JP3018742B2 - 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 photographic camera for 35 mm film, a video camera of an electronic recording system, an SV camera, and the like. It has a lens group,
By appropriately setting the lens configurations of these four lens groups, the overall lens system can be downsized.
The present invention relates to a negative lead type zoom lens having an F number of 5.5 to 8 and a shooting angle of view of about 75 ° to 25 °.

[0002]

2. Description of the Related Art Conventionally, a so-called negative lead type zoom lens, which is preceded by a lens group having a negative refractive power, is relatively easy to widen the angle of view. Is often used. For example, JP-B-49-23912 and JP-A-57-16321.
In the publication No. 3 and the like, four lens groups of a first group having a negative refractive power, a second group having a positive refractive power, a third group having a negative refractive power, and a fourth group having a positive refractive power are arranged in this order from the object side. When zooming from the wide-angle end to the telephoto end, the first lens unit is moved to the image surface side,
A zoom lens has been proposed in which the group and the fourth group are moved to the object side, and the third group is fixed or moved.

The negative lead type zoom lens, which is preceded by such a lens group having a negative refractive power, has features such as a relatively wide angle of view and a short close-up distance. On the other hand, it has disadvantages such as an increase in the aperture diameter and difficulty in increasing the zoom ratio.

[0004] A zoom lens in which these disadvantages are improved and the entire lens system is miniaturized and a high zoom ratio is achieved is disclosed in, for example, JP-A-55-14403, JP-A-57-11315, and JP-A-57-11315. No. 58-4113, and Japanese Patent Application Laid-Open
No. 95315.

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

[0006]

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 80 mm.
A zoom lens having a wide angle of view of about mm is used as a standard zoom lens.

[0007] More recently, the focal length is 28 mm to 105 m.
There is a demand for a standard zoom lens having a high zoom ratio by expanding the zoom range to the telephoto side with a focal length of about 28 mm to 135 mm.

However, in general, when the photographing angle of view is at this level and the zoom ratio is high, the entire length of the lens becomes long, and in zooming, a complicated zoom movement is required. As a result, the lens barrel has a multiplex configuration. There is a problem that the lens barrel becomes larger and more complicated.

According to the present invention, the zoom lens is composed of four lens groups as a whole, and by appropriately setting the refractive power of each lens group and the moving conditions of each lens group accompanying zooming,
The objective is to provide a zoom lens that has a relatively wide angle of view that reduces the overall length of the lens, prevents the lens barrel from becoming large and complicated, and has high optical performance over the entire zoom range with a high zoom ratio. I do.

[0010]

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. The zoom lens system has four lens groups, each of which has a refractive power of? 4. When zooming from the wide-angle end to the telephoto end, the first group is moved while having a convex locus on the image side. The second group is moved so that the distance between the second group and the first group is reduced, and the distance between the third group and the third group is reduced. A zoom lens that is moved so as to be larger, and moves the fourth group so as to reduce the distance between the fourth group and the third group,
The first group includes a meniscus-shaped negative lens having a convex surface facing the object side closest to the object side, a meniscus-shaped positive lens having a convex surface facing the object side closest to the image plane, and an object side of the positive lens. A second lens having a negative lens,
When the combined imaging magnification of the third and fourth units is βT, the focal length of the i-th unit is fi, and the focal length of the entire system at the telephoto end is fT, 2.8 <−βT <3.8Ｔ ‥ (1) 0.17 <f2 / fT <0.27 ‥‥‥ (2)

[0011]

FIG. 1 is an explanatory diagram of a paraxial refractive power arrangement of a zoom lens according to the present invention. In the figure, (A) shows the wide-angle end, (B) shows the middle, and (C) shows the telephoto end. 2 to 7 are lens cross-sectional views at the wide-angle end of zoom lenses according to Numerical Examples 1 to 6 of the present invention.

In the figure, L1 is a first lens unit having a negative refractive power, L2 is a second lens unit having a positive refractive power, L3 is a third lens unit having a negative refractive power, and L4 is a negative lens.
Denotes a fourth group having a positive refractive power. SP is an aperture, and F is an image plane. Arrows indicate the trajectories of the movements of the respective lens units when zooming from the wide-angle end to the telephoto end.

In this embodiment, as shown in FIG. 1, when changing the magnification from the wide-angle end to the telephoto end, the first unit L1 is moved while having a convex locus on the image plane side, and the image accompanying the magnification is changed. The surface fluctuation is corrected, and the second lens unit L2 is moved so that the distance between the second lens unit and the first lens unit is reduced, and the third lens unit L3 is moved such that the distance between the third lens unit and the second lens unit is increased. Then, the fourth lens unit L4 is moved so that the distance between the fourth lens unit and the third lens unit is reduced. or,
Focusing is performed by moving the first lens unit.

In this embodiment, the refracting power of each lens unit and the moving condition of each lens unit during zooming are set as described above, and the imaging magnification, the refracting power of each lens unit, and the like are determined by the conditional expression (1).
By setting so as to satisfy (2), a zoom lens having a wide angle of view and high optical performance over the entire zoom range with a high zoom ratio can be obtained while shortening the overall length of the lens.

Next, the technical meaning of the conditional expressions (1) and (2) will be described.

Conditional expression (1) appropriately sets the combined imaging magnification βT of the second, third, and fourth lens groups at the telephoto end, and favorably reduces off-axis aberrations while mainly shortening the overall lens length. It is for correcting to.

When the value exceeds the lower limit of conditional expression (1), the imaging magnification β
If T is too small, the outer diameter of the lens of the first group increases and the overall length of the lens increases. If the imaging magnification βT is too large beyond the upper limit, off-axis aberrations such as distortion and astigmatism increase, and it becomes difficult to correct these aberrations in a well-balanced manner.

Conditional expression (2) is for appropriately setting the positive refracting power of the second lens unit and for mainly correcting spherical aberration favorably.

If the positive refractive power of the second lens unit becomes too strong beyond the lower limit of conditional expression (2), it becomes difficult to satisfactorily correct spherical aberration generated in the second lens unit. If the positive refracting power of the second lens unit becomes too weak beyond the upper limit, the second lens unit which accompanies zooming will be reduced.
This is not good because the amount of movement of the group increases and the overall length of the lens increases.

In the present invention, in terms of aberration correction, it is more preferable to set the lower limit and the upper limit of conditional expressions (1) and (2) as follows.

2.8 <-βT <3.8 0.17 <f2 / fT <0.27 The zoom lens aimed at by the present invention can be achieved by satisfying the above-mentioned conditions. In order to perform good aberration correction over the magnification range, the above-mentioned conditional expression (1)
(2) 1 <| f1 / f2 | <2 (3) 1 <| f4 / f3 | <2.5 (2.5) 4) It is better to satisfy the following conditions.

Conditional expression (3) sets the ratio of the focal lengths of the first and second lens groups appropriately, shortens the overall length of the lens mainly at the telephoto end, and improves the spherical aberration on the wide-angle side. It is for correcting to.

If the negative refractive power of the first lens unit becomes too strong beyond the lower limit of conditional expression (3), it becomes difficult to make the entire lens system a telephoto type on the telephoto side, and the overall length of the lens becomes longer. . On the other hand, if the positive refractive power of the second lens unit becomes too high beyond the upper limit, the axial luminous flux incident on the third lens unit on the wide-angle side converges too much, so that the negative refractive power of the third lens unit must be increased. As a result, spherical aberration increases, which is not good.

Conditional expression (4) is for appropriately setting the ratio between the focal lengths of the fourth and third lens units, and for correcting various aberrations in a well-balanced manner while achieving a high zoom ratio.

If the positive refractive power of the fourth lens unit becomes too strong beyond the lower limit value of conditional expression (4), it becomes difficult to make the entire lens system into a telephoto type on the telephoto side, and the overall length of the lens becomes longer. . If the positive refractive power of the fourth group is too weak beyond the upper limit, the zooming burden of the fourth group will be too small,
As a result, the burden on the other lens groups increases and the amount of movement accompanying zooming increases, which is not good.

In the present invention, in terms of aberration correction, it is more preferable to set the lower limit and the upper limit of conditional expressions (3) and (4) as follows.

1.2 <| f1 / f2 | <1.6 1.4 <| f4 / f3 | <2.4 In addition, in the present invention, while correcting distortion mainly on the wide-angle side favorably, In order to properly correct various aberrations such as spherical aberration and coma when the close-up shooting distance is reduced and to reduce the lens outer diameter, it is preferable to set the lens configuration of the first group as follows.

That is, the first group includes a meniscus-shaped negative lens having a convex surface facing the object side closest to the object side, a meniscus-shaped positive lens having a convex surface facing the object side closest to the image plane side, and It is preferable to provide a negative lens on the object side, or to apply an aspheric surface to at least one lens surface of the first group.

Further, in the present invention, in particular, in order to reduce fluctuations of various aberrations over the entire zoom range and obtain high optical performance, the second lens unit having a positive refractive power is sequentially formed from the object side with a cemented lens of a negative lens and a positive lens. The third lens unit having at least one positive lens, the third lens unit having a negative refractive power includes a cemented lens of a positive lens and a negative lens, and the fourth lens unit having a positive refractive power includes a single or laminated positive lens. It is good to have a lens, a positive lens, and a negative lens.

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 space 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, and R represents paraxial curvature radii A, B, C, D, and E each representing an aspherical coefficient. And when

[0032]

(Equation 1) It is represented by the following equation.

Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples. Numerical example 1 f = 29.0 to 130.5 fno = 1: 5.8 to 8.32 ω = 73.4 ° to 18.8 ° r 1 = 77.49 d 1 = 2.20 n 1 = 1.69680 ν 1 = 55.5 r 2 = 28.52 d 2 = 6.50 r 3 = -2151.09 d 3 = 1.80 n 2 = 1.58313 ν 2 = 59.4 r 4 = 28.76 d 4 = 0.60 r 5 = 27.62 d 5 = 3.10 n 3 = 1.84666 ν 3 = 23.9 r 6 = 42.55 d 6 = Variable r 7 = 33.73 d 7 = 1.00 n 4 = 1.84666 ν 4 = 23.9 r 8 = 20.36 d 8 = 4.20 n 5 = 1.48749 ν 5 = 70.2 r 9 = -174.77 d 9 = 0.12 r10 = 38.60 d 10 = 2.20 n 6 = 1.48749 ν 6 = 70.2 r11 = 624.67 d 11 = 0.12 r12 = 39.89 d 12 = 2.40 n 7 = 1.51633 ν 7 = 64.2 r13 = -369.18 d 13 = Variable r14 = (Aperture) d 14 = 1.20 r15 = 611.38 d 15 = 4.87 n 8 = 1.78472 ν 8 = 25.7 r16 = -14.63 d 16 = 1.00 n 9 = 1.78590 ν 9 = 44.2 r17 = 45.22 d 17 = 1.30 r18 = -39.50 d 18 = 1.00 n10 = 1.83400 ν10 = 37.2 r19 = -3000.00 d 19 = Variable r20 = 579.83 d 20 = 5.60 n11 = 1.60311 ν11 = 60.7 r21 = -15.92 d 21 = 1.10 n12 = 1.84666 ν12 = 23.9 r22 = -23.27 d 22 = 0.12 r23 = 93.37 d 23 = 2.90 n13 = 1.51633 ν13 = 64.2 r24 = -58.10 d 24 = 8.62 r25 = -23.15 d 25 = 1.20 n14 = 1.69680 ν14 = 55.5 r26 = -74 .56

[0034]

[Table 1] r4 is an aspherical surface, and the aspherical surface coefficient is as follows. Aspheric coefficient A = 0 B = -2.413 × 10 ^-6 C = -1.458 × 10 ^-9 D = -7.468 × 10 ^-12 E = -9.831 × 10 ^-15 Numerical example 2 f = 29.0 〜 130.5 fno = 1 : 5.8〜8.32 ω = 73.4 ° 〜18.8 ° r 1 = 93.30 d 1 = 2.20 n 1 = 1.77250 ν 1 = 49.6 r 2 = 32.51 d 2 = 7.20 r 3 = -415.46 d 3 = 3.00 n 2 = 1.69895 ν 2 = 30.1 r 4 = -71.57 d 4 = 0.12 r 5 = -102.43 d 5 = 1.80 n 3 = 1.58313 ν 3 = 59.4 r 6 = 28.85 d 6 = 0.60 r 7 = 25.81 d 7 = 3.10 n 4 = 1.69895 ν 4 = 30.1 r 8 = 39.21 d 8 = Variable r 9 = 30.86 d 9 = 1.00 n 5 = 1.84666 ν 5 = 23.9 r10 = 19.72 d 10 = 4.20 n 6 = 1.48749 ν 6 = 70.2 r11 = -577.48 d 11 = 0.12 r12 = 56.25 d 12 = 2.20 n 7 = 1.48749 ν 7 = 70.2 r13 = 425.77 d 13 = 0.12 r14 = 37.09 d 14 = 2.40 n 8 = 1.51633 ν 8 = 64.2 r15 = -229.81 d 15 = Variable r16 = (Aperture) d 16 = 1.20 r17 = -137.34 d 17 = 5.15 n 9 = 1.78472 ν 9 = 25.7 r18 = -12.93 d 18 = 1.00 n10 = 1.78590 ν10 = 44.2 r19 = 89.91 d 19 = 1.30 r20 = -44.89 d 20 = 1.00 n11 = 1.83400 ν11 = 37.2 r21 = 533.24 d 21 = Variable r22 = 257.38 d 22 = 5.60 n12 = 1.60311 ν12 = 60.7 r23 = -15.84 d 23 = 1.10 n13 = 1.84666 13 = 23.9 r24 = -24.19 d 24 = 0.12 r25 = 69.40 d 25 = 2.90 n14 = 1.51633 ν14 = 64.2 r26 = -63.81 d 26 = 11.02 r27 = -24.96 d 27 = 1.20 n15 = 1.69680 ν15 = 55.5 r28 = -139.55

[0035]

[Table 2] Numerical example 3 f = 29.0 to 101.0 fno = 1: 5.8 to 7.2 2 ω = 73.4 ° to 24.2 ° r 1 = 86.63 d 1 = 2,20 n 1 = 1.69680 ν 1 = 55.5 r 2 = 21.10 d 2 = 5.30 r 3 = 299.93 d 3 = 1.80 n 2 = 1.58313 ν 2 = 59.4 r 4 = 28.58 d 4 = 0.60 r 5 = 27.59 d 5 = 2,90 n 3 = 1.84666 ν 3 = 23.9 r 6 = 48.12 d 6 = Variable r 7 = 32.76 d 7 = 1.00 n 4 = 1.84666 ν 4 = 23.9 r 8 = 18.97 d 8 = 3.80 n 5 = 1.48749 ν 5 = 70.2 r 9 = -231.21 d 9 = 0.12 r10 = 34.20 d 10 = 2.20 n 6 = 1.48749 ν 6 = 70.2 r11 = 9218.27 d 11 = 0.12 r12 = 31.37 d 12 = 2,40 n 7 = 1.51633 ν 7 = 64.2 r13 = -585.26 d 13 = Variable r14 = (Aperture) d 14 = 1.20 r15 =- 91.19 d 15 = 2.30 n 8 = 1.78472 ν 8 = 25.7 r16 = -15.00 d 16 = 1.00 n 9 = 1.78590 ν 9 = 44.2 r17 = 35.99 d 17 = variable r18 = 206.64 d 18 = 4.20 n10 = 1.60311 ν10 = 60.7 r19 = -14.83 d 19 = 1.10 n11 = 1.84666 ν11 = 23.9 r20 = -20.73 d 20 = 0.12 r21 = 55.96 d 21 = 2.90 n12 = 1.51633 ν12 = 64.2 r22 = -119.28 d 22 = 4.91 r23 = -21.93 d 23 = 1.20 n13 = 1.69680 ν13 = 55.5 r24 = -1917.92

[0036]

[Table 3] r4 is an aspherical surface, and the aspherical surface coefficient is as follows. Aspheric coefficient A = 0 B = -6.316 × 10 ^-6 C = -8.647 × 10 ^-9 D = 1.608 × 10 ^-11 E = -8.052 × 10 ^-14 Numerical example 4 f = 29.0 to 101.0 fno = 1: 5.8 ~ 7.2 2ω = 73.4 ° ~ 24.2 ° r 1 = 92.46 d 1 = 2.20 n 1 = 1.69680 ν 1 = 55.5 r 2 = 23.50 d 2 = 4.80 r 3 = 160.41 d 3 = 1.80 n 2 = 1.58313 ν 2 = 59.4 r 4 = 28.15 d 4 = 0.60 r 5 = 25.54 d 5 = 2.50 n 3 = 1.84666 ν 3 = 23.9 r 6 = 37.98 d 6 = variable r 7 = 28.93 d 7 = 1.00 n 4 = 1.84666 ν 4 = 23.9 r 8 = 17.52 d 8 = 4.50 n 5 = 1.48749 ν 5 = 70.2 r 9 = -48.08 d 9 = 0.12 r10 = 22.18 d 10 = 2.50 n 6 = 1.60311 ν 6 = 60.7 r11 = 128.30 d 11 = Variable r12 = (Aperture) d 12 = 1.20 r13 = -169.24 d 13 = 2.30 n 7 = 1.78472 ν 7 = 25.7 r14 = -13.89 d 14 = 1.00 n 8 = 1.78590 ν 8 = 44.2 r15 = 45.99 d 15 = 1.30 r16 = -57.61 d 16 = 1.00 n 9 = 1.83400 ν 9 = 37.2 r17 = -1156.32 d 17 = Variable r18 = -404.18 d 18 = 4.20 n10 = 1.60311 ν10 = 60.7 r19 = -13.99 d 19 = 1.10 n11 = 1.84666 ν11 = 23.9 r20 = -19.70 d 20 = 0.12 r21 = 61.94 d 21 = 2.90 n12 = 1.51633 ν12 = 64.2 r22 = -47.55 d 22 = 4.52 r23 = -20.25 d 23 = 1.20 n13 = 1.69680 ν1 3 = 55.5 r24 = -150.49

[0037]

[Table 4] r4 is an aspherical surface, and the aspherical surface coefficient is as follows. Aspheric coefficient A = 0 B = -4.262 × 10 ^-6 C = -4.619 × 10 ^-9 D = 1.543 × 10 ^-11 E = -4.461 × 10 ^-14 Numerical example 5 f = 29.0 to 101.0 fno = 1: 5.8 ~ 7.2 2 ω = 73.4 ° ~ 24.2 ° r 1 = 93.37 d 1 = 2.20 n 1 = 1.69680 ν 1 = 55.5 r 2 = 23.31 d 2 = 5.20 r 3 = 1102.26 d 3 = 1.80 n 2 = 1.58313 ν 2 = 59.4 r 4 = 26.73 d 4 = 0.60 r 5 = 25.27 d 5 = 2.90 n 3 = 1.84666 ν 3 = 23.9 r 6 = 41.21 d 6 = Variable r 7 = 31.05 d 7 = 1.00 n 4 = 1.84666 ν 4 = 23.9 r 8 = 17.86 d 8 = 3.80 n 5 = 1.48749 ν 5 = 70.2 r 9 = -192.10 d 9 = 0.12 r10 = 34.07 d 10 = 2.20 n 6 = 1.48749 ν 6 = 70.2 r11 = -295.39 d 11 = 0.12 r12 = 29.20 d 12 = 2.40 n 7 = 1.51633 ν 7 = 64.2 r13 = -1090.62 d 13 = Variable r14 = (Aperture) d 14 = 1.20 r15 = -320.25 d 15 = 2.30 n 8 = 1.78472 ν 8 = 25.7 r16 = -16.96 d 16 = 1.00 n 9 = 1.78590 ν 9 = 44.2 r17 = 42.34 d 17 = 1.30 r18 = -67.71 d 18 = 1.00 n10 = 1.83400 ν10 = 37.2 r19 = -3000.00 d 19 = Variable r20 = -57.66 d 20 = 3.00 n11 = 1.48749 ν11 = 70.2 r21 = -17.37 d 21 = 0.12 r22 = 52.47 d 22 = 2.90 n12 = 1.48749 ν12 = 70.2 r23 = -48.57 d 23 = 4.25 r24 = -17.03 d 24 = 1.20 n13 = 1.83400 ν13 = 37.2 r25 = -44.35

[0038]

[Table 5] r4 is an aspherical surface, and the aspherical surface coefficient is as follows. Aspheric coefficient A = 0 B = -4.019 × 10 ^-6 C = -1.462 × 10 ^-9 D = -2.416 × 10 ^-12 E = 2.604 × 10 ^-14 Numerical example 6 f = 29.0 to 101.0 fno = 1: 5.8 ~ 7.2 2 ω = 73.4 ° ~ 24.2 ° r 1 = 74.75 d 1 = 2.20 n 1 = 1.69680 ν 1 = 55.5 r 2 = 20.52 d 2 = 5.50 r 3 = 150.24 d 3 = 1.80 n 2 = 1.58313 ν 2 = 59.4 r 4 = 30.91 d 4 = 0.60 r 5 = 27.22 d 5 = 2.90 n 3 = 1.84666 ν 3 = 23.9 r 6 = 42.40 d 6 = Variable r 7 = 28.02 d 7 = 1.00 n 4 = 1.84666 ν 4 = 23.9 r 8 = 17.30 d 8 = 4.30 n 5 = 1.48749 ν 5 = 70.2 r 9 = -68.11 d 9 = 0.12 r10 = 23.48 d 10 = 2.50 n 6 = 1.60311 ν 6 = 60.7 r11 = 243.67 d 11 = Variable r12 = (Aperture ) d 12 = 1.20 r13 = -72.31 d 13 = 2.30 n 7 = 1.78472 ν 7 = 25.7 r14 = -13.74 d 14 = 1.00 n 8 = 1.78590 ν 8 = 44.2 r15 = 37.27 d 15 = Variable r16 = 103.26 d 16 = 4.70 n 9 = 1.60311 ν 9 = 60.7 r17 = -14.29 d 17 = 1.10 n10 = 1.84666 ν10 = 23.9 r18 = -20.51 d 18 = 0.12 r19 = 59.91 d 19 = 2.90 n11 = 1.51633 ν11 = 64.2 r20 = -68.46 d 20 = 4.26 r21 = -21.45 d 21 = 1.20 n12 = 1.69680 ν12 = 55.5 r22 = 244.99

[0039]

[Table 6] r4 is an aspherical surface, and the aspherical surface coefficient is as follows. Aspheric coefficient A = 0 B = -5.366 × 10 ^-6 C = -9.979 × 10 ^-9 D = 1.329 × 10 ^-11 E = -8.142 × 10 ^-14

[0040]

[Table 7]

[0041]

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 an explanatory diagram of a paraxial refractive power arrangement of a zoom lens according to the present invention.

FIG. 2 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 1 of the present invention.

FIG. 3 is a sectional view of a lens at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 4 is a sectional view of a lens at a wide-angle end according to a third numerical embodiment of the present invention.

FIG. 5 is a sectional view of a lens at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 6 is a sectional view of a lens at a wide angle end according to Numerical Example 5 of the present invention.

FIG. 7 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 6 of the present invention.

FIG. 8 is an aberration diagram at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 9 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 10 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

FIG. 11 is an aberration diagram at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 12 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 13 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

FIG. 14 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 15 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 16 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 17 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 18 is an intermediate aberration diagram of the numerical example 4 of the present invention.

FIG. 19 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

FIG. 20 is an aberration diagram at a wide angle end according to Numerical Example 5 of the present invention.

FIG. 21 is an intermediate aberration diagram of the numerical example 5 of the present invention.

FIG. 22 is an aberration diagram at a telephoto end in Numerical Example 5 of the present invention.

FIG. 23 is an aberration diagram at a wide angle end according to Numerical Example 6 of the present invention.

FIG. 24 is an intermediate aberration diagram of the numerical example 6 of the present invention.

FIG. 25 is an aberration diagram at a telephoto end in Numerical Example 6 of the present invention.

[Explanation of symbols]

 L1 First lens unit L2 Second lens unit L3 Third lens unit L4 Fourth lens unit F Image plane SP stop ΔS Sagittal image plane ΔM Meridional image plane dd line gg line S. C sine condition

Continuation of front page (56) References JP-A-53-34539 (JP, A) JP-A-54-151027 (JP, A) JP-A-59-214009 (JP, A) JP-A-59-229517 (JP) JP-A-60-87312 (JP, A) JP-A-61-231517 (JP, A) JP-A-63-241511 (JP, A) JP-A-1-216310 (JP, A) JP-A-2-136812 (JP, A) JP-A-2-201310 (JP, A) JP-A-2-296208 (JP, A) JP-A-4-235514 (JP, A) JP-A-4-235515 (JP, A A) JP-A-5-19170 (JP, A) JP-A-5-134184 (JP, A) JP-A-5-173071 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (2)

(57) [Claims] A first group having a negative refractive power , in order from the object side;
It has four lens groups, a second group having a positive refractive power, a third group having a negative refractive power, and a fourth group having a positive refractive power. The first lens group is moved while having a convex locus on the image plane side to correct the image plane fluctuation due to zooming,
The second group is moved so that the distance between the second group and the first group is reduced, and the third group is moved so that the distance between the third group and the second group is increased. in the fourth group and the fourth group zoom lens Before moving and the interval between the third group becomes small
The first lens group has a convex surface facing the object side closest to the object side.
With a meniscus-shaped negative lens,
Meniscus-shaped positive lens with a convex surface, and the positive lens
A negative lens on the object side of the zoom lens, the combined imaging magnification of the second, third, and fourth units at the telephoto end is βT, the focal length of the i-th unit is fi, and the focal length of the entire system at the telephoto end is To f
A zoom lens characterized by satisfying the following condition : 2.8 <−βT <3.8 0.17 <f2 / fT <0.27 2. The zoom lens according to claim 1, wherein the following condition is satisfied: 1 <| f1 / f2 | <21.ltoreq. | F4 / f3 | <2.5.