JP2003090958A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens capable of realizing vibration-proof photographing while maintaining excellent optical performance. SOLUTION: This zoom lens is equipped with a 1st lens group G1 having positive refractive power, a 2nd lens group G2 having negative refractive power, a 3rd lens group G3 having positive refractive power, and a 4th lens group G4 having positive refractive power in order from an object side. In the zoom lens, power is varied by moving the 2nd and the 3rd lens groups G2 and G3 along an optical axis, and the 4th lens group G4 is constituted of a front group G4f having positive refractive power, a middle group G4m having negative refractive power and a rear group G4r having positive refractive power in order from the object side, then the middle group G4m is made eccentric in a perpendicular direction to the optical axis so as to displace an image forming position, whereby vibration-proof correction is performed and a specified condition is satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens which is suitable for a single-lens reflex camera, an electronic still camera and the like and which is capable of performing image stabilization.

[0002]

2. Description of the Related Art Conventionally, an optical system of this type has been disclosed in Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Laid-Open No. 234115 and Japanese Patent Laid-Open No. 9-325269, an optical system is used that corrects an image-forming position by decentering a part of a lens or a lens group perpendicularly to an optical axis. There is.

[0003]

However, in the optical system disclosed in JP-A-2-234115, in order to accurately control the entire master lens of the zoom lens perpendicularly to the optical axis, the drive actuator It is not practical because it cannot be enlarged. In addition, JP-A-2-23411
The optical system disclosed in Japanese Patent No. 5 does not mention the imaging performance. Further, since the optical system disclosed in Japanese Patent Laid-Open No. 9-325269 corrects the image stabilization with a part of the master lens, the drive actuator can be downsized and the aberration can be corrected well, but the FNO is 4 and the sports It was not suitable for use with photographs.

The present invention has been made in view of the above problems, and is a zoom lens capable of performing image stabilization photography while maintaining excellent optical performance, particularly a focal length at the telephoto end of 180 mm.
As described above, an object is to provide a large aperture ratio in-focus telephoto zoom lens having a zoom ratio of 2 or more and an FNO of 3 or less.

[0005]

[Means for Solving the Problems] In order to achieve the above object,
In the present invention, in order from the object side, the first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, the third lens group G3 having a positive refractive power, and the fourth lens group having a positive refractive power.
A lens group G4 is provided, and the second lens group G2 and the third lens group G3 are moved along the optical axis to perform zooming.
In the 4-group afocal zoom lens, the fourth lens group G4 includes, in order from the object side, a front group G having a positive refractive power.
4f, a middle group G4m having a negative refractive power, and a rear group G4r having a positive refractive power, the middle group G4m is decentered in a direction perpendicular to the optical axis to displace the image forming position, and the front group G4f includes one lens having positive refracting power and one lens having negative refracting power, the middle group G4m includes one lens having positive refracting power and two lenses having negative refracting power, and the rear group G4r includes , Including two lenses having positive refracting power and one lens having negative refracting power, the focal length of the fourth lens group G4 is F4, the front group G4f
Is F4f, and the focal length of the middle group G4m is F4.
m, where F4r is the focal length of the rear group G4r: 0.70 <| (F4 × F4m) / (F4f × F4r) |
Provided is a zoom lens which satisfies the condition of <1.20.

Further, in the zoom lens of the present invention, when the average refractive index at the d-line of the lenses constituting the fourth lens group G4 is Nd, 0.008 <F4 / (F4f × F4r × Nd) <0 .0
It is preferable that the condition 15 is satisfied.

In the zoom lens of the present invention, when the maximum effective diameter of the front group G4f is Φf and the maximum effective diameter of the middle group G4m is Φm, 0.40 <| (Φf × F4r) / (F4 × Φm) ｜ ＜
It is preferable to satisfy the condition of 0.80.

In the zoom lens of the present invention, the focal length at the telephoto end is Ft, and the focal length of the first lens group G1 is Ft.
1. When the combined focal length of the second lens group G2 and the third lens group G3 at the telephoto end focal length is F23t, 0.70 <| (Ft × F23t × F4m) / (F1 × F4
It is preferable to satisfy the condition of f × F4r) | <1.20.

In the zoom lens according to the present invention, the front group G4f is composed of two lenses having positive refractive power and one lens having negative refractive power, and the rear group G4r is composed of the lens 2 having positive refractive power.
It is preferable that it is composed of one lens and one lens of negative refractive power.

In the zoom lens according to the present invention, the first lens group G1 having the positive refractive power is composed of a front group G1f which is fixed in the optical axis direction with respect to the image plane and a rear group G1r which is movable. However, it is preferable to perform short-distance focusing by moving the rear group G1r in the optical axis direction.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the embodiment, the large-aperture-ratio in-focus telephoto zoom lens of the present invention includes, as shown in FIG. 1, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, in order from the object side. A third lens group G3 having a positive refracting power and a fourth lens group G4 having a positive refracting power,
In a four-group afocal zoom lens that performs zooming by moving the second lens group G2 and the third lens group G3 along the optical axis, the fourth lens group G4 includes positive refraction in order from the object side. A front group G4f having power, a middle group G4m having negative refracting power, and a rear group G4r having positive refracting power,
The middle group G4m is decentered in a direction perpendicular to the optical axis to displace the image forming position (hereinafter referred to as image stabilization). The front group G4f includes one lens having a positive refractive power and one having a negative refractive power. The middle group G4m includes one lens, one lens having positive refracting power and two lenses having negative refracting power, and the rear group G4r includes two lenses having positive refracting power and lens 1 having negative refracting power. The focal length of the fourth lens group G4 is F4, and the front group G4f is
Is F4f, and the focal length of the middle group G4m is F4.
m, where F4r is the focal length of the rear group G4r, the condition of 0.70 <| (F4 × F4m) / (F4f × F4r) | <1.20 (1) is satisfied.

If the upper limit of conditional expression (1) is exceeded, the flatness of the image plane is deteriorated, which is not preferable. When the value goes below the lower limit of conditional expression (1), the spherical aberration fluctuates significantly due to image stabilization, which is not preferable. Here, preferably, if the upper limit value is set to 1.10, a good balance between the outer diameter of the middle group G4m and the variation of spherical aberration due to image stabilization can be achieved. Further, preferably, if the lower limit value is set to 0.85, it is possible to achieve a good balance between the outer diameter of the middle group G4m and the variation of spherical aberration due to image stabilization.

Next, in order to obtain a good image stabilizing performance, 0.008 <F4 / (F4f × F4r × Nd), where Nd is the average refractive index of the lenses constituting the middle group G4m at the d-line. ) <0.015 (2) It is preferable to satisfy the condition.

If the upper limit of conditional expression (2) is exceeded, the deterioration of the image-forming performance due to image stabilization becomes large around the screen, which is not preferable. When falling below the lower limit of conditional expression (2), the middle group G4m
Is large, and the lens weight of the middle group G4m, which is the image stabilization lens group, is heavy, which is not preferable. Here, if the upper limit value is set to 0.012, it is possible to achieve a good balance between the deterioration of the imaging performance due to image stabilization and the weight of the image stabilization lens group. Further, preferably, if the lower limit value is set to 0.010, a good balance between deterioration of the imaging performance due to image stabilization and the weight of the image stabilization lens group can be achieved.

Next, the relationship between the lens outer diameter of the fourth lens group including the image stabilizing lens group and the lens group refracting power is as follows.
When the maximum effective diameter of 4f is Φf and the maximum effective diameter of the middle group G4m is Φm, the condition of 0.40 <| (Φf × F4r) / (F4 × Φm) | <0.80 (3) is satisfied. It is preferable to do.

If the upper limit of conditional expression (3) is exceeded, the distortion at the telephoto end focal length becomes positively large, which is not preferable. When the value goes below the lower limit of conditional expression (3), the telephoto ratio (telephoto ratio) of the entire fourth lens group becomes large, and the overall length of the entire optical system becomes long, which is not preferable. Furthermore, the outer diameter of the middle group G4m becomes large, and the lens weight of the middle group G4m, which is the image stabilization lens group, becomes heavy, which is also undesirable. Here, the upper limit is preferably 0.70. Further, the lower limit value is preferably 0.50.

Next, the favorable refractive power arrangement of each lens group will be shown.

The focal length at the telephoto end shooting is Ft,
The focal length of the lens group G1 is F1, and the second lens group G2 is
And the combined focal length of the third lens group G3 at the telephoto end shooting at F
In the case of 23t, it is preferable that the condition of 0.70 <| (Ft × F23t × F4m) / (F1 × F4f × F4r) | <1.20 (4) is satisfied.

If the upper limit of conditional expression (4) is exceeded, the effective diameter of each lens unit disposed closer to the image side than the second lens unit becomes large, and the lens barrel as a whole becomes thick, which is not preferable. In addition, the total length of the entire optical system becomes long, which is not preferable. When the value goes below the lower limit of the conditional expression (4), fluctuation of spherical aberration due to zooming becomes large, which is not preferable. Here, preferably, if the upper limit value is set to 1.00, the balance between the total length and thickness of the optical system and the aberration becomes good. Further, preferably, the lower limit value is 0.
When it is 90, the balance between the total length and thickness of the optical system and the aberration becomes good. (Example) Hereinafter, an example according to the embodiment of the present invention,
It will be described with reference to the accompanying drawings. In Examples, the large-aperture-ratio in-focus telephoto zoom lens of the present invention is shown in FIGS.
5, as shown in FIG. 22, in order from the object side, the first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, the third lens group G3 having a positive refractive power, and the positive refractive power. And a second lens group G4 having
2 and the third lens group G3 are moved along the optical axis to perform zooming, and the fourth lens group G4 has, in order from the object side, a front group G4f having a positive refractive power and a negative refractive power. It is configured by a middle group G4m and a rear group G4r having a positive refractive power, and the middle group G4m is decentered in the direction perpendicular to the optical axis to displace the image forming position to perform image stabilization.

The first lens group G1 having the positive refracting power is fixed in the optical axis direction with respect to the image plane I.
f and a movable rear group G1r, and the rear group G1r
Is moving in the direction of the optical axis for focusing at a short distance. (Embodiment 1) FIG. 1 is a diagram showing the structure of a large aperture ratio in-focus telephoto zoom lens according to the first embodiment of the present invention, showing the position of each lens group in the wide-angle end focal length and infinity in-focus condition. ing. The illustrated large aperture ratio in-focus telephoto zoom lens includes a meniscus negative lens L11 having a convex shape on the object side and a meniscus positive lens L1 having a convex shape on the object side in order from the object side.
The front lens group G1f of the first lens group G1 including a negative lens cemented to 2 and a meniscus positive lens L13 having a convex surface on the object side.
And a rear lens group G1r of the first lens group G1 including a convex meniscus negative lens L14 on the object side and a convex meniscus positive lens L15 on the object side, and a biconcave lens L21 having a strong concave surface on the image side. , Biconcave lens L22 and biconvex lens L2
A second lens group G2 including a positive lens cemented with 3 and a biconcave lens L24 having a strong concave surface facing the object side, a positive meniscus lens L31 having a concave shape on the object side, a biconvex lens L32, and a meniscus negative shape having a concave shape on the object side. The third lens group G3 including a cemented positive lens of the lens L33, the aperture stop S1, the meniscus negative lens L41 having a convex shape on the object side, and the biconvex lens L4.
2 is a positive lens cemented to the object side, a meniscus positive lens L43 having a convex shape on the object side, a front group G4f of a fourth lens group G4 including a field stop S2 with a large spacing, and a biconvex lens L44 and a biconcave lens L45. A middle lens group G4m including a negative lens and a biconcave lens L46, and a field stop S4.
3, a rear lens group G4r of a fourth lens group G4 including a cemented positive lens having a concave meniscus positive lens L47 on the object side, a biconvex lens L48, and a concave meniscus negative lens L49 on the object side.

Table 1 shows the values in the specifications table of the first embodiment of the present invention. In Table 1, F is the focal length of the entire lens system,
NO represents the F number, β represents the photographing magnification, Bf represents the back focus, and D0 represents the distance from the object to the object side surface of the lens L11 in the first lens group G1 (shooting distance). Furthermore, the leftmost number is the order of the lens surfaces from the object, r is the radius of curvature of each lens surface, d is the distance between the lens surfaces, and nd and ν are d lines (λ = 587.6).
(nm) and the Abbe number of the medium are shown, and the refractive index of air of 1.0000000 is omitted. Φf represents the maximum effective diameter of the front group G4f, and Φr represents the maximum effective diameter of the middle group G4m.

In the table, the values corresponding to the conditions are summarized in Table 5 for each of the examples.

The meanings of the above-mentioned symbols are the same in the tables of other embodiments.

The unit of the focal length, radius of curvature, surface spacing and other lengths in the specification table is generally "mm",
The optical system is not limited to this, because the same optical performance can be obtained even if the optical system is enlarged or reduced proportionally.

[0025]

[Table 1] F = 71.40 to 194.00 FNO = 2.9 rd ν νnd Φ 1) 136.2696 2.2000 46.58 1.804000 2) 65.9210 9.0000 82.52 1.497820 3) 184.6175 0.1000 4) 73.1041 8.9000 82.52 1.497820 5) 435.0246 (d5 = 6) 65.0851 1.8000 23.78 1.846660 7) 51.8175 1.9200 8) 63.2160 8.7000 60.09 1.640000 9) 1772.4929 (d9 = variable) 10) -1067.2040 1.9000 52.67 1.741000 11) 34.3923 6.8350 12) -61.8566 1.8000 70.41 1.487490 13) 39.4340 7.0000 25.43 1.43 14) -223.2401 1.8030 15) -64.5266 1.9000 39.59 1.804400 16) 872.3457 (d16 = variable) 17) -599.1428 3.9000 82.52 1.497820 18) -73.5485 0.2000 19) 93.8405 8.0000 82.52 1.497820 20) -48.5670 2.0000 52.67 1.741000 21) -149.5043 ( d21 = variable) 22> (aperture stop) 1.0000 23) 117.0055 2.0000 25.43 1.805180 Φf = 37.4 24) 44.6950 7.0000 55.52 1.696800 25) -325.3499 0.1000 26) 76.1777 3.5000 65.47 1.603000 27) 152.3247 19.0000 28) (field stop) 1.6216 29) 376.5966 3.8000 23.78 1.846660 Φm = 30.4 30) -57.8860 1.5000 52.67 1 .741000 31) 50.0430 3.9000 32) -246.5579 1.5000 52.67 1.741000 33) 102.2448 2.6784 34) (field diaphragm) 4.0000 35) -427.7771 4.0000 82.52 1.497820 36) -58.2736 0.1000 37) 68.1118 7.5000 52.67 1.741000 38) -60.1400 2.0000 23.78 1.846660 39 ) -641.0882 Bf (variable distance when focused) infinity F, β 71.4000 105.0000 194.0000 D0 ∞ ∞ ∞ d5 14.15950 14.15950 14.15950 d9 2.52314 17.06549 31.15139 d16 34.06279 25.29743 1.96176 d21 7.92945 2.15247 11.40223 Bf 66.21049, Bf 66.21049, Bf 66.21049. 0.06001 -0.08825 -0.16473 D0 1241.9566 1241.9566 1241.9566 d5 4.43994 4.43994 4.43994 d9 12.24271 26.78505 40.87095 d16 34.06279 25.29743 1.96176 d21 7.92945 2.15247 11.40223 Bf 66.21049 0.6. -0.374 -0.550 -1.026 Close range F, β -0.06001 -0.08825 -0.16473 G4m 0.324 0.477 0.890 Image plane -0.471 -0.693 -1.294 (Values corresponding to conditions) Lenses Ft 196.0000 F1 99.1163 F23t -56.8024 F4 110.8427 F4f 94.9170 F4m -46.9447 F4r 55.9165 Φf 37.4 Φm 30.4 nd1 1.84666 nd2 1.74100 nd3 1.74100 Nd 1.77622 Conditional expression (1) | F4 ・ F4m / (F4 0.98) | F4 / (F4f ・ F4r ・ Nd) 0.012 Conditional expression (3) | Φf ・ F4r / (F4 ・ Φm) | 0.62 Conditional expression (4) | Ft ・ F23t ・ F4m / (F1 ・ F4f ・ F4r) | 0.99 Second 4 to 4 are graphs showing various aberrations in the infinite state in which the focal lengths at the wide-angle end, the middle, and the telephoto end are arranged in this order, and FIGS.
FIG. 7 is a diagram of various aberrations in the in-focus state at the closest distance (R = 1500 mm) in the order of the wide-angle end, the middle, and the telephoto end focal length. As a result, it is apparent that the large aperture ratio in-focus telephoto zoom lens according to the present invention achieves very good imaging performance not only during normal use but also during image stabilization.

In each aberration diagram, Y is the image height, NA is the numerical aperture, d is the d line (λ = 587.6 nm), g is the g line (λ = 435.6 nm), and C is the C line. (Λ = 656.3
nm) and F indicates the F line (λ = 486.1 nm). In the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. Further, the aberration diagram showing the chromatic aberration of magnification is shown with reference to the d line.

The same applies to the aberration diagrams of the other examples. (Embodiment 2) FIG. 8 is a view showing the arrangement of a large aperture ratio in-focus telephoto zoom lens according to the second embodiment of the present invention, showing the positions of the respective lens groups in the wide-angle end focal length and infinity in-focus condition. ing. The illustrated large aperture ratio in-focus telephoto zoom lens includes a meniscus negative lens L11 having a convex shape on the object side and a meniscus positive lens L1 having a convex shape on the object side in order from the object side.
The front lens group G1f of the first lens group G1 including a negative lens cemented to 2 and a meniscus positive lens L13 having a convex surface on the object side.
And a rear lens group G1r of the first lens group G1 including a convex meniscus negative lens L14 on the object side and a convex meniscus positive lens L15 on the object side, and a biconcave lens L21 having a strong concave surface on the image side. , Biconcave lens L22 and biconvex lens L2
A second lens group G2 including a positive lens cemented with 3 and a biconcave lens L24 having a strong concave surface facing the object side, a positive meniscus lens L31 having a concave shape on the object side, a biconvex lens L32, and a meniscus negative shape having a concave shape on the object side. The third lens group G3 including a cemented positive lens of the lens L33, the aperture stop S1, the meniscus negative lens L41 having a convex shape on the object side, and the biconvex lens L4.
2 is a positive lens cemented to the object side, a meniscus positive lens L43 having a convex shape on the object side, a front group G4f of a fourth lens group G4 including a field stop S2 with a large spacing, and a biconvex lens L44 and a biconcave lens L45. A middle lens group G4m including a negative lens and a biconcave lens L46, and a field stop S4.
3, a biconvex lens L47, a biconvex lens L48, and a rear group G4r of a fourth lens group G4 including a cemented positive lens of a biconcave lens L49 having a strong concave surface facing the object side.

Table 2 shows the values of the specifications table of the second embodiment of the present invention.

[0029]

[Table 2] F = 71.40 to 194.00 FNO = 2.9 rd ν ν nd Φ 1) 126.3773 2.2000 46.58 1.804000 2) 65.7766 9.0000 82.52 1.497820 3) 159.5964 0.1000 4) 73.8770 8.9000 82.52 1.497820 5) 451.9658 (d5 = 6) 67.1317 1.8000 23.78 1.846660 7) 51.9368 1.9200 8) 60.7960 8.7000 60.09 1.640000 9) 1565.8593 (d9 = variable) 10) -1112.7902 1.9000 52.67 1.741000 11) 34.3494 6.8350 12) -62.3446 1.8000 70.41 1.487490 13) 38.8362 7.0000 25.43 1. 14) -193.0012 1.8030 15) -63.6864 1.9000 39.59 1.804400 16) 540.0800 (d16 = variable) 17) -1202.2321 3.9000 82.52 1.497820 18) -76.5701 0.2000 19) 90.1566 8.0000 82.52 1.497820 20) -48.0656 2.0000 52.67 1.741000 21) -122.4072 ( d21 = variable) 22> (aperture diaphragm) 1.0000 23) 129.6536 2.0000 25.43 1.805180 Φf = 36.53 24) 45.4526 7.0000 55.52 1.696800 25) -1801.6164 0.1000 26) 82.8502 3.5000 65.47 1.603000 27) 216.6834 16.0000 28) (field diaphragm) 4.5189 29) 335.1253 3.8000 23.78 1.846660 Φm = 30.10 30) -64.4592 1.5000 52.6 7 1.741000 31) 51.9884 3.9000 32) -251.8830 1.5000 52.32 1.754999 33) 110.1392 4.7734 34) (Field diaphragm) 4.0000 35) 201.3765 4.0000 47.10 1.623741 36) -72.0797 0.1000 37) 72.9037 7.5000 52.67 1.741000 38) -66.5189 2.0000 23.78 1.846660 39) 302.5105 Bf (Variable distance when focused) Infinity F, β 71.40000 105.00000 196.00000 D0 ∞ ∞ ∞ ∞ d5 13.31963 13.31963 13.31963 d9 2.58690 17.43453 31.12481 d16 33.75993 24.90255 1.83433 df21.30745 2.31703 11.69497 Bf 64.5353 -53. 0.08825 -0.16473 D0 1241.9624 1241.9624 1241.9624 d5 3.60012 3.60012 3.60012 d9 12.30641 27.15404 40.84432 d16 33.75993 24.90255 1.83433 d21 8.30728 2.31703 11.69497 Bf 64.53713 64.54015 64.0.344m 0.340000. -0.550 -1.026 Close range F, β -0.06003 -0.08827 -0.16478 G4m 0.342 0.502 0.939 Image plane -0.471 -0.693 -1.294 (Values corresponding to conditions) Len Specifications Ft 196.0000 F1 99.1163 F23t -64.4749 F4 121.2375 F4f 115.2040 F4m -49.5136 F4r 55.9165 Φf 36.6 Φm 30.1 nd1 1.84666 nd2 1.74100 nd3 1.75500 Nd 1.78089 Conditional expression (1) | F4 ・ F4F3f / r4 (4) / F4m / 4 (F4f / r4) (2) F4 / (F4f ・ F4r ・ Nd) 0.011 Conditional expression (3) | Φf ・ F4r / (F4 ・ Φm) | 0.56 Conditional expression (4) | Ft ・ F23t ・ F4m / (F1 ・ F4f ・ F4r) | 0.98 FIGS. 9 to 11 are various aberration diagrams in the infinite state in which the focal lengths at the wide-angle end, the middle, and the telephoto end are arranged in this order, and FIG.
FIG. 14 to FIG. 14 are graphs showing various aberrations in the in-focus state at the closest distance (R = 1500 mm) in the order of the wide-angle end, the middle, and the telephoto end focal length. As a result, the large aperture ratio in-focus telephoto zoom lens according to the present invention is
It is clear that a very good imaging performance is achieved even in the image stabilization. (Embodiment 3) FIG. 15 is a diagram showing the structure of a large aperture ratio in-focus telephoto zoom lens according to a third embodiment of the present invention, showing the positions of the respective lens groups in the wide-angle end focal length and infinity in-focus condition. ing. The illustrated large aperture ratio in-focus telephoto zoom lens includes a meniscus negative lens L11 having a convex shape on the object side and a meniscus positive lens L1 having a convex shape on the object side in order from the object side.
The front lens group G1f of the first lens group G1 including a negative lens cemented to 2 and a meniscus positive lens L13 having a convex surface on the object side.
A rear lens group G1r of the first lens group G1 including a convex meniscus negative lens L14 on the object side, a convex meniscus positive lens L15 on the object side, and a meniscus negative lens L21 on the object side. Concave lens L22 and biconvex lens L2
3, a second lens group G2 including a positive meniscus negative lens L24 having a concave shape on the object side, and an aperture stop S.
1. biconvex lens L31, third lens group G3 composed of cemented positive lens of biconvex lens L32 and biconcave lens L33, cemented positive lens of meniscus negative lens L41 convex on the object side and biconvex lens L42, object side A convex meniscus positive lens L43, a front group G4f of a fourth lens group G4 composed of a field stop S2 with a large spacing, and a biconvex lens L4.
4 and biconcave lens L45 cemented negative lens, biconcave lens L4
A rear group of a fourth lens group G4 composed of a middle group G4m of a fourth lens group G4 composed of 6 and a field stop S3, a biconvex lens L47, a biconvex lens L48 and a cemented positive lens of a meniscus negative lens L49 having a concave surface on the object side. It is composed of G4r.

Table 3 shows the values in the specifications table of the third embodiment of the present invention.

[0031]

[Table 3] F = 71.40 to 194.00 FNO = 2.9 rd ν nd Φ 1) 109.0944 2.2000 46.58 1.804000 2) 55.0918 10.0000 82.52 1.497820 3) 135.5123 0.1000 4) 65.5193 11.0000 82.52 1.497820 5) 878.5311 (d5 = 6) 59.8131 1.8000 23.78 1.846660 7) 47.9430 1.9200 8) 59.3584 8.7000 60.09 1.640000 9) 1206.2633 (d9 = variable) 10) 1053.7403 1.9000 52.67 1.741000 11) 31.2921 7.5000 12) -69.6566 1.8000 70.41 1.487490 13) 35.4608 7.0000 25.43 1.805180 14) ) -419.3723 2.5000 15) -56.2072 1.9000 39.59 1.804400 16) -2565.1581 (d16 = variable) 17> (aperture diaphragm) 3.0000 18) 687.5841 5.0000 69.98 1.518601 19) -74.6081 0.2000 20) 75.9721 8.0000 82.52 1.497820 21) -56.4588 2.0000 52.67 1.741000 22) 878.4289 (d22 = variable) 23) 113.7215 2.0000 25.43 1.805180 Φf = 38.8 24) 45.3259 7.0000 55.52 1.696800 25) -307.1976 0.1000 26) 75.0582 3.5000 65.47 1.603000 27) 156.8938 15.0000 28) (field diaphragm) 4.4821 29) 2411.5564 3.8000 23.78 1.846660 Φm = 28.8 30) -46.0408 1.5000 52.6 7 1.741000 31) 51.6170 3.9000 32) -331.9035 1.5000 48.04 1.716999 33) 88.9391 2.2442 34) (Field diaphragm) 3.8000 35) 814.4461 4.0000 82.52 1.497820 36) -65.2212 0.1000 37) 66.7128 7.5000 52.67 1.741000 38) -60.5069 2.0000 23.78 1.846660 39) -682.7106 Bf (variable distance when focused) Infinity F, β 71.40000 105.00000 196.00000 D0 ∞ ∞ ∞ d5 11.75253 11.75253 11.75253 d9 1.19540 12.93312 24.62715 d16 39.76191 30.17697 3.78764 d22 4.19534 2.04255 16.73787 Bf 73.81741 73,817. -0.08815 -0.16455 D0 1235.2254 1235.2254 1235.2254 d5 3.48889 3.48889 3.48889 d9 9.45904 21.19676 32.89078 d16 39.76191 30.17697 3.78763 d22 4.19534 2.04255 16.73787 Bf 73.81741 73.81741 73.81741 73.81741 73.81741 73.81741 73.81741 74.4000. 0.374 -0.550 -1.026 Close range F, β -0.06001 -0.08825 -0.16473 G4m 0.285 0.419 0.782 Image plane -0.472 -0.694 -1.296 (Values corresponding to conditions) Lens Original Ft 196.0000 F1 89.3190 F23t -47.3622 F4 105.1234 F4f 90.0000 F4m -44.5975 F4r 53.1207 Φf 38.8 Φm 29.8 nd1 1.84666 nd2 1.74100 nd3 1.71700 Nd 1.76822 Conditional expression (1) | F4 ・ F4m / (F4f8 ・ F4f8F4 ・ 8) ) F4 / (F4f ・ F4r ・ Nd) 0.012 Conditional expression (3) | Φf ・ F4r / (F4 ・ Φm) | 0.66 Conditional expression (4) | Ft ・ F23t ・ F4m / (F1 ・ F4f ・ F4r) | 0.97 No. FIGS. 16 to 18 are aberration charts in the infinity state in which the focal lengths at the wide-angle end, the middle, and the telephoto end are arranged in this order.
FIG. 9 to FIG. 21 are various aberration diagrams in the in-focus state at the close-up distance (R = 1500 mm) in the order of the wide-angle end, the middle, and the telephoto end focal length. As a result, it is apparent that the large aperture ratio in-focus telephoto zoom lens according to the present invention achieves very good imaging performance not only during normal use but also during image stabilization. (Embodiment 4) FIG. 22 is a diagram showing the structure of a large aperture ratio in-focus telephoto zoom lens according to a fourth embodiment of the present invention, showing the positions of the respective lens groups in the wide-angle end focal length and infinity in-focus condition. ing. The illustrated large aperture ratio in-focus telephoto zoom lens includes a meniscus negative lens L11 having a convex shape on the object side and a meniscus positive lens L1 having a convex shape on the object side in order from the object side.
The front lens group G1f of the first lens group G1 including a negative lens cemented to 2 and a meniscus positive lens L13 having a convex surface on the object side.
A rear lens group G1r of the first lens group G1 including a convex meniscus negative lens L14 on the object side and a convex positive meniscus lens L15 on the object side, and a biconcave lens L21 having a strong concave surface on the image side. , Biconcave lens L22 and biconvex lens L2
A second lens group G2 composed of a positive lens cemented with 3 and a negative meniscus negative lens L24 on the object side, a positive meniscus lens L31 concave on the object side, a biconvex lens L32 and a negative meniscus negative lens on the object side. A third lens group G3 including a cemented positive lens L33, an aperture stop S1, a meniscus negative lens L41 having a convex shape on the object side, and a biconvex lens L4.
2 cemented positive lens, a meniscus positive lens L43 having a convex shape on the object side, a front group G4f of a fourth lens group G4 composed of a field stop S2 with a large spacing, and a cemented biconvex lens L44 and biconcave lens L45. A middle lens group G4m including a negative lens and a biconcave lens L46, and a field stop S4.
3, a rear lens group G4r of a fourth lens group G4 including a positive meniscus lens L47 having a concave shape on the object side, a biconvex lens L48 and a cemented positive lens having a negative meniscus lens L49 having a concave surface shape on the object side.

Table 4 shows the values in the specifications table of the fourth embodiment of the present invention.

[0033]

[Table 4] F = 71.40 to 194.00 FNO = 2.9 rd ν nd Φ 1) 112.7919 2.2000 46.58 1.804000 2) 61.3912 10.0000 82.52 1.497820 3) 152.6280 0.1000 4) 70.7792 9.5000 82.52 1.497820 5) 490.0069 (d5 = 6) 65.8897 1.8000 23.78 1.846660 7) 50.2390 1.9200 8) 58.8118 8.7000 60.09 1.640000 9) 1374.5711 (d9 = variable) 10) -1062.4201 1.9000 52.67 1.741000 11) 31.8517 6.8350 12) -57.1143 1.8000 70.41 1.487490 13) 38.1561 7.0000 25.43 1.43 14) -212.6685 1.8030 15) -63.9088 1.9000 39.59 1.804400 16) -1030.2355 (d16 = variable) 17) -8754.5308 3.9000 82.52 1.497820 18) -95.7952 0.2000 19) 106.0199 8.0000 82.52 1.497820 20) -53.8938 2.0000 52.67 1.741000 21) -168.9201 (D21 = variable) 22> (aperture diaphragm) 1.0000 23) 108.4963 2.0000 25.43 1.805180 Φf = 37.4 24) 39.3588 7.0000 55.52 1.696800 25) -284.6682 0.1000 26) 72.8187 3.5000 46.54 1.804109 27) 112.6497 19.0000 28) (field diaphragm) 1.4631 29 ) 376.5966 3.8000 23.78 1.846660 Φm = 26.8 30) -57.8860 1.5000 52. 67 1.741000 31) 50.0430 3.9000 32) -246.5579 1.5000 52.67 1.741000 33) 102.2448 2.7087 34) (field diaphragm) 4.0000 35) -996.3581 4.0000 82.52 1.497820 36) -63.7397 0.1000 37) 68.7664 7.5000 52.67 1.741000 38) -63.3264 2.0000 23.78 1.846660 39 ) -580.2262 (Variable distance when focusing) Infinity F, β 71.40000 105.00000 196.00000 D0 ∞ ∞ ∞ d5 12.68549 12.68549 12.68549 d9 3.33478 15.78418 28.06737 d16 39.14669 29.08243 1.82331 β21 close to 66.5886 66, 5.78049 20.75642 Bf66 66.58866. -0.08833 -0.16487 D0 1235.4488 1235.4488 1235.4488 d5 3.55394 3.55394 3.55394 d9 12.46633 24.91574 37.19892 d16 39.14669 29.08243 1.82331 d21 8.16563 5.78049 20.75642 Bf 66.58874 0.60 0000 0000. 0.374 -0.550 -1.026 Close range F, β -0.06001 -0.08825 -0.16473 G4m 0.323 0.475 0.886 Image plane -0.472 -0.694 -1.295 (Values corresponding to conditions) Lens Former Ft 196.0000 F1 94.0200 F23t -50.7126 F4 105.7238 F4f 90.0000 F4m -46.9447 F4r 55.9165 Φf 36.4 Φm 30.4 nd1 1.84666 nd2 1.74100 nd3 1.74100 Nd 1.77622 Conditional formula (1) | F4 ・ F4m / (F4f ・ F4f0.99) ) F4 / (F4f ・ F4r ・ Nd) 0.012 Conditional expression (3) | Φf ・ F4r / (F4 ・ Φm) | 0.63 Conditional expression (4) | Ft ・ F23t ・ F4m / (F1 ・ F4f ・ F4r) | 0.99 23 to 25 are various aberration diagrams in the infinite state in which the focal lengths at the wide-angle end, the middle, and the telephoto end are arranged in this order, and FIG.
FIGS. 6 to 28 are various aberration diagrams in the in-focus state at the close-up distance (R = 1500 mm) in the order of the wide-angle end, the middle, and the telephoto end focal length. As a result, it is apparent that the large aperture ratio in-focus telephoto zoom lens according to the present invention achieves very good imaging performance not only during normal use but also during image stabilization.

In the above-described embodiment, if the size of the lens barrel in the outer diameter direction is increased, it is possible to perform image stabilization with the front group G4f of the fourth lens group G4.

[0035]

As described above, according to the zoom lens of the present invention, it is possible to perform vibration-proof shooting while maintaining excellent optical performance. Further, according to the zoom lens of the present invention, excellent image forming performance can be maintained from the infinity state to the close-range in-focus state. Further, according to the zoom lens of the present invention, since the focusing lens group, the variable power lens group, and the anti-vibration lens group are independent, a simple mechanical structure can be obtained.
It is possible to have a structure that is resistant to vibration and impact due to dropping.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a large aperture ratio in-focus telephoto zoom lens according to Example 1 of the present invention.

FIG. 2 is a diagram of various types of aberration in the wide-angle end focal length and infinity in-focus state according to the first embodiment of the present invention.

FIG. 3 is a diagram of various types of aberration in the first embodiment of the present invention when focused on an intermediate focal length and at infinity.

FIG. 4 is a diagram of various types of aberration in the telephoto end focal length and the infinity in-focus state according to the first embodiment of the present invention.

FIG. 5 is a diagram showing various aberrations of the first embodiment of the present invention at the wide-angle end focal length and in the closest focusing state.

FIG. 6 is a diagram of various types of aberration in the first embodiment of the present invention at the intermediate focal length and in the closest focusing state.

FIG. 7 is a diagram showing various aberrations of the first embodiment of the present invention at the telephoto end focal length and in a close-up in-focus state.

FIG. 8 is a diagram showing a configuration of a large aperture ratio in-focus telephoto zoom lens according to Example 2 of the present invention.

FIG. 9 is a diagram showing various aberrations of the second embodiment of the present invention at the wide-angle end focal length and in focus at infinity.

FIG. 10 is a diagram of various types of aberration in the second embodiment of the present invention when focused on an intermediate focal length and at infinity.

FIG. 11 is a diagram of various types of aberration in the telephoto end focal length and the infinity in-focus state of the second embodiment of the present invention.

FIG. 12 is a diagram showing various aberrations of the second embodiment of the present invention at the wide-angle end focal length and in the closest focusing state.

FIG. 13 is a diagram of various types of aberration in the second embodiment of the present invention at the intermediate focal length and in the closest focusing state.

FIG. 14 is a diagram of various types of aberration in the telephoto end focal length and the closest focusing state according to the second example of the present invention.

FIG. 15 is a diagram showing a configuration of a large aperture ratio in-focus telephoto zoom lens according to Example 3 of the present invention.

FIG. 16 is a diagram of various types of aberration of the third embodiment of the present invention at the wide-angle end focal length and infinity.

FIG. 17 is a diagram of various types of aberration in the third embodiment of the present invention with an intermediate focal length and infinity in focus.

FIG. 18 is a diagram of various types of aberration in the telephoto end focal length and the infinity in-focus state according to the third embodiment of the present invention.

FIG. 19 is a diagram showing various aberrations of the third embodiment of the present invention at the wide-angle end focal length and in the closest focusing state.

FIG. 20 is a diagram of various types of aberration in the third embodiment of the present invention at the intermediate focal length and in the closest focusing state.

FIG. 21 is a diagram of various types of aberration in the telephoto end focal length and the closest focusing state according to the third example of the present invention.

FIG. 22 is a diagram showing a configuration diagram of a large aperture ratio in-focus telephoto zoom lens according to Example 4 of the present invention.

FIG. 23 is a diagram of various types of aberration of the fourth embodiment of the present invention at the wide-angle end focal length and infinity.

FIG. 24 is a diagram of various types of aberration in the fourth embodiment of the present invention with an intermediate focal length and infinity in focus.

FIG. 25 is a diagram of various types of aberration in the fourth embodiment of the present invention at the telephoto end focal length and infinity in focus.

FIG. 26 is a diagram of various types of aberration of the fourth embodiment of the present invention at the wide-angle end focal length and in the closest focusing state.

FIG. 27 is a diagram of various types of aberration in the fourth embodiment of the present invention at the intermediate focal length and in the closest focusing state.

FIG. 28 is a diagram of various types of aberration in the fourth embodiment of the present invention at the telephoto end focal length and in the closest focusing state.

[Explanation of symbols]

G1 first lens group G2 Second lens group G3 Third lens group G4 4th lens group G1f Front group of the first lens group G1r Rear group of first lens group G4f Front group of fourth lens group G4m Middle group of 4th lens group G4r Rear group of 4th lens group S1 aperture stop S2 Field stop S3 Field stop I image plane

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H087 KA02 KA03 MA18 NA07 PA15                       PA16 PB20 QA02 QA06 QA07                       QA17 QA21 QA25 QA37 QA39                       QA41 QA45 RA31 RA32 SA23                       SA27 SA29 SA32 SA63 SA64                       SA72 SA75 SB06 SB15 SB24                       SB31

Claims (6)

[Claims] 1. 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, and a fourth lens group having a positive refractive power in order from the object side.
A lens group G4 is provided, and the second lens group G2 and the third lens group G3 are moved along the optical axis to perform zooming.
In the 4-group afocal zoom lens, the fourth lens group G4 is composed of, in order from the object side, a front group G4f having a positive refractive power, a middle group G4m having a negative refractive power, and a rear group G4r having a positive refractive power. A configuration in which the middle group G4m is decentered in a direction perpendicular to the optical axis to displace the image forming position, and the front group G4f includes one lens having a positive refracting power and one lens having a negative refracting power, The middle group G4m includes one lens having positive refracting power and two lenses having negative refracting power, and the rear group G4r includes two lenses having positive refracting power and one lens having negative refracting power, and the fourth group The focal length of the lens group G4 is F4, and the front group G4 is
The focal length of f is F4f, and the focal length of the middle group G4m is F4.
The zoom lens is characterized by satisfying the following conditions when the focal length of the rear group G4r is 4 m and F4r. 0.70 <| (F4 × F4m) / (F4f × F4r) |
<1.20 2. The zoom lens according to claim 1, wherein the following conditions are satisfied when the average refractive index at the d-line of the lenses constituting the fourth lens group G4 is Nd. 0.008 <F4 / (F4f × F4r × Nd) <0.0
15 3. The zoom according to claim 1, wherein the following conditions are satisfied when the maximum effective diameter of the front group G4f is Φf and the maximum effective diameter of the middle group G4m is Φm. lens. 0.40 <| (Φf × F4r) / (F4 × Φm) | <
0.80 4. The telephoto end focal length is Ft, the focal length of the first lens group G1 is F1, and the combined focal length of the second lens group G2 and the third lens group G3 at the telephoto end focal length is F23.
The zoom lens according to claim 1, wherein the following condition is satisfied when t is set. 0.70 <| (Ft × F23t × F4m) / (F1 × F4
f × F4r) | <1.20 5. The front group G4f is composed of two lenses having positive refractive power and one lens having negative refractive power, and the rear group G4r is
5. The zoom lens according to claim 1, comprising two lenses having positive refracting power and one lens having negative refracting power. 6. A first lens group G1 having the positive refractive power.
Is composed of a front group G1f which is fixed in the optical axis direction with respect to the image plane and a rear group G1r which is movable. The rear group G1r moves in the optical axis direction to perform short-distance focusing. The zoom lens according to claim 1, wherein the zoom lens is a zoom lens.