JPH05323196A - Rear focus type zoom lens - Google Patents

Abstract

PURPOSE:To obtain the rear focus type zoom lens with a X8-17 power variation ratio and an about 1.8 F number by providing five lens groups on the whole, putting the lens system in focus by a lens group behind a power variation system, and reducing the size of the whole lens system. CONSTITUTION:The zoom lens has the 1st group L1 with negative refracting power, the 2nd group L2 with positive refracting power, the 3rd group L3 with negative refracting power, the 4th group L4 with positive refracting power, and the 5th group L4 with positive refracting power in order from the object side; and the 3rd group L3 is moved toward the image plane to vary the power from the wide-angle end to the telephoto end, variation in the image plane due to the power variation is corrected by moving the 2nd group L2 and 5th group L5, and the lens system is put in focus by moving the 5th group L5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear focus type zoom lens, and more particularly to a photographic camera, a video camera,
Further, the present invention relates to a rear focus type zoom lens suitable for a zoom lens having a large zoom ratio of about 8 to 17 and an F number of about 1.8 at the wide-angle end, which is used for a broadcasting camera or the like and a high zoom ratio.

[0002]

2. Description of the Related Art Hitherto, various zoom lenses for photographic cameras, video cameras and the like have been proposed which employ a so-called rear focus type in which focusing is performed by moving a lens unit other than the first lens unit on the object side. ing.

In particular, in recent years, in a rear focus type zoom lens used in a consumer video camera, due to technical progress of an electrical processing system, image plane correction and focusing accompanying zooming are performed for each zoom position and object distance. The movement information of the lens group to be performed is stored in a memory, and the movement information of the memory is used to move the lens group by an electric driving means such as a motor.

Generally, in a rear focus type zoom lens, the effective diameter of the first lens group is smaller than that of a zoom lens in which the first lens group is moved to perform focusing, which facilitates downsizing of the entire lens system and close-up photography. Especially, it is easy to perform very close-up photography, and since the relatively small and lightweight lens group is moved, the driving force of the lens group is small, and quick focusing is possible.

As such a rear focus type zoom lens, for example, in Japanese Patent Laid-Open No. 63-44614, a first lens group having a positive refractive power, a second lens group having a negative refractive power for zooming, and a zoom lens are arranged in order from the object side. In a so-called 4-group zoom lens composed of four lens groups, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, for correcting the image plane variation due to doubling, the third lens group is moved. Focus is on. However, this zoom lens tends to increase the total lens length because it is necessary to secure a moving space for the third lens group.

In Japanese Patent Laid-Open No. 58-136012, the variable power portion is composed of three or more lens groups, and some of these lens groups are moved for focusing.

In Japanese Patent Laid-Open No. 63-247316, a first group having a positive refractive power, a second group having a negative refractive power, are arranged in this order from the object side.
It has four lens groups, a third lens group having a positive refractive power and a fourth lens group having a positive refractive power. The second lens group is moved to perform zooming, and the fourth lens group is moved to perform zooming. Image plane variation and focusing are performed.

In Japanese Patent Application Laid-Open No. 58-160913, a first group having a positive refractive power, a second group having a negative refractive power, are arranged in this order from the object side.
The third lens unit has a positive refracting power and the fourth lens unit has a positive refracting power, and there are four lens units. The first lens unit and the second lens unit are moved to perform zooming, and the image plane changes due to zooming. Is performed by moving the fourth group. Then, one or more of these lens groups are moved to perform focusing.

In Japanese Patent Laid-Open No. 58-129404 and Japanese Patent Laid-Open No. 61-258217, the first group having a positive refractive power, the second group having a negative refractive power, and the third group having a positive refractive power are arranged in this order from the object side.
In a five-group zoom lens consisting of five lens groups, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power, a fifth lens group or a plurality of lens groups including the fifth lens group is moved. Focus. In JP-A-60-6914, in the same five-group zoom lens as described above, a zoom lens having a property that the position of the focus lens group on the optical axis with respect to a specific finite distance object is constant regardless of zooming. Is proposed.

[0010]

Generally, when a rear focus system is adopted in a zoom lens, the entire lens system is downsized as described above, quick focusing is possible, and further close-up photography is facilitated. ..

On the other hand, however, the aberration variation during focusing becomes large, and it becomes very difficult to obtain high optical performance while miniaturizing the entire lens system over the entire object distance from an object at infinity to a near object. Dots come up.

Particularly, in a zoom lens having a large aperture ratio and a high zoom ratio, it becomes very difficult to obtain high optical performance over the entire zoom range and over the entire object distance.

The present invention has five lens groups having a predetermined refracting power as a whole, and adopts a rear focus system, and when a large aperture ratio and a high zoom ratio are intended, the entire lens system is enlarged. The rear focus type zoom lens with a simple structure that has good optical performance over the entire zoom range from the wide-angle end to the telephoto end, and over the entire object distance from the infinity object to the short-distance object while preventing For the purpose of providing.

[0014]

A rear focus type zoom lens according to the present invention comprises a first group having a negative refractive power, a second group having a positive refractive power, and a third group having a negative refractive power in order from the object side. , A fourth lens unit having a positive refractive power, and a fifth lens unit having a positive refractive power, and moving the third lens unit linearly toward the image plane to move from the wide-angle end to the telephoto end. It is characterized in that the zooming is performed, the image plane variation due to the zooming is corrected by non-linearly moving the second group and the fifth group, and the fifth group is moved for focusing.

[0015]

1 is a schematic view of an embodiment showing the paraxial refractive power arrangement of a rear focus type zoom lens according to the present invention.

2 to 7 are lens cross-sectional views of Numerical Embodiments 1 to 6 described later of the present invention, and FIGS. 8 to 10 are various values at the wide-angle end, the middle, and the telephoto end of Numerical Embodiment 1 described later of the present invention. It is an aberration diagram. 11 to 13 are various aberration diagrams at the wide-angle end, the middle, and the telephoto end of Numerical Embodiment 2 which will be described later. 14 to 1
6 is a diagram of various aberrations at the wide-angle end, the middle, and the telephoto end of Numerical Example 3 described later of the present invention. 17 to 19 are various aberration diagrams at the wide-angle end, the middle, and the telephoto end of Numerical Example 4 described later of the present invention,
20 to 22 are various aberration diagrams at the wide-angle end, the middle, and the telephoto end of Numerical Example 5 described later of the present invention, and FIGS. 23 to 25 are the wide-angle end, the middle, and telephoto of Numerical Example 6 described later of the present invention. FIG. 7 is a diagram of various aberrations at the edge.

In the figure, 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, and L4.
Is a fourth group having a positive refractive power, and L5 is a fifth group having a positive refractive power. SP is an aperture stop, which is arranged in front of the fourth lens unit L4. G is a glass block such as a face plate.

Upon zooming from the wide-angle end to the telephoto end, as shown by the arrow, the second lens unit is directed toward the object side as shown by the curve 2a, the third lens unit is directed toward the image plane side, and the fifth lens unit is directed toward the object side. It is moved so as to have a locus that moves to the object side as going from the wide-angle end to the telephoto side from curve 5a).

In this embodiment, zooming is mainly performed in the third lens unit,
The image plane variation due to zooming is corrected by moving the second and fifth groups non-linearly along the optical axis.

In particular, the first lens unit having a negative refractive power is arranged apart from the second lens unit having a positive refractive power at the wide-angle end, and the second lens unit is moved closer to the telephoto end to change the magnification to the second lens unit. It has a function to facilitate high zooming. In addition, the second group is moved non-linearly so as to be convex or close to a convex toward the object side as it goes from the wide-angle end on the optical axis to the telephoto end as shown by the curve 2a in accordance with zooming. The amount of movement of the fifth lens unit during correction of surface variation is reduced.

With such a structure, the variation of aberration caused by zooming when achieving high zooming is reduced, and high optical performance is obtained over the entire zooming range.

Further, a rear focus type is adopted in which the fifth lens unit is moved on the optical axis for focusing. The solid curve 5a and the dotted curve 5b of the fifth group shown in the same figure show the image plane variation during zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and a near object, respectively. The movement locus for correction is shown. In this embodiment, in order to simplify the mechanism, the first and fourth groups are fixed during zooming and focusing.

In this embodiment, the second group and the fifth group are moved to correct the image plane variation due to the magnification change, and the fifth group is moved to perform the focusing. In particular, as shown by the curves 5a and 5b in the figure, the lens is moved so as to have a convex locus toward the object side during zooming from the wide-angle end to the telephoto end. As a result, the space between the fourth lens unit and the fifth lens unit is effectively used, and the total lens length is effectively shortened.

In the present embodiment, for example, when focusing from an object at infinity to a near object at the telephoto end, the fifth group is moved forward as indicated by a straight line 5c in the figure.

In the present embodiment, in the zoom lens composed of the five lens groups as described above, the rear focus method is adopted in which the fifth group is moved on the optical axis to correct the image plane variation due to the magnification change and to perform focusing. As a result, a zoom lens having high optical performance with little aberration variation over the entire object distance from an object at infinity to a near object is obtained.

By arranging the aperture stop SP immediately in front of the fourth lens unit, variation in aberrations caused by the movable lens unit is reduced, and by shortening the distance between the lens units in front of the aperture stop, the front lens diameter is reduced. Is easily achieved.

The rear focus type zoom lens, which is the object of the present invention, can be achieved by satisfying the above-mentioned conditions. However, the variation of aberration caused by zooming when further zooming is attempted. In order to obtain high optical performance over the entire zoom range, it is preferable to satisfy the following conditions.

(B) Upon zooming from the wide-angle end to the telephoto end, the second lens unit moves to the object side, and the moving amount at this time is M
2. M3 is the amount of movement of the third lens unit during zooming from the wide-angle end to the telephoto end, fw is the focal length of the entire system at the wide-angle end, and Z is the zoom ratio, and the focal length of the entire system is

[0029]

[Outside 2] When Δ × 2 and Δ × 3 respectively

[0030]

[Equation 2] To satisfy the condition.

When the upper limit of conditional expression (1) is exceeded, the air gap between the first group and the second group is expanded in order to prevent mechanical interference between the first group and the second group during zooming. This is not preferable because the lens diameter of the first lens group increases and the total lens length also increases.

If the value goes below the lower limit, the amount of movement of the fifth lens unit for correcting the image plane during zooming increases, and the total length of the lens increases, and at the same time, the driving means for the fifth lens unit becomes difficult. So not good.

(B) When the focal length of the i-th group is fi 0.08 <| f2 / f1 | <0.75 (2) 0.8 <| f3 / fw | <2.0 (3) To satisfy the following condition.

Conditional expression (2) relates to the ratio of the refracting power of the second lens group to the refracting power of the first lens group, and is mainly for shortening the total lens length while favorably correcting the image plane curvature. ..

If the negative refractive power of the first lens group becomes too strong beyond the upper limit of conditional expression (2), the zooming action of the first lens group and the second lens group with respect to the constant movement amount of the second lens group due to zooming. However, the curvature of each lens surface in the first lens group is increased, various aberrations are increased, the Petzval sum is increased in the negative direction, and the curvature of field is increased.

When the value goes below the lower limit, the zooming action against the constant moving amount of the second lens unit is weakened, and the moving amount of the second lens unit is adjusted by the first and second lens units in order to secure a predetermined zooming ratio. This is not desirable because the total lens length must be increased and the lens diameter of the first lens group must be increased.

Conditional expression (3) relates to the ratio of the focal length of the third lens unit having negative refracting power for zooming to the focal length of the entire system at the wide-angle end, and mainly relates to downsizing of the entire lens system. This is to reduce aberration variation over the entire magnification range and obtain good optical performance.

When the upper limit of conditional expression (3) is exceeded and the refractive power of the third lens unit becomes too weak, the amount of movement of the third lens unit must be increased in order to ensure a predetermined zoom ratio. The total lens length is getting longer.

If the lower limit value is exceeded and the refractive power of the third lens unit becomes too strong, the aberration variation due to zooming will increase, and the Petzval sum will increase in the negative direction and the image surface curvature will increase. So not good.

(C) The first group is composed of one or more negative lenses and one or more positive lenses with a strong refracting surface facing the image side, and the average Abbe number of the materials of the positive and negative lenses. Where νA _n and νA _p , respectively, satisfy the following condition: νA _p > νA _n (4).

Conditional expression (4) is mainly for satisfactorily correcting chromatic aberration over the entire zoom range. Particularly, in the present embodiment, since the first group and the second group approach each other during zooming from the wide-angle end to the telephoto end, the Abbe number of the material of each lens forming the first group satisfies the conditional expression (4). By satisfying the above condition, the variation of chromatic aberration due to zooming is corrected well.

If it is desired to further improve the correction, it is preferable to set the above condition as 15 <νA _p −νA _n .

(D) The second lens unit should be composed of a positive 21st lens element having convex lens surfaces on both sides and a meniscus positive 22nd lens element having a convex surface directed toward the object side.

By adopting such a lens configuration, aberration fluctuations due to zooming are satisfactorily corrected. Further, the 21st lens and the 22nd lens may each be a cemented lens of a negative lens and a positive lens for better correcting chromatic aberration.

(E) The negative 51st meniscus lens with the fifth lens unit having the convex surface directed toward the object side, and the fifth lens element having convex lens surfaces on both sides.
Consists of two lenses and a positive 53rd lens which is a single lens or a combination of a positive lens and a negative lens.

By adopting such a lens structure, the aberration variation when focusing is performed by the fifth lens unit is favorably corrected.

When an aspherical surface is introduced into the fifth lens group, the 52nd lens and the 53rd lens may be omitted.

Next, numerical examples of the present invention will be shown. 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 gap from the object side, and Ni and νi are the values of the i-th lens in order from the object side, respectively. The refractive index of glass and the Abbe number.

R2 in Numerical Embodiments 1, 2, and 3
6, R27, and R27 and R28 in Numerical Example 4 are glass materials such as a face plate.

The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the traveling direction of light is positive, R ₀ is the paraxial radius of curvature, and B, C and D are the aspherical surface coefficients. When

[0051]

[Equation 3] Table 1 shows the relationship with each conditional expression in each numerical example. <Numerical Example 1> f = 1 to 14.26 fno = 1: 1.85 to 2.38 2 ω = 60.7 ° to 4.7 ° R 1 = 45.801 D 1 = 0.390 N 1 = 1.80518 ν 1 = 25.4 R 2 = 8.315 D 2 = 0.410 R 3 = 13.380 D 3 = 0.976 N 2 = 1.48749 ν 2 = 70.2 R 4 = -49.267 D 4 = Variable R 5 = 8.122 D 5 = 1.367 N 3 = 1.61800 ν 3 = 63.4 R 6 = -27.334 D 6 = 0.039 R 7 = 5.100 D 7 = 0.781 N 4 = 1.56384 ν 4 = 60.7 R 8 = 10.515 D 8 = Variable R 9 = 25.955 D 9 = 0.156 N 5 = 1.77250 ν 5 = 49.6 R10 = 1.161 D 10 = 0.585 R11 =- 2.300 D 11 = 0.136 N 6 = 1.60311 ν 6 = 60.7 R12 = 17.157 D 12 = 0.039 R13 = 2.438 D 13 = 0.371 N 7 = 1.84666 ν 7 = 23.8 R14 = 77.711 D 14 = 0.156 N 8 = 1.60311 ν 8 = 60.7 R15 = 3.714 D 15 = Variable R16 = ∞ (Aperture) D 16 = 0.351 R17 = 5.761 D 17 = 0.625 N 9 = 1.69680 ν 9 = 55.5 R18 = -3.326 D 18 = 0.078 R19 = -2.658 D 19 = 0.195 N10 = 1.72342 ν10 = 38.0 R20 = -5.116 D 20 = Variable R21 = 8.171 D 21 = 0.156 N11 = 1.80518 ν11 = 25.4 R22 = 2.381 D 22 = 0.781 N12 = 1.48749 ν12 = 70.2 R23 = -5.305 D 23 = 0.029 R24 = 2.803 D 24 = 0.605 N13 = 1.48749 ν13 = 70.2 R25 = -25.069 D 25 = Variable R 26 = ∞ D 26 = 0.976 N14 = 1.51633 ν14 = 64.2 R27 = ∞

[0052]

[Table 1] <Numerical Example 2> f = 1 to 17.1 fno = 1: 2.0 to 3.0 2 ω = 54.7 ° to 3.5 ° R 1 = 17.032 D 1 = 0.344 N 1 = 1.84666 ν 1 = 23.8 R 2 = 6.863 D 2 = 0.362 R 3 = 10.011 D 3 = 0.862 N 2 = 1.48749 ν 2 = 70.2 R 4 = 1462.023 D 4 = Variable R 5 = 6.871 D 5 = 1.258 N 3 = 1.60311 ν 3 = 60.7 R 6 = -26.745 D 6 = 0.034 R 7 = 4.256 D 7 = 0.724 N 4 = 1.48749 ν 4 = 70.2 R 8 = 7.759 D 8 = Variable R 9 = 40.704 D 9 = 0.137 N 5 = 1.71300 ν 5 = 53.8 R10 = 1.000 D 10 = 0.482 R11 = -1.586 D 11 = 0.120 N 6 = 1.60311 ν 6 = 60.7 R12 = 16.188 D 12 = 0.034 R13 = 2.325 D 13 = 0.310 N 7 = 1.84666 ν 7 = 23.8 R14 = 41.950 D 14 = 0.103 N 8 = 1.48749 ν 8 = 70.2 R15 = 3.279 D 15 = Variable R16 = ∞ (Aperture) D 16 = 0.310 R17 = 7.375 D 17 = 0.655 N 9 = 1.69680 ν 9 = 55.5 R18 = -2.869 D 18 = 0.103 R19 = -2.307 D 19 = 0.172 N10 = 1.74077 ν10 = 27.8 R20 = -3.513 D 20 = Variable R21 = 5.660 D 21 = 0.137 N11 = 1.84666 ν11 = 23.8 R22 = 2.432 D 22 = 0.637 N12 = 1.48749 ν12 = 70.2 R23 = -6.322 D 23 = 0.025 R24 = 2.383 D 24 = 0.517 N13 = 1.48749 ν13 = 70.2 R25 = 24.038 D 25 = Variable R26 = ∞ D 26 = 0.862 N14 = 1.51633 ν14 = 64.2 R27 = ∞

[0053]

[Table 2] <Numerical Example 3> f = 1 to 11.5 fno = 1: 1.85 to 2.40 2 ω = 60.7 ° to 5.8 ° R 1 = 28.577 D 1 = 0.390 N 1 = 1.80518 ν 1 = 25.4 R 2 = 6.693 D 2 = 0.566 R 3 = 12.600 D 3 = 1.171 N 2 = 1.51742 ν 2 = 52.4 R 4 = -26.072 D 4 = Variable R 5 = 6.357 D 5 = 1.328 N 3 = 1.48749 ν 3 = 70.2 R 6 = -24.775 D 6 = 0.039 R 7 = 4.896 D 7 = 0.839 N 4 = 1.48749 ν 4 = 70.2 R 8 = 26.740 D 8 = Variable R 9 = 18.752 D 9 = 0.156 N 5 = 1.88300 ν 5 = 40.8 R10 = 1.296 D 10 = 0.488 R11 =- 1.431 D 11 = 0.117 N 6 = 1.60311 ν 6 = 60.7 R12 = 2.177 D 12 = 0.546 N 7 = 1.84666 ν 7 = 23.8 R13 = -11.283 D 13 = Variable R14 = ∞ (Aperture) D 14 = 0.351 R15 = 4.196 D 15 = 0.625 N 8 = 1.51602 ν 8 = 56.8 R16 = -3.177 D 16 = 0.097 R17 = -2.466 D 17 = 0.195 N 9 = 1.68250 ν 9 = 44.7 R18 = -4.218 D 18 = 0.029 R19 = 5.197 D 19 = 0.390 N10 = 1.51602 ν10 = 56.8 R20 = 10.456 D 20 = Variable R21 = 4.823 D 21 = 0.156 N11 = 1.84666 ν11 = 23.8 R22 = 1.948 D 22 = 0.820 N12 = 1.51633 ν12 = 64.2 R23 = -6.666 D 23 = 0.029 R24 = 2.326 D 24 = 0.585 N13 = 1.51633 ν13 = 64.2 R25 = 10.052 D 25 = Variable R 26 = ∞ D 26 = 0.976 N14 = 1.51633 ν14 = 64.2 R27 = ∞

[0054]

[Table 3] <Numerical Example 4> f = 1 to 7.6 fno = 1:85 to 1.95 2 ω = 69.8 ° to 10.5 ° R 1 = -101.291 D 1 = 0.465 N 1 = 1.80518 ν 1 = 25.4 R 2 = 7.327 D 2 = 0.915 R 3 = 18.071 D 3 = 1.348 N 2 = 1.48749 ν 2 = 70.2 R 4 = -15.148 D 4 = Variable R 5 = 8.114 D 5 = 1.511 N 3 = 1.69680 ν 3 = 55.5 R 6 = -23.089 D 6 = 0.046 R 7 = 7.638 D 7 = 0.581 N 4 = 1.60311 ν 4 = 60.7 R 8 = 14.130 D 8 = Variable R 9 = 10.758 D 9 = 0.186 N 5 = 1.60311 ν 5 = 60.7 (aspherical) R 10 = 1.202 D 10 = 0.883 R11 = -2.967 D 11 = 0.162 N 6 = 1.60311 ν 6 = 60.7 R12 = 6.939 D 12 = 0.046 R13 = 2.653 D 13 = 0.441 N 7 = 1.84666 ν 7 = 23.8 R14 = 46.280 D 14 = 0.186 N 8 = 1.60311 ν 8 = 60.7 R15 = 4.292 D 15 = Variable R16 = ∞ (Aperture) D 16 = 0.418 R17 = 8.661 D 17 = 0.581 N 9 = 1.74400 ν 9 = 44.8 R18 = -3.725 D 18 = 0.093 R19 = -2.868 D 19 = 0.186 N10 = 1.72342 ν10 = 38.0 R20 = -5.195 D 20 = Variable R21 = 16.988 D 21 = 0.186 N11 = 1.84666 ν11 = 23.8 R22 = 3.040 D 22 = 0.697 N12 = 1.60311 ν12 = 60.7 R23 = -5.936 D 23 = 0.034 R24 = 4.014 D 24 = 0.604 N13 = 1.67000 ν13 = 57.3 R25 = -6.682 D 25 = 0.186 N14 = 1.84666 ν14 = 23.8 R26 = -27.187 D 26 = Variable R27 = ∞ D 27 = 1.162 N15 = 1.51633 ν15 = 64.2 R28 = ∞

[0055]

[Table 4] R9 surface aspherical surface k = 21.661 A = 0 B = 7.987 × 10 ^-3 C = -5.202 × 10 ^-3 D = 9.643 × 10 ^-4 <Numerical example 5> f = 1 to 11.4 fno = 1: 1.85 to 2.49 2 ω = 60.7 ° ~ 5.9 ° R 1 = -372.977 D 1 = 0.390 N 1 = 1.80518 ν 1 = 25.4 R 2 = 8.277 D 2 = 0.390 R 3 = 16.479 D 3 = 0.781 N 2 = 1.51633 ν 2 = 64.2 R 4 = -22.862 D 4 = Variable R 5 = 7.703 D 5 = 0.937 N 3 = 1.60311 ν 3 = 60.7 R 6 = -21.340 D 6 = 0.039 R 7 = 4.635 D 7 = 0.683 N 4 = 1.56384 ν 4 = 60.7 R 8 = 11.415 D 8 = Variable R 9 = 20.079 D 9 = 0.156 N 5 = 1.77250 ν 5 = 49.6 R10 = 1.148 D 10 = 0.585 R11 = -2.425 D 11 = 0.136 N 6 = 1.60311 ν 6 = 60.7 R12 = 10.770 D 12 = 0.097 R13 = 2.424 D 13 = 0.371 N 7 = 1.84666 ν 7 = 23.8 R14 = 30.709 D 14 = 0.156 N 8 = 1.60311 ν 8 = 60.7 R15 = 3.609 D 15 = Variable R16 = ∞ (diaphragm) D 16 = 0.351 R17 = 4.237 D 17 = 0.546 N 9 = 1.60311 ν 9 = 60.7 R18 = -9.630 D 18 = Variable R19 = 2.674 D 19 = 0.156 N10 = 1.80518 ν10 = 25.4 R20 = 1.309 D 20 = 0.957 N11 = 1.60311 ν11 = 60.7 R21 = -5.731 D 21 = Variable R22 = ∞ D 22 = 0.976 N12 = 1.51633 ν12 = 64.2 R23 = ∞

[0056]

[Table 5] R17 surface: aspherical surface k = -4.767 × 10 ^-4 A = 0, B = -3.093 × 10 ^-3 , C = -3.101 × 10 ^-3 D = 1.045 × 10 ^-3 R21 surface: aspherical surface k = -9.075 × 10 ^-4 A = 0, B = 2.623 × 10 ^-3 , C = -2.713 × 10 ^-3 D = -1.990 × 10 ^-3 <Numerical Example 6> f = 1 to 10.35 fno = 1: 2.0 to 2.51 2 ω = 73.7 ° ~ 8.3 ° R 1 = 18.880 D 1 = 0.500 N 1 = 1.80100 ν 1 = 35.0 R 2 = 7.688 D 2 = 1.263 R 3 = 28.049 D 3 = 0.425 N 2 = 1.83400 ν 2 = 37.2 R 4 = 9.162 D 4 = 0.593 R 5 = 16.395 D 5 = 1.050 N 3 = 1.51823 ν 3 = 59.0 R 6 = -61.692 D 6 = Variable R 7 = 7.864 D 7 = 0.300 N 4 = 1.79952 ν 4 = 42.2 R 8 = 4.892 D 8 = 2.250 N 5 = 1.65160 ν 5 = 58.5 R 9 = -36.237 D 9 = 0.050 R10 = 8.762 D 10 = 1.125 N 6 = 1.58913 ν 6 = 61.2 R11 = -67.487 D 11 = variable R12 = 4.974 D 12 = 0.200 N 7 = 1.88 300 ν 7 = 40.8 R13 = 1.591 D 13 = 0.629 R14 = -2.311 D 14 = 0.150 N 8 = 1.65160 ν 8 = 58.5 R15 = 2.304 D 15 = 0.450 N 9 = 1.84666 ν 9 = 23.8 R16 = 18.279 D 16 = Variable R 17 = ∞ (Aperture) D 17 = 0.250 R18 = 6.708 D 18 = 0.550 N10 = 1.51602 ν10 = 56.8 R19 = -4.694 D 19 = 0.195 R20 = -3.112 D 20 = 0 .250 N11 = 1.68250 ν11 = 44.7 R21 = -5.288 D 21 = 0.037 R22 = 6.760 D 22 = 0.425 N12 = 1.51602 ν12 = 56.8 R23 = 17.202 D 23 = variable R24 = 4.836 D 24 = 0.200 N13 = 1.84666 ν13 = 23.8 R25 = 2.560 D 25 = 0.750 N14 = 1.48749 ν14 = 70.2 R26 = -6.453 D 26 = 0.037 R27 = 3.822 D 27 = 0.575 N15 = 1.48749 ν15 = 70.2 R28 = 47.107 D 28 = Variable R29 = ∞ D 29 = 1.250 N16 = 1.51633 ν16 = 64.2 R30 = ∞

[0057]

[Table 6]

[0058]

[Table 7]

[0059]

According to the present invention, as described above, the refractive powers of the five lens groups and the moving conditions of the second, third, and fifth groups in zooming are set, and the fifth group is moved during focusing. By adopting a lens configuration, while achieving compactness of the entire lens system and achieving good aberration correction over the entire zoom range with a zoom ratio of approximately 8 to 17, high optical performance with little aberration fluctuation during focusing. It is possible to achieve a rear focus type zoom lens having a wide-angle end F number of about 1.8 and a large aperture ratio.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment showing a paraxial refractive power arrangement of the present invention.

FIG. 2 is a lens cross-sectional view of Numerical Example 1 of the present invention.

FIG. 3 is a lens sectional view of Numerical Example 2 of the present invention.

FIG. 4 is a lens cross-sectional view of Numerical Example 3 of the present invention.

FIG. 5 is a lens cross-sectional view of Numerical Example 4 of the present invention.

FIG. 6 is a lens cross-sectional view of Numerical Example 5 of the present invention.

FIG. 7 is a lens cross-sectional view of Numerical Example 6 of the present invention.

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

FIG. 9 is a diagram of various aberrations in the middle of Numerical example 1 of the present invention.

FIG. 10 is a diagram of various types of aberration at the telephoto end according to Numerical Example 1 of the present invention.

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

FIG. 12 is a diagram of various aberrations in the middle of Numerical example 2 of the present invention.

FIG. 13 is a diagram of various types of aberration at the telephoto end according to Numerical Example 2 of the present invention.

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

FIG. 15 is a diagram of various aberrations in the middle of Numerical example 3 of the present invention.

FIG. 16 is a diagram of various types of aberration at the telephoto end according to Numerical Example 3 of the present invention.

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

FIG. 18 is a diagram of various aberrations in the middle of Numerical example 4 of the present invention.

FIG. 19 is a diagram of various types of aberration at the telephoto end according to Numerical Example 4 of the present invention.

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

FIG. 21 is a diagram of various aberrations in the middle of Numerical example 5 of the present invention.

FIG. 22 is a diagram of various types of aberration at the telephoto end according to Numerical Example 5 of the present invention.

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

FIG. 24 is a diagram of various aberrations in the middle of Numerical example 6 of the present invention.

FIG. 25 is a diagram showing various types of aberration at the telephoto end according to Numerical Example 6 of the present invention.

[Explanation of symbols]

 L1 1st group L2 2nd group L3 3rd group L4 4th group L5 5th group d d line ΔM Meridional image surface ΔS Sagittal image surface SP Aperture

Claims (3)

[Claims] 1. A first group having negative refracting power, a second group having positive refracting power, a third group having negative refracting power, a fourth group having positive refracting power, and a positive refracting power in order from the object side. Of the fifth lens group of No. 5, and the third group is moved linearly to the image plane side to perform zooming from the wide-angle end to the telephoto end, and the image-plane variation due to zooming Two
A rear focus type zoom lens, wherein the fifth and fifth groups are moved non-linearly for correction, and the fifth group is moved for focusing. 2. In zooming from the wide-angle end to the telephoto end, the second group moves toward the object side, and the moving amount at this time is M2, and the third group of the third group in zooming from the wide-angle end to the telephoto end. The amount of movement is M
3, the focal length of the entire system at the wide-angle end is fw, and the zoom ratio is Z
And [Outer 1] The amount of movement of the second group and the third group from the wide-angle end is ΔX, respectively.
2 and ΔX3 [Equation 1] The rear focus type zoom lens according to claim 1, wherein the following condition is satisfied. 3. When the focal length of the i-th group is fi, 0.08 <| f2 / f1 | <0.75 0.8 <| f3 / fw | <2.0 is satisfied. The rear focus type zoom lens according to claim 2.