JP4921842B2 - Wide-angle lens system for close-up photography - Google Patents

Wide-angle lens system for close-up photography Download PDF

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JP4921842B2
JP4921842B2 JP2006120149A JP2006120149A JP4921842B2 JP 4921842 B2 JP4921842 B2 JP 4921842B2 JP 2006120149 A JP2006120149 A JP 2006120149A JP 2006120149 A JP2006120149 A JP 2006120149A JP 4921842 B2 JP4921842 B2 JP 4921842B2
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lens
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wide
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JP2007292978A (en
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浩司 加藤
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Ricoh Imaging Co Ltd
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本発明は、一眼レフ（ＳＬＲ）カメラ用として好適な、フローティングフォーカス方式の広角レンズ系に関する。   The present invention relates to a floating focus type wide-angle lens system suitable for a single-lens reflex (SLR) camera.

一般に広角レンズ系では最短時（近接時）に球面収差の悪化、像面湾曲がオーバーにいってしまう傾向がある。それを解決するためにリアフォーカスやフローティングフォーカスなどのフォーカシング方式が取られてきた。しかし、特開平４−１９１７１５や特開２００２-４０３２５のような２群タイプで、近距離（例えば撮影倍率-０．５）に合焦した場合、コマ収差の補正が十分にできない。一方、２群の後方にさらに３群を配置してコマ収差補正を行うようにした変形フローティングフォーカス方式が提案されている。
特開平０４-１９１７１５号公報 特開２００２-０４０３２５公報 特開平０２-０１９８１４公報 特開２００３-１８５９１６公報 In general, in a wide-angle lens system, spherical aberration tends to deteriorate and field curvature tends to be over at the shortest time (close proximity). In order to solve this problem, focusing methods such as rear focus and floating focus have been adopted. However, when a two-group type such as JP-A-4-191715 or JP-A-2002-40325 is focused on a short distance (for example, an imaging magnification of -0.5), coma aberration cannot be corrected sufficiently. On the other hand, a modified floating focus method has been proposed in which three groups are arranged behind the second group to perform coma aberration correction.
Japanese Patent Laid-Open No. 04-191715 JP 2002-040325 A Japanese Patent Laid-Open No. 02-019814 JP 2003-185916 A

本発明は、物体側から順に、正又は負の第１レンズ群、正の第２レンズ群、及び負の第３レンズ群からなり、無限遠から近距離物体にフォーカシングする際に、第１レンズ群と第２レンズ群は、互いの群間隔を縮小させながら、第３レンズ群に対して相対的に物体側へ移動する変形フローティングフォーカス方式の広角レンズ系において、諸収差、特に球面収差、像面湾曲、コマ収差が良好に補正された画角が８０゜前後の高性能な広角レンズ系を得ることを目的とする。   The present invention includes, in order from the object side, a positive or negative first lens group, a positive second lens group, and a negative third lens group. When focusing from infinity to a short distance object, the first lens group And the second lens group in the modified floating focus wide-angle lens system that moves toward the object side relative to the third lens group while reducing the distance between the groups. An object of the present invention is to obtain a high-performance wide-angle lens system with an angle of view of approximately 80 ° in which curvature and coma are corrected satisfactorily.

本発明の近接撮影可能な広角レンズ系は、物体側から順に、正又は負の第１レンズ群、正の第２レンズ群、及び負の第３レンズ群からなり、第３レンズ群は正レンズと負レンズの２枚で構成されており、無限遠から近距離物体にフォーカシングする際に、第３レンズ群は固定であり、第１レンズ群と第２レンズ群は、互いの群間隔を縮小させながら、固定の第３レンズ群に対して相対的に物体側へ移動し、次の条件式（１）を満足することを特徴としている。
（１）０．４＜Ｘ１／Ｘ２＜０．６
但し、
Ｘ１；フォーカシングの際の第１レンズ群の移動量、
Ｘ２；フォーカシングの際の第２レンズ群の移動量、
である。 The wide-angle lens system capable of close-up photography according to the present invention includes, in order from the object side, a positive or negative first lens group, a positive second lens group, and a negative third lens group, and the third lens group is a positive lens. And the negative lens. When focusing from infinity to a close object, the third lens group is fixed, and the first lens group and the second lens group reduce the mutual group distance. However, it moves relative to the fixed third lens group toward the object side, and satisfies the following conditional expression (1).
(1) 0.4 <X1 / X2 <0.6
However,
X1: the amount of movement of the first lens unit during focusing,
X2: amount of movement of the second lens group during focusing,
It is.

本発明の広角レンズ系は、次の条件式（２）を満足することが好ましい。
（２）-８．０＜ｆ３／ｆ＜-６．５
但し、
ｆ３；第３レンズ群の焦点距離、
ｆ；全系の焦点距離、
である。 The wide-angle lens system of the present invention preferably satisfies the following conditional expression (2).
(2) -8.0 <f3 / f <-6.5
However,
f3: focal length of the third lens group,
f: focal length of the entire system
It is.

また、次の条件式（３）及び（４）を満足することが好ましい。
（３）０．２５＜｜ｆ３ｐ／ｆ３｜＜０．４５
（４）０．４＜ｆ３ｎ／ｆ３＜０．７５
但し、
ｆ３；第３レンズ群の焦点距離、
ｆ３ｐ：第３レンズ群中の正レンズの焦点距離、
ｆ３ｎ：第３レンズ群中の負レンズの焦点距離、
である。 Moreover, it is preferable that the following conditional expressions (3) and (4) are satisfied.
(3) 0.25 <| f3p / f3 | <0.45
(4) 0.4 <f3n / f3 <0.75
However,
f3: focal length of the third lens group,
f3p: the focal length of the positive lens in the third lens group,
f3n: focal length of the negative lens in the third lens group,
It is.

第１レンズ群は、例えば、物体側から順に、物体側に凸面を向けた負メニスカスレンズと正レンズの２枚で構成し、次の条件式（５）を満足させるのがよい。
（５）-０．１＜ｆ／ｆ１＜０．１
但し、
ｆ；全系の焦点距離、
ｆ１：第１レンズ群の焦点距離、
である。
For example, it is preferable that the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side and a positive lens, and satisfies the following conditional expression (5).
(5) -0.1 <f / f1 <0.1
However,
f: focal length of the entire system,
f1: the focal length of the first lens group,
It is.

第２レンズ群は、例えば、物体側から順に、負の第２ａレンズ群と、絞りと、正の第２ｂレンズ群から構成し、次の条件式（６）を満足させるのがよい。
（６）-３．０＜ｆ２ａ／ｆ２ｂ＜-２．０
但し、
ｆ２ａ；第２ａレンズ群の焦点距離、
ｆ２ｂ；第２ｂレンズ群の焦点距離、
である。 For example, it is preferable that the second lens group includes, in order from the object side, a negative second a lens group, a stop, and a positive second b lens group, and satisfies the following conditional expression (6).
(6) -3.0 <f2a / f2b <-2.0
However,
f2a: focal length of the 2a lens group,
f2b; the focal length of the 2b lens group,
It is.

さらに具体的には、第２ｂレンズ群は、物体側から順に、物体側から順に位置する両凸正レンズと両凹負レンズの貼合せレンズ、両凹負レンズ、像側に凸の正レンズ、及び両凸正レンズから構成し、次の条件式（７）を満足させることが好ましい。
（７）ν2b-4＞７０
但し、
ν2b-4：第２ｂレンズ群中の像側から２枚目の正レンズのアッベ数、
である。 More specifically, the 2b lens group includes, in order from the object side, a cemented lens of a biconvex positive lens and a biconcave negative lens positioned in order from the object side, a biconcave negative lens, a positive lens convex to the image side, And a biconvex positive lens, and the following conditional expression (7) is preferably satisfied.
(7) ν 2b-4 > 70
However,
ν 2b-4 : Abbe number of the second positive lens from the image side in the 2b lens group,
It is.

本発明によれば、３群からなる変形フローティングフォーカス方式の広角レンズ系において、諸収差、特に球面収差、像面湾曲、コマ収差が良好に補正された画角が８０゜前後の高性能な広角レンズ系を得ることができる。   According to the present invention, in a wide-angle lens system of a three-group modified floating focus method, a high-performance wide-angle with an angle of view of about 80 ° in which various aberrations, particularly spherical aberration, field curvature, and coma are corrected satisfactorily. A lens system can be obtained.

本実施形態の広角レンズ系は、図１、図４、図７、図１０、図１３及び図１６の各実施例に示すように、物体側から順に、正又は負の第１レンズ群１０、正の第２レンズ群２０、及び負の第３レンズ群３０からなっており、無限遠から近距離物体にフォーカシングする際に、第１レンズ群１０と第２レンズ群２０は、互いの群間隔を縮小させながら、第３レンズ群３０に対して相対的に物体側へ移動する。つまり、第２レンズ群２０の移動量は第１レンズ群１０の移動量より大きい。各レンズ群の群分けは、フォーカシング時の移動量の違いによって行われている。第１レンズ群１０は正負のいずれのパワーも可能である。   The wide-angle lens system of the present embodiment includes a first lens group 10 that is positive or negative in order from the object side, as shown in the examples of FIGS. 1, 4, 7, 10, 13, and 16. The first lens group 10 and the second lens group 20 are composed of a positive second lens group 20 and a negative third lens group 30. When focusing from infinity to a short distance object, the first lens group 10 and the second lens group 20 are spaced apart from each other. The lens moves toward the object side relative to the third lens group 30 while being reduced. That is, the movement amount of the second lens group 20 is larger than the movement amount of the first lens group 10. The lens groups are grouped according to the amount of movement during focusing. The first lens group 10 can have either positive or negative power.

このように無限遠から近距離物体にフォーカシングする際に、第１レンズ群１０と第２レンズ群２０を互いの群間隔を縮小させながら物体側に移動させると、近距離撮影時の特に球面収差と像面湾曲を良好に補正することができるが、近距離撮影時に軸外で発生するコマ収差の補正が困難になる。第３レンズ群３０は、特にこのコマ収差の補正に効果的である。第３レンズ群３０は、固定とするのが実際的である。   Thus, when focusing from infinity to a short distance object, if the first lens group 10 and the second lens group 20 are moved toward the object side while reducing the mutual group distance, particularly spherical aberration during close-up shooting is obtained. Although field curvature can be corrected satisfactorily, it is difficult to correct coma that occurs off-axis during short-distance shooting. The third lens group 30 is particularly effective for correcting this coma aberration. The third lens group 30 is practically fixed.

仮に、固定の第３レンズ群に対して、第１レンズ群１０と第２レンズ群２０を一体として物体側に移動させると、球面収差の変動を抑えることはできるが、像面湾曲が正の方向に大きく変動し、近距離において画面中心と周辺とで像面のズレが生じる。これに対し、本実施形態のように、第１レンズ群１０と第２レンズ群２０を異なる量だけ物体側にフォーカシングするフローティング方式を用いると、無限遠から近距離物体にフォーカシングした際、球面収差と像面湾曲を負の方向に変動させ、近距離でも画面中心と周辺の像面のズレを小さく保つことができる。また、フローティング方式とすることで、無限遠から近距離物体までの第１レンズ群の繰り出し量を小さくして、レンズ系の全長変化を小さくすることができる。   If the first lens group 10 and the second lens group 20 are moved together with the fixed third lens group toward the object side, fluctuations in spherical aberration can be suppressed, but the field curvature is positive. The direction fluctuates greatly and the image plane shifts between the center and the periphery of the screen at a short distance. On the other hand, when using a floating method in which the first lens group 10 and the second lens group 20 are focused on the object side by different amounts as in the present embodiment, spherical aberration is reduced when focusing from infinity to a short distance object. The curvature of field can be changed in the negative direction, and the deviation between the image center at the center and the periphery can be kept small even at a short distance. Further, by adopting the floating system, it is possible to reduce the amount of extension of the first lens group from infinity to a close object and to reduce the change in the entire length of the lens system.

本実施形態は、第一に第３レンズ群３０の構成に特徴があり、正レンズと負レンズの２枚で構成されている。各実施例では、物体側から順に、負レンズ（物体側に凸の負メニスカスレンズ）と正レンズ（両凸正レンズ）からなっているが、正負の順番は逆にすることが可能である。   This embodiment is primarily characterized by the configuration of the third lens group 30, and is composed of two lenses, a positive lens and a negative lens. Each embodiment includes a negative lens (a negative meniscus lens convex toward the object side) and a positive lens (biconvex positive lens) in order from the object side, but the order of positive and negative can be reversed.

第１レンズ群１０は、物体側から順に、物体側に凸面を向けた負メニスカスレンズと正レンズの２枚からなっている。また、第２レンズ群２０は、物体側から順に、負の第２ａレンズ群２１と、絞りＳと、正の第２ｂレンズ群２２から構成されている。第２レンズ群２０の第２ａレンズ群２１は、各実施例では、物体側から順に、２枚の物体側に凸の負メニスカスレンズと両凸正レンズからなり、第２ｂレンズ群２２は、物体側から順に、物体側から順に位置する両凸正レンズと両凹負レンズの貼合せレンズ、両凹負レンズ、像側に凸の正レンズ、及び両凸正レンズからなっている。   The first lens group 10 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side and a positive lens. The second lens group 20 includes, in order from the object side, a negative second a lens group 21, a diaphragm S, and a positive second b lens group 22. In each embodiment, the second lens group 21 of the second lens group 20 includes, in order from the object side, two negative meniscus lenses and a biconvex positive lens that are convex on the object side, and the second lens group 22 includes an object lens. It consists of a cemented lens of a biconvex positive lens and a biconcave negative lens, a biconcave negative lens, a positive lens convex to the image side, and a biconvex positive lens located in order from the object side.

条件式（１）は、第１レンズ群と第２レンズ群の移動量の比に関する条件である。条件式（１）の上限を超えると、補正不足で正の像面湾曲が出てしまう。条件式（１）の下限を超えると、過剰補正で負の像面湾曲が出てしまい好ましくない。   Conditional expression (1) is a condition regarding the ratio of the movement amounts of the first lens group and the second lens group. If the upper limit of conditional expression (1) is exceeded, a positive curvature of field will occur due to insufficient correction. Exceeding the lower limit of conditional expression (1) is not preferable because it causes negative field curvature due to overcorrection.

条件式（２）は、第３レンズ群のパワーに関する条件である。条件式（２）の上限を超えて第３レンズ群の負のパワーが強まると、レンズ全長が長くなる。また、第１レンズ群、第２レンズ群で発生した諸収差、特に球面収差とコマ収差が大きく発生してしまい補正が困難である。条件式（２）の下限を超えて第３レンズ群の負のパワーが弱まると、球面収差、像面湾曲、歪曲収差が大きく発生し好ましくない。また、第３レンズ群は固定すると、近距離での周辺光量を確保するためにレンズ群の有効径を大きくしなければならない。   Conditional expression (2) is a condition regarding the power of the third lens group. When the negative power of the third lens unit increases beyond the upper limit of conditional expression (2), the total lens length becomes longer. In addition, various aberrations generated in the first lens group and the second lens group, particularly spherical aberration and coma aberration, are greatly generated and are difficult to correct. If the lower power of the conditional expression (2) is exceeded and the negative power of the third lens group is weakened, spherical aberration, curvature of field, and distortion are greatly generated, which is not preferable. When the third lens group is fixed, the effective diameter of the lens group must be increased in order to secure a peripheral light amount at a short distance.

条件式（３）と（４）は、第３レンズ群を正レンズと負レンズの２枚から構成したとき、同正レンズと負レンズが満足すべき条件である。各条件式の下限を超えると、正レンズのパワーが強くなり、それにつれて負のパワーも強くなり過ぎるため、非点収差やコマ収差などの軸外収差が発生し補正が困難である。逆に各条件式の上限を超えると、正レンズのパワーが弱くなり、それにつれて負レンズのパワーも弱くなり、近距離に合焦する際に非点収差補正が不十分になり好ましくない。   Conditional expressions (3) and (4) are conditions that the positive lens and the negative lens should satisfy when the third lens group is composed of two lenses, a positive lens and a negative lens. When the lower limit of each conditional expression is exceeded, the power of the positive lens becomes strong, and the negative power becomes too strong along with it, so that off-axis aberrations such as astigmatism and coma occur, and correction is difficult. On the other hand, if the upper limit of each conditional expression is exceeded, the power of the positive lens becomes weak, and accordingly the power of the negative lens also becomes weak. As a result, astigmatism correction becomes insufficient when focusing on a short distance, which is not preferable.

条件式（５）は、正負いずれのパワーもとりうる第１レンズ群のパワーに関する条件である。条件式（５）の範囲を超えて第１レンズ群の正又は負のパワーが強くなると、バックフォーカスは確保できるが、このレンズ群で発生する諸収差、特に歪曲収差の補正が困難となる。また、第２レンズ群への軸上光束の入射角度がきつくなるため、球面収差の変動が大きくなり好ましくない。   Conditional expression (5) is a condition relating to the power of the first lens group that can take either positive or negative power. When the positive or negative power of the first lens group becomes strong beyond the range of the conditional expression (5), the back focus can be secured, but it is difficult to correct various aberrations, particularly distortion, generated in the lens group. Further, since the incident angle of the axial light beam on the second lens group becomes tight, the variation of spherical aberration becomes large, which is not preferable.

条件式（６）は、第２レンズ群中の絞りの前後に位置する負の第２ａレンズ群と正の第２ｂレンズ群とのパワー（焦点距離）比に関する条件である。条件式（６）の下限を超えて第２ａレンズ群のパワーが弱くなる（第２ｂレンズ群のパワーが強くなる）と、バックフォーカスが不足すると共に、球面収差も悪化する。条件式（６）の上限を超えて第２ｂレンズ群のパワーが弱くなる（第２ａレンズ群のパワーが強くなる）と、像面湾曲、非点収差が悪化し補正が困難である。   Conditional expression (6) is a condition relating to the power (focal length) ratio between the negative 2a lens group and the positive 2b lens group positioned before and after the stop in the second lens group. When the power of the 2a lens group becomes weaker than the lower limit of the conditional expression (6) (the power of the 2b lens group becomes strong), the back focus is insufficient and the spherical aberration is also deteriorated. If the power of the 2b lens group becomes weaker than the upper limit of the conditional expression (6) (the power of the 2a lens group becomes strong), field curvature and astigmatism will deteriorate and correction will be difficult.

負の第２ａレンズ群は、各実施例のように、物体側から順に、２枚の物体側に凸の負メニスカスレンズと両凸正レンズから構成すると、特に物体側の２枚の負メニスカスレンズによって高次の発散のパワーを分担させながら像面湾曲を抑えることができ、その結果発生する負の歪曲収差を両凸正レンズで補正することができる。絞りの物体側の正レンズは、この負の歪曲収差を補正するために、厚くするのが好ましい。   When the negative second a lens group is composed of two negative meniscus lenses convex to the object side and biconvex positive lenses in order from the object side as in each embodiment, two negative meniscus lenses, particularly on the object side, are used. Thus, the curvature of field can be suppressed while sharing the power of higher-order divergence, and the negative distortion generated as a result can be corrected by the biconvex positive lens. The positive lens on the object side of the diaphragm is preferably thick in order to correct this negative distortion.

正の第２ｂレンズ群は、軸外収差に与える影響を小さく保ったまま全系で発生する球面収差を補正するために、負レンズを配置することによりそこで負の球面収差を発生させ、更に該第２ｂレンズ群で強い正のパワーを得たときに、球面収差やコマ収差などの発生を抑えるために少なくとも３枚の正レンズを配置することが望ましい。また、絞りに近い正レンズと負レンズと貼り合せることにより、高次の球面収差を良好に補正する。各実施例では、正の第２ｂレンズ群は、物体側から順に、物体側から順に位置する両凸正レンズと両凹負レンズの貼合せレンズ、両凹負レンズ、像側に凸の正レンズ、及び両凸正レンズからなっている。   In order to correct the spherical aberration that occurs in the entire system while keeping the influence on the off-axis aberration small, the positive second lens group b generates a negative spherical aberration there by disposing a negative lens. It is desirable to arrange at least three positive lenses in order to suppress the occurrence of spherical aberration, coma aberration, etc. when strong positive power is obtained with the 2b lens group. In addition, high-order spherical aberration is favorably corrected by bonding a positive lens and a negative lens close to the stop. In each embodiment, the positive second b lens group includes, in order from the object side, a biconvex positive lens and a biconcave negative lens that are positioned in order from the object side, a biconcave negative lens, and a positive lens convex to the image side. And a biconvex positive lens.

条件式（７）は、第２ｂレンズ群を、物体側から順に、物体側から順に位置する両凸正レンズと両凹負レンズの貼合せレンズ、両凹負レンズ、像側に凸の正レンズ、及び両凸正レンズから構成したときに、像側から２枚目の両凸正レンズが満足すべき条件である。
この特定のレンズに条件式（７）の下限を超えるアッベ数をもつ硝材を使用すると、軸上色収差、倍率色収差の補正が困難になる。この条件式（７）の下限を８０にする（（７’）ν2b-4＞８０）と、より良好な収差補正が行える。 Conditional expression (7) indicates that the second lens group is arranged in order from the object side, a cemented lens of a biconvex positive lens and a biconcave negative lens positioned in order from the object side, a biconcave negative lens, and a positive lens convex to the image side. , And a biconvex positive lens, the second biconvex positive lens from the image side should be satisfied.
If a glass material having an Abbe number exceeding the lower limit of conditional expression (7) is used for this specific lens, it becomes difficult to correct axial chromatic aberration and lateral chromatic aberration. If the lower limit of conditional expression (7) is set to 80 ((7 ′) ν 2b-4 > 80), better aberration correction can be performed.

次に具体的な実施例を示す。諸収差図及び表中、ＳＡは球面収差、ＳＣは正弦条件、球面収差で表される色収差（軸上色収差）図及び倍率色収差図中のｄ線、ｇ線、Ｃ線はそれぞれの波長に対する収差、Ｓはサジタル、Ｍはメリディオナル、Ｗは半画角（゜）、ｙは最大像高、F、FnoはＦナンバー、FEは有効Ｆナンバー、ｆは全系の焦点距離、fBはバックフォーカス、ｒは曲率半径、ｄはレンズ厚またはレンズ間隔、Ｎd はｄ線の屈折率、νはアッベ数、ｍは撮影倍率、Ｄ０は最前レンズの物体側の面（第１面）の頂点から物体までの距離である。 Next, specific examples will be described. In the various aberration diagrams and tables, SA is spherical aberration, SC is a sine condition, chromatic aberration (axial chromatic aberration) diagram represented by spherical aberration, and d-line, g-line, and C-line are chromatic aberrations for each wavelength. , S for sagittal, M for meridional, W for half angle of view (°), y for maximum image height, F, Fno for F number, FE for effective F number, f for focal length of entire system, fB for back focus, r is the radius of curvature, d is the lens thickness or lens spacing, N d is the refractive index of the d-line, ν is the Abbe number, m is the magnification, and D0 is the object from the top of the object side surface (first surface) of the front lens. It is the distance to.

図１、図２及び図３と表１は本発明による広角レンズ系の実施例１を示している。図１は無限遠撮影状態におけるレンズ構成図、図２はその諸収差図、図３は撮影倍率−０．５倍における諸収差図、表１はその無限遠撮影状態における数値データである。
本実施例の広角レンズ系は、物体側から順に、第１レンズ群１０、正の第２レンズ群２０、及び負の第３レンズ群３０からなっており、第１レンズ群１０のパワーはこの実施例では正である。第１レンズ群１０は、物体側から順に、物体側に凸面を向けた負メニスカスレンズと正レンズの２枚からなり、第３レンズ群３０は、物体側から順に、物体側に凸の負メニスカスレンズと両凸正レンズからなる。一方、第２レンズ群２０は、物体側から順に、負の第２ａレンズ群２１と、絞りＳと、正の第２ｂレンズ群２２からなり、第２ａレンズ群２１は、各実施例では、物体側から順に、２枚の物体側に凸の負メニスカスレンズと両凸正レンズからなり、第２ｂレンズ群２２は、物体側から順に、物体側から順に位置する両凸正レンズと両凹負レンズの貼合せレンズ、両凹負レンズ、像側に凸の正レンズ、及び両凸正レンズからなっている。絞りＳは、第１１面（第２ｂレンズ群２２）の極から前方1.657にある。
無限遠から近距離物体へのフォーカシングは、第１レンズ群１０と第２レンズ群２０を、互いの群間隔を縮小させながら、固定の第３レンズ群３０に対して相対的に物体側へ移動させて行う。
（表１）
F = 1: 2.9
f = 27.32
W = 38.6
fB = 40.45
面NO r d Nd ν
1 63.076 1.46 1.69697 55.5
2 27.086 4.03
3 77.781 4.08 1.66441 43.3
4 -125.579 （ｄ４＝可変）
5 38.732 1.17 1.77250 49.6
6 16.575 2.15
7 60.782 1.33 1.78861 43.4
8 18.240 6.02
9 30.935 7.05 1.84666 23.9
10 -207.514 4.03
11 25.435 6.50 1.67702 56.4
12 -60.470 3.12 1.78610 26.6
13 36.903 2.12
14 -110.999 1.33 1.78469 25.8
15 30.212 0.95
16 114.338 2.75 1.49700 81.6
17 -22.533 2.00
18 49.603 3.76 1.81925 44.5
19 -44.728 （ｄ１９＝可変）
20 83.174 1.26 1.76352 50.2
21 31.394 2.11
22 127.929 2.45 1.58913 59.4
23 -112.811 -
撮影倍率ｍ ｆ＝27.316 ｍ＝-0.500
Ｄ０ ∞ 44.908
ｄ４ 4.544 0.166
ｄ１９ 0.066 9.001 1, 2 and 3 and Table 1 show Example 1 of the wide-angle lens system according to the present invention. FIG. 1 is a lens configuration diagram in the infinity shooting state, FIG. 2 is a diagram of various aberrations, FIG. 3 is a diagram of various aberrations at a shooting magnification of −0.5, and Table 1 is numerical data in the infinity shooting state.
The wide-angle lens system of the present embodiment includes, in order from the object side, a first lens group 10, a positive second lens group 20, and a negative third lens group 30, and the power of the first lens group 10 is this. In the embodiment it is positive. The first lens group 10 includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side and a positive lens, and the third lens group 30 includes a negative meniscus convex toward the object side in order from the object side. It consists of a lens and a biconvex positive lens. On the other hand, the second lens group 20 includes, in order from the object side, a negative second a lens group 21, an aperture stop S, and a positive second b lens group 22, and the second a lens group 21 is an object in each embodiment. In order from the side, there are two negative meniscus lenses convex to the object side and a biconvex positive lens, and the second b lens group 22 includes a biconvex positive lens and a biconcave negative lens positioned in order from the object side and sequentially from the object side. A cemented lens, a biconcave negative lens, a positive lens convex on the image side, and a biconvex positive lens. The stop S is 1.657 ahead from the pole of the eleventh surface (second b lens group 22).
Focusing from an infinite distance to a close object moves the first lens group 10 and the second lens group 20 toward the object side relative to the fixed third lens group 30 while reducing the mutual group interval. Do it.
(Table 1)
F = 1: 2.9
f = 27.32
W = 38.6
fB = 40.45
NO rd Nd ν
1 63.076 1.46 1.69697 55.5
2 27.086 4.03
3 77.781 4.08 1.66441 43.3
4 -125.579 (d4 = variable)
5 38.732 1.17 1.77250 49.6
6 16.575 2.15
7 60.782 1.33 1.78861 43.4
8 18.240 6.02
9 30.935 7.05 1.84666 23.9
10 -207.514 4.03
11 25.435 6.50 1.67702 56.4
12 -60.470 3.12 1.78610 26.6
13 36.903 2.12
14 -110.999 1.33 1.78469 25.8
15 30.212 0.95
16 114.338 2.75 1.49700 81.6
17 -22.533 2.00
18 49.603 3.76 1.81925 44.5
19 -44.728 (d19 = variable)
20 83.174 1.26 1.76352 50.2
21 31.394 2.11
22 127.929 2.45 1.58913 59.4
23 -112.811-
Shooting magnification m f = 27.316 m = -0.500
D0 ∞ 44.908
d4 4.544 0.166
d19 0.066 9.001

図４、図５及び図６と表２は本発明による広角レンズ系の実施例２を示している。図４は無限遠撮影状態におけるレンズ構成図、図５はその諸収差図、図６は撮影倍率−０．５倍における諸収差図、表２はその無限遠撮影状態における数値データである。基本的なレンズ構成は、実施例１と同様であり、第１レンズ群１０のパワーは正である。絞りＳは、第１１面（第２ｂレンズ群２２）の極から前方1.657にある。
（表２）
F = 1: 2.9
f = 27.32
W = 38.6
fB = 40.46
面NO r d Nd ν
1 63.046 1.46 1.71412 53.7
2 27.218 3.81
3 69.942 4.20 1.68409 42.1
4 -137.879 （ｄ４＝可変）
5 41.133 1.17 1.78102 48.8
6 16.575 2.10
7 57.062 1.33 1.80196 43.0
8 18.216 6.03
9 30.960 7.80 1.84666 23.8
10 -201.895 3.63
11 25.469 6.50 1.67781 56.3
12 -60.197 3.12 1.78648 26.6
13 36.881 2.12
14 -111.442 1.33 1.78469 25.8
15 30.268 0.95
16 116.668 2.75 1.49700 81.6
17 -22.511 1.93
18 49.600 3.74 1.81944 44.5
19 -44.733 （ｄ１９＝可変）
20 83.571 1.26 1.75790 50.6
21 31.696 2.15
22 143.286 2.42 1.58913 59.4
23 -106.303 -
撮影倍率ｍ ｆ＝27.316 ｍ＝-0.500
Ｄ０ ∞ 44.918
ｄ４ 4.515 0.204
ｄ１９ 0.066 9.047 4, 5 and 6 and Table 2 show Example 2 of the wide-angle lens system according to the present invention. FIG. 4 is a lens configuration diagram in the infinity photographing state, FIG. 5 is a diagram of various aberrations, FIG. 6 is a diagram of various aberrations at a photographing magnification of −0.5, and Table 2 is numerical data in the infinity photographing state. The basic lens configuration is the same as in Example 1, and the power of the first lens group 10 is positive. The stop S is 1.657 ahead from the pole of the eleventh surface (second b lens group 22).
(Table 2)
F = 1: 2.9
f = 27.32
W = 38.6
fB = 40.46
NO rd Nd ν
1 63.046 1.46 1.71412 53.7
2 27.218 3.81
3 69.942 4.20 1.68409 42.1
4 -137.879 (d4 = variable)
5 41.133 1.17 1.78102 48.8
6 16.575 2.10
7 57.062 1.33 1.80196 43.0
8 18.216 6.03
9 30.960 7.80 1.84666 23.8
10 -201.895 3.63
11 25.469 6.50 1.67781 56.3
12 -60.197 3.12 1.78648 26.6
13 36.881 2.12
14 -111.442 1.33 1.78469 25.8
15 30.268 0.95
16 116.668 2.75 1.49700 81.6
17 -22.511 1.93
18 49.600 3.74 1.81944 44.5
19 -44.733 (d19 = variable)
20 83.571 1.26 1.75790 50.6
21 31.696 2.15
22 143.286 2.42 1.58913 59.4
23 -106.303-
Shooting magnification m f = 27.316 m = -0.500
D0 ∞ 44.918
d4 4.515 0.204
d19 0.066 9.047

図７、図８及び図９と表３は本発明による広角レンズ系の実施例３を示している。図７は無限遠撮影状態におけるレンズ構成図、図８はその諸収差図、図９は撮影倍率−０．５倍における諸収差図、表３はその無限遠撮影状態における数値データである。基本的なレンズ構成は、実施例１と同様であり、第１レンズ群１０のパワーは正である。絞りＳは、第１１面（第２ｂレンズ群２２）の極から前方1.658にある。
（表３）
F = 1: 2.9
f = 27.32
W = 38.6
fB = 40.46
面NO r d Nd ν
1 61.996 1.46 1.78562 48.3
2 27.839 2.88
3 50.236 4.74 1.70154 41.2
4 -201.597 （ｄ４＝可変）
5 47.885 1.17 1.80400 46.6
6 16.575 2.12
7 58.550 1.33 1.80400 44.9
8 17.901 6.33
9 31.301 8.51 1.80000 25.6
10 -97.162 3.45
11 24.682 6.50 1.68900 55.8
12 -102.598 2.65 1.80246 26.0
13 34.926 2.25
14 -81.272 1.33 1.78470 25.8
15 30.021 1.02
16 157.728 2.74 1.49700 81.6
17 -21.487 1.14
18 45.849 3.57 1.81035 45.7
19 -46.060 （ｄ１９＝可変）
20 148.283 1.26 1.69715 55.5
21 32.845 1.87
22 120.062 2.56 1.58914 59.4
23 -92.793 -
撮影倍率ｍ ｆ＝27.315 ｍ＝-0.500
Ｄ０ ∞ 44.645
ｄ４ 4.309 0.602
ｄ１９ 0.066 8.894 7, 8 and 9 and Table 3 show Example 3 of the wide-angle lens system according to the present invention. FIG. 7 is a lens configuration diagram in the infinity photographing state, FIG. 8 is a diagram of various aberrations, FIG. 9 is a diagram of various aberrations at a photographing magnification of −0.5, and Table 3 is numerical data in the infinity photographing state. The basic lens configuration is the same as in Example 1, and the power of the first lens group 10 is positive. The stop S is 1.658 ahead from the pole of the eleventh surface (second b lens group 22).
(Table 3)
F = 1: 2.9
f = 27.32
W = 38.6
fB = 40.46
NO rd Nd ν
1 61.996 1.46 1.78562 48.3
2 27.839 2.88
3 50.236 4.74 1.70154 41.2
4 -201.597 (d4 = variable)
5 47.885 1.17 1.80 400 46.6
6 16.575 2.12
7 58.550 1.33 1.80 400 44.9
8 17.901 6.33
9 31.301 8.51 1.80000 25.6
10 -97.162 3.45
11 24.682 6.50 1.68900 55.8
12 -102.598 2.65 1.80246 26.0
13 34.926 2.25
14 -81.272 1.33 1.78470 25.8
15 30.021 1.02
16 157.728 2.74 1.49700 81.6
17 -21.487 1.14
18 45.849 3.57 1.81035 45.7
19 -46.060 (d19 = variable)
20 148.283 1.26 1.69715 55.5
21 32.845 1.87
22 120.062 2.56 1.58914 59.4
23 -92.793-
Shooting magnification m f = 27.315 m = -0.500
D0 ∞ 44.645
d4 4.309 0.602
d19 0.066 8.894

図１０、図１１及び図１２と表４は本発明による広角レンズ系の実施例４を示している。図１０は無限遠撮影状態におけるレンズ構成図、図１１はその諸収差図、図１２は撮影倍率−０．５倍における諸収差図、表４はその無限遠撮影状態における数値データである。基本的なレンズ構成は、実施例１と同様であるが、第１レンズ群１０のパワーは負である。絞りＳは、第１１面（第２ｂレンズ群２２）の極から前方1.658にある。
（表４）
F = 1: 2.9
f = 27.32
W = 38.5
fB = 40.45
面NO r d Nd ν
1 79.411 1.46 1.69680 55.5
2 28.717 4.02
3 87.477 4.10 1.70154 41.2
4 -115.971 （ｄ４＝可変）
5 37.517 1.17 1.77250 49.6
6 16.575 2.03
7 55.709 1.33 1.80400 40.6
8 18.045 5.80
9 30.464 8.62 1.84267 24.0
10 -224.581 3.45
11 25.717 6.50 1.67906 56.3
12 -65.506 3.03 1.79033 26.5
13 36.929 2.14
14 -109.889 1.33 1.78470 25.8
15 30.917 0.95
16 122.381 2.74 1.49700 81.6
17 -22.800 1.64
18 49.486 3.70 1.82366 44.0
19 -43.849 （ｄ１９＝可変）
20 67.513 1.26 1.75491 50.8
21 29.743 2.28
22 153.339 2.24 1.58914 59.4
23 -126.429 -
撮影倍率ｍ ｆ＝27.315 ｍ＝-0.500
Ｄ０ ∞ 45.299
ｄ４ 5.245 0.162
ｄ１９ 0.133 8.897 10, 11 and 12 and Table 4 show a fourth embodiment of the wide-angle lens system according to the present invention. FIG. 10 is a lens configuration diagram in the infinity shooting state, FIG. 11 is a diagram of various aberrations, FIG. 12 is a diagram of various aberrations at a shooting magnification of −0.5, and Table 4 is numerical data in the infinity shooting state. The basic lens configuration is the same as in Example 1, but the power of the first lens group 10 is negative. The stop S is 1.658 ahead from the pole of the eleventh surface (second b lens group 22).
(Table 4)
F = 1: 2.9
f = 27.32
W = 38.5
fB = 40.45
NO rd Nd ν
1 79.411 1.46 1.69680 55.5
2 28.717 4.02
3 87.477 4.10 1.70154 41.2
4 -115.971 (d4 = variable)
5 37.517 1.17 1.77250 49.6
6 16.575 2.03
7 55.709 1.33 1.80 400 40.6
8 18.045 5.80
9 30.464 8.62 1.84267 24.0
10 -224.581 3.45
11 25.717 6.50 1.67906 56.3
12 -65.506 3.03 1.79033 26.5
13 36.929 2.14
14 -109.889 1.33 1.78470 25.8
15 30.917 0.95
16 122.381 2.74 1.49700 81.6
17 -22.800 1.64
18 49.486 3.70 1.82366 44.0
19 -43.849 (d19 = variable)
20 67.513 1.26 1.75491 50.8
21 29.743 2.28
22 153.339 2.24 1.58914 59.4
23 -126.429-
Shooting magnification m f = 27.315 m = -0.500
D0 ∞ 45.299
d4 5.245 0.162
d19 0.133 8.897

図１３、図１４及び図１５と表５は本発明による広角レンズ系の実施例５を示している。図１３は無限遠撮影状態におけるレンズ構成図、図１４はその諸収差図、図１５は撮影倍率−０．５倍における諸収差図、表５はその無限遠撮影状態における数値データである。基本的なレンズ構成は、実施例４と同様であり、第１レンズ群１０のパワーは負である。絞りＳは、第１１面（第２ｂレンズ群２２）の極から前方1.658にある。
（表５）
F = 1: 2.9
f = 27.32
W = 38.5
fB = 40.46
面NO r d Nd ν
1 69.862 1.46 1.70346 54.9
2 27.975 4.07
3 85.389 4.00 1.70085 41.3
4 -123.497 （ｄ４＝可変）
5 37.978 1.17 1.77251 49.6
6 16.575 2.11
7 58.789 1.33 1.80400 41.2
8 18.324 5.95
9 30.935 8.23 1.84666 23.8
10 -205.968 3.52
11 25.474 6.50 1.67827 56.3
12 -63.285 3.12 1.78704 26.6
13 36.926 2.13
14 -110.697 1.33 1.78469 25.8
15 30.342 0.95
16 116.098 2.75 1.49700 81.6
17 -22.622 1.97
18 49.731 3.75 1.81861 44.6
19 -44.714 （ｄ１９＝可変）
20 76.860 1.26 1.74852 51.2
21 30.723 2.20
22 138.423 2.36 1.58913 59.4
23 -118.294 -
撮影倍率ｍ ｆ＝27.316 ｍ＝-0.500
Ｄ０ ∞ 45.172
ｄ４ 4.938 0.127
ｄ１９ 0.066 8.976 FIGS. 13, 14 and 15 and Table 5 show Example 5 of the wide-angle lens system according to the present invention. FIG. 13 is a lens configuration diagram in the infinity photographing state, FIG. 14 is a diagram of various aberrations, FIG. 15 is a diagram of various aberrations at a photographing magnification of −0.5, and Table 5 is numerical data in the infinity photographing state. The basic lens configuration is the same as in Example 4, and the power of the first lens group 10 is negative. The stop S is 1.658 ahead from the pole of the eleventh surface (second b lens group 22).
(Table 5)
F = 1: 2.9
f = 27.32
W = 38.5
fB = 40.46
NO rd Nd ν
1 69.862 1.46 1.70346 54.9
2 27.975 4.07
3 85.389 4.00 1.70085 41.3
4 -123.497 (d4 = variable)
5 37.978 1.17 1.77251 49.6
6 16.575 2.11
7 58.789 1.33 1.80 400 41.2
8 18.324 5.95
9 30.935 8.23 1.84666 23.8
10 -205.968 3.52
11 25.474 6.50 1.67827 56.3
12 -63.285 3.12 1.78704 26.6
13 36.926 2.13
14 -110.697 1.33 1.78469 25.8
15 30.342 0.95
16 116.098 2.75 1.49700 81.6
17 -22.622 1.97
18 49.731 3.75 1.81861 44.6
19 -44.714 (d19 = variable)
20 76.860 1.26 1.74852 51.2
21 30.723 2.20
22 138.423 2.36 1.58913 59.4
23 -118.294-
Shooting magnification m f = 27.316 m = -0.500
D0 ∞ 45.172
d4 4.938 0.127
d19 0.066 8.976

図１６、図１７及び図１８と表６は本発明による広角レンズ系の実施例６を示している。図１６は無限遠撮影状態におけるレンズ構成図、図１７はその諸収差図、図１８は撮影倍率−０．５倍における諸収差図、表６はその無限遠撮影状態における数値データである。基本的なレンズ構成は、実施例１と同様であり、第１レンズ群１０のパワーは正である。絞りＳは、第１１面（第２ｂレンズ群２２）の極から前方1.658にある。
（表６）
F = 1: 2.9
f = 27.32
W = 38.5
fB = 40.46
面NO r d Nd ν
1 71.868 1.46 1.73408 52.3
2 28.820 3.46
3 66.836 4.35 1.70154 41.2
4 -144.889 （ｄ４＝可変）
5 40.352 1.17 1.80400 46.6
6 16.575 2.09
7 56.638 1.33 1.80400 42.8
8 17.901 5.97
9 30.921 9.33 1.84464 24.2
10 -165.528 3.45
11 25.721 6.50 1.68396 56.1
12 -66.299 2.67 1.79732 26.2
13 36.575 2.15
14 -111.060 1.33 1.78469 25.8
15 30.831 0.99
16 136.984 2.74 1.49700 81.6
17 -22.617 1.74
18 49.685 3.73 1.82320 44.0
19 -44.356 （ｄ１９＝可変）
20 57.141 1.26 1.77250 49.6
21 29.217 2.45
22 194.797 2.09 1.58913 59.4
23 -141.525 -
撮影倍率ｍ ｆ＝27.316 ｍ＝-0.500
Ｄ０ ∞ 44.979
ｄ４ 4.850 0.044
ｄ１９ 0.066 8.806 FIGS. 16, 17 and 18 and Table 6 show Example 6 of the wide-angle lens system according to the present invention. FIG. 16 is a lens configuration diagram in the infinity photographing state, FIG. 17 is a diagram showing various aberrations thereof, FIG. 18 is a diagram showing various aberrations at a photographing magnification of −0.5 times, and Table 6 is numerical data in the infinity photographing state. The basic lens configuration is the same as in Example 1, and the power of the first lens group 10 is positive. The stop S is 1.658 ahead from the pole of the eleventh surface (second b lens group 22).
(Table 6)
F = 1: 2.9
f = 27.32
W = 38.5
fB = 40.46
NO rd Nd ν
1 71.868 1.46 1.73408 52.3
2 28.820 3.46
3 66.836 4.35 1.70154 41.2
4 -144.889 (d4 = variable)
5 40.352 1.17 1.80 400 46.6
6 16.575 2.09
7 56.638 1.33 1.80 400 42.8
8 17.901 5.97
9 30.921 9.33 1.84464 24.2
10 -165.528 3.45
11 25.721 6.50 1.68396 56.1
12 -66.299 2.67 1.79732 26.2
13 36.575 2.15
14 -111.060 1.33 1.78469 25.8
15 30.831 0.99
16 136.984 2.74 1.49700 81.6
17 -22.617 1.74
18 49.685 3.73 1.82320 44.0
19 -44.356 (d19 = variable)
20 57.141 1.26 1.77250 49.6
21 29.217 2.45
22 194.797 2.09 1.58913 59.4
23 -141.525-
Shooting magnification m f = 27.316 m = -0.500
D0 ∞ 44.979
d4 4.850 0.044
d19 0.066 8.806

各実施例の各条件式に対する値を表７に示す。
（表７）
実施例１ 実施例２ 実施例３ 実施例４ 実施例５ 実施例６
条件式（１） 0.51 0.52 0.58 0.42 0.46 0.46
条件式（２） -7.59 -7.78 -7.67 -7.01 -7.45 -6.94
条件式（３） 0.32 0.32 0.29 0.37 0.34 0.42
条件式（４） 0.49 0.49 0.43 0.62 0.53 0.74
条件式（５） 0.01 0.02 0.08 -0.01 -0.01 0.03
条件式（６） -2.39 -2.27 -2.32 -2.46 -2.45 -2.33
条件式（７） 81.61 81.61 81.61 81.61 81.61 81.61 Table 7 shows values for each conditional expression in each example.
(Table 7)
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
Conditional expression (1) 0.51 0.52 0.58 0.42 0.46 0.46
Conditional expression (2) -7.59 -7.78 -7.67 -7.01 -7.45 -6.94
Conditional expression (3) 0.32 0.32 0.29 0.37 0.34 0.42
Conditional expression (4) 0.49 0.49 0.43 0.62 0.53 0.74
Conditional expression (5) 0.01 0.02 0.08 -0.01 -0.01 0.03
Conditional expression (6) -2.39 -2.27 -2.32 -2.46 -2.45 -2.33
Conditional expression (7) 81.61 81.61 81.61 81.61 81.61 81.61

実施例１ないし６は条件式（１）〜（７）を満足しており、また諸収差図から明らかなように諸収差、特に球面収差、像面湾曲、コマ収差（非点収差）が比較的よく補正されている。   Examples 1 to 6 satisfy the conditional expressions (1) to (7), and various aberrations, particularly spherical aberration, curvature of field, and coma (astigmatism) are compared, as is apparent from the various aberration diagrams. Correctly corrected.

本発明による広角レンズ系の実施例１の無限遠撮影状態におけるレンズ構成図である。It is a lens block diagram in the infinity photographing state of Example 1 of the wide angle lens system by this invention. 図１の構成における諸収差図である。FIG. 2 is a diagram illustrating various aberrations in the configuration of FIG. 1. 本発明による広角レンズ系の実施例１の撮影倍率−０．５倍における諸収差図である。FIG. 7 is a diagram illustrating various aberrations of the wide-angle lens system according to Example 1 of the present invention at an imaging magnification of −0.5 times. 本発明による広角レンズ系の実施例２の無限遠撮影状態におけるレンズ構成図である。It is a lens block diagram in the infinite distance imaging | photography state of Example 2 of the wide angle lens system by this invention. 図４の構成における諸収差図である。FIG. 5 is a diagram illustrating various aberrations in the configuration of FIG. 4. 本発明による広角レンズ系の実施例２の撮影倍率−０．５倍における諸収差図である。FIG. 10 is a diagram illustrating various aberrations of the wide-angle lens system according to Example 2 of the present invention at an imaging magnification of −0.5 times. 本発明による広角レンズ系の実施例３の無限遠撮影状態におけるレンズ構成図である。It is a lens block diagram in the infinite point photographing state of Example 3 of the wide angle lens system by this invention. 図７の構成における諸収差図である。FIG. 8 is a diagram illustrating various aberrations in the configuration of FIG. 7. 本発明による広角レンズ系の実施例３の撮影倍率−０．５倍における諸収差図である。FIG. 10 is a diagram illustrating various aberrations of the wide-angle lens system according to Example 3 of the present invention at an imaging magnification of −0.5 times. 本発明による広角レンズ系の実施例４の無限遠撮影状態におけるレンズ構成図である。It is a lens block diagram in the infinite point imaging | photography state of Example 4 of the wide angle lens system by this invention. 図１０の構成における諸収差図である。FIG. 11 is a diagram illustrating various aberrations in the configuration of FIG. 10. 本発明による広角レンズ系の実施例４の撮影倍率−０．５倍における諸収差図である。FIG. 9 is a diagram illustrating various aberrations of the wide-angle lens system according to Example 4 of the present invention at an imaging magnification of −0.5 times. 本発明による広角レンズ系の実施例５の無限遠撮影状態におけるレンズ構成図である。It is a lens block diagram in the infinite point imaging | photography state of Example 5 of the wide angle lens system by this invention. 図１３の構成における諸収差図である。FIG. 14 is a diagram illustrating various aberrations in the configuration of FIG. 13. 本発明による広角レンズ系の実施例５の撮影倍率−０．５倍における諸収差図である。FIG. 12 is a diagram illustrating various aberrations of the wide-angle lens system according to Example 5 of the present invention at an imaging magnification of −0.5 times. 本発明による広角レンズ系の実施例６の無限遠撮影状態におけるレンズ構成図である。It is a lens block diagram in the infinite point photographing state of Example 6 of the wide angle lens system by this invention. 図１６の構成における諸収差図である。FIG. 17 is a diagram of various aberrations in the configuration of FIG. 16. 本発明による広角レンズ系の実施例６の撮影倍率−０．５倍における諸収差図である。FIG. 10 is a diagram illustrating various aberrations of the wide-angle lens system according to Example 6 of the present invention at an imaging magnification of −0.5 times.

Claims (6)

物体側から順に、正又は負の第１レンズ群、正の第２レンズ群、及び負の第３レンズ群からなり、
第３レンズ群は正レンズと負レンズの２枚で構成されており、
無限遠から近距離物体にフォーカシングする際に、第３レンズ群は固定であり、第１レンズ群と第２レンズ群は、互いの群間隔を縮小させながら、固定の第３レンズ群に対して相対的に物体側へ移動し、次の条件式（１）を満足することを特徴とする広角レンズ系。
（１）０．４＜Ｘ１／Ｘ２＜０．６
但し、
Ｘ１；フォーカシングの際の第１レンズ群の移動量、
Ｘ２；フォーカシングの際の第２レンズ群の移動量。 In order from the object side, it consists of a positive or negative first lens group, a positive second lens group, and a negative third lens group,
The third lens group consists of two lenses, a positive lens and a negative lens.
When focusing from infinity to a short distance object, the third lens group is fixed, and the first lens group and the second lens group are relative to the fixed third lens group while reducing the mutual group interval. A wide-angle lens system characterized in that it moves to the object side and satisfies the following conditional expression (1).
(1) 0.4 <X1 / X2 <0.6
However,
X1: the amount of movement of the first lens unit during focusing,
X2: The amount of movement of the second lens group during focusing. 請求項１記載の広角レンズ系において、次の条件式（２）を満足する広角レンズ系。
（２）-８．０＜ｆ３／ｆ＜-６．５
但し、
ｆ３；第３レンズ群の焦点距離、
ｆ；全系の焦点距離。 The wide-angle lens system according to claim 1, wherein the wide-angle lens system satisfies the following conditional expression (2).
(2) -8.0 <f3 / f <-6.5
However,
f3: focal length of the third lens group,
f: Focal length of the entire system. 請求項１または２記載の広角レンズ系において、次の条件式（３）及び（４）を満足する広角レンズ系。
（３）０．２５＜｜ｆ３ｐ／ｆ３｜＜０．４５
（４）０．４＜ｆ３ｎ／ｆ３＜０．７５
但し、
ｆ３；第３レンズ群の焦点距離、
ｆ３ｐ：第３レンズ群中の正レンズの焦点距離、
ｆ３ｎ：第３レンズ群中の負レンズの焦点距離。 3. The wide-angle lens system according to claim 1, wherein the wide-angle lens system satisfies the following conditional expressions (3) and (4).
(3) 0.25 <| f3p / f3 | <0.45
(4) 0.4 <f3n / f3 <0.75
However,
f3: focal length of the third lens group,
f3p: the focal length of the positive lens in the third lens group,
f3n: focal length of the negative lens in the third lens group. 請求項１ないし３のいずれか１項記載の広角レンズ系において、第１レンズ群は、物体側から順に、物体側に凸面を向けた負メニスカスレンズと正レンズの２枚で構成され、次の条件式（５）を満足する広角レンズ系。
（５）-０．１＜ｆ／ｆ１＜０．１
但し、
ｆ；全系の焦点距離、
ｆ１：第１レンズ群の焦点距離。 The wide-angle lens system according to any one of claims 1 to 3 , wherein the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side and a positive lens. A wide-angle lens system that satisfies conditional expression (5).
(5) -0.1 <f / f1 <0.1
However,
f: focal length of the entire system,
f1: Focal length of the first lens group. 請求項１ないし４のいずれか１項記載の広角レンズ系において、第２レンズ群は、物体側から順に、負の第２ａレンズ群と、絞りと、正の第２ｂレンズ群から構成され、次の条件式（６）を満足する広角レンズ系。
（６）-３．０＜ｆ２ａ／ｆ２ｂ＜-２．０
但し、
ｆ２ａ；第２ａレンズ群の焦点距離、
ｆ２ｂ；第２ｂレンズ群の焦点距離。 5. The wide-angle lens system according to claim 1 , wherein the second lens group includes, in order from the object side, a negative second a lens group, a diaphragm, and a positive second b lens group. A wide-angle lens system that satisfies the conditional expression (6).
(6) -3.0 <f2a / f2b <-2.0
However,
f2a: focal length of the 2a lens group,
f2b: focal length of the 2b lens group. 請求項５記載の広角レンズ系において、第２ｂレンズ群は、物体側から順に、物体側から順に位置する両凸正レンズと両凹負レンズの貼合せレンズ、両凹負レンズ、像側に凸の正レンズ、及び両凸正レンズからなっており、次の条件式（７）を満足する広角レンズ系。
（７）ν2b-4＞７０
但し、
ν2b-4：第２ｂレンズ群中の像側から２枚目の正レンズのアッベ数。 6. The wide-angle lens system according to claim 5 , wherein the 2b lens group includes, in order from the object side, a cemented lens of a biconvex positive lens and a biconcave negative lens positioned in order from the object side, a biconcave negative lens, and a convex on the image side. A wide-angle lens system that satisfies the following conditional expression (7).
(7) ν 2b-4 > 70
However,
ν 2b-4 : Abbe number of the second positive lens from the image side in the 2b lens group.
JP2006120149A 2006-04-25 2006-04-25 Wide-angle lens system for close-up photography Expired - Fee Related JP4921842B2 (en)

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