JP4593716B2 - Rear focus zoom lens and optical apparatus using the same - Google Patents

Description

【０００１】
【発明の属する技術分野】
本発明は、リヤーフォーカス式のズームレンズ及びそれを用いた光学機器に関し、特にビデオカメラやフィルムカメラ、そして放送用カメラ等に好適に用いられる高変倍比でありながら、大口径比であり、構成するレンズ枚数が比較的少ないリヤーフォーカス式のズームレンズ及びそれを用いた光学機器に関するものである。
【０００２】
【従来の技術】
従来よりビデオカメラや写真カメラ等の光学機器に用いられるズームレンズにおいて、物体側の第１レンズ群以外のレンズ群を移動させてフォーカスを行なう所謂リヤーフォーカス式を採用したものが種々提案されている。一般にリヤーフォーカス式ズームレンズは比較的小型軽量のレンズ群を移動させて焦点合せを行なう為にフォーカスレンズ群の駆動力が小さくなり、迅速な焦点合せが出来る等の特長がある。
【０００３】
例えば、特開昭６２−２４２１３号公報、特開平２−４８６２１号公報、そして特開平４−４３３１１号公報などでは、物体側より順に正の屈折力の第１レンズ群、変倍作用の負の屈折力の第２レンズ群、正の屈折力の第３レンズ群、そして正の第４レンズ群の４つのレンズ群を有し、前記第１、第３レンズ群の各レンズ群を固定とし、前記第２レンズ群を光軸に沿って移動させて変倍を行い、前記第４レンズ群を変倍に伴う像面位置変動を補正するように光軸に沿って移動させるとともに、該第４レンズ群を移動させて合焦を行うリヤーフォーカス式ズームレンズが提案されている。
【０００４】
又、特開昭６３−２９７１８号公報では、物体側より順に正の屈折力の第１群と、負レンズ、負レンズ、正レンズの３枚のレンズにて構成され、全体として負の屈折力で変倍時に可動であって主として変倍をつかさどる第２群と、正の屈折力を有し非球面を含む第３群と、少し大きな空気間隔をあけて正の屈折力を有し変倍に伴う像面変動を補正し、合焦のために移動する第４群より構成したズームレンズを開示している。
【０００５】
又、特開平５−７２４７２号公報では、物体側より順に正の屈折力で固定の第１群、負の屈折力で変倍のための第２群、固定で集光作用を有し正の屈折力の第３群、像面位置を維持するために光軸上を移動する正の屈折力の第４群を有する非球面を用いたズームレンズを開示している。同公報において第２群はメニスカス状の負レンズと両凹レンズと正レンズを配し、第３群は１面以上の非球面である単レンズから構成され、第４群は１面以上の非球面を有するレンズで構成されている。
【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リヤーフォーカス方式を採用すると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等の特長が得られる。
【０００７】
しかしながら反面、フォーカスの際の収差変動が大きくなり、無限遠物体から近距離物体に至る物体距離全般に渡り高い光学性能を得るのが大変難しくなってくる。
【０００８】
特に大口径比で高変倍比のズームレンズでは機構の簡素化を図りつつ、全変倍範囲にわたり、又、物体距離全般にわたり高い光学性能を得るのが大変難しくなってくる。
【０００９】
例えば、先の特開昭６２−２４２１３号公報で提案されているリヤーフォーカス式のズームレンズの実施例をみると、変倍の機能を有する第２レンズ群は、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の単レンズ、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せレンズより構成されている。該貼合せレンズは主に軸上の色収差、球面収差および軸外のコマ収差の補正を行なっている。
【００１０】
前記ズームタイプにおいて更に小型化、高変倍化を図ろうとして第２レンズ群の屈折力を強めると、該第２レンズ群の貼合せレンズ面での収差補正の負担が大きくなり過ぎ、全ズーム域で高性能を実現するのが困難となる。
【００１１】
また、該第２レンズ群の屈折力を強めると、該第２レンズ群を構成する各レンズの曲率が小さくなると共に高次の収差発生量が増加し、ズーム全域で良好に収差補正を行うことが困難になってくる。
【００１２】
本発明は、レンズ系全体を小型化し、高変倍比であるにもかかわらず高い光学性能を有し、かつレンズの構成枚数を減らした簡易な構成のレンズ全長の短いズームレンズ及びそれを用いた光学機器の提供を目的とする。
【００１３】
【課題を解決するための手段】
請求項１の発明のリヤーフォーカス式のズームレンズは、物体側より順に正の屈折力の第１群、負の屈折力の第２群、絞り、正の屈折力の第３群、正の屈折力の第４群より構成され、広角端から望遠端への変倍に際して、前記第１群と前記第３群は不動であり、前記第２群が像面側へ移動し、前記第４群は物体側に凸状の軌跡を有するように移動し、合焦に際して前記第４群が移動し、前記第２群は、物体側から順に、物体側に凸面を向けたメニスカス状の負の第２１レンズ、両レンズ面が凹面の負の第２２レンズ、両レンズ面が凸面の正の第２３レンズと負の第２４レンズとを接合した貼合わせレンズより構成され、前記第３群は非球面を有する１枚の正レンズより構成され、前記第２３レンズの材質のアッベ数をν２３、前記第２４レンズの材質のアッベ数をν２４、前記第２レンズ群の焦点距離をｆ２、前記第２３レンズと前記第２４レンズとの接合レンズ面の曲率半径をＲ２３４とするとき、
１５＜（ν２４−ν２３）＜３０
４．１≦Ｒ２３４／ｆ２≦７．４
なる条件を満足することを特徴としている。
【００１４】
請求項２の発明は請求項１の発明において、前記第２２レンズの像側のレンズ面の曲率半径をＲ２２２、前記第２３レンズの物体側のレンズ面の曲率半径をＲ２３１とするとき、
０＜Ｒ２３１／Ｒ２２２＜０．５
なる条件を満足することを特徴としている。
【００１５】
請求項３の発明の光学機器は、請求項１または２に記載のリヤーフォーカス式のズームレンズを有することを特徴としている。
【００２２】
【発明の実施の形態】
図１は本発明のリヤーフォーカス式のズームレンズの実施形態１の要部断面図、図２，図３，図４は実施形態１の広角端，中間，望遠端のズーム位置における収差図である。
【００２３】
図５は本発明のリヤーフォーカス式のズームレンズの実施形態２の要部断面図、図６，図７，図８は実施形態２の広角端，中間，望遠端のズーム位置における収差図である。
【００２４】
図９は本発明のリヤーフォーカス式のズームレンズの参考例１の要部断面図、図１０，図１１，図１２は参考例１の広角端，中間，望遠端のズーム位置における収差図である。
【００２５】
図１３は本発明のリヤーフォーカス式のズームレンズの実施形態３の要部断面図、図１４，図１５，図１６は実施形態３の広角端，中間，望遠端のズーム位置における収差図である。
【００２６】
図１７は本発明のリヤーフォーカス式のズームレンズの参考例２の要部断面図、図１８，図１９，図２０は参考例２の広角端，中間，望遠端のズーム位置における収差図である。
【００２７】
図２１は本発明のリヤーフォーカス式のズームレンズの実施形態４の要部断面図、図２２，図２３，図２４は実施形態４の広角端，中間，望遠端のズーム位置における収差図である。
【００２８】
図２５は本発明のリヤーフォーカス式のズームレンズの実施形態５の要部断面図、図２６，図２７，図２８は実施形態５の広角端，中間，望遠端のズーム位置における収差図である。
【００２９】
図中Ｌ１は正の屈折力の第１群、Ｌ２は負の屈折力の第２群、Ｌ３は正の屈折力の第３群、Ｌ４は正の屈折力の第４群である。ＳＰは開口絞りであり、第３群Ｌ３の前方に配置している。Ｇは色分解プリズムやフェースプレートやフィルター等のガラスブロックである。ＩＰは像面であり、ＣＣＤ等の撮像素子が配置されている。
【００３０】
本実施形態では広角端から望遠端への変倍に際して矢印のように第２群を像面側へ移動させると共に、変倍に伴う像面変動を第４群の一部又は全部（本実施形態では全部）を物体側に凸状の軌跡を有しつつ移動させて補正している。
【００３１】
又、第４群の一部又は全部（本実施形態では全部）を光軸上移動させてフォーカスを行うリヤーフォーカス式を採用している。同図に示す第４群の実線の曲線４ａと点線の曲線４ｂは各々無限遠物体と近距離物体にフォーカスしているときの広角端から望遠端への変倍に伴う際の像面変動を補正するための移動軌跡を示している。尚、第１群と第３群は変倍及びフォーカスの際固定である。
【００３２】
本実施形態においては第４群を移動させて変倍に伴う像面変動の補正を行うと共に第４群を移動させてフォーカスを行うようにしている。特に同図の曲線４ａ，４ｂに示すように広角端から望遠端への変倍に際して物体側へ凸状の軌跡を有するように移動させている。これにより第３群と第４群との空間の有効利用を図りレンズ全長の短縮化を効果的に達成している。
【００３３】
本実施形態において、例えば望遠端において無限遠物体から近距離物体へフォーカスを行う場合は同図の直線４ｃに示すように第４群を前方へ繰り出すことにより行っている。
【００３４】
本発明において最も特徴的な点は、第２群Ｌ２を前述したレンズ形状の３枚の負レンズと１枚の正レンズの３群４枚のレンズより構成し、更に第３群Ｌ３を構成する１つの正レンズに非球面を用いている点にある。
【００３５】
高変倍比のズームレンズにおいて、小型でズーム全域に渡り良好に収差補正するためには、主に変倍作用を担うバリエータと呼ばれる該第２レンズ群（以下バリエータとも呼ぶ）での収差変動を小さく押さえる事が重要である。しかし、小型で高変倍のレンズ仕様を満たすためには変倍作用を担うバリエータに強い負の屈折力を設定する必要があり、収差補正には不利な条件となる。
【００３６】
従来のバリエータは例えば特開平４−８８３０９号公報実施例に見られるような負レンズ、負レンズと正レンズの接合レンズの２群３枚構成のレンズタイプが主流であった、このタイプのバリエータで高変倍比のズームレンズを実現しようとすると、バリエーターの負の屈折力が強くなるに伴い、バリエータ内の負レンズと正レンズの接合レンズの接合レンズ面の曲率がきつくなり、この接合レンズ面での高次収差の発生がズーム全域での収差変動を大きくする原因となっていた。
【００３７】
そこで本発明のズームレンズにおいては、変倍に大きく寄与する第２レンズ群Ｌ２を上記のようなレンズ構成にすることにより、各レンズのパワーの分担を減らしペッツバール和の低減を図っている。これによって、高変倍比にしてもズーミングによる像面の変動を少なくしている。更に該第２レンズ群から発散で入ってくる光束を受け止める第３レンズ群の正レンズに非球面を配することにより光学性能の向上も図っている。各実施形態においては、第３レンズ群Ｌ３の物体側のレンズ面に非球面を用いている。
【００３８】
又、各数値実施例では、第１群を物体側に凸面を向けたメニスカス状の負の第１１レンズ、両レンズ面が凸面の正レンズ、そしてメニスカス状の正レンズより構成している。又、第４群を両レンズ面が凹面の負レンズ、両レンズ面が凸面の正レンズ、そして両レンズ面が凸面の正レンズより構成している。
【００３９】
本実施形態では以上のようにレンズ構成を設定することにより、全変倍範囲にわたり、又、物体距離全体にわたり高い光学性能を得ている。
【００４０】
本発明のリヤーフォーカス式のズームレンズは、以上のような構成を満足することにより実現されるが、更に高変倍比を維持しつつ光学性能を良好に維持する為には、以下の条件のうち少なくとも１つを満足することが望ましい。
【００４１】
(ア-1)前記第２２レンズの像側のレンズ面の曲率半径をＲ２２２、前記第２３レンズの物体側のレンズ面の曲率半径をＲ２３１とするとき
【００４２】
【数５】
【００４３】
なる条件を満足することである。
【００４４】
バリエータ（第２レンズ群）を物体側から順に、負レンズ、負レンズ、正レンズと負レンズの接合レンズとし、従来タイプ（特開平４−８８３０９号公報）のバリエータでは接合レンズであった物体側より２番目の負レンズと正レンズの間に空気層を設け空隙レンズ作用をもたせた。この空隙レンズを積極的に活用し条件式(1)を満足することで従来、接合レンズ面であったバリエータの物体側より２番目の負レンズと正レンズの向き合ったレンズ面の曲率を緩くすることを可能としている。このレンズ面の曲率を緩くすることにより、高次の球面収差や高次のコマ収差発生を少なくしている。
【００４５】
条件式(1)の下限を超えると、空隙レンズ自体で発生する高次球面収差が増大し収差補正困難となる、上限の０．５を超え１に近づくと空隙レンズ作用の効果が薄れる。
【００４６】
(ア-2)前記第２３レンズの材質のアッベ数をν２３、前記第２４レンズの材質のアッベ数をν２４とするとき
１５＜（ν２４−ν２３）＜３０…(2)
なる条件を満足することである。
【００４７】
(ア-3) 前記第２レンズ群の焦点距離をｆ２、前記第２３レンズと前記第２４レンズとの接合レンズ面の曲率半径をＲ２３４とするとき
【００４８】
【数６】
【００４９】
なる条件を満足することである。
前述の条件式(1)で第２２レンズの像面側のレンズ面と第２３レンズの物体側のレンズ面の曲率を緩くしたため色収差が補正不足となる場合がある。そこでバリエータの色収差をバランスよく補正するために、バリエータの第２３レンズの後ろに第２４レンズを接合し、条件式(2)及び(3)を満足することで、ズーム全域に渡り色収差変動を少なく押さえ、良好な収差補正を可能にしている。
【００５０】
条件式(2)の下限を超えると色収差補正が不足になり、上限を超えると現存する硝材では屈折率の低いものとなり高次球面収差や高次コマ収差の発生が問題になる。
【００５１】
条件式(3)の下限を超えると色収差補正には有利となるが、この接合レンズ面での高次球面収差、コマ収差の発生が問題となる、下限を超えると色収差補正が不足となり、ズーム広角端から望遠端での色収差変動が困難となる。
【００５２】
上記条件を満たし第２レンズ群であるバリエータでの高次収差発生量と収差変動を少なく押さえることにより、第３レンズ群を１枚の非球面レンズ構成で収差補正を可能にしている。
【００５３】
次に本発明のリヤーフォーカス式のズームレンズを撮影光学系として用いたビデオカメラ（光学機器）の実施形態を図２９を用いて説明する。
【００５４】
図２９において、１０はビデオカメラ本体、１１は本発明のズームレンズによって構成された撮影光学系、１２は撮影光学系１１によって被写体像を受光するＣＣＤ等の撮像素子、１３は撮像素子１２が受光した被写体像を記録する記録手段、１４は不図示の表示素子に表示された被写体像を観察するためのファインダーである。上記表示素子は液晶パネル等によって構成され、撮像素子１２上に形成された被写体像が表示される。
【００５５】
このように本発明のズームレンズをビデオカメラ等の光学機器に適用することにより、小型で高い光学性能を有する光学機器を実現している。
【００５６】
以下に本発明の実施形態１乃至５と参考例１、２の数値例を記載する。
【００５７】
各数値実施例においてＲｉは物体側より順に第ｉ番目の面の曲率半径、Ｄｉは物体側より順に第ｉ番目の面と第（ｉ＋１）番目の面の間隔、Ｎｉとνｉは各々物体側より順に第ｉ番目の光学部材のガラスの屈折率とアッベ数である。
【００５８】
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、各非球面係数をＫ，Ｂ，Ｃ，Ｄ，Ｅ，Ｆとしたとき、
【００５９】
【数７】
【００６０】
なる式で表している。
【００６１】
また、例えば「ｅ−Ｚ」の表示は「１０^-Z」を意味する。
【００６２】
数値実施例において最終の２つのレンズ面はフェースプレートやフィルター等のガラスブロックである。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。
【００６３】
【００６４】
【表１】
【００６５】
【００６６】
【表２】
【００６７】
参考例 数値実施例１
f=5.91〜57.79 fno=1:2.90〜3.01 2ω=59.2°〜6.02°
r1=68.270 d1=1.35 n1=1.84666 ν1=23.9
r2=27.077 d2=5.60 n2=1.48749 ν2=70.2
r3=-127.735 d3=0.20
r4=25.006 d4=3.35 n3=1.83481 ν3=42.7
r5=84.576 d5=可変
r6=39.094 d6=0.80 n4=1.88300 ν4=40.8
r7=6.603 d7=2.92
r8=-34.526 d8=0.70 n5=1.88300 ν5=40.8
r9=38.104 d9=0.60
r10=12.977 d10=2.70 n6=1.84666 ν6=23.9
r11=-36.129 d11=0.60 n7=1.83481 ν7=42.7
r12=35.704 d12=可変
r13=（絞り） d13=2.20
＊r14=44.157 d14=1.80 n8=1.58313 ν8=59.4
r15=-28.817 d15=可変
r16=-37.417 d16=0.70 n9=1.84666 ν9=23.9
r17=18.709 d17=2.80 n10=1.67790 ν10=54.9
＊r18=-20.373 d18=0.50
r19=20.715 d19=1.80 n11=1.77250 ν11=49.6
r20=-92.038 d20=可変
r21=∞ d21=3.17 n12=1.51680 ν12=64.2
r22=∞

非球面係数
r14面 r=4.41567D+01 k=-3.79319D+01 B=1.28884D-05
C=-2.45252D-08 D=3.55930D-08 E=7.85890D-10 F=-2.43503D-10
r18面 r=-2.03734D+01 k=-1.30631D-01 B=3.41480D-06
C=1.83231D-07 D=-2.36926D-09 E=-2.35948D-11 F=3.24000D-13
【００６８】
【表３】
【００６９】
数値実施例３
f=6.00〜58.83 fno=1:2.89〜3.00 2ω=58.2°〜6.4°
r1=70.307 d1=1.30 n1=1.84666 ν1=23.9
r2=26.658 d2=5.10 n2=1.48749 ν2=70.2
r3=-175.593 d3=0.20
r4=26.160 d4=3.15 n3=1.88300 ν3=40.8
r5=93.149 d5=可変
r6=30.946 d6=0.80 n4=1.88300 ν4=40.8
r7=6.518 d7=2.99
r8=-36.767 d8=0.70 n5=1.88300 ν5=40.8
r9=38.324 d9=0.60
r10=12.527 d10=2.70 n6=1.84666 ν6=23.9
r11=-65.030 d11=0.60 n7=1.83481 ν7=42.7
r12=29.726 d12=可変
r13=（絞り） d13=2.20
＊r14=42.592 d14=1.80 n8=1.58313 ν8=59.4
r15=-24.975 d15=可変
r16=-40.384 d16=0.70 n9=1.84666 ν9=23.9
r17=18.252 d17=2.80 n10=1.67790 ν10=54.9
＊r18=-19.890 d18=0.50
r19=20.267 d19=1.80 n11=1.77250 ν11=49.6
r20=-199.591 d20=5.00
r21=∞ d21=3.17 n12=1.51680 ν12=64.2
r22=∞

非球面係数
r14面 r=4.25924D+01 k=-3.51255D+01 B=1.27254D-05
C=-2.17513D-07 D=2.57324D-08 E=1.69969D-09 F=-2.13852D-10
r18面 r=-1.98900D+01 k=-1.17923D-01 B=1.39270D-07
C=9.06409D-08 D=2.70260D-09 E=-1.94211D-10 F=1.65295D-12
【００７０】
【表４】
【００７１】
参考例 数値実施例２
f=6.01〜59.01 fno=1:2.89〜2.89 2ω=59.8°〜6.4°
r1=64.967 d1=1.30 n1=1.84666 ν1=23.9
r2=29.027 d2=5.15 n2=1.48749 ν2=70.2
r3=-177.652 d3=0.20
r4=25.154 d4=3.05 n3=1.88481 ν3=42.7
r5=61.808 d5=可変
r6=34.762 d6=0.80 n4=1.88300 ν4=40.8
r7=6.432 d7=2.85
r8=-27.224 d8=0.70 n5=1.88300 ν5=40.8
r9=41.608 d9=0.60
r10=13.918 d10=2.70 n6=1.84666 ν6=23.9
r11=-28.983 d11=0.60 n7=1.83481 ν7=42.7
r12=53.374 d12=可変
r13=（絞り） d13=2.20
＊r14=36.600 d14=1.80 n8=1.58313 ν8=59.4
r15=-28.083 d15=可変
r16=-44.150 d16=0.70 n9=1.84666 ν9=23.9
r17=20.380 d17=2.80 n10=1.67790 ν10=54.9
r18=-22.314 d18=0.50
r19=29.859 d19=1.95 n11=1.77250 ν11=49.6
r20=-94.191 d20=5.00
r21=∞ d21=3.17 n12=1.51680 ν12=64.2
r22=∞

非球面係数
r14面 r=3.66003D+01 k=-2.21824D+01 B=1.91217D-05
C=-9.28714D-07 D=3.22454D-08 E=1.31625D-09 F=-8.90730D-1
【００７２】
【表５】
【００７３】
数値実施例４
f=6.01〜59.00 fno=1:2.89〜2.93 2ω=59.2°〜6.4°
r1=70.577 d1=1.30 n1=1.84666 ν1=23.9
r2=28.102 d2=5.25 n2=1.48749 ν2=70.2
r3=-135.912 d3=0.20
r4=25.710 d4=3.20 n3=1.83481 ν3=42.7
r5=85.671 d5=可変
r6=48.172 d6=0.80 n4=1.88300 ν4=40.8
r7=6.784 d7=2.81
r8=-34.302 d8=0.70 n5=1.88300 ν5=40.8
r9=41.261 d9=0.60
r10=13.312 d10=2.70 n6=1.84666 ν6=23.9
r11=-35.939 d11=0.60 n7=1.83481 ν7=42.7
r12=36.888 d12=可変
r13=（絞り） d13=2.20
＊r14=41.177 d14=1.80 n8=1.58313 ν8=59.4
r15=-29.537 d15=可変
r16=-39.851 d16=0.70 n9=1.84666 ν9=23.9
r17=19.986 d17=2.80 n10=1.67790 ν10=54.9
＊r18=-20.589 d18=0.50
r19=22.582 d19=1.95 n11=1.77250 ν11=49.6
r20=-116.734 d20=5.00
r21=∞ d21=3.17 n12=1.51680 ν12=64.2
r22=∞

非球面係数
r14面 r=4.11772D+01 k=-3.06458D+01 B=1.49123D-05
C=-9.25985D-08 D=1.59599D-08 E=1.57343D-09 F=-1.66189D-10
r18面 r=-2.05892D+01 k=-1.61879D-01 B=2.46942D-07
C=2.33996D-07 D=-6.83658D-09 E=2.80776D-11 F=1.30665D-12
【００７４】
【表６】
【００７５】
数値実施例５
f=6.03〜59.02 fno=1:2.87〜2.89 2ω=59.0°〜6.4°
r1=62.095 d1=1.30 n1=1.84666 ν1=23.9
r2=28.268 d2=4.70 n2=1.48749 ν2=70.2
r3=-228.219 d3=0.20
r4=25.507 d4=2.95 n3=1.83481 ν3=42.7
r5=67.193 d5=可変
r6=26.771 d6=0.80 n4=1.88300 ν4=40.8
r7=6.365 d7=3.15
r8=-23.692 d8=0.70 n5=1.88300 ν5=40.8
r9=74.962 d9=0.60
r10=13.790 d10=2.50 n6=1.84666 ν6=23.9
r11=-49.225 d11=0.60 n7=1.77250 ν7=49.6
r12=33.632 d12=可変
r13=（絞り） d13=3.00
＊r14=41.241 d14=2.00 n8=1.58313 ν8=59.4
r15=-25.592 d15=可変
r16=-29.471 d16=0.70 n9=1.84666 ν9=23.9
r17=25.818 d17=2.85 n10=1.67790 ν10=54.9
r18=-17.943 d18=0.50
r19=28.075 d19=1.80 n11=1.77250 ν11=49.6
r20=-137.571 d20=5.00
r21=∞ d21=3.17 n12=1.51680 ν12=64.2
r22=∞

非球面係数
r14面 r=4.12412D+01 k=-2.09653D+01 B=-9.81742D-06
C=-2.33933D-07 D=7.49268D-09 E=2.16763D-09 F=-1.21645D-10
【００７６】
【表７】
【００７７】
【表８】
【００７８】
【発明の効果】
本発明によれば、レンズ系全体を小型化し、高変倍比であるにもかかわらず高い光学性能を有し、かつレンズの構成枚数を減らした簡易な構成のレンズ全長の短いズームレンズ及びそれを用いた光学機器を達成することができる。
【００７９】
この他、本発明によれば変倍比１０倍に及ぶ高変倍比でありながら、小型軽量の全変倍範囲に渡り良好に収差補正を行った高い光学性能を有したリアーフォーカス式ズームレンズを達成する事ができる。
【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１の広角端の収差図
【図３】 本発明の数値実施例１の中間の収差図
【図４】 本発明の数値実施例１の望遠端の収差図
【図５】 本発明の数値実施例２のレンズ断面図
【図６】 本発明の数値実施例２の広角端の収差図
【図７】 本発明の数値実施例２の中間の収差図
【図８】 本発明の数値実施例２の望遠端の収差図
【図９】 本発明の参考例１のレンズ断面図
【図１０】 本発明の参考例１の広角端の収差図
【図１１】 本発明の参考例１の中間の収差図
【図１２】 本発明の参考例１の望遠端の収差図
【図１３】 本発明の数値実施例３のレンズ断面図
【図１４】 本発明の数値実施例３の広角端の収差図
【図１５】 本発明の数値実施例３の中間の収差図
【図１６】 本発明の数値実施例３の望遠端の収差図
【図１７】 本発明の参考例２のレンズ断面図
【図１８】 本発明の参考例２の広角端の収差図
【図１９】 本発明の参考例２の中間の収差図
【図２０】 本発明の参考例２の望遠端の収差図
【図２１】 本発明の数値実施例４のレンズ断面図
【図２２】 本発明の数値実施例４の広角端の収差図
【図２３】 本発明の数値実施例４の中間の収差図
【図２４】 本発明の数値実施例４の望遠端の収差図
【図２５】 本発明の数値実施例５のレンズ断面図
【図２６】 本発明の数値実施例５の広角端の収差図
【図２７】 本発明の数値実施例５の中間の収差図
【図２８】 本発明の数値実施例５の望遠端の収差図
【図２９】 本発明の光学機器の要部概略図
【符号の説明】
Ｌ１ 第１群
Ｌ２ 第２群
Ｌ３ 第３群
Ｌ４ 第４群
ＳＰ 絞り
Ｇ ガラスブロック
ＩＰ 像面
ｄ ｄ線
ｇ ｇ線
ΔＭ メリディオナル像面
ΔＳ サジタル像面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rear focus type zoom lens and an optical apparatus using the same, and in particular, a high aperture ratio suitable for a video camera, a film camera, a broadcast camera, etc., and a large aperture ratio, The present invention relates to a rear focus type zoom lens having a relatively small number of lenses and an optical apparatus using the same.
[0002]
[Prior art]
Conventionally, various zoom lenses used in optical devices such as a video camera and a photo camera adopt a so-called rear focus type in which focusing is performed by moving a lens group other than the first lens group on the object side. . In general, the rear focus type zoom lens has a feature that a focusing lens group is moved by moving a relatively small and light lens group, so that the driving force of the focus lens group is reduced and quick focusing can be performed.
[0003]
For example, in JP-A-62-24213, JP-A-2-48621, and JP-A-4-43311, a first lens unit having a positive refractive power in order from the object side, and a negative zooming effect are disclosed. There are four lens groups, a second lens group having a refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, and the first and third lens groups are fixed, The second lens group is moved along the optical axis to perform zooming, the fourth lens group is moved along the optical axis so as to correct image plane position fluctuations accompanying zooming, and the fourth lens group is moved along the optical axis. There has been proposed a rear focus type zoom lens that moves a lens group to perform focusing.
[0004]
Japanese Patent Laid-Open No. 63-29718 is composed of a first lens unit having a positive refractive power in order from the object side and three lenses, a negative lens, a negative lens, and a positive lens, and has a negative refractive power as a whole. The second group that is movable at the time of zooming and mainly controls zooming, and the third group that has positive refractive power and includes an aspherical surface, and has a positive refractive power with a slight air gap, and zooming 4 discloses a zoom lens composed of a fourth lens group that corrects image plane fluctuations accompanying the movement and moves for focusing.
[0005]
Japanese Patent Laid-Open No. 5-72472 discloses a first group fixed with positive refractive power in order from the object side, a second group for zooming with negative refractive power, and a positive and positive light collecting function. A zoom lens using an aspherical surface having a third group of refractive power and a fourth group of positive refractive power that moves on the optical axis in order to maintain the image plane position is disclosed. In this publication, the second group includes a meniscus negative lens, a biconcave lens, and a positive lens, the third group is composed of a single lens having one or more aspheric surfaces, and the fourth group is one or more aspheric surfaces. It is comprised with the lens which has.
[0006]
[Problems to be solved by the invention]
In general, when a rear focus method is used in a zoom lens, the entire lens system is reduced in size, rapid focusing is possible, and further close-up photography is facilitated.
[0007]
However, on the other hand, aberration fluctuations during focusing become large, and it becomes very difficult to obtain high optical performance over the entire object distance from an object at infinity to a near object.
[0008]
In particular, in a zoom lens having a large aperture ratio and a high zoom ratio, it is very difficult to obtain high optical performance over the entire zoom range and the entire object distance while simplifying the mechanism.
[0009]
For example, in the example of the rear focus type zoom lens proposed in Japanese Patent Laid-Open No. 62-24213, the second lens group having a zooming function is convex on the object side in order from the object side. Meniscus-shaped negative single lens, and a cemented lens obtained by bonding a negative lens having a concave surface on both lens surfaces and a positive lens. The cemented lens mainly corrects axial chromatic aberration, spherical aberration, and off-axis coma.
[0010]
If the refractive power of the second lens unit is increased in order to further reduce the size and increase the zoom ratio in the zoom type, the burden of aberration correction on the cemented lens surface of the second lens unit becomes too great, and the entire zoom It becomes difficult to achieve high performance in the region.
[0011]
Further, when strengthening the refractive power of the second lens group, the aberration generation amount of higher-order co of curvature of each lens composing the second lens group becomes small is increased, it performs satisfactorily correct aberrations over the entire zoom range It becomes difficult.
[0012]
The present invention provides a zoom lens having a short overall lens length and a simple configuration in which the entire lens system is downsized, has high optical performance despite a high zoom ratio, and has a reduced number of lenses. The purpose is to provide optical equipment.
[0013]
[Means for Solving the Problems]
The rear focus type zoom lens according to the first aspect of the present invention includes, in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a stop , a third group having a positive refractive power, and a positive refraction. The fourth group of forces, and at the time of zooming from the wide-angle end to the telephoto end, the first group and the third group are stationary, the second group moves toward the image plane side, and the fourth group Moves so as to have a convex trajectory on the object side, the fourth group moves upon focusing, and the second group moves in order from the object side to a negative meniscus shape with a convex surface facing the object side. 21 lens, a negative second 22 lens of which both surfaces are concave, both lens surfaces are composed of a positive 23 lens and a negative of the 24 lens and joining the cemented lens convex, the third group of aspherical It is composed of one positive lens having the Abbe number of the material of the first 23 lens Nyu23, the 24th lens When the material of the Abbe number Nyu24, the focal length of the second lens group f2, and R234 curvature radius of the contact lens surface between the first 23 lens and the 24 lens,
15 <(ν24−ν23) <30
4.1 ≦ R234 / f2 ≦ 7.4
It is characterized by satisfying the following conditions.
[0014]
The invention of claim 2 is the invention of claim 1, wherein the radius of curvature of the lens surface on the image side of the 22nd lens is R222, and the radius of curvature of the lens surface of the object side of the 23rd lens is R231.
0 <R231 / R222 <0.5
It is characterized by satisfying the following conditions.
[0015]
An optical apparatus according to a third aspect of the invention includes the rear focus zoom lens according to the first or second aspect.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view of a main part of a first embodiment of a rear focus type zoom lens according to the present invention, and FIGS. 2, 3 and 4 are aberration diagrams at zoom positions of a wide angle end, an intermediate position and a telephoto end of the first embodiment. .
[0023]
FIG. 5 is a cross-sectional view of a main part of the rear focus type zoom lens according to the second embodiment of the present invention, and FIGS. 6, 7, and 8 are aberration diagrams at the zoom positions at the wide-angle end, the middle, and the telephoto end. .
[0024]
FIG. 9 is a cross-sectional view of the main part of Reference Example 1 of the rear focus type zoom lens of the present invention, and FIGS. 10, 11 and 12 are aberration diagrams at the zoom positions at the wide-angle end, intermediate position and telephoto end of Reference Example 1 . .
[0025]
FIG. 13 is a cross-sectional view of a main part of the rear focus type zoom lens according to the third embodiment of the present invention, and FIGS. 14, 15, and 16 are aberration diagrams at the zoom positions at the wide-angle end, the middle, and the telephoto end of the third embodiment. .
[0026]
FIG. 17 is a cross-sectional view of the main part of Reference Example 2 of the rear focus type zoom lens of the present invention, and FIGS. 18, 19, and 20 are aberration diagrams at the zoom positions at the wide-angle end, intermediate position, and telephoto end of Reference Example 2 . .
[0027]
FIG. 21 is a cross-sectional view of a main part of a rear focus zoom lens according to a fourth embodiment of the present invention, and FIGS. 22, 23, and 24 are aberration diagrams at the zoom positions at the wide-angle end, the middle, and the telephoto end according to the fourth embodiment. .
[0028]
FIG. 25 is a cross-sectional view of a main part of the rear focus type zoom lens according to the fifth embodiment of the present invention, and FIGS. 26, 27, and 28 are aberration diagrams at the zoom positions at the wide-angle end, the middle, and the telephoto end of the fifth embodiment. .
[0029]
In the figure, L1 is a first group having a positive refractive power, L2 is a second group having a negative refractive power, L3 is a third group having a positive refractive power, and L4 is a fourth group having a positive refractive power. SP is an aperture stop, which is disposed in front of the third lens unit L3. G is a glass block such as a color separation prism, a face plate or a filter. IP is an image plane, and an image pickup device such as a CCD is disposed.
[0030]
In the present embodiment, the second lens unit is moved to the image plane side as indicated by an arrow during zooming from the wide-angle end to the telephoto end, and the image plane variation caused by zooming is part or all of the fourth lens group (this embodiment Are all corrected while having a convex locus on the object side.
[0031]
Further, a rear focus type is adopted in which focusing is performed by moving a part or all of the fourth group (all in the present embodiment) on the optical axis. The solid curve 4a and the dotted curve 4b of the fourth group shown in the figure show the image plane fluctuations accompanying the zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and an object at close distance, respectively. A movement trajectory for correction is shown. The first group and the third group are fixed during zooming and focusing.
[0032]
In the present embodiment , the fourth group is moved to correct the image plane variation accompanying zooming, and the fourth group is moved to perform focusing. In particular, as shown by the curves 4a and 4b in the figure, the zoom lens is moved so as to have a convex locus toward the object side upon zooming from the wide-angle end to the telephoto end. As a result, the space between the third group and the fourth group is effectively used, and the overall length of the lens is effectively shortened.
[0033]
In the present embodiment, for example, when the focusing from infinity to a close object at the telephoto end is performed by moving the fourth group forward as shown by a straight line 4c in FIG.
[0034]
In the present invention, the most characteristic point is that the second group L2 is composed of the three negative lenses having the above-mentioned lens shape and the four positive lenses, and further the third group L3. This is in that an aspheric surface is used for one positive lens.
[0035]
In a zoom lens with a high zoom ratio, in order to correct aberrations satisfactorily over the entire zoom range, aberration variation in the second lens group (hereinafter also referred to as a variator) mainly called a variator is mainly responsible for the zooming action. It is important to keep it small. However, it is necessary to set a strong negative refracting power for the variator responsible for zooming in order to satisfy the specifications of a compact and high zoom lens, which is a disadvantageous condition for aberration correction.
[0036]
A conventional variator is a variator of this type in which a lens type of two groups and three elements of a negative lens and a cemented lens of a negative lens and a positive lens, as seen in, for example, JP-A-4-88309, is the mainstream. When trying to realize a zoom lens with a high zoom ratio, as the negative refractive power of the variator increases, the curvature of the cemented lens surface between the negative lens and the positive lens in the variator becomes tight, and this cemented lens surface The occurrence of high-order aberrations at the zoom lens caused a large variation in aberrations throughout the entire zoom range.
[0037]
Therefore, in the zoom lens of the present invention, the second lens unit L2 that greatly contributes to zooming is configured as described above, thereby reducing the power sharing of each lens and reducing the Petzval sum. As a result, even if the zoom ratio is high, fluctuations in the image plane due to zooming are reduced. Further, the optical performance is improved by arranging an aspherical surface on the positive lens of the third lens group that receives the light beam diverging from the second lens group. In each embodiment, an aspheric surface is used as the object-side lens surface of the third lens unit L3.
[0038]
In each numerical example, the first lens unit is composed of a negative meniscus eleventh lens having a convex surface facing the object side, a positive lens having convex surfaces on both lens surfaces, and a positive meniscus lens. The fourth lens unit is composed of a negative lens having concave surfaces, a positive lens having convex surfaces, and a positive lens having convex surfaces.
[0039]
In this embodiment, by setting the lens configuration as described above, high optical performance is obtained over the entire zoom range and over the entire object distance.
[0040]
The rear focus type zoom lens according to the present invention is realized by satisfying the above-described configuration, and in order to maintain good optical performance while maintaining a high zoom ratio, the following conditions are satisfied. It is desirable to satisfy at least one of them.
[0041]
(A-1) When the radius of curvature of the image-side lens surface of the 22nd lens is R222 and the radius of curvature of the object-side lens surface of the 23rd lens is R231
[Equation 5]
[0043]
To satisfy the following conditions.
[0044]
Variator (second lens group) in order from the object side, a negative lens, a negative lens, a positive lens and a negative lens of the cemented lens, a conventional type object side was cemented lens in the variator (JP-A 4-88309 JP) In addition , an air layer was provided between the second negative lens and the positive lens to provide an air gap lens action. By actively using this air gap lens and satisfying conditional expression (1), the curvature of the lens surface facing the second negative lens and the positive lens from the object side of the variator, which was a cemented lens surface, is relaxed. Making it possible. By reducing the curvature of the lens surface, the occurrence of higher-order spherical aberration and higher-order coma aberration is reduced.
[0045]
When the lower limit of conditional expression (1) is exceeded, higher-order spherical aberration generated in the air gap lens itself increases, making it difficult to correct aberrations. When the upper limit of 0.5 is approached and 1 is approached, the effect of the air gap lens is diminished.
[0046]
(A-2) When the Abbe number of the material of the 23rd lens is ν23 and the Abbe number of the material of the 24th lens is ν24, 15 <(ν24−ν23) <30 (2)
To satisfy the following conditions.
[0047]
(A-3) When the focal length of the second lens group is f2, and the radius of curvature of the cemented lens surface of the 23rd lens and the 24th lens is R234.
[Formula 6]
[0049]
To satisfy the following conditions.
In the above-described conditional expression (1), the curvature of the lens surface on the image side of the 22nd lens and the lens surface on the object side of the 23rd lens may be loosened, so that chromatic aberration may be undercorrected. Therefore, in order to correct the chromatic aberration of the variator in a well-balanced manner, the 24th lens is cemented after the 23rd lens of the variator, and the conditional expressions (2) and (3) are satisfied, so that the chromatic aberration fluctuation is reduced over the entire zoom range. This makes it possible to suppress aberrations and correct aberrations.
[0050]
If the lower limit of conditional expression (2) is exceeded, chromatic aberration correction will be insufficient, and if the upper limit is exceeded, existing glass materials will have a low refractive index, causing the occurrence of higher-order spherical aberration and higher-order coma aberration.
[0051]
If the lower limit of conditional expression (3) is exceeded, it is advantageous for chromatic aberration correction, but the occurrence of higher-order spherical aberration and coma on the cemented lens surface becomes a problem. It becomes difficult to change chromatic aberration from the wide-angle end to the telephoto end.
[0052]
By satisfying the above conditions and suppressing generation of high-order aberrations and aberration fluctuations in the variator, which is the second lens group, the third lens group can be corrected for aberration with a single aspheric lens configuration.
[0053]
Next, an embodiment of a video camera (optical apparatus) using the rear focus zoom lens of the present invention as a photographing optical system will be described with reference to FIG.
[0054]
In FIG. 29, 10 is a video camera body, 11 is a photographic optical system constituted by the zoom lens of the present invention, 12 is an image sensor such as a CCD that receives a subject image by the photographic optical system 11, and 13 is received by the image sensor 12. A recording means 14 for recording the subject image, and a finder for observing the subject image displayed on a display element (not shown). The display element is constituted by a liquid crystal panel or the like, and a subject image formed on the image sensor 12 is displayed.
[0055]
Thus, by applying the zoom lens of the present invention to an optical apparatus such as a video camera, a small-sized optical apparatus having high optical performance is realized.
[0056]
Numerical examples of Embodiments 1 to 5 and Reference Examples 1 and 2 of the present invention will be described below.
[0057]
In each numerical example, Ri is the radius of curvature of the i-th surface in order from the object side, Di is the distance between the i-th surface and the (i + 1) -th surface in order from the object side, and Ni and νi are from the object side, respectively. It is the refractive index and Abbe number of the glass of the i-th optical member in order.
[0058]
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 each aspheric coefficient is K, B, C, D, E, When F
[0059]
[Expression 7]
[0060]
It is expressed by the following formula.
[0061]
For example, “e-Z” means “10 ^−Z ”.
[0062]
In the numerical examples, the last two lens surfaces are glass blocks such as face plates and filters. Table 1 shows the relationship between the above-described conditional expressions and numerical values in the numerical examples.
[0063]
[0064]
[Table 1]
[0065]
[0066]
[Table 2]
[0067]
Reference Example Numerical Example 1
f = 5.91 ~ 57.79 fno = 1: 2.90 ~ 3.01 2ω = 59.2 ° ~ 6.02 °
r1 = 68.270 d1 = 1.35 n1 = 1.84666 ν1 = 23.9
r2 = 27.077 d2 = 5.60 n2 = 1.48749 ν2 = 70.2
r3 = -127.735 d3 = 0.20
r4 = 25.006 d4 = 3.35 n3 = 1.83481 ν3 = 42.7
r5 = 84.576 d5 = variable
r6 = 39.094 d6 = 0.80 n4 = 1.88300 ν4 = 40.8
r7 = 6.603 d7 = 2.92
r8 = -34.526 d8 = 0.70 n5 = 1.88300 ν5 = 40.8
r9 = 38.104 d9 = 0.60
r10 = 12.977 d10 = 2.70 n6 = 1.84666 ν6 = 23.9
r11 = -36.129 d11 = 0.60 n7 = 1.83481 ν7 = 42.7
r12 = 35.704 d12 = variable
r13 = (Aperture) d13 = 2.20
* R14 = 44.157 d14 = 1.80 n8 = 1.58313 ν8 = 59.4
r15 = -28.817 d15 = variable
r16 = -37.417 d16 = 0.70 n9 = 1.84666 ν9 = 23.9
r17 = 18.709 d17 = 2.80 n10 = 1.67790 ν10 = 54.9
* R18 = -20.373 d18 = 0.50
r19 = 20.715 d19 = 1.80 n11 = 1.77250 ν11 = 49.6
r20 = -92.038 d20 = variable
r21 = ∞ d21 = 3.17 n12 = 1.51680 ν12 = 64.2
r22 = ∞

Aspheric coefficient
r14 surface r = 4.41567D + 01 k = -3.79319D + 01 B = 1.28884D-05
C = -2.45252D-08 D = 3.55930D-08 E = 7.85890D-10 F = -2.43503D-10
r18 surface r = -2.03734D + 01 k = -1.30631D-01 B = 3.41480D-06
C = 1.83231D-07 D = -2.36926D-09 E = -2.35948D-11 F = 3.24000D-13
[0068]
[Table 3]
[0069]
Numerical Example 3
f = 6.00 ~ 58.83 fno = 1: 2.89 ~ 3.00 2ω = 58.2 ° ~ 6.4 °
r1 = 70.307 d1 = 1.30 n1 = 1.84666 ν1 = 23.9
r2 = 26.658 d2 = 5.10 n2 = 1.48749 ν2 = 70.2
r3 = -175.593 d3 = 0.20
r4 = 26.160 d4 = 3.15 n3 = 1.88300 ν3 = 40.8
r5 = 93.149 d5 = variable
r6 = 30.946 d6 = 0.80 n4 = 1.88300 ν4 = 40.8
r7 = 6.518 d7 = 2.99
r8 = -36.767 d8 = 0.70 n5 = 1.88300 ν5 = 40.8
r9 = 38.324 d9 = 0.60
r10 = 12.527 d10 = 2.70 n6 = 1.84666 ν6 = 23.9
r11 = -65.030 d11 = 0.60 n7 = 1.83481 ν7 = 42.7
r12 = 29.726 d12 = variable
r13 = (Aperture) d13 = 2.20
* R14 = 42.592 d14 = 1.80 n8 = 1.58313 ν8 = 59.4
r15 = -24.975 d15 = variable
r16 = -40.384 d16 = 0.70 n9 = 1.84666 ν9 = 23.9
r17 = 18.252 d17 = 2.80 n10 = 1.67790 ν10 = 54.9
* R18 = -19.890 d18 = 0.50
r19 = 20.267 d19 = 1.80 n11 = 1.77250 ν11 = 49.6
r20 = -199.591 d20 = 5.00
r21 = ∞ d21 = 3.17 n12 = 1.51680 ν12 = 64.2
r22 = ∞

Aspheric coefficient
r14 surface r = 4.25924D + 01 k = -3.51255D + 01 B = 1.27254D-05
C = -2.17513D-07 D = 2.57324D-08 E = 1.69969D-09 F = -2.13852D-10
r18 surface r = -1.98900D + 01 k = -1.17923D-01 B = 1.39270D-07
C = 9.06409D-08 D = 2.70260D-09 E = -1.94211D-10 F = 1.65295D-12
[0070]
[Table 4]
[0071]
Reference Example Numerical Example 2
f = 6.01 ~ 59.01 fno = 1: 2.89 ~ 2.89 2ω = 59.8 ° ~ 6.4 °
r1 = 64.967 d1 = 1.30 n1 = 1.84666 ν1 = 23.9
r2 = 29.027 d2 = 5.15 n2 = 1.48749 ν2 = 70.2
r3 = -177.652 d3 = 0.20
r4 = 25.154 d4 = 3.05 n3 = 1.88481 ν3 = 42.7
r5 = 61.808 d5 = variable
r6 = 34.762 d6 = 0.80 n4 = 1.88300 ν4 = 40.8
r7 = 6.432 d7 = 2.85
r8 = -27.224 d8 = 0.70 n5 = 1.88300 ν5 = 40.8
r9 = 41.608 d9 = 0.60
r10 = 13.918 d10 = 2.70 n6 = 1.84666 ν6 = 23.9
r11 = -28.983 d11 = 0.60 n7 = 1.83481 ν7 = 42.7
r12 = 53.374 d12 = variable
r13 = (Aperture) d13 = 2.20
* R14 = 36.600 d14 = 1.80 n8 = 1.58313 ν8 = 59.4
r15 = -28.083 d15 = variable
r16 = -44.150 d16 = 0.70 n9 = 1.84666 ν9 = 23.9
r17 = 20.380 d17 = 2.80 n10 = 1.67790 ν10 = 54.9
r18 = -22.314 d18 = 0.50
r19 = 29.859 d19 = 1.95 n11 = 1.77250 ν11 = 49.6
r20 = -94.191 d20 = 5.00
r21 = ∞ d21 = 3.17 n12 = 1.51680 ν12 = 64.2
r22 = ∞

Aspheric coefficient
r14 surface r = 3.66003D + 01 k = -2.21824D + 01 B = 1.91217D-05
C = -9.28714D-07 D = 3.22454D-08 E = 1.31625D-09 F = -8.90730D-1
[0072]
[Table 5]
[0073]
Numerical Example 4
f = 6.01 ~ 59.00 fno = 1: 2.89 ~ 2.93 2ω = 59.2 ° ~ 6.4 °
r1 = 70.577 d1 = 1.30 n1 = 1.84666 ν1 = 23.9
r2 = 28.102 d2 = 5.25 n2 = 1.48749 ν2 = 70.2
r3 = -135.912 d3 = 0.20
r4 = 25.710 d4 = 3.20 n3 = 1.83481 ν3 = 42.7
r5 = 85.671 d5 = variable
r6 = 48.172 d6 = 0.80 n4 = 1.88300 ν4 = 40.8
r7 = 6.784 d7 = 2.81
r8 = -34.302 d8 = 0.70 n5 = 1.88300 ν5 = 40.8
r9 = 41.261 d9 = 0.60
r10 = 13.312 d10 = 2.70 n6 = 1.84666 ν6 = 23.9
r11 = -35.939 d11 = 0.60 n7 = 1.83481 ν7 = 42.7
r12 = 36.888 d12 = variable
r13 = (Aperture) d13 = 2.20
* R14 = 41.177 d14 = 1.80 n8 = 1.58313 ν8 = 59.4
r15 = -29.537 d15 = variable
r16 = -39.851 d16 = 0.70 n9 = 1.84666 ν9 = 23.9
r17 = 19.986 d17 = 2.80 n10 = 1.67790 ν10 = 54.9
* R18 = -20.589 d18 = 0.50
r19 = 22.582 d19 = 1.95 n11 = 1.77250 ν11 = 49.6
r20 = -116.734 d20 = 5.00
r21 = ∞ d21 = 3.17 n12 = 1.51680 ν12 = 64.2
r22 = ∞

Aspheric coefficient
r14 surface r = 4.11772D + 01 k = -3.06458D + 01 B = 1.49123D-05
C = -9.25985D-08 D = 1.59599D-08 E = 1.57343D-09 F = -1.66189D-10
r18 surface r = -2.05892D + 01 k = -1.61879D-01 B = 2.46942D-07
C = 2.33996D-07 D = -6.83658D-09 E = 2.80776D-11 F = 1.30665D-12
[0074]
[Table 6]
[0075]
Numerical Example 5
f = 6.03 ~ 59.02 fno = 1: 2.87 ~ 2.89 2ω = 59.0 ° ~ 6.4 °
r1 = 62.095 d1 = 1.30 n1 = 1.84666 ν1 = 23.9
r2 = 28.268 d2 = 4.70 n2 = 1.48749 ν2 = 70.2
r3 = -228.219 d3 = 0.20
r4 = 25.507 d4 = 2.95 n3 = 1.83481 ν3 = 42.7
r5 = 67.193 d5 = variable
r6 = 26.771 d6 = 0.80 n4 = 1.88300 ν4 = 40.8
r7 = 6.365 d7 = 3.15
r8 = -23.692 d8 = 0.70 n5 = 1.88300 ν5 = 40.8
r9 = 74.962 d9 = 0.60
r10 = 13.790 d10 = 2.50 n6 = 1.84666 ν6 = 23.9
r11 = -49.225 d11 = 0.60 n7 = 1.77250 ν7 = 49.6
r12 = 33.632 d12 = variable
r13 = (Aperture) d13 = 3.00
* R14 = 41.241 d14 = 2.00 n8 = 1.58313 ν8 = 59.4
r15 = -25.592 d15 = variable
r16 = -29.471 d16 = 0.70 n9 = 1.84666 ν9 = 23.9
r17 = 25.818 d17 = 2.85 n10 = 1.67790 ν10 = 54.9
r18 = -17.943 d18 = 0.50
r19 = 28.075 d19 = 1.80 n11 = 1.77250 ν11 = 49.6
r20 = -137.571 d20 = 5.00
r21 = ∞ d21 = 3.17 n12 = 1.51680 ν12 = 64.2
r22 = ∞

Aspheric coefficient
r14 surface r = 4.12412D + 01 k = -2.09653D + 01 B = -9.81742D-06
C = -2.33933D-07 D = 7.49268D-09 E = 2.16763D-09 F = -1.21645D-10
[0076]
[Table 7]
[0077]
[Table 8]
[0078]
【The invention's effect】
According to the present invention, a zoom lens having a short overall lens length and a simple configuration in which the entire lens system is reduced in size, has high optical performance despite a high zoom ratio, and has a reduced number of lenses. An optical instrument using can be achieved.
[0079]
In addition to this, according to the present invention, a rear focus zoom lens having high optical performance in which aberration correction is satisfactorily performed over the entire zoom range of a small size and light weight while having a high zoom ratio of 10 times. 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 an aberration diagram at the wide angle end of Numerical Example 1 of the present invention. FIG. 3 is an intermediate aberration diagram of Numerical Example 1 of the present invention. 4 is an aberration diagram at the telephoto end of Numerical Example 1 of the present invention. FIG. 5 is a sectional view of a lens of Numerical Example 2 of the present invention. FIG. 6 is an aberration diagram at the wide-angle end of Numerical Example 2 of the present invention. FIG. 8 is an aberration diagram at the telephoto end of Numerical Example 2 according to the present invention. FIG. 9 is a sectional view of a lens according to Reference Example 1 of the present invention. FIG. 11 is an aberration diagram at the wide-angle end of Reference Example 1 of the present invention. FIG. 11 is an aberration diagram at the middle of Reference Example 1 of the present invention. FIG. 12 is an aberration diagram at the telephoto end of Reference Example 1 of the present invention. lens sectional view of an example 3 [14] intermediate aberration diagram of numerical example 3 of the aberrations of the wide-angle end according to numerical embodiment 3 [15] the present invention of the present invention [16] the present invention Reference Example of aberration at the telephoto end according to Numerical Embodiment 3 Figure 17 is a present aberrations of the wide-angle end of Reference Example 2 Reference Example lens sectional view of 2 [18] The present invention [Figure 19] The present invention aberrations of the second intermediate [20] numerical wide angle according to a fourth embodiment of the present lens sectional view of numerical example 4 of the aberration diagrams at the telephoto end [21] the present invention of example 2 of the invention [22] the present invention FIG. 23 is an aberration diagram in the middle of Numerical Example 4 of the present invention. FIG. 24 is an aberration diagram at the telephoto end of Numerical Example 4 of the present invention. FIG. 25 is a lens of Numerical Example 5 of the present invention. sectional view FIG. 26 of the numerical embodiment aberrations of the wide-angle end of example 5 aberration diagram of an intermediate numerical example 5 of FIG. 27 the present invention Figure 28 numerical telephoto end according to embodiment 5 of the present invention of the present invention Aberration diagram [FIG. 29] Schematic diagram of essential parts of the optical apparatus of the present invention [Explanation of symbols]
L1 1st group L2 2nd group L3 3rd group L4 4th group SP Aperture G Glass block IP Image plane dd line g g line ΔM Meridional image plane ΔS Sagittal image plane

Claims (3)

物体側より順に正の屈折力の第１群、負の屈折力の第２群、絞り、正の屈折力の第３群、正の屈折力の第４群より構成され、広角端から望遠端への変倍に際して、前記第１群と前記第３群は不動であり、前記第２群が像面側へ移動し、前記第４群は物体側に凸状の軌跡を有するように移動し、合焦に際して前記第４群が移動し、前記第２群は、物体側から順に、物体側に凸面を向けたメニスカス状の負の第２１レンズ、両レンズ面が凹面の負の第２２レンズ、両レンズ面が凸面の正の第２３レンズと負の第２４レンズとを接合した貼合わせレンズより構成され、前記第３群は非球面を有する１枚の正レンズより構成され、前記第２３レンズの材質のアッベ数をν２３、前記第２４レンズの材質のアッベ数をν２４、前記第２レンズ群の焦点距離をｆ２、前記第２３レンズと前記第２４レンズとの接合レンズ面の曲率半径をＲ２３４とするとき、
１５＜（ν２４−ν２３）＜３０
４．１≦Ｒ２３４／ｆ２≦７．４
なる条件を満足することを特徴とするリヤーフォーカス式のズームレンズ。The first group of positive refractive power from the object side, a second lens unit of negative refractive power, a stop, a third lens unit of positive refractive power, is composed of a fourth unit having a positive refractive power, the telephoto end from the wide-angle end During zooming, the first group and the third group are stationary, the second group moves to the image plane side, and the fourth group moves so as to have a convex locus on the object side. The fourth group moves during focusing, and the second group includes, in order from the object side, a meniscus negative 21st lens with a convex surface facing the object side, and a negative 22nd lens with both lens surfaces concave. , both lens surfaces are composed of a positive 23 lens and a negative of the 24 lens and joining the cemented lens convex, the third group is composed of one positive lens having an aspherical surface, the third 23 The Abbe number of the lens material is ν23, the Abbe number of the 24th lens material is ν24, and the focal length of the second lens group F2 and the radius of curvature of the cemented lens surface of the 23rd lens and the 24th lens is R234,
15 <(ν24−ν23) <30
4.1 ≦ R234 / f2 ≦ 7.4
A rear focus zoom lens that satisfies the following conditions: 前記第２２レンズの像側のレンズ面の曲率半径をＲ２２２、前記第２３レンズの物体側のレンズ面の曲率半径をＲ２３１とするとき、
０＜Ｒ２３１／Ｒ２２２＜０．５
なる条件を満足することを特徴とする請求項１に記載のリヤーフォーカス式のズームレンズ。When the radius of curvature of the image side lens surface of the 22nd lens is R222 and the radius of curvature of the object side lens surface of the 23rd lens is R231,
0 <R231 / R222 <0.5
The rear focus type zoom lens according to claim 1 , wherein the following condition is satisfied. 請求項１または２に記載のリヤーフォーカス式のズームレンズを有することを特徴とする光学機器。An optical apparatus comprising the rear focus zoom lens according to claim 1 .