JP2004239974A

JP2004239974A - Zoom lens

Info

Publication number: JP2004239974A
Application number: JP2003026253A
Authority: JP
Inventors: Daisaku Arai; 大作荒井
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 2003-02-03
Filing date: 2003-02-03
Publication date: 2004-08-26

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact zoom lens having high image quality and suitable for a video camera and an electronic still camera or the like using a solid-state imaging device or the like. <P>SOLUTION: The zoom lens has a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power and a third lens group G3 having positive refractive power in order from an object side, and an aperture diaphragm S is arranged near the object side of the second lens group G2. In zooming from a wide end state to a telephoto end state, the first lens group G1, the second lens group G2 and the third lens group G3 are each moved so that space between the first lens group G1 and the second lens group G2 may be decreased and space between the second lens group G2 and the third lens group G3 may be changed, and the aperture diaphragm S is moved together with the second lens group G2, and the third lens group G3 is moved in zooming from the wide end state to the telephoto end state, and positioned nearer the object side in the wide end state than in the telephoto end state. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【産業上の利用分野】
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群構成のズームレンズが開示されている（特許文献１、２、３参照。）。
【０００３】
【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。
【０００４】
【発明が解決しようとする課題】
しかしながら特許文献１の各開示例では、第３レンズ群が３つまたは４つのレンズより構成されているので、第３レンズ群のレンズ室の構造が複雑になり組立調整に時間を要してしまう問題がある。また、特許文献２の各開示例では、第１レンズ群が３つのレンズより構成されているので、小型化に限界があるという問題がある。また、特許文献３の各開示例では、第１レンズ群を２つのレンズで構成しているが、非球面を４面以上使用しており、製造条件が厳しく、コストが掛るという問題がある。
【０００５】
本発明は、上記問題に鑑みてなされたものであり、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、小型、高画質なズームレンズを提供することを目的としている。
【０００６】
【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とから成り、前記第２レンズ群は、前記物体側より順に、正レンズと、正レンズと負レンズとの接合レンズと、正レンズとから成り、前記第３レンズ群は、単一レンズ成分から成り、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変化するように、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前記物体側に位置し、且つ、全系の広角端状態での焦点距離をｆｗ、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ｆｒ２、前記第２レンズ群の光軸中心厚をＧＬ２、前記第２レンズ群の最も像面側に位置する前記正レンズの前記物体側の空気間隔をＧｄ２、前記第１レンズ群の最も像面側に位置する前記正レンズの焦点距離をｆｒ１、前記第３レンズ群の前記単一レンズ成分の屈折率をｎ３、としたとき、以下の条件式（１）から（５）を満足することを特徴とするズームレンズを提供する。
【０００７】
（１）２．１＜｜ｆ１｜／ｆｗ＜２．４、
（２）３．０＜｜ｆｒ２／ｆ２｜＜５．０、
（３）５．０＜（ＧＬ２／Ｇｄ２）＜６．０、
（４）０．４＜｜ｆ１／ｆｒ１｜＜０．５、
（５）１．７＜ｎ３＜１．８。
【０００８】
【発明の実施の形態】
以下、本発明の実施の形態に関し詳説する。
【０００９】
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とから成り、第２レンズ群は、物体側より順に、正レンズと、正レンズと負レンズとの接合レンズと、正レンズとから成り、第３レンズ群は、単一レンズ成分から成り、第２レンズ群の物体側近傍に開口絞りが配置されており、広角端状態から望遠端状態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変化するように、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、開口絞りは第２レンズ群と共に移動し、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するように構成されている。なお、開口絞りの配置によって、広角端状態から望遠端状態へのズーミングによる光線の位置を適切にすることができ、ズーミングによる瞳位置の変動を適切な値にすることができる。
【００１０】
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とで構成し、第３レンズ群は単一レンズ成分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レンズ群は物体側より順に、正レンズと、正レンズと負レンズとの接合レンズと、正レンズ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。
また、ズームレンズ全系における広角端状態での焦点距離をｆｗ、第１レンズ群の焦点距離をｆ１としたとき、
（１）２．１＜｜ｆ１｜／ｆｗ＜２．４
の条件を満足することが望ましい。
【００１１】
条件式（１）は、第１レンズ群の焦点距離の適切な範囲を示している。条件式（１）の上限値を超えると、ズームレンズの全長が長くなり好ましくない。条件式（１）の下限値を超えると、第１レンズ群によって発生する収差を良好に除去できないので好ましくない。
また、第２レンズ群の焦点距離をｆ２、前記第２レンズ群Ｇ２の最も像面側に位置する正レンズの焦点距離をｆｒ２としたとき、
（２）３．０＜｜ｆｒ２／ｆ２｜＜５．０
の条件を満足することが望ましい。
【００１２】
条件式（２）は、第２レンズ群の最も像面側に位置する正レンズの焦点距離の適切な範囲を示している。条件式（２）の上限値を超えると、収差補正上好ましくない。条件式（２）の下限値を超えると、広角端状態での瞳位置が像面に近くなり、球面収差も劣化するので好ましくない。
【００１３】
また、第２レンズ群の光軸における厚さをＧＬ２、第２レンズ群の最も像面側に位置する正レンズの物体側の空気間隔をＧｄ２としたとき、
（３）５．０＜（ＧＬ２／Ｇｄ２）＜６．０
の条件を満足することが望ましい。
【００１４】
条件式（３）は、第２レンズ群の光軸における厚さと、第２レンズ群の最も像面側に位置する正レンズの物体側の空気間隔との関係を示している。条件式（３）の上限値を超えると、球面収差が劣化する為好ましくない。条件式（３）の下限値を超えると、第２レンズ群全体が大きくなり好ましくない。
【００１５】
また、第１レンズ群の最も像面側に位置する正レンズの焦点距離をｆｒ１、第１レンズ群の焦点距離をｆ１としたとき、
（４）０．４＜｜ｆ１／ｆｒ１｜＜０．５
の条件を満足することが望ましい。
【００１６】
条件式（４）は、第１レンズ群の最も像面側の正レンズの屈折力を規定している。条件式の下限値を下回ると、コマ収差が劣化し好ましくない。条件式の上限値を超えると、負メニスカスレンズと正レンズとの偏芯公差及び間隔公差が厳しくなり好ましくない。
【００１７】
また、前記第３レンズ群の単一レンズ成分は、その屈折率をｎ３としたとき、
（５）１．７＜ｎ３
の条件を満足することが望ましい。
【００１８】
条件式（５）は、第３レンズ群における単一レンズ成分の屈折率の最適な範囲を規定している。条件式（５）の下限値を超えると、第３レンズ群における単一レンズ成分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。
【００１９】
また、本発明のズームレンズでは、第１レンズ群の負メニスカスレンズは、少なくとも１つ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。
また、第２レンズ群は、少なくとも１つ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。
【００２０】
また、第２レンズ群の最も像面側に配置した正レンズは、像面側に凸面を向けた正メニスカスレンズである。これにより第２レンズ群によるコマ収差補正能力が向上する。
【００２１】
また、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。
【００２２】
また、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。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。
【００２３】
あるいは、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。さらに、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の全長に変化がなく、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。
【００２４】
このような構成にすることによって、ズーム比が２．５倍以上で小型、高性能なズームレンズが可能となる。
【００２５】
「実施例」
以下、本発明の実施の形態に係る各実施例を、添付図面に基づいて説明する。各実施例において、本発明のズームレンズは、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、広角端状態から望遠端状態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Ｇ２２と第３レンズ群Ｇ３との間隔が変化するように、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、ズーミングを行っている。また、フォーカシングの際に、第１レンズ群Ｇ１あるいは、第３レンズ群Ｇ３を移動させる。
【００２６】
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。
【００２７】
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。
【００２８】
また、前記第１レンズ群Ｇ１から前記第３レンズ群Ｇ３のいずれかのレンズ群あるいはいずれかのレンズ群の一部を光軸と直交方向または、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。
以下に示す各表に各実施例の諸元値を示す。各表において、［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。また、［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＝５８７．６ｎｍ）に対する屈折率をそれぞれ表わしている。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。
【００２９】
【数１】

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］は、広角端状態、中間焦点距離状態、望遠端状態の各状態における焦点距離、可変間隔の値を示す。
【００３０】
なお、以下の全ての諸元値において、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、全ての実施例においての表中の符号は同様の符号を用い説明を省略する。
【００３１】
（第１実施例）
図１は、本発明の第１実施例に係るズームレンズのレンズ構成を示す図である。
【００３２】
本第１実施例では、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Ｌ１１と正レンズＬ１２から成り、第２レンズ群Ｇ２は、物体側より順に、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、正レンズＬ２４とから成り、第３レンズ群Ｇ３は、単一レンズ成分Ｌ３１から成り、第２レンズ群Ｇ２の物体側の近傍に開口絞りＳが配置されており、広角端状態から望遠端状態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との間隔が変化するように、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、開口絞りＳは第２レンズ群Ｇ２と共に移動し、第３レンズ群Ｇ３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するように構成されている。
【００３３】
また、本実施例および以下の全実施例では、第３レンズ群Ｇ３と像面Ｉとの間に、像面Ｉに配設されるＣＣＤ等の固体撮像素子の限界解像以上の空間周波数をカットするためのローパスフィルターＰ１と、固体撮像素子を保護するためのカバーガラスＰ２とが設けられている。
【００３４】
以下に、第１実施例のズームレンズの諸元値を示す。
【００３５】
【表１】

図２は本第１実施例の広角端状態における無限遠撮影状態での諸収差図を示し、図３は本第１実施例の中間焦点距離状態における無限遠撮影状態での諸収差図を示し、図４は本第１実施例の望遠端状態における無限遠撮影状態での諸収差図を示す。
【００３６】
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）ｇはｇ線（λ＝４３５．６ｎｍ）、ＣはＣ線（λ＝６５６．３ｎｍ）、およびＦはＦ線（λ＝４８６．１ｎｍ）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。なお、以下の全実施例において同様の符号を用い説明を省略する。
【００３７】
上述の各収差図から、本第１実施例の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。
【００３８】
（第２実施例）
図５は、本発明の第２実施例に係るズームレンズのレンズ構成を示す図である。
【００３９】
本第１実施例では、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Ｌ１１と正レンズＬ１２から成り、第２レンズ群Ｇ２は、物体側より順に、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、正レンズＬ２４とから成り、第３レンズ群Ｇ３は、単一レンズ成分Ｌ３１から成り、第２レンズ群Ｇ２の物体側の近傍に開口絞りＳが配置されており、広角端状態から望遠端状態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との間隔が変化するように、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、開口絞りＳは第２レンズ群Ｇ２と共に移動し、第３レンズ群Ｇ３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するように構成されている。
【００４０】
以下に、第２実施例のズームレンズの諸元値を示す。
【００４１】
【表２】

図６は本第２実施例の広角端状態における無限遠撮影状態での諸収差図を示し、図７は本第２実施例の中間焦点距離状態における無限遠撮影状態での諸収差図を示し、図８は本第２実施例の望遠端状態における無限遠撮影状態での諸収差図を示す。
【００４２】
上述の各収差図から、本第２実施例の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。
【００４３】
（第３実施例）
図９は、本発明の第１実施例に係るズームレンズのレンズ構成を示す図である。
【００４４】
本第１実施例では、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Ｌ１１と正レンズＬ１２から成り、第２レンズ群Ｇ２は、物体側より順に、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、正レンズＬ２４とから成り、第３レンズ群Ｇ３は、単一レンズ成分Ｌ３１から成り、第２レンズ群Ｇ２の物体側の近傍に開口絞りＳが配置されており、広角端状態から望遠端状態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との間隔が変化するように、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、開口絞りＳは第２レンズ群Ｇ２と共に移動し、第３レンズ群Ｇ３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するように構成されている。
【００４５】
以下に、第３実施例のズームレンズの諸元値を示す。
【００４６】
【表３】

図１０は本第３実施例の広角端状態における無限遠撮影状態での諸収差図を示し、図１１は本第３実施例の中間焦点距離状態における無限遠撮影状態での諸収差図を示し、図１２は本第３実施例の望遠端状態における無限遠撮影状態での諸収差図を示す。
【００４７】
上述の各収差図から、本第３実施例の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。
【００４８】
【発明の効果】
以上説明したように、本発明によればズームレンズ、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、小型、高画質な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実施例に係るズームレンズのレンズ構成を示す図。
【図２】本発明の第１実施例の広角端状態における無限遠撮影状態での諸収差図を示す。
【図３】本発明の第１実施例の中間焦点距離状態における無限遠撮影状態での諸収差図を示す。
【図４】本発明の第１実施例の望遠端状態における無限遠撮影状態での諸収差図を示す。
【図５】本発明の第２実施例に係るズームレンズのレンズ構成を示す図。
【図６】本発明の第２実施例の広角端状態における無限遠撮影状態での諸収差図を示す。
【図７】本発明の第２実施例の中間焦点距離状態における無限遠撮影状態での諸収差図を示す。
【図８】本発明の第２実施例の望遠端状態における無限遠撮影状態での諸収差図を示す。
【図９】本発明の第３実施例に係るズームレンズのレンズ構成を示す図。
【図１０】本発明の第３実施例の広角端状態における無限遠撮影状態での諸収差図を示す。
【図１１】本発明の第３実施例の中間焦点距離状態における無限遠撮影状態での諸収差図を示す。
【図１２】本発明の第３実施例の望遠端状態における無限遠撮影状態での諸収差図を示す。
【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[0001]
[Industrial applications]
The present invention relates to a zoom lens, and more particularly to a zoom lens suitable for a video camera, an electronic still camera, or the like using a solid-state imaging device or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there have been disclosed three-group zoom lenses having a negative, positive, and positive refractive power arrangement suitable for a solid-state imaging device and the like (see

Patent Documents

1, 2, and 3).
[0003]
[Patent Document 1]
JP-A-63-292106.
[Patent Document 2]
JP-A-6-94996.
[Patent Document 3]
JP-A-2000-284177.
[0004]
[Problems to be solved by the invention]
However, in each disclosed example of Patent Literature 1, since the third lens group includes three or four lenses, the structure of the lens chamber of the third lens group becomes complicated, and it takes time for assembly adjustment. There's a problem. Further, in each disclosed example of Patent Literature 2, since the first lens group includes three lenses, there is a problem that miniaturization is limited. Further, in each disclosed example of Patent Document 3, the first lens group is composed of two lenses, but four or more aspherical surfaces are used, and there is a problem that manufacturing conditions are strict and costs increase.
[0005]
The present invention has been made in view of the above problems, and has as its object to provide a small, high-quality zoom lens suitable for a video camera, an electronic still camera, or the like using a solid-state imaging device or the like.
[0006]
[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 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 positive lens and a positive lens The third lens group is composed of a single lens component. When zooming from the wide-angle end state to the telephoto end state, the third lens group includes the first lens group and the second lens group. The first lens group, the second lens group, and the third lens group move so that the distance between the lens groups decreases and the distance between the second lens group and the third lens group changes. The third lens group is telephoto from the wide-angle end state. The zoom lens moves during zooming to a state, is located closer to the object side than the wide-angle end state in the telephoto end state, and the focal length in the wide-angle end state of the entire system is fw, 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 lens located closest to the image plane side of the second lens group is fr2, the optical axis center thickness of the second lens group is GL2, and the focal length of the second lens group is Gd2 is the air distance on the object side of the positive lens located on the image plane side, fr1 is the focal length of the positive lens located closest to the image plane of the first lens group, and the single lens of the third lens group is Provided is a zoom lens characterized by satisfying the following conditional expressions (1) to (5), where n3 is the refractive index of the lens component.
[0007]
(1) 2.1 <| f1 | / fw <2.4,
(2) 3.0 <| fr2 / f2 | <5.0,
(3) 5.0 <(GL2 / Gd2) <6.0,
(4) 0.4 <| f1 / fr1 | <0.5,
(5) 1.7 <n3 <1.8.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0009]
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 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 positive lens, and a cemented lens of a positive lens and a negative lens. The third lens group includes a single lens component. An aperture stop is arranged near the object side of the second lens group. When zooming from the wide-angle end state to the telephoto end state, the third lens group 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 decreases and the distance between the second lens group and the third lens group changes. The aperture stop moves with the second lens group, and the third lens 'S group moves during zooming from the wide-angle end state to the telephoto end state, and is configured to be positioned on the object side of the wide-angle end state in the telephoto end state. The position of the light beam by zooming from the wide-angle end state to the telephoto end state can be made appropriate by the arrangement of the aperture stop, and the pupil position change due to zooming can be made an appropriate value.
[0010]
The first lens group is composed of a negative meniscus lens having a convex surface facing the object side and a positive lens, and the third lens group is composed of a single lens component, thereby assembling and adjusting the first lens group and the third lens group. Is extremely easy, which is effective for cost reduction. In addition, the second lens group includes, in order from the object side, a positive lens, a cemented lens of a positive lens and a negative lens, and a positive lens to effectively and satisfactorily correct spherical aberration, coma, and chromatic aberration. it can.
When the focal length in the wide-angle end state of the entire zoom lens system is fw and the focal length of the first lens group is f1,
(1) 2.1 <| f1 | / fw <2.4
It is desirable to satisfy the following condition.
[0011]
Conditional expression (1) indicates an appropriate range of the focal length of the first lens group. If the value exceeds the upper limit of conditional expression (1), the total length of the zoom lens becomes undesirably long. Exceeding the lower limit of conditional expression (1) is not preferable because aberrations generated by the first lens group cannot be satisfactorily removed.
When the focal length of the second lens group is f2 and the focal length of the positive lens closest to the image plane of the second lens group G2 is fr2,
(2) 3.0 <| fr2 / f2 | <5.0
It is desirable to satisfy the following condition.
[0012]
Conditional expression (2) indicates an appropriate range of the focal length of the positive lens closest to the image plane in the second lens group. Exceeding the upper limit of conditional expression (2) is not preferable for aberration correction. If the lower limit of conditional expression (2) is exceeded, the pupil position in the wide-angle end state will be close to the image plane, and spherical aberration will also deteriorate, which is not preferable.
[0013]
When the thickness of the second lens unit on the optical axis is GL2, and the air gap on the object side of the positive lens located closest to the image plane of the second lens unit is Gd2,
(3) 5.0 <(GL2 / Gd2) <6.0
It is desirable to satisfy the following condition.
[0014]
Conditional expression (3) shows the relationship between the thickness of the second lens unit on the optical axis and the air gap on the object side of the positive lens located closest to the image plane side of the second lens unit. Exceeding the upper limit of conditional expression (3) is not preferred because spherical aberration deteriorates. If the lower limit of conditional expression (3) is exceeded, the entire second lens group becomes undesirably large.
[0015]
When the focal length of the positive lens located closest to the image plane side of the first lens group is fr1, and the focal length of the first lens group is f1,
(4) 0.4 <| f1 / fr1 | <0.5
It is desirable to satisfy the following condition.
[0016]
Conditional expression (4) defines the refractive power of the positive lens closest to the image plane in the first lens group. When the value goes below the lower limit of the conditional expression, coma aberration is undesirably deteriorated. Exceeding the upper limit of the conditional expression is not preferable because the eccentricity tolerance and the interval tolerance between the negative meniscus lens and the positive lens become strict.
[0017]
The single lens component of the third lens group has a refractive index of n3.
(5) 1.7 <n3
It is desirable to satisfy the following condition.
[0018]
Conditional expression (5) defines an optimum range of the refractive index of the single lens component in the third lens group. If the lower limit of conditional expression (5) is exceeded, the radius of curvature of the single lens component in the third lens group will be small, and the lens center thickness will be increased, which is not preferable.
[0019]
In the zoom lens according to 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.
The second lens group has at least one aspheric surface. Thus, spherical aberration and coma can be favorably corrected over the entire zoom range.
[0020]
The positive lens disposed closest to the image plane in the second lens group is a positive meniscus lens having a convex surface facing the image plane. Thereby, the ability of the second lens group to correct coma aberration is improved.
[0021]
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.
[0022]
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. Further, the focusing movement amount can be reduced, which is preferable in manufacturing.
[0023]
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. Further, since the first lens group does not move during focusing, there is no change in the overall length of the zoom lens during focusing, so that usability in macro photography or the like can be improved.
[0024]
With this configuration, a compact, high-performance zoom lens having a zoom ratio of 2.5 times or more can be realized.
[0025]
"Example"
Hereinafter, examples according to embodiments of the present invention will be described with reference to the accompanying drawings. In each embodiment, 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 second lens group G2 having a positive refractive power. When zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 decreases, and the second lens group G22 and the third lens group G3 are provided. The first lens group G1, the second lens group G2, and the third lens group G3 are moved so that the distance between the first lens group G1 and the second lens group G3 is changed, thereby performing zooming. During focusing, the first lens group G1 or the third lens group G3 is moved.
[0026]
In each embodiment, any surface of the first lens group G1 to the third lens group G3 may be a diffraction surface.
[0027]
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.
[0028]
Further, any one of the first lens group G1 to the third lens group G3 or a part of any one of the lens groups is moved in a direction orthogonal to the optical axis or in a curved shape around a certain point. By doing so, it is also possible to use a camera shake correction lens.
The following tables show the specification values of each embodiment. In each table, in [Overall Specifications], f represents the focal length, Bf represents the back focus, FNo represents the F number, and 2ω represents the 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 lens surface interval, ν is the Abbe number, and n is the d line (λ = 587.6 nm). ) Respectively. Further, [Aspherical surface data] shows an aspherical surface coefficient when an aspherical surface is expressed by the following equation.
[0029]
(Equation 1)

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. [Zooming data] indicates the values of the focal length and the variable interval in each of the wide-angle end state, the intermediate focal length state, and the telephoto end state.
[0030]
In all the following specification values, “mm” is generally used for the focal length f, radius of curvature r, surface distance d, and other lengths unless otherwise specified. However, the present invention is not limited to this, since the same optical performance can be obtained even if the magnification or proportional reduction is performed. Further, the unit is not limited to “mm”, and another appropriate unit can be used. Further, the reference numerals in the tables in all the embodiments are the same, and the description is omitted.
[0031]
(First embodiment)
FIG. 1 is a diagram illustrating a lens configuration of a zoom lens according to a first example of the present invention.
[0032]
In the first embodiment, 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. The first lens group G1 includes 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 positive lens L21, a positive lens L22, and The third lens group G3 includes a single lens component L31, and an aperture stop S is arranged near the object side of the second lens group G2. The third lens group G3 includes a cemented lens with the negative lens L23 and the positive lens L24. During zooming from the wide-angle end state to the telephoto end state, 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 changes. , The first lens group G1 and the second lens The group G2 and the third lens group G3 move respectively, the aperture stop S moves together with the second lens group G2, and the third lens group G3 moves during zooming from the wide-angle end state to the telephoto end state, and moves to the telephoto end state. At the object side from the wide-angle end state.
[0033]
In this embodiment and all the following embodiments, a spatial frequency equal to or higher than the limit resolution of a solid-state imaging device such as a CCD disposed on the image plane I is provided between the third lens group G3 and the image plane I. A low-pass filter P1 for cutting and a cover glass P2 for protecting the solid-state imaging device are provided.
[0034]
Hereinafter, the specification values of the zoom lens of the first embodiment will be described.
[0035]
[Table 1]

FIG. 2 is a diagram illustrating various aberrations of the first embodiment in the infinity shooting state in the wide-angle end state, and FIG. 3 is a diagram illustrating various aberrations of the first embodiment in the infinity shooting state in the intermediate focal length state. FIG. 4 shows various aberration diagrams of the first embodiment at the telephoto end in the infinity photographing state.
[0036]
In each aberration diagram, FNO is the F number, Y is the image height, d is the d line (λ = 587.6 nm), g is the g line (λ = 435.6 nm), C is the C line (λ = 656.3 nm), And F indicate the F line (λ = 486.1 nm). In the astigmatism diagram, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Note that the same reference numerals are used in all the following embodiments, and the description is omitted.
[0037]
From the aberration diagrams described above, it is clear that the zoom lens according to the first embodiment has excellent aberrations corrected for various aberrations and excellent imaging performance.
[0038]
(Second embodiment)
FIG. 5 is a diagram illustrating a lens configuration of a zoom lens according to Example 2 of the present invention.
[0039]
In the first embodiment, 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. The first lens group G1 includes 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 positive lens L21, a positive lens L22, and The third lens group G3 includes a single lens component L31, and an aperture stop S is arranged near the object side of the second lens group G2. The third lens group G3 includes a cemented lens with the negative lens L23 and the positive lens L24. During zooming from the wide-angle end state to the telephoto end state, 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 changes. , The first lens group G1 and the second lens The group G2 and the third lens group G3 move respectively, the aperture stop S moves together with the second lens group G2, and the third lens group G3 moves during zooming from the wide-angle end state to the telephoto end state, and moves to the telephoto end state. At the object side from the wide-angle end state.
[0040]
Hereinafter, the specification values of the zoom lens of the second embodiment will be shown.
[0041]
[Table 2]

FIG. 6 is a diagram showing various aberrations of the second embodiment in an infinity shooting state in the wide-angle end state, and FIG. 7 is a diagram showing various aberrations of the second embodiment in an infinity shooting state in an intermediate focal length state. FIG. 8 shows various aberration diagrams of the second embodiment at the telephoto end in the infinity shooting state.
[0042]
From the aberration diagrams described above, it is clear that the zoom lens of the second embodiment has excellent correction of various aberrations and excellent imaging performance.
[0043]
(Third embodiment)
FIG. 9 is a diagram illustrating a lens configuration of a zoom lens according to Example 1 of the present invention.
[0044]
In the first embodiment, 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. The first lens group G1 includes 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 positive lens L21, a positive lens L22, and The third lens group G3 includes a single lens component L31, and an aperture stop S is arranged near the object side of the second lens group G2. The third lens group G3 includes a cemented lens with the negative lens L23 and the positive lens L24. During zooming from the wide-angle end state to the telephoto end state, 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 changes. , The first lens group G1 and the second lens The group G2 and the third lens group G3 move respectively, the aperture stop S moves together with the second lens group G2, and the third lens group G3 moves during zooming from the wide-angle end state to the telephoto end state, and moves to the telephoto end state. At the object side from the wide-angle end state.
[0045]
Hereinafter, the specification values of the zoom lens of the third example will be shown.
[0046]
[Table 3]

FIG. 10 is a diagram showing various aberrations of the third embodiment in an infinity shooting state in the wide-angle end state, and FIG. 11 is a diagram showing various aberrations of the third embodiment in an infinity shooting state in an intermediate focal length state. FIG. 12 is a diagram showing various aberrations of the third embodiment in an infinity photographing state in a telephoto end state.
[0047]
From the aberration diagrams described above, it is clear that the zoom lens of the third embodiment has excellent aberrations corrected for various aberrations and has excellent imaging performance.
[0048]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a compact, high-quality zoom lens suitable for a video camera, an electronic still camera, or the like using a zoom lens, a solid-state imaging device, or the like.
[Brief description of the drawings]
FIG. 1 is a diagram showing a lens configuration of a zoom lens according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating various aberrations of the first embodiment of the present invention in an infinity shooting state in a wide-angle end state.
FIG. 3 is a diagram illustrating various aberrations of the first embodiment of the present invention in an infinity shooting state in an intermediate focal length state.
FIG. 4 is a diagram illustrating various aberrations of the first embodiment of the present invention 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 Example 2 of the present invention.
FIG. 6 is a diagram illustrating various aberrations of the second embodiment of the present invention in an infinity shooting state in a wide-angle end state.
FIG. 7 is a diagram showing various aberrations of the second embodiment of the present invention in an intermediate focal length state in an infinity shooting state.
FIG. 8 is a diagram showing various aberrations of the second embodiment of the present invention in an infinity shooting state in a telephoto end state.
FIG. 9 is a diagram showing a lens configuration of a zoom lens according to Example 3 of the present invention.
FIG. 10 is a diagram illustrating various aberrations of the third embodiment of the present invention in an infinity shooting state in a wide-angle end state.
FIG. 11 is a diagram illustrating various aberrations of the third embodiment of the present invention in an infinity imaging state in an intermediate focal length state.
FIG. 12 is a diagram illustrating various aberrations of the third embodiment of the present invention 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

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 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 positive lens, a cemented lens of a positive lens and a negative lens, and a positive lens,
The third lens group includes 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 decreases, and the distance between the second lens group and the third lens group changes. The first lens group, the second lens group, and the third lens group move,
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 entire system at the wide-angle end state is fw, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the second lens group is located closest to the image plane. The focal length of the lens is fr2, the thickness of the second lens group at the optical axis is GL2, the air gap of the positive lens located closest to the image plane side of the second lens group on the object side is Gd2, When the focal length of the positive lens located closest to the image plane side of the lens group is fr1, and the refractive index of the single lens component of the third lens group is n3, the following conditional expression is satisfied. And zoom lens.
2.1 <| f1 | / fw <2.4
3.0 <| fr2 / f2 | <5.0
5.0 <(GL2 / Gd2) <6.0
0.4 <| f1 / fr1 | <0.5
1.7 <n3 <1.8

The zoom lens according to claim 1, wherein the negative meniscus lens of 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 one aspheric surface.

4. The zoom lens according to claim 1, wherein the second lens group has an aperture stop on the object side, and moves together with the second lens group during zooming. 5.

The zoom according to any one of claims 1 to 4, wherein the positive lens disposed closest to the image plane in the second lens group is a positive meniscus lens having a convex surface facing the image plane. lens.

The zoom lens according to claim 1, wherein the single lens component of the third lens group includes a biconvex positive lens.

The zoom lens according to any one of claims 1 to 6, wherein focusing is performed by moving the first lens group toward the object side.

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