JP2000267005A5

JP2000267005A5 -

Info

Publication number: JP2000267005A5
Application number: JP1999069817A
Authority: JP
Filing date: 1999-03-16
Publication date: 2005-02-24
Anticipated expiration: 2019-03-16

Description

【００３７】
(ア-1) 前記第１１レンズは物体側に凸面を向けたメニスカス形状をしており、前記第１２レンズは像側に比べて物体側に強い屈折力の凸面を向けた両レンズ面が凸面形状をしており、前記第１３レンズは物体側に強い凸面を向けたメニスカス形状をしていることである。[0037]
(A-1) The eleventh lens has a meniscus shape with a convex surface facing the object side, and the twelfth lens has both convex surfaces having a convex surface having a strong refractive power on the object side compared to the image side. The thirteenth lens has a meniscus shape with a strong convex surface facing the object side.

【００４５】
また十分な長さのバックフォーカスの確保も困難になる。逆に下限値を超えて軸上光束の発散度が強くなると第４レンズ群に入射する入射高が高くなり、球面収差が多く発生してくる。さらに第４レンズ群が大型化し、迅速なるフォーカスが困難になるという問題が生じる。[0045]
It also becomes difficult to secure a sufficiently long back focus. On the contrary, when the divergence of the axial light beam increases beyond the lower limit value, the incident height incident on the fourth lens group increases, and a large amount of spherical aberration occurs. Furthermore, the fourth lens group becomes large, and there arises a problem that quick focusing becomes difficult.

【００５０】
−８．０＜Ｆ _１／Ｆ _２＜−５．０（６）
なる条件を満足することである。[0050]
_{_{-8.0 <F 1 / F 2 <}} -5.0 (6)
To satisfy the following conditions.

【００５８】
−７．５＜Ｆ _１／Ｆ _２＜−５．５ ‥‥‥（６ａ）
(ア-9)前玉径を小型化しつつ、ズーミングによる色収差の変動を小さくするには、第２レンズ群を物体側から順に凸面を有するメニスカス状の負レンズ、両レンズ面が凹面の負レンズ、空気間隔を挟んで両レンズ面が凸面の正レンズ、負レンズの順に配置することである。この空気間隔によって第２レンズ群の物体側主点が第１レンズ群よりになり、広角側における第１レンズ群と第２レンズ群の主点感覚を短く取りやすくなり第１レンズ群寄りになり、広角側における第１レンズ群と第２レンズ群の主点間隔を短く取りやすくなり、第１レンズ群の小型化に有効であり、色消しを対称に近づけることで、ズーミングによる色収差の変動を抑えるのにも有効である。[0058]
_{_{-7.5 <F 1 / F 2 <}} -5.5 ‥‥‥ (6a)
(A-9) In order to reduce the variation in chromatic aberration due to zooming while reducing the front lens diameter, the second lens unit is a meniscus negative lens having a convex surface in order from the object side, and both lens surfaces are concave negative lenses. The positive lens and the negative lens are arranged in this order with both lens surfaces having convex surfaces across the air gap. By this air gap, the object side principal point of the second lens group becomes closer to that of the first lens group, and the sense of the principal point of the first lens group and the second lens group on the wide angle side can be easily shortened and closer to the first lens group. The distance between the principal points of the first lens group and the second lens group on the wide-angle side can be easily shortened, which is effective for miniaturization of the first lens group, and the variation of chromatic aberration due to zooming can be achieved by bringing achromaticity closer to symmetry. It is also effective to suppress.

【００６１】
−６．８＜Ｆ _１／Ｆ _２＜−６．０ ‥‥‥（６ｂ）
の如く設定するのが良い。[0061]
_{_{-6.8 <F 1 / F 2 <}} -6.0 ‥‥‥ (6b)
It is better to set as follows.

【００６６】
なる式で表している。ｆは焦点距離、ＦｎｏはＦナンバー、ωは半画角である。又「ｅ−０ｘ」は「１０ ^−ｘ」を意味している。 [0066]
It is expressed by the following formula. f is a focal length, Fno is an F number, and ω is a half angle of view. “E-0x” means “10 ^−x ”.

Claims

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, and a wide angle When zooming from the end to the telephoto end, in the zoom lens that moves the second lens group toward the image plane side and moves the fourth lens group along a convex locus toward the object side, the first lens group is It is composed of three single lenses of an eleventh lens, a positive twelfth lens, and a positive thirteenth lens in order from the object side, and the Abbe number of the material of one positive lens in the first lens group is νd1p, When the focal length of the twelfth lens is f12 and the focal length at the telephoto end of the entire system is ft, νdlp> 80
0.5 <f12 / ft <1.5
A zoom lens characterized by satisfying the following conditions:

The eleventh lens has a meniscus shape with a convex surface facing the object side, and the twelfth lens has both lens surfaces with a convex surface having a strong refractive power on the object side compared to the image side, and has a convex shape. The zoom lens according to claim 1, wherein the thirteenth lens has a meniscus shape with a strong convex surface facing the object side.

The zoom lens according to claim 1 or 2, wherein each of the third lens group and the fourth lens group has at least one aspherical surface.

4. The zoom lens according to claim 1, wherein the third lens group includes a cemented lens including a positive lens and a negative lens, and the fourth lens includes a cemented lens including a negative lens and a positive lens.

5. The zoom lens according to claim 1, wherein the second lens group includes a negative lens, a negative lens, a positive lens, and a negative lens in order from the object side.

When the combined focal length from the first lens group to the third lens group at the telephoto end at infinity is ft13, the focal length of the i-th lens group is Fi, and the focal length at the wide-angle end of the entire system is fw. 1 <ft / ft13 <0.7

The zoom lens according to claim 1, wherein the following conditional expression is satisfied.

An imaging apparatus comprising the zoom lens according to claim 1.