JP7451232B2 - Zoom lens and imaging device - Google Patents

Description

The present invention relates to a zoom lens and an imaging device, and particularly to a zoom lens and an imaging device suitable for an imaging device using a solid-state imaging device (CCD, CMOS, etc.) such as a digital still camera or a digital video camera.

Conventionally, zoom lenses with a large aperture ratio and an F number of about 2.8 over the entire zoom range have been well known as zoom lenses for interchangeable lens imaging devices such as single-lens reflex cameras and mirrorless single-lens cameras. ing. In recent years, even small-sized imaging devices such as mirrorless single-lens cameras are equipped with large-sized imaging elements such as 35 mm full size (hereinafter referred to as full size). Even for imaging devices equipped with such large imaging elements, there is a demand for zoom lenses with smaller F-numbers.

However, in imaging devices such as surveillance cameras that have relatively small image sensors, bright zoom lenses with an F number smaller than 2.0 over the entire zoom range are also used; Among zoom lenses for interchangeable lens image pickup devices, zoom lenses with an F number smaller than 2.0 over the entire zoom range have rarely been realized.

By the way, there are two known configurations of zoom lenses: positive lead type and negative lead type. In a positive lead type zoom lens, the first lens group with positive refractive power is placed closest to the object side, and the second lens group with strong negative refractive power is placed on the image side. It is common to have a variable power effect. In a positive lead type zoom lens, it is easy to use a telephoto type refractive power arrangement as described above, and a high variable power ratio can be easily achieved, and the total optical length can be shortened compared to the focal length.

On the other hand, in a negative lead type zoom lens, the first lens group with negative refractive power is placed closest to the object side, and the second lens group with positive refractive power is placed on the image side. It is attempted to have a magnification changing effect. Although it is difficult to obtain a large zoom ratio with a negative lead type zoom lens compared to a positive lead type zoom lens, it has a configuration suitable for obtaining a zoom lens with a wide angle of view, which is called a wide-angle zoom. known as. As a negative lead type zoom lens, there are those disclosed in Patent Documents 1 to 3 that adopt a negative-positive-positive or negative-positive-negative refractive power arrangement in order from the object side.

In any of the above types of zoom lenses, if you try to realize a zoom lens with a small F number and a large aperture ratio, the lens diameter and aperture diameter will become large, the total optical length will become long, and the mechanical parts and parts associated with these will become large. The problem arises that the actuator also becomes larger, and the entire zoom lens system becomes larger.

In particular, when attempting to increase the aperture, a so-called retrofocus type refractive power arrangement, in which a lens group having a strong positive refractive power is arranged on the image side, is often adopted. In that case, the aperture diameter tends to increase, and in order to suppress this, it is important to appropriately set the power arrangement for each lens group, the lens configuration of each lens group, the aperture stop position, etc. Furthermore, when increasing the aperture, the sensitivity of the lens increases, which dramatically increases the difficulty of manufacturing. Therefore, it is required to minimize the number of lens groups that are moved during zooming to provide a simple zooming mechanism.

Looking at conventional zoom lenses from these viewpoints, the zoom lens described in Patent Document 1 achieves an F number of about 1.6. In addition, by arranging the aperture stop on the image side of the convex lens located closest to the object side of the second lens group with a relatively large air gap, the aperture diameter can be reduced. However, the size of the corresponding image sensor is small, and in order to accommodate a larger size image sensor, the effect of the lens surface that is the diverging surface placed in the second lens group is small, resulting in curvature of field and astigmatism. It becomes difficult to sufficiently correct the Further, since the positive composite refractive power disposed in the second and third lens groups is weaker than the negative refractive power disposed in the first lens group, the overall optical length cannot be sufficiently reduced.

In the zoom lens described in Patent Document 2, the third lens group includes at least one positive lens and at least one negative lens, and effectively suppresses various aberrations occurring in a wide wavelength range from the visible light region to the near-infrared region. It is possible to correct this. However, the F number at the telephoto end is as dark as 2.26 (Example 4), and the large aperture is not sufficient. Furthermore, since an aperture stop is disposed between the first lens group and the second lens group, it is difficult to reduce the aperture diameter at the telephoto end. Furthermore, as in Patent Document 1, since the positive combined refractive power disposed in the second and third lens groups is weaker than the negative refractive power disposed in the first lens group, the overall optical length is small. Not enough.

In the zoom lens described in Patent Document 3, the half angle of view at the wide-angle end is 90° or more, achieving a wide angle of view. However, the F number is dark at around 4 at the telephoto end, and the large aperture is not sufficient. In addition, in this zoom lens, a strong negative refractive power is arranged in the first lens group in order to achieve a wide angle, so as in the case of Patent Document 1 and Patent Document 2, the first lens group has Since the positive composite refractive power disposed in the second lens group and the third lens group is weak, the overall optical length cannot be sufficiently reduced.

Japanese Patent Application Publication No. 2018-66879 JP2017-129825A Japanese Patent Application Publication No. 2012-194238

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a zoom lens and an imaging device that have a large aperture, are compact overall, can employ a simple variable magnification mechanism, and have high optical performance.

In order to solve the above problems, the zoom lens according to the present invention includes, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a positive or negative refractive power. The front group F has one or more lens groups, the middle group M and the rear group R each have one lens group, and the middle group M has: It consists of, in order from the object side, an object side subgroup A that includes at least one lens having a concave lens surface on the image side, an aperture stop, and an image side subgroup B that includes at least one lens. , the air gap between the front group F and the middle group M becomes maximum, and when changing from the wide-angle end to the telephoto end, the gap between the front group F and the middle group M becomes smaller, and the gap between the front group F and the middle group M becomes the maximum. The distance between M and the rear group R becomes wider, and the distance between the lens groups constituting the front group F changes, so that when focusing from infinity to a short distance, the entire intermediate group M moves the object on the optical axis. It is characterized by moving to the side and satisfying the following conditional expression.
1.15 ≦ Hm/Hs ≦ 2.0 (1)
0.2 ≦ Ra/ft ≦ 1.3 (2)
however,
Hm: Height from the optical axis of the axial marginal ray passing through the lens surface closest to the object side of the intermediate group M when focused at infinity at the telephoto end Hs: When focused at infinity at the telephoto end, The height from the optical axis of the axial marginal ray passing through the aperture stop Ra: The radius of curvature of the lens surface having the smallest radius of curvature among the lens surfaces having a concave shape on the image side included in the object side subgroup A. ft: The above Focal length of the zoom lens in a state where the distance between the front group F and the intermediate group M on the optical axis is the minimum

Further, in order to solve the above problem, an imaging device according to the present invention is characterized by comprising the above zoom lens and an image sensor that converts an optical image formed by the zoom lens into an electrical signal. .

According to the present invention, it is possible to provide a zoom lens and an imaging device that have a large aperture, are overall compact, can employ a simple variable magnification mechanism, and have high optical performance.

FIG. 2 is a cross-sectional view of the zoom lens according to Example 1 of the present invention at a wide-angle end. FIG. 4 is a diagram of various aberrations of the zoom lens of Example 1 at the wide-angle end. FIG. 4 is a diagram of various aberrations of the zoom lens of Example 1 in an intermediate focal length state. 3 is a diagram showing various aberrations of the zoom lens of Example 1 at the telephoto end. FIG. FIG. 2 is a cross-sectional view of a zoom lens according to a second embodiment of the present invention at a wide-angle end. FIG. 7 is a diagram of various aberrations at the wide-angle end of the zoom lens of Example 2. FIG. 7 is a diagram showing various aberrations of the zoom lens of Example 2 in an intermediate focal length state. FIG. 7 is a diagram of various aberrations at the telephoto end of the zoom lens of Example 2. FIG. 7 is a cross-sectional view of a zoom lens according to a third embodiment of the present invention at a wide-angle end. FIG. 7 is a diagram of various aberrations at the wide-angle end of the zoom lens of Example 3. FIG. 7 is a diagram of various aberrations of the zoom lens of Example 3 in an intermediate focal length state. FIG. 7 is a diagram of various aberrations at the telephoto end of the zoom lens of Example 3. FIG. 4 is a cross-sectional view of a zoom lens according to a fourth embodiment of the present invention at a wide-angle end. FIG. 7 is a diagram of various aberrations at the wide-angle end of the zoom lens of Example 4. FIG. 7 is a diagram showing various aberrations of the zoom lens of Example 4 in an intermediate focal length state. FIG. 7 is a diagram of various aberrations at the telephoto end of the zoom lens of Example 4.

Embodiments of a zoom lens and an imaging device according to the present invention will be described below. However, the zoom lens and imaging device described below are one embodiment of the zoom lens and imaging device according to the present invention, and the zoom lens and imaging device according to the present invention are not limited to the following embodiments.

1. Zoom lens 1-1. Optical Configuration The zoom lens is composed of, in order from the object side, a front group F having a negative refractive power as a whole, an intermediate group M having a positive refractive power, and a rear group R having a positive or negative refractive power. Ru.

(1) Front group F
The front group F has negative refractive power as a whole, and its specific group configuration is not particularly limited as long as it includes one or more lens groups. When the front group F is composed of one lens group, that lens group is assumed to be a negative lens group. When the front group F is composed of two or more lens groups, as long as the front group F has at least one negative lens group, the other lens groups may have a negative refractive power or a positive refractive power. It may have a refractive power of

Here, the lens group refers to a group consisting of one lens or a plurality of adjacent lenses that move by the same amount of movement along the optical axis along the same trajectory during zooming, and one lens group consists of a plurality of lenses. When the lens is composed of lenses, it is assumed that the distance on the optical axis between the lenses included in one lens group does not change during zooming. Further, it is assumed that the distance between adjacent lens groups on the optical axis changes during zooming.

If the front group F is composed of two or more lens groups, the distance between each lens group on the optical axis can be changed during zooming, so the movable position of each lens group during zooming can be changed. Increased degree of design freedom. As a result, aberration fluctuations can be easily suppressed, and a zoom lens with high optical performance can be obtained. In addition, if a positive refractive power is placed in the lens group located closest to the object side in the front group F, it becomes a positive lead type refractive power arrangement, resulting in a high zoom ratio, a small aperture diameter, and an overall optical length. The configuration allows for easy miniaturization. Furthermore, when a negative refractive power is arranged in the lens group disposed closest to the object side of the front group F, the refractive power arrangement becomes a negative lead type, which is an easy configuration for obtaining a zoom lens with a wide angle of view.

(2) Intermediate group M
The intermediate group M is a lens group having positive refractive power and is composed of one lens group. In this zoom lens, the aperture stop is arranged within the intermediate group M. Here, a group consisting of lenses arranged closer to the object side than the aperture stop is referred to as an object side partial group A, and a group consisting of lenses arranged closer to the image side than the aperture stop is referred to as an image side partial group B. In the intermediate group M, the object side subgroup A, the aperture stop, and the image side subgroup B move together on the optical axis during zooming. That is, the intermediate group M including the object-side partial group A and the image-side partial group B is configured as one lens group. Furthermore, the aperture diaphragm also moves together with the object side subgroup A and the image side subgroup B on the optical axis during zooming, and the object side subgroup A and the aperture diaphragm, and the aperture diaphragm and the image side subgroup B It is assumed that the distance on the optical axis does not change when changing the magnification. By configuring the intermediate group M in this manner and moving the intermediate group M together as a unit during zooming, the number of lens groups to be moved during zooming is reduced, and the zooming mechanism can be simplified. At the same time, manufacturing errors can be made less likely to occur.

Both the object side subgroup A and the image side subgroup B have positive refractive power. This makes it possible to create a bright zoom lens with an F number of around 1.4 and a large aperture ratio, while also making it possible to reduce the diameter of the aperture, making it easier to make the diaphragm mechanism for opening and closing the aperture diaphragm smaller and lighter. , the entire zoom lens can be made smaller and lighter.

The object side subgroup A includes at least one lens having a concave lens surface on the image side. By arranging such a lens in the object-side partial group A, which is arranged closer to the object side than the aperture stop in the intermediate group M, it becomes easy to satisfactorily correct spherical aberration and curvature of field. Further, it is preferable that the most object-side lens surface of the object-side subgroup A has a convex shape toward the object side. With such a lens shape, it becomes easy to reduce the aperture diameter.

Although the specific lens configuration of the image-side subgroup B is not particularly limited, it is preferably composed of at least two negative lenses and at least two positive lenses. By configuring the image-side subgroup B in this manner, it becomes easy to realize a zoom lens with little variation in aberrations such as spherical aberration and curvature of field over the entire object distance.

(3) Rear group R
Similarly to the middle group M, the rear group R is also composed of one lens group. That is, it is assumed that the distance between the lenses constituting the rear group R on the optical axis does not change during zooming. The refractive power of the rear group R may be positive or negative, but is more preferably negative. By setting the rear group R to have a negative refractive power, it becomes easy to satisfactorily correct the curvature of field in the under direction that occurs in the intermediate group M.

Although the specific lens configuration of the rear group R is not particularly limited, it is preferable to have at least one positive lens and at least one negative lens. By configuring the rear group R in this way, it is possible to satisfactorily correct field curvature for off-axis light beams. Further, it is preferable that the rear group R includes an air lens having negative refractive power. The air lens is formed by two opposing lens surfaces of two lenses arranged adjacent to each other with an interval on the optical axis. By configuring the rear group R to include an air lens having negative refractive power, it becomes easy to satisfactorily correct the curvature of field in the under direction that occurs in the intermediate group M.

1-2. Operation (1) Magnification Variation The zoom lens adopts the above-mentioned configuration, and changes the magnification by changing the distance between the front group F, the intermediate group M, and the rear group R on the optical axis. At that time, each lens group is moved so that the distance on the optical axis between the front group F and middle group M is maximum at the wide-angle end, and the distance on the optical axis between the middle group M and rear group R is maximum at the telephoto end. let By moving each lens group in this way, the power of the front group F is not forced to be strong, and it becomes easy to obtain good optical performance over the entire zoom range.

When the front group F has two or more lens groups, the distance between each lens group on the optical axis changes during zooming, as described above. At this time, all the lens groups constituting the front group F may move in the optical axis direction, or some of the lens groups may be fixed in the optical axis direction. However, it is preferable that the lens group having the strongest negative refractive power among the lens groups constituting the front group F be moved toward the image side during zooming from the wide-angle end to the telephoto end. By moving in this way, it becomes difficult to strain the magnification change burden of each lens group, and it becomes easy to achieve both a high zoom ratio and high performance.

As described above, the intermediate group M constitutes one lens group by the object-side partial group A and the image-side partial group B, so that they move together in the optical axis direction during zooming.
The rear group R may also be moved in the optical axis direction during zooming, but it is more preferably fixed. By making the rear group R a fixed group, the number of lens groups to be moved during zooming is reduced, and the zooming mechanism can be simplified. At the same time, manufacturing errors can be made less likely to occur.

(2) Focusing In this zoom lens, when focusing from infinity to close distance, the entire intermediate group M moves on the optical axis toward the object side. By using the entire intermediate group M having an aperture stop as a focus group, it becomes easy to obtain a zoom lens with little variation in field curvature over the entire object distance range from infinity to short distances. At this time, it is preferable that the front group F and the rear group R be fixed in the optical axis direction during focusing. In particular, if the rear group R is fixed in the optical axis direction both during zooming and focusing, there is no need for a mechanism to move the lens group located closest to the image side of the zoom lens in the optical axis direction. It becomes easier to simplify the mechanism and realize a zoom lens with fewer manufacturing errors.

1-3. Conditional Expression It is desirable that the zoom lens adopts the above-mentioned configuration and satisfies at least one conditional expression described below.

1-3-1. Conditional expression (1)
1.15 ≦ Hm/Hs ≦ 2.0 (1)
however,
Hm: Height from the optical axis of the axial marginal ray passing through the lens surface closest to the object side of the intermediate group M when focusing on infinity at the telephoto end Hs: When focusing on infinity at the telephoto end, Height from the optical axis of the axial marginal ray passing through the aperture stop

The above conditional expression (1) is based on the height of the axial marginal ray passing through the lens surface closest to the object of the intermediate group M and the height of the axial marginal ray passing through the aperture stop when focusing at infinity at the telephoto end. This is a conditional expression that defines the ratio. By satisfying conditional expression (1), it becomes easy to reduce the size of the aperture diaphragm and to reduce the size and weight of the diaphragm mechanism.

On the other hand, if the value of conditional expression (1) becomes less than the lower limit value, it becomes difficult to reduce the diameter of the aperture stop, so the aperture stop and the stop mechanism become larger. On the other hand, if the value of conditional expression (1) exceeds the upper limit, the positive refractive power of the object side subgroup A becomes too strong, making it difficult to satisfactorily correct spherical aberration.

In order to obtain the above effects, the upper limit of conditional expression (1) is preferably 1.8, more preferably 1.7, and even more preferably 1.6. Further, the lower limit of conditional expression (1) is preferably 1.2, more preferably 1.25, and even more preferably 1.3. Note that when these preferable lower limit values or upper limit values are adopted, the inequality sign with an equal sign (≦) may be replaced with an inequality sign (<) in conditional expression (1). The same principle applies to other conditional expressions.

1-3-2. Conditional expression (2)
0.2 ≦ Ra/ft ≦ 1.3 (2)
however,
Ra: The radius of curvature of the lens surface with the smallest radius of curvature among the lens surfaces having a concave shape on the image side included in the object side subgroup A. ft: The distance on the optical axis between the front group F and the intermediate group M is the minimum. Focal length of the zoom lens when

Conditional expression (2) is a conditional expression for defining the radius of curvature of the lens surface having the smallest radius of curvature among the lens surfaces included in the object side subgroup A and having a concave shape on the image side. By satisfying conditional expression (2), it becomes easy to realize a bright zoom lens with an F number of about 1.4 and a large aperture ratio, while also satisfactorily correcting spherical aberration.

On the other hand, if the value of conditional expression (2) is less than the lower limit value, the diverging effect of the lens surface becomes too strong, making it difficult to satisfactorily correct spherical aberration. On the other hand, if the value of conditional expression (2) exceeds the upper limit, the diverging effect of the lens surface becomes weaker, making it impossible to increase the positive refractive power of the object-side subgroup A. It becomes difficult to make the diaphragm smaller, and the aperture mechanism also becomes larger accordingly.

In order to obtain the above effects, the upper limit of conditional expression (2) is preferably 1.2, more preferably 1.1, and even more preferably 1.0. Further, the lower limit of conditional expression (2) is preferably 0.35, more preferably 0.4, and even more preferably 0.45.

Here, in the zoom lens, it is preferable that the distance between the front group F and the intermediate group M on the optical axis be the minimum at the telephoto end. That is, it is preferable that the above "ft" is the focal length of the zoom lens at the telephoto end. Furthermore, when the distance between the front group F and the middle group M on the optical axis is the minimum, the distance between the front group F and the middle group M on the optical axis is "D", and the total optical length at this time is " L", the ratio "D/L" between the two is preferably 0.12 or less. By satisfying this condition, the zoom lens can easily secure a desired zoom ratio even though it has a large aperture. At this time, "D/L" is preferably 0.10 or less. Note that the same applies to other expressions including ft.

1-3-3. Conditional expression (3)
-3.0 ≦ (Rrf + Rrb) / (Rrf - Rrb) ≦ 2.0 (3)
however,
Rrf: radius of curvature of the object side surface forming the air lens Rrb: radius of curvature of the image side surface forming the air lens

As mentioned above, the rear group R preferably includes an air lens having negative refractive power. When the rear group R includes such an air lens, it is preferable that the air lens has a shape that satisfies the above conditional expression (3). By arranging an air lens having a shape that satisfies conditional expression (3) in the rear group R, it becomes easy to satisfactorily correct field curvature over the entire zoom range.

On the other hand, when the value of conditional expression (3) becomes less than the lower limit value, the diverging effect of the air lens becomes weaker, and it becomes difficult to satisfactorily correct the curvature of field in the under direction that occurs in the intermediate group M. Become. On the other hand, if the value of conditional expression (3) exceeds the upper limit, the divergence effect of the air lens becomes too strong and the curvature of field of the entire zoom lens system tends to be excessive, which is not preferable.

In order to obtain the above effects, the upper limit of conditional expression (3) is preferably 1.7, more preferably 1.4, and even more preferably 1.2. Further, the lower limit of conditional expression (3) is preferably −2.5, more preferably −2.0, and even more preferably −1.7.

1-3-4. Conditional expression (4)
0.3 ≦ BF/Y ≦ 1.5 (4)
however,
BF: Back focus of the zoom lens at the wide-angle end Y: Maximum image height of the zoom lens

The above conditional expression (4) is a conditional expression for defining the back focus at the wide-angle end with respect to the maximum image height of the zoom lens. By satisfying conditional expression (4), the back focus becomes short at the wide-angle end, the total optical length can be shortened, and a compact zoom lens can be realized.

On the other hand, when the value of conditional expression (4) becomes less than the lower limit value, the back focus becomes too short and the inclination angle with respect to the light incident on the image sensor becomes too large. Therefore, there is a problem in that peripheral light reduction (shading) due to a mismatch between the on-chip microlens provided to efficiently receive incident light in the image sensor and the exit pupil of the zoom lens becomes noticeable. On the other hand, if the value of conditional expression (4) exceeds the upper limit, the back focus becomes too long, making it difficult to shorten the total optical length of the zoom lens at the wide-angle end.

In order to obtain the above effect, the upper limit of conditional expression (4) is preferably 1.3, more preferably 1.2, and even more preferably 1.1. Furthermore, the lower limit of conditional expression (4) is preferably 0.4, more preferably 0.5.

1-3-5. Conditional expression (5)
0.5 ≦ fa/fb ≦ 3.0 (5)
however,
fa: Focal length of object side subgroup A fb: Focal length of image side subgroup B

Conditional expression (5) is a conditional expression for defining the ratio of the focal length of the object side subgroup A to the focal length of the image side subgroup B. By satisfying conditional expression (5), the diameter of the aperture stop can be reduced, and a zoom lens with higher optical performance can be obtained.

On the other hand, if the value of conditional expression (5) is less than the lower limit value, it is advantageous in reducing the diameter of the aperture stop, but it is also possible to effectively correct the field curvature in the under direction that occurs in the object side subgroup A. It becomes difficult to do so. On the other hand, if the value of conditional expression (5) exceeds the upper limit, it becomes difficult to reduce the diameter of the aperture stop.

In order to obtain the above effect, the upper limit of conditional expression (5) is preferably 2.7, more preferably 2.4, even more preferably 2.2, and even more preferably 2.0. It is even more preferable. Further, the lower limit of conditional expression (5) is preferably 0.55, more preferably 0.6, and even more preferably 0.65.

1-3-6. Conditional expression (6)
0.5 ≦ Rmf/ft ≦ 2.2 (6)
however,
Rmf: radius of curvature of the lens surface located closest to the object in the intermediate group M

The above conditional expression (6) expresses the radius of curvature of the lens surface closest to the object side of the intermediate group M with respect to the focal length (ft) of the zoom lens in a state where the distance between the front group F and the intermediate group M on the optical axis is the minimum. This is a conditional expression for defining the ratio. By satisfying conditional expression (6), the diameter of the aperture stop can be reduced and a zoom lens with higher optical performance can be obtained.

On the other hand, if the value of conditional expression (6) is less than the lower limit, it is advantageous in reducing the diameter of the aperture stop, but the under effect of spherical aberration becomes too strong, making it difficult to correct it. . On the other hand, if the value of conditional expression (6) exceeds the upper limit, it becomes difficult to reduce the diameter of the aperture stop.

In order to obtain the above effect, the upper limit of conditional expression (6) is preferably 2.3, more preferably 2.1, even more preferably 2.0, and even more preferably 1.9. It is even more preferable. Further, the lower limit of conditional expression (6) is preferably 0.6, more preferably 0.65, and even more preferably 0.7.

1-3-7. Conditional expression (7)
-1.8 ≦ Rmr/ft ≦ -0.2 (7)
however,
Rmr: radius of curvature of the lens surface located closest to the image side in the intermediate group M

Conditional expression (7) is expressed as This is a conditional expression for defining the ratio of curvature radii. By satisfying conditional expression (7), it is possible to obtain a zoom lens with higher optical performance while increasing the aperture.

On the other hand, if the value of conditional expression (7) becomes less than the lower limit value, it becomes easy to maintain the balance between spherical aberration and comatic aberration, but it is necessary to reduce the image-side NA (numerical aperture) of the intermediate group M. Therefore, it becomes difficult to reduce the F number of the zoom lens. On the other hand, if the value of conditional expression (7) exceeds the upper limit, it will be easy to reduce the F number of the zoom lens, but it will be difficult to correct spherical aberration and coma while maintaining a balance between them. become.

In order to obtain the above effects, the upper limit of conditional expression (7) is preferably −0.25, more preferably −0.3, and even more preferably −0.35. Further, the lower limit of conditional expression (7) is preferably −1.6, more preferably −1.5, and even more preferably −1.4.

1-3-8. Conditional expression (8)
-4.0 ≦ ff/fm ≦ -1.0 (8)
however,
ff: Focal length of front group F at wide-angle end fm: Focal length of intermediate group M

The above conditional expression (8) is a conditional expression for defining the ratio of the focal length of the front group F to the focal length of the intermediate group M. By satisfying conditional expression (8), it is possible to obtain a zoom lens with higher optical performance while reducing the total optical length.

On the other hand, when the value of conditional expression (8) becomes less than the lower limit, the total optical length becomes longer, especially at the wide-angle end, and the effective diameter of the lens forming the front group F becomes larger, so the size of the zoom lens becomes smaller. becomes difficult. On the other hand, if the value of conditional expression (8) exceeds the upper limit, it is advantageous for downsizing the zoom lens, but it becomes difficult to suppress fluctuations in field curvature due to changes in object distance. .

In order to obtain the above effect, the upper limit of conditional expression (8) is preferably −1.1, more preferably −1.2, and even more preferably −1.3. Further, the lower limit of conditional expression (8) is preferably −3.6, more preferably −3.3, and even more preferably −3.0.

1-3-9. Conditional expression (9)
0.8 ≦ fm/fw ≦ 2.5 (9)
however,
fm: Focal length of intermediate group M fw: Focal length of the zoom lens at the wide-angle end

Conditional expression (9) is a conditional expression for defining the ratio of the focal length of the intermediate group M to the focal length of the entire system at the wide-angle end. By satisfying conditional expression (9), it is possible to optimize the zooming load on the intermediate group M and obtain a zoom lens with higher optical performance.

On the other hand, if the value of conditional expression (9) becomes less than the lower limit value, the refractive power of the intermediate group M, which is the focus group, becomes too strong, and the fluctuations in spherical aberration and curvature of field due to changes in object distance are suppressed. It becomes difficult to suppress. On the other hand, if the value of conditional expression (9) exceeds the upper limit, the burden of variable magnification on the intermediate group M becomes small, making it difficult to achieve the required variable magnification ratio. In order to increase the variable power ratio, it is necessary to increase the negative refractive power disposed in the front group F. If the negative refractive power disposed in the front group F becomes too large, variations in field curvature due to changes in object distance will become large.

In order to obtain the above effects, the upper limit of conditional expression (9) is preferably 2.4, more preferably 2.3, and even more preferably 2.2. Further, the lower limit of conditional expression (9) is preferably 0.9, more preferably 1.0, and even more preferably 1.1.

2. Imaging Device Next, an imaging device according to the present invention will be described. An imaging device according to the present invention is characterized by comprising the zoom lens according to the present invention, and an image sensor that converts an optical image formed by the zoom lens into an electrical signal. Note that the image sensor is preferably provided on the image side of the zoom lens.

Here, there is no particular limitation on the image sensor, and a solid-state image sensor such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used. The imaging device according to the present invention is suitable for imaging devices using these solid-state imaging devices, such as digital cameras and video cameras. Further, the imaging device can be applied to various imaging devices such as a single-lens reflex camera, a mirrorless single-lens camera, a digital still camera, a surveillance camera, a vehicle-mounted camera, and a drone-mounted camera. Furthermore, these imaging devices may be of an interchangeable lens type, or may be of a fixed lens type in which the lens is fixed to a housing. In particular, the zoom lens according to the present invention is suitable as a zoom lens for an imaging device equipped with a large-sized image sensor, such as a full-size image sensor. Although the zoom lens has a large aperture with an F number of approximately 1.4 over the entire zoom range, it is compact overall, can use a simple zoom mechanism, and has high optical performance. Even when used as a zoom lens for such an imaging device, high-quality captured images can be obtained.

Next, the present invention will be specifically explained with reference to Examples. However, the present invention is not limited to the following examples.

(1) Optical configuration FIG. 1 shows a cross-sectional view of the zoom lens of Example 1. As shown in FIG. 1, the zoom lens includes, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a rear group R having a negative refractive power. It consists of

In the zoom lens of Example 1, the front group F is composed only of the first lens group G1 having negative refractive power. The intermediate group M and the rear group R are each composed of one lens group. During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the intermediate group M moves toward the object side, and the rear group R is fixed in the optical axis direction. Further, the distance between the front group F and the intermediate group M on the optical axis is maximum at the wide-angle end, and the distance between the intermediate group M and the rear group R on the optical axis is maximum at the telephoto end. Further, when focusing from infinity to a short distance, the entire intermediate group M moves on the optical axis toward the object, and the front group F and the rear group R are fixed in the optical axis direction. The configuration of each lens group will be explained below.

The first lens group G1 includes, in order from the object side, a negative meniscus lens L1 with a convex surface facing the object side, a negative meniscus lens L2 with a concave surface facing the object side, and a positive meniscus lens L3 with a convex surface facing the object side. It consists of The negative meniscus lens L1 is a glass molded aspherical lens having aspherical surfaces on both sides.

The intermediate group M includes, in order from the object side, a biconvex lens L4, a cemented lens made of a biconvex lens L5 and a biconcave lens L6, a cemented lens made of a biconvex lens L7 and a biconcave lens L8, and a concave surface facing the object side. It is composed of a cemented lens in which a positive meniscus lens L9 and a biconcave lens L10 are cemented together, a cemented lens in which a biconvex lens L11 and a biconcave lens L12 are cemented together, and a biconvex lens L13. The biconvex lens L5 is a glass molded aspherical lens whose object side surface is aspherical. The biconvex lens L13 is a glass-molded aspherical lens having aspherical surfaces on both sides. The aperture diaphragm S is arranged between the biconcave lens L8 and the positive meniscus lens L9, and the lens arranged on the object side of the aperture diaphragm S in the intermediate group M constitutes the object side subgroup A according to the present invention. , lenses disposed on the image side of the aperture stop S constitute an image side subgroup B according to the present invention.

The rear group R includes, in order from the object side, a biconvex lens L14, a negative meniscus lens L15 with a convex surface facing the object side, and a negative meniscus lens L16 with a concave surface facing the object side. The negative meniscus lens L15 is a glass molded aspherical lens with aspherical surfaces on both sides. The rear group R has a biconvex air lens formed by the image side surface of the negative meniscus lens L15 and the object side surface of the negative meniscus lens L16. The air lens has negative refractive power.

In FIG. 1, "IP" is an image plane, and specifically indicates the imaging plane of a solid-state image sensor such as a CCD sensor or CMOS sensor, or the film plane of a silver halide film. Further, a cover glass CG or the like is provided on the object side of the IP. This point is also the same in each lens cross-sectional view shown in other examples, so the explanation will be omitted hereafter.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Below, "lens data", "specification table", "variable interval", "aspheric coefficient", and "lens group data" are shown. Further, the values of each conditional expression (Table 1) and various numerical values used to determine the value of each conditional expression (Table 2) are shown together after Example 4.

In "lens data", "surface number" is the order of the lens surface counted from the object side, "r" is the radius of curvature of the lens surface, "d" is the lens thickness or air gap on the optical axis, and "nd" is The refractive index “νd” at the d-line (wavelength λ=587.6 nm) indicates the Abbe number at the d-line. Furthermore, in the "Surface Number" column, "ASPH" added next to the surface number indicates that the lens surface is an aspheric surface, and "S" indicates that the surface is an aperture stop. In the "d" column, "d(0)", "d(6)", etc. indicate that the distance between the lens surfaces on the optical axis is a variable distance that changes when changing the magnification. Further, "∞" in the radius of curvature column means infinity, and means that the lens surface is flat.

In the "specification table", "f" is the focal length of the zoom lens, "FNo." is the F number, "ω" is the half angle of view, and "Y" is the maximum image height. The values are shown at the wide-angle end, intermediate focal length, and telephoto end, respectively.

In "variable interval", values are shown for infinity focusing at the wide-angle end, intermediate focal length, and telephoto end, and for finite object focusing (object distance 500 mm). Note that the object distance refers to the distance from the object plane to the image plane. The same applies to other embodiments.

"Aspheric coefficient" indicates an aspheric coefficient when an aspheric shape is defined as follows. However, x is the displacement from the reference plane in the optical axis direction, r is the paraxial radius of curvature, H is the height from the optical axis in the direction perpendicular to the optical axis, k is the conic coefficient, and An is the n-th order aspheric surface. Let it be a coefficient. Further, in the table of "aspherical coefficients", "E±XX" represents an index notation and means "×10 ^±XX ".

Since the items in each of these tables are the same in each table shown in other examples, the explanation will be omitted below.

Further, FIGS. 2, 3, and 4 show longitudinal aberration diagrams of the zoom lens when focusing on an object at infinity at the wide-angle end, intermediate focal length, and telephoto end. The longitudinal aberration diagrams shown in each figure show spherical aberration (mm), astigmatism (mm), and distortion aberration (%) in order from the left side as viewed from the drawing. In the spherical aberration diagram, the solid line shows the spherical aberration at the d-line (wavelength 587.56 nm), the broken line shows the spherical aberration at the C-line (wavelength 656.28 nm), and the dashed-dot line shows the spherical aberration at the g-line (wavelength 435.84 nm). In the astigmatism diagram, the vertical axis is the half angle of view (ω), the horizontal axis is the defocus, the solid line shows the sagittal image plane (ds) of the d-line, and the broken line shows the meridional image plane (dm) of the d-line. show. In the distortion aberration diagram, the vertical axis is the half angle of view (ω), and the horizontal axis is the distortion aberration. Since these matters are the same in each aberration diagram shown in other examples, their explanation will be omitted below.

(lens data)
Surface number rd nd νd
Object plane ∞ d(0)
1ASPH 208.0366 2.5000 1.69350 53.18
2ASPH 43.1440 14.7464
3 -170.0000 2.5000 1.48749 70.44
4 -500.0000 0.1500
5 75.4314 4.4049 1.91082 35.25
6 135.3954 d(6)
7 52.9863 7.4329 1.92286 20.88
8 -587.2022 0.1500
9ASPH 131.9915 6.7000 1.85135 40.10
10 -69.0480 1.5000 1.76182 26.52
11 26.6232 0.1500
12 26.9862 10.6601 1.87070 40.73
13 -81.6597 1.5000 1.76182 26.52
14 29.3525 5.9088
15S ∞ 1.7455
16 -470.2024 7.2585 1.55032 75.50
17 -22.0352 1.3000 1.80518 25.46
18 72.0913 0.1500
19 43.6868 6.8300 1.77250 49.62
20 -67.0118 1.3000 1.84666 23.78
21 70.2743 1.4367
22ASPH 78.6661 6.4470 2.00178 19.32
23ASPH -44.0721 d(23)
24 170.0607 5.0000 1.49700 81.61
25 -71.3608 0.1500
26ASPH 27.7497 1.5000 1.88202 37.22
27ASPH 21.7485 6.3203
28 -52.8123 2.0000 1.64769 33.79
29 -127.3247 13.5000
30 ∞ 2.5000 1.51680 64.20
31 ∞ 1.0000
Image plane ∞

(Specifications table)
Wide-angle end Intermediate Telephoto end
f 36.0000 41.9995 48.4990
FNo. 1.4497 1.4499 1.4501
ω 31.3763 27.0233 23.5165
Y 21.6330 21.6330 21.6330

(variable interval)
Wide-angle end Intermediate Telephoto end Wide-angle end Intermediate Telephoto end
d(0) ∞ ∞ ∞ 320.0000 343.1586 361.0361
d(6) 56.9844 31.1762 10.4159 53.1128 25.6628 2.0714
d(23) 6.2746 8.9240 11.8069 10.1462 14.4374 20.1515

(Aspheric coefficient)
Surface number k A4 A6 A8 A10 A12
1 0.0000 -4.73868E-07 5.76767E-11 2.35266E-15 -8.19880E-19 0.00000E+00
2 0.0000 -8.98773E-07 -6.08068E-10 1.91595E-13 -2.25493E-16 0.00000E+00
9 0.0000 -2.04937E-06 -4.47485E-10 2.56633E-13 2.64628E-17 0.00000E+00
22 0.0000 -3.67660E-06 3.92915E-10 -1.33523E-11 3.92607E-15 0.00000E+00
23 0.0000 -4.65247E-07 1.75590E-09 -1.19419E-11 0.00000E+00 0.00000E+00
26 0.0000 -5.19037E-05 7.29161E-08 -4.61509E-11 -8.66177E-14 0.00000E+00
27 0.0000 -5.68629E-05 7.56871E-08 -5.08331E-11 -1.76677E-13 0.00000E+00

(lens group data)
Group number Focal length
F -119.0535
M 53.6068
R -237.4300

(1) Optical configuration FIG. 5 shows a cross-sectional view of the zoom lens of Example 2. As shown in FIG. 5, the zoom lens includes, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a rear group R having a negative refractive power. It consists of

In the zoom lens of Example 2, the front group F is composed only of the first lens group G1 having negative refractive power. The intermediate group M and the rear group R are each composed of one lens group. During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the intermediate group M moves toward the object side, and the rear group R is fixed in the optical axis direction. Further, the distance between the front group F and the intermediate group M on the optical axis is maximum at the wide-angle end, and the distance between the intermediate group M and the rear group R on the optical axis is maximum at the telephoto end. Further, when focusing from infinity to a short distance, the entire intermediate group M moves on the optical axis toward the object, and the front group F and the rear group R are fixed in the optical axis direction. The configuration of each lens group will be explained below.

The first lens group G1 includes, in order from the object side, a negative meniscus lens L1 with a convex surface facing the object side, a negative meniscus lens L2 with a convex surface facing the object side, a biconcave lens L3, and a biconvex lens L4. Ru. The negative meniscus lens L2 is a glass molded aspherical lens having aspherical surfaces on both sides.

The intermediate group M includes, in order from the object side, a positive meniscus lens L5 with a convex surface facing the object side, a cemented lens made by cementing a biconvex lens L6 and a biconcave lens L7, a positive meniscus lens L8 with a convex surface facing the object side, and the object. A cemented lens in which a negative meniscus lens L9 with a convex surface facing the side is cemented, a cemented lens in which a biconvex lens L10 and a biconcave lens L11 are cemented, a cemented lens in which a biconvex lens L12 and a biconcave lens L13 are cemented, and a biconvex lens L14. configured. The positive meniscus lens L5 is a glass molded aspherical lens whose object side surface is aspherical. The biconvex lens L14 is a glass molded aspherical lens having aspherical surfaces on both sides. The aperture diaphragm S is arranged between the negative meniscus lens L9 and the biconvex lens L10, and the lens arranged on the object side of the aperture diaphragm S in the intermediate group M constitutes the object side subgroup A according to the present invention. , lenses disposed on the image side of the aperture stop S constitute an image side subgroup B according to the present invention.

The rear group R includes, in order from the object side, a biconvex lens L15, a biconcave lens L16, and a negative meniscus lens L17 with a concave surface facing the object side. The negative meniscus lens L17 is a glass molded aspherical lens whose both surfaces are aspherical. The rear group R has a biconvex air lens formed by the image side surface of the biconcave lens L16 and the object side surface of the negative meniscus lens L17. The air lens has negative refractive power.

(2) Numerical Example Next, as a numerical example applying specific numerical values of the zoom lens, "lens data", "specification table", "variable interval", "aspheric coefficient", "lens group data" ” is shown. Further, FIGS. 6, 7, and 8 show longitudinal aberration diagrams of the zoom lens when focusing on an object at infinity at the wide-angle end, intermediate focal length, and telephoto end.

(lens data)
Surface number rd nd νd
Object plane ∞ d(0)
1 329.0942 2.5000 1.69680 55.46
2 45.6109 6.0000
3ASPH 99.8315 2.2000 1.69350 53.18
4ASPH 44.9764 12.9696
5 -808.0584 2.0000 1.49700 81.61
6 122.9480 0.1500
7 62.8322 10.0000 1.51742 52.43
8 -324.2464 d(8)
9ASPH 51.5805 5.8000 2.00178 19.32
10 334.9596 0.1500
11 53.8878 6.5000 1.88300 40.80
12 -174.7829 1.5000 1.75520 27.53
13 28.7542 2.5000
14 42.0953 3.9208 1.87070 40.73
15 114.8657 1.5000 1.72825 28.46
16 53.8149 3.9971
17S ∞ 1.5000
18 83.3970 7.9089 1.49700 81.61
19 -25.7217 1.3000 1.92286 20.88
20 44.8048 0.1500
21 39.5238 7.8409 1.72916 54.67
22 -43.6143 1.3000 1.85478 24.80
23 92.0109 4.1679
24ASPH 100.5923 6.8408 2.00178 19.32
25ASPH -40.1920 d(25)
26 29.3028 8.6958 1.49700 81.61
27 -85.5083 0.1500
28 -324.4041 1.3000 1.62004 36.26
29 25.2345 6.9795
30ASPH -92.8503 2.0000 1.88202 37.22
31ASPH -144.4884 13.5003
32 ∞ 2.5000 1.51680 64.20
33 ∞ 1.0000
Image plane ∞

(Specifications table)
Wide-angle end Intermediate Telephoto end
f 24.7005 32.0004 33.9997
FNo. 1.4497 1.4500 1.4501
ω 42.2378 33.3403 31.5208
Y 21.6330 21.6330 21.6330

(variable interval)
Wide-angle end Intermediate Telephoto end Wide-angle end Intermediate Telephoto end
d(0) ∞ ∞ ∞ 320.0000 345.3090 349.9140
d(8) 49.6756 18.5628 12.3734 47.5262 14.4032 7.2487
d(25) 1.5031 7.3054 8.8915 3.6525 11.4651 14.0162

(Aspheric coefficient)
Surface number k A4 A6 A8 A10 A12
3 -7.0352 2.83823E-06 -4.76570E-09 4.39545E-12 -1.56944E-15 0.00000E+00
4 -4.1630 7.03826E-06 -8.66714E-09 7.63232E-12 -2.86431E-15 0.00000E+00
9 0.0000 -5.67200E-07 -4.50542E-11 -3.79457E-13 3.44884E-16 0.00000E+00
24 0.0000 -2.47743E-06 1.49290E-09 -9.20107E-12 3.26671E-15 0.00000E+00
25 0.0000 9.52507E-07 3.00697E-10 -5.70088E-12 0.00000E+00 0.00000E+00
30 0.0000 -2.65938E-05 4.25695E-08 -7.90330E-11 2.67121E-13 0.00000E+00
31 0.0000 -1.51357E-05 4.21053E-08 1.67665E-11 1.00172E-13 0.00000E+00

(lens group data)
Group number Focal length
F -67.4147
M 51.6675
R -241.5591

(1) Optical configuration FIG. 9 shows a cross-sectional view of the zoom lens of Example 3. As shown in FIG. 9, the zoom lens includes, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a rear group R having a positive refractive power. It consists of

In the zoom lens of Example 3, the front group F is composed only of the first lens group G1 having negative refractive power. The intermediate group M and the rear group R are each composed of one lens group. During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the intermediate group M moves toward the object side, and the rear group R is fixed in the optical axis direction. Further, the distance between the front group F and the intermediate group M on the optical axis is maximum at the wide-angle end, and the distance between the intermediate group M and the rear group R on the optical axis is maximum at the telephoto end. Further, when focusing from infinity to a short distance, the entire intermediate group M moves on the optical axis toward the object, and the front group F and the rear group R are fixed in the optical axis direction. The configuration of each lens group will be explained below.

The first lens group G1 includes, in order from the object side, a negative meniscus lens L1 with a convex surface facing the object side, a biconcave lens L2, and a positive meniscus lens L3 with a convex surface facing the object side. The negative meniscus lens L1 is a glass molded aspherical lens having aspherical surfaces on both sides.

The intermediate group M includes, in order from the object side, a positive meniscus lens L4 with a convex surface facing the object side, a cemented lens made of a biconvex lens L5 and a biconcave lens L6, and a cemented lens made of a biconvex lens L7 and a biconcave lens L8. , a cemented lens in which a biconvex lens L9 and a biconcave lens L10 are cemented together, a cemented lens in which a positive meniscus lens L11 with a concave surface facing the object side and a biconcave lens L12 are cemented together, and a cemented lens in which a biconvex lens L13 and a biconcave lens L14 are cemented together. , a biconvex lens L15. The positive meniscus lens L4 is a glass molded aspherical lens whose both surfaces are aspherical. The biconvex lens L15 is a glass molded aspherical lens having aspherical surfaces on both sides. The aperture diaphragm S is disposed between the biconcave lens L10 and the positive meniscus lens L11, and the lens disposed on the object side of the aperture diaphragm S in the intermediate group M constitutes the object side subgroup A according to the present invention. , lenses disposed on the image side of the aperture stop S constitute an image side subgroup B according to the present invention.

The rear group R includes, in order from the object side, a biconvex lens L16, a negative meniscus lens L17 with a convex surface facing the object side, and a cemented lens formed by cementing a biconcave lens L18 and a biconvex lens L19. The negative meniscus lens L17 is a glass molded aspherical lens whose both surfaces are aspherical. It has a convex air lens formed by the image side surface of the negative meniscus lens L17 and the object side surface of the biconcave lens L18. The air lens has negative refractive power.

(2) Numerical Example Next, as a numerical example applying specific numerical values of the zoom lens, "lens data", "specification table", "variable interval", "aspheric coefficient", "lens group data" ” is shown. Further, FIGS. 6, 7, and 8 show longitudinal aberration diagrams of the zoom lens when focusing on an object at infinity at the wide-angle end, intermediate focal length, and telephoto end.

(lens data)
Surface number rd nd νd
Object plane ∞ d(0)
1ASPH 198.8974 2.5000 1.69350 53.18
2ASPH 40.5849 13.7317
3 -307.9897 2.0000 1.48749 70.44
4 361.8935 0.1500
5 68.2433 4.7487 1.91082 35.25
6 120.9279 d(6)
7ASPH 46.3704 6.0224 1.85135 40.10
8ASPH 156.4506 0.8709
9 59.3410 8.0191 1.87070 40.73
10 -115.6536 1.0000 1.67300 38.26
11 33.3190 1.9557
12 42.8689 6.6933 1.87070 40.73
13 -238.3599 1.0000 1.64769 33.79
14 26.4862 2.8681
15 50.3199 5.1426 1.87070 40.73
16 -133.5555 1.0000 1.69895 30.13
17 62.7002 3.3342
18S ∞ 2.0278
19 -196.4788 6.1739 1.49700 81.61
20 -22.2376 1.0000 1.78880 28.43
21 52.9706 0.1500
22 42.7152 10.8079 1.69680 55.46
23 -19.9107 1.0690 1.72825 28.46
24 56.8789 0.1500
25ASPH 58.5950 6.0314 2.00178 19.32
26ASPH -47.1385 d(26)
27 1501.3206 5.0000 1.48749 70.44
28 -59.5911 0.1500
29ASPH 33.1753 1.5000 1.85135 40.10
30ASPH 23.9536 4.7676
31 -111.7174 1.5000 1.80000 29.84
32 58.4075 6.5636 1.90043 37.37
33 -142.0609 13.5977
34 ∞ 2.5000 1.51680 64.20
35 ∞ 1.0000
Image plane ∞

(Specifications table)
Wide-angle end Intermediate Telephoto end
f 36.0007 41.9984 48.5931
FNo. 1.4800 1.4801 1.4800
ω 31.5822 27.1709 23.5671
Y 21.6330 21.6330 21.6330

(variable interval)
Wide-angle end Intermediate Telephoto end Wide-angle end Intermediate Telephoto end
d(0) ∞ ∞ ∞ 320.0000 338.1045 351.8894
d(6) 51.8424 30.3910 12.9170 47.3384 23.6218 1.2458
d(26) 3.1320 6.4786 10.1681 7.6360 13.2477 21.8392

(Aspheric coefficient)
Surface number k A4 A6 A8 A10 A12
1 0.0000 -6.24256E-07 3.18906E-10 -2.00253E-13 5.51575E-17 0.00000E+00
2 0.0000 -1.14572E-06 -3.14935E-10 -6.57253E-14 -3.03110E-16 0.00000E+00
7 0.0000 -4.21603E-07 -9.68602E-11 6.83920E-14 7.85951E-16 0.00000E+00
8 0.0000 8.57444E-07 -6.72500E-11 8.36425E-13 7.52202E-17 0.00000E+00
25 0.0000 -1.26324E-06 -1.08689E-09 -1.64293E-12 1.04355E-14 0.00000E+00
26 0.0000 2.18065E-07 1.39808E-09 -1.17361E-11 2.81957E-14 0.00000E+00
29 0.0000 -7.19643E-05 1.69460E-07 -2.70814E-10 1.61170E-13 0.00000E+00
30 0.0000 -7.67922E-05 1.85884E-07 -3.28538E-10 1.97721E-13 0.00000E+00

(lens group data)
Group number Focal length
F -99.8218
M 54.9097
R 1499.5300

(1) Optical configuration FIG. 13 shows a cross-sectional view of the zoom lens of Example 4. As shown in FIG. 13, the zoom lens includes, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a rear group R having a negative refractive power. It consists of

In the zoom lens of Example 4, the front group F is composed of a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power. The intermediate group M and the rear group R are each composed of one lens group. During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the image side, the second lens group G2 moves to the image side, the middle group M moves to the object side, and the rear group R moves to the image side. Fixed in the axial direction. Further, the distance between the front group F and the intermediate group M on the optical axis is maximum at the wide-angle end, and the distance between the intermediate group M and the rear group R on the optical axis is maximum at the telephoto end. Further, when focusing from infinity to a short distance, the entire intermediate group M moves on the optical axis toward the object, and the front group F and the rear group R are fixed in the optical axis direction. The configuration of each lens group will be explained below.

The first lens group G1 is composed of a positive meniscus lens L1 with a convex surface facing the object side.

The second lens group G2 includes, in order from the object side, a negative meniscus lens L2 with a convex surface facing the object side, a biconcave lens L3, and a positive meniscus lens L4 with a convex surface facing the object side.

The intermediate group M includes, in order from the object side, a positive meniscus lens L5 with a convex surface facing the object side, a positive meniscus lens L6 with a convex surface facing the object side, a negative meniscus lens L7 with a convex surface facing the object side, and both lenses. A cemented lens in which a concave lens L8, a biconvex lens L9, a biconvex lens L10, and a negative meniscus lens L11 with a concave surface facing the object side are cemented together, and a cemented lens in which a negative meniscus lens L12 with a convex surface facing the object side and a biconvex lens L13 are cemented together. It consists of a lens. The positive meniscus lens L5 is a glass molded aspherical lens whose object side surface is aspherical. The biconvex lens L13 is a glass molded aspherical lens with an aspherical surface on the image side. The aperture stop S is arranged between the negative meniscus lens L7 and the biconcave lens L8 in the intermediate group M, and the lens arranged on the object side of the aperture stop S in the intermediate group M forms the object side partial group according to the present invention. The lens arranged on the image side of the aperture stop S constitutes the image side partial group B according to the present invention.

The rear group R includes, in order from the object side, a biconvex lens L14, a negative meniscus lens L15 with a convex surface facing the object side, and a cemented lens made up of a biconcave lens L16 and a positive meniscus lens L17 with a convex surface facing the object side. configured. The negative meniscus lens L15 is a glass molded aspherical lens with aspherical surfaces on both sides. It has a convex air lens formed by the image side surface of the negative meniscus lens L15 and the object side surface of the biconcave lens L16. The air lens has negative refractive power.

(2) Numerical Example Next, as a numerical example applying specific numerical values of the zoom lens, "lens data", "specification table", "variable interval", "aspheric coefficient", "lens group data" ” is shown. Further, FIGS. 14, 15, and 16 show longitudinal aberration diagrams of the zoom lens when focusing on an object at infinity at the wide-angle end, intermediate focal length, and telephoto end.

(lens data)
Surface number rd nd νd
Object plane ∞ d(0)
1 165.7633 4.8202 1.72916 54.67
2 1333.9829 d(2)
3 695.3060 2.0000 1.90366 31.31
4 50.8534 10.1877
5 -203.5528 1.8000 1.49700 81.61
6 102.1706 5.2134
7 84.0300 5.2886 1.92286 20.88
8 454.9074 d(8)
9ASPH 52.0250 5.7206 1.88202 37.22
10 4869.8234 2.1420
11 39.3316 9.0000 1.87070 40.73
12 126.5072 0.1500
13 70.6711 1.3000 1.76182 26.52
14 22.7879 7.2053
15S ∞ 2.6637
16 -92.5922 1.0000 1.76182 26.52
17 48.0201 1.4024
18 123.2479 3.3071 1.72916 54.67
19 -114.9968 0.1500
20 125.9760 9.6753 1.43700 95.10
21 -18.5857 1.2000 1.67300 38.26
22 -88.3908 0.1500
23 64.8822 1.2000 1.65844 50.88
24 26.8647 11.7584 1.59201 67.02
25ASPH -29.7799 d(25)
26 102.7895 5.0000 1.92119 23.96
27 -171.4539 0.1500
28ASPH 27.3978 1.5000 1.85135 40.10
29ASPH 19.0852 6.5648
30 -59.7737 1.5000 1.67270 32.10
31 28.7451 5.4800 1.92286 20.88
32 100.0000 13.5001
33 ∞ 2.5000 1.51680 64.20
34 ∞ 1.0000
Image plane ∞

(Specifications table)
Wide-angle end Intermediate Telephoto end
f 36.0006 41.9999 48.6000
FNo. 1.4801 1.4801 1.4800
ω 31.7803 27.1832 23.4709
Y 21.6330 21.6330 21.6330

(variable interval)
Wide-angle end Intermediate Telephoto end Wide-angle end Intermediate Telephoto end
d(0) ∞ ∞ ∞ 330.0000 339.7072 344.0992
d(2) 1.3000 8.4207 17.0478 1.3000 8.4207 17.0478
d(8) 42.6615 23.7995 8.8952 39.0309 18.6911 1.5476
d(25) 1.5090 3.5428 5.4283 5.1396 8.6512 12.7759

(Aspheric coefficient)
Surface number k A4 A6 A8 A10 A12
9 0.0000 -1.43431E-06 -4.02444E-10 2.32652E-13 -1.91326E-16 0.00000E+00
25 0.0000 3.64806E-06 2.14907E-09 -3.46789E-13 3.27350E-15 0.00000E+00
28 0.0000 -5.83173E-05 2.04628E-07 -5.62437E-10 6.49865E-13 0.00000E+00
29 0.0000 -6.58835E-05 2.14413E-07 -6.16486E-10 4.86817E-13 0.00000E+00

(lens group data)
Group number Focal length
G1 259.1410
G2 -75.0877
M 52.1137
R -121.6650

[Table 1]
Example 1 Example 2 Example 3 Example 4
Conditional expression (1) Hm / Hs 1.481 1.329 1.576 1.429
Conditional expression (2) Ra / ft 0.549 0.846 0.545 0.469
Conditional expression (3)(Rrf+Rrb)/(Rrf-Rrb) -0.417 -0.573 -0.647 -0.516
Conditional expression (4)BF / Y 0.746 0.746 0.751 0.746
Conditional expression (5) fa / fb 1.382 0.950 0.761 1.163
Conditional expression (6) Rmf / ft 1.093 1.517 0.954 1.070
Conditional expression (7) Rmr / ft -0.909 -1.182 -0.970 -0.613
Conditional expression (8) ff / fm -2.221 -1.305 -1.818 -2.035
Conditional expression (9) fm / fw 1.489 2.092 1.525 1.448

[Table 2]
Example 1 Example 2 Example 3 Example 4
Hm 22.698 21.199 23.202 21.230
Hs 15.331 15.950 14.723 14.858
Ra 26.623 28.754 26.486 22.788
Rrf 21.749 25.235 23.954 19.085
Rrb -52.812 -92.850 -111.717 -59.774
BF 16.148 16.149 16.246 16.148
Y 21.633 21.633 21.633 21.633
fa 73.868 57.850 55.994 61.059
fb 53.456 60.894 73.571 52.493
Rmf 52.986 51.581 46.370 52.025
Rmr -44.072 -40.192 -47.138 -29.780
ff -119.054 -67.415 -99.822 -106.052
fm 53.607 51.668 54.910 52.114

According to the present invention, it is possible to provide a zoom lens and an imaging device that have a large aperture, are overall compact, can employ a simple variable magnification mechanism, and have high optical performance.

G1...First lens group G2...Second lens group S...Aperture stop CG...Cover glass IP...Image surface

Claims (11)

Consisting of, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a rear group R having a positive or negative refractive power,
The front group F has one or more lens groups, the intermediate group M and the rear group R each consist of one lens group, and the zoom lens changes magnification by changing the distance between adjacent lens groups. And,
The intermediate group M includes, in order from the object side, an object side partial group A that includes at least one lens having a concave lens surface on the image side, an aperture stop, and an image side partial group B that includes at least one lens. It consists of
The rear group R includes an air lens that includes at least one positive lens and at least one negative lens and has a negative refractive power,
At the wide-angle end, the air gap between the front group F and the middle group M becomes maximum, and when changing power from the wide-angle end to the telephoto end, the gap between the front group F and the middle group M becomes smaller, and The distance between the intermediate group M and the rear group R becomes wider, and the distance between the lens groups constituting the front group F changes,
A zoom lens characterized in that when focusing from infinity to a short distance, the entire intermediate group M moves on the optical axis toward the object side, and satisfies the following conditional expression.
1.15 ≦ Hm/Hs ≦ 2.0 (1)
0.2 ≦ Ra/ft ≦ 1.3 (2)
-3.0 ≦ (Rrf + Rrb) / (Rrf - Rrb) ≦ 2.0 (3)
however,
Hm: Height from the optical axis of the axial marginal ray passing through the lens surface closest to the object side of the intermediate group M when focused at infinity at the telephoto end Hs: When focused at infinity at the telephoto end, Height from the optical axis of the axial marginal ray passing through the aperture stop Ra: Radius of curvature of a lens surface having the smallest radius of curvature among the lens surfaces having a concave shape on the image side included in the object side subgroup A: Front Focal length of the zoom lens when the distance between the group F and the intermediate group M on the optical axis is the minimum
Rrf: radius of curvature of the side surface of the object forming the air lens
Rrb: radius of curvature of the image side surface forming the air lens Consisting of, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a rear group R having a positive or negative refractive power,
The front group F has one or more lens groups, the intermediate group M and the rear group R each consist of one lens group, and the zoom lens changes magnification by changing the distance between adjacent lens groups. And,
The intermediate group M includes, in order from the object side, an object side partial group A that includes at least one lens having a concave lens surface on the image side, an aperture stop, and an image side partial group B that includes at least one lens. It consists of
At the wide-angle end, the air gap between the front group F and the middle group M is maximum, and when changing power from the wide-angle end to the telephoto end, the gap between the front group F and the middle group M becomes smaller, and The distance between the intermediate group M and the rear group R becomes wider, and the distance between the lens groups constituting the front group F changes,
A zoom lens characterized in that when focusing from infinity to a short distance, the entire intermediate group M moves on the optical axis toward the object side, and satisfies the following conditional expression.
1.15 ≦ Hm/Hs ≦ 2.0 (1)
0.2 ≦ Ra/ft ≦ 1.1 (2)
0.954 ≦ Rmf/ft ≦ 2.1 (6)
however,
Hm: Height from the optical axis of the axial marginal ray passing through the lens surface closest to the object side of the intermediate group M when focused at infinity at the telephoto end Hs: When focused at infinity at the telephoto end, Height from the optical axis of the axial marginal ray passing through the aperture stop Ra: Radius of curvature of a lens surface having the smallest radius of curvature among the lens surfaces having a concave shape on the image side included in the object side partial group A: Front Focal length of the zoom lens when the distance between the group F and the intermediate group M on the optical axis is the minimum
Rmf: radius of curvature of the lens surface located closest to the object in the intermediate group M Consisting of, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a rear group R having a positive or negative refractive power,
The front group F has one or more lens groups, the intermediate group M and the rear group R each consist of one lens group, and the zoom lens changes magnification by changing the distance between adjacent lens groups. And,
The intermediate group M includes, in order from the object side, an object side partial group A that includes at least one lens having a concave lens surface on the image side, an aperture stop, and an image side partial group B that includes at least one lens. At the wide-angle end, the air distance between the front group F and the middle group M is maximum, and when changing power from the wide-angle end to the telephoto end, the distance between the front group F and the middle group M is becomes smaller, the distance between the intermediate group M and the rear group R becomes wider, and the distance between the lens groups forming the front group F changes,
The rear group R is fixed with respect to the image plane both during zooming and when focusing,
A zoom lens characterized in that when focusing from infinity to a short distance, the entire intermediate group M moves on the optical axis toward the object side, and satisfies the following conditional expression.
1.15 ≦ Hm/Hs ≦ 2.0 (1)
0.2 ≦ Ra/ft ≦ 1.3 (2)
0.5 ≦ fa/fb ≦ 3.0 (5)
however,
Hm: Height from the optical axis of the axial marginal ray passing through the lens surface closest to the object side of the intermediate group M when focused at infinity at the telephoto end Hs: When focused at infinity at the telephoto end, Height from the optical axis of the axial marginal ray passing through the aperture stop Ra: Radius of curvature of a lens surface having the smallest radius of curvature among the lens surfaces having a concave shape on the image side included in the object side subgroup A: Front Focal length of the zoom lens when the distance between the group F and the intermediate group M on the optical axis is the minimum
fa: focal length of the object side subgroup A
fb: focal length of the image side partial group B Consisting of, in order from the object side, a front group F having an overall negative refractive power, an intermediate group M having a positive refractive power, and a rear group R having a positive or negative refractive power,
The front group F has one or more lens groups, the intermediate group M and the rear group R each consist of one lens group, and the zoom lens changes magnification by changing the distance between adjacent lens groups. And,
The intermediate group M includes, in order from the object side, an object side partial group A that includes at least one lens having a concave lens surface on the image side, an aperture stop, and an image side partial group B that includes at least one lens. It consists of
The rear group R includes an air lens that includes at least one positive lens and at least one negative lens and has a negative refractive power,
At the wide-angle end, the air gap between the front group F and the middle group M becomes maximum, and when changing power from the wide-angle end to the telephoto end, the gap between the front group F and the middle group M becomes smaller, and The distance between the intermediate group M and the rear group R becomes wider, and the distance between the lens groups constituting the front group F changes,
The rear group R is fixed with respect to the image plane both during zooming and when focusing,
A zoom lens characterized in that when focusing from infinity to a short distance, the entire intermediate group M moves on the optical axis toward the object side, and satisfies the following conditional expression.
1.15 ≦ Hm/Hs ≦ 2.0 (1)
0.2 ≦ Ra/ft ≦ 1.3 (2)
however,
Hm: Height from the optical axis of the axial marginal ray passing through the lens surface closest to the object side of the intermediate group M when focused at infinity at the telephoto end Hs: When focused at infinity at the telephoto end, Height from the optical axis of the axial marginal ray passing through the aperture stop Ra: Radius of curvature of a lens surface having the smallest radius of curvature among the lens surfaces having a concave shape on the image side included in the object side subgroup A: Front Focal length of the zoom lens when the distance between the group F and the intermediate group M on the optical axis is the minimum The zoom lens according to any one of claims 1 to 4, which satisfies the following conditional expression.
0.3 ≦ BF/Y ≦ 1.5 (4)
however,
BF: Back focus of the zoom lens at the wide-angle end Y: Maximum image height of the zoom lens 6. The zoom lens according to claim 1 , wherein the lens disposed closest to the object side in the intermediate group M is a positive lens. The zoom lens according to any one of claims 1 to 6 , which satisfies the following conditional expression.
-1.8 ≦ Rmr/ft ≦ -0.2 (7)
however,
Rmr: radius of curvature of the lens surface located closest to the image side in the intermediate group M The zoom lens according to any one of claims 1 to 7 , which satisfies the following conditional expression.
-4.0 ≦ ff/fm ≦ -1.0 (8)
however,
ff: Focal length of the front group F at the wide-angle end fm: Focal length of the intermediate group M The zoom lens according to any one of claims 1 to 8 , which satisfies the following conditional expression.
0.8 ≦ fm/fw ≦ 2.5 (9)
however,
fm: Focal length of the intermediate group M fw: Focal length of the zoom lens at the wide-angle end The front group F has at least one negative lens group, and the negative lens group moves toward the image side during zooming from a wide-angle end to a telephoto end . zoom lens. An imaging device comprising: the zoom lens according to any one of claims 1 to 10 ; and an imaging element that converts an optical image formed by the zoom lens into an electrical signal.

Images