JP2004012505A

JP2004012505A - Zoom lens and optical equipment having the same

Info

Publication number: JP2004012505A
Application number: JP2002161577A
Authority: JP
Inventors: Koji Hoshi; 星　浩二
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2002-06-03
Filing date: 2002-06-03
Publication date: 2004-01-15
Anticipated expiration: 2022-06-03
Also published as: JP4250378B2

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a zoom lens consisting of a small number of component lenses, made compact, and having excellent optical performance, and optical equipment using the same. <P>SOLUTION: The zoom lens has a 1st lens group having a negative refractive power, a 2nd lens group having a positive refractive power, and a 3rd lens group having a positive refractive power in this order from the object side, and performs zooming by changing the space between the 2nd lens group and lens groups in front and behind the 2nd lens group. The 2nd lens group is constituted of a 2a lens group and a 2b lens group with the largest space in the lens group as a boundary. The 2a lens group is constituted of a single lens group having a positive lens in order from the object side and the 2b lens group is constituted of a doublet constituted by bonding one positive lens and one negative lens. The zoom lens has a diaphragm between the 2a lens group and the 2b lens group and satisfies a conditional expression; 0.05<Dn/Dab<0.81 when it is assumed that Dn is the thickness of the negative lens in the 2b lens group and Dab is the space between the 2a lens group and the 2b lens group on an optical axis. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明はスチルカメラやビデオカメラ、そしてデジタルスチルカメラ等に好適なズームレンズ及びそれを有する光学機器に関するものである。
【０００２】
【従来の技術】
最近、固体撮像素子を用いたビデオカメラ、デジタルスチルカメラ等、撮像装置（カメラ）の小型化及び高機能化にともない、それに用いる光学系に小型で高い光学性能を有したズームレンズが求められている。
【０００３】
特開平７−５２２５６号公報では、負、正、正、の屈折力のレンズ群の３つのレンズ群を有し、広角端より望遠端へのズーミング中、第２レンズ群と第３レンズ群の間隔が広がるズームレンズが提案されている。
【０００４】
米国特許第５４３４７１０号では、負、正、正、の屈折力のレンズ群の３つのレンズ群を有し、広角端より望遠端へのズーミング中、第２レンズ群と第３レンズ群の間隔が減少するズームレンズが開示されている。
【０００５】
本出願人は、特開２０００−１１１７９８号公報にて物体側より順に、負の屈折力の第１レンズ群、正の屈折力の第２レンズ群、および正の屈折力の第３レンズ群より成る３群ズームレンズを提案している。この３群ズームレンズでは第２レンズ群を正レンズと負レンズと正レンズのいわゆるトリプレット構成とし、第２レンズ群の直前に絞りを配置している。
【０００６】
【発明が解決しようとする課題】
ビデオカメラやデジタルカメラ等に用いるズームレンズには、小型でかつ高い光学性能を有するレンズ系が要望されている。
【０００７】
前述した、物体側から順に、負、正、正、の屈折力のレンズ群配置の３群ズームレンズは、広画角用のズームレンズに好適であるが、第２レンズ群内のレンズがレンズ群内で相対軸ずれが発生したとき像性能が著しく劣化してしまい、製造による光学性能のばらつきが大きくなる傾向があった。
【０００８】
本発明は、各レンズ群の製造上のばらつきが少なく、優れた光学性能を有するズームレンズ及びそれを有する光学機器の提供を目的とする。
【０００９】
この他、本発明は負、正、正の屈折力のレンズ群の３つのレンズ群を有し、全系のレンズ枚数が少なく、レンズ系全体が小型で、製造が容易で高い光学性能を有したデジタルスチルカメラやビデオカメラ等に適したズームレンズ及びそれを用いた光学機器の提供を目的とする。
【００１０】
【課題を解決するための手段】
請求項１の発明のズームレンズは、
物体側より順に、負の屈折力の第１レンズ群、正の屈折力の第２レンズ群、正の屈折力の第３レンズ群を有し、第２レンズ群とその前後のレンズ群との間隔を変えてズーミングを行うズームレンズであって、該第２レンズ群は物体側より順に、第２ａレンズ群、絞り、第２ｂレンズ群より構成され、該第２ａレンズ群は物体側より順に正レンズを有する単一のレンズ群より成り、該第２ｂレンズ群は、１枚の正レンズと１枚の負レンズを接合してなる接合レンズよりなり、
Ｄｎを該第２ｂレンズ群中の負レンズの肉厚、Ｄａｂを該第２ａレンズ群と該第２ｂレンズ群の光軸上の間隔とするとき、
０．０５＜Ｄｎ／Ｄａｂ＜０．８１
の条件式を満足することを特徴としている。
【００１１】
請求項２の発明は請求項１の発明において、
前記第２ａレンズ群は単一の正レンズよりなることを特徴としている。
【００１２】
請求項３の発明のズームレンズは、
物体側より順に、負の屈折力の第１レンズ群、正の屈折力の第２レンズ群、正の屈折力の第３レンズ群を有し、第２レンズ群とその前後のレンズ群との間隔を変えてズーミングを行うズームレンズであって、該第２レンズ群は物体側より順に、第２ａレンズ群、絞り、第２ｂレンズ群より構成され、
該第２ａレンズ群と該第２ｂレンズ群はいずれも、屈折力の符号が異なるレンズを接合した単一の接合レンズより成ることを特徴としている。
【００１３】
請求項４の発明は請求項３の発明において、
Ｄｎを前記第２ｂレンズ群中の負レンズの肉厚、Ｄａｂを前記第２ａレンズ群と該第２ｂレンズ群の光軸上の間隔とするとき、
０．０５＜Ｄｎ／Ｄａｂ＜０．８１
の条件式を満足することを特徴としている。
【００１４】
請求項５の発明は請求項１から４のいずれか１項の発明において、
前記第２レンズ群は、非球面を有していることを特徴としている。
【００１５】
請求項６の発明は請求項１から５のいずれか１項の発明において、
前記第３レンズ群を光軸上移動させてフォーカスをおこなうことを特徴としている。
【００１６】
請求項７の発明は請求項１から６のいずれか１項の発明において、
物体側より順に、前記第１レンズ群は、負レンズと正レンズを有し、Ｌ１を該負レンズと正レンズの間隔、ｆｗを広角端における全系の焦点距離とするとき、
０．０５＜Ｌ１／ｆｗ＜０．８１
の条件式を満足することを特徴としている。
【００１７】
請求項８の発明は請求項１から７のいずれか１項の発明において、
前記第３レンズ群は単一のレンズ群より成ることを特徴としている。
【００１８】
請求項９の発明は請求項１から８のいずれか１項の発明において、
前記第１レンズ群は非球面を有することを特徴としている。
【００１９】
請求項１０の発明は請求項１から９のいずれか１項の発明において、
撮像素子に像を形成する為の光学系であることを特徴としている。
【００２０】
請求項１１の発明は請求項１から１０のいずれか１項の発明において、
前記ズーミングは、広角端に対し望遠端での前記第１レンズ群と前記第２レンズ群の間隔が小さく、該第２レンズ群と前記第３レンズ群の間隔が大きくなるように各レンズ群を移動させて行なうことを特徴としている。
【００２１】
請求項１２の発明は請求項１から１１のいずれか１項の発明において、
前記第１レンズ群は、物体側に凸面を向けたメニスカス状の負レンズと、物体側に凸面を向けたメニスカス状の正レンズより成り、
前記第２ａレンズ群は、物体側に凸面を向けたメニスカス形状の正レンズ又は両レンズ面が凸面の正レンズ又は正レンズと負レンズとの接合レンズより成り、
前記第３レンズ群は、物体側に凸面を向けた正レンズ又は両レンズ面が凸面の正レンズより成ることを特徴としている。
【００２２】
請求項１３の発明の光学機器は、
請求項１から請求項１２のいずれか１項のズームレンズを有していることを特徴としている。
【００２３】
【発明の実施の形態】
図１は本発明の実施形態１のズームレンズの広角端のレンズ断面図である。図２〜図４は本発明の実施形態１のズームレンズの広角端、中間のズーム位置、望遠端の収差図である。
【００２４】
図５は本発明の実施形態２のズームレンズの広角端のレンズ断面図である。図６〜図８は本発明の実施形態２のズームレンズの広角端、中間のズーム位置、望遠端の収差図である。
【００２５】
図９は本発明の実施形態３のズームレンズの広角端のレンズ断面図である。図１０〜図１２は本発明の実施形態３のズームレンズの広角端、中間のズーム位置、望遠端の収差図である。
【００２６】
図１３は本発明の実施形態４のズームレンズの広角端のレンズ断面図である。図１４〜図１６は本発明の実施形態４のズームレンズの広角端、中間のズーム位置、望遠端の収差図である。
【００２７】
図１７は本発明の実施形態５のズームレンズの広角端のレンズ断面図である。図１８〜図２０は本発明の実施形態５のズームレンズの広角端、中間のズーム位置、望遠端の収差図である。
【００２８】
図１、５、９、１３、１７に示した各実施形態のズームレンズのレンズ断面図において、Ｌ１は負の屈折力の第１レンズ群、Ｌ２は正の屈折力の第２レンズ群、Ｌ３は正の屈折力の第３レンズ群、ＳＰは開口絞り、ＩＰは像面であり、撮像素子が配置されている。Ｇはフィルターやフェースプレート等に想到するガラスブロックである。収差図において、ｄはｄ線、ｇはｇ線、Ｍはメリディオナル像面、Ｓはサジタル像面、倍率色収差はｇ線によって表している。
【００２９】
第２レンズ群Ｌ２はそのレンズ群中で最も大きな空気間隔を境に正の屈折力の第２ａレンズ群Ｌ２ａと正の屈折力の第２ｂレンズ群Ｌ２ｂより成っている。
【００３０】
各実施形態のズームレンズは、物体側より順に、負の屈折力の第１レンズ群Ｌ１、正の屈折力の第２レンズ群Ｌ２、正の屈折力の第３レンズ群Ｌ３を有し、広角端に対し望遠端での第１レンズ群Ｌ１と第２レンズ群Ｌ２の間隔が小さく、第２レンズ群Ｌ２と第３レンズ群Ｌ３の間隔が大きくなるように矢印の如く各レンズ群を移動させている。
【００３１】
各実施形態のズームレンズでは、正の屈折力の第２レンズ群Ｌ２を移動させることにより主な変倍を行い、負の屈折力の第１レンズ群Ｌ１を移動させることによって変倍に伴う像点の移動を補正している。
【００３２】
正の屈折力の第３レンズ群Ｌ３は、撮像素子の小型化に伴う撮影レンズの屈折力の増大を分担し、第１、第２レンズ群Ｌ１，Ｌ２で構成されるショートズーム系の屈折力を減らすことで、特に第１レンズ群Ｌ１を構成する各レンズでの収差の発生を抑え、良好な光学性能を達成している。
【００３３】
また、固体撮像素子等を用いた撮影装置に必要な像側のテレセントリックな結像を正の屈折力の第３レンズ群Ｌ３にフィールドレンズの役割を持たせることで達成している。
【００３４】
フォーカスは、小型軽量の第３レンズ群Ｌ３を移動させて行なう、所謂インナーフォーカス式を採用することにより、迅速なるフォーカスを容易にし、かつ、レンズ構成を適切に設定することにより、フォーカスの際の収差変動が少なくなるようにしている。
【００３５】
各実施形態のズームレンズは、撮像素子としてセルピッチ３ミクロン程度のＣＣＤ又はＣＭＵＳ等の固体撮像素子に対応した光学性能を有している。
【００３６】
次に各実施形態の特徴について説明する。まず実施形態１〜５の特徴について説明する。
【００３７】
第２レンズ群Ｌ２を物体側より順に、単一のレンズ群より成る第２ａレンズ群Ｌ２ａ、絞りＳＰ、単一のレンズ群より成る第２ｂレンズ群Ｌ２ｂより構成し、全系の最長焦点距離端（望遠端）で最小となる第１レンズ群Ｌ１と第２レンズ群Ｌ２の間隔を、絞りＳＰが第２レンズ群Ｌ２の直前にあるズームタイプに比べて小さくし、変倍効率をよくし、レンズ全長の小型化を容易にしている。
【００３８】
また、第２ａレンズ群Ｌ２ａと第２ｂレンズ群Ｌ２ｂの間に絞りＳＰを配置できる間隔を空けて構成し、第２レンズ群Ｌ２内の第２ａレンズ群Ｌ２ａと第２ｂレンズ群Ｌ２ｂの相対軸ずれによる性能劣化を抑えている。さらに、第２ａレンズ群Ｌ２ａと第２ｂレンズ群Ｌ２ｂを各々単一のレンズ群で構成し、第２ａレンズ群Ｌ２ａ内および第２ｂレンズ群Ｌ２ｂ内での軸ずれによる性能劣化を抑えるとともに、空気間隔を排除したことにより全系の小型化を図っている。
【００３９】
第２レンズ群Ｌ２内で絞りＳＰの前後に正の屈折力のレンズ群を配置し、正レンズ群の軸ずれによる性能劣化を抑えている。
【００４０】
第２ｂレンズ群Ｌ２ｂを１枚の正レンズと１枚の負レンズを接合してなる接合レンズとした簡単なレンズ構成で軸上色収差の良好な補正を可能にしている。
【００４１】
第２レンズ群Ｌ２に１以上の非球面を用いて少ないレンズ枚数で球面収差がアンダーになるのを良好に抑えている。
【００４２】
又、第１レンズ群Ｌ１を負レンズと正レンズを有する構成にし色収差を良好に補正している。
【００４３】
第３レンズ群Ｌ３を単一のレンズ群とすることによりレンズ系全体の小型化を容易にしている。
【００４４】
第１レンズ群Ｌ１に１以上の非球面を用いることにより、少ないレンズ枚数で広角端のズーム位置における歪曲収差を良好に補正している。
【００４５】
又、実施形態１、２では第２ａレンズ群Ｌ２ａを単レンズより構成しており、これにより簡易な鏡筒構造あるいはレンズ系の小型化を容易にしている。
【００４６】
実施形態３、４、５では、第２レンズ群Ｌ２を物体側より順に、屈折力（焦点距離の逆数）の符合の異なるレンズを接合した単一の接合レンズよりなる第２ａレンズ群Ｌ２ａより構成し、全系の最長焦点距離端（望遠端）で最小となる第１レンズ群Ｌ１と第２レンズ群Ｌ２の間隔を絞りＳＰが第２レンズ群Ｌ２の直前にあるズームタイプに比べて小さくし、変倍効率をよくし、レンズ全長の小型化を容易にしている。また、第２ａレンズ群Ｌ２ａと第２ｂレンズ群Ｌ２ｂの各々を接合レンズにし、色収差を良好に補正している。
【００４７】
各実施形態では、第２ｂレンズ群Ｌ２ｂ中の負レンズの肉厚（光軸上の厚さ）をＤｎ、第２ａレンズ群Ｌ２ａと第２ｂレンズ群Ｌ２ｂとの間隔をＤａｂ、第１レンズ群Ｌ１の負レンズと正レンズとの間隔をＬ１、広角端のズーム位置における全系の焦点距離をｆｗとするとき、
０．０５＜Ｄｎ／Ｄａｂ＜０．８１　‥‥（１）
０．０５＜Ｌ１／ｆｗ＜０．８１　‥‥（２）
なる条件式のうち１以上を満足している。
【００４８】
条件式（１）は、第２ｂレンズ群Ｌ２ｂ中の負レンズの肉厚と第２ａレンズ群Ｌ２ａと第２ｂレンズ群Ｌ２ｂの光軸上間隔の比に関するものである、上限を超えると負レンズが厚くなりレンズ全長が大型になる、さらに望ましくは上限を０．５７またさらには０．４２にするとよりよい。下限を超えると負レンズの肉厚が薄くなり良好な面精度加工が困難になる。更に望ましくは下限を０．１５とするのが良い。
【００４９】
条件式（２）は第１レンズ群Ｌ１中の負レンズと正レンズの間隔に関するものである。上限をこえるとレンズ間隔が広くなりレンズが大型化してしまう、さらに上限を０．５７またさらに０．４２にするとよりよい。下限を超えると２つのレンズが接近してしまい各レンズの相対軸ずれによる性能劣化が大きくなってしまう。更に望ましくは下限を０．１５とするのが良い。
【００５０】
以下に、本発明の実施形態１〜５に各々対応する数値実施例１〜５を示す。各数値実施例において、ｉは物体側からの面の順番を示し、ｒｉは各面の曲率半径、ｄｉは第ｉ面と第ｉ＋１面との間の部材肉厚又は空気間隔、ｎｉ、νｉはそれぞれｄ線に対する屈折率、アッベ数を示す。また、もっとも像側の２つの面は水晶ローパスフィルター、赤外カットフィルター等に相当するガラスブロックＧである。非球面形状は光軸からの高さＨの位置での光軸方向の変位を面頂点を基準にしてＸとするとき、
【００５１】
【数１】

【００５２】
で表される。但しＲは曲率半径、Ｋは円錐定数、Ａ，Ｂ，Ｃ，Ｄ，Ｅは非球面係数である。
【００５３】
又、「ｅ−Ｘ」は「×１０^−Ｘ」を意味している。ｆは焦点距離、ＦＮｏはＦナンバー、ωは半画角を示す。
【００５４】
又、前述の各条件式と数値実施例における諸数値との関係を表１に示す。
【００５５】
【外１】

【００５６】
【外２】

【００５７】
【外３】

【００５８】
【外４】

【００５９】
【外５】

【００６０】
【表１】

【００６１】
次に本発明のズームレンズを撮影光学系として用いたデジタルスチルカメラ（光学機器）の実施形態を図２１を用いて説明する。
【００６２】
図２１において、２０はカメラ本体、２１は本発明のズームレンズによって構成された撮影光学系、２２はカメラ本体に内蔵されたストロボ、２３は外部式ファインダー、２４はシャッターボタンである。
【００６３】
このように本発明のズームレンズをデジタルスチルカメラ等の光学機器に適用することにより、小型で高い光学性能を有する光学機器を実現している。
【００６４】
以上説明したように、ズームレンズを構成する各要素を適切に設定することにより、特に、固体撮像素子を用いた撮影系に好適な、構成レンズ枚数が少なくコンパクトで、優れた光学性能を有するズームレンズ及びそれを有する光学機器が達成できる。
【００６５】
【発明の効果】
本発明によれば、製造による光学性能のバラツキが小さく、構成レンズ枚数の少ない、コンパクトで、優れた光学性能を有するズームレンズ及びそれを有する光学機器を達成することができる。
【図面の簡単な説明】
【図１】本発明のズームレンズの実施形態１の光学断面図
【図２】実施形態１の広角端での収差図
【図３】実施形態１の中間のズーム位置での収差図
【図４】実施形態１の望遠端での収差図
【図５】本発明のズームレンズの実施形態２の光学断面図
【図６】実施形態２の広角端での収差図
【図７】実施形態２の中間のズーム位置での収差図
【図８】実施形態２の望遠端での収差図
【図９】本発明のズームレンズの実施形態３の光学断面図
【図１０】実施形態３の広角端での収差図
【図１１】実施形態３の中間のズーム位置での収差図
【図１２】実施形態３の望遠端での収差図
【図１３】本発明のズームレンズの実施形態４の光学断面図
【図１４】実施形態４の広角端での収差図
【図１５】実施形態４の中間のズーム位置での収差図
【図１６】実施形態４の望遠端での収差図
【図１７】本発明のズームレンズの実施形態５の光学断面図
【図１８】実施形態５の広角端での収差図
【図１９】実施形態５の中間のズーム位置での収差図
【図２０】実施形態５の望遠端での収差図
【図２１】本発明の光学機器の概略図
【符号の説明】
Ｌ１　　第１レンズ群
Ｌ２　　第２レンズ群
Ｌ２ａ　第２ａレンズ群
Ｌ３ａ　第３ａレンズ群
Ｌ３　　第３レンズ群
ＳＰ　　絞り
ＩＰ　　像面
ｄ　　　ｄ線
ｇ　　　ｇ線
Ｓ　　　サジタル像面
Ｍ　　　メリディオナル像面
Ｇ　　　ガラスブロック[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a zoom lens suitable for a still camera, a video camera, a digital still camera, and the like, and an optical apparatus having the same.
[0002]
[Prior art]
2. Description of the Related Art Recently, with the miniaturization and enhancement of functions of an imaging device (camera) such as a video camera and a digital still camera using a solid-state imaging device, a compact zoom lens having high optical performance has been required for an optical system used therein. I have.
[0003]
Japanese Patent Application Laid-Open No. 7-52256 has three lens groups of negative, positive, positive, and positive refractive powers. During zooming from the wide-angle end to the telephoto end, the second lens group and the third lens group A zoom lens with an increased interval has been proposed.
[0004]
U.S. Pat. No. 5,434,710 has three lens units of negative, positive, positive and negative refractive powers. During zooming from the wide-angle end to the telephoto end, the distance between the second and third lens units is increased. A decreasing zoom lens is disclosed.
[0005]
The applicant of the present application has described in Japanese Patent Application Laid-Open No. 2000-111798, 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. Has been proposed. In this three-unit zoom lens, the second lens group has a so-called triplet configuration of a positive lens, a negative lens, and a positive lens, and an aperture is disposed immediately before the second lens group.
[0006]
[Problems to be solved by the invention]
For a zoom lens used for a video camera, a digital camera, or the like, a lens system having a small size and high optical performance is demanded.
[0007]
The above-described three-unit zoom lens having a lens unit arrangement of negative, positive, positive, and refracting power in order from the object side is suitable for a zoom lens for a wide angle of view, but the lens in the second lens unit is a lens. When a relative axis shift occurs in the group, the image performance is remarkably deteriorated, and the variation in optical performance due to manufacturing tends to increase.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens having excellent optical performance with little variation in manufacturing of each lens group, and an optical apparatus having the same.
[0009]
In addition, the present invention has three lens groups of negative, positive and positive refractive power, the number of lenses in the entire system is small, the entire lens system is small, easy to manufacture, and has high optical performance. It is an object of the present invention to provide a zoom lens suitable for a digital still camera, a video camera, or the like, and an optical device using the same.
[0010]
[Means for Solving the Problems]
The zoom lens according to claim 1 is
The first lens unit has a negative refractive power, the second lens unit has a positive refractive power, and the third lens unit has a positive refractive power, in order from the object side. A zoom lens that performs zooming by changing an interval, wherein the second lens group includes, in order from the object side, a 2a lens group, a diaphragm, and a 2b lens group, and the 2a lens group is positive in order from the object side. The second b lens group includes a cemented lens formed by cementing one positive lens and one negative lens;
When Dn is the thickness of the negative lens in the second b lens group and Dab is the interval on the optical axis between the second a lens group and the second b lens group,
0.05 <Dn / Dab <0.81
Is satisfied.
[0011]
The invention of claim 2 is the invention according to claim 1,
The 2a-th lens unit comprises a single positive lens.
[0012]
The zoom lens of the invention according to claim 3 is:
The first lens unit has a negative refractive power, the second lens unit has a positive refractive power, and the third lens unit has a positive refractive power, in order from the object side. A zoom lens that performs zooming by changing an interval, wherein the second lens group includes, in order from the object side, a second a lens group, a diaphragm, and a second b lens group;
Each of the second lens group and the second lens group comprises a single cemented lens in which lenses having different refractive power signs are cemented.
[0013]
The invention of claim 4 is the invention of claim 3,
When Dn is the thickness of the negative lens in the 2b lens group and Dab is the interval on the optical axis between the 2a lens group and the 2b lens group,
0.05 <Dn / Dab <0.81
Is satisfied.
[0014]
The invention according to claim 5 is the invention according to any one of claims 1 to 4,
The second lens group has an aspherical surface.
[0015]
The invention according to claim 6 is the invention according to any one of claims 1 to 5,
The focus is performed by moving the third lens group on the optical axis.
[0016]
The invention according to claim 7 is the invention according to any one of claims 1 to 6,
In order from the object side, the first lens group has a negative lens and a positive lens, and L1 is the distance between the negative lens and the positive lens, and fw is the focal length of the entire system at the wide-angle end.
0.05 <L1 / fw <0.81
Is satisfied.
[0017]
The invention of claim 8 is the invention according to any one of claims 1 to 7,
The third lens group comprises a single lens group.
[0018]
The invention according to claim 9 is the invention according to any one of claims 1 to 8,
The first lens group has an aspherical surface.
[0019]
The invention according to claim 10 is the invention according to any one of claims 1 to 9,
It is an optical system for forming an image on an image sensor.
[0020]
The invention according to claim 11 is the invention according to any one of claims 1 to 10,
The zooming is performed such that the distance between the first lens group and the second lens group at the telephoto end with respect to the wide-angle end is small, and the distance between the second lens group and the third lens group is large. It is characterized by being moved.
[0021]
The invention of claim 12 is the invention according to any one of claims 1 to 11,
The first lens group includes a meniscus negative lens having a convex surface facing the object side, and a meniscus positive lens having a convex surface facing the object side.
The 2a-th lens group is composed of a meniscus-shaped positive lens having a convex surface facing the object side or a cemented lens of a positive lens or a positive lens having both convex surfaces and a negative lens,
The third lens group is characterized by comprising a positive lens whose convex surface faces the object side or a positive lens whose both lens surfaces are convex.
[0022]
The optical apparatus according to claim 13 is:
A zoom lens according to any one of claims 1 to 12 is provided.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a lens cross-sectional view at the wide-angle end of a zoom lens according to a first embodiment of the present invention. 2 to 4 are aberration diagrams of the zoom lens according to the first embodiment of the present invention at the wide-angle end, an intermediate zoom position, and a telephoto end.
[0024]
FIG. 5 is a lens cross-sectional view at the wide angle end of a zoom lens according to a second embodiment of the present invention. 6 to 8 are aberration diagrams at the wide-angle end, at an intermediate zoom position, and at a telephoto end of the zoom lens according to the second embodiment of the present invention.
[0025]
FIG. 9 is a lens cross-sectional view at the wide-angle end of a zoom lens according to Embodiment 3 of the present invention. 10 to 12 are aberration diagrams at the wide-angle end, an intermediate zoom position, and a telephoto end of the zoom lens according to Embodiment 3 of the present invention.
[0026]
FIG. 13 is a sectional view of a zoom lens according to a fourth embodiment of the present invention at the wide-angle end. 14 to 16 are aberration diagrams at the wide-angle end, at an intermediate zoom position, and at a telephoto end of the zoom lens according to Embodiment 4 of the present invention.
[0027]
FIG. 17 is a sectional view of a zoom lens according to a fifth embodiment of the present invention at the wide-angle end. 18 to 20 are aberration diagrams at the wide-angle end, at an intermediate zoom position, and at a telephoto end of the zoom lens according to Embodiment 5 of the present invention.
[0028]
In the lens cross-sectional views of the zoom lenses according to the embodiments shown in FIGS. 1, 5, 9, 13, and 17, L1 is a first lens group having a negative refractive power, L2 is a second lens group having a positive refractive power, and L3. Denotes a third lens group having a positive refractive power, SP denotes an aperture stop, IP denotes an image plane, and an image sensor is disposed. G is a glass block conceived of a filter, a face plate or the like. In the aberration diagrams, d is the d line, g is the g line, M is the meridional image plane, S is the sagittal image plane, and the chromatic aberration of magnification is represented by the g line.
[0029]
The second lens unit L2 includes a second-a lens unit L2a having a positive refractive power and a second-b lens unit L2b having a positive refractive power with the largest air gap in the lens unit.
[0030]
The zoom lens of each embodiment includes, in order from the object side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens unit L3 having a positive refractive power. The lens units are moved as indicated by arrows so that the distance between the first lens unit L1 and the second lens unit L2 at the telephoto end is small and the distance between the second lens unit L2 and the third lens unit L3 is large. ing.
[0031]
In the zoom lens of each embodiment, the main zooming is performed by moving the second lens unit L2 having a positive refractive power, and the image accompanying the zooming is performed by moving the first lens unit L1 having a negative refractive power. Corrects point movement.
[0032]
The third lens unit L3 having a positive refractive power shares the increase in the refractive power of the photographing lens with the downsizing of the imaging device, and the refractive power of the short zoom system including the first and second lens units L1 and L2. Reduces the occurrence of aberrations in each lens that constitutes the first lens unit L1, and achieves good optical performance.
[0033]
Further, telecentric imaging on the image side required for a photographing apparatus using a solid-state imaging device or the like is achieved by providing the third lens unit L3 having a positive refractive power as a field lens.
[0034]
Focusing is performed by moving the third lens group L3, which is small and light, so-called inner focus type. This facilitates quick focusing, and by appropriately setting the lens configuration, focussing is performed. Aberration fluctuation is reduced.
[0035]
The zoom lens according to each embodiment has optical performance corresponding to a solid-state imaging device such as a CCD or CMUS having a cell pitch of about 3 microns as an imaging device.
[0036]
Next, the features of each embodiment will be described. First, features of the first to fifth embodiments will be described.
[0037]
The second lens unit L2 includes, in order from the object side, a second lens unit L2a including a single lens unit, a stop SP, and a second lens unit L2b including a single lens unit. The distance between the first lens unit L1 and the second lens unit L2, which is minimum at the telephoto end, is made smaller than that of the zoom type in which the stop SP is located immediately before the second lens unit L2, and the zooming efficiency is improved. This makes it easier to reduce the overall length of the lens.
[0038]
The second lens unit L2a and the second b lens unit L2b are spaced apart from each other so that the stop SP can be arranged, and the relative axial displacement between the second lens unit L2a and the second b lens unit L2b in the second lens unit L2 is set. To suppress performance degradation. Further, the 2a-th lens unit L2a and the 2b-th lens unit L2b are each constituted by a single lens unit, so that the performance deterioration due to axial misalignment in the second-a lens unit L2a and the second-b lens unit L2b is suppressed, and the air gap The size of the entire system has been reduced by eliminating.
[0039]
In the second lens unit L2, a lens unit having a positive refractive power is arranged before and after the stop SP, so that performance deterioration due to axial displacement of the positive lens unit is suppressed.
[0040]
Good correction of axial chromatic aberration is possible with a simple lens configuration in which the second lens unit L2b is a cemented lens in which one positive lens and one negative lens are cemented.
[0041]
By using one or more aspherical surfaces for the second lens unit L2, it is possible to satisfactorily prevent spherical aberration from being under with a small number of lenses.
[0042]
Further, the first lens unit L1 is configured to have a negative lens and a positive lens, and chromatic aberration is corrected well.
[0043]
By making the third lens unit L3 a single lens unit, it is easy to reduce the size of the entire lens system.
[0044]
By using one or more aspherical surfaces for the first lens unit L1, distortion at the zoom position at the wide-angle end is favorably corrected with a small number of lenses.
[0045]
In the first and second embodiments, the second-a lens unit L2a is formed of a single lens, thereby facilitating a simple lens barrel structure or downsizing of the lens system.
[0046]
In the third, fourth, and fifth embodiments, the second lens unit L2 is composed of a second a lens unit L2a composed of a single cemented lens in which lenses having different signs of refractive power (reciprocal of focal length) are cemented in order from the object side. Then, the distance between the first lens unit L1 and the second lens unit L2, which is the minimum at the longest focal length end (telephoto end) of the entire system, is made smaller than that of the zoom type in which the aperture SP is located immediately before the second lens unit L2. The zooming efficiency is improved, and the overall length of the lens is easily reduced. In addition, each of the second-a lens unit L2a and the second-b lens unit L2b is a cemented lens, and chromatic aberration is satisfactorily corrected.
[0047]
In each embodiment, the thickness (thickness on the optical axis) of the negative lens in the second lens unit L2b is Dn, the distance between the second lens unit L2a and the second lens unit L2b is Dab, and the first lens unit L1 is Let L1 be the distance between the negative lens and the positive lens, and fw be the focal length of the entire system at the zoom position at the wide-angle end.
0.05 <Dn / Dab <0.81 (1)
0.05 <L1 / fw <0.81 (2)
At least one of the following conditional expressions is satisfied.
[0048]
Conditional expression (1) relates to the ratio of the thickness of the negative lens in the second lens subunit L2b to the interval on the optical axis between the second lens subunit L2a and the second lens subunit L2b. It is better to increase the thickness and the overall length of the lens, and more desirably to set the upper limit to 0.57 or even 0.42. If the lower limit is exceeded, the thickness of the negative lens becomes thin, and it becomes difficult to perform good surface precision processing. More preferably, the lower limit is set to 0.15.
[0049]
Conditional expression (2) relates to the distance between the negative lens and the positive lens in the first lens unit L1. If the upper limit is exceeded, the lens interval becomes wider and the lens becomes larger. It is better to set the upper limit to 0.57 or 0.42. If the lower limit is exceeded, the two lenses come close to each other, and the performance deterioration due to the relative axis shift of each lens increases. More preferably, the lower limit is set to 0.15.
[0050]
Hereinafter, Numerical Examples 1 to 5 corresponding to Embodiments 1 to 5 of the present invention will be described. In each numerical example, i indicates the order of the surface from the object side, ri is the radius of curvature of each surface, di is the member thickness or air space between the i-th surface and the (i + 1) -th surface, and ni and νi are Each shows the refractive index and Abbe number for the d-line. The two surfaces closest to the image are glass blocks G corresponding to a quartz low-pass filter, an infrared cut filter, and the like. The aspherical shape is defined as follows: When the displacement in the optical axis direction at the position of height H from the optical axis is X with respect to the surface vertex,
[0051]
(Equation 1)

[0052]
Is represented by Here, R is a radius of curvature, K is a conical constant, and A, B, C, D, and E are aspherical coefficients.
[0053]
“E−X” means “× 10 ^−X ”. f indicates a focal length, FNo indicates an F number, and ω indicates a half angle of view.
[0054]
Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.
[0055]
[Outside 1]

[0056]
[Outside 2]

[0057]
[Outside 3]

[0058]
[Outside 4]

[0059]
[Outside 5]

[0060]
[Table 1]

[0061]
Next, an embodiment of a digital still camera (optical apparatus) using the zoom lens of the present invention as a photographic optical system will be described with reference to FIG.
[0062]
In FIG. 21, reference numeral 20 denotes a camera main body, reference numeral 21 denotes a photographing optical system constituted by the zoom lens of the present invention, reference numeral 22 denotes a strobe built in the camera main body, reference numeral 23 denotes an external finder, and reference numeral 24 denotes a shutter button.
[0063]
As described above, by applying the zoom lens of the present invention to an optical device such as a digital still camera, an optical device having a small size and high optical performance is realized.
[0064]
As described above, by appropriately setting each element constituting the zoom lens, a zoom having a small number of constituent lenses, compact size, and excellent optical performance, which is particularly suitable for an imaging system using a solid-state image sensor, is provided. A lens and an optical device having the same can be achieved.
[0065]
【The invention's effect】
According to the present invention, it is possible to achieve a compact zoom lens having excellent optical performance with small variations in optical performance due to manufacturing, a small number of constituent lenses, and an optical apparatus having the same.
[Brief description of the drawings]
FIG. 1 is an optical cross-sectional view of Embodiment 1 of the zoom lens of the present invention. FIG. 2 is an aberration diagram at the wide angle end of Embodiment 1. FIG. 3 is an aberration diagram at an intermediate zoom position of Embodiment 1. FIG. 5 is an aberration diagram at the telephoto end of Embodiment 1. FIG. 5 is an optical sectional view of Embodiment 2 of the zoom lens according to the present invention. FIG. 6 is an aberration diagram at the wide-angle end of Embodiment 2. FIG. FIG. 8 is an aberration diagram at the telephoto end of Embodiment 2; FIG. 9 is an optical cross-sectional view of Embodiment 3 of the zoom lens of the present invention; FIG. 10 is a wide-angle end of Embodiment 3; FIG. 11 is an aberration diagram at the intermediate zoom position of Embodiment 3. FIG. 12 is an aberration diagram at the telephoto end of Embodiment 3. FIG. 13 is an optical cross-sectional view of Embodiment 4 of the zoom lens of the present invention. 14 is an aberration diagram at the wide-angle end according to the fourth embodiment. FIG. 15 is an aberration diagram at an intermediate zoom position according to the fourth embodiment. FIG. 17 is an aberration diagram at the telephoto end of Embodiment 4. FIG. 17 is an optical sectional view of Embodiment 5 of the zoom lens of the present invention. FIG. 18 is an aberration diagram at the wide-angle end of Embodiment 5. FIG. FIG. 20 is an aberration diagram at the telephoto end according to the fifth embodiment. FIG. 21 is a schematic diagram of the optical apparatus of the present invention.
L1 First lens unit L2 Second lens unit L2a Second lens unit L3a Third lens unit L3 Third lens unit SP Aperture IP Image plane d d-line g g-line S Sagittal image plane M Meridional image plane G Glass block

Claims

The first lens unit has a negative refractive power, the second lens unit has a positive refractive power, and the third lens unit has a positive refractive power, in order from the object side. A zoom lens that performs zooming by changing the interval, wherein the second lens group includes, in order from the object side, a 2a lens group, an aperture, and a 2b lens group, and the 2a lens group is positive in order from the object side. The second lens group includes a cemented lens obtained by cementing one positive lens and one negative lens;
When Dn is the thickness of the negative lens in the second b lens group and Dab is the interval on the optical axis between the second a lens group and the second b lens group,
0.05 <Dn / Dab <0.81
A zoom lens characterized by satisfying the following conditional expression:

2. The zoom lens according to claim 1, wherein the second lens group comprises a single positive lens.

The first lens unit has a negative refractive power, the second lens unit has a positive refractive power, and the third lens unit has a positive refractive power, in order from the object side. A zoom lens that performs zooming by changing an interval, wherein the second lens group includes, in order from the object side, a second a lens group, a diaphragm, and a second b lens group;
A zoom lens, wherein each of the second-a lens group and the second-b lens group comprises a single cemented lens in which lenses having different signs of refractive power are cemented.

When Dn is the thickness of the negative lens in the 2b lens group and Dab is the interval on the optical axis between the 2a lens group and the 2b lens group,
0.05 <Dn / Dab <0.81
The zoom lens according to claim 3, wherein the following conditional expression is satisfied.

The zoom lens according to claim 1, wherein the second lens group has an aspheric surface.

The zoom lens according to any one of claims 1 to 5, wherein focus is performed by moving the third lens group on the optical axis.

In order from the object side, the first lens group has a negative lens and a positive lens, and L1 is the distance between the negative lens and the positive lens, and fw is the focal length of the entire system at the wide-angle end.
0.05 <L1 / fw <0.81
The zoom lens according to any one of claims 1 to 6, wherein the following conditional expression is satisfied.

The zoom lens according to any one of claims 1 to 7, wherein the third lens group comprises a single lens group.

9. The zoom lens according to claim 1, wherein the first lens group has an aspheric surface.

The zoom lens according to any one of claims 1 to 9, wherein the zoom lens is an optical system for forming an image on an image sensor.

The zooming is performed such that the distance between the first lens group and the second lens group at the telephoto end with respect to the wide-angle end is small, and the distance between the second lens group and the third lens group is large. 11. The zoom lens according to claim 1, wherein the zoom lens is moved.

The first lens group includes a meniscus negative lens having a convex surface facing the object side, and a meniscus positive lens having a convex surface facing the object side.
The second lens group includes a meniscus-shaped positive lens having a convex surface facing the object side, or a positive lens having both convex lens surfaces or a cemented lens of a positive lens and a negative lens. The zoom lens according to any one of claims 1 to 11, wherein a positive lens having a convex surface facing the first lens or both lens surfaces is formed of a positive lens having a convex surface.

An optical apparatus comprising the zoom lens according to claim 1.