JP4181790B2

JP4181790B2 - Zoom lens and optical apparatus having the same

Info

Publication number: JP4181790B2
Application number: JP2002102765A
Authority: JP
Inventors: 宏志遠藤
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2002-04-04
Filing date: 2002-04-04
Publication date: 2008-11-19
Anticipated expiration: 2022-04-04
Also published as: JP2003295060A

Description

【０００１】
【発明の属する技術分野】
本発明は、ズームレンズ及びそれを有する光学機器に関し、更に詳しくは、光学系の一部のレンズ群を光軸に対し垂直方向の成分を持つように移動させてズームレンズが振動（傾動）したときの画像ぶれ（像ぶれ）を高い光学性能を有しつつ、良好に補正した銀塩写真カメラ、ビデオカメラ、電子スチルカメラ、デジタルカメラ等の光学機器に好適なものである。
【０００２】
【従来の技術】
進行中の車等移動物体上からの撮影では撮影系（撮影レンズ）に振動が伝わり撮影画像にブレが生じる。また焦点距離の長い撮影レンズやＦナンバー（ＦＮｏ）の大きい撮影レンズでの手持ち撮影では手ブレにより、撮影画像にブレ（画像ブレ）が生じることがある。近年、これらの画像ブレを光学的または電気的に補正した防振機能を有した銀塩カメラ、ビデオカメラ、デジタルカメラ等が提案されている。
【０００３】
従来より防振機能を有したズームレンズが、例えば特開平５−２３２４１０号公報（従来例１）、特開平８−１３６８６３号公報（従来例２）、特開平８―１０６０４７（従来例３）、特開平９−２３０２３７（従来例４）、特開平１１−６４７２８号公報（従来例５）等で提案されている。
【０００４】
このうち従来例１は、物体側より順に正、負、正、正の屈折力の４つのレンズ群で構成された望遠ズームレンズであり、第２レンズ群を光軸と垂直方向に移動して防振を行っている。従来例２は、物体側より順に正、負、正、正、負の屈折力の５つのレンズ群より成るズームレンズであり、第２レンズ群の一部を光軸と垂直方向に移動して防振を行っている。従来例３は、物体側より順に正、負、正、正、負の屈折力の５つのレンズ群より成るズームレンズであり、第４レンズ群の一部を光軸と垂直方向に移動して防振を行っている。従来例４は、物体側より順に正、負、正、正の屈折力の４つのレンズ群を有したズームレンズであり、レンズ群内の一部のレンズ群を光軸と垂直方向に移動して防振を行っている。従来例５は、物体側より順に正、負、正、正、負の屈折力の５つのレンズ群を有し、第４レンズ群を光軸と垂直方向に移動させて、防振を行ったズームレンズと、物体側より順に正、負、正、正の屈折力の４つのレンズ群を有し、第４レンズ群を正と負の屈折力のレンズ群に分割し、このうち正の屈折力のレンズ群を光軸と垂直方向に移動させて防振を行ったズームレンズを開示している。
【０００５】
この他、特開平１１−２３７５５０号公報では物体側より正の屈折力を有する第１レンズ群、負の屈折力を有する第２レンズ群、正の屈折力を有する第３レンズ群、正の屈折力を有する第４レンズ群を有し、該第２、第４レンズ群を光軸上移動させて変倍を行い、該第３レンズ群は第３１レンズ群と第３２レンズ群とを有し、該第３２レンズ群を光軸に対し垂直方向に移動することにより結像位置の変位を行っているズームレンズを開示している。
【０００６】
【発明が解決しようとする課題】
一般に、撮影系の一部のレンズを光軸に対して垂直方向に平行偏心させて画像ぶれの補正を行う光学系においては、比較的容易に画像ぶれを補正することができる利点はあるが、移動させるレンズの為の駆動手段を必要とし、又防振時における偏心収差の発生量が多くなってくるという問題点がある。
【０００７】
例えば画像ぶれの補正を行う補正光学系がレンズ構成枚数が多く、高重量であると電気的駆動を行う際に大きなトルクを必要とする。又、画像ぶれを補正する為の、補正レンズ群を適切に設定しないと一定量の画像ぶれの補正効果を得るために補正光学系の移動量を多くとる必要が生じてしまい、光学系全体が大型化してくるという問題がある。
【０００８】
一方、補正光学系の移動に対する像の補正効果を強めてしまうと、一定の像ぶれ補正に対する正確な補正を行うためには、偏心に対して結像変位作用が敏感になりすぎてくるため正確なレンズ移動制御を行うことが難しくなってくる。
【０００９】
本発明は像ぶれ補正用の補正光学系の配置を適切に行うことにより、高画質を維持しつつ補正光学系の小型化、かつ一定量の像ぶれ補正効果を行うための補正光学系の移動量のコントロールを容易に行い、補正光学系の電気的駆動を容易に行うことができるズームレンズ及びそれを有する光学機器の提供を目的とする。
【００１０】
この他本発明は、３５ｍｍ一眼レフカメラ換算で焦点距離２８ｍｍ程度の広角域から３００ｍｍ更には３５０ｍｍ程度の望遠域までをカバーし、防振機能を有する、コンパクトで、特に防振時の収差も良好に補正されたズームレンズ及びそれを有する光学機器の提供を目的とする。
【００１１】
【課題を解決するための手段】
請求項１の発明のズームレンズは、物体側より順に、正の屈折力の第１レンズ群と、負の屈折力の第２レンズ群と、正の屈折力の第３レンズ群と、正の屈折力の第４レンズ群より構成され、各レンズ群の間隔を変化させてズーミングを行うズームレンズに於いて、該第３レンズ群は、正の屈折力の第３ａレンズ群と負の屈折力の第３ｂレンズ群より構成され、該第３ｂ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ることにより結像位置を変位させており、ＤｉＷ、ＤｉＴを各々広角端と望遠端での第ｉレンズ群と第（ｉ＋１）レンズ群との間隔、ｆＷ、ｆＴを各々広角端と望遠端での全系の焦点距離、ｆ２、ｆ３ｂを各々該第２レンズ群と第３ｂレンズ群の焦点距離、ＴＳ３ｂＴを望遠端における該第３ｂレンズ群の光軸と垂直方向の変位量に対する結像位置の光軸と垂直方向の変位量とするとき、
【数５】
の条件式を満足することを特徴としている。
【００１２】
請求項２の発明は請求項１の発明において、ｆ３、ｆ４を前記第３レンズ群と前記第４レンズ群の焦点距離、ＬＷを広角端における光学全長とするとき、
【数６】
の条件式を満足することを特徴としている。
【００１３】
請求項３の発明は請求項１の発明において、前記第３ｂレンズ群は、１枚の正レンズと１枚の負レンズより成ることを特徴としている。
【００１４】
請求項４の発明は請求項１の発明において、前記第３ａレンズ群は２枚の正レンズと１枚の負レンズより成ることを特徴としている。
【００１５】
請求項５の発明は請求項１の発明において、前記第２レンズ群は３枚の負レンズと１枚の正レンズより成ることを特徴としている。
【００１６】
請求項６の発明は請求項１の発明において、前記第２レンズ群は３枚の負レンズと２枚の正レンズより成ることを特徴としている。
【００１７】
請求項７の発明は請求項１の発明において、前記第１レンズ群はメニスカス状の負レンズと２枚の正レンズより成ることを特徴としている。
【００１８】
請求項８の発明は請求項２の発明において、前記第４レンズ群は１枚の正レンズと１枚の負レンズより成り、レンズ中心からレンズ周辺へ行くに従って正の屈折力が弱くなる形状の非球面を有することを特徴としている。
【００１９】
請求項９の発明は請求項２の発明において、前記第４レンズ群は２枚の正レンズと１枚の負レンズより成り、レンズ中心からレンズ周辺へ行くに従って正の屈折力が弱くなる形状の非球面を有することを特徴としている。
【００２０】
請求項１０の発明は請求項１の発明において、前記第２レンズ群を光軸方向に移動させてフォーカシングを行い、β２Ｔを望遠端において無限遠物体にフォーカスしているときの該第２レンズ群の横倍率とするとき、
−０．９５＜ β２Ｔ＜−０．５
なる条件式を満足することを特徴としている。
【００２１】
請求項１１の発明は請求項１の発明において、前記第１レンズ群は、１枚の負レンズと２枚の正レンズより成り、ｆ１を該第１レンズ群の焦点距離、νｄを該２枚の正レンズのうちの１つの正レンズの材料のアッベ数、θｇｄを該２枚の正レンズのうちの１つの正レンズの材料の部分分数比とするとき、
【数７】
なる条件式を満足することを特徴としている。
【００２２】
請求項１２の発明は請求項１の発明において、無限遠物体から近距離物体へのフォーカシングを前記第１レンズ群と第２レンズ群を物体側へ一体的に又は互いに異なった速度で移動させて行うことを特徴とする請求項１のズームレンズ。
【００２３】
請求項１３の発明のズームレンズは、物体側より順に、正の屈折力の第１レンズ群と、負の屈折力の第２レンズ群と、正の屈折力の第３レンズ群と、正の屈折力の第４レンズ群より構成され、各レンズ群の間隔を変化させてズーミングを行うズームレンズに於いて、該第３レンズ群は、正の屈折力の第３ａレンズ群と負の屈折力の第３ｂレンズ群より構成され、該第３ｂ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ることにより結像位置の変位を行い、該第２レンズ群を光軸方向に移動させてフォーカシングを行い、ＤｉＷ、ＤｉＴを各々広角端と望遠端での第ｉレンズ群と第（ｉ＋１）レンズ群との間隔、ｆＷ、ｆＴを各々、広角端と望遠端での全系の焦点距離、ｆｉを第ｉレンズ群の焦点距離、ｆ３ｂを該第３ｂレンズ群の焦点距離、ＴＳ３ｂＴを望遠端における該第３ｂレンズ群の光軸と垂直方向の変位量に対する結像位置の光軸と垂直方向の変位量、ＬＷを広角端における光学全長、β２Ｔを望遠端において無限遠物体にフォーカスしているときの該第２レンズ群の横倍率とするとき、
【数８】
の条件式を満足することを特徴としている。
【００２４】
請求項１４の発明は請求項１から１３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ための光学系であることを特徴としている。
【００２５】
請求項１５の発明の光学機器は、請求項１から１４のいずれか１項のズームレンズと、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していることを特徴としている。
【００３２】
【発明の実施の形態】
図１は実施形態１のズームレンズの広角端におけるレンズ断面図、図２、図３は実施形態１のズームレンズの広角端、望遠端における縦収差図、図４、図５は実施形態１のズームレンズの広角端、望遠端における横収差図、図６、図７は実施形態１のズームレンズの広角端、望遠端における画角の０．３°分に相当する像位置を変化させた後での横収差図である。
【００３３】
図８は実施形態２のズームレンズの広角端におけるレンズ断面図、図９、図１０は実施形態２のズームレンズの広角端、望遠端における縦収差図、図１１、図１２は実施形態２のズームレンズの広角端、望遠端における横収差図、図１３、図１４は実施形態２のズームレンズの広角端、望遠端における画角の０．３°分に相当する像位置を変化させた後での横収差図である。
【００３４】
図１５は実施形態３のズームレンズの広角端におけるレンズ断面図、図１６、図１７は実施形態３のズームレンズの広角端、望遠端における縦収差図、図１８、図１９は実施形態３のズームレンズの広角端、望遠端における横収差図、図２０、図２１は実施形態３のズームレンズの広角端、望遠端における画角の０．３°分に相当する像位置を変化させた後での横収差図である。
【００３５】
図２２は実施形態４のズームレンズの広角端におけるレンズ断面図、図２３、図２４は実施形態４のズームレンズの広角端、望遠端における縦収差図、図２５、図２６は実施形態４のズームレンズの広角端、望遠端における横収差図、図２７、図２８は実施形態４のズームレンズの広角端、望遠端における画角の０．３°分に相当する像位置を変化させた後での横収差図である。
【００３６】
図２９は実施形態５のズームレンズの広角端におけるレンズ断面図、図３０、図３１は実施形態５のズームレンズの広角端、望遠端における縦収差図、図３２、図３３は実施形態５のズームレンズの広角端、望遠端における横収差図、図３４、図３５は実施形態５のズームレンズの広角端、望遠端における画角の０．３°分に相当する像位置を変化させた後での横収差図である。
【００３７】
レンズ断面図において、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。矢印は広角側から望遠側へのズームングを行う際の各レンズ群の移動方向を示す。ＳＰは絞りで第２レンズ群と第３レンズ群との間に設けている。ＩＰは像面であり、ＣＣＤやＭＯＳ等の撮像素子やフィルム等の感光材料が配置されている。ＦＰはフレアーカット絞りである。
【００３８】
第３レンズ群Ｌ３は正の屈折力の第３ａレンズ群Ｌ３ａと防振の為に光軸と垂直方向の成分を持つように移動する負の屈折力の第３ｂレンズ群Ｌ３ｂを有している。尚、絞りＳＰはズーミングに際し、第３ａレンズ群Ｌ３ａと一体となって移動している。
【００３９】
各実施形態のズームレンズにおいては、物体側より正の屈折力を有する第１レンズ群Ｌ１、負の屈折力を有する第２レンズ群Ｌ２、正の屈折力を有する第３レンズ群Ｌ３、正の屈折力を有する第４レンズ群Ｌ４を有し、各レンズ群を光軸上移動を行いつつ各レンズ群の空気間隔を変化させてズーミングを行い、前記第３レンズ群中の負の屈折力の第３ｂレンズ群Ｌ３ｂを光軸に対し垂直方向の成分を有するように移動を行うことにより結像位置を変化させている。
【００４０】
ズーミングに際して第１レンズ群Ｌ１と第２レンズ群Ｌ２の空気間隔を変化させることにより主に第２レンズ群Ｌ２で変倍作用を行い、第３レンズ群Ｌ３の移動で主に変倍に伴い変動する像面の補正作用を行うと同時に第３レンズ群Ｌ３と第４レンズ群Ｌ４の空気間隔を変化させることによりズーミングに伴う軸外収差の変動を補正している。そして正の屈折力を有する第３レンズ群Ｌ３中に負の屈折力の第３ｂレンズ群Ｌ３ｂを配置することにより、第３レンズ群Ｌ３中の第３ｂレンズ群Ｌ３ｂ以外のレンズ系のうち正の屈折作用のレンズ群で発生する諸収差を第３ｂレンズ群Ｌ３ｂの負の屈折作用でキャンセルしている。又それと同時に少ない移動量で大きい像位置の変位作用（防振作用）を行っている。
【００４１】
無限遠物体から近距離物体へのフォーカスは第２レンズ群Ｌ２又は第１レンズ群Ｌ１と第２レンズ群Ｌ２を一体的に又は互いに異なった速度で物体側に移動することにより行っている。特に第２レンズ群Ｌ２を移動させる方式は第１レンズ群Ｌ１のレンズ外径を増大させないために良い。また第１、第２レンズ群Ｌ１、Ｌ２を共に物体側に移動させる方式をとることによってフォーカスの際の収差変動が少なくなるようにしている。
【００４２】
各実施形態のズームレンズにおいて、ＤｉＷ、ＤｉＴを各々広角端と望遠端での第ｉレンズ群と第（ｉ＋１）レンズ群との間隔、ｆＷ、ｆＴを各々、広角端と望遠端での全系の焦点距離、ｆｉを第ｉレンズ群の焦点距離、ｆ３ｂを該第３ｂレンズ群の焦点距離とする。ＴＳ３ｂＴを望遠端において、該第３ｂレンズ群を光軸と垂直方向に単位量移動させたときの結像位置の光軸と垂直方向の変位量、即ち第３ｂレンズ群の光軸と垂直方向の変位量に対する結像点の光軸と垂直方向の変位量とする。ＬＷを広角端における光学全長とする。このとき、
【００４３】
【数９】
【００４４】
の条件式のうち１以上の条件式を満足している。これらの条件式のうち１つでも満足すれば、その条件式に対応した後述する効果が得られる。
【００４５】
又、β２Ｔを望遠端において無限遠物体にフォーカスしているときの該第２レンズ群の横倍率とするとき、
−０．９５＜ β２Ｔ＜−０．５・・・（１１）
なる条件式を満足するようにしている。
【００４６】
又、第１レンズ群は、１枚の負レンズと２枚の正レンズを有し、ｆ１を第１レンズ群の焦点距離、νｄを該２枚の正レンズのうちの１つの正レンズの材料のアッベ数、θｇｄを該２枚の正レンズのうちの１つの正レンズの材料の部分分数比とするとき、
【００４７】
【数１０】
【００４８】
なる条件式を満足するようにしている。
【００４９】
ここでアッベ数νｄ、部分分数比θｇｄは、フラウンフォーファー線のｄ線、ｇ線、Ｃ線、Ｆ線における材料の屈折率を各々、ｎｄ、ｎｇ、ｎＣ、ｎＦとするとき、
νｄ＝（ｎｄ−１）／（ｎＦ−ｎＣ）
θｇｄ＝（ｎｇ−ｎｄ）／（ｎＦ−ｎＣ）
なる式で表される。
【００５０】
次に前述の各条件式の技術的意味について説明する。
【００５１】
広角端から望遠端へのズーミングに際して、条件式（１）、（２）を満足しつつ第１レンズ群Ｌ１と第２レンズ群Ｌ２が物体側へ移動することで、スペース効率よく第２レンズ群Ｌ２での変倍を行い、広角端での光学全長（第１レンズ面から像面までの距離）を短くしている。また、広角側ではレンズ全系としてレトロタイプとすることで、必要な長さのバックフォーカスを確保し、望遠側ではレンズ全系としてテレフォトタイプとすることで、レンズ系のコンパクト化を図っている。さらに、第３レンズ群Ｌ３と第４レンズ群Ｌ４を条件式（６）を満足しつつ物体側に移動させることで、広角端から望遠端へのズーミングに伴って第３レンズ群Ｌ３と第４レンズ群Ｌ４の合成の主点位置をより物体側へ移動させることで第３レンズ群Ｌ３と第４レンズ群Ｌ４での変倍効果を高めている。
【００５２】
絞りＳＰを第３レンズ群Ｌ３の物体側に配置することで、絞り径を小さく抑え、前玉径すなわち最も物体側のレンズ径、後玉径すなわち最も像面側のレンズ径の大きさを適切な大きさにし、レンズ全系のコンパクト化を図っている。また、第２レンズ群Ｌ２を３枚の負レンズと１枚または２枚の正レンズを有するようにし、良好な収差補正を可能としている。
【００５３】
そして、第２レンズ群Ｌ２の焦点距離ｆ２が条件式（３）を満足することでレンズ系全体のコンパクト化と高性能を達成している。条件式（３）は、広角端と望遠端における全系の焦点距離の積の平方根に対する第２レンズ群Ｌ２の焦点距離の範囲を規定したものであり、下限値を超えて第２レンズ群Ｌ２の負の屈折力が弱くなるとレンズ全系が増大してくる。又、上限値を超えて第２レンズ群Ｌ２の負の屈折力が強くなるとレンズ全系のコンパクト化には有利だが、第２レンズ群Ｌ２で発生する諸収差が増大し、これを他のレンズ群でバランス良く補正することが困難となってくる。
【００５４】
また、各実施形態では、防振レンズ群（第３ｂレンズ群Ｌ３ｂ）を１枚の正レンズと１枚の負レンズで構成し、この第３ｂレンズ群Ｌ３ｂで色消しを行うことで、防振時の色収差の発生を少なくしており、二枚レンズ構成とすることで、防振レンズ群Ｌ３ｂのレンズ重量を軽くしている。又、条件式（４）、（５）、（７）を満足することで防振のための防振レンズ群Ｌ３ｂの変位量を小さくし、該第３ｂレンズ群Ｌ３ｂの防振駆動用アクチュエータにかかる負荷を小さく抑え、エネルギーの消費を小さくすることで良好な防振駆動特性を達成している。
【００５５】
一般に、防振のための防振レンズ群の駆動量を小さくするためには、防振レンズ群の変位量に対する結像点の変位量、すなわちラジアル敏感度を大きくすれば良い。ここで、ラジアル敏感度（偏心敏感度）をＴＳとし、防振レンズ群の焦点距離をｆ、防振のために想定される手振れ角度をφ、防振のための防振レンズ群の光軸と直交する方向の変位量をＸとする。このとき、
ＴＳ×Ｘ＝ｆ×ｔａｎφ
となる。ここで、ｆ×ｔａｎφは結像点の光軸と直交する方向の変位量である。従ってラジアル敏感度ＴＳは防振レンズ群の光軸と直交する方向の変位量Ｘに対する結像点の変位量ｆ×ｔａｎφである。
又、変位量Ｘは
Ｘ＝ｆ×ｔａｎφ／ＴＳ
となる。
【００５６】
したがって、手振れ角度φが一定としたとき、防振レンズ群の変位量Ｘは、防振レンズ群の焦点距離に比例し、ラジアル敏感度ＴＳに反比例することがわかる。したがって、防振の際の防振レンズの変位量Ｘを小さく抑えるには、望遠端の焦点距離が長くなると、それに比例してラジアル敏感度ＴＳを大きくする必要が生じる。
【００５７】
条件式（４）は広角端と望遠端における全系の焦点距離ｆＷ、ｆＴの積の平方根に対する第３ｂレンズ群Ｌ３ｂの焦点距離ｆ３ｂを規定するものであり、条件式（７）は第３レンズ群Ｌ３の焦点距離ｆ３に対する第３ｂレンズ群Ｌ３ｂの焦点距離ｆ３ｂの比を規定するものであり、両条件式とも下限値を超えて第３ｂレンズ群Ｌ３ｂの負の屈折力が弱くなると第３ｂレンズ群Ｌ３ｂのラジアル敏感度ＴＳ３ｂＴが大きくなり、上限値を超えて第３ｂレンズ群Ｌ３ｂの負の屈折力が強くなると収差補正が困難となり、特に防振時の光学性能が劣化してくる。
【００５８】
各実施形態では、第３ｂレンズ群Ｌ３ｂの望遠端でのラジアル敏感度ＴＳ３ｂＴを条件式（５）の範囲とすることで、防振のための第３ｂレンズ群Ｌ３ｂの変位量を小さく押さえつつ、良好な光学性能を得ている。
【００５９】
条件式（８）は広角端と望遠端における全系の焦点距離ｆＷ，ｆＴの積の平方根に対する第４レンズ群Ｌ４の焦点距離の比を規定するものであり、条件式（８）の下限値を越えて第４レンズ群Ｌ４の正の屈折力が強くなるとレンズ全長の短縮には有利だが収差補正が困難となる。又、条件式（８）の上限値を越えて第４レンズ群Ｌ４の正の屈折力が弱くなると収差補正には有利だが、レンズ系が増大してくる。
【００６０】
条件式（９）は望遠端における全系の焦点距離ｆＴに対する広角端での光学全長（最も物体側のレンズ面から像面までの長さ）の比であり、条件式（９）の下限値を越えてコンパクト化を図ろうとすると、各レンズ群の屈折力を強くする必要が生じ、この結果光学性能が劣化してくる。又、条件式（９）の上限値を越えるとレンズ全系コンパクト化を図りつつ、高い光学性能を得るのが難しくなってくる。
【００６１】
条件式（１０）は広角端から望遠端へのズーミングに際して、第１レンズ群Ｌ１と第２レンズ群Ｌ２との間隔変化量と、第２レンズ群Ｌ２と第３レンズ群Ｌ３との間隔変化量の比を規定したものであり、第３レンズ群Ｌ３の物体側に配置されている絞りＳＰの外径を小さくし、各レンズ群のレンズ外径を最適にするためのものである。
【００６２】
条件式（１０）の下限値を越えて第１レンズ群Ｌ１と第２レンズ群Ｌ２との間隔変化量が第２レンズ群Ｌ２と第３レンズ群Ｌ３との間隔変化量に対し小さくなることは、所定の変倍比を得るために第２レンズ群Ｌ２と第３レンズ群Ｌ３との間隔変化量が大きくなることを意味し、広角端における絞りＳＰと第１レンズ群Ｌ１の間隔が大きくなり画面周辺への光量を確保するために第１レンズ群Ｌ１のレンズ外径が増大する。
【００６３】
条件式（１０）の上限値を越えて第１レンズ群Ｌ１と第レンズ２群Ｌ２との間隔変化量が第２レンズ群Ｌ２と第３レンズ群Ｌ３との間隔変化量に対し大きくなると今度は望遠側での画面周辺への光量を確保するために第１レンズ群Ｌ１のレンズ外径が増大する。
【００６４】
また、第１レンズ群Ｌ１はメニスカス状の負レンズと２枚の正レンズより構成し、第３ａレンズ群Ｌ３ａを１枚の負レンズと２枚の正レンズで構成し、第４レンズ群Ｌ４を少なくとも１枚の正レンズと少なくとも１枚の負レンズより構成し、第４レンズ群Ｌ４にレンズ中心からレンズ周辺へ行くに従って正の屈折力が弱くなる形状の非球面を用いることで、レンズ系全体がコンパクトで良好な光学性能のズームレンズを達成している。
【００６５】
次に各実施形態のフォーカシングについて説明する。
【００６６】
ズームレンズのフォーカシング方法としては、第１レンズ群Ｌ１の移動によるフォーカシング、所謂前玉フォーカシング方法が適用できる。この方法は、同一距離物体へのフォーカシングにおけるレンズ群の繰り出し量が焦点距離によらず一定となる性質があるため、鏡筒構造が簡単にできる利点がある。又、広角端の焦点距離が画面対角線長より短かい高変倍ズームレンズでは、広角側のズーム位置で近距離物体のとき画面周辺の光量を十分多く確保しようとすると、第１レンズ群Ｌ１のレンズ外径が極端に増大してくる。
【００６７】
そこで各実施形態では、フォーカシング方式として、第２レンズ群Ｌ２を移動させるフォーカシング方法が適用できる。これは、第１レンズ群Ｌ１に比べて比較的重量の軽い第２レンズ群Ｌ２をもちいるため、フォーカシングの操作性が良好であり、特に、近年普及しているオートフォーカスに対しても、フォーカスモーターへの負荷を少なくでくるので好ましい。
【００６８】
また、同一距離物体に対する第２レンズ群Ｌ２の繰り出し量が広角側に比べ望遠側では増大してくるが、ズーミングで空いたスペース（レンズ群とレンズ群との間隔）を利用できるためフォーカシングのためのスペースの確保が容易となり、周辺光量を多く確保するために第１レンズ群Ｌ１のレンズ外径が増大することがない。
【００６９】
尚、超高変倍ズームレンズになると広角端から望遠端へのズーミングにおいて第２レンズ群Ｌ２の横倍率が等倍をはさむ傾向がある。この場合、等倍を境にフォーカシングのための第２レンズ群Ｌ２の繰り出し方向が変化し、また、等倍となる焦点距離では、第２レンズ群Ｌ２でのフォーカシングできなくなる。この場合は、第１レンズ群Ｌ１及び第２レンズ群Ｌ２を同時に光軸上を同一又は異なった速度で移動させることでフォーカシングを行っている。
【００７０】
実施形態２、３では、無限遠物体から近距離物体へのフォーカシングを第２レンズ群Ｌ２を物体側に移動させて行っている。この場合、前述の理由により条件式（１１）を満足するように第２レンズ群Ｌ２の横倍率を設定している。
【００７１】
また、実施形態４では、無限遠物体から近距離物体へのフォーカシングを第１レンズ群Ｌ１と第２レンズ群Ｌ２とを一体で物体側に移動させて行っている。実施形態１、５では、無限遠物体から近距離物体へのフォーカシングを第１レンズ群Ｌ１と第２レンズ群Ｌ２とを各々１対２の割合で物体側に移動して行っている。
【００７２】
一般に、望遠端の焦点距離が長くなってくると、望遠側での色収差が増大してくる。条件式（１２）〜（１４）は望遠側での軸上色収差及び倍率色収差を良好に補正するための条件式である。条件式（１２）は広角端と望遠端における全系の焦点距離ｆＷ，ｆＴの積の平方根に対する第１レンズ群Ｌ１の焦点距離ｆ１の範囲を規定したものであり、条件式（１２）の下限値を越えて第１レンズ群Ｌ１の正の屈折力が強くなると第１レンズ群Ｌ１で発生する諸収差、特に球面収差、色収差が増大し、条件式（１２）の上限値を超えて第１レンズ群Ｌ１の正の屈折力が弱くなるとレンズ系全体のコンパクト化が困難となってくる。
【００７３】
条件式（１３）は第１レンズ群Ｌ１で発生する色収差を少なくするためのものであり、条件式（１４）は撮影波長全域に渡って色収差を小さく抑える、すなわち、２次スペクトルを小さくするためのものである。この範囲を越えると色収差を良好に補正するのが難しくなってくる。
【００７４】
各実施形態において、更に好ましくは条件式（３）〜（５）、（７）〜（１０）、（１２）の数値を次の如く設定するのが良い。
【００７５】
【数１１】
【００７６】
次に、本発明の実施形態１〜５に各々対応する数値実施例１〜５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番目の光学部材の屈折率、アッベ数を示す。ｆは焦点距離、ＦＮｏはＦナンバー、ωは半画角である。Ｓｋｉｎｆはフレアー絞りから像面までの距離である。またｋを離心率、ｂ、ｃ、ｄ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。又、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。
【００７７】
【外１】
【００７８】
【外２】
【００７９】
【外３】
【００８０】
【外４】
【００８１】
【外５】
【００８２】
【表１】
【００８３】
次に、本発明のズームレンズを用いた一眼レフカメラシステムの実施形態を、図３６を用いて説明する。図３６において、１０は一眼レフカメラ本体、１１は本発明によるズームレンズを搭載した交換レンズ、１２は交換レンズ１１を通して得られる被写体像を記録するフィルムや撮像素子などの記録手段、１３は交換レンズ１１からの被写体像を観察するファインダー光学系、１４は交換レンズ１１からの被写体像を記録手段１２とファインダー光学系１３に切り替えて伝送するための回動するクイックリターンミラーである。ファインダーで被写体像を観察する場合は、クイックリターンミラー１４を介してピント板１５に結像した被写体像をペンタプリズム１６で正立像としたのち、接眼光学系１７で拡大して観察する。撮影時にはクイックリターンミラー１４が矢印方向に回動して被写体像は記録手段１２に結像して記録される。１８はサブミラー、１９は焦点検出装置である。
【００８４】
このように本発明のズームレンズを一眼レフカメラ交換レンズ等の光学機器に適用することにより、高い光学性能を有した光学機器が実現できる。
【００８５】
尚、本発明はクイックリターンミラーのないＳＬＲ（Single lens Reflex）カメラにも同様に適用することができる。
【００８６】
【発明の効果】
本発明によれば、像ぶれ補正用の補正光学系の配置を適切に行うことにより、高画質を維持しつつ補正光学系の小型化、かつ一定量の像ぶれ補正効果を行うための補正光学系の移動量のコントロールを容易に行い、補正光学系の電気的駆動を容易に行う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。
【００８７】
この他本発明によれば、３５ｍｍ一眼レフカメラ換算で焦点距離２８ｍｍ程度の広角域から３００ｍｍ更には３５０ｍｍ程度の望遠域までをカバーし、防振機能を有する、コンパクトで、特に防振時の収差も良好に補正され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。
【図面の簡単な説明】
【図１】本発明の実施形態１の広角端のレンズ断面図
【図２】本発明の実施形態１の通常状態の広角端における縦収差図
【図３】本発明の実施形態１の通常状態の望遠端における縦収差図
【図４】本発明の実施形態１の通常状態の広角端における横収差図
【図５】本発明の実施形態１の通常状態の望遠端における横収差図
【図６】本発明の実施形態１の画角０．３°分の画像ぶれの補正の広角端における横収差図
【図７】本発明の実施形態１の画角０．３°分の画像ぶれの補正の望遠端における横収差図
【図８】本発明の実施形態２の広角端のレンズ断面図
【図９】本発明の実施形態２の通常状態の広角端における縦収差図
【図１０】本発明の実施形態２の通常状態の望遠端における縦収差図
【図１１】本発明の実施形態２の通常状態の広角端における横収差図
【図１２】本発明の実施形態２の通常状態の望遠端における横収差図
【図１３】本発明の実施形態２の画角０．３°分の画像ぶれの補正の広角端における横収差図
【図１４】本発明の実施形態２の画角０．３°分の画像ぶれの補正の望遠端における横収差図
【図１５】本発明の実施形態３の広角端のレンズ断面図
【図１６】本発明の実施形態３の通常状態の広角端における縦収差図
【図１７】本発明の実施形態３の通常状態の望遠端における縦収差図
【図１８】本発明の実施形態３の通常状態の広角端における横収差図
【図１９】本発明の実施形態３の通常状態の望遠端における横収差図
【図２０】本発明の実施形態３の画角０．３°分の画像ぶれの補正の広角端における横収差図
【図２１】本発明の実施形態３の画角０．３°分の画像ぶれの補正の望遠端における横収差図
【図２２】本発明の実施形態４の広角端のレンズ断面図
【図２３】本発明の実施形態４の通常状態の広角端における縦収差図
【図２４】本発明の実施形態４の通常状態の望遠端における縦収差図
【図２５】本発明の実施形態４の通常状態の広角端における横収差図
【図２６】本発明の実施形態４の通常状態の望遠端における横収差図
【図２７】本発明の実施形態４の画角０．３°分の画像ぶれの補正の広角端における横収差図
【図２８】本発明の実施形態４の画角０．３°分の画像ぶれの補正の望遠端における横収差図
【図２９】本発明の実施形態５の広角端のレンズ断面図
【図３０】本発明の実施形態５の通常状態の広角端における縦収差図
【図３１】本発明の実施形態５の通常状態の望遠端における縦収差図
【図３２】本発明の実施形態５の通常状態の広角端における横収差図
【図３３】本発明の実施形態５の通常状態の望遠端における横収差図
【図３４】本発明の実施形態５の画角０．３°分の画像ぶれの補正の広角端における横収差図
【図３５】本発明の実施形態５の画角０．３°分の画像ぶれの補正の望遠端における横収差図
【図３６】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
ＳＰ開口絞り
ＩＰ像面
ｄｄ線
ｇｇ線
Ｓサジタル像面
Ｍメリディオナル像面
ω 画角
ＦＮｏＦナンバー
Ｓ．Ｃ正弦条件[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens and an optical apparatus having the zoom lens. More specifically, the zoom lens is vibrated (tilted) by moving a part of a lens group of the optical system so as to have a component in a direction perpendicular to the optical axis. It is suitable for optical devices such as a silver halide photographic camera, a video camera, an electronic still camera, a digital camera, etc., which have a high optical performance and a good correction of image blur (image blur).
[0002]
[Prior art]
When shooting from a moving object such as a car in progress, vibration is transmitted to the shooting system (shooting lens), and the shot image is blurred. In addition, in hand-held shooting with a shooting lens with a long focal length or a shooting lens with a large F number (FNo), blurring (image blurring) may occur in the shot image due to camera shake. In recent years, a silver salt camera, a video camera, a digital camera, and the like having an image stabilization function that optically or electrically corrects these image blurs have been proposed.
[0003]
Conventional zoom lenses having an anti-vibration function include, for example, Japanese Patent Laid-Open No. 5-232410 (Conventional Example 1), Japanese Patent Laid-Open No. 8-136863 (Conventional Example 2), Japanese Patent Laid-Open No. 8-106047 (Conventional Example 3), JP-A-9-230237 (conventional example 4), JP-A-11-64728 (conventional example 5), etc.
[0004]
Conventional example 1 is a telephoto zoom lens composed of four lens groups of positive, negative, positive, and positive refractive power in order from the object side, and the second lens group is moved in a direction perpendicular to the optical axis. Anti-vibration is performed. Conventional Example 2 is a zoom lens composed of five lens groups of positive, negative, positive, positive, and negative refractive power in order from the object side. A part of the second lens group is moved in a direction perpendicular to the optical axis. Anti-vibration is performed. Conventional Example 3 is a zoom lens composed of five lens groups of positive, negative, positive, positive, and negative refractive power in order from the object side. A part of the fourth lens group is moved in a direction perpendicular to the optical axis. Anti-vibration is performed. Conventional Example 4 is a zoom lens having four lens groups of positive, negative, positive, and positive refractive power in order from the object side, and moves some lens groups in the lens group in a direction perpendicular to the optical axis. To prevent vibration. Conventional Example 5 has five lens groups of positive, negative, positive, positive, and negative refractive power in order from the object side, and the fourth lens group is moved in the direction perpendicular to the optical axis to perform vibration isolation. The zoom lens has four lens groups of positive, negative, positive and positive refractive power in order from the object side, and the fourth lens group is divided into lens groups of positive and negative refractive power, of which positive refraction A zoom lens is disclosed in which a lens group of force is moved in a direction perpendicular to the optical axis to perform image stabilization.
[0005]
In addition, in JP-A-11-237550, a first lens group having a positive refractive power from the object side, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refraction. A fourth lens group having power, and moving the second and fourth lens groups on the optical axis to perform zooming. The third lens group has a thirty-first lens group and a thirty-second lens group. Discloses a zoom lens in which the imaging position is displaced by moving the thirty-second lens group in a direction perpendicular to the optical axis.
[0006]
[Problems to be solved by the invention]
In general, in an optical system that corrects image blur by decentering a part of lenses of a photographing system in a direction perpendicular to the optical axis, there is an advantage that image blur can be corrected relatively easily. There is a problem that a driving means for the lens to be moved is required, and the amount of decentration aberrations generated during image stabilization increases.
[0007]
For example, if the correction optical system for correcting image blur has a large number of lenses and is heavy, a large torque is required for electrical driving. In addition, if the correction lens group for correcting image blur is not set appropriately, it is necessary to increase the movement amount of the correction optical system in order to obtain a fixed amount of image blur correction effect. There is a problem of increasing the size.
[0008]
On the other hand, if the correction effect of the image with respect to the movement of the correction optical system is strengthened, in order to perform an accurate correction with respect to a constant image blur correction, the imaging displacement action becomes too sensitive to the decentration. It becomes difficult to perform proper lens movement control.
[0009]
According to the present invention, by appropriately arranging the correction optical system for image blur correction, the correction optical system can be downsized while maintaining high image quality, and the correction optical system can be moved to achieve a certain amount of image blur correction effect. An object of the present invention is to provide a zoom lens capable of easily controlling the amount and easily driving the correction optical system, and an optical apparatus having the zoom lens.
[0010]
In addition, the present invention covers a wide-angle range of a focal length of about 28 mm in terms of a 35 mm single-lens reflex camera to a telephoto range of about 300 mm and further about 350 mm, has a vibration-proof function, is compact, and has particularly good aberrations during vibration prevention. An object of the present invention is to provide a zoom lens corrected to 1 and an optical apparatus having the same.
[0011]
[Means for Solving the Problems]
The zoom lens according to the first aspect of the invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens In a zoom lens that includes a fourth lens unit having a refractive power and performs zooming by changing the interval between the lens units, the third lens unit includes a third lens unit having a positive refractive power and a negative refractive power. the constructed from 3b lens group, the said 3b lens and by displacing the imaging position by moving so as to have an optical axis vertical component, DiW, at each wide angle end and the telephoto end the DiT of The distance between the i-th lens group and the (i + 1) -th lens group, fW and fT are the focal lengths of the entire system at the wide-angle end and the telephoto end, and f2 and f3b are the distances between the second lens group and the 3b lens group, respectively. Focal length, TS3bT perpendicular to the optical axis of the 3b lens group at the telephoto end When the amount of displacement in the direction perpendicular to the optical axis of the imaging position with respect to the amount of displacement in the direction,
[Equation 5]
It satisfies the following conditional expression.
[0012]
The invention of claim 2 is the invention of claim 1, wherein f3 and f4 are focal lengths of the third lens group and the fourth lens group, and LW is an optical total length at the wide angle end.
[Formula 6]
It satisfies the following conditional expression.
[0013]
According to a third aspect of the present invention, in the first aspect of the invention, the 3b lens group is composed of one positive lens and one negative lens.
[0014]
According to a fourth aspect of the present invention, in the first aspect of the invention, the 3a lens group is composed of two positive lenses and one negative lens.
[0015]
The invention of claim 5 is the invention of claim 1, wherein the second lens group is characterized by consisting of three negative lenses and one positive lens.
[0016]
According to a sixth aspect of the present invention, in the first aspect of the invention, the second lens group includes three negative lenses and two positive lenses.
[0017]
The invention of claim 7 is the invention of claim 1, wherein the first lens group is characterized by comprising a negative lens and two positive lenses of meniscus shape.
[0018]
The invention according to claim 8 is the invention according to claim 2, wherein the fourth lens group is composed of one positive lens and one negative lens , and has a shape in which the positive refractive power decreases from the lens center to the lens periphery. It has an aspherical surface.
[0019]
According to a ninth aspect of the present invention, in the second aspect of the present invention, the fourth lens group includes two positive lenses and one negative lens, and has a shape in which the positive refractive power decreases from the lens center toward the lens periphery. It has an aspherical surface.
[0020]
According to a tenth aspect of the present invention, in the first aspect of the invention, the second lens group when the second lens group is moved in the optical axis direction to perform focusing, and β2T is focused on an infinite object at the telephoto end. When the horizontal magnification is
−0.95 <β2T <−0.5
It satisfies the following conditional expression.
[0021]
In the invention the present invention of claim 1 of claim 11, wherein the first lens group consists of one negative lens and two positive lenses, the focal length of the first lens group f1, two said the νd When the Abbe number of the material of one positive lens of the positive lenses and θgd is the fractional ratio of the material of one positive lens of the two positive lenses,
[Expression 7]
It satisfies the following conditional expression.
[0022]
According to a twelfth aspect of the present invention, in the first aspect of the invention, focusing from an object at infinity to a short distance object is performed by moving the first lens group and the second lens group integrally or at different speeds toward the object side. The zoom lens according to claim 1, wherein the zoom lens is performed.
[0023]
A zoom lens according to a thirteenth aspect of the invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens It is a fourth lens unit of power, by changing the distances between the lens groups at the zoom lens to perform zooming, the third lens group, the 3a lens unit having a positive refractive power and the negative refractive power is composed of the 3b lens unit performs displacement of the imaging position by moving the said 3b lens group to have a direction perpendicular to the optical axis of the component, moving the second lens group along the optical axis Focusing, DiW and DiT are the distance between the i-th lens group and the (i + 1) -th lens group at the wide-angle end and the telephoto end, respectively, and fW and fT are the focal lengths of the entire system at the wide-angle end and the telephoto end, respectively. , Fi is the focal length of the i-th lens group, and f3b is the focal length of the 3b-lens group. Distance, perpendicular to the optical axis direction of displacement of the imaging position with respect to the optical axis and the vertical displacement of the said 3b lens group at the telephoto end the TS3bT, overall optical length and LW at the wide-angle end, infinity at the telephoto end the β2T When the lateral magnification of the second lens group when focusing on the object,
[Equation 8]
It satisfies the following conditional expression.
[0024]
A fourteenth aspect of the present invention is the optical system according to any one of the first to thirteenth aspects, which is an optical system for forming an image on an image sensor.
[0025]
An optical apparatus according to a fifteenth aspect of the present invention includes the zoom lens according to any one of the first to fourteenth aspects, and an image sensor that receives an image formed by the zoom lens.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 1, FIGS. 2 and 3 are longitudinal aberration diagrams at the wide-angle end and the telephoto end of Embodiment 1, and FIGS. Horizontal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens, FIGS. 6 and 7 are diagrams after changing the image position corresponding to 0.3 ° of the angle of view at the wide-angle end and the telephoto end of the zoom lens of Embodiment 1. FIG.
[0033]
8 is a lens cross-sectional view at the wide-angle end of the zoom lens according to the second embodiment, FIGS. 9 and 10 are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to Embodiment 2, and FIGS. Lateral aberration diagrams at the wide-angle end and the telephoto end of the zoom lens, FIGS. 13 and 14 are diagrams after changing the image position corresponding to 0.3 ° of the angle of view at the wide-angle end and the telephoto end of the zoom lens of Embodiment 2. FIG.
[0034]
15 is a lens cross-sectional view at the wide-angle end of the zoom lens according to the third embodiment, FIGS. 16 and 17 are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to Embodiment 3, and FIGS. Lateral aberration diagrams at the wide-angle end and the telephoto end of the zoom lens, FIGS. 20 and 21 are views after changing the image position corresponding to the angle of view of 0.3 ° at the wide-angle end and the telephoto end of the zoom lens of Embodiment 3. FIG.
[0035]
FIG. 22 is a lens cross-sectional view at the wide-angle end of the zoom lens of Embodiment 4, FIGS. 23 and 24 are longitudinal aberration diagrams at the wide-angle end and the telephoto end of Embodiment 4, and FIGS. 25 and 26 are those of Embodiment 4. Lateral aberration diagrams at the wide-angle end and the telephoto end of the zoom lens, FIGS. 27 and 28 are diagrams after changing the image position corresponding to 0.3 ° of the angle of view at the wide-angle end and the telephoto end of the zoom lens of Embodiment 4. FIG.
[0036]
FIG. 29 is a lens cross-sectional view at the wide-angle end of the zoom lens according to the fifth embodiment, FIGS. 30 and 31 are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to the fifth embodiment, and FIGS. Horizontal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens, and FIGS. 34 and 35 are diagrams after changing the image position corresponding to the angle of view of 0.3 ° at the wide-angle end and the telephoto end of the zoom lens of Embodiment 5. FIG.
[0037]
In the lens sectional view, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, L3 is a third lens group having a positive refractive power, and L4 is a fourth lens having a positive refractive power. It is a lens group. An arrow indicates the moving direction of each lens unit when zooming from the wide-angle side to the telephoto side. SP is a stop provided between the second lens group and the third lens group. IP is an image plane, on which an image sensor such as a CCD or MOS, or a photosensitive material such as a film is disposed. FP is a flare cut stop.
[0038]
The third lens unit L3 includes a 3a lens unit L3a having a positive refractive power and a 3b lens unit L3b having a negative refractive power that moves so as to have a component perpendicular to the optical axis for image stabilization. . Note that the aperture stop SP moves together with the 3a lens unit L3a during zooming.
[0039]
In the zoom lens of each embodiment, the first lens unit L1 having a positive refractive power from the object side, the second lens unit L2 having a negative refractive power, the third lens unit L3 having a positive refractive power, and a positive lens A fourth lens unit L4 having refractive power is provided, and zooming is performed by changing the air interval of each lens unit while moving each lens unit on the optical axis, and the negative refractive power in the third lens unit is reduced. The imaging position is changed by moving the third lens group L3b so as to have a component in a direction perpendicular to the optical axis.
[0040]
During zooming, the air gap between the first lens unit L1 and the second lens unit L2 is changed to change the magnification mainly in the second lens unit L2, and the movement of the third lens unit L3 changes mainly due to the change in magnification. At the same time as correcting the image plane, the air gap between the third lens unit L3 and the fourth lens unit L4 is changed to correct the fluctuation of off-axis aberrations due to zooming. By disposing the third lens unit L3b having a negative refractive power in the third lens unit L3 having a positive refractive power, the positive lens system other than the third lens unit L3b in the third lens unit L3 is positive. Various aberrations occurring in the refractive lens group are canceled by the negative refractive action of the third lens group L3b. At the same time, a large image position displacement action (anti-vibration action) is performed with a small amount of movement.
[0041]
Focusing from an infinitely distant object to a close object is performed by moving the second lens unit L2 or the first lens unit L1 and the second lens unit L2 integrally or at different speeds toward the object side. In particular, the method of moving the second lens unit L2 is good in order not to increase the lens outer diameter of the first lens unit L1. Further, by adopting a system in which both the first and second lens groups L1 and L2 are moved to the object side, aberration variation during focusing is reduced.
[0042]
In the zoom lens of each embodiment, DiW and DiT are the distance between the i-th lens group and the (i + 1) th lens group at the wide-angle end and the telephoto end, respectively, and fW and fT are the entire system at the wide-angle end and the telephoto end, respectively. , Fi is the focal length of the i-th lens group, and f3b is the focal length of the 3b lens group . When the TS3bT is moved at a telephoto end by a unit amount in the direction perpendicular to the optical axis, the amount of displacement in the direction perpendicular to the optical axis of the image forming position, that is, in the direction perpendicular to the optical axis of the 3b lens group. The amount of displacement in the direction perpendicular to the optical axis of the imaging point with respect to the amount of displacement is taken. Let LW be the optical total length at the wide-angle end . At this time
[0043]
[Equation 9]
[0044]
Of these conditional expressions, one or more conditional expressions are satisfied. If any one of these conditional expressions is satisfied, an effect described later corresponding to the conditional expression can be obtained.
[0045]
When β2T is set as the lateral magnification of the second lens group when focusing on an object at infinity at the telephoto end,
−0.95 <β2T <−0.5 (11)
The following conditional expression is satisfied.
[0046]
The first lens group has one negative lens and two positive lenses, f1 is the focal length of the first lens group, and νd is the material of one positive lens of the two positive lenses. When the Abbe number of θgd is the fractional ratio of the material of one positive lens of the two positive lenses,
[0047]
[Expression 10]
[0048]
The following conditional expression is satisfied.
[0049]
Here, the Abbe number νd and the partial fraction ratio θgd are the refractive indices of the materials in the d-line, g-line, C-line, and F-line of the Fraunhofer line, respectively, nd, ng, nC, and nF.
νd = (nd−1) / (nF−nC)
θgd = (ng−nd) / (nF−nC)
It is expressed by the following formula.
[0050]
Next, the technical meaning of each conditional expression described above will be described.
[0051]
During zooming from the wide-angle end to the telephoto end, the first lens unit L1 and the second lens unit L2 move toward the object side while satisfying the conditional expressions (1) and (2). The magnification at L2 is performed to shorten the optical total length (distance from the first lens surface to the image plane) at the wide angle end. In addition, the wide-angle side has a retro lens as the entire lens system to ensure the required length of back focus, while the telephoto side has the entire lens system as a telephoto type to reduce the size of the lens system. Yes. Further, by moving the third lens unit L3 and the fourth lens unit L4 to the object side while satisfying the conditional expression (6), the third lens unit L3 and the fourth lens unit L4 are moved along with the zooming from the wide angle end to the telephoto end. The magnification effect in the third lens unit L3 and the fourth lens unit L4 is enhanced by moving the main point position of the synthesis of the lens unit L4 to the object side.
[0052]
By disposing the aperture stop SP on the object side of the third lens unit L3, the aperture diameter is suppressed to be small, and the front lens diameter, that is, the lens diameter closest to the object side, and the rear lens diameter, that is, the lens diameter closest to the image surface side, are appropriately The entire lens system is made compact. In addition, the second lens unit L2 includes three negative lenses and one or two positive lenses to enable good aberration correction.
[0053]
Further, since the focal length f2 of the second lens unit L2 satisfies the conditional expression (3), the entire lens system is made compact and high performance is achieved. Conditional expression (3) defines the range of the focal length of the second lens unit L2 with respect to the square root of the product of the focal lengths of the entire system at the wide-angle end and the telephoto end, and exceeds the lower limit value and exceeds the lower limit value. When the negative refractive power of the lens becomes weak, the entire lens system increases. If the negative refractive power of the second lens unit L2 is increased beyond the upper limit, it is advantageous for making the entire lens system compact. However, various aberrations generated in the second lens unit L2 increase, and this is applied to other lenses. It becomes difficult to correct with good balance in groups.
[0054]
In each embodiment, the anti-vibration lens group (the 3b lens group L3b) is composed of one positive lens and one negative lens, and the third anti-vibration lens group L3b is used to eliminate the vibration. Occurrence of chromatic aberration at the time is reduced, and the lens weight of the image stabilizing lens unit L3b is reduced by adopting a two-lens configuration. Further, by satisfying the conditional expressions (4), (5), and (7), the amount of displacement of the vibration-proof lens unit L3b for vibration reduction is reduced, and the vibration-proof drive actuator of the third lens unit L3b is used. Good vibration-proof drive characteristics are achieved by reducing such load and reducing energy consumption.
[0055]
In general, in order to reduce the drive amount of the image stabilizing lens group for image stabilization, the displacement amount of the imaging point relative to the displacement amount of the image stabilizing lens group, that is, the radial sensitivity may be increased. Here, TS is the radial sensitivity (eccentric sensitivity), f is the focal length of the image stabilization lens group, φ is the camera shake angle assumed for image stabilization, and the optical axis of the image stabilization lens group for image stabilization. Let X be the amount of displacement in the direction perpendicular to the axis . At this time
TS × X = f × tanφ
Doo ing. Here, f × tan φ is a displacement amount in a direction orthogonal to the optical axis of the image formation point. Therefore, the radial sensitivity TS is a displacement amount f × tanφ of the imaging point with respect to the displacement amount X in the direction orthogonal to the optical axis of the image stabilizing lens group.
Further, the displacement amount X is X = f × tanφ / TS.
It becomes.
[0056]
Therefore, when the camera shake angle φ is constant, the displacement amount X of the image stabilizing lens group is proportional to the focal length of the image stabilizing lens group and inversely proportional to the radial sensitivity TS. Therefore, in order to keep the amount of displacement X of the anti-vibration lens at the time of anti-vibration small, it is necessary to increase the radial sensitivity TS in proportion to the focal length at the telephoto end.
[0057]
Conditional expression (4) defines the focal length f3b of the third lens unit L3b with respect to the square root of the product of the focal lengths fW and fT of the entire system at the wide-angle end and the telephoto end, and conditional expression (7) is the third lens. This defines the ratio of the focal length f3b of the third lens group L3b to the focal length f3 of the lens group L3. If both conditional expressions exceed the lower limit and the negative refractive power of the third lens group L3b becomes weaker, the third lens b When the radial sensitivity TS3bT of the group L3b increases and the negative refractive power of the third b lens group L3b increases beyond the upper limit value, it becomes difficult to correct aberrations, and the optical performance particularly during image stabilization deteriorates.
[0058]
In each embodiment, by setting the radial sensitivity TS3bT at the telephoto end of the 3b lens unit L3b within the range of the conditional expression (5), the displacement amount of the 3b lens unit L3b for image stabilization is suppressed to a small value. Good optical performance is obtained.
[0059]
Conditional expression (8) defines the ratio of the focal length of the fourth lens unit L4 to the square root of the product of the focal lengths fW and fT of the entire system at the wide-angle end and the telephoto end, and is the lower limit of conditional expression (8). If the positive refracting power of the fourth lens unit L4 is increased beyond this, it is advantageous for shortening the total lens length, but it is difficult to correct aberrations. If the upper limit of conditional expression (8) is exceeded and the positive refractive power of the fourth lens unit L4 becomes weak, this is advantageous for aberration correction, but the lens system increases.
[0060]
Conditional expression (9) is the ratio of the total optical length (length from the lens surface closest to the object side to the image plane) at the wide-angle end with respect to the focal length fT of the entire system at the telephoto end, and is the lower limit value of conditional expression (9). If it is attempted to make the lens compact beyond this, it becomes necessary to increase the refractive power of each lens unit, and as a result, the optical performance deteriorates. If the upper limit of conditional expression (9) is exceeded, it will be difficult to obtain high optical performance while reducing the size of the entire lens system.
[0061]
Conditional expression (10) shows the amount of change in the distance between the first lens unit L1 and the second lens unit L2 and the amount of change in the distance between the second lens unit L2 and the third lens unit L3 during zooming from the wide-angle end to the telephoto end. This ratio is for reducing the outer diameter of the stop SP disposed on the object side of the third lens unit L3 and optimizing the lens outer diameter of each lens unit.
[0062]
Exceeding the lower limit of conditional expression (10), the amount of change in the distance between the first lens unit L1 and the second lens unit L2 is less than the amount of change in the interval between the second lens unit L2 and the third lens unit L3. This means that the amount of change in the distance between the second lens unit L2 and the third lens unit L3 is increased in order to obtain a predetermined zoom ratio, and the interval between the aperture stop SP and the first lens unit L1 at the wide angle end is increased. In order to secure the amount of light to the periphery of the screen, the lens outer diameter of the first lens unit L1 increases.
[0063]
If the amount of change in the distance between the first lens unit L1 and the second lens unit L2 exceeds the upper limit value of the conditional expression (10), the amount of change in the distance between the second lens unit L2 and the third lens unit L3 will increase. In order to secure the amount of light to the periphery of the screen on the telephoto side, the lens outer diameter of the first lens unit L1 increases.
[0064]
The first lens unit L1 includes a meniscus negative lens and two positive lenses, the third a lens unit L3a includes one negative lens and two positive lenses, and the fourth lens unit L4. The entire lens system is configured by using at least one positive lens and at least one negative lens, and using an aspherical surface whose positive refractive power becomes weaker from the center of the lens toward the periphery of the lens in the fourth lens unit L4. Has achieved a zoom lens with compact and good optical performance.
[0065]
Next, focusing in each embodiment will be described.
[0066]
As a focusing method for the zoom lens, a so-called front lens focusing method by moving the first lens unit L1 can be applied. This method has an advantage that the lens barrel structure can be simplified because the amount of extension of the lens unit in focusing to the same distance object is constant regardless of the focal length. In addition, in a high magnification zoom lens in which the focal length at the wide-angle end is shorter than the diagonal length of the screen, if it is intended to secure a sufficient amount of light around the screen when the object is a close distance at the zoom position on the wide-angle side, the first lens unit L1 The lens outer diameter increases extremely.
[0067]
Therefore, in each embodiment, a focusing method for moving the second lens unit L2 can be applied as the focusing method. This is because the second lens unit L2, which is relatively light compared to the first lens unit L1, uses the second lens unit L2, so that the operability of focusing is good. This is preferable because it reduces the load on the motor.
[0068]
Further, the amount of extension of the second lens unit L2 with respect to an object of the same distance increases on the telephoto side compared to the wide-angle side, but because of the space vacated by zooming (interval between the lens unit and the lens unit), it can be used for focusing. It is easy to secure the space, and the lens outer diameter of the first lens unit L1 does not increase in order to secure a large amount of peripheral light.
[0069]
In the case of an ultra-high zoom lens, the lateral magnification of the second lens unit L2 tends to be equal to the same magnification during zooming from the wide-angle end to the telephoto end. In this case, the extension direction of the second lens unit L2 for focusing changes at the same magnification, and the focusing by the second lens unit L2 cannot be performed at a focal length that is the same magnification. In this case, focusing is performed by simultaneously moving the first lens unit L1 and the second lens unit L2 on the optical axis at the same or different speeds.
[0070]
In the second and third embodiments, focusing from an infinitely distant object to a close object is performed by moving the second lens unit L2 to the object side. In this case, the lateral magnification of the second lens unit L2 is set so as to satisfy the conditional expression (11) for the reason described above.
[0071]
In the fourth embodiment, focusing from an object at infinity to a near object is performed by moving the first lens unit L1 and the second lens unit L2 integrally to the object side. In the first and fifth embodiments, focusing from an infinite object to a close object is performed by moving the first lens unit L1 and the second lens unit L2 to the object side at a ratio of 1: 2.
[0072]
In general, as the focal length at the telephoto end increases, the chromatic aberration on the telephoto side increases. Conditional expressions (12) to (14) are conditional expressions for favorably correcting axial chromatic aberration and lateral chromatic aberration on the telephoto side. Conditional expression (12) defines the range of the focal length f1 of the first lens unit L1 with respect to the square root of the product of the focal lengths fW and fT of the entire system at the wide-angle end and the telephoto end, and is the lower limit of conditional expression (12). When the positive refracting power of the first lens unit L1 is increased beyond this value, various aberrations, particularly spherical aberration and chromatic aberration, generated in the first lens unit L1 increase, exceeding the upper limit of the conditional expression (12). If the positive refractive power of the lens unit L1 becomes weak, it becomes difficult to make the entire lens system compact.
[0073]
Conditional expression (13) is for reducing chromatic aberration generated in the first lens unit L1, and conditional expression (14) is for reducing chromatic aberration over the entire imaging wavelength range, that is, for reducing the secondary spectrum. belongs to. Beyond this range, it becomes difficult to correct chromatic aberration well.
[0074]
In each embodiment, it is more preferable to set the numerical values of conditional expressions (3) to (5), (7) to (10), and (12) as follows.
[0075]
## EQU11 ##
[0076]
Next, Numerical Examples 1 to 5 respectively corresponding to Embodiments 1 to 5 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 represent the refractive index and Abbe number of the i-th optical member for the d-line, respectively. f is a focal length, FNo is an F number, and ω is a half angle of view. Skinf is the distance from the flare stop to the image plane. Further, when k is an eccentricity, b, c, and d are aspherical coefficients, and the displacement in the optical axis direction at the position of the height h from the optical axis is x based on the surface vertex, the aspherical shape is
x = (h ² / R) / [1+ [1- (1 + k) (h / R) ² ] ^1/2 ] + bh ⁴ + ch ⁶ + dh ⁸ Where R is the radius of curvature. For example, “e-Z” means “10 ^−Z ”. Table 1 shows the correspondence with the above-described conditional expressions in each numerical example.
[0077]
[Outside 1]
[0078]
[Outside 2]
[0079]
[Outside 3]
[0080]
[Outside 4]
[0081]
[Outside 5]
[0082]
[Table 1]
[0083]
Next, an embodiment of a single-lens reflex camera system using the zoom lens of the present invention will be described with reference to FIG. In FIG. 36, 10 is a single-lens reflex camera body, 11 is an interchangeable lens equipped with a zoom lens according to the present invention, 12 is a recording means such as a film or an image sensor for recording a subject image obtained through the interchangeable lens 11, and 13 is an interchangeable lens. A finder optical system for observing the subject image from 11, and a rotating quick return mirror 14 for switching and transmitting the subject image from the interchangeable lens 11 to the recording means 12 and the finder optical system 13. When observing the subject image with the finder, the subject image formed on the focusing plate 15 via the quick return mirror 14 is converted into an erect image with the pentaprism 16 and then magnified with the eyepiece optical system 17 for observation. At the time of shooting, the quick return mirror 14 rotates in the direction of the arrow, and the subject image is formed and recorded on the recording means 12. Reference numeral 18 denotes a submirror, and 19 denotes a focus detection device.
[0084]
Thus, by applying the zoom lens of the present invention to an optical device such as a single lens reflex camera interchangeable lens, an optical device having high optical performance can be realized.
[0085]
The present invention can be similarly applied to an SLR (Single Lens Reflex) camera having no quick return mirror.
[0086]
【The invention's effect】
According to the present invention, by appropriately arranging the correction optical system for image blur correction, the correction optical system for reducing the size of the correction optical system and performing a certain amount of image blur correction effect while maintaining high image quality. It is possible to achieve a zoom lens that can easily control the amount of movement of the system and easily drive the correction optical system and an optical apparatus having the same.
[0087]
In addition to this, according to the present invention, in terms of a 35 mm single-lens reflex camera, it covers a wide-angle range with a focal length of about 28 mm to a telephoto range of about 300 mm and further about 350 mm, has a vibration-proof function, is compact, and particularly has an aberration during vibration prevention. Also, a well-corrected zoom lens and an optical apparatus having the same can be achieved.
[Brief description of the drawings]
FIG. 1 is a lens cross-sectional view at a wide-angle end according to Embodiment 1 of the present invention. FIG. 2 is a longitudinal aberration diagram at a wide-angle end in a normal state according to Embodiment 1 of the present invention. FIG. 4 is a lateral aberration diagram at the wide-angle end in the normal state of Embodiment 1 of the present invention. FIG. 5 is a lateral aberration diagram at the telephoto end in the normal state of Embodiment 1 of the present invention. FIG. 7 is a lateral aberration diagram at the wide-angle end of image blur correction for an angle of view of 0.3 ° according to Embodiment 1 of the present invention. FIG. 7 is a diagram of image blur correction for an angle of view of 0.3 ° according to Embodiment 1 of the present invention. Fig. 8 is a lateral aberration diagram at the telephoto end of Fig. 8. Fig. 9 is a lens cross-sectional view at the wide angle end of Embodiment 2 of the invention. Fig. 9 is a longitudinal aberration diagram at the wide angle end in the normal state of Embodiment 2 of the invention. Fig. 11 is a longitudinal aberration diagram at the telephoto end in the normal state according to Embodiment 2 of the present invention. Fig. 12 is a lateral aberration diagram at the wide-angle end. Fig. 12 is a transverse aberration diagram at the telephoto end in the normal state according to the second embodiment of the present invention. Fig. 14 is a lateral aberration diagram at the wide-angle end. Fig. 14 is a lateral aberration diagram at the telephoto end of image blur correction for an image angle of 0.3 ° according to the second embodiment of the present invention. FIG. 16 is a longitudinal aberration diagram at the wide-angle end in the normal state of Embodiment 3 of the present invention. FIG. 17 is a longitudinal aberration diagram at the telephoto end in the normal state of Embodiment 3 of the present invention. Fig. 19 is a lateral aberration diagram at the wide-angle end in the normal state according to the third embodiment. Fig. 19 is a lateral aberration diagram at the telephoto end in the normal state according to the third embodiment of the present invention. Fig. 21 is a lateral aberration diagram at the wide-angle end of minute image blur correction. Fig. 22 is a lateral aberration diagram at the telephoto end of image blur correction for an angle of view of 0.3 °. Fig. 22 is a lens cross-sectional view at the wide angle end according to Embodiment 4 of the present invention. Fig. 24 is a longitudinal aberration diagram at the telephoto end in the normal state according to Embodiment 4 of the present invention. Fig. 25 is a lateral aberration diagram at the wide angle end in the normal state in Embodiment 4 of the present invention. FIG. 27 is a lateral aberration diagram at the telephoto end in the normal state of Embodiment 4 of the present invention. FIG. 27 is a lateral aberration diagram at the wide angle end of image blur correction for an angle of view of 0.3 ° according to Embodiment 4 of the present invention. FIG. 29 is a lateral aberration diagram at the telephoto end for correcting image blur for an angle of view of 0.3 ° according to Embodiment 4 of the present invention. FIG. 29 is a sectional view of a lens at the wide angle end according to Embodiment 5 of the present invention. FIG. 31 is a longitudinal aberration diagram at the wide-angle end in the normal state according to Embodiment 5 of the present invention. Fig. 32 is a longitudinal aberration diagram at the telephoto end in the normal state of Fig. 32. Fig. 33 is a transverse aberration diagram at the wide-angle end in the normal state in Embodiment 5 of the present invention. FIG. 34 is a lateral aberration diagram at the wide-angle end of image blur correction for an angle of view of 0.3 ° according to Embodiment 5 of the present invention. FIG. 35 is an image for an angle of view of 0.3 ° according to Embodiment 5 of the present invention. Fig. 36 is a lateral aberration diagram at the telephoto end for camera shake correction.
L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group SP Aperture stop IP Image plane d d-line g g-line S Sagittal image plane M Meridional image plane ω Angle of view FNo F number S. C sine condition

Claims

In order from the object side, the lens unit includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. , in the zoom lens to perform zooming by changing the distances between the lens groups, the third lens group is composed of the 3b lens unit having a positive 3a-th lens group refractive power and the negative refractive power, the The imaging position is displaced by moving the third lens group so as to have a component perpendicular to the optical axis, and DiW and DiT are respectively (i + 1) th to the i-th lens group at the wide-angle end and the telephoto end. The distance from the lens group, fW and fT are the focal lengths of the entire system at the wide-angle end and the telephoto end, f2 and f3b are the focal lengths of the second lens group and the 3b lens group, respectively, and TS3bT is the first focal length at the telephoto end. The optical axis of the imaging position with respect to the amount of displacement in the direction perpendicular to the optical axis of the 3b lens group And the amount of displacement in the vertical direction,
A zoom lens that satisfies the following conditional expression:

When f3 and f4 are focal lengths of the third lens group and the fourth lens group, and LW is an optical total length at the wide angle end,
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.

The zoom lens according to claim 1, wherein the third lens group includes one positive lens and one negative lens.

The zoom lens according to claim 1, wherein the third-a lens group includes two positive lenses and one negative lens.

The second lens group is three negative lens and the zoom lens of claim 1, characterized in that consists of one positive lens.

The zoom lens according to claim 1, wherein the second lens group includes three negative lenses and two positive lenses.

The first lens group zoom lens according to claim 1, characterized by comprising a negative lens and two positive lenses of meniscus shape.

3. The fourth lens group according to claim 2, wherein the fourth lens group is composed of one positive lens and one negative lens , and has an aspherical surface whose positive refractive power decreases from the lens center to the lens periphery. Zoom lens.

3. The fourth lens group according to claim 2, wherein the fourth lens group includes two positive lenses and one negative lens, and has an aspherical surface whose positive refractive power decreases from the lens center toward the lens periphery. Zoom lens.

When focusing is performed by moving the second lens group in the optical axis direction, and β2T is set to the lateral magnification of the second lens group when focusing on an infinite object at the telephoto end,
−0.95 <β2T <−0.5
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.

The first lens group is composed of one negative lens and two positive lenses , and f1 is a focal length of the first lens group, and νd is a material of one positive lens of the two positive lenses. When the Abbe number, θgd, is the fractional ratio of the material of one of the two positive lenses,
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.

2. The zoom lens according to claim 1, wherein focusing from an infinitely distant object to a close object is performed by moving the first lens group and the second lens group integrally or at different speeds toward the object side.

In order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power and a fourth lens unit having a positive refractive power , in the zoom lens to perform zooming by changing the distances between the lens groups, the third lens group is composed of the 3b lens unit having a positive 3a-th lens group refractive power and the negative refractive power, the The image forming position is displaced by moving the third lens group so as to have a component perpendicular to the optical axis, the focusing is performed by moving the second lens group in the optical axis direction, and DiW and DiT are set respectively. The distance between the i-th lens group and the (i + 1) th lens group at the wide-angle end and the telephoto end, fW and fT are the focal lengths of the entire system at the wide-angle end and the telephoto end, and fi is the focal length of the i-th lens group. , F3b is the focal length of the 3b lens group, and TS3bT is at the telephoto end. The amount of displacement in the direction perpendicular to the optical axis of the imaging position with respect to the amount of displacement in the direction perpendicular to the optical axis of the third lens group, LW is the total optical length at the wide angle end, and β2T is focused on an object at infinity at the telephoto end When the lateral magnification of the second lens group of
A zoom lens that satisfies the following conditional expression:

Any one of the zoom lens of claims 1 to 13, characterized in that an optical system for forming an image on the imaging device.

An optical apparatus and any one of the zoom lens of claims 1 14, characterized by having an image sensor for receiving an image formed by the zoom lens.