JP2004333768A - Zoom lens and imaging device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a zoom lens which is suitable to a camera using a solid-state imaging element by excellently correcting a chromatic aberration over the entire power variation range from a wide-angle end to a telephoto end. <P>SOLUTION: The zoom lens has a 1st lens group L1 with positive refracting power, a 2nd lens group L2 with negative refracting power, and a 3rd lens group L3 with positive refracting power in this order from the object side; and the gap between the 1st lens group L1 and 2nd lens group L2 is larger at the telephoto end than at the wide-angle end, and the gap between the 2nd lens group L2 and 3rd lens group L3 is smaller. At least one positive lens that the 3rd lens group L3 includes satisfies a conditional expressions of νd>90 and Θg, F>0.530, where νd is the Abbe number of its material and Θg, F is the partial dispersion ratio. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５２】
【数２】

【００５３】
とおいたとき、
該第３レンズ群の少なくとも一つの正レンズは、
νｄ＞８０ ・・・・（１）
Θｇ，Ｆ＞０．５３０ ・・・・（２）
の条件式を満足している。
【００５４】
条件式（１）、（２）は望遠側のズーム位置での軸上色収差の二次スペクトルの補正を良好に行うための条件式である。望遠側のズーム位置での軸上色収差に対し一次の色消しがなされている状態では一般的にｇ線等の短波長側にて補正過剰となり、基準波長のピント位置に対し短波長のピント位置はオーバー傾向となる。一般にあるガラス媒質においては短波長ほど屈折率が高くなる傾向があるため、短波長側における屈折率が高くなる度合いがより強い材料を正レンズに用いれば、基準波長に対する短波長のピントのオーバー傾向が低減される。よって部分分散比Θｇ，Ｆが大きい場合、すなわち主分散（ＮＦ−ＮＣ）に対して（Ｎｇ−ＮＦ）が大きい場合、Ｆ線とＣ線の屈折率差を基準としたときにＦ線とｇ線の屈折率差が大きいことを意味している。部分分散比Θｇ，Ｆが大きいガラスを正レンズに用いるとｇ線のピントのオーバー傾向が低減されることになる。よって条件式（１）を満たす低分散域においては条件式（２）を満たす部分分散比にて短波長におけるピントを基準波長のピント位置に近づけられる効果が高く二次スペクトルが低減される。条件式（１）、（２）の範囲外ではこのような異常分散特性が不十分なため二次スペクトルの補正が不足となる。
【００５５】
また各実施形態のズームレンズは条件式（１）においてさらに以下限定を加えるとより二次スペクトルの補正効果が高まる。
【００５６】
νｄ＞９０ ・・・・（３）
図２２はアッベ数νｄと部分分散比Θｇ，Ｆの関係を示したグラフである。図２２において点Ａは株式会社オハラ社製の商品名ＰＢＭ２（νｄ＝３６．２６、Θｇ，Ｆ＝０．５８２８）、点Ｂは株式会社オハラ社製の商品名ＮＳＬ７（νｄ＝６０．４９、Θｇ，Ｆ＝０．５４３６）を示す。点Ａ，点Ｂを結んだ線を基準線とすると、光学ガラスの分布としては大まかにはアッベ数νｄが３５程度より小さい高分散ガラスは基準線より上側に、アッベ数νｄが３５から６５程度までの低分散ガラスは基準線より下側に位置するものが多く、アッベ数νｄが６０以上にて基準線より上側に位置する異常分散性ガラスが存在している。低分散ガラスに関しては基準線より上側に位置するものを使用するのが二次スペクトルの補正に対し効果的であり基準線から離れるほど補正効果が高まる。条件式（１）をさらに条件式（３）に限定すると図２２における基準線からより大きく上側に離れた範囲にガラスを限定するため二次スペクトルの補正効果がより高まることになる。
◎第３レンズ群Ｌ３の正レンズのうち最もアッベ数の大きい性レンズの焦点距離をｆ３ａ、該第３レンズＬ３の焦点距離をｆ３、望遠端における全系の焦点距離をｆｔとするとき、
１．０＜ｆ３ａ／ｆ３＜３．０ ・・・・（４）
０．３＜ｆ３／ｆｔ＜０．５ ・・・・（５）
の条件式を満足している。
【００５７】
条件式（４）は第３レンズ群Ｌ３を構成する異常分散性を有する正レンズの屈折力を規定する式である。上限を超えて該正レンズの屈折力が弱すぎると異常分散性により二次スペクトルを低減する効果が弱まるため良くない。各実施形態のズームレンズではある程度の屈折力を異常分散性ガラスのレンズに持たせることが必要である。条件式（４）の下限を超えて屈折力が強すぎると二次スペクトルを低減する効果は高まるが、アンダー側に球面収差が過渡に発生するため良くない。
【００５８】
条件式（５）は第３レンズ群Ｌ３の屈折力を規定する式である。上限を超えて第３レンズＬ３の屈折力が弱すぎる場合、第３レンズ群Ｌ３の異常分散性を有する正レンズの屈折力を強めるには屈折力の強い負レンズを第３レンズ群Ｌ３に用いる必要がある。一次の色消しのためには負レンズは比較的高分散なガラスとなるため、二次スペクトルの補正のためには妨げとなる。よって第３レンズ群Ｌ３にて一次の色消しがなされかつ二次スペクトルの補正効果を高めるには第３レンズ群Ｌ３はある程度屈折力を強めた上で異常分散性ガラスの屈折力を強めるのが好ましい。条件式（５）の上限値を越えるとこれらの両立が困難となる。また下限を越えて第３レンズ群Ｌ３の屈折力が強すぎると変倍時に第３レンズ群Ｌ３で発生する球面収差、コマ収差等の収差変動が大きくなり変倍全域に渡って良好な性能を維持するのが難しくなる。
【００５９】
更に好ましくは条件式（４）、（５）を次の如く設定するのが良い、
１．２＜ｆ３ａ／ｆ３＜２．６ （４ａ）
０．３３＜ｆ３／ｆｔ＜０．４６ （５ａ）
◎第３レンズ群Ｌ３の物体側に開口絞りを有し、該開口絞りＳＰから該第３レンズ群Ｌ３のレンズのうち、材料のアッベ数が８０より大きい正レンズのうち最も像側に位置する正レンズの像側レンズ面までの光軸上の距離をＬ３ａ、広角端における全系の焦点距離をｆｗとするとき、
１．８＜Ｌ３ａ／ｆｗ＜３．０ ・・・・（６）
の条件式を満足している。
【００６０】
条件式（６）は広角端のズーム位置において、第３レンズ群Ｌ３を構成する異常分散性を有する正レンズの開口絞りＳＰからの位置を規定する式である。上限を超えて開口絞りＳＰからの距離が遠すぎるとレンズ径の増大を招く。又下限を越えて開口絞りＳＰからの距離が近すぎると広角端のズーム位置における倍率色収差の二次スペクトルの補正効果が薄れるためよくない。
【００６１】
更に好ましくは条件式（６）を次の如く設定をするのが良い、
２．０＜Ｌ３ａ／ｆｗ＜２．９ （６ａ）
◎広角端から望遠タンへのズーミングに際して、前記第１レンズ群Ｌ１および第３レンズ群Ｌ３は物体側へ移動し、第３レンズ群Ｌ３の広角端と、望遠端における倍率を各々β３ｗ、β３ｔ、広角端および望遠端における全系の焦点距離を各々ｆｗ、ｆｔとするとき、
０．２＜（β３ｔ／β３ｗ）／（ｆｔ／ｆｗ）＜ ０．４・・・・（７）
の条件式を満足している。
【００６２】
条件式（７）は第３レンズ群Ｌ３の変倍分担を規定する式である。上限を超えて第３レンズ群Ｌ３の変倍分担が大きすぎると変倍時に第３レンズ群Ｌ３にて発生する球面収差、コマ収差、非点隔差等の収差変動が大きくなり、変倍全域にて良好な光学性能を得るのが難しくなる。又下限を超えて第３レンズ群Ｌ３の変倍分担が小さすぎると、望遠端のズーム位置における第１レンズ群Ｌ１と第２レンズ群Ｌ２の間隔を広げて全系の変倍比を確保する必要があり、レンズ全長が大きくなるので良くない。
【００６３】
更に好ましくは条件式（７）を次の如く設定するのが良い、
０．２３＜（β３ｔ／β３ｗ）／（ｆｔ／ｆｗ）＜０．３５ （７ａ）
◎第３レンズ群Ｌ３を構成する接合レンズの正レンズの接合レンズ面の曲率半径をＲ３ｃ、第３レンズ群の焦点距離をｆ３とするとき、
０．４＜｜Ｒ３ｃ｜／ｆ３＜０．６ ・・・・（８）
の条件式を満足している。
【００６４】
条件式（８）は第３レンズ群を構成する異常分散性を有する正レンズを有する接合レンズの接合レンズ面の曲率を規定する式である。上限を超えて接合レンズ面の曲率半径が大きすぎると、すなわち曲率が緩すぎる場合は異常分散性により二次スペクトルを低減する効果が薄れる。又下限を超えて接合レンズ面の曲率半径が小さすぎると、すなわち曲率がきつすぎる場合は二次スペクトルを低減する効果は高まるが、接合レンズ面としても球面収差、コマ収差の高次成分が無視できなくなり補正が困難となるため良くない。
【００６５】
更に好ましくは条件式（８）を次の如く設定するのが良い、
０．４２＜｜Ｒ３ｃ｜／ｆ３＜０．５９ （８ａ）
次に、本実施形態１〜５に各々対応する数値実施例１〜５を示す。各数値実施例においてｉは物体側からの光学面の順序を示し、Ｒｉは第ｉ番目の光学面（第ｉ面）の曲率半径、Ｄｉは第ｉ面と第（ｉ＋１）面との間の間隔、Ｎｉとνｉはそれぞれｄ線に対する第ｉ番目の光学部材の材料の屈折率、アッベ数を示す。またｋを円錐係数Ｂ、Ｃ、Ｄ、Ｅを非球面係数、光軸からの高さｈの位置での光軸方向の変位を面頂点を基準にしてｘとするとき、非球面形状は、
【００６６】
【数３】

【００６７】
で表示される。但しＲは近軸曲率半径である。また例えば「ｅ−Ｚ」の表示は「１０^−Ｚ」を意味する。また、各数値実施例における上述した条件式との対応を表１に示す。ｆは焦点距離、ＦｎｏはＦナンバー、ωは半画各を示す。
【００６８】
数値実施例において、Ｒ２６，Ｒ２７は光学ブロックＧである。
【００６９】
【外１】

【００７０】
【外２】

【００７１】
【外３】

【００７２】
【外４】

【００７３】
【外５】

【００７４】
【表１】

【００７５】
次に、数値実施例１〜５のズームレンズを備えたデジタルスチルカメラ（撮像装置）の実施形態について、図２３を用いて説明する。
【００７６】
図２３（ａ）はデジタルスチルカメラの正面図、図２３（ｂ）は側部断面図である。図中、１０はカメラ本体（筐体）、１１は数値実施例１〜５いずれかのズームレンズを用いた撮影光学系、１２はファインダー光学系、１３はＣＣＤセンサ、ＣＭＯＳセンサ等の固体撮像素子（光電変換素子）である。固体撮像素子１３は撮影光学系１１に形成された被写体の像を受けて電気的な情報への変換を行う。電気的な情報に変換された被写体の画像情報は不図示の記憶部に記録される。
【００７７】
このように数値実施例１〜５のズームレンズをデジタルスチルカメラの撮影光学系に適用することで、コンパクトな撮影装置が実現できる。
【００７８】
【発明の効果】
本発明によれば、広角端から望遠端に至る全変倍範囲にわたり色収差を良好に補正した良好なる光学性能を有するズームレンズ及びそれを有する撮像装置を達成することができる。
【００７９】
。
【図面の簡単な説明】
【図１】本発明のズームレンズの近軸屈折力配置の説明図
【図２】実施形態１のズームレンズの広角端におけるレンズ断面図
【図３】実施形態１のズームレンズの広角端の収差図
【図４】実施形態１のズームレンズの中間のズーム位置の収差図
【図５】実施形態１のズームレンズの望遠端の収差図
【図６】実施形態２のズームレンズの広角端におけるレンズ断面図
【図７】実施形態２のズームレンズの広角端の収差図
【図８】実施形態２のズームレンズの中間のズーム位置の収差図
【図９】実施形態２のズームレンズの望遠端の収差図
【図１０】実施形態３のズームレンズの広角端におけるレンズ断面図
【図１１】実施形態３のズームレンズの広角端の収差図
【図１２】実施形態３のズームレンズの中間のズーム位置の収差図
【図１３】実施形態３のズームレンズの望遠端の収差図
【図１４】実施形態４のズームレンズの広角端におけるレンズ断面図
【図１５】実施形態４のズームレンズの広角端の収差図
【図１６】実施形態４のズームレンズの中間のズーム位置の収差図
【図１７】実施形態４のズームレンズ４の望遠端の収差図
【図１８】実施形態５のズームレンズの広角端におけるレンズ断面図
【図１９】実施形態５のズームレンズの広角端の収差図
【図２０】実施形態５のズームレンズの中間のズーム位置の収差図
【図２１】実施形態５のズームレンズの望遠端の収差図
【図２２】アッベ数νｄと部分分散比Θｇ，Ｆとの関係を示す説明図
【図２３】本発明の撮像装置の要部概略図
【符号の説明】
Ｌ１ 第１レンズ群
Ｌ２ 第２レンズ群
Ｌ３ 第３レンズ群
Ｌ４ 第４レンズ群
ｄ ｄ線
ｇ ｇ線
ΔＭ メリディオナル像面
ΔＳ サジタル像面
ＳＰ 絞り
ＩＰ 結像面
Ｇ ＣＣＤのフォースプレートやローパスフィルター等のガラスブロック
ω 半画各
Ｆｎｏ Ｆナンバー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a zoom lens suitable for a digital still camera, a video camera, and the like, and an imaging apparatus having the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, imaging devices (cameras) such as video cameras and digital still cameras often use solid-state imaging devices having a large number of pixels (high pixels), and high-performance zoom lenses are required for optical systems used therefor. I have.
[0003]
In particular, there is a demand for a zoom lens for an image sensor having a high number of pixels to sufficiently correct not only monochromatic aberration as chromatic aberration but also chromatic aberration in a wide wavelength range. In general, in a zoom lens having a high zoom ratio, if the focal length of the entire system is long at the zoom position on the telephoto side, reduction of the secondary spectrum in addition to primary achromatism is strongly required for chromatic aberration.
[0004]
2. Description of the Related Art Conventionally, many zoom lenses using a lens made of glass having anomalous dispersion for correcting a secondary spectrum of axial chromatic aberration at a zoom position on the telephoto side are known. As a zoom configuration of a zoom lens suitable for high zoom ratio, a positive lead type zoom lens in which a lens group closest to the object side has a positive refractive power is exemplified.
[0005]
2. Description of the Related Art A zoom lens using a lens made of glass having anomalous dispersion is known as a zoom lens having a three-group configuration including lens groups having positive, negative, and positive refractive powers in order from the object side (for example, Patent Documents 1 to 3). ).
[0006]
Also, a zoom lens using a lens made of glass having anomalous dispersion is known as a four-group zoom lens composed of lens groups having positive, negative, positive, and positive refractive powers in order from the object side (for example, see Patent Document 1). 4-8).
[0007]
In addition, a zoom lens using a lens made of glass having anomalous dispersion is known as a zoom lens having a five-group configuration including lens groups having positive, negative, positive, negative, and positive refractive powers in order from the object side (for example, see, for example). Patent Documents 9 to 12).
[Patent Document 1]
Patent No. 308580
[Patent Document 2]
JP-A-6-43363
[Patent Document 3]
Japanese Patent Publication No. 3-58490
[Patent Document 4]
Patent No. 3097399
[Patent Document 5]
JP-A-2002-62478
[Patent Document 6]
JP-A-2000-32499
[Patent Document 7]
JP-A-8-248317
[Patent Document 8]
JP 2001-194590 A
[Patent Document 9]
JP-A-9-5624
[Patent Document 10]
JP-A-2002-62478
[Patent Document 11]
JP 2001-350093 A
[Patent Document 12]
JP 2001-194590 A
[0008]
[Problems to be solved by the invention]
In a positive lead type zoom lens, a secondary spectrum of axial chromatic aberration at a zoom position on the telephoto side is likely to be generated in the first lens unit having a positive refractive power and a high axial ray height. Therefore, in many cases, the secondary spectrum is reduced by using glass having anomalous dispersion as the material of the positive lens of the first lens group. However, in general, glass having anomalous dispersion is more difficult to process than ordinary glass, and it is difficult to obtain a lens with high processing accuracy particularly when used for the first lens group having a large effective diameter.
[0009]
In a three-unit zoom lens composed of lens units having positive, negative, and positive refractive powers in order from the object side, the axial ray height also increases in the third lens unit. Even when glass having anomalous dispersion is used, there is a large effect of correcting the secondary spectrum of axial chromatic aberration. In this case, the third lens group has a smaller lens effective diameter than the first lens group, which is advantageous in manufacturing.
[0010]
In Patent Documents 7, 8, and 11, the first lens group having a positive refractive power has a lens made of anomalous dispersion glass, but the third lens group has no lens made of anomalous dispersion glass and corrects chromatic aberration. Is not always enough.
[0011]
In Patent Document 6, the fourth lens group has a lens made of anomalous dispersion glass, but neither the first lens group nor the third lens group has a lens made of anomalous dispersion glass. The lens made of anomalous dispersion glass in the fourth lens group is effective in reducing the secondary spectrum of chromatic aberration of magnification, and the zoom ratio of the embodiment is about 4, but the zoom ratio in the case of increasing the zoom ratio is high. The correction of the axial secondary spectrum on the telephoto side is not always sufficient.
[0012]
In general, in a three- or four-unit zoom lens having lens units having positive, negative, and positive refractive powers in order from the object side, it is necessary to reduce the overall length of the lens at the wide-angle end at a high zoom ratio of about 7 or more. Is suitable for a lens configuration in which the first lens group moves during zooming.
[0013]
However, in Patent Documents 1 to 4 and 9 described above, since the first lens group is fixed during zooming, it is difficult to achieve both reduction in the overall length of the lens at the wide angle end and high zooming.
[0014]
In Patent Documents 3, 4, and 10, chromatic aberration correction is good because the first lens group and the third lens group use lenses made of anomalous dispersion glass. There has been a tendency that the effective diameter of the lens has become large and the manufacture of the lens has become difficult.
[0015]
In Patent Document 4, since the fourth lens group is provided with a diaphragm, the front lens diameter increases when the focal length at the wide-angle end is shortened to widen the angle. Each embodiment of Patent Document 4 has a configuration in which the half angle of view at the wide angle end is narrow at 16.7 °, and is not suitable for a lens specification in which the half angle of view exceeds 30 °.
[0016]
Generally, it is effective to use a large number of lenses made of a glass material having a high anomalous dispersion to enhance the effect of correcting the secondary spectrum. In particular, the Abbe number of the material is larger than 90, and the partial dispersion ratio Δg, F is larger than 0.53. Larger glass materials (eg, fluorite) are effective. In all of the above conventional examples, such a glass material having a high anomalous dispersion is not used. Therefore, when the pixel pitch of the solid-state imaging device is increased in a digital camera or the like and the pixel pitch is reduced, the correction of the secondary spectrum is insufficient. It becomes.
[0017]
The present invention provides a zoom lens having high optical performance by appropriately correcting chromatic aberration over the entire zoom range from the wide-angle end to the telephoto end by appropriately using a lens made of an anomalous dispersion glass material, and an imaging apparatus having the same. The purpose is to provide.
[0018]
[Means for Solving the Problems]
The zoom lens of the present invention
◎ In order from the object side, it has 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, and the first lens group at the telephoto end compared to the wide-angle end. In a zoom lens in which the distance between the lens group and the second lens group is large and the distance between the second lens group and the third lens group is small,
At least one positive lens in the third lens group has an Abbe number νd and a partial dispersion ratio Δg, F of the material of the positive lens,
νd> 90 (1)
Θg, F> 0.530 (2)
Satisfy the following conditions,
Or
◎ In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power are provided. In zooming from the end to the telephoto end, the first lens group moves toward the object side, and the second lens group moves along a locus convex toward the image side.
At least one positive lens in the third lens group has an Abbe number νd and a partial dispersion ratio Δg, F of the material of the positive lens,
νd> 80 (3)
Θg, F> 0.530 (2)
Satisfy the following conditions,
Or
◎ In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power are provided. In a zoom lens in which the distance between the first lens group and the second lens group is larger at the telephoto end than at the end and the distance between the second lens group and the third lens group is smaller, An aperture stop that moves along the optical axis during zooming between the third lens group and the third lens group has a cemented lens in which a positive lens and a negative lens are cemented; When the number is νd and the partial dispersion ratio is Θg, F,
νd> 80 (3)
Θg, F> 0.530 (2)
Satisfy the following conditions,
And / or when the radius of curvature of the cemented lens surface of the positive lens of the cemented lens of the third lens group is R3c, and the focal length of the third lens group is f3,
0.4 <| R3c | / f3 <0.6
Satisfying the conditional expression of
And so on.
[0019]
In addition to this, the zoom lens of the present invention
The focal length of the positive lens having the largest Abbe number among the positive lenses of the third lens group is f3a, the focal length of the third lens group is f3, the focal length of the entire system at the telephoto end is ft,
An aperture stop is provided on the object side of the third lens group, and from the aperture stop, a positive lens located closest to the image side among the positive lenses of the third lens group, wherein the Abbe number of the material is larger than 80. The distance on the optical axis from the lens to the image side lens surface is L3a, the focal length of the entire system at the wide-angle end is fw,
When the magnifications at the wide-angle end and the telephoto end of the third lens group are respectively β3w and β3t,
1.0 <f3a / f3 <3.0
0.3 <f3 / ft <0.5
1.8 <L3a / fw <3.0
0.2 <(β3t / β3w) / (ft / fw) <0.4
At least one of the conditional expressions is satisfied.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a zoom lens according to the present invention and an imaging apparatus having the same will be described.
[0021]
FIG. 1 is an explanatory diagram of a paraxial refractive power arrangement of the zoom lens according to the embodiment.
[0022]
FIG. 2 is a sectional view of a main part of the zoom lens according to the first embodiment, and FIGS. 3 to 5 are aberration diagrams of the zoom lens according to the first embodiment at a wide-angle end, an intermediate focal length, and a telephoto end.
[0023]
FIG. 6 is a sectional view of a main part of the zoom lens according to the second embodiment, and FIGS. 7 to 9 are aberration diagrams at the wide-angle end, an intermediate focal length, and a telephoto end of the zoom lens according to the second embodiment.
[0024]
FIG. 10 is a sectional view of a main part of the zoom lens according to the third embodiment. FIGS. 11 to 13 are aberration diagrams of the zoom lens according to the third embodiment at the wide-angle end, at the intermediate focal length, and at the telephoto end.
[0025]
FIG. 14 is a sectional view of a main part of the zoom lens according to the fourth embodiment. FIGS. 15 to 17 are aberration diagrams of the zoom lens according to the fourth embodiment at the wide-angle end, an intermediate focal length, and a telephoto end.
[0026]
FIG. 18 is a sectional view of a main part of the zoom lens according to the fifth embodiment, and FIGS. 19 to 21 are aberration diagrams at the wide-angle end, an intermediate focal length, and a telephoto end of the zoom lens according to the fifth embodiment.
[0027]
FIG. 22 is an explanatory diagram showing the relationship between the Abbe number νd and the partial dispersion ratio Θg, F.
[0028]
FIG. 23 is a schematic diagram of the imaging device of the present invention.
[0029]
In the explanatory view of the paraxial refractive power arrangement and the lens cross-sectional views of the zoom lens of each embodiment, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, and L3 is a positive refractive lens. The third lens unit having a positive refractive power, L4, is a fourth lens unit having a positive refractive power. SP denotes an aperture stop, which is located in front of the third lens unit L3.
[0030]
G is an optical block corresponding to an optical filter, a face plate, and the like, and is provided in design. IP is an image plane, on which an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is located.
[0031]
In the aberration diagrams, d and g are d and g lines, ΔM and ΔS are meridional image planes, sagittal image planes, and chromatic aberration of magnification are g lines.
[0032]
In each embodiment, the first, second, and third lens units L1, L2, and L3 are moved as indicated by arrows during zooming from the wide-angle end to the telephoto end.
[0033]
Note that the wide-angle end and the telephoto end refer to zoom positions when the lens units for zooming are mechanically located at both ends of a movable range in the optical axis direction.
[0034]
In the first to fifth embodiments, the distance between the first lens unit L1 and the second lens unit L2 at the telephoto end is larger than that at the telephoto end, the distance between the second lens unit L2 and the third lens unit L3 is smaller, and the third lens unit The first, second, and third lens units L1, L2, and L3 move so that the distance between the lens unit L3 and the fourth lens unit L4 increases, thereby performing zooming.
[0035]
Specifically, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 and the second lens unit L2 move toward the object side along a part of a locus convex toward the image side, and the third lens unit L3 moves toward the object side. It is moving to the object side. The fourth lens unit L4 is fixed for zooming. Focusing is performed by the second lens unit L2 or the fourth lens unit L4.
[0036]
By moving the first lens unit L1 during zooming, the overall length of the lens at the zoom position at the wide-angle end is reduced, and the size in the optical axis direction is reduced. Further, by shortening the distance between the first lens unit L1 and the stop SP at the wide-angle zoom position, the effective diameter of the first lens unit L1 is reduced, and the diameter of the front lens is reduced.
[0037]
In addition, the third lens unit L3 is moved to the object side when zooming from the wide-angle end to the telephoto end, and the distance between the third lens unit L3 and the fourth lens unit L4 is increased when zooming from the wide-angle end to the telephoto end. As the movement trajectory, the third lens unit L3 shares the zooming action. As a result, the zooming effect due to a change in the distance between the first lens unit L1 and the second lens unit L2 can be weakened, so that the distance between the first lens unit L1 and the second lens unit L2 at the telephoto end zoom position can be reduced. As a result, the total length of the lens on the telephoto side is reduced, and the diameter of the front lens is reduced.
[0038]
The stop SP may move integrally with the third lens unit L3 during zooming, or may move separately. When integrated, the number of moving groups can be reduced, so that the mechanical structure can be simplified easily. In addition, when the diaphragm SP is moved separately from the third lens unit L3, moving the stop SP along a locus convex toward the object side is advantageous for reducing the diameter of the front lens.
[0039]
The second lens unit L2 is moved along a locus convex toward the image side during zooming from the wide-angle end to the telephoto end. As a result, the primary achromatism at the intermediate zoom position is improved, and the chromatic aberration is favorably corrected over the entire zoom range.
[0040]
In the zoom lens of each embodiment, the first lens unit L1 is composed of a cemented lens composed of a negative lens and a positive lens (or a cemented lens composed of a positive lens and a negative lens) and a positive lens in order from the object side. Correction of axial chromatic aberration, chromatic aberrations such as chromatic aberration of magnification, and spherical aberration is performed while the zoom ratio is high with the minimum number of constituent lenses. In order to correct the secondary spectrum at the zoom position on the telephoto side with such a lens configuration, it is effective to use glass having low dispersion and anomalous dispersion for the positive lens. However, the glass material having anomalous dispersion is difficult to process, and when it is used for the first lens unit L1 having a large effective diameter, manufacturing becomes difficult. In addition, since low-dispersion anomalous dispersion glass generally has a low refractive index, the curvature becomes tight (the radius of curvature is small) in order to obtain a desired refractive power, and it becomes difficult to correct spherical aberration at a zoom position on the telephoto side. . In particular, if the refractive power of the first lens unit L1 is increased, it becomes difficult to correct spherical aberration.
[0041]
In view of these, in the zoom lens of each embodiment, the secondary spectrum of the axial chromatic aberration at the zoom position on the telephoto side is corrected by using a lens made of anomalous dispersion glass in the third lens unit L3 instead of the first lens unit L1. ing. The correction of the secondary spectrum of the axial chromatic aberration is effective when anomalous dispersive glass is used for a lens group having a high axial ray height, but in each embodiment, the axial ray height is high next to the first lens group L1. Correction is performed using the positive lens of the third lens unit L3. Thus, the processing problem is solved because the lens outer diameter is as small as half or less than that used in the first lens unit L1.
[0042]
For example, in Embodiment 1 of FIG. 2, the fourth lens G34 and the fifth lens G35 from the object side of the third lens unit L3 are positive lenses having anomalous dispersion, and the positive lens G34 on the object side is Ohara Corporation. S-FPL51 (refractive index: 1.49700, Abbe number: 81.5) manufactured by Optron Co., Ltd .: CAF2 (refractive index: 1.443387, Abbe number: 95.1) manufactured by Optron Co., Ltd. It is.
[0043]
In the second to fifth embodiments as well, the Abbe number values of the positive lens G34 and the positive lens G35 in the third lens unit L3 are slightly different, but all of them use anomalous dispersion glass.
[0044]
In each embodiment, the two positive lenses G12 and G13 of the first lens unit L1 are both S-BSM14 (trade name: 60311, Abbe number 60.6) manufactured by Ohara Corporation, and have anomalous dispersion. Is not provided, but because the refractive index is higher than that of the anomalous dispersion glass, the curvature of the lens surface is reduced (the radius of curvature is increased) to reduce the occurrence of spherical aberration on the telephoto side in the first lens unit L1. I have.
[0045]
As described above, in each embodiment, the first lens unit L1 and the third lens unit L3 are configured so that the secondary spectrum of the axial chromatic aberration and the spherical aberration are favorably corrected at the zoom position on the telephoto side. .
[0046]
In order to enhance the effect of correcting the secondary spectrum by the lens made of anomalous dispersion glass of the third lens unit L3, it is necessary to increase the refractive power of the lens surface to some extent. If it is not a cemented lens, the refractive power of a single lens may be increased. When anomalous dispersion glass is used for a cemented lens, the correction effect can be enhanced by increasing the curvature of the cemented lens surface. In particular, in the case of a cemented lens surface, the secondary spectrum can be corrected without extremely generating high-order components of spherical aberration and coma. Further, the correction can be performed by increasing the curvature of the cemented lens surface without increasing the refractive power of the cemented lens itself. Therefore, the refractive power of the lens made of anomalous dispersion glass can be increased without unnecessarily increasing the refractive power of the third lens unit L3. For example, in each embodiment, when trying to increase the correction effect by increasing the refractive power of all the lenses made of a plurality of anomalous dispersion glasses, the use of such a cemented lens is effective.
[0047]
If the positive lens made of anomalous dispersive glass of the third lens unit L3 is arranged at a position distant from the stop SP in the optical axis direction to some extent, the off-axis chief ray bends at a position distant from the optical axis, causing chromatic aberration of magnification. It is also effective in correcting the secondary spectrum. For example, in each embodiment, both the positive lenses G34 and G35 are arranged on the image side in the third lens unit L3. In particular, the positive lens G35 has a role of guiding the off-axis light beam telecentrically as a field lens together with the fourth lens unit L4 at the zoom position on the wide angle side. When bending off-axis luminous flux, primary achromatization in magnification chromatic aberration can be performed by using a negative lens made of a highly dispersive glass material, but to correct the secondary spectrum, anomalous dispersion glass is used for the positive lens Is valid. The positive lens G35 has such an effect, and particularly contributes to the correction of the secondary spectrum of the chromatic aberration of magnification at the zoom position on the wide-angle side.
[0048]
In each embodiment, the third lens unit L3 has two sets of cemented lenses. When the third lens unit L3 is moved to share the magnification, it is necessary to satisfactorily correct various aberrations generated in the third lens unit L3, including the fluctuation components caused by the magnification. In the case where the lateral magnification of the third lens unit L3 is near unity, if the third lens unit L3 is provided with symmetry, it is easy to correct various aberrations in a well-balanced manner. A typical example of a symmetric lens arrangement is a triplet, but in each embodiment, the negative and positive lens components of the triplet are each divided into two components to increase the degree of freedom of aberration correction, thereby achieving spherical aberration and coma aberration. And various aberrations such as curvature of field are corrected more favorably.
[0049]
Note that the zoom lens of each embodiment focuses on the fourth lens unit L4 or the second lens unit L2. When focusing is performed by the fourth lens unit L4, rear focusing is performed, and the relatively small and lightweight lens unit is moved compared with the front lens unit. Therefore, the driving force of the lens unit can be small, and quick focusing can be performed. It has good compatibility with the auto focus system. In addition, when focusing is performed by the second lens unit L2, there is an advantage that the focusing amount is high at the zoom position on the telephoto side, so that the amount of extension can be reduced, and aberration fluctuation in a short-distance object hardly occurs.
[0050]
Next, features of the embodiments other than those described above will be described.
The third lens unit L3 has one or more positive lenses, and the refractive indices of the materials at the d-line, F-line, C-line, and g-line of the Fraunhofer line are set to Nd, NF, NC, and Ng, respectively. The number is νd, the partial dispersion ratio is Θg, F,
[0051]
(Equation 1)

[0052]
(Equation 2)

[0053]
When I put it,
At least one positive lens of the third lens group includes:
νd> 80 (1)
Θg, F> 0.530 (2)
Satisfies the conditional expression.
[0054]
The conditional expressions (1) and (2) are conditional expressions for favorably correcting the secondary spectrum of the axial chromatic aberration at the zoom position on the telephoto side. In the state where the primary achromatism is performed on the axial chromatic aberration at the zoom position on the telephoto side, the correction is generally overcorrected on the short wavelength side such as the g line, and the focus position of the short wavelength with respect to the focus position of the reference wavelength. Tends to be over. In general, in a glass medium, the refractive index tends to increase as the wavelength becomes shorter. Therefore, if a material having a higher refractive index on the shorter wavelength side is used for the positive lens, the short wavelength tends to be out of focus with respect to the reference wavelength. Is reduced. Therefore, when the partial dispersion ratio Θg, F is large, that is, when (Ng-NF) is large with respect to the main dispersion (NF-NC), the F-line and g-line are based on the refractive index difference between the F-line and the C-line. It means that the refractive index difference of the line is large. When glass having a large partial dispersion ratio Δg, F is used for the positive lens, the tendency of the g-line to be out of focus is reduced. Therefore, in the low dispersion region satisfying the conditional expression (1), the effect of bringing the focus at the short wavelength closer to the focus position at the reference wavelength with a partial dispersion ratio satisfying the conditional expression (2) is high, and the secondary spectrum is reduced. Outside the range of the conditional expressions (1) and (2), such anomalous dispersion characteristics are insufficient, so that the correction of the secondary spectrum is insufficient.
[0055]
Further, in the zoom lens of each embodiment, when the following restriction is further added in the conditional expression (1), the effect of correcting the secondary spectrum is further enhanced.
[0056]
νd> 90 (3)
FIG. 22 is a graph showing the relationship between the Abbe number νd and the partial dispersion ratio Θg, F. In FIG. 22, point A is a brand name PBM2 (νd = 36.26, Δg, F = 0.5828) manufactured by Ohara Corporation, and point B is a brand name NSL7 (νd = 60.49, manufactured by Ohara Corporation). Θg, F = 0.5436). Assuming that a line connecting points A and B is a reference line, the distribution of the optical glass is, as a rule, a high dispersion glass having an Abbe number νd smaller than about 35 is above the reference line, and an Abbe number νd is about 35 to 65. Most of the low dispersion glasses described above are located below the reference line, and there is an anomalous dispersion glass located above the reference line when the Abbe number νd is 60 or more. As for the low dispersion glass, it is effective to use the one located above the reference line for the correction of the secondary spectrum, and the correction effect increases as the distance from the reference line increases. If the conditional expression (1) is further limited to the conditional expression (3), the glass is limited to a range farther upward from the reference line in FIG. 22, so that the effect of correcting the secondary spectrum is further enhanced.
When the focal length of the sex lens having the largest Abbe number among the positive lenses of the third lens unit L3 is f3a, the focal length of the third lens L3 is f3, and the focal length of the entire system at the telephoto end is ft,
1.0 <f3a / f3 <3.0 (4)
0.3 <f3 / ft <0.5 (5)
Satisfies the conditional expression.
[0057]
Conditional expression (4) is an expression that defines the refractive power of the positive lens having anomalous dispersion that forms the third lens unit L3. If the upper limit is exceeded and the refractive power of the positive lens is too weak, the effect of reducing the secondary spectrum is weakened due to anomalous dispersion, which is not good. In the zoom lens of each embodiment, it is necessary that the lens of anomalous dispersion glass has a certain degree of refractive power. If the refractive power exceeds the lower limit of conditional expression (4) and the refractive power is too strong, the effect of reducing the secondary spectrum increases, but this is not good because spherical aberration occurs transiently on the under side.
[0058]
Conditional expression (5) is an expression that defines the refractive power of the third lens unit L3. If the upper limit is exceeded and the refractive power of the third lens L3 is too weak, a negative lens having a strong refractive power is used for the third lens group L3 in order to increase the refractive power of the positive lens having anomalous dispersion of the third lens group L3. There is a need. For primary achromatization, the negative lens is a relatively high-dispersion glass, which hinders the correction of the secondary spectrum. Therefore, in order to perform primary achromatism in the third lens unit L3 and enhance the effect of correcting the secondary spectrum, it is necessary to increase the refractive power of the third lens unit L3 to some extent and then increase the refractive power of the anomalous dispersion glass. preferable. If the upper limit of conditional expression (5) is exceeded, it is difficult to achieve both. If the lower limit is exceeded and the refractive power of the third lens unit L3 is too strong, fluctuations in spherical aberration, coma and the like generated in the third lens unit L3 during zooming will increase, and good performance will be obtained over the entire zooming range. Difficult to maintain.
[0059]
More preferably, conditional expressions (4) and (5) should be set as follows:
1.2 <f3a / f3 <2.6 (4a)
0.33 <f3 / ft <0.46 (5a)
を An aperture stop is provided on the object side of the third lens unit L3, and among the lenses of the third lens unit L3 from the aperture stop SP, the positive lens whose Abbe number of the material is larger than 80 is located closest to the image side. When the distance on the optical axis to the image side lens surface of the positive lens is L3a, and the focal length of the entire system at the wide-angle end is fw,
1.8 <L3a / fw <3.0 (6)
Satisfies the conditional expression.
[0060]
Conditional expression (6) defines the position of the positive lens having anomalous dispersion constituting the third lens unit L3 from the aperture stop SP at the zoom position at the wide-angle end. If the distance from the aperture stop SP is too far beyond the upper limit, the lens diameter will increase. On the other hand, if the distance from the aperture stop SP is too small below the lower limit, the effect of correcting the secondary spectrum of the chromatic aberration of magnification at the zoom position at the wide-angle end is undesirably weak.
[0061]
More preferably, conditional expression (6) should be set as follows:
2.0 <L3a / fw <2.9 (6a)
During zooming from the wide-angle end to the telephoto tongue, the first lens unit L1 and the third lens unit L3 move toward the object side, and the magnifications of the third lens unit L3 at the wide-angle end and at the telephoto end are β3w and β3t, respectively. When the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and ft,
0.2 <(β3t / β3w) / (ft / fw) <0.4 (7)
Satisfies the conditional expression.
[0062]
Conditional expression (7) is an expression that defines the variable power distribution of the third lens unit L3. If the upper limit is exceeded and the variable power sharing of the third lens unit L3 is too large, fluctuations in spherical aberration, coma, astigmatism, and other aberrations generated in the third lens unit L3 during zooming will increase, and the entire zoom range will be increased. And it is difficult to obtain good optical performance. If the lower limit is exceeded and the variable power sharing of the third lens unit L3 is too small, the distance between the first lens unit L1 and the second lens unit L2 at the telephoto end zoom position is increased to secure the zoom ratio of the entire system. It is necessary, and it is not good because the overall length of the lens becomes large.
[0063]
More preferably, conditional expression (7) should be set as follows:
0.23 <(β3t / β3w) / (ft / fw) <0.35 (7a)
When the radius of curvature of the cemented lens surface of the positive lens of the cemented lens constituting the third lens unit L3 is R3c, and the focal length of the third lens unit is f3,
0.4 <| R3c | / f3 <0.6 (8)
Satisfies the conditional expression.
[0064]
Conditional expression (8) is an expression that defines the curvature of the cemented lens surface of the cemented lens having the anomalous dispersive positive lens that forms the third lens unit. If the radius of curvature of the cemented lens surface exceeds the upper limit and is too large, that is, if the curvature is too gentle, the effect of reducing the secondary spectrum due to anomalous dispersion is diminished. If the radius of curvature of the cemented lens surface is too small below the lower limit, that is, if the curvature is too tight, the effect of reducing the secondary spectrum increases, but the spherical lens and the higher-order components of coma are ignored even for the cemented lens surface. It is not good because it becomes impossible and the correction becomes difficult.
[0065]
More preferably, conditional expression (8) should be set as follows:
0.42 <| R3c | / f3 <0.59 (8a)
Next, numerical examples 1 to 5 corresponding to the first to fifth embodiments will be described. In each numerical example, i indicates the order of the optical surfaces from the object side, Ri is the radius of curvature of the i-th optical surface (i-th surface), and Di is the distance between the i-th surface and the (i + 1) -th surface. The intervals, Ni and νi, indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. When k is a cone coefficient, B, C, D, and E are aspherical coefficients, and the displacement in the optical axis direction at a height h from the optical axis is x with respect to the surface vertex, the aspherical shape is
[0066]
[Equation 3]

[0067]
Is displayed with. Here, R is a paraxial radius of curvature. For example, the display of "e-Z" is "10 ^-Z Means. Table 1 shows the correspondence with the above-described conditional expressions in each numerical example. f indicates the focal length, Fno indicates the F number, and ω indicates each half image.
[0068]
In the numerical examples, R26 and R27 are optical blocks G.
[0069]
[Outside 1]

[0070]
[Outside 2]

[0071]
[Outside 3]

[0072]
[Outside 4]

[0073]
[Outside 5]

[0074]
[Table 1]

[0075]
Next, an embodiment of a digital still camera (imaging device) including the zoom lenses of Numerical Examples 1 to 5 will be described with reference to FIG.
[0076]
FIG. 23A is a front view of the digital still camera, and FIG. 23B is a side sectional view. In the figure, 10 is a camera body (housing), 11 is a photographing optical system using any one of Numerical Examples 1 to 5, 12 is a finder optical system, 13 is a solid-state image sensor such as a CCD sensor or a CMOS sensor. (Photoelectric conversion element). The solid-state imaging device 13 receives an image of a subject formed in the imaging optical system 11 and converts the image into electrical information. The image information of the subject converted into the electrical information is recorded in a storage unit (not shown).
[0077]
By applying the zoom lenses of Numerical Examples 1 to 5 to the photographing optical system of the digital still camera, a compact photographing device can be realized.
[0078]
【The invention's effect】
According to the present invention, it is possible to achieve a zoom lens having good optical performance in which chromatic aberration is satisfactorily corrected over the entire zoom range from the wide-angle end to the telephoto end, and an imaging apparatus having the same.
[0079]
.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a paraxial refractive power arrangement of a zoom lens according to the present invention.
FIG. 2 is a sectional view of a zoom lens according to a first embodiment at a wide-angle end.
FIG. 3 is an aberration diagram at a wide-angle end of the zoom lens according to the first embodiment.
FIG. 4 is an aberration diagram at an intermediate zoom position of the zoom lens according to the first embodiment.
FIG. 5 is an aberration diagram at a telephoto end of the zoom lens according to the first embodiment.
FIG. 6 is a sectional view of a zoom lens according to a second embodiment at a wide-angle end.
FIG. 7 is an aberration diagram at a wide-angle end of a zoom lens according to a second embodiment.
FIG. 8 is an aberration diagram at an intermediate zoom position of the zoom lens according to the second embodiment.
FIG. 9 is an aberration diagram at a telephoto end of a zoom lens according to a second embodiment.
FIG. 10 is a sectional view of a zoom lens according to a third embodiment at a wide-angle end.
FIG. 11 is an aberration diagram at a wide-angle end of a zoom lens according to a third embodiment.
FIG. 12 is an aberration diagram at an intermediate zoom position of the zoom lens according to the third embodiment;
FIG. 13 is an aberration diagram at a telephoto end of a zoom lens according to a third embodiment.
FIG. 14 is a sectional view of a zoom lens according to a fourth embodiment at a wide-angle end.
FIG. 15 is an aberration diagram at a wide-angle end of a zoom lens according to a fourth embodiment.
FIG. 16 is an aberration diagram at an intermediate zoom position of the zoom lens according to the fourth embodiment.
FIG. 17 is an aberration diagram at a telephoto end of a zoom lens 4 according to a fourth embodiment.
FIG. 18 is a sectional view of a zoom lens according to a fifth embodiment at a wide-angle end.
FIG. 19 is an aberration diagram at a wide-angle end of a zoom lens according to a fifth embodiment.
FIG. 20 is an aberration diagram at an intermediate zoom position of the zoom lens according to the fifth embodiment.
FIG. 21 is an aberration diagram at a telephoto end of a zoom lens according to a fifth embodiment.
FIG. 22 is an explanatory diagram showing a relationship between Abbe number νd and partial dispersion ratio Θg, F.
FIG. 23 is a schematic view of a main part of an imaging device according to the present invention.
[Explanation of symbols]
L1 First lens group
L2 Second lens group
L3 Third lens group
L4 4th lens group
dd line
g g line
ΔM Meridional image plane
ΔS sagittal image plane
SP aperture
IP imaging surface
Glass blocks such as G CCD force plate and low pass filter
ω half stroke each
Fno F number

Claims (12)

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, in order from the object side, and the first lens at the telephoto end compared to the wide-angle end. In a zoom lens in which a distance between a group and the second lens group is large and a distance between the second lens group and the third lens group is small,
At least one positive lens in the third lens group has an Abbe number νd and a partial dispersion ratio Δg, F of the material of the positive lens,
νd> 90
Θg, F> 0.530
A zoom lens that satisfies certain conditions. 2. The zoom lens according to claim 1, wherein the Abbe number νd of all the positive lens materials in the first lens group is 80 or less. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. When zooming from to the telephoto end, the first lens group moves toward the object side, and the second lens group moves along a locus convex toward the image side.
At least one positive lens in the third lens group has an Abbe number νd and a partial dispersion ratio Δg, F of the material of the positive lens,
νd> 80
Θg, F> 0.530
A zoom lens that satisfies certain conditions. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. In a zoom lens in which the distance between the first lens group and the second lens group at the telephoto end is larger and the distance between the second lens group and the third lens group is smaller than at the telephoto end, The third lens group has a cemented lens in which a positive lens and a negative lens are cemented, and has an Abbe number of a material of the positive lens between the lens group and the lens group. Is νd and the partial dispersion ratio is Θg, F,
νd> 80
Θg, F> 0.530
A zoom lens that satisfies certain conditions. When the focal length of the positive lens having the largest Abbe number among the positive lenses in the third lens group is f3a, the focal length of the third lens group is f3, and the focal length of the entire system at the telephoto end is ft,
1.0 <f3a / f3 <3.0
0.3 <f3 / ft <0.5
5. The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The third lens group has a plurality of positive lenses, and Abbe number νd and partial dispersion ratio Δg, F of two or more positive lens materials among the plurality of positive lenses are νd> 80.
Θg, F> 0.53
The zoom lens according to any one of claims 1 to 5, wherein the following conditional expression is satisfied. An aperture stop is provided on the object side of the third lens group, and from the aperture stop, a positive lens located closest to the image side among the positive lenses of the third lens group, wherein the Abbe number of the material is larger than 80. When the distance on the optical axis from the lens to the image side lens surface is L3a, and the focal length of the entire system at the wide-angle end is fw,
1.8 <L3a / fw <3.0
The zoom lens according to any one of claims 1 to 6, wherein the following conditional expression is satisfied. During zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group move toward the object side, and the magnification at the wide-angle end and the telephoto end of the third lens group are β3w, β3t, the wide-angle end, and When the focal lengths of the entire system at the telephoto end are respectively fw and ft,
0.2 <(β3t / β3w) / (ft / fw) <0.4
The zoom lens according to any one of claims 1 to 7, wherein the following conditional expression is satisfied. When the radius of curvature of the cemented lens surface of the positive lens of the cemented lens of the third lens group is R3c, and the focal length of the third lens group is f3,
0.4 <| R3c | / f3 <0.6
The zoom lens according to claim 4, wherein the following conditional expression is satisfied. The zoom lens according to any one of claims 1 to 9, wherein the third lens group includes two sets of cemented lenses. The zoom lens according to claim 1, wherein an image is formed on a solid-state imaging device. An imaging apparatus comprising: the zoom lens according to claim 1; and a solid-state imaging device on which an image is formed by the zoom lens.

Images