JP3018723B2 - Zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens suitable for a single-lens reflex camera, a video camera and the like, and more particularly to a so-called negative lead type lens group having four lens groups as a whole, which is preceded by a lens group having a negative refractive power. The present invention relates to a large-aperture zoom lens having a wide angle of view and a high zoom ratio.

[0002]

2. Description of the Related Art A negative lead type zoom lens, which is preceded by a lens group having a negative refractive power, has features such as a relatively wide angle of view and a short close-up distance. However, there are drawbacks such as an increase in the aperture diameter and difficulty in increasing the zoom ratio.

[0003] A zoom lens which has improved these drawbacks and has achieved miniaturization and high zoom ratio of the whole lens system is disclosed in, for example, JP-B-49-23912, JP-A-53-34539, and JP-A-57-34539. 163213, JP-A-58-4
No. 113, JP-A-63-241511, and JP-A-2-201310.

In each of these publications, a zoom lens is composed of four lens groups as a whole in order from the object side, having negative, positive, negative, and positive refractive power, and a predetermined lens group is appropriately moved. Let me change the magnification.

[0005]

In recent years, as a standard zoom lens used for a single-lens reflex camera, a video camera, or the like, a zoom lens having a wide angle of view and a high zoom ratio has been demanded. For example, a single-lens reflex camera for 35 mm film already has a focal length of 35 mm to 70 mm or a focal length of 28 mm to 7 mm.
A zoom lens having a wide angle of view of about 0 mm is used as a standard zoom lens.

[0006] More recently, the focal length is 28 mm to 80 m.
There is a demand for a standard zoom lens having a large aperture ratio, which enlarges the magnification range to the telephoto side with a focal length of about 28 mm to 85 mm and achieves high magnification.

However, in general, when the photographing angle of view is as large as this and the zoom ratio is high, the entire length of the lens becomes long, and in zooming, a complicated zoom movement is required. There is a problem that the lens barrel becomes large and complicated.

According to the present invention, the zoom lens is composed of four lens groups as a whole, and the refracting power of each lens group and the moving conditions of each lens group for zooming are appropriately set.
The objective is to provide a zoom lens that has a relatively wide angle of view and high optical performance over the entire zoom range with a high zoom ratio, while reducing the overall length of the lens and preventing the lens barrel from becoming large and complicated. .

[0009]

A zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a positive lens unit. 4th of refractive power
The zoom lens system has four lens groups. When changing the magnification from the wide-angle end to the telephoto end, the air gap between the first and second groups decreases, and the air gap between the second and third groups increases. In addition, at least the first, second, and fourth groups are so arranged that the air gap between the third and fourth groups is reduced.
A zoom lens which is moved by moving a group, wherein the third group includes two independent lenses including a positive lens and a negative lens or one cemented lens, and the fourth group includes a negative lens and a positive lens. It is composed of two independent lenses or one cemented lens. The focal lengths of the second and third groups are F2 and F3, the focal length of the fourth group is F4, and the total length at the telephoto end is F4. When the focal length of the system is FT, the following inequality is satisfied: F2 <| F3 | ‥‥‥ (1-a) 0.5 <F4 / FT <2 ‥‥‥ (1-b)

[0010]

1 to 3 show numerical examples 1 to 3 of the present invention, respectively.
It is a lens sectional view of. In the lens sectional view, L1 is a first group having a negative refractive power, L2 is a second group having a positive refractive power, L3 is a third group having a negative refractive power, L4 is a fourth group having a positive refractive power, SP
Is an aperture.

In the present invention, the magnification is changed by moving a predetermined lens group so that the air interval between the lens groups changes.

In particular, in the zooming from the wide-angle end to the telephoto end, the air gap between the first and second groups is reduced, the air gap between the second and third groups is increased, and the third and fourth groups are changed. At least the first, second, and fourth groups are moved so that the air gap between the groups is reduced. Specifically, zooming from the wide-angle end to the telephoto end is performed by moving the first unit to the image plane side, moving the second unit to the object side, and moving the fourth unit to the object side.

At this time, the second lens unit and the fourth lens unit may be independently moved to the object side, or may be integrally moved to simplify the lens barrel. Focusing is performed by moving the entire first group, and the first group is divided into two lens groups, a 11th group and a twelfth group, from the object side, and the twelfth group is moved. .

Next, the features of each numerical example shown in FIGS. 1 to 3 will be described in order.

(1-1) In Numerical Examples 1, 2, and 3 shown in FIGS. 1, 2 and 3, the magnification from the wide-angle end to the telephoto end is changed by the air gap between the first and second lens units. At least the first, second, and fourth groups are moved so that the air gap between the second group and the third group increases, and the air gap between the third group and the fourth group decreases. The third group has an independent or laminated lens of a positive lens and a negative lens, and the fourth group has an independent or laminated lens of a negative lens and a positive lens. As a result, high optical performance with a wide angle of view and little aberration variation over the entire zoom range is achieved while shortening the overall length of the lens.

The second group includes, in order from the object side, a meniscus-shaped negative lens having a stronger negative refraction surface on the image surface side than the object side, a positive lens, and a positive lens having a convex surface facing the object side. It is configured to have a lens. Thereby, excellent aberration correction is performed while the second lens unit has a relatively strong positive refractive power. In particular, the diameter of the light beam emitted from the second lens unit on the telephoto side is reduced, the aperture diameter is reduced, and the lens barrel diameter is reduced.

The first lens unit includes, in order from the object side, a negative meniscus lens having a concave surface facing the image surface side, a negative lens, and a positive meniscus lens having a convex surface facing the object side. Generally, if a positive lens is arranged closest to the object, distortion on the wide-angle side can be corrected well, but the outer diameter of the lens increases.

Therefore, in the present invention, as described above, the first lens unit is configured so that the negative lens is located closest to the object side, distortion is corrected by the other lens units, the outer diameter of the lens is reduced, and the close-up distance is reduced. Is being shortened.

The third lens unit is fixed during zooming to simplify the lens barrel structure. The zooming from the wide-angle end to the telephoto end may be performed by moving the second and fourth units together toward the object side, thereby simplifying the lens barrel structure as described above. Can be.

The focal lengths of the second and third lens units are F2 and F, respectively.
F2 <| F3 | ‥‥‥ (1-a) when 3 is set.

By giving the second group a strong positive refractive power, the diameter of the stop is reduced and the diameter of the lens barrel is reduced in the same manner as described above. In addition, the third group has a relatively low refractive power as compared with the second group, so that good aberration correction can be performed even if the third group is composed of two lenses.

When the focal length of the fourth lens unit is F4, and the focal length of the entire system at the telephoto end is FT, the relationship is 0.5 <F4 / FT <2Ｆ (1-b). As a result, good aberration correction is performed while reducing the size of the entire lens system.

If the refracting power of the fourth lens unit becomes too strong beyond the lower limit value of the conditional expression (1-b), the fourth lens unit can be properly corrected for aberrations by using two lenses, a negative lens and a positive lens. Becomes more difficult. If the refractive power of the fourth group is too weak beyond the upper limit, the amount of movement of each lens group during zooming increases,
It is not good because the entire length of the lens becomes longer.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air spacing from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass.

The aspherical surface has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R is a paraxial radius of curvature,
When A, B, C, D, and E are each aspheric coefficients

[0026]

(Equation 1)

This is expressed by the following equation. Numerical Example 1 F = 28.8 to 77.3 FNO = 1: 3.5 to 4.5 2ω = 73.8 ° to 31.3 ° R 1 = 57.039 D 1 = 1.80 N 1 = 1.77250 ν 1 = 49.6 R 2 = 23.561 D 2 = 6.90 R 3 = -13365.018 D 3 = 1.60 N 2 = 1.77250 ν 2 = 49.6 R 4 = 40.913 D 4 = 0.10 R 5 = 30.586 D 5 = 3.90 N 3 = 1.80518 ν 3 = 25.4 R 6 = 65.175 D 6 = Variable R 7 = 61.327 D 7 = 1.50 N 4 = 1.84666 ν 4 = 23.9 R 8 = 25.956 D 8 = 0.07 R 9 = 27.135 D 9 = 4.00 N 5 = 1.69680 ν 5 = 55.5 R10 = -157.956 D10 = 0.10 R11 = 35.052 D11 = 3.15 N 6 = 1.69680 ν 6 = 55.5 R12 = -166.755 D12 = Variable R13 = (Aperture) D13 = 1.75 R14 = -51.650 D14 = 2.10 N 7 = 1.80518 ν 7 = 25.4 R15 = -25.090 D15 = 1.30 N 8 = 1.60311 ν 8 = 60.7 R16 = 46.084 D16 = Variable R17 = 122.517 D17 = 1.30 N 9 = 1.80518 ν 9 = 25.4 R18 = 31.966 D18 = 0.42 R19 = 35.150 D19 = 5.00 N10 = 1.58313 ν10 = 59.4 R20 = -37.015 Aspheric

[0028]

[Table 1]

R20: Aspherical coefficient A = 0 B = 4.888934 × 10 ^-6 C = -6.38115 × 10 ^-9 D = 1.53483 × 10 ^-10 E = -5.17930 × 10 ^-13 Numerical Example 2 F = 28.8 to 77.01 FNO = 1: 3.5 to 4.5 2ω = 73.8 ° to 31.4 ° R 1 = 69.290 D 1 = 1.80 N 1 = 1.77250 ν 1 = 49.6 R 2 = 26.715 D 2 = 6.90 R 3 = 3674.837 D 3 = 1.60 N 2 = 1.77250 ν 2 = 49.6 R 4 = 37.386 D 4 = 0.10 R 5 = 31.958 D 5 = 3.90 N 3 = 1.80518 ν 3 = 25.4 R 6 = 69.851 D 6 = Variable R 7 = 62.034 D 7 = 1.50 N 4 = 1.84666 ν 4 = 23.9 R 8 = 25.952 D 8 = 0.07 R 9 = 26.641 D 9 = 4.00 N 5 = 1.69680 ν 5 = 55.5 R10 = -110.081 D10 = 0.10 R11 = 31.365 D11 = 3.15 N 6 = 1.69680 ν 6 = 55.5 R12 =- 395.214 D12 = Variable R13 = (Aperture) D13 = 1.75 R14 = -55.195 D14 = 2.10 N 7 = 1.80518 ν 7 = 25.4 R15 = -25.214 D15 = 1.30 N 8 = 1.60311 ν 8 = 60.7 R16 = 38.462 D16 = Variable R17 = 78.946 D17 = 1.30 N 9 = 1.80518 ν 9 = 25.4 R18 = 26.654 D18 = 0.42 R19 = 29.350 D19 = 5.00 N10 = 1.58313 ν10 = 59.4 R20 = -44.797 Aspheric

[0030]

[Table 2]

R20: Aspherical coefficient A = 0 B = 4.54988 × 10 ^-6 C = 3.91367 × 10 ^-9 D = 1.11697 × 10 ^-10 E = -6.30557 × 10 ^-13 Numerical example 3 F = 28.8 to 77.38 FNO = 1: 3.5 to 4.5 2ω = 73.8 ° to 31.2 ° R 1 = 67.090 D 1 = 1.80 N 1 = 1.77250 ν 1 = 49.6 R 2 = 27.602 D 2 = 6.80 R 3 = -912.555 D 3 = 1.60 N 2 = 1.77250 ν 2 = 49.6 R 4 = 36.134 D 4 = 0.10 R 5 = 31.918 D 5 = 3.90 N 3 = 1.80518 ν 3 = 25.4 R 6 = 73.004 D 6 = Variable R 7 = 48.711 D 7 = 1.50 N 4 = 1.84666 ν 4 = 23.9 R 8 = 22.792 D 8 = 4.00 N 5 = 1.69680 ν 5 = 55.5 R 9 = -89.964 D 9 = 0.10 R10 = 31.729 D10 = 3.10 N 6 = 1.69680 ν 6 = 55.5 R11 = 248.913 D11 = Variable R12 = ( Aperture) D12 = 1.75 R13 = -51.342 D13 = 2.10 N 7 = 1.80518 ν 7 = 25.4 R14 = -23.117 D14 = 1.30 N 8 = 1.60311 ν 8 = 60.7 R15 = 38.796 D15 = Variable R16 = 76.641 D16 = 1.30 N 9 = 1.84666 ν 9 = 23.9 R17 = 29.240 D17 = 0.45 R18 = 32.398 D18 = 5.00 N10 = 1.58313 ν10 = 59.4 R19 = -45.125 Aspheric

[0032]

[Table 3]

R19: Aspherical surface coefficient A = 0 B = 4.7416 × 10 ^-6 C = 3.16871 × 10 ^-8 D = -1.19894 × 10 ^-10 E = 2.29582 × 10 ^-13

[0034]

According to the present invention, the total length of the lens is reduced and the lens barrel structure is reduced by specifying the refracting power of the four lens units and the moving conditions of each lens unit upon zooming as described above. It is possible to achieve a zoom lens which has a relatively wide angle of view and high optical performance over the entire zoom range with a high zoom ratio while being simple.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 4 is an aberration diagram at a zoom position at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 5 is an aberration diagram at a zoom position in a numerical example 1 of the present invention.

FIG. 6 is an aberration diagram at a telephoto end zoom position according to Numerical Embodiment 1 of the present invention;

FIG. 7 is an aberration diagram at a zoom position at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 8 is an aberration diagram at a zoom position in a numerical example 2 of the present invention.

FIG. 9 is an aberration diagram at a zoom position at a telephoto end according to Numerical Example 2 of the present invention;

FIG. 10 is an aberration diagram at a zoom position at a wide-angle end according to Numerical Embodiment 3 of the present invention.

FIG. 11 is an aberration diagram at a zoom position in a numerical example 3 of the present invention.

FIG. 12 is an aberration diagram at a zoom position at a telephoto end according to Numerical Example 3 of the present invention;

[Explanation of symbols]

 L1 First group L2 Second group L3 Third group L4 Fourth group SP Aperture d Spherical aberration at Fraunhofer d-line g Spherical aberration at Fraunhofer g-line S, C Unsatisfactory amount under sine condition S Sagittal section Image plane M Image plane in meridional section

Continuation of the front page (56) References JP-A-53-34539 (JP, A) JP-A-59-214009 (JP, A) JP-A-59-229517 (JP, A) JP-A-60-87312 (JP, A) JP-A-61-231517 (JP, A) JP-A-63-241511 (JP, A) JP-A-2-136812 (JP, A) JP-A-2-201310 (JP, A) 2-296208 (JP, A) JP-A-57-163213 (JP, A) JP-A-58-95315 (JP, A) JP-A-61-62013 (JP, A) JP-A-61-279817 (JP, A) A) JP-A-62-63909 (JP, A) JP-A-1-193709 (JP, A) JP-A-4-235514 (JP, A) JP-A-4-235515 (JP, A) JP-A-5 -19170 (JP, A) JP-A-5-27175 (JP, A) JP-A-5-134184 (JP, A) JP-A-5-173071 (JP, A) JP-A-6-11650 (JP, A) JP-A-4-163415 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/0 2-21/04 G02B 25/00-25/04

Claims (5)

(57) [Claims] 1. A first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power. The zooming from the wide-angle end to the telephoto end reduces the air gap between the first and second units,
The air gap between the second and third groups increases, and the air gap between the third and fourth groups decreases so that at least the first,
Second, a row earthenware pots zoom lens by moving the fourth group,
The third group has two independent lenses consisting of a positive lens and a negative lens .
Along with a lens or one laminated lens,
The fourth group is composed of two independent lenses consisting of a negative lens and a positive lens .
Lens or is composed of one cemented lens, the focal length of the third group second group each F2, F3, the focal length of the fourth group F4, the focal length of the entire system at the telephoto end FT
0.5 <F4 / FT <2. A zoom lens characterized by satisfying F2 <| F3 | 0.5 <F4 / FT <2. 2. The second group includes, in order from the object side, a meniscus-shaped negative lens having a strong negative refraction surface facing the image surface side, a positive lens, and a positive lens having a convex surface facing the object side. The zoom lens according to claim 1, wherein: 3. The first group includes, in order from the object side, a negative meniscus lens having a concave surface facing the image surface side, a negative lens, and a positive meniscus lens having a convex surface facing the object side. The zoom lens according to claim 1, wherein: 4. The zoom lens according to claim 1, wherein the third unit is fixed during zooming. 5. The zoom lens according to claim 1, wherein the zooming from the wide-angle end to the telephoto end is performed by moving the second and fourth units together toward the object side.