JP4904676B2 - Zoom lens - Google Patents

Description

  The present invention relates to a zoom lens suitable for a video camera, an electronic still camera, or the like using a solid-state imaging device.

  Conventionally, many zoom lenses suitable for video cameras and electronic still cameras using a solid-state imaging device as a photographing medium have been proposed. As zoom lenses having a high zoom ratio of about 5 times or more, there are five or more zoom lenses. There is known a type of lens group in which the most object side lens group has a positive refractive power (see, for example, Patent Document 1).

On the other hand, a zoom lens with a high zoom ratio has a problem that camera shake is likely to occur on the telephoto side. Therefore, in order to avoid the deterioration of the photographed image due to the camera shake, a method of moving the image by moving a part of the optical system in a direction substantially perpendicular to the optical axis and canceling the image blur due to the camera shake. Various proposals have been made. Many optical systems having such a vibration-proof function have been proposed (see, for example, Patent Document 2).
JP 2002-98893 A JP 2003-207715 A

  Recently, in video cameras and electronic still cameras using a solid-state imaging device or the like, the number of pixels has increased, and high optical performance has been strongly demanded for photographing lenses. In addition, zooming with a high zoom ratio is required from the viewpoint of convenience in photographing, and compactness is also required from the viewpoint of portability. However, the zoom lens disclosed in Patent Document 1 has a sufficiently high optical performance over the entire focal length from the wide-angle end state to the telephoto end state, while it is required to satisfy these requirements simultaneously. However, although a high zoom ratio is ensured, it cannot be said that downsizing is sufficiently achieved.

  On the other hand, there is an increasing demand for a function for canceling camera shake. Recently, the zoom lens disclosed in Patent Document 2 has sufficiently high optical performance over the entire focal length from the wide-angle end state to the telephoto end state. In addition, the optical performance in a state in which a part of the optical system is moved in a direction substantially perpendicular to the optical axis was not high. In addition, since the zoom ratio is less than 5 times, it cannot be said that a high zoom ratio is secured.

Accordingly, the present invention has been made in view of the above problems, and is a compact size having high optical performance suitable for a video camera or an electronic still camera using a solid-state imaging device or the like and having a zoom ratio of about 5 times or more. An object of the present invention is to provide a zoom lens.
In addition, from the viewpoint of image stabilization, it has high optical performance suitable for video cameras and electronic still cameras that use solid-state image sensors, etc. In addition, part of the optical system has been moved in a direction substantially perpendicular to the optical axis. An object of the present invention is to provide a small zoom lens that maintains high optical performance even in a state and has a zoom ratio of about 5 times or more.

In order to solve the above problems, the present invention
A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power in order from the object side along the optical axis. And a fourth lens group having a positive refractive power,
When zooming from the wide-angle end state to the telephoto end state, the variable air gap between the first lens group and the second lens group increases along the optical axis in the infinite focus state, and the second lens group Variable air gap between the third lens group and the third lens group decreases, variable air gap between the third lens group and the fourth lens group decreases, and variable air between the fourth lens group and the fifth lens group decreases. The first lens group moves relative to the image plane so that the distance increases, the second lens group moves to the object side after moving once to the image plane side, and the third lens group Moves to the object side, the fourth lens group moves to the object side, the fifth lens group moves relative to the image plane,
Provided is a zoom lens that satisfies the following conditional expressions (1) and (2).
(1) 0.02 <(D5iT- D5iW) / fW ≦ 0.15
(2) 0.09 <(− f2) / fT <0.18
However,
fW: focal length of the entire zoom lens system in the wide-angle end state fT: focal length of the entire zoom lens system in the telephoto end state f2: focal length of the second lens group D5iW: in the fifth lens group in the wide-angle end state The distance D5iT from the lens surface closest to the image plane to the image plane: the distance from the lens surface closest to the image plane in the fifth lens group in the telephoto end state to the image plane

According to the present invention, it is possible to provide a small zoom lens having high optical performance suitable for a video camera or an electronic still camera using a solid-state imaging device or the like and having a zoom ratio of about 5 times or more.
In addition, according to the present invention, high optical performance suitable for a video camera or an electronic still camera using a solid-state imaging device or the like is provided, and a part of the optical system is moved in a direction substantially perpendicular to the optical axis. It is possible to provide a small zoom lens that maintains high optical performance even in a state and has a zoom ratio of about 5 times or more.

  The zoom lens of the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power in order from the object side along the optical axis. And a fourth lens group having a positive refractive power and a fifth lens group having a positive refractive power.

Video cameras and electronic still cameras that use a solid-state image sensor as the imaging medium are required to move the exit pupil position of the zoom lens away from the image plane due to the characteristics of the solid-state image sensor. The near lens group preferably has a positive refractive power as a whole.
Therefore, as described above, the zoom lens according to the present invention, in order from the object side along the optical axis, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the positive refraction. The above-mentioned requirement with the third lens group having power, the fourth lens group having positive refracting power, and the fifth lens group having positive refracting power so that the exit pupil position is far from the image plane. Meet.

  In the zoom lens of the present invention, when zooming from the wide-angle end state to the telephoto end state, the variable air gap between the first lens group and the second lens group is along the optical axis in the infinite focus state. The variable air gap between the second lens group and the third lens group decreases, the variable air gap between the third lens group and the fourth lens group decreases, and the fourth lens group and the The first lens group moves relative to the image plane so that the variable air gap with the fifth lens group increases, and the second lens group once moves to the image plane side and then moves to the object side. The third lens group moves toward the object side, the fourth lens group moves toward the object side, and the fifth lens group moves relative to the image plane. With this configuration, a zooming effect can be obtained efficiently.

The zoom lens according to the present invention is configured to satisfy the following conditional expressions (1) and (2). The zoom lens according to the present invention has high optical performance and a high zoom ratio of about 5 times or more. The object of the present invention to achieve a small zoom lens secured is achieved.
(1) 0.02 <(D5iT-D5iW) / fW <0.50
(2) 0.09 <(− f2) / fT <0.18
However,
fW: focal length of the entire zoom lens system in the wide-angle end state fT: focal length of the entire zoom lens system in the telephoto end state f2: focal length of the second lens group D5iW: in the fifth lens group in the wide-angle end state The distance D5iT from the lens surface closest to the image plane to the image plane: the distance from the lens surface closest to the image plane in the fifth lens group in the telephoto end state to the image plane

Conditional expression (1) is a conditional expression for defining an optimum amount of movement of the fifth lens group.
If the upper limit value of conditional expression (1) is exceeded, the fifth lens group moves greatly toward the fourth lens group in the telephoto end state. For this reason, off-axis rays pass relatively near the optical axis of the lens, making it difficult to move the exit pupil position of the zoom lens away from the image plane. Accordingly, it is not possible to satisfy the requirements on the characteristics of the solid-state imaging device. In addition, since the fluctuation of the image plane cannot be corrected efficiently, the object of the present invention to obtain high optical performance cannot be achieved.

On the other hand, if the lower limit value of conditional expression (1) is not reached, the position of the fifth lens group in the telephoto end state hardly changes or approaches the image plane as compared with the wide-angle end state. As a result, off-axis rays pass through a position relatively far from the optical axis of the lens, so that the exit pupil position of the zoom lens varies greatly compared to the wide-angle end state. Therefore, it becomes impossible to satisfy the requirements on the characteristics of the solid-state imaging device. In addition, since it becomes impossible to efficiently correct fluctuations in the image plane, the object of the present invention to obtain high optical performance cannot be achieved.
More preferably, it is desirable that the zoom lens of the present invention satisfies the upper limit value of conditional expression (1) as 0.35.

Conditional expression (2) is a conditional expression for defining the optimum focal length of the second lens group.
If the upper limit of conditional expression (2) is exceeded, the focal length of the second lens group becomes relatively long, so that the second lens group cannot efficiently contribute to zooming. For this reason, a high zoom ratio of about 5 times or more cannot be ensured, or the amount of movement of the second lens group becomes large, making it impossible to reduce the size, and the object of the present invention cannot be achieved. .
On the other hand, if the lower limit of conditional expression (2) is not reached, the focal length of the second lens group becomes relatively short, so that the refractive power becomes too strong and the aberration generated in the second lens group becomes too large. For this reason, high optical performance cannot be obtained, and the object of the present invention cannot be achieved.
More preferably, it is desirable that the zoom lens of the present invention satisfies the upper limit value of conditional expression (2) as 0.16. Moreover, it is desirable that the lower limit value of conditional expression (1) be 0.10.

  According to a preferred aspect of the zoom lens of the present invention, when zooming from the wide-angle end state to the telephoto end state, the fifth lens group moves to the image plane side from the wide-angle end state to the wide-angle intermediate focal length state. It is desirable to move from the wide-angle side intermediate focal length to the telephoto side intermediate focal length toward the object side, and from the telephoto side intermediate focal length to the telephoto end state to move toward the image plane side.

  By moving the fifth lens group along such a movement locus, the curvature of field can be efficiently corrected over the entire intermediate focal length region between the wide-angle end state and the telephoto end state, and high optical performance can be obtained. Aim can be achieved.

According to a preferable aspect of the zoom lens of the present invention, it is desirable that the following conditional expression (3) is satisfied.
(3) 0.40 <f5 / fT <0.50
However,
fT: focal length of the entire zoom lens system in the telephoto end state f5: focal length of the fifth lens group

Conditional expression (3) is a conditional expression for defining the optimum focal length of the fifth lens group.
If the upper limit of conditional expression (3) is exceeded, the focal length of the fifth lens group becomes relatively long, so that the fifth lens group cannot efficiently move the exit pupil position away from the image plane. For this reason, it becomes impossible to satisfy the characteristic requirements of the solid-state imaging device.
On the other hand, if the lower limit of conditional expression (3) is not reached, the refractive power of the fifth lens group becomes relatively strong. For this reason, it becomes difficult to correct the curvature of field over the entire region from the wide-angle end state to the telephoto end state while suppressing fluctuations in the exit pupil position to satisfy the requirements on the characteristics of the solid-state imaging device. Therefore, the object of the present invention to obtain high optical performance cannot be achieved.

  According to a preferred aspect of the zoom lens of the present invention, the third lens group includes a front group having a positive refractive power, an aperture stop, and a rear group in order from the object side along the optical axis. The front group includes only a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis, and the rear group includes a positive lens and a negative lens in order from the object side along the optical axis. It is desirable to consist only of these cemented lenses.

  In the zoom lens of the present invention, the third lens group greatly contributes to the zooming action, and plays an important role in aberration correction of the entire zoom lens. Therefore, it is possible to efficiently correct the on-axis aberration by adopting a configuration in which the front group and the rear group having positive refractive power sandwich the aperture stop. Further, the front group located on the object side of the aperture stop is composed only of a cemented lens of a negative lens and a positive lens, and the rear group located on the image side of the aperture stop is composed of only a cemented lens of a positive lens and a negative lens. By configuring, a so-called symmetrical configuration with an aperture stop interposed therebetween can be used to further correct axial aberration. For this reason, aberration correction can be performed very well for the entire zoom lens, and the object of the present invention of obtaining high optical performance can be achieved.

According to a preferred aspect of the zoom lens of the present invention, the third lens group includes a front group having a positive refractive power, an aperture stop, and a rear group in order from the object side along the optical axis. It is desirable that the following conditional expression (4) is satisfied.
(4) -0.50 <f3a / f3b <0.50
However,
f3a: focal length of the front group f3b: focal length of the rear group

The reason why the third lens group is configured to include the front group having a positive refractive power, the aperture stop S, and the rear group is as described above, and conditional expression (4) indicates the focal length of the front group and the rear group. It is a conditional expression for prescribing the optimal ratio of the focal length of the group.
When the upper limit of conditional expression (4) is exceeded, the refractive power of the rear group becomes relatively stronger than the refractive power of the front group. For this reason, when combined with the fourth lens group having positive refractive power arranged on the image side of the rear group, the positive refractive power on the image side of the aperture stop becomes too stronger than the positive refractive power on the object side. Therefore, it becomes difficult to correct off-axis aberrations, and the object of the present invention to obtain high optical performance cannot be achieved.

On the other hand, if the lower limit value of conditional expression (4) is not reached, the refractive power of the entire third lens group becomes weak, so that it is impossible to efficiently contribute to zooming, and a high zoom ratio of about 5 times or more can be secured. Otherwise, the amount of movement of the third lens group becomes large and the size cannot be reduced, and the object of the present invention cannot be achieved.
More preferably, it is desirable that the zoom lens of the present invention satisfies the upper limit value of conditional expression (4) as 0.40. In addition, it is desirable that the lower limit value of conditional expression (4) be −0.20.
It is desirable to satisfy the lower limit value of −0.20.

  According to a preferred aspect of the zoom lens of the present invention, the third lens group includes a front group having a positive refractive power and a rear group in order from the object side along the optical axis, and the front group It is desirable to move the image by moving the lens in a direction substantially perpendicular to the optical axis.

  With such a configuration, a function for canceling camera shake can be realized. Furthermore, since excellent aberration correction can be performed even when the front group is moved in a direction substantially perpendicular to the optical axis, it is possible to obtain high optical performance and achieve the object of the present invention. can do.

  According to a preferred aspect of the zoom lens of the present invention, it is desirable that the third lens group has an aperture stop, and the aperture stop is disposed between the front group and the rear group.

  In the zoom lens of the present invention, the third lens group greatly contributes to zooming and plays an important role in aberration correction of the entire zoom lens. Therefore, with the above-described configuration, it is possible to efficiently correct the on-axis aberration, the aberration correction can be performed satisfactorily for the entire zoom lens, and the object of the present invention is to obtain high optical performance. Can be achieved.

According to still another preferable aspect of the zoom lens of the present invention, it is desirable that the front group includes only a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis.
By configuring the front group only with a cemented lens of a negative lens and a positive lens, it becomes possible to reduce variations in various aberrations when the front group is moved in a direction substantially perpendicular to the optical axis. Therefore, aberration correction can be performed satisfactorily for the entire zoom lens, and the object of the present invention of obtaining high optical performance can be achieved.

According to still another preferable aspect of the zoom lens of the present invention, the front group includes only a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis, and the rear group extends along the optical axis. Thus, it is desirable that the lens is composed only of a cemented lens of a positive lens and a negative lens in order from the object side.
The front group located on the object side of the aperture stop is composed only of a cemented lens of a negative lens and a positive lens, and the rear group located on the image side of the aperture stop is composed of only a cemented lens of a positive lens and a negative lens. Thus, a so-called symmetric configuration with the aperture stop interposed therebetween can further correct the axial aberration. Therefore, aberration correction can be performed satisfactorily for the entire zoom lens, and the object of the present invention of obtaining high optical performance can be achieved.

According to a preferred aspect of the zoom lens of the present invention, it is desirable that the same conditional expression (4) as described above is satisfied.
(4) -0.50 <f3a / f3b <0.50
However,
f3a: focal length of the front group f3b: focal length of the rear group

  Conditional expression (4) is a conditional expression for defining an optimum ratio of the focal length of the front group and the focal length of the rear group, and the description thereof is omitted for the above.

According to a preferable aspect of the zoom lens of the present invention, it is desirable that the following conditional expression (5) is satisfied.
(5) 0.2 <(1-β3aT) βRT <3.0
However,
β3aT: used lateral magnification of the front group in the telephoto end state βRT: used lateral magnification of the entire optical system between the front group and the image plane in the telephoto end state

Conditional expression (5) is a condition that defines an optimal range of the amount of movement in the direction perpendicular to the optical axis of the image relative to the amount of movement in the direction perpendicular to the optical axis of the front group in the telephoto end state, so-called blur correction coefficient. It is a formula.
If the upper limit of conditional expression (5) is exceeded, the amount of movement in the direction perpendicular to the optical axis of the image relative to the amount of movement in the direction perpendicular to the optical axis of the front group becomes too large. For this reason, the control accuracy required for the front group becomes too high, so that sufficient accuracy cannot be obtained, and the object of the present invention to obtain high optical performance cannot be achieved.
On the other hand, if the lower limit of conditional expression (5) is not reached, the amount of movement in the direction perpendicular to the optical axis of the image relative to the amount of movement in the direction perpendicular to the optical axis of the front group becomes relatively small. Therefore, in order to secure the amount of image movement necessary to cancel image blur due to camera shake, the amount of movement in the direction perpendicular to the optical axis of the front group must be increased, and a small zoom The object of the present invention of obtaining a lens cannot be achieved.
More preferably, it is desirable that the zoom lens of the present invention satisfies the upper limit value of conditional expression (5) as 2.0. Moreover, it is desirable that the lower limit value of conditional expression (5) be 0.4.

According to a preferred aspect of the zoom lens of the present invention, it is desirable that the fourth lens group includes only a spherical lens, includes a single lens having a positive refractive power, and satisfies the following conditional expression (6): .
(6) nL4P> 1.700
However,
nL4P: Refractive index with respect to d-line (wavelength λ = 587.6 nm) of the medium of the single lens

  In the zoom lens according to the present invention, the fourth lens group, along with the third lens group, greatly contributes to zooming and plays an important role in aberration correction of the entire zoom lens. Therefore, the fourth lens group is composed of only spherical lenses that can easily ensure manufacturing accuracy as described above. As a result, by suppressing the deterioration in performance in manufacturing individual lenses, finally high optical performance can be ensured, and the object of the present invention can be achieved.

Conditional expression (6) is a conditional expression that defines an optimal range of the refractive index of a single lens having positive refractive power included in the fourth lens group.
If the lower limit value of conditional expression (6) is not reached, the spherical aberration occurring in the single lens becomes negatively large. For this reason, it becomes difficult to correct spherical aberration by the fourth lens group, and the object of the present invention to obtain high optical performance cannot be achieved.
More preferably, it is desirable that the zoom lens of the present invention satisfies the lower limit value of conditional expression (6) as 1.740.

  According to a preferred aspect of the zoom lens of the present invention, it is desirable that all the lenses in the zoom lens are spherical lenses.

  As described above, all the lenses in the zoom lens according to the present invention are composed of only spherical lenses that are easy to ensure manufacturing accuracy. Thereby, it is possible to suppress degradation in performance of manufacturing individual lenses, and finally to secure high optical performance, thereby achieving the object of the present invention.

  According to a preferred aspect of the zoom lens of the present invention, it is desirable that the fourth lens group includes an aspheric lens.

Since the fourth lens group has an aspheric lens, spherical aberration generated in the fourth lens group can be efficiently corrected. For this reason, the object of the present invention of obtaining high optical performance can be achieved.
Here, the spherical lens refers to a lens that is not an aspheric lens, and it goes without saying that a lens including a flat surface is also a spherical lens. The following description is also the same.

  The zoom lens according to another aspect of the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive lens in order from the object side along the optical axis. A third lens group having a refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power are configured.

As with the previous invention, video cameras and electronic still cameras that use a solid-state image sensor as the imaging medium are required to move the exit pupil position of the zoom lens away from the image plane due to the characteristics of the solid-state image sensor. Therefore, it is preferable that the lens group close to the image plane has a positive refractive power as a whole.
Therefore, as described above, the zoom lens according to another aspect of the present invention includes a first lens group having a positive refractive power and a second lens group having a negative refractive power in order from the object side along the optical axis. And a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power, the exit pupil position is far from the image plane. The above-mentioned requirements are satisfied.

  According to another aspect of the zoom lens of the present invention, when zooming from the wide-angle end state to the telephoto end state, the first lens group and the second lens group are arranged along the optical axis in the infinite focus state. The variable air gap between the second lens group and the third lens group decreases, the variable air gap between the third lens group and the fourth lens group decreases, The first lens group moved relative to the image plane, and the second lens group once moved to the image plane side so that the variable air gap between the four lens groups and the fifth lens group was increased. Later, it moves to the object side, the third lens group moves to the object side, and the fourth lens group moves to the object side. With this configuration, the object of the present invention is achieved, in which a zooming effect can be obtained efficiently and a small zoom lens having a high zooming ratio of about 5 times or more can be realized.

  According to another aspect of the zoom lens of the present invention, the third lens group includes, in order from the object side along the optical axis, a front group having a positive refractive power, an aperture stop, and a rear group. The image can be moved by moving the front group in a direction substantially perpendicular to the optical axis.

  With such a configuration, a function for canceling camera shake can be realized. Furthermore, since excellent aberration correction can be performed even when the front group is moved in a direction substantially perpendicular to the optical axis, it is possible to obtain high optical performance and achieve the object of the present invention. can do.

According to still another preferred aspect of the zoom lens of the present invention, it is desirable that the front group includes only a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis.
By configuring the front group only with a cemented lens of a negative lens and a positive lens, it becomes possible to reduce variations in various aberrations when the front group is moved in a direction substantially perpendicular to the optical axis. Therefore, aberration correction can be performed satisfactorily for the entire zoom lens, and the object of the present invention of obtaining high optical performance can be achieved.

According to another aspect of the zoom lens of the present invention from another aspect, the front group includes only a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis, and the rear group includes It is desirable that the lens is composed only of a cemented lens of a positive lens and a negative lens in order from the object side along the optical axis.
Thus, the front group located on the object side of the aperture stop is composed only of a cemented lens of a negative lens and a positive lens, and the rear group located on the image side of the aperture stop is composed only of a cemented lens of a positive lens and a negative lens. With this configuration, a so-called symmetrical configuration with the aperture stop interposed therebetween can be further corrected for axial aberration. Therefore, aberration correction can be performed satisfactorily for the entire zoom lens, and the object of the present invention of obtaining high optical performance can be achieved.

According to another preferred aspect of the zoom lens of the present invention, it is desirable that the same conditional expression (4) as described above is satisfied.
(4) -0.50 <f3a / f3b <0.50
However,
f3a: focal length of the front group f3b: focal length of the rear group

  Conditional expression (4) is a conditional expression for defining an optimum ratio of the focal length of the front group and the focal length of the rear group, and the description thereof is omitted for the above.

According to another preferred aspect of the zoom lens of the present invention, it is desirable that the same conditional expression (5) as described above is satisfied.
(5) 0.2 <(1-β3aT) βRT <3.0
However,
β3aT: used lateral magnification of the front group in the telephoto end state βRT: used lateral magnification of the entire optical system between the front group and the image plane in the telephoto end state

  Conditional expression (5) is a condition that defines an optimal range of the amount of movement in the direction perpendicular to the optical axis of the image relative to the amount of movement in the direction perpendicular to the optical axis of the front group in the telephoto end state, so-called blur correction coefficient. Since this is an equation, the description thereof is omitted.

According to another aspect of the zoom lens of the present invention, the fifth lens unit moves relative to the image plane when zooming from the wide-angle end state to the telephoto end state, and It is desirable to satisfy the following conditional expression (1).
(1) 0.02 <(D5iT-D5iW) / fW <0.50
However,
fW: focal length of the entire zoom lens system in the wide-angle end state D5iW: distance from the lens surface closest to the image plane in the fifth lens group in the wide-angle end state to the image plane D5iT: the fifth lens in the telephoto end state Distance from the lens surface closest to the image plane in the group to the image plane

By moving the fifth lens group relative to the image plane as described above, a zooming effect can be obtained more efficiently, and a small zoom that ensures a high zooming ratio of about 5 times or more. The object of the present invention of obtaining a lens can be achieved.
Conditional expression (1) is a conditional expression for prescribing the optimum amount of movement of the fifth lens group, and the description thereof is omitted for the above.

According to another preferred aspect of the zoom lens of the present invention, it is preferable that the same conditional expression (2) as described above is satisfied.
(2) 0.09 <(− f2) / fT <0.18
However,
fT: focal length of the entire zoom lens system in the telephoto end state f2: focal length of the second lens group

  Conditional expression (2) is a conditional expression for defining the optimum focal length of the second lens group, and the description thereof is omitted for the above.

  According to another preferred aspect of the zoom lens of the present invention, when zooming from the wide-angle end state to the telephoto end state, the fifth lens group does not move from the wide-angle end state to the wide-angle-side intermediate focal length state. It is desirable to move to the image plane side, move to the object side from the wide-angle-side intermediate focal length to the telephoto-side intermediate focal length, and move to the image-plane side from the telephoto-side intermediate focal length to the telephoto end state.

  By moving the fifth lens group along such a movement locus, the curvature of field can be efficiently corrected over the entire intermediate focal length region between the wide-angle end state and the telephoto end state, and high optical performance can be obtained. Aim can be achieved.

According to another preferred aspect of the zoom lens of the present invention, it is desirable that the same conditional expression (3) as described above is satisfied.
(3) 0.40 <f5 / fT <0.50
However,
fT: focal length of the entire zoom lens system in the telephoto end state f5: focal length of the fifth lens group

  Conditional expression (3) is a conditional expression for defining the optimum focal length of the fifth lens group, and the description thereof is omitted for the above.

According to another aspect of the zoom lens of the present invention from another aspect, the fourth lens group includes only a spherical lens and includes a single lens having a positive refractive power. It is desirable to satisfy 6).
(6) nL4P> 1.700
However,
nL4P: Refractive index with respect to d-line (wavelength λ = 587.6 nm) of the medium of the single lens

In the zoom lens according to the present invention, the fourth lens group, along with the third lens group, greatly contributes to zooming and plays an important role in aberration correction of the entire zoom lens. Therefore, the fourth lens group is composed of only spherical lenses that can easily ensure manufacturing accuracy as described above. As a result, by suppressing the deterioration in performance in manufacturing individual lenses, finally high optical performance can be ensured, and the object of the present invention can be achieved.
Conditional expression (6) is a conditional expression that prescribes the optimum range of the refractive index of a single lens having a positive refractive power included in the fourth lens group.

  According to another aspect of the zoom lens of the present invention, it is desirable that all the lenses in the zoom lens are spherical lenses.

  As described above, all the lenses in the zoom lens according to the present invention are composed of only spherical lenses that are easy to ensure manufacturing accuracy. Thereby, it is possible to suppress degradation in performance of manufacturing individual lenses, and finally to secure high optical performance, thereby achieving the object of the present invention.

  According to another aspect of the zoom lens of the present invention, it is preferable that the fourth lens group includes an aspheric lens.

Since the fourth lens group has an aspheric lens, spherical aberration generated in the fourth lens group can be efficiently corrected. For this reason, the object of the present invention of obtaining high optical performance can be achieved.
Here, the spherical lens refers to a lens that is not an aspheric lens, and it goes without saying that a lens including a flat surface is also a spherical lens. The following description is also the same.

Hereinafter, zoom lenses according to embodiments of the present invention will be described with reference to the accompanying drawings.
[First embodiment]
FIG. 1 is a cross-sectional view showing the lens configuration of the zoom lens according to the first embodiment of the present invention when focusing on infinity, and in the order from the top in the drawing, the wide-angle end state (W) and the wide-angle-side intermediate focal length state ( M1), a telephoto side intermediate focal length state (M2), and a telephoto end state (T) are shown.
The zoom lens according to the present example has, in order from the object side along the optical axis, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. The third lens group G3 includes a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power.

When the zoom lens according to the present embodiment is zoomed from the wide-angle end state to the telephoto end state, the variable air between the first lens group G1 and the second lens group G2 along the optical axis in the infinite focus state. The distance increases, the variable air distance between the second lens group G2 and the third lens group G3 decreases, the variable air distance between the third lens group G3 and the fourth lens group G4 decreases, and the fourth lens group G4 After the first lens group G1 moves relative to the image plane I and the second lens group G2 once moves to the image plane I side, the variable air gap between the first lens group G5 and the fifth lens group G5 increases. The third lens group G3 moves to the object side, the fourth lens group G4 moves to the object side, and the fifth lens group G5 moves relative to the image plane I.
Specifically, when zooming from the wide-angle end state to the telephoto end state, the fifth lens group G5 moves to the image plane I side from the wide-angle end state to the wide-angle side intermediate focal length state, and from the wide-angle side intermediate focal length. It moves to the object side until the telephoto side intermediate focal length, and moves to the image plane I side from the telephoto side intermediate focal length to the telephoto end state.

The first lens group G1 in the zoom lens according to the present embodiment includes, in order from the object side along the optical axis, a positive meniscus lens having a large curvature and a negative meniscus lens having a convex surface facing the object side and a lens surface on the object side. It consists of a cemented positive lens with a lens and a positive meniscus lens with a convex surface facing the object side.
The second lens group G2, in order from the object side along the optical axis, is a biconcave negative lens having a strong refractive power on the lens surface on the image plane I side, and a biconcave shape having a strong refractive power on the lens surface on the object side. Negative lens, and a cemented positive lens composed of a biconvex positive lens and a biconcave negative lens having a small curvature on the image side lens surface.

The third lens group G3 includes, in order from the object side along the optical axis, a front group G3a having a positive refractive power, an aperture stop S, and a rear group G3b having a positive refractive power. The front group G3a is composed of, in order from the object side along the optical axis, a cemented positive lens of a negative meniscus lens L31N having a convex surface facing the object side and a biconvex positive lens L31P. The rear group G3b is composed of, in order from the object side along the optical axis, a cemented positive lens of a biconvex positive lens L32P and a biconcave negative lens L32N.
Further, in order to move the image in a direction substantially perpendicular to the optical axis, the front group G3a is provided so as to be movable in a direction substantially perpendicular to the optical axis.

The fourth lens group G4 includes, in order from the object side along the optical axis, a biconvex positive lens having an aspheric lens surface on the object side, and a biconvex positive lens having a small curvature on the object side lens surface. And a cemented negative lens with a biconcave negative lens.
The fifth lens group G5 includes a positive meniscus lens having a convex surface directed toward the object side.
Further, between the fifth lens group G5 and the image plane I, an optical low-pass filter LPF and a cover glass CG are arranged in order from the object side along the optical axis.

Table 1 below provides values of specifications of the zoom lens according to the present embodiment.
In (total specifications) in the table, f is a focal length (unit: mm), FNO is an F number, 2ω is an angle of view (unit: degree), and TL is a full length (unit: mm).
In (lens data), the surface number indicates the order of the lens surfaces from the object side along the direction in which the light beam travels, and the refractive index and the Abbe number indicate values for the d-line (λ = 587.6 nm), respectively. . Note that the curvature radius ∞ indicates a plane, and the refractive index of air of 1.0000 is omitted. Bf represents back focus.
In (Overall specifications) and (Variable interval data), the lens state W indicates the wide angle end state, M1 indicates the wide angle side intermediate focal length state, M2 indicates the telephoto side intermediate focal length state, and T indicates the telephoto end state.

In this embodiment and all the following embodiments, the aspherical surface has a height in the direction perpendicular to the optical axis y, and the distance along the optical axis from the tangential plane of the apex of the aspherical surface to the aspherical surface at height y ( (Sag amount) is x, the reciprocal of the radius of curvature of the reference sphere is c, the conic constant is κ, and the fourth, sixth, eighth and tenth-order aspheric coefficients are C4, C6, C8 and C10, respectively. expressed.
x = cy ² / {1+ (1−κc ² y ² ) ^1/2 } + C4y ⁴ + C6y ⁶ + C8y ⁸ + C10y ¹⁰
In (aspherical surface data), “En” indicates “× 10 ⁻ⁿ ”. For example, 1.234E-5 = 1.234 × 10 ⁻⁵ .

Here, in general, “mm” is used as a unit of the focal length f, the radius of curvature r, and other lengths listed in all the specification values of the following embodiments. However, since the optical system can obtain the same optical performance even when proportionally enlarged or reduced, the unit is not limited to “mm”.
In addition, also in the specification values of all the following examples, the same symbols as in this example are used.

[Table 1]
(Overall specifications)
Lens condition W M1 M2 T
f 9.17 14.00 40.00 86.40
FNO 2.9 3.2 4.1 5.7
2ω 66.6 44.1 16.0 7.4

(Lens data)
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 104.9674 1.800 1.84666 23.78
2 57.7700 6.900 1.64000 60.09
3 -449.0606 0.100
4 37.6081 5.500 1.49782 82.52
5 146.3156 (D5)
6 -383.8145 1.200 1.83400 37.17
7 11.0333 4.950
8 -27.7390 0.900 1.81600 46.63
9 59.3532 0.300
10 25.1431 3.750 1.84666 23.78
11 -25.1270 0.900 1.71300 53.85
12 133.1648 (D12)
13 50.4203 1.600 1.62004 36.26
14 19.0995 3.000 1.49782 82.52
15 -34.0289 0.800
16 ∞ 1.800 (aperture stop)
17 13.0090 3.600 1.65844 50.88
18 -16.3853 2.000 1.79952 42.24
19 18.9993 (D19)
20 21.2799 3.100 1.76802 49.23
21 -24.3268 0.100
22 31.6627 3.900 1.48749 70.24
23 -16.2608 0.900 1.83400 37.17
24 13.1942 (D24)
25 17.1071 2.900 1.48749 70.24
26 104.4871 (D26)
27 ∞ 1.720 1.54437 70.51 (LPF)
28 ∞ 1.441
29 ∞ 0.500 1.51680 64.20 (CG)
30 ∞ (Bf)

(Aspheric data)
The twentieth lens surface in the zoom lens according to the present embodiment is an aspheric surface, and the aspheric surface data is shown below.
[20th page]
κ = 1.0000
C4 = -6.13040E-05
C6 = -1.43250E-07
C8 = + 1.90490E-09
C10 = -3.14900E-11

(Variable interval data)
Lens condition W M1 M2 T
f 9.17 14.00 40.00 86.40
D5 3.8000 10.5769 26.0958 31.7742
D12 28.0445 21.0041 8.6209 2.1979
D19 6.2596 4.4013 2.2032 1.6021
D24 5.9789 10.0029 16.8265 32.7317
D26 3.2010 3.1976 6.4023 4.6811

(Values for conditional expressions)
(1) (D5iT-D5iW) /fW=0.15
(2) (−f2) /fT=0.13
(3) f5 / fT = 0.48
(4) f3a / f3b = 0.37
(5) (1-β3aT) βRT = 1.08

From Table 1 above, it can be seen that the zoom lens according to the present example is downsized.
2 (a), 3 (a), 4 (a), and 5 (a) are respectively a wide-angle end state, a wide-angle-side intermediate focal length state of the zoom lens according to the first embodiment of the present invention, It is an aberration diagram with respect to d line (λ = 587.6 nm) at the time of focusing on infinity in the telephoto side intermediate focal length state and the telephoto end state.
2 (b), 3 (b), 4 (b), and 5 (b) are respectively the wide-angle end state and the wide-angle-side intermediate focal length state of the zoom lens according to the first embodiment of the present invention. FIG. 6B is a coma aberration diagram with respect to d line (wavelength λ = 587.6 nm) when the front group G3a is moved by 0.1 mm in a direction perpendicular to the optical axis in the telephoto side intermediate focal length state and the telephoto end state. .

In each aberration diagram, FNO denotes an F number, and A denotes a light incident angle (half angle of view, unit: degree). In the spherical aberration diagram, the F-number value corresponding to the maximum aperture is shown, and in the astigmatism diagram and the distortion diagram, the maximum value of the light incident angle is shown. The coma aberration diagram shows coma aberration at each light incident angle. In the astigmatism diagrams, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane.
In addition, in the various aberration diagrams of each example shown below, the same reference numerals as those in this example are used.

2 (a), 3 (a), 4 (a), and 5 (a), the zoom lens according to the present example has excellent aberrations from the wide-angle end state to the telephoto end state. It can be seen that the optical performance is corrected.
2B, FIG. 3B, FIG. 4B, and FIG. 5B, the zoom lens according to the present example moves the front group G3a in a direction substantially perpendicular to the optical axis. It can be seen that even in the moved state, various aberrations are favorably corrected from the wide-angle end state to the telephoto end state, and the optical performance is high.

[Second Embodiment]
FIG. 6 is a cross-sectional view showing the lens configuration of the zoom lens according to the second embodiment of the present invention when focusing on infinity, and in the order from the top in the drawing, the wide-angle end state (W) and the wide-angle-side intermediate focal length state ( M1), a telephoto side intermediate focal length state (M2), and a telephoto end state (T) are shown.
The zoom lens according to the present example has, in order from the object side along the optical axis, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. The third lens group G3 includes a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power.

When the zoom lens according to the present embodiment is zoomed from the wide-angle end state to the telephoto end state, the variable air between the first lens group G1 and the second lens group G2 along the optical axis in the infinite focus state. The distance increases, the variable air distance between the second lens group G2 and the third lens group G3 decreases, the variable air distance between the third lens group G3 and the fourth lens group G4 decreases, and the fourth lens group G4 After the first lens group G1 moves relative to the image plane I and the second lens group G2 once moves to the image plane I side, the variable air gap between the first lens group G5 and the fifth lens group G5 increases. The third lens group G3 moves to the object side, the fourth lens group G4 moves to the object side, and the fifth lens group G5 moves relative to the image plane I.
Specifically, when zooming from the wide-angle end state to the telephoto end state, the fifth lens group G5 moves to the image plane I side from the wide-angle end state to the wide-angle side intermediate focal length state, and from the wide-angle side intermediate focal length. It moves to the object side until the telephoto side intermediate focal length, and moves to the image plane I side from the telephoto side intermediate focal length to the telephoto end state.

The first lens group G1 in the zoom lens according to the present embodiment includes, in order from the object side along the optical axis, a positive meniscus lens having a large curvature and a negative meniscus lens having a convex surface facing the object side and a lens surface on the object side. It consists of a cemented positive lens with a lens and a positive meniscus lens with a convex surface facing the object side.
The second lens group G2 includes, in order from the object side along the optical axis, a positive meniscus lens having a convex surface directed toward the object side, a biconcave negative lens having a strong refractive power on the object side lens surface, and a biconvex shape And a cemented positive lens composed of a biconcave negative lens having a small curvature of the lens surface on the image side.

The third lens group G3 includes, in order from the object side along the optical axis, a front group G3a having a positive refractive power, an aperture stop S, and a rear group G3b having a positive refractive power. The front group G3a is composed of, in order from the object side along the optical axis, a cemented positive lens of a negative meniscus lens L31N having a convex surface facing the object side and a biconvex positive lens L31P. The rear group G3b is composed of, in order from the object side along the optical axis, a cemented positive lens of a biconvex positive lens L32P and a biconcave negative lens L32N.
Further, in order to move the image in a direction substantially perpendicular to the optical axis, the front group G3a is provided so as to be movable in a direction substantially perpendicular to the optical axis.

The fourth lens group G4 includes, in order from the object side along the optical axis, a biconvex positive lens L4P having a weak refractive power on the object side lens surface, and a biconvex positive lens having a large curvature on the object side lens surface. The lens is composed of a cemented negative lens and a biconcave negative lens having a large curvature of the lens surface on the image plane I side.
The fifth lens group G5 includes, in order from the object side along the optical axis, a cemented positive lens composed of a biconvex positive lens and a biconcave negative lens having a large curvature on the object side lens surface.
Further, between the fifth lens group G5 and the image plane I, an optical low-pass filter LPF and a cover glass CG are arranged in order from the object side along the optical axis.
Table 2 below shows values of specifications of the zoom lens according to the present embodiment.

[Table 2]
(Overall specifications)
Lens condition W M1 M2 T
f 9.17 11.85 40.00 86.40
FNO 2.9 3.1 4.1 5.5
2ω 66.6 51.8 16.1 7.5

(Lens data)
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 82.5209 1.800 1.84666 23.78
2 49.8330 6.550 1.62041 60.29
3 -2162.3403 0.100
4 37.3675 5.200 1.49782 82.56
5 148.7011 (D5)
6 345.7589 1.200 1.83400 37.16
7 10.6448 5.150
8 -29.4991 0.900 1.77250 49.60
9 39.4838 0.400
10 23.0042 3.700 1.84666 23.78
11 -34.2530 0.900 1.65844 50.88
12 180.0276 (D12)
13 35.6811 1.700 1.74950 35.28
14 18.4110 2.900 1.49782 82.56
15 -36.7771 0.950
16 ∞ 1.650 (aperture stop)
17 14.5358 4.000 1.67003 47.23
18 -17.5011 3.000 1.79952 42.22
19 17.5011 (D19)
20 38.2155 3.000 1.80400 46.57
21 -29.6242 0.100
22 13.6535 4.100 1.48749 70.23
23 -19.2970 0.900 1.83400 37.16
24 13.2469 (D24)
25 20.9062 3.800 1.80400 46.57
26 -44.9980 0.900 1.68893 31.07
27 44.9980 (D27)
28 ∞ 1.720 1.54437 70.51 (LPF)
29 ∞ 0.956
30 ∞ 0.500 1.51680 64.20 (CG)
31 ∞ (Bf)

(Variable interval data)
Lens condition W M1 M2 T
f 9.17 11.85 40.00 86.40
D5 2.8000 7.3481 25.4371 31.2435
D12 30.8768 26.2826 9.4395 2.1507
D19 6.5581 5.3364 1.9683 1.6177
D24 5.9883 8.4626 16.9019 32.8851
D27 3.6766 3.6141 6.8119 5.0128

(Values for conditional expressions)
(1) (D5iT-D5iW) /fW=0.14
(2) (−f2) /fT=0.14
(3) f5 / fT = 0.43
(4) f3a / f3b = 0.09
(5) (1-β3aT) βRT = 1.05
(6) nL4P = 1.80400

From Table 2 above, it can be seen that the zoom lens according to the present example is downsized.
FIGS. 7A, 8A, 9A, and 10A are respectively a wide-angle end state, a wide-angle-side intermediate focal length state of the zoom lens according to the second embodiment of the present invention, It is an aberration diagram with respect to d line (λ = 587.6 nm) at the time of focusing on infinity in the telephoto side intermediate focal length state and the telephoto end state.
FIGS. 7B, 8B, 9B, and 10B are respectively the wide-angle end state and the wide-angle-side intermediate focal length state of the zoom lens according to the second embodiment of the present invention. FIG. 6B is a coma aberration diagram with respect to d line (wavelength λ = 587.6 nm) when the front group G3a is moved by 0.1 mm in a direction perpendicular to the optical axis in the telephoto side intermediate focal length state and the telephoto end state. .

7 (a), 8 (a), 9 (a), and 10 (a), the zoom lens according to the present example has excellent aberrations from the wide-angle end state to the telephoto end state. It can be seen that the optical performance is corrected.
7B, FIG. 8B, FIG. 9B, and FIG. 10B, the zoom lens according to the present example moves the front group G3a in a direction substantially perpendicular to the optical axis. It can be seen that even in the moved state, various aberrations are favorably corrected from the wide-angle end state to the telephoto end state, and the optical performance is high.

[Third embodiment]
FIG. 11 is a cross-sectional view illustrating the lens configuration of the zoom lens according to the third embodiment of the present invention when focusing on infinity, and is in the wide-angle end state (W) and the wide-angle-side intermediate focal length state ( M1), a telephoto side intermediate focal length state (M2), and a telephoto end state (T) are shown.
The zoom lens according to the present example has, in order from the object side along the optical axis, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. The third lens group G3 includes a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power.

When the zoom lens according to the present embodiment is zoomed from the wide-angle end state to the telephoto end state, the variable air between the first lens group G1 and the second lens group G2 along the optical axis in the infinite focus state. The distance increases, the variable air distance between the second lens group G2 and the third lens group G3 decreases, the variable air distance between the third lens group G3 and the fourth lens group G4 decreases, and the fourth lens group G4 After the first lens group G1 moves relative to the image plane I and the second lens group G2 once moves to the image plane I side, the variable air gap between the first lens group G5 and the fifth lens group G5 increases. The third lens group G3 moves to the object side, the fourth lens group G4 moves to the object side, and the fifth lens group G5 moves relative to the image plane I.
Specifically, when zooming from the wide-angle end state to the telephoto end state, the fifth lens group G5 moves to the image plane I side from the wide-angle end state to the wide-angle side intermediate focal length state, and from the wide-angle side intermediate focal length. It moves to the object side until the telephoto side intermediate focal length, and moves to the image plane I side from the telephoto side intermediate focal length to the telephoto end state.

The first lens group G1 in the zoom lens according to the present embodiment includes, in order from the object side along the optical axis, a positive meniscus lens having a large curvature and a negative meniscus lens having a convex surface facing the object side and a lens surface on the object side. It consists of a cemented positive lens with a lens and a positive meniscus lens with a convex surface facing the object side.
The second lens group G2, in order from the object side along the optical axis, has a negative meniscus lens having a convex surface facing the object side and an aspheric lens surface on the image plane I side, and a strong refractive power on the object side lens surface. The lens includes a biconcave negative lens and a biconvex positive lens having a strong refractive power on the object side lens surface.

The third lens group G3 includes, in order from the object side along the optical axis, a front group G3a having a positive refractive power, an aperture stop S, and a rear group G3b having a positive refractive power. The front group G3a is a cemented positive lens of a negative meniscus lens L31N having a convex surface directed toward the object side and a biconvex positive lens L31P having a small curvature on the image side along the optical axis. It is configured. The rear group G3b includes, in order from the object side along the optical axis, a cemented negative lens of a biconvex positive lens L32P having a large curvature on the object side lens surface and a biconcave negative lens L32N. ing.
Further, in order to move the image in a direction substantially perpendicular to the optical axis, the front group G3a is provided so as to be movable in a direction substantially perpendicular to the optical axis.

The fourth lens group G4 includes, in order from the object side along the optical axis, a biconvex positive lens having an aspheric lens surface on the object side, and a biconvex positive lens having a small curvature on the object side lens surface. And a cemented negative lens with a biconcave negative lens having a small curvature of the lens surface on the image side.
The fifth lens group G5 is composed of a biconvex positive lens having a strong refractive power on the object-side lens surface.
Further, between the fifth lens group G5 and the image plane I, an optical low-pass filter LPF and a cover glass CG are arranged in order from the object side along the optical axis.
Table 3 below provides values of specifications of the zoom lens according to the present embodiment.

[Table 3]
(Overall specifications)
Lens condition W M1 M2 T
f 9.17 14.00 40.00 86.94
FNO 2.9 3.3 4.2 5.6
2ω 64.9 43.5 16.1 7.4

(Lens data)
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 71.2698 1.200 1.85026 32.35
2 35.1339 6.900 1.49782 82.52
3 -1401.4800 0.100
4 32.8607 5.200 1.62041 60.29
5 161.2228 (D5)
6 93.9250 1.950 1.74330 49.23
7 8.9940 6.200
8 -18.1325 0.900 1.58913 61.18
9 27.1703 0.700
10 23.7608 2.750 1.84666 23.78
11 -162.3377 (D11)
12 31.1726 0.900 1.85026 32.35
13 17.8107 2.750 1.49782 82.52
14 -32.0272 1.200
15 ∞ 1.200 (Aperture stop)
16 12.5579 4.100 1.60562 43.73
17 -15.9905 2.200 1.76200 40.11
18 15.8803 (D18)
19 23.6848 3.000 1.79668 45.37
20 -21.5414 0.700
21 49.7067 3.100 1.49782 82.52
22 -11.1874 2.100 1.83400 37.17
23 17.7867 (D23)
24 21.1435 3.000 1.48749 70.24
25 -288.8441 (D25)
26 ∞ 2.760 1.51680 64.20 (LPF)
27 ∞ 1.441
28 ∞ 0.500 1.51680 64.20 (CG)
29 ∞ (Bf)

(Aspheric data)
The seventh and nineteenth lens surfaces in the zoom lens according to the present embodiment are aspheric surfaces, and the aspheric data are shown below.
[Seventh side]
κ = 0.9000
C4 = -1.76750E-05
C6 = -1.30430E-07
C8 = -2.02420E-09
C10 = + 1.06150E-11

[19th page]
κ = 1.0000
C4 = -3.16770E-05
C6 = + 5.29120E-08
C8 = -4.59950E-10
C10 = + 6.02460E-12

(Variable interval data)
Lens condition W M1 M2 T
f 9.17 14.00 40.00 86.94
D5 1.8000 8.5666 22.6824 28.3033
D11 30.2796 24.8673 10.3997 3.2000
D18 6.0750 4.3760 1.9073 1.8900
D23 4.5813 10.6699 15.9370 30.8487
D25 3.9359 2.0000 6.5627 4.3992

(Values for conditional expressions)
(1) (D5iT-D5iW) /fW=0.05
(2) (−f2) /fT=0.13
(3) f5 / fT = 0.47
(4) f3a / f3b = -0.002
(5) (1-β3aT) βRT = 1.25

From Table 3 above, it can be seen that the zoom lens according to the present example is downsized.
FIGS. 12 (a), 13 (a), 14 (a), and 15 (a) are respectively the wide-angle end state, the wide-angle-side intermediate focal length state of the zoom lens according to the third embodiment of the present invention, It is an aberration diagram with respect to d line (λ = 587.6 nm) at the time of focusing on infinity in the telephoto side intermediate focal length state and the telephoto end state.
FIGS. 12B, 13B, 14B, and 15B are respectively the wide-angle end state and the wide-angle-side intermediate focal length state of the zoom lens according to the third embodiment of the present invention. FIG. 6B is a coma aberration diagram with respect to d line (wavelength λ = 587.6 nm) when the front group G3a is moved by 0.1 mm in a direction perpendicular to the optical axis in the telephoto side intermediate focal length state and the telephoto end state. .

From FIG. 12A, FIG. 13A, FIG. 14A, and FIG. 15A, the zoom lens according to the present example has excellent aberrations from the wide-angle end state to the telephoto end state. It can be seen that the optical performance is corrected.
From FIGS. 12B, 13B, 14B, and 15B, the zoom lens according to the present example moves the front group G3a in a direction substantially perpendicular to the optical axis. It can be seen that even in the moved state, various aberrations are favorably corrected from the wide-angle end state to the telephoto end state, and the optical performance is high.

According to the present invention, it is possible to provide a small zoom lens having high optical performance suitable for a video camera or an electronic still camera using a solid-state imaging device or the like and having a zoom ratio of about 5 times or more.
In addition, according to the present invention, high optical performance suitable for a video camera or an electronic still camera using a solid-state imaging device or the like is provided, and a part of the optical system is moved in a direction substantially perpendicular to the optical axis. It is possible to provide a small zoom lens that maintains high optical performance even in a state and has a zoom ratio of about 5 times or more.

  In addition, although the lens system of 5 groups structure was shown as an Example of this invention, it cannot be overemphasized that the lens system of 6 groups including this 5 groups and the group structure beyond it is also a lens system which has the effect of this invention. Yes. In addition, in the configuration in each lens group, it goes without saying that a lens group in which an additional lens is added to the configuration in the embodiment is an equivalent lens group that has the effect of the present invention.

It is sectional drawing which shows the lens structure at the time of infinity focusing of the zoom lens which concerns on 1st Example of this invention. FIG. 5A is a diagram illustrating various aberrations with respect to the d-line at the time of focusing on infinity in the wide-angle end state of the zoom lens according to Example 1 of the present invention, and FIG. FIG. 10 is a coma aberration diagram with respect to d line when the front group G3a is moved 0.1 mm in a direction perpendicular to the optical axis in the end state. FIG. 5A is a diagram illustrating various aberrations with respect to the d-line during focusing on infinity in the intermediate focal length state on the wide angle side of the zoom lens according to the first example of the present invention, and FIG. 5B is a zoom according to the first example of the present invention. It is a coma aberration diagram with respect to the d-line when the front group G3a is moved 0.1 mm in a direction perpendicular to the optical axis in the wide-angle-side intermediate focal length state of the lens. FIG. 5A is a diagram illustrating various aberrations with respect to the d-line at the time of focusing on infinity in the intermediate focal length state on the telephoto side of the zoom lens according to the first example of the present invention, and FIG. It is a coma aberration diagram with respect to the d-line when the front group G3a is moved by 0.1 mm in the direction perpendicular to the optical axis in the telephoto side intermediate focal length state of the lens. FIG. 5A is a diagram illustrating various aberrations with respect to the d-line during focusing on infinity in the telephoto end state of the zoom lens according to the first example of the present invention, and FIG. 5B is a telephoto of the zoom lens according to the first example of the present invention. FIG. 10 is a coma aberration diagram with respect to d line when the front group G3a is moved 0.1 mm in a direction perpendicular to the optical axis in the end state. It is sectional drawing which shows the lens structure at the time of infinity focusing of the zoom lens which concerns on 2nd Example of this invention. FIG. 5A is a diagram illustrating various aberrations with respect to d-line at the time of focusing on infinity in the wide-angle end state of the zoom lens according to Example 2 of the present invention, and FIG. FIG. 10 is a coma aberration diagram with respect to d line when the front group G3a is moved 0.1 mm in a direction perpendicular to the optical axis in the end state. FIG. 6A is a diagram illustrating various aberrations with respect to the d-line at the time of focusing on infinity in the intermediate focal length state on the wide angle side of the zoom lens according to the second example of the present invention, and FIG. It is a coma aberration diagram with respect to the d-line when the front group G3a is moved by 0.1 mm in a direction perpendicular to the optical axis in a state where the lens has a wide intermediate focal length. FIG. 6A is a diagram illustrating various aberrations with respect to the d-line during focusing on infinity in the telephoto side intermediate focal length state of the zoom lens according to the second example of the present invention, and FIG. It is a coma aberration diagram with respect to the d-line when the front group G3a is moved by 0.1 mm in the direction perpendicular to the optical axis in the telephoto side intermediate focal length state of the lens. FIG. 6A is a diagram illustrating various aberrations with respect to the d-line during focusing on infinity in the telephoto end state of the zoom lens according to the second example of the present invention, and FIG. 5B is the telephoto of the zoom lens according to the second example of the present invention. FIG. 10 is a coma aberration diagram with respect to d line when the front group G3a is moved 0.1 mm in a direction perpendicular to the optical axis in the end state. It is sectional drawing which shows the lens structure at the time of infinity focusing of the zoom lens which concerns on 3rd Example of this invention. FIG. 5A is a diagram illustrating various aberrations with respect to d-line at the time of focusing on infinity in the wide-angle end state of the zoom lens according to the third example of the present invention, and FIG. 5B is the wide angle of the zoom lens according to the third example of the present invention. FIG. 10 is a coma aberration diagram with respect to d line when the front group G3a is moved 0.1 mm in a direction perpendicular to the optical axis in the end state. FIG. 5A is a diagram illustrating various aberrations with respect to the d-line at the time of focusing on infinity in the intermediate focal length state on the wide angle side of the zoom lens according to the third example of the present invention, and FIG. It is a coma aberration diagram with respect to the d-line when the front group G3a is moved 0.1 mm in a direction perpendicular to the optical axis in the wide-angle-side intermediate focal length state of the lens. FIG. 5A is a diagram illustrating various aberrations with respect to the d-line at the time of focusing on infinity in the telephoto side intermediate focal length state of the zoom lens according to the third example of the present invention, and FIG. It is a coma aberration diagram with respect to the d-line when the front group G3a is moved by 0.1 mm in the direction perpendicular to the optical axis in the telephoto side intermediate focal length state of the lens. FIG. 6A is a diagram illustrating various aberrations with respect to the d-line at the time of focusing on infinity in the telephoto end state of the zoom lens according to the third example of the present invention, and FIG. FIG. 10 is a coma aberration diagram with respect to d line when the front group G3a is moved 0.1 mm in a direction perpendicular to the optical axis in the end state.

Explanation of symbols

G1 first lens group G2 second lens group G3 third lens group G3a front group G3b in the third lens group rear group G4 in the third lens group fourth lens group G5 fifth lens group S aperture stop LPF optical low-pass filter CG cover Glass I Image plane W Wide angle end state M1 Wide angle side intermediate focal length state M2 Telephoto side intermediate focal length state T Telephoto end state

Claims (14)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power in order from the object side along the optical axis. And a fourth lens group having a positive refractive power,
When zooming from the wide-angle end state to the telephoto end state, the variable air gap between the first lens group and the second lens group increases along the optical axis in the infinite focus state, and the second lens group Variable air gap between the third lens group and the third lens group decreases, variable air gap between the third lens group and the fourth lens group decreases, and variable air between the fourth lens group and the fifth lens group decreases. The first lens group moves relative to the image plane so that the distance increases, the second lens group moves to the object side after moving once to the image plane side, and the third lens group Moves to the object side, the fourth lens group moves to the object side, the fifth lens group moves relative to the image plane,
A zoom lens satisfying the following conditional expression:
0.02 <(D5iT-D5iW) / fW ≦ 0.15
0.09 <(− f2) / fT <0.18
However,
fW: focal length of the entire zoom lens system in the wide-angle end state fT: focal length of the entire zoom lens system in the telephoto end state f2: focal length of the second lens group D5iW: in the fifth lens group in the wide-angle end state The distance D5iT from the lens surface closest to the image plane to the image plane: the distance from the lens surface closest to the image plane in the fifth lens group in the telephoto end state to the image plane   When zooming from the wide-angle end state to the telephoto end state, the fifth lens unit moves to the image plane side from the wide-angle end state to the wide-angle intermediate focal length state, and from the wide-angle intermediate focal length to the telephoto-side intermediate focal length. The zoom lens according to claim 1, wherein the zoom lens moves toward the object side and moves toward the image plane side from the telephoto side intermediate focal length to the telephoto end state. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.40 <f5 / fT <0.50
However,
fT: focal length of the entire zoom lens system in the telephoto end state f5: focal length of the fifth lens group The third lens group includes, in order from the object side along the optical axis, a front group having a positive refractive power, an aperture stop, and a rear group.
The front group consists of a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis,
The zoom lens according to any one of claims 1 to 3, wherein the rear group includes only a cemented lens of a positive lens and a negative lens in order from the object side along the optical axis. The third lens group includes, in order from the object side along the optical axis, a front group having a positive refractive power, an aperture stop, and a rear group.
The zoom lens according to any one of claims 1 to 4, wherein the following conditional expression is satisfied.
-0.50 <f3a / f3b <0.50
However,
f3a: focal length of the front group f3b: focal length of the rear group The third lens group includes, in order from the object side along the optical axis, a front group having a positive refractive power, and a rear group.
4. The zoom lens according to claim 1, wherein the image is moved by moving the front group in a direction substantially perpendicular to the optical axis. 5. The third lens group has an aperture stop,
The zoom lens according to claim 6, wherein the aperture stop is disposed between the front group and the rear group.   The zoom lens according to claim 6 or 7, wherein the front group includes only a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis. The front group consists of a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis,
The zoom lens according to claim 6, wherein the rear group includes only a cemented lens of a positive lens and a negative lens in order from the object side along the optical axis. The zoom lens according to any one of claims 6 to 9, wherein the following conditional expression is satisfied.
-0.50 <f3a / f3b <0.50
However,
f3a: focal length of the front group f3b: focal length of the rear group The zoom lens according to any one of claims 6 to 10, wherein the following conditional expression is satisfied.
0.2 <(1-β3aT) βRT <3.0
However,
β3aT: used lateral magnification of the front group in the telephoto end state βRT: used lateral magnification of the entire optical system between the front group and the image plane in the telephoto end state The fourth lens group includes only a spherical lens and includes a single lens having a positive refractive power,
The zoom lens according to any one of claims 1 to 11, wherein the following conditional expression is satisfied.
nL4P> 1.700
However,
nL4P: Refractive index with respect to d-line (wavelength λ = 587.6 nm) of the medium of the single lens   The zoom lens according to any one of claims 1 to 12, wherein all the lenses in the zoom lens are spherical lenses.   The zoom lens according to any one of claims 1 to 13, wherein the fourth lens group includes an aspherical lens.

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