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JP2970083B2 - Rear focus type zoom lens with gradient index lens - Google Patents

Rear focus type zoom lens with gradient index lens

Info

Publication number
JP2970083B2
JP2970083B2 JP3174391A JP17439191A JP2970083B2 JP 2970083 B2 JP2970083 B2 JP 2970083B2 JP 3174391 A JP3174391 A JP 3174391A JP 17439191 A JP17439191 A JP 17439191A JP 2970083 B2 JP2970083 B2 JP 2970083B2
Authority
JP
Japan
Prior art keywords
lens
group
refractive power
unit
positive refractive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP3174391A
Other languages
Japanese (ja)
Other versions
JPH04369611A (en
Inventor
昭永 堀内
博之 浜野
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
Original Assignee
Canon Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
Priority to JP3174391A priority Critical patent/JP2970083B2/en
Priority to US07/899,375 priority patent/US5321552A/en
Publication of JPH04369611A publication Critical patent/JPH04369611A/en
Application granted granted Critical
Publication of JP2970083B2 publication Critical patent/JP2970083B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B15/00Optical objectives with means for varying the magnification
    • G02B15/14Optical 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
    • G02B15/144Optical 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
    • G02B15/1441Optical 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
    • G02B15/144113Optical 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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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)

Description

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

【0001】[0001]

【産業上の利用分野】本発明は屈折率分布型レンズを有
した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
られる変倍比6、Fナンバー1.8程度の大口径比で高
変倍比のズームレンズに好適なものである。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear focus type zoom lens having a gradient index lens, and more particularly to a zoom ratio of 6 and an F-number of 1.about.1, which are used in photographic cameras, video cameras, broadcast cameras and the like. It is suitable for a zoom lens having a large aperture ratio of about 8 and a high zoom ratio.

【0002】[0002]

【従来の技術】従来より写真用カメラやビデオカメラ等
のズームレンズにおいては物体側の第1群以外のレンズ
群を移動させてフォーカスを行なう、所謂リヤーフォー
カス式を採用したものが種々と提案されている。
2. Description of the Related Art Conventionally, various types of zoom lenses such as a photographic camera and a video camera adopting a so-called rear focus type in which a lens group other than the first group on the object side is moved to perform focusing is proposed. ing.

【0003】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なうズームレンズ
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
行なっているので、レンズ群の駆動力が小さくてすみ迅
速な焦点合わせが出来る等の特長がある。この為、小型
化及び高変倍化が要望されているビデオカメラ用のズー
ムレンズに多く用いられている。
In general, a rear focus type zoom lens has a smaller effective diameter of the first lens group than a zoom lens which moves and focuses the first lens group, so that the entire lens system can be easily miniaturized, and close-up photography can be performed. In particular, extremely close-up photographing is facilitated, and since the relatively small and light lens group is moved, the driving force of the lens group is small, so that quick focusing can be performed. For this reason, it is often used for a zoom lens for a video camera, which is required to have a small size and a high zoom ratio.

【0004】このようなリヤーフォーカス式のズームレ
ンズとして特開昭62−247316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ない、第
4群を移動させて変倍に伴なう像面変動とフォーカスを
行なっている。
Japanese Patent Laid-Open Publication No. Sho 62-247316 discloses such a rear focus type zoom lens. The first lens unit has a positive refractive power, the second lens unit has a negative refractive power, and the second lens unit has a positive refractive power. It has three lens units and a fourth lens unit of a fourth lens unit having a positive refractive power. The second unit is moved to perform zooming, and the fourth unit is moved to change the image plane due to zooming. The focus is on.

【0005】一般にズームレンズの小型化を図りつつ、
所定の変倍比を確保するにはズームタイプを適切に設定
し、かつ各レンズ群の屈折力を強めることが必要となっ
てくる。
In general, while miniaturizing a zoom lens,
In order to secure a predetermined zoom ratio, it is necessary to appropriately set the zoom type and to increase the refractive power of each lens unit.

【0006】しかしながら単にレンズ群の屈折力を強め
ると変倍に伴なう収差変動が増大し、これを補正する為
に各レンズ群のレンズ枚数を増加させねばならず、この
結果レンズ群の光軸方向の厚みが増し、主点間隔を広げ
なければならず結果的にレンズ全長が増大してきてしま
う。この為例えば特開平2−39011号公報では球面
の他に非球面を用いてレンズ系全体の小型化を図りつ
つ、所定の変倍比を確保したズームレンズを提案してい
る。
However, if the refractive power of the lens units is simply increased, aberration fluctuations accompanying zooming increase, and the number of lenses in each lens unit must be increased in order to correct the fluctuation. The thickness in the axial direction increases, and the distance between the principal points must be increased. As a result, the overall length of the lens increases. For this reason, for example, Japanese Patent Application Laid-Open No. 2-39011 proposes a zoom lens that uses a non-spherical surface in addition to a spherical surface to reduce the size of the entire lens system and secure a predetermined zoom ratio.

【0007】[0007]

【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。
Generally, when a rear focus system is employed in a zoom lens, the overall lens system can be reduced in size and quick focusing becomes possible as described above, and further advantages such as close-up photographing can be easily obtained. .

【0008】又、非球面を利用すれば光学性能を良好に
維持しつつレンズ全長を比較的短縮化することができ
る。
Further, if an aspherical surface is used, the overall length of the lens can be relatively shortened while maintaining good optical performance.

【0009】しかしながら非球面は色収差やペッツバー
ル和を小さくするといった光学的な効果がない。この為
色消しが必要となるレンズ群には少なくとも分散の異な
る2枚のレンズを用いてレンズ群内で色収差を補正しな
くてはならず、又レンズ群の屈折力もペッツバール和が
あまり大きくならない範囲に設定しなければならないと
いった制約があった。
However, an aspherical surface has no optical effect such as reducing chromatic aberration and Petzval sum. Therefore, at least two lenses having different dispersion must be used to correct chromatic aberration in the lens group that requires achromatism, and the refracting power of the lens group does not greatly increase the Petzval sum. There was a restriction that it must be set to.

【0010】この為、非球面を用いたとしても所定の変
倍比を確保しつつレンズ系全体の小型化を図るには自と
限界があった。
Therefore, even if an aspherical surface is used, there is a limit to reducing the size of the entire lens system while maintaining a predetermined zoom ratio.

【0011】本発明は非球面の代わりに又は非球面と共
に連続的に屈折率が変化する材質より成る屈折率分布型
レンズを用い、かつリヤーフォーカス方式を採用するこ
とにより、レンズ系全体の小型化を図りつつ、高変倍比
が容易に得られ、しかも全変倍範囲にわたり良好なる光
学性能が得られる屈折率分布型レンズを有したリヤーフ
ォーカス式のズームレンズの提供を目的とする。
The present invention uses a refractive index distribution type lens made of a material whose refractive index changes continuously instead of or together with an aspherical surface, and adopts a rear focus method to reduce the size of the entire lens system. It is an object of the present invention to provide a rear focus type zoom lens having a refractive index distribution type lens that can easily obtain a high zoom ratio and obtain good optical performance over the entire zoom range.

【0012】[0012]

【課題を解決するための手段】請求項1の発明の屈折率
分布型レンズを有した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、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、該第2群を移動させて変
倍を行い変倍に伴う像面変動を該第4群を移動させて補
正すると共に該第4群を移動させてフォーカスを行い、
第1群は周辺部にいくに従って屈折率が低下する材質よ
り成るラジアル型の1枚の屈折率分布型レンズより成
り、Nod,Nogを各々d線,g線の光軸上における屈折
率、N1d,N1gを各々d線,g線のレンズの有効径の7
5%の箇所における屈折率、f1,fTを第1群及び全
系の望遠端の焦点距離としたとき、 0.53<fT/(Nod 2・f1)<0.65‥‥‥(1)
According to the first aspect of the present invention, a rear focus type zoom lens having a gradient index lens is a first lens unit having a positive refractive power and a negative lens having a negative refractive power in order from the object side. The zoom lens has four lens groups: a second lens group, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The fourth group is moved and corrected, and the fourth group is moved and focused.
The first group is composed of a single radial type gradient index lens made of a material whose refractive index decreases toward the periphery, and Nod and Nog are the refractive indices on the optical axis of the d-line and g-line, respectively. , N 1d and N 1g are the effective diameters of the d-line and g-line lenses, respectively.
Refractive index at 5% point, f1, fT when was the first group and the focal length at the telephoto end of the entire system, 0.53 <fT / (N od 2 · f1) <0.65 ‥‥‥ (1 )

【数3】 を満足することを特徴としている。請求項2の発明は、
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、該第2群を移動させて変倍を行
い変倍に伴う像面変動を該第4群を移動させて補正する
と共に該第4軍を移動させてフォーカスを行い、該第3
群はラジアル型の1枚の屈折率分布型レンズより成り、
全系の広角端の焦点距離を1としたとき、γ3,1を第3
群の第1レンズ面の曲率半径、f3を第3群の焦点距
離、ΔN7dを第3群の屈折率分布型レンズの最も屈折率
の高い部分と最も低い部分のd線の屈折率差としたと
き、 0.65<γ3,1/f3<0.98 ‥‥‥(3) 0.002<ΔN7d/f3<0.006‥‥‥(4) を満足することを特徴としている。請求項3の発明は、
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、該第2群を移動させて変倍を行
い変倍に伴う像面変動を該第4群を移動させて補正する
と共に該第4群を移動させてフォーカスを行い、該第4
群はラジアル型の1枚の屈折率分布型レンズより成り、
od,Nogを各々d線,g線の光軸上における屈折率、
1d,N1gを各々d線,g線のレンズの有効径の75%
の箇所における屈折率、f4を第4群の焦点距離、fw
を全系の広角端の焦点距離としたとき、 0.04<fw/(Nod 2・f4)<0.31‥‥‥(5)
(Equation 3) Is satisfied. The invention of claim 2 is
The first group of positive refractive power and the second group of negative refractive power in order from the object side.
The zoom lens has four lens groups: a first lens group, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The fourth group is moved and corrected, and the fourth arm is moved to perform focusing.
The group consists of one radial type gradient index lens,
Assuming that the focal length at the wide-angle end of the entire system is 1, γ 3,1 is the third
The radius of curvature of the first lens surface of the group, f3 is the focal length of the third group, and ΔN 7d is the difference between the refractive index difference between the highest refractive index part and the lowest d-line of the gradient index lens of the third group. Then, 0.65 <γ 3,1 / f3 <0.98 {(3) 0.002 <ΔN 7d /f3<0.006} (4). The invention of claim 3 is
The first group of positive refractive power and the second group of negative refractive power in order from the object side.
The zoom lens has four lens groups: a first lens group, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The fourth unit is moved and corrected, and the fourth unit is moved to perform focusing.
The group consists of one radial type gradient index lens,
Nod and Nog are the refractive indices of the d-line and the g-line on the optical axis, respectively.
N 1d and N 1g are 75% of the effective diameter of the d-line and g-line lenses, respectively.
, F4 is the focal length of the fourth group, fw
When was the focal length at the wide angle end of the entire system, 0.04 <fw / (N od 2 · f4) <0.31 ‥‥‥ (5)

【数4】 を満足することを特徴としている。(Equation 4) Is satisfied.

【0013】請求項4の発明は、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、該第2群を移動させて変倍を行い変倍に伴う像面変
動を該第4群を移動させて補正すると共に該第4群を移
動させてフォーカスを行い、該4つのレンズ群のうち少
なくとも1つのレンズ群に屈折率分布型レンズを設けて
おり、該第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とするとき 0.7 <|f2/fw|<0.9 ‥‥‥(7) 0.58< f3/f4 <0.837 ‥‥‥(8) なる条件を満足することを特徴としている。
According to a fourth aspect of the present invention, there is provided a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power.
A fourth lens group having a positive refractive power and a fourth lens group. The second lens group is moved to perform zooming, and the image plane fluctuation caused by zooming is corrected by moving the fourth lens group. At the same time, the fourth unit is moved to perform focusing, and at least one of the four lens units is provided with a refractive index distribution type lens. When the focal length of the system is fw, the following condition is satisfied: 0.7 <| f2 / fw | <0.9 | (7) 0.58 <f3 / f4 <0.837 ‥‥‥ (8) It is characterized by:

【0014】[0014]

【実施例】図1〜図4は本発明の数値実施例1〜4のレ
ンズ断面図である。図5〜図7は本発明の数値実施例1
の広角端、中間、望遠端の収差図である。図8〜図10
は本発明の数値実施例2の広角端、中間、望遠端の収差
図である。図11〜図13は本発明の数値実施例3の広
角端、中間、望遠端の収差図である。図14〜図16は
本発明の数値実施例4の広角端、中間、望遠端の収差図
である。
1 to 4 are sectional views of lenses according to numerical examples 1 to 4 of the present invention. 5 to 7 show Numerical Embodiment 1 of the present invention.
7 is an aberration diagram at a wide-angle end, a middle position, and a telephoto end. 8 to 10
FIG. 9 is an aberration diagram at a wide-angle end, a middle position, and a telephoto end in Numerical Example 2 of the present invention. 11 to 13 are aberration diagrams at the wide-angle end, a middle position, and a telephoto end according to Numerical Embodiment 3 of the present invention. 14 to 16 are aberration diagrams at the wide-angle end, at the middle, and at the telephoto end according to Numerical Embodiment 4 of the present invention.

【0015】図中L1は正の屈折力の第1群、L2は負
の屈折力の第2群、L3は正の屈折力の第3群、L4は
正の屈折力の第4群である。SPは開口絞りであり、第
3群L3の前方に配置している。Gはフェースプレート
等のガラス材である。FPは像面である。
In the drawing, 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 denotes an aperture stop, which is arranged in front of the third lens unit L3. G is a glass material such as a face plate. FP is an image plane.

【0016】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、変倍に伴な
う像面変動を第4群を移動させて補正している。
At the time of zooming from the wide-angle end to the telephoto end, the second lens unit is moved to the image plane side as indicated by an arrow, and the image plane fluctuation accompanying the zooming is corrected by moving the fourth lens unit. .

【0017】又、第4群を光軸上移動させてフォーカス
を行なうリヤーフォーカス式を採用している。同図に示
す第4群の実線の曲線4aと点線の曲線4bは各々無限
遠物体と近距離物体にフォーカスしているときの広角端
から望遠端への変倍に伴な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。
Also, a rear focus system is employed in which the fourth unit is moved on the optical axis to perform focusing. A solid line curve 4a and a dotted line curve 4b of the fourth lens group shown in the same figure are image planes during 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 fluctuation is shown. The first and third units are fixed during zooming and focusing.

【0018】本実施例においては第4群を移動させて変
倍に伴なう像面変動の補正を行なうと共に第4群を移動
させてフォーカスを行なうようにしている。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 lens unit is moved to correct the image plane fluctuation accompanying zooming, and the fourth lens unit is moved to perform focusing. In particular, as shown by curves 4a and 4b in the same figure, 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. Thereby, the space between the third and fourth units is effectively used, and the overall length of the lens is effectively reduced.

【0019】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なう場合は
同図の直線4cに示すように第4群を前方へ繰り出すこ
とにより行なっている。
In this embodiment, for example, when focusing from an object at infinity to an object at a short distance at the telephoto end, the fourth unit is moved forward as indicated by a straight line 4c in FIG.

【0020】そして図1の数値実施例1では従来より2
群3枚で構成した第1群を光軸と垂直方向に屈折率が変
化する材質より成るラジアル型の1枚の屈折率分布型レ
ンズを用いて構成している。これによりレンズ枚数の低
減を図り、レンズ全長の短縮化を図っている。
In the first numerical embodiment shown in FIG.
The first group, which is composed of three groups, is constructed using a single radial type gradient index lens made of a material whose refractive index changes in the direction perpendicular to the optical axis. As a result, the number of lenses is reduced, and the overall length of the lens is reduced.

【0021】特に第1群の屈折率分布型レンズは周辺に
いくに従って屈折率が低下すると共にd線とg線の屈折
率差が周辺にいくに従って大きくなるような分布が良
い。
In particular, the refractive index distribution type lens of the first group preferably has such a distribution that the refractive index decreases toward the periphery and the difference in the refractive index between the d-line and the g-line increases toward the periphery.

【0022】そしてレンズ枚数を少なくしたときにも良
好な光学性能を維持するためには屈折率分布型レンズを
次の条件式を満足するように構成するのが良い。
In order to maintain good optical performance even when the number of lenses is reduced, it is preferable to configure the gradient index lens so as to satisfy the following conditional expression.

【0023】 0.53<fT/(Nod 2 ・f1)<0.65 ‥‥‥‥(1)0.53 <fT / ( Nod 2 · f1) <0.65 ‥‥‥‥ (1)

【0024】[0024]

【数1】 尚、Nod,Nogは各々d線、g線の光軸上における屈折
率、N1d,N1gは各々d線、g線のレンズの有効径の7
5%の箇所における屈折率、f1,fTは第1群及び全
系の望遠端の焦点距離である。尚、本実施形態における
焦点距離は全て広角端の焦点距離を1として正規化して
いる為、以下で用いる焦点距離は無次元量となってい
る。
(Equation 1) Incidentally, N od, N og each d-line, the refractive index on the optical axis of the g-line, N 1d, N 1 g denote the d line, the effective diameter of the g-line of a lens 7
The refractive indices f1 and fT at the position of 5% are the focal lengths of the first group and the entire system at the telephoto end. Note that the focal lengths in this embodiment are all normalized with the focal length at the wide-angle end being 1, so that the focal lengths used below are dimensionless.

【0025】条件式(1)は第1群の屈折力を規定する
もので下限値を越えるとレンズ系全体で負のパッツバー
ル和が増大するので良くない。又上限値を越えると望遠
端で発生する球面収差等の補正が困難になってしまう。
Conditional expression (1) defines the refractive power of the first lens unit. If the lower limit is exceeded, the negative Patzval sum increases in the entire lens system, which is not good. If the upper limit is exceeded, it becomes difficult to correct spherical aberration and the like generated at the telephoto end.

【0026】条件式(2)は屈折率分布型レンズの屈折
率分布を適切に設定するものである。下限値を越えると
望遠端で軸上色収差が補正不足になってくる。逆に上限
値を越えると軸上色収差が補正過剰になってくるので良
くない。
Conditional expression (2) is for appropriately setting the refractive index distribution of the gradient index lens. If the lower limit value is exceeded, axial chromatic aberration will be undercorrected at the telephoto end. Conversely, if the value exceeds the upper limit, axial chromatic aberration will be overcorrected, which is not good.

【0027】図2の数値実施例2では第2群の貼り合わ
せレンズの負レンズにラジアル型の屈折率分布型レンズ
を用いて第2群の負の屈折力を所定の値に維持しつつ、
ペッツバール和の増大を防止している。即ち屈折率分布
型レンズで発生するペッツバール和Pはその内部の収斂
効果又は発散効果による屈折力(全系の焦点距離を1に
規格化したとき)をφ、ベースとなる屈折率をN0 とし
たとき P=φ/N0 2 となる。即ち屈折率N0 の2乗に反比例する。従って通
常のレンズのペッツバール和P=φ/Nに比べて小さく
なる。
In Numerical Embodiment 2 of FIG. 2, a radial type gradient index lens is used as the negative lens of the second group of cemented lenses, while maintaining the negative refractive power of the second group at a predetermined value.
This prevents the Petzval sum from increasing. That is, the Petzval sum P generated by the gradient index lens is φ, the refractive power (when the focal length of the entire system is normalized to 1) due to the convergence effect or divergence effect, and N 0 as the base refractive index. the P = φ / N 0 2 when. That is, it is inversely proportional to the square of the refractive index N 0 . Therefore, the sum is smaller than the Petzval sum P = φ / N of a normal lens.

【0028】これにより変倍に伴なう第2群の移動量を
少なくし、第1群との主点間隔を短くし、全変倍範囲に
わたり良好なる光学性能を維持しつつレンズ全長の短縮
化を図っている。又第1群を通る軸外光束の入射高を低
くし、第1群の有効径を小さくし、レンズ系全体の小型
軽量化を図っている。
As a result, the amount of movement of the second lens unit during zooming is reduced, the distance between principal points with the first lens unit is shortened, and the overall length of the lens is shortened while maintaining good optical performance over the entire zooming range. It is trying to make it. Further, the height of incidence of the off-axis light beam passing through the first group is reduced, the effective diameter of the first group is reduced, and the entire lens system is reduced in size and weight.

【0029】図3の数値実施例3では第3群をラジアル
型の1枚の屈折率分布型レンズで構成し、所定の正の屈
折力を確保しつつ球面収差とコマ収差を良好に補正しつ
つレンズ全長の短縮化を図っている。
In Numerical Example 3 shown in FIG. 3, the third lens unit is composed of a single radial type gradient index lens element, and corrects spherical aberration and coma well while securing a predetermined positive refractive power. While shortening the overall length of the lens.

【0030】従来、このレンズに非球面レンズを用いて
球面収差を補正しているものがあるが、ラジアルタイプ
の屈折率分布型レンズを用いることにより、同様の効果
があるだけでなく本ズームタイプの問題点であるパッツ
バール和がオーバーにいくのを抑えている。
Conventionally, there is a lens in which spherical aberration is corrected by using an aspherical lens. However, by using a radial type gradient index lens, not only the same effect is obtained but also this zoom type is used. The problem of Patzval, which is a problem, is suppressed from going over.

【0031】特に物体面側に凸の曲率を付けることによ
り、球面収差、コマ収差とペッツバール和をバランス良
く補正している。更に本実施例において良好な光学性能
を得る為には次の条件式を満足するのが良い。
In particular, by providing a convex curvature on the object surface side, spherical aberration, coma, and Petzval sum are corrected in a well-balanced manner. Further, in order to obtain good optical performance in this embodiment, it is preferable to satisfy the following conditional expression.

【0032】 0.65 <γ3,1 /f3<0.98 ‥‥‥‥(3) 0.002<ΔN7d/f3<0.006 ‥‥‥‥(4) γ3,1 は第3群の第1レンズ面の曲率半径、f3は第3
群の焦点距離、ΔN7dは第3群の屈折率分布型レンズの
最も屈折率の高い部分と最も低い部分のd線の屈折率差
である。
0.65 <γ 3,1 / f3 <0.98 ‥‥‥‥ (3) 0.002 <ΔN 7d /f3<0.006)(4) γ 3,1 is the third The radius of curvature of the first lens surface of the group, f3, is the third
The group focal length, ΔN 7d, is the refractive index difference between the d-line at the highest refractive index and the lowest at the lowest refractive index portion of the third group of gradient index lenses.

【0033】条件式(3)は第3群の第1レンズ面の曲
率半径に関するものであり、条件式(4)とも相互に関
係があり、ラジアルタイプの屈折率分布型レンズに曲率
を付けることにより、球面収差を良好に補正している。
The conditional expression (3) relates to the radius of curvature of the first lens surface of the third lens unit. The conditional expression (3) is also related to the conditional expression (4). Thus, spherical aberration is favorably corrected.

【0034】条件式(4)は第3群の屈折率分布型レン
ズの光軸に対する垂直方向の屈折率差に関するものであ
り、ペッツバール和の発生を抑えている。上限値を越え
るとペッツバール和が減少するが、第1レンズ面で発生
する球面収差とのバランスが保てなくなる。逆に下限値
を越えると正のペッツバール和が発生して好ましくな
い。
Conditional expression (4) relates to the refractive index difference in the direction perpendicular to the optical axis of the refractive index distribution type lens of the third group, and suppresses the occurrence of Petzval sum. If the value exceeds the upper limit, the Petzval sum decreases, but the balance with the spherical aberration generated on the first lens surface cannot be maintained. Conversely, if the value exceeds the lower limit, a positive Petzval sum is generated, which is not preferable.

【0035】図4の数値実施例4では従来より2〜3枚
で構成している正の屈折力の第4群をラジアル型の1枚
の屈折率分布型レンズで構成し、変倍に伴なう収差変動
を良好に補正しつつレンズ全長の短縮化を図っている。
In Numerical Example 4 shown in FIG. 4, the fourth unit having a positive refractive power, which is composed of two or three lenses in comparison with the prior art, is composed of one radial type gradient index lens element. The overall length of the lens is shortened while favorably correcting aberration fluctuations.

【0036】特に第4群は変倍に伴なう像面変動を補正
するように移動させると共に、該第4群を移動させて合
焦を行なうので第3群とある程度の空気間隔をあけなけ
ればならない。この為、該第4群のレンズ構成枚数が削
減することは厚さが減少し、レンズ全長を短縮するのに
有効である。又該第4群のレンズ重量が軽くなるので、
該第4群を移動する為のモーター等のアクチュエーター
のトルクが軽減されたり消費電力が少なくなりレンズシ
ステムとしても大変有効である。
In particular, since the fourth lens unit is moved so as to correct the image plane fluctuation accompanying zooming, and the fourth lens unit is moved to perform focusing, a certain air gap must be provided between the third lens unit and the third lens unit. Must. Therefore, reducing the number of lenses constituting the fourth group is effective in reducing the thickness and shortening the overall length of the lens. Also, since the lens weight of the fourth group is reduced,
The torque of an actuator such as a motor for moving the fourth unit is reduced or the power consumption is reduced, which is very effective as a lens system.

【0037】又、本実施例においてレンズ枚数削減時に
も良好な光学性能を維持する為には、次の条件式を満足
するのが良い。
In this embodiment, in order to maintain good optical performance even when the number of lenses is reduced, it is preferable to satisfy the following conditional expression.

【0038】 0.04<fw/(Nod 2 ・f4)<0.31 ‥‥‥‥(5)0.04 <fw / ( Nod 2 · f4) <0.31 ‥‥‥‥ (5)

【0039】[0039]

【数2】 f4は第4群の焦点距離、fwは全系の広角端の焦点距
離である。
(Equation 2) f4 is the focal length of the fourth lens unit, and fw is the focal length of the entire system at the wide-angle end.

【0040】条件式(5)は第4群の屈折力とレンズの
屈折率に関するものである。下限値を越えると第4群の
焦点距離が長くなると該第4群の移動量が大きくなり、
レンズ系の小型化が困難になる。逆に上限値を越えて第
4群の焦点距離が短くなるとペッツバール和が増大し、
像面がアンダーになる。
Conditional expression (5) relates to the refractive power of the fourth lens unit and the refractive index of the lens. When the lower limit value is exceeded, when the focal length of the fourth unit increases, the amount of movement of the fourth unit increases,
It becomes difficult to reduce the size of the lens system. Conversely, when the focal length of the fourth lens group becomes shorter than the upper limit, the Petzval sum increases,
The image plane becomes under.

【0041】条件式(6)は屈折率分布型レンズの屈折
率分布に関し、第4群で発生する軸上色収差と倍率色収
差をバランス良く補正している。又該第4群は像面側に
凸面を向けた正のメニスカス形状にすることによりレン
ズの屈折率分布と関係して非点収差を良好に補正してい
る。
Conditional expression (6) relates to the refractive index distribution of the refractive index distribution type lens and corrects axial chromatic aberration and chromatic aberration of magnification occurring in the fourth lens unit in a well-balanced manner. The fourth lens unit has a positive meniscus shape with the convex surface facing the image surface side, so that astigmatism is favorably corrected in relation to the refractive index distribution of the lens.

【0042】本実施例では従来の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なう場合に比べ
て前述のような屈折率分布型レンズを用いると共にリヤ
ーフォーカス方式を採ることにより第1群のレンズ有効
径の増大化を効果的に防止している。
In this embodiment, as compared with a conventional four-unit zoom lens in which focusing is performed by extending the first unit, the refractive index distribution type lens as described above and the rear focus method are employed to achieve the first group. This effectively prevents the effective diameter of the lens from increasing.

【0043】又、開口絞りを第3群の直前に配置するこ
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
玉レンズ径の縮少化を容易に達成している。
Also, by disposing the aperture stop immediately before the third lens unit, aberration fluctuation due to the movable lens unit is reduced, and the distance between the lens units in front of the aperture stop is shortened, thereby reducing the diameter of the front lens. Is easily achieved.

【0044】本実施例では以上のようにして各要素を構
成することにより全変倍範囲にわたり更に物体距離全般
にわたり良好なる光学性能を有した高変倍比のズームレ
ンズを得ている。
In this embodiment, by configuring each element as described above, a zoom lens having a high zoom ratio having good optical performance over the entire zoom range and over the entire object distance is obtained.

【0045】又、本発明において全変倍範囲にわたり収
差変動を補正し良好なる光学性能を得る為に、前記第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とするとき 0.7 <|f2/fw|<0.9 ‥‥‥(7) 0.58< f3/f4 <0.837‥‥(8) なる条件を満足するようにしている。
In the present invention, in order to correct aberration fluctuations over the entire zoom range and obtain good optical performance, the i-th lens is used.
When the focal length of the group is fi and the focal length of the entire system at the wide-angle end is fw, 0.7 <| f2 / fw | <0.9 (7) 0.58 <f3 / f4 <0.837 ‥‥ (8) The following condition is satisfied.

【0046】条件式(7)は第2群の屈折力に関し、変
倍に伴なう収差変動を少なくしつつ所定の変倍比を効果
的に得る為のものである。下限値を越えて第2群の屈折
力が強くなりすぎるとレンズ系全体の小型化は容易とな
るが、ペッツバール和が負の方向に増大し像面湾曲が大
きくなると共に変倍に伴なう収差変動が大きくなってく
る。
Conditional expression (7) is for effectively obtaining a predetermined zoom ratio while reducing aberration fluctuations caused by zooming with respect to the refractive power of the second lens unit. If the refractive power of the second lens unit becomes too strong beyond the lower limit, miniaturization of the entire lens system is facilitated, but the Petzval sum increases in the negative direction, field curvature increases, and zooming occurs. Aberration fluctuation increases.

【0047】又、上限値を越えて第2群の屈折力が弱く
なりすぎると変倍に伴なう収差変動は少なくなるが所定
の変倍比を得る為の第2群の移動量が増大し、レンズ全
長が長くなってくるので良くない。
If the refractive power of the second lens unit is excessively weakened beyond the upper limit, the fluctuation of aberration due to zooming decreases, but the amount of movement of the second lens unit for obtaining a predetermined zoom ratio increases. Also, the overall length of the lens becomes longer, which is not good.

【0048】条件式(8)は第3群と第4群の屈折力の
比に関し、第3群から像面までの距離を短縮しつつ、所
定の光学性能を得るためのものである。条件式(8)の
下限値を越えて第3群の屈折力が強くなりすぎると広角
端からズーム中間にかけて球面収差やコマ収差の補正が
困難になり、又所定のバックフォーカスが得られなくな
ってくるので良くない。
Conditional expression (8) relates to the ratio of the refractive power of the third lens unit to that of the fourth lens unit, and is intended to obtain a predetermined optical performance while reducing the distance from the third lens unit to the image plane. If the lower limit of conditional expression (8) is exceeded and the refractive power of the third lens unit becomes too strong, it becomes difficult to correct spherical aberration and coma from the wide-angle end to the middle of the zoom, and a predetermined back focus cannot be obtained. Not good because it comes.

【0049】逆に条件式(8)の上限値を越えて第3群
の屈折力が弱くなりすぎるとレンズ全長の短縮化が十分
に達成されないので良くない。
Conversely, if the upper limit of conditional expression (8) is exceeded and the refractive power of the third lens unit becomes too weak, the overall length of the lens will not be sufficiently reduced, which is not good.

【0050】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.

【0051】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、
A,B,C,D,Eを各々非球面係数としたとき
The aspheric surface 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, R is a paraxial radius of curvature,
When A, B, C, D, and E are each aspheric coefficients

【0052】[0052]

【数3】 なる式で表わしている。又表−1に各数値実施例におけ
る各条件式との関係を示す。
(Equation 3) It is represented by the following equation. Table 1 shows the relationship with each conditional expression in each numerical example.

【0053】又、屈折率分布型レンズの屈折率分布は光
軸から垂直方向の高さhに応じて変化するものであり、
高さhにおける屈折率をN(h)としたとき N(h)=N0 +N12 +N24 +N36 +N4
8 +‥‥なる式を用いて表わしている。 数値実施例 1 F=1〜5.70 FNO=1:1.85 〜2.65 2ω= 56.0°〜10.6° R 1= 2.608 D 1= 0.715 N 1= (h) R 2= -39.624 D 2= 可変 R 3= 6.473 D 3= 0.083 N 2=1.88300 ν 2= 40.8 R 4= 0.765 D 4= 0.391 R 5= -1.346 D 5= 0.083 N 3=1.51742 ν 3= 52.4 R 6= 1.126 D 6= 0.282 N 4=1.84666 ν 4= 23.8 R 7= 18.137 D 7= 可変 R 8= 絞り D 8= 0.20 R 9= 非球面 D 9= 0.482 N 5=1.58913 ν 5= 61.2 R10= -9.928 D10= 可変 R11= 2.755 D11= 0.083 N 6=1.84666 ν 6= 23.8 R12= 1.208 D12= 0.032 R13= 1.375 D13= 0.624 N 7=1.58913 ν 7= 61.2 R14= 非球面 D14= 0.831 R15= ∞ D15= 1.081 N 8=1.51633 ν 8= 64.1 R16= ∞ R15,R16はフェースプレート等のフィルターである。
The refractive index distribution of the gradient index lens changes according to the height h in the vertical direction from the optical axis.
When the refractive index in the height h and the N (h) N (h) = N 0 + N 1 h 2 + N 2 h 4 + N 3 h 6 + N 4
h 8 + ‥‥. Numerical Example 1 F = 1 to 5.70 FNO = 1: 1.85 to 2.65 2ω = 56.0 ° to 10.6 ° R 1 = 2.608 D 1 = 0.715 N 1 = (h) R 2 = -39.624 D 2 = Variable R 3 = 6.473 D 3 = 0.083 N 2 = 1.88300 ν 2 = 40.8 R 4 = 0.765 D 4 = 0.391 R 5 = -1.346 D 5 = 0.083 N 3 = 1.51742 ν 3 = 52.4 R 6 = 1.126 D 6 = 0.282 N 4 = 1.84666 ν 4 = 23.8 R 7 = 18.137 D 7 = Variable R 8 = Aperture D 8 = 0.20 R 9 = Aspherical surface D 9 = 0.482 N 5 = 1.58913 ν 5 = 61.2 R10 = -9.928 D10 = Variable R11 = 2.755 D11 = 0.083 N 6 = 1.84666 ν 6 = 23.8 R12 = 1.208 D12 = 0.032 R13 = 1.375 D13 = 0.624 N 7 = 1.58913 ν 7 = 61.2 R14 = Aspherical surface D14 = 0.831 R15 = ∞ D15 = 1.081 N 8 = 1.51633 ν 8 = 64.1 R16 = ∞ R15 and R16 are filters such as a face plate.

【0054】[0054]

【表1】 R 9:非球面 R0 = 1.917 B= -4.248 ×10-2 C = -6.468 ×10-3 D= -5.306 ×10-3 R14:非球面 R0 = -2.045 B= 1.140 ×10-2 C = -6.871 ×10-3 D= -5.809 ×10-2 [Table 1] R 9: aspheric R 0 = 1.917 B = -4.248 × 10 -2 C = -6.468 × 10 -3 D = -5.306 × 10 -3 R14: aspheric R 0 = -2.045 B = 1.140 × 10 -2 C = -6.871 × 10 -3 D = -5.809 × 10 -2

【0055】[0055]

【表2】 数値実施例 2 F=1〜5.69 FNO=1:1.85 〜2.65 2ω= 53.8°〜10.2° R 1= 8.104 D 1= 0.134 N 1=1.80518 ν 1= 25.4 R 2= 2.485 D 2= 0.555 N 2=1.60311 ν 2= 60.7 R 3= -15.459 D 3= 0.031 R 4= 2.345 D 4= 0.341 N 3=1.80400 ν 3= 46.6 R 5= 8.535 D 5= 可変 R 6= 4.430 D 6= 0.079 N 4=1.88300 ν 4= 40.8 R 7= 0.799 D 7= 0.381 R 8= -1.034 D 8= 0.079 N 5= (h) R 9= 1.107 D 9= 0.269 N 6=1.84666 ν 6= 23.8 R10= 10.856 D10= 可変 R11= 絞り D11= 0.19 R12= 非球面 D12= 0.460 N 7=1.58313 ν 7= 59.4 R13= -8.244 D13= 可変 R14= 2.788 D14= 0.079 N 8=1.84666 ν 8= 23.8 R15= 1.090 D15= 0.034 R16= 1.220 D16= 0.595 N 9=1.58313 ν 9= 59.4 R17= 非球面 D17= 0.793 R18= ∞ D18= 1.031 N10=1.51633 ν10= 64.1 R19= ∞ R18,R19はフェースプレート等のフィルターである。[Table 2] Numerical example 2 F = 1 to 5.69 FNO = 1: 1.85 to 2.65 2ω = 53.8 ° to 10.2 ° R 1 = 8.104 D 1 = 0.134 N 1 = 1.80518 ν 1 = 25.4 R 2 = 2.485 D 2 = 0.555 N 2 = 1.60311 ν 2 = 60.7 R 3 = -15.459 D 3 = 0.031 R 4 = 2.345 D 4 = 0.341 N 3 = 1.80400 ν 3 = 46.6 R 5 = 8.535 D 5 = Variable R 6 = 4.430 D 6 = 0.079 N 4 = 1.88300 ν 4 = 40.8 R 7 = 0.799 D 7 = 0.381 R 8 = -1.034 D 8 = 0.079 N 5 = (h) R 9 = 1.107 D 9 = 0.269 N 6 = 1.84666 ν 6 = 23.8 R10 = 10.856 D10 = Variable R11 = Aperture D11 = 0.19 R12 = Aspherical surface D12 = 0.460 N 7 = 1.58313 ν 7 = 59.4 R13 = -8.244 D13 = Variable R14 = 2.788 D14 = 0.079 N 8 = 1.84666 ν 8 = 23.8 R15 = 1.090 D15 = 0.034 R16 = 1.220 D16 = 0.595 N 9 = 1.58313 ν 9 = 59.4 R17 = Aspherical surface D17 = 0.793 R18 = ∞ D18 = 1.031 N10 = 1.51633 ν10 = 64.1 R19 = ∞ R18 and R19 are filters such as a face plate.

【0056】[0056]

【表3】 R12:非球面 R0 = 1.684 B= -5.581 ×10-2 C = -3.566 ×10-3 D= -8.379 ×10-3 R17:非球面 R0 = -2.003 B= 1.480 ×10-3 C = 2.480 ×10-2 D= -1.284 ×10-1 [Table 3] R12: aspheric R 0 = 1.684 B = -5.581 × 10 -2 C = -3.566 × 10 -3 D = -8.379 × 10 -3 R17: aspheric R 0 = -2.003 B = 1.480 × 10 -3 C = 2.480 × 10 -2 D = -1.284 × 10 -1

【0057】[0057]

【表4】 F=1〜5.7 FNO=1:1.85 〜2.61 2ω= 56.1°〜10.7° R 1= 8.413 D 1= 0.141 N 1=1.80518 ν 1= 25.4 R 2= 2.710 D 2= 0.582 N 2=1.60311 ν 2= 60.7 R 3= -15.678 D 3= 0.033 R 4= 2.416 D 4= 0.357 N 3=1.80400 ν 3= 46.6 R 5= 8.039 D 5= 可変 R 6= 9.604 D 6= 0.083 N 4=1.88300 ν 4= 40.8 R 7= 0.799 D 7= 0.379 R 8= -1.222 D 8= 0.083 N 5=1.51742 ν 5= 52.4 R 9= 1.222 D 9= 0.282 N 6=1.84666 ν 6= 23.8 R10=-232.481 D10= 可変 R11= 絞り D11= 0.199 R12= 1.950 D12= 0.416 N 7= (h) R13= -23.935 D13= 可変 R14= 2.806 D14= 0.083 N 8=1.84666 ν 8= 23.8 R15= 1.100 D15= 0.031 R16= 1.255 D16= 0.624 N 9=1.58313 ν 9= 59.4 R17= 非球面 D17= 0.831 R18= ∞ D18= 1.081 N10=1.51633 ν10= 64.2 R19= ∞ R18,R19はフェースプレート等のフィルターである。[Table 4] F = 1〜5.7 FNO = 1: 1.85 〜2.61 2ω = 56.1 ° 〜10.7 ° R 1 = 8.413 D 1 = 0.141 N 1 = 1.80518 ν 1 = 25.4 R 2 = 2.710 D 2 = 0.582 N 2 = 1.60311 ν 2 = 60.7 R 3 = -15.678 D 3 = 0.033 R 4 = 2.416 D 4 = 0.357 N 3 = 1.80400 ν 3 = 46.6 R 5 = 8.039 D 5 = Variable R 6 = 9.604 D 6 = 0.083 N 4 = 1.88300 ν 4 = 40.8 R 7 = 0.799 D 7 = 0.379 R 8 = -1.222 D 8 = 0.083 N 5 = 1.51742 ν 5 = 52.4 R 9 = 1.222 D 9 = 0.282 N 6 = 1.84666 ν 6 = 23.8 R10 = -232.481 D10 = Variable R11 = Aperture D11 = 0.199 R12 = 1.950 D12 = 0.416 N 7 = (h) R13 = -23.935 D13 = Variable R14 = 2.806 D14 = 0.083 N 8 = 1.84666 ν 8 = 23.8 R15 = 1.100 D15 = 0.031 R16 = 1.255 D16 = 0.624 N 9 = 1.58313 ν 9 = 59.4 R17 = Aspherical surface D17 = 0.831 R18 = ∞ D18 = 1.081 N10 = 1.51633 ν10 = 64.2 R19 = ∞ R18 and R19 are filters such as a face plate.

【0058】物体距離が無限遠時の間隔Interval when the object distance is infinity

【0059】[0059]

【表5】 R17:非球面 R = -2.191 A = 0 B= -5.442 ×10-3 C = 7.177 ×10-3 D= -1.112 ×10-1 [Table 5] R17: aspheric surface R = −2.191 A = 0 B = −5.442 × 10 −3 C = 7.177 × 10 −3 D = −1.112 × 10 −1

【0060】[0060]

【表6】 数値実施例 4 F=1〜5.7 FNO=1:1.85 〜2.65 2ω= 56.1°〜10.7° R 1= 5.755 D 1= 0.141 N 1=1.80518 ν 1= 25.4 R 2= 2.204 D 2= 0.582 N 2=1.60311 ν 2= 60.7 R 3= 73.270 D 3= 0.033 R 4= 2.376 D 4= 0.357 N 3=1.80400 ν 3= 46.6 R 5= 9.817 D 5= 可変 R 6= 5.639 D 6= 0.083 N 4=1.88300 ν 4= 40.8 R 7= 0.740 D 7= 0.394 R 8= -1.168 D 8= 0.083 N 5=1.51742 ν 5= 52.4 R 9= 1.169 D 9= 0.282 N 6=1.84666 ν 6= 23.8 R10= -37.983 D10= 可変 R11= 絞り D11= 0.199 R12= 非球面 D12= 0.482 N 7=1.58313 ν 7= 59.4 R13= -7.850 D13= 可変 R14= -3.626 D14= 0.332 N 8= (h) R15= -1.723 D15= 0.831 R16= ∞ D16= 1.081 N 9=1.51633 ν 9= 64.2 R17= ∞ R16,R17はフェースプレート等のフィルターである。[Table 6] Numerical example 4 F = 1 to 5.7 FNO = 1: 1.85 to 2.65 2ω = 56.1 ° to 10.7 ° R 1 = 5.755 D 1 = 0.141 N 1 = 1.80518 ν 1 = 25.4 R 2 = 2.204 D 2 = 0.582 N 2 = 1.60311 ν 2 = 60.7 R 3 = 73.270 D 3 = 0.033 R 4 = 2.376 D 4 = 0.357 N 3 = 1.80400 ν 3 = 46.6 R 5 = 9.817 D 5 = Variable R 6 = 5.639 D 6 = 0.083 N 4 = 1.88300 ν 4 = 40.8 R 7 = 0.740 D 7 = 0.394 R 8 = -1.168 D 8 = 0.083 N 5 = 1.51742 ν 5 = 52.4 R 9 = 1.169 D 9 = 0.282 N 6 = 1.84666 ν 6 = 23.8 R10 = -37.983 D10 = Variable R11 = Aperture D11 = 0.199 R12 = Aspherical surface D12 = 0.482 N 7 = 1.58313 ν 7 = 59.4 R13 = -7.850 D13 = Variable R14 = -3.626 D14 = 0.332 N 8 = (h) R15 = -1.723 D15 = 0.831 R16 = ∞ D16 = 1.081 N 9 = 1.551633 ν 9 = 64.2 R17 = ∞ R16 and R17 are filters such as a face plate.

【0061】物体距離が無限遠時の間隔Interval when the object distance is infinity

【0062】[0062]

【表7】 R12:非球面 R = 1.962 A = 0 B= -5.064 ×10-2 C = 5.536 ×10-3 D= -8.944 ×10-3 [Table 7] R12: aspheric surface R = 1.962 A = 0 B = -5.064 × 10 -2 C = 5.536 × 10 -3 D = -8.944 × 10 -3

【0063】[0063]

【表8】 (表−1)[Table 8] (Table-1)

【0064】[0064]

【表9】 [Table 9]

【0065】[0065]

【発明の効果】本発明によれば以上のように所定の屈折
力を有する4つのレンズ群より成るズームレンズにおい
て、非球面の代わりに又は非球面と共に連続的に屈折率
が変化する材質より成る屈折率分布型レンズを用い、か
つリヤーフォーカス方式を採用することにより、レンズ
系全体の小型化を図りつつ、高変倍比が容易に得られ、
しかも全変倍範囲にわたり良好なる光学性能が得られる
屈折率分布型レンズ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, as described above, a zoom lens comprising four lens groups having a predetermined refractive power is made of a material whose refractive index changes continuously instead of or together with an aspheric surface. By using a refractive index distribution type lens and adopting a rear focus method, a high zoom ratio can be easily obtained while miniaturizing the entire lens system,
Moreover, it is possible to achieve a rear focus type zoom lens having a refractive index distribution type lens capable of obtaining good optical performance over the entire zoom range.

【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1の広角端の収差図FIG. 5 is an aberration diagram at a wide-angle end according to Numerical Embodiment 1 of the present invention.

【図6】 本発明の数値実施例1の中間の収差図FIG. 6 is an intermediate aberration diagram of the numerical example 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の中間の収差図FIG. 9 is an intermediate aberration diagram of the numerical example 2 of the present invention.

【図10】 本発明の数値実施例2の望遠端の収差図FIG. 10 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

【図11】 本発明の数値実施例3の広角端の収差図FIG. 11 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

【図12】 本発明の数値実施例3の中間の収差図FIG. 12 is an intermediate aberration diagram of the numerical example 3 of the present invention.

【図13】 本発明の数値実施例3の望遠端の収差図FIG. 13 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

【図14】 本発明の数値実施例4の広角端の収差図FIG. 14 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

【図15】 本発明の数値実施例4の中間の収差図FIG. 15 is an intermediate aberration diagram of the numerical example 4 of the present invention.

【図16】 本発明の数値実施例4の望遠端の収差図FIG. 16 is an aberration diagram at a telephoto end in Numerical Example 4 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 開口絞り G ガラス材 FP 像面 L1 First group L2 Second group L3 Third group L4 Fourth group SP Aperture stop G Glass material FP Image plane

───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平3−33710(JP,A) 特開 平2−287415(JP,A) 特開 平2−53017(JP,A) 特開 平2−48621(JP,A) 特開 平2−48620(JP,A) 特開 平2−39011(JP,A) 特開 平2−12118(JP,A) 特開 昭64−68709(JP,A) 特開 昭63−123009(JP,A) 特開 昭63−29719(JP,A) 特開 昭63−29718(JP,A) 特開 昭58−193512(JP,A) 特開 平2−55308(JP,A) 特開 昭63−81215(JP,A) 特開 昭62−24213(JP,A) 特開 昭58−160913(JP,A) 特開 昭62−247316(JP,A) 特開 平4−104114(JP,A) 特開 平4−343313(JP,A) 特開 平4−317018(JP,A) 特開 平4−310910(JP,A) 特開 平4−296809(JP,A) 特開 平4−242708(JP,A) 特開 平4−242707(JP,A) 特開 平4−171411(JP,A) 特開 平4−153615(JP,A) 特開 平4−5609(JP,A) 特開 平3−296706(JP,A) (58)調査した分野(Int.Cl.6,DB名) G02B 9/00 - 17/08 G02B 21/02 - 21/04 G02B 25/00 - 25/04 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-33710 (JP, A) JP-A-2-287415 (JP, A) JP-A-2-53017 (JP, A) JP-A-2-302 48621 (JP, A) JP-A-2-48620 (JP, A) JP-A-2-39011 (JP, A) JP-A-2-12118 (JP, A) JP-A-64-68709 (JP, A) JP-A-63-123009 (JP, A) JP-A-63-29719 (JP, A) JP-A-63-29718 (JP, A) JP-A-58-193512 (JP, A) JP-A-2-55308 (JP, A) JP-A-63-81215 (JP, A) JP-A-62-24213 (JP, A) JP-A-58-160913 (JP, A) JP-A-62-247316 (JP, A) JP-A-4-104114 (JP, A) JP-A-4-343313 (JP, A) JP-A-4-317018 (JP, A) JP-A-4-310910 (JP A) JP-A-4-296809 (JP, A) JP-A-4-242708 (JP, A) JP-A-4-242707 (JP, A) JP-A-4-171411 (JP, A) JP-A-4 -153615 (JP, A) JP-A-4-5609 (JP, A) JP-A-3-296706 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) G02B 9/00- 17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (4)

(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、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、該第2群を移動
させて変倍を行い変倍に伴う像面変動を該第4群を移動
させて補正すると共に該第4群を移動させてフォーカス
を行い、第1群は周辺部にいくに従って屈折率が低下す
る材質より成るラジアル型の1枚の屈折率分布型レンズ
より成り、Nod,Nogを各々d線,g線の光軸上におけ
る屈折率、N1d,N1gを各々d線,g線のレンズの有効
径の75%の箇所における屈折率、f1,fTを第1群
及び全系の望遠端の焦点距離としたとき、 0.53<fT/(Nod 2・f1)<0.65 【数1】 を満足することを特徴とする屈折率分布型レンズを有し
たリヤーフォーカス式のズームレンズ。
1. A first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power. The second lens unit is moved to perform zooming, and the image plane variation caused by zooming is corrected by moving the fourth lens unit, and the fourth lens unit is moved to perform focusing. Is composed of one radial type gradient index lens made of a material whose refractive index decreases toward the periphery, and N od and N og are the refractive indices on the optical axis of d-line and g-line, respectively, N 1d , N 1g are the refractive indices at 75% of the effective diameter of the d-line and g-line lenses, respectively, and f1 and fT are the focal lengths of the first group and the telephoto end of the entire system. (N od 2 · f1) < 0.65 [number 1] A rear focus type zoom lens having a gradient index lens which satisfies the following.
【請求項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、そして正の屈
折力の第4群の4つのレンズ群を有し、該第2群を移動
させて変倍を行い変倍に伴う像面変動を該第4群を移動
させて補正すると共に該第4群を移動させてフォーカス
を行い、該第3群はラジアル型の1枚の屈折率分布型レ
ンズより成り、全系の広角端の焦点距離を1としたと
き、γ3,1を第3群の第1レンズ面の曲率半径、f3を
第3群の焦点距離、ΔN7dを第3群の屈折率分布型レン
ズの最も屈折率の高い部分と最も低い部分のd線の屈折
率差とし、 0.65<γ3,1/f3<0.98 0.002<ΔN7d/f3<0.006 を満足することを特徴とする屈折率分布型レンズを有し
たリヤーフォーカス式のズームレンズ。
2. Four lens groups of 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, in this order from the object side. The second unit is moved to perform zooming, and the image plane fluctuation caused by zooming is corrected by moving the fourth unit, and the fourth unit is moved to perform focusing. The group consists of a single radial type gradient index lens element. When the focal length at the wide-angle end of the entire system is 1, γ 3,1 is the radius of curvature of the first lens surface of the third group, and f3 is the third. The focal length of the third group, ΔN 7d , is defined as the difference between the refractive index of the d-line of the highest refractive index and the refractive index of the lowest part of the gradient index lens of the third group, 0.65 <γ 3,1 / f3 <0 .98 0.002 <ΔN 7d /f3<0.006. A rear focus type zoom lens having a refractive index distribution type lens, characterized by satisfying the following condition.
【請求項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、そして正の屈
折力の第4群の4つのレンズ群を有し、該第2群を移動
させて変倍を行い変倍に伴う像面変動を該第4群を移動
させて補正すると共に該第4群を移動させてフォーカス
を行い、該第4群はラジアル型の1枚の屈折率分布型レ
ンズより成り、Nod,Nogを各々d線,g線の光軸上に
おける屈折率、N1d,N1gを各々d線,g線のレンズの
有効径の75%の箇所における屈折率、f4を第4群の
焦点距離、fwを全系の広角端の焦点距離としたとき、 0.04<fw/(Nod 2・f4)<0.31 【数2】 を満足することを特徴とする屈折率分布型レンズを有し
たリヤーフォーカス式のズームレンズ。
3. Four lens groups of 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 are arranged in this order from the object side. The second unit is moved to perform zooming, and the image plane variation accompanying the zooming is corrected by moving the fourth unit, and the fourth unit is moved to perform focusing. group consists of one gradient index lens radial type, N od, each d line N og, refractive index on the optical axis of the g-line, N 1d, each d line N 1 g, g-line of a lens refractive index at 75% point of the effective diameter of the focal length of the f4 fourth group, when the focal length at the wide angle end of the entire system fw, 0.04 <fw / (N od 2 · f4) <0 .31 A rear focus type zoom lens having a gradient index lens which satisfies the following.
【請求項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、そして正の屈
折力の第4群の4つのレンズ群を有し、該第2群を移動
させて変倍を行い変倍に伴う像面変動を該第4群を移動
させて補正すると共に該第4群を移動させてフォーカス
を行い、該4つのレンズ群のうち少なくとも1つのレン
ズ群に屈折率分布型レンズを設けており、該第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
するとき 0.7 <|f2/fw|<0.9 0.58< f3/f4 <0.837 なる条件を満足することを特徴とする屈折率分布型レン
ズを有したリヤーフォーカス式のズームレンズ。
4. Four lens groups of 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, in this order from the object side. The second lens unit is moved to perform zooming, and the image plane variation accompanying zooming is corrected by moving the fourth lens unit, and the fourth lens unit is moved to perform focusing. When at least one of the lens units has a gradient index lens, and the focal length of the i-th unit is fi and the focal length of the entire system at the wide-angle end is fw, 0.7 <| f2 / fw | <0.9 0.58 <f3 / f4 <0.837 A rear focus type zoom lens having a gradient index lens, characterized by satisfying the following condition.
JP3174391A 1990-02-08 1991-06-19 Rear focus type zoom lens with gradient index lens Expired - Fee Related JP2970083B2 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP3174391A JP2970083B2 (en) 1991-06-19 1991-06-19 Rear focus type zoom lens with gradient index lens
US07/899,375 US5321552A (en) 1990-02-08 1992-06-16 Rear-focus-type zoom lens equipped with index-distribution-type lens

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP3174391A JP2970083B2 (en) 1991-06-19 1991-06-19 Rear focus type zoom lens with gradient index lens

Publications (2)

Publication Number Publication Date
JPH04369611A JPH04369611A (en) 1992-12-22
JP2970083B2 true JP2970083B2 (en) 1999-11-02

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Family Applications (1)

Application Number Title Priority Date Filing Date
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Country Link
JP (1) JP2970083B2 (en)

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Publication number Priority date Publication date Assignee Title
JPH1195101A (en) 1997-09-22 1999-04-09 Minolta Co Ltd Zoom lens

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JPH04369611A (en) 1992-12-22

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