JP3925926B2 - High zoom ratio zoom lens - Google Patents

Description

ただし、ｒは近軸曲率半径、Ｐは円錐係数、A₄、A₆、A₈、A₁₀ はそれぞれ４次、６次、８次、１０次の非球面係数である。
【００４７】
また、本発明のズームレンズにおいては、第１レンズ群の構成が、物体側より順に、負のパワーを持つ第１レンズ、物体側に凸面を向けたメニスカス形状の負パワーを持つ第２レンズ、及び、それに続く正のパワーを持つレンズ群を有し、さらに、第２レンズ群が、物体側より順に、負レンズ、正レンズ、負レンズの順に配置された構成を採用することによっても、前述してきたような効果を得ることができ、高変倍化を達成するのに十分である。
【００４８】
【実施例】
次に、本発明のズームレンズの実施例１〜３について説明する。
【００４９】
図１〜図３は、それぞれ実施例１〜３の広角端、中間焦点距離、望遠端でのレンズ群配置を対比して示す断面図である。各実施例の数値データは後記するが、以下に各実施例の構成を説明する。
【００５０】
第１レンズ群Ｇ１の構成は、実施例１〜３共に、両凹レンズの第１レンズＬ₁ 、物体側に凸面を向けた負メニスカスレンズの第２レンズＬ₂ 、及び、それに続く、両凸レンズ、物体側に凸面を向けた負メニスカスレンズと両凸レンズの接合レンズでなる正レンズ群Ｌ_P からなる。なお、絞りが第１レンズ群Ｇ１の最も像面側に一体に移動するように配置されている。
【００５１】
第２レンズ群Ｇ２の構成は、実施例１の場合、物体側より順に、像面側に凸面を向けた負メニスカスレンズ、両凸レンズ、像面側に凸面を向けた負メニスカスレンズから構成され、実施例２の場合、物体側より順に、両凹レンズと両凸レンズの接合レンズ、像面側に凸面を向けた負メニスカスレンズから構成され、実施例３の場合、両凹レンズ、像面側に凸面を向けた正メニスカスレンズ、像面側に凸面を向けた負メニスカスレンズから構成されている。
【００５２】
非球面は、実施例１〜３共に、第１レンズ群Ｇ１の第２レンズＬ₂ の物体側の面、第２レンズ群Ｇ２の最も物体側の面の２面に用いられている。
【００５３】
以下に、上記各実施例の数値データを示すが、記号は上記の外、ｆは全系焦点距離、Ｆ_NOはＦナンバー、ωは半画角、ｆ_B はバックフォーカス、ｒ₁ 、ｒ₂ …は各レンズ面の曲率半径、ｄ₁ 、ｄ₂ …は各レンズ面間の間隔、ｎ_d1、ｎ_d2…は各レンズのｄ線の屈折率、ν_d1、ν_d2…は各レンズのアッベ数である。なお、非球面形状は、前記（ａ）式にて表す。
【００５４】

【００５５】

【００５６】

【００５７】
次に、上記実施例１の無限遠合焦時の広角端、中間焦点距離、望遠端での収差図をそれぞれ図４〜図６に、実施例２の同様な収差図を図７〜図９に、実施例３の同様な収差図を図１０〜図１２に示す。各収差図において、（ａ）は球面収差、（ｂ）は非点収差、（ｃ）は歪曲収差、（ｄ）は倍率色収差を示す。
【００５８】
以上の本発明の高変倍ズームレンズは、例えば次のように構成することができる。
〔１〕 物体側より順に、正のパワーの第１レンズ群と、負のパワーの第２レンズ群とを備え、これらのレンズ群の間隔を変化させることにより全系の焦点距離を変化させるズームレンズにおいて、
前記第１レンズ群は、物体側から順に、負のパワーを持つ第１レンズと、物体側に凸面を向けたメニスカス形状の負パワーを持つ第２レンズと、正のパワーを持つレンズ群とを有することを特徴とする高変倍ズームレンズ。
〔２〕 物体側より順に、正のパワーの第１レンズ群と、負のパワーの第２レンズ群とを備え、これらのレンズ群の間隔を変化させることにより全系の焦点距離を変化させるズームレンズにおいて、
前記第２レンズ群は、物体側から順に、負レンズと、正レンズと、負レンズとを有することを特徴とする高変倍ズームレンズ。
〔３〕 物体側より順に、正のパワーの第１レンズ群と、負のパワーの第２レンズ群とを備え、これらのレンズ群の間隔を変化させることにより全系の焦点距離を変化させるズームレンズにおいて、
前記第１レンズ群は、物体側から順に、負のパワーを持つ第１レンズと、物体側に凸面を向けたメニスカス形状の負パワーを持つ第２レンズと、正のパワーを持つレンズ群とを有し、
前記第２レンズ群は、物体側から順に、負レンズと、正レンズと、負レンズとを有することを特徴とする高変倍ズームレンズ。
〔４〕 上記〔１〕又は〔３〕において、前記第１レンズが以下の条件を満足することを特徴とする高変倍ズームレンズ。
【００５９】
（１） −５＜ＳＦ_L1＜０
ここで、ＳＦ_L1は第１レンズ群内の第１レンズのシェイピングファクタであり、第１レンズの物体側面及び像側面の曲率半径をｒ₁ 、ｒ₂ とするとき、ＳＦ_L1＝（ｒ₁ ＋ｒ₂ ）／（ｒ₁ −ｒ₂ ）で与えられるパラメータである。
〔５〕 上記〔１〕又は〔３〕において、前記第２レンズが以下の条件を満足することを特徴とする高変倍ズームレンズ。
【００６０】
（２） １＜ＳＦ_L2＜１０
ここで、ＳＦ_L2は第１レンズ群内の第２レンズのシェイピングファクタであり、第２レンズの物体側面及び像側面の曲率半径をｒ₃ 、ｒ₄ とするとき、ＳＦ_L2＝（ｒ₃ ＋ｒ₄ ）／（ｒ₃ −ｒ₄ ）で与えられるパラメータである。
〔６〕 上記〔１〕又は〔３〕において、以下の条件を満足することを特徴とする高変倍ズームレンズ。
【００６１】
（３） −２＜ｆ_W ／ｒ₁ ＜−０．６
ここで、ｆ_W は全系の広角端での焦点距離、ｒ₁ は第１レンズの第１面の曲率半径である。
〔７〕 上記〔１〕、〔３〕又は〔６〕において、以下の条件を満足することを特徴とする高変倍ズームレンズ。
【００６２】
（４） ０．２＜ｆ_L1／ｆ_L2＜１
ここで、ｆ_L1は第１レンズ群の第１レンズの焦点距離、ｆ_L2は第１レンズ群の第２レンズの焦点距離である。
〔８〕 上記〔２〕又は〔３〕において、以下の条件を満足することを特徴とする高変倍ズームレンズ。
【００６３】
（５） ν₁ ＞ν₂
ここで、ν₁ は第２レンズ群の負パワーの第１レンズのアッベ数、ν₂ は第２レンズ群の正パワーの第２レンズのアッベ数である。
〔９〕 上記〔２〕、〔３〕又は〔８〕において、以下の条件を満足することを特徴とする高変倍ズームレンズ。
【００６４】
（６） −３＜ｆ₂₂／ｆ₂₁＜０
ここで、ｆ₂₁は第２レンズ群の負パワーの第１レンズの焦点距離、ｆ₂₂は第２レンズ群の正パワーの第２レンズの焦点距離である。
〔１０〕 上記〔１〕において、前記第１レンズ群内の正のレンズ群が正レンズと接合正レンズとからなることを特徴とする高変倍ズームレンズ。
〔１１〕 上記〔２〕又は〔３〕において、前記第２レンズ群内の物体側の負レンズと正レンズとが接合されていることを特徴とする高変倍ズームレンズ。
〔１２〕 上記〔１〕、〔２〕又は〔３〕において、少なくとも１つの非球面を含むことを特徴とする高変倍ズームレンズ。
〔１３〕 上記〔１〕又は〔３〕において、前記第１レンズと第２レンズとの間隔が、前記第２レンズとこれに続く正のパワーを持つレンズ群との間隔より狭いことを特徴とする高変倍ズームレンズ。
【００６５】
【発明の効果】
以上の説明から明らかなように、本発明によると、２群ズームレンズ方式という簡素な構成を採用しながら、３倍クラスの高変倍比であり、さらに良好に収差補正された高変倍ズームレンズを得ることができる。
【図面の簡単な説明】
【図１】本発明の実施例１の高変倍ズームレンズの広角端、中間焦点距離、望遠端での群配置を対比して示すレンズ断面図である。
【図２】実施例２の高変倍ズームレンズの図１と同様なレンズ断面図である。
【図３】実施例３の高変倍ズームレンズの図１と同様なレンズ断面図である。
【図４】実施例１の無限遠合焦時の広角端での収差図である。
【図５】実施例１の無限遠合焦時の中間焦点距離での収差図である。
【図６】実施例１の無限遠合焦時の望遠端での収差図である。
【図７】実施例２の無限遠合焦時の広角端での収差図である。
【図８】実施例２の無限遠合焦時の中間焦点距離での収差図である。
【図９】実施例２の無限遠合焦時の望遠端での収差図である。
【図１０】実施例３の無限遠合焦時の広角端での収差図である。
【図１１】実施例３の無限遠合焦時の中間焦点距離での収差図である。
【図１２】実施例３の無限遠合焦時の望遠端での収差図である。
【符号の説明】
Ｇ１…第１レンズ群
Ｇ２…第２レンズ群
Ｌ₁ …第１レンズ群の第１レンズ
Ｌ₂ …第１レンズ群の第２レンズ
Ｌ_P …第１レンズ群の正レンズ群[0001]
[Industrial application fields]
The present invention relates to a high-magnification zoom lens, and more particularly to a high-magnification zoom lens suitable for an imaging lens for a compact camera with little limitation on back focus.
[0002]
[Prior art]
Conventionally, as the simplest zoom lens system, a so-called two-group zoom lens system having two groups is known. This method has an advantage such as a simple lens frame structure, but has a disadvantage that the zoom ratio cannot be increased so much because aberration variation is large.
[0003]
By the way, in recent years, there has been a strong demand for a zoom lens with a high zoom ratio. Patent Document 1 and the like are aimed at achieving a high zoom ratio using this two-group zoom lens system. The zoom ratio has achieved about 2.8 times.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 4-218013
[Problems to be solved by the invention]
However, if an attempt is made to achieve a further high zoom ratio using the configuration of the preceding example, both monochromatic aberration and chromatic aberration are broken, and a practical level of imaging performance cannot be achieved.
[0006]
The present invention has been made in view of such problems of the prior art, and the object thereof is a high zoom ratio of 3 × class while adopting a simple configuration of a two-group zoom lens system. It is to provide a zoom lens with good aberration correction.
[0007]
[Means for Solving the Problems]
The high-magnification zoom lens of the present invention that achieves the above object comprises, in order from the object side, a first lens group having a positive power and a second lens group having a negative power, and the interval between these lens groups is changed. In a zoom lens that changes the focal length of the entire system by
The first lens group includes, in order from the object side, a first lens having a negative power, a second lens having a meniscus negative power with a convex surface facing the object side, and a lens group having a positive power. Have
The second lens group includes, in order from the object side, a negative lens, a positive lens, and a negative lens.
The second lens satisfies the following conditions.
(2) 1 <SF _L2 <10
Here, SF _L2 is the shaping factor of the second lens in the first lens group, and when the curvature radii of the object side surface and the image side surface of the second lens are r ₃ and r ₄ , SF _L2 = (r ₃ + r ₄ ) / (r ₃ −r ₄ ).
[0008]
Another high-magnification zoom lens according to the present invention includes a first lens group having a positive power and a second lens group having a negative power in order from the object side, and changes the interval between these lens groups. In the zoom lens that changes the focal length of the whole system by
The first lens group includes, in order from the object side, a first lens having a negative power, a second lens having a meniscus negative power with a convex surface facing the object side, and a lens group having a positive power. Have
The second lens group includes, in order from the object side, a negative lens, a positive lens, and a negative lens.
The following conditions are satisfied.
(3) -2 <f _W / r ₁ <−0.6
Here, f _W is the focal length at the wide-angle end of the entire system, and r ₁ is the radius of curvature of the first surface of the first lens.
[0009]
[Action]
Hereinafter, the reason why the above configuration is adopted in the present invention and the operation thereof will be described.
[0010]
First, regarding the configuration in the first lens group, it is necessary to reduce the amount of chromatic aberration generated in each group in order to achieve a high zoom ratio, so at least one negative lens is required. It is necessary to have a component and a positive lens component.
[0011]
In addition, the positive zoom lens + negative zoom lens group has a disadvantage that the back focus is shortened particularly when aiming at wide angle.
[0012]
For this reason, problems such as mechanical interference are likely to occur, which is not preferable. However, by adopting a configuration in which a negative lens is arranged on the object side as in the configuration of the present invention, a relatively long back focus is secured. It becomes possible to do.
[0013]
Next, the reason why it is preferable to employ a configuration of a negative lens and a negative meniscus lens convex toward the object side in order from the object side will be described.
[0014]
The first lens group has a configuration of a negative lens group + a positive lens group. Here, since the first lens group as a whole is a positive lens group, the power of the positive lens group is relatively strong within the group. For this reason, the amount of under spherical aberration or the like generated here increases. In addition, when the zoom ratio of the zoom lens according to the present invention is set to a high zoom ratio of 3 × class, there is a problem that the amount of astigmatism generated in the intermediate zoom state increases. The image performance was significantly degraded. Such a problem becomes more prominent when the group power is increased to shorten the overall length.
[0015]
Therefore, in order to cancel various aberrations generated in the positive lens group, first, in particular, with respect to spherical aberration and coma aberration, by providing a convex negative meniscus lens on the object side, a large amount of over spherical aberration is generated, The amount of aberration can be reduced as a whole by the canceling action.
[0016]
For correction of astigmatism and distortion, it is preferable to provide a lens that satisfies the following conditional expression (1).
[0017]
(1) -5 <SF _L1 <0
Here, SF _L1 is a shaping factor of the first lens in the first lens group, and when the curvature radii of the object side surface and the image side surface of the first lens are r ₁ and r ₂ , SF _L1 = (r ₁ + r ₂ ) / (r ₁ −r ₂ ).
[0018]
That is, Equation (1) defines the shape of the negative first lens. According to Equation (1), the first lens has a relatively larger curvature on the first surface than on the second surface. It is configured. Therefore, by defining within the range of this equation, it is possible to increase the amount of astigmatism and distortion, and to cancel out the amount generated in the positive group. Further, since the main plane position of this lens is closer to the object side, the shift of the main plane position toward the image side by the meniscus negative lens is canceled, and the wide angle of view or the axial thickness in the first lens group is canceled. There is also a reduction effect. If the upper limit value 0 or the lower limit value −5 of the above equation (1) is exceeded, the action of canceling the astigmatism and distortion will not be achieved, and the wide angle of view or the axis in the first lens group will not be achieved. It becomes difficult to reduce the upper thickness.
[0019]
Further, regarding the arrangement order of the above two negative lenses, a lens that generates a lot of aberrations such as astigmatism and distortion is arranged at a place where the off-axis rays are high, that is, closer to the image plane side, and spherical aberration. And a lens having a large amount of coma aberration is arranged at a position where the axial ray is relatively high, that is, close to the object side, so that the first lens unit is most efficient in terms of aberration correction. Arrangement.
[0020]
With the above configuration, a zoom lens having a high zoom ratio in which various aberrations are corrected can be obtained. In addition, regarding the equation (1),
(1) '-2 <SF _L1 <-0.1
This is preferable because the balance of the amount of astigmatism and distortion is optimal and a high-quality image can be obtained without difficulty.
[0021]
In the zoom lens according to the present invention, it is further desirable to define the shape of the negative meniscus convex on the object side of the second lens in the first lens group as shown in the following equation (2).
[0022]
(2) 1 <SF _L2 <10
Here, SF _L2 is the shaping factor of the second lens in the first lens group, and when the curvature radii of the object side surface and the image side surface of the second lens are r ₃ and r ₄ , SF _L2 = (r ₃ + r ₄ ) / (r ₃ −r ₄ ).
[0023]
That is, if the upper limit value 10 of the expression (2) is exceeded, the radius of curvature becomes too small in order to maintain the same power, which is not preferable because the amount of high-order aberrations increases. On the other hand, if the lower limit value 1 is exceeded, the meniscus shape as defined above is lost, and the effect of correcting the aberration does not appear, which is not preferable.
[0024]
In the zoom lens according to the present invention, the range of the radius of curvature of the first surface of the first lens is determined as shown in the following expression (3), which makes the configuration more desirable from the viewpoint of aberration correction.
[0025]
(3) -2 <f _W / r ₁ <−0.6
Here, f _W is the focal length at the wide-angle end of the entire system, and r ₁ is the radius of curvature of the first surface of the first lens.
[0026]
That is, if the upper limit value of −0.6 in the expression (3) is exceeded, the incident angle with respect to the off-axis ray is too small to obtain a desired aberration correction capability, but conversely if the lower limit value −2 is exceeded. This is not preferable because the curvature of the first surface becomes too small, and the amount of aberration generated on this surface increases too much, and in particular, the amount of astigmatism and field curvature aberration increases.
[0027]
Regarding (3), in particular,
(3) '−1.6 <f _W / r ₁ <−0.8
This is more desirable because the amount of aberration generated on the first surface is in the optimum range and the number of lenses and the number of aspheric surfaces can be suppressed.
[0028]
Furthermore, in the zoom lens of the present invention, it is more desirable to determine the ratio of the focal lengths of the first lens and the second lens in the first lens group as follows.
[0029]
(4) 0.2 <f _L1 / f _L2 <1
Here, f _L1 is the focal length of the first lens of the first lens group, and f _L2 is the focal length of the second lens of the first lens group.
[0030]
That is, by defining within the range of the conditional expression (4), the power of the first lens having a negative power is made stronger than the power of the negative meniscus lens, thereby shifting the main plane position toward the image plane side. As a result, the back focus is secured, which is preferable.
[0031]
Also, with regard to equation (4),
(4) '0.2 <f _L1 / f _L2 <0.6
If it is within the range, the balance of the power ratio will be optimal.
[0032]
Furthermore, in the zoom lens according to the present invention, since the aspherical surface is used for any surface in the first lens group, the total amount of aberrations generated can be reduced. It is effective for size reduction by deleting the number of sheets and increasing power.
[0033]
Furthermore, the zoom lens of the present invention can provide a simple zoom lens having a high zoom ratio even when the following configuration is adopted.
[0034]
That is, the first lens group having a positive power and the second lens group having a negative power are sequentially arranged from the object side, and the second lens group is sequentially arranged from the object side, the negative lens, the positive lens, and the negative lens. The zoom lenses are arranged in this order.
[0035]
This mainly relates to the configuration of the second lens group. In the second group zoom lens, however, only the second lens group has a zooming action. It is important to reduce the amount of chromatic aberration generated. Therefore, regarding the lens arrangement, first, it is necessary to provide at least one negative lens group and a positive lens group, and a configuration in which a negative lens group with relatively strong power is arranged on the image side has a main plane position as an image plane. This is preferable because it is located on the side, which ensures the back focus.
[0036]
Here, from the viewpoint of correcting chromatic aberration of magnification, it is preferable to use a glass material having a large Abbe number for the negative lens. However, in the above glass material usage method, the axial chromatic aberration fluctuates greatly when the zoom ratio is increased.
[0037]
Therefore, for this correction, it is desirable to provide a negative lens where the axial ray is high, that is, on the object side of the positive lens, so that fluctuations in both magnification and axial chromatic aberration can be reduced.
[0038]
Further, when the above configuration is adopted, it is desirable that the following conditional expression (5) is satisfied, the amount of axial chromatic aberration generated can be reduced as achromaticity of the negative lens group.
[0039]
(5) ν ₁ > ν ₂
Here, ν ₁ is the Abbe number of the first lens with negative power of the second lens group, and ν ₂ is the Abbe number of the second lens with positive power of the second lens group.
[0040]
As described above, the above effect can be achieved by using negative, positive, and negative three lenses. However, from the viewpoint of manufacturing, using any one of these combinations as a cemented lens reduces the influence of eccentricity. It is desirable because it can.
[0041]
Furthermore, a zoom lens with higher performance can be obtained by satisfying the following conditional expression (6), which will be described.
[0042]
_{(6) -3 <f 22 /} f 21 <0
Here, f ₂₁ is the focal length of the first lens with negative power of the second lens group, and f ₂₂ is the focal length of the second lens with positive power of the second lens group.
[0043]
Equation (6) defines the ratio of the refractive power of the negative lens on the object side of the second lens group to the positive lens. By keeping it within the range of Equation (6), the amount of chromatic aberration generated can be reduced by using a general glass material. It is because it can be made small in the range to be used. Here, exceeding the lower limit of −3 of the conditional expression (6) makes the power of the second lens relatively strong, and the achromatic action with the positive lens becomes insufficient. If it exceeds 0, the effect of providing a negative lens on the object side will be lost, and it will be difficult to reduce the variation of axial chromatic aberration.
[0044]
As described above, it has been explained that a zoom lens having a high zoom ratio can also be obtained by adopting the above-described configuration. Further, the second lens group is not on any surface. Providing a spherical surface is desirable because it has the same effect as the aspherical surface in the first lens group described above.
[0045]
These aspherical shapes are represented by the following equations, where x is an optical axis with the light traveling direction being positive and y is a direction perpendicular to the optical axis.
[0046]

Here, r is a paraxial radius of curvature, P is a conical coefficient, and A ₄ , A ₆ , A ₈ , and A ₁₀ are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.
[0047]
Further, in the zoom lens according to the present invention, the first lens group has a first lens having negative power in order from the object side, a second lens having meniscus negative power with a convex surface facing the object side, And a lens group having a positive power subsequent thereto, and further adopting a configuration in which the second lens group is arranged in the order of a negative lens, a positive lens, and a negative lens in this order from the object side. The effect as described above can be obtained and is sufficient to achieve high zooming.
[0048]
【Example】
Next, Examples 1 to 3 of the zoom lens according to the present invention will be described.
[0049]
FIGS. 1 to 3 are cross-sectional views showing the lens group arrangements at the wide-angle end, the intermediate focal length, and the telephoto end of Examples 1 to 3, respectively. The numerical data of each embodiment will be described later, but the configuration of each embodiment will be described below.
[0050]
The configuration of the first lens group G1 includes the first lens L _{1 of} a biconcave lens, the second lens L ₂ of a negative meniscus lens having a convex surface facing the object side, and a biconvex lens that follows the first lens L ₁ . a positive lens group L _P consisting of a negative meniscus lens and a cemented lens of a biconvex lens having a convex surface directed toward the object side. The stop is disposed so as to move integrally to the most image plane side of the first lens group G1.
[0051]
In the case of Example 1, the configuration of the second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the image surface side, a biconvex lens, and a negative meniscus lens having a convex surface facing the image surface side. In the case of Example 2, the lens is composed of a cemented lens of a biconcave lens and a biconvex lens and a negative meniscus lens having a convex surface on the image surface side in order from the object side. In the case of Example 3, the biconcave lens has a convex surface on the image surface side. It is composed of a positive meniscus lens and a negative meniscus lens having a convex surface on the image side.
[0052]
Aspherical surface, both Examples 1 to 3 are used second lens surface on the object side of the L ₂ of the first lens group G1, the second surface of the most object side surface of the second lens group G2.
[0053]
Hereinafter, numerical data of each embodiment described above, but the symbols are outside the above, f is the focal length, F _NO is the F-number, omega denotes a half angle, f _B designates the back focal distance, r _1, r ₂ ... is the radius of curvature of each lens surface, d ₁ , d ₂ ... are the distances between the lens surfaces, n _d1 , n _d2 ... are the refractive indices of the d-line of each lens, ν _d1 , ν _d2 are the Abbe of each lens. Is a number. The aspheric shape is represented by the above formula (a).
[0054]

[0055]

[0056]

[0057]
Next, aberration diagrams at the wide-angle end, the intermediate focal length, and the telephoto end at the time of focusing on infinity in Example 1 are shown in FIGS. 4 to 6, respectively, and similar aberration diagrams of Example 2 are shown in FIGS. Similar aberration diagrams of Example 3 are shown in FIGS. In each aberration diagram, (a) shows spherical aberration, (b) shows astigmatism, (c) shows distortion, and (d) shows lateral chromatic aberration.
[0058]
The above high zoom lens of the present invention can be configured as follows, for example.
[1] A zoom including a first lens group having a positive power and a second lens group having a negative power in order from the object side, and changing the focal length of the entire system by changing the distance between these lens groups. In the lens,
The first lens group includes, in order from the object side, a first lens having a negative power, a second lens having a meniscus negative power with a convex surface facing the object side, and a lens group having a positive power. A high-magnification zoom lens comprising:
[2] A zoom including a first lens group having a positive power and a second lens group having a negative power in order from the object side, and changing the focal length of the entire system by changing the distance between these lens groups. In the lens,
The second lens group includes, in order from the object side, a negative lens, a positive lens, and a negative lens.
[3] A zoom including a first lens group having a positive power and a second lens group having a negative power in order from the object side, and changing the focal length of the entire system by changing the distance between these lens groups. In the lens,
The first lens group includes, in order from the object side, a first lens having a negative power, a second lens having a meniscus negative power with a convex surface facing the object side, and a lens group having a positive power. Have
The second lens group includes, in order from the object side, a negative lens, a positive lens, and a negative lens.
[4] The high zoom ratio zoom lens according to [1] or [3], wherein the first lens satisfies the following condition.
[0059]
(1) -5 <SF _L1 <0
Here, SF _L1 is a shaping factor of the first lens in the first lens group, and when the curvature radii of the object side surface and the image side surface of the first lens are r ₁ and r ₂ , SF _L1 = (r ₁ + r ₂ ) / (r ₁ −r ₂ ).
[5] The high zoom lens according to [1] or [3], wherein the second lens satisfies the following condition.
[0060]
(2) 1 <SF _L2 <10
Here, SF _L2 is the shaping factor of the second lens in the first lens group, and when the curvature radii of the object side surface and the image side surface of the second lens are r ₃ and r ₄ , SF _L2 = (r ₃ + r ₄ ) / (r ₃ −r ₄ ).
[6] A high-magnification zoom lens that satisfies the following conditions in [1] or [3].
[0061]
(3) -2 <f _W / r ₁ <−0.6
Here, f _W is the focal length at the wide-angle end of the entire system, and r ₁ is the radius of curvature of the first surface of the first lens.
[7] A high-magnification zoom lens characterized by satisfying the following conditions in [1], [3] or [6].
[0062]
(4) 0.2 <f _L1 / f _L2 <1
Here, f _L1 is the focal length of the first lens of the first lens group, and f _L2 is the focal length of the second lens of the first lens group.
[8] A high-magnification zoom lens characterized by satisfying the following conditions in [2] or [3].
[0063]
(5) ν ₁ > ν ₂
Here, ν ₁ is the Abbe number of the first lens with negative power of the second lens group, and ν ₂ is the Abbe number of the second lens with positive power of the second lens group.
[9] A high-magnification zoom lens characterized by satisfying the following conditions in [2], [3] or [8].
[0064]
(6) -3 <f ₂₂ / f ₂₁ <0
Here, f ₂₁ is the focal length of the first lens with negative power of the second lens group, and f ₂₂ is the focal length of the second lens with positive power of the second lens group.
[10] The zoom lens according to [1], wherein the positive lens group in the first lens group includes a positive lens and a cemented positive lens.
[11] The zoom lens according to [2] or [3], wherein the object side negative lens and the positive lens in the second lens group are cemented.
[12] A high zoom lens according to [1], [2], or [3], including at least one aspherical surface.
[13] In the above [1] or [3], an interval between the first lens and the second lens is narrower than an interval between the second lens and a lens group having a positive power following the second lens. High magnification zoom lens.
[0065]
【The invention's effect】
As is clear from the above description, according to the present invention, a high zoom ratio zoom lens that has a high zoom ratio of 3 × class and has excellent aberration correction while adopting a simple configuration of a two-group zoom lens system. A lens can be obtained.
[Brief description of the drawings]
FIG. 1 is a lens cross-sectional view showing a group arrangement at a wide angle end, an intermediate focal length, and a telephoto end of a high zoom lens according to Embodiment 1 of the present invention in comparison.
2 is a lens cross-sectional view similar to FIG. 1 of a high zoom ratio zoom lens according to Embodiment 2. FIG.
3 is a lens cross-sectional view similar to FIG. 1 of a high zoom lens according to Embodiment 3. FIG.
FIG. 4 is an aberration diagram at the wide-angle end when focusing on infinity according to Example 1.
FIG. 5 is an aberration diagram at an intermediate focal length at the time of focusing on infinity according to Example 1.
6 is an aberration diagram at the telephoto end upon focusing on infinity according to Example 1. FIG.
7 is an aberration diagram at the wide-angle end when focusing on infinity according to Example 2. FIG.
FIG. 8 is an aberration diagram at an intermediate focal length at the time of focusing on infinity according to Example 2.
FIG. 9 is an aberration diagram at the telephoto end upon focusing on infinity according to Example 2.
10 is an aberration diagram at the wide-angle end when focusing on infinity according to Example 3. FIG.
11 is an aberration diagram at an intermediate focal length at the time of focusing on infinity according to Example 3. FIG.
12 is an aberration diagram at the telephoto end upon focusing on infinity according to Example 3. FIG.
[Explanation of symbols]
G1 ... positive lens group of the first lens group G2 ... second lens L _P ... first lens group of the first lens L ₂ ... the first lens group in the second lens group L ₁ ... the first lens group

Claims (11)

In order from the object side, a zoom lens that includes a first lens group having a positive power and a second lens group having a negative power, and changes the focal length of the entire system by changing the distance between these lens groups.
The first lens group includes, in order from the object side, a first lens having a negative power, a second lens having a meniscus negative power with a convex surface facing the object side, and a lens group having a positive power. Have
The second lens group includes, in order from the object side, a negative lens, a positive lens, and a negative lens.
The high-magnification zoom lens, wherein the second lens satisfies the following conditions.
(2) 1 <SF _L2 <10
Here, SF _L2 is the shaping factor of the second lens in the first lens group, and when the curvature radii of the object side surface and the image side surface of the second lens are r ₃ and r ₄ , SF _L2 = (r ₃ + r ₄ ) / (r ₃ −r ₄ ). In order from the object side, a zoom lens that includes a first lens group having a positive power and a second lens group having a negative power, and changes the focal length of the entire system by changing the distance between these lens groups.
The first lens group includes, in order from the object side, a first lens having a negative power, a second lens having a meniscus negative power with a convex surface facing the object side, and a lens group having a positive power. Have
The second lens group includes, in order from the object side, a negative lens, a positive lens, and a negative lens.
A high-magnification zoom lens characterized by satisfying the following conditions:
(3) -2 <f _W / r ₁ <−0.6
Here, f _W is the focal length at the wide-angle end of the entire system, and r ₁ is the radius of curvature of the first surface of the first lens. 3. The high zoom ratio zoom lens according to claim 2, wherein the following condition is satisfied.
(4) 0.2 <f _L1 / f _L2 <1
Here, f _L1 is the focal length of the first lens of the first lens group, and f _L2 is the focal length of the second lens of the first lens group. In claim 2, a high-zoom-ratio zoom lens and satisfies the following condition.
(5) ν ₁ > ν ₂
Here, ν ₁ is the Abbe number of the first lens with negative power of the second lens group, and ν ₂ is the Abbe number of the second lens with positive power of the second lens group. 5. The zoom lens according to claim 2, wherein the zoom lens satisfies the following condition.
(6) -3 <f ₂₂ / f ₂₁ <0
Here, f ₂₁ is the focal length of the first lens with negative power of the second lens group, and f ₂₂ is the focal length of the second lens with positive power of the second lens group. 3. The zoom lens according to claim 2 , wherein the object side negative lens and the positive lens in the second lens group are cemented. 3. The high zoom ratio zoom lens according to claim 2 , comprising at least one aspherical surface.   3. The high zoom ratio zoom lens according to claim 2, wherein an interval between the first lens and the second lens is narrower than an interval between the second lens and a lens group having a positive power following the second lens. 3. The zoom lens according to claim 2, wherein the first lens satisfies the following conditions.
(1) '-2 <SF _L1 <-0.1
Here, SF _L1 is a shaping factor of the first lens in the first lens group, and when the curvature radii of the object side surface and the image side surface of the first lens are r ₁ and r ₂ , SF _L1 = (r ₁ + r ₂ ) / (r ₁ −r ₂ ). 3. The high zoom ratio zoom lens according to claim 2, wherein the following condition is satisfied.
(3) '−1.6 <f _W / r ₁ <−0.8
Here, f _W is the focal length at the wide-angle end of the entire system, and r ₁ is the radius of curvature of the first surface of the first lens. 3. The high zoom ratio zoom lens according to claim 2, wherein the following condition is satisfied.
(4) '0.2 <f _L1 / f _L2 <0.6
Here, f _L1 is the focal length of the first lens of the first lens group, and f _L2 is the focal length of the second lens of the first lens group.

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