JP3593400B2 - Rear focus zoom lens - Google Patents
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- JP3593400B2 JP3593400B2 JP32337395A JP32337395A JP3593400B2 JP 3593400 B2 JP3593400 B2 JP 3593400B2 JP 32337395 A JP32337395 A JP 32337395A JP 32337395 A JP32337395 A JP 32337395A JP 3593400 B2 JP3593400 B2 JP 3593400B2
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Description
【０００１】
【発明の属する技術分野】
本発明は特にスチルカメラやビデオカメラ等に好適な，変倍比が約１０に及びしかも望遠端でもＦ３以内の口径比を持ちながり，レンズ系全体の小型化を図ったリアフォーカス式ズームレンズに関する。
【０００２】
【従来の技術】
従来よりスチルカメラや，ビデオカメラ等のズームレンズにおいて用いられている比較的高変倍比でしかも大口径比のズームレンズとして４群ズームレンズが知られている。この４群ズームレンズは物体側より順に焦点合わせに用いる第１レンズ群と，変倍に用いる第２レンズ群と，変倍に伴う像面変動を一定位置に保つように補正する第３レンズ群と，全系の焦点距離や収差補正のバランスを取る為の第４レンズ群から成り立っている。この様な４群ズームレンズでは変倍のために第２レンズ群と第３レンズ群を移動させ，焦点合わせに第１レンズ群を移動させている為，合計３つのレンズ群を移動させなければならず，比較的レンズ鏡筒の機構が複雑になる傾向があった。また，近距離物体に焦点合わせを行う際，第１レンズ群を物体側に繰り出して行うため，軸外光東を十分確保しようとすると前玉レンズ径が増大する傾向があった。又，大径化した前玉を移動させるための大きな駆動力を要し，オートフォーカスに際しての合焦時間も長くなるという問題もあった。これらの問題を防止するため，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う，いわゆるリアフォーカス式を採用したズームレンズが種々提案されている。一般にリアフォーカス式ズームレンズは，前玉の繰り出しを伴わないため，光量確保のために前玉径を大型化する必要がなく，又，比較的小型軽量のレンズ群を移動させて焦点合わせを行っているため，フォーカスを行う際の駆動力が小さくて済み，迅速な焦点合わせが出来る。更に，リアフォーカス式ズームレンズでは，第１レンズ群を移動させて焦点合わせを行うズームレンズに比べて第１レンズ群の有効径が小さくなり，レンズ系全体の小型化が図りやすくなり，さらに近接撮影が容易になる等の優れた特長がある。
【０００３】
【発明が解決しようとする課題】
しかしながらリアフォーカス式ズームレンズでは，フォーカスの際における収差変動が大きくなり，無限物体距離から近距離物体距離に至るまで全般にわたりレンズ系全体の小型化を図りつつ，諸収差の良好に補正された高い光学性能を得ることが大変困難であった。
【０００４】
【課題を解決するための手段】
本発明は，この様な問題点を解決するためになされたものであり，リアフォーカス式ズームレンズを前提として，非球面を有するレンズを適切に配置する事により，リアフォーカス式を採用したにもかかわらず，変倍比１０で，かつ大口径比を持ったズームレンズでありながら，レンズ系全体の小型化を図り，広角端から望遠端まで全物体距離で諸収差を良好に補正された高い光学性能を有するリアフォーカス式ズームレンズを得ることを目的とする。
【０００５】
上記目的を達成するため、本発明は物体側より順に、全体として正の屈折力を持つ第１レンズ群と、全体として負の屈折力を有する第２レンズ群と、全体として正の屈折力を有する第３レンズ群と、全体として正の屈折力を有する第４レンズ群と、全体として負の屈折力を有する第５レンズ群よりなり、上記第１レンズ群、第３レンズ群、第５レンズ群を固定させ、上記第２レンズ群を光軸に沿って物体側から像面側へ移動させることにより広角側から望遠側への変倍を行い、変倍に伴う像面変動を上記第４レンズ群の光軸方向への移動により補正すると共に、第４レンズ群を物体の移動によって変動する像面を一定位置に保つように光軸に沿って移動させて焦点調節を行う光学系において、上記第３レンズ群は、両凸レンズと物体側に凹面を向けた負のメニスカスレンズとの貼り合わせレンズを有し、物体側の凸面に少なくとも一面の非球面形状を有し、上記第４レンズ群は、両凸レンズと物体側に凹面を向けた負のメニスカスレンズとの貼り合わせレンズを有し、物体側の凸面に少なくとも一面の非球面形状を有し、上記第５レンズ群は、像面側の凸面に少なくとも一面の非球面形状を有していて、以下の条件式を満足するリアフォーカス式ズームレンズ、としたことにより達成される。
（条件１）νｗ−νｘ＞２０
（条件２）νｙ−νｚ＞２０
（条件３）０．７＜｜ｆ５／ｆ４｜＜１．７
（条件４）０．７＜｜ｆ２／ｆｗ｜＜１．１
（条件５）
但し、νｗは第３レンズ群の両凸レンズのアッベ数、
νｘは第３レンズ群の物体側に凹面を向けた負のメニスカスレンズのアッベ数、
νｙは第４レンズ群の両凸レンズのアッベ数、
νｚは第４レンズ群の物体側に凹面を向けた負のメニスカスレンズのアッベ数、
ｆｗは広角端におけるレンズ系全系の合成焦点距離、
ｆ２は第２レンズ群の合成焦点距離、
ｆ４は第４レンズ群の合成焦点距離、
ｆ５は第５レンズ群の合成焦点距離。
【０００６】
望ましくは，本発明のリアフォーカス式ズームレンズは，上記を前提として，前記第３レンズ群Ｃと前記第４レンズ群Ｄは，それぞれ両凸レンズと物体側に強い凹面を向けた負のメニスカスレンズとの張り合わせレンズを有し，第３レンズ群Ｃの両凸レンズのアッべ数をνｗ，第３レンズ群Ｃの物体側に強い凹面を向けた負のメニスカスレンズのアッべ数をνｘ，第４レンズ群Ｄの両凸レンズのアッべ数をνｙ，第４レンズ群Ｄの物体側に強い凹面を向けた負のメニスカスレンズのアッべ数をνｚとするとき，条件１及び条件２に規定する条件を満足する。
【０００７】
（条件１）νｗ−νｘ＞２０
【０００８】
（条件２）νｙ−νｚ＞２０
【０００９】
更に望ましくは，本発明のリアフォーカス式ズームレンズは，上記を前提として，広角端におけるレンズ系全系の合成焦点距離をｆｗ，第２レンズ群Ｂの合成焦点距離をｆ２，第４レンズ群Ｄの合成焦点距離をｆ４，第５レンズ群Ｅの合成焦点距離をｆ５とするとき，条件３及び条件４に規定する条件を満足する。
【００１０】
（条件３）０．７＜｜ｆ５／ｆ４｜＜１．７
【００１１】
（条件４）０．７＜｜ｆ２／ｆｗｌ＜１．１
【００１２】
【作用】
本発明は，図１の光軸断面図に示すように，物体側より順に，全体として正の屈折力を持つ第１レンズ群Ａと，全体として負の屈折力を有する第２レンズ群Ｂと，全体として正の屈折力を有する第３レンズ群Ｃと，全体として正の屈折力を有する第４レンズ群Ｄと，全体として負の屈折力を有する第５レンズ群Ｅよりなり，上記第１レンズ群Ａ，第３レンズ群Ｃ，第５レンズ群Ｅは固定されている。従って，変倍動作や合焦動作によってレンズ系全体としての全長が変化することはなく，又，可動レンズも第２レンズ群Ｂと第４レンズ群Ｄとに限定されるので，駆動機構を簡素化することが可能となる。
【００１３】
変倍に際しては，固定レンズである第１レンズ群Ａと第３レンズ群Ｃとの間に形成された空間において第２レンズ群Ｂを光軸に沿って物体側から像面側へ移動させることにより広角側から望遠側への変倍がなされ，又，この変倍に伴う像面変動の補正のために固定レンズである第３レンズ群Ｃと第５レンズ群Ｅとの間に形成された空間において第４レンズ群Ｄを物体側に凸状の軌跡を有する様に移動させる。又，合焦動作に際しては，固定レンズである第３レンズ群Ｃと第５レンズ群Ｅとの間に形成された空間において第４レンズＤ群を物体側に移動させることによって近距離側への焦点調整を行う。この様に，固定レンズである第１レンズ群Ａと第３レンズ群Ｃとの間に形成された固定空間，及び第３レンズ群Ｃと第５レンズ群Ｅとの間に形成された固定空間で可動レンズである第２レンズ群Ｂ及び第４レンズ群Ｄを移動させる様になされているので，可動レンズ群の限定や固定空間の有効利用がなされ，駆動機構の簡素化やレンズ系全体の小型化が達成される。
【００１４】
第３レンズ群Ｃ，第４レンズ群Ｄの物体側の凸面に配置された少なくとも１面の非球面形状及び第５レンズ群Ｅの像面側の凸面に配置された少なくとも１面の非球面形状は，変倍ならびに合焦動作の際における収差変動を少なくし，諸収差を良好に補正するためのものである。
【００１５】
これらの非球面中，第３レンズ群Ｃの物体側の凸面に配置される非球面は主に広角側での球面収差やコマ収差を良好に補正するのに有効である。又，第４レンズ群Ｄの物体側の凸面に配置される非球面は，主に球面収差や非点収差を良好に補正するのに有効である。更に，第５レンズ群Ｅの像面側の凸面に配置される非球面は，主に非点収差やコマ収差を良好に補正するのに有効である。
【００１６】
さらに諸収差を良好に補正するために上述の条件１乃至条件４に規定する条件を満足する事が好ましい。条件１に規定する条件は第３レンズ群Ｃの張り合わせレンズのアッべ数を適切に設定するものである。条件１に規定する条件が満足されないと，変倍および合焦動作の際の色収差の変動を良好に補正するのが困難になる。
【００１７】
条件２に規定する条件は第４レンズ群の張り合わせレンズのアッべ数を適切に設定するものである。条件２に規定する条件が満足されないと，変倍および合焦動作の際の色収差の変動を良好に補正するのが難しくなってくる。
【００１８】
条件３に規定する条件は第４レンズ群Ｄと，第５レンズ群Ｅの焦点距離に関するものであり，変倍および合焦動作の際における第４レンズ群Ｄの移動量を抑制してレンズ系全体の小型化を図る一方で，良好な光学性能を維持するためのものである。条件３の上限値を越えると，変倍および合焦動作の際における第４レンズ群Ｄの移動量が大きくなり，収差変動が大きくなると共にレンズ系全体の小型化が望めなくなる。条件３の下限値を越えると変倍および合焦動作の際における第４レンズ群Ｄの移動量は小さくなるが，非点収差およびコマ収差の補正が困難となる。
【００１９】
条件４に規定する条件は第２レンズ群Ｂの焦点距離に関するものであり，変倍の際の収差変動を抑えつつ，レンズ系全体の小型化を図るためのものである。条件４の上限値を越えると，一定の変倍比を確保する為に第２レンズ群Ｂの移動量が大きくなり，レンズ系全体の小型化が望めなくなる。条件４の下限値を越えると，負のべッツバール和が増大し，像面湾曲が大きくなる。またコマ収差の補正も困難となる。
【００２０】
【実施例】
次に，具体的な数値実施例を表１及び表２に示すとともに，各々の実施例の光軸断面を図１乃至図３及び図７乃至図９に示し，又，各々の実施例の収差線図を図４乃至図６及び図１０乃至図１２に示す。尚，図１及び図７は各々の実施例の広角端での光軸断面を，図２及び図８は各々実施例の中間焦点距離での光軸断面を，図３及び図９は各々の実施例の望遠端での光軸断面図を示す，図４及び図１０は各々の実施例の広角端での収差線図を，図５及び図１１は各々の実施例の中間焦点距離での収差線図を，図６及び図１２は各々の実施例の望遠端での収差線図を示している。又，各々の光軸断面図において，Ａ乃至Ｅは各々第１レンズ群から第５レンズ群を示すとともに，ＦはＣＣＤにおけるカバーガラスや赤外カットフィルター等のガラス材を表す。
【００２１】
【表１】
【表２】
各々の実施例において，ｒｉは物体側からｉ番目の面の曲率半径を，ｄｉは物体からｉ番目のレンズ肉厚或いは空気間隔を，ｎｉは物体からｉ番目のレンズのｄ線に対する屈折率を，νｉは物体からｉ番目のレンズのｄ線に対するアッベ数を各々示している。又，表１に示す実施例ではｒ１２面，ｒ１４面，ｒ１７面，ｒ２１面が非球面に形成され，表２に示す実施例ではｒ１２面，ｒ１５面，ｒ１７面，ｒ１９面が非球面に形成され，その非球面形状は数１によって規定されている。
【００２４】
【数１】
尚，数１において，Ｚは光軸から高さがｙの非球面上の点の非球面頂点の接平面からの距離を，ｙは光軸からの高さを，Ｃは非球面頂点の曲率（＝１／ｒ）を，εは円錐定数を，Ｄ，Ｅ，Ｆ及びＧは非球面係数を表し，ε，Ｄ，Ｅ，Ｆ及びＧの具体的な数値は各々表１及び表２に示されている。又，各々の収差線図における非点収差は，図面の煩雑化を避けるためにサジタル方向ＤＳとメリジオナル方向とを各々区分して示している。
【００２６】
【発明の効果】
以上説明した実施例や収差線図に見られる様に，本発明は，リアフォーカス式を採用しつつ，約１０倍の広域な変倍比と望遠端でもＦ３以内の口径を有する高変倍比，大口径のズームレンズでありながら，レンズ系全体の小型化を図りつつ，広角端から望遠端まで全物体距離にわたって諸収差が良好に補正された高い光学性能を有するリアフォーカス式ズームレンズを得ることが出来た。
【図面の簡単な説明】
【図１】本発明の第１実施例に係るズームレンズの広角端での光軸断面図。
【図２】本発明の第１実施例に係るズームレンズの中間焦点距離での光軸断面図。
【図３】本発明の第１実施例に係るズームレンズの望遠端での光軸断面図。
【図４】本発明の第１実施例に係るズームレンズの広角端での収差線図。
【図５】本発明の第１実施例に係るズームレンズの中間焦点距離での収差線図。
【図６】本発明の第１実施例に係るズームレンズの望遠端での収差線図。
【図７】本発明の第２実施例に係るズームレンズの広角端での光軸断面図。
【図８】本発明の第２実施例に係るズームレンズの中間焦点距離での光軸断面図。
【図９】本発明の第２実施例に係るズームレンズの望遠端での光軸断面図。
【図１０】本発明の第２実施例に係るズームレンズの広角端での収差線図。
【図１１】本発明の第２実施例に係るズームレンズの中間焦点距離での収差線図。
【図１２】本発明の第２実施例に係るズームレンズの望遠端での収差線図。
【符号の説明】
Ａ 第１レンズ群
Ｂ 第２レンズ群
Ｃ 第３レンズ群
Ｄ 第４レンズ群
Ｅ 第５レンズ群[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is particularly suitable for a still camera or a video camera, etc., and has a zoom ratio of about 10 and at the telephoto end has an aperture ratio of F3 or less, and is a rear-focusing type zoom lens with a reduced overall lens system. About.
[0002]
[Prior art]
Conventionally, a four-group zoom lens is known as a zoom lens having a relatively high zoom ratio and a large aperture ratio, which has been used in a zoom lens such as a still camera or a video camera. The four-unit zoom lens includes, in order from the object side, a first lens unit used for focusing, a second lens unit used for zooming, and a third lens unit for correcting an image plane variation caused by zooming to be kept at a fixed position. And a fourth lens group for balancing the focal length and aberration correction of the entire system. In such a four-unit zoom lens, the second lens unit and the third lens unit are moved for zooming, and the first lens unit is moved for focusing. Therefore, a total of three lens units must be moved. However, the mechanism of the lens barrel tends to be relatively complicated. In addition, when focusing on a short-distance object, the first lens group is extended toward the object side, so that if the off-axis light east is sufficiently secured, the diameter of the front lens tends to increase. In addition, there is a problem that a large driving force is required to move the large-diameter front lens, and the focusing time for autofocusing is also long. In order to prevent these problems, various zoom lenses adopting a so-called rear focus system in which focusing is performed by moving a lens group other than the first lens group have been proposed. In general, a rear-focusing zoom lens does not involve the extension of the front lens, so there is no need to increase the diameter of the front lens to secure the amount of light, and the focusing is performed by moving a relatively small and light lens group. As a result, a small driving force is required for focusing, and quick focusing can be performed. Further, in the rear-focusing type zoom lens, the effective diameter of the first lens group is smaller than that of a zoom lens that performs focusing by moving the first lens group. It has excellent features such as easy shooting.
[0003]
[Problems to be solved by the invention]
However, in the rear-focusing zoom lens, aberration fluctuation during focusing becomes large, and the entire lens system is reduced in size from infinite object distance to short-distance object distance, and various aberrations are well corrected and high. It was very difficult to obtain optical performance.
[0004]
[Means for Solving the Problems]
The present invention has been made in order to solve such a problem. Assuming that a rear-focusing type zoom lens is used, a rear-focusing type is adopted by appropriately disposing a lens having an aspherical surface. Regardless, despite being a zoom lens with a zoom ratio of 10 and a large aperture ratio, the overall size of the lens system has been reduced, and various aberrations have been successfully corrected at all object distances from the wide-angle end to the telephoto end. It is an object of the present invention to obtain a rear focus type zoom lens having optical performance.
[0005]
In order to achieve the above object, the present invention provides, in order from the object side, a first lens group having a positive refractive power as a whole, a second lens group having a negative refractive power as a whole, and a positive refractive power as a whole. A third lens group, a fourth lens group having a positive refractive power as a whole, and a fifth lens group having a negative refractive power as a whole. The first lens group, the third lens group, and the fifth lens The lens group is fixed, and the second lens group is moved from the object side to the image plane side along the optical axis to perform zooming from the wide-angle side to the telephoto side. In an optical system for correcting focus by moving the lens group in the direction of the optical axis and moving the fourth lens group along the optical axis so as to keep the image plane that fluctuates due to the movement of the object at a fixed position, focus adjustment is performed. The third lens group has a biconvex lens and a concave surface on the object side. A negative meniscus lens having a negative meniscus lens having at least one aspherical surface on the object-side convex surface, and a bi-convex lens and a concave surface facing the object side. A lens bonded to the lens, the object-side convex surface has at least one aspherical shape, and the fifth lens group has at least one image-side aspherical shape on the image-side convex surface, This is achieved by a rear focus zoom lens satisfying the following conditional expressions.
(Condition 1) νw−νx> 20
(Condition 2) νy−νz> 20
(Condition 3) 0.7 <| f5 / f4 | <1.7
(Condition 4) 0.7 <| f2 / fw | <1.1
(Condition 5)
Where νw is the Abbe number of the biconvex lens of the third lens group,
νx is the Abbe number of a negative meniscus lens having a concave surface facing the object side of the third lens group,
νy is the Abbe number of the biconvex lens of the fourth lens group,
νz is the Abbe number of a negative meniscus lens having a concave surface facing the object side of the fourth lens group,
fw is the combined focal length of the entire lens system at the wide-angle end,
f2 is the composite focal length of the second lens group,
f4 is the composite focal length of the fourth lens group,
f5 is the composite focal length of the fifth lens group.
[0006]
Preferably, in the rear focus type zoom lens according to the present invention, on the premise of the above, the third lens group C and the fourth lens group D each include a biconvex lens and a negative meniscus lens having a strong concave surface facing the object side. The Abbe number of the biconvex lens of the third lens group C is νw, the Abbe number of the negative meniscus lens having a strong concave surface facing the object side of the third lens group C is νx, and the fourth lens When the Abbe number of the biconvex lens of the group D is νy, and the Abbe number of the negative meniscus lens of the fourth lens group D having a strong concave surface on the object side is νz, the conditions defined in the
[0007]
(Condition 1) νw−νx> 20
[0008]
(Condition 2) νy−νz> 20
[0009]
More preferably, the rear-focusing zoom lens of the present invention is based on the premise that the combined focal length of the entire lens system at the wide-angle end is fw, the combined focal length of the second lens group B is f2, and the fourth lens group D is When the combined focal length of the fifth lens group E is f4 and the combined focal length of the fifth lens unit E is f5, the conditions specified in the conditions 3 and 4 are satisfied.
[0010]
(Condition 3) 0.7 <| f5 / f4 | <1.7
[0011]
(Condition 4) 0.7 <| f2 / fwl <1.1
[0012]
[Action]
As shown in the optical axis sectional view of FIG. 1, the present invention includes, in order from the object side, a first lens group A having a positive refractive power as a whole, and a second lens group B having a negative refractive power as a whole. A third lens group C having an overall positive refractive power, a fourth lens group D having an overall positive refractive power, and a fifth lens group E having an overall negative refractive power. The lens unit A, the third lens unit C, and the fifth lens unit E are fixed. Accordingly, the overall length of the entire lens system does not change due to the zooming operation and the focusing operation, and the movable lens is limited to the second lens group B and the fourth lens group D, so that the driving mechanism is simplified. Can be realized.
[0013]
Upon zooming, the second lens group B is moved from the object side to the image plane side along the optical axis in a space formed between the first lens group A and the third lens group C, which are fixed lenses. The zooming is performed from the wide-angle side to the telephoto side, and is formed between the third lens group C and the fifth lens group E, which are fixed lenses, in order to correct the image plane fluctuation accompanying the zooming. In the space, the fourth lens unit D is moved so as to have a locus convex toward the object side. In the focusing operation, the fourth lens group D is moved toward the object side in the space formed between the third lens group C and the fifth lens group E, which are fixed lenses, so as to move to the short distance side. Perform focus adjustment. As described above, the fixed space formed between the first lens group A and the third lens group C, which are fixed lenses, and the fixed space formed between the third lens group C and the fifth lens group E The second lens group B and the fourth lens group D, which are movable lenses, are moved, so that the movable lens groups are limited and the fixed space is effectively used, so that the drive mechanism is simplified and the entire lens system is simplified. Miniaturization is achieved.
[0014]
At least one aspherical surface disposed on the object-side convex surface of the third lens unit C and the fourth lens unit D and at least one aspherical surface disposed on the image-side convex surface of the fifth lens unit E Is to reduce aberration fluctuations at the time of zooming and focusing operation, and to satisfactorily correct various aberrations.
[0015]
Among these aspheric surfaces, the aspheric surface disposed on the object-side convex surface of the third lens unit C is effective in favorably correcting spherical aberration and coma mainly on the wide-angle side. The aspherical surface arranged on the object-side convex surface of the fourth lens unit D is effective in favorably correcting mainly spherical aberration and astigmatism. Further, the aspherical surface arranged on the convex surface on the image plane side of the fifth lens unit E is effective mainly in favorably correcting astigmatism and coma.
[0016]
Further, in order to favorably correct various aberrations, it is preferable to satisfy the conditions defined in the above conditions 1 to 4. The condition specified in Condition 1 is to appropriately set the Abbe number of the cemented lens of the third lens unit C. If the condition specified in Condition 1 is not satisfied, it becomes difficult to satisfactorily correct the fluctuation of chromatic aberration during zooming and focusing operation.
[0017]
The condition defined in
[0018]
The condition defined in Condition 3 relates to the focal length of the fourth lens unit D and the fifth lens unit E, and suppresses the amount of movement of the fourth lens unit D during zooming and focusing operations to reduce the lens system. This is to maintain good optical performance while reducing the overall size. If the upper limit of Condition 3 is exceeded, the amount of movement of the fourth lens unit D during zooming and focusing operations will increase, and aberration fluctuation will increase, and miniaturization of the entire lens system cannot be expected. If the lower limit of Condition 3 is exceeded, the amount of movement of the fourth lens unit D during zooming and focusing operations will be small, but it will be difficult to correct astigmatism and coma.
[0019]
The condition defined in Condition 4 relates to the focal length of the second lens unit B, and is intended to reduce the variation in aberrations during zooming and to reduce the size of the entire lens system. When the value exceeds the upper limit of the condition 4, the moving amount of the second lens unit B becomes large in order to secure a constant zoom ratio, and it is impossible to reduce the size of the entire lens system. When the value exceeds the lower limit of the condition 4, the negative Betzval sum increases, and the field curvature increases. In addition, it becomes difficult to correct coma.
[0020]
【Example】
Next, specific numerical examples are shown in Tables 1 and 2, the optical axis cross sections of the respective examples are shown in FIGS. 1 to 3 and FIGS. 7 to 9, and the aberrations of the respective examples are shown. Diagrams are shown in FIGS. 4 to 6 and FIGS. 10 to 12. 1 and 7 show the optical axis cross sections at the wide-angle end of each embodiment, FIGS. 2 and 8 show the optical axis cross sections at the intermediate focal length of each embodiment, and FIGS. 3 and 9 show the respective optical axis cross sections. 4 and 10 are aberration diagrams at the wide-angle end of each embodiment, and FIGS. 5 and 11 are graphs showing the optical axis cross sections at the telephoto end of the embodiments. FIGS. 6 and 12 show aberration diagrams at the telephoto end of each embodiment. In each optical axis sectional view, A to E respectively denote a first lens group to a fifth lens group, and F denotes a glass material such as a cover glass or an infrared cut filter in a CCD.
[0021]
[Table 1]
[Table 2]
In each embodiment, ri is the radius of curvature of the i-th surface from the object side, di is the i-th lens thickness or air gap from the object, and ni is the refractive index of the i-th lens from the object with respect to the d-line. , Νi denote Abbe numbers of the i-th lens from the object with respect to the d-line, respectively. In the embodiment shown in Table 1, the r12, r14, r17, and r21 surfaces are formed as aspherical surfaces, and in the embodiment shown in Table 2, the r12, r15, r17, and r19 surfaces are formed as aspherical surfaces. The aspherical shape is defined by Equation 1.
[0024]
(Equation 1)
In Equation 1, Z is the distance from the optical axis to a point on the aspheric surface having a height of y from the tangent plane of the aspherical vertex, y is the height from the optical axis, and C is the curvature of the aspherical vertex. (= 1 / r), ε represents a conical constant, D, E, F, and G represent aspheric coefficients. Specific numerical values of ε, D, E, F, and G are shown in Tables 1 and 2, respectively. It is shown. In addition, astigmatism in each aberration diagram shows the sagittal direction DS and the meridional direction separately in order to avoid complication of the drawings.
[0026]
【The invention's effect】
As can be seen from the above-described embodiments and aberration diagrams, the present invention employs a rear-focusing type, and has a wide zoom ratio of about 10 times and a high zoom ratio having an aperture within F3 even at the telephoto end. Despite being a large-aperture zoom lens, a rear-focusing zoom lens with high optical performance has been successfully corrected for various aberrations over the entire object distance from the wide-angle end to the telephoto end while miniaturizing the entire lens system. I was able to do it.
[Brief description of the drawings]
FIG. 1 is a sectional view of an optical axis at a wide-angle end of a zoom lens according to a first embodiment of the present invention.
FIG. 2 is an optical axis cross-sectional view at an intermediate focal length of the zoom lens according to Example 1 of the present invention.
FIG. 3 is an optical axis sectional view at a telephoto end of a zoom lens according to a first example of the present invention.
FIG. 4 is an aberration diagram at a wide-angle end of the zoom lens according to Example 1 of the present invention.
FIG. 5 is an aberration diagram at an intermediate focal length of the zoom lens according to Example 1 of the present invention.
FIG. 6 is an aberration diagram at a telephoto end of a zoom lens according to a first example of the present invention.
FIG. 7 is an optical axis cross-sectional view at a wide angle end of a zoom lens according to Example 2 of the present invention.
FIG. 8 is an optical axis cross-sectional view at an intermediate focal length of a zoom lens according to Example 2 of the present invention.
FIG. 9 is an optical axis sectional view at a telephoto end of a zoom lens according to Example 2 of the present invention.
FIG. 10 is an aberration diagram at a wide-angle end of a zoom lens according to Example 2 of the present invention.
FIG. 11 is an aberration diagram at an intermediate focal length of the zoom lens according to Example 2 of the present invention.
FIG. 12 is an aberration diagram at a telephoto end of a zoom lens according to Example 2 of the present invention.
[Explanation of symbols]
A first lens group B second lens group C third lens group D fourth lens group E fifth lens group
Claims (1)
上記第３レンズ群は、両凸レンズと物体側に凹面を向けた負のメニスカスレンズとの貼り合わせレンズを有し、物体側の凸面に少なくとも一面の非球面形状を有し、
上記第４レンズ群は、両凸レンズと物体側に凹面を向けた負のメニスカスレンズとの貼り合わせレンズを有し、物体側の凸面に少なくとも一面の非球面形状を有し、
上記第５レンズ群は、像面側の凸面に少なくとも一面の非球面形状を有していて、以下の条件式を満足するリアフォーカス式ズームレンズ。
（条件１）νｗ−νｘ＞２０
（条件２）νｙ−νｚ＞２０
（条件３）０．７＜｜ｆ５／ｆ４｜＜１．７
（条件４）０．７＜｜ｆ２／ｆｗ｜＜１．１
（条件５）
但し、νｗは第３レンズ群の両凸レンズのアッベ数、
νｘは第３レンズ群の物体側に凹面を向けた負のメニスカスレンズのアッベ数、
νｙは第４レンズ群の両凸レンズのアッベ数、
νｚは第４レンズ群の物体側に凹面を向けた負のメニスカスレンズのアッベ数、
ｆｗは広角端におけるレンズ系全系の合成焦点距離、
ｆ２は第２レンズ群の合成焦点距離、
ｆ４は第４レンズ群の合成焦点距離、
ｆ５は第５レンズ群の合成焦点距離。 In order from the object side, a first lens group having an overall positive refractive power, a second lens group having an overall negative refractive power, a third lens group having an overall positive refractive power, and an overall positive A fourth lens group having a negative refractive power, and a fifth lens group having a negative refractive power as a whole. The first lens group, the third lens group, and the fifth lens group are fixed, and the second lens group is formed. Is moved from the object side to the image plane side along the optical axis to change the magnification from the wide-angle side to the telephoto side, and the image plane fluctuation accompanying the magnification is changed by moving the fourth lens group in the optical axis direction. In the optical system for performing the focus adjustment by correcting and moving the fourth lens group along the optical axis so as to keep the image plane fluctuated by the movement of the object at a constant position,
The third lens group has a cemented lens of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and has at least one aspherical surface on the object side convex surface;
The fourth lens group has a cemented lens of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and has at least one aspherical surface on the object side convex surface;
The fifth lens group is a rear-focusing zoom lens that has at least one aspherical surface on the convex surface on the image surface side and satisfies the following conditional expression.
(Condition 1) νw−νx> 20
(Condition 2) νy−νz> 20
(Condition 3) 0.7 <| f5 / f4 | <1.7
(Condition 4) 0.7 <| f2 / fw | <1.1
(Condition 5)
Where νw is the Abbe number of the biconvex lens of the third lens group,
νx is the Abbe number of a negative meniscus lens having a concave surface facing the object side of the third lens group,
νy is the Abbe number of the biconvex lens of the fourth lens group,
νz is the Abbe number of a negative meniscus lens having a concave surface facing the object side of the fourth lens group,
fw is the combined focal length of the entire lens system at the wide-angle end,
f2 is the composite focal length of the second lens group,
f4 is the composite focal length of the fourth lens group,
f5 is the composite focal length of the fifth lens group.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32337395A JP3593400B2 (en) | 1995-12-12 | 1995-12-12 | Rear focus zoom lens |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32337395A JP3593400B2 (en) | 1995-12-12 | 1995-12-12 | Rear focus zoom lens |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09159917A JPH09159917A (en) | 1997-06-20 |
| JP3593400B2 true JP3593400B2 (en) | 2004-11-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP32337395A Expired - Fee Related JP3593400B2 (en) | 1995-12-12 | 1995-12-12 | Rear focus zoom lens |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH09269452A (en) * | 1996-03-29 | 1997-10-14 | Canon Inc | Rear focus system zoom lens |
| JP4579568B2 (en) | 2004-04-01 | 2010-11-10 | キヤノン株式会社 | Zoom lens and shooting system |
| JP2008102398A (en) * | 2006-10-20 | 2008-05-01 | Olympus Imaging Corp | Variable power optical system and imaging apparatus using the same |
| JP4822074B2 (en) * | 2007-10-01 | 2011-11-24 | 株式会社ニコン | Zoom lens and optical apparatus provided with the zoom lens |
| JP6090650B2 (en) * | 2012-11-19 | 2017-03-08 | 株式会社リコー | Imaging lens, imaging device, and information device |
| CN104965297B (en) * | 2015-06-25 | 2017-05-24 | 福建省光学技术研究所 | Rear group adjusting video shooting high-definition zoom lens and rear group adjusting method for lens |
| JP7217935B2 (en) * | 2018-12-25 | 2023-02-06 | 株式会社シグマ | Variable magnification imaging optical system |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2750775B2 (en) * | 1990-05-07 | 1998-05-13 | コニカ株式会社 | Compact zoom lens |
| JP2543780B2 (en) * | 1990-07-23 | 1996-10-16 | コニカ株式会社 | Zoom lenses |
| JPH0460509A (en) * | 1990-06-29 | 1992-02-26 | Konica Corp | Zoom lens |
| JPH0688940A (en) * | 1991-01-18 | 1994-03-29 | Konica Corp | Compact zoom lens |
| JP2832092B2 (en) * | 1991-03-29 | 1998-12-02 | キヤノン株式会社 | Rear focus zoom lens |
| JP3015192B2 (en) * | 1992-03-26 | 2000-03-06 | キヤノン株式会社 | Rear focus zoom lens |
| JPH0627376A (en) * | 1992-07-08 | 1994-02-04 | Canon Inc | Zoom lens of rear focusing type |
| JPH05188295A (en) * | 1992-01-14 | 1993-07-30 | Canon Inc | Rear focus type zoom lens |
| JP3196283B2 (en) * | 1992-02-13 | 2001-08-06 | ミノルタ株式会社 | Zoom lens device |
| JPH06175024A (en) * | 1992-12-02 | 1994-06-24 | Canon Inc | Rear-focusing type zoom lens |
| JPH06331891A (en) * | 1993-05-20 | 1994-12-02 | Canon Inc | Image pickup device using solid-state image pickup element |
| JPH08129202A (en) * | 1994-10-31 | 1996-05-21 | Canon Inc | Variable power finder optical system |
| JP3513265B2 (en) * | 1995-05-30 | 2004-03-31 | キヤノン株式会社 | Small zoom lens |
| JPH0968653A (en) * | 1995-08-30 | 1997-03-11 | Olympus Optical Co Ltd | Zoom lens |
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1995
- 1995-12-12 JP JP32337395A patent/JP3593400B2/en not_active Expired - Fee Related
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| JPH09159917A (en) | 1997-06-20 |
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