JP2000019398A - Large aperture ratio inner focus type telephoto zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a telephoto zoom lens whose telephoto end focal distance, variable power ratio and f-number are respectively set to specified values while maintaining excellent optical performance by moving a rear group in a 1st lens group along the optical axis, performing focusing and constituting the zoom lens so as to satisfy a specified condition. SOLUTION: Focusing is performed by moving a rear group G1R in a 1st lens group G1 along the optical axis. Then, when the focal distance of a front group G1F in the 1st lens group G1 is f1F, the focal distance of the rear group G1R is f1R and a distance along the optical axis between the surface of the front group G1F nearest to an image side and the surface of the rear group G1R nearest to an object side in the focusing state of an infinity object is D1, this lens is constituted to satisfy the condition expressed by expression; 0.005<f1 R/(f1F.D1)<0.055. By such constitution, the weight and the focusing moving amount of a focusing lens group are made small, the telephoto end focal distance is made >=180 mm, the variable power ratio is made >=2 times and the f-number is made <=3 while maintaining the excellent optical performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-aperture-ratio inner focus telephoto zoom lens, and more particularly to a focusing objective lens suitable for a single-lens reflex camera, an electronic still camera, and the like. More specifically, the focal length at the telephoto end is 180
mm or more, the zoom ratio is 2 times or more, and the F-number is 3
The present invention relates to a so-called large-aperture-ratio inner-focus telephoto zoom lens which is smaller than the above.

[0002]

2. Description of the Related Art Conventionally, a first object disposed closest to an object side has been disclosed.
2. Description of the Related Art A large-aperture-ratio telephoto zoom lens of a so-called single-unit extension focusing system that performs focusing by moving a lens group is used in a single-lens reflex camera, an electronic still camera, and the like. In such a large-aperture-ratio telephoto zoom lens of the one-group extension focusing system, the effective diameter and the weight of the focusing lens group (first lens group) that moves along the optical axis during focusing are large. During automatic focusing (AF: auto focus), the load on the driving motor increases. As a result, a camera using a large-aperture-ratio telephoto zoom lens of the one-group extension focusing system has a disadvantage that the battery consumption becomes excessive and the battery life is shortened. In addition, since the amount of movement of the focusing lens unit (focusing movement amount) associated with focusing is large, the AF driving time becomes long, which is not suitable for quick shooting.

In order to solve the above-mentioned drawbacks, Japanese Patent Laid-Open No.
No. 51202 discloses that a first lens group fixed during zooming is divided into a front group having a positive refractive power and a rear group having a positive refractive power, and the rear group is moved in the optical axis direction as a focusing lens group. A focus method has been proposed. Further, in order to solve the above-mentioned drawbacks, in the zoom lens disclosed in JP-A-7-294816, a portion corresponding to the rear group of JP-A-6-51202 is changed from a wide-angle end focal length state to a telephoto end focal length state. The lens is moved toward the image side when changing the magnification to the distance state, and is also moved independently in the optical axis direction when focusing.

[0004]

Problems to be Solved by the Invention
In the telephoto zoom lens disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, the weight of the focusing lens group has been successfully reduced by forming the focusing lens group with one positive lens, but the closest focusing distance is at the telephoto end. The distance is very large, ranging from 8.3 m to 8.4 m, which is insufficient for a general photographing lens. If the focusing lens group is moved to the shooting distance (1.5 m) targeted by the present invention, the required focusing movement amount of the focusing lens group is 16.6.
mm to 18.7 mm, which makes it impossible to perform quick AF driving. Further, since only one positive lens is used in the focusing lens group, the spherical aberration of the focusing lens group is not satisfactorily corrected. As a result, the closest variation of spherical aberration due to focusing at the telephoto end focal length state is too large, which is also unusable as a general photographing lens.

On the other hand, in the zoom lens disclosed in Japanese Patent Application Laid-Open No. 7-294816, the effective diameter of the focusing lens group can be reduced by the above-described configuration, so that the focusing lens group can be reduced in weight. ing. In addition, the amount of movement of the focusing lens group has been successfully reduced to a relatively small value of 8.3 mm to 13.4 mm. Furthermore, by forming the focusing lens group with two groups of a negative meniscus lens and a positive meniscus lens, it is possible to satisfactorily correct the spherical aberration of the focusing lens group, and the spherical aberration due to focusing is very close. Fluctuations (especially at the telephoto end focal length) are reduced.

However, in the zoom lens disclosed in Japanese Patent Application Laid-Open No. 7-294816, since the focusing lens group is moved during zooming, the amount of focusing movement of the focusing lens group changes depending on the focal length. Will do. This indicates that this optical system is not actually a zoom lens but a varifocal lens. Therefore,
In order to treat this optical system as if it were a zoom lens, an interlocking member for interlocking the moving tube for focusing and the cam tube for zooming at the time of zooming must be added. As a result, the weight of the focusing lens group to be driven by the AF drive motor (including the weight of hardware) includes not only the weight of the hardware for the focusing lens group but also the weight of the interlocking member with the variable power lens group. In addition, the burden on the AF driving motor becomes considerably heavy as a whole.

Further, considering the technology disclosed in Japanese Patent Application Laid-Open No. 7-294816 from the viewpoint of lens assembly, it can be seen that a part of the front group of the telephoto type (here, the lens group located before the variable power lens group) is used. Despite the fact that when a certain focusing lens group is decentered, the image forming surface tends to be greatly inclined, the play of the focusing lens group is caused by the play of the movable part for focusing and the connection play of the variable magnification lens group. Because of the sum, the amount of eccentricity of the focusing lens group becomes extremely large, and it is extremely difficult to maintain the flatness of the imaging surface in an actual product.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a small weight and a small focusing movement amount while maintaining excellent optical performance, and has a focal length at the telephoto end of 1 mm.
80mm or more, magnification ratio is 2 times or more, F-number is 3
It is an object to provide the following large-aperture-ratio inner focus telephoto zoom lens. A large-aperture-ratio inner-focus telephoto system in which the effective diameters of the second lens unit and the third lens unit are reduced, and an AF drive motor can be disposed at a step around the effective diameter of the first lens unit. It is an object to provide a zoom lens.

[0009]

In order to solve the above problems, according to the present invention, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power are arranged in order from the object side. And a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power, and moving the second lens group G2 and the third lens group G3 along the optical axis. In the telephoto zoom lens that performs zooming by performing zooming, the first lens group G1 includes, in order from the object side, a front group G1F having a positive refractive power, and a rear group having a stronger positive refractive power than the front group G1F. G1R, and the rear group G1R in the first lens group G1 is composed of, in order from the object side, a meniscus negative lens having a convex surface facing the object side, and a positive lens component. The rear group G1R in G1 is moved along the optical axis to focus. The focal length of the front group G1F in the first lens group G1 is set to f1F, the focal length of the rear group G1R in the first lens group G1 is set to f1R, and the front group in an infinity object focus state is set. When the distance along the optical axis between the most image-side surface of G1F and the most object-side surface of the rear unit G1R is D1, 0.005 <f1R / (f1F · D1) <0.055. Provided is a large-aperture-ratio inner-focus telephoto zoom lens that satisfies the conditions.

According to a preferred embodiment of the present invention, the first
The focal length of the lens group G1 is f1, the focal length of the second lens group G2 is f2, the focal length of the fourth lens group G4 is f4, and the second lens group G2 and the third lens group G3 are Is set to f23, the focal length of the entire zoom lens system in the wide-angle end focal length state is set to FW, and the closest distance from an object at infinity (the focal length at the telephoto end of 7.0).
When the amount of movement of the rear group G1R in the optical axis direction due to focusing on an object of (5 ×) is ΔD1, 0.04 <(| f23 | · FW) / (f1 · f4 · ΔD)
1) <0.13 2 × 10 ⁻³ <| f2 | / (f1 · FW) <3.8 × 10
Satisfies condition ^-3 .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, A fourth lens group G4 having a refractive power. Then, by moving the second lens group G2 and the third lens group G3 along the optical axis, zooming from the wide-angle end focal length state to the telephoto end focal length state is performed. The first lens group G1 includes, in order from the object side, a front group G1F having a positive refractive power, and a rear group G1R having a stronger positive refractive power than the front group G1F. Further, the rear group G1R in the first lens group G1 includes, in order from the object side, a meniscus negative lens having a convex surface facing the object side, and a positive lens component. Further, as a focusing method, a so-called inner focus method is employed in which the rear group G1R in the first lens group G1 is moved along the optical axis to perform focusing. Hereinafter, the configuration of the present invention will be described in more detail with reference to the conditional expressions of the present invention.

First, in the present invention, the following conditional expression (1) is satisfied. 0.005 <f1R / (f1F.D1) <0.055 (1) Here, f1F is the focal length of the front group G1F in the first lens group G1. F1R is the focal length of the rear group G1R in the first lens group G1. Further, D1 is the distance along the optical axis between the most image-side surface of the front group G1F and the most object-side surface of the rear group G1R in the in-focus state of an object at infinity, that is, the front group G1F and the rear group G1R. Between the on-axis air gaps.

When the value exceeds the upper limit of conditional expression (1), the effective diameter and the required focusing movement of the rear group G1R, which is the focusing lens unit, become too large, and the excellent AF performance aimed at by the present invention is not achieved. Can not be achieved. On the other hand, when the value goes below the lower limit value of the conditional expression (1), the closest variation of the spherical aberration due to focusing becomes too large, so that the excellent optical performance aimed at by the present invention cannot be achieved. In order to ensure a better balance between AF performance and the closest variation of spherical aberration due to focusing, it is preferable to set the upper limit of conditional expression (1) to 0.05 and the lower limit to 0.015. .

Further, in the present invention, a more favorable AF
In order to obtain performance and imaging performance and to improve portability, it is desirable to satisfy the following conditional expressions (2) and (3). 0.04 <(| f23 | · FW) / (f1 · f4 · ΔD1) <0.13 (2) 2 × 10 ⁻³ <| f2 | / (f1 · FW) <3.8 × 10 ⁻³ ( 3) Here, f1 is the focal length of the first lens group G1, and f1
2 is the focal length of the second lens group G2, and f4 is the focal length of the fourth lens group G4. F23 is a composite focal length of the second lens group G2 and the third lens group G3, and F23
W is the focal length of the entire zoom lens system in the wide-angle end focal length state. Further, △ D1 is the movement amount (focus movement amount) of the rear group G1R in the optical axis direction upon focusing from an infinitely distant object to an object at the shortest distance (7.5 times the focal length at the telephoto end). .

When the value exceeds the upper limit of conditional expression (2), the effective diameters of the second lens group G2 and the third lens group G3 become too large, and a step portion around the effective diameter of the first lens group G1 is formed. It is not preferable because a motor for driving the AF cannot be built in the camera. On the other hand, when the value goes below the lower limit value of the conditional expression (2), the focusing movement amount becomes too large, and the AF operation becomes slow. In order to obtain better AF performance, it is preferable to set the lower limit of conditional expression (2) to 0.055.

If the value exceeds the upper limit of conditional expression (3), the effective diameter of the second lens group G2 becomes too large, and it becomes impossible to incorporate a motor for driving the AF. On the other hand, when the value goes below the lower limit of conditional expression (3), the Petzval sum becomes too large in the negative direction, and the field curvature becomes undesirably large. In order to obtain even better image plane flatness, the lower limit of conditional expression (3) should be set to 3 × 10 ^−3.
It is preferable that

In the present invention, the first lens group G
The front group G1F in 1 comprises, in order from the object side, a cemented positive lens of a meniscus negative lens having a convex surface facing the object side and a meniscus positive lens having a convex surface facing the object side, and a positive lens component. It is desirable to satisfy the conditional expression (4). 0 <(R2-R1) / (R2 + R1) <1 (4) Here, R1 is a radius of curvature of the object-side surface of the cemented positive lens in the front group G1F. R2 is the radius of curvature of the image-side surface of the cemented positive lens in the front group G1F.

Conditional expression (4) defines the lens shape of the cemented positive lens in the front group G1F. Exceeding the upper limit of conditional expression (4) is not preferable because the fluctuation of spherical aberration due to focusing increases. On the other hand, when the value goes below the lower limit value of the conditional expression (4), the required focusing movement amount becomes too large, and the AF operation becomes slow. In order to further reduce the fluctuation of spherical aberration due to focusing and to further improve the AF performance, it is preferable to set the upper limit of conditional expression (4) to 0.95 and the lower limit to 0.25.

Further, in the present invention, in order to more appropriately correct chromatic aberration, the third lens group G3 includes, in order from the object side, a positive lens component, and a cemented positive lens of a positive lens component and a negative lens component. And it is desirable to satisfy the following conditional expressions (5) and (6). 1.4 <Np3 <1.6 (5) 62 <νp3 <100 (6) where Np3 is the refractive index of the positive lens component constituting the third lens group G3 with respect to the d-line (λ = 587.6 nm). It is. Νp3 is the Abbe number of the positive lens component constituting the third lens group G3.

If the value exceeds the upper limit of conditional expression (5), it is not preferable because only an optical glass having a poor secondary chromatic aberration can be used as a positive lens. The lower limit of the conditional expression (5) is the limit of the existing optical glass for visible light. If the lower limit of the conditional expression (5) is less than the lower limit, the range greatly deviates from the field of application of the present invention.

The upper limit of conditional expression (6) is the limit value of existing optical glass for visible light when considered in combination with conditional expression (5). , Which is not preferable. On the other hand, when the value goes below the lower limit value of the conditional expression (6), it is not preferable because only the optical glass whose secondary chromatic aberration deteriorates can be used as the positive lens.

In the present invention, it is desirable to satisfy the following conditional expressions (7) to (9) in order to obtain better optical performance. 0.25 <Nn1-Np1 <0.55 (7) 65 <vp1 <100 (8) 20 <vn1 <30 (9) Here, Np1 and vp1 constitute the rear group G1R in the first lens group G1. Are the refractive index and Abbe number of the positive lens component with respect to the d-line. Nn1 and vn1 are the refractive index and Abbe number for the d-line of the negative meniscus lens constituting the rear group G1R in the first lens group G1.

Conditional expression (7) is a conditional expression for favorably correcting the spherical aberration of the rear group G1R in the first lens group G1. There is no optical glass for visible light exceeding the upper limit of conditional expression (7) at present. On the other hand, when the value goes below the lower limit of conditional expression (7), the refractive index difference between the positive lens component and the negative meniscus lens becomes too small, and the curvature of spherical aberration becomes large. In order to obtain better optical performance, it is preferable to set the upper limit of conditional expression (7) to 0.45 and the lower limit to 0.35.

The upper limit of conditional expression (8) is the limit of existing optical glass for visible light. Exceeding this upper limit is not preferable because it greatly departs from the field of application of the present invention.
On the other hand, when the value goes below the lower limit of conditional expression (8), it is not preferable because the secondary chromatic aberration cannot be sufficiently corrected. In addition,
In order to obtain better optical performance, it is preferable to set the lower limit of conditional expression (8) to 70. In order to obtain good optical performance while further reducing the cost, it is preferable to set the upper limit of conditional expression (8) to 85.

The upper limit of the conditional expression (9) is a limit value of the existing optical glass for visible light when considered in combination with the conditional expression (7). , Which is not preferable. The lower limit of conditional expression (9) is also the limit of the existing optical glass for visible light. Even if the lower limit of this condition is not reached, the secondary chromatic aberration cannot be sufficiently corrected. In order to obtain even better optical performance, it is preferable to set the lower limit of conditional expression (9) to 25.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each embodiment, the large-aperture-ratio inner-focus telephoto zoom lens according to the present invention includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive lens group. Third lens group G3 having a refractive power of
And a fourth lens group G4 having a positive refractive power. The first lens group G1 includes, in order from the object side, a front group G1F having a positive refractive power and a rear group G1R having a stronger positive refractive power than the front group G1F.

The rear group G1R in the first lens group G1 is
In order from the object side, it is composed of a meniscus negative lens having a convex surface facing the object side and a positive lens component. further,
Upon zooming from the wide-angle end focal length state to the telephoto end focal length state, the second lens group G2 moves toward the image side, and the third lens group G3 moves along the concave locus toward the object side (ie, Once to the image side and then to the object side)
The first lens group G1 and the fourth lens group G4 are fixed during zooming. In focusing from an object at infinity to an object at a short distance, the rear group G1R in the first lens group G1 moves to the object side.

FIG. 1 is a view showing the configuration of a large-aperture-ratio inner-focus telephoto zoom lens according to a first embodiment of the present invention, and focuses on infinity at the wide-angle end focal length. The position of each lens group in the state is shown. In the inner focus telephoto zoom lens shown in FIG. 1, the front group G1F in the first lens group G1 includes, in order from the object side, a meniscus negative lens having a convex surface facing the object side and a meniscus positive lens having a convex surface facing the object side. And a meniscus positive lens L12 having a convex surface facing the object side. The rear group G1R in the first lens group G1 includes, in order from the object side, a negative meniscus lens L13 having a convex surface facing the object side and a positive meniscus lens L14 having a convex surface facing the object side.

Further, the second lens group G2 includes, in order from the object side, a meniscus negative lens L21 having a convex surface facing the object side.
It is composed of a cemented positive lens L22 composed of a biconcave lens and a biconvex lens, and a biconcave lens L23 having a concave surface with a strong curvature directed to the object side. The third lens group G3 is composed of, in order from the object side, a biconvex lens L31, and a cemented positive lens L32 of a biconvex lens and a meniscus negative lens having a concave surface facing the object side. Further, the fourth lens group G4 includes, in order from the object side, a positive meniscus lens L41 having a convex surface facing the object side, a cemented positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a convex surface facing the object side. A negative lens L42, a biconvex lens L43 arranged at a large interval,
It comprises a negative meniscus lens L44 having a concave surface facing the object side, and a biconvex lens L45. An aperture stop S is provided between the third lens group G3 and the fourth lens group G4, and the aperture stop S is fixed together with the fourth lens group G4 during zooming.

Table 1 below summarizes data values of the first embodiment of the present invention. In Table (1), F is the focal length of the entire zoom lens system, FNO is the F number, β is the photographing magnification, Bf is the back focus, and D0 is the lens surface of the lens system closest to the object (from the object). The distance (object distance) along the optical axis to the object-side surface of the cemented positive lens L11 in one lens group G1 is shown. The surface number indicates the order of each lens surface from the object side, r indicates the radius of curvature of each lens surface, d indicates the distance between the lens surfaces, and n and ν indicate refraction with respect to the d line (λ = 587.6 nm). The rates and Abbe numbers are shown. Further, Φ1F is the effective diameter of the cemented positive lens L11 disposed closest to the object side in the front group G1F,
1R is the effective diameter of the negative meniscus lens L13 located closest to the object side in the rear group G1R, and Φ2 is the negative meniscus lens L21 located closest to the object side in the second lens group G2.
Represents the effective diameter of the biconvex lens L31 disposed closest to the object side in the third lens group G3.

[0031]

[Table 1] F = 81.55 to 194.00 FNO = 2.9 Face number rd ν n Φ 1 97.0939 3.8000 25.41 1.805182 Φ1F = 71.5 2 72.6165 10.4000 82.52 1.497820 3 268.0849 0.1000 4 157.7721 5.3000 82.52 1.497820 5 894.9563 (d5 = Variable) 6 50.7516 2.2000 23.82 1.846660 Φ1R = 56.0 7 44.4939 1.8100 8 53.1452 9.0000 70.41 1.487490 9 17654.5990 (d9 = variable) 10 365.8054 1.5000 45.37 1.796681 Φ2 = 34.8 11 33.8586 7.5200 12 -51.2952 1.8000 70.41 1.487490 13.4 6000. 287.2535 2.1100 15 -60.5102 1.8000 45.37 1.796681 16 8969.2140 (d16 = variable) 17 165.9894 4.5000 82.52 1.497820 Φ3 = 36.8 18 -106.8038 0.2000 19 772.1751 7.1000 82.52 1.497820 20 -40.2253 2.0000 45.00 1.744000 21 -100.1483 (d21 = variable) 22 ∞ 1.0000 Aperture stop S) 23 78.6671 3.5000 47.47 1.787971 24 216.2251 0.2000 25 39.9627 6.0000 82.52 1.497820 26 168.8230 4.4000 36.27 1.620040 27 38.2994 30.5000 28 272.2610 5.0000 48.97 1.531721 29 -62.3609 14.8000 30 -36.5028 1.9000 33.8 9 1.803840 31 -160.6086 0.2000 32 137.3427 4.6000 49.45 1.772789 33 -111.8713 (Bf) [Variable spacing in focusing and zooming] Infinity in-focus condition Wide-angle end focal length Intermediate focal length Telephoto end focal length F 81.5500 135.0000 194.0000 D0 ∞ ∞ ∞ d5 17.08501 17.08501 17.08501 d9 1.99906 16.04981 22.87155 d16 32.05530 18.13596 1.61457 d21 3.43076 3.29935 12.99901 Bf 57.01947 57.01947 57.01947 Closest focus wide-angle end focal length Intermediate focal length Telephoto end focal length β -0.06776 -0.1121245.16 8.48886 8.48886 d9 10.60231 24.65306 31.47480 d16 32.05530 18.13596 1.61457 d21 3.43076 3.29935 12.99901 Bf 57.01947 57.01947 57.01947 [Values corresponding to the conditional expressions] f1 = 92.4694 f2 = -27.4621 f3 = 105.4937 f4 = 98.3299 f. 5687 f1F = 206.1071 f1R = 142.2645 FW = 81.5500 D = 17.0850 ΔD1 = 8.5962 (1) f1R / (f1F · D1) = 0.040 (2) (| f23 | · FW) / (f1 · f4 · ΔD1) = 0.09 (3) | f2 | / (F1.FW) = 3.6 × 10 ⁻³ (4) (R2−R1) / (R2 + R1) = 0.47 (5) Np3 = 1.4978 (L31 and L32) (6) νp3 = 82 0.52 (L31 and L32) (7) Nn1-Np1 = 0.36 (8) vp1 = 70.41 (9) vn1 = 23.82

Referring to Table (1), in the first embodiment,
The effective diameter Φ1R of the rear group G1R in the first lens group G1 is equal to or less than 80% of the effective diameter ratio of the front lens group G1F in the first lens group G1.
6.0 mm, which indicates that the design is very compact. In addition, it can be seen that the focusing movement amount ΔD1 of the focusing lens unit (the rear group G1R) associated with focusing from an object at infinity to an object at the closest distance is very small, about 8.60 mm.
2 to 7 are diagrams illustrating various aberrations of the first example. That is, FIG. 2 is a diagram of various aberrations at the infinity in-focus condition at the wide-angle end focal length state, FIG. 3 is a diagram of various aberrations at the infinity in-focus condition at the intermediate focal length state, and FIG. FIG. 4 is a diagram illustrating various aberrations in a focusing state at infinity in a focal length state.
FIG. 5 is a diagram showing various aberrations in a focusing state at a close distance (photographing distance R = 1500 mm) in the focal length state at the wide angle end, and FIG. 6 is a drawing showing a close distance (R = 150 in the intermediate focal length state).
FIG. 7 is a diagram of various aberrations in a focusing state at a close distance (R = 1500 mm) in a focal length state at a telephoto end.

In each aberration diagram, FNO represents an F number,
NA is the numerical aperture, Y is the image height, and d is the d-line (λ = 587.
6 nm), g is a g-line (λ = 435.8 nm), C is a C-line (λ = 656.3 nm), F is an F-line (λ = 48
6.1 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, the aberration diagram showing the chromatic aberration of magnification is shown based on the d-line. As is clear from the aberration diagrams, in the first embodiment, various aberrations are satisfactorily corrected in each focal length state from an infinity in-focus state to a close distance in-focus state, and excellent imaging performance is secured. You can see that it is.

[Second Embodiment] FIG. 8 is a view showing the configuration of a large aperture ratio inner focus telephoto zoom lens according to a second embodiment of the present invention, and focuses on infinity at the wide-angle end focal length. The position of each lens group in the state is shown. 8, the front group G1F in the first lens group G1 includes, in order from the object side, a meniscus negative lens having a convex surface facing the object side and a meniscus positive lens having a convex surface facing the object side. And a meniscus positive lens L12 having a convex surface facing the object side. The rear group G1R in the first lens group G1 includes, in order from the object side, a meniscus negative lens L13 having a convex surface facing the object side and a biconvex lens L14 having a convex surface having a strong curvature facing the object side. .

Further, the second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface facing the object side.
A cemented positive lens L22 composed of a biconcave lens and a biconvex lens, and a meniscus negative lens L having a concave surface with a strong curvature directed to the object side
Consists of 23. The third lens group G3 includes, in order from the object side, a biconvex lens L31 and a cemented positive lens L32 of a meniscus positive lens having a concave surface facing the object side and a meniscus negative lens having a concave surface facing the object side. I have. Further, the fourth lens group G4 includes, in order from the object side, a positive meniscus lens L41 having a convex surface facing the object side, a cemented positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a convex surface facing the object side. It comprises a negative lens L42, a biconvex lens L43 arranged at a large distance, a negative meniscus lens L44 having a concave surface facing the object side, and a positive meniscus lens L45 having a convex surface facing the object side. An aperture stop S is provided between the third lens group G3 and the fourth lens group G4.
4 and fixed during zooming.

Table 2 below summarizes data values of the second embodiment of the present invention. In Table (2), F is the focal length of the entire zoom lens system, FNO is the F-number, β is the imaging magnification, Bf is the back focus, and D0 is the object-to-object-side lens surface of the lens system. The distance (object distance) along the optical axis to the object-side surface of the cemented positive lens L11 in one lens group G1 is shown. The surface number indicates the order of each lens surface from the object side, r indicates the radius of curvature of each lens surface, d indicates the distance between the lens surfaces, and n and ν indicate refraction with respect to the d line (λ = 587.6 nm). The rates and Abbe numbers are shown. Further, Φ1F is the effective diameter of the cemented positive lens L11 disposed closest to the object side in the front group G1F,
1R is the effective diameter of the negative meniscus lens L13 located closest to the object side in the rear group G1R, and Φ2 is the negative meniscus lens L21 located closest to the object side in the second lens group G2.
Represents the effective diameter of the biconvex lens L31 disposed closest to the object side in the third lens group G3.

[0037]

[Table 2] F = 81.55 to 194.00 FNO = 2.9 Surface number rd ν n Φ 1 95.6835 2.8000 25.41 1.805182 Φ1F = 69.8 2 69.9345 9.0000 82.52 1.497820 3 419.6538 0.1000 4 145.4966 5.0000 82.52 1.497820 5 311.1124 (d5 = Variable) 6 50.6221 2.2000 23.82 1.846660 Φ1R = 56.3 7 44.8400 1.7000 8 54.5779 9.0000 70.41 1.487490 9 -15627.6829 (d9 = variable) 10 168.4621 1.5000 46.54 1.804109 Φ2 = 34.8 11 30.5148 8.0000 12 -54.1893 1.5000 70.41 1.487490 13.6000 5.6000 -544.2645 2.4000 15 -50.7200 1.5000 46.54 1.804109 16 -290.4023 (d16 = variable) 17 151.0644 3.5000 67.87 1.593189 Φ3 = 37.2 18 -168.9103 0.2000 19 -1957.4846 6.7000 82.52 1.497820 20 -38.3700 1.5000 39.61 1.804540 21 -77.5643 (d21 = variable) 22 ∞ 1.0000 (Aperture stop S) 23 75.8673 3.9000 46.54 1.804109 24 159.3674 0.1000 25 38.5965 7.1000 82.52 1.497820 26 282.4316 4.2000 36.27 1.620040 27 41.0820 28.4000 28 107.1704 6.2000 51.35 1.526820 29 -77.1837 14.8000 30 -34.2661 1.9000 33. 89 1.803840 31 -90.1631 0.1000 32 90.4748 4.6000 49.52 1.744429 33 608.1616 (Bf) [Variable spacing for focusing and zooming] Infinity in-focus condition Wide-angle end focal length Intermediate focal length Telephoto end focal length F 81.5500 135.0000 194.0000 D0 ∞ ∞ ∞ d5 18.29019 18.29019 18.29019 d9 1.83871 16.27602 23.30105 d16 32.56913 19.09128 3.04815 d21 4.16373 3.20427 12.22237 Bf 52.22757 52.22757 52.22756 Close focal length Wide-angle end focal length Intermediate focal length Telephoto end focal length 9.64204 d9 10.48686 24.92417 31.94920 d16 32.56913 19.09128 3.04815 d21 4.16373 3.20427 12.22237 Bf 52.22757 52.22757 52.22756 [Values corresponding to the conditional expressions] f1 = 90.9065 f2 = -27.4554 f3 = 105.9381 f4 = 97.1867836. f1F = 211.88000 f1R = 142.2492 FW = 81.5500 D1 18.2902 ΔD1 = 8.6482 (1) f1R / (f1F · D1) = 0.037 (2) (| f23 | · FW) / (f1 · f4 · ΔD1) = 0.09 (3) | f2 | /(F1.FW)=3.7×10 ⁻³ (4) (R2−R1) / (R2 + R1) = 0.63 (5) Np3 = 1.5932 (L31), 1.4978 (L32) (6) ) Vp3 = 67.87 (L31), 82.52 (L32) (7) Nn1-Np1 = 0.36 (8) vp1 = 70.41 (9) vn1 = 23.82

Referring to Table (2), in the second embodiment,
The effective diameter Φ1R of the rear group G1R in the first lens group G1 is equal to or less than 80% of the effective diameter ratio of the front lens group G1F in the first lens group G1.
6.3 mm, which indicates that the design is very compact as in the first embodiment. Further, it can be seen that the focusing movement amount ΔD1 of the focusing lens group (the rear group G1R) associated with focusing from an object at infinity to an object at the closest distance is very small, about 8.65 mm. 9 to 14 are diagrams illustrating various aberrations of the second example. That is, FIG. 9 is a diagram showing various aberrations at the infinity in-focus condition at the wide-angle end focal length state, FIG. 10 is a diagram showing various aberrations at the infinity in-focus condition at the intermediate focal length state, and FIG. FIG. 4 is a diagram illustrating various aberrations in a focusing state at infinity in a focal length state. FIG. 12 is a diagram of various types of aberration in a close distance (photographing distance R = 1500 mm) focus state in a wide-angle end focal length state, and FIG. 13 is a close distance (R = 1500 mm) focus state in an intermediate focal length state. FIG. 14 is a diagram of various types of aberration at the closest focal length (R = 1500 mm) in the focal length state at the telephoto end.

In each aberration diagram, FNO represents an F number,
NA is the numerical aperture, Y is the image height, and d is the d-line (λ = 587.
6 nm), g is a g-line (λ = 435.8 nm), C is a C-line (λ = 656.3 nm), F is an F-line (λ = 48
6.1 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, the aberration diagram showing the chromatic aberration of magnification is shown based on the d-line. As is clear from the aberration diagrams, the first embodiment also has the first
As in the example, it can be seen that various aberrations are satisfactorily corrected in each focal length state from an infinity in-focus state to a close distance in-focus state, and excellent imaging performance is secured.

[Third Embodiment] FIG. 15 is a view showing the configuration of a large-aperture-ratio inner focus telephoto zoom lens according to a third embodiment of the present invention, and focuses on infinity at the wide-angle end focal length. The position of each lens group in the state is shown. In the inner focus telephoto zoom lens shown in FIG. 15, the front group G1F in the first lens group G1 includes, in order from the object side, a meniscus negative lens having a convex surface facing the object side and a meniscus positive lens having a convex surface facing the object side. And a meniscus positive lens L12 having a convex surface facing the object side. The rear group G1R in the first lens group G1 includes, in order from the object side, a negative meniscus lens L13 having a convex surface facing the object side and a positive meniscus lens L14 having a convex surface facing the object side.

Further, the second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface facing the object side.
It is composed of a cemented positive lens L22 composed of a biconcave lens and a biconvex lens, and a biconcave lens L23 having a concave surface with a strong curvature directed to the object side. The third lens group G3 is composed of, in order from the object side, a biconvex lens L31, and a cemented positive lens L32 of a biconvex lens and a meniscus negative lens having a concave surface facing the object side. Further, the fourth lens group G4 includes, in order from the object side, a meniscus positive lens L41 having a concave surface facing the object side, a cemented positive lens L42 of a biconvex lens and a biconcave lens,
It comprises a biconvex lens L43 arranged at a large distance, a negative meniscus lens L44 having a concave surface facing the object side, and a biconvex lens L45. Note that the third lens group G3
An aperture stop S is provided between the zoom lens and the fourth lens group G4.
The aperture stop S is fixed during zooming together with the fourth lens group G4.

Table 3 below summarizes the data values of the third embodiment of the present invention. In Table (3), F is the focal length of the entire zoom lens system, FNO is the F number, β is the photographing magnification, Bf is the back focus, and D0 is the lens surface of the lens system closest to the object (No. The distance (object distance) along the optical axis to the object-side surface of the cemented positive lens L11 in one lens group G1 is shown. The surface number indicates the order of each lens surface from the object side, r indicates the radius of curvature of each lens surface, d indicates the distance between the lens surfaces, and n and ν indicate refraction with respect to the d line (λ = 587.6 nm). The rates and Abbe numbers are shown. Further, Φ1F is the effective diameter of the cemented positive lens L11 disposed closest to the object side in the front group G1F,
1R is the effective diameter of the negative meniscus lens L13 located closest to the object side in the rear group G1R, and Φ2 is the negative meniscus lens L21 located closest to the object side in the second lens group G2.
Represents the effective diameter of the biconvex lens L31 disposed closest to the object side in the third lens group G3.

[0043]

[Table 3] F = 81.55 to 194.00 FNO = 2.9 Surface number rd ν n Φ 1 103.0304 3.8000 25.41 1.805182 Φ1F = 70.0 2 75.9319 10.4000 82.52 1.497820 3 2098.0323 0.1000 4 98.3401 5.3000 82.52 1.497820 5 112.4831 (d5 (Variable) 6 50.6238 2.2000 23.82 1.846660 Φ1R = 55.6 7 44.6607 1.8100 8 53.8307 9.0000 70.41 1.487490 9 54805.0040 (d9 = variable) 10 567.2324 1.5000 45.37 1.796681 Φ2 = 33.4 11 32.7801 7.5200 12 -48.3877 1.8000 82.52 1.497820 13 4.2.6565 6.0000 23.82.82 319.5118 2.1100 15 -59.3823 1.8000 45.37 1.796681 16 2391.4031 (d16 = variable) 17 559.3605 5.0000 64.10 1.516800 Φ3 = 36.4 18 -120.6075 0.2000 19 164.0804 9.0000 95.25 1.433852 20 -40.1294 2.0000 45.37 1.796681 21 -74.7207 (d21 = variable) 22 ∞ 2.0000 Aperture stop S) 23 -309.4489 3.5000 47.47 1.787971 24 -119.7066 0.2000 25 58.1442 8.0000 82.52 1.497820 26 -101.2693 4.4000 36.27 1.620040 27 124.9247 30.5000 28 244.9041 5.0000 48.97 1.531721 29 -65.6297 14.8000 30 -40.8352 1.9000 33.89 1.803840 31 -124.0269 0.2000 32 322.3504 5.5000 49.45 1.772789 33 -158.3912 (Variable spacing for focusing and zooming) Infinity in-focus condition Wide-angle end focal length Intermediate focal length Telephoto end focal length F 81.5500 135.0000 194.0000 D0 ∞ ∞ ∞ d5 19.67023 19.67023 19.67023 d9 2.00000 17.94895 25.98066 d16 25.01804 15.90695 4.24008 d21 12.67257 5.83471 9.46987 Bf 69.71305 69.71305 69.71305 Focus at close range Wide-angle end focal length Intermediate focal length Telephoto end focal length 10.14062 10.14062 d9 11.52962 27.47857 35.51028 d16 25.01804 15.90695 4.24008 d21 12.67257 5.83471 9.46987 Bf 69.71305 69.71305 69.71305 [Values corresponding to conditional expressions] f1 = 97.5933 f2 = −25.0000 f3 = 106.6982 f4 = 91.1032 f. 9706 f1F = 230.0000 f1R = 142.0000 FW = 81.550 D1 = 19.6702 ΔD1 = 9.5296 (1) f1R / (f1F · D1) = 0.031 (2) (| f23 | · FW) / (f1 · f4 · ΔD1) = 0.06 (3) | f2 | / (f1.FW) = 3.1 × 10 ⁻³ (4) (R2−R1) / (R2 + R1) = 0.91 (5) Np3 = 1.5168 (L31), 1.4339 (L32) (6) vp3 = 64.10 (L31), 95.25 (L32) (7) Nn1-Np1 = 0.36 (8) vp1 = 70.41 (9) vn1 = 23.82

Referring to Table (3), in the third embodiment,
The effective diameter Φ1R of the rear group G1R in the first lens group G1 is equal to or less than 80% of the effective diameter ratio of the front lens group G1F in the first lens group G1.
It is 5.6 mm, which indicates that the design is very compact as in the first and second embodiments.
The focusing movement amount ΔD1 of the focusing lens unit (rear group G1R) associated with focusing from an object at infinity to an object at the closest distance is about 9.5.
It turns out that it is very small, 3 mm. 16 to 21
FIG. 9 is a diagram illustrating various aberrations of the third example. That is, FIG. 16 is a diagram of various aberrations at the infinity in-focus condition at the wide-angle end focal length state, FIG. 17 is a diagram of various aberrations at the infinity in-focus condition at the intermediate focal length state, and FIG. FIG. 4 is a diagram illustrating various aberrations in a focusing state at infinity in a focal length state. Also,
FIG. 19 shows the closest distance (photographing distance R in the wide-angle end focal length state).
FIG. 20 is a diagram illustrating various aberrations in a focused state. FIG. 20 illustrates a close distance (R = 1500 m) in an intermediate focal length state.
m) Various aberration diagrams in a focused state, and FIG. 21 is a diagram of various aberrations in a short-distance (R = 1500 mm) focused state in a focal length state at a telephoto end.

In each aberration diagram, FNO represents the F number,
NA is the numerical aperture, Y is the image height, and d is the d-line (λ = 587.
6 nm), g is a g-line (λ = 435.8 nm), C is a C-line (λ = 656.3 nm), F is an F-line (λ = 48
6.1 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, the aberration diagram showing the chromatic aberration of magnification is shown based on the d-line. As is clear from the aberration diagrams, the first embodiment also has the first
As in the example and the second example, various aberrations are favorably corrected in each focal length state from an infinity in-focus state to a close distance in-focus state, and excellent imaging performance is secured. Understand.

FIG. 22 is a schematic diagram schematically showing an AF drive mechanism and a zoom mechanism of a large-aperture-ratio inner focus telephoto zoom lens according to each embodiment of the present invention. In FIG. 22, the zoom lens of the first embodiment is exemplarily used, but the same applies to other embodiments. In FIG. 22, a front group G1F and a fourth lens group G4 of the first lens group G1 are attached to a fixed portion K via a lens fixed barrel R1F and a lens fixed barrel R4, respectively. Also,
The second lens group G2 and the third lens group G3 are attached to the zoom cam barrel Z supported by the fixed part K via the lens fixed barrel R2 and the lens fixed barrel R3.
Further, the rear group G1R of the first lens group G1 is attached to the focus cam barrel F via a lens fixing barrel R1R. The focus cam barrel F is configured to be driven to rotate around the optical axis by an annular motor M supported by a fixed part K.

As shown in FIG. 22, in the large-aperture-ratio inner-focus telephoto zoom lens according to the present invention, since the zoom mechanism and the focusing mechanism are independent of each other, the AF drive mechanism and the zoom mechanism are simplified. And it is easy to provide a structure that is strong against vibrations and shocks caused by falling. As described above, in the large-aperture-ratio inner-focal telephoto zoom lens according to the present invention, the effective diameters of the second lens unit and the third lens unit are reduced, and a step around the effective diameter of the first lens unit is set to A.
An F drive motor can be arranged.

[0048]

As described above, according to the present invention,
While maintaining excellent optical performance, the weight and focusing movement of the focusing lens group are small, the focal length at the telephoto end is 180 mm or more, the zoom ratio is 2 times or more, and the F-number is 3 or less. A focus telephoto zoom lens can be realized.
Therefore, the large-aperture-ratio inner focus telephoto zoom lens of the present invention is particularly suitable for a single-lens reflex camera, an electronic still camera, and the like. In the present invention, the effective diameter of the focusing lens group is small for a large-aperture-ratio inner-focus telephoto zoom lens, so that the focusing lens group can be reduced in weight. Also,
According to the present invention, excellent imaging performance can be maintained from a focusing state at infinity to a focusing state at a close distance, even though the focusing movement amount is small.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a large-aperture-ratio inner-focus telephoto zoom lens according to a first embodiment of the present invention, showing positions of respective lens groups in an infinity in-focus state at a wide-angle end focal length state. ing.

FIG. 2 is a diagram illustrating various aberrations of the first embodiment at a wide-angle end focal length in an infinity in-focus condition;

FIG. 3 is a diagram illustrating various aberrations of the first embodiment in an infinity in-focus state at an intermediate focal length state;

FIG. 4 is a diagram illustrating various aberrations of the first embodiment at a telephoto end focal length in an infinity in-focus condition;

FIG. 5 is a diagram illustrating various aberrations of the first example in a state of focusing at a close distance in a focal length state at a wide-angle end.

FIG. 6 is a diagram illustrating various aberrations of the first example in an intermediate focal length state and at a close focus state;

FIG. 7 is a diagram illustrating various types of aberrations in the focal length state at the telephoto end in the first embodiment in the short-distance in-focus state;

FIG. 8 is a diagram showing a configuration of a large-aperture-ratio inner-focus telephoto zoom lens according to a second embodiment of the present invention, showing the position of each lens group in an infinity in-focus condition at the wide-angle end focal length. ing.

FIG. 9 is a diagram of various aberrations in the infinity in-focus condition at the wide-angle end focal length in the second example.

FIG. 10 is a diagram illustrating various aberrations of the second example in an intermediate focal length state and focused on infinity.

FIG. 11 is a diagram illustrating various aberrations of the second embodiment at a telephoto end focal length in an infinity in-focus condition;

FIG. 12 is a diagram illustrating various aberrations of the second example in a state of focusing at a short distance in a focal length state at a wide-angle end.

FIG. 13 is a diagram illustrating various aberrations of the second example in an intermediate focal length state and in a close focusing state;

FIG. 14 is a diagram illustrating various aberrations of the second embodiment in a state of focusing on a short distance at a telephoto end focal length.

FIG. 15 is a diagram showing a configuration of a large-aperture-ratio inner-focus telephoto zoom lens according to a third embodiment of the present invention, showing the position of each lens group in an infinity in-focus condition at the wide-angle end focal length. ing.

FIG. 16 is a diagram illustrating various aberrations of the third embodiment at a wide-angle end focal length in an infinity in-focus condition;

FIG. 17 is a diagram illustrating various aberrations of the third example in an intermediate focal length state and focused on infinity.

FIG. 18 is a diagram illustrating various aberrations of the third embodiment at a telephoto end focal length in an infinity in-focus condition;

FIG. 19 is a diagram illustrating various aberrations of the third example in the short-distance in-focus state at the wide-angle end focal length state.

FIG. 20 is a diagram illustrating various aberrations of the third example in the intermediate focal length state and in the close focusing state;

FIG. 21 is a diagram illustrating various aberrations of the third example in a state of focusing at a short distance in a telephoto end focal length state.

FIG. 22 is a schematic diagram schematically showing an AF drive mechanism configuration and a zoom mechanism configuration of a large-aperture-ratio inner-focus telephoto zoom lens according to each embodiment of the present invention.

[Explanation of symbols]

 G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G1F Front group in first lens group G1R Rear group in first lens group M Ring motor Z Zoom cam barrel F Focus cam barrel K fixing part R lens fixing cylinder

Claims (6)

[Claims] 1. A first lens group G1 having a positive refractive power and a second lens group G having a negative refractive power in order from the object side.
2, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power. The second lens group G2 and the third lens group G3 are arranged along the optical axis. In the telephoto zoom lens that performs zooming by moving, the first lens group G1 includes, in order from the object side, a front group G1F having a positive refractive power and a rear group having a positive refractive power stronger than the front group G1F. The rear group G1R in the first lens group G1 is composed of, in order from the object side, a meniscus negative lens having a convex surface facing the object side, and a positive lens component. The rear group G1R in the group G1 is moved along the optical axis to perform focusing, and the focal length of the front group G1F in the first lens group G1 is set to f.
1F, the focal length of the rear group G1R in the first lens group G1 is f1R, and the most image-side surface of the front group G1F and the most object-side surface of the rear group G1R in the in-focus state of an object at infinity. Where a distance along the optical axis between D1 and D1 satisfies the following condition: 0.005 <f1R / (f1F.D1) <0.055. 2. The focal length of the first lens group G1 is f1.
The focal length of the second lens group G2 is f2, the focal length of the fourth lens group G4 is f4, the combined focal length of the second lens group G2 and the third lens group G3 is f23, The focal length of the entire zoom lens system at the wide-angle end focal length state is FW, and the optical axis of the rear group G1R upon focusing from an object at infinity to an object at the shortest distance (7.5 times the focal length at the telephoto end) 0.04 <(| f23 | .FW) / (f1.f4..DELTA.D
1) <0.13 2 × 10 ⁻³ <| f2 | / (f1 · FW) <3.8 × 10
^3. The large-aperture-ratio inner-focus telephoto zoom lens according to claim 1, wherein the following condition is satisfied. 3. The front group G1F in the first lens group G1.
Is composed of, in order from the object side, a cemented positive lens of a meniscus negative lens having a convex surface facing the object side and a meniscus positive lens having a convex surface facing the object side, and a positive lens component. When the radius of curvature of the object-side surface of the cemented positive lens is R1, and the radius of curvature of the image-side surface of the cemented positive lens is R2,
The large-aperture-ratio inner-focus telephoto zoom lens according to claim 1, wherein the following condition is satisfied: 0 <(R2−R1) / (R2 + R1) <1. 4. The third lens group G3 includes, in order from the object side, a positive lens component and a cemented positive lens of a positive lens component and a negative lens component. When the refractive index of the lens component with respect to the d-line is Np3 and the Abbe number of the positive lens component constituting the third lens group G3 is νp3, the following condition is satisfied: 1.4 <Np3 <1.662 <νp3 <100 The large-aperture-ratio inner-focal telephoto zoom lens according to claim 1, wherein the zoom lens system satisfies the following conditions. 5. The rear group G1R in the first lens group G1.
The refractive index for the d-line of the positive lens component
p1, the Abbe number of the positive lens component constituting the rear group G1R is νp1, the refractive index for the d-line of the meniscus negative lens constituting the rear group G1R is Nn1, and the rear group G1R is constituted. 5. The condition of 0.25 <Nn1−Np1 <0.5565 <νp1 <100 20 <νn1 <30 when the Abbe number of the meniscus negative lens is νn1. 2. The large-aperture-ratio inner-focus telephoto zoom lens according to claim 1. 6. When zooming from the wide-angle end focal length state to the telephoto end focal length state, the second lens group G2 moves to the image side, and the third lens group G3 moves to the image side once and then moves to the object side. 6. The large-aperture-ratio internal focusing system according to claim 1, wherein the first lens group G <b> 1 and the fourth lens group G <b> 4 are fixed along the optical axis. 7. Telephoto zoom lens.