JP2001091833A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact zoom lens that sufficient image forming performance is maintained and a proper focusing method is applied even when a wide angle end is over 70 deg. and a variable power ratio is over about 10. SOLUTION: This zoom lens is composed of a 1st lens group G1 whose refractive power is positive, a 2nd lens group G2 whose refractive power is negative, a 3rd lens group G3 whose refractive power is positive, a 4th lens group G4 whose refractive power is negative and a 5th lens group G5 whose refractive power is positive. When variable power is executed to a telephoto end from the wide angle end, space between the groups G1 and G2 and space between the groups G3 and G4 become large. Besides, space between the groups G2 and G3 and space between the groups G4 and G5 become small. By moving the group G3 or one lens group out of the lens groups, the zoom lens is focused on a finite-point object.

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 more particularly to a wide-angle high-magnification zoom lens most suitable for a camera or the like.

[0002]

2. Description of the Related Art A high-magnification zoom lens for a camera has been developed for a television camera or a cine camera in a studio for a relatively long time. In addition, since video cameras have become widespread, development has been performed for business use or home use. It is also known that when the magnification is high and the angle of view on the wide angle side is 70 ° or more, a very high level of optical design is required. In old times, the configuration is, 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 positive refractive power. Constituent types have become widespread. For example, Tokuho 2
No. -48087. This is characterized in that the first lens unit and the fourth lens unit are fixed during zooming.

There is also a system developed based on the concept of arranging a front converter in the first lens group in this type. For example, US Pat. No. 3,682,534. These had large numbers of lens components and were large.
In this type, a method in which the first lens group having the basic configuration is used for focusing has been mainly used.

Further, in order from the object side, the first lens unit has a positive refractive power, the second lens unit has a negative refractive power, the third lens unit has a positive refractive power, and the fourth lens unit has a positive refractive power. A wide-angle, high-magnification zoom lens has been proposed in which the second lens group to the fourth lens group are movable at the time of zooming, and the fourth lens group focuses. For example, there is Japanese Patent Application Laid-Open No. 6-148520. This was for conventional video.

Further, in order from the object side, the first lens unit has a positive refractive power, the second lens unit has a negative refractive power, the third lens unit has a negative refractive power, and the fourth lens unit has a positive refractive power. There is a type which is similar to the wide-angle and high-magnification zoom lens of the present invention to be described later.
No. 8 and others. Also in this type, the same focusing method as in the above-mentioned type was adopted.

Further, in order from the object side, the first lens unit has a positive refractive power, the second lens unit has a negative refractive power, the third lens unit has a positive refractive power, and the fourth lens unit has a positive refractive power. Japanese Patent Application Laid-Open No. 7-20381 discloses a type in which the first lens unit and the following units are movable at the time of zooming.

[0007] These proposals have a simple lens configuration, but have a problem to cope with a future increase in the number of pixels of an image sensor. Rather, these zoom lens types have begun to be developed in cameras using conventional silver halide films. For example, the configuration 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 positive refractive power. This is a zoom system in which each lens group moves, and the angle of view at the wide-angle end exceeds 80 °.
U.S. Pat. No. 4,299,454.

Japanese Patent Publication No. Sho 58-33531 proposes a lens having an angle of view of about 74 ° to about 19 ° and a zoom ratio of about 5 times. In this proposal, the configuration is such that, 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. Also, there is a feature in the focusing method in which the fifth lens unit having a positive refractive power is formed, and the first lens unit and the second lens unit are integrated.

As a zoom lens covering an angle of view of about 74 ° to about 8.3 °, US Pat.
No. 6,950. This is because, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, the third lens group having a positive refractive power, and the fourth lens group having a negative refractive power.
This is a type including a lens group and a fifth lens group having a positive refractive power, and the fifth lens group is fixed during zooming.
As a focus method of this type, a method of moving the second lens group having a large power is used. For example, there is one disclosed in Japanese Patent Application Laid-Open No. 9-184982.

Japanese Patent Application Laid-Open No. Hei 10-133109 proposes a method of moving the third lens group. This lens system is large and is characterized by a power arrangement. As a method of moving the fourth lens group down, Japanese Patent Application Laid-Open
No. 133303.

Although these have no problem for use in silver halide film cameras, they should be used as they are in order not to impair the aperture ratio including the microlenses used in CCDs for digital cameras in the future. Can not. Also,
In consideration of the problem of color unevenness including chromatic aberration, it must be said that it is necessary to sufficiently consider the exit angle of the off-axis chief ray and to perform optical design in consideration of the image plane illuminance.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to develop a wide-angle, high-magnification zoom lens most suitable for a camera or the like.

Conventional video cameras have been proposed as wide-angle, high-magnification zoom lenses, but no proposal has been made for an optical system having an optical performance corresponding to a high-pixel image sensor. In the case of a silver halide camera, there are still many problems in terms of optical performance and affinity for characteristics such as a CCD.

Further, in the optical design based on the conventional zoom lens for a video camera, an extremely large zoom lens is required, which may cause a serious problem in practical use.

The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to obtain a sufficient image formation even when the wide-angle end exceeds 70 ° and the zoom ratio exceeds about 10 times. An object of the present invention is to provide a small zoom lens that maintains performance and has an appropriate focusing method.

[0016]

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 negative refractive power, and a second lens unit having a positive refractive power. 3
A lens group, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power. When the magnification is changed from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group; The distance between the third lens group and the fourth lens group is increased, the distance between the second lens group and the third lens group, and the distance between the fourth lens group and the fifth lens group are reduced. Alternatively, it focuses on an object at a finite distance by moving some of the lens units in the lens unit.

Another zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power.
The first lens unit includes a lens unit, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power. The distance between the second lens group and the second lens group, the distance between the third lens group and the fourth lens group are increased, the distance between the second lens group and the third lens group, and the distance between the fourth lens group and the fifth lens group. Becomes smaller,
The present invention is characterized in that a finite object is focused by moving the fourth lens group or a part of the lens groups in the fourth lens group.

Still another zoom lens according to the present invention comprises, 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 negative lens having a negative refractive power. The fourth lens unit includes a fifth lens unit having a positive refractive power, and includes a space between the first lens unit and the second lens unit, and a distance between the third lens unit and the third lens unit during zooming from the wide-angle end to the telephoto end. The distance between the four lens groups is increased, the distance between the second lens group and the third lens group, and the distance between the fourth lens group and the fifth lens group is reduced. It is characterized by focusing on an object at a finite distance by moving a lens group of the unit.

Hereinafter, the reason for adopting the above configuration in the present invention and its operation will be described.

As described above, an object of the present invention is to provide a wide-angle, high-magnification zoom lens having a small size, high performance, and an appropriate focusing method.

In order from the conventional object side, the first lens unit has a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power. Zoom lenses have become mainstream in silver halide film cameras, and in high-magnification zoom lenses, it is common for the first and subsequent lens groups to be movable. Further, the movement of the third lens unit and the fourth lens unit is necessary to correct the fluctuation of the field curvature at the time of zooming in addition to the zooming, and basically these groups are one group. In some cases it may even be considered. However, in order to achieve a wider angle of view and a larger zoom ratio, one negative lens group is provided in addition to the positive lens group, and the lens is moved. This is advantageous. In particular, as in the present invention, when the zoom ratio is about 10 times or more, the superiority becomes very clear. Generally, as the number of lens groups increases, it is considered that chromatic aberration correction is required for each lens group, and it is considered that the number of lens components increases. However, in the present invention,
The aspherical surface is utilized so that the second lens group can solve distortion aberration correction effectively and the rear lens group can sufficiently correct coma and the like.

That is, in the first zoom lens of the present invention, the first lens unit having a positive refractive power, in order from the object side,
The zoom lens system includes a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power. Sometimes, the distance between the first lens group and the second lens group, and the distance between the third lens group and the fourth lens group.
The distance between the lens groups is increased, the distance between the second lens group and the third lens group, and the distance between the fourth lens group and the fifth lens group is reduced, so that the third lens group or a part of the lens group. By moving the lens group of (1), focusing on an object at a finite distance is characterized.

This focusing method is based on moving the third lens group. The paraxial arrangement of the focus group changes depending on the zoom position, and the amount of focusing to the same distance differs. The third lens group having a positive refractive power has a third-order spherical aberration coefficient and a third-order astigmatism coefficient both under the lens group. By focusing on an object at a finite distance, the aberration variation of each group is substantially equal to the aberration coefficient. Related to change.
For example, the third lens group according to the present invention may be moved from infinity to 1.
In the case of focusing on 5 m, the third-order aberration coefficients of the lens unit of Example 1 described below are shown below.

[0024]

[0025] Here, SA3 is a spherical aberration coefficient, CM3 is a coma aberration coefficient, AS3 is an astigmatism coefficient, DT3 is a distortion aberration coefficient, PZ3 is a field curvature aberration coefficient, PAC is a magnification chromatic aberration coefficient, and PLC is a On-axis chromatic aberration coefficient.

In this embodiment, it can be seen that even when the third lens group is a single lens, the fluctuation of aberration due to focusing is very stable.

According to the aberration coefficients described above, since the focusing group is a single lens, the chromatic aberration varies slightly, but the performance change during focusing is small as a whole.

In the first zoom lens according to the present invention, it is desirable that the following conditional expression is satisfied.

2.0 <f ₁ / f _W <8.0 (1) 0.4 <| f ₂ / f _W | <1.0 (2) 0.3 <f ₃ / f _T345 <1.2 (3) 0.6 <| f ₄ | / f _T345 <5.0 (4) 0.5 <f ₅ / f _T345 <4.0 (4) 5) where f _W is the focal length of the entire system at the wide-angle end f ₁ is the focal length of the first lens group f ₂ is the focal length of the second lens group f ₃ is the focal length of the third lens group f ₄ is the focal length f ₅ of the fourth lens group, the focal length f _T345 in the fifth lens group, the focal length of the third lens group at the telephoto end to the fifth lens group.

It is a major object of the present invention to provide a zoom lens optical system which can sufficiently cope with an angle of view at the wide-angle end of about 70 ° or more and has high imaging performance. For this purpose, as a zoom method, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are sequentially arranged from the object side.
A lens group, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power, and an appropriate power arrangement suitable for the conditional expressions (1) to (5) is found. This was realized by arranging the actual lens configuration. Also,
This solves the problem of large size and reduced performance that are common in wide-angle high-magnification zoom lenses.

Conditional expression (1) defines the power arrangement of the first lens group. Since the first lens group moves at the time of zooming in the case of the zoom method as in the present invention, it is important to maintain the imaging performance while paying attention to the amount of movement and the increase of the front lens diameter.

When the value exceeds the upper limit of 8.0 in the conditional expression (1), the amount of residual aberration of the first lens unit decreases, which is advantageous for aberration correction. However, the amount of movement during zooming increases, and Since the outer diameter of the lens also increases, the overall size tends to increase, which is not desirable. If the lower limit of 2.0 is exceeded, the size tends to be reduced, and the front lens diameter and the amount of movement during zooming tend to decrease, but this is not preferable from the viewpoint of aberration correction.

Conditional expression (2) is a conditional expression for determining the power arrangement of the second lens unit having a negative refractive power. The second lens group is also involved in determining the power of the first lens group. If the second lens group has a small power, the first lens group becomes the same,
It will tend to be larger.

When the value exceeds the upper limit of 1.0 in the conditional expression (2), the lens configuration can be reduced and an advantage in aberration correction can be obtained.
However, the power of the first lens group other than the second lens group also becomes smaller, which leads to an increase in the diameter of the front lens of the first lens group and an increase in the amount of movement during zooming. This has undesirable consequences. On the other hand, if the lower limit of 0.4 is exceeded, it is possible to reduce the lens diameter, but it becomes difficult to correct the aberration, and the occurrence of distortion and off-axis coma become remarkable. . Further, if the conditional expression is satisfied, it is possible to obtain a small lens diameter and high imaging performance by using an appropriate lens configuration.

The conditional expression (3) is a conditional expression relating to the determination of the power of the third lens group. In this zoom system, the image forming unit is configured by the third lens group to the fifth lens group, and it can be said that the zoom system includes three independent lens groups in view of the zooming system. In many conventional zoom methods, the third lens group differs from the positive refractive power method and the fourth lens group in the positive refractive power method and its zooming method. The third lens group has a role of converging a light beam from the second lens group having a strong divergent power and correcting spherical aberration and off-axis aberration. Further, it has a role of favorably correcting on-axis spherical aberration.

Exceeding the upper limit of 1.2 to condition (3) is very advantageous for the aberration correction surface of the third lens unit, but increases the amount of movement of the third lens unit during zooming, which is preferable. Absent. If the lower limit of 0.3 is exceeded, the amount of movement during zooming is reduced, which is desirable for miniaturization. However, from the viewpoint of aberration correction, not only is it difficult to correct spherical aberration, but also off-axis coma Is difficult to correct, which is undesirable.

Conditional expression (4) is a conditional expression for determining the power of the fourth lens unit having negative refractive power. When the value exceeds the upper limit of 5.0 to condition (4), the amount of movement of the fourth lens unit increases, and a large zoom ratio is required to move between the third lens unit and the fifth lens unit. It becomes difficult. Also, the lower limit of 0.
If it exceeds 6, the amount of movement at the time of zooming is reduced, but it becomes difficult from the viewpoint of aberration correction. Therefore, it is not desirable to set a numerical value below this range. Further, in the present invention, the first to fourth lens groups constitute a nearly afocal light flux particularly near the wide-angle end.

Conditional expression (5) is a conditional expression for determining the power of the fifth lens unit. This lens group plays an important role in controlling the principal ray of the off-axis light beam. Particularly, in the use of a CCD image pickup device or the like, it plays a large role in giving the off-axis principal ray a certain degree of telecentricity. Exceeding the upper limit of 4.0 to 4.0 in this conditional expression facilitates aberration correction of the fifth lens group, but undesirably increases the amount of movement during zooming. If the lower limit of 0.5 is exceeded, it becomes difficult to correct off-axis aberrations, and at the same time, it becomes difficult to correct aberrations unless the lens configuration is increased. Furthermore, this lens group
An increase in the lens configuration leads to an increase in the size of the entire lens system, so that a desired result cannot be obtained in many cases.

The zoom lens of the present invention is intended to be as small as possible by making the lens configuration as simple as possible. In such a case, the refractive power arrangement of each lens group is important, and is related not only to the lens configuration of each group but also to the amount of movement of the lens group during zooming.

Further, in the present invention, it is intended that the wide-angle end encompasses about 70 ° or more even though the magnification is high, and an advanced optical system having a simpler configuration than the conventional prior art is proposed. Is what you do.

That is, in terms of the focal length, it is desirable that the focal length at the wide-angle end is shorter than the imaging surface of the optical system or the effective diagonal length of the image sensor.

As will be seen from the following embodiments of the present invention, including the case where a CCD is considered as an image pickup device, the effective diagonal line length is considered in consideration of the color problem such as aliasing and shading on the image plane. Despite being larger than before,
An optical system that can maintain a certain degree of telecentricity has been proposed.

That is, it is desirable that the principal ray emitted from the optical system is determined based on the following conditional expression.

10 <| Expd _W × Y | / L _W (6) where Expd _W is the distance on the optical axis from the image plane position to the exit pupil Y is the actual maximum on the image plane The image height _LW is the distance on the optical axis from the vertex of the first lens unit at the wide-angle end to the image side, from the vertex on the object side surface.

By satisfying this conditional expression, it is possible to satisfy the condition for obtaining a clear image.

When zooming from the wide-angle end to the telephoto end, it is desirable to satisfy the following relationship.

1.6 <Δ _1T / f _W <5.0 (7) 1.0 <Δ _3T / f _W <4.0 (8) where Δ _1T is based on the wide angle end. moving amount delta _3T during zooming to the telephoto end of the first lens group, which is the amount of zooming movement of to the telephoto end of the third lens unit at the wide angle end reference.

Conditional expression (7) is a conditional expression that regulates the amount of movement of the first lens unit during zooming from the wide-angle end to the telephoto end during zooming. The conditional expression (8) is a conditional expression that regulates the movement amount of the third lens unit during zooming from the wide-angle end to the telephoto end during zooming.

Conditional expression (7) is a conditional expression intended to make the amount of movement of the first lens unit at the time of zooming appropriate and to reduce the size. When the value exceeds the upper limit of 5.0 to condition (7), even if the overall length at the wide-angle end is relatively short, a large amount of movement is required when moving to the telephoto end. Becomes difficult. If the lower limit of 1.6 is exceeded, the amount of movement will not be sufficient, and it will not be possible to increase the zoom ratio, which is not desirable.

When the value exceeds the upper limit of 4.0 in the conditional expression (8), the amount of movement of the third lens unit increases, which is not desirable because it increases in size. If the lower limit of 1.0 is exceeded, it is possible to realize a zoom method other than this method.

Next, the imaging magnification will be described. The zoom lens according to the present invention is characterized in that the whole of the five constituent units moves during zooming. In addition, when moving from the wide-angle end to the telephoto end, the second lens unit changes magnification according to the following relationship, and has a large zooming action. The second lens group itself is a lens group that can be fixed during zooming.

That is, it is desirable that the paraxial lateral magnification of the second lens unit satisfies the following relationship.

2.5 <β _2T / β _2W <7 (9) where β _2W is the imaging magnification at the wide-angle end of the second lens group, and β _2T is the imaging magnification at the telephoto end of the second lens group. Is the imaging magnification of.

When the paraxial configuration is determined by the above conditional expression, the thick lens configuration is determined next. First, it is desirable that the first lens group includes at least one negative lens and one positive lens.

In the present invention, the first lens group is basically composed of a set of cemented lenses or an air separation type doublet, and is further composed of one positive lens. When the telephoto end is in the telephoto range of the high-magnification zoom lens, use of anomalous dispersion glass makes it easier to cope with an image sensor with a higher pixel count.

It is preferable that the second lens group includes at least two negative lenses and one positive lens.

In the present invention, as shown in conditional expression (2),
The second lens group is intended to be downsized by configuring with a large power, and it is desirable to configure a negative meniscus lens, a biconcave negative lens, a positive lens, and a negative lens in order from the object side.

It is desirable that the third lens group is composed of at least one positive lens. For miniaturization, it is advantageous to have a simple lens configuration. However, if the magnification is further increased, it goes without saying that the lens configuration becomes more complicated.

The fourth lens group comprises at least one negative lens. It is a negative lens group, and if a miniaturization is intended, a single lens is desirable.

It is preferable that the fifth lens group includes at least one positive lens and one negative lens.

It is desirable that the fifth lens group is composed of a cemented lens of at least one positive lens and one negative lens or an air separation type doublet.

Further, by using at least one aspherical surface for the second lens group, it becomes easy to correct distortion and coma. Especially the first of negative meniscus lenses
When used on a surface, the balance between distortion and coma can be corrected relatively easily.

When at least one aspherical surface is used for the third lens unit, it becomes very easy to correct spherical aberration.

If at least one aspherical surface is used for the fourth lens group, it is possible to correct minute curvature of field.

When at least one aspherical surface is used for the fifth lens group, it is possible to realize an optical system that maintains a certain degree of telecentricity and maintains a peripheral light amount.

In the present invention, the first lens unit and the third lens unit move substantially linearly in the zooming operation. However, for the other lens units, the magnification relationship at the time of zooming is the fourth lens unit. Except for the relationship between the groups, generally speaking, regarding the movement from the wide-angle end to the telephoto end, the absolute value of the magnification maintains the directionality of the multiplication. This enables efficient zooming.

Further, with respect to focusing, in a wide-angle and high-magnification zoom lens according to the present invention, the method of moving the first lens group used in the past zoom lens is impractical due to enlargement and aberration fluctuation. 1 lens group and 2nd
It is rather better to move the lens groups together. In addition, from the viewpoint of aberration variation, movement of the second lens group or the like can also be used if it is used for close-up photography. Focusing can also be achieved by moving at least one lens group behind the third lens group.

According to the first zoom lens, not only a high-magnification zoom lens but also an angle of view exceeding 70 °
High magnification zoom lens including wide angle is possible. For this reason, it was possible to realize an appropriate zoom method, a power position, an appropriate lens configuration, and an effective method of using an aspheric surface.

Next, in the second zoom lens of the present invention, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a negative lens unit. A fourth lens unit having a refractive power and a fifth lens unit having a positive refractive power, and when changing the magnification from the wide-angle end to the telephoto end, an interval between the first lens unit and the second lens unit and a third lens unit The distance between the group and the fourth lens group is increased, the distance between the second lens group and the third lens group, and the distance between the fourth lens group and the fifth lens group are reduced, and the fourth lens group or its lens group is reduced. Focusing on an object at a finite distance is achieved by moving some of the lens groups within the lens.

For example, in the case where the fourth lens group in the present invention is focused from infinity to 2.0 m, the third-order aberration coefficients related to the lens group of Example 4 described below are shown below.

[0071]

[0072]

The above table shows that the fourth embodiment focuses by moving the fourth lens group.
m) is the third-order aberration coefficient at the telephoto end. This is a focusing method by extending the fourth lens group. Since the fourth lens unit and the fifth lens unit are close to each other at the telephoto end, extending the fourth lens unit is a great advantage. In the embodiment of the present invention, the fourth lens group is constituted by a single lens, and there is a great advantage as a focus mechanism. The variation of the third-order aberration coefficient during focusing is such that the pincushion distortion becomes smaller at a finite distance. Further, it can be said that fluctuations of various aberrations are very small. Further, there is a margin in the actual axial distance between the third lens group and the fourth lens group, and although it is necessary to evaluate aberration fluctuation, this method can shorten the short distance.

This is a focusing method using a single lens.
Actually, since the chromatic aberration of magnification contains a higher-order component, it is necessary to evaluate the actual aberration. actually,
In order to further improve the chromatic aberration of magnification, it is preferable that the chromatic aberration is corrected in the fourth lens group, that is, a cemented lens or a doublet having an air space is used.

Next, in the third zoom lens of the present invention, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a negative lens unit. A fourth lens unit having a refractive power and a fifth lens unit having a positive refractive power, and when changing the magnification from the wide-angle end to the telephoto end, an interval between the first lens unit and the second lens unit and a third lens unit The distance between the group and the fourth lens group increases, the distance between the second lens group and the third lens group, and the distance between the fourth lens group and the fifth lens group decrease, and the fifth lens group or its lens group Focusing on an object at a finite distance is achieved by moving some of the lens groups within the lens.

For example, in the case where the fifth lens unit according to the present invention is focused to 2.0 m from infinity, an example of the third-order aberration coefficient is shown below.

[0077]

[0078]

The above table shows a case where focusing is performed by moving the fifth lens group. In this method, only the fifth lens group is inappropriate when the exit pupil distance is long. Therefore, the fifth lens group is divided into two groups, and they are floated with each other during zooming.
Thereby, the actual aberration correction can be better performed at each zoom position. In this example, the spherical aberration slightly fluctuates, and the third-order spherical aberration coefficient and the coma aberration coefficient are slightly more remarkable than in the above two examples. However, it can be said that there is little problem if chromatic aberration is corrected by the group itself as a cemented lens.

[0080]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 4 of the zoom lens according to the present invention will be described below. FIGS. 1 to 4 show lens cross-sectional views of Examples 1 to 4 at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) at infinity. The numerical data of each embodiment will be described later.

(Embodiment 1) The embodiment 1 has a focal length of 14.1.
55-140.01mm, F-number 3.6-4.4
1 is a wide-angle, high-magnification zoom lens. In this embodiment, as shown in FIG. 1, at the time of zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side. Second lens group G2
Moves slightly. The third lens group G3 moves to the object side together with the aperture stop. The fourth lens group G4 is the third lens group G
The fourth lens group G5 is arranged such that the distance from the third lens group G5 increases and the distance between the fifth lens group G5 and the fourth lens group G4 decreases.
The fourth and fifth lens groups G5 move nonlinearly.

The first lens group G1 comprises a cemented lens of a negative meniscus lens having a strong curvature on the image side and a biconvex lens having a strong curvature on the object side, and a positive meniscus lens having a strong curvature on the object side. Have been. Second lens group G2
Is composed of a negative meniscus lens having a strong curvature on the image side, a biconcave lens, a biconvex lens, and a negative meniscus lens having a strong curvature on the object side. Also, the third
The lens group G3 includes a single biconvex lens following the aperture stop S. The fourth lens group G4 has a single biconcave lens configuration. The fifth lens group G5 includes a cemented lens of a biconvex lens and a negative meniscus lens, and a biconvex lens.

The aspheric surface includes the first surface of the first lens and the object side surface of the second lens of the second lens group G2, and the third lens group G3
Of the biconvex lens on the object side, and on both surfaces of the most image-side biconvex lens of the fifth lens group G5.

In this embodiment, the third lens group G3
Are retracted as a focusing group F.

FIG. 5 is an aberration diagram for this embodiment when focusing on infinity, and FIG. 6 is an aberration diagram when the third lens group G3 is focused to 1.5 m. In these aberration diagrams, (a) is the wide-angle end, (b) is the intermediate state, (c)
Indicates spherical aberration SA, astigmatism AS, distortion DT, and lateral chromatic aberration CC at the telephoto end. However, in the figure, "FI
Y ″ represents the image height.

Aberration fluctuation due to focusing from infinity to 1.5 m is gentle. At the telephoto end, the fluctuations of the spherical aberration and the chromatic aberration of magnification are slightly observed, and good results are obtained.

(Embodiment 2) The embodiment 2 has a focal length of 14.1.
55-140.01 mm, F-number 3.67-4.
Thirteen wide-angle high-magnification zoom lenses. This embodiment is an embodiment shown for reference, and is an example in which the first lens group G1 and the second lens group G2 are integrated and fed out as a focusing group F.

In this embodiment, as shown in FIG. 2, at the time of zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side. The second lens group G2 moves slightly. Third
The lens group G3 moves to the object side together with the aperture stop. 4th
The fourth lens group G4 and the fifth lens group G5 are arranged such that the distance between the lens group G4 and the third lens group G3 increases, and the distance between the fifth lens group G5 and the fourth lens group G4 decreases.
Moves non-linearly.

The first lens group G1 comprises a cemented lens composed of a negative meniscus lens having a strong curvature on the image side and a biconvex lens having a strong curvature on the object side, and a positive meniscus lens having a strong curvature on the object side. Have been. Second lens group G2
Is composed of a negative meniscus lens having a strong curvature on the image side, a biconcave lens, a biconvex lens, and a negative meniscus lens having a strong curvature on the object side. Also, the third
The lens group G3 includes a single biconvex lens following the aperture stop S. The fourth lens group G4 has a single biconcave lens configuration. The fifth lens group G5 includes a cemented lens of a biconvex lens and a negative meniscus lens, and a positive meniscus lens having a strong curvature on the object side.

The aspheric surface includes the first surface of the first lens of the second lens group G2, the object side surface of the second lens, and the third lens group G3.
And the both surfaces of the positive meniscus lens closest to the image in the fifth lens group G5.

FIG. 7 shows an aberration diagram of this embodiment at the time of focusing on infinity. Further, the first lens unit G1 and the second lens unit G2
FIG. 8 shows an aberration diagram when the lens is extended integrally and focused to 1.5 m.

The aberration fluctuation is stable to some extent.
It goes without saying that there is a problem in moving the heavy lens group between the lens group G1 and the second lens group G2.

(Embodiment 3) The embodiment 3 has a focal length of 14.3.
55-140.01 mm, F-number 3.77-4.
61 is a wide-angle, high-magnification zoom lens. This example is
As shown in FIG. 3, when zooming from the wide-angle end to the telephoto end,
The first lens group G1 moves to the object side. Second lens group G
2 moves slightly. The third lens group G3 moves to the object side together with the aperture stop. The fourth lens group G4 moves nonlinearly so that the distance between the fourth lens group G4 and the third lens group G3 increases. Fifth
The lens group G5 is divided into two, a front group G5F and a rear group G5R, and moves nonlinearly so as to reduce the distance between the fourth lens group G4 and the front group G5F of the fifth lens group G5.
Also, the fifth lens group G5 moves nonlinearly so that the distance between the front group G5F and the rear group G5R is also reduced.

The first lens group G1 comprises a cemented lens of a negative meniscus lens having a strong curvature on the image side and a biconvex lens having a strong curvature on the object side, and a positive meniscus lens having a strong curvature on the object side. Have been. Second lens group G2
Is composed of a negative meniscus lens having a strong curvature on the image side, a biconcave lens, a biconvex lens, and a negative meniscus lens having a strong curvature on the object side. Also, the third
The lens group G3 includes a single biconvex lens following the aperture stop S. The fourth lens group G4 has a single biconcave lens configuration. The front group G5F of the fifth lens group G5 is a cemented lens of a biconvex lens and a negative meniscus lens, and then the group G5R is composed of a positive meniscus lens having a strong curvature on the object side.

The aspheric surface includes the first surface of the first lens and the object side surface of the second lens of the second lens group G2, and the third lens group G3.
Side surface of the biconvex lens, rear group G5 of the fifth lens group G5
It is used on both sides of the R positive meniscus lens.

This embodiment is designed to solve the problem that focusing is difficult when the fifth lens group G5 itself is a telecentric optical system. Focusing is performed by the group G5F, and thereafter, the group G5R is a so-called field flattener. By changing the distance between the front group G5F and the rear group G5R, the group G5R has a function of suppressing aberration fluctuation during focusing and zooming.

FIG. 9 is an aberration diagram when focusing on infinity in this embodiment, and FIG. 10 is an aberration diagram when focusing on a finite distance of 2.0 m.

The fluctuation of the astigmatism at the telephoto end is somewhat conspicuous, but other than this, it can be said that the astigmatism is substantially good and stable.

(Embodiment 4) In Embodiment 4, the focal length is set to 14.4.
55-140.01 mm, F-number 3.78-4.
49 wide-angle high-magnification zoom lens. This example is
As shown in FIG. 4, when zooming from the wide-angle end to the telephoto end,
The first lens group G1 moves to the object side. Second lens group G
2 moves slightly. The third lens group G3 moves to the object side together with the aperture stop. The fourth lens group G4 moves nonlinearly so that the distance between the fourth lens group G4 and the third lens group G3 increases. Fifth
The lens group G5 is divided into two, a front group G5F and a rear group G5R, and moves nonlinearly so as to reduce the distance between the fourth lens group G4 and the front group G5F of the fifth lens group G5.
Also, the fifth lens group G5 moves nonlinearly so that the distance between the front group G5F and the rear group G5R is also reduced.

The first lens group G1 comprises a cemented lens composed of a negative meniscus lens having a strong curvature on the image side and a biconvex lens having a strong curvature on the object side, and a positive meniscus lens having a strong curvature on the object side. Have been. Second lens group G2
Is composed of a negative meniscus lens having a strong curvature on the image side, a biconcave lens, a biconvex lens, and a negative meniscus lens having a strong curvature on the object side. Also, the third
The lens group G3 includes a single biconvex lens following the aperture stop S. The fourth lens group G4 has a single biconcave lens configuration. The front group G5F of the fifth lens group G5 is a cemented lens of a biconvex lens and a negative meniscus lens, and the subsequent group G5R is composed of a biconvex lens.

The aspheric surfaces are the first surface of the first lens and the object side surface of the second lens of the second lens group G2, and the third lens group G3.
Side surface of the biconvex lens, rear group G5 of the fifth lens group G5
It is used on both sides of the R biconvex lens.

This embodiment employs a focusing method for moving the fourth lens group G4.

FIG. 11 is an aberration diagram when focusing on infinity in this embodiment, and FIG. 12 is an aberration diagram when focusing on a finite distance of 2.0 m.

Since the moving space of the third lens group G3 and the fourth lens group G4 has a margin, if the aberration fluctuation at the time of focusing can be corrected to some extent, the close-up shooting distance can be considerably shortened.

The numerical data of each of the above embodiments is shown below.
F _NO is the F-number, FB is the back focus, WE is the wide-angle end, ST is the intermediate state, TE is the telephoto end, r ₁ , r ₂ … are the radii of curvature of the respective lens surfaces, d ₁ , d ₂ … are the respective lens surfaces , N _d1 , n _d2 ... are the d-line refractive indices of each lens, ν _d1 ,
ν _d2 ... is the Abbe number of each lens. The aspherical shape is represented by the following equation, where x is an optical axis where the traveling direction of light is positive, and y is a direction orthogonal to the optical axis.

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 the conic coefficient, A ₄ , A ₆ ,
A ₈ and A ₁₀ are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

(Example 1) r ₁ = 96.148 d ₁ = 1.500 n _d1 = 1.84666 v _d1 = 23.78 r ₂ = 58.919 d ₂ = 8.600 n _d2 = 1.60300 v _d2 = 65.44 r ₃ = -485.689 d ₃ = 0.100 r _{4 = 51.466 d 4 = 5.000 n} d3 = 1.49700 ν d3 = 81.54 r 5 = 154.194 d 5 = ( variable) r ₆ = 181.666 _{(aspherical) d 6 = 0.850 n d4 =} 1.80100 ν d4 = 34.97 r 7 = 17.710 d ₇ = 5.989 r ₈ = -35.508 (aspheric _{surface) d 8 = 0.850 n d5 =} 1.67003 ν d5 = 47.23 r 9 = 19.375 d 9 = 0.100 r 10 = 19.051 d 10 = 4.700 n d6 = 1.84666 ν d6 = 23.78 r 11 _{= -46.161 d 11 = 1.830 r 12} = -17.851 d 12 = 0.750 n d7 = 1.74100 ν d7 = 52.64 r 13 = -234.238 d 13 = ( variable) r ₁₄ = ∞ _{(stop) d 14 = 1.021 r 15 =} 27.177 _{(aspherical) d 15 = 3.750 n d8 =} 1.48749 ν d8 = 70.23 r 16 = -27.602 d 16 = ( _{variable) r 17 = -50.167 d 17 =} 0.650 n d9 = 1.77250 ν d9 = 49.60 r 18 = 131.563 d 18 = _{(variable) r 19 = 94.372 d 19 =} 4.115 n d10 = 1.49700 ν d10 = 81.54 _{20 = -15.230 d 20 = 0.600 n} d11 = 1.80518 ν d11 = 25.42 r 21 = -23.459 d 21 = 10.508 r 22 = 43.472 ( _{aspherical) d 22 = 5.483 n d12 =} 1.60311 ν d12 = 60.64 r 23 = -511.216 (Aspherical surface) Aspherical coefficient 6th surface K = 0.0000 A ₄ = 1.1577 × 10 ^-5 A ₆ = 2.5463 × 10 ^-8 A ₈ = 8.1116 × 10 ^-11 A ₁₀ = 0.0000 8th surface K = 0.0000 A ₄ = -4.4549 × 10 ^-6 A ₆ = -9.6370 × 10 ^-8 A ₈ = -1.2314 × 10 ^-9 A ₁₀ = 1.2357 × 10 ^-11 Surface 15 K = 0.0000 A ₄ = -2.7369 × 10 ^-5 A ₆ = 1.2966 × 10 ^-8 A ₈ = 4.7574 × 10 ^-10 A ₁₀ = -4.4510 × 10 ^-12 Surface 22 K = 0.0000 A ₄ = 1.0579 × 10 ^-5 A ₆ = 1.8428 × 10 ^-8 A ₈ = 3.1382 × 10 ^-10 A ₁₀ = -1.4942 × 10 ^-13 Surface 23 K = 0.0000 A ₄ = 1.6674 × 10 ^-5 A ₆ = 1.5129 × 10 ^-8 A ₈ = 4.1935 × 10 ^-10 A ₁₀ = 0.0000 Zoom data (∞) WEST TE f (mm) 14.550 46.770 140.010 F _NO 3.600 4.151 4.412 2ω (°) 73.7 24.1 8.0 FB (mm) 28.650 50.381 50.955 d ₅ 0.778 22.603 45.158 d ₁₃ 23.682 6.989 0.100 d ₁₆ 7.181 13.277 21.412 d ₁₈ 12.118 3.325 0.100 Focus data (1.5 m) WEST TE d ₁₄ 1.391 1.577 4.477 d ₁₆ 6.811 12.721 17.956

(Example 2) r ₁ = 91.054 d ₁ = 1.500 n _d1 = 1.84666 v _d1 = 23.78 r ₂ = 54.532 d ₂ = 8.600 n _d2 = 1.60311 v _d2 = 60.64 r ₃ = -661.853 d ₃ = 0.100 r _{4 = 46.573 d 4 = 5.000 n} d3 = 1.49700 ν d3 = 81.54 r 5 = 142.871 d 5 = ( variable) r ₆ = 95.771 _{(aspherical) d 6 = 0.850 n d4 =} 1.80100 ν d4 = 34.97 r 7 = 15.110 d ₇ = 6.363 r ₈ = -35.351 (aspheric _{surface) d 8 = 0.850 n d5 =} 1.74400 ν d5 = 44.78 r 9 = 18.436 d 9 = 0.100 r 10 = 18.410 d 10 = 4.700 n d6 = 1.84666 ν d6 = 23.78 r 11 _{= -41.901 d 11 = 1.510 r 12} = -19.590 d 12 = 0.750 n d7 = 1.74100 ν d7 = 52.64 r 13 = -80.542 d 13 = ( variable) r ₁₄ = ∞ _{(stop) d 14 = 0.282 r 15 =} 24.082 _{(aspherical) d 15 = 3.750 n d8 =} 1.48749 ν d8 = 70.23 r 16 = -35.766 d 16 = ( _{variable) r 17 = -51.102 d 17 =} 0.750 n d9 = 1.77250 ν d9 = 49.60 r 18 = 81.248 d 18 = _{(variable) r 19 = 68.833 d 19 =} 4.215 n d10 = 1.49700 ν d10 = 81.54 r 2 _{0 = -14.308 d 20 = 0.600 n} d11 = 1.80518 ν d11 = 25.42 r 21 = -20.792 d 21 = 14.798 r 22 = 19.914 ( _{aspherical) d 22 = 1.972 n d12 =} 1.60311 ν d12 = 60.64 r 23 = 30.732 ( Aspherical surface coefficient Aspherical surface 6th surface K = 0.0000 A ₄ = 3.8600 × 10 ^-6 A ₆ = 1.8443 × 10 ^-8 A ₈ = 3.8163 × 10 ^-11 A ₁₀ = 0.0000 8th surface K = 0.0000 A ₄ = 4.7757 × 10 ^-6 A ₆ = -4.2943 × 10 ^-8 A ₈ = -9.0332 × 10 ^-10 A ₁₀ = 5.7484 × 10 ^-12 15th surface K = 0.0000 A ₄ = -2.4127 × 10 ^-5 A ₆ = -5.6179 × 10 ^-8 A ₈ = 1.9592 × 10 ^-9 Surface 22 K = 0.0000 A ₄ = -4.2522 × 10 ^-7 A ₆ = -7.5812 × 10 ^-9 A ₈ = 4.7213 × 10 ^-11 A ₁₀ = 1.3999 × 10 ^-13 23rd surface _{K = 0.0000 A 4 = 1.2987 ×} 10 -5 A 6 = -5.1984 × 10 -10 A 8 = 1.2972 × 10 -10 A 10 = 0.0000 zoom data (∞) WE ST TE f ( mm) 14.550 46.770 140.010 F _NO 3.672 4.171 4.133 2ω (°) 73.7 24.2 8.2 FB (mm) 27.005 41.973 52.142 d ₅ 0.778 25.830 41.824 d ₁₃ 28.150 10.799 0.100 d ₁₆ 7.647 12.713 20.000 d ₁₈ 8.506 4.515 1.068 Focus data (1.5 m) WEST TE d ₁₃ 28.399 11.627 3.701.

(Example 3) r ₁ = 95.816 d ₁ = 1.500 n _d1 = 1.84666 v _d1 = 23.78 r ₂ = 57.080 d ₂ = 8.600 n _d2 = 1.60311 v _d2 = 60.64 r ₃ = -595.877 d ₃ = 0.100 r _{4 = 51.891 d 4 = 5.000 n} d3 = 1.49700 ν d3 = 81.54 r 5 = 159.655 d 5 = ( variable) r ₆ = 60.918 _{(aspherical) d 6 = 0.850 n d4 =} 1.80100 ν d4 = 34.97 r 7 = 13.633 d ₇ = 6.759 r ₈ = -30.855 (aspheric _{surface) d 8 = 0.850 n d5 =} 1.74400 ν d5 = 44.78 r 9 = 22.170 d 9 = 0.100 r 10 = 21.443 d 10 = 4.700 n d6 = 1.84666 ν d6 = 23.78 r 11 _{= -37.460 d 11 = 1.540 r 12} = -18.028 d 12 = 0.750 n d7 = 1.74100 ν d7 = 52.64 r 13 = -51.094 d 13 = ( variable) r ₁₄ = ∞ _{(stop) d 14 = 1.132 r 15 =} 21.530 _{(aspherical) d 15 = 3.750 n d8 =} 1.48749 ν d8 = 70.23 r 16 = -30.476 d 16 = ( _{variable) r 17 = -33.630 d 17 =} 0.750 n d9 = 1.77250 ν d9 = 49.60 r 18 = 37.540 d 18 = _{(variable) r 19 = 34.660 d 19 =} 4.369 n d10 = 1.49700 ν d10 = 81.54 r 2 _{0 = -13.974 d 20 = 0.600 n} d11 = 1.80518 ν d11 = 25.42 r 21 = -20.668 d 21 = ( Variable) r ₂₂ = 24.634 _{(aspherical) d 22 = 2.383 n d12 =} 1.60311 ν d12 = 60.64 r 23 = 66.482 (Aspherical surface) Aspherical surface coefficient 6th surface K = 0.0000 A ₄ = 8.1433 × 10 ^-7 A ₆ = 1.0353 × 10 ^-8 A ₈ = 5.3072 × 10 ^-11 A ₁₀ = 0.0000 8th surface K = 0.0000 A ₄ = 9.3299 × 10 ^-6 A ₆ = -3.4823 × 10 ^-8 A ₈ = -7.3408 × 10 ^-10 A ₁₀ = 4.7042 × 10 ^-12 15th page K = 0.0000 A ₄ = -2.8541 × 10 ^-5 A ₆ = -1.0861 × 10 ^-8 A ₈ = 5.2954 × 10 ^-10 A ₁₀ = -5.5308 × 10 ^-12 Surface 22 K = 0.0000 A ₄ = 8.4723 × 10 ^-6 A ₆ = 1.4247 × 10 ^-8 A ₈ = -7.7053 × 10 ^-11 A ₁₀ = -3.9331 × 10 ^-14 Surface 23 K = 0.0000 A ₄ = 2.3171 × 10 ^-5 A ₆ = 1.9749 × 10 ^-8 A ₈ = -9.1947 × 10 ^-11 A ₁₀ = 0.0000 Zoom data (∞) WE ST TE f ( mm) 14.552 46.776 140.007 F NO 3.774 4.390 4.610 2ω (°) 73.7 24.1 8.1 FB (mm) 26.992 47.883 50.064 d 5 0.778 24.541 46.406 d 13 29.032 8.977 0.100 d 16 10.019 13.654 20. 000 d ₁₈ 4.093 2.113 1.089 d ₂₁ 14.116 13.418 11.011 Focus data (2.0 m) WEST TE d ₁₈ 6.347 2.677 4.707 d ₂₁ 11.862 12.855 7.393

(Example 4) r ₁ = 92.253 d ₁ = 1.500 n _d1 = 1.84666 v _d1 = 23.78 r ₂ = 54.366 d ₂ = 8.600 n _d2 = 1.60311 v _d2 = 60.64 r ₃ = -726.787 d ₃ = 0.100 r _{4 = 48.804 d 4 = 5.000 n} d3 = 1.49700 ν d3 = 81.54 r 5 = 157.176 d 5 = ( variable) r ₆ = 92.290 _{(aspherical) d 6 = 0.850 n d4 =} 1.80100 ν d4 = 34.97 r 7 = 15.216 d ₇ = 6.827 r ₈ = -29.675 (aspheric _{surface) d 8 = 0.850 n d5 =} 1.74400 ν d5 = 44.78 r 9 = 20.119 d 9 = 0.100 r 10 = 20.429 d 10 = 4.700 n d6 = 1.84666 ν d6 = 23.78 r 11 _{= -31.752 d 11 = 1.748 r 12} = -17.416 d 12 = 0.750 n d7 = 1.74100 ν d7 = 52.64 r 13 = -63.633 d 13 = ( variable) r ₁₄ = ∞ _{(stop) d 14 = 0.862 r 15 =} 23.893 _{(aspherical) d 15 = 3.750 n d8 =} 1.49700 ν d8 = 81.54 r 16 = -32.227 d 16 = ( _{variable) r 17 = -20.715 d 17 =} 0.700 n d9 = 1.77250 ν d9 = 49.60 r 18 = 72.399 d 18 = _{(variable) r 19 = 34.516 d 19 =} 4.000 n d10 = 1.49700 ν d10 = 81.54 r 2 _{0 = -15.986 d 20 = 0.600 n} d11 = 1.80518 ν d11 = 25.42 r 21 = -21.973 d 21 = ( Variable) r ₂₂ = 30.431 _{(aspherical) d 22 = 3.605 n d12 =} 1.49700 ν d12 = 81.54 r 23 = -93.324 (Aspherical surface) Aspherical surface coefficient 6th surface K = 0.0000 A ₄ = 3.5498 × 10 ^-6 A ₆ = 2.1901 × 10 ^-8 A ₈ = 3.7413 × 10 ^-11 A ₁₀ = 0.0000 8th surface K = 0.0000 A ₄ = 5.7125 × 10 ^-6 A ₆ = -1.8826 × 10 ^-8 A ₈ = -1.2043 × 10 ^-9 A ₁₀ = 8.1735 × 10 ^-12 Surface 15 K = 0.0000 A ₄ = -1.5544 × 10 ^-5 A ₆ = -1.2826 × 10 ^-8 A ₈ = 4.4582 × 10 ^-10 A ₁₀ = -4.6850 × 10 ^-12 Surface 22 K = 0.0000 A ₄ = 3.1293 × 10 ^-6 A ₆ = 1.3890 × 10 ^-8 A ₈ = 1.2058 × 10 ^-10 A ₁₀ = 1.5944 × 10 ^-13 Surface 23 K = 0.0000 A ₄ = 2.6066 × 10 ^-5 A ₆ = 2.1615 × 10 ^-8 A ₈ = 1.9517 × 10 ^-10 A ₁₀ = 0.0000 Zoom data (∞ ) WEST TE f (mm) 14.550 46.780 140.010 F _NO 3.777 3.995 4.486 2ω (°) 73.7 24.2 8.2 FB (mm) 32.496 56.263 56.430 d ₅ 0.778 22.488 43.818 d ₁₃ 27.986 5.791 0.100 d ₁₆ 10.827 15.345 24. 345 d ₁₈ 2.034 2.114 0.330 d ₂₁ 10.101 7.132 4.676 Focus data (2.0 m) WEST TE d ₁₆ 10.480 15.058 22.299 d ₁₈ 2.381 2.400 2.376

Next, the conditional expression (1) in each of the above embodiments is used.
The values of (9) are shown below: (1) (2) (3) (4) (5) Example 1 5.5936 0.8477 0.8288 1.3538 0.9289 Example 2 5.3362 0.8928 0.9010 1.2109 0.9357 Example 3 5.7316 0.9159 0.7348 0.6337 0.7045 Example 4 5.5056 0.8894 0.8395 0.6180 0.6660 (6) (7) (8) (9) Example 1 13.4069 1.7400 1.6851 4.4130 Example 2 12.1372 2.9586 2.0654 4.2023 Example 3 12.5236 2.9989 1.5855 4.3006 Example 4 11.6802 3.1256 2.0841 4.2529.

The above-described zoom lens of the present invention can be constituted, for example, as follows.

[1] In order from the object side, the first positive refractive power
The zoom lens includes a lens unit, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power. At the time of zooming, the distance between the first lens group and the second lens group and the distance between the third lens group and the fourth lens group are increased, and the distance between the second lens group and the third lens group and the fourth lens group are increased. A zoom lens, wherein the distance between the lens group and the fifth lens group is reduced, and the third lens group or a part of the lens groups is moved to focus on an object at a finite distance.

[2] The zoom lens as described in [1], wherein the following conditional expression is satisfied.

2.0 <f ₁ / f _W <8.0 (1) 0.4 <| f ₂ / f _W | <1.0 (2) 0.3 <f ₃ / f _T345 <1.2 (3) 0.6 <| f ₄ | / f _T345 <5.0 (4) 0.5 <f ₅ / f _T345 <4.0 (4) 5) where f _W is the focal length of the entire system at the wide-angle end f ₁ is the focal length of the first lens group f ₂ is the focal length of the second lens group f ₃ is the focal length of the third lens group f ₄ is the focal length f ₅ of the fourth lens group, the focal length f _T345 in the fifth lens group, the focal length of the third lens group at the telephoto end to the fifth lens group.

[3] The zoom lens as described in [1] or [2] above, wherein the focal length at the wide-angle end is shorter than the imaging surface of the optical system or the effective diagonal length of the image sensor.

[4] The principal ray emitted from the optical system is determined based on the following conditional expression.
The zoom lens according to any one of claims 1 to 3, wherein

10 <| Expd _W × Y | / L _W (6) where Expd _W is the distance on the optical axis from the image plane position to the exit pupil Y is the actual maximum on the image plane The image height _LW is the distance on the optical axis from the vertex of the first lens unit at the wide-angle end to the image side, from the vertex on the object side surface.

[5] The zoom lens as described in any one of [1] to [4] above, wherein the following relationship is satisfied when zooming from the wide-angle end to the telephoto end.

1.6 <Δ _1T / f _W <5.0 (7) 1.0 <Δ _3T / f _W <4.0 (8) where Δ _1T is based on the wide angle end. moving amount delta _3T during zooming to the telephoto end of the first lens group, which is the amount of zooming movement of to the telephoto end of the third lens unit at the wide angle end reference.

[6] The zoom lens as described in any one of [1] to [5] above, wherein the paraxial lateral magnification of the second lens unit satisfies the following relationship.

2.5 <β _2T / β _2W <7 (9) where β _2W is the imaging magnification at the wide-angle end of the second lens group, and β _2T is the imaging magnification at the telephoto end of the second lens group. Is the imaging magnification of.

[7] In order from the object side, the first positive refractive power
The zoom lens includes a lens unit, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power. At the time of zooming, the distance between the first lens group and the second lens group and the distance between the third lens group and the fourth lens group are increased, and the distance between the second lens group and the third lens group and the fourth lens group are increased. A zoom lens, wherein a distance between a lens group and a fifth lens group is reduced, and a fourth lens group or a part of the lens groups is moved to focus on an object at a finite distance.

[8] The zoom lens as described in the above item 7, wherein the following conditional expression is satisfied.

2.0 <f ₁ / f _W <8.0 (1) 0.4 <| f ₂ / f _W | <1.0 (2) 0.3 <f ₃ / f _T345 <1.2 (3) 0.6 <| f ₄ | / f _T345 <5.0 (4) 0.5 <f ₅ / f _T345 <4.0 (4) 5) where f _W is the focal length of the entire system at the wide-angle end f ₁ is the focal length of the first lens group f ₂ is the focal length of the second lens group f ₃ is the focal length of the third lens group f ₄ is the focal length f ₅ of the fourth lens group, the focal length f _T345 in the fifth lens group, the focal length of the third lens group at the telephoto end to the fifth lens group.

[0126]

[9] The zoom lens as described in [7] or [8] above, wherein the focal length at the wide-angle end is shorter than the imaging surface of the optical system or the effective diagonal length of the image sensor.

[10] The zoom lens as described in any one of [7] to [9] above, wherein the principal ray emitted from the optical system is determined based on the following conditional expression.

10 <| Expd _W × Y | / L _W (6) where Expd _W is the distance on the optical axis from the image plane position to the exit pupil Y is the actual maximum on the image plane The image height _LW is the distance on the optical axis from the vertex on the object side surface of the first lens unit at the wide-angle end to the image plane.

[11] The zoom lens according to any one of items 7 to 10, wherein the following relationship is satisfied when zooming from the wide-angle end to the telephoto end.

[0130] _{1.6 <Δ 1T / f W <} 5.0 ··· (7) 1.0 <Δ 3T / f W <4.0 ··· (8) However, Δ _1T is, the wide-angle end standard moving amount delta _3T during zooming to the telephoto end of the first lens group, which is the amount of zooming movement of to the telephoto end of the third lens unit at the wide angle end reference.

[12] The zoom lens according to any one of the above items 7 to 11, wherein the paraxial lateral magnification of the second lens unit satisfies the following relationship.

2.5 <β _2T / β _2W <7 (9) where β _2W is the imaging magnification at the wide-angle end of the second lens group, and β _2T is the imaging magnification at the telephoto end of the second lens group. Is the imaging magnification of.

[13] In order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power
A lens group, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power. When the magnification is changed from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group; The distance between the third lens group and the fourth lens group is increased, the distance between the second lens group and the third lens group, and the distance between the fourth lens group and the fifth lens group are reduced. Alternatively, a zoom lens characterized by focusing on an object at a finite distance by moving some of the lens units in the lens unit.

[14] The zoom lens as described in [13], wherein the following conditional expression is satisfied.

2.0 <f ₁ / f _W <8.0 (1) 0.4 <| f ₂ / f _W | <1.0 (2) 0.3 <f ₃ / f _T345 <1.2 (3) 0.6 <| f ₄ | / f _T345 <5.0 (4) 0.5 <f ₅ / f _T345 <4.0 (4) 5) where f _W is the focal length of the entire system at the wide-angle end f ₁ is the focal length of the first lens group f ₂ is the focal length of the second lens group f ₃ is the focal length of the third lens group f ₄ is the focal length f ₅ of the fourth lens group, the focal length f _T345 in the fifth lens group, the focal length of the third lens group at the telephoto end to the fifth lens group.

[15] The zoom lens as described in [13] or [14] above, wherein the focal length at the wide-angle end is shorter than the imaging surface of the optical system or the effective diagonal length of the image sensor.

[16] The zoom lens as described in any one of [13] to [15] above, wherein the principal ray emitted from the optical system is determined based on the following conditional expression.

10 <| Expd _W × Y | / L _W (6) where Expd _W is the distance on the optical axis from the image plane position to the exit pupil Y is the actual maximum on the image plane The image height _LW is the distance on the optical axis from the vertex on the object side surface of the first lens unit at the wide-angle end to the image plane.

[17] The following 13 is characterized in that the following relationship is satisfied when zooming from the wide-angle end to the telephoto end.
The zoom lens according to any one of claims 1 to 16, wherein

[0140] _{1.6 <Δ 1T / f W <} 5.0 ··· (7) 1.0 <Δ 3T / f W <4.0 ··· (8) However, Δ _1T is, the wide-angle end standard moving amount delta _3T during zooming to the telephoto end of the first lens group, which is the amount of zooming movement of to the telephoto end of the third lens unit at the wide angle end reference.

[18] The paraxial lateral magnification of the second lens group satisfies the following relationship:
The zoom lens according to any one of the preceding claims.

2.5 <β _2T / β _2W <7 (9) where β _2W is the imaging magnification at the wide-angle end of the second lens group, and β _2T is the imaging magnification at the telephoto end of the second lens group. Is the imaging magnification of.

[0143]

According to the present invention, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a negative refractive power. It was possible to invent a method of focusing by using a third lens group and subsequent lens groups in a zoom lens composed of a fifth lens group having a positive refractive power. In the zoom lens having the refractive power arrangement according to the present invention, the simple method of moving only the single lens or the cemented lens and the method of suppressing the fluctuation of the aberration are very effective, and include a wide angle including a wide angle in the future. This is a focus method that has a wide application range for a zoom lens for a video or still video having a magnification.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens according to a first embodiment of the present invention at a wide-angle end (a), in an intermediate state (b), and at a telephoto end (c) during focusing on infinity.

FIG. 2 is a sectional view of a zoom lens according to a second embodiment of the present invention, similar to FIG.

FIG. 3 is a sectional view of a zoom lens according to a third embodiment of the present invention, similar to FIG.

FIG. 4 is a sectional view of a zoom lens according to a fourth embodiment of the present invention, similar to FIG.

FIG. 5 is an aberration diagram for Example 1 upon focusing on infinity.

FIG. 6 is an aberration diagram for Example 1 at the time of focusing at finite distance (1.5 m).

FIG. 7 is an aberration diagram for Example 2 upon focusing on infinity.

FIG. 8 is an aberration diagram for Example 2 when focusing at finite distance (1.5 m).

FIG. 9 is an aberration diagram for Example 3 upon focusing on infinity.

FIG. 10 is an aberration diagram for Example 3 upon focusing on finite distance (2.0 m).

FIG. 11 is an aberration diagram for Example 4 upon focusing on infinity.

12 is an aberration diagram for Example 4 upon focusing on finite distance (2.0 m). FIG.

[Explanation of symbols]

 G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group G5 fifth lens group G5F front group of fifth lens group G5R rear group of fifth lens group S Aperture stop F: Focusing group

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H087 KA01 MA14 MA15 MA16 MA18 PA10 PA19 PB12 QA02 QA06 QA07 QA17 QA21 QA25 QA32 QA34 QA42 QA45 RA05 RA12 RA13 RA36 SA43 SA47 SA49 SA53 SA55 SA62 SA63 SA64 SA65 SA66 SB04 SB15 SB

Claims (3)

[Claims] 1. 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, a fourth lens group having a negative refractive power, and a positive refractive power. The fifth lens group has a power, and at the time of zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group and the distance between the third lens group and the fourth lens group are increased. The distance between the second lens group and the third lens group and the distance between the fourth lens group and the fifth lens group are reduced, and by moving the third lens group or a part of the lens groups in the third lens group, A zoom lens that focuses on a finite object. 2. 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, a fourth lens group having a negative refractive power, and a positive refractive power, in that order from the object side. The fifth lens group has a power, and at the time of zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group and the distance between the third lens group and the fourth lens group are increased. The distance between the second lens group and the third lens group and the distance between the fourth lens group and the fifth lens group are reduced, and by moving the fourth lens group or some of the lens groups in the lens group, A zoom lens that focuses on a finite object. 3. 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, a fourth lens group having a negative refractive power, and a positive refractive power, in that order from the object side. The fifth lens group has a power, and at the time of zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group and the distance between the third lens group and the fourth lens group are increased. The distance between the second lens group and the third lens group and the distance between the fourth lens group and the fifth lens group are reduced, and by moving the fifth lens group or a part of the lens groups in the fifth lens group, A zoom lens that focuses on a finite object.