JPH03158815A - Zoom lens with simple constitution - Google Patents

Abstract

PURPOSE:To shorten the whole length of a lens system and to obtain a zoom lens having high optical performance over the whole variable power range by specifying the lens shapes and refractive power of respective lens groups having the zoom lens for executing variable power operation while moving two lens groups having respective prescribed refractive power. CONSTITUTION:The zoom lens has two groups, i.e. the 1st group having positive refractive power and the 2nd group having negative refractive power, arranged successively from the object side, and at the time of executing variable power operation by changing the distance between both the lens groups, the 1st group is constituted of the 11th negative lens and the 12th positive lens and the 2nd group is constituted of the 21th negative lens. When the 12th lens is constituted of a lens having convex faces on both sides, the air distance between the 11th and 12th lenses is d1-2, the Abbe number of the material of the 12th lens is nu12, the focal distance of the whole system at the wide angle end is FW, the zoom lens is constituted so as to satisfy the conditions of 0.1<d1-2/FW<1.5 and 50<nu12. Consequently, the zoom lens constituted of three lenses and having effective optical performance over the whole variable power range of about 2 variable power ratio and 62 to 35 deg. photographing picture angle can be obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a zoom lens with a simple configuration consisting of two lens groups suitable for lens shutter cameras, digital cameras, etc. This invention relates to a simple, unused zoom lens with a short overall lens length (the microscope section from the lens surface to the image 1 m), which reduces the amount of aberrations and performs good aberration compensation.

(Prior Art) As lens shutter cameras, video cameras, and the like become increasingly popular, various types of simple zoom lenses with short overall lens lengths have been proposed.

The present applicant previously published Japanese Patent Application Laid-Open No. 57-20121:l,
Japanese Patent Application Publication No. ShofiO-170816+I11. Tokukai 1986
In JP-A-191215, JP-A-62-56917, etc., two lenses ET, a first group with positive refractive power and a second group with negative refractive power, are used in order from the object side. We proposed a compact zoom lens that changes the magnification by changing the distance between the two.

This publication adopts a positive and negative refractive power arrangement in order from the object side, achieving a zoom lens with a relatively short back focus and a high optical rim with a shortened overall lens length. There is.

In addition, a zoom lens that consists of a first group with positive refractive power and a second lens group with negative refractive power and whose magnification is varied by changing the distance between both lenses has been proposed, for example, in Japanese Patent Application Laid-Open No. 62-251710. There is. Doses? [In J, the first group consists of a triplet type consisting of three lenses, and the 21st group consists of two lenses, a positive lens and a negative lens, and the zoom ratio is 1.5J5, which consists of five lenses in total! p! We are proposing a zoom lens with a simple configuration.

In addition, in Japanese Patent Application Laid-Open No. 6:1-27501:1, the first group consists of two lenses, a negative lens and a positive lens, and the second group consists of two lenses, a positive lens and a negative lens, and the total number of lenses is 4. We have proposed a simple Iδ zoom lens with a variable fn ratio of 2 degrees, which is composed of two lenses, and uses gradient index lenses for a plurality of the lenses.

(Problems to be Solved by the Invention) In general, in a zoom lens consisting of the two lens groups described above, in order to simplify the lens configuration, it is preferable to form each lens group with as few lenses as possible, ie, 14 lenses.

However, in order to secure the desired zoom ratio and shooting angle of view, the lens configuration of each lens group must be properly set, otherwise fluctuations in various aberrations due to zooming will increase, making it difficult to correct these well. It's coming.

Furthermore, as proposed in the above-mentioned Japanese Patent Application Laid-Open No. 63-276013, a gradient index lens is used to create a lens JI.
# The problem with the method of simplifying the construction is that it is difficult to manufacture the gradient index lens with high precision.

The present invention is a zoom lens having two lens groups, and by appropriately setting the lens configuration of each lens group, the present invention provides a zoom lens that has a predetermined magnification ratio and shooting angle of view while simplifying the lens configuration. The purpose of the present invention is to provide a simply constructed zoom lens that has good optical performance over a variable power range.

(Means for Solving the Problems) A zoom lens of the present invention having a simple configuration includes two lenses 7!, a first group having a positive refractive power, and a second group having a negative refractive power, in order from the object side. When zooming is performed by changing the flu interval of both lens groups, the first group is made up of a negative 11th lens and a positive 12th lens, and the second group is made up of a negative 11th lens and a positive 12th lens. It is characterized by being composed of 21 lenses.

In this Ikemizu invention, the 11th lens has a meniscus shape with the convex surface facing the object side, or the 12th lens has a shape with both convex surfaces. * If the air distance between the 'ds 1 lens and the 12th lens is 'I -2s, the Atsbe number of the material of the 12th lens is 2, and the focal length of the entire system at the wide-angle end is FW, then 0, 1 <d+-z/FW< 1, 5 ・
・・−(1)50 kuυ１□ ・・
It is characterized by satisfying the condition (2).

(Example) FIGS. 1 and 2 are cross-sectional views of lenses of Numerical Example 1.2 of the present invention. In the figure, (A) shows the zoom position at the wide-angle end, (B) shows the zoom position in the middle, and (C) shows the zoom position at the telephoto end.

In the figure, ■ is the first J! with positive refractive power. T, 11 is the second ffT with negative refractive power, and while decreasing the distance between both lens groups, both lens groups are moved to the object fil as shown by the arrows, and the magnification is changed from the wide-angle end to the C1l far end. ing. sp is the aperture.

In this embodiment, by adopting such a zoom system and refractive power arrangement, the overall lens length can be shortened, and especially a wide fQ V
The overall length of the lens is shortened.

And the lens configuration of each lens ffT, and Shinzuno Tani;
The lens shape of the lens is configured as described above, and the entire lens system is arranged in a symmetrical manner when changing the magnification. This results in a variable 47" S ratio of about 2, and a 11c internal shadow angle of 62° to 35° J".
A zoom lens having a simple structure consisting of three lenses in total, which has good 9' and performance over the entire zoom range of 1 degree, is obtained.

Next, the technical aspects of each of the above-mentioned conditional expressions will be explained.

Conditional expression (1) relates to the 5;-air spacing between the 11th lens and the 12th lens in the 1st group, and is intended to favorably correct -kl+ external aberrations while mainly reducing the size of the entire lens system. It is.

The air spacing exceeds the lower limit A of formula (1).
Once this is reached, it becomes difficult to maintain a good field curvature over the entire magnification range.

Also, beyond 1-period A〆1? ;If the gap becomes wide, the effective diameter of the 11th lens becomes large and the entire lens system becomes large, which is not good.

Conditional expression (2) is the 11th! When T is composed of a negative lens and an iE lens, the material of the positive 12th lens is appropriately set,
This is to satisfactorily correct 4III+J dichromatic aberration per day. If Equation (2) is not met, the axis and envelope y' at the wide-angle end will exceed the allowable limit IIt.

In this Ikemizu invention, it is particularly preferable in terms of aberration correction that the object fll+ of the 21st lens constituting the second BT having a negative refractive power
and the curvature ゛r-diameter of the lens surface of the image plane full are RA and R, respectively.
It is better to satisfy the condition that becomes B.

Conditional expression (3) is for correcting various aberrations of the entire screen in a well-balanced manner over all magnification changes, and even if the upper limit or lower limit is exceeded, it becomes difficult to maintain the optical performance of the entire screen in a well-balanced manner. come.

Further, in the present invention, in order to further reduce the size of the entire lens system and to satisfactorily correct aberration fluctuations due to zooming, the focal lengths of the first group and the second group are each set to Fl.

F2, 0.6<|F1/F2 when the principal point spacing at the wide-angle end and telephoto end of the first and second groups is eW and eT, respectively.
|<1.2 −(451,7< eW/eT <
It is preferable to satisfy the condition 2.8-(5).

Conditional expression (4) relates to the refractive power ratio of the first group and the second group, and is intended to reduce aberration fluctuations while obtaining a predetermined variable power ratio when changing magnification by moving both lens groups. .

The first and second groups exceed the upper limit or lower limit of conditional expression (4).
When one of the refractive powers of the group becomes larger than the other, it becomes difficult to satisfactorily correct aberration fluctuations while ensuring a predetermined zoom ratio.

Conditional expression (5) sets the principal point spacing at the wide-angle end and telephoto end of the first and second groups appropriately, and achieves a predetermined variable power ratio while shortening the overall lens length based on conditional expression (4). , for example, when the magnification ratio is 2
This is to obtain the degree.

If the upper or lower limit of conditional expression (5) is exceeded, it becomes difficult to obtain a predetermined variable power ratio while shortening the overall lens length.

In this Ikemizu invention, in order to maintain good optical performance of the entire screen over the entire zoom range, an aspherical surface is provided on the object side or image side of the 11th lens in the 1st group, and the 4th order aspherical surface of the aspherical surface is When the spherical coefficient is B and the diagonal length of the effective screen is Y, |<IB-Y'l<15 (6
) It is better to satisfy the following conditions.

Here, when the aspheric surface is applied to the object-side lens surface of the eleventh lens, the aspheric coefficient B has a negative sign, and when it is applied to the image-side lens surface, the aspheric coefficient B has a positive sign.

If you change the limit A of formula (fi), the J1 spherical effect will be insufficient, and it will become unclear whether the rill can be properly corrected to the image plane, and if you exceed the lower limit A,゛The effective surface becomes stronger, and the image surface: l'l; +lI+ or Jon +
However, in Numerical Example 1.2, which will be described later, the 11th lens is made from a single-plane lens made of polycarbonate, and the curvature of field is well compensated for. I'm getting a lens.

Next, several embodiments of the present invention will be described. In the first embodiment, Ri is the radius of curvature of the 1st 11th lens surface from the object side, Di is the 1st 11th lens J1- and the air distance from the object side, and Ni and νi are respectively from the object 1!1. first in order
These are the refractive index and Abbe number of the glass of lens No. 11.

41 The spherical shape has the X axis in the optical axis direction and the H1 in the direction perpendicular to the optical axis.
1t, the traveling direction of light is positive and R is paraxial curve +4 'l'
- diameter, A.

B, C.

D.

Let E be each aspherical coefficient time + Dll”+ El+’.

It is expressed as a formula.

Also, the number of words (1
Table 1 shows the relationship with 'l.

Numerical Example 1 F-39,19 ~ 67.72 Rl-20,90 112-14,61 13-200,48 1 (impression -12,51 1t', r-(aperture) R6・-17,77 117=1252.95 FNo=I:5.79 2ω-61,71°~10
．． 87 ~35.43°1-1.5
N+-1,58:106 ν I-:]0.2
2- 8.45 3~3.0 N2・1.49700ν 2-Old, 6
4-1.0 5・Variable 6-1.7 N 3-1.60:III υ 3・
60.7 Numerical Example 2 F-39,2!1 ~67.7 R1~ BOO, D8 R2-34,81 0a-a2. :1O It 4- -20.42 1t5=(Aperture) Mouth 6--18.81 171I-611,57 FNo=I near, 14 2ω-61,73°~12
．． 32 ~ 35.430D 1.5
N I-1, 58:176 v l-30,
22-11,9: I duck 3. ON 2-1.1?49 ν 2-7
0.24- 4.34 5・Variable 6-1.7 N 3-1.511376 ν 3-
30.2 First aspherical: Aspherical coefficient 8 −〇 Low −
9,01X 10-'C--9,3xlO-'D
-2,l2xlO-9F--7,4:lx 10-" First aspherical: Aspherical coefficient 8-0 Rho 4.60X10-ri C--9,I7x 10-' D-1,06x 10
-riE--1,22xlO-6th aspherical surfaceAspherical coefficient 8-OB・-5,31X10-' C--2,02x J(1-' D-1,a2x J
O-'1 Knee -3,62 By setting the lens shape, refractive power, etc. as described above, the overall length of the lens has been shortened. A zoom lens with a simple structure consisting of lenses can be achieved.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of lenses of numerical example 1.2 of the present invention, and Figures 3 and 4 are numerical actual/Ih example 1.2 of the present invention.
It is a diagram of various aberrations. In the lens cross-sectional view and aberration diagram, (A) is wide-angle);
(B) is an aberration diagram at the intermediate position, and (C) is an aberration diagram at the telephoto end. In the figure, I and II are respectively 1st. In the second lens group, sp indicates an aperture, and arrows indicate the movement direction of each group during zooming. Figure (A) Figure 3 (A) Figure [21 (B) Figure (C) Figure (A)

Claims (1)

[Claims] (1) It has two lens groups, a first group with positive refractive power and a second group with negative refractive power, in order from the object side, and magnification can be changed by changing the distance between both lens groups. When performing this, the first group is composed of a negative 11th lens and a positive 12th lens, and the second group is composed of a negative 21st lens.
A zoom lens with a simple configuration characterized by being composed of lenses. (2) The twelfth lens is configured such that both lenses have convex surfaces, the air distance between the eleventh lens and the twelfth lens is d_1_-_2, and the Abbe number of the material of the twelfth lens is ν.
_1_2, the simple structure according to claim 1, satisfying the following conditions: 0.1<d_1_-_2/FW<1.5 50<ν_1_2, where FW is the focal length at the wide-angle end of the entire system. zoom lens. (3) When the radius of curvature of the object-side and image-side lens surfaces of the 21st lens is RA and RB, respectively, 0.8<(RB+
3. A zoom lens having a simple configuration according to claim 2, wherein the zoom lens satisfies the following condition: RA)/(RB-RA)<1.9. (4) The focal lengths of the first group and the second group are F1 and F2, respectively.
, 0.6<|F1/F2|<, where eW and eT are the principal point spacings at the wide-angle end and telephoto end of the first and second groups, respectively.
4. A zoom lens having a simple configuration according to claim 3, wherein the zoom lens satisfies the following conditions: 1.2 1.7<eW/eT<2.8. (5) An aspherical surface is formed on the object side or image side of the eleventh lens, and when the fourth-order aspherical coefficient of the aspherical surface is B and the diagonal length of the effective screen is Y, 1<|B・Y＾3｜<
15. A zoom lens having a simple configuration according to claim 1 or 2, characterized in that the zoom lens satisfies the following condition.