JPH06123836A - Zoom lens with vibration preventing function - Google Patents

Abstract

PURPOSE:To provide the telephoto zoom lens which is equipped with the vibration preventing function and is small-sized and high in performance. CONSTITUTION:This zoom lens has a 1st lens group G1 with positive refracting power, a 2nd lens group G2 with negative refracting power, a 3rd lens group G3 with negative refracting power, a 4th lens group G4 with positive refracting power, and a 5th lens group G5 with negative refracting power in order from the object side, and the lens groups are moved when the power is varied from the wide-angle end to the telephoto end so that the interval between the 1st lens group G1 and 2nd lens group G2 increases, the interval between the 2nd lens group G2 and 3rd lens group G3 varies linearly or nonlinearly, and the interval between the 4th lens group G4 and 5th lens group G5 decreases. In this zoom lens, the 3rd lens group G3 is provided with a displacing means for movement across the optical axis at right angles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-vibration method for a 35 mm photographic lens, particularly a telephoto zoom lens.

[0002]

2. Description of the Related Art Conventionally, any lens of a zoom lens composed of two or more lens groups as disclosed in JP-A-1-189621, JP-A-1-191112, and JP-A-1-191113. The correction is performed by displacing the optical axis across the optical axis for image stabilization in the group, and as described in Japanese Patent Laid-Open No. 1-284823, correction is performed by a part of the first lens group fixed during zooming. There was something to do.

[0003]

However, the above-mentioned conventional techniques have drawbacks such as insufficient back focus for a single-lens reflex camera and a large zoom ratio, and are not suitable for 35 mm photographs. It was not suitable for small and high-performance single-lens reflex lenses, especially for telephoto zoom lenses for 35mm photography.

Therefore, an object of the present invention is to provide a compact and high-performance telephoto zoom lens having a vibration isolation function.

[0005]

In order to solve the above problems, in the present invention, the first lens group G ₁ having a positive refractive power and the second lens having a negative refractive power are arranged in order from the object side. Group G ₂
And a third lens group G ₃ having a negative refractive power, a fourth lens group G ₄ having a positive refractive power, and a fifth lens group G ₅ having a negative refractive power, from the wide angle end. When changing the magnification to the telephoto end,
The distance between the first lens group G ₁ and the second lens group G ₂ increases,
The zoom lens in which the distance between the second lens group G ₂ and the third lens group G ₃ changes linearly or non-linearly, and the distance between the fourth lens group G ₄ and the fifth lens group G ₅ decreases so that the lens group moves. In the above, displacement means is provided for moving the third lens group G ₃ in a direction substantially orthogonal to the optical axis for vibration isolation.

[0006]

The present invention employs a zoom lens basically composed of five groups of positive, negative, negative, positive and negative so as to be suitable for a telephoto zoom lens for 35 mm size photographs. The features and advantages of this type of zoom lens will be briefly described below. INDUSTRIAL APPLICABILITY The present invention can achieve a telephoto zoom lens that makes full use of the characteristics of a multi-group structure of positive, negative, negative, positive, and negative, has excellent image-forming performance, and is applicable to high magnification. This type of zoom lens can reduce the overall length, especially at the wide-angle end. Further, because of the multi-group configuration, the degree of freedom of aberration correction including the degree of freedom of the movement of the lens groups is large, so that excellent imaging performance can be obtained even with a large zoom ratio. In particular, the zoom lens of the type such as the present invention, which has a short total length at the wide-angle end and extends when zooming to the telephoto end during zooming, is compared to a conventional telephoto zoom lens such as a 4-group afocal type. It is possible to reduce the total length at the wide-angle end and the weight of the entire zoom lens. Further, since the height of the light ray passing through each lens group at the wide-angle end also becomes small, the occurrence of aberration in each lens group becomes small, which is particularly advantageous when correcting aberrations on the wide-angle side. Furthermore, because the number of groups is large,
The degree of freedom in selecting the refractive power distribution is increased, and a sufficient back focus for a single-lens reflex camera can be easily obtained.

Generally, in a telephoto zoom lens, the first lens group is the largest lens group, and it is often extended during focusing. For this reason, it is not possible to use a correction optical system that displaces the first lens group with respect to the optical axis for image stabilization.
The holding mechanism and the drive mechanism are undesirably large in size. Therefore, it is not preferable that the positive / negative / negative / negative type in the present invention similarly uses the first lens group as an image stabilization optical system. Further, a lens group such as the fifth lens group of the present invention, which has a large amount of movement in the optical axis direction at the time of zooming, is not preferable because the mechanism becomes complicated.

However, the lens group near the aperture stop has a relatively small lens diameter because the bundles of light rays at each angle of view are densely gathered. Therefore, using a correction optical system that displaces such a group with respect to the optical axis is convenient for downsizing of the holding mechanism and the driving mechanism, and there is a difference in image quality change between the central portion and the peripheral portion in terms of aberration. The image position can be corrected without attaching it. In such a 5-group zoom type, it is advantageous in terms of aberration correction to place the aperture stop on the third lens group or the fourth lens group.

From the above, according to the present invention, in order to reduce the size of the entire lens system, the displacement means for performing image stabilization is provided in the third lens group, and the aperture stop is provided in order to prevent the mechanism of the third lens group from becoming complicated. It was provided in 4 lens groups. In order to simplify the image stabilization drive mechanism, it is preferable that the image stabilization correction is performed by moving the third lens group in a direction substantially orthogonal to the optical axis. Further, when the lens group is displaced across the optical axis for image stabilization, providing a fixed flare diaphragm on the optical axis in addition to the aperture diaphragm is more effective in blocking unnecessary light rays. .

Further, it is preferable that the following conditional expression is satisfied in the above structure. 0.3 <f ₁ / (f _W · f _T ) ^1/2 <1.5 (1) 0.3 <f ₂ / f ₃ <5 (2) 0.8 <| f ₃ | / f _W <2 (3) Formulas (1) to (3) will be described.

Conditional expression (1) is defined by the focal length f _W at the wide-angle end of the zoom lens, the focal length f _T at the telephoto end, and the first lens group G.
_An appropriate range is defined for the focal length f _{1 of 1} . If the upper limit of conditional expression (1) is exceeded, the overall length at the telephoto end becomes longer, which is against the compactness, and it is not preferable because the peripheral light amount at the telephoto end becomes insufficient and the front lens diameter increases. If the upper limit is set to 1.0 or less, the effect of the present invention can be more exerted. On the other hand, if the lower limit of conditional expression (1) is exceeded, the focal length f _{1 of} the first lens group G ₁ becomes too small, and spherical aberration at the telephoto end tends to be undercorrected, and the image surface during zooming due to zooming becomes large. The fluctuation of the curvature becomes enormous. Also,
The image forming magnification at the telephoto end by the lens system of the second lens group G _{2 and} thereafter becomes excessively large, and the axial chromatic aberration generated in the first lens group G ₁ is enlarged, so that good image forming performance can be obtained. I can't. In order to obtain a better imaging performance,
The lower limit is preferably 0.6 or more.

[0012] Condition (2) is a condition where any proportion of appropriate refractive power from the focal length f ₃ of the focal length f ₂ and the third lens group G ₃ of the second lens group G _2. If the upper limit of conditional expression (2) is exceeded, the focal length f _{3 of} the third lens group G ₃ becomes too short, the fluctuation of coma aberration during zooming due to zooming becomes large, and the distortion at the telephoto end becomes large on the negative side. Moving. Also,
Negative lower coma occurs at the wide-angle end, spherical aberration at the telephoto end tends to be overcorrected on the positive side, and good imaging performance cannot be obtained. Incidentally, if the upper limit is set to 3 or less, better imaging performance can be obtained. Conversely, if the lower limit of conditional expression (2) is exceeded, the second
Focal length of the lens group G ₂ f ₂ is too short, variations in coma upon zooming becomes large due to zooming, the distortion at the telephoto end is moved largely toward the positive side. In addition, positive lower coma occurs at the wide-angle end, and spherical aberration at the telephoto end tends to be overcorrected. Therefore, good imaging performance cannot be obtained.

Conditional expression (3) defines an appropriate ratio of the focal length f ₃ of the third lens group G ₃ to the focal length f _W of the entire system at the wide-angle end. When the upper limit of the conditional expression (3) is exceeded, the focal length f _{3 of} the third lens group G ₃ becomes too long. For example, in explaining the conditional expression, the fourth lens group G _{4 and} thereafter are fixed for convenience. Considering this state, it is difficult to secure sufficient back focus at the wide-angle end, and the field curvature and coma aberration during zooming due to zooming become too large, which is inconvenient. Further, since the third lens group G _{3 is used} for image stabilization, the amount of displacement across the optical axis becomes large, which is inconvenient because the mechanism tends to be large and complicated. On the other hand, if the lower limit of conditional expression (3) is exceeded, the focal length of the third lens group G ₃ becomes too short. For example, if it is considered that the fourth lens group G _{4 and} thereafter are in a constant state, This is inconvenient because the total length at the wide-angle end becomes long and the lens diameter of the fifth lens group G ₅ becomes large. Further, since the third lens group G ₃ is a vibration isolation group, the amount of displacement across the optical axis is small, which makes it difficult to control the position of the displacement, which is inconvenient.

Further, the third lens group G ₃ and the fourth lens group G ₃ at the wide-angle end.
When the distance from the lens group G ₄ is Dw _3-4 , it is desirable to satisfy the following conditions. 0.25 <Dw _3-4 / f _W <0.65 (4) For example, if the fifth lens group G ₅ is considered to be in a constant state for the sake of convenience, if the upper limit of conditional expression (4) is exceeded, spherical aberration and coma will be reduced. Aberration becomes very large, and its correction becomes difficult. In addition, the lens diameter of the fifth lens group G ₅ becomes large and the total length becomes long, which is inconvenient. On the other hand, when the value goes below the lower limit, it becomes difficult to secure a space required for zooming, which is not suitable for high magnification. Further, at the wide-angle end, outward coma occurs, which makes it difficult to secure the back focus, which is inconvenient.

Further, when the use magnification at the wide-angle end of the third lens group G ₃ is β _W3 and the use magnification at the telephoto end is β _T3 , −20 <β _T3 / β _W3 <10 (5) It is desirable to meet. If the range of conditional expression (5) is exceeded, fluctuations in various aberrations, especially fluctuations in field curvature, become excessive, which is inconvenient.

In order to obtain better performance, the average of the lenses constituting the third lens group G ₃ When the refractive index of each lens component forming the lens group G ₃ is n ₁ .... n _L and the refractive power (= reciprocal of focal length) is ψ ₁ .... ψ _L , Desired. It is desirable to satisfy. When the radius of curvature of the surface of the third lens group G ₃ closest to the object side is R ₃₁ , it is desirable that R ₃₁ > −200 (8) be satisfied.

[0017]

Each embodiment according to the present invention has a first lens group G ₁ having a positive refractive power, a second lens group G ₂ having a negative refractive power, and a negative refractive power in order from the object side. Third lens group G
_3, a fourth lens group G ₄ having a positive refractive power, and a fifth lens group G ₅ Metropolitan having negative refractive power.

During zooming from the wide-angle end to the telephoto end, the distance between the first lens group G ₁ and the second lens group G ₂ increases, and the distance between the second lens group G ₂ and the third lens group G ₃ increases. Changes linearly or non-linearly, the lens group moves so that the distance between the fourth lens group G ₄ and the fifth lens group G ₅ decreases, and the third lens group G ₃ moves in a direction substantially orthogonal to the optical axis. Displacement means is provided for vibration isolation.

Each embodiment according to the present invention will be described below. Example 1 FIG. 1 is a lens configuration diagram of Example 1,
From the object side, in order from the object side, a first lens group G ₁ consisting of a negative meniscus lens and a biconvex positive lens, a second lens group G ₂ of a cemented lens of a biconcave negative lens and a biconvex positive lens, and a biconcave negative lens. a third lens group G _3, biconvex lens, the fourth lens group G ₄ consisting of cemented lens of a double convex lens and a negative meniscus lens, a biconvex lens, and a fifth lens group G ₅ consisting of a biconcave lens .

Table 1 below lists values of specifications of the first embodiment of the present invention. In the specification table of the embodiment, f is the focal length, F _NO is the F number, and 2ω is the angle of view. The leftmost number represents the order from the object side, r is the radius of curvature of the lens surface, and d
Is the lens surface distance, the refractive index n and the Abbe number ν are d lines (λ = 5
87.6 nm).

[0021]

Table 1 Specifications of Example 1 f = 82 to 196 F _NO = 4.6 to 5.7 2ω = 29.66 to 12.16 ° (Variable spacing in zooming) f 82.0000 135.0000 196.0000 D0 ∞ ∞ ∞ d 4 2.1562 23.7506 39.4991 d 7 4.1898 2.7190 8.8577 d 9 24.9438 14.6750 2.8315 d14 22.0952 12.2404 2.1968 d18 43.0664 64.6608 80.4093 ( Condition corresponding values) f ₁ = 111.021, f _{W = 82, f T = 196 f} 2 = -145.113 f 3 = -75.564 D W3-4 = 24.9438 β W3 = -0.2444, β T3 = -1.8630 R 31 = -250.166 (Anti-vibration data) Wide-angle end Telephoto end Moving amount of the third lens group in the direction perpendicular to the optical axis (mm) 0.198 0.350 Moving amount of image (mm) 0.2 0.5 Figures 2 and 3 show the wide-angle end of Example 1, respectively. The various aberration diagrams of and the various aberration diagrams at the telephoto end state are shown. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in this example.

In each aberration diagram, FNO is shown as F number, Y as image height, and D as d line (λ = 587.6 nm). The solid line in the aberration diagram showing astigmatism indicates the sagittal image plane, and the broken line indicates the meridional image plane. Example 2 FIG. 4 is a lens configuration diagram of Example 2,
From the object side, in order from the object side, a first lens group G ₁ consisting of a negative meniscus lens and a biconvex positive lens, a second lens group G ₂ of a cemented lens of a biconcave negative lens and a biconvex positive lens, and a biconcave negative lens. The third lens group G ₃ of No. 4 and a biconvex positive lens, and a fourth lens including a cemented lens of a biconvex positive lens and a negative meniscus lens.
It is composed of a lens group G ₄ and a fifth lens group G ₅ including a cemented lens of a positive lens having a strong convex surface on the image side and a biconcave lens.

The second embodiment has substantially the same configuration as the first embodiment described above, but the refractive power and shape of each group are different. Table 2 below lists values of specifications of Example 2 of the present invention. In the specification table of the embodiment, f is the focal length, F _NO is the F number, and 2ω is the angle of view. The leftmost number represents the order from the object side, r is the radius of curvature of the lens surface, d is the lens surface spacing, refractive index n and Abbe number ν are d lines (λ = 587.6
nm).

[0024]

Table 2 Specifications of Example 2 f = 82 to 196 F _NO = 4.62 to 5.7 2ω = 29.24 to 12.08 ° (Variable interval during zooming) f 82.0000 135.0000 196.0000 D0 ∞ ∞ ∞ d 4 2.8064 24.7099 39.9550 d 7 2.9810 .5461 7.4257 d 9 24.5298 14.9373 2.7893 d14 23.3891 13.5130 3.5363 d17 40.6047 62.50817 77.7533 (Condition corresponding value) f ₁ = 107.913 _W = 82, f _T = 196 f ₂ = -179.085 f ₃ = -70.823 D _W3-4 = 24.5298 β _W3 = -0.4285, β _T3 = -3.4888 R ₃₁ = -300.511 (Anti-vibration data) Wide-angle end Telephoto end Moving amount (mm) in the direction perpendicular to the optical axis of the third lens unit 0.188 0.341 Image moving amount 0.2 0.5 FIGS. 5 and 6 show various aberrations at the wide-angle end in Example 2, respectively. The figure shows various aberration diagrams in the telephoto end state. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in this example.

In each aberration diagram, FNO is shown as F number, Y is shown as image height, and D is shown as d line (λ = 587.6 nm). The solid line in the aberration diagram showing astigmatism indicates the sagittal image plane, and the broken line indicates the meridional image plane.
In each of the embodiments, if the zooming range is sufficiently large and aberrations can be sufficiently corrected, the second lens group G ₂ may be fixed during zooming.

[0026]

According to the present invention, it is possible to provide a compact and high-performance telephoto zoom lens having an image stabilizing function.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram of a first embodiment according to the present invention.

FIG. 2 is an aberration diagram at a wide-angle end of Example 1 according to the present invention.

FIG. 3 is an aberration diagram at a telephoto limit of Embodiment 1 according to the present invention.

FIG. 4 is a lens configuration diagram of a second embodiment according to the present invention.

FIG. 5 is an aberration diagram at a wide-angle end of Example 2 according to the present invention.

FIG. 6 is an aberration diagram at a telephoto limit of Embodiment 2 according to the present invention.

[Explanation of symbols]

G ₁ · · · · first lens group G ₂ · · · · second lens group G ₃ · · · · the third lens group G ₄ · · · · fourth lens group G ₅ · · · · fifth lens group S ... Aperture

Claims (3)

[Claims] 1. A first lens having a positive refractive power in order from the object side.
Group G₁And the second lens group G having a negative refractive power₂When,
Third lens group G having negative refractive power₃And has a positive refractive power
4th lens group G_FourAnd the fifth lens group having negative refracting power
G_FiveAnd when changing the magnification from the wide-angle end to the telephoto end,
First lens group G₁And the second lens group G ₂The interval between
The second lens group G₂And the third lens group G₃Interval of
Changes linearly or non-linearly, and the fourth lens group G_Four
And the fifth lens group G_FiveThe lens so that the spacing of the
In the zoom lens in which the group moves, the third lens group G₃Move in a direction almost orthogonal to the optical axis
Displacement means is provided for vibration isolation.
Zoom lens with anti-vibration function. 2. The focal length of the first lens group G ₁ is f ₁ ,
The focal length of the second lens group G ₂ is f ₂ , and the third lens group G ₃
, F _{3 is} the focal length of the whole system at the wide-angle end, and f _{W is}
The zoom lens with an anti-vibration function according to claim 1, wherein the following condition is satisfied, where f _T is a focal length of the entire system at the telephoto end. 0.3 <f ₁ / (f _W · f _T ) ^1/2 <1.5 (1) 0.3 <f ₂ / f ₃ <5 (2) 0.8 <| f ₃ | / f _W <2 (3) 3. The third lens group G ₃ has a fixed flare stop on the optical axis when moving in a direction substantially orthogonal to the optical axis for image stabilization. Two
A zoom lens with the described anti-vibration function.