JP3019664B2 - Rear focus zoom lens - Google Patents

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【産業上の利用分野】本発明はリヤーフォーカス式のズ
ームレンズに関し、特に写真用カメラやビデオカメラ、
そして放送用カメラ等に用いられる広角端の撮影画角が
６５度以上の広画角を含み、しかも変倍比１０〜１３の
高変倍比のバックフォーカスの長いリヤーフォーカス式
のズームレンズに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear focus type zoom lens, and more particularly, to a photographic camera, a video camera,
The present invention relates to a rear focus type zoom lens having a wide angle of view of 65 degrees or more at the wide-angle end used for a broadcast camera, etc., and a high zoom ratio of 10 to 13 and a long back focus. It is.

【０００２】[0002]

【従来の技術】最近、３５ｍｍフィルム用の写真用カメ
ラやホームビデオカメラ等ではカメラ全体の小型軽量化
に伴い、それに用いる撮影用のズームレンズにも所定の
変倍比を有し、広画角でかつレンズ全長が短く、しかも
前玉レンズ径の小さなレンズ系全体が小型軽量であるこ
とが要望されている。2. Description of the Related Art In recent years, with the reduction in size and weight of photographic cameras and home video cameras for 35 mm film, zoom lenses used for photographing have a predetermined zoom ratio, and have a wide angle of view. It is demanded that the entire lens system having a short lens length and a small front lens diameter is small and lightweight.

【０００３】これらの要望を比較的良く満足させるズー
ムレンズとして、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リヤーフォーカス式のズームレ
ンズがある。As a zoom lens which satisfies these needs relatively well, there is a rear focus type zoom lens which performs focusing by moving a lens unit other than the first unit on the object side.

【０００４】一般にリヤー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前玉フォーカス
式の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り、又近接撮影、
特に極近接撮影が容易となり、更に比較的小型軽量のレ
ンズ群を移動させて行っているので、レンズ群の駆動力
が小さくてすみ、迅速な焦点合わせができる等の特長が
ある。In general, a rear focus type zoom lens has a smaller effective diameter of the first lens group than a front lens focus type zoom lens which moves and focuses the first lens group, so that the size of the entire lens system can be easily reduced. Become, close-up photography,
In particular, extremely close-up photography is facilitated, and the relatively small and lightweight lens group is moved, so that the driving force of the lens group can be small and quick focusing can be performed.

【０００５】このようなリヤーフォーカス式のズームレ
ンズとして、例えば特開昭６２−２４７３１６号公報や
特開昭６２−２４２１３号公報では、物体側より順に正
の屈折力の第１群、負の屈折力の第２群、正の屈折力の
第３群、そして正の屈折力の第４群の４つのレンズ群を
有し、第２群を移動させて変倍を行い、第４群を移動さ
せて変倍に伴う像面変動の補正とフォーカスを行ってい
る。As such a rear focus type zoom lens, for example, Japanese Patent Application Laid-Open Nos. 62-247316 and 62-24213 disclose a first group having a positive refractive power and a negative refractive power in order from the object side. It has four lens groups, a second group of power, a third group of positive refractive power, and a fourth group of positive refractive power. The second group is moved to perform zooming, and the fourth group is moved. In this way, correction and focusing of the image plane fluctuation due to zooming are performed.

【０００６】特開昭５８−１６０９１３号公報では、物
体側より順に正の屈折力の第１群、負の屈折力の第２
群、正の屈折力の第３群、そして正の屈折力の第４群の
４つのレンズ群を有し、第１群と第２群を移動させて変
倍を行い、変倍に伴う像面変動の補正を第４群を移動さ
せて行っている。そしてこれらのレンズ群のうちの１つ
又は２つ以上のレンズ群を移動させてフォーカスを行っ
ている。Japanese Patent Application Laid-Open No. 58-160913 discloses a first group of positive refractive power and a second group of negative refractive power in order from the object side.
It has four lens groups: a group, a third group having a positive refractive power, and a fourth group having a positive refractive power. The first group and the second group are moved to perform zooming, and an image accompanying the zooming is performed. The correction of the surface variation is performed by moving the fourth lens unit. Then, focusing is performed by moving one or more of these lens groups.

【０００７】又特開昭５７−１１１５０７号公報では、
ズーミング中、固定でフォーカスを行う正の屈折力の第
１レンズ群、負の屈折力の第２レンズ群、正の屈折力の
第３レンズ群を有し、これら第２レンズ群と第３レンズ
群がズーミング中、反対方向に動き、第３レンズ群には
２つの正レンズ群があり、それぞれが別々の動きをする
所謂、正、負、正、正の屈折力の４群構成のズームレン
ズを提案している。同公報では、アパーチャストップ
（開口絞り）を第３レンズ群内に位置決めしている。In Japanese Patent Application Laid-Open No. 57-111507,
A first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power for performing focusing during zooming; these second lens group and third lens group are provided. During zooming, the third lens group moves in opposite directions, and the third lens group includes two positive lens groups, each of which moves independently, a so-called four-group zoom lens having positive, negative, positive, and positive refractive powers. Has been proposed. In this publication, an aperture stop (aperture stop) is positioned in the third lens group.

【０００８】しかしながらこの構成では、第２レンズ群
と第３レンズ群が逆の方向に動く為、第２・３レンズ群
の間隔を広角端で広くあける必要があり、又絞りが第３
レンズ群内にある為、広角端における入射瞳位置が最も
像面側にあることになり、前玉径・全系の小型化には適
当でない。However, in this configuration, since the second lens unit and the third lens unit move in opposite directions, it is necessary to widen the distance between the second and third lens units at the wide-angle end, and the diaphragm is required to have the third lens unit.
Since it is in the lens group, the entrance pupil position at the wide-angle end is closest to the image plane, which is not suitable for downsizing the front lens diameter and the entire system.

【０００９】そして第１レンズ群でフォーカスを行って
いる為に、至近距離での周辺画角への光束を確保する
為、前玉径が大型化し、これを小型化の為にリヤーフォ
ーカス方式に適応しようとすると、最適な屈折力配置で
はなかったり、リヤーフォーカシングに伴うフォーカス
収差変動が充分に補正されていないといった問題があっ
た。Since the first lens group focuses, the diameter of the front lens is increased in order to secure a luminous flux to the peripheral angle of view at a close distance, and the rear focus method is used to reduce the size of the front lens. When trying to adapt, there is a problem that the refractive power arrangement is not optimal, and the fluctuation of the focus aberration due to the rear focusing is not sufficiently corrected.

【００１０】又、特開平３−２００１１３号公報でも同
様な構成で、物体側から順にズーミング中、固定の正の
第１レンズ群、変倍の為前後に移動する負の第２レンズ
群、第２レンズ群の動きに関連して移動する正の第３レ
ンズ群、変倍に伴う焦点位置の補正を一部又は全部を移
動させて行う正の第４レンズ群から成るズームレンズを
提案している。In Japanese Patent Application Laid-Open No. 3-200113, a similar configuration is adopted. During zooming in order from the object side, a fixed positive first lens group, a negative second lens group moving back and forth for zooming, A zoom lens comprising a positive third lens group that moves in association with the movement of the two lens groups, and a positive fourth lens group that partially or wholly moves the correction of the focal position accompanying zooming is proposed. I have.

【００１１】同公報によると、第２レンズ群の動きに関
連して移動する正の第３レンズ群の動きとは、第４レン
ズ群で行う像面移動補正量を軽減させる為に行うもの
で、補正機能の一部を第３レンズ群に分担させる為の動
きである。具体的には中間焦点距離から望遠端にかけて
像側から物体側に移動することが望ましいとしている。According to the publication, the movement of the positive third lens group, which moves in relation to the movement of the second lens group, is performed to reduce the amount of image plane movement correction performed by the fourth lens group. , A part of the correction function is assigned to the third lens group. Specifically, it is desirable to move from the image side to the object side from the intermediate focal length to the telephoto end.

【００１２】しかしながらこの構成では、第２レンズ群
と第３レンズ群が逆の方向に動く為、第２・３レンズ群
の間隔を広角側で広くあける必要があり、広角端におけ
る入射瞳位置が最も像面側にあることになり、前玉径・
全系の小型化が難しいという問題があった。However, in this configuration, since the second lens group and the third lens group move in opposite directions, it is necessary to widen the interval between the second and third lens groups on the wide-angle side, and the entrance pupil position at the wide-angle end becomes large. It will be closest to the image surface side,
There was a problem that miniaturization of the whole system was difficult.

【００１３】又、同様に特開平３−１５８８１３号公報
でも、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レンズ群より構成さ
れ、第２レンズ群と第３レンズ群を光軸に沿って移動さ
せて変倍を行い、開口絞りを第３レンズ群と一体で移動
させるズームレンズを開示している。Similarly, in Japanese Patent Application Laid-Open No. 3-158613, the first lens unit, the second negative lens unit, the third positive lens unit, and the fourth positive lens unit are arranged in this order from the object side. Discloses a zoom lens in which the second lens group and the third lens group are moved along the optical axis to perform zooming, and the aperture stop is moved integrally with the third lens group.

【００１４】同公報によると広角端から望遠端へのズー
ミングに伴い第２レンズ群と第３レンズ群の間隔は減少
している。又開口絞りを有する第３レンズ群が広角端で
最も像側に位置しており、最も前玉径が大きくなる広角
端もしくは広角端から多少ズームした位置で、絞りのあ
る第３レンズ群近傍が最も像側付近にあり入射瞳位置が
奥まってしまい前玉径の縮小に不利であり、又広角端で
の歪曲が大きく、これを除去した良好な性能での前玉径
の縮小化・全系の小型化を行うのが難しいという問題が
あった。According to the publication, the distance between the second lens group and the third lens group decreases with zooming from the wide-angle end to the telephoto end. The third lens group having an aperture stop is located closest to the image at the wide-angle end, and at the wide-angle end where the front lens diameter is the largest or at a position slightly zoomed from the wide-angle end. Near the image side, the entrance pupil position is deeper, which is disadvantageous for reduction of the front lens diameter. Also, distortion at the wide angle end is large, and the front lens diameter is reduced with good performance by removing this. There is a problem that it is difficult to reduce the size.

【００１５】又、本出願人は特開平３−２１５８１０号
公報において、物体側より順に正の屈折力の第１群、負
の屈折力の第２群、絞り、正の屈折力の第３群、そして
正の屈折力の第４群の４つのレンズ群を有し、広角端か
ら望遠端への変倍の際には、該第２群を像面側へ移動さ
せると共に該絞り、該第３群、そして第４群を何れも物
体側に凸状の軌跡を有するように互いに独立に移動さ
せ、合焦の際には該第４群を移動させて行ったリヤーフ
ォーカス式のズームレンズを提案している。The present applicant discloses in Japanese Patent Application Laid-Open No. 3-215810 a first group of positive refractive power, a second group of negative refractive power, a stop, and a third group of positive refractive power in order from the object side. And a fourth lens unit having a positive refractive power. In zooming from the wide-angle end to the telephoto end, the second unit is moved to the image plane side, and the stop, A rear-focusing type zoom lens which is moved independently of each other so that each of the third lens unit and the fourth lens unit has a locus convex toward the object side and moves the fourth lens unit for focusing. is suggesting.

【００１６】[0016]

【発明が解決しようとする課題】一般にズームレンズに
おいてリヤーフォーカス方式を採用すると、前述の如く
レンズ系全体が小型化され又迅速なるフォーカスが可能
となり、更に近接撮影が容易となる等の特長が得られ
る。In general, when a rear focus system is employed in a zoom lens, the entire lens system can be reduced in size as described above, quick focusing can be achieved, and close-up photographing can be easily performed. Can be

【００１７】しかしながら半面、フォーカスの際の収差
変動が大きくなり、無限遠物体から近距離物体に至る物
体距離全般にわたりレンズ系全体の小型化を図りつつ高
い光学性能を得るのが大変難しくなってくるという問題
点が生じてくる。On the other hand, however, aberration fluctuations during focusing become large, and it becomes very difficult to obtain high optical performance while reducing the size of the entire lens system over the entire object distance from an object at infinity to an object at a short distance. The problem arises.

【００１８】現在、民生用のビデオカメラには主に単板
式が用いられており、又業務用のビデオカメラには主に
多板式が用いられている。At present, single-panel video cameras are mainly used for consumer video cameras, and multi-panel video cameras are mainly used for professional video cameras.

【００１９】多板式のビデオカメラには色分解系として
色分解プリズムが用いられている。この為、多板式のビ
デオカメラ用のズームレンズには色分解プリズムの光路
長を十分確保するだけの長いバックフォーカスを有して
いることが必要となっている。しかしながら単にバック
フォーカスを長くしようとするとレンズ系全体が大型化
してくるという問題点が生じてくる。In a multi-plate video camera, a color separation prism is used as a color separation system. For this reason, it is necessary for a zoom lens for a multi-plate video camera to have a long back focus enough to secure a sufficient optical path length of the color separation prism. However, simply increasing the back focus causes a problem that the entire lens system becomes large.

【００２０】本発明はリヤーフォーカス方式を採用しつ
つ、大口径比及び高変倍比を図る際、レンズ系全体の小
型化を図りつつ、広角端から望遠端に至る物体距離全般
にわたり、良好なる光学性能を有し、しかもバックフォ
ーカスの長い簡易な構成のリヤーフォーカス式のズーム
レンズの提供を目的とする。In the present invention, when a large aperture ratio and a high zoom ratio are to be achieved while adopting the rear focus method, the entire lens system is improved over the entire object distance from the wide-angle end to the telephoto end, while miniaturizing the entire lens system. It is an object of the present invention to provide a rear focus zoom lens having an optical performance and a simple configuration having a long back focus.

【００２１】[0021]

【課題を解決するための手段】本発明のリヤーフォーカ
ス式のズームレンズは、物体側より順に正の屈折力の第
１群、負の屈折力の第２群、絞りを有する正の屈折力の
第３群、そして正の屈折力の第４群の４つのレンズ群を
有し、広角端から望遠端への変倍の際には、該第２群を
像面側へ移動させると共に該絞りと該第３群を一体的に
物体側に凸状の軌跡を有するように移動させ、かつ第４
群を物体側に凸状の軌跡を有するように移動させ、合焦
の際には該第４群を移動させて行い、第ｉ群の焦点距離
をＦｉとしたとき、 ２．５＜Ｆ３／Ｆ４ ‥‥‥（１） なる条件を満足することを特徴としている。A rear focus type zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a positive refractive power having a stop. The zoom lens has four lens units, a third unit and a fourth unit having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the second unit is moved to the image plane side and the stop is moved. And the third group are integrally moved to have a locus convex toward the object side, and
When the group is moved so as to have a locus convex toward the object side, focusing is performed by moving the fourth group, and when the focal length of the i-th group is Fi, 2.5 <F3 / F4 ‥‥‥ (1) is satisfied.

【００２２】[0022]

【実施例】図１〜図５は本発明の後述する数値実施例１
〜５の広角端のレンズ断面図、図６〜図１５は本発明の
後述する数値実施例１〜５の諸収差図である。1 to 5 show a first numerical embodiment of the present invention, which will be described later.
6 to 15 are various aberration diagrams of Numerical Examples 1 to 5 described later of the present invention.

【００２３】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群の前方に配置している。Ｇは色分解プリズム、フ
ェースプレート、そしてフィルター等のガラスブロッ
ク、ＩＰは像面である。In the figure, L1 is a first lens unit having a positive refractive power, L2 is a second lens unit having a negative refractive power, L3 is a third lens unit having a positive refractive power, and L4 is a positive lens.
Denotes a fourth group having a positive refractive power. SP is an aperture stop,
It is arranged in front of the third group. G is a glass block such as a color separation prism, a face plate, and a filter, and IP is an image plane.

【００２４】本実施例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群を像面側へ単調に移動させる
と共に、絞りＳＰと第３群とを一体的に物体側に凸状の
軌跡を有するように移動させ、かつ第４群を物体側に凸
状の軌跡を有するように互いに独立に移動させている。In this embodiment, when zooming from the wide-angle end to the telephoto end, the second unit is monotonously moved to the image plane side as indicated by an arrow, and the stop SP and the third unit are integrally convex to the object side. The fourth group is moved independently so as to have a locus, and the fourth group is moved independently so as to have a locus convex toward the object side.

【００２５】本実施例ではこのようなズームタイプを採
用することにより、所定のバックフォーカスを確保しつ
つ広角端において撮影画角７０度程度と広画角化を容易
にすると共に全変倍範囲にわたり良好なる光学性能を得
ている。又第４群を光軸上移動させてフォーカスを行う
リヤーフォーカス式を採用している。In this embodiment, by adopting such a zoom type, it is possible to easily obtain a wide angle of view of about 70 degrees at the wide angle end while securing a predetermined back focus, and to cover the entire zoom range. Good optical performance is obtained. In addition, a rear focus type in which the fourth unit is moved on the optical axis to perform focusing is adopted.

【００２６】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
群は変倍及びフォーカスの際固定である。A solid line curve 4a and a dotted line curve 4b of the fourth lens group shown in FIG. 4 are images when zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and an object at a short distance, respectively. The movement locus for correcting the surface fluctuation is shown. The first
The group is fixed during zooming and focusing.

【００２７】本実施例においては、第４群を移動させて
変倍を行うと共に第４群を移動させてフォーカスを行う
ようにしている。In the present embodiment, zooming is performed by moving the fourth lens unit, and focusing is performed by moving the fourth lens unit.

【００２８】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 particular, as shown by the curves 4a and 4b in the drawing, the zoom lens is moved so as to have a convex locus toward the object side when zooming from the wide-angle end to the telephoto end. As a result, the third group and the fourth group
By effectively utilizing the space with the group, the overall length of the lens has been effectively reduced.

【００２９】本実施例において、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群を前方へ繰り返すこ
とにより行っている。In this embodiment, for example, when focusing from an object at infinity to an object at a short distance at the telephoto end,
This is performed by repeating the fourth group forward as indicated by the straight line 4c in FIG.

【００３０】このように本実施例では第４群を用いてフ
ォーカスを行うことにより、第１群を移動させてフォー
カスを行う、所謂前玉フォーカス方式に比べて広角側で
至近物体撮影時における画面周辺での光束の確保を容易
にして前玉レンズ群（第１群）の有効径の縮小化を図っ
ている。As described above, in the present embodiment, focusing is performed by using the fourth lens group, so that the first lens group is moved to perform focusing. The effective diameter of the front lens group (first group) is reduced by making it easy to secure a light beam in the periphery.

【００３１】そして開口絞りＳＰを第２群と第３群の間
に配置し、変倍の際、前述の如く第３群と一体的に移動
させることにより、変倍に伴う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
第１群（前玉レンズ群）のレンズ有効径の縮小化を容易
に達成している。By disposing the aperture stop SP between the second and third lens units and moving the lens unit integrally with the third lens unit during zooming as described above, aberration variations due to zooming can be reduced. By shortening the distance between the lens units in front of the aperture stop, it is easy to reduce the effective lens diameter of the first unit (front lens unit).

【００３２】又、第３群と第４群の屈折力を条件式
（１）を満足させるようにして、これによりレンズ系全
体の小型化を図りつつ所定のバックフォーカスを確保
し、かつ変倍に伴う収差変動の補正を容易にしている。Further, the refractive powers of the third and fourth units are set so as to satisfy the conditional expression (1), whereby a predetermined back focus is ensured while miniaturizing the whole lens system, and zooming is performed. This makes it easier to correct aberration fluctuations caused by the above.

【００３３】条件式（１）は第３群と第４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を十分長くして良好な光学性
能を維持する為のものである。条件式（１）の下限値を
越えて第３群の焦点距離が短くなると変倍に伴う、或い
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。又十分なバックフォーカスの確保が困難となった
り、変倍及びフォーカシングに伴う第４群の移動量が大
きくなり、変倍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点が生じてくるので良くない。Conditional expression (1) relates to the ratio of the focal length of the third lens unit to the focal length of the fourth lens unit. To achieve compactness after the stop and sufficiently long back focus to maintain good optical performance. belongs to. If the focal length of the third lens unit becomes short beyond the lower limit value of conditional expression (1), it becomes difficult to correct a change in spherical aberration due to zooming or during focusing. In addition, it is difficult to secure a sufficient back focus, and the amount of movement of the fourth lens unit during zooming and focusing increases, causing problems such as a large variation in aberrations during zooming and focusing. Absent.

【００３４】尚、本発明において更にレンズ系全体の小
型化を図りつつ画面全体にわたり高い光学性能を確保す
るには、次の諸条件のうち少なくとも１つを満足するの
が良い。In the present invention, in order to secure high optical performance over the entire screen while further reducing the size of the entire lens system, it is preferable to satisfy at least one of the following conditions.

【００３５】（１−１）広角端における全系の焦点距離
をＦｗとしたとき −０．７０＜Ｆｗ／Ｆ２＜−０．４ ‥‥‥（２） なる条件を満足することである。(1-1) Assuming that the focal length of the entire system at the wide-angle end is Fw, the condition of -0.70 <Fw / F2 <-0.4 (2) is satisfied.

【００３６】条件式（２）は広角端における全系の焦点
距離と第２群の焦点距離の比に関するものである。条件
式（２）の上限値を越えて第２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
群の焦点距離が長くなると、変倍に伴う第２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点が生じて
くる。Conditional expression (2) relates to the ratio of the focal length of the entire system at the wide-angle end to the focal length of the second lens unit. If the focal length of the second lens unit becomes shorter than the upper limit of conditional expression (2), the Petzval sum increases in the under direction, and it becomes difficult to correct aberrations such as image plane tilt. Conversely, the second
When the focal length of the lens group becomes longer, the amount of movement of the second lens group due to zooming increases, causing a problem that the front lens diameter becomes too large.

【００３７】（１−２）第３群より射出する軸上光束の
射出光を略アフォーカル若しくは弱発散光にすることが
良い。これによればズーミング時又はフォーカシング時
の収差変動を極力抑えつつ、バックフォーカスや射出瞳
を効果的に長くすることができる。(1-2) It is preferable that the emitted light of the on-axis light flux emitted from the third lens unit be substantially afocal or weakly divergent. According to this, the back focus and the exit pupil can be effectively lengthened while minimizing aberration fluctuations during zooming or focusing.

【００３８】（１−３）本発明に係るズームタイプにお
いて、例えば絞りが第３群と第４群との間にあると入射
瞳が第１群から深い所（奥まった位置）となる為、第１
群への軸外光束の入射高は広角端寄りの中間ズーム位置
で最も高くなる。(1-3) In the zoom type according to the present invention, for example, if the stop is between the third and fourth units, the entrance pupil is deeper (recessed position) from the first unit. First
The incident height of the off-axis light beam to the group becomes highest at the intermediate zoom position near the wide angle end.

【００３９】そこで本発明では絞りを第３群の物体側
に、又は第３群中に配置させて広角端から望遠端への変
倍に伴い第３群と一体的に物体側に凸状の軌跡を有する
ように移動させて、入射瞳が第１群から近い位置になる
ようにして入射高の最も高いズーム位置が広角端近傍と
なるように設定して、これにより第１群の有効径を効率
的に小さくしている。Therefore, in the present invention, the stop is arranged on the object side of the third lens unit or in the third lens unit so that the stop is formed integrally with the third lens unit as the zoom ratio changes from the wide-angle end to the telephoto end. The zoom lens is moved so as to have a locus so that the entrance pupil is located closer to the first lens group, and the zoom position having the highest entrance height is set near the wide-angle end. Is effectively smaller.

【００４０】尚、本発明においては絞りと第３群は物体
側に凸状の軌跡で略完全往復させて、前玉径の小型化及
び広画角化を容易に達成している。In the present invention, the aperture stop and the third lens unit reciprocate almost completely along a locus convex toward the object side, so that the diameter of the front lens can be easily reduced and the angle of view can be easily widened.

【００４１】次に本発明のズームレンズのレンズ構成の
前述以外の特徴について説明する。Next, other features of the lens configuration of the zoom lens according to the present invention will be described.

【００４２】（１−４）全系を小型化するときは、以下
の条件を満たすのが好ましい。(1-4) When miniaturizing the whole system, it is preferable to satisfy the following conditions.

【００４３】 ３．５＜Ｂｆｗ／Ｆｗ＜６．０ ‥‥‥（３） ここでＢｆｗは広角端での物体距離無限遠時のバックフ
ォーカス（ガラスブロック、フィルター等実施例中の
“Ｇ”を除く）である。3.5 <Bfw / Fw <6.0 (3) Here, Bfw is the back focus at the infinity of the object distance at the wide-angle end (“G” in the embodiment such as a glass block or a filter). Excluding).

【００４４】この（３）式は全系を効果的に小型化する
のに必要な式であり、下限値を越えるとフィルターや色
分解プリズム等のブロックを入れるのが無理になるばか
りでなく、射出瞳が短めとなり、例えば本発明をビデオ
カメラ等に適用したときは撮像素子への結像がテレセン
トリック系からズレてくる。又上限値を越えると大型化
してくる。Equation (3) is an equation necessary for effectively reducing the size of the entire system. If the value exceeds the lower limit, it is not only impossible to insert a block such as a filter or a color separation prism, but also The exit pupil becomes shorter, and, for example, when the present invention is applied to a video camera or the like, an image formed on an image sensor is shifted from a telecentric system. If the upper limit is exceeded, the size will increase.

【００４５】（１−５）前玉径を小型にするには以下の
式を満たすのが好ましい。(1-5) In order to reduce the diameter of the front lens, it is preferable to satisfy the following expression.

【００４６】 ６．０＜Ｆ１／Ｆｗ＜１５．０ ‥‥‥（４） この式は、第２群に対する物点、即ち倍率に関わる式で
ある。全系を小さく設定するには、第２群がズーミング
に際して等倍を挟んでいるのが好ましい。等倍を挟むと
第４群のズーミングの軌跡は略往復になり、最も効果的
なスペース効率で高変倍が可能となる。6.0 <F1 / Fw <15.0 ‥‥‥ (4) This equation is an equation relating to the object point for the second group, that is, the magnification. In order to set the entire system to be small, it is preferable that the second lens unit be placed at the same magnification during zooming. With the same magnification, the locus of zooming of the fourth lens unit is substantially reciprocating, and high zooming is possible with the most effective space efficiency.

【００４７】具体的にはこの（４）式の上限を越えると
第２群に対する物点が遠くなり、第２群の結像倍率が低
くなり、効果的な小型化が難しくなる。More specifically, if the value exceeds the upper limit of the expression (4), the object point for the second lens unit becomes farther, the imaging magnification of the second lens unit becomes lower, and it is difficult to effectively reduce the size.

【００４８】更に第１群と第２群の間隔が大きくなり、
小型化の達成が難しくなる。又下限値を越えると、第２
群の倍率が大きくなり、高倍化の達成が難しくなってく
る。Further, the distance between the first group and the second group is increased,
It is difficult to achieve miniaturization. If the lower limit is exceeded, the second
The magnification of the group increases, making it difficult to achieve high magnification.

【００４９】（１−６）第１群と第２群の主点間隔ｅ１
を広角端でいかに小さくできるかは、広角化に際して重
要な点の１つである。その為には第１群の形状は具体的
には以下のような構成が好ましい。(1-6) Principal point distance e1 between first and second lens units
Is one of the important points in widening the angle of view. For this purpose, the first group preferably has the following configuration.

【００５０】第１群の物体側より順に物体側に凸面を有
するメニスカス状の負レンズＬ１１、空気間隔を空けて
物体側に凸面を有する正レンズＬ１２、更に物体側に凸
面を有する正レンズＬ１３で構成され、前記負レンズＬ
１１，正レンズＬ１２で構成される空気レンズは負の屈
折力を有することである。The first lens unit includes, in order from the object side, a negative meniscus lens L11 having a convex surface on the object side, a positive lens L12 having a convex surface on the object side with an air gap, and a positive lens L13 having a convex surface on the object side. The negative lens L
11. The air lens constituted by the positive lens L12 has a negative refractive power.

【００５１】このような構成にすることにより、第１群
の像側主点が第２群寄りに設定され、広角端における第
１群と第２群の主点間隔ｅ１が短く取れ、広角化には有
効である。With this configuration, the image-side principal point of the first lens group is set closer to the second lens group, and the distance e1 between the principal points of the first lens group and the second lens group at the wide-angle end can be shortened. Is effective.

【００５２】（１−７）第２群においても主点間隔ｅ１
を広角端で短くする為に第２群の物体側主点を物体側に
設定するような構成にすることが広角化には望ましい。(1-7) Principal point interval e1 also in the second lens unit
It is desirable to widen the angle that the second group has the object-side principal point set to the object side in order to shorten the distance at the wide-angle end.

【００５３】具体的には、第２群の物体側より順に、物
体側に凸面を有する負メニスカスレンズＬ２１、両凹の
負レンズＬ２１、空気間隔を挟んで正レンズＬ２３の順
に配置することである。この空気間隔によって第２群の
物体側主点が第１群寄りになり、広角側における主点間
隔ｅ１を短く取りやすくなり広角化に有効である。Specifically, in order from the object side in the second group, a negative meniscus lens L21 having a convex surface on the object side, a biconcave negative lens L21, and a positive lens L23 with an air gap therebetween are arranged in this order. . Due to this air gap, the object-side principal point of the second group is closer to the first group, and the principal point interval e1 on the wide-angle side can be easily shortened, which is effective for widening the angle.

【００５４】（１−８）絞りと第３群の移動量が大きめ
になると、特にズーミングの中間領域で球面収差のズー
ム変動が大きくなり、球面収差が補正過剰となりがちに
なる。これを除去するには第３群内に少なくとも１面の
非球面を導入するのが好ましい。具体的な非球面の形状
はレンズ周辺に向かうに従い、正の屈折力が弱くなる
か、負の屈折力が強くなる構成のものが好ましい。(1-8) If the amount of movement between the diaphragm and the third lens unit is relatively large, the zoom fluctuation of spherical aberration becomes large, especially in the middle area of zooming, and spherical aberration tends to be overcorrected. In order to eliminate this, it is preferable to introduce at least one aspheric surface into the third lens unit. The specific shape of the aspherical surface is preferably such that the positive refractive power becomes weaker or the negative refractive power becomes stronger toward the periphery of the lens.

【００５５】又、第４群の少なくとも１つのレンズ面に
非球面を施せばコマ収差を良好に補正することができる
ので好ましい。Further, it is preferable that at least one lens surface of the fourth group has an aspherical surface, because coma aberration can be satisfactorily corrected.

【００５６】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。Next, numerical examples of the present invention will be described. 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 from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass.

【００５７】数値実施例において最終の３つのレンズ面
は色分解プリズムやフェースプレートやフィルター等の
ガラスブロックである。又前述の各条件式と数値実施例
における諸数値との関係を表−１に示す。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、Ｋ，Ａ，Ｂ，Ｃ，Ｄ，Ｅ
を各々非球面係数としたとき、In the numerical examples, the last three lens surfaces are glass blocks such as a color separation prism, a face plate, and a filter. Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples. The aspherical shape has an X axis in the optical axis direction, an H axis in a direction perpendicular to the optical axis, a positive traveling direction of light, and R represents a paraxial radius of curvature, K, A, B, C, D, and E.
Are each aspherical coefficients,

【００５８】[0058]

【数１】 なる式で表している。(Equation 1) It is represented by the following expression.

【００５９】〈数値実施例１〉 F= 1 〜 12.65 Fno=1:1.6 〜 1.9 2ω= 66.2°〜 5.9 ° R 1= 35.931 D 1= 0.391 N 1=1.80518 ν 1= 25.4 R 2= 8.393 D 2= 0.342 R 3= 12.050 D 3= 1.239 N 2=1.69680 ν 2= 55.5 R 4= -36.035 D 4= 0.043 R 5= 6.370 D 5= 1.043 N 3=1.69680 ν 3= 55.5 R 6= 58.643 D 6=可変 R 7= 9.634 D 7= 0.173 N 4=1.88300 ν 4= 40.8 R 8= 1.857 D 8= 0.844 R 9= -3.185 D 9= 0.152 N 5=1.69680 ν 5= 55.5 R10= 3.140 D10= 0.217 R11= 3.696 D11= 0.500 N 6=1.84666 ν 6= 23.8 R12= -21.979 D12=可変 R13=（絞り） D13= 0.326 R14= -31.104 D14= 0.152 N 7=1.60311 ν 7= 60.7 R15= 4.653 D15= 0.264 R16= -9.342 D16= 0.434 N 8=1.60342 ν 8= 38.0 R17= -4.597 D17= 0.652 R18= 4.592 D18= 0.239 N 9=1.60342 ν 9= 38.0 R19= -2.721 D19= 0.195 N10=1.78590 ν10= 44.2 R20= -51.472 D20=可変 R21= 47.709 D21= 0.652 N11=1.51633 ν11= 64.2 R22= -4.925 D22= 0.032 R23= 11.157 D23= 0.195 N12=1.80518 ν12= 25.4 R24= 2.984 D24= 1.130 N13=1.48749 ν13= 70.2 R25= -23.396 D25= 0.032 R26= 5.008 D26= 0.739 N14=1.48749 ν14= 70.2 R27= -15.870 D27= 0.869 R28= ∞ D28= 0.543 N15=1.51633 ν15= 64.2 R29= ∞ D29= 4.347 N16=1.60342 ν16= 38.0 R30= ∞<Numerical Example 1> F = 1 to 12.65 Fno = 1: 1.6 to 1.92 ω = 66.2 ° to 5.9 ° R 1 = 35.931 D 1 = 0.391 N 1 = 1.80518 ν 1 = 25.4 R 2 = 8.393 D 2 = 0.342 R 3 = 12.050 D 3 = 1.239 N 2 = 1.69680 ν 2 = 55.5 R 4 = -36.035 D 4 = 0.043 R 5 = 6.370 D 5 = 1.043 N 3 = 1.69680 ν 3 = 55.5 R 6 = 58.643 D 6 = Variable R 7 = 9.634 D 7 = 0.173 N 4 = 1.88300 ν 4 = 40.8 R 8 = 1.857 D 8 = 0.844 R 9 = -3.185 D 9 = 0.152 N 5 = 1.69680 ν 5 = 55.5 R10 = 3.140 D10 = 0.217 R11 = 3.696 D11 = 0.500 N 6 = 1.84666 ν 6 = 23.8 R12 = -21.979 D12 = Variable R13 = (Aperture) D13 = 0.326 R14 = -31.104 D14 = 0.152 N 7 = 1.60311 ν 7 = 60.7 R15 = 4.653 D15 = 0.264 R16 = -9.342 D16 = 0.434 N 8 = 1.60342 ν 8 = 38.0 R17 = -4.597 D17 = 0.652 R18 = 4.592 D18 = 0.239 N 9 = 1.60342 ν 9 = 38.0 R19 = -2.721 D19 = 0.195 N10 = 1.78590 ν10 = 44.2 R20 =- 51.472 D20 = variable R21 = 47.709 D21 = 0.652 N11 = 1.51633 ν11 = 64.2 R22 = -4.925 D22 = 0.032 R23 = 11.157 D23 = 0.195 N12 = 1.80518 ν12 = 25.4 R24 = 2.984 D24 = 1.130 N13 = 1.48749 ν13 = 70.2 R25 =- 23.396 D25 = 0.032 R26 = 5.008 D26 = 0.739 N14 = 1 .48749 ν14 = 70.2 R27 = -15.870 D27 = 0.869 R28 = ∞ D28 = 0.543 N15 = 1.51633 ν15 = 64.2 R29 = ∞ D29 = 4.347 N16 = 1.60342 ν16 = 38.0 R30 =.

【００６０】[0060]

【表１】 〈数値実施例２〉 F= 1 〜 12.65 Fno=1:1.8 〜 1.9 2ω= 66.2°〜 5.9 ° R 1= 35.975 D 1= 0.391 N 1=1.80518 ν 1= 25.4 R 2= 8.396 D 2= 0.272 R 3= 11.644 D 3= 1.130 N 2=1.69680 ν 2= 55.5 R 4= -37.605 D 4= 0.043 R 5= 6.400 D 5= 1.195 N 3=1.69680 ν 3= 55.5 R 6= 60.254 D 6=可変 R 7= 8.615 D 7= 0.173 N 4=1.88300 ν 4= 40.8 R 8= 1.785 D 8= 0.823 R 9= -3.019 D 9= 0.152 N 5=1.69680 ν 5= 55.5 R10= 3.112 D10= 0.217 R11= 3.676 D11= 0.500 N 6=1.84666 ν 6= 23.8 R12= -16.603 D12=可変 R13=（絞り） D13= 1.413 R14= 5.119 D14= 1.043 N 7=1.60342 ν 7= 38.0 R15= -3.506 D15= 0.195 N 8=1.88300 ν 8= 40.8 R16= -46.563 D16=可変 R17= 58.011 D17= 0.434 N 9=1.51633 ν 9= 64.2 R18= -5.449 D18= 0.032 R19= 7.785 D19= 0.195 N10=1.80518 ν10= 25.4 R20= 2.794 D20= 0.869 N11=1.48749 ν11= 70.2 R21= -14.358 D21= 0.032 R22= 3.399 D22= 0.434 N12=1.48749 ν12= 70.2 R23= 23.023 D23= 0.869 R24= ∞ D24= 0.543 N13=1.51633 ν13= 64.2 R25= ∞ D25= 3.260 N14=1.60342 ν14= 38.0 R26= ∞[Table 1] <Numerical Example 2> F = 1 to 12.65 Fno = 1: 1.8 to 1.9 2ω = 66.2 ° to 5.9 ° R 1 = 35.975 D 1 = 0.391 N 1 = 1.80518 ν 1 = 25.4 R 2 = 8.396 D 2 = 0.272 R 3 = 11.644 D 3 = 1.130 N 2 = 1.69680 ν 2 = 55.5 R 4 = -37.605 D 4 = 0.043 R 5 = 6.400 D 5 = 1.195 N 3 = 1.69680 ν 3 = 55.5 R 6 = 60.254 D 6 = Variable R 7 = 8.615 D 7 = 0.173 N 4 = 1.88300 ν 4 = 40.8 R 8 = 1.785 D 8 = 0.823 R 9 = -3.019 D 9 = 0.152 N 5 = 1.69680 ν 5 = 55.5 R10 = 3.112 D10 = 0.217 R11 = 3.676 D11 = 0.500 N 6 = 1.84666 ν 6 = 23.8 R12 = -16.603 D12 = Variable R13 = (Aperture) D13 = 1.413 R14 = 5.119 D14 = 1.043 N 7 = 1.60342 ν 7 = 38.0 R15 = -3.506 D15 = 0.195 N 8 = 1.88300 ν 8 = 40.8 R16 = -46.563 D16 = variable R17 = 58.011 D17 = 0.434 N 9 = 1.51633 ν 9 = 64.2 R18 = -5.449 D18 = 0.032 R19 = 7.785 D19 = 0.195 N10 = 1.80518 ν10 = 25.4 R20 = 2.794 D20 = 0.869 N11 = 1.48749 ν11 = 70.2 R21 = -14.358 D21 = 0.032 R22 = 3.399 D22 = 0.434 N12 = 1.48749 ν12 = 70.2 R23 = 23.023 D23 = 0.869 R24 = ∞ D24 = 0.543 N13 = 1.51633 ν13 = 64.2 R25 = ∞ D25 = 3.260 N14 = 1.60342 ν14 = 38.0 R26 = ∞

【００６１】[0061]

【表２】 非球面係数 Ｒ１４面 Ｋ＝ 2.597 × 10^-2 Ａ＝ -9.137 × 10^-4 Ｂ＝ 1.986 × 10^-4 Ｃ＝ -1.129 × 10^-4 Ｄ＝ -1.168 × 10^-5 〈数値実施例３〉 F= 1 〜 12.65 Fno=1:1.8 〜 1.9 2ω= 66.2°〜 5.9 ° R 1= 36.928 D 1= 0.391 N 1=1.80518 ν 1= 25.4 R 2= 8.368 D 2= 0.312 R 3= 11.877 D 3= 1.130 N 2=1.69680 ν 2= 55.5 R 4= -36.615 D 4= 0.043 R 5= 6.411 D 5= 1.195 N 3=1.69680 ν 3= 55.5 R 6= 66.685 D 6=可変 R 7= 9.469 D 7= 0.173 N 4=1.88300 ν 4= 40.8 R 8= 1.788 D 8= 0.820 R 9= -3.019 D 9= 0.152 N 5=1.69680 ν 5= 55.5 R10= 3.123 D10= 0.217 R11= 3.695 D11= 0.500 N 6=1.84666 ν 6= 23.8 R12= -14.962 D12=可変 R13=（絞り） D13= 1.413 R14= 5.247 D14= 0.652 N 7=1.60342 ν 7= 38.0 R15= 17.260 D15=可変 R16= -13.719 D16= 0.434 N 8=1.51633 ν 8= 64.2 R17= -5.243 D17= 0.032 R18= 7.556 D18= 0.195 N 9=1.80518 ν 9= 25.4 R19= 2.779 D19= 0.869 N10=1.48749 ν10= 70.2 R20= -23.427 D20= 0.032 R21= 3.644 D21= 0.434 N11=1.48749 ν11= 70.2 R22= -16.329 D22= 0.869 R23= ∞ D23= 0.543 N12=1.51633 ν12= 64.2 R24= ∞ D24= 3.260 N13=1.60342 ν13= 38.0 R25= ∞[Table 2] Aspherical surface coefficient R14 surface K = 2.597 × 10 ^-2 A = -9.137 × 10 ^-4 B = 1.986 × 10 ^-4 C = -1.129 × 10 ^-4 D = -1.168 × 10 ^-5 <Numerical example 3> F = 1 to 12.65 Fno = 1: 1.8 to 1.9 2ω = 66.2 ° to 5.9 ° R 1 = 36.928 D 1 = 0.391 N 1 = 1.80518 ν 1 = 25.4 R 2 = 8.368 D 2 = 0.312 R 3 = 11.877 D 3 = 1.130 N 2 = 1.69680 ν 2 = 55.5 R 4 = -36.615 D 4 = 0.043 R 5 = 6.411 D 5 = 1.195 N 3 = 1.69680 ν 3 = 55.5 R 6 = 66.685 D 6 = Variable R 7 = 9.469 D 7 = 0.173 N 4 = 1.88300 ν 4 = 40.8 R 8 = 1.788 D 8 = 0.820 R 9 = -3.019 D 9 = 0.152 N 5 = 1.69680 ν 5 = 55.5 R10 = 3.123 D10 = 0.217 R11 = 3.695 D11 = 0.500 N 6 = 1.84666 ν 6 = 23.8 R12 = -14.962 D12 = Variable R13 = (Aperture) D13 = 1.413 R14 = 5.247 D14 = 0.652 N 7 = 1.60342 ν 7 = 38.0 R15 = 17.260 D15 = Variable R16 = -13.719 D16 = 0.434 N 8 = 1.51633 ν 8 = 64.2 R17 = -5.243 D17 = 0.032 R18 = 7.556 D18 = 0.195 N 9 = 1.80518 ν 9 = 25.4 R19 = 2.779 D19 = 0.869 N10 = 1.48749 ν10 = 70.2 R20 = -23.427 D20 = 0.032 R21 = 3.644 D21 = 0.434 N11 = 1.48749 ν11 = 70.2 R22 = -16.329 D22 = 0.869 R23 = ∞ D23 = 0.543 N12 = 1.51633 ν12 = 64.2 R24 = ∞ D24 = 3.260 N13 = 1.60342 ν13 = 38.0 R25 = ∞

【００６２】[0062]

【表３】 非球面係数 Ｒ１４面 Ｋ＝ -2.612 × 10^-1 Ａ＝ -2.388 × 10^-3 Ｂ＝ 2.364 × 10^-4 Ｃ＝ -6.451 × 10^-5 Ｄ＝ -3.051 × 10^-5 〈数値実施例４〉 F= 1 〜 12.65 Fno=1:1.8 〜 1.9 2ω= 66.2°〜 5.9 ° R 1= 25.907 D 1= 0.391 N 1=1.84666 ν 1= 23.8 R 2= 8.416 D 2= 0.312 R 3= 12.008 D 3= 1.130 N 2=1.69680 ν 2= 55.5 R 4= -45.235 D 4= 0.043 R 5= 6.531 D 5= 1.195 N 3=1.69680 ν 3= 55.5 R 6= 73.064 D 6=可変 R 7= 8.118 D 7= 0.173 N 4=1.88300 ν 4= 40.8 R 8= 1.730 D 8= 0.861 R 9= -2.748 D 9= 0.152 N 5=1.69680 ν 5= 55.5 R10= 3.014 D10= 0.217 R11= 3.614 D11= 0.434 N 6=1.84666 ν 6= 23.8 R12= -11.227 D12=可変 R13=（絞り） D13= 1.413 R14= 5.282 D14= 0.434 N 7=1.60311 ν 7= 60.7 R15= 15.536 D15=可変 R16= -5.179 D16= 0.434 N 8=1.51742 ν 8= 52.4 R17= -4.751 D17= 0.032 R18= 6.988 D18= 0.195 N 9=1.80518 ν 9= 25.4 R19= 3.039 D19= 0.760 N10=1.48749 ν10= 70.2 R20= -5.586 D20= 0.032 R21= 3.239 D21= 0.543 N11=1.48749 ν11= 70.2 R22= 13.677 D22= 0.869 R23= ∞ D23= 0.543 N12=1.51633 ν12= 64.2 R24= ∞ D24= 3.260 N13=1.60342 ν13= 38.0 R25= ∞[Table 3] Aspherical surface coefficient R14 surface K = -2.612 x 10 ^-1 A = -2.388 x 10 ^-3 B = 2.364 x 10 ^-4 C = -6.451 x 10 ^-5 D = -3.051 x 10 ^-5 <Numerical example 4> F = 1 to 12.65 Fno = 1: 1.8 to 1.9 2ω = 66.2 ° to 5.9 ° R 1 = 25.907 D 1 = 0.391 N 1 = 1.84666 ν 1 = 23.8 R 2 = 8.416 D 2 = 0.312 R 3 = 12.008 D 3 = 1.130 N 2 = 1.69680 ν 2 = 55.5 R 4 = -45.235 D 4 = 0.043 R 5 = 6.531 D 5 = 1.195 N 3 = 1.69680 ν 3 = 55.5 R 6 = 73.064 D 6 = Variable R 7 = 8.118 D 7 = 0.173 N 4 = 1.88300 ν 4 = 40.8 R 8 = 1.730 D 8 = 0.861 R 9 = -2.748 D 9 = 0.152 N 5 = 1.69680 ν 5 = 55.5 R10 = 3.014 D10 = 0.217 R11 = 3.614 D11 = 0.434 N 6 = 1.84666 ν 6 = 23.8 R12 = -11.227 D12 = Variable R13 = (Aperture) D13 = 1.413 R14 = 5.282 D14 = 0.434 N 7 = 1.60311 ν 7 = 60.7 R15 = 15.536 D15 = Variable R16 = -5.179 D16 = 0.434 N 8 = 1.51742 ν 8 = 52.4 R17 = -4.751 D17 = 0.032 R18 = 6.988 D18 = 0.195 N 9 = 1.80518 ν 9 = 25.4 R19 = 3.039 D19 = 0.760 N10 = 1.48749 ν10 = 70.2 R20 = -5.586 D20 = 0.032 R21 = 3.239 D21 = 0.543 N11 = 1.48749 ν11 = 70.2 R22 = 13.677 D22 = 0.869 R23 = ∞ D23 = 0.543 N 12 = 1.51633 ν12 = 64.2 R24 = ∞ D24 = 3.260 N13 = 1.60342 ν13 = 38.0 R25 =

【００６３】[0063]

【表４】 非球面係数 Ｒ１４面 Ｋ＝ 3.610 × 10^-3 Ａ＝ -1.746 × 10^-3 Ｂ＝ 4.681 × 10^-5 Ｃ＝ 4.104 × 10^-5 Ｄ＝ -3.320 × 10^-5 〈数値実施例５〉 F= 1 〜 10 Fno=1:1.6 〜 1.7 2ω= 60.0°〜 6.6 ° R 1= 12.083 D 1= 0.346 N 1=1.80518 ν 1= 25.4 R 2= 5.692 D 2= 1.538 N 2=1.60311 ν 2= 60.7 R 3= -26.824 D 3= 0.038 R 4= 5.854 D 4= 0.653 N 3=1.71300 ν 3= 53.8 R 5= 15.975 D 5=可変 R 6= 9.280 D 6= 0.173 N 4=1.88300 ν 4= 40.8 R 7= 1.826 D 7= 0.685 R 8= -2.629 D 8= 0.153 N 5=1.69680 ν 5= 55.5 R 9= 2.658 D 9= 0.192 R10= 3.057 D10= 0.403 N 6=1.84666 ν 6= 23.8 R11= 145.551 D11=可変 R12= -13.497 D12= 0.134 N 7=1.60311 ν 7= 60.7 R13= 4.849 D13= 0.192 R14= -10.238 D14= 0.384 N 8=1.60342 ν 8= 38.0 R15= -4.381 D15= 0.288 R16=（絞り） D16= 0.288 R17= 4.709 D17= 0.961 N 9=1.60342 ν 9= 38.0 R18= -2.543 D18= 0.173 N10=1.78590 ν10= 44.2 R19= -52.529 D19=可変 R20= 24.257 D20= 0.576 N11=1.51633 ν11= 64.2 R21= -5.630 D21= 0.028 R22= 10.997 D22= 0.211 N12=1.80518 ν12= 25.4 R23= 3.332 D23= 0.961 N13=1.48749 ν13= 70.2 R24= -8.681 D24= 0.028 R25= 4.292 D25= 0.576 N14=1.48749 ν14= 70.2 R26= 128.098 D26= 0.769 R27= ∞ D27= 0.384 N15=1.51633 ν15= 64.2 R28= ∞ D28= 3.846 N16=1.60342 ν16= 38.0 R29= ∞[Table 4] Aspheric coefficient R14 surface K = 3.610 × 10 ^-3 A = -1.746 × 10 ^-3 B = 4.681 × 10 ^-5 C = 4.104 × 10 ^-5 D = -3.320 × 10 ^-5 <Numerical example 5> F = 1 to 10 Fno = 1: 1.6 to 1.7 2ω = 60.0 ° to 6.6 ° R 1 = 12.083 D 1 = 0.346 N 1 = 1.80518 ν 1 = 25.4 R 2 = 5.692 D 2 = 1.538 N 2 = 1.60311 ν 2 = 60.7 R 3 = -26.824 D 3 = 0.038 R 4 = 5.854 D 4 = 0.653 N 3 = 1.71300 ν 3 = 53.8 R 5 = 15.975 D 5 = Variable R 6 = 9.280 D 6 = 0.173 N 4 = 1.88300 ν 4 = 40.8 R 7 = 1.826 D 7 = 0.685 R 8 = -2.629 D 8 = 0.153 N 5 = 1.69680 ν 5 = 55.5 R 9 = 2.658 D 9 = 0.192 R10 = 3.057 D10 = 0.403 N 6 = 1.84666 ν 6 = 23.8 R11 = 145.551 D11 = Variable R12 = -13.497 D12 = 0.134 N 7 = 1.60311 ν 7 = 60.7 R13 = 4.849 D13 = 0.192 R14 = -10.238 D14 = 0.384 N 8 = 1.60342 ν 8 = 38.0 R15 = -4.381 D15 = 0.288 R16 = (Aperture) D16 = 0.288 R17 = 4.709 D17 = 0.961 N 9 = 1.60342 ν 9 = 38.0 R18 = -2.543 D18 = 0.173 N10 = 1.78590 ν10 = 44.2 R19 = -52.529 D19 = Variable R20 = 24.257 D20 = 0.576 N11 = 1.51633 ν11 = 64.2 R21 = -5.630 D21 = 0.028 R22 = 10.997 D22 = 0.211 N12 = 1.80518 ν12 = 25. 4 R23 = 3.332 D23 = 0.961 N13 = 1.48749 ν13 = 70.2 R24 = -8.681 D24 = 0.028 R25 = 4.292 D25 = 0.576 N14 = 1.48749 ν14 = 70.2 R26 = 128.098 D26 = 0.769 R27 = ∞ D27 = 0.384 N15 = 1.51633 ν15 = 64.2 R28 = ∞ D28 = 3.846 N16 = 1.60342 ν16 = 38.0 R29 =

【００６４】[0064]

【表５】 [Table 5]

【００６５】[0065]

【発明の効果】本発明によれば以上のように各要素を設
定することによりレンズ系全体の小型化を図りつつ広角
端の撮影画角が６５度以上と広画角で、かつ大口径比、
高変倍比で、しかも広角端から望遠端に至る全変倍範囲
にわたり、又無限遠物体から近距離物体に至る物体距離
全般にわたり、良好なる光学性能を有し、又所定のバッ
クフォーカスを有したリヤーフォーカス式のズームレン
ズを達成することができる。According to the present invention, by setting each element as described above, the size of the entire lens system can be reduced, and the angle of view at the wide-angle end can be as wide as 65 degrees or more, and the large aperture ratio can be obtained. ,
It has a high zoom ratio, good optical performance over the entire zoom range from the wide-angle end to the telephoto end, and over the entire object distance from an object at infinity to a close object, and has a predetermined back focus. A rear-focus type zoom lens can be achieved.

【図面の簡単な説明】[Brief description of the drawings]

【図１】 本発明の数値実施例１のレンズ断面図FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

【図２】 本発明の数値実施例２のレンズ断面図FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention.

【図３】 本発明の数値実施例３のレンズ断面図FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention.

【図４】 本発明の数値実施例４のレンズ断面図FIG. 4 is a sectional view of a lens according to a numerical example 4 of the present invention.

【図５】 本発明の数値実施例５のレンズ断面図FIG. 5 is a sectional view of a lens according to a numerical example 5 of the present invention.

【図６】 本発明の数値実施例１の広角端の収差図FIG. 6 is an aberration diagram at a wide angle end according to Numerical Embodiment 1 of the present invention.

【図７】 本発明の数値実施例１の望遠端の収差図FIG. 7 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention.

【図８】 本発明の数値実施例２の広角端の収差図FIG. 8 is an aberration diagram at a wide angle end according to Numerical Example 2 of the present invention.

【図９】 本発明の数値実施例２の望遠端の収差図FIG. 9 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

【図１０】 本発明の数値実施例３の広角端の収差図FIG. 10 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

【図１１】 本発明の数値実施例３の望遠端の収差図FIG. 11 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

【図１２】 本発明の数値実施例４の広角端の収差図FIG. 12 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

【図１３】 本発明の数値実施例４の望遠端の収差図FIG. 13 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

【図１４】 本発明の数値実施例５の広角端の収差図FIG. 14 is an aberration diagram at a wide angle end according to Numerical Example 5 of the present invention.

【図１５】 本発明の数値実施例５の望遠端の収差図FIG. 15 is an aberration diagram at a telephoto end in Numerical Example 5 of the present invention.

【符号の説明】[Explanation of symbols]

Ｌ１ 第１群 Ｌ２ 第２群 Ｌ３ 第３群 Ｌ４ 第４群 ＳＰ 絞り ＩＰ 像面 Ｇ ガラスブロック ｄ ｄ線 ｇ ｇ線 ΔＳ サジタル像面 ΔＭ メリディオナル像面 L1 First lens unit L2 Second lens unit L3 Third lens unit L4 Fourth lens unit SP Aperture IP image plane G Glass block d d line g g line ΔS Sagittal image plane ΔM Meridional image plane

Claims (6)

(57)【特許請求の範囲】(57) [Claims] 【請求項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、絞りを有する正の屈折力の第３群、
そして正の屈折力の第４群の４つのレンズ群を有し、広
角端から望遠端への変倍の際には、該第２群を像面側へ
移動させると共に該絞りと該第３群を一体的に物体側に
凸状の軌跡を有するように移動させ、かつ第４群を物体
側に凸状の軌跡を有するように移動させ、合焦の際には
該第４群を移動させて行い、第ｉ群の焦点距離をＦｉと
したとき、 ２．５＜Ｆ３／Ｆ４ なる条件を満足することを特徴とするリヤーフォーカス
式のズームレンズ。1. a first unit having a positive refractive power, a second unit having a negative refractive power, a third unit having a positive refractive power having an aperture, and
The zoom lens has four lens units of a fourth group having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the second unit is moved to the image plane side, and the stop and the third lens unit are moved. The group is moved integrally so as to have a convex trajectory toward the object side, and the fourth group is moved so as to have a convex trajectory toward the object side, and the fourth group is moved during focusing. A rear focus type zoom lens, wherein a condition of 2.5 <F3 / F4 is satisfied, where Fi is the focal length of the i-th lens unit. 【請求項２】 広角端における全系の焦点距離をＦｗと
したとき、 −０．７０＜Ｆｗ／Ｆ２＜−０．４ なる条件を満足することを特徴とする請求項１のリヤー
フォーカス式のズームレンズ。2. A rear focus type lens system according to claim 1, wherein a condition of -0.70 <Fw / F2 <-0.4 is satisfied, where Fw is a focal length of the entire system at the wide-angle end. Zoom lens. 【請求項３】 前記第２群は物体側より順に物体側に凸
面を向けたメニスカス状の負の第２１レンズ、両レンズ
面が凹面の負の第２２レンズそして物体側に凸面を向け
た正の第２３レンズの３つの単レンズより構成したこと
を特徴とする請求項１のリヤーフォーカス式のズームン
レズ。3. The second group is a meniscus negative second lens having a convex surface facing the object side in order from the object side, a negative second lens having both concave lens surfaces concave, and a positive lens having a convex surface facing the object side. 2. A rear focus zoom-in lens according to claim 1, wherein said single lens is constituted by three single lenses of said 23rd lens. 【請求項４】 前記第３群からの出射光が略アフォーカ
ル又は弱い発散光束となるように各要素を設定したこと
を特徴とする請求項１のリヤーフォーカス式のズームレ
ンズ。4. The rear focus type zoom lens according to claim 1, wherein each element is set such that light emitted from said third group is substantially afocal or weakly divergent. 【請求項５】 広角端での物体距離無限遠時のバックフ
ォーカスをＢｆｗとしたとき ３．５＜Ｂｆｗ／Ｆｗ＜６．０ なる条件を満足することを特徴とする請求項２のリヤー
フォーカス式のズームレンズ。5. The rear focus system according to claim 2, wherein a condition of 3.5 <Bfw / Fw <6.0 is satisfied when a back focus at an object distance infinity at the wide angle end is Bfw. Zoom lens. 【請求項６】 ６．０＜Ｆ１／Ｆｗ＜１５．０ なる条件を満足することを特徴とする請求項２のリヤー
フォーカス式のズームレンズ。6. The rear focus type zoom lens according to claim 2, wherein a condition of 6.0 <F1 / Fw <15.0 is satisfied.