# Patent

## Title
Zoom lens and image pickup apparatus including the same

## Abstract

Provided is a zoom lens, including, in order from an object side to an image side: a positive first lens unit that does not move for zooming; a negative second lens unit that moves during zooming; and a positive N-th lens unit that does not move for zooming and is arranged closest to the image side. Among lenses constructing the second lens unit, two lenses closest to the image side are a positive lens and a negative lens, and partial dispersion ratios for g-line and F-line and Abbe numbers for a d-line of the positive and negative lenses, and an average value of refractive indices of all the lenses of the second lens unit are appropriately set.

## Background
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, which are suitable for a broadcasting television camera, a movie camera, a video camera, a digital still camera, a monitoring camera, and a silver-halide film camera, for example.
Description of the Related Art
In recent years, a zoom lens having a wide angle of field, a high zoom ratio, and high optical performance is required for an image pickup apparatus such as a television camera, a movie camera, a silver-halide film camera, a digital camera, or a video camera. There has been known, as a zoom lens having a wide angle of field and a high zoom ratio, a four-unit zoom lens including a first lens unit having a positive refractive power, a second lens unit having a negative refractive power that is used for zooming, a third lens unit having a negative refractive power that is used to correct image plane variation accompanying zooming, and a fourth lens unit having a positive refractive power that is used for image formation (Japanese Patent Application Laid-Open No. H09-15501 and Japanese Patent Application Laid-Open No. 2004-341237).
In Japanese Patent Application Laid-Open No. H09-15501, there is disclosed a zoom lens having a zoom ratio of approximately 8 and an angle of field of photography at a wide angle end of approximately 87°. In Japanese Patent Application Laid-Open No. 2004-341237, there is disclosed a zoom lens having a zoom ratio of approximately 2.9 and an angle of field of photography at a wide angle end of approximately 94°.
In the four-unit zoom lens having the structure described above, it is relatively easy to achieve the increased angle of field. However, in order to obtain high optical performance in the four-unit zoom lens, it is important to satisfactorily correct a lateral chromatic aberration in the entire zoom range. If an optical material having characteristics of anomalous dispersion is used, the lateral chromatic aberration is satisfactorily corrected with ease. However, even if a lens made of the material having the characteristics of anomalous dispersion is merely used, it is difficult to satisfactorily correct the chromatic aberration. In order to obtain the high optical performance over the entire zoom range in the above-mentioned four-unit zoom lens, it is important to appropriately set the materials of the lenses included in the second lens unit that moves during the zooming.
In addition, in the four-unit zoom lens having the structure described above, the high zoom ratio is relatively easy to achieve, but in order to achieve both the increased high zoom ratio and the reduction in size, it is important to appropriately set the arrangement of the refractive powers of the lenses. In particular, in the four-unit zoom lens having the structure described above, the second lens unit mainly plays a role of changing the zoom. Therefore, it is important to satisfactorily set the lens structure of the second lens unit and the materials of the lenses included in the second lens unit.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a zoom lens having a wide angle of field, a high zoom ratio, high optical performance over an entire zoom range, and good zoom action, and to provide an image pickup apparatus including the zoom lens.
According to one embodiment of the present invention, there is provided a zoom lens, including, in order from an object side to an image side: a first lens unit having a positive refractive power that does not move for zooming; a second lens unit having a negative refractive power that moves during zooming; a third lens unit that moves during zooming; and an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side, in which, among lenses constructing the second lens unit or among lenses constructing the second lens unit and the third lens unit, two lenses disposed closest to the image side comprise a positive lens and a negative lens, and satisfy the following conditional expressions:

−3.0×10−3<(θp−θn)/(νp−νn)<0; and

1.7<nave<2.0,

where θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit, provided that the Abbe number ν and the partial dispersion ratio θ are respectively expressed as follows:

ν=(nd−1)/(nF−nC); and

θ=(ng−nF)/(nF−nC),

where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.

According to one embodiment of the present invention, it is possible to provide the zoom lens having a wide angle of field, a high zoom ratio, and high optical performance over the entire zoom range, and to provide the image pickup apparatus including the zoom lens.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a lens cross-sectional view when focusing on an infinite object at a wide angle end of a zoom lens according to Numerical Embodiment 1 of the present invention.
FIG. 2A is an aberration diagram when focusing on the infinite object at the wide angle end of the zoom lens according to Numerical Embodiment 1 of the present invention.
FIG. 2B is an aberration diagram when focusing on the infinite object at an intermediate zoom position of the zoom lens according to Numerical Embodiment 1 of the present invention.
FIG. 2C is an aberration diagram when focusing on the infinite object at a telephoto end of the zoom lens according to Numerical Embodiment 1 of the present invention.
FIG. 3 is a lens cross-sectional view when focusing on an infinite object at a wide angle end of a zoom lens according to Numerical Embodiment 2 of the present invention.
FIG. 4A is an aberration diagram when focusing on the infinite object at the wide angle end of the zoom lens according to Numerical Embodiment 2 of the present invention.
FIG. 4B is an aberration diagram when focusing on the infinite object at an intermediate zoom position of the zoom lens according to Numerical Embodiment 2 of the present invention.
FIG. 4C is an aberration diagram when focusing on the infinite object at a telephoto end of the zoom lens according to Numerical Embodiment 2 of the present invention.
FIG. 5 is a lens cross-sectional view when focusing on an infinite object at a wide angle end of a zoom lens according to Numerical Embodiment 3 of the present invention.
FIG. 6A is an aberration diagram when focusing on the infinite object at the wide angle end of the zoom lens according to Numerical Embodiment 3 of the present invention.
FIG. 6B is an aberration diagram when focusing on the infinite object at an intermediate zoom position of the zoom lens according to Numerical Embodiment 3 of the present invention.
FIG. 6C is an aberration diagram when focusing on the infinite object at a telephoto end of the zoom lens according to Numerical Embodiment 3 of the present invention.
FIG. 7 is a lens cross-sectional view when focusing on an infinite object at a wide angle end of a zoom lens according to Numerical Embodiment 4 of the present invention.
FIG. 8A is an aberration diagram when focusing on the infinite object at the wide angle end of the zoom lens according to Numerical Embodiment 4 of the present invention.
FIG. 8B is an aberration diagram when focusing on the infinite object at an intermediate zoom position of the zoom lens according to Numerical Embodiment 4 of the present invention.
FIG. 8C is an aberration diagram when focusing on the infinite object at a telephoto end of the zoom lens according to Numerical Embodiment 4 of the present invention.
FIG. 9 is a lens cross-sectional view when focusing on an infinite object at a wide angle end of a zoom lens according to Numerical Embodiment 5 of the present invention.
FIG. 10A is an aberration diagram when focusing on the infinite object at the wide angle end of the zoom lens according to Numerical Embodiment 5 of the present invention.
FIG. 10B is an aberration diagram when focusing on the infinite object at an intermediate zoom position of the zoom lens according to Numerical Embodiment 5 of the present invention.
FIG. 10C is an aberration diagram when focusing on the infinite object at a telephoto end of the zoom lens according to Numerical Embodiment 5 of the present invention.
FIG. 11 is a lens cross-sectional view when focusing on an infinite object at a wide angle end of a zoom lens according to Numerical Embodiment 6 of the present invention.
FIG. 12A is an aberration diagram when focusing on the infinite object at the wide angle end of the zoom lens according to Numerical Embodiment 6 of the present invention.
FIG. 12B is an aberration diagram when focusing on the infinite object at an intermediate zoom position of the zoom lens according to Numerical Embodiment 6 of the present invention.
FIG. 12C is an aberration diagram when focusing on the infinite object at a telephoto end of the zoom lens according to Numerical Embodiment 6 of the present invention.
FIG. 13 is a lens cross-sectional view when focusing on an infinite object at a wide angle end of a zoom lens according to Numerical Embodiment 7 of the present invention.
FIG. 14A is an aberration diagram when focusing on the infinite object at the wide angle end of the zoom lens according to Numerical Embodiment 7 of the present invention.
FIG. 14B is an aberration diagram when focusing on the infinite object at an intermediate zoom position of the zoom lens according to Numerical Embodiment 7 of the present invention.
FIG. 14C is an aberration diagram when focusing on the infinite object at a telephoto end of the zoom lens according to Numerical Embodiment 7 of the present invention.
FIG. 15 is a schematic diagram illustrating a main part of an image pickup apparatus of the present invention.
FIG. 16 is a schematic graph showing a distribution of an Abbe number and a partial dispersion ratio of optical materials.
FIG. 17 is an optical path diagram at a wide angle end and at a telephoto end of the zoom lens of the present invention.
FIG. 18 is a schematic diagram illustrating a main part of the image pickup apparatus of the present invention.



DESCRIPTION OF THE EMBODIMENT
Now, an embodiment of the present invention is described in detail with reference to the attached drawings. A zoom lens according to each of Embodiments 1 to 6 of the present invention includes, in order from an object side to an image side: a first lens unit having a positive refractive power that does not move for zooming; a second lens unit having a negative refractive power that moves during zooming; a third lens unit having a negative refractive power that moves during zooming; and a fourth lens unit having a positive refractive power that does not move for zooming.
A zoom lens according to Embodiment 7 of the present invention includes, in order from an object side to an image side: a first lens unit having a positive refractive power that does not move for zooming; a second lens unit having a negative refractive power that moves during zooming; a third lens unit having a negative refractive power that moves during zooming; a fourth lens unit having a negative refractive power that moves during zooming; and a fifth lens unit having a positive refractive power that does not move for zooming.
The expression that “a lens unit does not move for zooming” means herein that the lens unit is not driven for a purpose of zooming, but the lens unit may move for focusing if zooming and focusing are performed simultaneously.
FIG. 1 is a lens cross-sectional view of a zoom lens according to Embodiment 1 (Numerical Embodiment 1) of the present invention when focusing on an infinite object at a wide angle end (focal length f=18.00 mm). FIGS. 2A, 2B, and 2C are aberration diagrams respectively at the wide angle end, at an intermediate zoom position (focal length f=63.00 mm), and at a telephoto end (focal length f=180.00 mm) of the zoom lens according to Numerical Embodiment 1 when focusing on an infinite object. Here, the focal length is a value of this numerical embodiment expressed in millimeters. The same is true for the following embodiments.
FIG. 3 is a lens cross-sectional view of a zoom lens according to Embodiment 2 (Numerical Embodiment 2) of the present invention at a wide angle end (focal length f=15.00 mm) when focusing on an infinite object. FIGS. 4A, 4B, and 4C are aberration diagrams respectively at the wide angle end, at an intermediate zoom position (focal length f=35.00 mm), and at a telephoto end (focal length f=75.00 mm) of the zoom lens according to Numerical Embodiment 2 when focusing on an infinite object.
FIG. 5 is a lens cross-sectional view of a zoom lens according to Embodiment 3 (Numerical Embodiment 3) of the present invention at a wide angle end (focal length f=20.00 mm) when focusing on an infinite object. FIGS. 6A, 6B, and 6C are aberration diagrams respectively at the wide angle end, at an intermediate zoom position (focal length f=60.00 mm), and at a telephoto end (focal length f=160.00 mm) of the zoom lens according to Numerical Embodiment 3 when focusing on an infinite object.
FIG. 7 is a lens cross-sectional view of a zoom lens according to Embodiment 4 (Numerical Embodiment 4) of the present invention at a wide angle end (focal length f=19.00 mm) when focusing on an infinite object. FIGS. 8A, 8B, and 8C are aberration diagrams respectively at the wide angle end, at an intermediate zoom position (focal length f=45.00 mm), and at a telephoto end (f=95.00 mm) of the zoom lens according to Numerical Embodiment 4 when focusing on an infinite object.
FIG. 9 is a lens cross-sectional view of a zoom lens according to Embodiment 5 (Numerical Embodiment 5) of the present invention at a wide angle end (focal length f=14 mm) when focusing on an infinite object. FIGS. 10A, 10B, and 10C are aberration diagrams respectively at the wide angle end, at an intermediate zoom position (focal length f=28.00 mm), and at a telephoto end (focal length f=56.00 mm) of the zoom lens according to Numerical Embodiment 5 when focusing on an infinite object.
FIG. 11 is a lens cross-sectional view of a zoom lens according to Embodiment 6 (Numerical Embodiment 6) of the present invention at a wide angle end (focal length f=8.00 mm) when focusing on an infinite object. FIGS. 12A, 12B, and 12C are aberration diagrams respectively at the wide angle end, at an intermediate zoom position (focal length f=32.00 mm), and at a telephoto end (focal length f=120.00 mm) of the zoom lens according to Numerical Embodiment 6 when focusing on an infinite object.
FIG. 13 is a lens cross-sectional view of a zoom lens according to Embodiment 7 (Numerical Embodiment 7) of the present invention at a wide angle end (focal length f=18.50 mm) when focusing on an infinite object. FIGS. 14A, 14B, and 14C are aberration diagrams respectively at the wide angle end, at an intermediate zoom position (focal length f=45.00 mm), and at a telephoto end (focal length f=120.25 mm) of the zoom lens according to Numerical Embodiment 7 when focusing on an infinite object.
FIG. 15 illustrates the principle of correction of a secondary spectrum of a lateral chromatic aberration.
FIG. 16 is a schematic graph showing a distribution of an Abbe number ν and a partial dispersion ratio θ of optical materials.
FIG. 17 is an optical path diagram at a wide angle end and at a telephoto end of the zoom lens of the present invention.
FIG. 18 is a schematic diagram illustrating a main part of an image pickup apparatus of the present invention.
In each lens cross-sectional view, the left side is the subject (object) side (front), and the right side is the image side (rear). In the lens cross-sectional view, a first lens unit (front lens unit) U1 has a positive refractive power and does not move for zooming. A focus lens unit U12 in the first lens unit U1 moves to the image side in FIGS. 1, 3, 5, 7, 9, and 13 during focusing from an infinite object to a short-distance object, and moves to the object side in FIG. 11 during focusing from the infinite object to the short-distance object. Fixed lens units U11 and U13 in the first lens unit U1 do not move for focusing. In FIGS. 1, 3, 5, 7, 9, and 11, a second lens unit U2 and a third lens unit U3 each has a negative refractive power and move during zooming. The two lens units: the second lens unit U2; and the third lens unit U3 construct a zoom optical system. A fourth lens unit U4 (relay lens unit) has a positive refractive power and an imaging action, and does not move for zooming. In FIG. 13, a second lens unit U2, a third lens unit U3, and a fourth lens unit U4 each have a negative refractive power and move during zooming. The three lens units: the second lens unit U2; the third lens unit U3; and the fourth lens unit U4 construct a zoom optical system. A fifth lens unit U5 (relay lens unit) has a positive refractive power and an imaging action, and does not move for zooming.
A stop (aperture stop) SP is arranged. When used as an image pickup optical system for a broadcasting television camera, a movie camera, a video camera, or a digital still camera, an image pickup surface I corresponds to an image pickup surface of a solid-state image pickup element (photoelectric conversion element) or the like for receiving an image formed by the zoom lens and converting light to electricity. When used as an image pickup optical system for a film camera, the image pickup surface I corresponds to a film surface on which the image formed by the zoom lens is exposed.
In the aberration diagrams, a straight line, a two-dot chain line, a dashed line, and a broken line in a spherical aberration indicate an e-line, a g-line, a C-line, and an F-line, respectively. A broken line and a solid line in astigmatism indicate a meridional image plane and a sagittal image plane, respectively. In addition, a two-dot chain line, a dashed line, and a broken line in a lateral chromatic aberration indicate a g-line, a C-line, and an F-line, respectively. Symbol A represents a half angular field of view, and symbol Fno represents an F number. Note that, in the following embodiments, the case where a lens unit for zooming is located at the shortest focal length side is referred to as “wide angle end”, and the case where a lens unit for zooming is located at the longest focal length side is referred to as “telephoto end”.
In each of the embodiments, the zoom lens of the present invention includes, in order from the object side to the image side, a first lens unit U1 having a positive refractive power that does not move for zooming and a second lens unit U2 having a negative refractive power that moves during zooming. The zoom lens further includes an N-th lens unit UN having a positive refractive power, which is arranged closest to the image side and which does not move for zooming. Two lenses closest to the image side of the second lens unit U2 include a positive lens and a negative lens.
In this case, the following conditional expression is satisfied:

−3.0×10−3<(θp−θn)/(νp−νn)<0  (1)

where θp and νp respectively represent a partial dispersion ratio and an Abbe number of the positive lens of the second lens unit U2, and θn and νn respectively represent a partial dispersion ratio and an Abbe number of the negative lens of the second lens unit U2.

In this case, symbols νp and νn represent the Abbe numbers for the d-line and symbols θp and θn represent the partial dispersion ratios for the g-line and the F-line.
The zoom lens of each of the embodiments has a feature in that the conditions of the lens structure and the dispersion characteristics of the materials of the lenses in the second lens unit U2 are appropriately defined. Here, the conditional expression (1) represents a condition under which the secondary spectrum of the lateral chromatic aberration is appropriately corrected in all the focal lengths. In the zoom lens of each of the embodiments, the lens structure and the dispersion characteristics of the materials of the lenses in the second lens unit U2 are important factors for satisfactorily correcting the secondary spectrum of the lateral chromatic aberration in all the focal lengths. By satisfying the conditional expression (1), a residual secondary spectrum of the lateral chromatic aberration is reduced in the second lens unit U2. As a result, the secondary spectrum of the lateral chromatic aberration is reduced at the wide angle end. In general, the secondary spectrum of the lateral chromatic aberration remains in a direction of being apart from the optical axis at the wide angle end, and remains in a direction of being closer to the optical axis at the telephoto end. Therefore, the secondary spectrum of the lateral chromatic aberration of the second lens unit U2 is increased by reducing the residual secondary spectrum of the lateral chromatic aberration of the second lens unit U2. However, a correction amount of secondary spectrum at the wide angle end is more than the residual secondary spectrum of the lateral chromatic aberration at the telephoto end, and hence the zoom variation of the lateral chromatic aberration is corrected.
FIG. 15 is a schematic diagram about dichroic achromatism by a lens unit LN having a negative refractive power, and the residual secondary spectrum. FIG. 16 is a schematic graph showing a distribution of the Abbe number ν and the partial dispersion ratio θ of the existing optical materials. Here, the Abbe number ν and the partial dispersion ratio θ are respectively expressed as follows:

ν=(nd−1)/(nF-nC)  (i)

θ=(ng-nF)/(nF-nC)  (ii)

where ng represents a refractive index for the g-line, nF represents a refractive index for the F-line, nd represents a refractive index for the d-line, and nC represents a refractive index for the C-line. As shown in FIG. 16, in the existing optical materials, the partial dispersion ratio θ distributes in a narrower range than that of the Abbe number ν. Hence, the existing optical materials have such a tendency that the partial dispersion ratio θ is large as the Abbe number ν becomes smaller.

A correction condition of the lateral chromatic aberration of a thin lens system (having a combined refractive power φ) including two lenses G1 and G2 whose refractive powers are represented by φ1 and φ2, respectively, and whose Abbe numbers of the materials are represented by ν1 and ν2, respectively, is expressed as follows.

φ1/ν1+φ2/ν2=E  (iii)

φ=φ1+φ2  (iv)

When E=0 in the expression (iii), the image formation positions of the C-line and the F-line are matched with each other.

In FIG. 15, for the achromatism by the lens unit LN having the negative refractive power, a material having a smaller Abbe number ν1 is used as the positive lens G1, and a material having a larger Abbe number ν2 is used as the negative lens G2. Therefore, with reference to FIG. 16, the positive lens G1 becomes larger in the partial dispersion ratio θ 1 and the negative lens G2 becomes smaller in the partial dispersion ratio θ 2. Under this condition, if the lateral chromatic aberration is corrected for the F-line and the C-line, the image formation point of the g-line deviates to the image side. When this deviation amount is defined as a secondary spectrum amount Δ, the secondary spectrum amount Δ is expressed as follows.

Δ=−(1/φ)×(θ1−θ2)/(ν1−ν2)  (v)

In addition, an amount Y of lateral chromatic aberration is expressed as follows:

Y=−(Σ(h×hbar×E))tan ω  (vi)

where h represents an axial marginal ray height in each plane, and hbar represents a pupil paraxial ray height in each plane. In other words, the amount Y of lateral chromatic aberration is proportional to the product of the axial marginal ray height h and the pupil paraxial ray height hbar.

FIG. 17 illustrates an optical path diagram at the wide angle end and at the telephoto end. In this case, the axial marginal beam is indicated by a solid line, and the pupil paraxial ray is indicated by a broken line. In the second lens unit U2, the axial marginal ray height h is successively lowered from the object side to the image side, and the pupil paraxial ray height hbar is successively raised from the object side to the image side. In addition, the product of the axial marginal ray height h and the pupil paraxial ray height hbar in each lens of the second lens unit U2 is hardly changed. In other words, in the second lens unit U2, there is almost no difference in the correction amounts of lateral chromatic aberration depending on the lens positions.
On the other hand, at the telephoto end, the axial marginal ray height is successively raised from the object side to the image side, and the pupil paraxial ray height is successively lowered from the object side to the image side. In addition, the product of the axial marginal ray height h and the pupil paraxial ray height hbar in each lens of the second lens unit U2 is smaller in the lens on the image side than the lens on the object side. The reason for this is because the second lens unit U2 approaches the aperture stop at the telephoto end so that the pupil paraxial ray height hbar is low. Therefore, in order to correct the zoom variation of the secondary spectrum of the lateral chromatic aberration, it is effective to select the suitable material for the lens on the image side of the second lens unit U2. Specifically, it is preferred that the lens having a smaller partial dispersion ratio be used as the positive lens on the image side, and the lens having a larger partial dispersion ratio be used as the negative lens on the image side.
If (θp−θn)/(νp−νn) in the conditional expression (1) exceeds an upper limit, an amount of secondary spectrum to be corrected in the second lens unit U2 is decreased at the telephoto end, and hence it becomes difficult to satisfactorily correct the axial chromatic aberration. On the other hand, if (θp−θn)/(νp−νn) in the conditional expression (1) exceeds a lower limit, the amount of secondary spectrum of the second lens unit U2 is increased at the wide angle end. As a result, it becomes difficult to satisfactorily correct the lateral chromatic aberration at the wide angle end and the zoom variation of the lateral chromatic aberration.
It is more preferred to set the numerical value range of the conditional expression (1) as follows.

−2.9×10−3<(θp−θn)/(νp−νn)<−1.0×10−3  (1a)

Moreover, the zoom lens of the present invention satisfies the following conditional expression:

1.7<nave<2.0  (2)

where nave represents an average value of the refractive indices of all the lenses in the second lens unit U2.

The conditional expression (2) defines an average refractive index of all the lenses in the second lens unit U2. In the zoom lens of each of the embodiments, the average refractive index of all the lenses in the second lens unit U2 is set for suppressing the increase in size of the lens and correcting various aberrations. By satisfying the conditional expression (2), the zoom lens in which the various aberrations can be satisfactorily corrected can be obtained while the increase in size of the lens is suppressed.
If nave in the conditional expression (2) exceeds an upper limit, in the existing optical materials, a difference in Abbe number between the positive lens and the negative lens is decreased. As a result, as shown in the expressions (iii) and (iv), the refractive powers of the lenses in the second lens unit U2 are increased. Therefore, it becomes difficult to satisfactorily correct the various aberrations, especially, the off-axis aberration variation on the wide angle side and the spherical aberration variation on the telephoto side. On the other hand, if nave in the conditional expression (2) exceeds a lower limit, the refractive powers of the lenses in the second lens unit U2 cannot be increased. As a result, the movement amount required for zooming is increased, which leads to the increase in size of the lens.
It is more preferred to set the numerical value range of the conditional expression (2) as follows.

1.74<nave<1.95  (2a)

By satisfying the above-mentioned conditions, each of the embodiments of the present invention obtains the small and lightweight zoom lens in which the aberration correction is satisfactorily carried out in the entire zoom range.
In each of the embodiments, it is more preferred to satisfy the following conditional expression:

−2.5<f2/fw<0  (3)

where f2 represents the focal length of the second lens unit, and fw represents the focal length at the wide angle end.

The conditional expression (3) defines a ratio of the focal length of the second lens unit U2 to the focal length at the wide angle end.
If f2/fw in the conditional expression (3) exceeds an upper limit, the focal length of the second lens unit U2 becomes relatively short. As a result, it becomes difficult to attain the suppression of the variation of various off-axis aberrations following zooming on the wide angle side, especially, the suppression of the distortion and the field curvature, and the suppression of the variation of various aberrations following zooming on the telephoto side, especially, the suppression of the spherical aberration. On the other hand, if f2/fw in the conditional expression (3) exceeds a lower limit, the focal length of the second lens unit U2 becomes relatively long. As a result, the movement amount required for zooming is increased, which leads to the increase in size of the entire lens.
It is more preferred to set the numerical value range of the conditional expression (3) as follows.

−1.50<f2/fw<−1.00  (3a)

In each of the embodiments, it is more preferred to satisfy the following conditional expression:

−5.0<f1/f2<0  (4)

where f1 represents the focal length of the first lens unit U1.

The conditional expression (4) defines a ratio of the focal length of the first lens unit U1 to the focal length of the second lens unit U2.
If f1/f2 in the conditional expression (4) exceeds an upper limit, the focal length of the first lens unit U1 becomes relatively short. As a result, the correction of the various aberrations, especially, the correction of the chromatic aberration at the telephoto end becomes difficult to attain. In addition, the performance reduction due to manufacturing fluctuations becomes larger because a manufacturing error greatly affects the performance.
On the other hand, if f1/f2 in the conditional expression (4) exceeds a lower limit, the focal length of the first lens unit U1 becomes relatively short. As a result, the movement amount required for zooming is increased, which leads to the increase in size of the entire lens.
It is more preferred to set the numerical value range of the conditional expression (4) as follows.

−2.55<f1/f2<−1.00  (4a)

In each of the embodiments, it is more preferred to include at least one positive lens that satisfies the following conditional expressions:

1.8<ni<2.2  (5)

15<νi<30  (6)

where ni represents a refractive index of an i-th lens counted from the object side to the image side of the second lens unit U2, and νi represents an Abbe number thereof. In this case, symbol ni is the refractive index for the d-line, and symbol νi is the Abbe number for the d-line.

The conditional expression (5) defines the refractive index of the at least one positive lens included in the second lens unit U2.
If ni in the conditional expression (5) exceeds an upper limit, noise is easily generated in a blue subject when the sensitivity correction is carried out by using the camera because in the existing optical materials, especially, a transmittance on the short wavelength side is low. On the other hand, if ni in the conditional expression (5) exceeds a lower limit, this leads to deterioration of various aberrations or an increase in the number of lenses.
The conditional expression (6) defines the Abbe number of the at least one positive lens included in the second lens unit U2.
If νi in the conditional expression (6) exceeds an upper limit, as shown in the expressions (iii) and (iv), in order to match the image formation positions of the C-line and the F-line with each other, the positive lens of the second lens unit U2 needs to have a small Abbe number, and hence the chromatic aberration remains.
On the other hand, if νi in the conditional expression (6) exceeds a lower limit, as shown in FIG. 16, because the existing optical materials have such a tendency that the partial dispersion ratio becomes larger as the Abbe number becomes smaller, it becomes difficult to satisfactorily correct the zoom variation of the lateral chromatic aberration.
It is more preferred to set the numerical value ranges of the conditional expressions (5) and (6) as follows.

1.82<ni<2.05  (5a)

20<νi<27  (6a)

In each of the embodiments, it is more preferred to include at least one positive lens that satisfies the following conditional expression:

0.648<θi+2.53×10−3×νi<0.678  (7)

where θi represents the partial dispersion ratio for the g-line and the F-line of the i-th lens counted from the object side to the image side of the second lens unit U2, and νi represents the Abbe number for the d-line of the i-th lens.

The conditional expression (7) defines the partial dispersion ratio of the at least one positive lens included in the second lens unit U2.
If θi+2.53×10−3×νi in the conditional expression (7) exceeds an upper limit, as shown in the expression (v), the secondary spectrum amount of the second lens unit U2 is increased at the wide angle end. As a result, it becomes difficult to satisfactorily correct the lateral chromatic aberration at the wide angle end and the zoom variation of the lateral chromatic aberration.
On the other hand, if θi+2.53×10−3×νi in the conditional expression (7) exceeds a lower limit, as shown in the expression (v), the secondary spectrum amount corrected by the second lens unit U2 is reduced at the telephoto end. As a result, it becomes difficult to satisfactorily correct the axial chromatic aberration.
It is more preferred to set the numerical value range of the conditional expression (7) as follows.

0.658<θi+2.53×10−3×νi<0.670  (7a)

In each of the embodiments, it is more preferred that the positive lens satisfying the conditional expressions (5) to (7) be a positive lens closest to the object side of the second lens unit U2. As a result, the zoom variation of the secondary spectrum of the lateral chromatic aberration is easily corrected.
In each of the embodiments, it is more preferred that the second lens unit U2 include three negative lenses and one positive lens. As a result, the suppression of various aberrations, especially, the correction of the zoom variation of various off-axis aberrations on the wide angle side is easily carried out.
In Numerical Embodiment 7, the zoom lens includes, in order from the object side to the image side, a first lens unit U1 having a positive refractive power that does not move for zooming, a second lens unit U2 having a negative refractive power that moves during zooming, and a third lens unit U3 that moves during zooming. In addition, the zoom lens further includes an N-th lens unit UN having a positive refractive power, which is arranged closest to the image side and which does not move for zooming. Of the lenses constructing the second lens unit U2 and the third lens unit U3, two lenses closest to the image side are a positive lens and a negative lens. Specifically, two lenses closest to the image side of the third lens unit U3, or lenses closest to the image side of the third lens unit U3 and the second lens unit U2 when the third lens unit U3 includes one lens, are a positive lens and a negative lens. In this case, the following conditional expression is satisfied:

−3.0×10−3<(θp23−θn23)/(νp23−νn23)<0  (8)

where θp23 and νp23 respectively represent the partial dispersion ratio and the Abbe number of the positive lens, and θn23 and νn23 respectively represent the partial dispersion ratio and the Abbe number of the negative lens.

In this case, symbols νp23 and νn23 represent the Abbe numbers for the d-line, and symbols θp23 and θn23 represent the partial dispersion ratios for the g-line and the F-line.
If (θp23−θn23)/(νp23−νn23) in the conditional expression (8) exceeds an upper limit, the secondary spectrum amount corrected by the second lens unit U2 and the third lens unit U3 is reduced at the telephoto end. As a result, it becomes difficult to satisfactorily correct the axial chromatic aberration. On the other hand, if (θp23−θn23)/(νp23−νn23) in the conditional expression (8) exceeds a lower limit, the secondary spectrum amounts of the second lens unit U2 and the third lens unit U3 are increased at the wide angle end. As a result, it becomes difficult to satisfactorily correct the lateral chromatic aberration at the wide angle end and the zoom variation of the lateral chromatic aberration.
It is more preferred to set the numerical value range of the conditional expression (8) as follows.

−2.9×10−3<(θp23−θn23)/(νp23−νn23)<−1.0×10−3  (8a)

In addition, the zoom lens of Embodiment 7 satisfies the following conditional expression:

1.7<nave23<2.0  (9)

where nave23 represents an average value of the refractive indices of all the lenses in the second lens unit U2 and the third lens unit U3.

The conditional expression (9) defines an average refractive index of all the lenses in the second lens unit U2 and the third lens unit U3. In the zoom lens of Embodiment 7, the average refractive index of all the lenses in the second lens unit U2 and the third lens unit U3 is set for suppressing the increase in size of the lens and correcting various aberrations. By satisfying the conditional expression (9), the zoom lens in which the various aberrations can be satisfactorily corrected can be obtained while the increase in size of the lens is suppressed.
If nave23 in the conditional expression (9) exceeds an upper limit, in the existing optical materials, a difference in Abbe number between the positive lens and the negative lens is decreased. As a result, as shown in the expressions (iii) and (iv), the refractive powers of the lenses in the second lens unit U2 and the third lens unit U3 are increased. Therefore, it becomes difficult to satisfactorily correct the various aberrations, especially, the variation of the off-axis aberration on the wide angle side and the variation of the spherical aberration on the telephoto side. On the other hand, if nave23 in the conditional expression (9) exceeds a lower limit, the refractive powers of the lenses in the second lens unit U2 and the third lens unit U3 cannot be increased. As a result, the movement amount required for zooming is increased, and hence the lens is increased in size.
It is more preferred to set the numerical value range of the conditional expression (9) as follows.

1.74<nave23<1.95  (9a)

It is more preferred that the zoom lens in Embodiment 7 include a third lens unit U3 having a negative refractive power, which moves for zooming and satisfies the following conditional expression:

−2.5<f23/fw<0  (10)

where f23 represents a combined focal length at the wide angle end of the second lens unit U2 and the third lens unit U3.

The conditional expression (10) defines a ratio of the combined focal length at the wide angle end of the second lens unit U2 and the third lens unit U3 to the focal length at the wide angle end.
If f23/fw in the conditional expression (10) exceeds an upper limit, the combined focal length f23 at the wide angle end becomes relatively short. As a result, it becomes difficult to attain the suppression of the variation of various off-axis aberrations following zooming on the wide angle side, especially, the suppression of the distortion and the field curvature, and the suppression of the variation of various aberrations following zooming on the telephoto side, especially, the suppression of the spherical aberration. On the other hand, if f23/fw in the conditional expression (10) exceeds a lower limit, the combined focal length f23 at the wide angle end becomes relatively long. As a result, the movement amount required for zooming is increased, which leads to the increase in size of the entire lens.
It is more preferred to set the numerical value range of the conditional expression (10) as follows.

−1.50<f23/fw<−1.00  (10a)

It is more preferred that the zoom lens in Embodiment 7 include a third lens unit U3 having a negative refractive power, which moves for zooming and satisfies the following conditional expression:

−5.0<f1/f23<0  (11)

where f23 represents the combined focal length at the wide angle end of the second lens unit U2 and the third lens unit U3.

The conditional expression (11) defines a ratio of the focal length at the wide angle end of the second lens unit U2 and the third lens unit U3 to that of the first lens unit U1.
If f1/f23 in the conditional expression (11) exceeds an upper limit, the focal length of the first lens unit U1 becomes relatively short. As a result, the correction of the various aberrations, especially, the correction of the chromatic aberration at the telephoto end becomes difficult to attain. In addition, the performance reduction due to manufacturing fluctuations becomes larger because a manufacturing error greatly affects the performance.
On the other hand, if f1/f23 in the conditional expression (11) exceeds a lower limit, the focal length of the first lens unit U1 becomes relatively short. As a result, the movement amount required for zooming is increased, which leads to the increase in size of the entire lens.
It is more preferred to set the numerical value range of the conditional expression (11) as follows.

−2.55<f1/f23<−1.00  (11a)

It is more preferred that the zoom lens of Embodiment 7 include at least one positive lens that satisfies the following conditional expressions:

1.8<ni23<2.2  (12)

15<νi23<30  (13)

where ni23 represents a refractive index of an i-th lens counted from the object side to the image side of the second lens unit U2 and the third lens unit U3, and νi23 represents an Abbe number thereof. In this case, symbol ni23 is the refractive index for the d-line, and symbol νi23 is the Abbe number for the d-line.

The conditional expression (12) defines the refractive index of the at least one positive lens included in the second lens unit U2 and the third lens unit U3.
If ni23 in the conditional expression (12) exceeds an upper limit, noise is easily generated in a blue subject when the sensitivity correction is carried out by using the camera because in the existing optical materials, especially, a transmittance on the short wavelength side is low. On the other hand, if ni23 in the conditional expression (12) exceeds a lower limit, this leads to deterioration of various aberrations or an increase in the number of lenses.
The conditional expression (13) defines the Abbe number of the at least one positive lens included in the second lens unit U2 and the third lens unit U3.
If νi23 in the conditional expression (13) exceeds an upper limit, as shown in the expressions (iii) and (iv), in order to match the image formation positions of the C-line and the F-line with each other, the positive lens of the second lens U2 and the third lens unit U3 needs to have a small Abbe number, and hence the chromatic aberration remains.
On the other hand, if νi23 in the conditional expression (13) exceeds a lower limit, as shown in FIG. 16, because the existing optical materials have such a tendency that the partial dispersion ratio becomes larger as the Abbe number becomes smaller, it becomes difficult to satisfactorily correct the zoom variation of the lateral chromatic aberration.
It is more preferred to set the numerical value ranges of the conditional expressions (12) and (13) as follows.

1.82<ni23<2.05  (12a)

20<νi23<27  (13a)

It is more preferred that the zoom lens of Embodiment 7 include at least one positive lens that satisfies the following conditional expression:

0.648<θi23+2.53×10−3×νi23<0.678  (14)

where θi23 represents the partial dispersion ratio for the g-line and the F-line of the i-th lens counted from the object side to the image side of the second lens unit U2 and the third lens unit U3, and νi23 represents the Abbe number for the d-line of the i-th lens.

The conditional expression (14) defines the partial dispersion ratio of the at least one positive lens included in the second lens unit U2 and the third lens unit U3.
If θi23+2.53×10−3×νi23 in the conditional expression (14) exceeds an upper limit, as shown in the expression (v), the secondary spectrum amounts of the second lens unit U2 and the third lens unit U3 are increased at the wide angle end. As a result, it becomes difficult to satisfactorily correct the lateral chromatic aberration at the wide angle end and the zoom variation of the lateral chromatic aberration.
On the other hand, if θi23+2.53×10−3×νi23 in the conditional expression (14) exceeds a lower limit, as shown in the expression (v), the secondary spectrum amounts corrected by the second lens unit U2 and the third lens unit U3 are reduced at the telephoto end. As a result, it becomes difficult to satisfactorily correct the axial chromatic aberration.
It is more preferred to set the numerical value range of the conditional expression (14) as follows.

0.658<θi23+2.53×10−3×νi23<0.670  (14a)

In the zoom lens of Embodiment 7, it is more preferred that the positive lens satisfying the conditional expressions (12) to (14) be a positive lens closest to the object side of the second lens unit U2 and the third lens unit U3. As a result, the zoom variation of the secondary spectrum of the lateral chromatic aberration is easily corrected.
In each of the zoom lenses of Embodiments 1 to 5 and 7, it is more preferred that the first lens unit U1 include, in order from the object side to the image side, a first sub-lens unit U11 having a negative refractive power that does not move for focusing, a second sub-lens unit U12 having a positive refractive power that moves along the optical axis during focusing, and a third sub-lens unit U13 having a positive refractive power that does not move for focusing. It is preferred to satisfy the following conditional expression:

−9.0<f11/f1<−0.9  (15)

where f11 represents a focal length of the first sub-lens unit U11.

The conditional expression (15) defines a ratio of the focal length of the first sub-lens unit U11 to the focal length of the first lens unit U1.
If f11/f1 in the conditional expression (15) exceeds an upper limit, the focal length of the first sub-lens unit U11 becomes relatively short. As a result, it becomes difficult to attain the suppression of the variation of various off-axis aberrations following zooming on the wide angle side, especially, the suppression of the distortion and the field curvature. On the other hand, if f11/f1 in the conditional expression (15) exceeds a lower limit, the focal length of the first sub-lens unit U11 becomes relatively long. As a result, the lens diameter of the first lens unit U1 is increased, and hence it becomes difficult to attain the wide angle. In addition, it becomes difficult to suppress the change in image field during focusing.
It is more preferred to set the numerical value range of the conditional expression (15) as follows.

−1.45<f11/f1<−0.95  (15a)

It is more preferred that the zoom lens of each of Embodiments 1 to 5 and 7 satisfy the following conditional expression:

−1.5<f13/f11<−0.5  (16)

where f11 represents the focal length of the first sub-lens unit U11, and f13 represents a focal length of the third sub-lens unit U13.

The conditional expression (16) defines a ratio of the focal length of the third sub-lens unit U13 to the focal length of the first sub-lens unit U11.
If f13/f11 in the conditional expression (16) exceeds an upper limit, the focal length of the first sub-lens unit U11 becomes relatively long. As a result, it becomes difficult to make the principal point of the first lens unit U1 approach the image side, and hence the lens diameter of the first lens unit U1 becomes large, and it becomes difficult to attain the wide angle. On the other hand, if f13/f11 in the conditional expression (16) exceeds a lower limit, the focal length of the first sub-lens unit U11 becomes relatively short, which leads to an increase in the number of lenses of the first sub-lens unit U11. As a result, the lens diameter of the first lens unit U1 becomes large, and it becomes difficult to attain the wide angle.
It is more preferred to set the numerical value range of the conditional expression (13) as follows.

−1.35<f13/f11<−0.80  (16a)

In addition, it is preferred that the zoom lens of each of the embodiments satisfy the following conditional expression.

1.5<f1/fw<9.0  (17)

The conditional expression (17) defines a ratio of the focal length of the first lens unit U1 to the focal length at the wide angle end. In the zoom lens of each of the embodiments, the focal length of the first lens unit U1 is the important factor for achieving both the high optical performance and the reduction in size. By satisfying the conditional expression (17), the height of the off-axis ray that passes through the first lens unit U1 can be defined at the wide angle end and the various aberrations can be satisfactorily corrected while the increase in size of the lens is suppressed.
If f1/fw in the conditional expression (17) exceeds an upper limit, the refractive power of the first lens unit U1 is reduced. As a result, the height of the off-axis ray that passes through the first lens unit U1 is increased, to thereby increase the size of the lens. On the other hand, if f1/fw in the conditional expression (17) exceeds a lower limit, the refractive power of the first lens unit U1 is increased. In particular, it becomes difficult to correct the chromatic aberration and the various aberrations at the telephoto end.
It is more preferred to set the numerical value range of the conditional expression (17) as follows.

2.00<f1/fw<3.30  (17a)

In addition, it is more preferred that the zoom lens of each of the embodiments satisfy the following conditional expression:

−2.7<βnw<−1.0  (18)

where βnw represents the lateral magnification at the wide angle end of the N-th lens unit UN when the axial ray enters from infinity in a state of focusing on infinity.

The conditional expression (18) defines the lateral magnification of the N-th lens unit UN. In the zoom lens of each of the embodiments, in order to suppress the influence of the increase in size and the manufacturing error of the lens on the optical performance, the lateral magnification of the N-th lens unit UN is appropriately set. By satisfying the conditional expression (18), the zoom lens that is superior in the manufacturability can be obtained while the increase in size of the lens is suppressed.
If βnw in the conditional expression (18) exceeds an upper limit, this leads to the increase in size of the lenses arranged before the N-th lens unit UN, and especially, the effective diameter of the first lens unit U1 is increased. On the other hand, if βnw in the conditional expression (18) exceeds a lower limit, the enlargement ratios of the lenses arranged before the N-th lens unit UN are increased, and hence it becomes difficult to correct various aberrations, especially, the chromatic aberration on the telephoto side. In addition, the performance reduction due to manufacturing fluctuations becomes larger because a manufacturing error greatly affects the performance.
It is more preferred to set the numerical value range of the conditional expression (18) as follows.

−2.40<βnw<−1.50  (18a)

Next, features of a lens configuration of each embodiment are described.
In Embodiment 1, the first lens unit U1 corresponds to a first lens surface to a twenty-first lens surface. The second lens unit U2 corresponds to a twenty-second lens surface to a thirty-first lens surface. The third lens unit U3 corresponds to a thirty-second lens surface to a thirty-fourth lens surface. The fourth lens unit U4 corresponds to a thirty-sixth lens surface to a fifty-third lens surface.
During the zooming from the wide angle end to the telephoto end, when the second lens unit U2 linearly moves to the image side, the third lens unit U3 substantially reciprocates while drawing a convex locus on the object side.
As shown in Table 1 below, Numerical Embodiment 1 satisfies any of the conditional expressions (1) to (4) and (15) to (18). In addition, as shown in the numerical value data of Numerical Embodiments, Numerical Embodiment 1 also satisfies the conditional expressions (5) and (6). In addition, the third and fifth lenses counted from the object side to the image side of the second lens unit U2 are positive lenses each satisfying the conditional expression (7). With this configuration, the wide angle of field of photography (angle of field) of 81.65° at the wide angle end is attained at the high zoom ratio of 10.00. Moreover, the high optical performance with which the various aberrations are satisfactorily corrected in the entire zoom range is obtained.
In Embodiment 2, the first lens unit U1 corresponds to a first lens surface to an eighteenth lens surface. The second lens unit U2 corresponds to a nineteenth lens surface to a twenty-fifth lens surface. The third lens unit U3 corresponds to a twenty-sixth lens surface to a twenty-eighth lens surface. The fourth lens unit U4 corresponds to a thirtieth lens surface to a forty-eighth lens surface.
During the zooming from the wide angle end to the telephoto end, when the second lens unit U2 linearly moves to the image side, the third lens unit U3 substantially reciprocates while drawing a convex locus on the object side.
As shown in Table 1 below, Numerical Embodiment 2 satisfies any of the conditional expressions (1) to (4) and (15) to (18). In addition, as shown in the numerical value data of Numerical Embodiments, Numerical Embodiment 2 also satisfies the conditional expressions (5) and (6). In addition, the third lens counted from the object side to the image side of the second lens unit U2 is a positive lens satisfying the conditional expression (7). With this configuration, the wide angle of field of photography (angle of field) of 92.06° at the wide angle end is attained at the high zoom ratio of 5.00. Moreover, the high optical performance with which the various aberrations are satisfactorily corrected in the entire zoom range is obtained.
In Embodiment 3, the first lens unit U1 corresponds to a first lens surface to an eighteenth lens surface. The second lens unit U2 corresponds to a nineteenth lens surface to a twenty-seventh lens surface. The third lens unit U3 corresponds to a twenty-eighth lens surface to a thirtieth lens surface. The fourth lens unit U4 corresponds to a thirty-second lens surface to a fifty-first lens surface.
During the zooming from the wide angle end to the telephoto end, when the second lens unit U2 linearly moves to the image side, the third lens unit U3 substantially reciprocates while drawing a convex locus on the object side.
As shown in Table 1 below, Numerical Embodiment 3 satisfies any of the conditional expressions (1) to (4) and (15) to (18). In addition, as shown in the numerical value data of Numerical Embodiments, Numerical Embodiment 3 also satisfies the conditional expressions (5) and (6). In addition, the second and fifth lenses counted from the object side to the image side of the second lens unit U2 are positive lenses each satisfying the conditional expression (7). With this configuration, the wide angle of field of photography (angle of field) of 75.73° at the wide angle end is attained at the high zoom ratio of 8.00. Moreover, the high optical performance with which the various aberrations are satisfactorily corrected in the entire zoom range is obtained.
In Embodiment 4, the first lens unit U1 corresponds to a first lens surface to a fifteenth lens surface. The second lens unit U2 corresponds to a sixteenth lens surface to a twenty-third lens surface. The third lens unit U3 corresponds to a twenty-fourth lens surface to a twenty-sixth lens surface. The fourth lens unit U4 corresponds to a twenty-eighth lens surface to a forty-fifth lens surface.
During the zooming from the wide angle end to the telephoto end, when the second lens unit U2 linearly moves to the image side, the third lens unit U3 substantially reciprocates while drawing a convex locus on the object side.
As shown in Table 1 below, Numerical Embodiment 4 satisfies any of the conditional expressions (1) to (4) and (15) to (18). In addition, as shown in the numerical value data of Numerical Embodiments, Numerical Embodiment 4 also satisfies the conditional expressions (5) and (6). In addition, the third lens counted from the object side to the image side of the second lens unit U2 is a positive lens satisfying the conditional expression (7). With this configuration, the wide angle of field of photography (angle of field) of 78.60° at the wide angle end is attained at the high zoom ratio of 5.00. Moreover, the high optical performance with which the various aberrations are satisfactorily corrected in the entire zoom range is obtained.
In Embodiment 5, the first lens unit U1 corresponds to a first lens surface to a nineteenth lens surface. The second lens unit U2 corresponds to a twentieth lens surface to a twenty-seventh lens surface. The third lens unit U3 corresponds to a twenty-eighth lens surface to a thirtieth lens surface. The fourth lens unit U4 corresponds to a thirty-second lens surface to a forty-eighth lens surface.
During the zooming from the wide angle end to the telephoto end, when the second lens unit U2 linearly moves to the image side, the third lens unit U3 substantially reciprocates while drawing a convex locus on the object side.
As shown in Table 1 below, Numerical Embodiment 5 satisfies any of the conditional expressions (1) to (4) and (15) to (18). In addition, as shown in the numerical value data of Numerical Embodiments, Numerical Embodiment 5 also satisfies the conditional expressions (5) and (6). In addition, the third lens counted from the object side to the image side of the second lens unit U2 is a positive lens satisfying the conditional expression (7). With this configuration, the wide angle of field of photography (angle of field) of 96.01° at the wide angle end is attained at the high zoom ratio of 4.00. Moreover, the high optical performance with which the various aberrations are satisfactorily corrected in the entire zoom range is obtained.
In Embodiment 6, the first lens unit U1 corresponds to a first lens surface to an eleventh lens surface. The second lens unit U2 corresponds to a twelfth lens surface to a twentieth lens surface. The third lens unit U3 corresponds to a twenty-first lens surface to a twenty-third lens surface. The fourth lens unit U4 corresponds to a twenty-fifth lens surface to a forty-first lens surface. The forty-second lens surface to the forty-fourth lens surface correspond to the glass block that imitates the optical filter or the color separation optical system of the camera.
During the zooming from the wide angle end to the telephoto end, when the second lens unit U2 linearly moves to the image side, the third lens unit U3 substantially reciprocates while drawing a convex locus on the object side.
As shown in Table 1 below, Numerical Embodiment 6 satisfies any of the conditional expressions (1) to (4), (15), (17), and (18). In addition, as shown in the numerical value data of Numerical Embodiments, Numerical Embodiment 6 also satisfies the conditional expressions (5) and (6). In addition, the fourth lens counted from the object side to the image side of the second lens unit U2 is a positive lens satisfying the conditional expression (7). With this configuration, the wide angle of field of photography (angle of field) of 69.02° at the wide angle end is attained at the high zoom ratio of 15.00. Moreover, the high optical performance with which the various aberrations are satisfactorily corrected in the entire zoom range is obtained.
In Embodiment 7, the first lens unit U1 corresponds to a first lens surface to a twenty-first lens surface. The second lens unit U2 corresponds to a twenty-second lens surface to a twenty-sixth lens surface. The third lens unit U3 corresponds to a twenty-seventh lens surface to a thirtieth lens surface. The fourth lens unit U4 corresponds to a thirty-first lens surface to a thirty-third lens surface. The fifth lens unit U5 corresponds to a thirty-fifth lens surface to a fifty-second lens surface.
During the zooming from the wide angle end to the telephoto end, when the second lens unit U2 linearly moves to the image side, the third lens unit U3 also moves substantially linearly to the image side. The second lens unit U2 and the third lens unit U3 move in such a direction that an interval between the second lens unit U2 and the third lens unit U3 increases during the zooming from the wide angle end to the telephoto end. In addition, the fourth lens unit U4 substantially reciprocates while drawing a convex locus on the object side.
As shown in Table 1 below, Numerical Embodiment 7 satisfies any of the conditional expressions (1) to (4) and (7) to (18). In addition, as shown in the numerical value data of Numerical Embodiments, Numerical Embodiment 7 also satisfies the conditional expressions (5), (6), (12), and (13). In addition, the second lens counted from the object side to the image side of the second lens unit U2 is a positive lens satisfying the conditional expressions (7) and (14). Further, the second lens counted from the object side to the image side of the third lens unit U3 is a positive lens satisfying the conditional expression (14). With this configuration, the wide angle of field of photography (angle of field) of 80.10° at the wide angle end is attained at the high zoom ratio of 6.50. Moreover, the high optical performance with which the various aberrations are satisfactorily corrected in the entire zoom range is obtained.
As described above, according to each embodiment, the refractive power arrangement of each lens unit, the movement locus of the moving lens unit for zooming, and the like are appropriately defined. Thus, it is possible to obtain the zoom lens having a higher zoom ratio and a wider angle of field, in which various aberrations are appropriately corrected.
FIG. 18 is a schematic diagram of a main part of an image pickup apparatus (TV camera system) employing the zoom lens of Embodiments 1 to 7 as an imaging optical system. FIG. 18 illustrates a zoom lens 101 according to any one of Embodiments 1 to 7 and a camera 124. The zoom lens 101 can be mounted into and removed from the camera 124. The zoom lens 101 is mounted into the camera 124 to form an image pickup apparatus 125. The zoom lens 101 includes a first lens unit F, a zoom section LZ, and an N-th lens unit R for image formation. The first lens unit F includes a focusing lens unit U12 that moves on the optical axis for focusing, and fixed lens units U11 and U13 that do not move during focusing.
The zoom section LZ includes the second and third lens units U2 and U3 that move on the optical axis for zooming according to Numerical Embodiments 1 to 6, and the second to fourth lens units U2 to U4 that move on the optical axis for zooming according to Numerical Embodiment 7. The zoom lens 101 also includes an aperture stop SP, and driving mechanisms 114 and 115, such as helicoids and cams, for driving the second sub-lens unit U12 and the zoom section LZ in the optical axis direction, respectively.
The image pickup apparatus 125 includes motors (driving units) 116 to 118 for electrically driving the driving mechanisms 114 and 115 and the aperture stop SP. The image pickup apparatus 125 also includes detectors 119 to 121, such as an encoder, a potentiometer, or a photo-sensor, which are configured to detect the positions of the second sub-lens unit U12 and the zoom section LZ on the optical axis, and the aperture diameter of the aperture stop SP. In addition, the camera 124 includes a glass block 109, which corresponds to an optical filter inside the camera 124. Further, the camera 124 includes a solid-state image pickup element (photoelectric conversion element) 110, such as a charge-coupled device (CCD) sensor or a complementary metal-oxide semiconductor (CMOS) sensor. The solid-state image pickup element 110 is configured to receive a subject image formed by the zoom lens 101.
Further, central processing units (CPUs) 111 and 122 control various types of driving of the camera 124 and the zoom lens 101, respectively. Through application of the zoom lens according to the present invention to a TV camera as described above, an image pickup apparatus having high optical performance is implemented.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
Now, Numerical Embodiments 1 to 7, corresponding to Embodiments 1 to 7 of the present invention, are described. In each of Numerical Embodiments, symbol i represents an order of a surface from the object side, symbol ri represents a curvature radius of an i-th surface from the object side, symbol di represents an interval between the i-th surface and the (i+1)th surface from the object side, and symbols ndi and νdi respectively represent a refractive index and an Abbe number of the i-th optical member. An aspherical surface is represented by “*” next to the surface number. Table 1 shows correspondences between each embodiment and the conditional expressions described above.
The aspherical shape is expressed by the following expression:




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        H
        16
      
    
  




where an X axis corresponds to the optical axis, an H axis corresponds to an axis perpendicular to the optical axis, a traveling direction of light corresponds to a positive direction, R represents a paraxial curvature radius, k represents a conic constant, A4, A6, A8, A10, A12, A14, and A16 each represent an aspherical coefficient, and “e-Z” means “×10−z”.

In each of Embodiments 1 to 6, two lens units move during the zooming, and hence when the movement locus of one lens unit is determined, the movement locus of the other lens unit is also determined. However, in Embodiment 7, three lens units move during the zooming, and hence even when the movement locus of one lens unit is determined, the movement loci of the other two lens units cannot be determined. Therefore, Embodiment 7 shows the movement loci of the second lens unit and the third lens unit.
The movement locus is expressed by the following expression:

fj(y)=Bj1y+Bj2y2+Bj3y3+Bj4y4+Bj5y5+Bj6y6 

where j represents a number of a lens unit, fj(y) represents a movement amount in the optical axis direction, a traveling direction of light corresponds to a positive direction, y represents the amount of movement from the wide angle end to the telephoto end as 1, and Bj1, Bj2, Bj3, Bj4, Bj5, and Bj6 each represent a movement coefficient.

Numerical Embodiment 1










Unit: mm







Surface data














Surface





Effective
Focal


number
r
d
nd
vd
θgF
diameter
length





 1*
107.07477
3.50000
1.772499
49.60
0.5521
94.999
−94.002


 2
42.77453
29.44657



74.747


 3
−111.18408
2.00000
1.772499
49.60
0.5521
74.020
−86.187


 4
169.27879
0.19853



73.831


 5
111.15261
6.53424
1.959060
17.47
0.6599
74.684
162.844


 6
362.57244
4.83576



74.310


 7*
402.11683
9.52789
1.620411
60.29
0.5426
73.646
143.795


 8
−114.18218
7.22051



73.330


 9
273.53589
11.14023
1.496999
81.54
0.5374
67.740
131.565


10
−85.09102
1.32713



67.551


11
−74.32274
2.00000
1.805181
25.42
0.6161
67.398
−164.470


12
−169.44313
1.00002



68.351


13
2516.57481
1.80000
1.850259
32.27
0.5929
68.012
−98.133


14
81.30733
11.18444
1.438750
94.93
0.5343
67.555
149.790


15
−332.76941
0.20010



67.981


16
7491.62170
5.08975
1.496999
81.54
0.5374
68.578
390.027


17
−199.54524
0.20000



69.118


18
1595.58460
5.39098
1.595220
67.74
0.5442
69.947
305.715


19
−205.94799
0.20000



70.201


20
216.17076
10.28079
1.730000
49.00
0.5575
70.182
104.355


21
−116.13168
(Variable)



69.897


 22*
50.60782
1.00000
1.882997
40.76
0.5667
31.807
−41.311


23
21.07209
6.61768



27.724


24
−79.54129
1.00000
1.754998
52.32
0.5476
27.582
−47.508


25
66.22881
0.99806



26.863


26
48.90892
4.02300
1.882210
23.78
0.6036
26.802
40.333


27
−130.21404
1.94929



26.376


28
−37.12529
1.00000
1.618000
63.33
0.5441
26.194
−55.128


29
438.13751
0.20000



25.725


30
34.72260
1.88615
1.613397
44.30
0.5633
25.302
287.073


31
42.29949
(Variable)



24.759


32
−46.20252
1.00000
1.696797
55.53
0.5433
22.167
−45.199


33
101.17257
2.21450
1.808095
22.76
0.6307
23.128
112.579


34
−994.45522
(Variable)



23.547


35
∞
1.29695



28.883


(Aperture


stop)


36
143.50842
4.48049
1.816000
46.62
0.5568
29.930
47.136


37
−52.16988
0.20000



30.182


38
52.13637
6.23615
1.487490
70.23
0.5300
29.349
48.593


39
−41.96851
1.20000
2.000690
25.46
0.6133
28.856
−39.407


40
781.32347
0.19891



28.725


41
22.82507
9.56381
1.516330
64.14
0.5352
28.572
29.895


42
−41.33452
1.00000
1.834000
37.16
0.5775
27.399
−26.832


43
50.02430
6.99907



25.923


44
386.69864
3.99920
1.487490
70.23
0.5300
25.416
67.610


45
−36.04126
1.08491



25.291


46
34.86509
4.96949
1.922860
20.88
0.6282
22.498
20.574


47
−39.79509
0.90000
1.882997
40.76
0.5667
21.517
−18.496


48
28.27246
8.88270



18.955


49
37.01797
4.62848
1.438750
94.93
0.5343
16.005
25.301


50
−15.30482
1.00000
1.953750
32.32
0.5898
15.736
−12.619


51
60.19086
2.75426



16.455


52
45.70173
3.00473
1.620411
60.29
0.5426
18.630
48.353


53
−86.09140
50.07000



18.983


Image
∞


surface










Aspherical surface data





First surface










K = 1.92497e+000
A4 = 1.92902e−009
A6 = 6.26259e−011
A8 = −9.53828e−014


A10 = 6.21216e−017
A12 = −2.17747e−020
A14 = 3.29927e−024
A16 = −2.10130e−028







Seventh surface










K = −2.29488e+001
A4 = −4.72874e−007
A6 = 4.95024e−011
A8 = 4.20753e−014


A10 = −7.75550e−017
A12 = 9.10273e−020
A14 = −5.11370e−023
A16 = 1.17437e−026







Twenty-second surface










K = 5.48442e−001
A4 = 1.59884e−007
A6 = −3.77659e−009
A8 = 1.79255e−011


A10 = −4.48568e−014
A12 = −3.70888e−016
A14 = 2.09083e−018
A16 = −2.91328e−021










Various data


Zoom ratio 10.00













Wide






angle
Intermediate
Telephoto







Focal length
18.00
63.00
180.00



F number
4.00
4.00
4.95



Half angular field
40.82
13.86
4.94



of view



Image height
15.55
15.55
15.55



Total lens length
320.10
320.10
320.10



BF
50.07
50.07
50.07



d21
0.70
45.74
65.06



d31
60.47
8.62
6.48



d34
11.50
18.30
1.12



Entrance pupil position
57.50
105.61
175.05



Exit pupil position
−33.80
−33.80
−33.80



Front principal point
71.63
121.28
−31.27



position



Rear principal point
32.07
−12.93
−129.93



position











Zoom lens unit data


















Front
Rear






Lens
principal
principal




Leading
Focal
structure
point
point



Unit
surface
length
length
position
position







1
1
57.00
113.08
71.51
43.38



2
22
−26.70
18.67
3.98
−9.70



3
32
−76.10
3.21
−0.16
−1.98



4
35
31.05
62.40
−11.09
−41.97










Numerical Embodiment 2












Unit: mm





Surface data














Surface





Effective
Focal


number
r
d
nd
vd
θgF
diameter
length





 1*
86.96069
2.80000
1.772499
49.60
0.5521
99.506
−85.846


 2
37.19554
28.65314



72.568


 3
287.18991
2.20000
1.772499
49.60
0.5521
71.378
−151.018


 4
82.96532
9.79457



68.012


 5
233.30951
2.20000
1.772499
49.60
0.5521
67.303
−81.001


 6
49.32285
9.90654
1.922860
18.90
0.6495
64.827
83.114


 7
122.07948
4.11145



64.165


 8
174.57379
7.40358
1.496999
81.54
0.5374
63.832
170.294


 9*
−162.88781
10.55549



63.329


10
219.22560
11.10101
1.618000
63.33
0.5441
61.797
87.081


11
−70.29224
0.51997



61.501


12
−90.66362
2.00000
1.805181
25.42
0.6161
58.344
−51.316


13
77.98219
9.18481
1.496999
81.54
0.5374
56.765
117.857


14
−228.82556
0.21692



57.161


15
229.51464
10.00000
1.595220
67.74
0.5442
57.792
89.884


16
−68.94195
0.20000



57.805


17
57.54531
5.56934
1.730000
49.00
0.5575
50.901
114.868


18
174.06610
(Variable)



50.045


 19*
222.99988
1.30000
1.772499
49.60
0.5521
29.397
−31.652


20
22.07423
8.73811



24.622


21
−46.00024
0.90000
1.772499
49.60
0.5521
21.288
−21.359


22
26.14240
4.04203
1.846660
23.78
0.6034
21.985
24.438


23
−96.70044
2.91044



22.088


24
−20.39226
0.90000
1.800999
34.97
0.5863
22.088
−89.160


25
−29.02640
(Variable)



23.053


26
−33.53567
0.90000
1.729157
54.68
0.5444
23.727
−29.601


27
62.00299
2.73134
1.846660
23.78
0.6205
25.908
73.336


28
5426.95120
(Variable)



26.494


29
∞
1.04258



27.557


(Aperture


stop)


30
144.60763
5.80564
1.834807
42.71
0.5642
29.049
38.100


31
−40.31316
0.20000



29.778


32
140.01330
2.90947
1.570989
50.80
0.5588
29.573
116.796


33
−127.51474
0.20000



29.431


34
62.82013
7.44444
1.496999
81.54
0.5374
28.583
43.611


35
−31.93064
1.20000
2.000690
25.46
0.6133
27.614
−30.706


36
1097.65571
0.20000



27.561


37
27.33320
3.43062
1.531717
48.84
0.5630
27.568
130.948


38
42.89669
17.98679



26.842


39
−77.25420
4.44564
1.487490
70.23
0.5300
23.060
306.323


40
−51.93660
20.78154



22.786


41
72.70188
7.72582
1.487490
70.23
0.5300
25.172
30.867


42
−18.39119
0.85000
1.953750
32.32
0.5898
25.094
−21.994


43
−145.10189
2.61020



27.091


44
837.85153
6.19253
2.102050
16.77
0.6721
29.071
32.378


45
−37.66305
0.85000
2.000690
25.46
0.6133
29.817
−29.178


46
136.96902
0.19086



30.863


47
42.04543
7.61002
1.487490
70.23
0.5300
32.756
52.334


48
−61.55333
33.54000



33.050


Image
∞


surface










Aspherical surface data





First surface










K = 1.16599e+000
A4 = 2.14949e−007
A6 = −3.88534e−011
A8 = 1.50332e−014







Ninth surface










K = −9.49193e+000
A4 = 5.68085e−007
A6 = 2.51185e−010
A8 = 5.19688e−014







Nineteenth surface










K = −4.37435e+002
A4 = 1.00143e−005
A6 = −1.61464e−008
A8 = 2.99969e−011










Various data


Zoom ratio 5.00













Wide






angle
Intermediate
Telephoto







Focal length
15.00
35.00
75.00



F number
3.00
3.00
3.00



Half angular field of
46.03
23.96
11.71



view



Image height
15.55
15.55
15.55



Total lens length
300.20
300.20
300.20



BF
33.54
33.54
33.54



d18
0.99
21.34
32.89



d25
32.46
9.59
1.98



d28
2.70
5.23
1.28



Entrance pupil position
50.74
66.16
86.04



Exit pupil position
−158.40
−158.40
−158.40



Front principal point
64.57
94.78
131.73



position



Rear principal point
18.54
−1.46
−41.46



position











Zoom lens unit data


















Front
Rear






Lens
principal
principal




Leading
Focal
structure
point
point



Unit
surface
length
length
position
position







1
1
32.00
116.42
59.75
30.90



2
19
−18.80
18.79
3.92
−10.58



3
26
−50.00
3.63
−0.04
−2.03



4
29
40.41
91.68
23.49
−102.31










Numerical Embodiment 3










Unit: mm







Surface data














Surface





Effective
Focal


number
r
d
nd
vd
θgF
diameter
length





 1
1464.37780
3.20000
1.772499
49.60
0.5521
96.525
−86.352


 2
64.03231
23.73215



82.301


 3
−120.19877
2.70000
1.772499
49.60
0.5521
81.903
−157.539


 4
−7122.29818
0.19535



83.622


 5
135.38385
5.79104
1.922860
20.88
0.6282
85.855
267.092


 6
290.21299
1.99903



85.522


 7
251.24989
14.76690
1.620411
60.29
0.5426
85.401
125.798


 8*
−111.29663
0.19558



84.900


 9
15648.74980
11.63370
1.496999
81.54
0.5374
79.023
170.753


10
−85.55687
2.50000
1.800000
29.84
0.6017
78.575
−158.224


11
−263.13162
7.30434



78.571


12
122.72575
2.50000
1.737999
32.26
0.5899
76.826
−152.090


13
58.33771
17.98321
1.496999
81.54
0.5374
74.254
99.970


14
−306.67066
0.20000



74.127


15
103.17491
9.28268
1.537150
74.81
0.5390
72.301
169.230


16
−760.39964
0.20000



71.562


17
86.72637
6.50027
1.790000
45.50
0.5720
66.388
174.512


18
224.07742
(Variable)



64.720


19*
74.69742
1.20000
1.882997
40.76
0.5667
31.251
−28.364


20
18.69569
4.61081



25.802


21
111.19420
6.40794
1.846660
23.78
0.6034
25.666
21.564


22
−21.51662
0.70000
1.882997
40.76
0.5667
24.826
−21.788


23
195.15304
3.40085



22.613


24
−23.61290
0.70000
1.531717
48.84
0.5630
22.613
−35.863


25
102.69381
0.16000



24.460


26
51.03251
3.67799
1.613397
44.30
0.5633
25.331
56.753


27
−108.33345
(Variable)



25.686


28
−33.59267
0.90000
1.651597
58.55
0.5426
26.194
−41.043


29
135.24634
2.33683
1.808095
22.76
0.6307
28.358
123.681


30
−395.42324
(Variable)



28.934


31
∞
1.29353



35.132


(Aperture


stop)


32
1023.63042
4.51438
1.754998
52.32
0.5476
36.234
72.802


33
−58.25333
0.20000



36.777


34
68.98860
5.01187
1.618000
63.33
0.5441
37.923
83.414


35
−201.24720
0.20000



37.777


36
57.87442
5.13367
1.496999
81.54
0.5374
36.631
95.079


37
−253.95832
1.20000
2.001000
29.13
0.5997
36.011
−95.535


38
155.76709
0.19935



35.264


39
43.83937
10.52855
1.516330
64.14
0.5352
34.451
47.261


40
−50.95133
1.10000
1.772499
49.60
0.5521
32.346
−41.715


41
89.67330
22.97015



30.835


42
50.15394
4.85521
1.487490
70.23
0.5300
24.993
49.076


43
−44.57995
0.24116



24.899


44
28.14197
5.77865
1.487490
70.23
0.5300
23.118
33.581


45
−36.79546
1.00000
2.000690
25.46
0.6133
22.243
−15.155


46
26.56639
2.41025



21.159


47
180.15182
7.09223
1.808095
22.76
0.6307
21.404
18.393


48
−16.09271
1.00000
1.882997
40.76
0.5667
21.883
−16.763


49
204.71944
6.09212



23.295


50
34.10624
4.80075
1.487490
70.23
0.5300
28.643
66.313


51
−632.14267
37.88000



28.727


Image
∞


surface










Aspherical surface data





Eighth surface










K = 7.64826e−001
A4 = 2.02728e−007
A6 = 5.93168e−011
A8 = −1.76160e−013


A10 = 2.73743e−016
A12 = −2.26960e−019
A14 = 9.46924e−023
A16 = −1.56898e−026







Nineteenth surface










K = 1.02944e+000
A4 = 4.84636e−006
A6 = −9.64701e−009
A8 = 5.80327e−011


A10 = −3.77375e−013
A12 = 1.18904e−015
A14 = −9.44522e−019
A16 = −1.67064e−021










Various data


Zoom ratio 8.00













Wide angle
Intermediate
Telephoto







Focal length
20.00
60.00
160.00



F number
2.80
2.80
3.60



Half angular
37.87
14.53
5.55



field of view



Image height
15.55
15.55
15.55



Total lens
310.06
310.06
310.06



length



BF
37.88
37.88
37.88



d18
0.69
30.37
44.35



d27
41.68
8.49
6.50



d30
9.40
12.91
0.93



Entrance pupil
60.15
110.86
190.18



position



Exit pupil
−75.15
−75.15
−75.15



position



Front principal
76.61
139.01
123.71



point position



Rear principal
17.88
−22.12
−122.12



point position











Zoom lens unit data


















Front
Rear






Lens
principal
principal




Leading
Focal
structure
point
point



Unit
surface
length
length
position
position







1
1
52.10
110.68
61.22
20.90



2
19
−21.50
20.86
3.10
−11.59



3
28
−62.00
3.24
−0.27
−2.11



4
31
35.32
85.62
5.69
−68.37










Numerical Embodiment 4










Unit: mm







Surface data














Surface





Effective
Focal


number
r
d
nd
vd
θgF
diameter
length





 1
131.14622
3.00000
1.772499
49.60
0.5521
90.070
−91.906


 2
45.74280
23.07058



73.485


 3
−190.51759
2.50000
1.754998
52.32
0.5476
73.046
−92.545


 4
111.76131
2.70555



72.305


 5
102.35624
6.78100
1.922860
20.88
0.6282
73.869
158.066


 6
323.65984
2.07854



73.551


 7*
198.12409
7.52728
1.620411
60.29
0.5426
73.308
200.459


 8
−332.71985
10.42728



72.900


 9
105.74456
10.78155
1.595220
67.74
0.5442
72.731
130.062


10
−281.63972
0.20000



72.228


11
125.39952
2.00000
1.882210
23.78
0.6036
68.470
−90.324


12
48.64939
16.97372
1.438750
94.93
0.5343
64.323
93.643


13
−239.97566
0.20000



64.141


14
84.45216
10.77658
1.772499
49.60
0.5521
62.316
78.504


15
−206.62606
(Variable)



61.136


16*
48.27098
1.20000
2.001000
29.13
0.5997
30.013
−27.936


17
17.57501
7.48668



24.778


18
−36.17012
0.80000
1.816000
46.62
0.5568
24.550
−28.913


19
69.54013
0.49278



24.066


20
43.80124
4.88511
2.000690
25.46
0.6133
24.142
21.424


21
−40.36572
1.36383



23.790


22
−25.24489
0.90000
1.834807
42.71
0.5642
23.574
−52.907


23
−59.44507
(Variable)



24.246


24
−27.96339
0.80000
1.639999
60.08
0.5370
24.628
−34.341


25
105.79038
2.64502
1.808095
22.76
0.6307
26.665
93.540


26
−271.51570
(Variable)



27.221


27
∞
1.47466



28.069


(Aperture


stop)


28
−9897.87302
3.30206
1.772499
49.60
0.5521
28.982
78.066


29
−60.23523
0.20000



29.488


30
192.97751
3.93909
1.589130
61.14
0.5406
30.056
79.968


31
−62.17424
0.20000



30.172


32
69.45008
5.69407
1.516330
64.14
0.5352
29.533
52.091


33
−42.92720
1.20000
2.000690
25.46
0.6133
29.123
−41.036


34
1216.75385
0.19979



29.063


35
25.32639
3.68828
1.516330
64.14
0.5352
29.028
132.828


36
38.07596
18.18838



28.193


37
63.74293
0.90000
1.953750
32.32
0.5898
23.376
−27.840


38
18.71075
5.95175
1.808095
22.76
0.6307
22.225
18.964


39
−76.92161
1.38274



21.851


40
76.61712
4.87566
1.438750
94.93
0.5343
21.406
42.347


41
−24.13109
1.00000
1.805181
25.42
0.6161
21.080
−17.668


42
36.10887
11.09401



21.337


43
41.85392
7.51316
1.595220
67.74
0.5442
29.338
35.307


44
−39.65572
1.20000
1.882997
40.76
0.5667
29.517
−92.149


45
−78.02765
39.99000



30.027


Image
∞


surface










Aspherical surface data





Seventh surface










K = −1.73761e+001
A4 = −3.20828e−007
A6 = 3.77274e−011
A8 = −1.60630e−014


A10 = −4.63233e−017
A12 = 1.16115e−019
A14 = −8.89475e−023
A16 = 2.36508e−026







Sixteenth surface










K = −9.35949e+000
A4 = 1.47026e−005
A6 = −1.49210e−008
A8 = 2.40783e−011


A10 = −3.38433e−014
A12 = 1.88004e−015
A14 = −1.26872e−017
A16 = 2.79931e−020










Various data


Zoom ratio 5.00













Wide angle
Intermediate
Telephoto







Focal length
19.00
45.00
95.00



F number
2.70
2.70
2.70



Half angular
39.30
19.06
9.30



field of view



Image height
15.55
15.55
15.55



Total lens
271.52
271.52
271.52



length



BF
39.99
39.99
39.99



d15
0.70
22.76
34.43



d23
29.03
6.96
4.48



d26
10.20
10.21
1.02



Entrance pupil
56.43
86.13
122.86



position



Exit pupil
−101.34
−101.34
−101.34



position



Front principal
72.88
116.80
154.00



point position



Rear principal
20.99
−5.01
−55.01



point position











Zoom lens unit data


















Front
Rear






Lens
principal
principal




Leading
Focal
structure
point
point



Unit
surface
length
length
position
position







1
1
45.00
99.02
57.71
19.90



2
16
−24.80
17.13
1.21
−12.13



3
24
−55.00
3.45
−0.37
−2.32



4
27
39.90
72.00
19.18
−64.39










Numerical Embodiment 5










Unit: mm







Surface data














Surface





Effective
Focal


number
r
d
nd
vd
θgF
diameter
length





 1*
81.52156
2.80000
1.772499
49.60
0.5521
97.279
−83.251


 2
35.50574
31.30681



70.026


 3
667.71915
2.20000
1.772499
49.60
0.5521
68.022
−135.261


 4
90.59457
4.47839



64.610


 5
197.06072
2.20000
1.834807
42.71
0.5642
64.321
−66.614


 6
43.33682
11.33919
1.922860
18.90
0.6495
60.874
69.654


 7
113.32971
2.55719



59.842


 8
115.11681
9.51685
1.496999
81.54
0.5374
59.385
153.156


 9*
−220.41107
0.20000



58.068


10
185.45912
9.63439
1.618000
63.33
0.5441
57.517
91.373


11
−80.00592
2.00000
1.846660
23.78
0.6205
57.026
−103.318


12
−857.68120
5.60166



56.350


13
−547.42488
2.00000
1.846660
23.78
0.6205
55.107
−95.810


14
96.50030
8.54469
1.496999
81.54
0.5374
56.048
126.294


15
−175.74550
0.20000



56.723


16
248.42762
12.85098
1.595220
67.74
0.5442
58.081
80.834


17
−58.77230
0.20000



58.452


18
56.55329
6.43207
1.763850
48.51
0.5587
50.476
91.827


19
271.97337
(Variable)



49.270


20*
75.52289
1.30000
1.816000
46.62
0.5568
27.970
−25.770


21
16.38581
7.94998



22.551


22
−35.35061
0.90000
1.754998
52.32
0.5476
20.890
−28.150


23
54.49701
0.20000



20.318


24
38.34698
4.04203
1.846660
23.78
0.6034
20.314
27.246


25
−56.47379
2.18661



19.859


26
−20.15327
0.90000
1.882997
40.76
0.5667
19.635
−76.243


27
−29.29552
(Variable)



20.447


28
−28.24173
0.90000
1.729157
54.68
0.5444
21.748
−31.883


29
136.58830
2.26264
1.846660
23.78
0.6205
23.610
90.643


30
−177.80079
(Variable)



24.238


31
∞
1.80831



26.366


(Aperture


stop)


32
1876.46717
5.41221
1.816000
46.62
0.5568
27.823
37.988


33
−31.64154
0.20000



28.604


34
60.10061
8.24256
1.496999
81.54
0.5374
28.186
38.709


35
−27.12183
1.20000
2.001000
29.13
0.5997
27.594
−34.449


36
−126.12274
0.20000



28.202


37
27.44643
3.25073
1.612929
37.00
0.5862
28.528
139.096


38
38.53198
22.34855



27.776


39
−524.12330
5.21590
1.517417
52.43
0.5564
24.011
121.284


40
−56.46271
11.54753



24.632


41
111.79736
8.05123
1.496999
81.54
0.5374
24.704
33.474


42
−19.14232
0.85000
1.953750
32.31
0.5898
24.498
−25.679


43
−87.28015
3.16563



25.890


44
436.69471
5.32440
1.959060
17.47
0.6599
27.387
38.954


45
−41.20307
0.85000
2.001000
29.13
0.5997
27.768
−24.479


46
62.31899
0.38161



28.514


47
43.43683
7.60385
1.496999
81.54
0.5374
29.721
43.773


48
−41.28677
41.02000



30.288


Image
∞


surface










Aspherical surface data





First surface










K = 1.15930e+000
A4 = 3.25637e−007
A6 = −7.92964e−012
A8 = 8.93227e−015







Ninth surface










K = −4.96791e+001
A4 = 8.83515e−007
A6 = 5.16367e−010
A8 = 5.70862e−014







Twentieth surface










K = 8.19089e+000
A4 = 5.61681e−006
A6 = −9.29022e−009
A8 = 2.78530e−011










Various data


Zoom ratio 4.00













Wide angle
Intermediate
Telephoto







Focal length
14.00
28.00
56.00



F number
3.00
3.00
3.00



Half angular
48.00
29.05
15.52



field of view



Image height
15.55
15.55
15.55



Total lens
297.27
297.27
297.27



length



BF
41.02
41.02
41.02



d19
1.00
17.72
28.94



d27
32.19
13.50
4.68



d30
2.70
4.67
2.27



Entrance pupil
48.68
60.09
76.35



position



Exit pupil
−122.20
−122.20
−122.20



position



Front principal
61.48
83.29
113.13



point position



Rear principal
27.02
13.02
−14.98



point position











Zoom lens unit data


















Front
Rear






Lens
principal
principal




Leading
Focal
structure
point
point



Unit
surface
length
length
position
position







1
1
30.00
114.06
57.47
29.47



2
20
−19.00
17.48
2.47
−11.25



3
28
−50.00
3.16
−0.44
−2.20



4
31
37.44
85.65
20.00
−79.28










Numerical Embodiment 6










Unit: mm







Surface data














Surface





Effective
Focal


number
r
d
nd
vd
θgF
diameter
length





 1
−327.39176
2.20000
1.800999
34.97
0.5863
77.240
−159.412


 2
212.30166
6.16736



73.645


 3
13317.83260
2.20000
1.846660
23.78
0.6036
71.962
−133.000


 4
112.75087
10.43625
1.438750
94.93
0.5343
69.683
162.621


 5
−190.12082
0.15000



69.612


 6
202.12097
8.24880
1.433870
95.10
0.5373
69.749
216.786


 7
−174.56398
5.52252



69.593


 8
130.72546
7.75647
1.729157
54.68
0.5444
66.803
122.285


 9
−277.21316
0.15000



66.223


10
51.26048
5.75366
1.816000
46.62
0.5568
55.986
117.969


11
103.50442
(Variable)



54.733


12
40.30167
1.00000
1.882997
40.76
0.5667
27.162
−25.624


13
14.37480
6.64137



21.653


14
−44.26823
4.12247
1.959060
17.47
0.6599
21.201
27.280


15
−17.34279
0.75000
1.882997
40.76
0.5667
20.813
−12.721


16
33.07750
0.30000



19.209


17
23.07848
5.06268
1.613397
44.30
0.5633
19.205
22.525


18
−31.97426
1.00000



18.664


19
−20.45576
0.75000
1.743198
49.34
0.5530
18.441
−37.760


20
−75.66571
(Variable)



18.299


21
−21.28881
0.75000
1.754998
52.32
0.5476
15.961
−16.353


22
30.16460
3.20766
1.846490
23.90
0.6217
17.695
36.371


23
962.85645
(Variable)



18.492


24
∞
1.33800



22.519


(Aperture


stop)


25
−513.75388
4.44000
1.670029
47.23
0.5627
23.522
46.335


26
−29.51785
0.15000



24.469


27
42.71785
3.88000
1.487490
70.23
0.5300
25.553
98.440


28
367.25885
0.15000



25.432


29
76.36769
5.32854
1.501270
56.50
0.5536
25.383
48.322


30
−34.85882
1.20000
1.882997
40.76
0.5667
25.102
−43.864


31
−336.68517
33.00000



25.244


32
79.35416
6.19589
1.487490
70.23
0.5300
25.746
81.814


33
−78.66323
0.15000



25.343


34
−174.28704
1.40000
1.834000
37.16
0.5775
25.117
−20.316


35
18.97040
7.07764
1.516330
64.15
0.5352
24.476
30.582


36
−84.05581
0.86168



24.889


37
38.64148
7.67377
1.517417
52.43
0.5564
25.766
28.911


38
−22.91864
1.40000
1.882997
40.76
0.5667
25.610
−29.857


39
−173.73960
0.15000



26.790


40
119.16208
6.64543
1.517417
52.43
0.5564
27.392
43.094


41
−27.05740
4.70000



27.767


42
0.00000
33.00000
1.608590
46.44
0.5664
40.000


43
0.00000
13.20000
1.516330
64.15
0.5352
40.000


44
0.00000
9.58000



40.000


Image
∞


surface










Various data


Zoom ratio 15.00













Wide angle
Intermediate
Telephoto







Focal length
8.00
32.00
120.00



F number
1.80
1.80
2.35



Half angular
34.51
9.75
2.62



field of view



Image height
5.50
5.50
5.50



Total lens
259.60
259.60
259.60



length



BF
9.58
9.58
9.58



d11
0.70
29.97
42.44



d20
40.32
8.35
2.77



d23
4.88
7.59
0.70



Entrance pupil
47.48
151.46
379.01



position



Exit pupil
109.13
109.13
109.13



position



Front principal
56.13
193.74
643.67



point position



Rear principal
1.58
−22.42
−110.42



point position











Zoom lens unit data


















Front
Rear






Lens
principal
principal




Leading
Focal
structure
point
point



Unit
surface
length
length
position
position







1
1
58.00
48.59
32.53
3.63



2
12
−14.00
19.63
3.63
−9.66



3
21
−30.00
3.96
0.02
−2.14



4
24
86.75
131.94
120.79
−198.70










Numerical Embodiment 7










Unit: mm







Surface data














Surface





Effective
Focal


number
r
d
nd
vd
θgF
diameter
length





 1
194.96209
3.00000
1.772499
49.60
0.5521
88.491
−88.490


 2
50.45050
23.69287



73.351


 3
−101.22704
2.50000
1.772499
49.60
0.5521
72.885
−111.690


 4
610.40944
0.19704



74.054


 5
112.46576
6.06429
1.922860
18.90
0.6495
75.732
194.404


 6
287.65098
4.86350



75.347


 7
−1837.00765
7.27013
1.651597
58.55
0.5426
75.086
230.062


 8
−139.33725
0.20000



74.929


 9
−472.70380
4.65675
1.595220
67.74
0.5442
72.970
424.413


10
−165.62101
8.66201



72.465


11
−192.35145
6.46656
1.537150
74.81
0.5390
66.913
268.083


12
−83.47137
0.99766



66.556


13
−78.26046
2.50000
1.800000
29.84
0.6017
66.067
−270.007


14
−123.92169
0.20000



67.015


15
144.80685
2.00000
1.846660
23.78
0.6034
66.705
−142.303


16
65.69817
13.00429
1.496999
81.54
0.5374
65.115
106.901


17
−263.45069
0.20000



65.049


18
131.23177
9.46925
1.496999
81.54
0.5374
64.015
146.867


19
−161.59164
0.20000



63.356


20
61.37933
6.25108
1.730000
49.00
0.5575
56.603
136.191


21
152.31744
(Variable)



55.097


22*
123.35380
1.20000
1.882997
40.76
0.5667
32.089
−28.857


23
21.12344
6.38054



26.928


24
−167.62168
4.33940
1.846660
23.78
0.6034
26.240
54.777


25
−37.04472
0.80000
1.772499
49.60
0.5521
25.538
−98.748


26
−72.37210
(Variable)



24.901


27
−25.91341
0.80000
1.834807
42.71
0.5642
24.536
−28.139


28
270.81861
0.16000



24.869


29
87.77809
3.31174
1.846660
23.78
0.6034
25.043
51.048


30
−85.31340
(Variable)



25.023


31
−31.89775
0.90000
1.696797
55.53
0.5433
25.027
−34.635


32
102.09398
2.46844
1.808095
22.76
0.6307
27.236
92.767


33
−290.19380
(Variable)



27.788


34
∞
1.28219



32.549


(Aperture


stop)


35
∞
5.00427
1.816000
46.62
0.5568
33.538
57.344


36
−47.02989
0.20000



34.253


37
121.66426
4.00000
1.589130
61.14
0.5406
34.746
118.312


38
−162.68134
0.20000



34.670


39
53.21128
7.67575
1.496999
81.54
0.5374
33.912
52.816


40
−49.60645
1.20000
1.846660
23.78
0.6205
33.197
−43.964


41
156.92657
0.19575



32.533


42
24.49279
7.89416
1.518229
58.90
0.5456
32.141
61.163


43
94.58401
1.10000
1.772499
49.60
0.5521
30.289
−78.875


44
36.97714
21.17659



28.740


45
55.51715
6.46969
1.805181
25.42
0.6161
22.663
21.616


46
−24.35459
0.90000
1.882997
40.76
0.5667
22.365
−19.627


47
62.39214
8.45794



22.051


48
118.59896
6.86089
1.438750
94.93
0.5343
23.601
34.489


49
−17.08788
1.00000
2.003300
28.27
0.5980
23.707
−26.491


50
−48.53765
7.21499



25.917


51
55.89004
6.66022
1.487490
70.23
0.5300
32.106
59.353


52
−58.04968
39.99000



32.395


Image
∞


surface










Aspherical surface data





Twenty-second surface










K = 3.15185e+001
A4 = 3.02637e−006
A6 = −5.86837e−009
A8 = −4.69891e−012










Movement locus data














B21 = 40.35954






B31 = 42.94793
B32 = 3.88703
B33 = −8.43442
B34 = 3.38458
B35 = 0.39726


B36 = 0.38969










Various data


Zoom ratio 6.50













Wide angle
Intermediate
Telephoto







Focal length
18.50
45.00
120.25



F number
2.80
2.80
3.43



Half angular
40.05
19.06
7.37



field of view



Image height
15.55
15.55
15.55



Total lens length
300.07
300.07
300.07



BF
39.99
39.99
39.99



d21
0.68
25.34
41.04



d26
2.39
4.03
4.61



d30
39.84
10.82
3.22



d33
6.92
9.65
0.98



Entrance pupil
54.12
84.17
136.89



position



Exit pupil
−165.72
−165.72
−165.72



position



Front principal
70.96
119.33
186.85



point position



Rear principal
21.49
−5.01
−80.26



point position











Zoom lens unit data


















Front
Rear






Lens
principal
principal




Leading
Focal
structure
point
point



Unit
surface
length
length
position
position







1
1
46.00
102.40
59.41
25.26



2
22
−42.00
12.72
−2.77
−13.83



3
27
−67.00
4.27
−1.89
−4.39



4
31
−56.00
3.37
−0.33
−2.23



5
34
46.94
87.49
26.91
−102.68

















TABLE 1







values corresponding to conditional expressions in Numerical Embodiments 1 to 7









Numerical Embodiment















1
2
3
4
5
6
7


















wide angle end
18.00
15.00
20.00
19.00
14.00
8.00
18.50


focal length fw


telephoto end focal
180.00
75.00
160.00
95.00
56.00
120.00
120.25


length


zoom magnification
10.00
5.00
8.00
5.00
4.00
15.00
6.50


f1
57.00
32.00
52.10
45.00
30.00
58.00
46.00


f2
−26.70
−18.80
−21.50
−24.80
−19.00
−14.00
−42.00


f3
−76.10
−50.00
−62.00
−55.00
50.00
−30.00
−67.00


f4
31.05
40.41
35.32
39.90
37.44
86.75
−56.00


f5
—
—
—
—
—
—
46.94


f23
—
—
—
—
—
—
−22.82


f11
−56.03
−43.99
−66.86
−64.61
−39.10
−457.59
−61.80


f12
143.79
170.29
133.83
200.46
124.97
60.11
150.18


f13
73.69
49.34
68.81
54.51
45.59
—
60.83


βnw
−1.96
−2.36
−2.01
−1.62
−2.22
−1.40
−2.04


θp
0.5633
0.6034
0.5633
0.6133
0.6034
0.5633
0.6034


θn
0.5441
0.5863
0.5630
0.5642
0.5667
0.5530
0.5521


νp
44.30
23.78
44.30
25.46
23.78
44.30
23.78


νn
63.33
34.97
48.84
42.71
40.76
49.34
49.600


θp23
—
—
—
—
—
—
0.6034


θn23
—
—
—
—
—
—
0.5642


νp23
—
—
—
—
—
—
23.78


νn23
—
—
—
—
—
—
42.71














Conditional









Expression















 (1)
(θp − θn)/
−1.01E−03
1.53E−03
−6.61E−05
−2.85E−03
−2.16E−03
−2.04E−03
−1.99E−03



(νp − νn)


 (2)
nave
1.75
1.80
1.78
1.91
1.83
1.84
1.83


 (3)
f2/fw
−1.48
−1.25
−1.08
−1.31
−1.36
−1.75
−2.27


 (4)
f1/f2
−2.13
−1.70
−2.42
−1.81
−1.58
−4.14
−1.10


 (8)
(θp23 − θn23)/
—
—
—
—
—
—
−2.07E−03



(νp23 − νn23)


 (9)
nave23
—
—
—
—
—
—
1.84


(10)
f23/fw
—
—
—
—
—
—
−1.23


(11)
f1/f23
—
—
—
—
—
—
−2.02


(12)
f11/f1
−0.98
−1.37
−1.28
−1.44
−1.30
−7.89
−1.34


(13)
f13/f11
−1.32
−1.12
−1.03
−0.84
−1.17
—
−0.98


(14)
f1/fw
3.17
2.13
2.61
2.37
2.14
7.25
2.49


(15)
βnw
−1.96
−2.36
−2.01
−1.62
−2.22
−1.40
−2.04









While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2013-234394, filed Nov. 12, 2013, which is hereby incorporated by reference herein in its entirety.

## Claims

1. A zoom lens, comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power that does not move for zooming;
a second lens unit having a negative refractive power that moves during zooming; and
an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side,
wherein the first lens unit comprises in order from the object side to the image side:
a first sub-lens unit having a negative refractive power that does not move for focusing;
a second sub-lens unit having a positive refractive power that moves along an optical axis during focusing; and
a third sub-lens unit having a positive refractive power that does not move for focusing,

wherein two lenses, among lenses of the second lens unit, disposed closest to the image side of the second lens unit, comprise a positive lens and a negative lens, and
wherein the following conditional expressions are satisfied:


−9.0<f11/f1<−0.9;



−1.5<f13/f11<−0.5;



−3.0×10−3<(θp−θn)/(νp−νn)<0; and



1.7<nave<2.0,



where f1 represents a focal length of the first lens unit, f11 represents a focal length of the first sub-lens unit, f13 represents a focal length of the third sub-lens unit, θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit,
provided that the Abbe number ν and the partial dispersion ratio θ are respectively expressed as follows:


ν=(nd−1)/(nF−nC); and



θ=(ng−nF)/(nF−nC),



where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.

2. The zoom lens according to claim 1, wherein the following conditional expression is satisfied:


−2.5<f2/fw<0,


where f2 represents a focal length of the second lens unit, and fw represents a focal length at a wide angle end of the zoom lens.

3. The zoom lens according to claim 1, wherein the following conditional expression is satisfied:


−5.0<f1/f2<0,


where f1 represents a focal length of the first lens unit.

4. The zoom lens according to claim 1, wherein the second lens unit includes a second positive lens having a refractive index n and an Abbe number v that satisfy the following conditional expressions:


1.8<n<2.2; and



15<ν<30.

5. The zoom lens according to claim 4, wherein the second positive lens is a positive lens disposed closest to the object side in the second lens unit.

6. The zoom lens according to claim 1, wherein the second lens unit includes a second positive lens having a partial dispersion ratio θi and an Abbe number νi that satisfy the following conditional expression:


0.648<θi+2.53×10−3×νi<0.678.

7. The zoom lens according to claim 1, wherein the second lens unit comprises three negative lenses and one positive lens.

8. The zoom lens according to claim 1, wherein the following conditional expressions are satisfied:


1.5<f1/fw<9.0; and



−2.7<βnw<−1.0,


where βnw represents a lateral magnification at a wide angle end of the N-th lens unit when an axial ray enters from infinity in a state of focusing on infinity.

9. The zoom lens according to claim 1, wherein the zoom lens comprises the first lens unit, the second lens unit, a third lens unit that moves during zooming, and the N-th lens unit.

10. A zoom lens comprising in order from an object side to an image side:
a first lens unit having a positive refractive power that does not move for zooming;
a second lens unit having a negative refractive power that moves during zooming;
a third lens unit that moves during focusing; and
an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side,
wherein the first lens unit comprises in order from the object side to the image side:
a first sub-lens unit having a negative refractive power that does not move for focusing;
a second sub-lens unit having a positive refractive power that moves along an optical axis during focusing; and
a third sub-lens unit having a positive refractive power that does not move for focusing,

wherein two lenses, among lenses of the second lens unit and the third lens unit, disposed closest to the image side comprise a positive lens and a negative lens, and
wherein the following conditional expressions are satisfied:


−9.0<f11/f1<−0.9;



−1.5<f13/f11<−0.5;



−3.0×10−3<(θp−θn)/(νp−νn)<0; and



1.7<nave<2.0,



where f1 represents a focal length of the first lens unit, f11 represents a focal length of the first sub-lens unit, f13 represents a focal length of the third sub-lens unit, θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit and the third lens unit,
provided that the Abbe number v and the partial dispersion ratio θ are respectively expressed as follows:


ν=(nd−1)/(nF−nC); and



θ=(ng−nF)/(nF−nC),



where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.

11. The zoom lens according to claim 10, wherein the following conditional expressions are satisfied:


−2.5<f23/fw<0; and



−5.0<f1/f23<0,


where f23 represents a combined focal length at a wide angle end of the second lens unit and the third lens unit.

12. The zoom lens according to claim 10, wherein a group of the second lens unit and the third lens unit includes a second positive lens having and a refractive index n23 and an Abbe number ν23 that satisfy the following conditional expressions:


1.8<ni23<2.2; and



15<νi23<30.

13. The zoom lens according to claim 10, wherein a group of the second lens unit and the third lens unit includes a second positive lens having a partial dispersion ratio θi23 and an Abbe number νi23 that satisfy the following conditional expression,


0.648<θi23+2.53×10−3×νi23<0.678.

14. The zoom lens according to claim 10, wherein the positive lens is a positive lens disposed closest to the object side in the group of the second lens unit and the third lens unit.

15. The zoom lens according to claim 10, wherein the following conditional expressions are satisfied:


1.5<f1/fw<9.0; and



−2.7<βnw<−1.0,


where βnw represents a lateral magnification at a wide angle end of the N-th lens unit when an axial ray enters from infinity in a state of focusing on infinity.

16. The zoom lens according to claim 10, wherein the zoom lens comprises the first lens unit, the second lens unit, the third lens unit, a fourth lens unit that moves during zooming, and the N-th lens unit.

17. An image pickup apparatus, comprising:
a zoom lens, comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power that does not move for zooming;
a second lens unit having a negative refractive power that moves during zooming; and
an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side,
wherein the first lens unit comprises in order from the object side to the image side:
a first sub-lens unit having a negative refractive power that does not move for focusing;
a second sub-lens unit having a positive refractive power that moves along an optical axis during focusing; and
a third sub-lens unit having a positive refractive power that does not move for focusing,

wherein two lenses, among lenses of the second lens unit, disposed closest to the image side of the second lens unit, comprise a positive lens and a negative lens, and
wherein the following conditional expressions are satisfied:


−9.0<f11/f1<−0.9;



−1.5<f13/f11<−0.5;



−3.0×10−3<(θp−θn)/(νp−νn)<0; and



1.7<nave<2.0,


 where f1 represents a focal length of the first lens unit, f11 represents a focal length of the first sub-lens unit, f13 represents a focal length of the third sub-lens unit, θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit,
provided that the Abbe number v and the partial dispersion ratio θ are respectively expressed as follows:


ν=(nd−1)/(nF−nC); and



θ=(ng−nF)/(nF−nC),




where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.

18. An image pickup apparatus comprising a zoom lens,
the zoom lens comprising in order from an object side to an image side:
a first lens unit having a positive refractive power that does not move for zooming;
a second lens unit having a negative refractive power that moves during zooming;
a third lens unit that moves during focusing; and
an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side,
wherein the first lens unit comprises in order from the object side to the image side:
a first sub-lens unit having a negative refractive power that does not move for focusing;
a second sub-lens unit having a positive refractive power that moves along an optical axis during focusing; and
a third sub-lens unit having a positive refractive power that does not move for focusing,

wherein two lenses, among lenses of the second lens unit and the third lens unit, disposed closest to the image side comprise a positive lens and a negative lens, and
wherein the following conditional expressions are satisfied:


−9.0<f11/f1<−0.9;



−1.5<f13/f11<−0.5;



−3.0×10−3<(θp−θn)/(νp−νn)<0; and



1.7<nave<2.0,


 where f1 represents a focal length of the first lens unit, f11 represents a focal length of the first sub-lens unit, f13 represents a focal length of the third sub-lens unit, θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit and the third lens unit,
provided that the Abbe number v and the partial dispersion ratio θ are respectively expressed as follows:


ν=(nd−1)/(nF−nC); and



θ=(ng−nF)/(nF−nC),



where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.