CN109975966B

CN109975966B - Zoom lens

Info

Publication number: CN109975966B
Application number: CN201811128756.9A
Authority: CN
Inventors: 太幡浩文
Original assignee: Tamron Co Ltd
Current assignee: Tamron Co Ltd
Priority date: 2017-12-27
Filing date: 2018-09-27
Publication date: 2021-11-30
Anticipated expiration: 2038-09-27
Also published as: JP2019117320A; CN109975966A; JP6786473B2

Abstract

The invention discloses a zoom lens which is small, light and good in aberration correction and can form an image corresponding to the characteristics of a solid-state imaging element. The zoom lens includes, in order from an 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, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power, wherein the zoom lens fixes the first lens group, the third lens group, and the fifth lens group when zooming from a wide-angle end to a telephoto end, the second lens group and the fourth lens group move on an optical axis, and an aperture stop is fixed to the third lens group, and a predetermined conditional expression is satisfied.

Description

Zoom lens

Technical Field

The present invention relates to a zoom lens which is small and light, can correct aberrations well, and has good resolution performance.

Background

In recent years, imaging devices equipped with solid-state imaging elements such as CCDs and COMSs have rapidly spread in a wide range of fields such as single-lens reflex cameras, digital cameras, video cameras, and monitoring cameras. With this, the demand for lenses corresponding to solid-state imaging devices with higher pixels and higher sensitivity has been increasing.

In recent years, a bright lens having a higher resolution has been demanded for an image pickup apparatus equipped with a solid-state image pickup device with higher pixel density and higher sensitivity. In addition, there is a great demand for downsizing an imaging device, and downsizing and weight reduction of an imaging lens are also desired.

On the other hand, in order to be widely used in applications such as video cameras and monitoring cameras, it is necessary to use the zoom lens in both daytime and nighttime in addition to a wide angle of view, and therefore, there is a strong demand for providing a bright and high-resolution zoom lens that can cope with not only a visible light band, which is a normal imaging band, but also a wide-range band covering a long-wavelength band including a near-infrared band.

The following zoom lenses are proposed with respect to conventionally known zoom lenses: the zoom lens has a positive-negative five-group structure, and includes a first lens, a third lens group, and a fifth lens group that are fixed, a second lens group that moves from the object side to the image plane side to perform zooming from the wide-angle end to the telephoto end, and a fourth lens group that moves to correct image surface variations caused by zooming and focus (see, for example, patent document 1).

As another zoom lens known in the related art, the following rear focus type zoom lens is proposed: the optical lens system is configured by a five-group structure of positive, negative, positive, and negative, and achieves excellent optical performance and downsizing of the entire lens system when a zoom ratio is set to be about three to five times (see, for example, patent document 2).

As still another zoom lens known in the art, the following zoom lenses are proposed: the zoom lens has a five-group structure of positive, negative, positive, and negative, and has a large aperture ratio, high resolution, small size, and light weight, and can secure a zoom magnification equivalent to that in the case of infinity even in the case of a finite distance (see, for example, patent document 3).

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5847675

Patent document 2: japanese Kokai publication No. 2004-354870

Patent document 3: japanese patent laid-open No. 2006-300969

The zoom lens proposed in patent document 1 and the like is suitable for a telephoto system, and when it is applied to a wide-angle system, it is difficult to correct aberrations such as field curvature and color aberration that occur when the angle of view is increased. Further, when the present invention is applied to an optical system having a wide angle and a large aperture ratio, it is impossible to sufficiently correct aberrations from the wide angle end to the telephoto end based on the ratio of focal lengths shown in the examples of the second lens group and the fourth lens group having the effect of correcting a phase difference caused by magnification variation, and it is difficult to achieve high performance.

In the zoom lens proposed in patent document 2 and the like, when the diameter is increased, it is difficult to correct spherical aberration accompanying the increase in diameter, and the number of lenses in the fifth lens group is small, so it is difficult to achieve both the increase in diameter and the improvement in performance.

In the zoom lens proposed in patent document 3 and the like, it is difficult to correct aberrations occurring in the case of a wide angle, and it is difficult to achieve further wide angle and high resolution.

Disclosure of Invention

(purpose of the invention)

The present invention has been made in view of the above problems of the conventional zoom lens and imaging device, and an object of the present invention is to provide a zoom lens which is small and light in weight, and which can correct aberrations well and has good resolution performance.

[ technical means to solve the problems ]

The present invention provides a zoom lens comprising, in order from an 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, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power, wherein the first lens group, the third lens group, and the fifth lens group are fixed when zooming from a wide-angle end to a telephoto end, and the second lens group and the fourth lens group move on an optical axis, and satisfy the following conditional expressions (1) and (2)

-40.0≦f1/f2≦-8.5.......................(1)

-1.1≦f2/f4≦-0.5.......................(2)

Wherein the content of the first and second substances,

f1 is the focal length of the first lens group,

f2 is the focal length of the above second lens group,

f4 is the focal length of the fourth lens group described above.

The invention has the following beneficial effects:

according to the present invention, it is possible to provide a zoom lens which is small and lightweight, and which can correct aberrations well and has good resolution performance.

Drawings

Fig. 1 is a lens configuration diagram of a zoom lens according to a first embodiment of the present invention at the wide angle end and the telephoto end.

Fig. 2 is various aberration diagrams at the wide angle end of the first embodiment of the zoom lens of the present invention.

Fig. 3 is various aberration diagrams of the telephoto end of the first embodiment of the zoom lens of the present invention.

Fig. 4 is a lens configuration diagram of a zoom lens according to a second embodiment of the present invention at the wide angle end and the telephoto end.

Fig. 5 is various aberration diagrams at the wide angle end of the second embodiment of the zoom lens of the present invention.

Fig. 6 is various aberration diagrams of the telephoto end of the second embodiment of the zoom lens of the present invention.

Fig. 7 is a lens configuration diagram of a zoom lens according to a third embodiment of the present invention at the wide angle end and the telephoto end.

Fig. 8 is various aberration diagrams at the wide angle end of the third embodiment of the zoom lens of the present invention.

Fig. 9 is various aberration diagrams of the telephoto end of the third embodiment of the zoom lens of the present invention.

Fig. 10 is a lens configuration diagram of a fourth embodiment of a zoom lens of the present invention at the wide angle end and the telephoto end.

Fig. 11 is various aberration diagrams at the wide angle end of the fourth embodiment of the zoom lens of the present invention.

Fig. 12 are various aberration diagrams of the telephoto end of the fourth embodiment of the zoom lens of the present invention.

Fig. 13 is a lens configuration diagram of a fifth embodiment of a zoom lens of the present invention at the wide angle end and the telephoto end.

Fig. 14 is various aberration diagrams at the wide angle end of a fifth embodiment of the zoom lens of the present invention.

Fig. 15 is various aberration diagrams of the telephoto end of the fifth embodiment of the zoom lens of the present invention.

Fig. 16 is a lens configuration diagram of a sixth embodiment of a zoom lens of the present invention at the wide angle end and the telephoto end.

Fig. 17 are various aberration diagrams at the wide angle end of the sixth embodiment of the zoom lens of the present invention.

Fig. 18 are various aberration diagrams of the telephoto end of the sixth embodiment of the zoom lens of the present invention.

Fig. 19 is a lens configuration diagram of a seventh embodiment of a zoom lens of the present invention at the wide angle end and the telephoto end.

Fig. 20 are various aberration diagrams at the wide angle end of the seventh embodiment of the zoom lens of the present invention.

Fig. 21 is various aberration diagrams of the telephoto end of the seventh embodiment of the zoom lens of the present invention.

Fig. 22 is a lens configuration view of an eighth embodiment of a zoom lens of the present invention at the wide angle end and the telephoto end.

Fig. 23 is various aberration diagrams at the wide angle end of the eighth embodiment of the zoom lens of the present invention.

Fig. 24 are various aberration diagrams of the telephoto end of the eighth embodiment of the zoom lens of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

(first embodiment)

The zoom lens of the present invention is composed of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power,

when the zoom lens is changed in magnification from a wide-angle end to a telephoto end, the first lens group, the third lens group, and the fifth lens group are fixed, and the second lens group and the fourth lens group move on an optical axis, thereby satisfying a predetermined conditional expression.

In the zoom lens of the present invention, when zooming is performed from a wide-angle end to a telephoto end, the first lens group, the third lens group, and the fifth lens group are fixed, and the second lens group and the fourth lens group move on an optical axis. And moving the second lens group on the optical axis during focusing. Therefore, the zoom lens of the present invention is of an internal focus type in which the number of lens groups moving on the optical axis during zooming and focusing is small, and the total length of the optical system does not change during zooming and focusing, and has an advantage that the zoom drive system and the focus drive system can be configured to have a simple configuration. The zoom lens of the present invention of the internal focus type has a general advantage that it is possible to reduce the driving force of an Autofocus (AF) system, and further, the center of gravity shift at the time of magnification change and at the time of focusing is small and stable, and the arrangement of the optical filter is easy. Further, since the third lens group has positive refractive power, the third lens group has an effect of converging the light flux diverging from the second lens group, and correction of spherical aberration of the lens groups subsequent to the third lens group becomes easy, and good resolving performance can be obtained. Further, since the third lens group has positive refractive power, it also contributes to shortening of the total length and downsizing of the zoom lens. Here, the total length refers to a distance on the optical axis from the object side first surface of the first lens group to the image forming surface.

Furthermore, the third lens group has at least a single lens component. A single lens assembly refers to a lens assembly that includes a cemented lens and a compound aspheric lens with only the object and image sides in contact with an air layer. In view of downsizing of the third lens group, the third lens group is preferably a single positive lens or a cemented lens in which a single positive lens and a single negative lens are cemented.

The position where the aperture stop is disposed is not particularly limited, but it is preferable to fix the aperture stop together with the third lens group at the time of magnification change. By disposing the aperture stop together with the third lens group having positive refractive power, spherical aberration can be effectively corrected. The aperture stop may be disposed at any position among the object side, the image side, and the lens of the third lens group, but is preferably disposed at the image side in consideration of the spherical aberration correction effect in the zoom lens of the present invention.

In addition, the zoom lens of the present invention preferably satisfies at least one of the following conditional expressions.

The zoom lens of the present invention preferably satisfies conditional expression (1) shown below.

-40.0≦f1/f2≦-8.5.......................(1)

Wherein the content of the first and second substances,

f1 is the focal length of the first lens group

f2 is the focal length of the second lens group described above.

Conditional expression (1) is an expression specifying a ratio of the focal length of the first lens group to the focal length of the second lens group. By satisfying the conditional expression (1), the focal lengths of the first lens group and the second lens group are appropriately set, spherical aberration is corrected well, and an optical system having a wide angle, a large aperture ratio, a small size, and good resolution performance can be obtained.

If the lower limit of conditional expression (1) is exceeded, the focal length of the first lens group becomes too long, the total length becomes long, and it becomes difficult to correct spherical aberration, and it becomes difficult to achieve a small size and good optical performance.

If the value is higher than the upper limit of conditional expression (1), the focal length of the first lens group becomes too short, spherical aberration becomes excessively corrected, and it becomes difficult to obtain an optical system having good performance.

The lower limit of the conditional expression (1) is preferably-35.0 or more, more preferably-30.0 or more. The upper limit of the conditional formula (1) is preferably-9.0 or less, more preferably-9.5 or less.

The zoom lens of the present invention preferably satisfies conditional expression (2) shown below.

-1.1≦f2/f4≦-0.5.......................(2)

Wherein the content of the first and second substances,

f2 is the focal length of the second lens group

f4 is the focal length of the fourth lens group described above.

Conditional expression (2) is an expression that specifies a ratio of the focal length of the second lens group to the focal length of the fourth lens group. By satisfying the conditional expression (2), the focal lengths of the second lens group and the fourth lens group are appropriately set. Accordingly, the fourth lens group can satisfactorily correct the field curvature caused by the second lens group when varying the magnification from the wide-angle end to the telephoto end.

If the lower limit of the conditional expression (2) is exceeded, the focal length of the second lens group becomes too long, and the field curvature generated in the second lens group becomes small, but the moving amount of the second lens group becomes large when zooming from the wide-angle end to the telephoto end, and it becomes difficult to downsize the zoom lens.

If the upper limit of the conditional expression (2) is exceeded, the focal length of the second lens group becomes too short, and the field curvature occurring in the second lens group becomes large, so that it becomes difficult for the fourth lens group to correct the field curvature occurring when the second lens group moves on the optical axis due to magnification change.

The lower limit of the conditional expression (2) is preferably-1.05 or more, more preferably-1.00 or more. The upper limit of the conditional expression (2) is preferably-0.51 or less, more preferably-0.52 or less.

(second embodiment)

The zoom lens of the present invention preferably satisfies conditional expression (3) shown below.

3.0≦f3/fw≦7.5.........................(3)

Wherein the content of the first and second substances,

fw is a focal length of the entire lens system at infinity focusing at the wide-angle end

f3 is the focal length of the above third lens group.

Conditional expression (3) is an expression specifying a ratio of a focal length of the third lens group to a focal length of the entire lens system at infinity focusing at the wide-angle end.

By satisfying the conditional expression (3), the refractive power of the third lens group at the wide-angle end is set to a range in which spherical aberration can be corrected well. Further, by satisfying the conditional expression (3), the light flux diverged by the second lens group can be converged, and the zoom lens can be miniaturized.

If the lower limit of conditional expression (3) is exceeded, the focal length of the third lens group becomes too short, the spherical aberration becomes overcorrected, and it becomes difficult to correct the spherical aberration satisfactorily.

If the value is higher than the upper limit of conditional expression (3), the focal length of the third lens group becomes too long, the spherical aberration becomes insufficient to be corrected, and the total length becomes long, so that it becomes difficult to miniaturize the optical system.

The lower limit of the conditional expression (3) is preferably 3.3 or more, and more preferably 3.5 or more. The upper limit of the conditional expression (3) is preferably 7.3 or less, and more preferably 7.0 or less.

(third embodiment)

The zoom lens of the present invention preferably satisfies the following conditional expression (4) when the second lens group moves on the optical axis during focusing from infinity to close distance.

-1.8≦f2/fw≦-0.7......................(4)

Wherein the content of the first and second substances,

f2 is the focal length of the second lens group described above.

In the zoom lens of the present invention, focusing from infinity to a finite distance (close distance) can suppress aberration variation accompanying focusing by moving the second lens group, and good imaging performance can be obtained from infinity to a finite distance (close distance).

Conditional expression (4) is an expression specifying a ratio of the focal length of the second lens group to the focal length of the entire system at infinity focusing at the wide-angle end. By satisfying conditional expression (4), the focal length of the second lens group at the wide-angle end can be set so as to be capable of correcting aberrations such as coma aberration and field curvature.

If the value is less than the lower limit of conditional expression (4), the focal length of the second lens group at the wide-angle end becomes too short, which increases aberrations such as coma aberration and field curvature, making it difficult to suppress aberration variation associated with focusing, and making it difficult to obtain good optical performance.

If conditional expression (4) is higher than the upper limit, the focal length of the second lens group becomes too long at the wide-angle end, and the amount of movement at the time of focusing or zooming becomes large, making it difficult to achieve miniaturization.

The lower limit of the conditional expression (4) is preferably-1.7 or more, more preferably-1.65 or more. The upper limit of the conditional expression (4) is preferably-0.8 or less, more preferably-0.9 or less.

(fourth embodiment)

In the zoom lens of the present invention, it is preferable that the first lens group is formed of one positive lens.

By constituting the first lens group by one positive lens, the light weight/miniaturization of the optical system is realized in addition to the reduction of the manufacturing cost. In addition, the first lens is fixed at the time of magnification change, which is advantageous for dust/water prevention on the lens object side.

(fifth embodiment)

In the zoom lens of the present invention, the fifth lens group is composed of a negative lens and a positive refractive power in this order from the object side, and preferably satisfies the following conditional expression (5).

-1.3≦f5a/f4≦-0.7......................(5)

Wherein the content of the first and second substances,

f4 is the focal length of the fourth lens group

f5a is the focal length of the negative lens disposed closest to the object side in the fifth lens group.

The fifth lens group is composed of a negative lens and a partial group having positive refractive power in order from the object side. By configuring the fifth lens group in this way, astigmatism and field curvature from the wide-angle end to the telephoto end can be corrected well.

Conditional expression (5) is an expression specifying a ratio of a focal length of the negative lens disposed closest to the object side in the fifth lens group to a focal length of the fourth lens group. By satisfying the conditional expression (5), astigmatism and field curvature can be appropriately corrected.

If the lower limit of conditional expression (5) is exceeded, the focal length of the negative lens disposed closest to the object side in the fifth lens group becomes too long, and astigmatism and field curvature are insufficiently corrected, making it difficult to obtain good optical performance.

If the value is higher than the upper limit of conditional expression (5), the focal length of the negative lens disposed closest to the object side in the fifth lens group becomes too short, and astigmatism and field curvature are excessively corrected, making it difficult to obtain good optical performance.

The lower limit of the conditional expression (5) is preferably-1.2 or more, more preferably-1.1 or more. The upper limit of the conditional expression (5) is preferably-0.8 or less, more preferably-0.9 or less.

(sixth embodiment)

In the zoom lens of the present invention, the fifth lens group includes at least two positive lenses, and preferably satisfies conditional expressions (6) and (7) shown below.

60.0≦vd5p1................................(6)

38.0≧vd5p2................................(7)

Wherein the content of the first and second substances,

vd5p1 is the Abbe number of at least one positive lens used in the fifth lens group

vd5p2 is the abbe number of at least one positive lens used in the fifth lens group.

The fifth lens group has at least two positive lenses, and therefore can suppress the occurrence of chromatic aberration. Further, when one of the two positive lenses satisfies conditional expression (6) and the other satisfies conditional expression (7), the occurrence of chromatic aberration can be further suppressed.

The fifth lens group is capable of correcting chromatic aberration favorably because it has at least two positive lenses and at least two negative lenses.

Conditional expression (6) is an expression for specifying the abbe number of at least one positive lens in the fifth lens group. Since the conditional expression (6) is satisfied, on-axis chromatic aberration and magnification chromatic aberration of the visible light wavelength band can be mainly corrected in the fifth lens group.

Conditional expression (7) is an expression for specifying the abbe number of at least one positive lens in the fifth lens group. Since the conditional expression (7) is satisfied, on-axis chromatic aberration and chromatic aberration of magnification in the near-infrared wavelength band can be mainly corrected in the fifth lens group.

Even in the case where the fifth lens group has three or more positive lenses, if one of the positive lenses satisfies conditional expression (6) and one of the other positive lenses satisfies conditional expression (7), the abbe numbers of the positive lenses other than the two positive lenses are not particularly limited.

The lower limit of conditional expression (6) is preferably 65.0 or more, and more preferably 68.0 or more. Further, it is considered that the dispersion becomes smaller as the abbe number is larger as described above, and it is not necessary to define the upper limit in accordance with the intention of the conditional expression, but when the upper limit is defined, for example, 120.0 or less, preferably 100.0 or less, more preferably 95.0 or less, and still more preferably 90.0 or less may be used.

The upper limit of conditional formula (7) is preferably 35.0, and more preferably 32.0. When the lower limit is defined, it is preferably greater than 0, more preferably 10 or more, and still more preferably 15 or more.

Further, if any one of the conditional expressions (6) and (7) is satisfied, the respective effects can be obtained. Further, it is preferable that the aberration correction can be performed more favorably by satisfying both the formulas.

(seventh embodiment)

In the zoom lens of the present invention, it is preferable that lenses constituting the third lens group satisfy conditional expressions (8) and (9) shown below.

1.7≦nd3_ave...............................(8)

45.0≧vd3_ave..............................(9)

Wherein the content of the first and second substances,

nd3_ ave is the average value of refractive indexes of the lenses used in the third lens group

vd3_ ave is the average value of abbe numbers of the lenses used in the third lens group.

Conditional expression (8) is an expression for defining an average value of refractive indexes of the lenses included in the third lens group. By satisfying the conditional expression (8), an effect of correcting spherical aberration in the third lens group can be obtained.

Conditional expression (9) is an expression for defining an average value of abbe numbers of lenses included in the third lens group. By satisfying the conditional expression (9), an effect of mainly correcting chromatic aberration on the axis of the near-infrared band in the third lens group can be obtained.

Even if either of conditional expression (8) and conditional expression (9) is satisfied, the respective effects can be obtained. Further, it is preferable that the aberration correction can be performed more favorably by satisfying both the formulas.

The lower limit of conditional formula (8) is preferably 1.8, more preferably 1.85. When the upper limit is defined, it is preferably 4.0 or less, preferably 3.0 or less, and more preferably 2.2 or less.

Further, the upper limit of conditional formula (9) is preferably 43.0, more preferably 40.0. When the lower limit is defined, it is preferably higher than 0, preferably 5.0 or more, preferably 10.0 or more, and more preferably 15.0 or more.

The third lens group is preferably composed of two or less lenses, and is preferably light in weight and simplified in a lens barrel. Furthermore, it is preferred to have at least one single lens assembly with a positive optical power. By having a positive single lens component, there is an effect of converging a light flux which becomes a divergent light flux by passing through the second lens group having a negative refractive power, and miniaturization of the optical system can be achieved.

The third lens group is preferably constituted by one positive lens or a cemented lens in which one positive lens and one negative lens are cemented. With this configuration, the third lens group can be made small, and the optical system can be downsized.

Further, by disposing the stop fixed to the third lens group, spherical aberration can be effectively corrected. In the case where the third lens group is composed of one positive lens, spherical aberration can be mainly corrected. In the case where the third lens group is composed of a cemented lens of one positive lens and one negative lens, axial chromatic aberration can be corrected together with spherical aberration, and an optical system having high optical performance can be obtained. When the third lens group is a cemented lens, it is preferable to dispose a positive lens and a negative lens in this order from the object side in view of aberration correction.

(eighth embodiment)

In the zoom lens of the present invention, it is preferable that the fourth lens group uses a plastic lens on the most object side.

The plastic lens used for the fourth lens group closest to the object side can easily adopt an aspherical surface in addition to reduction of manufacturing cost. By using an aspherical surface, spherical aberration is corrected extremely well, and cost reduction and weight reduction of the optical system can be achieved while maintaining high resolution performance.

(embodiment 9)

The zoom lens of the present invention preferably satisfies the conditional expression (10) shown below.

0.4≦f4/ft≦0.9.......................(10)

Wherein the content of the first and second substances,

ft is the focal length of the entire lens system at infinity focus at the telephoto end

f4 is the focal length of the fourth lens group described above.

Conditional expression (10) is an expression that specifies the ratio of the focal length of the entire system at infinity focusing at the telephoto end to the focal length of the fourth lens group. By satisfying the conditional expression (10), the focal length of the fourth lens group at the telephoto end is appropriately set, and spherical aberration and field curvature can be appropriately corrected at the telephoto end.

If the value is less than the lower limit of conditional expression (10), the focal length of the fourth lens group becomes too short, spherical aberration and field curvature become too much corrected, and it becomes difficult to obtain a good optical system.

If the value is higher than the upper limit of conditional expression (10), the focal length of the fourth lens group becomes too long, spherical aberration and field curvature are insufficiently corrected, and it becomes difficult to obtain good optical performance. Further, since the moving amount of the fourth lens group is increased and the total length is increased, it is difficult to miniaturize the optical system.

The lower limit of the conditional expression (10) is preferably 0.5 or more, and more preferably 0.55 or more. The upper limit of the conditional expression (10) is preferably 0.8 or less, and more preferably 0.75 or less.

(tenth embodiment)

The zoom lens of the present invention preferably satisfies conditional expression (11) shown below.

-50.0≦f5/fw≦-4.5..................(11)

Wherein the content of the first and second substances,

f5 is the focal length of the above fifth lens group.

Conditional expression (11) is an expression that specifies the ratio of the focal length of the fifth lens group to the focal length of the entire system at infinity focusing at the wide-angle end. By satisfying the conditional expression (11), the focal length of the fifth lens group at the wide-angle end is set to a range in which curvature of field and distortion aberration can be corrected, and curvature of field can be corrected well at the wide-angle end, whereby distortion can be corrected appropriately.

If the lower limit of conditional expression (11) is exceeded, the focal length of the fifth lens group becomes too long, the field curvature and distortion are insufficiently corrected, and the back focus becomes long at the wide-angle end, making it difficult to downsize the optical system.

If the value is higher than the upper limit of conditional expression (11), the focal length of the fifth lens group becomes too short, and the field curvature and distortion become excessively corrected, making it difficult to obtain an appropriate optical system.

The lower limit of the conditional expression (11) is preferably-45.0 or more, more preferably-40.0 or more. The upper limit of the conditional expression (11) is preferably-4.8 or less, more preferably-5.0 or less.

(eleventh embodiment)

The zoom lens of the present invention preferably satisfies conditional expression (12) shown below.

-19.0≦f5/ft≦-1.5.....................(12)

Wherein the content of the first and second substances,

ft is the focal length of the entire lens system at infinity at the telephoto end,

f5 is the focal length of the above fifth lens group.

Conditional expression (12) is an expression specifying the ratio of the focal length of the fifth lens group to the focal length of the entire system at infinity focusing at the telephoto end. By satisfying the conditional expression (12), the focal length of the fifth lens group at the telephoto end is set in a range in which curvature of field and distortion aberration can be corrected, and curvature of field is corrected favorably at the wide-angle end, whereby distortion can be corrected appropriately.

If the lower limit of conditional expression (12) is exceeded, the focal length of the fifth lens group becomes too long, the field curvature and distortion are insufficiently corrected, and the back focus at the wide-angle end becomes long, so that it becomes difficult to downsize the optical system.

If the value is higher than the upper limit of conditional expression (12), the focal length of the fifth lens group becomes too short, and the field curvature and distortion become excessively corrected, making it difficult to obtain an appropriate optical system.

The lower limit of the conditional expression (12) is preferably-17.0 or more, more preferably-15.0 or more. The upper limit of the conditional expression (12) is preferably-1.7 or less, more preferably-1.8 or less.

Another embodiment (hereinafter, referred to as a twelfth embodiment) of the present invention will be described.

A twelfth embodiment of the present invention is an imaging apparatus including: the zoom lens of the first embodiment described above; and a solid-state imaging element disposed at an imaging position of the zoom lens. The imaging apparatus according to the twelfth embodiment can efficiently form an image signal for forming a clear image by forming an image corresponding to the photoelectric conversion characteristics of the solid-state imaging device by the zoom lens according to the first embodiment.

First to eighth embodiments of a zoom lens according to the present invention are described below with reference to the drawings.

In each embodiment, F (focal length), Fno (F value), ω (angle of view), image height, total lens length, and BF (back focus) are shown. d2 denotes the spacing of the first lens group and the second lens group. d7 denotes the spacing of the second lens group and the third lens group. d12 denotes the spacing of the third lens group and the fourth lens group. d17 denotes the spacing of the fourth lens group and the fifth lens group.

However, in embodiment 8, d2 denotes the interval of the first lens group and the second lens group. d7 denotes the spacing of the second lens group and the third lens group. d11 denotes the spacing of the third lens group and the fourth lens group. d16 denotes the spacing of the fourth lens group and the fifth lens group.

The aspherical surface is expressed by the following aspherical surface formula.

[ formula 1 ]

In the above aspheric expression, k represents a conic coefficient. A denotes a second-order aspheric coefficient, B denotes a fourth-order aspheric coefficient, C denotes a sixth-order aspheric coefficient, D denotes an eighth-order aspheric coefficient, and E denotes a tenth-order aspheric coefficient. (E-n) represents (. times.10 to the power of-n).

In the following embodiments, the second lens group G2 is a focusing lens. In each embodiment, in the case where the telephoto end is focused from the infinity object to the close object, the second lens group G2 is moved to the object side as indicated by an arrow 2c in each lens configuration diagram. In each lens configuration diagram, a solid line 2a and a broken line 2b indicate movement loci for correcting image plane variation accompanying zooming from the wide-angle end to the telephoto end when focusing from each infinity object to a close-distance object.

In the lens structure diagrams of the respective examples, G1 to G5 represent the first to fifth lens groups. S denotes an aperture stop. CG denotes a cover glass. IMG denotes imaging.

(example 1)

The zoom ratio of example 1 was 2.82.

The lens data for example 1 is shown in table 1.

[ TABLE 1 ]

NS	R	D	nd	vd
							1	86.675	3.43	1.77250	49.62
2	309.707	d2
						3	100.999	0.80	1.87070	40.73
4	18.364	7.33
						5	-28.194	0.80	1.64000	60.08
6	31.328	2.00	1.98612	16.48
						7	57.231	d7
8	47.655	2.24	2.00100	29.13
						9	-54.877	0.60	1.90366	31.32
10	232.960	1.33
						11	inf	0.00			(aperture diaphragm)
12	inf	d12
						13	16.500	4.96	1.53500	56.71	Aspherical surface
14	-74.761	2.92			Aspherical surface
						15	27.340	0.80	2.05090	26.94
16	12.500	6.21	1.55032	75.50
						17	-26.321	d17
18	-75.493	0.80	1.84666	23.78
						19	20.395	5.48
20	87.677	3.33	1.55032	75.50
						21	-38.575	0.13
22	40.026	7.38	1.80809	22.76
						23	-18.925	0.80	1.48749	70.45
24	951.095	3.46
						25	-23.232	0.80	1.84666	23.78
26	-110.581	5.30
						27	inf	1.20	1.51680	64.20
28	inf	BF
						29	inf	-

Various data for example 1 are shown in table 2.

[ TABLE 2 ]

	Wide angle end	Intermediate (II)	Telescope end
				f	11.27	18.51	31.80
Fno	1.75	2.14	2.81
				ω	108.71	63.16	36.25
Image height	10.81	10.81	10.81
				Total length of lens	95.00	95.00	95.00
BF	0.60	0.60	0.60
				d2	1.50	11.43	15.73
d7	16.13	6.19	1.90
				d12	13.68	8.76	0.90
d17	0.95	5.87	13.73

The aspherical surface coefficients of example 1 are shown in table 3.

[ TABLE 3 ]

Noodle

R

k

A

B

C

D

E

13

16.500

0

-1.87632E-05

-3.41224E-08

1.50770E-09

-1.30213E-11

14

-74.761

0

4.40569E-05

-4.36637E-08

1.49759E-09

-1.36998E-11

(example 2)

The zoom ratio of example 2 was 2.70.

Lens data for example 2 is shown in table 4.

[ TABLE 4 ]

NS	R	D	nd	vd
							1	1010.315	2.98	1.542339	48.774
2	-306.859	d2
						3	74.696	0.80	1.87070	40.73
4	18.935	6.80
						5	-28.152	0.80	1.736363	46.808
6	23.688	1.95	1.98612	16.48
						7	38.650	d7
8	43.466	2.42	2.00100	29.13
						9	-45.900	0.60	1.90366	31.32
10	1440.626	1.22
						11	inf	0.00			(aperture diaphragm)
12	inf	d12
						13	16.500	5.63	1.53500	55.71	Aspherical surface
14	-70.000	2.99			Aspherical surface
						15	26.470	0.80	2.05090	26.94
16	12.500	6.20	1.55032	75.50
						17	-24.149	d17
18	-105.644	0.80	1.84666	23.78
						19	17.313	5.26
20	53.517	2.89	1.55032	75.50
						21	-71.140	0.66
22	48.917	7.15	1.80809	22.76
						23	-16.820	0.80	1.48749	70.45
24	-422.608	3.00
						25	-20.388	0.80	1.84666	23.78
26	-52.703	5.30
						27	inf	1.20	1.51680	64.20
28	inf	BF
						29	inf	-

Various data for example 2 are shown in table 5.

[ TABLE 5 ]

	Wide angle end	Intermediate (II)	Telescope end
				f	11.26	18.47	30.40
Fno	1.80	2.36	3.11
				ω	108.37	63.31	37.86
Image height	10.81	10.81	10.81
				Total length of lens	95.00	95.00	95.00
BF	0.60	0.60	0.60
				d2	3.28	12.45	15.07
d7	13.68	4.51	1.90
				d12	15.16	8.95	0.90
d17	1.19	7.40	15.45

The aspherical surface coefficients of example 2 are shown in table 6.

[ TABLE 6 ]

Noodle

R

k

A

B

C

D

E

13

16.500

0

-2.14275E-05

-1.38191E-07

2.78105E-09

-2.93736E-11

14

-70.000

0

4.82666E-05

-1.15954E-07

2.10029E-09

-2.81226E-11

(example 3)

The zoom ratio of example 3 is 2.65.

Lens data for example 3 is shown in table 7.

[ TABLE 7 ]

NS	R	D	nd	vd
							1	86.288	3.89	1.77250	49.62
2	670.236	d2
						3	254.750	0.80	1.87070	40.73
4	19.524	6.85
						5	-28.257	0.80	1.64000	60.08
6	32.410	2.15	1.98612	16.48
						7	74.316	d7
8	49.496	2.23	2.00100	29.13
						9	-56.005	0.60	1.90366	31.32
10	223.848	1.34
						11	inf	0.00			(aperture diaphragm)
12	inf	d12
						13	16.500	5.02	1.53500	55.71	Aspherical surface
14	-71.969	2.74			Aspherical surface
						15	28.239	0.80	2.05090	26.94
16	12.500	6.71	1.55032	75.50
						17	-29.064	d17
18	-82.982	0.80	1.84666	23.78
						19	21.567	5.53
20	91.041	3.50	1.55032	75.50
						21	-36.452	0.27
22	41.180	7.85	1.80809	22.76
						23	-20.009	0.80	1.48749	70.45
24	857.986	3.81
						25	-25.876	0.80	1.84666	23.78
26	-108.258	5.30
						27	inf	1.20	1.51680	64.20
28	inf	BF
						29	inf	-

Various data for example 3 are shown in table 8.

[ TABLE 8 ]

	Wide angle end	Intermediate (II)	Telescope end
				f	11.90	18.49	31.57
Fno	1.75	2.07	2.72
				ω	104.81	63.69	36.83
Image height	10.81	10.81	10.81
				Total length of lens	95.20	95.20	95.20
BF	0.60	0.60	0.60
				d2	1.56	9.90	14.34
d7	14.68	6.34	1.89
				d12	13.61	9.13	1.35
d17	0.95	5.43	13.22

The aspherical surface coefficients of example 3 are shown in table 9.

[ TABLE 9 ]

Noodle

R

k

A

B

C

D

E

13

16.500

0

-1.92456E-05

-6.94846E-08

1.73688E-09

-1.09315E-11

14

-71.969

0

3.82257E-05

-5.30992E-08

1.40612E-09

-9.39550E-12

(example 4)

The zoom ratio of example 4 was 2.69.

Lens data for example 4 is shown in table 10.

[ TABLE 10 ]

NS	R	D	nd	vd
							1	198.500	2.00	1.51680	64.20
2	717.310	d2
						3	482.960	0.80	1.87070	40.73
4	24.566	5.17
						5	-49.145	0.80	1.579262	48.65
6	24.991	2.27	1.98612	16.48
						7	45.407	d7
8	39.506	2.04	2.00100	29.13
						9	-132.000	0.60	1.90366	31.32
10	65.719	1.67
						11	inf	0.00			(aperture diaphragm)
12	inf	d12
						13	16.500	4.79	1.53500	55.71	Aspherical surface
14	-90.556	1.76			Aspherical surface
						15	23.438	0.80	2.05090	26.94
16	12.500	6.20	1.540611	68.90
						17	-27.666	d17
18	-131.532	0.80	1.84666	23.78
						19	17.004	6.42
20	68.293	3.56	1.55032	75.50
						21	-36.240	0.12
22	60.666	7.34	1.80809	22.76
						23	-16.098	0.80	1.48749	70.45
24	-55.236	2.59
						25	-17.733	0.80	1.84666	23.78
26	-66.190	5.30
						27	inf	1.20	1.51680	64.20
28	inf	BF
						29	inf	-

Various data for example 4 are shown in table 11.

[ TABLE 11 ]

The aspherical surface coefficients of example 4 are shown in table 12.

[ TABLE 12 ]

Noodle

R

k

A

B

C

D

E

13

16.500

0

-2.35718E-05

-2.50858E-08

1.67189E-09

-2.47187E-11

14

-90.556

0

4.24844E-05

-6.52048E-08

1.87931E-09

-2.67550E-11

(example 5)

The zoom ratio of example 5 was 2.63.

The lens data for example 5 are shown in table 13.

[ TABLE 13 ]

NS	R	D	nd	vd
							1	78.775	3.91	1.77250	49.62
2	341.935	d2
						3	145.779	0.80	1.87070	40.73
4	19.348	7.67
						5	-28.789	0.80	1.64000	60.08
6	27.696	1.59	1.98612	16.48
						7	35.412	d7
8	47.634	2.70	2.00100	29.13
						9	-30.092	0.60	1.90366	31.32
10	1705.398	1.22
						11	inf	0.00			(aperture diaphragm)
12	inf	d12
						13	16.500	5.23	1.53500	55.71	Aspherical surface
14	-71.025	3.85			Aspherical surface
						15	31.652	0.80	2.05090	26.94
16	12.500	6.26	1.55032	75.50
						17	-27.515	d17
18	-44.976	0.80	1.84666	23.78
						19	32.988	4.57
20	75.832	3.15	1.55032	75.50
						21	-47.063	0.13
22	37.063	7.35	1.80809	22.76
						23	-19.146	0.80	1.48749	70.45
24	-150.650	2.75
						25	-20.784	0.80	1.84666	23.78
26	-141.412	5.30
						27	inf	1.20	1.51680	64.20
28	inf	BF
						29	inf	-

Various data for example 5 are shown in table 14.

[ TABLE 14 ]

	Wide angle end	Intermediate (II)	Telescope end
				f	11.39	18.52	29.90
Fno	1.75	2.20	2.89
				ω	107.59	63.45	38.94
Image height	10.81	10.81	10.81
				Total length of lens	95.00	95.00	95.00
BF	0.60	0.60	0.60
				d2	1.62	9.18	11.66
d7	13.15	5.59	3.11
				d12	15.92	9.47	0.90
d17	1.40	7.85	16.42

The aspherical surface coefficients of example 5 are shown in table 15.

[ TABLE 15 ]

Noodle

R

k

A

B

C

D

E

13

16.500

0

-1.86291E-05

-1.02754E-07

1.72560E-09

-1.13713E-11

14

-71.025

0

3.28872E-05

-5.54188E-08

1.13262E-09

-8.57677E-12

(example 6)

The zoom ratio of example 6 was 2.79.

The lens data for example 6 is shown in table 16.

[ TABLE 16 ]

NS	R	D	nd	vd
							1	87.700	3.49	1.77250	49.62
2	361.770	d2
						3	181.694	0.80	1.87070	40.73
4	19.484	6.63
						5	-35.233	0.80	1.64000	60.08
6	27.684	2.19	1.98612	16.48
						7	53.794	d7
8	44.166	2.30	1.90043	37.37
						9	-53.747	0.60	1.88300	40.80
10	222.497	1.33
						11	inf	0.00			(aperture diaphragm)
12	inf	d12
						13	16.500	5.41	1.53500	55.71	Aspherical surface
14	-70.550	2.75			Aspherical surface
						15	26.742	0.80	2.05090	26.94
16	12.500	6.20	1.55032	75.50
						17	-30.833	d17
18	-71.213	0.80	1.84666	23.78
						19	21.434	5.41
20	-483.011	2.46	1.59282	68.63
						21	-43.417	0.12
22	36.499	7.87	1.90366	31.32
						23	-19.653	0.80	1.49700	81.61
24	3925.319	4.15
						25	-18.684	0.80	1.55032	75.50
26	-101.976	5.30
						27	inf	1.20	1.51680	64.20
28	inf	BF
						29	inf	-

Various data of example 6 are shown in table 17.

[ TABLE 17 ]

	Wide angle end	Intermediate (II)	Telescope end
				f	11.28	18.47	31.45
Fno	1.75	2.05	2.78
				ω	108.54	63.15	36.57
Image height	10.81	10.81	10.81
				Total length of lens	95.00	95.00	95.00
BF	0.60	0.60	0.60
				d2	1.50	11.39	15.70
d7	16.09	6.20	1.89
				d12	13.60	8.71	0.90
d17	0.95	5.83	13.65

The aspherical surface coefficients of example 6 are shown in table 18.

[ TABLE 18 ]

Noodle

R

k

A

B

C

D

E

13

16.500

0

-2.21183E-05

-3.93685E-08

1.42161E-09

-8.56316E-12

14

-70.550

0

3.70162E-05

-9.29072E-08

2.35310E-09

-1.36412E-11

(example 7)

The zoom ratio of example 7 was 2.79.

Lens data for example 7 is shown in table 19.

[ TABLE 19 ]

NS	R	D	nd	vd
							1	96.135	3.52	1.77250	49.62
2	471.016	d2
						3	107.823	0.80	1.87070	40.73
4	18.117	7.39
						5	-31.578	0.80	1.64000	60.08
6	31.972	1.81	1.98612	16.48
						7	50.254	d7
8	40.815	2.76	1.80809	22.76
						9	-37.859	0.60	1.92119	23.96
10	-314.486	1.20
						11	inf	0.00			(aperture diaphragm)
12	inf	d12
						13	16.500	5.41	1.53500	55.71	Aspherical surface
14	-70.662	2.52			Aspherical surface
						15	31.710	0.80	2.05090	26.94
16	13.351	6.20	1.55032	75.50
						17	-21.569	d17
18	-477.920	0.80	1.84666	23.78
						19	16.411	5.69
20	22.605	4.43	1.43700	95.10
						21	-180.632	1.51
22	49.412	5.42	1.98612	16.48
						23	-34.614	0.80	1.49700	81.61
24	-195.902	2.14
						25	-37.519	0.80	1.84666	23.78
26	80.911	5.30
						27	inf	1.20	1.51680	64.20
28	inf	BF
						29	inf	-

Various data for example 7 are shown in table 20.

[ TABLE 20 ]

	Wide angle end	Intermediate (II)	Telescope end
				f	11.26	18.47	31.47
Fno	1.77	2.20	2.85
				ω	108.50	64.55	37.69
Image height	10.81	10.81	10.81
				Total length of lens	95.00	95.00	95.00
BF	0.60	0.60	0.60
				d2	1.43	11.89	16.74
d7	17.23	6.77	1.92
				d12	12.76	8.18	0.90
d17	1.06	5.64	12.92

The aspherical surface coefficients of example 7 are shown in table 21.

[ TABLE 21 ]

Noodle

R

k

A

B

C

D

E

13

16.500

0

-2.44203E-05

-7.89315E-09

1.03879E-09

-2.64610E-11

14

-70.662

0

5.19811E-05

5.24191E-08

-9.43849E-10

-1.64144E-11

(example 8)

The zoom ratio of example 8 was 2.84.

The lens data for example 8 is shown in table 22.

[ TABLE 22 ]

NS	R	D	nd	vd
							1	90.956	3.32	1.77250	49.62
2	325.498	d2
						3	97.955	0.80	1.87070	40.73
4	18.424	7.29
						5	-28.620	0.80	1.64000	60.08
6	30.392	2.06	1.98612	16.48
						7	57.397	d7
8	48.584	2.10	2.00100	29.13
						9	581.514	1.61
10	inf	0.00			(aperture diaphragm)
						11	inf	d11
12	16.500	5.20	1.53500	55.71	Aspherical surface
						13	-75.692	2.89			Aspherical surface
14	27.459	0.80	2.05090	26.94
						15	12.500	6.21	1.55032	75.50
16	-26.762	d16
						17	-80.361	0.80	1.84666	23.78
18	19.960	5.34
						19	97.464	3.22	1.55032	75.50
20	-39.043	0.12
						21	37.852	7.46	1.80809	22.76
22	-19.064	0.80	1.48749	70.45
						23	736.671	3.34
24	-24.591	0.80	1.84666	23.78
						25	-146.083	5.30
26	inf	1.20	1.51680	64.20
						27	inf	BF
28	inf	-

Various data for example 8 are shown in table 23.

[ TABLE 23 ]

	Wide angle end	Intermediate (II)	Telescope end
				f	11.25	18.50	31.94
Fno	1.75	2.13	2.80
				ω	108.87	63.24	36.19
Image height	10.81	10.81	10.81
				Total length of lens	95.00	95.00	95.00
BF	0.60	0.60	0.60
				d2	1.49	11.76	16.27
d7	16.68	6.41	1.90
				d11	13.79	8.85	0.90
d16	0.95	5.89	13.84

The aspherical surface coefficients of example 8 are shown in table 24.

[ TABLE 24 ]

Noodle

R

k

A

B

C

D

E

12

16.500

0

-1.90636E-05

-3.20746E-08

1.33679E-09

-1.15923E-11

13

-75.692

0

4.33084E-05

-4.46771E-08

1.36336E-09

-1.24203E-11

Table 25 shows values related to the conditional expressions of examples 1 to 4. Table 26 shows values related to the conditional expressions of examples 5 to 8.

[ TABLE 25 ]

Numerical values related to conditional expressions	Example 1	Example 2	Example 3	Example 4
					f1	154.77	434.34	127.84	530.36
f2	-13.04	-11.58	-13.46	-18.30
					f3	52.69	40.84	55.54	78.26
f4	19.54	18.83	20.33	18.30
					f5	-92.51	-65.27	-254.40	-115.80
f5a	-18.89	-17.52	-20.15	-17.74

[ TABLE 26 ]

Numerical values related to conditional expressions	Example 5	Example 6	Example 7	Example 8
					f1	131.65	149.03	155.72	162.40
f2	-11.20	-14.04	-12.73	-13.30
					f3	42.28	59.31	50.69	52.86
f4	21.50	19.92	19.11	19.73
					f5	-128.81	-450.88	-58.11	-90.84
f5a	-22.37	-19.38	-18.73	-18.82

Table 27 shows the values of the conditional expressions of examples 1 to 4. Table 28 shows the values of the conditional expressions of examples 5 to 8.

[ TABLE 27 ]

[ TABLE 28 ]

[ description of reference ]

G1 first lens group

G2 second lens group

G3 third lens group

G4 fourth lens group

G5 fifth lens group

S-shaped opening diaphragm

CG protective glass

IMG imaging plane.

Claims

1. A zoom lens characterized in that a lens element is provided,

the zoom lens includes, in order from an 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, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power,

the zoom lens is configured such that, when zooming is performed from a wide-angle end to a telephoto end, the first lens group, the third lens group, and the fifth lens group are fixed, the second lens group moves on an optical axis toward an image side, and the fourth lens group moves on an object side, and the following conditional expressions (1) and (2) are satisfied:

-40.0≦f1/f2≦-8.5.......................(1)

-1.1≦f2/f4≦-0.5.......................(2)

wherein the content of the first and second substances,

f1 is the focal length of the first lens group

f2 is the focal length of the second lens group

f4 is the focal length of the fourth lens group.

2. Zoom lens according to claim 1,

satisfies the conditional formula (3) shown below:

3.0≦f3/fw≦7.5.........................(3)

wherein the content of the first and second substances,

fw is a focal length of the zoom lens in infinity focusing at the wide-angle end,

f3 is the focal length of the third lens group.

3. Zoom lens according to claim 1,

the second lens group moves on the optical axis when focusing from infinity to close distance, and satisfies the following conditional expression (4):

-1.8≦f2/fw≦-0.7......................(4)

wherein the content of the first and second substances,

f2 is the focal length of the second lens group.

4. Zoom lens according to claim 1,

the first lens group is composed of a positive lens.

5. Zoom lens according to claim 1,

the fifth lens group is composed of, in order from the object side, a negative lens and a partial group having a positive refractive power, and satisfies the following conditional expression (5):

-1.3≦f5a/f4≦-0.7....................(5)

wherein the content of the first and second substances,

f5a is the focal length of the negative lens of the fifth lens group disposed closest to the object side,

f4 is the focal length of the fourth lens group.

6. Zoom lens according to claim 1,

the fifth lens group has at least two positive lenses,

the following conditional expressions (6) and (7) are satisfied:

60.0≦vd5p1................................(6)

38.0≧vd5p2................................(7)

wherein the content of the first and second substances,

vd5p1 is the abbe number of one positive lens of the at least two positive lenses included in the fifth lens group,

vd5p2 is the abbe number of the other positive lens of the at least two positive lenses included in the fifth lens group.

7. Zoom lens according to claim 1,

the following conditional expressions (8) and (9) are satisfied:

1.7≦nd3_ave...............................(8)

45.0≧vd3_ave..............................(9)

wherein the content of the first and second substances,

nd3_ ave is an average value of refractive indexes of lenses included in the third lens group

vd3_ ave is an average value of abbe numbers of lenses included in the third lens group.

8. Zoom lens according to claim 1,

the fourth lens group has a plastic lens on the most object side.

9. Zoom lens according to claim 1,

the following conditional formula (10) is satisfied:

0.4≦f4/ft≦0.9.......................(10)

wherein the content of the first and second substances,

ft is the focal length of the zoom lens at infinity focusing at the telephoto end

f4 is the focal length of the fourth lens group.

10. Zoom lens according to claim 1,

the following conditional formula (11) is satisfied:

-50.0≦f5/fw≦-4.5..................(11)

wherein the content of the first and second substances,

f5 is the focal length of the fifth lens group.

11. Zoom lens according to claim 1,

the following conditional formula (12) is satisfied:

-19.0≦f5/ft≦-1.5.....................(12)

wherein the content of the first and second substances,

ft is the focal length of the zoom lens at infinity focus at the telephoto end,

f5 is the focal length of the fifth lens group.

12. An image pickup apparatus comprising:

a variable focus lens as claimed in any one of claims 1 to 11; and

and a solid-state imaging element disposed at an imaging position of the zoom lens.