JP2004061681A

JP2004061681A - Zoom lens and optical equipment with same

Info

Publication number: JP2004061681A
Application number: JP2002217416A
Authority: JP
Inventors: Teruhiro Nishio; 西尾　彰宏
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2002-07-26
Filing date: 2002-07-26
Publication date: 2004-02-26

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens for a lens shutter which has large variable power ratio. <P>SOLUTION: The zoom lens has a 1st lens group with negative refracting power, a 2nd lens group with positive or negative refracting power, a 3rd lens group with positive or negative refracting power, a 4th lens group with positive refracting power, and a 5th lens group with negative refracting power in order from the object side. For power variation from a wide-angle side to a telephoto side, the 1st lens group and 5th lens group, and 2nd lens group and 4th lens group are moved together integrally on the optical axis to vary air gaps between the respective lens groups. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は写真レンズ、ビデオカメラレンズ等の撮影光学系において特にコンパクトカメラ用の写真レンズとして好適な、変倍比４．５倍程度の高変倍でコンパクトなズームレンズの達成をおこなうものである。
【０００２】
【従来の技術】
近年、写真レンズやビデオレンズにおいてはよりコンパクトで高性能な撮影光学系が要求されている。
【０００３】
特にレンズシャッターカメラの撮影光学系においては高変倍なものの要求と共に、周辺のメカ機構、電気回路の発達によってカメラの小型化の達成に有利化と伴って光学系についてもより小型なものが望まれている。
【０００４】
レンズシャッターカメラ用の高変倍な撮影光学系としては、例えば特開平８−２６２３２５公報、特開平９−１２００２８公報等にて正、正、負の３群構成のズームレンズが提案されている。
【０００５】
また正、負、正、負の４群構成の変倍比が３倍程度のズームレンズが特許２８３２３７６号、変倍比３．８倍程度のズームレンズが特開平１１−３５２４０１公報で提案されている。
【０００６】
【発明が解決しようとする課題】
しかしながら、前記した正、正、負の３群構成のズームレンズの提案においては、レンズ構成枚数が多いため、高変倍でかつコンパクトなズームレンズとは言えなかった。
【０００７】
また、正、負、正、負の４群構成のズームレンズに対しては変倍比が３倍又は３．８倍程度であり、更にレンズ構成枚数も多いため、更なる高変倍化においても小型で高画質なズームレンズの達成要求のための光学的配置の工夫が要求されている。
【０００８】
本案は、適切なズームレンズ構成及びレンズ群配置を行うことにより、高画質を維持しつつコンパクトなズームレンズ光学系を達成をおこなうものである。
【０００９】
【課題を解決するための手段】
本発明は物体側より正の屈折力を有する第１レンズ群、正又は負の屈折力を有する第２レンズ群、正又は負の屈折力を有する第３レンズ群、正の屈折力を有する第４レンズ群、負の屈折力を有する第５レンズ群を有し、広角から望遠への変倍は、前記第１レンズ群と第５レンズ群を一体に、かつ第２レンズ群と第４レンズ群を一体に共に物体側へ光軸上の移動を行ない各レンズ群間の空気間隔を変化させることで行なうことを特徴としている。
【００１０】
【発明の実施の形態】
図面を用いて本実施形態のズームレンズについて説明する。
【００１１】
図１〜図５は各々後述する数値実施例１〜５のズームレンズのレンズ断面図、図６〜図１０は各々後述する数値実施例１〜５の各ズーム位置におけるレンズ配置図、図１１〜図２５は各々後述する数値実施例１〜５のズームレンズの広角端、中間、望遠端の収差図である。
【００１２】
一般的にレンズシャッターカメラの撮影系に用いられる正、正、負構成の３群ズームレンズは主に正の第２レンズ群と負の第３レンズ群の空気間隔変化により変倍作用を行い更に望遠に行くに従って正の第１レンズ群と正の第２レンズ群の空気間隔を狭めることにより更なる変倍作用を行うと同時に、変倍時の像面湾曲変動の補正を行うことを特徴としている。
【００１３】
しかしながら更なる高変倍化においては変倍時の色収差及び前記した３群構成のズームレンズにおいても補正困難な像面湾曲の収差変動が問題となってくる。他方、良好な画質を得ようとするならば、各レンズ群で発生する色収差の補正関係を良好に保つために各レンズ群で発生する色収差の量を小さくする必要が有る。そしてその色収差補正のためにレンズ構成枚数を増加させる必要が生じてしまうこととなりレンズ系の小型化や少レンズ枚数構成の要求に対しての達成が困難となっている。
【００１４】
本発明においては、物体側より正の屈折力を有する第１レンズ群、正または負の屈折力を有する第２レンズ群、正または負の屈折力を有する第３レンズ群、正の屈折力を有する第４レンズ群、負の屈折力を有する第５レンズ群を有し、広角から望遠への変倍の際は、前記した各レンズ群間の空気間隔を変化させ、かつ前記第１レンズ群と第５レンズ群及び第２レンズ群と第４レンズ群が一体に光軸上の移動を行ない、多群ズーム構成ながらズーム移動に際して簡易なメカ構成の達成を容易にするとともに、２つのレンズ群を一体化することによって互いの相対偏心量の低減を行い光学性能の維持を可能ならしめており、更に前記第３レンズ群を第２、第４レンズ群間において自由に光軸上移動を行なうことにより光学系を高変倍化したときに生ずる像面湾曲や色収差変動の良好な補正を可能としている。
【００１５】
また、ズームレンズ系の小型化を行う際には、以下の条件式を満足することが望ましい。
【００１６】
０．３　＜｜Ｆ５／Ｆｗ｜＜　０．８　・・・（１）
１．１　＜β５ｗ　＜　２　・・・（２）
但し、　　Ｆｗ　：広角端におけるレンズ全系の焦点距離
Ｆ５　：前記、第５レンズ群の焦点距離
β５ｗ：前記、第５レンズ群の広角端における横倍率
条件式（１）、（２）は、広角端における負の第５レンズ群の屈折力に関するものである。
【００１７】
条件式（１）の上限値を越えて第５レンズ群の負の屈折力が弱くなるか、条件式（２）の上限値を越えて第３レンズ群の広角端における横倍率が大きくなりすぎると、変倍時に第３レンズ群による変倍作用が弱くなってくるため一定の変倍比を得るために各レンズ群の移動量を大きくしなければならなくなり結果としてレンズ全長が長くなってくる。
【００１８】
他方、条件式（１）、（２）のどちらかが下限値を越えるとレンズ全体としてテレフォト系の作用が強まってくるため、バックフォーカスが短く成りすぎると同時に、一定の周辺光量を確保するために第５レンズ群のレンズ外径の大型化をまねいてしまうと同時に像面湾曲や非点収差が発生してくるため良くない。
【００１９】
また更に望ましくは、条件式（１）、（２）の数値範囲は以下のように限定するのがレンズ系の小型化と高い光学性能を両立することに対し良い。
【００２０】
０．４　＜｜Ｆ５／Ｆｗ｜＜　０．７　・・・（１）’
１．２　＜　β５ｗ　＜　１．８　・・・（２）’
より更に光学性能向上のためには、以下の条件式を満足することが望ましい。
【００２１】
０．５　＜　Ｆ２３４ｗ／Ｆｗ　＜　１．３　・・・（３）
但し、　Ｆ２３４ｗ：広角端における前記、第２，第３，第４レンズ群の合成焦点距離
条件式（３）は広角端における第２，第３，第４レンズ群の正の合成屈折力に関するものである。
【００２２】
上限値を越えると、第２，第３，第４レンズ群の正の合成屈折力が弱くなりすぎて球面収差の補正が不足してくると同時に一定の広角端の焦点距離を維持するためにレンズ全長が増加してしまう。
【００２３】
他方、下限値を越えると、負の球面収差が大きく発生してしまい他のレンズ群でこれを補正することが困難となってくる。
【００２４】
また、ズームレンズ系の小型化を達成しつつ高画質化を図るならば、以下の条件式を満足することが良い。
【００２５】
１．０　＜　Ｆ１／Ｆｗ　＜　３．５　・・・（４）
０．４　＜　Ｆ４／Ｆｗ　＜　１．３　・・・（５）
但し、Ｆ１：第１レンズ群の焦点距離
Ｆ４　：第４レンズ群の焦点距離
条件式（４）は広角端における第１レンズ群の正の合成屈折力に関するものである。下限値を越えると、広角端において前記正の合成屈折力が強くなり過ぎレンズ系全体としてテレフォト系の作用が強まってくるため、バックフォーカスが短く成りすぎたり、負の球面が大きく発生してしまいこれを補正することが困難になってくる。
【００２６】
一方、上限値を越えるとレンズ全長の増加を招くとともに広角端の焦点距離を維持するために第３レンズ群の正の屈折力を強くしなければならないため変倍域全域にわたって諸収差をバランス良く補正することが困難になってくる。
【００２７】
条件式（５）は広角端における第４群の正の屈折力に関するものである。条件式（５）の下限値を越えると、広角端においてバックフォーカスが取りずらくなり、結果として第５群のレンズ外径の増大をまねいてしまう。又、上限値を越えると、一定の焦点距離を得るために、他のレンズ群の正の屈折力が強くなってくるため変倍時の収差変動を補正することが難しくなってくる。更に前群の焦点距離をより長くしなければならず、レンズ全長が長くなってくるので良くない。
【００２８】
また前記第４レンズ群はレンズ系の小型化とそれに伴う光学性能劣化を防止するために非球面を有した正レンズとするのが望ましい。
【００２９】
そのとき、前記非球面は、生産性を考慮したときに使用できる硝種を拡大するために複合型非球面（レプリカ非球面）を用いても良い。
【００３０】
本発明に好適な第１レンズ群構成は、物体側より像面側に凸である負メニスカスレンズ、物体側に強い凸面を有する正レンズの２枚構成である。
【００３１】
それにより前記負レンズの物体側の凹面で発生する広角端におけるディストーションと望遠端にて発生する正の球面収差を前記正レンズの物体側の強い凸面にてキャンセル作用を生じさせ、良好な収差補正作用を行っている。
【００３２】
第４レンズ群構成は、物体側より正レンズ、物体側に強い凹面を向けた負レンズで構成するのが良く、第４レンズ群中には非球面を導入することが高い光学性能の達成に望ましい。
【００３３】
また正レンズは比較的屈折力の小さい正レンズとし、そのレンズ面に非球面を有することが温度変化による光学性能劣化を防止するとともに低コストを達成するのに望ましい。
【００３４】
フォーカスは第２，第３，第４レンズ群を一体に光軸上に物体側に移動させることにより行うのが望ましいが、レンズ系全体または他のレンズ群を同時に光軸上に物体側に移動させても良い。
【００３５】
虹彩絞りは第２レンズ群から第４レンズ群間中の空気間隔に配置することが望ましい、それにより第１群レンズ群径と第５レンズ群径の大きさのバランスが取りやすくなり、鏡筒径の大きさを抑えることが可能になる。また同時に高次の軸外収差をバランスよく補正することが容易になる。
【００３６】
但し、小絞り時に軸外の光線ケラレが生じなければ、レンズ群間中のどの空気間隔中に配置しても良い。
【００３７】
また変倍中、虹彩絞りは各レンズ群とは独立した光軸移動を行わせることで理想的な入射瞳位置を得ることが可能となってくるが、メカ機構の簡略化のために任意のレンズ群と一体に移動させても良い。
【００３８】
そして更なる光学性能向上のためレンズ系に更なる非球面の導入や回折光学素子、屈折分布型光学材料を導入しても良い。
【００３９】
また、レンズ群やレンズ群の一部を偏心させることにより手ぶれ等が原因となる像位置変位を補正する作用を持たせるのも良い。
【００４０】
（数値実施例）
次に、本発明の実施形態１〜５に各々対応する数値実施例１〜５を示す。各数値実施例においてｉは物体側からの光学面の順序を示し、Ｒｉは第ｉ番目の光学面（第ｉ面）の曲率半径、Ｄｉは第ｉ面と第ｉ＋１面との間の間隔、Ｎｉとνｉはそれぞれｄ線に対する第ｉ番目の光学部材の屈折率、アッベ数を示す。ｆは焦点距離、ＦＮｏはＦナンバー、ωは半画角である。またｋを離心率、Ａ、Ｂ、Ｃ、Ｄ、Ｅを非球面係数、光軸からの高さｈの位置での光軸方向の変位を面頂点を基準にしてｘとするとき、非球面形状は、
ｘ＝（ｈ^２／Ｒ）／［１＋［１−（１＋ｋ）（ｈ／Ｒ）^２］^１／２］＋Ａｈ^２＋Ｂｈ^４
＋Ｃｈ^６＋Ｄｈ^８＋Ｅｈ^１０
で表示される。但しＲは曲率半径である。また、例えば「ｅ−Ｚ」の表示は「１０^−Ｚ」を意味する。又、各数値実施例における上述した条件式との対応を表１に示す。
【００４１】
数値実施例１及び２は、物体側より、正、負，正、正、負レンズ群構成のズームレンズである。
【００４２】
数値実施例３は、物体側より、正、負，負、正、負レンズ群構成のズームレンズである。
【００４３】
数値実施例４及び５は、物体側より、正、正，負、正、負レンズ群構成のズームレンズである。
【００４４】
【外１】

【００４５】
【外２】

【００４６】
【外３】

【００４７】
【外４】

【００４８】
【外５】

【００４９】
【表１】

【００５０】
次に本発明のズームレンズを撮影光学系として用いたレンズシャッター形式のコンパクトカメラの実施形態を図２６を用いて説明する。
【００５１】
図２６において、１０はコンパクトカメラ本体、１１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、１２はカメラ本体に内蔵されたストロボ、１３は外部式ファインダー、１４はシャッターボタンである。
【００５２】
このように本発明のズームレンズをレンズシャッター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。
【００５３】
【発明の効果】
以上説明したように、本発明によれば、物体側より正、正または負、正または負、正、負レンズ群を有するズームレンズにおいて、変倍比が約４．５倍と高変倍ながら好適な光学配置を行うことにより、コンパクトでかつ良好な光学性能を維持できるズームレンズ光学系を達成することができる。
【図面の簡単な説明】
【図１】本発明の数値実施例１のレンズ断面図
【図２】本発明の数値実施例２のレンズ断面図
【図３】本発明の数値実施例３のレンズ断面図
【図４】本発明の数値実施例４のレンズ断面図
【図５】本発明の数値実施例５のレンズ断面図
【図６】本発明の数値実施例１の各ズーム位置におけるレンズ配置図
【図７】本発明の数値実施例２の各ズーム位置におけるレンズ配置図
【図８】本発明の数値実施例３の各ズーム位置におけるレンズ配置図
【図９】本発明の数値実施例４の各ズーム位置におけるレンズ配置図
【図１０】本発明の実施形態５の各ズーム位置におけるレンズ配置図
【図１１】本発明の数値実施例１の広角端の収差図
【図１２】本発明の数値実施例１の中間の収差図
【図１３】本発明の数値実施例１の望遠端の収差図
【図１４】本発明の数値実施例２の広角端の収差図
【図１５】本発明の数値実施例２の中間の収差図
【図１６】本発明の数値実施例２の望遠端の収差図
【図１７】本発明の数値実施例３の広角端の収差図
【図１８】本発明の数値実施例３の中間の収差図
【図１９】本発明の数値実施例３の望遠端の収差図
【図２０】本発明の数値実施例４の広角端の収差図
【図２１】本発明の数値実施例４の中間の収差図
【図２２】本発明の数値実施例４の望遠端の収差図
【図２３】本発明の数値実施例５の広角端の収差図
【図２４】本発明の数値実施例５の中間の収差図
【図２５】本発明の数値実施例５の望遠端の収差図
【図２６】本発明のズームレンズを撮影光学系として用いたレンズシャッター形式のコンパクトカメラの要部概略図
【符号の説明】
Ｂ１、Ｂ２、Ｂ３、Ｂ４、Ｂ５　それぞれ第１レンズ群、第２レンズ群、第３レンズ群、第４レンズ群、第５レンズ群
ＳＰ　光彩絞り
ＩＰ　結像面
ＳＡ　球面収差
ＡＳ　非点収差
ＤＩＳＴ　歪曲収差
ＣＨＲＯ　倍率色収差
ｄ−ＬＩＮＥ　ｄ線
ｇ−ＬＩＮＥ　ｇ線
ΔＳ　サジタル像面
ΔＭ　メリディオナル像面[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention achieves a high zoom ratio and compact zoom lens having a zoom ratio of about 4.5, which is particularly suitable as a photographic lens for a compact camera in a photographic optical system such as a photographic lens and a video camera lens. .
[0002]
[Prior art]
2. Description of the Related Art In recent years, more compact and high-performance photographing optical systems have been required for photographic lenses and video lenses.
[0003]
In particular, in addition to the demand for high-magnification imaging optics for lens shutter cameras, the development of peripheral mechanical mechanisms and electrical circuits has made it easier to achieve camera miniaturization. It is rare.
[0004]
As a high-magnification photographing optical system for a lens shutter camera, for example, JP-A-8-262325 and JP-A-9-120028 disclose a positive, positive, and negative three-group zoom lens.
[0005]
Japanese Patent No. 2832376 discloses a zoom lens having a zoom ratio of about 3 times in a four-group configuration including positive, negative, positive, and negative, and JP-A-11-352401 discloses a zoom lens having a zoom ratio of about 3.8. I have.
[0006]
[Problems to be solved by the invention]
However, in the above-mentioned proposal of the zoom lens having the three groups of positive, positive, and negative, the zoom lens cannot be said to be a high zoom ratio and compact zoom lens because of the large number of lens components.
[0007]
In addition, the zoom ratio of the four-group zoom lens of positive, negative, positive, and negative is about 3 or 3.8, and the number of lens elements is large. In addition, there is a demand for an optical arrangement to achieve a compact and high-quality zoom lens.
[0008]
The present invention achieves a compact zoom lens optical system while maintaining high image quality by performing appropriate zoom lens configuration and lens group arrangement.
[0009]
[Means for Solving the Problems]
The present invention provides a first lens group having a positive refractive power from the object side, a second lens group having a positive or negative refractive power, a third lens group having a positive or negative refractive power, and a third lens group having a positive refractive power. The zoom lens system includes a fourth lens group and a fifth lens group having a negative refractive power, and zooming from wide-angle to telephoto is performed by integrating the first lens group and the fifth lens group and the second lens group and the fourth lens. It is characterized in that the groups are moved together on the optical axis toward the object side and the air gap between the lens groups is changed.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The zoom lens according to the present embodiment will be described with reference to the drawings.
[0011]
1 to 5 are lens sectional views of zoom lenses of Numerical Examples 1 to 5 to be described later, respectively, and FIGS. 6 to 10 are lens arrangement diagrams at zoom positions of Numerical Examples 1 to 5 to be described later. FIG. 25 is an aberration diagram at a wide-angle end, a middle position, and a telephoto end of zoom lenses according to Numerical Examples 1 to 5 described below.
[0012]
In general, a three-group zoom lens having a positive, positive, and negative configuration generally used in a photographing system of a lens shutter camera performs a zooming function mainly by a change in an air gap between a positive second lens group and a negative third lens group. It is characterized in that further zooming action is performed by narrowing the air gap between the first positive lens unit and the second positive lens unit as the distance to the telephoto increases, and at the same time, the field curvature fluctuation at the time of zooming is corrected. I have.
[0013]
However, when the zoom ratio is further increased, chromatic aberration at the time of zooming and aberration fluctuation of the curvature of field, which is difficult to correct even in the above-described three-unit zoom lens, become problems. On the other hand, in order to obtain good image quality, it is necessary to reduce the amount of chromatic aberration generated in each lens group in order to maintain a good correction relationship of chromatic aberration generated in each lens group. In order to correct the chromatic aberration, it is necessary to increase the number of lens components, which makes it difficult to meet the demands for downsizing of the lens system and the configuration of a small number of lenses.
[0014]
In the present invention, the first lens group having a positive refractive power from the object side, the second lens group having a positive or negative refractive power, the third lens group having a positive or negative refractive power, and the positive refractive power A fourth lens group having a negative refractive power, a fifth lens group having a negative refractive power, and when changing magnification from wide angle to telephoto, the air gap between the lens groups is changed, and the first lens group is changed. And the fifth lens group and the second lens group and the fourth lens group move integrally on the optical axis, thereby facilitating the achievement of a simple mechanical configuration during zoom movement in a multi-group zoom configuration, and the two lens groups. By reducing the relative eccentricity of each other by maintaining the optical performance, it is possible to maintain the optical performance. Further, the third lens group can be freely moved on the optical axis between the second and fourth lens groups. When the magnification of the optical system is increased by Thereby making it possible to preferably correct sly curvature and chromatic aberration fluctuations.
[0015]
When downsizing the zoom lens system, it is desirable to satisfy the following conditional expressions.
[0016]
0.3 <| F5 / Fw | <0.8 (1)
1.1 <β5w <2 ... (2)
Where Fw: focal length of the entire lens system at the wide-angle end F5: focal length of the fifth lens group β5w: the lateral magnification conditional expressions (1) and (2) at the wide-angle end of the fifth lens group are: This relates to the refractive power of the negative fifth lens unit at the end.
[0017]
The negative refractive power of the fifth lens unit is weakened beyond the upper limit of conditional expression (1), or the lateral magnification at the wide angle end of the third lens unit is too large beyond the upper limit of conditional expression (2). Then, during zooming, the zooming action of the third lens unit is weakened, so that the moving amount of each lens unit must be increased in order to obtain a constant zoom ratio, and as a result, the overall length of the lens becomes longer. .
[0018]
On the other hand, if either of the conditional expressions (1) and (2) exceeds the lower limit, the effect of the telephoto system as a whole becomes stronger, so that the back focus becomes too short and at the same time, a constant peripheral light amount is secured. In addition, this leads to an increase in the outer diameter of the lens of the fifth lens group, and also causes curvature of field and astigmatism, which is not good.
[0019]
More preferably, the numerical ranges of the conditional expressions (1) and (2) are limited as follows in order to achieve both miniaturization of the lens system and high optical performance.
[0020]
0.4 <| F5 / Fw | <0.7 (1) '
1.2 <β5w <1.8 (2) ′
In order to further improve the optical performance, it is desirable to satisfy the following conditional expressions.
[0021]
0.5 <F234w / Fw <1.3 (3)
F234w: The combined focal length conditional expression (3) of the second, third, and fourth lens groups at the wide-angle end relates to the positive combined refractive power of the second, third, and fourth lens groups at the wide-angle end. It is.
[0022]
When the value exceeds the upper limit, the positive combined refractive power of the second, third, and fourth lens units becomes too weak to correct spherical aberration, and at the same time, to maintain a constant focal length at the wide-angle end. The overall length of the lens increases.
[0023]
On the other hand, if the lower limit is exceeded, a large amount of negative spherical aberration occurs, and it becomes difficult to correct this with another lens group.
[0024]
In order to achieve high image quality while achieving downsizing of the zoom lens system, it is preferable to satisfy the following conditional expressions.
[0025]
1.0 <F1 / Fw <3.5 (4)
0.4 <F4 / Fw <1.3 (5)
Here, F1: focal length of the first lens group F4: focal length of the fourth lens group Conditional expression (4) relates to the positive combined refractive power of the first lens group at the wide-angle end. If the lower limit value is exceeded, the positive combined refractive power at the wide-angle end becomes too strong and the effect of the telephoto system as a whole lens system becomes stronger, so that the back focus becomes too short or a large negative spherical surface is generated. It becomes difficult to correct this.
[0026]
On the other hand, when the value exceeds the upper limit, the total length of the lens is increased, and the positive refractive power of the third lens unit must be increased in order to maintain the focal length at the wide-angle end. It becomes difficult to correct.
[0027]
Conditional expression (5) relates to the positive refractive power of the fourth unit at the wide-angle end. If the lower limit of conditional expression (5) is exceeded, it becomes difficult to obtain a back focus at the wide-angle end, which results in an increase in the outer diameter of the fifth lens unit. If the value exceeds the upper limit, the positive refractive power of the other lens units increases in order to obtain a constant focal length, so that it becomes difficult to correct aberration fluctuations during zooming. Furthermore, the focal length of the front group must be made longer, which is not good because the overall length of the lens becomes longer.
[0028]
It is desirable that the fourth lens group be a positive lens having an aspheric surface in order to reduce the size of the lens system and prevent the optical performance from deteriorating.
[0029]
At this time, a composite aspherical surface (replica aspherical surface) may be used as the aspherical surface in order to expand the types of glass that can be used in consideration of productivity.
[0030]
The first lens group configuration suitable for the present invention is a two-lens configuration including a negative meniscus lens convex on the image surface side from the object side and a positive lens having a strong convex surface on the object side.
[0031]
Thereby, the distortion at the wide-angle end generated at the concave surface on the object side of the negative lens and the positive spherical aberration generated at the telephoto end have a canceling effect at the strong convex surface on the object side of the positive lens, thereby achieving good aberration correction. Is working.
[0032]
It is preferable that the fourth lens group is composed of a positive lens from the object side and a negative lens with a strong concave surface facing the object side. Introducing an aspheric surface into the fourth lens group achieves high optical performance. desirable.
[0033]
Further, it is desirable that the positive lens has a relatively small refractive power and has an aspherical surface on its lens surface in order to prevent deterioration of optical performance due to a temperature change and to achieve low cost.
[0034]
It is desirable to perform focusing by moving the second, third, and fourth lens groups integrally on the optical axis toward the object side. However, the entire lens system or another lens group is simultaneously moved on the optical axis toward the object side. You may let it.
[0035]
It is desirable that the iris diaphragm is arranged at an air space between the second lens unit and the fourth lens unit. This makes it easier to balance the diameters of the first lens unit and the fifth lens unit, and makes it easy to balance the lens barrel. The size of the diameter can be reduced. At the same time, it becomes easy to correct high-order off-axis aberrations in a well-balanced manner.
[0036]
However, if off-axis light-ray vignetting does not occur at the time of a small stop, it may be arranged in any air interval between the lens groups.
[0037]
Also, during zooming, the iris diaphragm can obtain an ideal entrance pupil position by moving the optical axis independently of each lens group. It may be moved integrally with the lens group.
[0038]
Then, in order to further improve the optical performance, a further aspherical surface may be introduced into the lens system, or a diffractive optical element or a refractive distribution type optical material may be introduced.
[0039]
It is also possible to provide an effect of correcting image position displacement caused by camera shake or the like by decentering a lens group or a part of the lens group.
[0040]
(Numerical example)
Next, Numerical Examples 1 to 5 respectively corresponding to Embodiments 1 to 5 of the present invention will be described. In each numerical example, i indicates the order of the optical surface from the object side, Ri is the radius of curvature of the i-th optical surface (i-th surface), Di is the distance between the i-th surface and the (i + 1) -th surface, Ni and νi represent the refractive index and Abbe number of the i-th optical member with respect to the d-line, respectively. f is the focal length, FNo is the F number, and ω is the half angle of view. When k is the eccentricity, A, B, C, D, and E are aspherical coefficients, and 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, the aspherical surface The shape is
^{x = (h 2 / R)} / [1+ [1- (1 + k) (h / R) 2] 1/2] + Ah 2 + Bh 4
+ Ch ⁶ + Dh ⁸ + Eh ¹⁰
Displayed with. Here, R is a radius of curvature. Further, for example, "e-Z" means ^{"10 -Z".} Table 1 shows the correspondence between the numerical expressions and the conditional expressions described above.
[0041]
Numerical Embodiments 1 and 2 are zoom lenses having a positive, negative, positive, positive, and negative lens group configuration from the object side.
[0042]
Numerical example 3 is a zoom lens having a positive, negative, negative, positive, and negative lens group configuration from the object side.
[0043]

Numerical Embodiments

4 and 5 are zoom lenses having a positive, positive, negative, positive, and negative lens unit configuration from the object side.
[0044]
[Outside 1]

[0045]
[Outside 2]

[0046]
[Outside 3]

[0047]
[Outside 4]

[0048]
[Outside 5]

[0049]
[Table 1]

[0050]
Next, an embodiment of a lens shutter type compact camera using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG.
[0051]
In FIG. 26, reference numeral 10 denotes a compact camera main body, 11 denotes a photographing optical system constituted by the zoom lens of the present invention, 12 denotes a flash built in the camera main body, 13 denotes an external viewfinder, and 14 denotes a shutter button.
[0052]
As described above, by applying the zoom lens of the present invention to an optical device such as a lens shutter camera, an optical device having a small size and high optical performance is realized.
[0053]
【The invention's effect】
As described above, according to the present invention, in a zoom lens having a positive, positive or negative, positive or negative, positive, or negative lens group from the object side, the zoom ratio is as high as about 4.5, and the zoom ratio is high. By performing a suitable optical arrangement, it is possible to achieve a zoom lens optical system that is compact and can maintain good optical performance.
[Brief description of the drawings]
1 is a sectional view of a lens according to a numerical example 1 of the present invention. FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention. FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention. FIG. 5 is a sectional view of a lens according to a fourth numerical embodiment of the present invention. FIG. 5 is a sectional view of a lens according to a fifth numerical embodiment of the present invention. FIG. FIG. 8 is a lens arrangement diagram at each zoom position in Numerical Example 2 of the present invention. FIG. 9 is a lens arrangement diagram at each zoom position in Numerical Example 3 of the present invention. FIG. 10 is a lens arrangement diagram at each zoom position in Embodiment 5 of the present invention. FIG. 11 is an aberration diagram at a wide-angle end of Numerical Embodiment 1 of the present invention. FIG. 12 is an intermediate diagram of Numerical Embodiment 1 of the present invention. FIG. 13 is an aberration diagram at the telephoto end in Numerical Example 1 of the present invention. FIG. 15 is an aberration diagram at the wide-angle end of Numerical Embodiment 2 of the present invention. FIG. 15 is an intermediate aberration diagram of Numerical Embodiment 2 of the present invention. FIG. 16 is an aberration diagram at a telephoto end of Numerical Embodiment 2 of the present invention. FIG. 18 is an aberration diagram at the wide angle end of Numerical Embodiment 3 of the present invention. FIG. 18 is an intermediate aberration diagram of Numerical Embodiment 3 of the present invention. FIG. 19 is an aberration diagram at a telephoto end of Numerical Embodiment 3 of the present invention. FIG. 21 is an aberration diagram at the wide angle end of Numerical Embodiment 4 of the present invention. FIG. 21 is an intermediate aberration diagram of Numerical Embodiment 4 of the present invention. FIG. 22 is an aberration diagram at a telephoto end of Numerical Embodiment 4 of the present invention. FIG. 24 is an aberration diagram at the wide angle end of Numerical Embodiment 5 of the present invention. FIG. 24 is an intermediate aberration diagram of Numerical Embodiment 5 of the present invention. FIG. 25 is an aberration diagram at a telephoto end of Numerical Embodiment 5 of the present invention. Schematic diagram of the main part of a lens shutter type compact camera using the zoom lens of the invention as a photographing optical system.
B1, B2, B3, B4, B5 First lens group, second lens group, third lens group, fourth lens group, fifth lens group SP Iris stop IP Image plane SA Spherical aberration AS Astigmatism DIST Distortion Aberration CHRO Magnification chromatic aberration d-LINE d-line g-LINE g-line ΔS Sagittal image plane ΔM Meridional image plane

Claims

A first lens group having a positive refractive power from the object side, a second lens group having a positive or negative refractive power, a third lens group having a positive or negative refractive power, a fourth lens group having a positive refractive power A fifth lens group having a negative refractive power, and zooming from wide angle to telephoto is performed by integrating the first lens group and the fifth lens group and integrating the second lens group and the fourth lens group. 1. A zoom lens and an optical apparatus having the zoom lens, wherein the zoom lens is moved by moving along the optical axis toward the object side and changing the air gap between the lens groups.

2. The zoom lens according to claim 1, wherein the following conditional expression is satisfied, and an optical apparatus having the zoom lens.
0.3 <| F5 / Fw | <0.8
1.1 <β5w <2
Here, Fw: focal length of the entire lens system at the wide-angle end F5: focal length of the fifth lens group β5w: lateral magnification of the fifth lens group at the wide-angle end

2. The zoom lens according to claim 1, wherein the following conditional expression is satisfied and an optical apparatus having the zoom lens.
0.5 <F234w / Fw <1.3
Where F234w is the combined focal length of the second, third, and fourth lens groups at the wide-angle end.

The zoom lens according to claim 1, wherein the following conditional expression is satisfied, and an optical apparatus having the same.
1.0 <F1 / Fw <3.5
0.4 <F4 / Fw <1.3
Where F1: focal length of the first lens group F4: focal length of the fourth lens group

The zoom lens according to claim 1, wherein the second lens group has a negative refractive power, and the third lens group has a positive refractive power.

The zoom lens according to claim 1, wherein the second lens group has a negative refractive power, and the third lens group has a negative refractive power.

The zoom lens according to claim 1, wherein the second lens group has a positive refractive power, and the third lens group has a negative refractive power.

2. The zoom lens according to claim 1, wherein the fourth lens group includes a positive lens having an aspheric surface.

An optical apparatus comprising the zoom lens according to any one of claims 1 to 8.