JP2004239973A

JP2004239973A - Zoom lens

Info

Publication number: JP2004239973A
Application number: JP2003026246A
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
Anticipated expiration: 2023-02-03
Also published as: JP4333151B2

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 a negative refractive index, a second lens group G2 having a positive refractive index and a third lens group G3 having a positive refractive index 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 and the second lens group G2 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 increased, and the aperture diaphragm S is moved together with the second lens group G2 and the third lens group G3 is fixed, and thus zooming is performed. <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増大するように、前記第１レンズ群および前記第２レンズ群がそれぞれ移動し、且つ前記第３レンズ群が固定されていることを特徴とするズームレンズを提供する。
【０００７】
【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。
【０００８】
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、第２レンズ群の物体側の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、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増大するように、前記第１レンズ群および前記第２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、且つ前記第３レンズ群が固定されて構成されている。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とすることができる。
【０００９】
第１レンズ群を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、前記第１レンズ群の焦点距離をｆ１、前記ズームレンズの広角端焦点距離をｆｗとしたとき、
（１）１．０＜｜ｆ１／ｆｗ｜＜４．０
の条件を満足することが望ましい。
【００１０】
条件式（１）は、第１レンズ群とズームレンズの広角端状態における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、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としたとき、
（２）１．０＜｜ｆ１／ｆ２｜＜２．０
の条件を満足することが望ましい。
【００１１】
条件式（２）は、第１レンズ群と第２レンズ群と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、歪曲収差および球面収差が悪化するか、ズームレンズの全長が長くなり好ましくない。条件式（２）の下限値を超えると、ズーミングによる収差変動が大きくなり好ましくない。
また、第３レンズ群の単一レンズ成分の焦点距離をｆ３、第２レンズ群の焦点距離をｆ２としたとき、
（３）｜ｆ２／ｆ３｜＜２．０
の条件を満足することが望ましい。
【００１２】
条件式（３）は、第２レンズ群と第３レンズ群との関係を規定している。条件式（３）の上限値を超えると、ズーミングによる収差変動が大きくなるので好ましくない。
また、第２レンズ群の正レンズと負レンズとの接合レンズは、接合レンズの焦点距離をｆｃ、第２レンズ群の焦点距離をｆ２としたとき、
（４）１．０＜｜ｆｃ／ｆ２｜＜１０．０
の条件を満足することが望ましい。
【００１３】
条件式（４）は、第２レンズ群中にある、接合レンズの焦点距離の最適な範囲を規定している。条件式（４）の上限値、および下限値を超えると、第２レンズ群による収差補正能力が著しく低下してしまうので好ましくない。
また、第３レンズ群の単一レンズ成分は、単一レンズ成分の焦点距離をｆ３、前記屈折率をｎ３としたとき、
（５）６．５＜｜ｆ３／ｎ３｜＜９．４
の条件を満足することが望ましい。
【００１４】
条件式（５）は、第３レンズ群の焦点距離と屈折率との関係を規定している。条件式（５）の上限値、および下限値を超えると、フォーカシングによる収差変動が大きくなるので好ましくない。
また、第１レンズ群の負メニスカスレンズは、負メニスカスレンズの物体側の曲率半径をｒ１、第１レンズ群の焦点距離をｆ１、としたとき、
（６）５．０＜ｒ１／ｆ１＜２０
の条件を満足することが望ましい。
条件式（６）は、負メニスカスレンズの非球面レンズの製造のしやすさを規定している。条件式（６）の下限値を下回ると、第１レンズ群の中心厚が増し光学系が大型化してしまうので好ましくない。条件式（６）の上限値を上回ると、非球面レンズの製造時に高い精度が要求されるため好ましくない。
また、第２レンズ群の接合レンズの最も物体側の曲率半径をｒ２１、接合面の曲率半径をｒ２２、最も像面側の曲率半径をｒ２３、としたとき、
（７）１．０＜ｒ２２／（ｒ２１＋ｒ２３）＜５．０
の条件を満足することが望ましい。
条件式（７）は、第２レンズ群中の接合レンズによる収差補正が良好に行なえる範囲を規定している。条件式（７）の下限値を下回ると、第２レンズ群内の他のレンズの曲率半径が小さくなり、第２レンズ群の中心厚が増し光学系が大型化してしまうので好ましくない。条件式（７）の上限値を上回ると、球面収差およびコマ収差が悪化してしまうので好ましくない。
また、第３レンズ群の単一レンズ成分の屈折率をｎ３としたとき、
（８）１．６＜ｎ３＜１．８０
の条件を満足することが望ましい。
条件式（８）は、第３レンズ群中にあ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（８）の下限値を下回ると、第３レンズ群を構成するレンズ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）の上限値を上回ると、コマ収差が悪化してしまうので好ましくない。
【００１５】
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。
【００１６】
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を持っている。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。
【００１７】
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。
【００１８】
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、第３レンズ群は常に固定となる為可動部分が少なくなり、製造上好ましい。
【００１９】
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全長変化がなく、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。
【００２０】
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。
【００２１】
「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。
【００２２】
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と前記第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との間隔が増大するように、第１レンズ群Ｇ１および第２レンズ群Ｇ２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、且つ第３レンズ群Ｇ３が固定されて、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を移動させている。
【００２３】
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。
次に、以下の各表に各実施例の諸元値を示す。
【００２４】
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。
【００２５】
【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］には、広角端、中間焦点距離、望遠端の各状態における焦点距離、可変間隔の値を示す。
【００２６】
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。
【００２７】
（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。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とから成り、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の接合レンズと、正レンズＬ２４とから成り、第３レンズ群は、両凸形状の正レンズ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との間隔が増大するように、第１レンズ群Ｇ１および第２レンズ群Ｇ２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、且つ第３レンズ群Ｇ３が固定されてズーミングを行う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あるいは、第３レンズ群Ｇ３を移動させている。
【００２８】
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。
【００２９】
以下に、第１実施例のズームレンズの諸元値を示す。
【００３０】
【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。
【００３１】
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。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。
【００３２】
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。
【００３３】
（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。本第２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とから成り、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の接合レンズと、正レンズＬ２４とから成り、第３レンズ群は、両凸形状の正レンズ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との間隔が増大するように、第１レンズ群Ｇ１および第２レンズ群Ｇ２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、且つ第３レンズ群Ｇ３が固定されてズーミングを行う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あるいは、第３レンズ群Ｇ３を移動させている。
【００３４】
以下に、第２実施例のズームレンズの諸元値を示す。
【００３５】
【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。
【００３６】
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。
【００３７】
（第３実施例）
図９は、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である。本第３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とから成り、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の接合レンズと、正レンズＬ２４とから成り、第３レンズ群は、両凸形状の正レンズ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との間隔が増大するように、第１レンズ群Ｇ１および第２レンズ群Ｇ２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、且つ第３レンズ群Ｇ３が固定されてズーミングを行う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あるいは、第３レンズ群Ｇ３を移動させている。
【００３８】
以下に、第３実施例のズームレンズの諸元値を示す。
【００３９】
【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。
【００４０】
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。
【００４１】
（第４実施例）
図１３は、本発明の第４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。本第４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とから成り、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の接合レンズと、正レンズＬ２４とから成り、第３レンズ群は、両凸形状の正レンズＬ４１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との間隔が増大するように、第１レンズ群Ｇ１および第２レンズ群Ｇ２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、且つ第３レンズ群Ｇ３が固定されてズーミングを行う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あるいは、第３レンズ群Ｇ３を移動させている。
【００４２】
以下に、第４実施例のズームレンズの諸元値を示す。
【００４３】
【表４】

図１４は本第４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１５は本第４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１６は本第４実施例４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。
【００４４】
上述の各収差図から、本第４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。
【００４５】
【発明の効果】
以上説明したように、本発明によれば、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駕できる。
【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。
【図１３】本発明の第４実施例に係るズームレンズのレンズ構成を示す図。
【図１４】本発明の第４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１５】本発明の第４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１６】本発明の第４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, and when zooming from the wide-angle end state to the telephoto end state, the first lens group and the second lens The first lens group and the second lens group move so that the distance between the first lens group and the third lens group decreases, and the third lens group moves. Zoom lens characterized in that is fixed To provide.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0008]
The zoom lens of 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 positive lens and negative lens. The third lens group is composed of a single lens component. An aperture stop is arranged near the object side of the second lens group, and the third lens group shifts from the wide-angle end state to the telephoto end state. At the time of zooming, the first lens group and the second lens group are arranged such 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 increases. The lens groups move, and the aperture stop is the second lens Go, and the third lens group is constituted by fixed together. 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 fluctuation of the pupil position due to zooming can be made an appropriate value.
[0009]
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, so that the first lens group and the third lens group are assembled. Adjustment becomes extremely easy, which is effective for cost reduction. Further, 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, so that spherical aberration, coma, and chromatic aberration can be effectively and favorably reduced. Can be corrected.
When the focal length of the first lens group is f1 and the focal length at the wide-angle end of the zoom lens is fw,
(1) 1.0 <| f1 / fw | <4.0
It is desirable to satisfy the following condition.
[0010]
Conditional expression (1) indicates an appropriate range of the focal length in the wide-angle end state of the first lens group and the zoom lens. 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 first lens group is f1 and the focal length of the second lens group is f2,
(2) 1.0 <| f1 / f2 | <2.0
It is desirable to satisfy the following condition.
[0011]
Conditional expression (2) indicates an appropriate range between the first lens unit and the second lens unit. If the upper limit of conditional expression (2) is exceeded, distortion and spherical aberration will worsen or the overall length of the zoom lens will increase, which is not desirable. Exceeding the lower limit of conditional expression (2) is not preferable because aberration fluctuations due to zooming increase.
When the focal length of the single lens component of the third lens group is f3 and the focal length of the second lens group is f2,
(3) | f2 / f3 | <2.0
It is desirable to satisfy the following condition.
[0012]
Conditional expression (3) defines the relationship between the second lens group and the third lens group. Exceeding the upper limit of conditional expression (3) is not preferred because aberration fluctuations due to zooming increase.
For a cemented lens of the positive lens and the negative lens in the second lens group, when the focal length of the cemented lens is fc and the focal length of the second lens group is f2,
(4) 1.0 <| fc / f2 | <10.0
It is desirable to satisfy the following condition.
[0013]
Conditional expression (4) defines an optimum range of the focal length of the cemented lens in the second lens group. Exceeding the upper limit and the lower limit of conditional expression (4) is not preferable because the aberration correction capability of the second lens group is significantly reduced.
The single lens component of the third lens group has a focal length f3 and a refractive index n3 of the single lens component, respectively.
(5) 6.5 <| f3 / n3 | <9.4
It is desirable to satisfy the following condition.
[0014]
Conditional expression (5) defines the relationship between the focal length of the third lens group and the refractive index. Exceeding the upper limit and the lower limit of conditional expression (5) is not preferable because aberration fluctuation due to focusing increases.
The negative meniscus lens in the first lens group has a radius of curvature on the object side of the negative meniscus lens r1 and a focal length of the first lens group f1.
(6) 5.0 <r1 / f1 <20
It is desirable to satisfy the following condition.
Conditional expression (6) defines the ease of manufacture of the negative meniscus aspherical lens. If the lower limit value of the conditional expression (6) is not reached, the thickness of the center of the first lens unit increases and the size of the optical system increases, which is not preferable. Exceeding the upper limit of conditional expression (6) is not preferable because high precision is required during the production of the aspherical lens.
When the radius of curvature of the cemented lens of the second lens group on the most object side is r21, the radius of curvature of the cemented surface is r22, and the radius of curvature on the most image side is r23,
(7) 1.0 <r22 / (r21 + r23) <5.0
It is desirable to satisfy the following condition.
Conditional expression (7) defines a range in which aberration correction by the cemented lens in the second lens group can be favorably performed. If the lower limit of conditional expression (7) is not reached, the radius of curvature of the other lenses in the second lens group will be small, and the center thickness of the second lens group will increase, which is not preferable because the optical system will become large. Exceeding the upper limit of conditional expression (7) is not preferable because spherical aberration and coma will deteriorate.
When the refractive index of the single lens component of the third lens group is n3,
(8) 1.6 <n3 <1.80
It is desirable to satisfy the following condition.
Conditional expression (8) 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 (8) is not reached, the radii of curvature of the lenses constituting the third lens group will become small, and the lens center thickness will increase, which is not preferable. If the value exceeds the upper limit of conditional expression (8), coma becomes worse, which is not preferable.
[0015]
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.
[0016]
The positive lens disposed closest to the image plane in the second lens group has 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.
[0017]
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.
[0018]
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, and the third lens group is always fixed, so that the number of movable parts is reduced, which is preferable in manufacturing.
[0019]
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. Furthermore, since the first lens group does not move during focusing, there is no change in the overall length during focusing, and the usability during macro shooting or the like can be improved.
[0020]
With this configuration, a compact, high-performance zoom lens having a zoom ratio of 2.5 times or more can be realized.
[0021]
"Example"
Hereinafter, examples according to embodiments of the present invention will be described with reference to the accompanying drawings.
[0022]
In each embodiment, the zoom lens according to the present invention has, 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. An aperture stop S is provided near the object side of the second lens group G2. When zooming from the wide-angle end state to the telephoto end state, the first lens group G1 and the third lens group G3 are disposed. The first lens group G1 and the second lens group G2 move so that the distance between the second lens group G2 and the distance between the second lens group G2 and the third lens group G3 increases, and the aperture stop S Moves together with the second lens group G2, and the third lens group G3 is fixed to perform zooming. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0023]
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 orthogonal to the optical axis or in a curved shape centered on a certain point. It is also possible to use a lens.
Next, the following tables show the specification values of each embodiment.
[0024]
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.
[0025]
(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. The [zooming data] shows the values of the focal length and the variable interval in each state of the wide-angle end, the intermediate focal length, and the telephoto end.
[0026]
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.
[0027]
(First embodiment)
FIG. 1 is a diagram illustrating a lens configuration of a zoom lens according to a first example of the present invention. In the first embodiment, a first lens group G1 having a negative refractive power, a second lens G2 having a positive refractive power, and a third lens group G3 having a positive refractive power are sequentially arranged from the object side. 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 is composed of a cemented lens of a negative lens L23 and a positive lens L24, and the third lens group is composed of a biconvex positive lens L31. An aperture stop S is arranged near the object side of the second lens group G2. 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 increases. , First lens group G1 and second lens G2 is moved respectively, an aperture stop S is configured to move together with the second lens group G2, zooming is and fixed third lens group G3. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0028]
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.
[0029]
Hereinafter, the specification values of the zoom lens of the first embodiment will be described.
[0030]
[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.
[0031]
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). 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.
[0032]
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.
[0033]
(Second embodiment)
FIG. 5 is a diagram illustrating a lens configuration of a zoom lens according to Example 2 of the present invention. In the second embodiment, a first lens group G1 having a negative refractive power, a second lens G2 having a positive refractive power, and a third lens group G3 having a positive refractive power are sequentially arranged from the object side. 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 is composed of a cemented lens of a negative lens L23 and a positive lens L24, and the third lens group is composed of a biconvex positive lens L31. An aperture stop S is arranged near the object side of the second lens group G2. 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 increases. , First lens group G1 and second lens G2 is moved respectively, an aperture stop S is configured to move together with the second lens group G2, zooming is and fixed third lens group G3. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0034]
Hereinafter, the specification values of the zoom lens of the second embodiment will be shown.
[0035]
[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.
[0036]
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.
[0037]
(Third embodiment)
FIG. 9 is a diagram illustrating a lens configuration of a zoom lens according to Example 3 of the present invention. In the third embodiment, a first lens group G1 having a negative refractive power, a second lens G2 having a positive refractive power, and a third lens group G3 having a positive refractive power are sequentially arranged from the object side. 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 is composed of a cemented lens of a negative lens L23 and a positive lens L24, and the third lens group is composed of a biconvex positive lens L31. An aperture stop S is arranged near the object side of the second lens group G2. 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 increases. , First lens group G1 and second lens G2 is moved respectively, an aperture stop S is configured to move together with the second lens group G2, zooming is and fixed third lens group G3. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0038]
Hereinafter, the specification values of the zoom lens of the third example will be shown.
[0039]
[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.
[0040]
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.
[0041]
(Fourth embodiment)
FIG. 13 is a diagram illustrating a lens configuration of a zoom lens according to Example 4 of the present invention. In the fourth embodiment, a first lens group G1 having a negative refractive power, a second lens G2 having a positive refractive power, and a third lens group G3 having a positive refractive power are sequentially arranged from the object side. 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 is composed of a cemented lens of a negative lens L23 and a positive lens L24, and the third lens group is composed of a biconvex positive lens L41. An aperture stop S is arranged near the object side of the second lens group G2. 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 increases. , First lens group G1 and second lens G2 is moved respectively, an aperture stop S is configured to move together with the second lens group G2, zooming is and fixed third lens group G3. Further, at the time of focusing, the first lens group G1 or the third lens group G3 is moved.
[0042]
Hereinafter, the specification values of the zoom lens of the fourth example will be described.
[0043]
[Table 4]

FIG. 14 is a diagram showing various aberrations of the fourth embodiment in an infinity shooting state in a wide-angle end state, and FIG. 15 is a diagram of various aberrations in an intermediate focal length state of the fourth embodiment in an infinity shooting state. FIG. 16 shows various aberration diagrams of the fourth embodiment in the telephoto end state in an infinity photographing state.
[0044]
From the aberration diagrams described above, it is clear that the zoom lens of the fourth embodiment has excellent correction of various aberrations and excellent imaging performance.
[0045]
【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 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.
FIG. 13 is a diagram showing a lens configuration of a zoom lens according to Example 4 of the present invention.
FIG. 14 is a diagram illustrating various aberrations of the fourth embodiment of the present invention in an infinity imaging state in a wide-angle end state.
FIG. 15 is a diagram illustrating various aberrations of the fourth embodiment of the present invention in an infinity imaging state in an intermediate focal length state.
FIG. 16 is a diagram illustrating various aberrations of the fourth embodiment of the present invention in an infinity imaging 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,
At the time of 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 increases. A zoom lens, wherein the first lens group and the second lens group move respectively, and the third lens group is fixed.

When the focal length of the first lens group is f1, and the focal length of the zoom lens in the wide-angle end state is fw,
1.0 <| f1 / fw | <4.0
The zoom lens according to claim 1, wherein the following condition is satisfied.

When the focal length of the first lens group is f1 and the focal length of the second lens group is f2,
1.0 <| f1 / f2 | <2.0
The zoom lens according to claim 1, wherein the following condition is satisfied.

When the focal length of the second lens group is f2 and the focal length of the single lens component of the third lens group is f3,
| F2 / f3 | <2.0
The zoom lens according to any one of claims 1 to 3, wherein the following condition is satisfied.

In the cemented lens of the positive lens and the negative lens in the second lens group, when the focal length of the cemented lens is fc and the focal length of the second lens group is f2,
1.0 <| fc / f2 | <10.0
The zoom lens according to any one of claims 1 to 4, wherein the following condition is satisfied.

The single lens component of the third lens group has a focal length f3 and a refractive index n3 of the single lens component,
6.5 <| f3 / n3 | <9.4
The zoom lens according to any one of claims 1 to 5, wherein the following condition is satisfied.

The negative meniscus lens of the first lens group has a radius of curvature on the object side as r1, and a focal length of the first lens group as f1,
5.0 <r1 / f1 <20.0
The zoom lens according to any one of claims 1 to 6, wherein the following condition is satisfied.

The cemented lens of the positive lens and the negative lens of the second lens group,
When the radius of curvature of the cemented lens closest to the object side is r21, the radius of curvature of the cemented surface is r22, and the radius of curvature of the most image side is r23,
1.0 <r22 / (r21 + r23) <5.0
The zoom lens according to any one of claims 1 to 7, wherein the following condition is satisfied.

When the refractive index of the single lens component of the third lens group is n3,
1.6 <n3 <1.80
The zoom lens according to any one of claims 1 to 8, wherein the following condition is satisfied.

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 any one of claims 1 to 10, wherein the second lens group has at least one aspheric surface.

The zoom lens according to any one of claims 1 to 11, wherein the second lens group has an aperture stop on the object side, and moves together with the second lens group during zooming.

The zoom according to any one of claims 1 to 12, wherein the positive lens disposed closest to the image plane of the second lens group is a positive meniscus lens having a convex surface facing the image plane. lens.

The zoom lens according to any one of claims 1 to 13, wherein the single lens component of the third lens group is a biconvex positive lens.

15. 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.