JP3733164B2

JP3733164B2 - Macro lens

Info

Publication number: JP3733164B2
Application number: JP03431796A
Authority: JP
Inventors: 秀樹小川
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1996-01-29
Filing date: 1996-01-29
Publication date: 2006-01-11
Anticipated expiration: 2016-01-29
Also published as: JPH09211319A

Description

【０００１】
【発明の属する技術分野】
本発明は写真用カメラ，ビデオカメラ，そして電子スチルカメラ等のオートフォーカス（自動焦点）機能を有したカメラに好適なマクロレンズに関し、特に無限遠物体から近距離物体（撮影倍率１．０ｘ）に至る広範囲の物体に対して焦点合わせをする際の収差補正を良好に行った高性能な画角１４度程度、Ｆナンバー３．５程度の中望遠のマクロレンズに関するものである。
【０００２】
【従来の技術】
従来より写真用カメラやビデオカメラ、そして電子スチルカメラ等において近距離物体の撮影を主たる目的とした撮影レンズにマクロレンズ又はマイクロレンズ（以下「マクロレンズ」という。）と呼ばれるものがある。
【０００３】
このうち３５ｍｍ一眼レフカメラ用のマクロレンズとしては、無限遠物体から撮影倍率１ｘ又は０．５ｘ程度の近距離物体までの広範囲の物体距離において撮影できるように構成されているものが多い。
【０００４】
マクロレンズは一般の標準レンズや望遠レンズ等の他の撮影レンズに比べて、特に近距離物体において高い光学性能が得られるように設計されている。又マクロレンズは多くの場合、近距離物体に限らず近距離物体から無限遠物体に至る広範囲の物体に対しても使用されている。
【０００５】
一般にマクロレンズにおいて物体距離範囲（撮影倍率範囲）の拡大を図ろうとするとフォーカスに伴う収差変動が増大してくる。例えば、撮影倍率が高くなると球面収差が補正不足となり、又外向性のコマ収差が多く発生してくる。
【０００６】
これに対して、特開昭５５−１４０８１０号公報では物体側より順に正，負、そして正の屈折力の第１，第２，第３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へのフォーカスに際して第１群を物体側へ、第２群を像面側へ移動させ、これによってフォーカスに伴う収差変動を良好に補正したマクロレンズが提案されている。
【０００７】
又特願平４−１２４４８０号では物体側より順に正の屈折力の第１ａ群、正の屈折力の第１ｂ群、負の屈折力の第２群、そして正の屈折力の第３群で構成し、無限遠物体から近距離物体へのフォーカシングに際し、第２群を像側へ移動すると共に第１ａ群を物体側へ凸状の円弧を描くように移動させた構成のマクロレンズが提案されている。
【０００８】
【発明が解決しようとする課題】
マクロレンズは広範囲の物体距離において撮影可能としている為に合焦用レンズの繰り出し量（移動量）が、一般の撮影レンズに比べて多い。又全系の焦点距離が長くなる程、それに比例して合焦用レンズの繰り出し量が多くなると共に合焦用レンズ群のレンズ重量が増加してくる傾向がある。
【０００９】
例えばフォーカス方式として全体繰り出し方式の撮影レンズ（マクロレンズ）を例にとると、同Ｆナンバーの焦点距離１００ｍｍと焦点距離２００ｍｍの撮影レンズで同撮影倍率の被写体へフォーカシングする場合、焦点距離２００ｍｍの撮影レンズは焦点距離１００ｍｍの撮影レンズに対して繰り出し量で２倍、レンズ重量もかなり増加してくる。
【００１０】
そして近年、開発の盛んなオートフォーカス方式のカメラにおいては、この様なフォーカス繰り出し量とレンズ重量の増加が高速オートフォーカスを実現する上で、非常に大きな問題となっている。
【００１１】
又マクロレンズにおいて撮影倍率範囲を拡大すると、特に高倍率の方に拡大すると撮影倍率の変化に伴い収差変動が多くなり、これを良好に補正するのが大変難しくなってくる。
【００１２】
このようにマクロレンズにおいてはフォーカス用のレンズ群のレンズ重量を軽減しつつ、又レンズ繰り出し量を少なくしつつ諸収差を良好に補正することが大きな課題となっている。
【００１３】
本発明は、主にレンズの構成と屈折力の分担を適切に設定することにより、無限遠物体から近距離物体に至る、特に撮影倍率が１．０倍付近に至る広範囲の物体距離に対して焦点合わせ（フォーカス）をする際の収差変動を良好に補正した、特にオートフォーカスカメラに好適なＦナンバー３．５程度の高い光学性能を有した中望遠のマクロレンズの提供を目的とする。
【００１４】
【課題を解決するための手段】
本発明のマクロレンズは、物体側より順に、正の屈折力の第１ａ群、正の屈折力の第１ｂ群、負の屈折力の第２群、正の屈折力の第３群、そして第４群のみをレンズ群として有し、該第１ｂ群は、物体側より順に、像面側に凹面を向けたメニスカス状の負の第１ｂ１レンズと正の第１ｂ２レンズのみをレンズとして有し、無限遠物体から近距離物体へのフォーカスに際し、該第２群を像面側へ移動させ、更に、該第３群又は第４群のいずれかを移動させるマクロレンズであって、該第１ａ群と第１ｂ群の合成焦点距離をｆ１、該第１ｂ群の焦点距離をｆ１ｂ、該第１ｂ１レンズの像面側のレンズ面の屈折力をφとしたとき
１．４＜｜φ｜・ｆ１＜２．６・・・（１）
２＜ｆ１ｂ／ｆ１＜１５・・・（２）
なる条件を満足することを特徴としている。
【００１５】
【発明の実施の形態】
図１〜図６、図９，１０は、本発明の数値実施例１〜８のレンズ断面図、図７、図８、図１１は各参考例１〜３のレンズ断面図である。図１２〜図３５、図４４〜図５１は本発明の数値実施例１〜８の収差図である。
図３６〜図４３、図５２〜図５５は参考例１〜３の収差図である。
収差図においては、順に無限遠物体、撮影倍率０．１ｘ，０．５ｘ，１．０ｘについて示している。
【００１６】
レンズ断面図において、Ｌ１ａは正の屈折力の第１ａ群，Ｌ１ｂは正の屈折力の第１ｂ群，Ｌ２は負の屈折力の第２群，Ｌ３は正の屈折力の第３群，Ｌ４は正又は負の屈折力の第４群，ＳＰは絞りであり、第２群Ｌ２と第３群Ｌ３との間に配置している。
【００１７】
そして各実施例において第１ｂ群を像面側に凹面を向けたメニスカス状の負の第１ｂ１レンズと正の第１ｂ２レンズを有するように構成している。無限遠物体から近距離物体へのフォーカスに際しては矢印の如く第２群Ｌ２を像面側へ移動させて行っている。尚第３群Ｌ３は必要に応じて物体側へ移動させているが、固定としても良い。
【００１８】
本実施形態では以上のように、レンズ構成を特定すると共に第１ｂ群や第１群、そして第１ｂ１レンズの像面側のレンズ面の屈折力等を条件式（１），（２）の如く設定し、これにより撮影倍率の変化に伴う収差変動を少なくし、無限遠物体から近距離物体に至る広範囲の物体に対して良好なる収差補正を可能としている。特に無限遠物体から撮影倍率１．０倍の近距離物体に至る広範囲の物体に対して良好なる収差補正を可能としている。
【００１９】
次に本発明のマクロレンズの収差補正の特徴を説明する。本発明に係るマクロレンズでは広範囲の物体距離でフォーカスしており、このときのフォーカスに伴う諸収差の変動について図５６の近軸屈折力配置を用いて説明する。
【００２０】
図５６は本発明のマクロレンズを構成する４つのレンズ群のうち、正の屈折力の第１ａ群Ｌ１ａ，正の屈折力の第１ｂ群Ｌ１ｂ，負の屈折力の第２群Ｌ２の３つのレンズ群を抽出し、このレンズ系に光線が通過するときの光路状態を示した説明図である。
【００２１】
図５６（Ａ）は無限遠物体にフォーカスしている状態、図５６（Ｂ）は第２群Ｌ２を矢印の如く像面側へ移動させて近距離物体にフォーカスしている状態を示している。前述したようにマクロレンズでは広い物体距離の撮影域を有している為にフォーカスの際に諸収差の変動を起こしやすい。特に基本となる球面収差が著しく補正不足になりやすい。これを図５６（Ａ）の軸上光束の通過図を用いて説明する。
【００２２】
まず図５６（Ａ）の無限遠物体への合焦状態において、第１ａ群Ｌ１ａ群から第２群Ｌ２までの合成系としての球面収差が良好なる補正状態にあるとする。その内部のキャンセル状態は第１ａ群Ｌ１ａと第１ｂ群Ｌ１ｂの正の屈折力の合成レンズ系では負の球面収差が発生し、それを負の屈折力の第２群で発生する正の球面収差で打ち消し合うことによってバランス良く補正している。
【００２３】
しかしながら図５６（Ｂ）の近距離物体への合焦状態になると、第２群Ｌ２が像面側へ移動する為に第２群中への軸上光束の入射高が低くなる。この為、第２群Ｌ２からは正の球面収差の発生量が少なくなってくる。
【００２４】
その結果、第１ａ群Ｌ１ａから第２群Ｌ２の合成系として球面収差が著しく補正不足となる傾向にある。従って、このようなレンズ構成から成るマクロレンズにおいてフォーカシングの際に球面収差が著しく補正不足とならないようにする為には被写体距離が近距離になるにつれて第２群の球面収差の負の方向への変位を打ち消すように第１ａ群と第１ｂ群の合成系で球面収差が正の方向に変位させるように構成することが必要となってくる。
【００２５】
そこで本発明では第１ｂ群を物体側より順に像側へ凹面を向けたメニスカス状の負レンズ（第１ｂ１レンズ）と正レンズ（第１ｂ２レンズ）を含むように構成し、これにより球面収差を大きく正の方向に変位させている。
【００２６】
つまり、軸上光線の第１ｂレンズ群への入射高が図５６（Ａ）の無限遠合焦状態よりも図５６（Ｂ）の近距離合焦状態の方が高くなることに着目し、それを利用して、そこに配置された前記メニスカス状の負レンズの主に像側のレンズ面で球面収差を大きく正の方向に変位させている。そして後続の正のレンズは特に第１ｂ群を全体として正の屈折力として維持せしめるのに用いている。この正レンズを除去した場合は第１ａ群の正の屈折力の分担が増え、第１ａ群内での諸収差の良好なる補正が困難になると同時に、前記メニスカス状の負レンズの像面側のレンズ面の曲率がゆるくなり、球面収差の正の方向への変位効果が弱まってしまうことになる。又メニスカス状の負レンズと正レンズを接合した場合は、球面収差の正方向への変位効果が弱まるので分離している。
【００２７】
本発明のマクロレンズは、以上のようなレンズ構成をとることにより、フォーカスの際の収差変動、特に球面収差の変動を良好に補正している。
【００２８】
次に前述の条件式の技術的意味について説明する。条件式（１）は第１ｂ群中の像面側へ凹面を向けたメニスカス状の負の第１ｂ１レンズの像面側レンズ面の屈折力に関し、主に近距離物体にフォーカスしたときの全系の諸収差の変動、特に球面収差の負の方向の変位を、このレンズ面で効率良く正の方向に変位させて全系の収差変動を抑える為の条件である。
【００２９】
条件式（１）の上限値を越えて該レンズ面の発散作用が強まると、近距離物体へのフォーカシングに際し、球面収差が大きく正の方向に変位し、近距離物体での合焦状態では補正過剰となるので良くない。又条件式（１）の下限値を越えて該レンズ面の発散作用が弱まると、逆に近距離物体へのフォーカシングに際し、球面収差の正の方向への変位量が小さくなり、近距離物体での合焦状態では補正不足となるので良くない。
【００３０】
本発明において更に好ましくは条件式（１）は
１．８＜｜φ｜・ｆ１＜２．１（φ＜０） ‥‥（１ａ）
とするのが良い。
【００３１】
次に条件式（２）は第１ｂ群での焦点距離に関し、第１ａ群と第１ｂ群の合成系（第１群）において第１ａ群との屈折力分担を適切なものとし、フォーカスの際の諸収差の変動を良好に抑える為の条件である。条件式（２）の上限値を越えて第１ｂ群の正の屈折力が弱まると、その結果、第１ａ群の正の屈折力の分担が増え、第１ａ群内での球面収差，コマ収差，非点収差，像面湾曲等の諸収差の補正が困難になる。特に近距離物体へのフォーカシングに際し、第１ａ群で発生する球面収差の変動が第１ａ群が持つ本質的な正の屈折力の作用により大きく負の方向に変位し、後続の第１ｂ群で除去しきれなくなるので良くない。
【００３２】
又条件式（２）の下限値を越えて第１ｂ群の正の屈折力の分担が弱まると第１ａ群内での収差補正はしやすくなるものの、第１ｂ群で発生する諸収差のバランスがくずれると共に、第１ｂ群全体でフォーカシング時の球面収差の正の方向の変位量も小さくなり、近距離物体での合焦状態では補正不足となるので良くない。
【００３３】
本発明は以上のようなレンズ構成において、各レンズ群の屈折力等を条件式（１），（２）の如く設定し、これにより無限遠物体から撮影倍率１．０程度の近距離物体に至る広範囲の物体に対して収差変動を少なくし、良好なる光学性能を得ている。
【００３４】
尚本発明において更にフォーカスの際の収差変動を少なくし、物体距離全般にわたり良好なる光学性能を得るには次の諸条件の内少なくとも１つを満足させるのが良い。
【００３５】
まず、前述の第１ａ群の焦点距離は、
（Ａ１）第１ａ群の焦点距離をｆ１ａとしたとき
１．０５＜ｆ１ａ／ｆ１＜１．７４ ‥‥（３）
とするのが良い。更に好ましくは
１．１０＜ｆ１ａ／ｆ１＜１．４５ ‥‥（３ａ）
とするのが良い。
【００３６】
（Ａ２）前記第１ａ群を物体側より順に両レンズ面が凸面の正レンズ、物体側へ凹面を向けたメニスカス状の負レンズ、そして物体側へ凸面を向けたメニスカス状の正レンズを有する構成とすると、フォーカスの際の諸収差の変動、特に色の球面収差の高次フレアーの変動が良好に補正できるので良い。
【００３７】
（Ａ３）前記第１ａ群を物体側より順に正レンズ、両レンズ面が凸面の正レンズ、物体側へ凹面を向けたメニスカス状の負レンズ、そして物体側へ凸面を向けたメニスカス状の正レンズを有する構成とすると、球面収差をはじめ、諸収差の変動を更に良好に補正することができるので良い。
【００３８】
（Ａ４）前記第１ａ群は前述のレンズ構成の他に物体側より順に、物体側に凸面を向けたメニスカス状の負レンズ、正レンズ、そして物体側へ凸面を向けたメニスカス状の正レンズを有する構成としても諸収差の変動を比較的良好に補正できるので良い。
【００３９】
フォーカスの際に第２群を移動させるとともに他のレンズ群を第２群に対し異なる速度で移動させる所謂フローティングを採用しても良い。
【００４０】
すなわち、
（Ａ５）無限遠物体から近距離物体へのフォーカスに際して前記第３群を移動させるのが良い。特に第３群を物体側へ移動させるのが良い。
【００４１】
（Ａ６）無限遠物体から近距離物体へのフォーカスに際して前記第４群を移動させるのが良い。特に、前記第４群は正の屈折力を有し、無限遠物体から近距離物体へのフォーカスに際して像面側に凸状の軌跡を有して移動させるのが良い。
【００４２】
（Ａ７）無限遠物体から近距離物体へのフォーカスに際して前記第１ｂ群を移動させるのが良い。特に第１ｂ群を像面側へ移動させるのが良い（参考例３）。
【００４３】
本発明においては、これらのレンズ群のうち、どのレンズ群を移動してもフローティング効果が得られ、特に中間撮影距離での像面の変動を更に良好に補正することができる。
【００４４】
特に（Ａ５）においてフォーカスの際に、第３群を物体側へ第２群と逆方向に移動させると，
（Ａ８）レンズ重量及び移動量を略等しく設定することにより、上向きの撮影及び下向きの撮影で互いにレンズ重量を打ち消し、安定したレンズ駆動速度が得られるので好ましい。
【００４５】
（Ａ９）前記第２群は物体側より順に像面側に凹面を向けた負レンズ、両レンズ面が凹面の負レンズＬ２ｎと正レンズとを接合した貼合わせレンズを有する構成とするのが良い。
【００４６】
このうち両レンズ面が凹面の負レンズＬ２ｎの材質の屈折率とアッベ数を各々Ｎ２ｎ，ν２ｎとしたとき
【００４７】
【数１】
とするのが良い。これによれば、第１ａ群と第１ｂ群の合成系の残存色収差、特に軸上色収差を良好に補正することができる。
【００４８】
（Ａ１０）第２群の焦点距離をｆ２、全系の無限遠物体に合焦させたときの全系の焦点距離をｆとしたとき
０．１５＜｜ｆ２｜／ｆ＜０．４５（ｆ２＜０） ‥‥（５）
とするのが良い。
【００４９】
条件式（５）の上限値を越えて第２群の負の屈折力が弱まると、収差補正しやすくなるが、フォーカシングに際し、第２群の移動量が多くなるので良くない。逆に下限値を越えて負の屈折力が強まると第２群内で発生する諸収差が大きくなり、同時に第１ａ群と第１ｂ群の合成系の正の屈折力も強まり、発生する諸収差も大きくなってレンズ系全体での諸収差が悪化してくるので良くない。
【００５０】
（Ａ１１）前記第３群は物体側に凸面を向けた正レンズ、物体側へ凸面を向けた正レンズＬ３ｐと負レンズとを接合した貼合わせレンズを有する構成とするのが良い。特に貼合わせレンズの正レンズＬ３ｐの材質の屈折率とアッベ数をＮ３ｐ，ν３ｐとしたとき
【００５１】
【数２】
とするのが良い。これによれば色収差、特に軸上色収差を良好に補正できるので好ましい。
【００５２】
（Ａ１２）前記第４群は像面側へ凸面を向けたメニスカス状の負レンズと、物体側へ凸面を向けた正レンズを有する構成とするのが良い。又は、前記第４群は正レンズと、像面側へ凸面を向けたメニスカス状の負レンズと、物体側へ凸面を向けた正レンズを有する構成とするのが良い。これによれば、軸外収差、特にコマ収差と非点収差を補正するのに有効となる。
【００５３】
（Ａ１３）絞りは第２群と一体若しくは第３群と一体でも良いが、第２群と第３群の間に固定して配置するのが比較的簡易な機構で構成できるので良い。
【００５４】
次に本発明の数値実施例１〜８と参考例１〜３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は各々物体側より順に第ｉ番目のレンズのガラスの屈折率とアッベ数である。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。
【００５５】
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
【００５６】
【数３】
なる式で表している。
【００５７】
【外１】
【００５８】
【外２】
【００５９】
【外３】
【００６０】
【外４】
【００６１】
【外５】
【００６２】
【外６】
【００６３】
【数１】
【００６４】
【数２】
【００６５】
【数３】
【００６６】
【数４】
【００６７】
【数５】
【００６８】
【表１】
【００６９】
【発明の効果】
本発明によれば以上のように、レンズ系全体の構成、特に合焦用レンズ群の構成を適切に設定することにより、無限遠物体から近距離物体に至る、特に撮影倍率が１．０倍付近に至る広範囲の物体距離に対して焦点合わせ（フォーカス）をする際の収差変動を良好に補正した、特にオートフォーカスカメラに好適なＦナンバー３．５程度の高い光学性能を有した中望遠のマクロ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６のレンズ断面図
【図７】本発明の参考例１のレンズ断面図
【図８】本発明の参考例２のレンズ断面図
【図９】本発明の数値実施例７のレンズ断面図
【図１０】本発明の数値実施例８のレンズ断面図
【図１１】本発明の参考例３のレンズ断面図
【図１２】本発明の数値実施例１の無限遠物体のときの収差図
【図１３】本発明の数値実施例１の撮影倍率０．１ｘのときの収差図
【図１４】本発明の数値実施例１の撮影倍率０．５ｘのときの収差図
【図１５】本発明の数値実施例１の撮影倍率１．０ｘのときの収差図
【図１６】本発明の数値実施例２の無限遠物体のときの収差図
【図１７】本発明の数値実施例２の撮影倍率０．１ｘのときの収差図
【図１８】本発明の数値実施例２の撮影倍率０．５ｘのときの収差図
【図１９】本発明の数値実施例２の撮影倍率１．０ｘのときの収差図
【図２０】本発明の数値実施例３の無限遠物体のときの収差図
【図２１】本発明の数値実施例３の撮影倍率０．１ｘのときの収差図
【図２２】本発明の数値実施例３の撮影倍率０．５ｘのときの収差図
【図２３】本発明の数値実施例３の撮影倍率１．０ｘのときの収差図
【図２４】本発明の数値実施例４の無限遠物体のときの収差図
【図２５】本発明の数値実施例４の撮影倍率０．１ｘのときの収差図
【図２６】本発明の数値実施例４の撮影倍率０．５ｘのときの収差図
【図２７】本発明の数値実施例４の撮影倍率１．０ｘのときの収差図
【図２８】本発明の数値実施例５の無限遠物体のときの収差図
【図２９】本発明の数値実施例５の撮影倍率０．１ｘのときの収差図
【図３０】本発明の数値実施例５の撮影倍率０．５ｘのときの収差図
【図３１】本発明の数値実施例５の撮影倍率１．０ｘのときの収差図
【図３２】本発明の数値実施例６の無限遠物体のときの収差図
【図３３】本発明の数値実施例６の撮影倍率０．１ｘのときの収差図
【図３４】本発明の数値実施例６の撮影倍率０．５ｘのときの収差図
【図３５】本発明の数値実施例６の撮影倍率１．０ｘのときの収差図
【図３６】参考例１の無限遠物体のときの収差図
【図３７】参考例１の撮影倍率０．１ｘのときの収差図
【図３８】参考例１の撮影倍率０．５ｘのときの収差図
【図３９】参考例１の撮影倍率１．０ｘのときの収差図
【図４０】参考例２の無限遠物体のときの収差図
【図４１】参考例２の撮影倍率０．１ｘのときの収差図
【図４２】参考例２の撮影倍率０．５ｘのときの収差図
【図４３】参考例２の撮影倍率１．０ｘのときの収差図
【図４４】本発明の数値実施例７の無限遠物体のときの収差図
【図４５】本発明の数値実施例７の撮影倍率０．１ｘのときの収差図
【図４６】本発明の数値実施例７の撮影倍率０．５ｘのときの収差図
【図４７】本発明の数値実施例７の撮影倍率１．０ｘのときの収差図
【図４８】本発明の数値実施例８の無限遠物体のときの収差図
【図４９】本発明の数値実施例８の撮影倍率０．１ｘのときの収差図
【図５０】本発明の数値実施例８の撮影倍率０．５ｘのときの収差図
【図５１】本発明の数値実施例８の撮影倍率１．０ｘのときの収差図
【図５２】参考例３の無限遠物体のときの収差図
【図５３】参考例３の撮影倍率０．１ｘのときの収差図
【図５４】参考例３の撮影倍率０．５ｘのときの収差図
【図５５】参考例３の撮影倍率１．０ｘのときの収差図
【図５６】本発明のマクロレンズの近軸屈折力配置の説明図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a macro lens suitable for a camera having an autofocus function such as a photographic camera, a video camera, and an electronic still camera, and more particularly, from an object at infinity to an object at a short distance (photographing magnification: 1.0 ×). The present invention relates to a medium telephoto macro lens having a high angle of view of about 14 degrees and an F number of about 3.5, in which aberration correction is well performed when focusing on a wide range of objects.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is a so-called macro lens or micro lens (hereinafter referred to as “macro lens”) as a photographing lens mainly intended for photographing a short distance object in a photographic camera, a video camera, an electronic still camera, and the like.
[0003]
Of these, a macro lens for a 35 mm single-lens reflex camera is often configured to be able to shoot at a wide range of object distances from an infinitely distant object to a close object with an imaging magnification of 1x or 0.5x.
[0004]
The macro lens is designed so as to obtain high optical performance particularly in a short distance object as compared with other photographing lenses such as a general standard lens and a telephoto lens. In many cases, the macro lens is used not only for a short distance object but also for a wide range of objects ranging from a short distance object to an infinite object.
[0005]
In general, when an attempt is made to expand the object distance range (imaging magnification range) in a macro lens, fluctuations in aberration associated with focus increase. For example, when the photographing magnification is increased, spherical aberration is insufficiently corrected, and a large amount of outward coma occurs.
[0006]
On the other hand, Japanese Patent Application Laid-Open No. 55-140810 comprises three lens groups of positive, negative, and positive refractive power in order from the object side, from an object at infinity. A macro lens has been proposed in which the first lens group is moved to the object side and the second lens group is moved to the image plane side when focusing on an object at a close distance, thereby favorably correcting aberration fluctuations associated with the focus.
[0007]
In Japanese Patent Application No. 4-124480, in order from the object side, the first group of positive refractive power, the first group of positive refractive power, the second group of negative refractive power, and the third group of positive refractive power. A macro lens having a configuration in which the second group is moved to the image side and the first a group is moved to draw a convex arc toward the object side during focusing from an object at infinity to a short distance object is proposed. ing.
[0008]
[Problems to be solved by the invention]
Since the macro lens can be photographed at a wide range of object distances, the amount of movement (movement amount) of the focusing lens is larger than that of a general photographing lens. In addition, as the focal length of the entire system increases, the amount of focusing lens that is fed out increases proportionally and the lens weight of the focusing lens group tends to increase.
[0009]
For example, taking an imaging lens (macro lens) of the entire extension system as a focus method, for example, when focusing on a subject having the same shooting magnification with a shooting lens having the same F number focal length of 100 mm and a focal length of 200 mm, shooting with a focal length of 200 mm The lens is doubled with respect to the photographing lens having a focal length of 100 mm, and the lens weight is considerably increased.
[0010]
In recent years, in an autofocus system camera that has been actively developed, such an increase in the focus feed amount and the lens weight has become a very big problem in realizing high-speed autofocus.
[0011]
Further, when the photographing magnification range is enlarged in the macro lens, especially when the magnification is enlarged to the higher magnification, the aberration fluctuation increases with the change of the photographing magnification, and it becomes very difficult to correct this well.
[0012]
As described above, in the macro lens, it is a big problem to satisfactorily correct various aberrations while reducing the lens weight of the focusing lens group and reducing the lens extension amount.
[0013]
In the present invention, mainly by appropriately setting the lens configuration and the distribution of refractive power, the present invention can be applied to a wide range of object distances from an infinite object to a close object, particularly an imaging magnification of approximately 1.0 times. An object of the present invention is to provide a medium telephoto macro lens having a high optical performance with an F number of about 3.5 suitable for an autofocus camera, in which aberration fluctuations at the time of focusing are well corrected.
[0014]
[Means for Solving the Problems]
Macro lens of the present invention includes, in order from the object side, the 1a lens unit of positive refractive power, a 1b lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power, and a The lens group includes only four groups, and the first group b includes , in order from the object side , only a meniscus negative first b1 lens having a concave surface on the image plane side and a positive first b2 lens as lenses . upon focusing from infinity to a close object, the second group is moved toward the image side, a further macro lens moving either the third group or the fourth group, said 1a group When the combined focal length of the first lens group and the first lens group is f1, the focal length of the first lens group is f1b, and the refractive power of the lens surface on the image surface side of the first lens lens is φ, 1.4 <| φ | · f1 < 2.6 (1)
2 <f1b / f1 <15 (2)
It is characterized by satisfying the following conditions.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
1 to 6, 9, and 10 are lens cross-sectional views of Numerical Examples 1 to 8 of the present invention, and FIGS. 7, 8, and 11 are lens cross-sectional views of Reference Examples 1 to 3, respectively. FIGS. 12 to 35 and FIGS. 44 to 51 are aberration diagrams of Numerical Examples 1 to 8 of the present invention.
36 to 43 and FIGS. 52 to 55 are aberration diagrams of Reference Examples 1 to 3. FIG.
In the aberration diagrams, an object at infinity and photographing magnifications of 0.1x, 0.5x, and 1.0x are shown in order .
[0016]
In the lens cross-sectional view, L1a is a first group of positive refractive power, L1b is a first group of positive refractive power, L2 is a second group of negative refractive power, L3 is a third group of positive refractive power, and L4. Is a fourth group having positive or negative refractive power, and SP is a stop, which is disposed between the second group L2 and the third group L3.
[0017]
In each embodiment, the first group 1b is configured to have a meniscus negative first b1 lens and a positive first b2 lens having a concave surface facing the image plane side. When focusing from an infinitely distant object to a close object, the second lens unit L2 is moved to the image plane side as indicated by an arrow. The third lens unit L3 is moved to the object side as necessary, but may be fixed.
[0018]
In the present embodiment, as described above, the lens configuration is specified, and the refractive power of the lens surface on the image surface side of the first b group, the first group, and the first b1 lens is expressed by the conditional expressions (1) and (2). Thus, aberration variation due to a change in photographing magnification is reduced, and good aberration correction can be performed for a wide range of objects ranging from an object at infinity to a near object. In particular, good aberration correction is possible for a wide range of objects ranging from an object at infinity to a short distance object with a photographing magnification of 1.0.
[0019]
Next, features of aberration correction of the macro lens of the present invention will be described. In the macro lens according to the present invention, focusing is performed over a wide range of object distance, and fluctuations of various aberrations accompanying the focusing at this time will be described using the paraxial refractive power arrangement of FIG.
[0020]
FIG. 56 shows three of the four lens groups constituting the macro lens of the present invention: a first refractive power 1a group L1a, a positive refractive power first b group L1b, and a negative refractive power second group L2. It is explanatory drawing which showed the optical path state when a lens group is extracted and a light ray passes through this lens system.
[0021]
FIG. 56 (A) shows a state in which an object at infinity is focused, and FIG. 56 (B) shows a state in which the second lens unit L2 is moved to the image plane side as shown by an arrow and focused on a short-distance object. . As described above, since the macro lens has a photographing range with a wide object distance, various aberrations are liable to occur during focusing. In particular, the basic spherical aberration tends to be significantly insufficiently corrected. This will be described with reference to the passage diagram of the axial light beam in FIG.
[0022]
First, in the focused state on the object at infinity in FIG. 56 (A), it is assumed that the spherical aberration as the combined system from the first a group L1a group to the second group L2 is in a corrected state. The internal cancellation state is that a negative spherical aberration occurs in the first lens unit L1a and the first lens unit L1b having a positive refractive power and a negative spherical aberration occurs in the second lens unit having a negative refractive power. Correct with good balance by canceling each other.
[0023]
However, in the in-focus state with respect to the short-distance object in FIG. 56 (B), the second group L2 moves to the image plane side, so the incident height of the axial light beam into the second group becomes low. For this reason, the amount of positive spherical aberration generated from the second lens unit L2 is reduced.
[0024]
As a result, the spherical aberration tends to be remarkably insufficiently corrected in the combined system of the first group L1a to the second group L2. Therefore, in the macro lens having such a lens configuration, in order to prevent the spherical aberration from being significantly undercorrected during focusing, the negative aberration of the second group of spherical aberration is reduced as the subject distance becomes shorter. It is necessary to configure the spherical aberration to be displaced in the positive direction in the combined system of the first group 1a and the first group 1b so as to cancel the displacement.
[0025]
Therefore, in the present invention, the 1b group is configured to include a meniscus negative lens (first b1 lens) and a positive lens (first b2 lens) having concave surfaces directed in order from the object side to the image side, thereby increasing spherical aberration. It is displaced in the positive direction.
[0026]
In other words, paying attention to the incidence height to the 1b lens group axial rays becomes higher in the short-distance focusing state in FIG. 56 (B) than the infinity in-focus state in FIG. 56 (A), it The spherical aberration is largely displaced in the positive direction mainly on the lens surface on the image side of the meniscus-shaped negative lens disposed there. The subsequent positive lens is used especially to maintain the first group b as a positive refractive power as a whole. When this positive lens is removed, the share of the positive refractive power of the 1a group increases, making it difficult to correct various aberrations in the 1a group, and at the same time, on the image plane side of the meniscus negative lens. The curvature of the lens surface becomes loose, and the effect of displacement of spherical aberration in the positive direction is weakened. Further, when a meniscus negative lens and a positive lens are cemented, they are separated because the effect of displacement of spherical aberration in the positive direction is weakened.
[0027]
The macro lens of the present invention has a lens configuration as described above, and thereby corrects aberration fluctuations during focusing, particularly spherical aberration fluctuations.
[0028]
Next, the technical meaning of the above conditional expression will be described. Conditional expression (1) relates to the refractive power of the image surface side lens surface of the negative meniscus first b1 lens with the concave surface facing the image surface side in the first group 1b, and the entire system when mainly focusing on a short distance object This is a condition for suppressing the aberration fluctuations of the entire system by efficiently displacing the fluctuations of these aberrations, in particular, the negative aberration of the spherical aberration in the positive direction on the lens surface.
[0029]
When the divergent action of the lens surface increases beyond the upper limit of conditional expression (1), the spherical aberration is greatly displaced in the positive direction when focusing on a close object, and is corrected in the focused state on the close object. It is not good because it becomes excessive. If the divergent action of the lens surface is weakened beyond the lower limit of conditional expression (1), the amount of displacement in the positive direction of spherical aberration becomes smaller when focusing on a close object, and the near object In the in-focus state, correction is insufficient, which is not good.
[0030]
In the present invention, it is more preferable that the conditional expression (1) is 1.8 <| φ | · f1 <2.1 (φ <0) (1a)
It is good to do.
[0031]
Next, Conditional Expression (2) relates to the focal length in the 1b group, in which the refractive power sharing between the 1a group and the 1a group and the 1b group in the combined system (first group) is appropriate. This is a condition for satisfactorily suppressing fluctuations in various aberrations. If the upper limit of conditional expression (2) is exceeded and the positive refractive power of the 1b group is weakened, the share of the positive refractive power of the 1a group increases, resulting in spherical aberration and coma in the 1a group. Therefore, it becomes difficult to correct various aberrations such as astigmatism and field curvature. In particular, when focusing on a short-distance object, the variation in spherical aberration occurring in the first group a is greatly displaced in the negative direction by the action of the essential positive refractive power of the first group, and is removed in the subsequent first group b. It ’s not good because it ca n’t be done.
[0032]
If the lower limit of the conditional expression (2) is exceeded and the positive refractive power sharing of the 1b group is weakened, it becomes easier to correct aberrations in the 1a group, but the balance of various aberrations occurring in the 1b group is balanced. In addition, the displacement amount in the positive direction of spherical aberration during focusing is reduced in the entire first group 1b, and correction is insufficient in a focused state with a short-distance object.
[0033]
In the lens configuration as described above, the refractive power of each lens group is set as in the conditional expressions (1) and (2), so that an object at infinity can be changed to a short distance object with a photographing magnification of about 1.0. Aberration variation is reduced for a wide range of objects, and good optical performance is obtained.
[0034]
In the present invention, it is preferable to satisfy at least one of the following conditions in order to further reduce aberration fluctuations during focusing and obtain good optical performance over the entire object distance.
[0035]
First, the focal length of the aforementioned first group a is
(A1) 1.05 <f1a / f1 <1.74 when the focal length of the 1a group is f1a (3)
It is good to do. More preferably 1.10 <f1a / f1 <1.45 (3a)
It is good to do.
[0036]
(A2) The first group a having a positive lens whose convex surfaces are convex in order from the object side, a meniscus negative lens having a concave surface facing the object side, and a meniscus positive lens having a convex surface facing the object side In this case, it is only necessary to satisfactorily correct fluctuations in various aberrations during focusing, particularly high-order flare fluctuations of color spherical aberration.
[0037]
(A3) The first lens group in the order from the object side is a positive lens, both lens surfaces are convex positive lenses, a meniscus negative lens having a concave surface facing the object side, and a meniscus positive lens having a convex surface facing the object side In this case, the variation of various aberrations including spherical aberration can be corrected more satisfactorily.
[0038]
(A4) The 1a group includes, in addition to the lens configuration described above, a meniscus negative lens having a convex surface directed toward the object side, a positive lens, and a meniscus positive lens having a convex surface directed toward the object side, in order from the object side. Even if it has the structure which has, it is good because the fluctuation | variation of various aberrations can be corrected comparatively favorable.
[0039]
So-called floating may be employed in which the second group is moved during focusing and the other lens groups are moved at different speeds relative to the second group.
[0040]
That is,
(A5) It is preferable to move the third group when focusing from an object at infinity to an object at a short distance. It is particularly preferable to move the third group to the object side.
[0041]
(A6) It is preferable to move the fourth group during focusing from an infinitely distant object to a close object. In particular, the fourth lens group has a positive refractive power, and is preferably moved with a convex locus on the image plane side when focusing from an object at infinity to a near object.
[0042]
(A7) It is preferable to move the first b group during focusing from an infinitely distant object to a close object. In particular, it is preferable to move the first group b toward the image plane side (Reference Example 3) .
[0043]
In the present invention, any of these lens groups can be moved to obtain a floating effect, and in particular, fluctuations in the image plane at the intermediate shooting distance can be corrected more satisfactorily.
[0044]
In particular, when focusing in (A5), if the third group is moved to the object side in the opposite direction to the second group,
(A8) It is preferable to set the lens weight and the movement amount substantially equal to each other so that the lens weight is canceled out in the upward shooting and the downward shooting, and a stable lens driving speed can be obtained.
[0045]
(A9) The second group preferably includes a negative lens having a concave surface directed toward the image surface side in order from the object side, and a cemented lens in which a negative lens L2n having both concave surfaces and a positive lens are cemented. .
[0046]
Among these, when the refractive index and Abbe number of the material of the negative lens L2n having concave lens surfaces are N2n and ν2n, respectively.
[Expression 1]
It is good to do. According to this, it is possible to satisfactorily correct the residual chromatic aberration, particularly axial chromatic aberration, of the combined system of the first group a and the first group b.
[0048]
(A10) 0.15 <| f2 | / f <0.45 (f2) where f2 is the focal length of the second lens unit and f is the focal length of the entire system when focusing on an infinitely distant object in the entire system <0) (5)
It is good to do.
[0049]
If the negative refractive power of the second group becomes weaker than the upper limit value of conditional expression (5), it becomes easier to correct aberrations, but this is not good because the amount of movement of the second group increases during focusing. Conversely, when the negative refractive power increases beyond the lower limit, various aberrations occurring in the second group increase, and at the same time, the positive refractive power of the combined system of the first group 1a and the first group 1b increases, and the generated aberrations also increase. This is not good because it increases and various aberrations in the entire lens system deteriorate.
[0050]
(A11) The third group preferably includes a positive lens having a convex surface facing the object side, and a cemented lens in which a positive lens L3p having a convex surface facing the object side and a negative lens are cemented. Especially when the refractive index and Abbe number of the material of the positive lens L3p of the laminated lens are N3p and ν3p.
[Expression 2]
It is good to do. This is preferable because chromatic aberration, particularly axial chromatic aberration, can be corrected satisfactorily.
[0052]
(A12) The fourth group preferably includes a meniscus negative lens having a convex surface directed toward the image surface side and a positive lens having a convex surface directed toward the object side. Alternatively, the fourth group may include a positive lens, a meniscus negative lens having a convex surface facing the image surface side, and a positive lens having a convex surface facing the object side. This is effective in correcting off-axis aberrations, particularly coma and astigmatism.
[0053]
(A13) The diaphragm may be integrated with the second group or integrated with the third group, but it may be configured with a mechanism that is relatively easy to fix and arrange between the second group and the third group.
[0054]
Then the numerical examples 1 to 8 of the present invention showing a numerical example of Example 1-3. 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 the i-th lens in order from the object side. The refractive index and Abbe number of the glass. Table 1 shows the relationship between the conditional expressions described above and the numerical values in the numerical examples.
[0055]
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. [0056]
[Equation 3]
It is expressed by the following formula.
[0057]
[Outside 1]
[0058]
[Outside 2]
[0059]
[Outside 3]
[0060]
[Outside 4]
[0061]
[Outside 5]
[0062]
[Outside 6]
[0063]
[Expression 1]
[0064]
[Expression 2]
[0065]
[Equation 3]
[0066]
[Expression 4]
[0067]
[Equation 5]
[0068]
[Table 1]
[0069]
【The invention's effect】
As described above, according to the present invention, by appropriately setting the configuration of the entire lens system, in particular, the configuration of the focusing lens group, the imaging magnification from the object at infinity to the object at a short distance, especially the imaging magnification is 1.0 times. A medium telephoto lens having a high optical performance of about F-number 3.5, particularly suitable for an autofocus camera, in which aberration fluctuations are corrected well when focusing on a wide range of object distances to the vicinity. Macro lens can be achieved.
[Brief description of the drawings]
1 is a lens cross-sectional view of Numerical Example 1 of the present invention. FIG. 2 is a lens cross-sectional view of Numerical Example 2 of the present invention. FIG. 3 is a lens cross-sectional view of Numerical Example 3 of the present invention. Lens Cross-sectional View of Numerical Example 4 of the Invention FIG. 5 Lens Cross-sectional View of Numerical Example 5 of the Invention FIG. 6 Lens Cross-sectional View of Numerical Example 6 of the Invention FIG. 7 Reference Example 1 of the Invention FIG. 8 is a lens sectional view of Reference Example 2 of the present invention. FIG. 9 is a lens sectional view of Numerical Example 7 of the present invention. FIG. 10 is a lens sectional view of Numerical Example 8 of the present invention. 11 is a lens cross-sectional view of Reference Example 3 of the present invention. FIG. 12 is an aberration diagram for an infinite object of Numerical Example 1 of the present invention. FIG. 13 is an imaging magnification of 0.1 × of Numerical Example 1 of the present invention. FIG. 14 is an aberration diagram when the photographing magnification is 0.5 × according to Numerical Example 1 of the present invention. FIG. 15 is a numerical value according to the present invention. FIG. 16 is an aberration diagram for an object at infinity according to Numerical Example 2 of the present invention. FIG. 17 is an imaging magnification of 0.1 according to Numerical Example 2 of the present invention. FIG. 18 is an aberration diagram at the photographing magnification of 0.5x in Numerical Example 2 of the present invention. FIG. 19 is an aberration diagram at the photographing magnification of 1.0x in Numerical Example 2 of the present invention. FIG. 20 is an aberration diagram for an object at infinity according to Numerical Example 3 of the present invention. FIG. 21 is an aberration diagram at a photographing magnification of 0.1 × according to Numerical Example 3 of the present invention. FIG. 23 is an aberration diagram when the imaging magnification is 0.5x in Example 3. FIG. 23 is an aberration diagram when the imaging magnification is 1.0x according to Numerical Example 3. FIG. 24 is infinity according to Numerical Example 4 according to the present invention. FIG. 25 is an aberration diagram when an object is used. FIG. 25 is an aberration diagram when the photographing magnification is 0.1 × in Numerical Example 4 of the present invention. FIG. 27 is an aberration diagram of the numerical example 4 when the photographing magnification is 0.5 ×. FIG. 27 is an aberration diagram of the numerical example 4 of the present invention when the photographing magnification is 1.0 ×. FIG. 28 is an infinite number of the numerical example 5 of the present invention. Aberration diagram for a distant object. FIG. 29 is an aberration diagram for Numerical Example 5 of the present invention at a photographing magnification of 0.1x. FIG. 30 is an aberration diagram of Numerical Example 5 of the present invention at a photographing magnification of 0.5x. FIG. 31 is an aberration diagram of the numerical example 5 of the present invention when the photographing magnification is 1.0 ×. FIG. 32 is an aberration diagram of the numerical example 6 of the present invention when the object is at infinity. FIG. 34 is an aberration diagram of the numerical example 6 when the photographing magnification is 0.1 ×. FIG. 34 is an aberration diagram of the numerical example 6 of the present invention when the photographing magnification is 0.5 ×. FIG. 35 is an image of the numerical example 6 of the present invention. aberration diagram when an object at infinity aberration diagram Figure 36 reference example 1 at a magnification 1.0x Figure 37 shooting multiple of reference example 1 Aberration diagram Figure 40 Reference Example when the aberration diagram 38 shows aberration chart at the Reference Example 1 imaging magnification 0.5x [39] Reference Example 1 imaging magnification 1.0x when the 0.1x aberration chart at the photographing magnification 0.5x aberration diagrams Figure 42 reference example 2 in the case of 2 infinite aberration chart at the distant object [41] photographing magnification 0.1x reference example 2 [Figure 43] photographing magnification 0 of numerical example 7 of the aberration diagrams Figure 45 the present invention when the numerical infinite object of example 7 of the aberration diagrams FIG. 44 the present invention when the shooting magnification 1.0x reference example 2. aberration chart at the aberration diagrams photographing magnification 1.0x numerical example 7 of the aberration chart at the photographing magnification 0.5x numerical example 7 of FIG. 46 the present invention Figure 47 the present invention when the 1x photographing magnification 0.1 of numerical example 8 of the aberration diagram when an object at infinity in the numerical value example 8 of FIG. 48 the present invention Figure 49 the invention Aberration chart at the aberration diagrams photographing magnification 1.0x numerical example 8 of the aberration chart at the photographing magnification 0.5x numerical example 8 of FIG. 50 the present invention Figure 51 the present invention when the [ Figure 52] aberration when the aberration diagram FIG. 53 is aberration chart at the photographing magnification 0.1x of reference example 3 [Figure 54] photographing magnification 0.5x of example 3 when an object at infinity reference example 3 FIG. 55 is an aberration diagram of the reference example 3 when the photographing magnification is 1.0 ×. FIG. 56 is an explanatory diagram of a paraxial refractive power arrangement of the macro lens of the present invention.

Claims

物体側より順に、正の屈折力の第１ａ群、正の屈折力の第１ｂ群、負の屈折力の第２群、正の屈折力の第３群、そして第４群のみをレンズ群として有し、該第１ｂ群は、物体側より順に、像面側に凹面を向けたメニスカス状の負の第１ｂ１レンズと正の第１ｂ２レンズのみをレンズとして有し、無限遠物体から近距離物体へのフォーカスに際し、該第２群を像面側へ移動させ、更に、該第３群又は第４群のいずれかを移動させるマクロレンズであって、該第１ａ群と第１ｂ群の合成焦点距離をｆ１、該第１ｂ群の焦点距離をｆ１ｂ、該第１ｂ１レンズの像面側のレンズ面の屈折力をφとしたとき
１．４＜｜φ｜・ｆ１＜２．６
２＜ｆ１ｂ／ｆ１＜１５
なる条件を満足することを特徴とするマクロレンズ。In order from the object side, the 1a lens unit of positive refractive power, a 1b lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power, and only the fourth group as a lens unit The first group 1b has, in order from the object side, a meniscus negative first b1 lens and a positive first b2 lens having a concave surface directed toward the image surface side as a lens, and a short distance object from an infinite object. upon focusing on the second group is moved toward the image side, further, a macro lens moving either the third group or the fourth group, the synthesis focal said 1a group and group the 1b When the distance is f1, the focal length of the first b group is f1b, and the refractive power of the lens surface on the image plane side of the first b1 lens is φ, 1.4 <| φ | · f1 <2.6
2 <f1b / f1 <15
A macro lens characterized by satisfying the following conditions.

前記第１ａ群の焦点距離をｆ１ａとしたとき
１．０５＜ｆ１ａ／ｆ１＜１．７４
なる条件を満足することを特徴とする請求項１のマクロレンズ。When the focal length of the first group a is f1a, 1.05 <f1a / f1 <1.74
The macro lens according to claim 1, wherein the following condition is satisfied.

前記第１ａ群は、物体側より順に、両レンズ面が凸面の正レンズ、物体側へ凹面を向けたメニスカス状の負レンズ、そして物体側へ凸面を向けたメニスカス状の正レンズのみをレンズとして有していることを特徴とする請求項２のマクロレンズ。The 1a group, in order from the object side, a positive lens of both lens surfaces is convex, the negative lens shaped meniscus with a concave surface directed toward the object side, and as only the lens meniscus-like positive lens having a convex surface directed toward the object side The macro lens according to claim 2, wherein the macro lens is provided.

無限遠物体から近距離物体へのフォーカスに際して前記第３群を移動させていることを特徴とする請求項２又は３のマクロレンズ。 4. The macro lens according to claim 2, wherein the third group is moved during focusing from an object at infinity to a near object.

無限遠物体から近距離物体へのフォーカスに際して前記第３群を物体側へ移動させていることを特徴とする請求項４のマクロレンズ。 5. The macro lens according to claim 4, wherein the third group is moved toward the object side when focusing from an object at infinity to an object at a short distance.

無限遠物体から近距離物体へのフォーカスに際して前記第４群を移動させていることを特徴とする請求項２又は３のマクロレンズ。 4. The macro lens according to claim 2, wherein the fourth group is moved during focusing from an object at infinity to an object at a short distance.

前記第４群は正の屈折力を有し、無限遠物体から近距離物体へのフォーカスに際して像面側に凸状の軌跡を有して移動させていることを特徴とする請求項６のマクロレンズ。 7. The macro according to claim 6, wherein the fourth group has a positive refractive power, and has a convex locus on the image plane side during focusing from an object at infinity to a near object. lens.

前記第２群は、物体側より順に、像面側に凹面を向けた負レンズ、両レンズ面が凹面の負レンズと正レンズとを接合した貼合わせレンズのみをレンズとして有していることを特徴とする請求項１又は２のマクロレンズ。The second group comprises, in order from the object side, that has a negative lens having a concave surface on the image side, only the cemented lens obtained by cementing a negative lens and a positive lens of which both surfaces are concave as a lens The macro lens according to claim 1 or 2, characterized in that:

前記第３群は、物体側より順に、物体側に凸面を向けた正レンズ、物体側へ凸面を向けた正レンズと負レンズとを接合した貼合わせレンズのみをレンズとして有していることを特徴とする請求項１又は２のマクロレンズ。The third group includes, in order from the object side, that has a positive lens with a convex surface on the object side, only the joined cemented lens of a positive lens and a negative lens having a convex surface directed toward the object side as a lens The macro lens according to claim 1 or 2, characterized in that:

前記第４群は、物体側より順に、物体側へ凹面を向けたメニスカス状の負レンズと、物体側へ凸面を向けた正レンズのみをレンズとして有していることを特徴とする請求項１又は２のマクロレンズ。The fourth group includes , in order from the object side, a meniscus negative lens having a concave surface directed toward the object side and a positive lens having a convex surface directed toward the object side as lenses. Or 2 macro lenses.

前記第４群は、物体側より順に、正レンズと、物体側へ凹面を向けたメニスカス状の負レンズと、物体側へ凸面を向けた正レンズのみをレンズとして有していることを特徴とする請求項１又は２のマクロレンズ。The fourth group comprises, in order from the object side, a positive lens, and characterized in that it has a meniscus shape negative lens having a concave surface facing toward the object side, only the positive lens having a convex surface directed toward the object side as a lens The macro lens according to claim 1 or 2.

前記第１ａ群は、物体側より順に、正レンズ、両レンズ面が凸面の正レンズ、物体側へ凹面を向けたメニスカス状の負レンズ、そして物体側へ凸面を向けたメニスカス状の正レンズのみをレンズとして有していることを特徴とする請求項２のマクロレンズ。The first group a includes , in order from the object side, a positive lens, a positive lens whose convex surfaces are convex, a meniscus negative lens with a concave surface facing the object side, and a meniscus positive lens with a convex surface facing the object side only macro lens according to claim 2, it characterized in that it has a as a lens.

前記第１ａ群は、物体側より順に、物体側に凸面を向けたメニスカス状の負レンズ、正レンズ、そして物体側へ凸面を向けたメニスカス状の正レンズのみをレンズとして有していることを特徴とする請求項２のマクロレンズ。The first group a has , in order from the object side, a meniscus negative lens having a convex surface facing the object side, a positive lens, and a meniscus positive lens having a convex surface facing the object side as lenses. The macro lens according to claim 2.