the overall lens length.
[0006]
In addition, the applicant of the present application disclosed in Japanese Patent Application No. 11-213370 in a zoom lens having a four-group configuration including first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers. A zoom lens that corrects image blur by vibrating the entire third lens group is disclosed. Further, the first lens group has a three-lens configuration in order from the object side: a cemented lens composed of a negative lens and a positive lens, and a meniscus positive lens having a convex surface facing the object side.
[0007]
Further, US Pat. No. 5,583,699, US Pat. No. 5,886,828, and Japanese Patent Laid-Open No. 7-92431 disclose first, second, and second refractive powers of positive, negative, positive, and positive refractive power. 3. In a four-group zoom lens composed of a fourth lens group, in order from the object side, the first lens group is composed of a cemented lens composed of a negative lens and a positive lens, and a meniscus-shaped positive lens having a convex surface facing the object side. There is disclosed a zoom lens that is provided with a total of four lenses.
[0008]
Also, in Japanese Patent Laid-Open No. 2000-305016, a zoom lens having a four-group configuration including first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers is dispersed in the first lens group. By using a lens made of a glass material with a small amount of light, the chromatic aberration is improved particularly at the telephoto end.
[0009]
[Problems to be solved by the invention]
In general, an image stabilization unit that corrects image blur is disposed in front of the imaging system, and a part of the movable lens group (movable member) that constitutes the image stabilization unit is vibrated to eliminate the blur of the captured image. However, there is a problem in that the whole apparatus becomes large and the moving mechanism for moving the movable lens group becomes complicated.
[0010]
Further, in an optical system that performs vibration isolation using a variable apex angle prism, there is a problem in that the amount of decentered magnification chromatic aberration generated increases during vibration isolation, particularly on the long focal length side.
[0011]
On the other hand, an anti-vibration optical system that performs anti-vibration by decentering some lenses in the photographing system in the direction perpendicular to the optical axis has the advantage that no extra optical system is required for anti-vibration However, there is a problem in that it requires a space for the lens to be moved, and the amount of decentration aberrations generated during image stabilization increases.
[0012]
Further, in the variable power optical system having a four-group configuration including the first, second, third, and fourth lens units having positive, negative, positive, and positive refractive powers, the entire third lens unit is moved in the direction perpendicular to the optical axis. When anti-vibration is performed, when the third lens group is configured with a telephoto type of a positive lens and a negative meniscus lens for shortening the overall length, a lot of decentration aberrations such as decentration coma and decentered field curvature occur. There was a problem that the image quality deteriorated.
[0013]
Further, in the above conventional example, a zoom ratio of 8 times or more can be applied to a video camera or the like, but aberration correction is required for use in a digital camera using an imaging means composed of many pixels of 1 million pixels or more. It was insufficient in terms.
[0014]
When the first lens group is composed of a total of three lenses including a cemented lens composed of a negative lens and a positive lens and one meniscus positive lens, the lens configuration is simplified but has a zoom ratio of 8 times or more. For an imaging apparatus using a solid-state imaging device including a large number of pixels, correction of axial chromatic aberration on the telephoto side is insufficient, and correction of the secondary spectrum is particularly insufficient.
[0015]
Further, when the first lens group is composed of a cemented lens composed of a negative lens and a positive lens and two meniscus positive lenses, the number of lenses is increased. At this time, a low dispersion glass is used as the material of the positive lens. The spectrum is reduced. A zoom lens having such an anti-vibration function has been proposed in Japanese Patent Application Laid-Open No. 7-92431. However, the fourth lens group is fixed at the time of zooming, and one of the fourth lens groups at the time of anti-vibration. Since the part is vibrated, the number of constituent lenses in the fourth lens group is large, which is disadvantageous in terms of miniaturization. In the zoom lens having no image stabilization function proposed in US Pat. No. 5,886,828 and US Pat. No. 5,583,699, the second lens group includes two negative lenses and one positive lens. Therefore, as a zoom lens for a digital camera using an imaging unit having a zoom ratio of 8 times or more and including pixels of 1 million pixels or more, the correction of lateral chromatic aberration in the entire zoom range is not always sufficient.
[0016]
In Japanese Patent Laid-Open No. 2000-305016, a glass material with little dispersion is used for the first lens group. However, since the partial dispersion of the negative lens is large, the effect of reducing the secondary spectrum is not sufficiently obtained.
[0017]
SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens having a high optical performance that can sufficiently cope with a solid-state imaging device including a large number of pixels with a high zoom ratio and an optical apparatus having the same.
[0018]
In addition, according to the present invention, a relatively small and light lens group constituting a part of the optical system is moved so as to have a component in a direction perpendicular to the optical axis, and the image of the optical system is vibrated (tilted). By configuring the lens group to correct blurring and making the lens group configuration suitable for correcting pixel blurring, the entire apparatus can be downsized, the mechanism can be simplified, and the load on the driving means can be reduced. An image pickup element having a vibration-proof function in which decentration aberration is corrected well when the lens group is decentered, and in which the secondary spectrum on the telephoto side is corrected well, and which includes pixels of 1 million pixels or more An object of the present invention is to provide a zoom lens and an optical apparatus having the zoom lens that can sufficiently cope with a camera using the lens.
[0019]
[Means for Solving the Problems]
  The zoom lens according to the first aspect of the present invention includes, in order from the object side, a first lens unit having a positive refractive power that does not move in the optical axis direction for zooming and focusing, and has a negative refractive power having a zooming function. In a zoom lens composed of two lens groups, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power having a correction function and a focusing function for an image plane that varies due to zooming,SaidThe first lens group has one or more negative lenses and a plurality of positive lenses,The second lens group includes, in order from the object side, a meniscus negative lens having a concave surface facing the image side, a negative lens, a positive lens having a convex surface facing the object side, and a negative lens,The Abbe number of the material of one negative lens in the first lens group is ν−, the partial dispersion ratio is Pgf−,SaidWhen the average Abbe number of the materials of the plurality of positive lenses in the first lens group is ν +,
30 <ν− <40
Pgf- <0.6
ν +> 75
It satisfies the following conditional expression.
[0020]
According to a second aspect of the present invention, in the first aspect of the invention, the first lens group includes, in order from the object side, a negative lens, a positive lens, and a positive lens having a concave surface having a larger absolute value of refractive power on the image side than the object side. It is characterized by having.
[0021]
According to a third aspect of the present invention, in the first aspect of the invention, the first lens group includes, in order from the object side, a negative lens, a positive lens, and a positive lens having a concave surface having a larger absolute value of refractive power on the image side than the object side. It is characterized by comprising a meniscus lens having a convex surface facing the object side.
[0022]
According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, when the focal length of the first lens group is f1, and the focal length of the negative lens in the first lens group is f1N,
1.2 <| f1N | / f1 <2.2
It satisfies the following conditional expression.
[0023]
According to a fifth aspect of the present invention, in the first, second, third, or fourth aspect of the invention, the first lens group has a material Abbe number of ν1 +,
ν1 +> 80
It is characterized by having two or more positive lenses satisfying the above.
[0024]
The invention of claim 6 is the invention according to any one of claims 1 to 5, wherein the focal length of the second lens group is f2, the focal length of the entire system at the wide angle end is fw, and the focal length of the entire system at the telephoto end is set. When ft,
[0025]
[Expression 2]

[0026]
It satisfies the following conditional expression.
[0027]
The invention of claim 7 is the invention of any one of claims 1 to 6, wherein the radius of curvature of the object side surface of one negative lens in the first lens group is R11a, and the radius of curvature of the image side surface is R11b. And when
−3.8 <(R11b + R11a) / (R11b−R11a) <− 2.0
It satisfies the following conditional expression.
[0028]
  An invention of claim 8 is the invention of any one of claims 1 to 7, wherein the first lens groupmostWhen the radius of curvature of the object side surface of the positive lens located on the object side is R12a, and the radius of curvature of the image side surface is R12b,
0.55 <(R12b + R12a) / (R12b-R12a) <1.1
It satisfies the following conditional expression.
[0029]
  According to a ninth aspect of the present invention, in the first aspect of the present invention, the entire third lens group is displaced so as to have a component perpendicular to the optical axis, and an image perpendicular to the optical axis is obtained. It is characterized by correcting the position.
[0030]
  According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, in the third lens group, in order from the object side, a positive lens G31 having a convex surface directed toward the object side, and a concave surface directed toward the image surface side. Meniscus negative lens G32SaidThe radius of curvature of the object side surface of the positive lens G31 is R31a, the radius of curvature of the image side surface is R31b,SaidWhen the radius of curvature of the object side surface of the negative lens G32 is R32a and the radius of curvature of the image side surface is R32b,
1.3 <(R31b + R31a) / (R31b-R31a) <2.3
−4.0 <(R32b + R32a) / (R32b−R32a) <− 1.5
It satisfies the following conditional expression.
[0031]
  The invention of claim 11 is the optical system for forming an image on the image sensor in the invention of any one of claims 1 to 10.
[0032]
  An optical instrument according to a twelfth aspect of the present invention includes:11The zoom lens according to any one of the above and an image sensor that receives an image formed by the zoom lens.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a zoom lens and an optical apparatus having the same according to the present invention will be described.
[0035]
1 is a lens cross-sectional view at the wide-angle end of Embodiment 1 of the present invention, and FIGS. 2, 3, and 4 are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Embodiment 1 of the present invention.
[0036]
FIG. 5 is a lens cross-sectional view at the wide-angle end according to the second embodiment of the present invention, and FIGS. 6, 7, and 8 are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end according to the second embodiment of the present invention.
[0037]
FIG. 9 is a lens cross-sectional view at the wide-angle end according to Embodiment 3 of the present invention, and FIGS. 10, 11, and 12 are aberration diagrams at the wide-angle end, intermediate zoom position, and telephoto end according to Embodiment 3 of the present invention.
[0038]
FIG. 13 is a schematic view of the main part of the paraxial refractive power arrangement of the zoom lens according to the present invention.
[0039]
FIG. 14 is an explanatory diagram of an optical principle for correcting image blurring that occurs when the optical system vibrates in the present invention.
[0040]
In the cross-sectional views of the zoom lens of each embodiment and FIG. 13, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, and L3 is a third lens group having a positive refractive power. , L4 is a fourth lens unit having a positive refractive power. SP is an aperture stop, which is located in front of the third lens unit L3.
[0041]
G is an optical block corresponding to an optical filter, a face plate, or the like. IP is an image plane, and the imaging plane of the imaging means is located. FP is a flare-cut stop and cuts unnecessary light.
[0042]
In each embodiment, the entire third lens unit L3 is moved (shifted) so as to have a component perpendicular to the optical axis, thereby correcting blurring of a captured image when the entire optical system vibrates (tilts). ing. Note that a blur of the photographed image may be corrected by moving a part of the third lens unit L3 so as to have a component perpendicular to the optical axis.
[0043]
  In each embodiment, as indicated by an arrow during zooming from the wide-angle end to the telephoto end,Has a zoom functionThe second lens unit L2 is moved to the image plane side, and the image plane variation due to zooming is corrected by moving the fourth lens unit L4. Also, the fourth lens unit L4 is moved on the optical axis for focusing.(Focus)The rear focus type is used. A solid line curve 4a and a dotted line curve 4b relating to the fourth lens unit L4 are for correcting image plane fluctuations accompanying zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and an object at close distance, respectively. The movement trajectory is shown. The first lens unit L1 and the third lens unit L3 are immovable in the optical axis direction for zooming and focusing.
[0044]
  In each embodiment, the fourth lens unit L4 is moved to correct the image plane variation accompanying zooming.(Image plane correction function)At the same time, the fourth lens unit L4 is moved to perform focusing.(Has focusing function)I am doing so. In particular, as shown by the curves 4a and 4b, the zoom lens is moved so as to have a convex locus toward the object side when zooming from the wide-angle end to the telephoto end. As a result, the space between the third lens unit L3 and the fourth lens unit L4 is effectively used, and the overall length of the lens is effectively shortened. In each embodiment, for example, when focusing from an infinitely distant object to a close object at the telephoto end, the fourth lens unit L4 is extended forward as indicated by an arrow 4c.
[0045]
In each embodiment, the third lens unit L3 is moved (shifted) so as to have a component perpendicular to the optical axis so as to correct image blur when the entire optical system vibrates. As a result, image stabilization is performed without newly adding an optical member such as a variable apex angle prism or a lens group for image stabilization, and the entire optical system is prevented from being enlarged.
[0046]
Next, the optical principle of the image stabilization system that corrects the shake of the captured image by moving the lens group so as to have a component perpendicular to the optical axis will be described with reference to FIG.
[0047]
As shown in FIG. 14A, the optical system includes a fixed group (fixed lens group) Y1, an eccentric group (decentered lens group, shift group) Y2, and a fixed group (fixed lens group) Y3 in order from the object point P side. It is assumed that the object point P on the optical axis La sufficiently away from the optical system is formed as an image point p at the center of the imaging surface IP. Assuming that the entire optical system including the imaging surface IP is instantaneously tilted due to camera shake as shown in FIG. 14B, the object point P is also instantaneously moved to the image point P ′. Become. On the other hand, when the eccentric group Y2 is moved in the direction perpendicular to the optical axis La, the image point p is moved to the point p ″ as shown in FIG. 14C, and the amount and direction of movement are determined by the refractive power arrangement of the optical system. 14B, the image point p ′ shifted due to camera shake is moved by an appropriate amount in the direction perpendicular to the optical axis in the eccentric group Y2. By returning to the original imaging position p, as shown in FIG. 14D, camera shake correction, that is, image stabilization is performed.
[0048]
Now, assuming that the movement amount (shift amount) of the eccentric group Y2 necessary for correcting the optical axis by θ is Δ, the focal length of the entire optical system is f, and the eccentric sensitivity of the eccentric group Y2 is TS, Δ is It is given by the formula.
[0049]
Δ = f · tan (θ) / TS
Now, if the eccentricity sensitivity TS of the eccentric group Y2 is too large, the movement amount Δ becomes a small value, and the movement amount of the shift group Y2 necessary for vibration isolation can be reduced, but control for appropriately performing vibration isolation becomes difficult. As a result, the correction remains. In particular, in video cameras and digital still cameras, the image size of an image sensor such as a CCD is smaller than that of a silver halide film, and the focal length for the same angle of view is short. Therefore, the shift amount of the eccentric group Y2 for correcting the same angle Δ becomes smaller. Therefore, if the accuracy of the mechanism is approximately the same, the remaining correction on the screen becomes relatively large.
[0050]
On the other hand, if the eccentricity sensitivity TS is too small, the amount of movement of the eccentric group Y2 required for control increases, and the driving means such as an actuator for driving the eccentric group Y2 also increases.
[0051]
In each embodiment, by setting the refractive power arrangement of each lens group to an appropriate value, the eccentricity sensitivity TS of the third lens group L3 is set to an appropriate value, and there is little residual vibration correction due to mechanical control errors. In addition, a zoom lens with a small load on driving means such as an actuator has been achieved.
[0052]
Next, features of the lens configuration of each embodiment will be described.
[0053]
(A-1) The first lens unit L1 is arranged in order from the object side, negative lens G11, positive lens G12 having a concave surface having a large refractive power on the image side, and a convex surface facing the object side. And two meniscus positive lenses G13 and G14. The negative lens G11 and the positive lens G12 are independent or cemented.
[0054]
In the first embodiment, the positive lens G12 and the positive lens G14, in the second embodiment, the positive lens G12, in the third embodiment, the positive lens G12, the positive lens G13, and the positive lens G14 are made of an anomalous dispersion glass material. The chromatic aberration generated in the group, particularly the secondary spectrum that is difficult to be corrected when the focal length is long, is corrected well.
[0055]
Particularly in the second embodiment, the secondary spectrum is favorably corrected by using an anomalous dispersion glass material having an Abbe number νd of 90 or more for the positive lens G12.
[0056]
When the Abbe number of the material of the negative lens G11 in the first lens unit L1 is ν− and the partial dispersion ratio is Pgf in order to suppress the secondary spectrum,
30 <ν− <40 (1)
Pgf− <0.6 (2)
The following conditional expression is satisfied.
However, Pgf = (Ng−Nf) / (Nf−Nc)
Ng, Nc, and Nf are the refractive indexes of the material with respect to g-line, c-line, and f-line, respectively.
[0057]
When the lower limit of the conditional expression (1) is exceeded, the difference in dispersion between the negative lens G11 and the positive lens G12 becomes large, and when achromatic at two wavelengths, the refractive power of each lens becomes weak and at the telephoto end. This is advantageous for the correction of the spherical aberration, but it becomes impossible to select an appropriate glass material for correcting the secondary spectrum. On the other hand, if the upper limit is exceeded, the refractive power of each lens becomes too strong, and spherical aberration at the telephoto end becomes difficult, which is not good.
If the upper limit of conditional expression (2) is exceeded, the difference in the partial dispersion ratio between the materials of the positive lens G12 and the negative lens G11 becomes large, and it becomes difficult to correct the secondary spectrum.
[0058]
More preferably, the numerical ranges of conditional expressions (1) and (2) are
32 <ν− <38 (1a)
Pgf− <0.59 (2a)
It is good to do.
[0059]
  (A-2) A plurality of lenses constituting the first lens unit L1(2 or more)When the average Abbe number of the positive lens material is ν +,
  ν +> 75 (3)
Is satisfied. If the lower limit of conditional expression (3) is exceeded, correction of chromatic aberration under the condition of conditional expression (1) will cause the refractive power of each lens to become too large and other aberrations, especially spherical aberration and coma at the telephoto end. It is not good because the correction becomes difficult.
[0060]
More preferably, the numerical range of conditional expression (3) is
ν +> 76 (3a)
It is good to do.
[0061]
(A-3) A negative lens is disposed closest to the object side of the first lens unit L1. This reduces the principal point interval between the first lens group and the second lens group so that the effective diameter of the front lens is reduced.
(A-4) Normally, in a zoom lens composed of four consumer lens groups, the first lens group is composed of one negative lens and two positive lenses, but the low dispersion glass material has a low refractive index. Therefore, if this is used as it is in the first lens group, the curvature of each lens becomes large and it becomes difficult to correct spherical aberration at the telephoto end.
[0062]
Therefore, in each embodiment, the first lens unit L1 is composed of one negative lens and three positive lenses, so that the curvature of each lens surface of the positive lens can be in an appropriate range, and the spherical surface at the telephoto end. Aberrations are corrected well.
[0063]
(A-5) When the focal length of the first lens unit L1 is f1, and the focal length of the negative lens G12 in the first lens unit L1 is f1N.
1.2 <| f1N | / f1 <2.2 (4)
The following conditional expression is satisfied.
[0064]
Exceeding the lower limit of conditional expression (4) is not good because it becomes difficult to correct distortion at the wide-angle end.
[0065]
If the upper limit is exceeded, chromatic aberration in the first lens unit L1 cannot be sufficiently corrected, which is not good.
[0066]
More preferably, the numerical range of conditional expression (4) is
1.4 <| f1N | f1 <2.0 (4a)
It is good to do.
[0067]
(A-6) In Embodiments 1 and 3, when the Abbe number of the material in the first lens unit L1 is ν + in order to obtain a sufficient chromatic aberration correction effect,
ν1 +> 80 (5)
A plurality of positive lenses that satisfy the following conditional expression:
[0068]
(A-7) In order to reduce the size of the entire zoom lens system while maintaining good optical performance, the focal length of the second lens unit L2 is f2, the focal length of the entire system at the wide angle end is fw, and telephoto. When the focal length of the entire system at the end is ft
[0069]
[Equation 3]

[0070]
The following conditional expression is satisfied.
[0071]
Conditional expression (6) defines the refractive power of the first lens unit L1. If the refractive power of the first lens unit L1 is increased beyond the lower limit of conditional expression (6), the amount of secondary spectrum generated is increased even if conditional expressions (1) and (2) are satisfied, which is not preferable. . In addition, the lateral chromatic aberration generated on the wide angle side becomes large and difficult to correct. Conversely, if the upper limit is exceeded and the refractive power of the first lens unit L1 is weakened, the total length of the lens becomes long and it becomes difficult to reduce the size of the entire system.
[0072]
Conditional expression (7) defines the refractive power of the second lens unit L2. When the refractive power of the second lens unit L2 increases beyond the lower limit of conditional expression (7), the amount of movement of the second lens unit L2 during zooming decreases, but the Petzval sum increases in the negative direction as a whole. This is not good because it is difficult to correct curvature of field. Conversely, if the upper limit of conditional expression (7) is exceeded, the amount of movement of the second lens unit L2 at the time of zooming becomes large, and the entire lens system is not downsized.
[0073]
More preferably, the numerical ranges of conditional expressions (6) and (7)
[0074]
[Expression 4]

[0075]
It is good to do.
[0076]
(A-8) A zoom lens for a digital still camera is required to have a high resolving power. In particular, the lateral chromatic aberration associated with zooming can be corrected more satisfactorily than a zoom lens for a normal video camera. It is requested. Therefore, the second lens unit L2 includes three or more negative lenses and one or more positive lenses. If only two negative lenses are used, it is difficult to correct lateral chromatic aberration if the refractive power of the second lens unit L2 is increased to reduce the amount of movement during zooming in order to reduce the overall length. For this reason, in order from the object side to the second lens unit L2, a negative meniscus lens having a concave surface having a large absolute value of refractive power on the image side compared to the object side, a negative lens, a positive lens having a convex surface directed to the object side, By having a negative lens, the principal point of the second lens unit L2 is effectively achromatic, and the change in lateral chromatic aberration due to zooming is corrected well.
[0077]
(A-9) In order to satisfactorily correct various aberrations such as spherical aberration and distortion, the radius of curvature of the object side surface of the negative lens G11 in the first lens unit L1 is R11a, and the radius of curvature of the image side surface is When R11b
−3.8 <(R11b + R11a) / (R11b−R11a) <− 2.0 (8)
The following conditional expression is satisfied.
[0078]
If the lower limit of conditional expression (8) is exceeded, it will be difficult to correct spherical aberration at the telephoto end. On the contrary, if the upper limit is exceeded, correction of distortion at the wide-angle end becomes difficult, which is not good.
[0079]
More preferably, the numerical range of conditional expression (8) is
−3.0 <(R11b + R11a) / (R11b−R11a) <− 2.2 (8a)
It is good to do.
[0080]
(A-10) When the radius of curvature of the object side surface of the first lens unit L1 closest to the object side is R12a and the radius of curvature of the image side surface is R12b.
0.55 <(R12b + R12a) / (R12b−R12a) <1.1 (9)
The following conditional expression is satisfied.
[0081]
If the lower limit of conditional expression (9) is exceeded, it will be difficult to correct spherical aberration at the telephoto end. Conversely, if the upper limit is exceeded, it becomes difficult to correct distortion at the telephoto end.
[0082]
More preferably, the numerical range of conditional expression (9) is
0.60 <(R12b + R12a) / (R12b-R12a) <1.0 (9a)
It is good to do.
[0083]
(A-11) Anti-vibration is performed by shifting the third lens group so that part or all of L3 has a component perpendicular to the optical axis. In each embodiment, the entire third lens L3 is shifted.
[0084]
The third lens unit L3 is composed of two or more positive lenses and one or more negative lenses in order to achieve a reduction in the overall optical length while maintaining good optical performance, particularly optical performance during image stabilization. Yes. In particular, in order from the object side to the third lens unit L3, a positive lens having a convex surface facing the object side and a meniscus negative lens having a concave surface having a larger absolute value of refractive power on the image surface side than the object side are arranged. Therefore, both aberration correction and overall length reduction are achieved.
[0085]
  Further, in order to achieve better optical performance, a positive lens located closest to the object side of the third lens unit L3G31The radius of curvature of the object side surface is R31a, the radius of curvature of the image side surface is R31b, and the negative lens of the third lens unit L3G32When the radius of curvature of the object side surface is R32a and the radius of curvature of the image side surface is R32b,
  1.3 <(R31b + R31a) / (R31b-R31a) <2.3 (10)
  −4.0 <(R32b + R32a) / (R32b−R32a) <− 1.5
                                                                (11)
Is satisfied.
[0086]
Conditional expression (10) is an expression that defines the shape factor of the most object-side positive lens of the third lens unit L3. When the upper limit of conditional expression (10) is exceeded and the degree of meniscus increases, coma generated on each lens surface increases, and higher order coma occurs. In particular, the occurrence of decentered coma during vibration isolation becomes significant, and the performance deteriorates during vibration isolation. Further, if the biconvex shape exceeds the lower limit, the effect of correcting lateral chromatic aberration generated on the object side surface on the image side surface is weakened, which is not good.
[0087]
Conditional expression (11) is an expression that defines the shape factor of the negative lens of the third lens unit L3. If the lower limit of conditional expression (11) is exceeded and the degree of meniscus is increased, the primary axial chromatic aberration will be overcorrected on the image side lens surface, and the g-line will be excessive with respect to the d-line. Also, if the degree of meniscus is weakened beyond the upper limit, the action of setting the third lens unit L3 to the telephoto structure is weakened, and the total lens length becomes long.
[0088]
When such a negative lens is provided, positive distortion occurs on the lens surface.
This causes a large eccentric distortion during vibration isolation.
[0089]
In order to reduce this decrease, it is only necessary to reduce the distortion occurring in the entire third lens unit L3.
[0090]
In each embodiment, by disposing a positive lens on the image plane side of the negative lens, while maintaining a certain degree of telephoto configuration, distortion is corrected in the third lens unit L3, and the third lens unit L3 is shifted. The occurrence of decentration aberrations that occur during vibration isolation is reduced.
[0091]
More preferably, the numerical ranges of conditional expressions (10) and (11) are
1.5 <(R31b + R31a) / (R31b-R31a) <2.0 (10a)
−3.5 <(R32b + R32a) / (R32b−R32a) <− 2.0 (11a)
It is good to do.
[0092]
(A-12) The fourth lens unit L4 is composed of two positive lenses and one negative lens, and spherical aberration and image plane that are generated when the fourth lens unit L4 moves during zooming or focusing. The variation of curvature is reduced.
[0093]
Furthermore, at least one positive lens of the fourth lens unit L4 has an aspherical surface.
[0094]
(A-13) In order to achieve a reduction in the change in the amount of light during image stabilization, the peripheral aperture is relatively increased by restricting the central beam by reducing the aperture diameter on the telephoto side during zooming. Yes.
[0095]
The third lens unit L3 needs to have a larger lens diameter for moving so as to have a component perpendicular to the main axis in order to prevent vibration. Accordingly, a fixed stop is disposed on the object side or the image plane side of the third lens unit L3 in order to prevent an excessive axial light beam other than that controlled by the F number from entering too much. In each embodiment, the fixed diaphragm FP is disposed between the third lens unit L3 and the fourth lens unit L4, so that an unnecessary light beam is prevented from passing through while effectively using the space.
[0096]
Next, an embodiment of a digital still camera (optical apparatus) using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG.
[0097]
In FIG. 15, 10 is a camera body, 11 is a photographing optical system constituted by the zoom lens of the present invention, and 12 is a viewfinder for observing a subject image.
[0098]
13 is a strobe device, 14 is a measurement window, 15 is a liquid crystal display window for notifying the operation of the camera, 16 is a release button, and 17 is an operation switch for switching various modes. Thus, by applying the zoom lens of the present invention to an optical device, an optical device having a small size and high optical performance is achieved.
[0099]
As described above, according to each embodiment, the zoom lens having a good optical performance over the entire zoom range is realized according to each embodiment.
[0100]
  In particular, while having a large zoom ratio of 8 or more, the secondary spectrum on the telephoto side is well corrected compared to a zoom lens for a conventional video camera, and has high optical performance. Have pixelsReceive the formed imageTherefore, it is possible to realize a zoom lens having optical performance that can sufficiently cope with a digital camera having a photographing element and various optical devices having the same.
[0101]
Next, Numerical Examples 1 to 3 respectively corresponding to Embodiments 1 to 3 of the present invention will be shown. In each numerical example, i indicates the order of the optical surfaces from the object side, Ri is the radius of curvature of the i-th optical surface (i-th surface), Di is the distance between the i-th surface and the i + 1-th surface, Ni and νi indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. When k is the eccentricity, B, C, D, E, F... Are aspherical coefficients, and the displacement in the optical axis direction at the position of the height h from the optical axis is x with reference to the surface vertex. The aspheric shape is
x = (h²/ R) / [1+ [1- (1 + k) (h / R)²]^1/2] + Bh^Four+ Ch⁶+ Dh⁸+ Eh^Ten+ Fh¹²+ Gh¹⁴+ Hh¹⁶
Is displayed. Where R is the radius of curvature. For example, the display of “e-Z” is “10^-Z"Means. Table 1 shows the correspondence with the above-described conditional expressions in each numerical example.
[0102]
f indicates a focal length, Fno indicates an F number ω indicates a half angle of view.
[0103]
[Outside 1]

[0104]
[Outside 2]

[0105]
[Outside 3]

[0106]
[Table 1]

[0107]
【The invention's effect】
According to the present invention, it is possible to achieve a zoom lens having high optical performance that can sufficiently cope with an optical apparatus having the same, even when a solid-state imaging device having many pixels with a high zoom ratio is used.
[0108]
In addition, according to the present invention, an image when the optical system is vibrated (tilted) by moving a relatively small and light lens group constituting a part of the optical system so as to have a component perpendicular to the optical axis. It is configured so as to correct blurring, and by appropriately configuring the lens group for correcting pixel blurring, it is possible to reduce the size of the entire apparatus, simplify the mechanism, and reduce the load on the driving means. Imaging with a vibration-proof function that corrects decentration aberrations when the lens group is decentered and corrects the secondary spectrum on the telephoto side, and has more than 1 million pixels Even with a camera using an element, it is possible to achieve a zoom lens and an optical apparatus having the zoom lens that can sufficiently cope with the camera.
[Brief description of the drawings]
FIG. 1 is a sectional view of a lens according to Numerical Example 1 of the present invention.
FIG. 2 is an aberration diagram at the wide-angle end according to Numerical Example 1 of the present invention.
FIG. 3 is an aberration diagram at an intermediate zoom position according to Numerical Example 1 of the present invention.
FIG. 4 is an aberration diagram at the telephoto end according to Numerical Example 1 of the present invention.
FIG. 5 is a sectional view of a lens according to Numerical Example 2 of the present invention.
FIG. 6 is an aberration diagram at the wide-angle end according to Numerical Example 2 of the present invention.
FIG. 7 is an aberration diagram at an intermediate zoom position according to Numerical Example 2 of the present invention.
FIG. 8 is an aberration diagram at the telephoto end according to Numerical Example 2 of the present invention.
FIG. 9 is a lens cross-sectional view of Numerical Example 3 of the present invention.
FIG. 10 is an aberration diagram at the wide-angle end according to Numerical Example 3 of the present invention.
FIG. 11 is an aberration diagram at an intermediate zoom position according to Numerical Example 3 of the present invention.
FIG. 12 is an aberration diagram at the telephoto end according to Numerical Example 3 of the present invention.
FIG. 13 is a schematic view of a paraxial refractive power arrangement of the zoom lens according to the present invention.
FIG. 14 is an explanatory diagram of the optical principle of image stabilization in the present invention.
FIG. 15 is a schematic view of the main part of the optical apparatus of the present invention.
[Explanation of symbols]
L1 first lens group
L2 Second lens group
L3 Third lens group
L4 4th lens group
d d line
g g line
ΔM Meridional image plane
ΔS Sagittal image plane
SP Aperture
FP flare cut diaphragm
IP imaging surface
G Glass blocks such as CCD force plate and low-pass filter
ω half angle of view
fno F number

Claims (12)

In order from the object side, a first lens unit having a positive refractive power that does not move in the optical axis direction for zooming and focusing, a second lens unit having a negative refractive power having a zooming function, and a first lens unit having a positive refractive power. third lens group, the positive fourth lens constructed zoom lens from the group refractive power having a correction function and the focusing function of the image plane which varies by zooming, the first lens group and one or more negative lenses The second lens group includes, in order from the object side, a meniscus negative lens having a concave surface facing the image side, a negative lens, a positive lens having a convex surface facing the object side, and a negative lens. and the Abbe number of the material of one negative lens in the first lens group Nyu-, the partial dispersion ratio Pgf-, the average Abbe number of the material of the plurality of positive lenses in said first lens group and [nu + When
30 <ν− <40
Pgf- <0.6
ν +> 75
A zoom lens satisfying the following conditional expression: The first lens group includes, in order from the object side, a negative lens, a positive lens, and a positive lens having a concave surface having a larger absolute value of refractive power on the image side than on the object side. Zoom lens. The first lens group includes, in order from the object side, a negative lens, a positive lens, a positive lens, and a meniscus lens having a convex surface facing the object side, with a concave surface having a larger absolute value of refractive power on the image side than the object side. The zoom lens according to claim 1, further comprising: When the focal length of the first lens group is f1, and the focal length of the negative lens in the first lens group is f1N,
1.2 <| f1N | / f1 <2.2
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The first lens group has a material Abbe number of ν1 +,
ν1 +> 80
The zoom lens according to claim 1, wherein the zoom lens has two or more positive lenses satisfying the above. When the focal length of the second lens group is f2, the focal length of the entire system at the wide angle end is fw, and the focal length of the entire system at the telephoto end is ft,
1.7 <f1 / √ (fw · ft) <2.9
0.3 <| f2 | / √ (fw · ft) <0.6
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the radius of curvature of the object side surface of one negative lens in the first lens group is R11a and the radius of curvature of the image side surface is R11b,
−3.8 <(R11b + R11a) / (R11b−R11a) <− 2.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the radius of curvature of the object side surface of the positive lens located closest to the object side in the first lens group is R12a, and the radius of curvature of the image side surface is R12b,
0.55 <(R12b + R12a) / (R12b-R12a) <1.1
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. Any one of claims 1 to 8, characterized in that to correct the image position in the vertical direction with respect to the optical axis is displaced to have the third lens group entire component in the vertical direction with respect to the optical axis Zoom lens described in 1. The third lens group in order from the object side, a positive lens G31 having a convex surface directed toward the object side, has a negative lens G32 of a meniscus shape with a concave surface facing the image side, the object-side surface of the positive lens G31 radius of curvature R31a of, R31b the radius of curvature of an image side, wherein the object side surface of the negative lens G32 radius of curvature R32a, when the radius of curvature of the image side surface and R32B,
1.3 <(R31b + R31a) / (R31b-R31a) <2.3
−4.0 <(R32b + R32a) / (R32b−R32a) <− 1.5
The zoom lens according to any one of claims 1 9, characterized by satisfying the conditional expression. The zoom lens according to claim 1, any one of 10, characterized in that an optical system for forming an image on the imaging device. An optical apparatus comprising: the zoom lens according to any one of claims 1 to 11, and an imaging element for receiving an image formed by the zoom lens.

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