JP2007128110A - Zoom lens of rear focus system - Google Patents
Zoom lens of rear focus system Download PDFInfo
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- JP2007128110A JP2007128110A JP2007011820A JP2007011820A JP2007128110A JP 2007128110 A JP2007128110 A JP 2007128110A JP 2007011820 A JP2007011820 A JP 2007011820A JP 2007011820 A JP2007011820 A JP 2007011820A JP 2007128110 A JP2007128110 A JP 2007128110A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B15/00—Optical objectives with means for varying the magnification
- G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
- G02B15/16—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group
- G02B15/163—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group having a first movable lens or lens group and a second movable lens or lens group, both in front of a fixed lens or lens group
- G02B15/167—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group having a first movable lens or lens group and a second movable lens or lens group, both in front of a fixed lens or lens group having an additional fixed front lens or group of lenses
- G02B15/173—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group having a first movable lens or lens group and a second movable lens or lens group, both in front of a fixed lens or lens group having an additional fixed front lens or group of lenses arranged +-+
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B15/00—Optical objectives with means for varying the magnification
- G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
- G02B15/144—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only
- G02B15/1441—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only the first group being positive
- G02B15/144113—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only the first group being positive arranged +-++
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Abstract
Description
本発明は、リアフォーカス式のズームレンズに関し、特に最終レンズと結像面（ＣＣＤ）との間に色分解プリズムやフィルター等のガラスブロックが入るような長いバックフォーカスと射出瞳を確保したリアーフォーカス式のズームレンズである。更に、超広角域をカバーした、ビデオカメラやスチルビデオカメラそして放送用カメラ等に用いられる変倍比３程度、Ｆナンバー１．８程度の大口径なリアフォーカス式のズームレンズに関するものである。 The present invention relates to a rear focus type zoom lens, and in particular, a rear focus that secures a long back focus and an exit pupil such that a glass block such as a color separation prism or a filter enters between a final lens and an image plane (CCD). This is a zoom lens of the type. Further, the present invention relates to a large-diameter rear focus zoom lens having a zoom ratio of about 3 and an F number of about 1.8, which is used for a video camera, a still video camera, a broadcast camera, etc., covering an ultra wide angle range.
最近、ホームビデオカメラ等の小型軽量化に伴い、撮像用のズームレンズの小型化にもめざましい進歩が見られ、特にレンズ全長の短縮化や前玉径の小型化、レンズ構成の簡略化に力が注がれている。これらの目的を達成する為の手段の一つとして、物体側の第１群以外のレンズ群を移動させてフォーカスを行う所謂リアフォーカス式のズームレンズが知られている。一般にリアフォーカス式のズームレンズは、第１群を移動させてフォーカスを行うズームレンズに比べて、第１群の有効径が小さくなり、レンズ系全体の小型化が容易になる。また、近接撮影、特に極近接撮影が可能となり、更に比較的小型軽量のレンズ群を移動させているため、レンズ群の駆動力が小さくてすみ迅速な焦点合わせができる等の利点がある。 Recently, with the reduction in size and weight of home video cameras and the like, remarkable progress has been made in reducing the size of zoom lenses for imaging, especially in reducing the overall lens length, reducing the front lens diameter, and simplifying the lens configuration. Has been poured. As one of means for achieving these objects, a so-called rear focus type zoom lens that performs focusing by moving a lens group other than the first group on the object side is known. In general, a rear focus type zoom lens has an effective diameter of the first lens unit that is smaller than that of a zoom lens that moves the first lens unit to perform focusing, and the entire lens system can be easily downsized. In addition, close-up photography, particularly close-up photography is possible, and the relatively small and light lens group is moved, so that there is an advantage that the lens group has a small driving force and can be quickly focused.
この様なリアフォーカス式のズームレンズとして例えば、物体側より順に正の（正の屈折力の）第１レンズ群と、負の第２レンズ群、負の第３レンズ群、そして正の第４レンズ群の４つのレンズ群よりなるものがある。そして、第２レンズ群を移動させて変倍を行い、第３レンズ群で変倍に伴う像面変動を補正すると共にフォーカシングを行うズームレンズが知られている（特許文献１）。 As such a rear focus type zoom lens, for example, a first lens group having positive (positive refractive power), a negative second lens group, a negative third lens group, and a positive fourth lens are sequentially arranged from the object side. Some lens groups consist of four lens groups. A zoom lens is known that performs zooming by moving the second lens unit, corrects image plane fluctuations accompanying zooming with the third lens unit, and performs focusing (Patent Document 1).
また、物体側より順に正の第１レンズ群、負の第２レンズ群、弱い屈折力の第３レンズ群、そして正の第４レンズ群の４つのレンズ群を有するズームレンズがある。そして、第２レンズ群を移動させて変倍を行い、第４レンズ群で変倍に伴う像面変動を補正すると共にフォーカシングを行うズームレンズが知られている（特許文献２）。 In addition, there is a zoom lens having four lens groups of a positive first lens group, a negative second lens group, a weak third power lens group, and a positive fourth lens group in order from the object side. A zoom lens is known that performs zooming by moving the second lens group, corrects image plane fluctuations accompanying zooming with the fourth lens group, and performs focusing (Patent Document 2).
また、物体側より順に正の第１レンズ群、負の第２レンズ群、正の第３レンズ群、正の第４レンズ群を有するズームレンズがある。そして、第２レンズ群を移動させて変倍を行い、第４レンズ群で変倍に伴う像面変動を補正すると共にフォーカシングを行うズームレンズが知られている（特許文献３〜６）。また、前述のタイプの４つのレンズ群より成るズームレンズにおいて第４レンズ群を凸レンズ（正レンズ）１枚または、凸レンズ２枚で構成された例が知られている（特許文献７〜１１）。 There is also a zoom lens having a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group in order from the object side. A zoom lens is known that performs zooming by moving the second lens group, corrects image plane fluctuations accompanying zooming with the fourth lens group, and performs focusing (Patent Documents 3 to 6). In addition, there is known an example in which the fourth lens group is composed of one convex lens (positive lens) or two convex lenses in the zoom lens composed of the four lens groups of the type described above (Patent Documents 7 to 11).
また、前述したタイプの４つのレンズ群より成るズームレンズにおいて第４レンズ群を凸凹レンズの２枚で構成されたズームレンズが知られている（特許文献１２）。 Further, there is known a zoom lens in which the fourth lens group is composed of two convex / concave lenses in the zoom lens composed of the four lens groups of the type described above (Patent Document 12).
更に、前述したタイプの４つのレンズ群より成るズームレンズにおいて、その実施例中に第３レンズ群、第４レンズ群がそれぞれが正レンズ、負レンズの２枚からなることが知られている（特許文献１３〜１７）。 Further, in the zoom lens composed of the four lens groups of the type described above, it is known that each of the third lens group and the fourth lens group is composed of two lenses, a positive lens and a negative lens. Patent Documents 13 to 17).
また、前述したタイプの４つのレンズ群より成るズームレンズにおいて第１レンズ群の物体側に凹、凸レンズの２枚のレンズを配置した、広角用のズームレンズが知られている（特許文献１８）。 In addition, a zoom lens for a wide angle is known in which two lenses, a concave lens and a convex lens, are arranged on the object side of the first lens group in the zoom lens including the four lens groups of the type described above (Patent Document 18). .
また、ビデオデッキの高性能化（デジタル化）に伴いビデオカメラの高画質化が進んできている。その一つの方法として色分解光学系による画像の分解により高画質を達成しているが、それに適したズームレンズが、知られている（特許文献１９〜２７）。
以上述べたように、一般にズームレンズにおいて、前玉径、全系の小型化を達成するには、第１レンズ群による距離合わせ（フォーカス）よりも、所謂、リアフォーカス方式の方が適している。 As described above, in general, in a zoom lens, the so-called rear focus method is more suitable than the distance adjustment (focus) by the first lens group in order to achieve a reduction in the front lens diameter and the entire system. .
しかしながら、特許文献１では、絞りの前に配置された第３群の移動空間を確保せねばならず、レンズ全長の短縮と前玉径の縮小には限界があった。 However, in Patent Document 1, it is necessary to secure the third group moving space arranged in front of the diaphragm, and there is a limit to shortening the total lens length and reducing the front lens diameter.
また、特許文献２では、その全ての実施例が第３レンズ群を負の屈折力とすることで達成させているため、第４レンズ群が大型化しフォーカスによる収差変動が大きくなってしまうという傾向があった。 Further, in Patent Document 2, since all of the embodiments achieve the third lens group with negative refractive power, the fourth lens group tends to be large and the aberration fluctuation due to focusing tends to increase. was there.
特許文献３〜１２、１６、１７等でも、そのレンズ構成において色分解プリズムを配置するのに充分なバックフォーカスを得るのが難しくて、広角端の画角も超広角域にとどいてはいない。 Even in Patent Documents 3 to 12, 16, 17, etc., it is difficult to obtain a back focus sufficient for disposing a color separation prism in the lens configuration, and the angle of view at the wide-angle end does not stay in the super-wide angle range.
特許文献１３〜１５で開示されている例では、第１レンズ群、または、第３レンズ群も変倍に伴って移動するため鏡筒構造が複雑化し、小型な広角用のズームレンズを達成するのが難しかった。また、特許文献１８では第１レンズ群の物体側に凹、凸レンズの２枚を配置した、所謂ワイドコンバータータイプとなっており、広角端における歪曲収差の補正や、色収差等が３色分解プリズムを使って狙うべき高画質化には不十分なレベルで止まっている。 In the examples disclosed in Patent Documents 13 to 15, since the first lens group or the third lens group also moves with zooming, the lens barrel structure is complicated, and a small zoom lens for wide angle is achieved. It was difficult. Further, Patent Document 18 is a so-called wide converter type in which two concave and convex lenses are arranged on the object side of the first lens group, and correction of distortion at the wide-angle end, chromatic aberration, etc. is performed using a three-color separation prism. It has stopped at a level that is insufficient for achieving high image quality.
又、特許文献１９〜２７では３色分解プリズムを想定したバックフォーカスを確保してはいるが、その実施例はいずれも広角端の半画角が４０゜以上を満足するような超広角となっていなかった。 In Patent Documents 19 to 27, although a back focus assuming a three-color separation prism is secured, all of the embodiments have an ultra-wide angle that satisfies a half angle of view of 40 ° or more at the wide-angle end. It wasn't.
本発明は、特に本出願人の先の提案である特許文献２０、２１、２４〜２７の改良に関する。この他本発明は、色分解用プリズムやフィルター等の光学素子やズームレンズ部の保護を目的とした光学素子が入る程度の十分なバックフォーカスを有するズームレンズの提供を目的とする。更に本発明は、全ズーム域、及び全物体距離範囲に渡って良好な光学性能を有しつつ、半画角で４０°以上の超広角域の撮像ができるリアフォーカス式のズームレンズの提供を目的とする。 The present invention particularly relates to improvements in Patent Documents 20, 21, and 24-27, which are the previous proposals of the present applicant. Another object of the present invention is to provide a zoom lens having a sufficient back focus so that an optical element such as a color separation prism or filter, or an optical element for the purpose of protecting the zoom lens unit can be inserted. Furthermore, the present invention provides a rear focus type zoom lens that has an excellent optical performance over the entire zoom range and the entire object distance range and can capture an image in a super wide angle range of 40 ° or more at a half angle of view. Objective.
本発明のリアーフォーカス式のズームレンズは、
（１−１） 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、正の屈折力の第３群、正の屈折力の第４群の４つのレンズ群からなり、該第２群を像面側へ移動させて広角端から望遠端への変倍を行い、変倍または被写体の距離変動に伴う像面変動を該第４群の一部または全体を移動させて補正し、該第４群と像面との間にガラスブロックを配置するズームレンズであって、該第３群は像面側に凹面を向けたメニスカス状の負の第３１レンズ、正の第３２レンズと負の第３３レンズとの接合レンズ３ａより成り、該第３１レンズと接合レンズ３ａとの空気間隔をｄとし、第３群の焦点距離をｆ３とするとき、
０．０６＜ｄ／ｆ３＜０．２５ ・・・（３ａ）
なる条件式を満足している。
（１−２） 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、正の屈折力の第３群、正の屈折力の第４群の４つのレンズ群からなり、該第２群を像面側へ移動させて広角端から望遠端への変倍を行い、変倍または被写体の距離変動に伴う像面変動を該第４群の一部または全体を移動させて補正し、該第４群と像面との間にガラスブロックを配置するズームレンズであって、該第２群は像面側に凹面を向けたメニスカス状の負の第２１レンズ、負の第２２レンズ、正の第２３レンズ、そして両レンズ面が凹面の負の第２４レンズより成り、広角端の焦点距離をＦｗ、第２群の焦点距離をｆ２、とするとき、
１．７＜｜ｆ２｜／Ｆｗ＜３．６ ・・・（４ａ）
なる条件式を満足している。
（１−３） 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、正の屈折力の第３群、正の屈折力の第４群の４つのレンズ群からなり、該第２群を像面側へ移動させて広角端から望遠端への変倍を行い、変倍または被写体の距離変動に伴う像面変動を該第４群の一部または全体を移動させて補正し、該第４群と像面との間にガラスブロックを配置するズームレンズであって、該第１群は負の屈折力の第１１群と正の屈折力の第１２群の２つのレンズ群を有し、該第１１群は像面側に凹面を向けたメニスカス状の負レンズを少なくとも２つ有し、該第１２群は正レンズ、正レンズ又は負レンズと正レンズとの接合レンズ、そして正レンズより成り、該第２群は負レンズ，負レンズ，負レンズそして正レンズの４つのレンズより成り、第ｉ群の焦点距離をｆｉ、広角端における全系の焦点距離をＦｗとしたとき
−５．０＜ｆ１／ｆ２＜−０．５ ・・・（１ｂ）
−５．０＜ｆ２／Ｆｗ＜−１．０ ・・・（２ｂ）
なる条件式を満足している。
（１−４） 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、正の屈折力の第３群、正の屈折力の第４群の４つのレンズ群からなり、該第２群を像面側へ移動させて広角端から望遠端への変倍を行い、変倍または被写体の距離変動に伴う像面変動を該第４群の一部または全体を移動させて補正し、該第４群と像面との間にガラスブロックを配置するズームレンズであって、該第３群は像面側に凹面を向けたメニスカス状の負の第３１レンズ、正の第３２レンズと負の第３３レンズとの接合レンズ３ａより成っており、該第３群の焦点距離をｆ３、広角端における全系の焦点距離をＦｗとするとき
３０＜ｆ３／Ｆｗ＜６０ ・・・（３ｃ）
なる条件を満足している。
The rear focus zoom lens of the present invention is
(1-1) From four lens groups in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power The second group is moved to the image plane side, and the magnification is changed from the wide-angle end to the telephoto end, and a part or the whole of the fourth group is moved by the magnification change or the image plane variation due to the subject distance variation. A zoom lens in which a glass block is disposed between the fourth group and the image plane, and the third group includes a meniscus negative 31st lens having a concave surface facing the image plane side, a positive lens When the air distance between the 31st lens and the cemented lens 3a is d and the focal length of the third lens unit is f3.
0.06 <d / f3 <0.25 (3a)
The following conditional expression is satisfied.
(1-2) From four lens groups in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power The second group is moved to the image plane side, and the magnification is changed from the wide-angle end to the telephoto end, and a part or the whole of the fourth group is moved by the magnification change or the image plane variation due to the subject distance variation. A zoom lens in which a glass block is disposed between the fourth group and the image plane, and the second group includes a meniscus negative 21st lens having a concave surface facing the image plane side, a negative lens 22th lens, positive 23rd lens, and negative 24th lens whose both lens surfaces are concave, and when the focal length of the wide angle end is Fw and the focal length of the second group is f2,
1.7 <| f2 | / Fw <3.6 (4a)
The following conditional expression is satisfied.
(1-3) From four lens groups in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power The second group is moved to the image plane side, and the magnification is changed from the wide-angle end to the telephoto end, and a part or the whole of the fourth group is moved by the magnification change or the image plane variation due to the subject distance variation. And a zoom lens in which a glass block is disposed between the fourth group and the image plane. The first group includes an eleventh group having a negative refractive power and a twelfth group having a positive refractive power. The eleventh group includes at least two meniscus negative lenses having a concave surface facing the image surface side, and the twelfth group includes a positive lens, a positive lens, or a negative lens and a positive lens. The second lens group is composed of four lenses, a negative lens, a negative lens, a negative lens, and a positive lens. When the focal length of the group is fi and the focal length of the entire system at the wide-angle end is Fw −5.0 <f1 / f2 <−0.5 (1b)
−5.0 <f2 / Fw <−1.0 (2b)
The following conditional expression is satisfied.
(1-4) From four lens groups in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power The second group is moved to the image plane side, and the magnification is changed from the wide-angle end to the telephoto end, and a part or the whole of the fourth group is moved by the magnification change or the image plane variation due to the subject distance variation. A zoom lens in which a glass block is disposed between the fourth group and the image plane, and the third group includes a meniscus negative 31st lens having a concave surface facing the image plane side, a positive lens When the focal length of the third lens unit is f3 and the focal length of the entire system at the wide angle end is Fw, 30 <f3 / Fw <60 ... (3c)
Is satisfied.
この他本発明のリアーフォーカス式のズームレンズは、
（２−１） 第１群は負の屈折力の第１１群と正の屈折力の第１２群の２つのレンズ群を有し、該第１１群は像面側に凹面を向けたメニスカス状の負レンズを少なくとも２つ有し、該第１２群は正レンズ、像面側に凹面を向けたメニスカス状の負レンズと正レンズとの接合レンズ、そして正レンズより成り、該第１１群と第１２群との空気間隔をＬ、第１群と第２群の焦点距離を各々ｆ１，ｆ２とするとき、
０．３＜Ｌ／ｆ１≦０．８５６ ・・・（１ａ）
１．９＜ｆ１／｜ｆ２｜＜４．３ ・・・（２ａ）
なる条件式を満足している。
（２−２） 第１群は負の屈折力の第１１群と正の屈折力の第１２群の２つのレンズ群を有し、該第１１群は像面側に凹面を向けたメニスカス状の負レンズを少なくとも２つ有し、該第１２群は正レンズ、像面側に凹面を向けたメニスカス状の負レンズと正レンズとの接合レンズ、そして正レンズより成り、該第２群の焦点距離をｆ２、広角端における全系の焦点距離をＦｗ、広角端で無限遠物体合焦時のバックフォーカスをｂＦｗとしたとき
５＜ｂＦｗ／Ｆｗ＜９ ・・・（１Ｃ）
−４＜ｆ２／Ｆｗ＜−２ ・・・（２Ｃ）
なる条件を満足している。
In addition, the rear focus zoom lens of the present invention is
(2-1) The first group has two lens groups of an eleventh group having a negative refractive power and a twelfth group having a positive refractive power, and the eleventh group has a meniscus shape with a concave surface facing the image surface side. The 12th group consists of a positive lens, a cemented lens of a meniscus negative lens with a concave surface facing the image surface side and a positive lens, and a positive lens. When the air distance from the twelfth group is L, and the focal lengths of the first and second groups are f1 and f2, respectively.
0.3 <L / f1 ≦ 0.856 (1a)
1.9 <f1 / | f2 | <4.3 (2a)
The following conditional expression is satisfied.
(2-2) The first group has two lens groups, an eleventh group having a negative refractive power and a twelfth group having a positive refractive power, and the eleventh group has a meniscus shape with a concave surface facing the image surface side. At least two negative lenses, and the twelfth group includes a positive lens, a cemented lens of a negative meniscus lens having a concave surface facing the image surface and a positive lens, and a positive lens. When the focal length is f2, the focal length of the entire system at the wide-angle end is Fw, and the back focus when focusing on an object at infinity at the wide-angle end is bFw 5 <bFw / Fw <9 (1C)
-4 <f2 / Fw <-2 (2C)
Is satisfied.
本発明によれば以上のように各要素を設定することにより、色分解用プリズムやフィルター等の光学素子やズームレンズ部の保護を目的とした光学素子が入る程度の十分なバックフォーカスを有するズームレンズが得られる。更に、全ズーム域、及び全物体距離範囲に渡って良好な光学性能を有しつつ、半画角で４０°以上の超広角域の撮像ができるリアフォーカス式のズームレンズを達成することができる。又、このリアーフォーカス式のズームレンズを備えるカメラが得られる。 According to the present invention, by setting each element as described above, the zoom has a sufficient back focus so that an optical element such as a color separation prism or a filter, or an optical element for the purpose of protecting the zoom lens unit is included. A lens is obtained. Furthermore, it is possible to achieve a rear focus type zoom lens capable of imaging in a super wide angle range of 40 ° or more at a half angle of view while having good optical performance over the entire zoom range and the entire object distance range. . In addition, a camera including this rear focus type zoom lens can be obtained.
図１，図３，図５，図７，図９，図１１，図１３，図１５，図１７，図１９，図２１，図２３は本発明のリアフォーカス式のズームレンズの数値実施例１〜１２のレンズ断面図である。図２，図４，図６，図８，図１０，図１２，図１４，図１６，図１８，図２０，図２２，図２４は本発明のリアフォーカス式のズームレンズの数値実施例１〜１２の諸収差図である。収差図において（Ａ）は広角端、（Ｂ）は望遠端を示している。 1, 3, 5, 7, 9, 11, 13, 15, 17, 17, 19, 21, and 23 are numerical examples 1 of the rear focus type zoom lens according to the present invention. It is lens sectional drawing of -12. 2, 4, 6, 8, 10, 12, 14, 16, 16, 18, 20, 22, and 24 are numerical examples 1 of the rear focus type zoom lens according to the present invention. FIG. In the aberration diagrams, (A) shows the wide-angle end, and (B) shows the telephoto end.
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の中又はその近傍に配置している。Ｇは色分離系やフェースプレートやフィルター（水晶フィルター，赤外フィルター）等のガラスブロックである。ＩＰは像面である。 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 arranged in or near the third lens unit L3. G is a glass block such as a color separation system, a face plate, or a filter (quartz filter, infrared filter). IP is the image plane.
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、変倍に伴うまたは被写体の距離変動に伴う像面変動を第４群の一部又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。 In the present embodiment, when zooming from the wide-angle end to the telephoto end, the second group is moved to the image plane side as indicated by an arrow, and image plane fluctuations accompanying zooming or subject distance fluctuations are A part or all of the object is moved and corrected while having a convex locus on the object side.
又、第４群を光軸上移動させて、フォーカスを行うリア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為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、固定であるが、必要に応じて移動させても良い。 Further, a rear focus type is employed in which the fourth group is moved on the optical axis to perform focusing. 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. The movement trajectory for correction is shown. The first group and the third group are fixed during zooming and focusing, but may be moved as necessary.
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。 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.
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。 In the present embodiment, for example, when focusing from an infinitely distant object to a close object at the telephoto end, the fourth group is moved forward as indicated by a straight line 4c in the figure.
本実施形態におけるズームレンズは第１群と第２群の合成系で形成した虚像を第３群と第４群で感光面上に結像するズーム方式をとっている。本実施形態では従来の所謂４群ズームレンズにおいて第１群を繰り出してフォーカスを行う場合に比べて前述のようなリアフォーカス方式を採ることにより第１群の偏心誤差による性能劣化を防止しつつ第１群のレンズ有効径の増大化を効果的に防止している。 The zoom lens according to the present embodiment employs a zoom system in which a virtual image formed by the combined system of the first group and the second group is formed on the photosensitive surface by the third group and the fourth group. In the present embodiment, compared with a conventional so-called four-group zoom lens in which the first group is extended to perform focusing, the rear focus method as described above is employed, thereby preventing performance degradation due to the eccentric error of the first group. This effectively prevents an increase in effective lens diameter of one group.
そして開口絞りを第３群中又はその近傍に配置することにより可動レンズ群による収差変動を少なくし、開口絞りより前方のレンズ群の間隔を短くすることにより前玉レンズ径の縮小化を容易に達成している。 By disposing the aperture stop in or near the third group, aberration fluctuation due to the movable lens group is reduced, and the distance between the lens groups in front of the aperture stop is shortened, so that the front lens diameter can be easily reduced. Have achieved.
数値実施例１〜１２に示すリアフォーカス式のズームレンズは以上のレンズ構成を基本構成としている。 The rear focus type zoom lens shown in Numerical Examples 1 to 12 has the above lens configuration as a basic configuration.
（ア）次に図１，図３，図５，図７の数値実施例１〜４のレンズ構成の特徴について説明する。 (A) Next, the features of the lens configurations of Numerical Examples 1 to 4 in FIGS. 1, 3, 5, and 7 will be described.
（ア−１） 数値実施例１〜４においては前述の基本構成の基で、第１群は負の屈折力の第１１群と正の屈折力の第１２群の２つのレンズ群を有し、該第１１群は像面側に凹面を向けたメニスカス状の負レンズを少なくとも２つ有している。そして、該第１２群は正レンズ、像面側に凹面を向けたメニスカス状の負レンズと正レンズとの接合レンズ、そして正レンズより成り、前述の条件式（１ａ），（２ａ）を満足している。 (A-1) In Numerical Examples 1 to 4, the first group has two lens groups of an eleventh group having a negative refractive power and a twelfth group having a positive refractive power based on the basic configuration described above. The eleventh group has at least two meniscus negative lenses having a concave surface facing the image surface side. The twelfth group includes a positive lens, a cemented lens of a meniscus negative lens having a concave surface facing the image surface and a positive lens, and a positive lens, and satisfies the above-described conditional expressions (1a) and (2a). is doing.
（ア−２） 又、数値実施例１〜４においては前述の基本構成の基で、該第３群は像面側に凹面を向けたメニスカス状の負の第３１レンズ、正の第３２レンズと負の第３３レンズとの接合レンズ３ａより成り、前述の条件式（３ａ）を満足している。 (A-2) Further, in Numerical Examples 1 to 4, the third group has a meniscus negative 31st lens and a positive 32nd lens with the concave surface facing the image plane side, based on the basic configuration described above. And a negative 33rd lens, which satisfies the above-mentioned conditional expression (3a).
（ア−３） 又、数値実施例１〜４においては前述の基本構成の基で、該第２群は像面側に凹面を向けたメニスカス状の負の第２１レンズ、負の第２２レンズ、正の第２３レンズを有している。そして両レンズ面が凹面の負の第２４レンズより成り、前述の条件式（４ａ）を満足している。 (A-3) In Numerical Examples 1 to 4, the second group has a meniscus negative 21st lens and a negative 22nd lens with a concave surface facing the image plane side, based on the basic configuration described above. And a positive 23rd lens. Both lens surfaces are composed of a negative 24th lens having a concave surface, which satisfies the above-mentioned conditional expression (4a).
数値実施例１〜４において、所謂４群のリアフォーカス式のズームレンズで、長いバックフォーカスを確保するためには第１、第２、第３群で構成される略アフォーカル倍率を小さくし、又第４群の焦点距離を長くすることによって可能となる。そのためには第１群の焦点距離を短くしなければならないが、このとき単に第１群の焦点距離を短くする第１群と第２群とが機械的に干渉をおこしてしまうことがある。そこで、本実施形態では前述の如く第１群を構成することによって第１群の主点位置を第２群側に押し出し所望の第１群、第２群の関係を得ている。 In Numerical Examples 1 to 4, the so-called four groups of rear focus zoom lenses have a substantially afocal magnification configured to reduce the afocal magnification formed by the first, second, and third groups in order to ensure a long back focus. This can be achieved by increasing the focal length of the fourth group. For this purpose, the focal length of the first group must be shortened. At this time, the first group and the second group that simply shorten the focal length of the first group may cause mechanical interference. Therefore, in the present embodiment, by configuring the first group as described above, the principal point position of the first group is pushed to the second group side to obtain a desired relationship between the first group and the second group.
具体的には前記第１１群は像面側に凹面を向けたメニスカス状の負の第１１，第１２，第１３レンズの３つの負レンズより成っている。そして、第１２群は正の第１４レンズ、像面側に凹面を向けたメニスカス状の負の第１５レンズと正の第１６レンズとの接合レンズ１ａ、正の第１７レンズより成っている。 Specifically, the eleventh group is composed of three negative lenses of meniscus negative eleventh, twelfth and thirteenth lenses with the concave surface facing the image surface side. The twelfth group includes a positive fourteenth lens, a cemented lens 1a of a meniscus negative fifteenth lens having a concave surface facing the image surface side and a positive sixteenth lens, and a positive seventeenth lens.
このレンズ構成の場合、そのレンズ群の主点位置はその群の像面側外に押し出されることになり、第１、第２群の主点間隔を負としても双方が機械的に干渉を起すことはなくなる。従って変倍部でもレトロ型のレンズ系を作り出すことが可能となり、第３群から略アフォーカルで射出する光線束を大きくとることが出来る。そのため、第４群の焦点距離にあまり負担をかけずに全系の焦点距離を短く（広角）にし、且つ長いバックフォーカスを確保することができるようにしている。 In the case of this lens configuration, the principal point position of the lens group is pushed out of the image plane side of the lens group, and both cause mechanical interference even if the distance between the principal points of the first and second groups is negative. There will be nothing. Accordingly, it is possible to create a retro-type lens system even in the zooming portion, and it is possible to obtain a large light bundle emitted from the third group approximately afocally. For this reason, the focal length of the entire system is shortened (wide angle) and a long back focus can be secured without imposing much burden on the focal length of the fourth group.
尚、接合レンズ１ａを単一の正レンズより構成しても良い（以下の数値実施例５〜１２について全て同じ）。そして１つの実施形態（ア−１） として条件式（１ａ），（２ａ）を満足させ、他の実施形態（ア−２） として条件式（３ａ）を満足させ、又、他の実施形態（ア−３） として条件式（４ａ）を満足させている。 In addition, you may comprise the cemented lens 1a from a single positive lens (all the following numerical examples 5-12 are the same). In addition, the conditional expressions (1a) and (2a) are satisfied as one embodiment (A-1), the conditional expression (3a) is satisfied as another embodiment (A-2), and the other embodiments ( Conditional expression (4a) is satisfied as a-3).
次に前述の条件式（１ａ），（２ａ），（３ａ），（４ａ）の技術的意味について説明する。 Next, the technical meaning of the conditional expressions (1a), (2a), (3a), and (4a) will be described.
条件式（１ａ）はかかる第１群のレンズ構成において主点を押し出すのに必要な条件である。下限値を超えると主点の押し出しが不十分となり、所望の第１、２群の焦点距離関係が保てず、しいては所望のバックフォーカスが得られないか、必要なだけの広い画角が得られなくなる。また、上限値を超えると第１群中の負レンズのパワーが第１群の前面に偏りすぎるため歪曲収差が強く発生し、良好な高画質を得ることが出来なくなり好ましくない。 Conditional expression (1a) is a condition necessary for pushing out the principal point in the lens configuration of the first group. If the lower limit is exceeded, the principal point will not be pushed out, the desired focal length relationship between the first and second lens groups will not be maintained, and the desired back focus will not be obtained, or a wide angle of view as necessary. Cannot be obtained. On the other hand, if the upper limit value is exceeded, the power of the negative lens in the first group is too biased toward the front surface of the first group, so that distortion is strongly generated and a good image quality cannot be obtained.
条件式（２ａ）はかかる条件の下で必要な第１群と第２群の焦点距離の比の関係を示している。下限値を超えると第１ 群の屈折力が強くなりすぎ、第１ 群の物体側に配置する負レンズの屈折力もそれに付随して強くなり、やはり負の歪曲収差が強く発生し補正が困難となり好ましくない。また上限値を超えると必要なアフォーカル倍率が得られず本発明の目的である全系の焦点距離を短くしかつ長いバックフォーカスを確保できなくなる。 Conditional expression (2a) shows the relationship between the focal length ratios of the first group and the second group that are necessary under such conditions. If the lower limit is exceeded, the refractive power of the first group becomes too strong, and the refractive power of the negative lens disposed on the object side of the first group also increases accordingly, which also causes negative distortion and becomes difficult to correct. It is not preferable. If the upper limit is exceeded, the necessary afocal magnification cannot be obtained, and the focal length of the entire system, which is the object of the present invention, can be shortened and a long back focus cannot be secured.
また、条件式（２ａ）の数値範囲を、
２．４ ＜ ｆ１／｜ｆ２｜ ＜ ３．５ ‥‥‥（２ａａ）
なる条件式を満足すると更に良好に収差補正を行うことが可能となる。
In addition, the numerical range of conditional expression (2a)
2.4 <f1 / | f2 | <3.5 (2aa)
If this conditional expression is satisfied, aberration correction can be performed more satisfactorily.
条件式（３ａ）は第３群においてもその主点位置を少しでも像面側に押し出し第１群から第３群の間で変倍によって生じる像面位置を像面側に寄せている。これにより、第４群との共役位置であるピント面をレンズの像面側に押し出す効果があり、掛かる効果によってバックフォーカスを所望の長さまで伸長可能とするものである。 Conditional expression (3a) also pushes the principal point position in the third group as much as possible to the image plane side, and brings the image plane position generated by zooming between the first group and the third group closer to the image plane side. Accordingly, there is an effect of pushing the focus surface, which is a conjugate position with the fourth group, toward the image surface side of the lens, and the back focus can be extended to a desired length by the applied effect.
条件式（３ａ）の下限値を超えて間隔が短くなると全系の焦点距離を短くしつつも所望の長さのバックフォーカスを確保することが困難となる。上限値を超えて間隔が開き過ぎると第２群から発散されてくる光線束が第３群中で大きく発散することとなり、第３群以降のレンズ径が大きくなり好ましくない。また、条件式（３ａ）の数値範囲を、
０．０７ ＜ ｄ／ｆ３ ＜ ０．１７ ‥‥‥（３ａａ）
とすると更に良好に収差補正を行うことが出来る。
If the interval is shortened beyond the lower limit of conditional expression (3a), it becomes difficult to secure a desired back focus while shortening the focal length of the entire system. If the interval exceeds the upper limit and the interval is too wide, the light beam diverged from the second group will diverge greatly in the third group, and the lens diameter after the third group will become large, which is not preferable. Also, the numerical range of conditional expression (3a) is
0.07 <d / f3 <0.17 (3aa)
Then, aberration correction can be performed more satisfactorily.
条件式（４ａ）は、超広角用のズームレンズを達成するための変倍部のパワーを規格するものである。上限値を超えて屈折力が弱くなると前述の変倍部における略アフォーカル倍率を充分高めることができずバックフォーカスを所望の長さ確保することが困難となる。又下限値を超えて屈折力が強くなりすぎるとペッツバール和が負で増大することにより、広い画角を確保することが困難となる。また、条件式（４ａ）の数値範囲を、
１．７ ＜ ｜ｆ２｜／Ｆｗ ＜ ３．０ ‥‥‥（４ａａ）
とすると更に良好に収差補正を行うことが出来る。
Conditional expression (4a) specifies the power of the zooming unit for achieving a zoom lens for an ultra-wide angle. If the refractive power is weakened beyond the upper limit value, the afocal magnification at the above-described zooming portion cannot be sufficiently increased, and it becomes difficult to secure a desired back focus length. If the refractive power is too strong beyond the lower limit, the Petzval sum increases negatively, making it difficult to ensure a wide angle of view. In addition, the numerical range of conditional expression (4a)
1.7 <| f2 | / Fw <3.0 (4aa)
Then, aberration correction can be performed more satisfactorily.
尚、数値実施例１〜４において、即ち構成（ア−１） 又は（ア−２） 又は（ア−３） において更に良好なる光学性能を得るには次の諸条件のうち少なくとも１つを満足させるのが良い。 In Numerical Examples 1 to 4, that is, in order to obtain better optical performance in the constitution (A-1) or (A-2) or (A-3), at least one of the following conditions is satisfied. It is good to let it.
（ａ１）負に増大しがちなペッツバール和を良好に保ち像面の平坦化を達成するためには、第１群の３枚の負の第１１，第１２，第１３レンズの材質の屈折率の平均値をＮＡ１、第２群の負の第２１，第２２，第２４レンズの材質の屈折率の平均値をＮＡ２とする。このとき、
１．６０ ＜ ＮＡ１ ‥‥‥（５ａ）
１．８０ ＜ ＮＡ２ ＜ １．８９ ‥‥‥（６ａ）
を満足することが好ましい。
(A1) In order to maintain the Petzval sum that tends to increase negatively and achieve flattening of the image plane, the refractive index of the material of the three negative eleventh, twelfth and thirteenth lenses in the first group Is NA1, and the average refractive index of the materials of the negative 21st, 22nd, and 24th lenses of the second group is NA2. At this time,
1.60 <NA1 (5a)
1.80 <NA2 <1.89 (6a)
Is preferably satisfied.
（ａ２）長い射出瞳を確保するために第３群中の負の第３１レンズと正の第３２レンズの間に絞りを配置しているが、射出瞳位置の要件は色分解プリズムの構成によって変わるため、絞りを第３群の前後に配置しても良い。 (A2) In order to secure a long exit pupil, a stop is disposed between the negative 31st lens and the positive 32nd lens in the third lens group. The exit pupil position requirements depend on the configuration of the color separation prism. Since it changes, you may arrange | position an aperture stop before and behind the 3rd group.
（ａ３）前記第１１群は像面側に凹面を向けたメニスカス状の負の第１１，第１２，第１３レンズの３つの負レンズより成る。第１２群は正の第１４レンズ、像面側に凹面を向けたメニスカス状の負の第１５レンズと正の第１６レンズとの接合レンズ１ａ、正の第１７レンズより成る。該第２群は像面側に凹面を向けたメニスカス状の負の第２１レンズ、負の第２２レンズ、正の第２３レンズ、そして両レンズ面が凹面の負の第２４レンズより成る。該第３群は像面側に凹面を向けたメニスカス状の負の第３１レンズ、正の第３２レンズと負の第３３レンズとの接合レンズ３ａより成ること。 (A3) The eleventh lens unit is composed of three negative lenses of meniscus negative eleventh, twelfth and thirteenth lenses with the concave surface facing the image surface side. The twelfth group includes a positive fourteenth lens, a cemented lens 1a formed of a meniscus negative fifteenth lens having a concave surface facing the image surface side and a positive sixteenth lens, and a positive seventeenth lens. The second group includes a meniscus negative 21st lens having a concave surface directed toward the image surface side, a negative 22nd lens, a positive 23rd lens, and a negative 24th lens whose both lens surfaces are concave. The third group includes a meniscus negative 31st lens having a concave surface facing the image surface side, and a cemented lens 3a composed of a positive 32nd lens and a negative 33rd lens.
（ａ４）前記第４群は像面側に凸面を向けたメニスカス状の正の第４１レンズ、像面側に凹面を向けた負の第４２レンズと両レンズ面が凸面の正の第４３レンズとの接合レンズ４ａ、そして両レンズ面が凸面の正の第４４レンズより成ること。
である。
(A4) The fourth group is a meniscus positive 41st lens with a convex surface facing the image surface side, a negative 42nd lens with a concave surface facing the image surface side, and a positive 43rd lens with convex surfaces on both lens surfaces And a cemented lens 4a and a positive 44th lens whose both lens surfaces are convex.
It is.
次に図９，図１１，図１３，図１５，図１７の数値実施例５〜９のレンズ構成の特徴について説明する。 Next, features of the lens configurations of Numerical Examples 5 to 9 in FIGS. 9, 11, 13, 15, and 17 will be described.
（イ−１） 数値実施例５〜９は前述の基本構成の基で、該第１群は負の屈折力の第１１群と正の屈折力の第１２群の２つのレンズ群を有している。該第１１群は像面側に凹面を向けたメニスカス状の負レンズを少なくとも２つ有している。該第１２群は正レンズ、正レンズ又は負レンズと正レンズとの接合レンズ、そして正レンズより成り、該第２群は負レンズ，負レンズ，負レンズそして正レンズの４つのレンズより成り、前述の条件式（１ｂ），（２ｂ）を満足している。 (A-1) Numerical Examples 5 to 9 are based on the basic configuration described above, and the first group has two lens groups of an eleventh group having a negative refractive power and a twelfth group having a positive refractive power. ing. The eleventh group has at least two meniscus negative lenses having a concave surface facing the image surface side. The twelfth group consists of a positive lens, a positive lens or a cemented lens of a negative lens and a positive lens, and a positive lens, and the second group consists of four lenses, a negative lens, a negative lens, a negative lens, and a positive lens, The above conditional expressions (1b) and (2b) are satisfied.
具体的には図９，図１１，図１３の数値実施例５，６，７では前記第１１群は像面側に凹面を向けたメニスカス状の負の第１１，第１２，第１３レンズの３つの負レンズより成っている。第１２群は正の第１４レンズ、像面側に凹面を向けたメニスカス状の負の第１５レンズと正の第１６レンズとの接合レンズ１ａ、正の第１７レンズより成っている。 Specifically, in Numerical Examples 5, 6, and 7 of FIGS. 9, 11, and 13, the eleventh group is composed of negative eleventh, twelfth, and thirteenth lenses having a meniscus shape with a concave surface facing the image surface side. It consists of three negative lenses. The twelfth group includes a positive fourteenth lens, a cemented lens 1a of a meniscus negative fifteenth lens having a concave surface facing the image surface side and a positive sixteenth lens, and a positive seventeenth lens.
又、図１５，図１７の数値実施例８，９では第１１群を像面側に凹面を向けたメニスカス状の負の第１１，第１２レンズより成っている。第１２群は正の第１４レンズ、像面側に凹面を向けたメニスカス状の負の第１５レンズと正の第１６レンズとの接合レンズ１ａ、正の第１７レンズより成っている。 In Numerical Examples 8 and 9 of FIGS. 15 and 17, the eleventh lens unit is composed of meniscus negative eleventh and twelfth lenses with the concave surface facing the image surface side. The twelfth group includes a positive fourteenth lens, a cemented lens 1a of a meniscus negative fifteenth lens having a concave surface facing the image surface side and a positive sixteenth lens, and a positive seventeenth lens.
数値実施例５，６，８，９では第２群を像面側に凹面を向けたメニスカス状の負の第２１レンズ、負の第２２レンズ、両レンズ面が凹面の負の第２３レンズ、そして両レンズ面が凸面の正の第２４レンズより構成している。 In Numerical Examples 5, 6, 8, and 9, a meniscus negative 21st lens having a concave surface facing the second group toward the image surface side, a negative 22nd lens, a negative 23rd lens having concave both lens surfaces, Both lens surfaces are composed of a positive 24th lens having a convex surface.
又、数値実施例７では第２群を像面側に凹面を向けたメニスカス状の負の第２１レンズ、負の第２２レンズ、両レンズ面が凹面の負の第２３レンズ、そして両レンズ面が凸面の正の第２４レンズより構成している。このうち第２３レンズと第２４レンズとを接合レンズ２ａより構成している。 In Numerical Example 7, the meniscus negative 21st lens with the second lens unit facing the image side and the negative 21st lens, the negative 22nd lens, the negative 23rd lens with both lens surfaces concave, and both lens surfaces Is composed of a positive 24th lens having a convex surface. Among these, the 23rd lens and the 24th lens are constituted by the cemented lens 2a.
数値実施例５〜９では、すべて球面レンズを用いているが、非球面を有するレンズを仕様することにより更に性能を向上させることやＦｎｏを明るくすることが可能となる。特に第３レンズ群に非球面を有するレンズを用いることによりレンズ枚数の削減を達成することが可能になり、同時に球面収差などを効果的に補正することが可能になる。更に第４レンズ群に非球面を有するレンズを用いることによりコマ収差などを効果的に補正することが可能となる。 In Numerical Examples 5 to 9, all spherical lenses are used. However, by specifying a lens having an aspherical surface, it is possible to further improve the performance and brighten Fno. In particular, it is possible to reduce the number of lenses by using a lens having an aspheric surface in the third lens group, and at the same time, it is possible to effectively correct spherical aberration and the like. Further, coma and the like can be effectively corrected by using a lens having an aspheric surface in the fourth lens group.
そして前述のごとく設定することにより、色分解用プリズム等の光学素子やズームレンズ部の保護を目的とした光学素子が入るバックフォーカス空間を十分確保している。そして、全ズーム域、全物体距離範囲に渡って良好な光学性能を提供しつつ、半画角で４０°以上の超広角域を撮像可能なリアフォーカス式のズームレンズを得ている。 By setting as described above, a sufficient back focus space is provided in which an optical element such as a color separation prism or an optical element for the purpose of protecting the zoom lens unit is placed. In addition, a rear focus type zoom lens that can capture a super wide angle range of 40 ° or more at a half angle of view while providing good optical performance over the entire zoom range and the entire object distance range is obtained.
次に前述の条件式（１ｂ），（２ｂ）の技術的な意味について説明する。 Next, the technical meaning of the conditional expressions (1b) and (2b) will be described.
条件式（１ｂ）は第１レンズ群と第２レンズ群の焦点距離の他に関するものであり、コンパクト化を達成しつつバックフォーカスの長くて良好な光学性能を維持するためのものである。条件式（１ｂ）の下限値を越えて第２レンズ群の焦点距離が長くなり、第１レンズ群の焦点距離が短くなると第２レンズ群の移動量が増大し、レンズ全長や前玉径を小型化する事が困難になる。また望遠端近傍での第４レンズ群の移動量が大きくなりズーミング時の収差の変動が大きくなるといった問題も生じる。逆に上限値を越えると歪曲等の諸収差を良好に補正することが困難になる。 Conditional expression (1b) relates to the other focal lengths of the first lens group and the second lens group, and is for maintaining good optical performance with a long back focus while achieving compactness. When the lower limit of conditional expression (1b) is exceeded, the focal length of the second lens group becomes longer, and when the focal length of the first lens group becomes shorter, the movement amount of the second lens group increases, and the total lens length and front lens diameter are reduced. It becomes difficult to downsize. In addition, there is a problem that the amount of movement of the fourth lens unit in the vicinity of the telephoto end becomes large and the variation in aberration during zooming becomes large. On the other hand, when the upper limit is exceeded, it is difficult to satisfactorily correct various aberrations such as distortion.
条件式（２ｂ）は第２レンズ群の焦点距離に関するものである。条件式（２ｂ）の上限値を越えて第２レンズ群の焦点距離が短くなるとペッツバール和がアンダー方向に大きくなり像面の倒れ等の収差補正が困難になる。逆に下限値を越えて第２レンズ群の焦点距離が長くなると第２レンズ群の移動量が増え、前玉径が大きくなりすぎるという問題が生じてくる。 Conditional expression (2b) relates to the focal length of the second lens group. If the upper limit of conditional expression (2b) is exceeded and the focal length of the second lens group is shortened, the Petzval sum increases in the under direction, making it difficult to correct aberrations such as image plane tilt. On the other hand, if the focal length of the second lens group is increased beyond the lower limit, the amount of movement of the second lens group increases and the front lens diameter becomes too large.
尚、数値実施例５〜９において即ち（イ−１）において更に良好なる光学性能を得るには次の諸条件のうち少なくとも１つを満足させるのが良い。 In Numerical Examples 5 to 9, that is, in order to obtain further excellent optical performance in (A-1), it is preferable to satisfy at least one of the following conditions.
（ｂ１）前記第３群は像面側に凹面を向けたメニスカス状の負の第３１レンズ、正の第３２レンズと負の第３３レンズとの接合レンズ３ａより成っていることである。 (B1) The third group includes a meniscus negative 31st lens having a concave surface directed toward the image surface side, and a cemented lens 3a composed of a positive 32nd lens and a negative 33rd lens.
（ｂ２）前記第４群は像面側に凸面を向けたメニスカス状の正の第４１レンズ、像面側に凹面を向けた負の第４２レンズと両レンズ面が凸面の正の第４３レンズとの接合レンズ４ａ、そして両レンズ面が凸面の正の第４４レンズより成っていることである。 (B2) The fourth lens group is a meniscus positive 41st lens with a convex surface facing the image surface, a negative 42nd lens with a concave surface facing the image surface, and a positive 43rd lens with both lens surfaces convex. And a cemented lens 4a, and both lens surfaces are composed of a convex positive 44th lens.
（ｂ３）前記第２１レンズと第２２レンズの合成焦点距離をｆ２ａ、前記第２３レンズと第２４レンズの合成焦点距離をｆ２ｂ、前記第１，第２，第３群の合成焦点距離をｆ１２３、望遠端における全系の焦点距離をｆＴとしたとき
２．５＜ ｆ３／ｆ４ ＜９ ‥‥‥（３ｂ）
−０．５＜ｆ２ａ／ｆ２ｂ ＜１ ‥‥‥（４ｂ）
−０．５＜ ｆＴ／ｆ１２３＜０ ‥‥‥（５ｂ）
なる条件を満足することである。
(B3) The combined focal length of the 21st lens and the 22nd lens is f2a, the combined focal length of the 23rd lens and the 24th lens is f2b, and the combined focal length of the first, second, and third lenses is f123, When the focal length of the entire system at the telephoto end is fT, 2.5 <f3 / f4 <9 (3b)
-0.5 <f2a / f2b <1 (4b)
-0.5 <fT / f123 <0 (5b)
To satisfy the following conditions.
条件式（３ｂ）は第３レンズ群と第４レンズ群の焦点距離の比に関するものであり、絞り以降のコンパクト化を達成しつつバックフォーカスや射出瞳位置を充分長くして良好な光学性能を維持するためのものである。 Conditional expression (3b) relates to the ratio of the focal lengths of the third lens group and the fourth lens group, and achieves good optical performance by sufficiently lengthening the back focus and exit pupil position while achieving compactness after the stop. It is for maintaining.
条件式（３ｂ）の下限を越えて第３レンズ群の焦点距離が短くなると変倍に伴うあるいはフォーカシング時の球面収差の変動の補正が困難となる。また充分なバックフォーカスの確保が困難となったり、ズーム中間位置での射出瞳が短くなったり、第４レンズ群の移動量が大きくなりズーミング時やフォーカシングによる収差の変動が大きくなるといった問題も生じる。 When the focal length of the third lens unit is shortened beyond the lower limit of conditional expression (3b), it becomes difficult to correct spherical aberration fluctuations during zooming or focusing. In addition, it is difficult to ensure sufficient back focus, the exit pupil at the intermediate position of the zoom is shortened, the amount of movement of the fourth lens unit is increased, and fluctuations in aberration due to zooming and focusing are increased. .
逆に上限値を越えて第３レンズ群の焦点距離が長くなると第３レンズ群から射出する光束の発散が大きくなり第４レンズ群の有効径が大きくなりレンズが重くなるためスムーズにフォーカシングが出来なくなるなどの問題が生じる。 On the other hand, if the focal length of the third lens group is increased beyond the upper limit value, the divergence of the light beam emitted from the third lens group becomes larger, the effective diameter of the fourth lens group becomes larger, and the lens becomes heavier, so that smooth focusing is possible. Problems such as disappearance occur.
条件式（４ｂ）は第２レンズ群中のレトロ比に関するものである。条件式（４ｂ）の上限値を超えてレトロ比が強くなると、ペッツバール和がアンダーに大きくなり像面の倒れ等の収差補正が困難になる。逆に下限を超えて小さくなると、第２レンズ群の前側主点位置がかなり像面側になり、第１レンズ群との主点間隔を大きくとらなければならないため、第１レンズ群の径が大型化するという問題が生じる。 Conditional expression (4b) relates to the retro ratio in the second lens group. When the retro ratio is increased beyond the upper limit value of conditional expression (4b), the Petzval sum becomes larger and the correction of aberrations such as image plane tilt becomes difficult. On the other hand, if the value becomes smaller than the lower limit, the front principal point position of the second lens group becomes considerably on the image plane side, and the principal point distance from the first lens group must be increased. The problem of increasing the size arises.
条件式（５ｂ）は第３レンズ群から射出する軸上光束の平行度（アフォーカル度）に関するものである。条件式（５ｂ）の上限値を越えて軸上光束の収斂度が強くなると至近距離物体での非点隔差が大きくなると共にメリディオナル像面が補正不足になってくる。 Conditional expression (5b) relates to the parallelism (afocal degree) of the axial light beam emitted from the third lens group. When the upper limit of conditional expression (5b) is exceeded and the convergence of the axial light beam becomes strong, the astigmatic difference at the close object increases and the meridional image plane becomes insufficiently corrected.
逆に下限値を越えて軸上光束の発散度が強くなると第４レンズ群に入射する入射高が高くなり、球面収差が多く発生してくるという問題が生じる。 On the contrary, when the divergence of the axial light beam is increased beyond the lower limit, the incident height incident on the fourth lens group increases, and a problem arises that a lot of spherical aberration occurs.
（ｂ４）尚、以上述べたように条件式（１ｂ）〜（５ｂ）はバックフォーカス（ガラスブロックを除いた最終レンズ面から像面までの距離）を長くするためのものである。更に、全ズーム域、全物体距離範囲に渡って良好な光学性能を提供しつつ、半画角で４０°以上の超広角域を撮像可能良好な光学性能を満足するための条件ではある。更に望ましくは
−４．０＜ｆ１ ／ｆ２ ＜−１．０ ‥‥‥（１ｂｂ）
−４．０＜ｆ２ ／Ｆｗ ＜−２．０ ‥‥‥（２ｂｂ）
３．０＜ｆ３ ／ｆ４ ＜ ７．０ ‥‥‥（３ｂｂ）
−０．３＜ｆ２ａ／ｆ２ｂ ＜ ０．８ ‥‥‥（４ｂｂ）
−０．４＜ｆＴ ／ｆ１２３＜−０．１ ‥‥‥（５ｂｂ）
なる条件を満足することである。
(B4) As described above, the conditional expressions (1b) to (5b) are for increasing the back focus (distance from the final lens surface excluding the glass block to the image plane). Furthermore, it is a condition for satisfying good optical performance that can provide an image with a super wide angle of 40 ° or more at a half angle of view while providing good optical performance over the entire zoom range and the entire object distance range. More desirably -4.0 <f1 / f2 <-1.0 (1bb)
-4.0 <f2 / Fw <-2.0 (2bb)
3.0 <f3 / f4 <7.0 (3bb)
-0.3 <f2a / f2b <0.8 (4bb)
−0.4 <fT / f123 <−0.1 (5bb)
To satisfy the following conditions.
（ｂ５）全ズーム域、全物体距離範囲に渡って良好な光学性能を提供しつつ、半画角で４０°以上の超広角域を撮像可能良好な光学性能を満足するためには、第２レンズ群中の負レンズの屈折率の平均値をｎａ２としたとき
１．７５＜ｎａ２ ‥‥‥（６ｂ）
なる条件を満足することである。
(B5) While providing good optical performance over the entire zoom range and the entire object distance range, it is possible to image an ultra-wide angle range of 40 ° or more at a half angle of view. When the average value of the refractive index of the negative lens in the lens group is na2, 1.75 <na2 (6b)
To satisfy the following conditions.
条件式（６ｂ）は、変倍のための第２群中の負レンズの材質の構成に関するものである。小型化のため第２群の屈折力を強くして変倍のための移動量を小さくする必要があるが、そうするとそれに伴って負のペッツバール和が増大し像面の平坦性が損なわれる可能性がある。 Conditional expression (6b) relates to the configuration of the material of the negative lens in the second group for zooming. In order to reduce the size, it is necessary to increase the refractive power of the second unit to reduce the amount of movement for zooming. However, in this case, the negative Petzval sum increases and the flatness of the image plane may be impaired. There is.
条件式（６ｂ）はこのようなことを考慮して第２群の屈折力を強めたときのペッツバール和の増大を防止して像面特性を良好に保つために第２群中の負レンズの３つの負レンズの材質の屈折力を適切に設定するためのものである。条件式（６ｂ）を外れると変倍にともなう像面湾曲の変動を良好に補正するのが困難になってくる。 Conditional expression (6b) takes this into consideration, in order to prevent the Petzval sum from increasing when the refractive power of the second group is increased, and to maintain good image plane characteristics, so that the negative lens in the second group This is for appropriately setting the refractive power of the materials of the three negative lenses. If the conditional expression (6b) is not satisfied, it will be difficult to satisfactorily correct the variation in field curvature due to zooming.
（ｂ６）このように半画角で４０°以上の超広角域を撮像可能良好な光学性能を満足するためのには上記条件式を満足することが望まれるが、更に良好な光学性能を満足するためには
−３．７ ＜ｆ１／ｆ２＜−１．２
−３．８ ＜ｆ２／Ｆｗ＜−２．４
３．１ ＜ｆ３／ｆ４＜６．１
−０．２８＜ｆ２ａ／ｆ２ｂ＜０．７
−０．３７＜ｆＴ／ｆ１２３＜−０．１
１．８０＜ｎａ２
なる条件式を満足することが望ましい。
(B6) In this way, it is possible to image a super wide angle region of 40 ° or more at a half angle of view. In order to satisfy good optical performance, it is desirable that the above conditional expression is satisfied, but further satisfactory optical performance is satisfied. -3.7 <f1 / f2 <-1.2
−3.8 <f2 / Fw <−2.4
3.1 <f3 / f4 <6.1
−0.28 <f2a / f2b <0.7
−0.37 <fT / f123 <−0.1
1.80 <na2
It is desirable to satisfy the following conditional expression.
次に図１９，図２１，図２３の数値実施例１０〜１２のレンズ構成の特徴について説明する。 Next, features of the lens configurations of Numerical Examples 10 to 12 in FIGS. 19, 21, and 23 will be described.
（ウ−１） 数値実施例１０〜１２は前述の基本構成の基で、第１群は負の屈折力の第１１群と正の屈折力の第１２群の２つのレンズ群を有し、該第１１群は像面側に凹面を向けたメニスカス状の負レンズを少なくとも２つ有している。そして、該第１２群は正レンズ、像面側に凹面を向けたメニスカス状の負レンズと正レンズとの接合レンズ、そして正レンズより成り、前述の条件式（１ｃ），（２ｃ）を満足している。 (C-1) Numerical Examples 10 to 12 are based on the above-described basic configuration, and the first group has two lens groups of an eleventh group having a negative refractive power and a twelfth group having a positive refractive power, The eleventh group has at least two meniscus negative lenses having a concave surface facing the image surface side. The twelfth group includes a positive lens, a cemented lens of a meniscus negative lens having a concave surface facing the image surface and a positive lens, and a positive lens, and satisfies the above-described conditional expressions (1c) and (2c). is doing.
（ウ−２） 又、数値実施例１０〜１２は前述の基本構成の基で、第３群は像面側に凹面を向けたメニスカス状の負の第３１レンズ、正の第３２レンズと負の第３３レンズとの接合レンズ３ａより成っており、前述の条件式（３ｃ）を満足している。 (C-2) Numerical Examples 10 to 12 are based on the basic configuration described above, and the third group is a negative meniscus 31st lens with a concave surface facing the image surface side, a positive 32nd lens and a negative 32nd lens. The 33rd lens and the cemented lens 3a satisfy the above-mentioned conditional expression (3c).
数値実施例１０〜１２において、所謂４群のリアフォーカス式のズームレンズで、長いバックフォーカスを確保するためには第１、第２、第３群で構成される略アフォーカル倍率を小さくし、又第４群の焦点距離を長くすることによって可能となる。そのためには第１群の焦点距離を短くしなければならないが、このとき単に第１群の焦点距離を短くする第１群と第２群とが機械的に干渉をおこしてしまうことがある。そこで、本実施形態では前述の如く第１群を構成することによって第１群の主点位置を第２群側に押し出し所望の第１群、第２群の関係を得ている。 In Numerical Examples 10 to 12, a so-called four-group rear focus type zoom lens is used to reduce the afocal magnification substantially composed of the first, second, and third groups in order to ensure a long back focus. This can be achieved by increasing the focal length of the fourth group. For this purpose, the focal length of the first group must be shortened. At this time, the first group and the second group that simply shorten the focal length of the first group may cause mechanical interference. Therefore, in the present embodiment, by configuring the first group as described above, the principal point position of the first group is pushed to the second group side to obtain a desired relationship between the first group and the second group.
又、前記第１１群は像面側に凹面を向けたメニスカス状の負の第１１，第１２，第１３レンズの３つの負レンズより成る。第１２群は正の第１４レンズ、像面側に凹面を向けたメニスカス状の負の第１５レンズと正の第１６レンズとの接合レンズ１ａ、正の第１７レンズより構成している。 The eleventh group is composed of three negative lenses of meniscus negative eleventh, twelfth and thirteenth lenses with the concave surface facing the image surface side. The twelfth group includes a positive fourteenth lens, a cemented lens 1a of a meniscus negative fifteenth lens having a concave surface directed toward the image surface side and a positive sixteenth lens, and a positive seventeenth lens.
このレンズ構成の場合、そのレンズ群の主点位置はその群の像面側外に押し出されることになり、第１、第２群の主点間隔を負としても双方が機械的に干渉を起すことはなくなる。従って変倍部でもレトロ型のレンズ系を作り出すことが可能となり、第３群から略アフォーカルで射出する光線束を大きくとることが出来る。そのため、第４群の焦点距離にあまり負担をかけずに全系の焦点距離を短く（広角）にし、且つ長いバックフォーカスを確保することができるようにしている。 In the case of this lens configuration, the principal point position of the lens group is pushed out of the image plane side of the lens group, and both cause mechanical interference even if the distance between the principal points of the first and second groups is negative. There will be nothing. Accordingly, it is possible to create a retro-type lens system even in the zooming portion, and it is possible to obtain a large light bundle emitted from the third group approximately afocally. For this reason, the focal length of the entire system is shortened (wide angle) and a long back focus can be secured without imposing much burden on the focal length of the fourth group.
次に前述の条件式（１ｃ）〜（３ｃ）の技術的意味について説明する。 Next, the technical meaning of the conditional expressions (1c) to (3c) will be described.
条件式（１ｃ）は交換レンズに対応するための十分なバックフォーカス（ガラスブロックＧを除去したときの最終レンズ面から像面までの距離）を得るのに必要な条件である。上限値を超えてバックフォーカスが長くなると第３レンズ群から第４レンズ群への光束の発散が大きくなり、第４レンズ群を大型化させ、像面補正や合焦のために第４レンズ群を動かすアクチュエーターへの負荷か増大する。それと同時に第４レンズ群移動時の収差変動も大きくなる。 Conditional expression (1c) is a condition necessary for obtaining a sufficient back focus (distance from the final lens surface to the image plane when the glass block G is removed) to cope with the interchangeable lens. If the back focus becomes longer than the upper limit, the divergence of the light flux from the third lens group to the fourth lens group becomes large, the fourth lens group is enlarged, and the fourth lens group is used for image surface correction and focusing. Increases the load on the actuator that moves At the same time, aberration fluctuations when the fourth lens unit moves are also increased.
又、下限値を超えて短くなると、色分解プリズム等の光学素子を入れるスペースの確保が困難になる。条件式（２ｃ）は超広角用のズームレンズを達成するための変倍部のパワーを規格するものである。上限値を超えて屈折力が弱くなると前述の変倍部における略アフォーカル倍率を充分高めることができずバックフォーカスを所望の長さ確保することが困難となる。又、下限値を超えて屈折力が強くなりすぎるとペッツバール和が負の方向で増大することにより、広い画角を確保することが困難となる。 On the other hand, if the length is shorter than the lower limit, it is difficult to secure a space for inserting an optical element such as a color separation prism. Conditional expression (2c) is for standardizing the power of the zooming unit for achieving a zoom lens for an ultra-wide angle. If the refractive power is weakened beyond the upper limit value, the afocal magnification at the above-described zooming portion cannot be sufficiently increased, and it becomes difficult to secure a desired back focus length. If the refractive power is too strong beyond the lower limit, the Petzval sum increases in the negative direction, making it difficult to ensure a wide angle of view.
条件式（３ｃ）も交換レンズに対応するための十分なバックフォーカスえるのに必要な条件である。上限値を超えて第３レンズ群の焦点距離がながくなると、第３レンズ群からの光束が発散し第４レンズが大型化し、収差変動も大きくなるという問題が生じ、下限値を超えて小さくなると十分なバックフォーカスの確保が困難になる。また、軸上の色収差のみならず倍率の色収差をも良好に補正するためには、全系の色消しのバランスをとることが重要であるが、そのためには第３群の正の第３２レンズと負の第３３レンズとを接合レンズとすることが好ましい。 Conditional expression (3c) is also a necessary condition for achieving sufficient back focus to accommodate the interchangeable lens. When the focal length of the third lens group becomes short beyond the upper limit value, there arises a problem that the light flux from the third lens group diverges, the fourth lens becomes large, and aberration fluctuations increase, and when the lower limit value is exceeded, the fourth lens group becomes large. Ensuring sufficient back focus is difficult. In order to satisfactorily correct not only axial chromatic aberration but also lateral chromatic aberration, it is important to balance the achromaticity of the entire system. For this purpose, a positive third lens of the third group is used. The negative 33rd lens is preferably a cemented lens.
尚、数値実施例１０〜１２において、即ち構成（ウ−１） 又は（ウ−２） において更に良好なる光学性能を得るには次の諸条件のうちの少なくとも１つを満足させるのが良い。 In Numerical Examples 10 to 12, that is, in order to obtain further excellent optical performance in the configuration (C-1) or (C-2), it is preferable to satisfy at least one of the following conditions.
（ｃ１）前記第１１群の負レンズに少なくとも１つの非球面を設けたことである。これより広角端近傍で発生する歪曲収差を良好に補正することができる。 (C1) The negative lens of the eleventh group is provided with at least one aspherical surface. As a result, it is possible to satisfactorily correct distortion occurring in the vicinity of the wide-angle end.
（ｃ２）前記第１１群は像面側に凹面を向けたメニスカス状の負の第１１，第１２，第１３レンズの３つの負レンズより成っており、該第１２レンズは非球面を有していることである。 (C2) The eleventh group includes three negative lenses of meniscus negative eleventh, twelfth and thirteenth lenses with the concave surface facing the image surface, and the twelfth lens has an aspherical surface. It is that.
これによれば、大口径の１番目に非球面を用いるよりも製造コストを下げることができ、これより像面側のレンズに用いるよも、軸外光束がレンズの端を通るため、歪曲収差に非常に効果的である。 According to this, the manufacturing cost can be reduced as compared with the case where the first aspherical surface having the large aperture is used, and since the off-axis light beam passes through the end of the lens as compared with the case of using the lens on the image plane side, the distortion aberration. It is very effective.
（ｃ３）前記第１１群と第１２群との空気間隔をＬ、前記第１群，第３群の焦点距離を各々ｆ１，ｆ３、前記第３群は像面側に凹面を向けたメニスカス状の負の第３１レンズ、正の第３２レンズと負の第３３レンズとの接合レンズ３ａより成っている。該第３１レンズと接合レンズ３ａとの空気間隔をｄとしたとき
０．２＜Ｌ／ｆ１＜１ ‥‥‥（４ｃ）
０．０２＜ｄ／ｆ３＜０．１‥‥‥（５ｃ）
なる条件を満足することである。
(C3) The air gap between the eleventh group and the twelfth group is L, the focal lengths of the first group and the third group are f1 and f3, respectively, and the third group has a meniscus shape with the concave surface facing the image surface side. A negative 31st lens, and a cemented lens 3a composed of a positive 32nd lens and a negative 33rd lens. When the air space between the 31st lens and the cemented lens 3a is d, 0.2 <L / f1 <1 (4c)
0.02 <d / f3 <0.1 (5c)
To satisfy the following conditions.
条件式（４ｃ）は本発明の第１群の構成において主点を押し出すのに必要な条件である。下限値を超えると主点の押し出しが不十分となり、所望の第１、第２群の焦点距離関係が保てず、しいては所望のバックフォーカスが得られないか、必要なだけの広い画角が得られなくなる。また、上限値を超えると第１群中の負レンズのパワーが第１群の前面に偏りすぎるため歪曲収差が強く発生し、良好な高画質を得ることが出来なくなり好ましくない。 Conditional expression (4c) is a condition necessary for pushing out the principal point in the configuration of the first group of the present invention. When the lower limit is exceeded, the principal point is not sufficiently pushed out, the desired focal length relationship between the first and second groups cannot be maintained, and the desired back focus cannot be obtained, or a wide image as necessary. A corner cannot be obtained. On the other hand, if the upper limit value is exceeded, the power of the negative lens in the first group is too biased toward the front surface of the first group, so that distortion is strongly generated and a good image quality cannot be obtained.
条件式（５ｃ）は第３群においてもその主点位置を少しでも像面側に押し出し第１群から第３群の間で変倍によって生じる像面位置を像面側に寄せることにより第４群との共役位置であるピント面をレンズの像面側に押し出す効果がある。掛かる効果によってバックフォーカスを所望の長さまで伸長可能とするものである。本条件式の下限値を超えて間隔が短くなると全系の焦点距離を短くしつつも所望の長さのバックフォーカスを確保することが困難となる。上限値を超えて間隔が開き過ぎると第２群から発散されてくる光線束が第３群中で大きく発散することとなり、第３群以降のレンズ径が大きくなり好ましくない。 Conditional expression (5c) indicates that the principal point position in the third group is pushed slightly toward the image plane side, and the image plane position generated by zooming between the first group and the third group is brought closer to the image plane side. There is an effect of pushing out the focus surface, which is a conjugate position with the group, to the image surface side of the lens. The back focus can be extended to a desired length by the applied effect. If the interval becomes shorter than the lower limit value of this conditional expression, it becomes difficult to secure a desired back focus while shortening the focal length of the entire system. If the interval exceeds the upper limit and the interval is too wide, the light beam diverged from the second group will diverge greatly in the third group, and the lens diameter after the third group will become large, which is not preferable.
（ｃ４）以上述べてきたように設定することで、バックフォーカス空間を保持し、良好な光学性能を提供しつつ、半画角で４５°以上の超広角域を撮像可能なリアフォーカス式のズームレンズを達成できる。さらに性能を良好にするには各条件式を以下のように設定するのが望ましい。 (C4) By setting as described above, a rear focus type zoom that can capture a super wide angle region of 45 ° or more at a half angle of view while maintaining a back focus space and providing good optical performance. Lens can be achieved. In order to further improve the performance, it is desirable to set each conditional expression as follows.
６．０＜ｂＦｗ／Ｆｗ＜８．０ ‥‥‥（１ｃｃ）
−３．０＜ｆ２／Ｆｗ＜−２．２ ‥‥‥（２ｃｃ）
３０． ０＜ｆ３／Ｆｗ＜ ５０．０ ‥‥（３ｃｃ）
０．４０＜Ｌ／ｆ１＜０．９０ ‥‥（４ｃｃ）
０．０４＜ｄ／ｆ３＜０．０７ ‥‥（５ｃｃ）
（ｃ５）また、負に増大しがちなペッツバール和を良好に保ち像面の平坦化を達成するためには、第１群の３枚の負の第１１，第１２，第１３レンズの材質の屈折率の平均値をＮＡ１とする。該第２群は像面側に凹面を向けたメニスカス状の負の第２１レンズ、負の第２２レンズ、正の第２３レンズ、そして両レンズ面が凹面の負の第２４レンズより成る。第２群の負の第２１，第２２，第２４レンズの材質の屈折率の平均値をＮＡ２とする。このとき、
１．６０ ＜ ＮＡ１ ‥‥‥（６ｃ）
１．７５ ＜ ＮＡ２ ＜ １．８９ ‥‥‥（７ｃ）
を満足することが好ましい。
6.0 <bFw / Fw <8.0 (1cc)
-3.0 <f2 / Fw <-2.2 (2cc)
30. 0 <f3 / Fw <50.0 (3cc)
0.40 <L / f1 <0.90 (4cc)
0.04 <d / f3 <0.07 (5cc)
(C5) Further, in order to maintain the Petzval sum that tends to increase negatively and achieve flattening of the image surface, the material of the three negative eleventh, twelfth, and thirteenth lenses in the first group is used. The average value of the refractive index is NA1. The second group includes a meniscus negative 21st lens having a concave surface directed toward the image surface side, a negative 22nd lens, a positive 23rd lens, and a negative 24th lens whose both lens surfaces are concave. The average value of the refractive indexes of the materials of the negative 21st, 22nd, and 24th lenses in the second group is NA2. At this time,
1.60 <NA1 (6c)
1.75 <NA2 <1.89 (7c)
Is preferably satisfied.
（ｃ６）半画角で４５°以上の超広角域を撮像可能良好な光学性能を満足する
ためのには上記条件式を満足することが望まれるが、更に良好な光学性能を満足するためには、
６．５＜ｂＦｗ／Ｆｗ＜７．５
−２．９＜ｆ２／Ｆｗ＜−２．５
３５．０＜ｆ３／Ｆｗ＜ ５０．０
０．６０＜Ｌ／ｆ１＜０．８０
０．０４５＜ｄ／ｆ３＜０．０６５
２．６２ ＜ ＮＡ１
１．７９ ＜ ＮＡ２ ＜ １．８９
なる条件式を満足するのが望ましい。
(C6) Capturing an ultra-wide angle region of 45 ° or more at a half angle of view In order to satisfy good optical performance, it is desirable to satisfy the above conditional expression, but in order to satisfy even better optical performance. Is
6.5 <bFw / Fw <7.5
-2.9 <f2 / Fw <-2.5
35.0 <f3 / Fw <50.0
0.60 <L / f1 <0.80
0.045 <d / f3 <0.065
2.62 <NA1
1.79 <NA2 <1.89
It is desirable to satisfy the following conditional expression.
（ｃ７）前記第４群は像面側に凸面を向けたメニスカス状の正の第４１レンズ、像面側に凹面を向けた負の第４２レンズと両レンズ面が凸面の正の第４３レンズとの接合レンズ４ａ、そして両レンズ面が凸面の正の第４４レンズより成っていることである。 (C7) The fourth group has a meniscus positive forty-first lens with a convex surface facing the image surface, a negative forty-second lens with a concave surface facing the image surface, and a positive forty-third lens with convex surfaces. And a cemented lens 4a, and both lens surfaces are composed of a convex positive 44th lens.
次に本発明の数値実施例を示す。数値実施例においてＲｉは物体側より順に第ｉ番目のレンズ面の曲率半径、Ｄｉは物体側より順に第ｉ番目のレンズ厚及び空気間隔、Ｎｉとνｉは各々物体側より順に第ｉ番目のレンズのガラスの屈折率とアッベ数である。又、数値実施例において最終の５つのレンズ面は光学フィルター、フェースプレート等を示すが、これらは必要に応じて省略し得る。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、Ｂ，Ｃ，Ｄ，Ｅを各々非球面係数としたとき、 Next, numerical examples of the present invention will be shown. In the 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. In the numerical examples, the last five lens surfaces indicate an optical filter, a face plate, etc., but these may be omitted if necessary. The aspheric 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 B, C, D, and E are the aspheric coefficients, respectively. ,
なる式で表している。又「ｅ−０Ｘ」は「×１０−Ｘ」を意味している。また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〜表３に示す。 It is expressed by the following formula. “E-0X” means “× 10 −X ”. Tables 1 to 3 show the relationship between the above-described conditional expressions and various numerical values in the numerical examples.
Ｌ１ 第１群
Ｌ１１ 第１１群
Ｌ１２ 第１２群
Ｌ２ 第２群
Ｌ３ 第３群
Ｌ４ 第４群
ＩＰ 像面
ＳＰ 絞り
ｄ ｄ線
ｇ ｇ線
ΔＳ サジタル像面
ΔＭ メリディオナル像面
L1 1st group L11 11th group L12 12th group L2 2nd group L3 3rd group L4 4th group IP image plane SP aperture d d line g g line ΔS sagittal image plane ΔM meridional image plane
Claims (14)
０．０６ ＜ ｄ／ｆ３ ＜ ０．２５
なる条件式を満足することを特徴とするリアフォーカス式のズームレンズ。 In order from the object side, there are four lens groups including a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. Move the group to the image plane side to perform zooming from the wide-angle end to the telephoto end, and correct the image plane variation caused by zooming or subject distance variation by moving part or all of the fourth group, A zoom lens in which a glass block is disposed between the fourth group and the image plane, and the third group includes a meniscus negative 31st lens having a concave surface facing the image plane side, a positive 32nd lens, When composed of a cemented lens 3a with a negative 33rd lens, the air distance between the 31st lens and the cemented lens 3a is d, and the focal length of the third group is f3.
0.06 <d / f3 <0.25
A rear focus zoom lens characterized by satisfying the following conditional expression:
１．７＜｜ｆ２｜／Ｆｗ＜３．６
なる条件式を満足することを特徴とするリアフォーカス式のズームレンズ。 In order from the object side, there are four lens groups including a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. Move the group to the image plane side to perform zooming from the wide-angle end to the telephoto end, and correct the image plane variation caused by zooming or subject distance variation by moving part or all of the fourth group, A zoom lens in which a glass block is disposed between the fourth group and the image plane, wherein the second group has a meniscus negative 21st lens having a concave surface facing the image plane side, a negative 22nd lens, When the positive 23rd lens and the negative 24th lens whose both lens surfaces are concave are formed, the focal length at the wide angle end is Fw, and the focal length of the second group is f2,
1.7 <| f2 | / Fw <3.6
A rear focus zoom lens characterized by satisfying the following conditional expression:
−５．０＜ｆ１／ｆ２＜−０．５
−５．０＜ｆ２／Ｆｗ＜−１．０
なる条件式を満足することを特徴とするリアフォーカス式のズームレンズ。 In order from the object side, there are four lens groups including a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. Move the group to the image plane side to perform zooming from the wide-angle end to the telephoto end, and correct the image plane variation caused by zooming or subject distance variation by moving part or all of the fourth group, A zoom lens in which a glass block is disposed between the fourth group and an image plane, wherein the first group includes two lens groups, an eleventh group having a negative refractive power and a twelfth group having a positive refractive power. The eleventh group includes at least two meniscus negative lenses having a concave surface facing the image surface side, the twelfth group includes a positive lens, a positive lens, or a cemented lens of a negative lens and a positive lens, and The second lens group consists of four lenses: a negative lens, a negative lens, a negative lens, and a positive lens. The fi, when set to Fw is a focal length of the entire system at the wide-angle end -5.0 <f1 / f2 <-0.5
−5.0 <f2 / Fw <−1.0
A rear focus zoom lens characterized by satisfying the following conditional expression:
２．５＜ ｆ３／ｆ４ ＜９
−０．５＜ｆ２ａ／ｆ２ｂ ＜１
−０．５＜ ｆＴ／ｆ１２３＜０
なる条件を満足することを特徴とする請求項４、５、６又は７のリアフォーカス式のズームレンズ。 The combined focal length of the 21st lens and the 22nd lens is f2a, the combined focal length of the 23rd lens and the 24th lens is f2b, the combined focal length of the first, second, and third groups is f123, and at the telephoto end. When the focal length of the entire system is fT, 2.5 <f3 / f4 <9
-0.5 <f2a / f2b <1
-0.5 <fT / f123 <0
The rear focus zoom lens according to claim 4, 5, 6, or 7, wherein the following condition is satisfied.
３０＜ｆ３／Ｆｗ＜６０
なる条件を満足することを特徴とするリアフォーカス式のズームレンズ。 In order from the object side, there are four lens groups including a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. Move the group to the image plane side to perform zooming from the wide-angle end to the telephoto end, and correct the image plane variation caused by zooming or subject distance variation by moving part or all of the fourth group, A zoom lens in which a glass block is disposed between the fourth group and the image plane, and the third group includes a meniscus negative 31st lens having a concave surface facing the image plane side, a positive 32nd lens, When the focal length of the third lens unit is f3 and the focal length of the entire system at the wide angle end is Fw, 30 <f3 / Fw <60
A rear-focus zoom lens that satisfies the following conditions:
０．２＜Ｌ／ｆ１＜１
０．０２＜ｄ／ｆ３＜０．１
なる条件を満足することを特徴とする請求項１０，１１又は１２のリアフォーカス式のズームレンズ。 The air distance between the eleventh group and the twelfth group is L, the focal lengths of the first group and the third group are f1 and f3, respectively, and the third group is a meniscus negative negative with the concave surface facing the image surface side. The lens includes a 31st lens, a cemented lens 3a composed of a positive 32nd lens and a negative 33rd lens. When d is an air distance between the 31st lens and the cemented lens 3a, 0.2 <L / f1 < 1
0.02 <d / f3 <0.1
The rear focus zoom lens according to claim 10, 11 or 12, wherein the following condition is satisfied.
A camera comprising the zoom lens according to claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007011820A JP4429325B2 (en) | 2007-01-22 | 2007-01-22 | Rear focus zoom lens |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007011820A JP4429325B2 (en) | 2007-01-22 | 2007-01-22 | Rear focus zoom lens |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10549898A Division JP3943704B2 (en) | 1998-03-31 | 1998-03-31 | Rear focus zoom lens |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2007128110A true JP2007128110A (en) | 2007-05-24 |
| JP4429325B2 JP4429325B2 (en) | 2010-03-10 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2007011820A Expired - Fee Related JP4429325B2 (en) | 2007-01-22 | 2007-01-22 | Rear focus zoom lens |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009037105A (en) * | 2007-08-03 | 2009-02-19 | Elmo Co Ltd | Zoom lens |
| US7589909B2 (en) | 2007-10-09 | 2009-09-15 | Fujinon Corporation | Rear-focusing type zoom lens and imaging apparatus |
| KR101844509B1 (en) * | 2010-10-27 | 2018-04-02 | 삼성전자주식회사 | Zoon lens and photographing apparatus |
| CN108318994A (en) * | 2018-01-10 | 2018-07-24 | 佛山华国光学器材有限公司 | A kind of low distortion camera lens |
| CN112099211A (en) * | 2020-09-27 | 2020-12-18 | 杭州海康威视数字技术股份有限公司 | Zoom optical system and image capturing apparatus |
-
2007
- 2007-01-22 JP JP2007011820A patent/JP4429325B2/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009037105A (en) * | 2007-08-03 | 2009-02-19 | Elmo Co Ltd | Zoom lens |
| US7589909B2 (en) | 2007-10-09 | 2009-09-15 | Fujinon Corporation | Rear-focusing type zoom lens and imaging apparatus |
| KR101844509B1 (en) * | 2010-10-27 | 2018-04-02 | 삼성전자주식회사 | Zoon lens and photographing apparatus |
| CN108318994A (en) * | 2018-01-10 | 2018-07-24 | 佛山华国光学器材有限公司 | A kind of low distortion camera lens |
| CN108318994B (en) * | 2018-01-10 | 2020-09-08 | 佛山华国光学器材有限公司 | Low-distortion lens |
| CN112099211A (en) * | 2020-09-27 | 2020-12-18 | 杭州海康威视数字技术股份有限公司 | Zoom optical system and image capturing apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| JP4429325B2 (en) | 2010-03-10 |
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