JP4478247B2 - Zoom lens - Google Patents

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Publication number
JP4478247B2
JP4478247B2 JP19151499A JP19151499A JP4478247B2 JP 4478247 B2 JP4478247 B2 JP 4478247B2 JP 19151499 A JP19151499 A JP 19151499A JP 19151499 A JP19151499 A JP 19151499A JP 4478247 B2 JP4478247 B2 JP 4478247B2
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Japan
Prior art keywords
lens
group
positive
refractive power
negative
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JP19151499A
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JP2001021804A (en
JP2001021804A5 (en
Inventor
清司 深見
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Canon Inc
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Canon Inc
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Priority to JP19151499A priority Critical patent/JP4478247B2/en
Priority to US09/562,933 priority patent/US6545818B2/en
Priority to EP00303851A priority patent/EP1052535B1/en
Priority to DE60033989T priority patent/DE60033989T2/en
Publication of JP2001021804A publication Critical patent/JP2001021804A/en
Publication of JP2001021804A5 publication Critical patent/JP2001021804A5/ja
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Publication of JP4478247B2 publication Critical patent/JP4478247B2/en
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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B15/00Optical objectives with means for varying the magnification
    • G02B15/14Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
    • G02B15/144Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only
    • G02B15/1441Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only the first group being positive
    • G02B15/144113Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only the first group being positive arranged +-++

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)

Description

【0001】
【発明の属する技術分野】
本発明はテレビカメラ、ビデオカメラ、写真用カメラ、そしてデジタルカメラ等に好適なズームレンズに関し、特に第1群中の一部のレンズ群でフォーカスを行う、いわゆるインナーフォーカス式を用いることにより至近撮影距離が短く、被写体距離全般にわたり、高い光学性能を有したズームレンズに関するものである。
【0002】
【従来の技術】
従来よりテレビカメラやビデオカメラ等のズームレンズにはカメラ全体の小型化に伴い、レンズ系全体が小型で、しかも大口径比、高変倍比、そして広角のものが要求されている。
【0003】
ズームレンズのうち物体側から順に合焦用の正の屈折力の第1群(合焦レンズ群)変倍用の負の屈折力の第2群(変倍レンズ群)、変倍に伴って変動する像面を補正する為の正又は負の屈折力の第3群(補正レンズ群)、開口絞り、そして結像用の正の屈折力の第4群(リレーレンズ群)の4つのレンズ群より成る、所謂4群ズームレンズにおいて、第1群中の一部のレンズを移動させてフォーカスを行う、インナーフォーカス式を採用したものが、特公昭59−4686号公報、特開平6−242378号公報等で提案されている。
【0004】
同公報等では第1群を負の屈折力の第11群、正の屈折力の第12群、そして正の屈折力の第13群の3つのレンズ群より構成し、無限遠物体から至近距離物体にかけてのフォーカスを第12群を像面側へ移動させて行っている。
【0005】
一般にインナーフォーカス式のズームレンズは第1群全体を移動させてフォーカスを行うズームレンズに比べて第1群の有効径が小さくなり、レンズ系全体の小型化が容易となり、又近接撮影、特に極近接撮影が容易となり、更に比較的小型軽量のレンズ群を移動させて行っているのでレンズ群の駆動力が小さくてすみ、迅速な焦点合わせができるなどの特徴を有している。
【0006】
【発明が解決しようとする課題】
一般にズームレンズにおいてインナーフォーカス方式を採用すると前述の如くレンズ系全体が小型化され、又迅速なるフォーカスが可能となり、更に近接撮影が容易になるなどの特徴が得られる。
【0007】
しかしながら反面、大口径比(Fナンバー1.6)で高変倍比(ズーム比8〜15程度)で至近物体距離を短縮しつつ広角化を行うと歪曲収差の増大、特に広角端における負の歪曲収差が増大してしまうという問題が顕著になる。
【0008】
これは、至近物体距離を短縮して広角化を達成しようとすると第1群中の最も物体側にあるレンズ群(第11群)のパワーを強める必要があり、これが広角端の負の歪曲収差を増大させるからである。
【0009】
一般に全変倍範囲にわたり高い光学性能を得るには、例えば各レンズ群のレンズ枚数を増加させて収差補正上の自由度を増やすことが必要となってくる。
【0010】
この為、大口径で広画角、高変倍比のズームレンズを達成しようとすると、レンズ枚数が増加し、レンズ系全体が大型化してくるという問題点が生じてきて、小型軽量化の要望に応えることができなくなってくる。
【0011】
本発明は、4群ズームレンズを構成するフォーカス用の第1群の一部のレンズ群を光軸上移動させてフォーカスを行うインナーフォーカスを採用しつつ、広画角化及び至近物体距離の短縮、及び高変倍化を図るとともに、レンズ系全体の小型化を図りつつ広角端の負の歪曲収差がよく補正された高い光学性能のズームレンズの提供を目的とする。
【0012】
請求項1の発明のズームレンズは、物体側より順に正の屈折力の第1群、変倍用の負の屈折力の第2群、変倍に伴う像面変動を補正する正又は負の屈折力の第3群、開口絞り、そして変倍中固定の結像作用を有する第4群とを有したズームレンズにおいて、該第2群は変倍の際に結像倍率が−1倍を含む領域内で変化し、該第1群は合焦時に固定で負の屈折力の第11群と、合焦時に光軸に沿って移動する第12群と、合焦時固定の正の屈折力の第13群を有し、第11群の焦点距離をf11、第12群の焦点距離をf12、第13群の焦点距離をf13、第1群の焦点距離をf1としたとき
1.2≦|f11/f1|≦1.7 ‥‥‥(1a)
4.451≦f12/f1≦7.0 ‥‥‥(2a)
1.1≦f13/f1≦1.7 ‥‥‥(3a)
を満足し、更に第12群中、軸上光束の最大入射高をhT、広角端での最大画角の軸外光束の最大入射高をhWとしたとき、hW>hTを満足する少なくとも1つのレンズ面に、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が強くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が弱くなる形状の非球面を有し、かつ第13群には、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が弱くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が強くなる形状の非球面を少なくとも1面有することを特徴としている。
請求項6の発明は、物体側より順に正の屈折力の第1群、変倍用の負の屈折力の第2群、変倍に伴う像面変動を補正する正又は負の屈折力の第3群、開口絞り、そして変倍中固定の結像作用を有する第4群とを有したズームレンズにおいて、該第2群は変倍の際に結像倍率が−1倍を含む領域内で変化し、該第1群は合焦時に固定で負の屈折力の第11群と、合焦時に光軸に沿って移動する第12群と、合焦時固定の正の屈折力の第13群を有し、第11群の焦点距離をf11、第12群の焦点距離をf12、第13群の焦点距離をf13、第1群の焦点距離をf1としたとき
1.2≦|f11/f1|≦1.259 ‥‥‥(1b)
4.0≦f12/f1≦7.0 ‥‥‥(2b)
1.1≦f13/f1≦1.7 ‥‥‥(3a)
を満足し、更に第12群中、軸上光束の最大入射高をhT、広角端での最大画角の軸外光束の最大入射高をhWとしたとき、hW>hTを満足する少なくとも1つのレンズ面に、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が強くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が弱くなる形状の非球面を有し、かつ第13群には、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が弱くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が強くなる形状の非球面を少なくとも1面有することを特徴としている。
請求項7の発明は、物体側より順に正の屈折力の第1群、変倍用の負の屈折力の第2群、変倍に伴う像面変動を補正する正又は負の屈折力の第3群、開口絞り、そして変倍中固定の結像作用を有する第4群とを有したズームレンズにおいて、該第2群は変倍の際に結像倍率が−1倍を含む領域内で変化し、該第1群は合焦時に固定で負の屈折力の第11群と、合焦時に光軸に沿って移動する第12群と、合焦時固定の正の屈折力の第13群を有し、第11群の焦点距離をf11、第12群の焦点距離をf12、第13群の焦点距離をf13、第1群の焦点距離をf1としたとき
1.2≦|f11/f1|≦1.7 ‥‥‥(1a)
4.0≦f12/f1≦7.0 ‥‥‥(2b)
1.1≦f13/f1≦1.605 ‥‥‥(3b)
を満足し、更に第12群中、軸上光束の最大入射高をhT、広角端での最大画角の軸外光束の最大入射高をhWとしたとき、hW>hTを満足する少なくとも1つのレンズ面に、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が強くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が弱くなる形状の非球面を有し、かつ第13群には、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が弱くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が強くなる形状の非球面を少なくとも1面有することを特徴としている。
【0013】
請求項2の発明は請求項1の発明において、前記第12群は1つの正の第12pレンズを有しており、該正の第12pレンズの材質の屈折力をN12pとし、前記第13群は1つの負の第13nレンズを有しており、該負の第13nレンズの材質の屈折力をN13nとし、広角端における前記第2群の横倍率をβVWとしたとき
N12p≦1.67 ‥‥‥(4)
1.76≦N13n ‥‥‥(5)
−0.4≦βVW≦−0.2 ‥‥‥(6)
を満足することを特徴としている。
【0014】
【発明の実施の形態】
図1,図6,図11は各々本発明の参考例1と数値実施例1,2の広角端におけるレンズ断面図である。
【0015】
図2,図3,図4,図5は本発明の参考例1のf=5.72で無限遠物体、f=22.88で無限遠物体、f=45.77で無限遠物体、f=45.77で至近距離物体での収差図である。
【0016】
図7,図8,図9,図10は本発明の数値実施例のf=5.72で無限遠物体、f=22.88で無限遠物体、f=45.77で無限遠物体、f=45.77で至近距離物体での収差図である。
【0017】
図12,図13,図14,図15は本発明の数値実施例のf=6.7で無限遠物体、f=26.63で無限遠物体、f=99.83で無限遠物体、f=99.83で至近距離物体での収差図である。
【0018】
図中、Fは第1群としての正の屈折力のフォーカス群(第1レンズ群)であり、合焦(フォーカス)時固定で負の屈折力の第11群F11と、正の屈折力で少なくとも1つの正の第12pレンズを有する光軸上移動してフォーカスを行う第12群F12、そして合焦時固定で正の屈折力で少なくとも1つの負の第13nレンズを有する第13群F13とを有している。
【0019】
無限遠物体から至近距離物体へのフォーカスは第12群F12を像面側へ移動させて行っている。Vは第2群としての変倍用の負の屈折力のバリエーター(第2群)であり、光軸上像面側へ単調に移動させることにより、広角端(ワイド)から望遠端(テレ)への変倍を行っている。
【0020】
第2群Vは広角端から望遠端への変倍の際に結像倍率が−1倍を含む領域内で変化させている。Cは第3群としての正又は負の屈折力のコンペンセーターであり、変倍に伴う像面変動を補正する為に、物体側へ直線的に又は物体側へ凸状の軌跡を有して移動している。
【0021】
SPは開口絞り、Rは第4群としての正の屈折力のリレー群である。Gは色分解プリズムや光学フィルター等であり、同図ではガラスブロックとして示している。
【0022】
本発明のような4群ズームレンズにおいて最も物体側の第1群全体を移動させて焦点合わせを行う、前玉フォーカス方式はどのような焦点距離においても同一物体距離であれば第1群の繰り出し量が一定になるため、レンズ鏡筒構造が簡単になるという特長がある。
【0023】
しかしながら第1群が正の屈折力を有し、広画角を含むズームレンズにおいては広角端において至近距離物体に焦点合わせをする際、第1群が物体側へ移動するため、軸外光束を確保するために第1群の有効径が増大し、又比較的重量の重い第1群を移動させるため駆動トルクが増大し、迅速なる合焦が難しくなってくる。
【0024】
又、4群ズームレンズにおいて、大口径化を図ろうとすると、前玉レンズ群(前玉)の有効径が著しく増大してくる。これは軸上光線の入射高が増加するためであり、これが原因となってズーミングやフォーカシングによる球面収差や色収差をはじめとする諸収差の発生量が多くなる。一般にこの時の諸収差を良好に補正するのが難しい。
【0025】
これに対しレンズ枚数を増やして設計の自由度を増加させると、レンズ系全体が大型化し重量や製造コストが増加してくる。
【0026】
そこで本発明においては各レンズ群を前述の如く構成し、かつ条件式(1a),(2a),(3a)又は(1b),(2b),(3a)又は(1a),(2b),(3b)を満足するとともに、無限遠物体から至近距離物体への焦点合わせを第1群中の第12群F12を像面側へ移動させて行うインナーフォーカス方式を採用することによって第1群Fのレンズ有効径の増大を防止し、レンズ系全体の小型化を図り、更に撮影可能な至近距離の短縮化を図っている。ここで条件式(1a),(1b)を条件式(1)と、条件式(2a),(2b)を条件式(2)と、条件式(3a),(3b)を条件式(3)と総称する。
【0027】
特に第1群を構成する第11群F11,第12群F12,第13群F13の3つのレンズ群と第1群Fとの焦点距離の比を条件式(1),(2),(3)を満足するように設定することによりレンズ系全体の小型化と広画角化を同時に達成している。
【0028】
次に前述の条件式(1)〜(3)の技術的意味について説明する。条件式(1)の下限値を越えるとレンズ系の小型化には有利になるが広角端において負の歪曲収差が増大し、後述する非球面を導入しても良好なる収差補正が難しくなる。
【0029】
条件式(2)の下限値を越えると望遠端において、物体距離が変化したときの球面収差の変動が増加し、良好な収差補正のためには、移動レンズ群の構成枚数を増やす必要が生じてくる。
【0030】
条件式(3)の下限値を越えると後述する非球面を導入したとしても望遠端の球面収差の良好なる補正が困難になるだけでなく、広角端からズーム中間にかけての歪曲収差の変動(樽型から糸巻き型への変化)が大きくなり好ましくない。
【0031】
又、条件式(1),(2)及び(3)のいずれの上限値を越えると収差補正上は有利になるが前玉径が増大し、フォーカスの際の第12群の移動量が増大し、大きな空間が必要になり、レンズ系全体の小型軽量化が難しくなってくる。
【0032】
更に本発明では、第12群と第13群に非球面を導入することにより広画角化をはかりつつ、全変倍範囲にわたり画面全体の光学性能を良好に維持している。
【0033】
第12群に施す非球面は軸上光束の最大入射高をhT、広角端での最大画角の軸外光束の最大入射高をhWとしたとき、hW>hTを満足する少なくとも1つのレンズ面に、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が強くなるが非球面、負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が弱くなる形状の非球面を施している。
【0034】
この非球面により広角端で増大する負の歪曲収差を軽減している。又第13群に施す非球面は、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が弱くなる非球面、負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が強くなる形状の非球面とするのが良い。これにより望遠端における球面収差を良好に補正している。又、広角端からズーム中間へズームした時に歪曲収差が負から正へ大きく変化するのを軽減している。
【0035】
本発明に係るインナーフォーカス式を用いたズームレンズは以上の諸条件を満足することにより達成されるが、更に物体距離全般にわたり、かつ全変倍範囲にわたり良好なる光学性能を得るには次の諸条件のうちの少なくとも1つを満足させるのが良い。
【0036】
(ア−1)前記第12群は1つの正の第12pレンズを有しており、該正の第12pレンズの材質の屈折力をN12pとし、前記第13群は1つの負の第13nレンズを有しており、該負の第13nレンズの材質の屈折力をN13nとし、広角端における前記第2群の横倍率をβVWとしたとき
N12p≦1.67 ‥‥‥(4)
1.76≦N13n ‥‥‥(5)
−0.4≦βVW≦−0.2 ‥‥‥(6)
を満足することである。
【0037】
条件式(4)を外れて第12群の正の第12pレンズの材質の屈折率が高くなると、該第12pレンズの曲率が小さくなり、非球面を導入しても広角端での負の歪曲収差の補正が困難になり、又正のペッツバール和が減少し、第2群で発生する負のペッツバール和を補正するのが困難になる。
【0038】
条件式(5)は望遠端における球面収差の補正に関する式で、下限を超えて負の第13nレンズの材質の屈折率が低くなると良好な球面収差の補正が困難になる。
【0039】
条件式(6)は前玉に対する第2群以降のパワーを規定する条件式であり、下限を超えると収差補正上は有利になるが、高変倍比の達成が困難になり、上限を超えると小型化、高変倍比化には有利であるが、収差補正上の困難さが増大してしまうので良くない。
【0040】
(ア−2) 物体側より順に前記第11群は物体側へ凸面を向けたメニスカス状の少なくとも1つの負レンズ、両レンズ面が凹面の負レンズ、そして物体側へ凸面を向けた正レンズを有していることである。
【0041】
(ア−3) 物体側より順に前記第12群は像面側に凸面を向けた正レンズより成り、又は像面側に凸面を向けた正レンズ、正レンズと負レンズとの接合レンズより成り、又は2つの正レンズと負レンズと正レンズとの接合レンズより成っていることである。
【0042】
(ア−4)物体側より順に前記第13群は正レンズと負レンズとの接合レンズ、負レンズと正レンズとの接合レンズ、そして正レンズより成り、又は負レンズと正レンズとの接合レンズ、そして正レンズより成り、又は負レンズと正レンズとの接合レンズ、正レンズそして正レンズより成っていることである。
【0043】
(ア−5)第12群の非球面と第13群の非球面に加えて、第2群V中のレンズ面に、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が強くなる非球面、負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が弱くなる形状の非球面を導入し、組み合わせるのが良い。これによれば広角端の負の歪曲収差と望遠端での球面収差の変動巾をより一層軽減することができる。
【0044】
次に前述の各実施例の特徴について説明する。
【0045】
参考例1
第12群を正の単レンズで構成している。そして第12群,第13群共正のパワー(屈折力)のレンズ面に非球面を導入している。
【0046】
(実施例
第12群を正の単レンズと正レンズと負レンズの張り合わせレンズで構成し、第12群の非球面は張り合わせレンズの負のパワーの面に、第13群の負のパワーの面に非球面を導入している。
【0047】
(実施例
ズーム比15倍の広角で高倍率のズームレンズである。第12群,第13群共に正のパワーの面に非球面を導入している。
【0048】
次に本発明の数値実施例を示す。数値実施例においてriは物体側より順に第i番目のレンズ面の曲率半径、diは物体側より順に第i番目のレンズ厚及び空気間隔、niとνiは各々各物体面側より第i番目のレンズのガラスの屈折率とアッベ数である。
【0049】
非球面形状は光軸方向にX軸、光軸と垂直方向にH軸、光の進行方向を正とし、Rを近軸曲率半径、A,B,C,D,Eを各々非球面係数としたとき
【0050】
【数1】
【0051】
なる式で表している。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。
【0052】
【外1】
【0053】
【外2】
【0054】
【外3】
【0055】
【外4】
【0056】
【外5】
【0057】
【外6】
【0058】
【表1】
【0059】
【発明の効果】
本発明によれば以上のように、4群ズームレンズを高瀬するフォーカス用の第1群の一部のレンズ群を光軸上移動させてフォーカスを行うインナーフォーカスを採用しつつ、広画角化及び至近物体距離の短縮、及び高変倍化を図るとともに、レンズ系全体の小型化を図りつつ広角端の負の歪曲収差がよく補正された高い光学性能のズームレンズを達成することができる。
【図面の簡単な説明】
【図1】本発明の参考例1の広角端のレンズ断面図
【図2】本発明の参考例1のf=5.72で無限遠物体での収差図
【図3】本発明の参考例1のf=22.88で無限遠物体での収差図
【図4】本発明の参考例1のf=45.77で無限遠物体での収差図
【図5】本発明の参考例1のf=45.77で至近距離物体での収差図
【図6】本発明の数値実施例の広角端のレンズ断面図
【図7】本発明の数値実施例のf=5.72で無限遠物体での収差図
【図8】本発明の数値実施例のf=22.88で無限遠物体での収差図
【図9】本発明の数値実施例のf=45.77で無限遠物体での収差図
【図10】本発明の数値実施例のf=45.77で至近距離物体での収差図
【図11】本発明の数値実施例の広角端のレンズ断面図
【図12】本発明の数値実施例のf=6.7で無限遠物体での収差図
【図13】本発明の数値実施例のf=26.63で無限遠物体での収差図
【図14】本発明の数値実施例のf=99.83で無限遠物体での収差図
【図15】本発明の数値実施例のf=99.83で至近距離物体での収差図
【符号の説明】
F 第1群
F11 第11群
F12 第12群
F13 第13群
V 第2群
C 第3群
R 第4群
SP 開口絞り
G 色分解プリズム及び光学フィルター等
e e線
ΔS サジタル像面
ΔM メリディオナル像面
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens suitable for a television camera, a video camera, a photographic camera, a digital camera, and the like, and in particular, close-up shooting by using a so-called inner focus type in which focusing is performed with a part of the first lens group. The present invention relates to a zoom lens having a short distance and high optical performance over the entire subject distance.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, zoom lenses for television cameras, video cameras, and the like have been required to have a compact lens system, a large aperture ratio, a high zoom ratio, and a wide angle as the entire camera is downsized.
[0003]
In the zoom lens, in order from the object side, the first lens unit (focusing lens unit) having a positive refractive power for focusing and the second lens unit (magnifying lens unit) having a negative refractive power for zooming. Four lenses of positive or negative refractive power third group (correction lens group) for correcting the fluctuating image plane, aperture stop, and positive positive power fourth group (relay lens group) for imaging In a so-called four-group zoom lens composed of a group, a lens adopting an inner focus type in which focusing is performed by moving a part of the lenses in the first group is disclosed in Japanese Patent Publication No. 59-4686, Japanese Patent Laid-Open No. 6-242378. It is proposed in the issue gazette.
[0004]
In the publication, etc., the first group is composed of three lens groups, ie, an eleventh group having a negative refractive power, a twelfth group having a positive refractive power, and a thirteenth group having a positive refractive power. Focusing on the object is performed by moving the 12th group to the image plane side.
[0005]
In general, an inner focus type zoom lens has a smaller effective diameter of the first lens unit than a zoom lens that focuses by moving the entire first lens unit, so that the entire lens system can be easily downsized, and close-up photography, Close-up photography is facilitated, and the lens group is moved by moving a relatively small and light lens group, so that the driving force of the lens group is small and quick focusing is possible.
[0006]
[Problems to be solved by the invention]
In general, when an inner focus method is employed in a zoom lens, the entire lens system can be miniaturized as described above, quick focusing can be performed, and close-up photography can be facilitated.
[0007]
On the other hand, widening the angle while reducing the closest object distance with a large aperture ratio (F number 1.6) and a high zoom ratio (zoom ratio of about 8 to 15) increases distortion, particularly negative at the wide-angle end. The problem of increased distortion becomes significant.
[0008]
In order to achieve a wide angle by shortening the close object distance, it is necessary to increase the power of the lens unit (11th group) closest to the object side in the first group, which is a negative distortion at the wide angle end. It is because it increases.
[0009]
In general, in order to obtain high optical performance over the entire zooming range, for example, it is necessary to increase the degree of freedom in aberration correction by increasing the number of lenses in each lens group.
[0010]
For this reason, when trying to achieve a zoom lens with a large aperture, a wide angle of view, and a high zoom ratio, the number of lenses increases, and the entire lens system becomes large. It becomes impossible to meet.
[0011]
The present invention adopts an inner focus that performs focusing by moving a part of the first lens group for focusing that constitutes a four-group zoom lens on the optical axis, while widening the angle of view and shortening the closest object distance. An object of the present invention is to provide a zoom lens with high optical performance in which negative distortion at the wide-angle end is well corrected while achieving high zoom ratio and miniaturization of the entire lens system.
[0012]
The zoom lens according to the first aspect of the present invention includes, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power for zooming, and a positive or negative lens that corrects an image plane variation caused by zooming. In a zoom lens having a third group of refractive power, an aperture stop, and a fourth group having an imaging function fixed during zooming, the second group has an imaging magnification of -1 when zooming. The first group is fixed at the time of focusing and the eleventh group has a negative refractive power, the twelfth group that moves along the optical axis at the time of focusing, and the positive refraction that is fixed at the time of focusing. It has a 13th group of forces, 1.2 when the focal length of the 11th group is f11, the focal length of the 12th group is f12, the focal length of the 13th group is f13, and the focal length of the 1st group is f1. ≦ | f11 / f1 | ≦ 1.7 (1a)
4.451 ≦ f12 / f1 ≦ 7.0 (2a)
1.1 ≦ f13 / f1 ≦ 1.7 (3a)
Further, in the 12th group, when the maximum incident height of the on-axis light beam is hT and the maximum incident height of the off-axis light beam having the maximum field angle at the wide angle end is hW, at least one satisfying hW> hT When the lens surface is applied to the positive refractive surface, the positive refractive power increases as it goes to the lens periphery. When applied to the lens surface, the negative refractive power decreases as it goes to the lens periphery. In the thirteenth group, when applied to a positive refracting surface, the positive refractive power decreases as it goes to the lens periphery. It is characterized by having at least one aspherical surface whose negative refractive power increases as it goes.
According to the sixth aspect of the present invention, in order from the object side, the first group having a positive refractive power, the second group having a negative refractive power for zooming, and the positive or negative refractive power for correcting image plane variation accompanying zooming. In a zoom lens having a third lens unit, an aperture stop, and a fourth lens unit having a fixed imaging function during zooming, the second lens group is located within an area including an imaging magnification of -1 during zooming. The first group is an eleventh group having a negative refractive power that is fixed at the time of focusing, a twelfth group that moves along the optical axis at the time of focusing, and a first refractive power having a positive refractive power that is fixed at the time of focusing. When there are 13 groups, the focal length of the 11th group is f11, the focal length of the 12th group is f12, the focal length of the 13th group is f13, and the focal length of the first group is f1.
1.2 ≦ | f11 / f1 | ≦ 1.259 (1b)
4.0 ≦ f12 / f1 ≦ 7.0 (2b)
1.1 ≦ f13 / f1 ≦ 1.7 (3a)
Further, in the 12th group, when the maximum incident height of the on-axis light beam is hT and the maximum incident height of the off-axis light beam having the maximum field angle at the wide angle end is hW, at least one satisfying hW> hT When the lens surface is applied to the positive refractive surface, the positive refractive power increases as it goes to the lens periphery. When applied to the lens surface, the negative refractive power decreases as it goes to the lens periphery. In the thirteenth group, when applied to a positive refracting surface, the positive refractive power decreases as it goes to the lens periphery. It is characterized by having at least one aspherical surface whose negative refractive power increases as it goes.
According to the seventh aspect of the present invention, in order from the object side, the first group having a positive refractive power, the second group having a negative refractive power for zooming, and the positive or negative refractive power for correcting image plane variation accompanying zooming. In a zoom lens having a third lens unit, an aperture stop, and a fourth lens unit having a fixed imaging function during zooming, the second lens group is located within an area including an imaging magnification of -1 during zooming. The first group is an eleventh group having a negative refractive power that is fixed at the time of focusing, a twelfth group that moves along the optical axis at the time of focusing, and a first refractive power having a positive refractive power that is fixed at the time of focusing. When there are 13 groups, the focal length of the 11th group is f11, the focal length of the 12th group is f12, the focal length of the 13th group is f13, and the focal length of the first group is f1, 1.2 ≦ | f11 /F1|≦1.7 (1a)
4.0 ≦ f12 / f1 ≦ 7.0 (2b)
1.1 ≦ f13 / f1 ≦ 1.605 (3b)
Further, in the 12th group, when the maximum incident height of the on-axis light beam is hT and the maximum incident height of the off-axis light beam having the maximum field angle at the wide angle end is hW, at least one satisfying hW> hT When the lens surface is applied to the positive refractive surface, the positive refractive power increases as it goes to the lens periphery. When applied to the lens surface, the negative refractive power decreases as it goes to the lens periphery. In the thirteenth group, when applied to a positive refracting surface, the positive refractive power decreases as it goes to the lens periphery. It is characterized by having at least one aspherical surface whose negative refractive power increases as it goes.
[0013]
According to a second aspect of the present invention, in the first aspect, the twelfth group has one positive twelfth p lens, and the refractive power of the material of the positive twelfth p lens is N12p, and the thirteenth group. Has one negative 13n lens, and the refractive power of the material of the negative 13n lens is N13n, and the lateral magnification of the second group at the wide angle end is βVW, N12p ≦ 1.67. (4)
1.76 ≦ N13n (5)
−0.4 ≦ βVW ≦ −0.2 (6)
It is characterized by satisfying.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
1, 6, and 11 are lens cross-sectional views at the wide-angle end of Reference Example 1 and Numerical Examples 1 and 2 , respectively.
[0015]
2, FIG. 3, FIG. 4 and FIG. 5 show an object at infinity when f = 5.72 of the reference example 1 of the present invention, an object at infinity when f = 22.88, an object at infinity when f = 45.77, f Is an aberration diagram at a close object at 45.77.
[0016]
7, 8, 9, and 10 are numerical examples 1 of the present invention, f = 5.72 at infinity, f = 22.28 at infinity, f = 45.77 at infinity, It is an aberration diagram at a close object at f = 45.77.
[0017]
12, FIG. 13, FIG. 14 and FIG. 15 show an object at infinity at f = 6.7, an object at infinity at f = 26.63, an object at infinity at f = 99.83, in Numerical Example 2 of the present invention. FIG. 10 is an aberration diagram at a close object at f = 99.83.
[0018]
In the drawing, F denotes a focus group (first lens group) having a positive refractive power as the first group, and an eleventh group F11 having a negative refractive power which is fixed at the time of focusing (focusing) and a positive refractive power. A twelfth group F12 which moves on the optical axis having at least one positive twelfth lens and performs focusing; and a thirteenth group F13 which has at least one negative thirteenth lens fixed at the time of focusing and having a positive refractive power; have.
[0019]
Focusing from an infinitely distant object to a close object is performed by moving the twelfth group F12 toward the image plane side. V is a variator (second group) having a negative refractive power for zooming as the second group, and is moved monotonically to the image plane side on the optical axis, so that the telephoto end (tele) is widened. The zoom is done.
[0020]
In the second lens group V, the magnification is changed within a region including -1 times when zooming from the wide-angle end to the telephoto end. C is a compensator having positive or negative refractive power as the third group, and has a locus that is linear toward the object side or convex toward the object side in order to correct image plane fluctuations accompanying zooming. Has moved.
[0021]
SP is an aperture stop, and R is a relay group of positive refractive power as the fourth group. G denotes a color separation prism, an optical filter, or the like, which is shown as a glass block in FIG.
[0022]
In the four-group zoom lens according to the present invention, focusing is performed by moving the entire first lens unit closest to the object side. The front lens focus method extends the first lens unit at the same object distance at any focal length. Since the amount is constant, the lens barrel structure is simple.
[0023]
However, the first lens unit has a positive refractive power, and in a zoom lens including a wide angle of view, when focusing on an object at a close distance at the wide angle end, the first lens unit moves toward the object side. In order to ensure, the effective diameter of the first group increases, and because the relatively heavy first group is moved, the driving torque increases, and quick focusing becomes difficult.
[0024]
Further, in the 4-group zoom lens, when trying to increase the aperture, the effective diameter of the front lens group (front lens) increases remarkably. This is because the incident height of the axial ray increases, and this causes an increase in the amount of various aberrations such as spherical aberration and chromatic aberration caused by zooming and focusing. In general, it is difficult to satisfactorily correct various aberrations at this time.
[0025]
On the other hand, if the number of lenses is increased to increase the degree of design freedom, the entire lens system becomes larger and the weight and manufacturing cost increase.
[0026]
Therefore, in the present invention, each lens group is configured as described above, and conditional expressions (1a), (2a), (3a) or (1b), (2b), (3a) or (1a), (2b), By satisfying (3b) and adopting an inner focus system in which focusing from an object at infinity to a close object is performed by moving the twelfth group F12 in the first group toward the image plane side, the first group F The effective lens diameter is prevented from increasing, the entire lens system is miniaturized, and the close-up distance that can be photographed is further shortened. Here, conditional expressions (1a) and (1b) are conditional expressions (1), conditional expressions (2a) and (2b) are conditional expressions (2), and conditional expressions (3a) and (3b) are conditional expressions (3). ).
[0027]
In particular, the ratios of the focal lengths of the three lens groups of the eleventh group F11, the twelfth group F12, and the thirteenth group F13 constituting the first group and the first group F are expressed by the conditional expressions (1), (2), (3 ) Is satisfied so that the entire lens system can be reduced in size and wide angle of view at the same time.
[0028]
Next, the technical meaning of the conditional expressions (1) to (3) will be described. Exceeding the lower limit of conditional expression (1) is advantageous for reducing the size of the lens system, but negative distortion increases at the wide-angle end, making it difficult to correct aberrations even if an aspheric surface described later is introduced.
[0029]
If the lower limit value of conditional expression (2) is exceeded, the variation of spherical aberration increases when the object distance changes at the telephoto end, and it is necessary to increase the number of components of the moving lens group for good aberration correction. Come.
[0030]
If the lower limit value of conditional expression (3) is exceeded, even if an aspheric surface described later is introduced, it is difficult not only to correct spherical aberration at the telephoto end, but also fluctuations in distortion from the wide angle end to the middle of the zoom (barrel) Change from the mold to the pincushion mold) is not preferable.
[0031]
If any of the upper limit values of the conditional expressions (1), (2), and (3) is exceeded, it is advantageous in terms of aberration correction, but the front lens diameter increases and the amount of movement of the 12th group during focusing increases. However, a large space is required, and it becomes difficult to reduce the size and weight of the entire lens system.
[0032]
Furthermore, in the present invention, by introducing an aspheric surface to the 12th group and the 13th group, the optical performance of the entire screen is satisfactorily maintained over the entire zoom range, while widening the angle of view.
[0033]
The aspherical surface applied to the twelfth group is at least one lens surface satisfying hW> hT, where hT is the maximum incident height of the on-axis light beam and hW is the maximum incident height of the off-axis light beam having the maximum field angle at the wide angle end. When applied to the positive refractive surface, the positive refractive power increases as it goes to the lens periphery, but when applied to the aspherical surface or negative refractive surface, the negative refractive power decreases as it goes to the lens periphery. Aspherical.
[0034]
This aspherical surface reduces negative distortion that increases at the wide-angle end. The aspherical surface applied to the thirteenth group is an aspherical surface whose positive refractive power decreases as it goes to the lens periphery when applied to a positive refracting surface, and is negative as it goes to the lens periphery when applied to a negative refracting surface. It is preferable to use an aspherical surface with a strong refractive power. Thereby, the spherical aberration at the telephoto end is corrected well. In addition, when the zoom is performed from the wide-angle end to the middle of the zoom, the distortion aberration is greatly reduced from negative to positive.
[0035]
The zoom lens using the inner focus type according to the present invention can be achieved by satisfying the above conditions, but in order to obtain good optical performance over the entire object distance and over the entire zoom range, Satisfy at least one of the conditions.
[0036]
(A-1) The twelfth group has one positive twelfth lens, the refractive power of the material of the positive twelfth lens is N12p, and the thirteenth lens group is one negative thirteenth lens. N12p ≦ 1.67 (4) where the refractive power of the material of the negative 13n lens is N13n and the lateral magnification of the second group at the wide-angle end is βVW
1.76 ≦ N13n (5)
−0.4 ≦ βVW ≦ −0.2 (6)
Is to satisfy.
[0037]
If the refractive index of the material of the twelfth group positive 12p lens is deviated from the conditional expression (4), the curvature of the twelfth lens becomes small, and negative distortion at the wide angle end is introduced even if an aspherical surface is introduced. It becomes difficult to correct aberrations, and the positive Petzval sum decreases, making it difficult to correct the negative Petzval sum generated in the second group.
[0038]
Conditional expression (5) is an expression relating to the correction of spherical aberration at the telephoto end. When the refractive index of the negative 13n lens material becomes lower than the lower limit, it becomes difficult to correct the spherical aberration.
[0039]
Conditional expression (6) is a conditional expression that prescribes the power of the second lens group and subsequent lenses with respect to the front lens. If the lower limit is exceeded, it is advantageous in terms of aberration correction, but it becomes difficult to achieve a high zoom ratio and exceeds the upper limit. This is advantageous for downsizing and a high zoom ratio, but it is not good because the difficulty in correcting aberrations increases.
[0040]
(A-2) In order from the object side, the eleventh group includes at least one meniscus negative lens having a convex surface directed toward the object side, a negative lens having concave surfaces on both lens surfaces, and a positive lens having a convex surface directed toward the object side. It is to have.
[0041]
(A-3) In order from the object side, the twelfth group consists of a positive lens having a convex surface facing the image surface side, or a positive lens having a convex surface facing the image surface side, and a cemented lens of a positive lens and a negative lens. Or a positive lens and a cemented lens of a negative lens and a positive lens.
[0042]
(A-4) In order from the object side, the thirteenth group includes a cemented lens of a positive lens and a negative lens, a cemented lens of a negative lens and a positive lens, and a positive lens, or a cemented lens of a negative lens and a positive lens. And a positive lens, or a cemented lens of a negative lens and a positive lens, a positive lens, and a positive lens.
[0043]
(A-5) In addition to the aspherical surface of the 12th group and the aspherical surface of the 13th group, when the lens surface in the second group V is applied to the positive refractive surface, the positive refractive power increases toward the lens periphery. In the case of application to an aspherical surface where the power increases and a negative refractive surface, it is preferable to introduce and combine an aspherical surface having a shape in which the negative refractive power becomes weaker toward the lens periphery. According to this, the fluctuation range of the negative distortion at the wide-angle end and the spherical aberration at the telephoto end can be further reduced.
[0044]
Next, features of the above-described embodiments will be described.
[0045]
( Reference Example 1 )
The twelfth group is composed of a positive single lens. In addition, an aspherical surface is introduced into the lens surface of the twelfth group and the thirteenth group having positive power (refractive power).
[0046]
(Example 1 )
The twelfth group is constituted by a cemented lens of a positive single lens, a positive lens, and a negative lens, and the aspherical surface of the twelfth group is an aspherical surface on the negative power surface of the cemented lens and the negative power surface of the thirteenth group. Has been introduced.
[0047]
(Example 2 )
This is a wide-angle, high-magnification zoom lens with a zoom ratio of 15 times. In both the 12th and 13th groups, an aspherical surface is introduced into the positive power surface.
[0048]
Next, numerical examples of the present invention will be shown. In numerical examples, ri is the radius of curvature of the i-th lens surface in order from the object side, di is the i-th lens thickness and air spacing in order from the object side, and ni and νi are i-th from the object surface side, respectively. Refractive index and Abbe number of lens glass.
[0049]
The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, and A, B, C, D and E are the aspheric coefficients. [0050]
[Expression 1]
[0051]
It is expressed by the following formula. Table 1 shows the relationship between the above-described conditional expressions and numerical values in the numerical examples.
[0052]
[Outside 1]
[0053]
[Outside 2]
[0054]
[Outside 3]
[0055]
[Outside 4]
[0056]
[Outside 5]
[0057]
[Outside 6]
[0058]
[Table 1]
[0059]
【The invention's effect】
According to the present invention, as described above, a wide angle of view is obtained while adopting an inner focus in which a part of the first lens group for focusing that raises the four-group zoom lens is moved on the optical axis. In addition, it is possible to achieve a zoom lens with high optical performance in which the close object distance is shortened and the zoom ratio is increased, and the negative distortion at the wide angle end is well corrected while the entire lens system is reduced in size.
[Brief description of the drawings]
Reference example of FIG. 1 is aberration diagrams in the infinity object at f = 5.72 Reference Example 1 of the present lens sectional view of a wide-angle end of Reference Example 1 of the invention the present invention; FIG 3 shows the present invention aberrations of an object at infinity at f = 45.77 reference example 1 of the aberration diagrams [4] the present invention in infinite object at the first f = 22.88 [5] of reference example 1 of the present invention f = 45.77 infinite at f = 5.72 numerical embodiment 1 of the aberration diagrams [6] lens sectional view of a wide-angle end according to numerical embodiment 1 of the present invention [7] the present invention in a close distance aberration diagram 8 infinite numerical example 1 of f = 45.77 aberration diagrams [9] the present invention in infinite object at f = 22.88 to numerical embodiment 1 of the present invention at far objects FIG. 10 is an aberration diagram at a close object at f = 45.77 in Numerical Example 1 of the present invention. FIG. 11 is a lens cross-sectional view at the wide angle end of Numerical Example 2 in the present invention. Figure Aberration diagram Figure 2] In Numerical Example 2 of f = 26.63 aberration diagrams [13] The present invention in infinite object numeric f = 6.7 Example 2 of the present invention an object at infinity 14 aberration diagrams in f = 99.83 numerical example 2 in a close distance of the aberrations of an object at infinity at f = 99.83 numerical example 2 [15] the present invention of the present invention codes Explanation of]
F 1st group F11 11th group F12 12th group F13 13th group V 2nd group C 3rd group R 4th group SP Aperture stop G Color separation prism, optical filter, etc. e line ΔS Sagittal image plane ΔM Meridional image plane

Claims (8)

物体側より順に正の屈折力の第1群、変倍用の負の屈折力の第2群、変倍に伴う像面変動を補正する正又は負の屈折力の第3群、開口絞り、そして変倍中固定の結像作用を有する第4群とを有したズームレンズにおいて、該第2群は変倍の際に結像倍率が−1倍を含む領域内で変化し、該第1群は合焦時に固定で負の屈折力の第11群と、合焦時に光軸に沿って移動する第12群と、合焦時固定の正の屈折力の第13群を有し、第11群の焦点距離をf11、第12群の焦点距離をf12、第13群の焦点距離をf13、第1群の焦点距離をf1としたとき
1.2≦|f11/f1|≦1.7
4.451≦f12/f1≦7.0
1.1≦f13/f1≦1.7
を満足し、更に第12群中、軸上光束の最大入射高をhT、広角端での最大画角の軸外光束の最大入射高をhWとしたとき、hW>hTを満足する少なくとも1つのレンズ面に、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が強くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が弱くなる形状の非球面を有し、かつ第13群には、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が弱くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が強くなる形状の非球面を少なくとも1面有することを特徴とするズームレンズ。
In order from the object side, a first group having a positive refractive power, a second group having a negative refractive power for zooming, a third group having a positive or negative refractive power for correcting image plane variation accompanying zooming, an aperture stop, In the zoom lens having the fourth lens group having a fixed imaging function during zooming, the second lens group changes within the region including the imaging magnification of -1 when zooming, The group has an eleventh group having a negative refractive power that is fixed at the time of focusing, a twelfth group that moves along the optical axis at the time of focusing, and a thirteenth group having a positive refractive power that is fixed at the time of focusing. When the focal length of the eleventh group is f11, the focal length of the twelfth group is f12, the focal length of the thirteenth group is f13, and the focal length of the first group is f1, 1.2 ≦ | f11 / f1 | ≦ 1.7.
4.451 ≦ f12 / f1 ≦ 7.0
1.1 ≦ f13 / f1 ≦ 1.7
Further, in the 12th group, when the maximum incident height of the on-axis light beam is hT and the maximum incident height of the off-axis light beam having the maximum field angle at the wide angle end is hW, at least one satisfying hW> hT When the lens surface is applied to the positive refractive surface, the positive refractive power increases as it goes to the lens periphery. When applied to the lens surface, the negative refractive power decreases as it goes to the lens periphery. In the thirteenth group, when applied to a positive refracting surface, the positive refractive power decreases as it goes to the lens periphery. A zoom lens comprising at least one aspherical surface whose negative refractive power increases as it goes.
前記第12群は1つの正の第12pレンズを有しており、該正の第12pレンズの材質の屈折力をN12pとし、前記第13群は1つの負の第13nレンズを有しており、該負の第13nレンズの材質の屈折力をN13nとし、広角端における前記第2群の横倍率をβVWとしたとき
N12p≦1.67
1.76≦N13n
−0.4≦βVW≦−0.2
を満足することを特徴とする請求項1記載のズームレンズ。
The twelfth group has one positive twelfth lens, the refractive power of the material of the positive twelfth lens is N12p, and the thirteenth group has one negative thirteenth lens. When the refractive power of the material of the negative thirteenth lens is N13n and the lateral magnification of the second group at the wide angle end is βVW, N12p ≦ 1.67
1.76 ≦ N13n
−0.4 ≦ βVW ≦ −0.2
The zoom lens according to claim 1, wherein:
前記第11群は、物体側より順に、物体側へ凸面を向けたメニスカス状の少なくとも1つの負レンズ、両レンズ面が凹面の負レンズ、そして物体側へ凸面を向けた正レンズを有していることを特徴とする請求項1又は2のズームレンズ。The eleventh group includes , in order from the object side, at least one meniscus negative lens having a convex surface directed toward the object side, a negative lens having concave surfaces on both lens surfaces, and a positive lens having a convex surface directed toward the object side. The zoom lens according to claim 1 or 2, wherein: 前記第12群は、物体側より順に、像面側に凸面を向けた正レンズより成り、又は像面側に凸面を向けた正レンズ、正レンズと負レンズとの接合レンズより成り、又は2つの正レンズと負レンズと正レンズとの接合レンズより成っていることを特徴とする請求項1,2又は3のズームレンズ。The twelfth group includes , in order from the object side, a positive lens having a convex surface facing the image surface side, or a positive lens having a convex surface facing the image surface side, a cemented lens of a positive lens and a negative lens, or 2 4. The zoom lens according to claim 1, comprising a cemented lens of two positive lenses, a negative lens, and a positive lens. 前記第13群、物体側より順に、正レンズと負レンズとの接合レンズ、負レンズと正レンズとの接合レンズ、そして正レンズより成り、又は負レンズと正レンズとの接合レンズ、そして正レンズより成り、又は負レンズと正レンズとの接合レンズ、正レンズそして正レンズより成っていることを特徴とする請求項1,2,3又は4のズームレンズ。 The thirteenth group includes , in order from the object side , a cemented lens of a positive lens and a negative lens, a cemented lens of a negative lens and a positive lens, and a positive lens, or a cemented lens of a negative lens and a positive lens, and a positive lens. 5. The zoom lens according to claim 1, comprising a lens, or a cemented lens of a negative lens and a positive lens, a positive lens, and a positive lens. 物体側より順に正の屈折力の第1群、変倍用の負の屈折力の第2群、変倍に伴う像面変動を補正する正又は負の屈折力の第3群、開口絞り、そして変倍中固定の結像作用を有する第4群とを有したズームレンズにおいて、該第2群は変倍の際に結像倍率が−1倍を含む領域内で変化し、該第1群は合焦時に固定で負の屈折力の第11群と、合焦時に光軸に沿って移動する第12群と、合焦時固定の正の屈折力の第13群を有し、第11群の焦点距離をf11、第12群の焦点距離をf12、第13群の焦点距離をf13、第1群の焦点距離をf1としたとき
1.2≦|f11/f1|≦1.259
4.0≦f12/f1≦7.0
1.1≦f13/f1≦1.7
を満足し、更に第12群中、軸上光束の最大入射高をhT、広角端での最大画角の軸外光束の最大入射高をhWとしたとき、hW>hTを満足する少なくとも1つのレンズ面に、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が強くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が弱くなる形状の非球面を有し、かつ第13群には、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が弱くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が強くなる形状の非球面を少なくとも1面有することを特徴とするズームレンズ。
In order from the object side, a first group having a positive refractive power, a second group having a negative refractive power for zooming, a third group having a positive or negative refractive power for correcting image plane variation accompanying zooming, an aperture stop, In the zoom lens having the fourth lens group having a fixed imaging function during zooming, the second lens group changes within the region including the imaging magnification of -1 when zooming, The group has an eleventh group having a negative refractive power that is fixed at the time of focusing, a twelfth group that moves along the optical axis at the time of focusing, and a thirteenth group having a positive refractive power that is fixed at the time of focusing. When the focal length of the 11th group is f11, the focal length of the 12th group is f12, the focal length of the 13th group is f13, and the focal length of the first group is f1
1.2 ≦ | f11 / f1 | ≦ 1.259
4.0 ≦ f12 / f1 ≦ 7.0
1.1 ≦ f13 / f1 ≦ 1.7
Further, in the 12th group, when the maximum incident height of the on-axis light beam is hT and the maximum incident height of the off-axis light beam having the maximum field angle at the wide angle end is hW, at least one satisfying hW> hT When the lens surface is applied to the positive refractive surface, the positive refractive power increases as it goes to the lens periphery. When applied to the lens surface, the negative refractive power decreases as it goes to the lens periphery. In the thirteenth group, when applied to a positive refracting surface, the positive refractive power decreases as it goes to the lens periphery. A zoom lens comprising at least one aspherical surface whose negative refractive power increases as it goes.
物体側より順に正の屈折力の第1群、変倍用の負の屈折力の第2群、変倍に伴う像面変動を補正する正又は負の屈折力の第3群、開口絞り、そして変倍中固定の結像作用を有する第4群とを有したズームレンズにおいて、該第2群は変倍の際に結像倍率が−1倍を含む領域内で変化し、該第1群は合焦時に固定で負の屈折力の第11群と、合焦時に光軸に沿って移動する第12群と、合焦時固定の正の屈折力の第13群を有し、第11群の焦点距離をf11、第12群の焦点距離をf12、第13群の焦点距離をf13、第1群の焦点距離をf1としたとき
1.2≦|f11/f1|≦1.7
4.0≦f12/f1≦7.0
1.1≦f13/f1≦1.605
を満足し、更に第12群中、軸上光束の最大入射高をhT、広角端での最大画角の軸外光束の最大入射高をhWとしたとき、hW>hTを満足する少なくとも1つのレンズ面に、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が強くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が弱くなる形状の非球面を有し、かつ第13群には、正の屈折面に施した場合はレンズ周辺に行くに従い正の屈折力が弱くなる非球面又は負の屈折面に施した場合はレンズ周辺に行くに従い負の屈折力が強くなる形状の非球面を少なくとも1面有することを特徴とするズームレンズ。
In order from the object side, a first group having a positive refractive power, a second group having a negative refractive power for zooming, a third group having a positive or negative refractive power for correcting image plane variation accompanying zooming, an aperture stop, In the zoom lens having the fourth lens group having a fixed imaging function during zooming, the second lens group changes within the region including the imaging magnification of -1 when zooming, The group has an eleventh group having a negative refractive power that is fixed at the time of focusing, a twelfth group that moves along the optical axis at the time of focusing, and a thirteenth group having a positive refractive power that is fixed at the time of focusing. When the focal length of the eleventh group is f11, the focal length of the twelfth group is f12, the focal length of the thirteenth group is f13, and the focal length of the first group is f1, 1.2 ≦ | f11 / f1 | ≦ 1.7.
4.0 ≦ f12 / f1 ≦ 7.0
1.1 ≦ f13 / f1 ≦ 1.605
Further, in the 12th group, when the maximum incident height of the on-axis light beam is hT and the maximum incident height of the off-axis light beam having the maximum field angle at the wide angle end is hW, at least one satisfying hW> hT When the lens surface is applied to the positive refractive surface, the positive refractive power increases as it goes to the lens periphery. When applied to the lens surface, the negative refractive power decreases as it goes to the lens periphery. In the thirteenth group, when applied to a positive refracting surface, the positive refractive power decreases as it goes to the lens periphery. A zoom lens comprising at least one aspherical surface whose negative refractive power increases as it goes.
請求項1乃至7のいずれか1項記載のズームレンズを備えたことを特徴とするカメラ。A camera comprising the zoom lens according to claim 1 .
JP19151499A 1999-05-10 1999-07-06 Zoom lens Expired - Lifetime JP4478247B2 (en)

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EP00303851A EP1052535B1 (en) 1999-05-10 2000-05-08 Zoom lens
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