JPS61296321A - Small-sized zoom lens - Google Patents

Abstract

PURPOSE:To reduce the size of the whole lens system by composing the lens system of four lens groups and composing the 4th group of two lens groups having negative refracting power and positive refracting power. CONSTITUTION:The lens system consists of the 1st group 31 for focusing which has positive refracting power, the 2nd group 32 which moves monotonously during power variation and has negative refracting power, the 3rd group 33 which moves monotonously in the opposite direction from the 2nd group 32 during power variation and has positive refracting power, and the 4th group 34 which performs fixed image forming operation and has positive refracting power, a fixed stop 35 is arranged between the 2nd group and the 3rd group, and the 4th group 34 consists of the 41st group 341 having negative refracting power and the 42nd group 342 having positive refracting power. Further, an inequality holds preferably, where f41 and f42 are the focal lengths of the 41st and the 42nd groups. The inequality is for compensating various aberrations of the whole image surface with good balance while obtaining specific back focus. Consequently, the overall length of the lens system is shortened and the diameter of the front lens of the 1st group 31 is decreased to reduce the weight of the lens system.

Description

【発明の詳細な説明】 （産業上の利用分野） 本発明は小型のズームレンズに関し、特に写真用カメラ
、ビデオカメラ等に好適な高変倍比のレンズ系全体の軽
量化を図った小型のズームレンズに関するものである。Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a compact zoom lens, and in particular to a compact zoom lens that is suitable for photo cameras, video cameras, etc. and is designed to reduce the weight of the entire lens system with a high zoom ratio. This relates to zoom lenses.

（従来の技術） 従来より写真用カメラやビデオカメラ等に用いられてい
る比較的高変倍比のズームレンズとして第１図に示す構
成のズームレンズがある。同図において１１は合焦用の
正の屈折力の第１群、１２は主に変倍作用をし単調移動
する負の屈折力の第２群、１３は変倍に伴う像面変動を
補正する為に物体側に凸状の往復移動をする負の屈折力
の第３群、１４は第１群から第３群を通過した光束な略
平行光束とする為の必要に応じて配置される固定の正の
屈折力の第４群、そして１５は結像作用をする固定の正
の屈折力の第５群である。(Prior Art) As a zoom lens with a relatively high zoom ratio that has been conventionally used in photographic cameras, video cameras, etc., there is a zoom lens having the configuration shown in FIG. In the figure, 11 is the first group with positive refractive power for focusing, 12 is the second group with negative refractive power that mainly functions to change the magnification and moves monotonically, and 13 is the correction for image plane fluctuations associated with changing the magnification. In order to do this, the third group 14 with negative refractive power, which moves convexly back and forth toward the object side, is arranged as necessary to make the light beam from the first group to the third group a substantially parallel light beam. A fourth group having a fixed positive refractive power, and 15 a fifth group having a fixed positive refractive power that performs an imaging function.

１６は絞りであり多くの場合第３群と第４群との間、若
しくは第４群と第５群との間に配置されている。第１図
に示すズームレンズは第２群と第３群が変倍の際、移動
空間を共有する為、比較的レンズ全長を短くしレンズ系
全体を小型にすることができるが更に、レンズ系全体の
小型化を図るには第２群の屈折力をなるべく強くし第２
群の移動量を少なくする必要がある。しかしながら２群
の屈折力を強くすると変倍に伴う収差変動が多くなり、
又製造精度を向上させねばならないという問題か生じて
くる。この他発明者の長年の研究結果によると第２群の
屈折力をあまり強くすると凸レンズのコバ環を確保する
為にレンズ厚を増加させねばならず、この結果逆にレン
ズ全長が長くなってくる場合がある。従って第２群の屈
折力をあまり強くすることが出来ない。Reference numeral 16 denotes a diaphragm, which is often arranged between the third and fourth groups or between the fourth and fifth groups. In the zoom lens shown in Figure 1, the second and third groups share the moving space when changing magnification, so the overall lens length can be relatively short and the entire lens system can be made compact. In order to reduce the overall size, the refractive power of the second group should be made as strong as possible.
It is necessary to reduce the amount of movement of the group. However, if the refractive power of the second group is strengthened, aberration fluctuations due to zooming will increase,
Another problem arises in that manufacturing precision must be improved. In addition, the inventor's long-term research results show that if the refractive power of the second group is made too strong, the lens thickness must be increased in order to secure the edge ring of the convex lens, and as a result, the overall length of the lens becomes longer. There are cases. Therefore, the refractive power of the second group cannot be made very strong.

又　広角端の焦点距離を短くし広画角化を図ろうとする
と第１群の前玉径が斜光束で決定されてくる為に広画角
化図る程、前玉径が増大しレンズ系全体が大型化してく
る。一方広角端の焦点距離を長い方にシフトすると前玉
径は広角端近傍での斜光束、若しくは望遠端の軸上最大
光束のより大きい方の径で決まってくるので所定の変倍
比を得ようとすると望遠端での焦点距離が長くなりすぎ
、これに伴い前玉径が増大してくる。又第１図に示すズ
ームレンズは第２群と第３群が共に負の屈折力の為、軸
上光束は発散し、その以降に配置されている絞り径が増
大する傾向となる。一般にズームレンズにおいては焦点
距離が長くなると絞り径は増大してくる。又絞りユニッ
トは最大絞り径の約２倍の径を必要とする。従って望遠
端の焦点距離が長くなるようなレンズ構成はレンズ系の
小型化を図るには好ましくない。Also, if you try to widen the angle of view by shortening the focal length at the wide-angle end, the diameter of the front lens of the first group will be determined by the oblique light beam, so the wider the angle of view is, the larger the diameter of the front lens will be, and the larger the diameter of the entire lens system. is becoming larger. On the other hand, if you shift the focal length at the wide-angle end to a longer one, the diameter of the front lens is determined by the larger diameter of the oblique light flux near the wide-angle end or the maximum axial light flux at the telephoto end, so you can obtain a predetermined zoom ratio. If you try to do this, the focal length at the telephoto end will become too long, and the diameter of the front lens will increase accordingly. Further, in the zoom lens shown in FIG. 1, since both the second and third groups have negative refractive power, the axial light beam diverges, and the diameter of the aperture disposed after it tends to increase. Generally, in a zoom lens, as the focal length increases, the aperture diameter increases. Further, the aperture unit requires a diameter approximately twice the maximum aperture diameter. Therefore, a lens configuration in which the focal length at the telephoto end is long is not preferable for downsizing the lens system.

一方、特公昭５１−１２４２４号公報ては第２図に示す
ように第１図と同様の５群より成るズームレンズを提案
している。同図では第３群２３を正の屈折力とし、負の
屈折力の第２群２２の移動方向と逆方向へ単調移動させ
て変倍を行い高変倍化を達成している。尚同図において
２１は合焦用の第１群、２４は第１群から第３群を通過
した光束を略平行光束とする為の第４群、２５は結像作
用をする第５群、２７はファインダー光束の取り出し用
の光学部材、２６は絞りである。第２図に示すズームレ
ンズでは光束は第３群を通過後、やや収斂・してくるの
で絞り系は比較的小さくなる。しかしなから第１群の前
玉径を小さくするには第２群と第３群との間隔をある程
度長くしなければならず、この結果レンズ全長が増大し
てくる。又第３群のレンズ系も増大する。レンズ全長を
短くする為には第２群と第３群の屈折力を強くし両群の
移動量を少なくすれば良いが、屈折力を強くすると変倍
に伴う収差変動が増大してくるので、あまり屈折力を強
くすることはできない。On the other hand, Japanese Patent Publication No. 51-12424 proposes a zoom lens consisting of five groups, as shown in FIG. 2, similar to that shown in FIG. In the figure, the third lens group 23 has a positive refractive power and is moved monotonically in the opposite direction to the movement direction of the second lens group 22 that has a negative refractive power to achieve a high zoom ratio. In the figure, 21 is a first group for focusing, 24 is a fourth group for converting the light beam that has passed from the first group to the third group into a substantially parallel light beam, 25 is a fifth group that performs an imaging function, 27 is an optical member for extracting the finder light beam, and 26 is an aperture. In the zoom lens shown in FIG. 2, the light beam converges somewhat after passing through the third group, so the aperture system becomes relatively small. However, in order to reduce the diameter of the front lens of the first group, it is necessary to increase the distance between the second and third groups to some extent, and as a result, the overall length of the lens increases. Furthermore, the lens system of the third group is also increased. In order to shorten the overall length of the lens, it is possible to increase the refractive power of the second and third groups and reduce the amount of movement of both groups, but increasing the refractive power increases aberration fluctuations that occur with zooming. , it is not possible to make the refractive power too strong.

この他ズームレンズにおいて大口径比化を達成する為に
は変倍部１り像面側に配置した変倍中固定の結像部のレ
ンズ構成を適切に設定し変倍部から発生する収差を良好
に補正する゛ことが必要である。しかしながら大口径比
化を図ろうとすると画面中心の球面収差及び画面周辺に
かけてのコマ収差やサジタルハロー収差等の高次の収差
か多く発生しこれらの諸収差を良好に補正するのが困難
になってくる。In addition, in order to achieve a large aperture ratio in a zoom lens, the lens configuration of the zooming section 1 and the imaging section, which is placed on the image plane side and is fixed during zooming, must be appropriately set to reduce aberrations generated from the zooming section. It is necessary to make good corrections. However, when trying to increase the aperture ratio, many higher-order aberrations such as spherical aberration at the center of the screen and coma aberration and sagittal halo aberration toward the periphery of the screen occur, making it difficult to properly correct these various aberrations. come.

（発明が解決しようとする問題点） 本発明は特に写真用カメラやビデオカメラ等に好適なレ
ンズ全長の短縮化及び第１群の前玉径の縮小化を計りレ
ンズ系全体の軽量化を図った高変倍比の小型のズームレ
ンズの提供を目的とする。(Problems to be Solved by the Invention) The present invention aims to reduce the weight of the entire lens system by shortening the overall length of the lens and reducing the diameter of the front lens of the first group, which is particularly suitable for photographic cameras and video cameras. The objective is to provide a compact zoom lens with a high zoom ratio.

（問題点を解決する為の手段） 物体側より順に合焦用の正の屈折力の第１群、変倍の際
単調移動する負の屈折力の第２群、変倍の際面記第２群
と逆方向に単調移動する正の屈折力の第３群、そして固
定の結像作用をする正の屈折力の第４群の４つのレンズ
群を有し、前記第２群と第°３群との間に固定絞りを配
置し、前記第４群を負の屈折力の第４１群と正の屈折力
の第４２群の２つのレンズ群より構成したことである。(Means for solving the problem) In order from the object side, the first group has a positive refractive power for focusing, the second group has a negative refractive power that moves monotonically when changing the magnification, and the second group has a positive refractive power for focusing when changing the magnification. It has four lens groups: a third group with a positive refractive power that moves monotonically in the opposite direction to the second group, and a fourth group with a positive refractive power that performs a fixed imaging function. A fixed diaphragm is disposed between the third lens group and the fourth lens group is composed of two lens groups: a 41st lens group with negative refractive power and a 42nd lens group with positive refractive power.

この側木発明の特徴は実施例において説明されている。The features of this side tree invention are explained in the examples.

（実施例） 第３図（Ａ）、（Ｂ）は本発明の一実施例の光学系の概
略図であり（Ａ）は広角側、（Ｂ）は望遠側である。同
図において３１は合焦用の正の屈折力の第１群、３２は
変倍の際、像面側へ単調移動する負の屈折力の第２群、
３３は変倍の際、第２群とは逆方向へ物体側へ単調移動
する正の屈折力の第３群、３４は固定の結像作用をする
結像部としての正の屈折力の第４群、３５は第２群と第
３群との間に配置した固定の絞りである。(Embodiment) FIGS. 3(A) and 3(B) are schematic diagrams of an optical system according to an embodiment of the present invention, in which (A) shows the wide-angle side and (B) shows the telephoto side. In the figure, 31 is a first group with positive refractive power for focusing, 32 is a second group with negative refractive power that moves monotonically toward the image plane during zooming,
33 is a third group with positive refractive power that monotonically moves toward the object side in the opposite direction to the second group when changing the magnification; 34 is a third group with positive refractive power as an imaging section that performs a fixed image forming function. The fourth group and 35 are fixed apertures arranged between the second and third groups.

３４１．３４２は各々第４群を構成する負の屈折力の第
４１群と正の屈折力の第４２群である。尚本実施例にお
いて第４１群と第４２群の２つのレンズ群は第４群中の
最も大きい空気間隔を境にして分けている。341 and 342 are a 41st group with negative refractive power and a 42nd group with positive refractive power, respectively, which constitute the fourth group. In this embodiment, the two lens groups, the 41st lens group and the 42nd lens group, are separated by the largest air gap in the 4th lens group.

本実施例では絞りを挟んだ第２群と第３群を変倍の際、
一方向へ単調移動させることにより第１群の前玉径の縮
小化を図り、レンズ全長の短縮化を図っている。In this embodiment, when changing the magnification of the second and third groups with the aperture in between,
By moving the lens monotonically in one direction, the diameter of the front lens of the first group is reduced, and the overall length of the lens is reduced.

一般に第３図に示すズームレンズにおいて絞りを第２群
と第３群との間に配置しても変倍の際第３群を物体側へ
凸状に往復移動させるズーム方式を採用すると第２群と
第３群との空間を共有するという利点が失われレンズ全
長が長くなってくる。Generally, in the zoom lens shown in Fig. 3, even if the aperture is placed between the second and third groups, if a zoom system is adopted in which the third group is reciprocated in a convex manner toward the object side during zooming, the second The advantage of sharing the space between the lens group and the third group is lost, and the overall length of the lens becomes longer.

即ち第３群が往復移動するズーム方式では第２群と第３
群が変倍の際中間位置で最も接近してくる為に両軍が機
械的に干渉しないように予め余分の空間を設けておかね
ばならなく、その分だけレンズ全長が長くなってくる。In other words, in a zoom system in which the third group moves back and forth, the second and third groups move back and forth.
Since the groups come closest at the intermediate position when changing magnification, extra space must be provided in advance to prevent mechanical interference between the two groups, and the overall length of the lens increases accordingly.

これに対して本実施例では第２群と第３群との間に絞り
を配置し、この絞りと干渉しないように第２群と第３群
を互いに逆方向へ単調移動させて変倍を行うズーム方式
を採っている為に余分な空間を必要としない。そして第
２群に変倍効果を持たせると共に第３群にも変倍効果を
持たせることにより所定の変倍比を効率的に得て後述す
る数値実施例では変倍比６程度の高変倍比を達成してい
る。又第２群と第３群との空間を有効利用し、更に第２
群と第３群の光軸上の移動量を全体的に少なくしてレン
ズ全長の短縮化を図っている。In contrast, in this embodiment, an aperture is placed between the second and third groups, and the magnification is changed by moving the second and third groups monotonically in opposite directions so as not to interfere with the aperture. Since the zoom method is adopted, no extra space is required. By providing the second group with a variable power effect and also providing a variable power effect with the third group, a predetermined variable power ratio can be efficiently obtained. Achieved double ratio. Also, by effectively utilizing the space between the second and third groups,
The overall length of the lens is shortened by reducing the amount of movement of the groups and the third group on the optical axis.

又一般のズームレンズでは多くの場合ズームレンズ全体
の重量のうち５〜８割を第１群が占めている。この為ズ
ームレンズの軽量化を図る為には第１群のレンズの材質
の比重を小さくするか第１群の前玉径を小さくし体積を
減少させることが有効となる。このうち比重の小さい材
質を選択するのは光学設計上自由度が少なくなり難しい
。この為光学性能を良好に維持しつつレンズ径の軽量化
を図るには第１群の前玉径を小さくすることが有効とな
ってくる。例えばレンズの体積を比例的に考えればレン
ズ径の３乗に比例するのでレンズ径を１０％小さくする
ことができれば（０，９）３から体積を約２７％小さく
することができるようになる。In addition, in a typical zoom lens, the first group often accounts for 50 to 80 percent of the weight of the entire zoom lens. Therefore, in order to reduce the weight of a zoom lens, it is effective to reduce the volume by reducing the specific gravity of the material of the first lens group or by reducing the diameter of the front lens of the first group. Among these materials, it is difficult to select a material with a small specific gravity because it reduces the degree of freedom in optical design. Therefore, in order to reduce the weight of the lens while maintaining good optical performance, it is effective to reduce the diameter of the front lens in the first group. For example, considering the volume of a lens proportionally, it is proportional to the cube of the lens diameter, so if the lens diameter can be reduced by 10%, the volume can be reduced from (0,9)3 to about 27%.

本実施例では特に第１群の前玉径の縮小化を優先的に行
いレンズ系全体の軽量化を図っている。即ち第１図や第
２図に示すように絞りを第４群よりも後方に配置したズ
ームレンズに比べて絞りを第１群に近い第２群と第３群
との間である光学系の略中間位置に配置することにより
第１群の前玉径の縮少化を優先させている。そして本実
施例では広角側で斜光束により決定される第１群の前玉
径と望遠側の軸上光束により決定される第１群の前玉径
の双方において共に前玉有効径が小さくなるように絞り
及びレンズ群を配置している。更に広画角化を図る際の
斜光束辷よる前玉有効系の増大を防止しつつ前玉有効径
の一部が望遠側の軸上光束により決定されるように構成
し望遠側のＦナンバーを規制することにより前玉有効径
の大きさを任意に決定できるようにして、レンズ系全体
の大きさをバランス良く制御している。In this embodiment, the diameter of the front lens of the first group is prioritized in order to reduce the weight of the entire lens system. In other words, compared to a zoom lens in which the aperture is located behind the fourth group as shown in Figures 1 and 2, an optical system with an aperture located closer to the first group between the second and third groups By arranging it at a substantially intermediate position, priority is given to reducing the diameter of the front lens of the first group. In this embodiment, the effective diameter of the front lens becomes smaller in both the diameter of the front lens of the first group determined by the oblique light flux on the wide-angle side and the diameter of the front lens of the first group determined by the axial light flux on the telephoto side. The aperture and lens groups are arranged like this. Furthermore, while preventing an increase in the front lens effective diameter due to the oblique light flux when widening the field of view, the effective diameter of the front lens is partially determined by the axial light flux on the telephoto side, and the F number on the telephoto side is increased. By regulating the size of the front lens, the effective diameter of the front lens can be arbitrarily determined, and the size of the entire lens system can be controlled in a well-balanced manner.

本実施例では変倍中固定の結像機能を有する第４群を全
体として正の屈折力のレンズ群で構成し、全系の焦点距
離範囲を適切に設定し又第４群を負の屈折力の第４１群
と正の屈折力の第４２群の２つのレンズ群で構成するこ
とにより所定のバックフォーカス容易に得ると共に画面
全体の諸収差を良好に補正しＦナンバー１．２程度の大
口径比化を達成している。In this example, the fourth group, which has a fixed imaging function during zooming, is composed of a lens group with a positive refractive power as a whole, and the focal length range of the entire system is set appropriately, and the fourth group has a negative refractive power. By being composed of two lens groups, the 41st group with positive refractive power and the 42nd group with positive refractive power, it is possible to easily obtain a predetermined back focus, and to satisfactorily correct various aberrations of the entire screen, resulting in a large F-number of about 1.2. The caliber ratio has been achieved.

即ち第１群から第３群までの部分系を正の屈折力で構成
し、レンズ系の小型化を図ったときに、収斂状態で入射
してくる光束をまず負の屈折力の第４１群の発散作用で
いったんアフォーカル近くにし、次いで正の屈折力の第
４２群で所定のバックフォーカスを維持しつつ結像させ
るようにしている。In other words, when the subsystems from the first group to the third group are configured with positive refractive power and the lens system is made smaller, the light beam incident in a convergent state is first transferred to the 41st group with negative refractive power. The diverging effect of the lens first makes it nearly afocal, and then the 42nd lens group with positive refractive power forms an image while maintaining a predetermined back focus.

又第１群から第３群に至る部分系より生じる補正不足の
球面収差を負の屈折力の第４１群で補正し、画面全体の
コマ収差やサジタルハロー等を正の屈折力の第４２群で
補正するようにしている。In addition, the 41st group with negative refractive power corrects undercorrected spherical aberrations caused by the subsystems from the 1st group to the 3rd group, and the 42nd group with positive refractive power corrects comatic aberrations and sagittal halos of the entire screen. I am trying to correct it.

更に第３群と第４２群の正の屈折力に起因する負の像面
湾曲を負の屈折力の第４１群で補正している。本発明の
目的とする小型のズームレンズは以上の諸条件を満足す
ることにより達成されるものであるが更に好ましくは第
４１群と第４２群の焦点距離を各々ｆ４１＋ｆ４２とす
るとき。Furthermore, the negative curvature of field caused by the positive refractive powers of the third and 42nd groups is corrected by the 41st group having negative refractive power. The compact zoom lens which is the object of the present invention can be achieved by satisfying the above-mentioned conditions, but more preferably, the focal lengths of the 41st group and the 42nd group are f41+f42.

１．３　＜　ｌ　ｆａｔ　／　ｆ４□　ｌ＜８．０　・
・・（１）の如く設定することである。1.3 < l fat / f4□ l < 8.0 ・
...The setting is as shown in (1).

条件式（１）は所定のバックフォーカスを得つつ画面全
体の諸収差をバランス良く補正する為のものであり、条
件式（１）の下限値を越えて第４１群の屈折力が強くな
るとバックフォーカスは十分長くなるが球面収差が補正
過剰となると共に像面湾曲が正の方向に増大し更に第４
２群の有効径が増大しレンズ系が大型化してくる。逆に
上限値を越えて第４１群の屈折力が弱くなってくるとバ
ックフォーカスが短くなりすぎ又球面収差は補正不足と
なり更に広角側での像面湾曲が負の方向へ増大してくる
ので好ましくない。Conditional expression (1) is for correcting various aberrations of the entire screen in a well-balanced manner while obtaining a predetermined back focus.If the lower limit of conditional expression (1) is exceeded and the refractive power of the 41st group becomes strong, Although the focus becomes sufficiently long, the spherical aberration becomes overcorrected and the curvature of field increases in the positive direction.
The effective diameter of the second group increases and the lens system becomes larger. On the other hand, if the upper limit is exceeded and the refractive power of the 41st group becomes weak, the back focus becomes too short and spherical aberration becomes insufficiently corrected, and the curvature of field at the wide-angle end increases in the negative direction. Undesirable.

更に本実施例において好ましくは第４１群に少なくとも
１枚の物体側に凹面を向けた負レンズを有するようにす
れば変倍部で発生した球面収差を全波長域にわたり良好
に補正することができる。又第４２群中に像面側に強い
凹面を向けた少なくとも１枚の負レンズＬ２Ｎを有する
ようにすれば変倍部及び第４１群の負レンズで発生した
コマ収差を良好に補正することができる。更に第４２群
を諸収差の発生量を少なくしつつ全体的に正の屈折力と
する為に１枚の正レンズでは各レンズ面の屈折力負担が
大きくなるので少なくとも２枚の正レンズを有するよう
に構成すれば大口径比を図りつつ画面全体の諸収差を良
好に補正することができる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番目のレンズのカラスの屈折率とアラへ数である
。Ｉ、ｎ、ｍ、ＴＶ−１，ＩＶ−２は各々第１゜７ＦＪ
２．第３．第４１．第４２群を示し、ｆ、、ｆ２ｆ３．
ｆ４は各々第１．第２．第３．第４群の焦点数値実施例
ｌ Ｒ２５−ｏｏ　　　　Ｄ２５−５．５ Ｒ２Ｂ−Ｃ０ 〜ｌ、７　２　ω−５１，５°〜１Ｏ１０゜Ｎ　　ｌ−
１，８０５１８ｖ　　１＝　　２５．４Ｎ　　２−１．
６０３１１　　　υ　２−　６０．７Ｎ　３諺１．６２
２９９　　　υ　３−　５８．２Ｎ　　４−１．７７２
５０　　　ν　４−　４９．６Ｎ　　７−１．７１３０
０　　　ν　７−　５３．８Ｎ　　８−１．６９６８０
　　　ν　８−　５５．５Ｎ　　９−１．８４６６６　
　　ν　９−　２３．９ＮＩＯ−１，６０３１１ν１０
−　６０．７Ｎｉｌ〜１．６９６８０　　　ν１１−　
５５．５Ｎ１２−１．８４６６６−　ν１２−　２３．
９８１３−１．７１３００　　　υ１３−　５３．８Ｎ
１４露１．５１［ｉ３３　　　ν１４−　６４．１数値
実施例３ Ｆ−１０，５〜５７．９　　ＦＮＯ−１：１．２０〜Ｒ
２７−ｏｏ　　　　　　　Ｄ２７−５．５Ｒ２８−（１
） １．７　２　ω−５６，３”〜１１．０”Ｎ　　１−１
．８０５１８　　　ν　１−　２５．４Ｎ　　２＝１．
５１６３３　　　ｖ　　２＝　　ａ４．ＩＮ　　３−１
．６３８５４　　　ν　３−　５５．４Ｎ　　４−１．
７８５９０　　　ν　４−　４４．２Ｎ　　７＝１．６
５８４４　　　ν　７−　５０．９Ｎ　　８＝１．８５
８４４　　　ｖ　　８−　５０．９Ｎ　９〜１．３４６
６８　　　ν　９＝　　２３．９ＮＩＯ−１，５１６３
３ｖｌＯ−６４，１Ｎｉｌ−１，６５８４４ν１１−　
５０．９Ｎ１２−１．８４６６６　　　ν１２−　２３
．９ＮＩ３−１．６２２９９　　　ν１３−　５８．２
Ｎ１４−１．６２２９９　　ν１４−　５８．シＮ１５
＝１．５１６３３　　　Ｚ／　１５＝　　６４．１ロ　
　ロ　　　ロ　　マ Ｃ＋４１＋＋ｈ口 み　　　ミ　　　ミ　　　ミ 数値実施例５ Ｆ寓１０．３〜５７．ＯＦＮＯ−１：１．２０／−Ｒ１
１−絞り　　Ｄｌｌ−可変 Ｒ２９＝　　　ｏｏ　　　Ｄ２９−５．５Ｒ３０−（１
） ・１．７０　２　　ω・５７．０°〜１１．２゜Ｎ　２
・１．６０３１１　　　υ　２−　６０．７Ｎ　　３−
１．６２２９９　　　ｖ　　３−　５８．２８　４−１
．６９６８０　　　ν　４−　５５．５Ｎ　　７−１．
７４９５０　　　ν　７−　３５．３Ｎ　　８＝１．８
２２９９　　　ｖ　　８−　５８．２Ｎ　９諺１．８４
６６６　　　ν　９−　２３．９ＮＩＯ−１，５９２７
０νｌＯ菖　３５．３Ｎｉｌ−１，７４４００ｖ　１１
−　４４．７ＮＩ２−１．７２０００　　　ν１２−　
５０．２Ｎ１３−１．８４６６６　　　ν１３−　２３
．９Ｎ１４−１．６４０００　　　ν１４−　６０．１
Ｎ１５率１．６０３１１　　　ν１５−　６０．７ＮＩ
６−１．５１６３３　　　ν１６−　６４．１ｆ　４１
　＝　−５３，３９ ｆ４２＝　　２２．２０ （発明の効果） 本発明によればレンズ全長の短縮化及び第１群つ前玉径
の縮小化を図り、レンズ系全体の軽量化１図った高変倍
の小型のズームレンズを達成することができる。Furthermore, in this embodiment, if the 41st group preferably includes at least one negative lens with a concave surface facing the object side, the spherical aberration generated in the variable power section can be corrected well over the entire wavelength range. . Furthermore, if the 42nd group includes at least one negative lens L2N with a strongly concave surface facing the image plane side, coma aberration generated in the variable power section and the negative lens of the 41st group can be well corrected. can. Furthermore, in order to make the 42nd group have positive refractive power overall while reducing the amount of various aberrations generated, at least two positive lenses are used, since a single positive lens would place a large burden on each lens surface. With this configuration, various aberrations of the entire screen can be corrected satisfactorily while achieving a large aperture ratio.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 from the object side, Di is the thickness of the i-th lens from the object side, and air spacing Ni and νi are the curvature radius of the i-th lens from the object side, respectively. These are the refractive index and the number of crows. I, n, m, TV-1, IV-2 are each 1°7FJ
2. Third. No. 41. The 42nd group is shown, f,, f2f3.
f4 is the first . Second. Third. Focus numerical example of 4th group l R25-oo D25-5.5 R2B-C0 ~ l, 7 2 ω-51,5° ~ 1O10°N l-
1,80518v 1=25.4N 2-1.
60311 υ 2- 60.7N 3 Proverbs 1.62
299 υ 3- 58.2N 4-1.772
50 ν 4- 49.6N 7-1.7130
0 ν 7- 53.8N 8-1.69680
ν 8-55.5N 9-1.84666
ν 9- 23.9NIO-1, 60311ν10
- 60.7 Nil ~ 1.69680 ν11-
55.5N12-1.84666- ν12- 23.
9813-1.71300 υ13- 53.8N
14 Dew 1.51 [i33 ν14- 64.1 Numerical Example 3 F-10,5~57.9 FNO-1:1.20~R
27-oo D27-5.5R28-(1
) 1.7 2 ω-56,3”~11.0”N 1-1
．． 80518 ν 1- 25.4N 2=1.
51633 v 2 = a4. IN 3-1
．． 63854 ν 3- 55.4N 4-1.
78590 ν 4- 44.2N 7=1.6
5844 ν 7- 50.9N 8=1.85
844 v 8-50.9N 9-1.346
68 ν 9= 23.9NIO-1,5163
3vlO-64,1Nil-1,65844ν11-
50.9N12-1.84666 ν12- 23
．． 9NI3-1.62299 ν13- 58.2
N14-1.62299 ν14- 58. ShiN15
=1.51633 Z/ 15= 64.1ro
Lo Lo Ma C+41++h Mouth Mi Mi Mi Numerical Example 5 F Fable 10.3-57. OFNO-1: 1.20/-R1
1-Aperture Dll-Variable R29=oo D29-5.5R30-(1
) ・1.70 2 ω・57.0°～11.2°N 2
・1.60311 υ 2- 60.7N 3-
1.62299 v 3- 58.28 4-1
．． 69680 ν 4- 55.5N 7-1.
74950 ν 7- 35.3N 8=1.8
2299 v 8- 58.2N 9 proverbs 1.84
666 ν 9- 23.9NIO-1, 5927
0νlO irises 35.3Nil-1,74400v 11
- 44.7NI2-1.72000 ν12-
50.2N13-1.84666 ν13- 23
．． 9N14-1.64000 ν14-60.1
N15 rate 1.60311 ν15- 60.7NI
6-1.51633 ν16- 64.1f 41
= -53,39 f42= 22.20 (Effects of the Invention) According to the present invention, the overall length of the lens is shortened, the diameter of the front lens of the first group is reduced, and the weight of the entire lens system is reduced. A zoom lens that is twice as small can be achieved.

又、本発明では広画角化を図っても広角側における斜光
束の第１群への入射高を比較的低くすることが出来るの
で、第１群の前玉径の増大を防止することが出来、更に
絞りより後方の第３群と第４群の有効径もあまり増大さ
せることがないので、レンズ径全体の／Ｊ％型化を図っ
た広画角の小型のズームレンズを容易に達成することが
できる。Further, in the present invention, even if the angle of view is widened, the height of incidence of the oblique light beam on the first group on the wide-angle side can be made relatively low, so it is possible to prevent the diameter of the front lens of the first group from increasing. Moreover, since the effective diameter of the third and fourth groups behind the aperture does not increase much, it is easy to create a compact zoom lens with a wide angle of view and a /J% overall lens diameter. can do.

又、各レンズ群の位置敏感度が小さくなるので組立を容
易にすることができ、更に一般に望遠側では画角が狭く
屋外で撮影する場合が多いので実用的な支障がない程度
に望遠側でのＦナンバーを規制すれば第１群の前玉径を
制御することができ小型のズームレンズを容易に達成す
ることができる。In addition, the positional sensitivity of each lens group is reduced, making assembly easier. Furthermore, since the angle of view is generally narrow at the telephoto end and is often taken outdoors, it is possible to use the telephoto end to the extent that there is no practical problem. By regulating the F number, the diameter of the front lens of the first group can be controlled, and a compact zoom lens can be easily achieved.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図、第２図は各々従来のズームレンズの光学系の概
略図、第３図は本発明に係るズームレンズの光学系の概
略図、第４図から第８図は各々本発明の数値実施例１〜
５のレンズ断面図、第９図から第１３図は各々本発明の
数値実施例１〜５の諸収差図である。収差図において（
Ａ）、（Ｂ）、は各々無限遠物体のときの広角端、望遠
端での収差を示す。図中矢印は変倍の際のレンズ群の、
移動方向、ｄはｄ 線、ｇはｇ線、ΔＳはサジタル像面、ΔＭはメリディオ
ナル像面である。Figures 1 and 2 are schematic diagrams of the optical system of a conventional zoom lens, Figure 3 is a schematic diagram of the optical system of a zoom lens according to the present invention, and Figures 4 to 8 are numerical values of the present invention. Example 1~
5 and 9 to 13 are aberration diagrams of numerical examples 1 to 5 of the present invention, respectively. In the aberration diagram (
A) and (B) show aberrations at the wide-angle end and the telephoto end, respectively, when the object is at infinity. The arrows in the figure indicate the lens group during zooming.
In the direction of movement, d is the d-line, g is the g-line, ΔS is the sagittal image plane, and ΔM is the meridional image plane.

Claims (1)

【特許請求の範囲】 （１）物体側より順に合焦用の正の屈折力の第１群、変
倍の際単調移動する負の屈折力の第２群、変倍の際前記
第２群と逆方向に単調移動する正の屈折力の第３群、そ
して固定の結像作用をする正の屈折力の第４群の４つの
レンズ群を有し、前記第２群と第３群との間に固定絞り
を配置し、前記第４群を負の屈折力の第４１群と正の屈
折力の第４２群の２つのレンズ群より構成したことを特
徴とする小型のズームレンズ。 （２）前記第４１群と第４２群の焦点距離を各々ｆ＿４
＿１、ｆ＿４＿２としたとき １．３＜｜ｆ＿４＿１／ｆ＿４＿２｜＜８．０なる条件
を満足することを特徴とする特許請求の範囲第１項記載
の小型のズームレンズ。 （３）前記第４１群は物体側に凹面を向けた少なくとも
１枚の負レンズを有しており、前記第４２群は像面側に
凹面を向けた少なくとも１枚の負レンズと少なくとも２
枚の正レンズを有していることを特徴とする特許請求の
範囲第２項記載の小型のズームレンズ。[Scope of Claims] (1) In order from the object side, a first group with a positive refractive power for focusing, a second group with a negative refractive power that moves monotonically when changing magnification, and the second group when changing magnification. It has four lens groups: a third group with a positive refractive power that moves monotonically in the opposite direction to the above, and a fourth group with a positive refractive power that performs a fixed imaging function. A small zoom lens, characterized in that a fixed diaphragm is disposed between them, and the fourth group is composed of two lens groups: a 41st group with negative refractive power and a 42nd group with positive refractive power. (2) The focal length of the 41st group and the 42nd group is f_4, respectively.
The compact zoom lens according to claim 1, wherein the compact zoom lens satisfies the following condition: 1.3<|f_4_1/f_4_2|<8.0 when _1 and f_4_2. (3) The 41st group includes at least one negative lens with a concave surface facing the object side, and the 42nd group includes at least one negative lens with a concave surface facing the image side, and at least two negative lenses with a concave surface facing the image side.
3. A compact zoom lens according to claim 2, characterized in that it has two positive lenses.