JP2004258516A

JP2004258516A - Zoom lens

Info

Publication number: JP2004258516A
Application number: JP2003051441A
Authority: JP
Inventors: Daisaku Arai; 大作荒井
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 2003-02-27
Filing date: 2003-02-27
Publication date: 2004-09-16

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens which scarcely causes the variation of a pupil and is suitable for the miniaturization in zooming. <P>SOLUTION: The zoom lens is provided with a first lens group G1 having a negative refractive force, a second lens group G2 having a positive refractive force, and a third lens group G3 having a positive refractive force in order from the object side. Therein, the first lens group, the second lens group, and the third lens group move respectively so that, in zooming from the wide angle state W to the telephoto end state T, the interval between the first lens group and the second lens group decreases and the interval between the second lens group and the third lens group increases. Further, a diaphragm S for adjusting light quantity is disposed on the object side of the second lens group and is singly moved to the object side in zooming from the wide angle state W to the telephoto end state T. The third lens group is moved in the zooming from the wide angle state W to the telephoto end state T, is located on the object side rather than the wide angle state W in the telephoto end state T, and satisfies prescribed conditions. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ズームレンズに関し、特に固体撮像素子等を用いたビデオカメラ、電子スチルカメラ等に好適なズームレンズに関する。
【０００２】
【従来の技術】
従来、固体撮像素子等に適した屈折力配置が負正正型の３群レンズ構成のズームレンズが提案されている（例えば、特許文献１、特許文献２、特許文献３、特許文献４参照。）。
【０００３】
上記３群構成のズームレンズは、ズームレンズのコンパクト化を図り、かつ収差補正を良好にするという観点から広く用いられている。
【０００４】
【特許文献１】
特開昭６３−２９２１０６号公報
【特許文献２】
特開平６−９４９９６号公報
【特許文献３】
特開２０００−２８４１７７号公報
【特許文献４】
特開２００１−２４２３７８号公報
【０００５】
【発明が解決しようとする課題】
近年急速に普及しつつあるデジタルカメラやビデオカメラにおいては、一般のカメラに用いるものと同様にレンズの小型化、高性能化が望まれる一方、固体撮像素子特有の条件を満足させる必要がある。
【０００６】
従来の固体撮像素子は、写真用フィルムとは異なり、撮影面に対して垂直に近い角度で光を入射させなければ効率よく受光することができない。したがって、固体撮像素子上に被写体像を結像させる光学系の条件として、撮影面上のどの位置でも主光線が垂直に入射するようでなければならない。つまり、撮影面からの射出瞳の位置を十分に遠くする必要があった。
【０００７】
しかしながら、近年の固体撮像素子は、撮影面の物体方向のある任意の位置に瞳があると、一番効率よく受光することができるようになっている。そのような固体撮像素子を使用する場合は、瞳の位置がズーミングによってほとんど変化しない構成がもっとも受光効率の面で有利であり、瞳の位置がズーミングによってほとんど変化しない構成のズームレンズが求められている。
【０００８】
本発明は上記課題に鑑みてなされたものであり、ズーミングに際して、瞳の位置の変動がほとんど無く、小型軽量化に適したズームレンズを提供する事を目的としている。
【０００９】
【課題を解決するための手段】
上記目的を達成するために、本発明は、物体側から順に、負の屈折力を持つ第１レンズ群と、正の屈折力を持つ第２レンズ群と、正の屈折力を持つ第３レンズ群とを有し、前記第１レンズ群は、前記物体側に凸面を向けた負メニスカスレンズと正レンズのみとから成り、前記第２レンズ群は、前記物体側より順に、第１正レンズと、正レンズと負レンズの接合レンズと、第２正レンズのみとから成り、前記第３レンズ群は、単一レンズ成分のみから成り、広角端状態から望遠端状態へのズーミングに際して、前記第１レンズ群と前記第２レンズ群との間隔が減少し、前記第２レンズ群と前記第３レンズ群との間隔が広がるように、前記第１レンズ群および前記第２レンズ群および前記第３レンズ群がそれぞれ移動し、前記第２レンズ群の前記物体側には光量を調節する開口絞りが配置され、広角端状態から望遠端状態へのズーミングに際して、物体側へ単独で移動し、前記第３レンズ群は、広角端状態から望遠端状態へのズーミングに際して移動し、望遠端状態で広角端状態より物体側に位置し、前記第１レンズ群の焦点距離をｆ１、前記第２レンズ群の焦点距離をｆ２、前記第３レンズ群の焦点距離をｆ３、全系の広角端状態での焦点距離をｆｗ、全系の望遠端状態での焦点距離をｆｔとしたとき、以下の条件式（１）、（２）を満足することを特徴とするズームレンズを提供する。
【００１０】
（１）｜ｆ１／ｆ２｜＜１．５
（２）０．２＜｜ｆ２／ｆ３｜＜０．７
また、本発明のズームレンズでは、以下の条件式（３）、（４）を満足することが望ましい。
【００１１】
（３）１．０＜ｆｔ／｜ｆ２｜＜２．０
（４）０．１＜ｆｗ／｜ｆ３｜＜０．４
また、本発明のズームレンズでは、前記第２レンズ群の最も物体側のレンズ面から、前記第３レンズ群の最も像面側のレンズ面までの距離を、広角端状態ではｄｗ、望遠端状態ではｄｔとしたとき、
（５）１．０＜（ｄｔ／ｄｗ）＜１．１５
の条件式（５）を満足することが望ましい。
【００１２】
また、本発明のズームレンズでは、前記第２レンズ群の正レンズと負レンズの前記接合レンズの焦点距離をＧｆ２としたとき、
（６）０．２＜｜ｆ２／Ｇｆ２｜＜０．６
の条件式（６）を満足することが望ましい。
【００１３】
また、本発明のズームレンズでは、前記第２レンズ群の最も像面側に位置するレンズの焦点距離をＲｆ２としたとき、
（７）０．２＜｜ｆ２／Ｒｆ２｜＜０．８
の条件式（７）を満足することが望ましい。
【００１４】
また、本発明のズームレンズでは、前記第３レンズ群の前記単一レンズ成分は、屈折率をｎ３としたとき、
（８）１．５５＜ｎ３＜１．６５
の条件式（８）を満足することが望ましい。
【００１５】
また、本発明のズームレンズでは、前記第１レンズ群の前記負メニスカスレンズは、少なくとも１面の非球面を持っていることが望ましい。
【００１６】
また、本発明のズームレンズでは、前記第２レンズ群は、少なくとも２面の非球面を持っていることが望ましい。
【００１７】
また、本発明のズームレンズでは、前記第３レンズ群の前記単一レンズ成分は、両凸形状の正レンズで構成されていることが望ましい。
【００１８】
また、本発明のズームレンズでは、前記第１レンズ群と前記第２レンズ群との間に、光量を調節する前記開口絞りが配置され、広角端状態から望遠端状態へのズーミングに際して、物体側へ単独で移動することが望ましい。
【００１９】
また、本発明のズームレンズでは、前記第１レンズ群を物体側に移動させることによってフォーカシングを行なうことが望ましい。
【００２０】
また、本発明のズームレンズでは、前記第３レンズ群を物体側に移動させることによってフォーカシングを行なうことが望ましい。
【００２１】
【発明の実施の形態】
以下、本発明の実施の形態について説明する。
【００２２】
本発明にかかるズームレンズは、物体側から順に、負の屈折力を持つ第１レンズ群と、正の屈折力を持つ第２レンズ群と、正の屈折力を持つ第３レンズ群とを有し、第１レンズ群は、物体側に凸面を向けた負メニスカスレンズと正レンズのみとから成り、第２レンズ群は、物体側より順に、第１正レンズと、正レンズと負レンズの接合レンズと、第２正レンズのみとから成り、第３レンズ群は、単一レンズ成分のみから成り、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、第１レンズ群と第２レンズ群との間隔が減少し、第２レンズ群と第３レンズ群との間隔が広がるように、第１レンズ群および第２レンズ群および第３レンズ群がそれぞれ移動し、第２レンズ群の前には光量を調節する開口絞りが配置され、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して物体側へ単独で移動し、第３レンズ群は、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して移動し、望遠端状態Ｔで広角端状態Ｗより物体側に位置するように構成されている。
【００２３】
第１レンズ群を物体側に凸面を向けた負メニスカスレンズと正レンズのみで構成し、第３レンズ群は単一レンズ成分のみから構成することにより、第１レンズ群と第３レンズ群の組立調整が極めて楽になり、低コスト化に効果的である。また、第２レンズ群は、前記物体側より順に、第１正レンズと、正レンズと負レンズの接合レンズと、第２正レンズのみとから構成することにより、球面収差、コマ収差および色収差を効果的かつ良好に補正できる。
【００２４】
以下、上述の各条件式について説明する。
【００２５】
条件式（１）は第１レンズ群と、第２レンズ群の屈折力を適切に配分するための条件式である。条件式（１）の上限値を上回ると、第２レンズ群の屈折力が過小となり、ズームレンズ全長が長くなってしまい好ましくない。
【００２６】
条件式（２）は第２レンズ群と、第３レンズ群の屈折力を適切に配分するための条件式である。条件式（２）の上限値を上回ると、第３レンズ群の屈折力が過大となり、第３レンズ群を１枚構成にすることが困難となり好ましくない。条件式（２）の下限値を下回ると、第３レンズ群の屈折力が過小となり、第３レンズ群によるフォーカシングの場合、フォーカシング移動量が大きくなり好ましくない。
【００２７】
条件式（３）は第２レンズ群の屈折力と、ズームレンズ全系の望遠端状態Ｔでの焦点距離の適切な範囲を指定している。条件式（３）の上限値を上回ると、第２レンズ群の屈折力が過大となり、球面収差の補正が困難となり好ましくない。条件式（３）の下限値を下回ると、第２レンズ群の屈折力が過小となり、ズームレンズ全長が長くなってしまい好ましくない。
【００２８】
条件式（４）は第３レンズ群の屈折力と、ズームレンズ全系の広角端状態Ｗでの焦点距離の適切な範囲を指定している。条件式（４）の上限値を上回ると、球面収差およびコマ収差の補正が困難となり好ましくない。また、瞳の変動が大きくなってしまうので好ましくない。条件式（４）の下限値を下回ると、第３レンズ群の中心厚が大きくなり好ましくない。
【００２９】
条件式（５）は第２レンズ群と第３レンズ群の距離の適切な範囲を指定している。条件式（５）の上限値を上回ると、望遠端状態Ｔでの第２レンズ群と第３レンズ群との間隔が過大となり、瞳位置の変動が大きくなり好ましくない。条件式（５）の下限値を下回ると、軸上の色収差が劣化し好ましくない。
【００３０】
条件式（６）は第２レンズ群と、第２レンズ群の正レンズと負レンズとの接合レンズの焦点距離の適切な範囲を指定している。条件式（６）の上限値を上回ると、球面収差が劣化し好ましくない。条件式（６）の下限値を下回ると、瞳位置の変動が大きくなり好ましくない。
【００３１】
条件式（７）は第２レンズ群の最も像面側に位置するレンズの焦点距離と第２レンズ群の焦点距離の適切な範囲を指定している。条件式（７）の上限値を上回ると、瞳位置の変動が大きくなり好ましくない。条件式（７）の下限値を下回ると、球面収差の補正が困難となり好ましくない。
【００３２】
条件式（８）は第３レンズ群の単一レンズ成分の、屈折率の適切な範囲を指定している。条件式（８）の上限値を上回ると、第３レンズ群の各曲率半径が小さくなり、レンズ中心厚が増加し大型化してしまうので好ましくない。条件式（８）の下限値を下回ると、コマ収差が悪化してしまうので好ましくない。
【００３３】
また、本発明の実施の形態にかかるズームレンズでは、第１レンズ群の負メニスカスレンズは、少なくとも１面の非球面を持っている。これにより、広角ズームにおいて問題になる歪曲収差を良好に補正できる。
【００３４】
また、本発明の実施形態に係るズームレンズでは、第２レンズ群は、少なくとも２面の非球面を持っている。これにより、ズーム全域において球面収差、コマ収差を良好に補正できる。
【００３５】
また、本発明の実施形態に係るズームレンズでは、第３レンズ群の単一レンズ成分は、両凸形状の正レンズを持っている。これによりフォーカシングの際に発生する収差変動を小さくすることが出来る。さらに、フォーカシング移動量を小さく出来、製造上好ましい。
【００３６】
また、本発明の実施形態に係るズームレンズでは、第１レンズ群と第２レンズ群との間に、光量を調節する開口絞りが配置され、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、物体側へ単独で移動する。これにより、瞳位置の変動がほとんど変化しないようにすることができる。
【００３７】
また、本発明の実施形態に係るズームレンズでは、第１レンズ群を物体側に移動させることによってフォーカシングを行なう。これにより、フォーカシングの際に発生する収差変動を小さくすることが出来る。または、第３レンズ群を物体側に移動させることによってフォーカシングを行なう。これにより、フォーカシングの際に発生する収差変動を小さくすることが出来る。この際、第１レンズ群がフォーカシングの際に移動しないので、フォーカシングの際にズームレンズ全長の変化がなく、マクロ撮影時などでの使い勝手を向上させることが出来る。
【００３８】
このように、本発明の実施の形態にかかるズームレンズによれば、固体撮像素子等を用いたビデオカメラ、および電子スチルカメラ等に好適なズームレンズ、特にズーム比が２．５倍以上で、小型、高画質なズームレンズが提供可能となる。
【００３９】
（実施例）
以下、本発明の各実施例に係るズームレンズについて図面を参照して説明する。
【００４０】
以下の各実施例において、本発明に係るズームレンズは、物体側から順に、負の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、正の屈折力を持つ第３レンズ群Ｇ３とを有し、第１レンズ群Ｇ１は、物体側に凸面を向けた負メニスカスレンズと正レンズのみとから成り、前記第２レンズ群Ｇ２は、前記物体側より順に、第１正レンズと、正レンズと負レンズとの接合レンズと、第２正レンズのみとから成り、第３レンズ群Ｇ３は、単一レンズ成分のみから成り、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、第１レンズ群Ｇ１と第２レンズ群Ｇ２との間隔が減少し、第２レンズ群Ｇ２と第３レンズ群Ｇ３との間隔が広がるように、第１レンズ群Ｇ１および第２レンズ群Ｇ２および第３レンズ群Ｇ３がそれぞれ移動し、第２レンズ群Ｇ２の前には光量を調節する開口絞りが配置され、広角端状態Ｗから望遠端状態Ｔへのズーミングに際し物体側へ単独で移動し、第３レンズ群Ｇ３は、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して移動し、望遠端状態Ｔで広角端状態Ｗより物体側に位置するように構成されている。
【００４１】
また、フォーカシングの際に、第１レンズ群Ｇ１、または第３レンズ群Ｇ３を移動させる。
【００４２】
なお、各実施例において、第１レンズ群Ｇ１から第３レンズ群Ｇ３の任意の面を回折面としてもよい。また、第１レンズ群Ｇ１から第３レンズ群Ｇ３の任意のレンズを屈折率分布型レンズ（ＧＲＩＮレンズ）あるいはプラスチックレンズとしてもよい。また、第１レンズ群Ｇ１から第３レンズ群Ｇ３のいずれかのレンズ群あるいはレンズ群の一部を光軸と直行方向または、ある１点を中心とした曲線状に移動させることによって、手ぶれ補正レンズとすることも可能である。
【００４３】
以下に示す表に本発明にかかる各実施例の諸元の値を示す。各表中において、［全体諸元］中、ｆは焦点距離、Ｂｆはバックフォーカス、ＦＮｏはＦナンバー、２ωは画角をそれぞれ表わしている。［レンズ諸元］中、面番号は物体側からのレンズ面の番号、ｒはレンズ面の曲率半径、ｄはレンズ面間隔、νはアッベ数、ｎはｄ線（λ＝５８７．５６ｎｍ）に対する屈折率をそれぞれ表わしており、空気の屈折率１．００００００は記載を省略している。さらに、［非球面データ］には、次式で非球面を表現した場合の非球面係数を示している。
【００４４】
【数１】
Ｘ（ｙ）＝ｙ^２／［ｒ×［１＋（１−ｋ×ｙ^２／ｒ^２）^１／２］］＋Ｃ４×ｙ^４＋Ｃ６ｙ^６＋Ｃ８ｙ^８＋Ｃ１０×ｙ^１０
ここで、Ｘ（ｙ）は非球面の頂点における接平面から高さｙにおける非球面上の位置までの光軸方向に沿った距離、ｒは基準球面の曲率半径（近軸曲率半径）、Ｋは円錐定数、Ｃｉは第ｉ次の非球面係数をそれぞれ示している。また、［ズーミングデータ］には、広角端状態Ｗ、中間焦点距離状態、望遠端状態Ｔの各状態における焦点距離、可変間隔の値を示す。
【００４５】
なお、以下の全ての諸元の値において、掲載されている焦点距離ｆ、曲率半径ｒ、面間隔ｄその他の長さ等は、特記の無い場合一般に「ｍｍ」が使われるが、光学系は比例拡大または比例縮小しても同等の光学性能が得られるので、これに限られるものではない。また、単位は「ｍｍ」に限定されること無く他の適当な単位を用いることもできる。さらに、これらの記号の説明は、以降の他の実施例においても同様とする。
【００４６】
（第１実施例）
図１は、本発明の第１実施例にかかるズームレンズのレンズ構成を示す図である。
【００４７】
図１において、物体側から順に、負の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、正の屈折力を持つ第３レンズ群Ｇ３とを有し、第１レンズ群Ｇ１は、物体側に凸面を向けた負メニスカスレンズＬ１１と正レンズＬ１２のみとから成り、第２レンズ群Ｇ２は、物体側より順に、第１正レンズＬ２１と、正レンズＬ２２と負レンズＬ２３との接合レンズと、第２正レンズＬ２４のみとから成り、第３レンズ群Ｇ３は、単一レンズ成分Ｌ３１のみから成り、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、第１レンズ群Ｇ１と第２レンズ群Ｇ２との間隔が減少し、第２レンズ群Ｇ２と第３レンズ群Ｇ３との間隔が広がるように、第１レンズ群Ｇ１および第２レンズ群Ｇ２および第３レンズ群Ｇ３がそれぞれ移動し、第２レンズ群Ｇ２の前には光量を調節する開口絞りＳが配置され、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、物体側へ単独で移動し、第３レンズ群Ｇ３は、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して移動し、望遠端状態Ｔで広角端状態Ｗより物体側に位置するように構成されている。また、フォーカシングの際に、第１レンズ群Ｇ１、または第３レンズ群Ｇ３を移動させている。
【００４８】
また、本第１実施例および以下のすべての実施例において、第３レンズ群Ｇ３と像面Ｉとの間には、像面Ｉに配置された固体撮像素子の限界解像度以上の空間周波数をカットするためのフィルタすなわちローパスフィルタＰ１と、固体撮像素子を保護するカバーガラスＰ２とを有している。
【００４９】
次の表１に本第１実施例にかかるズームレンズの諸元の値を示す。
【００５０】
【表１】

図２は、本第１実施例にかかるズームレンズの無限遠撮影状態での諸収差図を示し、（ａ）は広角端状態の無限遠撮影状態での諸収差図を、（ｂ）は中間焦点距離状態の無限遠撮影状態での諸収差図を、（ｃ）は望遠端状態の無限遠撮影状態での諸収差図をそれぞれ示す。
【００５１】
各収差図において、ＦＮＯはＦナンバー、Ｙは像高、ｄはｄ線（λ＝５８７．６ｎｍ）及びｇはｇ線（λ＝４３５．６ｎｍ）、ＣはＣ線（λ＝６５６．３ｎｍ）、ＦはＦ線（λ＝４８６．１ｎｍ）を示す。球面収差図では最大口径に対応するＦナンバーの値を示し、非点収差図、歪曲収差図では像高の最大値をそれぞれ示し、コマ収差図では各像高の値を示す。非点収差図において、実線はサジタル像面を、破線はメリジオナル像面をそれぞれ示す。以下のすべての収差図において同様の符号を用い説明を省略する。
【００５２】
各収差図から、本第１実施例にかかるズームレンズは、諸収差が良好に補正され、優れた結像性能を有していることが明らかである。
【００５３】
（第２実施例）
図３は、本発明の第２実施例にかかるズームレンズのレンズ構成を示す図である。
【００５４】
図３において、物体側から順に、負の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、正の屈折力を持つ第３レンズ群Ｇ３とを有し、第１レンズ群Ｇ１は、物体側に凸面を向けた負メニスカスレンズＬ１１と正レンズＬ１２のみとから成り、第２レンズ群Ｇ２は、物体側より順に、第１正レンズＬ２１と、正レンズＬ２２と負レンズＬ２３との接合レンズと、第２正レンズＬ２４のみとから成り、第３レンズ群Ｇ３は、単一レンズ成分Ｌ３１のみから成り、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、第１レンズ群Ｇ１と第２レンズ群Ｇ２との間隔が減少し、第２レンズ群Ｇ２と第３レンズ群Ｇ３との間隔が広がるように、第１レンズ群Ｇ１および第２レンズ群Ｇ２および第３レンズ群Ｇ３がそれぞれ移動し、第２レンズ群Ｇ２の前には光量を調節する開口絞りＳが配置され、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、物体側へ単独で移動し、第３レンズ群Ｇ３は、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して移動し、望遠端状態Ｔで広角端状態Ｗより物体側に位置するように構成されている。また、フォーカシングの際に、第１レンズ群Ｇ１、または第３レンズ群Ｇ３を移動させている。
【００５５】
次の表２に本第２実施例にかかるズームレンズの諸元の値を示す。
【００５６】
【表２】

図４は、本第２実施例にかかるズームレンズの無限遠撮影状態での諸収差図を示し、（ａ）は広角端状態の無限遠撮影状態での諸収差図を、（ｂ）は中間焦点距離状態の無限遠撮影状態での諸収差図を、（ｃ）は望遠端状態の無限遠撮影状態での諸収差図をそれぞれ示す。
【００５７】
各収差図から、本第２実施例にかかるズームレンズは、諸収差が良好に補正され、優れた結像性能を有していることが明らかである。
【００５８】
（第３実施例）
図５は、本発明の第３実施例にかかるズームレンズのレンズ構成を示す図である。
【００５９】
図５において、物体側から順に、負の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、正の屈折力を持つ第３レンズ群Ｇ３とを有し、第１レンズ群Ｇ１は、物体側に凸面を向けた負メニスカスレンズＬ１１と正レンズＬ１２のみとから成り、第２レンズ群Ｇ２は、物体側より順に、第１正レンズＬ２１と、正レンズＬ２２と負レンズＬ２３との接合レンズと、第２正レンズＬ２４のみとから成り、第３レンズ群Ｇ３は、単一レンズ成分Ｌ３１のみから成り、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、第１レンズ群Ｇ１と第２レンズ群Ｇ２との間隔が減少し、第２レンズ群Ｇ２と第３レンズ群Ｇ３との間隔が広がるように、第１レンズ群Ｇ１および第２レンズ群Ｇ２および第３レンズ群Ｇ３がそれぞれ移動し、第２レンズ群Ｇ２の前には光量を調節する開口絞りＳが配置され、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、物体側へ単独で移動し、第３レンズ群Ｇ３は、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して移動し、望遠端状態Ｔで広角端状態Ｗより物体側に位置するように構成されている。また、フォーカシングの際に、第１レンズ群Ｇ１、または第３レンズ群Ｇ３を移動させている。
【００６０】
次の表３に第３実施例にかかるズームレンズの諸元の値を示す。
【００６１】
【表３】

図６は、本第３実施例にかかるズームレンズの無限遠撮影状態での諸収差図を示し、（ａ）は広角端状態の無限遠撮影状態での諸収差図を、（ｂ）は中間焦点距離状態の無限遠撮影状態での諸収差図を、（ｃ）は望遠端状態の無限遠撮影状態での諸収差図をそれぞれ示す。
【００６２】
各収差図から、本第３実施例にかかるズームレンズは、諸収差が良好に補正され、優れた結像性能を有していることが明らかである。
【００６３】
（第４実施例）
図７は、本発明の第４実施例にかかるズームレンズのレンズ構成を示す図である。
【００６４】
図７において、物体側から順に、負の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、正の屈折力を持つ第３レンズ群Ｇ３とを有し、第１レンズ群Ｇ１は、物体側に凸面を向けた負メニスカスレンズＬ１１と正レンズＬ１２のみとから成り、第２レンズ群Ｇ２は、物体側より順に、第１正レンズＬ２１と、正レンズＬ２２と負レンズＬ２３との接合レンズと、第２正レンズＬ２４のみとから成り、第３レンズ群Ｇ３は、単一レンズ成分Ｌ３１のみから成り、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、第１レンズ群Ｇ１と第２レンズ群Ｇ２との間隔が減少し、第２レンズ群Ｇ２と第３レンズ群Ｇ３との間隔が広がるように、第１レンズ群Ｇ１および第２レンズ群Ｇ２および第３レンズ群Ｇ３がそれぞれ移動し、第２レンズ群Ｇ２の前には光量を調節する開口絞りＳが配置され、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して、物体側へ単独で移動し、第３レンズ群Ｇ３は、広角端状態Ｗから望遠端状態Ｔへのズーミングに際して移動し、望遠端状態Ｔで広角端状態Ｗより物体側に位置するように構成されている。また、フォーカシングの際に、第１レンズ群Ｇ１、または第３レンズ群Ｇ３を移動させている。
【００６５】
次の表４に第４実施例にかかるズームレンズの諸元の値を示す。
【００６６】
【表４】

図８は、本第４実施例にかかるズームレンズの無限遠撮影状態での諸収差図を示し、（ａ）は広角端状態の無限遠撮影状態での諸収差図を、（ｂ）は中間焦点距離状態の無限遠撮影状態での諸収差図を、（ｃ）は望遠端状態の無限遠撮影状態での諸収差図をそれぞれ示す。
【００６７】
各収差図から、本第第４実施例にかかるズームレンズは、諸収差が良好に補正され、優れた結像性能を有していることが明らかである。
【００６８】
【発明の効果】
以上説明したように、本発明によれば、ズーミングに際して、瞳の変動がほとんど無く、小型軽量化に適したズームレンズを提供することができる。
【図面の簡単な説明】
【図１】本発明の第１実施例にかかるズームレンズのレンズ構成を示す図である。
【図２】第１実施例にかかるズームレンズの無限遠撮影状態での諸収差図を示し、（ａ）は広角端状態の無限遠撮影状態での諸収差図を、（ｂ）は中間焦点距離状態の無限遠撮影状態での諸収差図を、（ｃ）は望遠端状態の無限遠撮影状態での諸収差図をそれぞれ示す。
【図３】本発明の第２実施例にかかるズームレンズのレンズ構成を示す図である。
【図４】第２実施例にかかるズームレンズの無限遠撮影状態での諸収差図を示し、（ａ）は広角端状態の無限遠撮影状態での諸収差図を、（ｂ）は中間焦点距離状態の無限遠撮影状態での諸収差図を、（ｃ）は望遠端状態の無限遠撮影状態での諸収差図をそれぞれ示す。
【図５】本発明の第３実施例にかかるズームレンズのレンズ構成を示す図である。
【図６】第３実施例にかかるズームレンズの無限遠撮影状態での諸収差図を示し、（ａ）は広角端状態の無限遠撮影状態での諸収差図を、（ｂ）は中間焦点距離状態の無限遠撮影状態での諸収差図を、（ｃ）は望遠端状態の無限遠撮影状態での諸収差図をそれぞれ示す。
【図７】本発明の第４実施例にかかるズームレンズのレンズ構成を示す図である。
【図８】第４実施例にかかるズームレンズの無限遠撮影状態での諸収差図を示し、（ａ）は広角端状態の無限遠撮影状態での諸収差図を、（ｂ）は中間焦点距離状態の無限遠撮影状態での諸収差図を、（ｃ）は望遠端状態の無限遠撮影状態での諸収差図をそれぞれ示す。
【符号の説明】
Ｇ１第１レンズ群
Ｇ２第２レンズ群
Ｇ３第３レンズ群
Ｓ開口絞り
Ｐ１ローパスフィルタ
Ｐ２カバーガラス
Ｉ像面
Ｗ広角端状態
Ｔ望遠端状態[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a zoom lens, and more particularly to a zoom lens suitable for a video camera, an electronic still camera, and the like using a solid-state imaging device or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a zoom lens having a three-group lens configuration having a negative, positive, and positive refractive power arrangement suitable for a solid-state imaging device or the like has been proposed (for example, see Patent Literature 1, Patent Literature 2, Patent Literature 3, and Patent Literature 4). ).
[0003]
The three-group zoom lens is widely used from the viewpoint of achieving a compact zoom lens and improving aberration correction.
[0004]
[Patent Document 1]
JP-A-63-292106 [Patent Document 2]
JP-A-6-94996 [Patent Document 3]
JP 2000-284177 A [Patent Document 4]
JP 2001-242378 A [0005]
[Problems to be solved by the invention]
In digital cameras and video cameras, which have been rapidly spreading in recent years, it is necessary to reduce the size and performance of lenses as in general cameras, but it is necessary to satisfy the conditions specific to solid-state imaging devices.
[0006]
Unlike a photographic film, a conventional solid-state imaging device cannot efficiently receive light unless light is incident on the imaging surface at an angle close to perpendicular. Therefore, as a condition of an optical system for forming a subject image on a solid-state imaging device, it is necessary that a chief ray is perpendicularly incident at any position on an imaging surface. That is, it is necessary to make the position of the exit pupil from the imaging plane sufficiently far.
[0007]
However, recent solid-state imaging devices can receive light most efficiently when the pupil is located at an arbitrary position in the object direction on the imaging surface. When such a solid-state imaging device is used, a configuration in which the position of the pupil hardly changes due to zooming is the most advantageous in terms of light receiving efficiency, and a zoom lens in which the position of the pupil hardly changes due to zooming is required. I have.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a zoom lens suitable for reduction in size and weight with little change in the position of a pupil during zooming.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens having a positive refractive power. The first lens group includes only a negative meniscus lens having a convex surface facing the object side and a positive lens, and the second lens group includes a first positive lens and a first positive lens in order from the object side. The third lens group includes only a single lens component, and includes the first lens when zooming from the wide-angle end state to the telephoto end state. The first lens group, the second lens group, and the third lens such that the distance between the lens group and the second lens group decreases and the distance between the second lens group and the third lens group increases. The groups move respectively, and the second lens group An aperture stop for adjusting the amount of light is disposed on the body side, and moves independently to the object side during zooming from the wide-angle end state to the telephoto end state, and the third lens group zooms from the wide-angle end state to the telephoto end state. In the telephoto end state, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the focal length of the third lens group is f3. Where fw is the focal length of the entire system at the wide-angle end state and ft is the focal length of the entire system at the telephoto end state, the following conditional expressions (1) and (2) are satisfied. Provide a lens.
[0010]
(1) | f1 / f2 | <1.5
(2) 0.2 <| f2 / f3 | <0.7
In the zoom lens according to the present invention, it is preferable that the following conditional expressions (3) and (4) are satisfied.
[0011]
(3) 1.0 <ft / | f2 | <2.0
(4) 0.1 <fw / | f3 | <0.4
In the zoom lens of the present invention, the distance from the most object side lens surface of the second lens group to the most image side lens surface of the third lens group is dw in the wide-angle end state and the telephoto end state. Then, when dt,
(5) 1.0 <(dt / dw) <1.15
It is desirable to satisfy the conditional expression (5).
[0012]
In the zoom lens of the present invention, when the focal length of the cemented lens of the positive lens and the negative lens of the second lens group is Gf2,
(6) 0.2 <| f2 / Gf2 | <0.6
It is desirable to satisfy the conditional expression (6).
[0013]
In the zoom lens of the present invention, when the focal length of the lens located closest to the image plane in the second lens group is Rf2,
(7) 0.2 <| f2 / Rf2 | <0.8
It is desirable to satisfy the conditional expression (7).
[0014]
In the zoom lens of the present invention, the single lens component of the third lens group has a refractive index of n3.
(8) 1.55 <n3 <1.65
It is desirable to satisfy the conditional expression (8).
[0015]
In the zoom lens according to the present invention, it is preferable that the negative meniscus lens of the first lens group has at least one aspheric surface.
[0016]
In the zoom lens according to the present invention, it is desirable that the second lens group has at least two aspheric surfaces.
[0017]
In the zoom lens according to the aspect of the invention, it is preferable that the single lens component of the third lens group is a biconvex positive lens.
[0018]
In the zoom lens of the present invention, the aperture stop for adjusting the light amount is disposed between the first lens group and the second lens group, and when zooming from the wide-angle end state to the telephoto end state, It is desirable to move alone to
[0019]
In the zoom lens according to the present invention, it is preferable that focusing is performed by moving the first lens group to the object side.
[0020]
In the zoom lens according to the present invention, it is preferable that focusing is performed by moving the third lens group to the object side.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0022]
The zoom lens according to the present invention includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. The first lens group includes only a negative meniscus lens having a convex surface facing the object side and a positive lens, and the second lens group includes, in order from the object side, a first positive lens, and a cemented positive and negative lens. The third lens group includes only a single lens component, and includes a first lens group and a second lens group when zooming from the wide-angle end state W to the telephoto end state T. The first lens group, the second lens group, and the third lens group move so that the distance between the first lens group and the second lens group increases, and the distance between the second lens group and the third lens group increases. An aperture stop for adjusting the amount of light is provided. The third lens group moves alone during zooming from the wide-angle end state W to the telephoto end state T during zooming to the end state T, and moves toward the object side from the wide-angle end state W in the telephoto end state T. It is configured to be located.
[0023]
By assembling the first and third lens groups, the first lens group includes only a negative meniscus lens having a convex surface facing the object side and a positive lens, and the third lens group includes only a single lens component. Adjustment becomes extremely easy, which is effective for cost reduction. The second lens group includes, in order from the object side, a first positive lens, a cemented lens of a positive lens and a negative lens, and only the second positive lens, so that spherical aberration, coma, and chromatic aberration are reduced. Effective and good correction can be made.
[0024]
Hereinafter, the above-described conditional expressions will be described.
[0025]
Conditional expression (1) is a conditional expression for appropriately distributing the refractive power of the first lens group and the second lens group. If the upper limit of conditional expression (1) is exceeded, the refractive power of the second lens group will be too small, and the overall length of the zoom lens will be undesirably long.
[0026]
Conditional expression (2) is a conditional expression for appropriately distributing the refractive power of the second lens unit and the third lens unit. When the value exceeds the upper limit of conditional expression (2), the refractive power of the third lens unit becomes excessively large, and it is difficult to form a single third lens unit. If the lower limit of conditional expression (2) is not reached, the refractive power of the third lens group will be too small, and in the case of focusing by the third lens group, the amount of focusing movement will be undesirably large.
[0027]
Conditional expression (3) specifies an appropriate range of the refracting power of the second lens group and the focal length in the telephoto end state T of the entire zoom lens system. When the value exceeds the upper limit of conditional expression (3), the refractive power of the second lens unit becomes excessively large, and it becomes difficult to correct spherical aberration. If the lower limit of conditional expression (3) is not reached, the refractive power of the second lens unit becomes too small, and the overall length of the zoom lens becomes undesirably long.
[0028]
Conditional expression (4) specifies an appropriate range of the refracting power of the third lens group and the focal length in the wide-angle end state W of the entire zoom lens system. When the value exceeds the upper limit of conditional expression (4), it becomes difficult to correct spherical aberration and coma, which is not preferable. In addition, the fluctuation of the pupil increases, which is not preferable. If the lower limit value of the conditional expression (4) is not reached, the center thickness of the third lens unit becomes undesirably large.
[0029]
Conditional expression (5) specifies an appropriate range of the distance between the second lens unit and the third lens unit. When the value exceeds the upper limit of conditional expression (5), the distance between the second lens unit and the third lens unit in the telephoto end state T becomes excessively large, and the fluctuation of the pupil position becomes undesirably large. When the value goes below the lower limit of conditional expression (5), axial chromatic aberration is undesirably deteriorated.
[0030]
Conditional expression (6) specifies an appropriate range of the focal length of the second lens group and the cemented lens of the positive lens and the negative lens of the second lens group. If the value exceeds the upper limit of conditional expression (6), spherical aberration is undesirably deteriorated. If the value goes below the lower limit of conditional expression (6), the fluctuation of the pupil position becomes undesirably large.
[0031]
Conditional expression (7) specifies an appropriate range of the focal length of the lens located closest to the image plane side of the second lens group and the focal length of the second lens group. Exceeding the upper limit of conditional expression (7) is not preferable because the pupil position greatly varies. When the value goes below the lower limit of conditional expression (7), it becomes difficult to correct spherical aberration.
[0032]
Conditional expression (8) specifies an appropriate range of the refractive index of the single lens component of the third lens group. If the upper limit of conditional expression (8) is exceeded, the radius of curvature of the third lens group will be small, and the thickness of the center of the lens will increase, which is not preferable. When the value goes below the lower limit of conditional expression (8), coma becomes worse.
[0033]
In the zoom lens according to the embodiment of the present invention, the negative meniscus lens in the first lens group has at least one aspheric surface. This makes it possible to satisfactorily correct distortion that becomes a problem in wide-angle zoom.
[0034]
In the zoom lens according to the embodiment of the present invention, the second lens group has at least two aspheric surfaces. Thus, spherical aberration and coma can be favorably corrected over the entire zoom range.
[0035]
In the zoom lens according to the embodiment of the present invention, the single lens component of the third lens group has a biconvex positive lens. As a result, it is possible to reduce the fluctuation of aberration that occurs during focusing. Further, the focusing movement amount can be reduced, which is preferable in manufacturing.
[0036]
Further, in the zoom lens according to the embodiment of the present invention, an aperture stop for adjusting the amount of light is disposed between the first lens group and the second lens group, and when zooming from the wide-angle end state W to the telephoto end state T, Move to the object side alone. As a result, it is possible to make the fluctuation of the pupil position hardly change.
[0037]
In the zoom lens according to the embodiment of the present invention, focusing is performed by moving the first lens group to the object side. As a result, it is possible to reduce the variation in aberrations that occurs during focusing. Alternatively, focusing is performed by moving the third lens group to the object side. As a result, it is possible to reduce the variation in aberrations that occurs during focusing. At this time, since the first lens group does not move during focusing, there is no change in the overall length of the zoom lens during focusing, and the usability during macro shooting or the like can be improved.
[0038]
Thus, according to the zoom lens according to the embodiment of the present invention, a video camera using a solid-state imaging device or the like, and a zoom lens suitable for an electronic still camera or the like, particularly, a zoom ratio of 2.5 times or more, A small, high-quality zoom lens can be provided.
[0039]
(Example)
Hereinafter, a zoom lens according to each embodiment of the present invention will be described with reference to the drawings.
[0040]
In each of the following embodiments, the zoom lens according to the present invention includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. The first lens group G1 includes only a negative meniscus lens having a convex surface facing the object side and a positive lens, and the second lens group G2 is sequentially arranged from the object side. , The first positive lens, a cemented lens of a positive lens and a negative lens, and only the second positive lens, and the third lens group G3 includes only a single lens component, and is shifted from the wide-angle end state W to the telephoto end state. During zooming to T, the first lens group G1 and the second lens group G1 are arranged such that the distance between the first lens group G1 and the second lens group G2 decreases and the distance between the second lens group G2 and the third lens group G3 increases. The second lens group G2 and the third lens group G3 An aperture stop for adjusting the amount of light is disposed in front of the second lens group G2, and moves independently to the object side during zooming from the wide-angle end state W to the telephoto end state T. The third lens group G3 The zoom lens moves during zooming from the wide-angle end state W to the telephoto end state T, and is positioned closer to the object side than the wide-angle end state W in the telephoto end state T.
[0041]
During focusing, the first lens group G1 or the third lens group G3 is moved.
[0042]
In each embodiment, any surface of the first lens group G1 to the third lens group G3 may be a diffraction surface. Further, any lens of the first lens group G1 to the third lens group G3 may be a gradient index lens (GRIN lens) or a plastic lens. In addition, camera shake correction is performed by moving any one of the first lens group G1 to the third lens group G3 or a part of the lens group in a direction perpendicular to the optical axis or in a curved shape centered on a certain point. It is also possible to use a lens.
[0043]
The table below shows the values of the specifications of each embodiment according to the present invention. In each table, in [overall specifications], f represents a focal length, Bf represents a back focus, FNo represents an F number, and 2ω represents an angle of view. In [lens specifications], the surface number is the number of the lens surface from the object side, r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, ν is the Abbe number, and n is the d line (λ = 587.56 nm). The refractive indices are respectively shown, and the refractive index of air, which is 1.00000, is omitted. Further, [Aspherical surface data] shows an aspherical surface coefficient when an aspherical surface is expressed by the following equation.
[0044]
(Equation 1)
^{X (y) = y 2 /} [r × [1+ (1-k × y 2 / r 2) 1/2]] + C4 × y 4 + C6y 6 + C8y 8 + C10 × y 10
Here, X (y) is the distance along the optical axis direction from the tangent plane at the vertex of the aspheric surface to a position on the aspheric surface at height y, r is the radius of curvature (paraxial radius of curvature) of the reference spherical surface, and K Denotes a conical constant, and Ci denotes an i-th order aspheric coefficient. The [zooming data] indicates the values of the focal length and the variable interval in each of the wide-angle end state W, the intermediate focal length state, and the telephoto end state T.
[0045]
In addition, in all the values of the following specifications, "mm" is generally used for the focal length f, the radius of curvature r, the surface distance d, and other lengths unless otherwise specified. The same optical performance can be obtained even if the magnification is proportionally enlarged or reduced, and the present invention is not limited to this. Further, the unit is not limited to “mm”, and another appropriate unit can be used. Further, the description of these symbols is the same in other embodiments described below.
[0046]
(First embodiment)
FIG. 1 is a diagram illustrating a lens configuration of a zoom lens according to a first example of the present invention.
[0047]
In FIG. 1, in order from the object side, there are a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The first lens group G1 includes only a negative meniscus lens L11 and a positive lens L12 with the convex surface facing the object side, and the second lens group G2 includes a first positive lens L21 and a positive lens L22 in order from the object side. The third lens group G3 comprises solely a single lens component L31, and comprises a single lens component L31, which is used for zooming from the wide-angle end state W to the telephoto end state T. The first lens group G1, the second lens group G2, and the second lens group G2 are arranged such that the distance between the first lens group G1 and the second lens group G2 decreases and the distance between the second lens group G2 and the third lens group G3 increases. Each of the three lens groups G3 An aperture stop S for adjusting the amount of light is disposed in front of the second lens group G2, moves independently to the object side during zooming from the wide-angle end state W to the telephoto end state T, and moves to the third lens group G3. Is configured to move during zooming from the wide-angle end state W to the telephoto end state T, and to be located closer to the object side than the wide-angle end state W in the telephoto end state T. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0048]
In the first embodiment and all the following embodiments, a spatial frequency equal to or higher than the limit resolution of the solid-state imaging device arranged on the image plane I is cut between the third lens group G3 and the image plane I. , A low-pass filter P1 and a cover glass P2 for protecting the solid-state imaging device.
[0049]
Table 1 below shows data values of the zoom lens according to the first example.
[0050]
[Table 1]

2A and 2B show various aberration diagrams of the zoom lens according to the first example in an infinity shooting state, FIG. 2A shows various aberration diagrams in an infinity shooting state at a wide-angle end state, and FIG. FIGS. 7A and 7B show various aberration diagrams in an infinity shooting state in a focal length state, and FIG. 7C shows various aberration diagrams in an infinity shooting state in a telephoto end state.
[0051]
In each aberration diagram, FNO is the F number, Y is the image height, d is the d line (λ = 587.6 nm) and g is the g line (λ = 435.6 nm), C is the C line (λ = 656.3 nm). , F indicate the F line (λ = 486.1 nm). The spherical aberration diagram shows the value of the F-number corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum value of the image height, and the coma diagram shows the value of each image height. In the astigmatism diagram, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. The same reference numerals are used in all the following aberration diagrams, and the description is omitted.
[0052]
From the aberration diagrams, it is clear that the zoom lens according to the first example has excellent aberrations corrected for various aberrations and has excellent imaging performance.
[0053]
(Second embodiment)
FIG. 3 is a diagram illustrating a lens configuration of a zoom lens according to a second example of the present invention.
[0054]
3, in order from the object side, there are a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The first lens group G1 includes only a negative meniscus lens L11 and a positive lens L12 with the convex surface facing the object side, and the second lens group G2 includes a first positive lens L21 and a positive lens L22 in order from the object side. The third lens group G3 comprises solely a single lens component L31, and comprises a single lens component L31, which is used for zooming from the wide-angle end state W to the telephoto end state T. The first lens group G1, the second lens group G2, and the second lens group G2 are arranged such that the distance between the first lens group G1 and the second lens group G2 decreases and the distance between the second lens group G2 and the third lens group G3 increases. Each of the three lens groups G3 An aperture stop S for adjusting the amount of light is disposed in front of the second lens group G2, moves independently to the object side during zooming from the wide-angle end state W to the telephoto end state T, and moves to the third lens group G3. Is configured to move during zooming from the wide-angle end state W to the telephoto end state T, and to be located closer to the object side than the wide-angle end state W in the telephoto end state T. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0055]
Table 2 below shows data values of the zoom lens according to the second example.
[0056]
[Table 2]

4A and 4B are diagrams illustrating various aberrations of the zoom lens according to the second example in an infinity shooting state, FIG. 4A is a diagram illustrating various aberrations in a wide-angle end state in infinity shooting, and FIG. FIGS. 7A and 7B show various aberration diagrams in an infinity shooting state in a focal length state, and FIG. 7C shows various aberration diagrams in an infinity shooting state in a telephoto end state.
[0057]
From the aberration diagrams, it is clear that the zoom lens according to the second example has excellent correction of various aberrations and excellent imaging performance.
[0058]
(Third embodiment)
FIG. 5 is a diagram illustrating a lens configuration of a zoom lens according to a third example of the present invention.
[0059]
In FIG. 5, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power are provided. The first lens group G1 includes only a negative meniscus lens L11 and a positive lens L12 with the convex surface facing the object side, and the second lens group G2 includes a first positive lens L21 and a positive lens L22 in order from the object side. The third lens group G3 comprises solely a single lens component L31, and comprises a single lens component L31, which is used for zooming from the wide-angle end state W to the telephoto end state T. The first lens group G1, the second lens group G2, and the second lens group G2 are arranged such that the distance between the first lens group G1 and the second lens group G2 decreases and the distance between the second lens group G2 and the third lens group G3 increases. Each of the three lens groups G3 An aperture stop S for adjusting the amount of light is disposed in front of the second lens group G2, moves independently to the object side during zooming from the wide-angle end state W to the telephoto end state T, and moves to the third lens group G3. Is configured to move during zooming from the wide-angle end state W to the telephoto end state T, and to be located closer to the object side than the wide-angle end state W in the telephoto end state T. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0060]
Table 3 below shows values of specifications of the zoom lens according to the third example.
[0061]
[Table 3]

6A and 6B show various aberration diagrams of the zoom lens according to the third example in an infinity shooting state. FIG. 6A shows various aberration diagrams in an infinity shooting state in a wide-angle end state, and FIG. FIGS. 7A and 7B show various aberration diagrams in an infinity shooting state in a focal length state, and FIG. 7C shows various aberration diagrams in an infinity shooting state in a telephoto end state.
[0062]
From each aberration diagram, it is clear that the zoom lens according to the third example has excellent correction of various aberrations and excellent imaging performance.
[0063]
(Fourth embodiment)
FIG. 7 is a diagram illustrating a lens configuration of a zoom lens according to Example 4 of the present invention.
[0064]
In FIG. 7, in order from the object side, there are a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The first lens group G1 includes only a negative meniscus lens L11 and a positive lens L12 with the convex surface facing the object side, and the second lens group G2 includes a first positive lens L21 and a positive lens L22 in order from the object side. The third lens group G3 comprises solely a single lens component L31, and comprises a single lens component L31, which is used for zooming from the wide-angle end state W to the telephoto end state T. The first lens group G1, the second lens group G2, and the second lens group G2 are arranged such that the distance between the first lens group G1 and the second lens group G2 decreases and the distance between the second lens group G2 and the third lens group G3 increases. Each of the three lens groups G3 An aperture stop S for adjusting the amount of light is disposed in front of the second lens group G2, moves independently to the object side during zooming from the wide-angle end state W to the telephoto end state T, and moves to the third lens group G3. Is configured to move during zooming from the wide-angle end state W to the telephoto end state T, and to be located closer to the object side than the wide-angle end state W in the telephoto end state T. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0065]
Table 4 below shows values of specifications of the zoom lens according to the fourth example.
[0066]
[Table 4]

8A and 8B show various aberration diagrams of the zoom lens according to the fourth example in infinity shooting, in which FIG. 8A shows various aberrations in infinity shooting at the wide-angle end state, and FIG. FIGS. 7A and 7B show various aberration diagrams in an infinity shooting state in a focal length state, and FIG. 7C shows various aberration diagrams in an infinity shooting state in a telephoto end state.
[0067]
From the aberration diagrams, it is apparent that the zoom lens according to the fourth example has excellent correction of various aberrations and excellent imaging performance.
[0068]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a zoom lens suitable for reduction in size and weight with little pupil change during zooming.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a lens configuration of a zoom lens according to a first example of the present invention.
FIGS. 2A and 2B are diagrams illustrating various aberrations of the zoom lens according to the first example in an infinity shooting state, in which FIG. 2A illustrates various aberration diagrams in an infinity shooting state at a wide-angle end state, and FIG. 7A and 7B show various aberration diagrams in an infinity shooting state in a distance state, and FIG. 7C shows various aberration diagrams in an infinity shooting state in a telephoto end state.
FIG. 3 is a diagram illustrating a lens configuration of a zoom lens according to a second example of the present invention.
4A and 4B are diagrams illustrating various aberrations of the zoom lens according to the second example in an infinity shooting state, in which FIG. 4A illustrates various aberration diagrams in a wide-angle end state in infinity shooting, and FIG. 7A and 7B show various aberration diagrams in an infinity shooting state in a distance state, and FIG. 7C shows various aberration diagrams in an infinity shooting state in a telephoto end state.
FIG. 5 is a diagram showing a lens configuration of a zoom lens according to a third example of the present invention.
FIGS. 6A and 6B are diagrams illustrating various aberrations of the zoom lens according to the third example in an infinity shooting state, in which FIG. 6A illustrates various aberration diagrams in an infinity shooting state at a wide-angle end state, and FIG. 7A and 7B show various aberration diagrams in an infinity shooting state in a distance state, and FIG. 7C shows various aberration diagrams in an infinity shooting state in a telephoto end state.
FIG. 7 is a diagram illustrating a lens configuration of a zoom lens according to Example 4 of the present invention.
8A and 8B are diagrams illustrating various aberrations of the zoom lens according to the fourth example in an infinity shooting state, in which FIG. 8A illustrates various aberration diagrams in a wide angle end state in infinity shooting, and FIG. 7A and 7B show various aberration diagrams in an infinity shooting state in a distance state, and FIG. 7C shows various aberration diagrams in an infinity shooting state in a telephoto end state.
[Explanation of symbols]
G1 first lens group G2 second lens group G3 third lens group S aperture stop P1 low-pass filter P2 cover glass I image plane W wide-angle end state T telephoto end state

Claims

A first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, in order from the object side,
The first lens group includes only a negative meniscus lens having a convex surface facing the object side and a positive lens,
The second lens group includes, in order from the object side, a first positive lens, a cemented lens of a positive lens and a negative lens, and only a second positive lens.
The third lens group includes only a single lens component,
During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group is reduced, and the distance between the second lens group and the third lens group is increased. The first lens group, the second lens group, and the third lens group move,
An aperture stop for adjusting the amount of light is arranged on the object side of the second lens group, and moves independently to the object side during zooming from the wide-angle end state to the telephoto end state,
The third lens group moves during zooming from the wide-angle end state to the telephoto end state, and is located closer to the object side than the wide-angle end state in the telephoto end state.
The focal length of the first lens group is f1, the focal length of the second lens group is f2, the focal length of the third lens group is f3, the focal length of the entire system at the wide angle end is fw, the telephoto of the entire system. A zoom lens characterized by satisfying the following conditional expression when a focal length in an end state is ft.
| F1 / f2 | <1.5
0.2 <| f2 / f3 | <0.7

The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.0 <ft / | f2 | <2.0
0.1 <fw / | f3 | <0.4

When the distance from the most object-side lens surface of the second lens group to the most image-side lens surface of the third lens group is dw in the wide-angle end state and dt in the telephoto end state,
1.0 <(dt / dw) <1.15
3. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.

When the focal length of the cemented lens of the positive lens and the negative lens of the second lens group is Gf2,
0.2 <| f2 / Gf2 | <0.6
The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.

When the focal length of the lens located closest to the image plane side of the second lens group is Rf2,
0.2 <| f2 / Rf2 | <0.8
The zoom lens according to any one of claims 1 to 4, wherein the following conditional expression is satisfied.

The single lens component of the third lens group has a refractive index of n3,
1.55 <n3 <1.65
The zoom lens according to any one of claims 1 to 5, wherein the following conditional expression is satisfied.

The zoom lens according to any one of claims 1 to 6, wherein the negative meniscus lens in the first lens group has at least one aspheric surface.

The zoom lens according to claim 1, wherein the second lens group has at least two aspheric surfaces.

The zoom lens according to any one of claims 1 to 8, wherein the single lens component of the third lens group is a biconvex positive lens.

The aperture stop for adjusting the amount of light is disposed between the first lens group and the second lens group, and moves independently to the object side during zooming from the wide-angle end state to the telephoto end state. The zoom lens according to any one of claims 1 to 9, wherein:

The zoom lens according to claim 1, wherein focusing is performed by moving the first lens group toward an object.

The zoom lens according to claim 1, wherein focusing is performed by moving the third lens group toward an object.