JP4268773B2 - Zoom group, zoom lens, and imaging device for zoom lens - Google Patents

Description

第１〜第３レンズが第１群を構成し、第４〜第６レンズが第２群を構成し、第７レンズが第３群を構成する。第２群における第４レンズと第５レンズは接合レンズである。
【００５０】

【００５１】

第１〜第３レンズが第１群を構成し、第４〜第６レンズが第２群を構成し、第７レンズが第３群を構成する。
【００５２】

【００５３】

第１〜第３レンズが第１群を構成し、第４〜第６レンズが第２群を構成し、第７レンズが第３群を構成する。
【００５４】

【００５５】

第１〜第３レンズが第１群を構成し、第４〜第６レンズが第２群を構成し、第７レンズが第３群を構成する。
【００５６】

【００５７】

第１〜第３レンズが第１群を構成し、第４〜第６レンズが第２群を構成し、第７レンズが第３群を構成する。
【００５８】

【００５９】

第１〜第３レンズが第１群を構成し、第４〜第７レンズが第２群を構成し、第８レンズが第３群を構成する。第２群における第４レンズと第５レンズは接合レンズである。
【００６０】

【００６１】

第１〜第３レンズが第１群を構成し、第４〜第７レンズが第２群を構成し、第８レンズが第３群を構成する。
【００６２】

【００６３】

第１、第２レンズが第１群を構成し、第３〜第５レンズが第２群を構成し、第６レンズが第３群を構成する。
【００６４】

【００６５】
図１〜図８に順次、上記実施例１〜８のズームレンズの「短焦点端におけるレンズ配置」と、長焦点端への変倍に伴う各群の移動の様子を矢印で示す。これらの図において、「Ｉ」は第１群、「ＩＩ」は第２群、「ＩＩＩ」は第３群を示し、「Ｓ」は絞り、「Ｆ」は各種フィルタを示している。各実施例とも「収差補正の自由度を増加させる」ために、変倍に際して、第３群ＩＩＩを少量移動させる構成としている。
【００６６】
実施例１に関する、短焦点端、中間焦点距離、長焦点端における収差曲線図を図９〜図１１に順次示す。実施例２に関する、短焦点端、中間焦点距離、長焦点端における収差曲線図を図１２〜図１４に順次示す。
【００６７】
実施例３に関する、短焦点端、中間焦点距離、長焦点端における収差曲線図を図１５〜図１７に順次示す。実施例４に関する、短焦点端、中間焦点距離、長焦点端における収差曲線図を図１８〜図２０に順次示す。
【００６８】
実施例５に関する、短焦点端、中間焦点距離、長焦点端における収差曲線図を図２１〜図２３に順次示す。実施例６に関する、短焦点端、中間焦点距離、長焦点端における収差曲線図を図２４〜図２６に順次示す。
【００６９】
実施例７に関する、短焦点端、中間焦点距離、長焦点端における収差曲線図を図２７〜図２９に順次示す。実施例８に関する、短焦点端、中間焦点距離、長焦点端における収差曲線図を図３０〜図３２に順次示す。
【００７０】
各収差曲線図において、球面収差の図中の破線は正弦条件を表す。また、非点収差の図中の実線はサジタル、破線はメリディオナルを表す。「Ｙ'」は最大像高であり、単位は「ｍｍ」である。また、球面収差・非点収差・歪曲収差の図における横軸の単位も「ｍｍ」である。各実施例とも、短焦点端・中間焦点距離・長焦点端において、収差が良好に補正され、性能良好である。
【００７１】
上記実施例１〜８のうちで、実施例１〜５および実施例８のズームレンズにおける第２群ＩＩは、物体側より順に、負の焦点距離を持つ第１群Ｉ、正の焦点距離を持つ第２群ＩＩ、正の焦点距離を持つ第３群ＩＩＩを配し、第２群の物体側に第２群ＩＩと一体に移動する絞りＳを有し、短焦点端から長焦点端への変倍に際し、第２群ＩＩが像側から物体側へ単調に移動し、第１群Ｉが変倍に伴う像面位置の変動を補正するように移動するズームレンズにおいて、第２群ＩＩとして構成されて実質的な変倍を行う変倍群であって、物体側から順に、物体側に曲率の大きな面を向けた正レンズ、像側に曲率の大きな面を向けた負レンズ、正レンズの３枚を配して構成され、最も物体側の面と最も像側の面が非球面である。
【００７２】
そして、実施例１〜５および実施例８のズームレンズの第２群ＩＩは、光軸方向の厚み：Ｌ_２、最大像高：Ｙ'が、条件：
（１） １．０＜(Ｌ_２／Ｙ’)＜２．５
を満足し、最も像側の正レンズの、物体側および像側の面の曲率半径をそれぞれＲ₃₁およびＲ₃₂とするとき、これらが条件：
（２） −０．４＜(Ｒ₃₁＋Ｒ₃₂)／(Ｒ₃₁−Ｒ₃₂)＜０．０
を満足する。
【００７３】
また、実施例１のズームレンズの第２群ＩＩでは、最も物体側の正レンズ（第４レンズ）と、これに続く負レンズ（第５レンズ）とが接合された接合レンズであり、実施例２〜５、実施例８のズームレンズの第２群ＩＩでは、３枚のレンズが互いに独立したレンズである。
【００７４】
実施例６および７のズームレンズの第２群ＩＩは、物体側より順に、負の焦点距離を持つ第１群Ｉ、正の焦点距離を持つ第２群ＩＩ、正の焦点距離を持つ第３群ＩＩＩからなり、第２群の物体側に第２群と一体に移動する絞りＳを有し、短焦点端から長焦点端への変倍に際し、第２群ＩＩが像側から物体側へ単調に移動し、第１群Ｉが変倍に伴う像面位置の変動を補正するように移動するズームレンズにおいて、第２群ＩＩとして構成されて実質的な変倍を行う変倍群であって、最も物体側の面と最も像側の面が非球面で、光軸方向の厚み：Ｌ_２、最大像高：Ｙ’が、条件：（１）
１．０＜(Ｌ_２／Ｙ')＜２．５
を満足し、物体側から順に、物体側に曲率の大きな面を向けた正レンズ（第４レンズ）、像側に曲率の大きな面を向けた負レンズ（第５レンズ）、正レンズ（第６レンズ）、正レンズ（第７レンズ）の４枚を配して構成され、実施例６では、最も物体側の正レンズ（第４レンズ）と、これに続く負レンズ（第５レンズ）が接合レンズとして一体化されている。従って、実施例６、７の各ズームレンズは、物体側より順に、負の焦点距離を持つ第１群Ｉ、正の焦点距離を持つ第２群ＩＩ、正の焦点距離を持つ第３群ＩＩＩを配し、第２群ＩＩの物体側に第２群と一体に移動する絞りＳを有してなり、短焦点端から長焦点端への変倍に際し、第２群ＩＩが像側から物体側へ単調に移動して実質的な変倍を行い、第１群Ｉが変倍に伴う像面位置の変動を補正するように移動するズームレンズにおいて、第２群ＩＩとして、請求項１記載の変倍群を用いたものである。
【００７５】
実施例１〜８のズームレンズはまた、第１群Ｉが、物体側から順に、像側に曲率の大きな面を向けた少なくとも１枚の負レンズ、物体側に曲率の大きな面を向けた少なくとも１枚の正レンズを配してなり、上記少なくとも１枚の負レンズの、最も像側の面が非球面である。
【００７６】
実施例１〜７のズームレンズは、第１群Ｉが、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（第１レンズ）、像側に曲率の大きな面を向けた負レンズ（第２レンズ）、物体側に曲率の大きな面を向けた正レンズ（第３レンズ）を配してなる３枚構成であって、像側に曲率の大きな面を向けた負レンズの像側の面（第４面）が非球面であり、第１群Ｉの最も物体側に配された負メニスカスレンズ（第１レンズ）の焦点距離：ｆ_L1、第１群の物体側から２番目に配された負レンズ（第２レンズ）の焦点距離：ｆ_L2が、条件：
（３） ０．７＜(ｆ_L1／ｆ_L2)＜２．０
を満足する。
【００７７】
実施例８のズームレンズの第１群Ｉ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（第１レンズ）、物体側に曲率の大きな面を向けた正レンズ（第２レンズ）を配してなる２枚構成で、負メニスカスレンズの像側の面（第２面）が非球面である。
【００７８】
実施例１〜８の各ズームレンズとも、第３群ＩＩＩは、物体側に曲率の大きな面を向けた正レンズにより構成され、少なくとも1面の非球面（物体側面）を有するものであり、実施例１〜８の各ズームレンズとも、全系の構成レンズ枚数が８枚以下（実施例１〜５において７枚構成、実施例６、７において８枚構成、実施例８において６枚構成）である。
【００７９】
図３３は、この発明の「撮像装置」の実施の１形態を説明するための図である。図３３（ａ）は正面側と上部面とを示す図、図３３（ｃ）は背面側を示す図である。撮像装置３０は、撮影レンズ３１として、上に説明した請求項１〜７の任意の１に記載のズームレンズ（実施例６または７）を「撮影用ズームレンズ」として有する。
【００８０】
図３３（ａ）において、符号３２はフラッシュ、符号３３はファインダを示す。ズームレバー３４とシャッタボタン３５は、本体の上面側に配置されている。図３３（ｂ）は撮影レンズ３１の使用状態を示す図である。撮影レンズ３１は、使用されないときは、図３３（ａ）に示すように、撮像装置本体に「沈胴式」に収納される。ズームレンズの上記各実施例とも、レンズ枚数が６〜８枚と少なく、第２群の厚さが小さいので、沈胴式に収納すると、薄いカメラ本体内に収納できる。
【００８１】
図３３（ｃ）に示すように、電源スイッチ３５、操作ボタン３７、液晶モニタ３８は撮像装置本体の背面側に配置され、通信カード用スロット３９Ａと、メモリカードスロット３９Ｂは、本体側面に配置されている。
【００８２】
図３４は、撮像装置の「システム構造」を示す図である。撮像装置３０は形態情報端末装置である（請求項２０）。図３４に示すように、撮像装置は、撮影レンズ３１と受光素子（エリアセンサ）４５を有し、撮影レンズ３１によって形成される撮影対象物の像を受光素子４５によって読取るように構成され、受光素子４５からの出力は中央演算装置４０の制御を受ける信号処理装置４２によって処理されてデジタル情報に変換される。即ち、撮像装置３０は「撮影画像をデジタル情報とする機能」を有している。
【００８３】
信号処理装置４２によってデジタル化された画像情報は、中央演算装置４０の制御を受ける画像処理装置４１において所定の画像処理を受けた後、半導体メモリ４４（前記メモリカードスロット３９Ｂにセットされる）に記録される。液晶モニタ３８には、撮影中の画像を表示することもできるし、半導体メモリ４４に記録されている画像を表示することもできる。また、半導体メモリ４４に記録した画像は、通信カード４３等（前記通信カードスロット３９Ａにセットされる）を使用して外部へ送信することも可能である。
【００８４】
図３３（ａ）に示すように、撮影レンズ３１は撮像装置３０の携帯時には「沈胴状態」にあり、ユーザが電源スイッチ３６を操作して電源を入れると、図３３（ｂ）に示すように鏡胴が繰り出される。このとき、鏡胴内部でズームレンズの各群は、例えば「短焦点端の配置」となっており、ズームレバー３４を操作することで各群の配置が変化して長焦点端への変倍を行うことができる。このとき、ファインダ３３も撮影レンズの画角変化に連動して変倍する。
【００８５】
シャッタボタン３５の「半押し」によりフォーカシングがなされる。フォーカシングは、第1群または第３群の移動、もしくは、受光素子の移動によって行うことができる。シャッタボタン３５を、半押し状態からさらに押し込むと撮影がなされ、その後は上記の画像情報処理が実行される。
【００８６】
半導体メモリ４４に記録した画像を、液晶モニタ３８に表示したり、通信カード４３等を使用して外部へ送信する場合は、操作ボタン３７の操作により行なう。撮影レンズ３１として、実施例１〜８の任意のものを使用すると、これらは性能良好であるので、受光素子４５として、２００万画素〜３００万画素クラスのものを使用した高画質で小型の撮像装置を実現できる。
【００８７】
【発明の効果】
以上に説明したように、この発明によれば新規な、ズームレンズにおける変倍群、ズームレンズ、撮像装置を実現できる。
この発明の変倍群は、光軸方向の厚みが有効に縮小されているので、ズームレンズをコンパクト化でき、特に、沈胴型の撮像装置における収納時の寸法を有効に小さくできる。
【００８８】
また、この発明のズームレンズは、デジタル画像撮影に要求される高性能を維持しつつ、従来のものよりも更なる小型化を図ることが可能であり、この発明のズームレンズを用いる撮像装置は、小型で且つ高性能に実現可能である。
【図面の簡単な説明】
【図１】実施例１のズームレンズの短焦点端におけるレンズ配置と、変倍に伴う各群の移動を示す図である。
【図２】実施例２のズームレンズの短焦点端におけるレンズ配置と、変倍に伴う各群の移動を示す図である。
【図３】実施例３のズームレンズの短焦点端におけるレンズ配置と、変倍に伴う各群の移動を示す図である。
【図４】実施例４のズームレンズの短焦点端におけるレンズ配置と、変倍に伴う各群の移動を示す図である。
【図５】実施例５のズームレンズの短焦点端におけるレンズ配置と、変倍に伴う各群の移動を示す図である。
【図６】実施例６のズームレンズの短焦点端におけるレンズ配置と、変倍に伴う各群の移動を示す図である。
【図７】実施例７のズームレンズの短焦点端におけるレンズ配置と、変倍に伴う各群の移動を示す図である。
【図８】実施例８のズームレンズの短焦点端におけるレンズ配置と、変倍に伴う各群の移動を示す図である。
【図９】実施例１のズームレンズの短焦点端における収差曲線図である。
【図１０】実施例１のズームレンズの中間焦点距離における収差曲線図である。
【図１１】実施例１のズームレンズの長焦点端における収差曲線図である。
【図１２】実施例２のズームレンズの短焦点端における収差曲線図である。
【図１３】実施例２のズームレンズの中間焦点距離における収差曲線図である。
【図１４】実施例２のズームレンズの長焦点端における収差曲線図である。
【図１５】実施例３のズームレンズの短焦点端における収差曲線図である。
【図１６】実施例３のズームレンズの中間焦点距離における収差曲線図である。
【図１７】実施例３のズームレンズの長焦点端における収差曲線図である。
【図１８】実施例４のズームレンズの短焦点端における収差曲線図である。
【図１９】実施例４のズームレンズの中間焦点距離における収差曲線図である。
【図２０】実施例４のズームレンズの長焦点端における収差曲線図である。
【図２１】実施例５のズームレンズの短焦点端における収差曲線図である。
【図２２】実施例５のズームレンズの中間焦点距離における収差曲線図である。
【図２３】実施例５のズームレンズの長焦点端における収差曲線図である。
【図２４】実施例６のズームレンズの短焦点端における収差曲線図である。
【図２５】実施例６のズームレンズの中間焦点距離における収差曲線図である。
【図２６】実施例６のズームレンズの長焦点端における収差曲線図である。
【図２７】実施例７のズームレンズの短焦点端における収差曲線図である。
【図２８】実施例７のズームレンズの中間焦点距離における収差曲線図である。
【図２９】実施例７のズームレンズの長焦点端における収差曲線図である。
【図３０】実施例８のズームレンズの短焦点端における収差曲線図である。
【図３１】実施例８のズームレンズの中間焦点距離における収差曲線図である。
【図３２】実施例８のズームレンズの長焦点端における収差曲線図である。
【図３３】撮像装置の実施の１形態を説明するための図である。
【図３４】図３３の実施の形態のシステム構成を説明するための図である。
【符号の説明】
Ｉ 第１群
ＩＩ 第２群
ＩＩＩ 第３群
Ｓ 絞り[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a zoom lens zoom lens, a zoom lens,Imaging deviceAbout. The present invention can be suitably applied to various photographing apparatuses such as a silver salt camera, in particular, a digital camera, a video camera, and an information device having a digital image photographing function.
[0002]
[Prior art]
Digital image capturing has spread not only to conventional digital cameras, but also to portable information terminal devices such as mobile phones, and the demands of users have been diversified. In particular, high image quality and miniaturization are always desired by users, and the weight of the various requests is large. For this reason, a zoom lens used as a photographic lens is also required to be compatible with both high performance and small size.
[0003]
  In order to reduce the size of the zoom lens, it is necessary to shorten the total lens length (the distance from the lens surface closest to the object side to the image plane). In addition, the so-called “collapsed” type is designed to be compact when storing the lens.Imaging deviceThen, in order to reduce the dimension during storage, it is also important to reduce the thickness in the optical axis direction of each group that moves during zooming.
[0004]
As types of zoom lenses suitable for miniaturization, a first group having a negative focal length, a second group having a positive focal length, and a third group having a positive focal length are arranged in order from the object side. The second group has an “aperture that moves integrally with the second group” on the object side of the second group, and the second group moves monotonically from the image side to the object side during zooming from the short focus end to the long focus end. It is known that the first group moves so as to correct fluctuations in the image plane position accompanying zooming.
[0005]
Japanese Patent Laid-Open No. 10-039214 is the earliest proposal of a zoom lens of the above type, and all basic configurations are disclosed, but it is not always sufficient in terms of miniaturization. An improved version of the zoom lens of the type described above is disclosed in Japanese Patent Application Laid-Open No. 11-287953. However, since the second lens group has only one aspheric surface, it is still possible to reduce the size. It is not sufficient, and it is hard to say that aberration correction is sufficient. Japanese Patent Application Laid-Open No. 2000-0891102 discloses an example 3 in which aberration correction is favorably performed using a two-surface aspheric surface in the second group, but the thickness of the second group is disclosed. However, it is not always advantageous for downsizing.
[0006]
[Problems to be solved by the invention]
In view of the above-described circumstances, an object of the present invention is to further reduce the size while maintaining high performance of a zoom lens used for digital image shooting.
[0007]
[Means for Solving the Problems]
  The “magnification changing group in the zoom lens” of the present invention includes “a first group having a negative focal length, a second group having a positive focal length, and a third group having a positive focal length in order from the object side.Consists ofAn aperture that moves integrally with the second group is provided on the object side of the second group, and the second group moves monotonically from the image side to the object side during zooming from the short focus end to the long focus end. In the zoom lens in which the group moves so as to correct the fluctuation of the image plane position due to zooming, it is configured as a second group and is a zooming group that performs substantial zooming.
[0008]
  Prior to describing the zooming group of the present invention, a similar “reference example” will be described.
  Reference example 1The zoom group has the following characteristics. In other words, the zooming group configured as the second group includes three lenses in order from the object side: a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, and a positive lens. The most object side surface and the most image side surface are aspherical.
[0009]
  The variable magnification group of Reference Example 1Is the thickness in the optical axis direction: L₂And the maximum image height: Y ′, the conditions are:
  (1) 1.0 <(L₂/Y′)<2.5
It is preferable to satisfy (Reference example 2).
[0010]
  Reference example 1 or 2, The curvature radius of the object-side and image-side surfaces of the most image-side positive lens is R₃₁And R₃₂And when these are the conditions:
  (2) -0.4 <(R₃₁+ R₃₂) / (R₃₁-R₃₂<0.0
It is preferable to satisfy (Reference example 3). In this case, since the image side surface is an aspherical surface, the radius of curvature: R₃₂Is the paraxial radius of curvature.
[0011]
  In the variable power group of Reference Example 1 or 2 or 3, a positive lens closest to the object side and a negative lens subsequent thereto may be cemented to form a cemented lens (Reference example 4) Three lenses can be made independent from each other (Reference Example 5).
[0012]
  Hereinafter, the variable power group of the present invention will be described.
  Claim 1The described zoom group has the following characteristics. That is, the variable power group that is configured as the second group and performs substantial variable power has an aspherical surface on the most object side and a surface on the most image side, and a thickness in the optical axis direction: L₂Maximum image height: Y ′, conditions:
  (1) 1.0 <(L₂/Y′)<2.5
Satisfied.
[0013]
  The zooming group according to claim 1 includes, in order from the object side, a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, a positive lens, and a positive lens. Four-sheet configuration consisting of a single sheetAndOf the four lenses that make up the variable power group, “the most positive lens on the object side and the negative lens that follows it are integrated as a cemented lens”Has been.
[0014]
  The zoom lens according to the present invention includes, in order from the object side, a first group having a negative focal length, a second group having a positive focal length, and a third group having a positive focal length.And consist ofThe second group has an aperture that moves integrally with the second group on the object side, and the second group moves monotonically from the image side to the object side during zooming from the short focal end to the long focal end. Zoom lens that performs substantial zooming and moves so that the first group corrects the variation in the image plane position accompanying zooming,Claim 1It is characterized by using the described zoom group (Claim 2).
[0015]
  The first lens group in the zoom lens according to claim 3 is “in order from the object side”.2 sheetsNegative lens1 sheetAmong the one or more negative lenses arranged on the object side with a positive lens, the image side surface of the negative lens located closest to the image side is defined as an aspherical surface.Is a three-sheet configuration "can do.
  “The two negative lenses on the object side are negative lenses with a large curvature surface facing the image side, and the one positive lens on the image side is a lens with a large curvature surface facing the object side”. it can.
[0016]
  The first group in the zoom lens according to claim 3 is “a three-lens configuration in which a negative meniscus lens having a convex surface facing the object side, a negative lens, and a positive lens in order from the object side”. The image side surface of the second negative lens arranged second can be an aspherical surface.. In this case, the focal length of the negative meniscus lens disposed on the most object side in the first group: f_L1The focal length of the negative lens arranged second from the object side of the first group: f_L2But the condition:
  (3) 0.7 <(f_L1/ F_L2<2.0
It is preferable to satisfy (Claim 5).
[0017]
  AlsoAs Reference Example 6, claim 3The first lens group in the zoom lens is “a two-lens configuration in which, in order from the object side, a negative meniscus lens having a convex surface facing the object side and a positive lens having a large curvature surface facing the object side” is arranged. The image side surface of the meniscus lens should be asphericalConceivable.
[0018]
  the aboveClaims 2-5In the zoom lens according to any one ofThe third group consists of one positive lensCan have at least one aspheric surface (Claim 6).
[0019]
  the aboveClaims 2-6The described zoom lens is the number of lenses in the entire system.8It is preferable (Claim 7).
[0020]
  The imaging apparatus according to the present invention is referred to as the “shooting zoom lens”.Claims 2-7The zoom lens according to any one of (1),Claim 8).
  thisClaim 8The described imaging apparatus can be configured such that “the photographing zoom lens is retracted” (see FIG.Claim 9).
[0021]
  Claim8 or 9The described imaging apparatus can have a “function of converting a captured image into digital information” (Claim 10In this case, the light receiving element that receives an image from the zoom lens can be 2 million pixels or more (see FIG.Claim 11).
[0022]
  the aboveClaims 10 and 11The described imaging device can be a “portable information terminal device”(Claim 12).
[0023]
As in the zoom lens according to the present invention, in a zoom lens including three groups of negative, positive, and positive, in general, the second group moves from the image side to the object side during zooming from the short focal end to the long focal end. It moves monotonously, and the first lens group moves so as to correct fluctuations in the image plane position accompanying zooming. Most of the zooming function is performed by the second group, and the third group is mainly given a function of moving the exit pupil away from the image plane.
[0024]
In order to realize a zoom lens with a small amount of various aberrations and a high resolving power, aberration variation due to zooming must be kept small, but it is a zooming group that performs substantial zooming, that is, a "main zooming group". In the second group, it is necessary that the aberration correction is satisfactorily corrected over the entire zooming range.
[0025]
Good correction of the aberration of the second group is basically possible by increasing the number of lenses constituting the second group. However, the increase in the number of constituent lenses is the “thickness in the optical axis direction of the second group”. Leads to an “increase”, and sufficient miniaturization cannot be achieved, leading to an increase in cost.
[0026]
  Therefore,Reference Examples 1-6Then, the second group, which is the main zooming group, is arranged in order from the object side, a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, and a positive lens In the configuration, the most object side surface and the most image side surface of the second group are aspherical surfaces.
[0027]
In other words, the second group is a triplet type, and the "minimum number of components that can achieve both chromatic aberration correction and field curvature correction" has been achieved for miniaturization, and aberration correction with a high degree of freedom using two aspheric surfaces. To achieve high performance.
[0028]
Since the most object-side surface of the second group is in the vicinity of the stop, the on-axis and off-axis light beams pass through almost without separation, and the aspheric surface provided on this surface is mainly used for spherical aberration and coma aberration. Contributes to correction. Since the surface closest to the image side of the second group is away from the stop, the on-axis and off-axis light beams are separated to some extent. Therefore, the aspheric surface provided on this surface contributes to correction of astigmatism and the like.
[0029]
In this way, two aspheric surfaces are used for the “most object-side surface and the most image-side surface”, and the effect of each aspheric surface is made different, thereby dramatically improving the degree of freedom in correcting monochromatic aberrations. Even with a triplet configuration with a small number of sheets, it is possible to sufficiently correct various aberrations including chromatic aberration.
[0030]
  The variable magnification group of Reference Example 1Then, since the second group is composed of three pieces, it is well suited to miniaturization, but in order to achieve further miniaturization, it is preferable that the condition (1) is satisfied. Parameter: L₂If / Y 'is equal to or greater than the upper limit of 2.5, the thickness of the second group in the optical axis direction increases, and sufficient miniaturization cannot be achieved. Conversely, parameter: L₂When Y / Y ′ is 1.0 or less, which is the lower limit value, the “most image side surface” of the second group approaches the stop, and the effect of the aspherical surface for performing the above “correction of astigmatism” is sufficiently obtained. It cannot be exhibited, and it becomes difficult to correct various aberrations such as astigmatism.
[0031]
When the second group has the “three-sheet configuration” as described above, a condition narrower than the condition (2):
(1 ') 1.0 <(L₂/Y’)<2.0
By satisfying the above, it becomes possible to realize further downsizing.
[0032]
When the configuration of the second group is a triplet type, the object side surface (aspherical surface) of the most object side positive lens of the second group and the image side surface of the subsequent negative lens are "I will communicate". For this reason, the influence of the assembling error (eccentricity, etc.) of these two lenses on the imaging performance tends to be large.
[0033]
  With respect to this point, it is possible to suppress the assembly error itself by joining these two lenses (Reference example 4).
[0034]
  But,The variable magnification group of Reference Example 1In this case, an aspherical surface is also used for the positive lens closest to the image side in the second group, and the effect of the assembly error of the positive lens closest to the image side has a great influence on the imaging performance. In order to suppress the influence on the image forming performance due to the assembly error of the “second positive lens on the most image side” of the second group, it is preferable to satisfy the condition (2).
[0035]
Condition (2) is that the exchange of aberrations is completed as much as possible between the object-side surface and the image-side surface (aspheric surface) of the most image-side positive lens in the second group. This is to prevent the positional relationship from becoming severe.
[0036]
Parameter: (R₃₁+ R₃₂) / (R₃₁-R₃₂) Exceeds the upper limit of 0.0, the aberration that occurs on the image-side surface of the most image-side positive lens is larger than the aberration that occurs on the object-side surface, and the lower limit of −0.4. In the following, the aberration generated on the object side surface is larger than the aberration generated on the image side surface, and in any case, “the exchange of aberrations with other lens surfaces” increases. The effect on the imaging performance due to the assembly error of the positive lens (most image side of the group) is increased.
[0037]
  As above,Reference Examples 1-5Then, the second group has a three-sheet configuration. However, if the above condition (1) is satisfied, the condition (1) limits the size of the second group, so the second group has a configuration other than the three-sheet configuration. Even if configured, the demand for high performance and miniaturization can be satisfied.
[0038]
  In this case,Claim 1As in the zooming group described, four lenses are arranged in order from the object side: a positive lens with a large curvature surface facing the object side, a negative lens with a large curvature surface facing the image side, a positive lens, and a positive lens. It is also possible to have a four-lens configuration, and “a most positive lens on the object side and a subsequent negative lens can be integrated as a cemented lens”.
[0039]
  Claim 2As described above, the zoom lens described is a three-group variable power group.Claim 1Although the zooming group described is used, for “better correction” of each aberration in the zoom lens,Claim 3As in the described invention, the first lens unit is classified as “from the object side, at least one negative lens having a large curvature surface facing the image side, and at least one positive lens having a large curvature surface facing the object side. Of the one or more negative lenses having a lens and disposed on the object side, the image side surface of the negative lens located closest to the image side is preferably an aspherical surface.
[0040]
By making the first group in such a configuration, it is possible to “reduce the field curvature” and to make the “surface having a large refraction angle of off-axis rays” an aspherical surface, particularly distortion at the short focal end. Aberration can be suppressed.
[0041]
  in this case,Claim 4As in the described zoom lens, the first lens unit is set to “a negative meniscus with a convex surface facing the object side in order from the object side.Lens, negative lens, positive lensThe image side surface of the negative lens arranged second from the object side is defined as an aspherical surface,Claim 5By satisfying the condition (3) as in the described invention, it is possible to reduce the influence on the imaging performance due to the formation error of the aspheric surface and to effectively exhibit the effect of the aspheric surface.
[0042]
That is, in the condition (3), the parameter: (f_L1/ F_L2) Represents the “power ratio” of the two negative lenses in the first group, and when this parameter exceeds the upper limit value: 2.0, the power of the second negative lens having an aspheric surface becomes stronger. In addition to the effect on the imaging performance due to the manufacturing error of the aspherical surface, the difference in thickness between the center and the periphery of the lens becomes large, and the difficulty in producing this lens by molding becomes high. On the other hand, parameter: (f_L1/ F_L2) Is below the lower limit of 0.7, the power of the second negative lens having an aspheric surface becomes weak, and the refraction angle of off-axis rays on the image side surface becomes small. End up.
[0043]
More preferably, the following conditions are further narrower than the condition (3):
(3 ') 0.7 <(f_L1/ F_L2<1.5
Is preferably satisfied.
[0044]
  Also, aboveReference Example 6Like the zoom lens, the first lens group is “a two-lens configuration in which a negative meniscus lens having a convex surface facing the object side and a positive lens having a large curvature surface facing the object side in order from the object side” The image side surface of the negative meniscus lens can be aspherical, and the first group having such a two-lens configuration is advantageous for downsizing with a simpler configuration. Also, aboveClaim 6In the case where the first lens unit has a three-lens configuration as in the zoom lens, it is “advantageous in widening the angle of view because the aberration correction capability is enhanced”.
[0045]
  The third group isClaim 6Like the zoom lens described,One positive lensAnd at least one surface is aspherical. With such a configuration, off-axis aberrations such as astigmatism can be corrected more favorably while minimizing the thickness of the third group.
[0046]
The third group may be fixed at the time of zooming, but can be “moved by a small amount to increase the degree of freedom of aberration correction”.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
  Specific numerical examples of the zoom lens according to the present invention will be described below. In each example, the aberration is sufficiently corrected, and it is possible to cope with a light receiving element of 2 million to 3 million pixels. By configuring the zoom lens as in the present invention, it is apparent from the embodiments that very good image performance can be ensured while achieving sufficient size reduction.
  Of Examples 1 to 8 shown below, Examples 1 to 5 and Example 8 relate to a zoom lens using the variable power group of Reference Examples 1 to 5, and Example 6 And 7 are embodiments of the zoom lens of the present invention.
[0048]
The meanings of the symbols in the examples are as follows.
f: Focal length of the entire system
F: F number
ω: Half angle of view
R: radius of curvature
D: Surface spacing
Nd: Refractive index
νd: Abbe number
K: Aspherical conical constant
A_Four: 4th order aspheric coefficient
A₆: 6th-order aspheric coefficient
A₈: 8th-order aspheric coefficient
A_Ten: 10th-order aspheric coefficient
A₁₂: 12th-order aspheric coefficient
A₁₄: 14th-order aspheric coefficient
A₁₆: 16th-order aspheric coefficient
A₁₈: 18th-order aspheric coefficient
For an aspheric surface, the reciprocal of the paraxial radius of curvature (paraxial curvature) is C (= 1 / R), the height from the optical axis is H, the depth in the optical axis direction is X, and the conic constant and the aspheric coefficient are And is defined by the following well-known formula:
X = CH²/ [1 + √ {1- (1 + K) C²H²}]
+ A_Four・ H^Four+ A₆・ H⁶+ A₈・ H⁸+ A_Ten・ H^Ten+ A₁₂・ H¹²+ A₁₄・ H¹⁴+ A₁₆・ H¹⁶+ A₁₈・ H¹⁸
In addition, "*" is attached to the surface number for the surface adopting the aspherical surface.
The unit of the quantity having the dimension of length is “mm”.
[0049]
【Example】

The first to third lenses constitute the first group, the fourth to sixth lenses constitute the second group, and the seventh lens constitutes the third group. The fourth lens and the fifth lens in the second group are cemented lenses.
[0050]

[0051]

The first to third lenses constitute the first group, the fourth to sixth lenses constitute the second group, and the seventh lens constitutes the third group.
[0052]

[0053]

The first to third lenses constitute the first group, the fourth to sixth lenses constitute the second group, and the seventh lens constitutes the third group.
[0054]

[0055]

The first to third lenses constitute the first group, the fourth to sixth lenses constitute the second group, and the seventh lens constitutes the third group.
[0056]

[0057]

The first to third lenses constitute the first group, the fourth to sixth lenses constitute the second group, and the seventh lens constitutes the third group.
[0058]

[0059]

The first to third lenses constitute the first group, the fourth to seventh lenses constitute the second group, and the eighth lens constitutes the third group. The fourth lens and the fifth lens in the second group are cemented lenses.
[0060]

[0061]

The first to third lenses constitute the first group, the fourth to seventh lenses constitute the second group, and the eighth lens constitutes the third group.
[0062]

[0063]

The first and second lenses constitute the first group, the third to fifth lenses constitute the second group, and the sixth lens constitutes the third group.
[0064]

[0065]
In FIGS. 1 to 8, the “lens arrangement at the short focal end” of the zoom lenses of Examples 1 to 8 and the movement of each group accompanying zooming to the long focal end are indicated by arrows. In these drawings, “I” represents the first group, “II” represents the second group, “III” represents the third group, “S” represents the aperture, and “F” represents the various filters. In each embodiment, in order to “increase the degree of freedom of aberration correction”, the third group III is moved by a small amount during zooming.
[0066]
Aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end regarding Example 1 are sequentially shown in FIGS. Aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end in Example 2 are sequentially shown in FIGS.
[0067]
Aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end regarding Example 3 are sequentially shown in FIGS. Aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end regarding Example 4 are sequentially shown in FIGS.
[0068]
Aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end regarding Example 5 are sequentially shown in FIGS. Aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end regarding Example 6 are sequentially shown in FIGS.
[0069]
Aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end regarding Example 7 are sequentially shown in FIGS. Aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end in Example 8 are sequentially shown in FIGS.
[0070]
In each aberration curve diagram, a broken line in the spherical aberration diagram represents a sine condition. In the figure of astigmatism, the solid line represents sagittal and the broken line represents meridional. “Y ′” is the maximum image height, and the unit is “mm”. Further, the unit of the horizontal axis in the diagrams of spherical aberration, astigmatism, and distortion is also “mm”. In each example, the aberration is corrected well at the short focal end, the intermediate focal length, and the long focal end, and the performance is good.
[0071]
  Among Examples 1 to 8, the second group II in the zoom lenses of Examples 1 to 5 and Example 8 has the first group I having a negative focal length and the positive focal length in order from the object side. A second group II having a positive focal length, a third group III having a positive focal length, and an aperture S that moves integrally with the second group II on the object side of the second group, from the short focal point to the long focal point. In the zoom lens in which the second group II moves monotonically from the image side to the object side during zooming, and the first group I moves so as to correct the fluctuation of the image plane position accompanying zooming, the second group II In order from the object side, a zoom lens group configured as a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, and a positive lens It consists of three lenses, and the most object side surface and most image side surface are aspherical.is there.
[0072]
  The second group II of the zoom lenses of Examples 1 to 5 and Example 8 has a thickness in the optical axis direction: L₂Maximum image height: Y ′, conditions:
  (1) 1.0 <(L₂/Y′)<2.5
TheSatisfied,The radius of curvature of the object-side and image-side surfaces of the most image-side positive lens is R₃₁And R₃₂And when these are the conditions:
  (2) -0.4 <(R₃₁+ R₃₂) / (R₃₁-R₃₂<0.0
Satisfied.
[0073]
  In the second lens group II of the zoom lens of Example 1, a cemented lens in which the most object side positive lens (fourth lens) and the subsequent negative lens (fifth lens) are cemented.AndIn the second group II of the zoom lenses of Examples 2 to 5 and Example 8, the three lenses are independent lenses.is there.
[0074]
  The second group II of the zoom lenses of Examples 6 and 7 includes, in order from the object side, the first group I having a negative focal length, the second group II having a positive focal length, and the third group having a positive focal length. Group IIIConsist ofThe second group II has a stop S that moves integrally with the second group on the object side of the second group, and the second group II moves monotonically from the image side to the object side upon zooming from the short focus end to the long focus end. In the zoom lens in which the first group I moves so as to correct the fluctuation of the image plane position due to zooming, the zoom lens is configured as the second group II and performs substantial zooming. Side surface and most image side surface are aspherical surfaces, thickness in the optical axis direction: L₂Maximum image height: Y ′, condition: (1)
  1.0 <(L₂/Y')<2.5
In order from the object side, a positive lens (fourth lens) with a large curvature surface facing the object side, a negative lens (fifth lens) with a large curvature surface facing the image side, and a positive lens (sixth lens) Lens), positive lens (seventh lens)Configured,In Example 6, the most object side positive lens (fourth lens) and the subsequent negative lens (fifth lens) are used as cemented lenses.Integrateding. Therefore, in each of the zoom lenses of Examples 6 and 7, in order from the object side, the first group I having a negative focal length, the second group II having a positive focal length, and the third group III having a positive focal length. And an aperture stop S that moves integrally with the second group on the object side of the second group II. When zooming from the short focus end to the long focus end, the second group II is moved from the image side to the object side. In a zoom lens that moves monotonically to the side and performs substantial zooming, and moves so that the first lens group I corrects the fluctuation of the image plane position accompanying zooming,Claim 1Using a variable magnification groupis there.
[0075]
  In the zoom lenses of Embodiments 1 to 8, the first lens unit I has at least one negative lens having a large curvature surface facing the image side and at least a large curvature surface facing the object side in order from the object side. A positive lens is arranged, and the most image side surface of the at least one negative lens is an aspherical surface.is there.
[0076]
  In the zoom lenses of Examples 1 to 7, the first lens unit I has, in order from the object side, a negative meniscus lens (first lens) with a convex surface facing the object side, and a negative lens with a large curvature surface facing the image side ( 2nd lens), and a three-lens configuration in which a positive lens (third lens) having a large curvature surface facing the object side is disposed, and the image side of a negative lens having a large curvature surface facing the image side The focal length of the negative meniscus lens (first lens) disposed on the most object side in the first group I is an aspheric surface (fourth surface): f_L1The focal length of the negative lens (second lens) arranged second from the object side of the first group: f_L2But the condition:
  (3) 0.7 <(f_L1/ F_L2<2.0
Satisfied.
[0077]
  The first group I of the zoom lens of Example 8 includes, in order from the object side, a negative meniscus lens (first lens) having a convex surface directed toward the object side, and a positive lens (second lens) having a surface having a large curvature directed toward the object side. )so,The image side surface (second surface) of the negative meniscus lensIt is aspheric.
[0078]
  In each of the zoom lenses of Examples 1 to 8, the third lens group III is composed of a positive lens having a surface with a large curvature facing the object side, and has at least one aspheric surface (object side surface).AndIn each of the zoom lenses of Examples 1 to 8, the total number of constituent lenses is 8 or less (7 in Example 1-5, 8 in Examples 6 and 7, and 6 in Example 8).Is.
[0079]
  FIG. 33 is a diagram for explaining an embodiment of an “imaging device” according to the present invention. FIG. 33A is a view showing the front side and the upper side, and FIG. 33C is a view showing the back side. The imaging device 30 has been described above as the photographic lens 31.Claims 1-7The zoom lens described in any one of (6 or 7) is referred to as a “shooting zoom lens”.Have.
[0080]
  In FIG. 33A, reference numeral 32 denotes a flash, and reference numeral 33 denotes a finder. The zoom lever 34 and the shutter button 35 are disposed on the upper surface side of the main body. FIG. 33B is a diagram illustrating a usage state of the photographic lens 31. When the photographic lens 31 is not used, as shown in FIG.Stored.In each of the above-described embodiments of the zoom lens, the number of lenses is as small as 6 to 8, and the thickness of the second group is small. Therefore, if the zoom lens is retracted, it can be accommodated in a thin camera body.
[0081]
  As shown in FIG. 33C, the power switch 35, the operation button 37, and the liquid crystal monitor 38 areImaging deviceThe communication card slot 39A and the memory card slot 39B are arranged on the side of the main body.
[0082]
  FIG. 34 is a diagram illustrating a “system structure” of the imaging apparatus. The imaging device 30 is a form information terminal device (claim 20). As shown in FIG. 34, the imaging apparatus includes a photographic lens 31 and a light receiving element (area sensor) 45, and is configured to read an image of a photographic subject formed by the photographic lens 31 with the light receiving element 45. The output from the element 45 is processed by a signal processing device 42 under the control of the central processing unit 40 and converted into digital information. In other words, the imaging device 30 has a “function of converting a captured image into digital information”.Yes.
[0083]
The image information digitized by the signal processing device 42 is subjected to predetermined image processing in the image processing device 41 under the control of the central processing unit 40 and then stored in the semiconductor memory 44 (set in the memory card slot 39B). To be recorded. The liquid crystal monitor 38 can display an image being photographed, or can display an image recorded in the semiconductor memory 44. The image recorded in the semiconductor memory 44 can also be transmitted to the outside using the communication card 43 or the like (set in the communication card slot 39A).
[0084]
  As shown in FIG. 33A, the taking lens 31 isImaging deviceWhen the user 30 is in the “collapsed state”, when the user operates the power switch 36 to turn on the power, the lens barrel is extended as shown in FIG. At this time, each group of the zoom lens in the lens barrel is, for example, “arrangement of the short focal point”, and by operating the zoom lever 34, the arrangement of each group is changed to change the magnification to the long focal point. It can be performed. At this time, the viewfinder 33 also zooms in conjunction with the change in the angle of view of the taking lens.
[0085]
Focusing is performed by “half-pressing” the shutter button 35. Focusing can be performed by moving the first group or the third group, or by moving the light receiving element. When the shutter button 35 is further pressed from the half-pressed state, shooting is performed, and thereafter the above-described image information processing is executed.
[0086]
  When the image recorded in the semiconductor memory 44 is displayed on the liquid crystal monitor 38 or transmitted to the outside using the communication card 43 or the like, the operation button 37 is operated. When any one of Examples 1 to 8 is used as the photographic lens 31, these have good performance. Therefore, the light receiving element 45 uses a 2,000,000 to 3,000,000 pixel class and has a small image quality. Realize equipmentit can.
[0087]
【The invention's effect】
  As described above, according to the present invention, a novel zooming group in a zoom lens, a zoom lens,Imaging deviceCan be realized.
  In the zooming group according to the present invention, since the thickness in the optical axis direction is effectively reduced, the zoom lens can be made compact.Imaging deviceThe dimensions during storage can be effectively reduced.
[0088]
  Further, the zoom lens of the present invention can achieve further miniaturization than the conventional one while maintaining the high performance required for digital image shooting, and uses the zoom lens of the present invention.Imaging deviceCan be realized with small size and high performance.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a lens arrangement at a short focal end of a zoom lens according to a first exemplary embodiment and movement of each group associated with zooming.
FIG. 2 is a diagram illustrating lens arrangement at the short focal point of the zoom lens of Example 2 and movement of each group accompanying zooming.
FIG. 3 is a diagram illustrating a lens arrangement at a short focal end of a zoom lens according to a third exemplary embodiment and movement of each group associated with zooming.
4 is a diagram illustrating lens arrangement at a short focal point of a zoom lens according to Example 4 and movement of each group accompanying zooming; FIG.
5 is a diagram illustrating lens arrangement at a short focal point of the zoom lens of Example 5 and movement of each group accompanying zooming; FIG.
6 is a diagram illustrating lens arrangement at a short focal point of a zoom lens according to Example 6 and movement of each group accompanying zooming; FIG.
7 is a diagram illustrating lens arrangement at a short focal point of a zoom lens according to Example 7 and movement of each group accompanying zooming; FIG.
8 is a diagram illustrating lens arrangement at a short focal point of a zoom lens according to Example 8 and movement of each group accompanying zooming; FIG.
FIG. 9 is an aberration curve diagram at the short focal point of the zoom lens according to Example 1;
10 is an aberration curve diagram at an intermediate focal length of the zoom lens of Example 1. FIG.
FIG. 11 is an aberration curve diagram at the long focal end of the zoom lens of Example 1;
FIG. 12 is an aberration curve diagram at the short focal point of the zoom lens according to Example 2;
13 is an aberration curve diagram at an intermediate focal length of the zoom lens of Example 2. FIG.
FIG. 14 is an aberration curve diagram at the long focal end of the zoom lens according to Example 2;
FIG. 15 is an aberration curve diagram at the short focal point of the zoom lens according to Example 3;
FIG. 16 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Example 3;
FIG. 17 is an aberration curve diagram at the long focal end of the zoom lens according to Example 3;
FIG. 18 is an aberration curve diagram at the short focal point of the zoom lens according to Example 4;
FIG. 19 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Example 4;
FIG. 20 is an aberration curve diagram at the long focal end of the zoom lens according to Example 4;
FIG. 21 is an aberration curve diagram at the short focal point of the zoom lens according to Example 5;
FIG. 22 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Example 5;
FIG. 23 is an aberration curve diagram at the long focal end of the zoom lens according to Example 5;
FIG. 24 is an aberration curve diagram at the short focus end of the zoom lens according to Example 6;
FIG. 25 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Example 6;
FIG. 26 is an aberration curve diagram at the long focal end of the zoom lens according to Example 6;
FIG. 27 is an aberration curve diagram at the short focal point of the zoom lens according to Example 7;
FIG. 28 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Example 7;
FIG. 29 is an aberration curve diagram at the long focal end of the zoom lens according to Example 7;
30 is an aberration curve diagram at the short focal point of the zoom lens according to Example 8; FIG.
FIG. 31 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Example 8;
FIG. 32 is an aberration curve diagram at the long focal end of the zoom lens according to Example 8;
FIG. 33Imaging deviceIt is a figure for demonstrating one Embodiment of.
34 is a diagram for explaining the system configuration of the embodiment of FIG. 33; FIG.
[Explanation of symbols]
I Group 1
II Second group
III Group 3
S Aperture

Claims (12)

In order from the object side, a first lens group having a negative focal length, a second group having a positive focal length, and a third group having a positive focal length, integrated with the second group on the object side of the second group The second lens group monotonically moves from the image side to the object side during zooming from the short focal point to the long focal point, and the first lens group changes the image plane position due to zooming. In a zoom lens that moves to correct,
A zooming group configured as a second group and performing substantial zooming,
In order from the object side, the lens is composed of a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, a positive lens, and a positive lens. The lens and the subsequent negative lens are integrated as a cemented lens,
The most object side surface and the most image side surface are aspherical surfaces, the thickness in the optical axis direction is L ₂ , and the maximum image height is Y ′.
(1) 1.0 <(L ₂ /Y′)<2.5
A zooming group in a zoom lens characterized by satisfying In order from the object side, the first group having a negative focal length, the second group having a positive focal length, and the third group having a positive focal length are integrated with the second group on the object side of the second group. When the zooming is performed from the short focal point to the long focal point, the second group monotonically moves from the image side to the object side to perform substantial zooming. In a zoom lens that moves so as to correct fluctuations in image plane position due to zooming,
  A zoom lens comprising the zooming group according to claim 1 as the second group.   The zoom lens according to claim 2.
  The first group has a three-lens configuration composed of two negative lenses and one positive lens in order from the object side, and the most negative image side surface of the second negative lens from the object side is A zoom lens characterized by being spherical. The zoom lens according to claim 3 .
First unit, in order from the object side, a negative meniscus lens convex on its object side, a three-element consisting of a negative lens, a positive lens,
A zoom lens, wherein the image side surface of the second negative lens from the object side is an aspherical surface. The zoom lens according to claim 4.
  Focal length of the negative meniscus lens disposed on the most object side in the first group: f L1 The focal length of the negative lens arranged second from the object side of the first group: f L2 But the condition:
(3) 0.7 < ( f L1 / F L2) <2.0
A zoom lens characterized by satisfying The zoom lens according to any one of claims 2 to 5,
  A zoom lens characterized in that the third lens group is composed of one positive lens and has at least one aspherical surface. The zoom lens according to any one of claims 2 to 6,
A zoom lens comprising eight lenses constituting the entire system.
  The zoom lens according to any one of claims 3 to 8,   The zoom lens according to any one of claims 2 to 7 is provided as a zoom lens for photographing.
Imaging device.   The imaging apparatus according to claim 8.
  An image pickup apparatus in which a zoom lens for photographing is retracted.   The imaging device according to claim 8 or 9,
  An imaging apparatus having a function of using a captured image as digital information.   The imaging apparatus according to claim 10.
  An image pickup apparatus, wherein a light receiving element for receiving an image by a zoom lens has 2 million pixels or more. The imaging apparatus according to claim 10, wherein the imaging apparatus is a portable information terminal device.

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