JP2000249921A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the entire length of a lens system, to excellently compensate aberration and to make a telephoto ratio small by constituting the lens of four lens groups, moving the respective lens groups to an object side and moving them so that a distance between the specified lens groups may be large or small at the time of varying power and satisfying a specified conditional expression. SOLUTION: This zoom lens is constituted of four lens groups G1 to G4 and the respective lens groups G1 to G4 are moved to the object side and moved so that the distance between the 1st and the 2nd lens groups G1 and G2 may be large and the distance between the 3rd and the 4th lens groups G3 and G4 may be small at the time of varying power. Then, it satisfies the conditional expressions (1) 0.02<|f4|/fr<0.3, (2) 0.1< ΔX4T/fr<0.5 and (3) 1.5<β4T/ β4W<6.0. Provided that f4 is the focal distance of the 4th lens group G4, fr is the focal distance of an entire system at a telephoto end, ΔX4T is the zooming moving amount of the 4th lens group G4 to the telephoto end when a wide-angle end is set as reference, β4T is the lateral magnification of the 4th lens group G4 at the telephoto end and β4W is the lateral magnification of the 4th lens group G4 at the wide-angle end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a zoom lens, and more particularly to a zoom lens having a small telephoto ratio.

[0002]

2. Description of the Related Art Conventionally, a zoom lens having a relatively low magnification employs a two-group zoom lens, and a higher-magnification zoom lens generally employs a three-group zoom lens. In these zoom lenses, there are many variations of the zoom type, but the result is that the number of lens groups increases. In addition, in order to reduce the number of lens groups or the number of lenses, a method in which the aperture ratio at the telephoto end is reduced and an aspheric surface is used depending on variations is adopted.

On the other hand, a 4-group zoom lens for a compact camera is disclosed in Japanese Patent Publication No. 8-30783 by the present applicant.
There is a zoom lens described in the issue. Tokuhei 8-307
The zoom lens of No. 83 includes, in order from the object side, 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. Wherein each of the lens units moves to the object side when zooming from the wide-angle end to the telephoto end.

The feature of this zoom lens is that a high magnification is achieved by moving each lens group to share the magnification with each lens group. Then, at the time of zooming from the wide-angle end to the telephoto end, the second lens group is moved to the object side, thereby achieving miniaturization at the wide-angle end.

In the past, many proposals utilizing an aspheric surface have been made in order to further reduce the size of the lens system, and the burden of aberration correction capability on the aspheric surface has been increased to increase the number of lenses constituting one group. Attempts have been made to reduce emissions. There have also been many proposals using radial type gradient index lenses.

[0006]

Many actual zoom lenses for compact cameras, regardless of the type of zoom lens, have a mechanism capable of housing the lens in the camera body. This achieves the downsizing of the camera at the time of storage by providing a collapsible mechanism and moving the lens in the space remaining at the lens position at the wide-angle end where the overall length is shortest.

However, in actual shooting, the lens arrangement of the original optical system is used, so that the lens barrel (a member holding the lens system) projects from the camera body. In particular, in the case of a zoom lens having a high zoom ratio, the amount of movement of the lens accompanying zooming at the telephoto end increases.
This means that the entire length of the lens system, that is, the lens barrel becomes very long. For this reason, the center of gravity moves greatly at the telephoto end compared to when the camera is stored or used at the wide-angle end, causing a problem that the balance is poor and the usability is not good.

The present invention has been made in view of the above-mentioned problems, and has a short overall length of the lens system and excellent correction of aberrations at the time of storage or at the wide-angle end as well as at the telephoto end despite having a high magnification ratio. It is an object of the present invention to provide a zoom lens having a small telephoto ratio.

[0009]

According to the present invention, there is provided a zoom lens system comprising: a first lens unit having a positive refractive power; a second lens unit having a positive refractive power; A third lens unit having a positive refractive power and a fourth lens unit having a negative refractive power. When the magnification is changed from the wide-angle end to the telephoto end, each of the lens units moves toward the object side and the first lens unit. The distance between the group and the second lens group is increased, the distance between the third lens group and the fourth lens group is reduced, and the following conditional expression is satisfied. . 0.02 <| f ₄ | / f _T <0.3 (1) 0.1 <ΔX _4T / f _T <0.5 (2) 1.5 <β _4T / β _4W < 6.0 (3) where f ₄ is the focal length of the fourth lens group, f _T is the focal length of the entire system at the telephoto end, and ΔX _4T is the focal length of the fourth lens group with reference to the wide-angle end. The amount of zooming movement to the telephoto end, β _4T is the lateral magnification of the fourth lens unit at the telephoto end, and β _4W is the lateral magnification of the fourth lens unit at the wide-angle end.

In this case, the first lens group has at least one lens.
Composed of a doublet of positive and negative lenses,
The lens group has an aperture stop and includes at least one negative lens. The third lens group includes at least one negative lens and a doublet of a positive lens.
It is desirable that the lens group includes at least a negative lens and a positive lens.

It is desirable that at least one aspherical surface be provided in any one of the first to fourth lens units or in a plurality of lens units.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the size of an optical system is reduced in order to reduce the size of a conventional zoom compact camera, so that a high-magnification lens unit can be housed in a small camera. did. Therefore, the zoom lens system is composed of four lens groups, and the second lens group and the third lens group are moved independently, so that the fluctuation of the field curvature in the intermediate focal length range is corrected, and the zoom ratio is changed. High magnification of 4 times or more was realized.

Specifically, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power When a zoom lens is formed by a group, and when zooming from the wide-angle end to the telephoto end, each of the lens groups moves to the object side, the distance between the first lens group and the second lens group increases, and 3
A method of moving the lens group and the fourth lens group so that the distance between the lens group and the fourth lens group is reduced is adopted.

Next, a description will be given of reducing the telephoto ratio while maintaining a high zoom ratio in the above-described lens configuration.
In a conventional method in which the aperture ratio at the telephoto end is reduced and an aspheric surface is used, the dimensions of the camera body at the wide-angle end and at the time of storage (when the lens is retracted) can be reduced, but up to the telephoto end. When the magnification is changed, the movement amount of the lens group becomes large, so that the balance is poor, which is not preferable. here,
The amount of movement of the lens system mainly depends on the magnification and the focal length of the magnification unit. Therefore, if the amount of movement of the lens system is reduced, the overall length of the lens at the telephoto end can be shortened, but the magnification itself must be reduced instead, and it becomes difficult to increase the magnification.

Therefore, in the zoom lens of the present invention, focusing on the fourth lens group, which is the main zooming section, and appropriately setting the magnification of the fourth lens group, that is, the focal length of the fourth lens group, The telephoto ratio has been reduced while maintaining a high zoom ratio. Specifically, it is preferable that the fourth lens group satisfies the following conditional expression (1).

0.02 <| f ₄ | / f _T <0.3 (1) where f ₄ is the focal length of the fourth lens unit, and f _T is the focal length of the entire system at the telephoto end. .

Conditional expression (1) is a condition for suppressing the movement amount of the entire zoom lens system when increasing the magnification, and is an important condition for reducing the telephoto ratio at the telephoto end. If the lower limit of 0.02 to condition (1) is surpassed, the focal length of the fourth lens unit will be very small and an advantageous power arrangement will be obtained in that the telephoto ratio will be reduced. It becomes too strong to make aberration correction difficult. Here, since a lens is required to satisfactorily correct the aberration, the number of lenses increases, which hinders miniaturization. On the other hand, if the upper limit of 0.3 to condition (1) is exceeded, it is preferable in terms of aberration correction because correction can be easily performed. However, the amount of movement of the fourth lens unit during zooming increases, which is contrary to miniaturization. Become.

In the zoom lens according to the present invention, it is preferable that the fourth lens unit satisfies the following conditional expression (2). 0.1 <ΔX _4T / f _T <0.5 (2) where f _T is the focal length of the entire system at the telephoto end, and ΔX _4T is the telephoto of the fourth lens group with reference to the wide-angle end. This is the zooming movement amount to the end.

Conditional expression (2) is satisfied when the magnification is increased.
This is an important condition for realizing miniaturization while maintaining a high zoom ratio under the condition of suppressing the moving amount of the lens group. If the lower limit of 0.1 to condition (2) is not reached, the amount of movement of the fourth lens unit is very small, which is suitable for miniaturization. However, the power of the fourth lens unit becomes too strong, making it difficult to correct aberrations. . Here, since a lens is required to satisfactorily correct the aberration, the number of lenses increases, which hinders miniaturization. On the other hand, when the value exceeds the upper limit of 0.5 to condition (2), it is preferable because aberrations can be easily corrected. However, the total lens length and the telephoto ratio at the telephoto end are similar to those of the conventional zoom lens.
A zoom lens with a small telephoto ratio cannot be realized.

In the zoom lens according to the present invention, it is preferable that the fourth lens unit satisfies the following conditional expression (3). 1.5 <β _4T / β _4W <6.0 (3) where β _4T is the lateral magnification of the fourth lens unit at the telephoto end, and β _4W is the lateral magnification of the fourth lens unit at the wide-angle end. .

Conditional expression (3) is also a condition for increasing the magnification, and defines the zoom ratio that the fourth lens group bears. When the lower limit of 1.5 to condition (3) is not reached, the zoom range of the zoom lens becomes too small to realize a high zoom lens which is one of the objects of the present invention. On the other hand, when the value exceeds the upper limit of 6.0 of the conditional expression (3), it is difficult to maintain the imaging performance while realizing the zooming movement amount within the range of the conditional expression (2).

Also, in the zoom lens according to the present invention, the first lens group comprises at least one doublet of a positive lens and a negative lens, and the second lens group has an aperture stop, and at least one negative lens. It is important that the third lens group includes a doublet of a negative lens and a positive lens, and the fourth lens group includes at least a negative lens and a positive lens. With this configuration, the overall length is the shortest at the wide-angle end. Therefore, for example, even if the second lens group and the third lens group are designed to perform focusing at the wide-angle end, the moving amount for focusing is small. can do. Therefore, it is not necessary to make the margin between the first lens group and the first lens group larger than necessary, so that downsizing can be achieved efficiently.

Further, even when the distance between the first lens unit and the second lens unit is widened during telephoto and the amount of focusing movement increases at the telephoto end, there is no need to consider mechanical interference. At this time,
Since the sensitivity of the distance between the second lens group and the third lens group to the image plane tends to increase, it is necessary to design each lens group to guarantee the holding accuracy.

In each of the above lens group configurations, the second
It is preferable that a positive lens is also arranged in the lens groups, and that each lens group includes at least a positive lens and a negative lens, because various aberrations and chromatic aberration generated in each group can be satisfactorily corrected. When a doublet is composed of a positive lens and a negative lens, the doublet may be configured such that two lenses are arranged with a small air gap (air separation type or non-joint type), One in which two lenses are physically adhered with an adhesive or the like (joined type) is included. Which configuration to use may be selected in consideration of the lens configuration of the entire zoom lens, balance of aberration correction, eccentric error sensitivity, and the like.

Next, the structure of each lens group will be described. When the first lens group is constituted by a doublet of a positive lens and a negative lens, it is desirable to provide at least one aspheric surface. As a result, spherical aberration at the telephoto end can be satisfactorily corrected. However, this effect can be particularly remarkable when used on the object side surface of the positive lens.

The configuration of the lens system of the second lens group varies depending on the position of the aperture stop, but includes the negative lens as described above. It is desirable to use at least one aspheric surface. Here, when the aspherical surface is used for the surface closest to the object side of the second lens group, distortion and coma can be favorably corrected.

It is preferable that the aspherical surface has a shape such that the amount of the aspherical surface increases in the radial direction from the optical axis with respect to the reference plane. In this case, the aspherical shape is generally a shape having no inflection point within the effective diameter.However, an inflection point may occur depending on the overall aberration correction situation. I can't say I don't have it.

In consideration of the fact that the second lens group extends (moves in the optical axis direction) during focusing, it is desirable that the second lens group alone reduce residual chromatic aberration. Although the amount of movement at this time is small, it is important to dispose a doublet in the second lens group and provide an appropriate power arrangement in order to satisfactorily correct residual chromatic aberration.

The position of the aperture stop is preferably located closest to the object side of the second lens group or in the second lens group, but may be located closest to the image side of the second lens group. In addition,
It goes without saying that the optimum lens configuration of the second lens group is determined by the position of the aperture stop.

Considering that the third lens group may move with the focusing together with the second lens group,
It is desirable to constitute a doublet composed of a positive lens and a negative lens, and to separately correct residual chromatic aberration. At this time, the doublet is composed of a negative lens and a positive lens in order from the object side,
When an aspheric surface is used as the convex surface closest to the image, the entire off-axis aberration can be corrected well. Further, if an aspherical surface is used for the lens surface having the concave surface facing the aperture stop of the second lens unit, various aberrations can be favorably corrected.

If the third lens unit and the second lens unit are configured symmetrically with respect to, for example, an aperture stop, the field curvature can be controlled well, and high optical performance can be obtained. Further, it is preferable that the entire system is configured symmetrically with respect to the aperture stop.

The fourth lens group plays an important role in achieving the object of the present invention. Therefore, it is necessary to arrange at least one positive lens and a negative lens on the image side of the positive lens in the fourth lens group. It is desirable that the negative lens has a shape that is arranged on the image side and has a strong concave surface facing the object side.

More preferably, the fourth lens group includes, in order from the object side, a doublet lens composed of one negative lens (particularly a negative meniscus lens) and a positive lens with a strong concave surface facing the object side, and a strong doublet lens on the object side. It is good in terms of aberration correction to be constituted by three lenses of a negative meniscus lens having a concave surface. In particular, such a configuration is desirable for maintaining good imaging performance (such as field curvature) in the peripheral portion.

Further, by using an aspheric surface on at least one or two of the above-mentioned strongly concave surfaces, it is possible to guarantee the imaging performance (coma aberration and astigmatism) at the wide-angle end. Furthermore, if an aspherical surface is used for the object-side surface of the positive lens, coma can be corrected in a well-balanced manner, and a higher magnification and a shorter telephoto ratio can be achieved in a state where the aberration is corrected more favorably.

At this time, since the strong concave portion is related to the peripheral performance at the wide-angle end, when an aspheric surface is introduced on this surface, the aspheric surface becomes more negative than the reference spherical surface from the optical axis toward the periphery. Desirably, the shape increases. At this time, in some cases, it is sometimes desirable to make the shape such that an inflection point appears near the effective diameter.

As described above, the use of the aspherical surface in the first lens group is mainly effective for correcting spherical aberration, and the use of the aspherical surface in the fourth lens group is effective for the peripheral portion. This is important for securing the imaging performance, particularly the flatness of the image plane.

The "strong" of the "concave surface strong on the object side" in the fourth lens group means the magnitude (absolute value) of the radius of curvature of the surface.
This means that the radius of curvature is small. Therefore, “facing to a concave surface that is strong on the object side” means that the concave surface with the smaller radius of curvature is on the object side.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 7 of the present invention will be described below. Embodiment 1 Embodiment 1 is a zoom lens having a focal length of 39.0 to 131 mm and an aperture ratio of 1: 4.54 to 11.74.
As shown in the figure, the zoom lens system includes nine zoom lenses in four groups. 1A is a lens cross-sectional view at the wide-angle end, FIG. 1B is an intermediate position, and FIG. 1C is a lens cross-sectional view at a telephoto end (the same applies to the following lens cross-sectional views).

The first lens group G1 comprises a doublet of a positive meniscus lens having a strong convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side (both are not joined). G2 is composed of a double convex positive lens and a doublet of a negative meniscus lens having a convex surface facing the image side (both are not joined), and an aperture stop is arranged thereafter. The third lens group G3 comprises a doublet cemented with a negative meniscus lens having a convex surface facing the object side and a biconvex positive lens. The fourth lens group G4 includes a non-junction doublet of a negative meniscus lens having a strong concave surface facing the object side, a positive meniscus lens having a strong convex surface facing the image side, and a negative meniscus lens having a strong concave surface facing the object side. Constitute. The aspheric surface is used on the object side surface of the positive meniscus lens of the first lens group G1. Also, the second
The lens group G2 is used on the object side surface of the biconvex positive lens.
In the third lens group G3, it is used on the surface closest to the image.
Further, the fourth lens group G4 having a large power is used for the strong concave surface of the first negative meniscus lens and the strong concave surface of the last negative meniscus lens. This fourth lens group G
The four aspheric surfaces are very important for correcting the field curvature in a wide-angle region. The telephoto ratio at the telephoto end is 0.68.

FIG. 2 shows aberration diagrams of this embodiment. In FIG. 2, (a) shows the wide-angle end, (b) shows the intermediate position, and (c) shows the spherical aberration SA, astigmatism AS, distortion DT, and chromatic aberration of magnification CC at the telephoto end. The same). However, in the figure, "IH" represents the image height. Although the magnitude of the chromatic aberration of magnification at the wide-angle end is somewhat problematic,
It can be seen that the other aberration correction situations are very balanced. In particular, it can be said that the correction of astigmatism is at a fairly good level.

Embodiment 2 Embodiment 2 is a zoom lens having a focal length of 39.0 to 131 mm and an aperture ratio of 1: 5 to 13.94. As shown in FIG. 3, the zoom lens has four groups and nine lenses. .

The first lens group G1 is composed of a non-junction doublet of a biconvex positive lens and a biconcave negative lens.
Reference numeral 2 denotes a doublet composed of a double-convex positive lens and a negative meniscus lens having a convex surface facing the image side, followed by an aperture stop. The third lens group G3 comprises a doublet cemented with a negative meniscus lens having a convex surface facing the object side and a biconvex positive lens. The fourth lens group G4 includes a cemented doublet composed of a negative meniscus lens having a strong concave surface facing the object side and a positive meniscus lens having a strong convex surface facing the image side, and a negative meniscus lens having a strong concave surface facing the object side. I do. The aspheric surface is used on the object side surface of the biconvex positive lens of the first lens group G1. The second lens group G2 is used on the object side surface of the biconvex positive lens, and the third lens group G3 is used on the most image side surface. further,
The fourth lens group G4 is used for the strong concave surface of the first negative meniscus lens and the strong concave surface of the last negative meniscus lens. This embodiment is an example in which the aperture ratio is yielded and the overall length of the lens system is shortened. The power of the fourth lens group G4 is further increased as compared with the first embodiment, and the telephoto ratio at the telephoto end is 0.624.

FIG. 4 shows an aberration diagram of this embodiment. The tendency of the lateral chromatic aberration is the same as that of the first embodiment, but the absolute amount of the axial chromatic aberration is large.

Embodiment 3 Embodiment 3 is a zoom lens having a focal length of 38.9 to 170.5 mm and an aperture ratio of 1: 4.23 to 12.36.
As shown in FIG. 5, the zoom lens includes four groups of nine lenses.

The first lens group G1 comprises a non-joint doublet of a biconvex positive lens and a biconcave negative lens.
Reference numeral 2 denotes a biconcave negative lens, a diaphragm, and a biconvex positive lens. The third lens group G3 comprises a doublet cemented with a negative meniscus lens having a convex surface facing the object side and a biconvex positive lens. The fourth lens group G4 includes a biconcave negative lens whose strong concave surface faces the object side, a non-joint doublet of a biconvex positive lens, and a negative meniscus lens whose strong concave surface faces the object side. The aspheric surface is used on the object side surface of the biconvex positive lens of the first lens group G1. The second lens group G2 is used on the object side surface of the biconcave negative lens and the object side surface of the biconvex positive lens, and the third lens group G3 is used on the most image side surface. Further, in the fourth lens group G4,
It is used for the strong concave surface of the biconcave negative lens and the image side surface of the biconvex positive lens. The telephoto ratio at the telephoto end of this embodiment is 0.58.
2. The overall length of the lens has been significantly reduced as compared with the related art.

FIG. 6 shows aberration diagrams of this embodiment. Although problems remain in the wide-angle side chromatic aberration and the axial chromatic aberration at the telephoto end, it is possible to obtain a good balance of performance as a whole. Also in this case, the distortion is corrected very well at the telephoto end.

Embodiment 4 Embodiment 4 has a focal length of 38.87 to 170.5 mm,
It is a zoom lens having an aperture ratio of 1: 5.4 to 15, and as shown in FIG.

The first lens group G1 is composed of a non-junction doublet of a biconvex positive lens and a biconcave negative lens.
Reference numeral 2 denotes a biconcave negative lens, a diaphragm, and a biconvex positive lens. The third lens group G3 comprises a doublet cemented with a negative meniscus lens having a convex surface facing the object side and a biconvex positive lens. The fourth lens group G4 includes a biconcave negative lens whose strong concave surface faces the object side, a non-joint doublet of a biconvex positive lens, and a negative meniscus lens whose strong concave surface faces the object side. The aspheric surface is used on the object side surface of the biconvex positive lens of the first lens group G1. The second lens group G2 is used on the object side surface of the biconcave negative lens and the object side surface of the biconvex positive lens, and the third lens group G3 is used on the most image side surface. Further, in the fourth lens group G4,
It is used for the strong concave surface of the biconcave negative lens and the image side surface of the biconvex positive lens. The telephoto ratio at the telephoto end of this embodiment is 0.55.
9 FIG. 8 shows aberration diagrams of this embodiment.

Embodiment 5 Embodiment 5 has a focal length of 38.9 to 170.51 mm,
A zoom lens with an aperture ratio of 1: 4.8 to 13.29,
As shown in FIG. 9, the zoom lens is composed of nine groups of four zoom lenses.

The first lens group G1 is composed of a non-junction doublet of a biconvex positive lens and a biconcave negative lens.
Reference numeral 2 denotes a biconcave negative lens, a diaphragm, and a biconvex positive lens. The third lens group G3 comprises a doublet cemented with a negative meniscus lens having a convex surface facing the object side and a biconvex positive lens. The fourth lens group G4 includes a biconcave negative lens whose strong concave surface faces the object side, a non-joint doublet of a biconvex positive lens, and a negative meniscus lens whose strong concave surface faces the object side. The aspheric surface is used on the object side surface of the biconvex positive lens of the first lens group G1. The second lens group G2 is used on the object side surface of the biconcave negative lens and the object side surface of the biconvex positive lens, and the third lens group G3 is used on the most image side surface. Further, in the fourth lens group G4,
It is used for the strong concave surface of the biconcave negative lens and the image side surface of the biconvex positive lens. The telephoto ratio at the telephoto end of this embodiment is 0.56.
4. FIG. 10 shows aberration diagrams of this embodiment.

Embodiment 6 Embodiment 6 has a focal length of 38.9 to 195.689 m.
m, a zoom lens having an aperture ratio of 1: 4.53 to 15.78. As shown in FIG. 11, the zoom lens includes four groups and ten lenses.

The first lens group G1 comprises a non-junction doublet of a biconvex positive lens and a negative meniscus lens having a convex surface facing the image side, and the second lens group G2 comprises a biconcave negative lens, a diaphragm and a It is composed of a convex positive lens. Third lens group G
Reference numeral 3 denotes a cemented doublet of a biconcave negative lens and a biconvex positive lens, and a positive meniscus lens having a convex surface facing the image side. The fourth lens group G4 includes a biconcave negative lens whose strong concave surface faces the object side, a non-joint doublet of a biconvex positive lens, and a negative meniscus lens whose strong concave surface faces the object side.

In this embodiment, the power of the fourth lens group G4 is very large, and is -9.4773 mm. This embodiment is basically the same as Embodiment 5 in basic configuration, but the point is that the third lens group G3 is used as a cemented lens and a positive lens to disperse power. Also,
The aspheric surface is used for the object side surface of the biconvex positive lens of the first lens group G1 and the image side surface of the negative meniscus lens. In the second lens group G2, the object side surface of the biconcave negative lens and the object side surface of the biconvex positive lens are used. In the third lens group G3, the image side surface of the cemented doublet and the image side of the positive meniscus lens are used. Used for surface. Further, the fourth lens group G4 is used for the strong concave surface of the biconcave negative lens and the image side surface of the biconvex positive lens. As a result, a zoom ratio of 5.03 times is achieved.

In this embodiment, the telephoto ratio at the telephoto end is 0.522.
It turns out that it shows a very phenomenal numerical value. FIG. 12 shows aberration diagrams of this embodiment.

Embodiment 7 Embodiment 7 is a zoom lens having a focal length of 38.9 to 195.5 mm and an aperture ratio of 1: 4.54 to 15.77.
As shown in FIG. 13, the zoom lens is composed of ten groups of four zoom lenses.

The first lens group G1 comprises a doublet cemented with a biconvex positive lens and a negative meniscus lens having a convex surface facing the image side. The second lens group G2 comprises a biconcave negative lens, followed by a diaphragm and a biconvex lens. It consists of a positive lens. Third lens group G3
Is composed of a doublet cemented with a biconcave negative lens and a biconvex positive lens, and a positive meniscus lens with the convex surface facing the image side. The fourth lens group G4 includes a biconcave negative lens whose strong concave surface faces the object side, a non-joint doublet of a biconvex positive lens, and a negative meniscus lens whose strong concave surface faces the object side. The aspheric surface is used for the object side surface and the image side surface of the cemented doublet of the first lens group G1. In the second lens group G2, the object side surface of the biconcave negative lens and the object side surface of the biconvex positive lens are used. In the third lens group G3, the image side surface of the cemented doublet and the image side of the positive meniscus lens are used. Used for surface. Further, the fourth lens group G4 is used for the strong concave surface of the biconcave negative lens and the image side surface of the biconvex positive lens.

FIG. 14 shows aberration diagrams of this embodiment. In this example, the first lens group G1 of the sixth embodiment is a doublet with an air lens interposed therebetween, but is constituted by a doublet. The telephoto ratio at the telephoto end is 0.51. In terms of chromatic aberration stability, it can be said that the correction is more excellent than in the sixth embodiment.

In the following, numerical data of the above embodiments are shown. Symbols other than those described above, f is the focal length of the entire system, F _NO is the F number, f _B is the back focus, r ₁ , r ₂ . The radius of curvature of the lens surfaces, d ₁ , d _2, ...
n _d1 , n _d2 ... are the d-line refractive indices of each lens, v _d1 , v _d2 ...
Is the Abbe number of each lens. Note that the aspheric shape is x
Let y be the optical axis where the traveling direction of light is positive and y be the direction orthogonal to the optical axis, it is expressed by the following equation. ^{x = (y 2 / r)} / [1+ {1- (K + 1) (y / r)
_{^{2} 1/2] + A 4 y}} 4 + A 6 y 6 + A 8 y 8 + A 10 y 10 where, r is the paraxial radius of curvature, K is a conical coefficient, A _4, A _6,
A ₈ and A ₁₀ are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

[0059] Example 1 f = 38.900 ~ 72.127 ~131.000 F NO = 4.539 ~ 7.253 ~ 11.736 f B = 7.130 ~ 23.328 ~ 55.788 r 1 = 12.3955 ( _{aspherical) d 1 = 2.0000 n d1 =} 1.49700 ν d1 = 81.54 r _{2 = 149.3462 d 2 = 0.1000 r} 3 = -184.3987 d 3 = 1.0000 n d2 = 1.78800 ν d2 = 47.37 r 4 = 48.1818 d 4 = ( variable) r ₅ = 39.7315 _{(aspherical) d 5 = 1.3500 n d3 =} 1.61772 v _d3 = 49.81 r ₆ = -19.8503 d ₆ = 0.1000 r ₇ = -19.4178 d ₇ = 0.8888 n _d4 = 1.78800 v _d4 = 47.37 r ₈ = -107.9985 d ₈ = 0.9242 r ₉ = ∞ (aperture) d ₉ = ( _{variable) r 10 = 64.0102 d 10 =} 0.7770 n d5 = 1.80440 ν d5 = 39.59 r 11 = 11.5871 d 11 = 5.0290 n d6 = 1.57135 ν d6 = 52.95 r 12 = -15.0152 ( aspherical) d ₁₂ = (variable) r ₁₃ = -10.0699 _{(aspherical) d 13 = 0.7500 n d7 =} 1.69680 ν d7 = 55.53 r 14 = -59.1291 d 14 = 0.1000 r 15 = -59.1293 d 15 = 3.70 _{00 n d8 = 1.84666 ν d8 =} 23.78 r 16 = -20.8670 d 16 = 1.5770 r 17 = -12.6393 ( _{aspherical) d 17 = 1.1000 n d9 =} 1.77250 ν d9 = 49.60 r 18 = -49.8003 zoom interval angle end intermediate position telephoto end _{f 38.900 72.127 131.000 d 4 1.70000 8.10722} 12.29582 d 9 4.77702 4.29345 0.70000 d 12 5.62694 2.00553 0.95000 aspherical coefficients first surface _{K = 0 A 4 = -3.5635 ×} 10 -6 A 6 = 8.0737 × 10 -8 A 8 = _{^{-2.7849 × 10 -9 A 10 = 4.1470}} × 10 -11 fifth surface _{K = 0 A 4 = -2.0608 ×} 10 -5 A 6 = -5.5658 × 10 -7 A 8 = 1.0980 × 10 -8 A 10 = - 1.4641 × 10 ^-10 Surface 12 K = 0 A ₄ = 9.7423 × 10 ^-5 A ₆ = -6.7565 × 10 ^-8 A ₈ = 7.1568 × 10 ^-9 A ₁₀ = -7.8485 × 10 ^-11 Surface 13 K = 0 A ₄ = 1.8346 × 10 ^-4 A ₆ = 3.8923 × 10 ^-7 A ₈ = 7.6 107 × 10 ^-9 A ₁₀ = -8.7159 × 10 ^-11 Surface 17 K = 0 A ₄ = 2.9258 × 10 ^-5 A ₆ = 4.9354 x 10 ^-7 A ₈ = -2.8024 x 10 ^-9 A ₁₀ = 3.8630 x 10 ^-11 .

[0060] Example 2 f = 38.900 ~ 68.000 ~131.000 F NO = 5.021 ~ 7.800 ~ 13.937 f B = 7.103 ~ 20.339 ~ 51.907 r 1 = 10.0913 ( _{aspherical) d 1 = 2.0000 n d1 =} 1.48749 ν d1 = 70.23 r _{2 = -49.4980 d 2 = 0.1000 r} 3 = -45.7408 d 3 = 1.0000 n d2 = 1.79952 ν d2 = 42.22 r 4 = 39.8705 d 4 = ( variable) r ₅ = 94.4892 (aspherical) d ₅ = 1.3500 n _d3 = 1.60562 v _d3 = 43.70 r ₆ = -10.7208 d ₆ = 0.8994 n _d4 = 1.78590 v _d4 = 44.20 r ₇ = -32.2467 d ₇ = 0.8223 r ₈ = ∞ (aperture) d ₈ = (variable) r ₉ = 48.6685 d _{9 = 0.7770 n d5 = 1.78590 ν d5} = 44.20 r 10 = 11.6896 d 10 = 4.7359 n d6 = 1.57099 ν d6 = 50.80 r 11 = -15.8138 ( aspherical) d ₁₁ = (variable) r ₁₂ = -7.9539 (aspherical) _{d 12 = 0.7500 n d7 = 1.77250} ν d7 = 49.60 r 13 = -94.6627 d 13 = 3.7000 n d8 = 1.74000 ν d8 = 28.28 r 14 = -16.6020 d 14 = 1.5770 r 1 ₅ = -11.7913 _{(aspherical) d 15 = 1.1000 n d9 =} 1.77250 ν d9 = 49.60 r 16 = -36.3246 zoom interval angle end intermediate position telephoto end _{f 38.900 68.000 131.000 d 4 1.70000 5.52766} 9.35963 d 8 3.89423 3.92395 0.70000 d 11 4.46489 1.80147 0.95000 aspherical coefficients first surface _{K = 0 A 4 = -6.1561 ×} 10 -6 A 6 = 5.4935 × 10 -8 A 8 = -6.6750 × 10 -9 A 10 = 2.2399 × 10 -10 fifth surface K = 0 A ₄ = -2.0608 x 10 ^-5 A ₆ = -5.5658 x 10 ^-7 A ₈ = 1.0980 x 10 ^-8 A ₁₀ = -1.4641 x 10 ^-10 Surface 11 K = 0 A ₄ = 1.8044 x 10 ^-4 A ₆ = -4.3057 × 10 ^-6 A ₈ = 1.8028 × 10 ^-7 A ₁₀ = -2.6432 × 10 ^-9 Surface 12 K = 0 A ₄ = 3.2466 × 10 ^-4 A ₆ = -2.9739 × 10 ^-6 A ₈ = 1.3414 × 10 ^-7 A ₁₀ = -1.0713 × 10 ^-9 Surface 15 K = 0 A ₄ = 2.7100 × 10 ^-5 A ₆ = 1.1157 × 10 ^-6 A ₈ = -9.0648 × 10 ^-9 A ₁₀ = 8.8990 × 10 ^-11 .

[0061] Example 3 f = 38.899 ~ 63.000 ~170.500 F NO = 4.233 ~ 6.064 ~ 12.355 f B = 7.153 ~ 18.142 ~ 56.984 r 1 = 15.2499 ( _{aspherical) d 1 = 3.0000 n d1 =} 1.49700 ν d1 = 81.54 r _{2 = -34.3500 d 2 = 0.1000 r} 3 = -34.0373 d 3 = 1.0000 n d2 = 1.78800 ν d2 = 47.37 r 4 = 141.6060 d 4 = ( variable) r ₅ = -23.6404 (aspherical) d ₅ = 0.7704 n _d3 = 1.78800 v _d3 = 47.37 r ₆ = 108.9119 d ₆ = 1.0871 r ₇ = ∞ (aperture) d ₇ = 0.6000 r ₈ = 51.9720 (aspherical surface) d ₈ = 1.0351 n _d4 = 1.72825 v _d4 = 28.46 r ₉ = -24.8664 d ₉ = _{(variable) r 10 = 30.7493 d 10 =} 0.7030 n d5 = 1.80518 ν d5 = 25.42 r 11 = 11.2456 d 11 = 4.0000 n d6 = 1.48749 ν d6 = 70.23 r 12 = -12.4600 ( aspherical) d ₁₂ = (variable) r ₁₃ = -9.3838 _{(aspherical) d 13 = 0.7000 n d7 =} 1.78800 ν d7 = 47.37 r 14 = 82.3876 d 14 = 0.1000 r 15 = 93.9940 d 1 _{5 = 3.8000 n d8 = 1.84666 ν} d8 = 23.78 r 16 = -18.5910 ( _{aspherical) d 16 = 3.1000 r 17 =} -10.7107 d 17 = 0.4800 n d9 = 1.78800 ν d9 = 47.37 r 18 = -29.5940 zoom interval angle end middle position telephoto end _{f 38.899 63.000 170.500 d 4 2.00000 7.03771} 16.83611 d 9 4.18635 3.44383 4.09255 d 12 7.57624 5.06826 0.7641
6 aspherical coefficients first surface _{K = 0 A 4 = 3.7309 ×} 10 -6 A 6 = 1.2867 × 10 -8 A 8 = 1.0173 × 10 -9 A 10 = -5.9905 × 10 -12 Fifth surface K = 0 A ₄ = -2.0608 x 10 ^-5 A ₆ = -5.5658 x 10 ^-7 A ₈ = 1.0980 x 10 ^-8 A ₁₀ = -1.4641 x 10 ^-10 Surface 8 K = 0 A ₄ = -4.2948 x 10 ^-5 A ₆ = -5.8967 × 10 ^-7 A ₈ = 4.3206 × 10 ^-8 A ₁₀ = -1.3004 × 10 ^-9 Surface 12 K = 0 A ₄ = 3.5172 × 10 ^-5 A ₆ = -5.0215 × 10 ^-7 A ₈ = -1.9435 x 10 ^-8 A ₁₀ = 2.9223 x 10 ^-10 Surface 13 K = 0 A ₄ = 2.9996 x 10 ^-4 A ₆ = 5.8601 x 10 ^-7 A ₈ = -2.2238 x 10 ^-8 A ₁₀ = 6.0535 × 10 ⁻¹⁰ 16th surface K = 0 A ₄ = 3.1651 × 10 ⁻⁵ A ₆ = −1.3318 × 10 ⁻⁷ A ₈ = −7.2577 × 10 ⁻⁹ A ₁₀ = 3.9663 × 10 ⁻¹¹ .

[0062] Example 4 f = 38.875 ~ 76.000 ~170.505 F NO = 5.401 ~ 9.190 ~ 14.996 f B = 7.183 ~ 24.380 ~ 53.073 r 1 = 13.5596 ( _{aspherical) d 1 = 2.5556 n d1 =} 1.49700 ν d1 = 81.54 r _{2 = -30.3701 d 2 = 0.1000 r} 3 = -30.7258 d 3 = 1.0000 n d2 = 1.78800 ν d2 = 47.37 r 4 = 102.1466 d 4 = ( variable) r ₅ = -28.3624 (aspherical) d ₅ = 0.8475 n _d3 = 1.78800 v _d3 = 47.37 r ₆ = 34.6645 d ₆ = 1.1855 r ₇ = ∞ (aperture) d ₇ = 0.6000 r ₈ = 30.4980 (aspheric surface) d ₈ = 0.8234 n _d4 = 1.72825 v _d4 = 28.46 r ₉ = -24.0049 d ₉ = _{(variable) r 10 = 47.4414 d 10 =} 0.7786 n d5 = 1.80518 ν d5 = 25.42 r 11 = 11.8417 d 11 = 4.0000 n d6 = 1.48749 ν d6 = 70.23 r 12 = -9.8436 ( aspherical) d ₁₂ = (variable) r ₁₃ = -8.3684 _{(aspherical) d 13 = 0.7000 n d7 =} 1.78800 ν d7 = 47.37 r 14 = 68.8908 d 14 = 0.1000 r 15 = 68.9885 d 15 _{= 3.7000 n d8 = 1.84666 ν d8} = 23.78 r 16 = -20.6437 ( _{aspherical) d 16 = 3.8000 r 17 =} -9.8902 d 17 = 0.7700 n d9 = 1.78800 ν d9 = 47.37 r 18 = -21.7642 zoom interval angle end intermediate position telephoto end _{f 38.875 76.000 170.505 d 4 2.00000 7.19289} 16.38487 d 9 3.62892 2.63768 4.16286 d 12 6.71060 4.14546 0.65343 aspherical coefficients first surface _{K = 0 A 4 = 3.5822 ×} 10 -6 A 6 = -7.2087 × 10 -8 A 8 = 3.9598 × 10 ^-9 A ₁₀ = -3.9823 × 10 ^-11 Fifth surface K = 0 A ₄ = -2.0608 × 10 ^-5 A ₆ = -5.5658 × 10 ^-7 A ₈ = 1.0980 × 10 ^-8 A ₁₀ = -1.4641 × 10 ^-10 Surface 8 K = 0 A ₄ = -8.9744 × 10 ^-5 A ₆ = -2.1252 × 10 ^-6 A ₈ = 2.0142 × 10 ^-7 A ₁₀ = -8.1010 × 10 ^-9 Surface 12 _{K = 0 A 4 = 7.5275 ×} 10 -5 A 6 = -4.3680 × 10 -7 A 8 = -2.7804 × 10 -8 A 10 = 4.7168 × 10 -10 13th surface _{K = 0 A 4 = 3.9428 ×} 10 - ^{_{4 A 6 = 2.6694 × 10 -6}} A 8 = -6.1052 × 10 -8 A 10 = 1.5157 × 10 -9 16th surface _{K = 0 A 4 = 2.9340 ×} 10 -5 A 6 = 1.0814 _{^{10 -7 A 8 = -1.0943 × 10}} -8 A 10 = 6.8944 × 10 -11.

[0063] Example 5 f = 38.901 ~ 76.003 ~170.510 F NO = 4.821 ~ 7.911 ~ 13.286 f B = 7.190 ~ 23.544 ~ 54.667 r 1 = 14.3382 ( _{aspherical) d 1 = 2.5556 n d1 =} 1.49700 ν d1 = 81.54 r _{2 = -32.8810 d 2 = 0.1000 r} 3 = -32.8810 d 3 = 1.0000 n d2 = 1.78800 ν d2 = 47.37 r 4 = 146.7425 d 4 = ( variable) r ₅ = -34.4464 (aspherical) d ₅ = 0.8259 n _d3 = 1.78800 v _d3 = 47.37 r ₆ = 31.0427 d ₆ = 1.2343 r ₇ = ∞ (aperture) d ₇ = 0.6000 r ₈ = 28.7619 (aspherical surface) d ₈ = 0.9265 n _d4 = 1.75251 v _d4 = 27.33 r ₉ = -33.6187 d ₉ = _{(variable) r 10 = 29.7595 d 10 =} 0.7123 n d5 = 1.80518 ν d5 = 25.42 r 11 = 10.1990 d 11 = 4.0000 n d6 = 1.48749 ν d6 = 70.23 r 12 = -10.3343 ( aspherical) d ₁₂ = (variable) r ₁₃ = -8.3096 _{(aspherical) d 13 = 0.7000 n d7 =} 1.78800 ν d7 = 47.37 r 14 = 61.6854 d 14 = 0.1000 r 15 = 73.2586 d 15 _{= 3.7000 n d8 = 1.84666 ν d8} = 23.78 r 16 = -18.5768 ( _{aspherical) d 16 = 3.8000 r 17 =} -10.0069 d 17 = 0.7700 n d9 = 1.78800 ν d9 = 47.37 r 18 = -23.5186 zoom interval angle end intermediate position telephoto end _{f 38.901 76.003 170.510 d 4 2.00000 8.28701} 16.24547 d 9 4.05726 2.79254 3.45195 d 12 6.61820 3.85187 0.70625 aspherical coefficients first surface _{K = 0 A 4 = 3.1413 ×} 10 -6 A 6 = -3.2310 × 10 -8 A 8 = 2.1936 x 10 ^-9 A ₁₀ = -1.6581 x 10 ^-11 Fifth surface K = 0 A ₄ = -2.0608 x 10 ^-5 A ₆ = -5.5658 x 10 ^-7 A ₈ = 1.0980 x 10 ^-8 A ₁₀ = -1.4641 × 10 ^-10 Surface 8 K = 0 A ₄ = -6.2449 × 10 ^-5 A ₆ = -1.4278 × 10 ^-6 A ₈ = 9.6247 × 10 ^-8 A ₁₀ = -3.4425 × 10 ^-9 Surface 12 _{K = 0 A 4 = 6.0235 ×} 10 -5 A 6 = -2.3375 × 10 -7 A 8 = -6.0300 × 10 -8 A 10 = 8.9424 × 10 -10 13th surface _{K = 0 A 4 = 3.8259 ×} 10 - ⁴ A ₆ = 2.8864 × 10 ^-6 A ₈ = -9.9366 × 10 ^-8 A ₁₀ = 2.0212 × 10 ^-9 Surface 16 K = 0 A ₄ = 2.6439 × 10 ^-5 A ₆ = 9.2963 × 10 ^-8 A ₈ = -1.5396 × 10 ^-8 A ₁₀ = 8.7003 × 10 ^-11 .

[0064] Example 6 f = 38.900 ~ 64.000 ~195.689 F NO = 4.534 ~ 7.076 ~ 15.782 f B = 7.128 ~ 19.361 ~ 52.905 r 1 = 16.3446 ( _{aspherical) d 1 = 2.5556 n d1 =} 1.49700 ν d1 = 81.54 r _{2 = -22.4860 d 2 = 0.1000 r} 3 = -20.6652 d 3 = 1.0000 n d2 = 1.79952 ν d2 = 42.22 r 4 = -564.8973 ( aspherical) d ₄ = (variable) r ₅ = -33.0967 (aspherical) d _{5 = 0.7359 n d3 = 1.49700 ν} d3 = 81.54 r 6 = 36.8748 d 6 = 1.2417 r 7 = ∞ ( _{stop) d 7 = 0.6000 r 8 =} 19.2468 ( _{aspherical) d 8 = 1.1380 n d4 =} 1.68893 ν d4 = 31.07 r ₉ = -44.8913 d ₉ = (variable) r ₁₀ = -30.9069 d ₁₀ = 0.4000 n _d5 = 1.78590 ν _d5 = 44.20 r ₁₁ = 7.6437 d ₁₁ = 2.5000 nd ₆ = 1.48749 ν _d6 = 70.23 r ₁₂ = -14.2605 ( _{aspherical) d 12 = 1.4109 r 13 =} -67.0280 d 13 = 3.0000 n d7 = 1.49700 ν d7 = 81.54 r 14 = -8.5250 ( aspherical) d ₁₄ = (variable) r ₁₅ -9.2654 _{(aspherical) d 15 = 0.7000 n d8 =} 1.77250 ν d8 = 49.60 r 16 = 46.6477 d 16 = 0.1000 r 17 = 42.1310 d 17 = 3.4847 n d9 = 1.69895 ν d9 = 30.13 r 18 = -18.5243 ( aspherical _{) d 18 = 3.6777 r 19 =} -10.3352 d 19 = 0.7700 n d10 = 1.77250 ν d10 = 49.60 r 20 = -33.1778 zoom interval angle end intermediate position telephoto end _{f 38.900 64.000 195.689 d 4 2.00000 4.74993} 18.90160 d 9 1.30395 0.72450 5.99970 d ₁₄ 8.39794 6.77987 0.47770 aspherical coefficients first surface _{K = 0 A 4 = -2.7646 ×} 10 -5 A 6 = -6.0389 × 10 -7 A 8 = 7.3423 × 10 -9 A 10 = -2.0840 × 10 -10 4 surface _{K = 0 A 4 = -4.6115 ×} 10 -5 A 6 = -4.0388 × 10 -7 A 8 = 4.7911 × 10 -9 A 10 = -1.0123 × 10 -10 fifth surface K = 0 A ₄ = -2.0608 _{^{× 10 -5 A 6 = -5.5658 ×}} 10 -7 A 8 = 1.0980 × 10 -8 A 10 = -1.4641 × 10 -10 8th surface _{K = 0 A 4 = -8.1613 ×} 10 -5 A 6 = -4.1056 _{^{× 10 -7 A 8 = 3.3730 ×}} 10 -8 A 10 = -1.1601 × 10 -9 12th surface _{K = 0 A 4 = 1.7833 ×} 10 ^{_{-4 A 6 = 6.3902 × 10 -6}} A 8 = -2.5179 × 10 -7 A 10 = 1.4001 × 10 -8 14th surface _{K = 0 A 4 = -4.0596 ×} 10 -5 A 6 = -2.6173 × 10 - ⁶ A ₈ = 3.9432 × 10 ^-8 A ₁₀ = -2.9819 × 10 ^-9 15th surface K = 0 A ₄ = 4.4633 × 10 ^-4 A ₆ = 9.7579 × 10 ^-7 A ₈ = -2.8289 × 10 ^-8 A ₁₀ = 5.0637 × 10 ^-10 Surface 18 K = 0 A ₄ = 1.0316 × 10 ^-4 A ₆ = 2.8 356 × 10 ^-8 A ₈ = -1.0128 × 10 ^-8 A ₁₀ = 4.1695 × 10 ^-11 .

[0065] Example 7 f = 38.899 ~ 63.997 ~195.501 F NO = 4.538 ~ 7.092 ~ 15.767 f B = 7.202 ~ 19.558 ~ 48.980 r 1 = 16.2017 ( _{aspherical) d 1 = 2.9000 n d1 =} 1.49700 ν d1 = 81.54 r _{2 = -19.9744 d 2 = 1.0000 n} d2 = 1.80440 ν d2 = 39.59 r 3 = -88490.000 ( aspherical) d ₃ = (variable) r ₄ = -24.4652 _{(aspherical) d 4 = 0.7423 n d3 =} 1.49700 ν d3 _{= 81.54 r 5 = 70.1741 d 5} = 1.1274 r 6 = ∞ ( _{stop) d 6 = 0.6000 r 7 =} 25.0730 ( _{aspherical) d 7 = 0.9391 n d4 =} 1.80518 ν d4 = 25.42 r 8 = -58.8960 d 8 = ( _{variable) r 9 = -30.6068 d 9 =} 0.4000 n d5 = 1.78800 ν d5 = 47.37 r 10 = 7.1455 d 10 = 2.5000 n d6 = 1.49700 ν d6 = 81.54 r 11 = -15.0067 ( aspherical) d ₁₁ = 1.6465 r _{12 = -305.2271 d 12 = 3.0000 n d7} = 1.49700 ν d7 = 81.54 r 13 = -8.6119 ( aspherical) d ₁₃ = (variable) r ₁₄ = -9.6215 (aspherical) d ₁₄ = 0. _{7000 n d8 = 1.78800 ν d8 =} 47.37 r 15 = 42.3893 d 15 = 0.1000 r 16 = 37.9381 d 16 = 3.6778 n d9 = 1.67270 ν d9 = 32.10 r 17 = -17.3559 ( _{aspherical) d 17 = 3.7777 r 18 =} - _{10.4451 d 18 = 0.7700 n d10 =} 1.78800 ν d10 = 47.37 r 19 = -34.2222 zoom interval angle end intermediate position telephoto end _{f 38.899 63.997 195.501 d 3 2.00000 4.67508} 18.83544 d 8 0.83701 0.27700 7.75213 d 13 9.04819 7.37482 0.35500 aspherical coefficients first surface _{K = 0 A 4 = -3.1325 ×} 10 -5 A 6 = -5.9183 × 10 -7 A 8 = 4.7621 × 10 -9 A 10 = -2.3762 × 10 -10 third surface K = 0 A ₄ = -4.6149 × 10 ^-5 A ₆ = -3.3764 × 10 ^-7 A ₈ = 1.8164 × 10 ^-11 A ₁₀ = -7.5224 × 10 ^-11 4th surface K = 0 A ₄ = -2.0608 × 10 ^-5 A ₆ = -5.5657 _{^{× 10 -7 A 8 = 1.0980 ×}} 10 -8 A 10 = -1.4641 × 10 -10 seventh surface _{K = 0 A 4 = -5.6017 ×} 10 -5 A 6 = -8.2392 × 10 -8 A 8 = 1.4472 × 10 ^-9 A ₁₀ = -4.1085 × 10 ^-11 Surface 11 K = 0 A ₄ = 1.4337 × 10 ^-4 A ₆ = 5.5698 × 10 ^-6 A ₈ = -1 _{^{.9751 × 10 -7 A 10 = 1.1794}} × 10 -8 13th surface _{K = 0 A 4 = -4.3762 ×} 10 -5 A 6 = -2.1626 × 10 -6 A 8 = 1.0046 × 10 -8 A 10 = - 1.9370 × 10 ^-9 Surface 14 K = 0 A ₆ = 8.9123 × 10 ^-7 A ₈ = -1.269 × 10 ^-8 A ₁₀ = 2.2980 × 10 ^-10 Surface 17 K = 0 A ₄ = 8.5322 × 10 ^-5 A ₆ = 9.8306 × 10 ^-8 A ₈ = -4.3369 × 10 ^-9 A ₁₀ = -4.1004 × 10 ^-12 .

Next, the values of the conditional expressions (1), (2) and (3) in the above embodiments are shown below. .

In each of the above embodiments, | f ₄ | / f _T , Δ
X _4T / f _T and β _4T / β _4W are the values shown in the above table, and are respectively within the following ranges. Therefore, the lens system naturally falls within the range of the conditions (1), (2), and (3), so that the overall length of the lens system is short at the time of storage or at the wide-angle end as well as at the telephoto end despite having a high zoom ratio. Moreover, it is a zoom lens in which aberration has been well corrected.

0.045 <| f ₄ | / f _T <0.10 0.21 <ΔX _4T / f _T <0.38 3.0 <β _4T / β _4W <3.3 As described above, the fourth lens group G4 includes a negative meniscus lens and a positive meniscus lens with a strong concave surface facing the object side, or a doublet negative lens and a double convex positive lens with a strong concave surface facing the object side. , A negative meniscus lens having a strong concave surface facing the object side. Also, when comparing the absolute value of the radius of curvature of the object-side concave surface of the negative lens on the object side with the radius of curvature of the object-side concave surface of the negative meniscus lens on the image side, the curvature of the object-side concave surface of the negative lens on the object side is obtained. The radius is smaller.

The radius of curvature of the object-side concave surface of the negative lens on the object side is the smallest or second smallest in the zoom optical system, and the fourth lens group G4 is smaller than the outer diameter of the third lens group G3.
Is large, and when the third lens group G3 and the fourth lens group G4 are closest to each other, the vertex of the lens surface closest to the image side of the third lens group G3 is positioned at the highest point of the fourth lens group G4. It is located closer to the image side than the peripheral portion of the lens on the object side (the position where the spherical surface and the spherical surface intersect). Therefore, the third
The lens closest to the image in the lens group G3 can move into the space formed by the concave surface. As a result, the overall length of the lens system at the telephoto end can be reduced, and the size of the camera when the lens is stored can be reduced.

The thickness of the positive lens at the optical axis center is larger than the thickness of each of the two negative lenses. Moreover, 2
Greater than the sum of the thicknesses of the two negative lenses, from two to three.
About three times larger.

The zoom lens according to the present invention is a zoom lens whose magnification continuously changes from the wide-angle end to the telephoto end. It can also be used for zoom lenses used at discontinuous magnifications.

The zoom lens according to the present invention is a zoom lens having a zoom ratio of 3 or more and a telephoto ratio of about 0.8 to 0.5. 03. A zoom lens having a telephoto ratio of 0.51 to 0.68 is disclosed.

The above-described zoom lens according to the present invention can be constituted, for example, as follows. [1] a first lens unit having a positive refractive power in order from the object side;
A second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power. When the magnification is changed from the wide-angle end to the telephoto end, each of the lens groups is on the object side. And the distance between the first lens group and the second lens group is increased, and the distance between the third lens group and the fourth lens group is reduced, and the following conditional expression is satisfied. A zoom lens.

0.02 <| f ₄ | / f _T <0.3 (1) 0.1 <ΔX _4T / f _T <0.5 (2) 1.5 <β _4T / β _4W <6.0 (3) where f ₄ is the focal length of the fourth lens group, f _T is the focal length of the entire system at the telephoto end, and ΔX _4T is the fourth focal length based on the wide-angle end. The amount of zooming movement of the lens unit to the telephoto end, β _4T is the lateral magnification of the fourth lens unit at the telephoto end, and β _4W is the lateral magnification of the fourth lens unit at the wide-angle end.

[2] In order from the object side, the first positive refractive power
A lens group, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power, each of which is a lens when zooming from a wide-angle end to a telephoto end. As the group moves to the object side, the distance between the first lens group and the second lens group increases, and the distance between the third lens group and the fourth lens group decreases, and the magnification ratio changes. Is 3 or more, and the telephoto ratio is 0.8 to 0.5.

[3] In order from the object side, the first positive refractive power
A lens group, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power, each of which is a lens when zooming from a wide-angle end to a telephoto end. As the group moves to the object side, the distance between the first lens group and the second lens group increases, and the distance between the third lens group and the fourth lens group decreases, and the fourth lens group moves.
In the lens group, the object side surface of the lens closest to the object side has a strong concave surface on the object side, and when the third lens group and the third lens group are closest to each other, the third lens group is closest to the image side. A zoom lens wherein a surface vertex of a certain lens surface is located closer to an image than a peripheral portion of the lens having a strong concave surface on the object side.

[4] In order from the object side, the first positive refractive power
A lens group, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power, each of which is a lens when zooming from a wide-angle end to a telephoto end. As the group moves to the object side, the distance between the first lens group and the second lens group increases, and the distance between the third lens group and the fourth lens group decreases, and the fourth lens group moves.
The lens group is composed of a negative lens, a positive lens, and a negative meniscus lens from the object side, wherein the radius of curvature of the object side surface of the negative lens is smaller than the radius of curvature of the object side surface of the negative meniscus lens. And zoom lens.

[5] In order from the object side, the first positive refractive power
A lens group, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power, each of which is a lens when zooming from a wide-angle end to a telephoto end. As the group moves to the object side, the distance between the first lens group and the second lens group increases, and the distance between the third lens group and the fourth lens group decreases, and the fourth lens group moves.
The lens group is composed of a negative lens, a positive lens, and a negative meniscus lens from the object side, and the thickness of the positive lens on the optical axis is larger than the thickness of each of the negative lens and the negative meniscus lens on the optical axis. A featured zoom lens.

[6] The first lens group includes at least one doublet of a positive lens and a negative lens, the second lens group includes an aperture stop, and includes at least one negative lens. The third lens group includes at least one doublet of a negative lens and a positive lens, and the fourth lens group includes at least a negative lens and a positive lens. 2. The zoom lens according to claim 1.

[7] The zoom lens as described in [6], wherein the first lens unit having a positive refractive power has at least one aspheric surface.

[8] The zoom lens as described in [6], wherein the second lens unit having a positive refractive power has at least one aspheric surface.

[0082]

[9] The zoom lens as described in [6], wherein the third lens unit having a positive refractive power has at least one aspheric surface.

[10] The zoom lens as described in [6], wherein the fourth lens unit having a negative refractive power has at least one aspheric surface.

[11] The zoom lens as described in [6], wherein the positive lens of the first lens unit having a positive refractive power has a strong convex surface on the object side.

[12] The zoom lens as described in [7], wherein the aspheric surface is provided on an object side surface of the positive lens.

[13] The zoom lens as described in [6], wherein the second lens unit having a positive refractive power further has a biconvex lens.

[14] The second lens unit having a positive refractive power comprises, in order from the object side, a biconvex lens, a negative meniscus having a convex surface facing the image side, and an aperture stop.
The zoom lens described.

[15] The zoom lens as described in [14], wherein an aspheric surface is provided on the object side of the biconvex lens in the second lens unit having a positive refractive power.

[16] The zoom lens as described in [13], wherein the second lens unit having a positive refractive power comprises, in order from the object side, a biconcave lens, an aperture stop, and a biconvex lens.

[17] The zoom lens as described in [16], wherein an aspheric surface is provided on the object side of the biconcave lens in the second lens unit having a positive refractive power.

[18] The zoom lens as described in [17], wherein an aspheric surface is provided on the object side of the biconvex lens.

[19] The above-mentioned item 6, wherein the third lens unit having a positive refractive power further comprises a positive meniscus lens.
The zoom lens described.

[20] The zoom lens as described in the above item 9, wherein the aspherical surface is provided on the image side surface of the doublet.

[21] The zoom lens as described in the above item 19, wherein an aspheric surface is provided on the image side surface of the positive meniscus lens.

[22] In the fourth lens group having a negative refractive power, the negative lens has a strong concave surface facing the object side, forms a doublet lens with one positive lens, and further has an object side lens on the image side of the doublet lens. 7. The zoom lens as described in 6 above, further comprising a negative lens having a concave surface that is strong to the lens.

[23] The zoom lens as described in the above item 22, wherein an aspheric surface having a shape for satisfactorily correcting a peripheral image surface at a wide-angle end is provided on one of the strong concave surfaces on the object side.

[24] The zoom lens as described in [6], wherein an aspheric surface is provided on the image side surface of the positive lens of the fourth lens group.

[25] The first to fourth lens groups
The zoom lens according to any one of claims 1 to 5, wherein the total number of lenses constituting the lens group is equal to or less than 10 lenses.

[26] The first to fourth lens groups
The zoom lens according to any one of claims 1 to 5, wherein the total number of lenses constituting the lens group is 9 or less.

[27] The zoom lens as described in any one of [1] to [5] above, wherein the most image side surface of the first lens group and the most object side surface of the second lens group are concave surfaces facing each other.

[28] The zoom lens as described in [2] above, wherein the zoom ratio is 3.3 or more and the telephoto ratio is 0.7 or less.

[28] The thickness of the positive lens in the fourth lens group having a negative refractive power on the optical axis is equal to the first and second lenses.
6. The zoom lens according to the above 5, wherein the total thickness of the negative meniscus lens on the optical axis is 2 to 3.2 times.

[29] The zoom lens as described in any one of [1] to [5] above, wherein the periphery of each lens of the fourth lens unit having a negative refractive power is in contact with each other.

[0104]

As is apparent from the above description, according to the present invention, among the solutions of the four-unit zoom lens having positive, positive, positive and negative refractive powers from the object side, even in the case of high magnification, Regardless, we have found an appropriate refractive power arrangement that reduces the amount of zooming movement from the wide-angle end to the telephoto end. In addition, the compensation of the aberration correction surface by this is solved by finding an effective use method of the aspherical surface together with an appropriate lens configuration.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a first embodiment of the present invention.

FIG. 2 is an aberration diagram of the first embodiment of the present invention.

FIG. 3 is a sectional view of a lens according to a second embodiment of the present invention.

FIG. 4 is an aberration diagram of the second embodiment of the present invention.

FIG. 5 is a sectional view of a lens according to a third embodiment of the present invention.

FIG. 6 is an aberration diagram for the third embodiment of the present invention.

FIG. 7 is a sectional view of a lens according to a fourth embodiment of the present invention.

FIG. 8 is an aberration diagram for the fourth embodiment of the present invention.

FIG. 9 is a sectional view of a lens according to a fifth embodiment of the present invention.

FIG. 10 is an aberration diagram for Example 5 of the present invention.

FIG. 11 is a sectional view of a lens according to a sixth embodiment of the present invention.

FIG. 12 is an aberration diagram for the sixth embodiment of the present invention.

FIG. 13 is a sectional view of a lens according to a seventh embodiment of the present invention.

FIG. 14 is an aberration diagram for the seventh embodiment of the present invention.

[Explanation of symbols]

 G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H087 KA02 PA06 PA08 PA09 PA18 PA20 PB09 PB10 QA02 QA07 QA12 QA14 QA22 QA25 QA26 QA37 QA41 QA46 RA05 RA12 RA13 RA36 SA23 SA26 SA29 SA33 SA62 SA63 SA64 SA65 SB03 SB34 SB23 SB24

Claims (2)

[Claims] 1. A first lens group having a positive refractive power, a second lens group having a positive 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. When the magnification is changed from the wide-angle end to the telephoto end, each of the lens units moves toward the object side, and the distance between the first lens unit and the second lens unit increases. A zoom lens that moves so as to reduce the distance between the four lens groups and satisfies the following conditional expression. 0.02 <| f ₄ | / f _T <0.3 (1) 0.1 <ΔX _4T / f _T <0.5 (2) 1.5 <β _4T / β _4W < 6.0 (3) where f ₄ is the focal length of the fourth lens group, f _T is the focal length of the entire system at the telephoto end, and ΔX _4T is the focal length of the fourth lens group with reference to the wide-angle end. The amount of zooming movement to the telephoto end, β _4T is the lateral magnification of the fourth lens unit at the telephoto end, and β _4W is the lateral magnification of the fourth lens unit at the wide-angle end. 2. The first lens group includes at least one doublet of a positive lens and a negative lens, the second lens group includes an aperture stop, includes at least one negative lens, and includes a third lens group. 2. The zoom lens according to claim 1, wherein the lens group includes at least one doublet of a negative lens and a positive lens, and the fourth lens group includes at least a negative lens and a positive lens.