JP2002357770A - Zoom lens and optical equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens having a high optical performance in the whole power variation range, having a comparatively short back focus, and whose optical whole length is short and having a high variation range up to power variation ratio of 4 to 5, and to provide optical equipment using the zoom lens. SOLUTION: The zoom lens is provided with 1st, 2nd and 3rd lens groups (L1 to L3) having positive, positive and negative refractive power, respectively, in this order from an object side, and the power is varied by moving the lens groups so that an axial air distance between the 1st lens group L1 and the 2nd lens group L2 may become longer at a telephoto end as compared with a wide angle end and an axial air distance between the 2nd lens group 2 and the 3rd lens group L3 may become shorter. In this case, the 2nd lens group L2 is composed of a 21st lens group L21 constituted of a bi-concave negative lens and a positive lens and a 22nd focusing lens group L22 in this order from the object side, and the focal distance of the 1st lens group L1, the focal distance of the 3rd lens group L3 and the focal distance of the whole system at the wide angle end and the telephoto end are appropriately set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens and an optical apparatus using the same, and more particularly to a zoom lens having a relatively short back focus (optical apparatus) such as a lens shutter camera, a video camera, and a digital camera. The present invention relates to a zoom lens having optical performance and an optical device using the same.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of optical devices such as lens shutter cameras, video cameras, and digital cameras,
There is a demand for a small zoom lens having a high zoom ratio and a short overall lens length as a photographing lens used therefor.

As a means for realizing miniaturization of a taking lens, a so-called positive lead type zoom lens, which is preceded by a lens group having a positive refractive power, is often used. A major feature of this type is that the back focus can be shortened, and it is particularly effective for a lens shutter camera which does not require a space for disposing a quick return mirror behind a lens system like a single-lens reflex camera.

As a positive lead type zoom lens having a short back focus, the zoom lens includes a first lens unit having a positive refractive power and a second lens unit having a negative refractive power. There is a two-group zoom lens. Although this zoom lens has a simple mechanical configuration, since there are only two lens groups and the degree of freedom is small, chromatic aberration fluctuations increase when trying to increase the zoom ratio. It becomes difficult. For this reason, in order to achieve both miniaturization and high optical performance in the positive / negative two-unit zoom lens, the zoom ratio is limited to about 3 to 3.5.

[0005] Therefore, in order to achieve a zoom lens having a zoom ratio of about 4 to 5, it is necessary to have three or more lens groups in which a positive and negative two-group zoom is further added and a lens group is further added.

The back focus is relatively shorter than before,
Further, as a zoom lens suitable for high zoom ratio, a three-unit zoom lens including lens units having positive, positive, and negative refractive powers has been proposed.

There have also been proposed various four-unit zoom lenses in which a three-unit zoom lens is added with a lens unit having relatively low refractive power.

The applicant of the present invention has disclosed Japanese Patent Application Laid-Open Nos. 6-214157, 6-214158 and 6-222.
267, JP-A-6-250087, JP-A-6-250088, JP-A-6-294932, JP-A-6-294932 and the like propose a three-group zoom lens and a four-group zoom lens. I have. Each of these proposed zoom lenses is a four-unit zoom lens composed of lens units having positive, positive or negative, positive, and negative refractive power in order from the object side, or a lens group having positive, positive, and negative refractive power. Consisting of 3
This is a group zoom lens.

In addition, a four-unit zoom lens composed of lens units having positive, negative, positive, and negative refractive powers in order from the object side is disclosed in Japanese Patent Publication No. 1-180180, Japanese Patent Laid-Open No. 10-301027, USP (US Patent) 4822152, USP52
72566, USP 5172273, USP 51702
92.

[0010]

In general, in order to increase the zoom ratio while reducing the size of the zoom lens, for example, the refractive power of each lens unit is increased and the moving distance of each lens unit for zooming is increased. There is a way to make it happen.

However, if the refractive power of the lens units is simply increased and the amount of movement of each lens unit for zooming is increased, aberration fluctuations accompanying zooming increase, and good optical performance is obtained over the entire zooming range. It becomes difficult.

According to the present invention, by appropriately setting the lens configuration of each lens group, it is possible to easily achieve a high zoom ratio, and to satisfactorily correct aberrations that fluctuate with zooming, thereby improving the optics over the entire zoom range. It is an object of the present invention to provide a high-performance zoom lens and an optical device using the same.

[0013]

According to a first aspect of the present invention, there is provided a zoom lens having a first lens unit having a positive refractive power, a second lens unit, a third lens unit, and a negative refractive power. A fourth lens unit having a large power, a large air gap between the first lens unit and the second lens unit at the telephoto end with respect to the wide-angle end, and a large air gap between the third lens unit and the fourth lens unit. The second lens group has, in order from the object side, a negative lens and a positive lens, both lens surfaces of which are concave, and performs focusing by moving the third lens group. Do
The focal lengths of the first lens group and the third lens group are f1,
When f4 and the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and ft, 0.2 <f1 / ft <0.5-0.2 <| f4 / ft | <-0.053 0.7 <ft / fw <6.0.

According to a second aspect of the present invention, in the first aspect of the present invention, the radii of curvature of the object-side and the image-side lens surfaces of the negative lens closest to the object side of the second lens unit are set to R21n1, R2
1n2, the radius of curvature of the object-side and image-surface-side lens surfaces of the most object-side positive lens of the second lens group is R21p1,
When R21p2, -1 <(R21n1 + R21n2) / (R21n1-R2
1n2) <1 0.5 <(R21p1-R21p2) / (R21p1 + R
21p2) <8.

According to a third aspect of the present invention, when the Abbe numbers of the materials of the negative lens and the positive lens of the second lens group are ν21n and ν21p, respectively, 20 <ν21n−ν21p <40. It is characterized by satisfying certain conditions.

According to a fourth aspect of the present invention, there is provided a zoom lens having a first lens unit having a positive refractive power, a second lens unit, a third lens unit, and a fourth lens unit having a negative refractive power. And a lens unit such that the axial air gap between the first lens group and the second lens group is large at the telephoto end with respect to the wide-angle end, and the axial air gap between the third lens group and the fourth lens group is small. The third lens group includes, in order from the object side, a negative meniscus lens having a concave surface facing the object side, and a positive meniscus lens having a convex surface facing the image surface side, and moves the third lens group. When focusing is performed, the focal lengths of the first lens unit and the fourth lens unit are respectively f1 and f4, and the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and ft. f1 / ft <0.5-0.2 <| f4 / ft | <-0.053 7 <is characterized by satisfying the ft / fw <6.0 The condition.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the radius of curvature of the object-side and image-side lens surfaces of the most object side negative meniscus lens in the third lens group is set to R31.
When n1 and R31n2, -1 <(R31n1-R31n2) / (R31n1 + R3
1n2) <0.

According to a sixth aspect of the present invention, in the first aspect of the present invention, a stop is provided between the second lens group and the third lens group, and the stop and the third lens are provided at a telephoto end. When the on-axis air interval of the group is Lp and the focal length of the entire system at the telephoto end is ft, the condition 0.02 <Lpa / ft <0.1 is satisfied.

According to a seventh aspect of the present invention, when the focal length of the second lens group is f2 and the focal length of the entire system at the telephoto end is ft, 0 < | Ft / f2 | <0.5.

In the zoom lens according to the present invention, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens group having a positive refractive power are arranged in order from the object side.
A lens group, and a fourth lens group having a negative refractive power,
At the telephoto end, the lens groups are moved such that the axial air gap between the first lens group and the second lens group is larger and the axial air gap between the third lens group and the fourth lens group is smaller at the telephoto end. The third lens group includes a negative meniscus lens having a concave surface facing the object side and a positive meniscus lens having a convex surface facing the image surface in order from the object side. When focusing is performed and the focal lengths of the first and fourth lens groups are f1 and f4, respectively, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and ft, respectively, 0.2 <f1 / ft <0.5−0.2 <| f4 / ft | <−0.05 3.7 <ft / fw <6.0 The condition is satisfied.

According to a ninth aspect of the present invention, there is provided a zoom lens having, in order from the object side, a first lens group having a positive refractive power, a second lens group having a stop, and a third lens group having a positive refractive power. A fourth lens unit having a negative refractive power, a large axial air gap between the first and second groups at the telephoto end with respect to the wide-angle end, and a large axial air gap between the third and fourth groups. The third lens group has, in order from the object side, a negative lens and a positive lens, and the focal length of the first lens group and the fourth lens group is changed. F1, f4, the focal length of the entire system at the telephoto end is ft, the Abbe number of the material of the negative lens closest to the object in the third lens group is ν3n, and the Abbe number of the material of the positive lens closest to the object in the third lens group. The number is ν3p
Where 0.2 <f1 / ft <0.5-0.2 <| f4 / ft | <-0.05 3.7 <ft / fw <6.020 <ν3p−ν3n <50 Is satisfied.

According to a tenth aspect of the present invention, when the focal length of the second lens group is f2 and the focal length of the entire system at the telephoto end is ft, 0 <| ft / f2 | <0.5 (11b) The following condition is satisfied.

The invention of claim 11 is the invention of claim 8, 9 or 10.
In the third aspect of the present invention, the third lens group is characterized in that the third lens group has an aspheric surface whose positive refractive power decreases from the center of the lens to the periphery of the lens.

According to a twelfth aspect of the present invention, in the eighth, ninth, tenth or eleventh aspect, a stop is provided between the second lens unit and the third lens unit, and the stop at the telephoto end and the third lens unit are provided. Where Lp is the on-axis air spacing and ft is the focal length of the entire system at the telephoto end, the following condition is satisfied: 0.02 <Lp / ft <0.1 (12b).

According to a thirteenth aspect of the present invention, in the invention according to any one of the eighth to twelfth aspects, the first lens group is a negative meniscus lens having a concave surface facing the object side in order from the object side;
It is characterized in that both lens surfaces are composed of convex positive lenses.

According to a fourteenth aspect of the present invention, in any one of the eighth to thirteenth aspects, the fourth lens group includes a positive lens, a negative lens, and a negative lens in order from the object side.

According to the fifteenth aspect of the present invention, there is provided an optical apparatus according to the first aspect.
Wherein the zoom lens according to any one of the above items 1 to 14 is provided.

[0028]

FIG. 1 is a lens sectional view of a numerical example 1 of the present invention described later. 2 and 3 are aberration diagrams at the wide-angle end and at the telephoto end in Numerical Embodiment 1 of the present invention.

FIG. 4 is a sectional view of a lens according to a second numerical example of the present invention. 5 and 6 show Numerical Embodiment 2 of the present invention.
4 is an aberration diagram at a wide-angle end and at a telephoto end of FIG.

FIG. 7 is a lens sectional view of a numerical example 3 of the present invention described later. 8 and 9 show Numerical Embodiment 3 of the present invention.
4 is an aberration diagram at a wide-angle end and a telephoto end of FIG.

FIG. 10 is a sectional view of a lens according to a fourth numerical example of the present invention, which will be described later. 11 and 12 are aberration diagrams at the wide-angle end and at the telephoto end in Numerical Embodiment 4 of the present invention.

FIG. 13 is a lens sectional view of a numerical example 5 of the present invention described later. 14 and 15 are aberration diagrams at the wide-angle end and at a telephoto end in Numerical Example 5 of the present invention.

FIG. 16 is a sectional view of a lens according to a sixth numerical example of the present invention, which will be described later. 17 and 18 are aberration diagrams at the wide-angle end and at the telephoto end in Numerical Example 6 of the present invention.

In the lens sectional view, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power,
Reference numeral 3 denotes a third lens unit having a positive refractive power, and L4 denotes a fourth lens unit having a negative refractive power. Arrows indicate the moving direction of each lens group when zooming from the wide-angle side to the telephoto side. SP is aperture,
IP is an image plane.

In the zooming, the axial air gap between the first lens unit L1 and the second lens unit L2 at the telephoto end with respect to the wide-angle end is large.
This is performed by moving the lens units so that the on-axis air gap between the third lens unit L3 and the fourth lens unit L4 is reduced.

The axial air gap between the second lens unit L2 and the third lens unit L3 at the telephoto end with respect to the wide-angle end is shown in FIGS.
0, and is large in Numerical Examples 1, 2, 4, and 5 in FIG. 13, and small in Numerical Example 3 in FIG. Numerical example 6 in FIG. 16 is unchanged. Numerical Examples 1 to 5 are four-group zoom lenses in which four lens groups move independently during zooming.

On the other hand, in the numerical example 6 of FIG. 16, the second lens unit L2 and the third lens unit L3 move integrally during zooming. For this reason, the zoom type can be handled as a three-unit zoom lens. The combined refractive power of the second lens unit L2 and the third lens unit L3 is positive.

In the embodiment of the present invention, focusing is performed by moving the third lens unit L3 with the above-described zoom lens configuration.

By performing focusing with the third lens group, the size and weight of the focusing group are reduced.

Since the refractive power of the third lens unit L3 is relatively easy to increase, the amount of extension of the third lens unit L3 in focusing on a close object can be reduced.

The first lens unit L1 includes a negative meniscus lens having a concave surface facing the object side in order from the object side, and a positive lens having both lens surfaces convex.

By configuring the first lens unit L1 in this manner, it is possible to satisfactorily correct the spherical aberration generated in the first lens unit L1 having a positive refractive power, and particularly to correct the spherical aberration at the telephoto end. In addition, distortion at the wide-angle end can be satisfactorily corrected.

Since the second lens unit L2 is composed of a negative lens 21 and a positive lens 22, both of which are concave in order from the object side, it is possible to appropriately correct spherical aberration particularly at the telephoto end. Correction of chromatic aberration, which worsens with doubling, is effectively performed.

Third lens unit L3 which is a focusing unit
A negative meniscus lens 31 having a concave surface facing the object side in order from the object side, and a positive meniscus lens 3 having a convex surface facing the image surface side
With the configuration of 2, the spherical aberration at the telephoto end, which increases with increasing the zoom ratio, is effectively compensated for, and good optical performance is maintained over the entire zoom range.

In the third lens unit L3, an aspheric surface having a weak positive refractive power is provided from the center of the lens to the periphery of the lens.

In order to correct the spherical aberration generated by the positive refractive power of the third lens unit L3, the third lens unit L3 is made to have an aspheric surface in which the positive refractive power becomes weaker from the center of the lens to the periphery of the lens.
The spherical aberration of the lens group alone is reduced to some extent. Thereby, good spherical aberration is obtained in the entire zoom range.

The fourth lens unit L4 comprises, in order from the object side, a positive lens, a negative lens, and a negative lens.

Since the fourth lens unit L4 has a relatively strong negative refractive power, the generation of various aberrations is suppressed by dividing the negative lens into two lenses. In addition, it is preferable to dispose the positive lens closest to the object side, since the on-axis ray is high, so that spherical aberration particularly at the telephoto end can be effectively corrected. In addition, by arranging the negative lens closer to the image plane than the positive lens, the lens diameter of the lens closest to the image plane can be reduced in size, and the back focus can be shortened, so that the overall optical length can be shortened. It is preferable because it can be achieved.

The third lens unit L3 has a negative meniscus lens and a positive meniscus lens in this order from the object side, and the focal lengths of the first lens unit L1 and the fourth lens unit L4 are respectively f.
1, f4, the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and ft, the Abbe number of the material of the negative lens closest to the object side of the third lens unit L3 is ν3n, and the most object side of the third lens unit L3. The Abbe number of the material of the positive meniscus lens is ν3p
0.2 <f1 / ft <0.5 (1) -0.2 <| f4 / ft | <-0.05 (2) 3.7 <ft / fw < 6.0 (3) 20 <ν3p−ν3n <50 (4) The following condition is satisfied.

The radii of curvature of the object-side and image-side lens surfaces of the negative lens 21 of the second lens unit L2 are R21n1, R2, respectively.
1n2, the radii of curvature of the object-side and image-side lens surfaces of the positive lens 22 of the second lens unit L2 are R22p1 and R22p, respectively.
Assuming that 2, -1 <(R21n1 + R21n2) / (R21n1-R21n2) <1 (5) 0.5 <(R22p1-R22p2) / (R22p1 + R22p2) <8 (6) I have.

When the Abbe numbers of the materials of the negative lens 21 and the positive lens 22 of the second lens unit L2 are ν21n and ν22p, respectively, the following condition is satisfied: 20 <ν21n−ν22p <40 (7) .

When the radii of curvature of the object-side and image-side lens surfaces of the negative meniscus lens 31 closest to the object side in the third lens unit L3 are R31n1 and R31n2, respectively, -1 <(R31n1-R31n2) / (R31n1 + R31n2) ) <0 The condition of (8) is satisfied.

When a stop SP is provided between the second lens unit L2 and the third lens unit L3, and the distance between the stop SP and the third lens unit L3 on the axis is Lp at the telephoto end, 0.02 <Lpa /Ft<0.1 (9) The following condition is satisfied.

Assuming that the focal length of the second lens unit L2 is f2, the following condition is satisfied: 0 <| ft / f2 | <0.5 (10)

Next, the technical meaning of each of the above-mentioned conditional expressions will be described below.

Conditional expression (1) defines the ratio between the first lens unit L1 and the focal length of the entire system at the telephoto end, and is mainly used to reduce the size and performance of the lens system.

If the lower limit value of the conditional expression (1) is exceeded, the refractive power of the first lens unit L1 becomes too strong, so that it becomes difficult to correct spherical aberration especially at the telephoto end, which is not good. If the refractive power of the first lens unit L1 is too weak below the lower limit, the variable power sharing of the last lens unit having a negative refractive power increases, making it difficult to obtain a sufficient zoom ratio. This is not good because the total lens length also increases.

In order to achieve both miniaturization and higher performance, it is preferable to set the lower limit of conditional expression (1) to 0.3. Further, it is desirable to set the upper limit to 0.4.

Conditional expression (2) defines the ratio between the last lens unit having a negative refractive power (the fourth lens unit L4) and the focal length of the entire system at the telephoto end. This is for achieving high performance.

If the lower limit of conditional expression (2) is exceeded, the refracting power of the final lens unit becomes too weak, so that the amount of movement of the final lens unit, particularly during zooming, increases, and the total optical length at the telephoto end increases. . On the other hand, when the value exceeds the upper limit, the refractive power of the final lens unit becomes too strong, and it becomes difficult to correct distortion particularly at the wide-angle end, and the image surface characteristics deteriorate, which is not good.

In order to achieve both miniaturization and higher performance, it is preferable to set the lower limit of conditional expression (2) to -0.16. Further, it is desirable to set the upper limit to -0.1.

Condition (3) defines the ratio of the focal length of the entire system at the wide-angle end and the telephoto end, and sets an appropriate zoom ratio in the present invention.

If the lower limit of conditional expression (3) is exceeded, it becomes difficult to achieve a high zoom ratio which is one of the objects of the present invention, which is not good. On the other hand, if the value exceeds the upper limit, the zoom ratio becomes too large, and it becomes difficult to obtain high optical performance, which is not good.

More preferably, the upper limit of condition (3) is set to 5.0.

Conditional expression (4) defines the difference between the Abbe number of the material of the negative lens and the material of the positive lens of the third lens group which is the focus lens group in the fourth invention, and is mainly for correcting chromatic aberration. Things.

If the lower limit of conditional expression (4) is exceeded, axial chromatic aberration generated in the third lens unit having a positive refractive power will be undercorrected, and in particular, axial chromatic aberration at the wide-angle end tends to be undercorrected. Not good because it becomes difficult. On the other hand, when the value exceeds the upper limit, axial chromatic aberration generated in the third lens unit having a positive refractive power is excessively corrected. In particular, axial chromatic aberration at the telephoto end tends to be excessive, and correction is difficult.

More preferably, the lower limit of condition (4) is set to 30. Further, it is preferable to set the upper limit to 35.

Conditional expression (5) is for appropriately setting the lens shape of the negative lens on the object side of the twenty-first lens group in the first invention.

If the lower limit of conditional expression (5) is exceeded, the radius of curvature of the lens surface on the object side of the negative lens becomes relatively too small, and spherical aberration at the telephoto end in particular is undesirably overcorrected. If the value exceeds the upper limit, the radius of curvature of the lens surface on the image surface side of the negative lens becomes relatively too small, and it becomes difficult to correct distortion particularly at the wide-angle end, which is not preferable.

More preferably, the lower limit of condition (5) should be set to -0.7. Further, it is desirable to set the upper limit to 0.3.

Conditional expression (6) is for appropriately setting the lens shape of the positive lens on the object side of the twenty-first lens group in the first invention.

If the lower limit of conditional expression (6) is exceeded, the radius of curvature of the lens surface of the positive lens on the object side becomes relatively large, and coma aberration particularly at the wide-angle end deteriorates, which is not preferable. If the value exceeds the upper limit, coma aberration particularly at the telephoto end deteriorates, which is not preferable.

It is more preferable that the lower limit of conditional expression (6) is 0.8. Further, it is desirable to set the upper limit value to 5.0.

The conditional expression (7) defines the difference between the Abbe numbers of the materials of the negative lens and the positive lens in the 21st lens group in the present invention, and is mainly for correcting axial chromatic aberration and lateral chromatic aberration. .

If the lower limit value of the conditional expression (7) is exceeded, the axial chromatic aberration particularly at the telephoto end is insufficiently corrected and tends to increase positively, and the chromatic aberration of magnification at the wide angle end undesirably increases. On the other hand, if the value exceeds the upper limit, the axial chromatic aberration at the wide-angle end is insufficiently corrected and tends to increase negatively, and the chromatic aberration of magnification at the telephoto end undesirably increases.

In order to balance axial chromatic aberration and chromatic aberration of magnification, it is desirable to set the lower limit of conditional expression (7) to 22. Further, it is desirable to set the upper limit to 30.

Conditional expression (8) is for appropriately setting the lens shape of the negative lens closest to the object in the third lens unit in the second invention.

If the lower limit value of conditional expression (8) is exceeded, the meniscus shape becomes too strong, making it difficult to manufacture a lens. In addition, spherical aberration at the telephoto end becomes excessively corrected and positively increases. On the other hand, when the value exceeds the upper limit, the refractive power of the negative lens becomes too weak, and the spherical aberration particularly at the telephoto end is insufficiently corrected to increase negatively and the coma aberration at the wide-angle end deteriorates, which is not preferable.

More preferably, the lower limit of condition (8) should be set at -0.6. Further, the upper limit is set to -0.0.
It is desirably set to 1.

In the present embodiment, a stop is provided between the second lens group and the third lens group to balance the front lens diameter and the rear lens diameter. When the stop is provided between the first lens group and the 21st lens group, the diameter of the rear lens increases,
As a result, the size of the camera is increased, which is not preferable. Further, if a diaphragm is provided between the third lens group and the fourth lens group, the diameter of the front lens increases, so that it is difficult to arrange a mechanical mechanism of the barrier in the lens barrel, which is not preferable.

Conditional expression (9) defines the distance between the stop and the third lens group. The conditional expression (9) is used to reduce the diameter of the lens and to make the third lens group, which is the focus group, extend at the closest object distance. This is to prevent interference with the aperture.

If the lower limit of conditional expression (9) is exceeded, the distance between the stop and the third lens unit becomes too small, and when the third lens unit is extended at the closest object distance, the stop interferes with the stop to ensure a sufficient close distance. It is not preferable because it becomes impossible. On the other hand, if the value exceeds the upper limit value, the aperture is located closer to the object side at the telephoto end, so that the aperture diameter increases, which is not preferable because the lens barrel diameter increases.

It is more preferable to set the upper limit of conditional expression (9) to 0.05.

The conditional expression (10) is for defining the refractive power of the second lens group.

If the value exceeds the upper limit of conditional expression (10), the refractive power of the second lens unit becomes strong, and the refractive power of the third lens unit becomes strong.

More preferably, the upper limit of condition (10) should be set at 0.4.

A stop is provided between the second lens unit and the third lens unit to balance the front lens diameter and the rear lens diameter. It is not preferable to provide an aperture between the first and second groups because the rear lens diameter increases and the number of cameras increases. In addition, if the stop is provided between the third and fourth units, the diameter of the front lens increases, which makes it difficult to dispose the mechanical mechanism of the barrier in the lens barrel.

The zoom lens according to the present invention includes, in order from the object side, a first lens unit having a positive refractive power, a second lens unit, a third lens unit, and a fourth lens unit having a negative refractive power. The zooming is performed by moving the lens units so that the distance between the first lens unit and the second lens unit is large and the distance between the third lens unit and the fourth lens unit is small at the telephoto end with respect to the wide-angle end. It has a basic configuration. The present invention broadly includes four inventions of the first to fourth inventions.

The first invention satisfies the lens configuration of the second lens unit and the conditional expressions (1) to (3), and the second invention provides the lens configuration of the third lens unit and the conditional expressions (1) to (3). Is satisfied.

The third invention satisfies the lens configuration of the third lens unit and the conditional expressions (1) to (3), and the fourth invention provides the lens configuration of the third lens unit and the conditional expressions (1) to (4). Is satisfied.

In the first to fourth inventions, any of the above-described configurations (including conditional expressions) may be added.
According to this, the effect of the added configuration can be obtained.

In the zoom lens of each embodiment, the diaphragm is moved integrally with the second lens group during zooming, but may be moved separately.

Further, the camera shake may be corrected by shifting a certain lens group or a part of the lens group in a direction substantially perpendicular to the optical axis.

In order to simplify the mechanical structure, the first
The lens group and the fourth lens group may be moved integrally during zooming.

Next, numerical examples of the present invention will be described. In the numerical examples, i indicates the order of the surfaces from the object side, Ri is the radius of curvature of each surface, Di is the i-th and i + 1-th member thickness or air gap, and Ni and νi are the i-th optical members. Are the refractive index and the Abbe number of the material for d-line. In the aspherical shape, the radius of curvature at the center of the lens surface is R, the magnification in the optical axis direction is X with respect to the surface apex, and the direction perpendicular to the optical axis is Y.
When K, B, C, D, E, and F are aspheric coefficients, respectively,

[0096]

(Equation 1)

This is expressed by the following equation.

Further, “e−X” means “× 10 ^−X ”.

Table 1 shows the relationship between the above-mentioned conditional expressions and numerical examples.

[0100]

[Outside 1]

[0101]

[Outside 2]

[0102]

[Outside 3]

[0103]

[Outside 4]

[0104]

[Outside 5]

[0105]

[Outside 6]

[0106]

[Table 1]

According to the embodiment described above, a zoom lens having high optical performance in the entire zoom range, a relatively short back focus, a short overall optical length, and a zoom ratio of 4 to 5 and a high zoom ratio is provided. realizable.

Next, an embodiment of a lens shutter camera (optical apparatus) using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG.

In FIG. 19, reference numeral 10 denotes a camera body;
Is a photographing optical system constituted by the zoom lens of the present invention, and 12 is a finder for observing a subject image.

13 is a strobe device, 14 is a measurement window, 15
Is a liquid crystal display window for notifying the operation of the camera, 16 is a release button, and 17 is an operation switch for switching various modes.

If the zoom lens of the present invention is applied as a photographing optical system of a lens shutter camera as described in the present embodiment, a small and high-performance camera can be realized.

[0112]

As described above, according to the present invention, by appropriately setting the lens configuration of each lens unit, it is possible to easily achieve a high zoom ratio, and to satisfactorily correct aberrations that fluctuate with zooming. It is possible to achieve a zoom lens and an optical apparatus using the zoom lens, which have excellent optical performance over a variable power range.

[Brief description of the drawings]

FIG. 1 is a lens sectional view of a zoom lens according to Numerical Example 1.

FIG. 2 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 1.

FIG. 3 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 1.

FIG. 4 is a lens cross-sectional view of a zoom lens according to Numerical Example 2.

FIG. 5 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 2.

FIG. 6 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 2.

FIG. 7 is a lens cross-sectional view of a zoom lens according to Numerical Data Example 3;

FIG. 8 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 3.

FIG. 9 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 3.

FIG. 10 is a sectional view of a zoom lens according to Numerical Data Example 4;

11 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 4. FIG.

12 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 4. FIG.

FIG. 13 is a sectional view of a zoom lens according to Numerical Data Example 5;

14 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 5. FIG.

FIG. 15 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 5.

FIG. 16 is a sectional view of a zoom lens according to a sixth numerical example;

FIG. 17 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 6.

FIG. 18 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 6.

FIG. 19 is a schematic diagram of a main part of an optical apparatus using the zoom lens of the present invention.

[Explanation of symbols]

 L1 1st lens group L2 2nd lens group L21 21st lens group L22 22nd lens group L3 3rd lens group L4 4th lens group SP stop IP Image plane d d line g g line c c line ΔS sagittal ΔM meridional

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[Procedure amendment]

[Submission date] September 26, 2001 (2001.9.2)
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 4

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] Claim 8

[Correction method] Change

[Correction contents]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] Claim 9

[Correction method] Change

[Correction contents]

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

[0013]

According to a first aspect of the present invention, there is provided a zoom lens having a first lens unit having a positive refractive power, a second lens unit, a third lens unit, and a negative refractive power. A fourth lens unit having a large power, a large air gap between the first lens unit and the second lens unit at the telephoto end with respect to the wide-angle end, and a large air gap between the third lens unit and the fourth lens unit. The second lens group has, in order from the object side, a negative lens and a positive lens, both lens surfaces of which are concave, and performs focusing by moving the third lens group. Do
The focal lengths of the first lens group and the third lens group are f1,
When f4 and fo and ft respectively denote the focal lengths of the entire system at the wide-angle end and the telephoto end, 0.2 <f1 / ft <0.5-0.2 <f4 / ft <-0.05 3.7 It is characterized by satisfying the condition of <ft / fw <6.0.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

According to a fourth aspect of the present invention, there is provided a zoom lens having a first lens unit having a positive refractive power, a second lens unit, a third lens unit, and a fourth lens unit having a negative refractive power. And a lens unit such that the axial air gap between the first lens group and the second lens group is large at the telephoto end with respect to the wide-angle end, and the axial air gap between the third lens group and the fourth lens group is small. The third lens group includes, in order from the object side, a negative meniscus lens having a concave surface facing the object side, and a positive meniscus lens having a convex surface facing the image surface, and moves the third lens group. When focusing is performed, the focal lengths of the first lens unit and the fourth lens unit are respectively f1 and f4, and the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and ft. f1 / ft <0.5-0.2 <f4 / ft <-0.053.7 It is characterized by satisfying the condition of <ft / fw <6.0.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

In the zoom lens according to the present invention, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens group having a positive refractive power are arranged in order from the object side.
A lens group, and a fourth lens group having a negative refractive power,
At the telephoto end, the lens groups are moved such that the axial air gap between the first lens group and the second lens group is larger and the axial air gap between the third lens group and the fourth lens group is smaller at the telephoto end. The third lens group includes a negative meniscus lens having a concave surface facing the object side and a positive meniscus lens having a convex surface facing the image surface in order from the object side. When focusing is performed and the focal lengths of the first and fourth lens groups are f1 and f4, respectively, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and ft, respectively, 0.2 <f1 / ft <0.5−0.2 <f4 / ft <−0.05 3.7 <ft / fw <6.0 The condition is satisfied.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

According to a ninth aspect of the present invention, there is provided a zoom lens having, in order from the object side, a first lens group having a positive refractive power, a second lens group having a stop, and a third lens group having a positive refractive power. A fourth lens unit having a negative refractive power, a large axial air gap between the first and second groups at the telephoto end with respect to the wide-angle end, and a large axial air gap between the third and fourth groups. The third lens group has, in order from the object side, a negative lens and a positive lens, and the focal length of the first lens group and the fourth lens group is changed. F1, f4, the focal length of the entire system at the telephoto end is ft, the Abbe number of the material of the negative lens closest to the object in the third lens group is ν3n, and the Abbe number of the material of the positive lens closest to the object in the third lens group. The number is ν3p
In this case, the condition 0.2 <f1 / ft <0.5-0.2 <f4 / ft <-0.05 3.7 <ft / fw <6.020 <ν3p−ν3n <50 is satisfied. It is characterized by doing.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction contents]

The third lens unit L3 has a negative meniscus lens and a positive meniscus lens in this order from the object side, and the focal lengths of the first lens unit L1 and the fourth lens unit L4 are respectively f.
1, f4, the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and ft, the Abbe number of the material of the negative lens closest to the object side of the third lens unit L3 is ν3n, and the most object side of the third lens unit L3. The Abbe number of the material of the positive meniscus lens is ν3p
0.2 <f1 / ft <0.5 (1) -0.2 <f4 / ft <-0.05 (2) 3.7 <ft / fw <6. 0 (3) 20 <ν3p−ν3n <50 (4) The following condition is satisfied.

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Claims (15)

[Claims] 1. A first lens group having a positive refractive power, a second lens group, a third lens group, and a fourth lens group having a negative refractive power are arranged in order from the object side. A zoom lens that performs zooming by moving a lens group so that a distance between a first lens group and a second lens group is large and a distance between a third lens group and a fourth lens group is small at a telephoto end. The second lens group includes, in order from the object side, a negative lens and a positive lens whose both lens surfaces are concave. The third lens group is moved to perform focusing, and the focal length of the first lens group and the fourth lens group is set. When the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and ft, 0.2 <f1 / ft <0.5-0.2 <| f4 / ft | <-0 0.05 <3.7 / ft / fw <6.0 A zoom lens characterized by satisfying the following condition: . 2. A radius of curvature of a lens surface on the object side and a lens surface on the image surface side of the negative lens closest to the object side in the second lens group is R21
n1, R21n2, and the radii of curvature of the object-side and image-surface-side lens surfaces of the most object-side positive lens of the second lens group are R, respectively.
-21 <(R21n1 + R21n2) / (R21n1-R2
1n2) <1 0.5 <(R21p1-R21p2) / (R21p1 + R
21p2) <8. The zoom lens according to claim 1, wherein the following condition is satisfied. 3. When the Abbe numbers of the materials of the negative lens and the positive lens of the second lens group are ν21n and ν21p, respectively, a condition of 20 <ν21n−ν21p <40 is satisfied. Or 2 zoom lenses. 4. It has a first lens group having a positive refractive power, a second lens group, a third lens group, and a fourth lens group having a negative refractive power in order from the object side. A zoom lens that performs zooming by moving a lens group such that the distance between the first lens group and the second lens group is large and the distance between the third lens group and the fourth lens group is small at the telephoto end. The three lens groups include a negative meniscus lens having a concave surface facing the object side in order from the object side, and a positive meniscus lens having a convex surface facing the image surface side,
Focusing is performed by moving the third lens unit, and the focal lengths of the first lens unit and the fourth lens unit are set to f1 and f, respectively.
4. Set the focal length of the entire system at the wide-angle end and the telephoto end to f
Assuming that w and ft, the condition 0.2 <f1 / ft <0.5-0.2 <| f4 / ft | <-0.05 3.7 <ft / fw <6.0 is satisfied. A zoom lens characterized by the following. 5. When the radii of curvature of the object-side and image-side lens surfaces of the negative meniscus lens closest to the object side of the third lens group are R31n1 and R31n2, respectively, -1 <(R31n1-R31n2) / ( R31n1 + R3
The zoom lens according to claim 4, wherein the following condition is satisfied: 1n2) <0. 6. An aperture is provided between the second lens group and the third lens group, and when the distance between the aperture and the third lens group at the telephoto end is Lp, 0.02 <Lpa / ft < The zoom lens according to any one of claims 1 to 5, wherein a condition of 0.1 is satisfied. 7. The optical system according to claim 1, wherein a condition of 0 <| ft / f2 | <0.5 is satisfied when a focal length of the second lens group is f2. Zoom lens. 8. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power are arranged in order from the object side. The lens group is moved such that the distance between the first lens group and the second lens group is large at the telephoto end with respect to the wide-angle end, and the distance between the third lens group and the fourth lens group is small. A zoom lens for zooming, wherein the third lens group includes a negative meniscus lens having a concave surface facing the object side and a positive meniscus lens having a convex surface facing the image surface in order from the object side; Is moved to perform focusing, and the focal lengths of the first lens unit and the fourth lens unit are respectively f1 and f4, and the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and ft. <F1 / ft <0.5-0.2 <| f4 / ft | <-0.05 3.7 < A zoom lens characterized by satisfying a condition of ft / fw <6.0. 9. A first lens unit having a positive refractive power, a second lens unit having a stop, a third lens unit having a positive refractive power, and a fourth lens unit having a negative refractive power are arranged in order from the object side. The zooming is performed by moving the lens units such that the distance between the first lens unit and the second lens unit is large at the telephoto end with respect to the wide-angle end, and the distance between the third lens unit and the fourth lens unit is small. Wherein the third lens group includes, in order from the object side, a negative lens and a positive lens, and the first lens group and the fourth lens group have focal lengths of f1, f4 and a wide-angle end, respectively. The focal lengths of the entire system at the telephoto end are respectively fw and ft, the Abbe number of the material of the negative lens closest to the object side of the third lens group is ν3n, and the Abbe number of the material of the positive lens closest to the object side of the third lens group is ν3n. When ν3p, 0.2 <f1 / ft <0.5−0.2 <| f4 / ft | <−0 05 3.7 <ft / fw <6.0 20 <zoom lens satisfies the ν3p-ν3n <50 following condition. 10. The zoom lens according to claim 8, wherein when a focal length of the second lens group is f2, a condition of 0 <| ft / f2 | <0.5 is satisfied. 11. The zoom lens according to claim 8, wherein the third lens group has an aspheric surface whose positive refractive power decreases from the center of the lens to the periphery of the lens. 12. When a stop is provided between the second lens unit and the third lens unit, and an air gap between the stop at the telephoto end and the third lens unit is Lp, 0.02 <Lp / ft <0.1, wherein the condition ft <0.1 is satisfied.
0 or 11 zoom lens. 13. The first lens group includes, in order from the object side,
The zoom lens according to any one of claims 8 to 12, wherein a negative meniscus lens having a concave surface facing the object side and a positive lens having both lens surfaces convex. 14. The fourth lens group is arranged in order from the object side.
14. The zoom lens according to claim 8, comprising a positive lens, a negative lens, and a negative lens. 15. An optical apparatus comprising the zoom lens according to claim 1. Description: