JP3536128B2 - Zoom lens with anti-vibration function - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens having an image stabilizing function, and more particularly to an internal focusing zoom lens having an image stabilizing function.

[0002]

2. Description of the Related Art A conventional zoom lens having an anti-vibration function is disclosed in JP-A-1-189621 and 1-1.
As disclosed in Japanese Patent Publication No. 91113, in a zoom lens composed of two or more lens groups, a zoom lens for correcting the image formation state by displacing the first lens group or the fourth lens group in a direction crossing the optical axis, As disclosed in JP-A-1-284823, there is disclosed a zoom lens which corrects an image formation state by displacing a part of lens groups in the first lens group, which are fixed during zooming operation, in a direction crossing the optical axis. Has been done. In this specification, moving all or some of the lens groups in a direction substantially orthogonal to the optical axis to correct a change in image position due to camera shake or the like is referred to as “anti-vibration”.

[0003]

However, the above-mentioned conventional techniques are supposed to be used for a small camera such as a so-called compact camera, and are used as a lens for a so-called single-lens reflex camera. There are the following inconveniences. First, if the structure of the conventional example is directly applied to a single-lens reflex lens, there is a disadvantage that the back focus generally required cannot be sufficiently secured. Furthermore, a large zoom ratio cannot be obtained with the zoom lens having the configuration shown in the conventional example. Therefore, there is an inconvenience that it is not possible to manufacture a zoom lens having a zoom ratio equivalent to that of a zoom lens commercially available as an interchangeable lens for a so-called single-lens reflex camera and having an image stabilizing function.

The present invention has been made in view of the above-mentioned problems, and can be applied as a lens for general photography while ensuring a required back focus and zoom ratio, and has an anti-vibration function and internal focusing. The objective is to provide a high-performance zoom lens that can also be used.

[0005]

In order to solve the above-mentioned problems, in the present invention, in order from the object side, at least a first lens group G1 having a positive refractive power and a second lens having a negative refractive power. It includes a group G2 and a third lens group G3 having a positive refractive power, and at the time of zooming from the wide-angle end to the telephoto end,
The distance between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 and the third lens group G
The distance between the second lens group G2 and the third lens group G2 changes, and the second lens group G2 has at least a negative refractive power in order from the object side.
1 and a lens group G22 having a negative refracting power, and a displacement means for moving the lens group G22 in the second lens group in a direction substantially orthogonal to the optical axis for vibration isolation. When the focal length of the two lens groups is f2 and the focal length of the lens group G22 in the second lens group is f22, the condition of 1.0 <f22 / f2 <5.0 is satisfied. Provided is a zoom lens having a vibration isolation function.

According to a preferred aspect 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 lens group G22 in the second lens group is f22, and the lens group G22 in the second lens group is When the magnitude of maximum displacement during vibration isolation is ΔSmax, the condition of ΔSmax / | f22 | <0.1 0.15 <| f2 | / f1 <0.5 is satisfied.

[0007]

The present invention is a zoom lens having an anti-vibration function that can be used in a general photographic camera, and has at least positive, negative, and positive refractive power lens units in order from the object side. Then, a part of the second lens group G2 (G
22) is provided with a vibration-proof function of a system in which the image forming position is appropriately changed in a direction perpendicular to the optical axis by moving 22) in a direction orthogonal to the optical axis to correct a change in the image forming state caused by camera shake or the like. There is. As described above, the zoom lens having a lens group having at least positive, negative, and positive refracting powers in order from the object side is widely used in the standard range and the telephoto range, and its imaging performance is at a sufficiently practical level. It is known to be in.

According to the present invention, as a method of the image stabilizing function of the zoom lens, the lens group or a part of the lens is moved by the image stabilizing displacement means in a direction substantially orthogonal to the optical axis to prevent the camera from shaking or vibrating. A method of correcting the variation of the image formation state caused by the method is adopted. In order to obtain a practical zoom lens by this method, it is important that the vibration-proof displacement means is small and mechanically simple. To that end, it is clear that it is preferable to perform image stabilization with a part of the lens groups rather than performing image stabilization with all the lens groups that make up the zoom lens, in order to reduce the size and simplification of the image stabilization mechanism. Is.

Therefore, in the present invention, the second lens group G
A part of the lens groups in 2, that is, the lens group G22 in the second lens group is a vibration isolation lens group (a lens group that moves in the direction orthogonal to the optical axis by the vibration isolation displacement means). With the lens configuration as described above, it is possible to minimize the aperture of the second lens group of the lens groups forming the zoom lens. Therefore, even if a vibration isolation function is added, the outer diameter (lens barrel diameter) of the lens does not increase, and it is advantageous for downsizing the zoom lens.

Each conditional expression of the present invention will be described below. The zoom lens of the present invention having the above-described configuration satisfies the following conditional expression (1). 1.0 <f22 / f2 <5.0 (1) where, f2: focal length of the second lens group G2 f22: focal length of the lens group G22 in the second lens group

Conditional expression (1) is the second lens unit for the image stabilizing lens group.
Regarding the focal length of the lens group G22 in the lens groups, the range of the appropriate focal length is set to the focal length f2 of the entire second lens group G2.
It is determined by the ratio with. If the upper limit of conditional expression (1) is exceeded, not only the refractive power of the lens group G22 in the second lens group becomes too weak, spherical aberration tends to become negative (-) too much, but also the Petzval sum is in the positive direction. It is not preferable because it is easy to change.

On the contrary, if the lower limit of conditional expression (1) is exceeded,
The refractive power of the lens group G22 in the second lens group becomes too strong, and the spherical aberration easily becomes positive (+) too much, and the Petzval sum easily shifts in the negative direction.
In either case, it is inconvenient to obtain excellent image forming characteristics. Further, since the chief ray passing through the first lens group G1 is largely separated from the optical axis, the aperture of the first lens group G1 is increased. Therefore, one of the objects of the present invention is
This is against the demand for smaller zoom lenses.
In order to obtain better imaging performance, conditional expression (1)
It is desirable that the lower limit value of the above is about 1.7 and the upper limit value of the conditional expression (1) is about 2.8.

In order to obtain a better imaging performance, it is preferable that the following conditional expressions (2) and (3) are satisfied in addition to the above-mentioned conditions. ΔSmax / | f22 | <0.1 (2) 0.15 <| f2 | / f1 <0.5 (3) where ΔSmax is the maximum of the lens group G22 in the second lens group during image stabilization. Magnitude of displacement f1: focal length of first lens group G1

Conditional expression (2) defines the amount of movement of the lens group G22 in the second lens group in the direction orthogonal to the optical axis during image stabilization. If the upper limit of conditional expression (2) is exceeded, the amount of movement of the lens group G22 in the second lens group during image stabilization will be large, and the amount of aberration fluctuation during image stabilization will be too large, and aberration correction will be sufficient. I can't do it. Especially at the peripheral position on the image plane, m (meridional)
This is inconvenient because the difference in the optical axis direction between the best image plane in the s-direction and the best image plane in the s (sagittal) direction widens. Furthermore, since the drive mechanism for image stabilization becomes large as the amount of movement of the lens group G22 in the second lens group during image stabilization increases, the zoom lens barrel becomes undesirably large. If the upper limit of conditional expression (2) is set to 0.05, it becomes possible to perform better aberration correction.

Further, the distribution of the refractive power between the first lens group G1 and the second lens group G2 is also important. Conditional expression (3) defines an appropriate range for the ratio between the focal length f1 of the first lens group G1 and the focal length f2 of the second lens group G2.
If the upper limit of conditional expression (3) is exceeded, the size of the focal length of the second lens group G2 becomes too large with respect to the focal length of the first lens group G1, and the spherical aberration becomes negative (-) excessive. Not only that, but also the Petzval sum easily shifts in the positive direction, so that good imaging performance cannot be obtained.

If the lower limit of conditional expression (3) is exceeded, the focal length of the second lens group G2 becomes too small with respect to the focal length of the first lens group G1, and the spherical aberration is positive (+).
In addition to being excessively large, the Petzval sum easily shifts in the negative direction, so that good imaging performance cannot be obtained. If the lower limit of conditional expression (3) is set to 0.2 and the upper limit of conditional expression (3) is set to 0.35, it becomes possible to perform better aberration correction.

Further, in order to construct an internally focused zoom lens, it is preferable that the following conditional expressions (4) and (5) are satisfied. 1.0 <f21 / f2 <5.0 (4) 0.06 <Δ / | f21 | <0.3 (5) where f21: focal length of lens group G21 in the second lens group Δ: wide angle The amount of movement of the lens group G21 in the second lens group on the optical axis when focusing from infinity to a close range at the edge

Conditional expression (4) shows that the range of the appropriate focal length of the lens group G21 in the second lens group G2 which is movable along the optical axis for internal focusing is the focal length of the entire second lens group G2. It is determined by the ratio with f2. When the value exceeds the upper limit of conditional expression (4), the refractive power of the lens group G21 in the second lens group becomes too weak, and the spherical aberration becomes negative (-) too large, and the Petzval sum is in the positive direction. It is inconvenient because it is easy to change to. Further, the amount of movement of the lens group G21 in the second lens group when focusing on a short distance tends to increase when a certain fixed shooting distance is considered. For this reason,
Aberration fluctuations, especially spherical aberration fluctuations, become too large,
Good imaging performance cannot be obtained.

On the contrary, if the lower limit of conditional expression (4) is exceeded,
The refractive power of the lens group G21 in the second lens group becomes too strong, spherical aberration tends to become excessively positive (+), the Petzval sum easily shifts to the negative direction, and both have excellent imaging characteristics. It is inconvenient to obtain. Furthermore, since the chief ray passing through the first lens group G1 is largely separated from the optical axis, the aperture of the first lens group G1 is increased, which violates the demand for downsizing of the zoom lens. Further, fluctuations in aberrations when focusing on a short distance, particularly fluctuations in field curvature, become too large, so that good imaging performance cannot be obtained. If the lower limit of conditional expression (4) is set to 1.7 and the upper limit of conditional expression (4) is set to 2.8, it is possible to perform better aberration correction.

Conditional expression (5) is obtained from infinity at the wide-angle end.
Lens group G in the second lens group during internal focusing to a close range
21 shows the ratio between the magnitude Δ of the amount of movement of 21 on the optical axis and the magnitude | f21 | of the focal length of the lens group G21 in the second lens group in an appropriate range. If the upper limit of conditional expression (5) is exceeded, the amount of movement of the lens group G21 in the second lens group on the optical axis becomes too large, and the drive mechanism for focusing tends to be complicated and large. , Is inconvenient.
Further, the fluctuation of the aberration at the time of internal focusing, especially the fluctuation of the spherical aberration becomes too large, so that good imaging performance cannot be obtained.

On the contrary, if the lower limit of conditional expression (5) is exceeded,
The amount of movement of the lens group G21 in the second lens group on the optical axis becomes too small, and the ability to focus at a short distance becomes insufficient, which makes it unsuitable for practical use. In addition, spherical aberration tends to increase toward the positive side, making aberration correction difficult.

In order to obtain better performance, it is desirable to satisfy the following conditional expressions (6) to (8). Here, r−: radius of curvature L of the image-side surface of the most object-side negative lens in the lens group G22 in the second lens group L: length along the optical axis of the lens group G22 in the second lens group fw: Focal length of entire lens system at wide-angle end φ22: Petzval sum of lens group G22 in the second lens group

If the range of conditional expression (6) is exceeded, it becomes difficult to correct lower coma and field curvature at the wide-angle end. Furthermore, it becomes difficult to correct spherical aberration at the telephoto end. In order to obtain further excellent imaging performance, it is preferable that the lower limit value of conditional expression (6) is about −20 and the upper limit value of conditional expression (6) is about +5.

If the condition (7) is not satisfied,
The total length (length along the optical axis from the surface closest to the object side to the surface closest to the image side) of the lens group G22 in the second lens group which is the image stabilizing group becomes too long, and the lens configuration becomes heavy This is inconvenient because the weight of the system increases and the structure of the anti-vibration mechanism becomes large and complicated.

Conditional expression (8) shows an appropriate range of Petzval sum of the lens group G22 in the second lens group which is the image stabilizing group. If the range of conditional expression (8) is exceeded, the curvature of the image plane becomes excessive during image stabilization, making it difficult to obtain good imaging performance over the entire screen.

When actually forming the lens group G22 in the second lens group which is the image stabilizing group, it is desirable that the following conditional expressions (9) and (10) are satisfied in addition to the above-mentioned conditions. 1.5 <N- (9) 45 <ν- (10) where N-: refractive index of the negative lens closest to the object side of the lens group G22 in the second lens group ν-: in the second lens group Abbe number of the negative lens closest to the object in the lens group G22

When the value goes below the lower limit of conditional expression (9), the spherical aberration at the telephoto end tends to be excessively positive, and the Petzval sum tends to shift to the negative side. As a result, good imaging performance cannot be obtained, which is inconvenient. Conditional expression (10)
If the value goes below the lower limit of, axial chromatic aberration will be excessive,
As a result, good imaging performance cannot be obtained, which is inconvenient.

Further, it is preferable to provide a flare stop other than the aperture stop in a state of being fixed with respect to the optical axis. This is because the lens group G22 in the second lens group is an anti-vibration lens group. Therefore, when the lens group G22 in the second lens group moves in a direction orthogonal to the optical axis, the lens group G22 moves away from the optical axis depending on the amount of movement. In addition, the light flux at the peripheral position may enter the third lens group G3 located on the rear side as an unnecessary light flux. Such unnecessary light causes, for example, ghost and unnecessary exposure. By providing the fixed flare stop, it is possible to prevent such harmful light from entering.

The position of the flare stop is not particularly limited, but unnecessary light can be most effectively eliminated by disposing the flare stop near the object side of the second lens group G2. Even if it is arranged at another position, it is sufficient if the unnecessary light at the image forming position can be effectively blocked. In the zoom lens according to the present invention, such a flare diaphragm is not an essential component, but has an effective function according to individual design conditions and the like. The second lens group G2 may be fixed or movable along the optical axis during zooming.

When actually constructing the zoom lens,
A three-group configuration including a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group having a positive refractive power is also possible (see the second embodiment). However, above 3
4th lens group G4 having positive refractive power is added to the basic structure of the lens group
It is clear from the first embodiment that, if the group configuration is adopted, a zoom lens having a large zoom ratio and a further excellent imaging performance can be obtained while satisfying the requirements of the present invention. In this way, even if an appropriate lens group is added to the basic configuration of the third lens group including the first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, and the third lens group having a positive refractive power, A zoom lens having the above performance can be easily obtained. Therefore, a zoom lens in which an appropriate lens group is added to the basic configuration of the third group is also included in the technical idea of the present invention.

The first lens group G1 preferably includes at least one biconvex lens and a concave lens. further,
The lens group G21 in the second lens group preferably has at least one concave lens and convex lens. Further, in order to obtain excellent close-range focusing performance, it is desirable that the lens group G21 in the second lens group has at least one cemented lens. The cemented lens is preferably composed of a convex lens having a refractive index of 1.6 or more and a concave lens having an Abbe number of 40 or more for d-line (λ = 587.6 nm).

By adopting an aspherical surface in the lens group G22 in the second lens group, which is the image stabilizing lens group of the present invention, it is possible to achieve even more excellent imaging performance. Further, by adopting an aspherical surface in the lens group G21 in the second lens group, it is possible to achieve further excellent short-distance focusing imaging performance. Furthermore, if the distance between the lens group G21 and the lens group G22 in the second lens group is changed slightly during zooming, the flatness of the image plane in the intermediate focal length state can be satisfactorily corrected. Image performance can be improved.

[0033]

EXAMPLES In each of the examples of the zoom lens having the image stabilizing function according to the present invention, the first lens group G1 having at least positive refractive power and the second lens group having negative refractive power are arranged in order from the object side. G2 and a third lens group G3 having a positive refractive power are provided, and the distance between the first lens group G1 and the second lens group G2 increases at the time of zooming from the wide-angle end to the telephoto end. The second lens group G2 and the third lens group G3
And the second lens group G2 has, in order from the object side, a lens group G21 having at least a negative refractive power.
And a lens unit G22 having a negative refracting power, and a displacement unit for moving the lens unit G22 in the second lens unit in a direction substantially orthogonal to the optical axis for vibration isolation.

Each embodiment of the present invention will be described below with reference to the accompanying drawings. Example 1 FIG. 1 is a diagram showing the configuration of a zoom lens according to Example 1 of the present invention. The zoom lens shown in the figure has, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a first lens group G1 including a biconvex lens and a positive meniscus lens having a convex surface facing the object side, and a concave surface facing the object side. From the cemented lens of the second lens group consisting of the cemented lens of the positive meniscus lens and the biconcave lens and the biconcave lens, and the cemented lens of the biconcave lens and the positive meniscus lens with the convex surface facing the object side, and the biconcave lens The second lens group G22 in the second lens group, the third lens group G3 including a biconvex lens, and a cemented lens of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and a convex surface facing the object side. Positive meniscus lens, positive meniscus lens with convex surface facing the object side, negative meniscus lens with convex surface facing the object side, biconvex lens and object And a fourth lens group G4 composed of a negative meniscus lens having a concave surface directed toward the.

The third lens group G3 and the fourth lens group G
An aperture stop S is provided between the first lens group 4 and the fourth lens group G4, and a flare stop FS is provided in the fourth lens group G4. FIG. 1 shows the positional relationship between the lens groups at the wide-angle end, which moves along the zoom orbit indicated by the arrow in the figure on the optical axis when the magnification is changed to the telephoto end. However, the first lens group G1 and the fourth lens group G
Reference numeral 4 is fixed in the optical axis direction during the variable power operation. Further, the lens group G22 in the second lens group is a vibration isolating mechanism 1 which is a displacement means.
Thus, the image is appropriately moved in a direction substantially orthogonal to the optical axis, and the image shake caused by the vibration of the zoom lens is corrected. In addition, when focusing on a near object, the second
The so-called internal focusing, in which the lens group G21 in the lens groups moves to the image side, is possible. Thus, Example 1
The present invention is applied to a bright telephoto zoom lens, and has a positive / negative / positive / four-group structure in which a positive / negative / positive three-group basic structure is added to a fourth lens group G4 having a positive refractive power.

The following table (1) lists the values of specifications of the first embodiment of the present invention. In Table (1), f is the focal length and F is
_NO represents the F number, 2ω represents the angle of view, and Bf represents the back focus. Further, the leftmost number is the order of the lens surfaces from the object side, r is the radius of curvature of each lens surface, d is the distance between the lens surfaces, and n (D) is the d line (λ = 587.6 nm).
N (G) is the g-line (λ = 435.8n
m is the refractive index, and ν is the Abbe number.

[0037]

[Table 1] (Variable distance for zooming and focusing) (Value corresponding to the condition) ΔSmax = 1.0 Δ = 13.060 r− = 40.4535 L = 10.7 fw = 81.499 (1) f22 / f2 = 2.095 (2) ΔSmax /|f22|=0.0152 ( 3) | f2 | /f1=0.256 (4) f21 / f2 = 2.1195 (5) Δ / | f21 | = 0.166 (6) r− / | f22 | = 0.614 (7) L / Fw = 0.131 (8) φ22 = -0.00992 mm ^-1 (9) N- = 1.51823 (10) ν- = 58.90

FIG. 2 and FIG. 3 are graphs showing various aberrations at the wide-angle end when focused on infinity and at the telephoto end when focused on infinity, respectively. 4 and 5 are graphs showing various aberrations at the wide-angle end at the close-up distance focus state (shooting magnification β = −0.074) and at the telephoto end on the close-up distance focus state (shooting magnification β = −0, respectively). 16) is a diagram showing various types of aberration. In each aberration diagram, F _NO indicates the F number, Y indicates the image height, and D indicates the d line (λ = 587.6 nm). Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, in the present example, it is understood that various aberrations are well corrected including in the case of image stabilization.

Example 2 FIG. 6 is a diagram showing the structure of a zoom lens according to Example 2 of the present invention. The illustrated zoom lens includes, in order from the object side, a first lens group G1 including a positive meniscus lens having a convex surface directed to the object side, and a cemented lens of a negative meniscus lens having a convex surface directed to the object side and a biconvex lens, A lens group G21 in the second lens group consisting of a cemented lens of a biconcave lens and a positive meniscus lens with a convex surface facing the object side, and a lens in the second lens group consisting of a negative meniscus lens with a concave surface facing the object side Group G22, a biconvex lens, and a cemented lens of a biconvex lens and a negative meniscus lens having a concave surface facing the object side,
The third lens group G3 includes a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a concave surface facing the object side, and a positive meniscus lens having a concave surface facing the object side.

An aperture stop S and a flare stop FS are provided in the third lens group G3 as shown in the figure. FIG. 6 shows the positional relationship of each lens group at the wide-angle end, and when the magnification is changed to the telephoto end, the lens units move on the optical axis along the zoom orbit indicated by the arrow in the figure. However, the second lens group G2 is fixed in the optical axis direction during the variable power operation. Also, the second
The lens group G22 in the lens groups is appropriately moved in a direction substantially orthogonal to the optical axis by the image stabilizing mechanism 1 which is a displacing means, and the image shake caused by the vibration of the zoom lens is corrected. Further, when focusing on a short-distance object, so-called internal focusing is possible in which the lens group G21 in the second lens group moves to the image side. As described above, the second embodiment also applies the present invention to the telephoto zoom lens, but unlike the first embodiment, has a positive / negative / positive three-group basic structure.

The following table (2) lists the values of specifications of the second embodiment of the present invention. In Table (2), f is the focal length, F
_NO represents the F number, 2ω represents the angle of view, and Bf represents the back focus. Further, the leftmost number is the order of the lens surfaces from the object side, r is the radius of curvature of each lens surface, d is the distance between the lens surfaces, and n (D) is the d line (λ = 587.6 nm).
N (G) is the g-line (λ = 435.8n
m is the refractive index, and ν is the Abbe number.

[0042]

[Table 2] f = 85.000 to 191 F _NO = 4.73 to 5.59 2ω = 28.96 ° to 12.66 ° (Variable distance for zooming and focusing) (Condition corresponding value) f1 = 119.099 f2 = −31.843 f21 = −66.102 f22 = −73.528 ΔSmax = 0.3 Δ = 8.637 r − = − 996.660 L = 1.0 fw = 85.500 (1) f22 / f2 = 2.309 (2) ΔSmax / | f22 | = 0.0041 (3) | f2 | /f1=0.268 (4) f21 / f2 = 2.309 (5) Δ / | f21 | = 0.130 (6) r− / | f22 | = −13.554 (7) L / fw = 0.012 (8) φ22 = −0.01225 mm ⁻¹ (9 ) N- = 1.65156 (10) ν- = 58.54

FIG. 7 and FIG. 8 are graphs showing various aberrations at the wide-angle end in the infinity in-focus condition and at the telephoto end in the infinity-in-focus condition, respectively. 9 and 10 are graphs showing various aberrations at the wide-angle end at the close-up distance focus state (shooting magnification β = −0.034) and at the telephoto end on the close-up distance focus state (shooting magnification β = −0, respectively). It is a various-aberration figure in (.072). In each aberration diagram, F _NO is the F number, Y is the image height, and D is the d line (λ = 587.6 nm).
Are shown respectively. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, in the present example, it is understood that various aberrations are well corrected including in the case of image stabilization.

In the above embodiment, the second lens group G
2 shows the configuration including the lens group G21 in the second lens group and the lens group G22 in the second lens group, the lens group G21 having a negative refractive power and the lens group G22 having a negative refractive power are shown. The second lens group G2 can also be configured by adding an appropriate lens group.

[0045]

As described above, according to the zoom lens of the present invention, it is possible to provide a compact and lightweight zoom lens capable of internal focusing, which is suitable for photography and video.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a zoom lens according to Example 1 of the present invention.

FIG. 2 is a diagram of various types of aberration in the in-focus state at infinity at the wide-angle end according to the first example of FIG.

FIG. 3 is a diagram of various types of aberration in the in-focus state at the telephoto end according to the first example of FIG. 1;

FIG. 4 is a diagram of various types of aberration in the closest-distance focusing state at the wide-angle end according to the first example of FIG. 1.

FIG. 5 is a diagram of various types of aberration in the closest distance focusing state at the telephoto end of the first example of FIG. 1.

FIG. 6 is a diagram showing a configuration of a zoom lens according to Example 2 of the present invention.

FIG. 7 is a diagram showing various types of aberration in the in-focus state at infinity at the wide-angle end according to the second example of FIG. 6;

FIG. 8 is a diagram of various types of aberration in the infinity in-focus state at the telephoto end according to the second example of FIG. 6;

FIG. 9 is a diagram of various types of aberration in the closest-distance focusing state at the wide-angle end according to the second example of FIG. 6;

FIG. 10 is a diagram of various types of aberration in the closest distance focus state at the telephoto end according to the second example of FIG. 6;

[Explanation of symbols]

G1 First lens group G2 Second lens group G21 Lens group G22 having negative refracting power closest to the object side in the second lens group G22 Anti-vibration lens group G3 Third lens having negative refracting power in the second lens group Group G4 4th lens group 1 Displacement means (anti-vibration mechanism) S Aperture stop FS Fixed flare stop

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-6-130330 (JP, A) JP-A-5-232410 (JP, A) JP-A-6-265827 (JP, A) JP-A-60- 57813 (JP, A) JP 61-62012 (JP, A) JP 6-250272 (JP, A) JP 6-95039 (JP, A) JP 6-123836 (JP, A) JP-A-2-93620 (JP, A) JP-A-2-103014 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02 -21/04 G02B 25/00-25/04

Claims (6)

(57) [Claims] 1. A first lens group G1 having at least a positive refractive power and a second lens group having a negative refractive power in order from the object side.
The lens group G2 and the third lens group G3 having a positive refractive power
And the first lens group G when zooming from the wide-angle end to the telephoto end.
1 and the second lens group G2 increase in distance,
The distance between the lens group G2 and the third lens group G3 changes, and the second lens group G2 includes, in order from the object side, a lens group G21 having at least a negative refractive power and a lens group G22 having a negative refractive power. And a displacement means for moving the lens group G22 in the second lens group in a direction substantially orthogonal to the optical axis for vibration isolation, and setting the focal length of the second lens group to f2, A zoom lens having an anti-vibration function, which satisfies the condition of 1.0 <f22 / f2 <5.0, where f22 is the focal length of the lens group G22 in the second lens group. 2. The focal length of the first lens group G1 is f1
And the focal length of the second lens group G2 is f2, and the focal length of the lens group G22 in the second lens group is f22.
And ΔSmax is the maximum displacement amount of the lens group G22 in the second lens group during vibration isolation, ΔSmax /|f22|<0.1 0.15 <| f2 | / f1 < The zoom lens according to claim 1, wherein the condition of 0.5 is satisfied. 3. A short distance object is focused by moving a lens group G21 in the second lens group along an optical axis, and a focal length of the second lens group G2 is f2, Two
The focal length of the lens group G21 in the lens group is f21,
Infinity at the wide-angle end of the lens group G21 in the second lens group
The amount of movement when focusing from a long distance to a very close distance
The zoom lens according to claim 1 or 2, wherein the following condition is satisfied: 1.0 <f21 / f2 <5.0 0.06 <Δ / | f21 | <0.3. 4. The focal length of the lens group G22 in the second lens group is f22, and the radius of curvature of the image-side surface of the most object-side negative lens in the lens group G22 in the second lens group is r. −, The length of the lens group G22 in the second lens group along the optical axis is L, the Petzval sum of the lens group G22 in the second lens group is φ22, and the focal point of the entire lens system at the wide-angle end is When the distance is fw, it is characterized in that the condition of −30 <r− / | f22 | <10 L / fw <0.5 −0.03 mm ⁻¹ <φ22 <−0.002 mm ⁻¹ is satisfied. The zoom lens according to any one of claims 1 to 3. 5. The refractive index of the most object-side negative lens in the lens group G22 in the second lens group is N-,
5. When the Abbe number of the negative lens closest to the object in the lens group G22 in the lens group is ν-, the condition of 1.5 <N- 45 <ν- is satisfied. The zoom lens according to any one of 1. 6. A fixed flare diaphragm is provided on the optical axis for blocking unnecessary light rays when the second lens group G22 moves in a direction substantially orthogonal to the optical axis for image stabilization. The zoom lens according to claim 1, wherein the zoom lens is a zoom lens.