JPS6068311A - Compact wide-angle zoom lens with large variable power - Google Patents

Abstract

PURPOSE:To obtain a compact zoom lens which has a 76 deg. field angle at the short-focus side and is about three times as large in the zoom ratio by composing the zoom lens of four positive, negative, negative, and positive groups and satisfying specific conditions. CONSTITUTION:The zoom lens consists of the 1st lens group 1 having negative composite refracting power, the 2nd lens group having positive composite refracting power, the 3rd lens group 3 having negative composite refracting power, and the 4th lens group 4 having positive composite refracting power successively from an object side, and the respective lens groups consist of lenses G1-G14 formed in prescribed shapes. The magnification is so varied that the air gap between the 1st and the 2nd lens groups 1 and 2 on the short-focus side and the air gap between the 3rd and the 4th lens groups 3 and 4 on the long-focus side are reduced respectively and the air gap between the 2nd and the 3rd lens groups 2 and 3 on the short-focus side is increased on the long-focus side. The lens is put in focus by moving independently the 1st lens group 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a 33-fin format eye reflex camera that has a wide angle of view of 76 mm on the short focus side, a zoom ratio of about 3 times, a short overall length of the lens system, and is extremely compact. The present invention relates to a zoom lens with good aberrations.

Zoom lenses with high magnification and compactness that include a wide-angle range and are highly desirable for use in small cameras are in high demand. Conventionally, a two-group zoom lens has been typical as a zoom lens preceded by a lens group having a negative composite refractive power. However, although this two-group zoom lens is simple to construct, if you try to construct a zoom lens system with a high variable power ratio of 2x or more, the fluctuation of various aberrations will be large and correction will be difficult.
Furthermore, it has been difficult to obtain a zoom lens with good aberrations and compactness because the amount of movement of each group becomes large.

The present invention has a positive lens group at the rear of the above-mentioned two-group zoom lens, which is divided into a positive second lens group, a negative third lens group, and a positive D-V lens group, and this is reversed on the short focus side. In a telephoto type configuration, the seventh lens group and the first lens group, and the third and fourth lens groups are close to each other at long focal length, and the combined refractive power is composed of positive and negative groups. It is structured. In order to create a more compact design than before, it is necessary to shorten the focal length of the first and third lens groups.
This caused an increase in various aberrations, making it extremely difficult to correct υ. The present invention aims to reduce aberration fluctuations and the amount of shift a of each group due to zooming, and to enable a compact structure with good aberrations.

As illustrated in FIGS. 1 and 2, the first lens group or 1'
is a negative meniscus G with a strongly concave surface facing the image side, , a positive meniscus G2 with a strongly convex surface facing the image side, or a positive lens with a strong convex surface facing the object side and a golden-white positive lens (/, ~ a fully concave surface strongly facing the image side). The first lens group 2, which has a positive composite refractive power, is composed of a thickened negative meniscus σ2, a negative lens G5 with a strongly concave surface facing the image side, and a positive meniscus 64 with a strongly convex surface facing the object side. 05 with a negative meniscus with a strong concave surface facing the image side
and a positive lens G6 with a strongly convex surface facing the object side, and a composite positive lens G7 with a strongly convex surface facing the object side and a negative meniscus 08 with a strongly concave surface facing the object side. The third lens group 8 or 8' consists of a positive lens having a negative synthetic refraction chip.
A positive lens G with a strongly convex surface facing the object side, and a negative lens G with a strongly concave surface facing the object side. The second lens group 4, which has a positive composite refractive power of 1, is composed of a single or cemented negative lens G or G'0, which is a negative lens with a strongly concave surface facing the object side. Positive lens G12 with a strong convex surface facing the image side, positive lens G with a strong convex surface facing the image side, G, 3, negative meniscus G with a strong concave surface facing the object side, successful from 4, the first lens group on the short focus side l or 1'
The air distance between the lens group 2 and the second lens group 2 and the nine air distance between the third lens group 8 or 8' and the converging lens group 4 decrease on the long focal length side, and The first, third, and third lens groups l or 1', 2.8
Or is it an optical system in which magnification is changed by the relative movement of each lens group 8' and small, and focusing is performed by independent movement of lens group J and 1', and the following conditions are met? It is a wide-angle, high-variable zoom lens that is characterized by the addition of f.

2 (110, 3,!-<--<0, 9.5-zuW 2 (31/, Otsu3<N6 *N7<'-7(41
! ;0 < white, shift +5) D2+D5=constant where +fw...minimum focal length of the entire zoom lens system ifl・
... Focal length of the lens group tS+ ... Radius of curvature N1 of the lens surface of the first eye...
The d-line refractive index ν1 of the first glass material...the d-line Abbe number D1 of the first glass material...th lenses m and m(1+i
) Distance between principal points of lens groups Next, to describe the features of the present invention in detail, in order to obtain a compact zoom lens system, the thermal performance distance of the second lens group 2 of the present invention is set at a distance compared to the shortest focal length of the zoom lens system. I set it short. Condition (11) is the range of the focal length of the second lens group 2 to obtain a compact zoom lens.If the upper limit is exceeded, the objective compactization is a.If the lower limit is exceeded, especially on the long focal length side. It becomes extremely difficult to correct spherical aberration.

The first lens group of the present invention is a negative lens G, and a positive lens G2.
In the case of the configuration shown in FIG. 1 in which the negative lens precedes the positive lens G71. in FIG. Compared to the previous configuration, the effective diameter may be smaller, and the filter diameter may be a φSS fin, although it has a large diameter of the FJJ class on the wide-angle side of 76 degrees. However, in this configuration, the spherical aberration changes toward the over side on the long focal point side during zooming, making correction difficult. In order to correct this, a positive lens with a strongly convex surface facing the object side is provided in the second lens group 2, but condition (2) is an appropriate range of this convex surface, and the upper limit '! If it exceeds r-, coma aberration worsens on the long focal point side and flare occurs. If the lower limit f is exceeded, the spherical aberration becomes even more excessive on the long focal point side, and the curvature of field aberration becomes considerably less, and it is impossible to correct these aberrations with other lens surfaces. Further, when the positive lens leading timing shown in FIG. 2 is used, fluctuations in spherical aberration due to zooming can be further reduced. Although the effective diameter of the front lens is larger than that of the negative lens leading tie fK shown in FIG. 1, it is not within the range that would be contrary to compactness.

In the case of a negative, positive, negative, positive nine group configuration, the light ray passing through the corner 7 on the long focal point side and the maximum 11 parallel to the optical axis pass at almost the same height in the $2 lens group 2. In such a case, it is very difficult to correct longitudinal chromatic aberration and lateral chromatic aberration on the long focal point side. The second lens group 2 of the present invention is composed of two cemented lenses having a positive composite refractive index, which are made by cementing a negative meniscus lens having a difference in refractive index and a difference in Abbe number, and a biconvex lens. As a result, all aberrations, especially chromatic aberration, are corrected within the entire focal length from the wide-angle side to the long focal length side. Condition (3
) and (4) are the appropriate ranges for the refractive index and Atsube number of the glass material of this biconvex lens, and if these conditions are deviated from, it is impossible to correct chromatic aberration, especially on the long focal length side, with other lens groups. . In addition to chromatic aberrations, if the upper limit of condition (3) is exceeded, coma aberration on the long focal point side worsens and flare occurs considerably. If the lower limit is exceeded by the λ hole, the meridional luminous flux will exceed on the long focal point side and the astigmatism difference will become large, and it is difficult to correct f'a with anything other than the second lens group.

In the present invention, as in condition (5), the zooming middle frame lens group 2 and the second lens group 4 move together, and the third lens group 8 or 1l-t8 moves in unison to absorb aberration fluctuations caused by zooming.
The format was such that the closing part moved to the German side. By doing this,
The number of lens group drive cams can be reduced, and even though it is a continuous structure, it can be easily assembled with high precision, reducing costs such as parts processing and assembly adjustment man-hours. It is easy to predict what will happen.

Note that 01. of the third lens group 8 of the present invention. A positive meniscus is joined to the image side, and a composite lens G'1. A strong concave surface on the image side? By placing it in a negative lens that is aimed at the lens, coma flare on the long focal length side can be further reduced.

Next, examples of the present invention will be shown.

Example 1 f=2g, ri~SO~g, 2. g FNo, 3.5~da, θ~I1. zaf2=,23. '7 Genke Rei Q ＼ ~ outside 6o6゜1.

＼ ＼ ＼ 〜 （＼ ）） へH〜 類 ah J／） ト ＼ ト ＼ 鵠升oS＞ Vine
Vine (kure \ to, -ori ゝ ゞ ″″ 9 ＼ tax II II II II II II
饗 ＼ Kurashi C ツ ト ＼ ＼ Fake c++ ト ＼ c'1J71J/) 〜 II II II II CC [ 仁 0 (-１１－－－－－－－－－－－－－－－－１－J
〜 Kurage Example f = 2g, 7~30-g2.9 FNo, 3.
3-4', 0-'1. gf2=2. ! ;,'/ 5 7 ＾6o Ch Cs 4 As can be seen from the fine aberration diagrams of FIGS. 3 and q in the example, it can be seen that the t1'fi-zoom lens maintains excellent imaging performance even when changing the magnification by zooming.

[Brief explanation of drawings]

Figure 1 is a lens configuration diagram of Example 1 of the present invention, Figure 2 is a lens configuration diagram of Example 1, each figure in Figure 3 is of Example 1, and each figure in Figure 7 is of Example 1. FIG. 4 is a diagram showing various aberrations at each focal length for an object at infinity. Furthermore, this figure 3,
In FIG. 7, S is a sasicle image plane, and M is a meridional image plane. G1...Each single lens from the object side, ■...First lens group-2...Core lens group, 8...Third lens group, 4...Derlens group. Kumiku 1 - Liang

Claims (1)

[Claims] 01 The second lens group is a negative meniscus lens having a concave surface facing toward the image side from the object side.
A synthetic positive lens made by cementing a positive lens with a convex surface facing the object side, and a synthetic positive lens made by cementing a positive lens with a convex surface facing the object side and a negative meniscus lens with a concave surface facing the object side. It is a lens group that has a positive composite refractive power consisting of a positive lens with a convex surface facing the image side, a positive lens with a convex surface facing the image side, and a negative lens with a concave surface facing the object side in order from the object side. The first lens group is composed of a meniscus lens having a positive composite refractive power, and the first lens group is, in order from the object side, a negative meniscus lens with a concave surface facing the image side, a positive meniscus lens with a convex surface facing the image side, and a positive meniscus lens with a convex surface facing the image side. This is a lens group with negative synthetic refractive power consisting of a negative lens with its concave surface facing toward the object side and a positive meniscus lens with its convex surface facing toward the object side, and the third lens group has a convex surface facing toward the image side in order from the object side. It consists of a lens group with negative composite refractive power, consisting of a composite negative lens made by cementing a positive lens and a negative lens with a concave surface facing the object side, and a reconnaissance lens with a concave surface facing the object side. The air distance between the first lens group and the first lens group and the air distance between the third lens group and the second lens group decrease on the long focal length side, and the second lens group and the third lens on the short focal length side An optical system that performs magnification by moving the 11th, 2nd, 3rd, and q-th lens groups relative to each other so that the air gap between the groups increases on the long focal point side, and performs focusing by moving the first lens group independently. A compact wide-angle, high-variability zoom lens that satisfies the following conditions. w '12 ko) 0. g << /, 2 2 3) /, lz3 (N6.NA (/, ri1I) so
<Shiro, shift, S-) D2+Ds=constant where fw...the shortest focal length of the entire zoom lens system 1...
Focal length of the third lens group R1...Radius of curvature of the first lens surface N1...D-line refractive index of the first glass material ν1...D-line Atsube number of the first glass material D1...first lens group and (l+/
) Principal point spacing of the lens group. (21) The first lens group is, in order from the object side, a positive lens with a convex surface facing the image side, a negative meniscus lens with a concave surface facing the image side, and a negative lens group with a concave surface facing the image side; The third lens group is a third lens group having a convex golden-white positive lens on the image side and a negative composite refractive power with a concave surface on the object side. Wide-angle high-power zoom lens.