JP2024088344A - Zoom lens and imaging device - Google Patents

Abstract

The present invention provides a zoom lens and an imaging device that are compact and have high optical performance over the entire focus range while achieving a high zoom ratio.
[Solution] A zoom lens that includes multiple lens groups G1 to G7 and zooms from the wide-angle end to the telephoto end by changing the spacing between adjacent lens groups, the object side being an object-side negative group GF having negative refractive power overall, and the image side being an image-side positive group GB having positive refractive power overall, separated by the largest variable spacing at the wide-angle end among the variable spacings during zooming, the object side being an object-side negative group GF having negative refractive power overall, and the image side being an image-side positive group GB having positive refractive power overall, the object-side negative group GF and the image-side positive group GB each including one or more lens groups and each including at least one focus group Fa, G5, the focus group Fa, G5 moving along the optical axis when focusing from infinity to a close object, the focus group Fa having negative refractive power, and moving toward the image side when focusing from an object at infinity to a close object. Also, an imaging device is provided that includes the zoom lens.
[Selected Figure] Figure 1

Description

This invention relates to a zoom lens and an imaging device.

Imaging devices using solid-state imaging elements, such as digital still cameras and digital video cameras, have become widespread. There are a variety of such imaging devices, including digital still cameras, digital video cameras, broadcast cameras/film cameras, surveillance cameras, and vehicle-mounted cameras. As the light-receiving elements that make up the solid-state imaging elements become more highly integrated, imaging devices of all kinds are becoming smaller while still offering higher functionality, and there is a demand for even higher performance and smaller size in the imaging optical systems of imaging devices.

As imaging optical systems used in imaging devices, there is a high demand for zoom lenses that can change the focal length depending on the subject. Zoom lenses are required to have a large variable power ratio while keeping the size small. There is also a demand for zoom lenses that have good correction for aberrations throughout the entire focus range, and the use of a floating system in which multiple lens groups are moved during focusing is becoming more common.

As an example of a zoom lens that performs focusing using this floating method, Patent Document 1 proposes a seven-group zoom lens in which the fourth and sixth lens groups are focus groups, and the first lens group moves toward the object side when zooming from the wide-angle end to the telephoto end. Patent Document 2 also proposes a seven-group zoom lens in which the third and fifth lens groups are focus groups, and the first lens group is fixed during zooming.

JP 2019-184632 A JP 2017-129668 A

In the zoom lens disclosed in Patent Document 1, the first lens group is extended significantly toward the object side when zooming from the wide-angle end to the telephoto end. Because the first lens group is composed of lenses with a relatively large outer diameter, when the movement amount of the first lens group increases, the drive mechanism, such as the drive motor and actuator for moving the first lens group, becomes larger and heavier, and the entire zoom becomes larger and heavier. Furthermore, as the first lens group moves, the center of gravity of the zoom lens moves significantly, making it difficult to maintain the attitude of the zoom lens.

In addition, the zoom lens disclosed in Patent Document 2 has a large telephoto ratio at the wide-angle end, and when attempting to widen the angle, the amount of peripheral light is insufficient. Also, because the first lens group is fixed relative to the image plane during zooming, the overall optical length at the wide-angle end is long compared to the focal length. If an attempt is made to shorten the overall optical length while widening the angle with a configuration similar to Patent Document 2, it is necessary to arrange strong negative refractive power in the first lens group and the second lens group, which increases the outer diameter of the lenses that make up the subsequent groups, making it difficult to reduce the size in the radial direction.

Therefore, the objective of the present invention is to provide a zoom lens and imaging device that is compact and has high optical performance across the entire focus range while achieving a high zoom ratio.

In order to solve the above problems, the zoom lens of the present invention is a zoom lens that includes a plurality of lens groups, and zooms from a wide-angle end to a telephoto end by changing the spacing between adjacent lens groups, the object side being separated by the largest variable spacing at the wide-angle end among variable spacings during zooming, an object-side negative group having negative refractive power as a whole, and an image-side positive group having positive refractive power as a whole,
each of the object-side negative group and the image-side positive group includes one or more lens groups;
each of the object-side negative lens unit and the image-side positive lens unit includes at least one focus lens unit;
When focusing from infinity to a close object, the focus group is moved along the optical axis;
The focus unit Fa included in the object-side negative unit has negative refractive power and moves toward the image side during focusing from an object at infinity to a close object.

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

The present invention makes it possible to provide a zoom lens and imaging device that is compact and has high optical performance across the entire focus range while achieving a high zoom ratio.

1 is a lens sectional view of a zoom lens according to a first embodiment. 5A to 5C are diagrams illustrating various aberrations of the zoom lens of Example 1 when focused on an object at infinity at the wide-angle end. 5A to 5C are diagrams illustrating various aberrations occurring when the zoom lens of Example 1 is focused on infinity at an intermediate focal position. 5A to 5C are diagrams illustrating various aberrations of the zoom lens of Example 1 when focused on an object at infinity at the telephoto end. 5A to 5C are diagrams illustrating various aberrations occurring when the zoom lens of Example 1 is focused on a close-distance object at the wide-angle end. 5A to 5C are diagrams illustrating various aberrations occurring when the zoom lens of Example 1 is focused on a close-distance object at an intermediate focal position. 5A to 5C are diagrams illustrating various aberrations occurring when the zoom lens of Example 1 is focused on a close-distance object at the telephoto end. FIG. 11 is a lens sectional view of a zoom lens according to a second embodiment. 8A to 8C are diagrams illustrating various aberrations of the zoom lens of Example 2 when focused on an object at infinity at the wide-angle end. 8A to 8C are diagrams illustrating various aberrations of the zoom lens of Example 2 when focused on infinity at an intermediate focal position. 8A to 8C are diagrams illustrating various aberrations of the zoom lens of Example 2 when focused on an object at infinity at the telephoto end. 8A to 8C are diagrams illustrating various aberrations occurring when the zoom lens of Example 2 is focused on a close-distance object at the wide-angle end. 8A to 8C are diagrams illustrating various aberrations when the zoom lens of Example 2 is focused on a close object at an intermediate focal position. 8A to 8C are diagrams illustrating various aberrations occurring when the zoom lens of Example 2 is focused on a close-distance object at the telephoto end. FIG. 11 is a lens sectional view of a zoom lens according to a third embodiment. 11A to 11C are diagrams illustrating various aberrations of the zoom lens of Example 3 when focused on an object at infinity at the wide-angle end. 11A to 11C are diagrams illustrating various aberrations occurring when the zoom lens of Example 3 is focused on infinity at an intermediate focal position. 11A to 11C are diagrams illustrating various aberrations of the zoom lens of Example 3 when focused on an object at infinity at the telephoto end. 11A to 11C are diagrams illustrating various aberrations occurring when the zoom lens of Example 3 is focused on a close-distance object at the wide-angle end. 11A to 11C are diagrams illustrating various aberrations occurring when the zoom lens of Example 3 is focused on a close object at an intermediate focal position. 11A to 11C are diagrams illustrating various aberrations occurring when the zoom lens of Example 3 is focused on a close-distance object at the telephoto end. 1 is a diagram illustrating an example of a configuration of an imaging device according to an embodiment of the present invention.

The following describes an embodiment of the zoom lens and imaging device according to the present invention. However, the zoom lens and imaging device described below are one aspect 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 aspects.

1. Zoom lens 1-1. Optical configuration The zoom lens is a zoom lens that includes a plurality of lens groups, and zooms from the wide-angle end to the telephoto end by changing the interval between adjacent lens groups, and the object side is an object side negative group (hereinafter, referred to as object side negative group GF) having negative refractive power as a whole, and the image side is an image side positive group (hereinafter, referred to as image side positive group GB) having positive refractive power as a whole, separated by the largest variable interval at the wide-angle end among the variable intervals during zooming, and the object side negative group GF and the image side positive group GB each include one or more lens groups, and each includes at least one focus group, and the focus group Fa included in the object side negative group GF has negative refractive power, and moves to the image side when focusing from an infinite object to a close object. Here, the variable interval during zooming refers to the interval between adjacent lens groups that changes when zooming from the wide-angle end to the telephoto end.

However, a lens group refers to a group of one or more lenses that move or stay stationary as a unit during zooming. That is, a lens group may be composed of one lens, or may be composed of multiple lenses. A lens group may also include an aperture stop. In the zoom lens according to the present invention, the spacing between adjacent lens groups changes during zooming. The same applies to the zoom lenses in the examples described below.

This zoom lens has multiple lens groups, and by varying the spacing between each lens group, it is possible to obtain a zoom lens with high optical performance by effectively correcting various aberrations throughout the entire zoom range while achieving a high zoom ratio. In this zoom lens, the object side negative group GF and the image side positive group GB are arranged separated by the maximum variable spacing during zooming at the wide-angle end, and a negative-positive refractive power arrangement, i.e., a retrofocus type refractive power arrangement, is adopted at the wide-angle end. Therefore, compared to when the refractive power arrangement at the wide-angle end is positive and negative, i.e., when a telephoto type refractive power arrangement is adopted, it is possible to achieve a high zoom ratio while preventing the overall optical length at the wide-angle end from becoming long even when the angle is increased.

Furthermore, in this zoom lens, the focus group Fa included in the object-side negative group GF has negative refractive power, so that the retrofocus type refractive power arrangement at the wide-angle end can be further strengthened, and while achieving a high zoom ratio, it is possible to better prevent the overall optical length at the wide-angle end from becoming too long even when the angle is increased.

In addition, in this zoom lens, by arranging at least one focus group in each of the object-side negative group GF and the image-side positive group GB, focusing can be performed using the so-called floating method. This makes it easy to suppress aberration fluctuations during focusing even when a high zoom ratio is achieved. Furthermore, in this zoom lens, by moving the focus group Fa toward the image side when focusing from an object at infinity to a close object, it is possible to suppress fluctuations in spherical aberration and field curvature during focusing, and high optical performance can be achieved throughout the entire focusing range.

The zoom lens has the object-side negative group GF and the image-side positive group GB, and as long as the object-side negative group GF and the image-side positive group GB each have at least one focus group, the number of lens groups constituting the zoom lens and the refractive power arrangement for each lens group are not particularly limited, but it is preferable that the zoom lens has, for example, the following configuration.

1-1-1. Object-side negative group GF
The object-side negative group GF is composed of at least one lens group. The object-side negative group GF has a focus group Fa. The object-side negative group GF is preferably provided with the most object-side lens group described next. Although the number of lens groups constituting the object-side negative group GF is not particularly limited, if the number of lens groups constituting the object-side negative group GF increases, it becomes difficult to configure the zoom lens in a compact size. From this viewpoint, the number of lens groups constituting the object-side negative group GF is preferably four or less, and more preferably three or less.

(1) Most Object-Side Lens Group The lens group arranged closest to the object in the object-side negative group GF, that is, the lens group arranged closest to the object in the zoom lens, may have either positive or negative refractive power. When the most object-side lens group has positive refractive power, the zoom lens becomes a so-called positive-lead type, which is more advantageous in terms of achieving a high zoom ratio. When the most object-side lens group has negative refractive power, the zoom lens becomes a so-called negative-lead type, which is more advantageous in terms of achieving a wide angle. In the zoom lens, it is more preferable that the most object-side lens group has positive refractive power in order to achieve a higher zoom ratio.

There is no limit to the number of lenses that make up the lens group closest to the object, but in order to reduce the size and weight of the zoom lens, it is preferable that the lens group closest to the object be made up of three lenses or less.

The lens group closest to the object may be a fixed group, but it is preferable to make it a movable group, and it is particularly preferable to move it toward the object side when zooming from the wide-angle end to the telephoto end. If the lens group closest to the object is moved toward the object side, the total optical length at the wide-angle end becomes shorter than the total optical length at the telephoto end, and by making the lens barrel a nested structure and extending it toward the object side during zooming, the zoom lens can be stored compactly when not in use.
Also, by moving the lens unit closest to the object side toward the object side, it becomes easy to realize a higher zoom ratio, although in this case, it is more preferable to provide the lens unit closest to the object side with positive refractive power in order to obtain a high zoom ratio.

(2) Focus group Fa
The focus group Fa arranged in the object-side negative group GF has a negative refractive power as described above. By arranging the focus group Fa on the object side of the maximum variable distance at the wide-angle end, it is possible to effectively suppress aberration fluctuations during focusing together with the focus group arranged on the image side of the maximum variable distance, and good optical performance can be obtained throughout the entire focus range. The focus group Fa may be any of the lens groups (zoom groups) constituting the object-side negative group GF in their entirety or a part thereof, but it is preferable that the focus group Fa is located closer to the image side than the most object-side lens group, and is preferably located closest to the image side of the object-side negative group GF.

It is preferable that a lens La having negative refractive power is disposed closest to the object side of the focus group Fa. It is also preferable that the lens La has a diverging surface on the object side. By adopting this configuration, it is possible to correct the chromatic aberration of magnification at the wide-angle end and the axial chromatic aberration at the telephoto end in a better and more balanced manner.

The number of lenses constituting the focus group Fa is not particularly limited, and it may be composed of only the lens La, or may be composed of multiple lenses including the lens La, but it is preferable that the focus group Fa is composed of two or less lenses. By constituting the focus group Fa of two or less lenses, the focus group can be made smaller and lighter. This prevents the drive mechanism, such as an actuator, for moving the focus group in the optical axis direction from becoming too large, and allows the entire zoom lens, including the lens barrel, to be made smaller.

When the focus group Fa includes two or more lenses, it is preferable that one of the lenses has a refractive power with a different sign from that of the lens La. In particular, it is preferable that the focus group Fa has a lens Lb with positive refractive power closest to the image side. By arranging the lens Lb with positive refractive power closest to the image side of the focus group Fa, it is possible to make the lens Lb converge the light beam incident on the subsequent lens group, thereby making it possible to reduce the diameter of the subsequent lens group.

The lenses constituting the focus group Fa may be arranged with an air gap between them, or may include a cemented lens in which two or more lenses are cemented together. If there is an air gap between the lenses constituting the focus group Fa, it is more preferable in terms of correcting various aberrations during focusing. Furthermore, if the focus group Fa includes a cemented lens, assembly errors and the like can be suppressed even when the focus sensitivity is high. However, in the present invention, one lens means one single lens component. Therefore, as described above, for a cemented lens in which two or more lenses (two or more single lens components) are cemented together, each of the single lens components constituting the cemented lens is counted as one lens.

In this zoom lens, there may be two or more focus groups arranged in the object-side negative group GF, but in order to prevent the drive mechanism from becoming too large, it is preferable that the focus group Fa is the only focus group arranged in the object-side negative group GF.

1-1-2. Image side positive group GB
The image side positive group GB is composed of at least one lens group including the focus group (hereinafter referred to as the "image side focus group"). The number of lens groups constituting the image-side positive group GB is not particularly limited, but it is preferable that the image-side positive group GB includes at least three lens groups and at least one lens It is preferable that the two lens groups sandwiching the group are moved along the optical axis on the same track during zooming. In this case, while the image side positive group GB is composed of three or more lens groups, The two lens groups can be fixed to the same ring frame or the like and moved by a single drive mechanism, which simplifies the mechanical configuration. If the number of lens groups increases, it becomes difficult to make the zoom lens compact. From this viewpoint, it is preferable that the number of lens groups constituting the image side positive group GB is four or less. The configuration of the positive group GB is not particularly limited, but for example, the image-side focus group and the like preferably have the following configuration.

(1) Image side focus group The image side focus group is composed of the lens group constituting the image side positive group GB, or a part thereof. The image side focus group includes at least one lens. In addition, from the viewpoint of making the focus group compact and lightweight, it is preferable that the image side focus group is also composed of two or less lenses.

The location of the image-side focus group is not particularly limited as long as it is included in the image-side positive group GB. However, it is preferable that it is located closer to the image side than the positive lens group described below. In addition, the image-side focus group may have positive or negative refractive power, but it is preferable that it has a refractive power with a different sign from that of the focus group La, i.e., positive refractive power. By giving the image-side focus group a refractive power with a different sign from that of the focus group Fa, it becomes possible to better suppress aberration fluctuations during focusing.

In this zoom lens, two or more image-side focus groups may be provided, but in order to prevent the drive mechanism from becoming too large, it is preferable to have only one image-side focus group.

(2) Positive Lens Group The image side positive group GB preferably includes a lens group (hereinafter, positive lens group) having a positive refractive power on the object side of the image side focus group. By arranging the image side focus group on the image side of the positive lens group, the light beam diverging in the object side negative group GF can be converged by the positive lens group and can be made to enter the image side focus group, so that the variation in the diameter of the light beam entering the image side focus group due to the zoom position can be suppressed, and the aberration variation during focusing can be suppressed.

In particular, it is preferable that the positive lens group is disposed closest to the object side of the image side positive lens group GB. In this case, it is preferable that the positive lens group includes an aperture stop, and the aperture stop is preferably disposed closest to the object side of the positive lens group.

When the positive lens group is disposed closest to the object side of the image side positive group GB, the positive lens group may be a fixed group, but it is preferable to make it a movable group, and it is preferable to move it toward the object side, particularly when zooming from the wide-angle end to the telephoto end. In the image side positive group GB, by moving the positive lens group toward the object side, the aperture stop also moves, making it possible to prevent the front lens diameter from becoming large even when a wide angle is attempted.

1-2. Operation Except for the points mentioned above, the operation of each lens group during zooming in the zoom lens and the operation of each focus group during focusing are not particularly limited.

(1) Operation during zooming Except for the above points, as long as the distance between adjacent lens groups on the optical axis changes during zooming, each lens group may be a movable group that is movable with respect to the image plane, or a fixed group that is fixed with respect to the image plane. If all lens groups are movable groups, the position of each lens group can be changed during zooming from the wide-angle end to the telephoto end, which is preferable in terms of correcting various aberrations. However, in order to move the lens groups along the optical axis, a driving mechanism such as an actuator or a motor is required, which increases the size of the entire zoom lens including the lens barrel. From these points of view, each lens group may be appropriately selected as a movable group or a fixed group.

(2) Operation during focusing As described above, when focusing from an object at infinity to an object at a close distance, the focus group Fa moves toward the image side. The direction of movement of the image side focus group during focusing is not limited, but it is preferable to move the image side focus group toward the image side when focusing from an object at infinity to an object at a close distance. It is also preferable to move the focus group La and the image side focus group by different amounts of movement, but they may be moved by the same amount of movement.

1-3. Conditional Expression It is preferable that the zoom lens has the above-mentioned configuration and satisfies the following conditional expression.

0.5 < |ff/fw| < 2.0
however,
ff: focal length of the object-side negative lens group at the wide-angle end when focusing on infinity fw: focal length of the zoom lens at the wide-angle end when focusing on infinity

The above conditional formula specifies the ratio between the focal length of the object-side negative group at the wide-angle end when focusing on infinity and the focal length of the zoom lens at the wide-angle end when focusing on infinity. When the above conditional formula is satisfied, the refractive power of the object-side negative group at the wide-angle end falls within an appropriate range, and even when a high zoom ratio is achieved and a wide angle is achieved, various aberrations can be well corrected while shortening the overall optical length of the zoom lens at the wide-angle end, making it easier to realize a compact zoom lens with high optical performance.

On the other hand, if the numerical value of the above conditional expression is below the lower limit, the negative refractive power of the object-side negative group GF becomes too strong, which is preferable for shortening the overall optical length at the wide-angle end, but it becomes difficult to achieve a high zoom ratio and also makes it difficult to correct various aberrations. On the other hand, if the numerical value of the above conditional expression is above the upper limit, the retrofocus type refractive power arrangement becomes weaker and the overall optical length at the wide-angle end becomes longer, making it difficult to miniaturize the zoom lens.

To obtain the above effect, the lower limit of the above conditional formula is preferably 0.75, and more preferably 1.0. The upper limit of the above conditional formula is preferably 1.75, and more preferably 1.50. When adopting these preferred values, the inequality sign (<) in the above conditional formula may be replaced with an inequality sign with an equal sign (≦).

2. Imaging device Next, the imaging device according to the present invention will be described. The imaging device according to the present invention is characterized by comprising the zoom lens according to the present invention and an imaging element that converts an optical image formed by the zoom lens into an electrical signal. The imaging element is preferably provided on the image side of the zoom lens. Here, the imaging element is not particularly limited, and solid-state imaging elements such as a CCD (Charge Coupled Device) sensor and a CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used. The imaging device according to the present invention is suitable for various imaging devices using these solid-state imaging elements, such as digital video cameras, broadcast cameras/film cameras, surveillance cameras, and vehicle-mounted cameras. In addition, these imaging devices may be fixed-lens imaging devices in which a lens is fixed to a housing, or may be interchangeable-lens imaging devices.

Figure 22 is a diagram showing a schematic example of the configuration of the imaging device. The imaging device 1 has an imaging device body 2, a lens barrel 3 attached to the imaging device body 2, an image sensor 21 arranged on the image side of the zoom lens, and a cover glass 22. The lens barrel 3 houses the zoom lens according to the present invention, an aperture stop 31, a drive mechanism for driving the lens group during zooming and focusing, etc.

Next, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples.

(1) Optical Configuration Fig. 1 is a cross-sectional view of a zoom lens according to a first embodiment of the present invention at the wide-angle end when focusing at infinity. The zoom lens includes multiple lens groups G1 to G7, and zooms from the wide-angle end to the telephoto end by changing the spacing between adjacent lens groups. The zoom lens includes an object-side negative group GF having negative refractive power overall on the object side, and an image-side positive group GB having positive refractive power overall on the image side, separated by the largest variable spacing at the wide-angle end during zooming.

The object-side negative group GF has a focus group Fa with negative refractive power, and the focus group Fa has a lens La, which is a negative meniscus lens with a diverging surface on the object side, closest to the object side, and a lens Lb, which is a positive lens, on the image side of the lens La, and is composed of these two lenses.

More specifically, the object-side negative group GF includes, in order from the object side, a lens group G1 (first lens group) most adjacent to the object that has positive refractive power, a lens group G2 (second lens group) that has negative refractive power, and a focus group Fa (third lens group G3).

An aperture stop S is disposed on the most object side of the image side positive group GB. The image side positive group GB includes an image side focus group having positive refractive power, and three lens groups having positive refractive power.
More specifically, the image side positive group GB includes, in order from the object side, four lens groups: a positive lens group G4 (fourth lens group) including the aperture stop S, an image side focus group G5 (fifth lens group), a lens group G6 (sixth lens group) having positive refractive power consisting of only one positive lens, and a most image side lens group G7 (seventh lens group) having negative refractive power consisting of a negative meniscus lens having a diverging surface on the object side. Note that the specific lens configuration of each lens group is as shown in the figure, and description thereof will be omitted here.

When zooming from the wide-angle end to the telephoto end, of the three lens groups G1 to G3 that make up the object-side negative group GF, the lens group G1 closest to the object moves toward the object side, and the remaining two lens groups G2 and G3, including the focus group Fa, move toward the image side. All of the lens groups G4 to G7 that make up the image-side positive group GB move toward the object side. At that time, the two positive lens groups G4 and G6 that sandwich the image-side focus group G5 are fixed to the same ring frame and mechanically linked, and move toward the object side along the same trajectory.

In addition, when focusing from infinity to a close-distance object, the focus group Fa and the image-side focus group G5 move toward the image side along the optical axis.

In FIG. 1, "IMG" stands for image plane, and more specifically, it refers to the imaging surface of an imaging element such as a CCD sensor or a CMOS sensor, or the film surface of a silver halide film. This is the same for the lens cross-sectional views shown in the other examples, so further explanation will be omitted.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. The "surface data", "aspheric data", "magnification data (when focusing on infinity)", and "magnification data (when focusing on a finite distance)" are shown below. Values corresponding to each conditional expression are shown in Table 1. Table 1 will be shown after Example 3.

In the "Surface Data" section, "No." 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 space on the optical axis, "Nd" is the refractive index at the d-line (wavelength λ=587.5618 nm), and "ABV" is the Abbe number at the d-line. In the "No." column, "ASPH" next to the surface number indicates that the surface is aspheric, and "STOP" indicates that it is an aperture stop. In the "d" column, "(d5)" and the like indicate that the spacing on the optical axis of the lens surface is a variable spacing that changes when changing magnification or focusing. In the radius of curvature column, "∞" means infinity, meaning that the surface is flat.

"Aspherical surface data" indicates the values of each coefficient when the aspherical surface is defined by the following equation.
z= ^ch2 /[1+{1-(1+K) ^{c2h2 } 1/2} ]+ ^A4h4 + ^A6h6 + ^A8h8 + ^A10h10 + ^A12h12
(where c is the curvature (1/r), h is the height from the optical axis, K is the cone coefficient, and A4, A6, A8, A10, and A12 are the aspheric coefficients of each order.)

"Magnification data (when focused at infinity)" shows various data when focused at infinity, "Fno" is the F-number, "ω" is the half angle of view, and d5 etc. are the variable intervals shown in the surface data, and show the respective values at the wide-angle end, intermediate focal position, and telephoto end.

"Magnification data (when focusing at a finite distance)" is each variable interval when focusing at a finite distance (predetermined shooting distance), and shows the respective values at the wide-angle end, the intermediate focal position, and the telephoto end.

The details in these tables are the same as those in the tables shown in the other examples, so we will not repeat the explanation below.

In addition, Figs. 2 to 4 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal position, and telephoto end when focusing at infinity, respectively, and Figs. 5 to 7 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal position, and telephoto end when focusing at infinity, respectively. The longitudinal aberration diagrams shown in each diagram are, from the left as you face the diagram, spherical aberration (mm), astigmatism (mm), and distortion aberration (%). In the spherical aberration diagram, the dashed line shows the characteristics of the C-line (656.2700 nm), the solid line shows the characteristics of the d-line (wavelength 587.5600 nm), and the dashed line shows the characteristics of the F-line (wavelength 486.1300 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 of the d-line (indicated by S in the diagram), and the dashed line shows the meridional image plane of the d-line (indicated by T in the diagram). In the distortion diagram, the vertical axis represents the half angle of view (ω) and the horizontal axis represents the distortion. These points are the same for the aberration diagrams shown in the other examples, so a description of them will be omitted below.

[Face data]
No. RD Nd ABV
1 133.0288 2.0000 1.90366 31.31
2 96.2695 9.1066 1.43700 95.10
3 -349.1188 0.2000
4 91.4877 5.2643 1.43700 95.10
5 247.3711 (d5)
6 126.0655 3.8839 1.90110 27.06
7 -327.8015 0.9259
8 -220.4940 1.0000 2.00069 25.46
9 40.8285 4.5387
10 -318.3667 1.0000 1.76506 34.95
11 49.8633 5.6972 1.92643 21.91
12 -106.8134 1.0000 1.78061 44.91
13 376.2041 (d13)
14 -46.4446 1.2000 1.58951 63.58
15 -1306.9477 0.2000
16 114.7778 2.9911 1.85986 25.26
17 -1011.2224 (d17)
18STOP∞0.8000
19 60.1664 3.0000 1.86407 34.78
20 296.6660 0.2000
21 35.3516 7.4774 1.49769 81.40
22 -306.5071 1.0000 1.85761 28.29
23 31.0704 4.3917 1.49825 81.24
24 65.9327 1.6424
25 35.0409 6.0622 1.77047 29.74
26 5258.0562 0.2397
27 44.3685 1.0636 1.80610 33.27
28 18.4438 6.4902 1.49710 81.56
29ASPH 96.2072 (d29)
30 829.3701 3.3667 1.92119 23.96
31 -72.6480 0.9000 1.74320 49.34
32 42.0231 (d32)
33 63.7357 6.9587 1.51680 64.20
34 -39.5462 (d34)
35ASPH -24.3046 1.3000 1.85108 40.12
36ASPH -98.1396 (d36)
37 ∞ 2.5000 1.51680 64.20
38∞1.0000

[Aspheric data]
No. K A4 A6 A8 A10 A12
29 0 1.05216E-05 7.88990E-09 9.32258E-12 4.02110E-14 9.23355E-17
35 0 -6.35691E-07 1.03143E-07 -4.21064E-10 9.61588E-13 -8.35481E-17
36 0 -8.28356E-06 7.79522E-08 -3.14763E-10 6.33345E-13 -5.08439E-17

[Magnification data (focused at infinity)]
Wide Angle Mid-Telephoto
Focal length 51.5015 99.9998 192.9993
Fno 2.9100 2.9100 2.9100
ω 22.9584 11.8287 6.1335
d 5 2.0000 38.3417 71.7058
d13 12.3084 7.4788 5.2384
d17 44.2080 23.1974 4.6996
d29 5.1774 7.3579 3.5000
d32 28.6122 26.4316 30.2896
d34 9.1946 9.2335 7.2110
d36 11.1000 15.7851 18.8052

[Magnification data (when focusing at finite distance)]
Shooting distance 1000 1000 1300
d13 16.3411 10.7417 6.4380
d17 40.1753 19.9344 3.5000
d29 7.6690 14.4253 18.9341
d32 26.1206 19.3643 14.8555

(1) Optical Configuration Fig. 8 is a cross-sectional view of a zoom lens according to Example 2 of the present invention at the wide-angle end when focusing at infinity. The zoom lens includes multiple lens groups G1 to G7, and zooms from the wide-angle end to the telephoto end by changing the spacing between adjacent lens groups. The zoom lens includes an object-side negative group GF having negative refractive power overall on the object side, and an image-side positive group GB having positive refractive power overall on the image side, separated by the largest variable spacing at the wide-angle end during zooming.

The object-side negative group GF has a focus group Fa with negative refractive power, and the focus group Fa has a lens La, which is a negative meniscus lens with a diverging surface on the object side, closest to the object side, and a lens Lb, which is a positive lens, on the image side of the lens La, and is composed of these two lenses.

More specifically, the object-side negative group GF includes, in order from the object side, a lens group G1 (first lens group) most adjacent to the object that has positive refractive power, a lens group G2 (second lens group) that has negative refractive power, and a focus group Fa (third lens group G3).

An aperture stop S is disposed on the most object side of the image side positive group GB. The image side positive group GB includes an image side focus group having positive refractive power, and three lens groups having positive refractive power.
More specifically, the image side positive group GB includes, in order from the object side, four lens groups: a positive lens group G4 (fourth lens group) including the aperture stop S, an image side focus group G5 (fifth lens group), a lens group G6 (sixth lens group) having positive refractive power and consisting of only one positive lens, and a most image side lens group G7 (seventh lens group) having negative refractive power and consisting of a negative meniscus lens having a diverging surface on the object side. Note that the specific lens configuration of each lens group is as shown in the figure, and description thereof will be omitted here.

When zooming from the wide-angle end to the telephoto end, of the three lens groups G1 to G3 that make up the object-side negative group GF, the lens group G1 closest to the object moves toward the object side, and the remaining two lens groups G2 and G3, including the focus group Fa, move toward the image side. All of the lens groups that make up the image-side positive group GB move toward the object side. At that time, the two positive lens groups G4 and G6 that sandwich the image-side focus group G5 are fixed to the same ring frame and mechanically linked, and move toward the object side along the same trajectory.

In addition, when focusing from infinity to a close-distance object, the focus group Fa and the image-side focus group G5 move toward the image side along the optical axis.

(2) Numerical Examples Numerical examples to which specific numerical values of the zoom lens are applied are shown below. Values corresponding to the conditional expressions are shown in Table 1 below. Figs. 9 to 11 respectively show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal position, and telephoto end when focused on infinity, and Figs. 12 to 14 respectively show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal position, and telephoto end when focused on infinity.

[Face data]
No. RD Nd ABV
1 110.2724 2.0000 1.90366 31.31
2 83.6373 8.9428 1.43700 95.10
3 -1498.5900 0.2000
4 113.5110 5.8537 1.43700 95.10
5 1484.4475 (d5)
6 960.4682 2.7908 1.90110 27.06
7 -188.0380 1.7184
8 -141.4735 1.0000 2.00069 25.46
9 55.4023 4.3585
10 -201.7889 1.0000 1.76869 49.80
11 78.4507 4.3850 1.92286 20.88
12 -129.9408 1.0000 1.82418 39.62
13 -364.7445 (d13)
14 -59.8599 1.2000 1.58103 60.71
15 70.3331 3.6659 1.90366 31.31
16 -2409.3139 (d16)
17STOP∞0.8000
18 59.2221 3.0000 1.86271 34.92
19 251.0984 0.2000
20 34.8929 7.5742 1.49806 81.29
21 -298.6902 1.0000 1.85779 28.75
22 31.0519 5.1114 1.49934 78.91
23 65.8351 0.9122
24 34.6956 6.1478 1.77047 29.74
25 2157.9603 0.2786
26 43.2577 1.0538 1.80610 33.27
27 18.2935 6.3640 1.49710 81.56
28ASPH 88.8730 (d28)
29 801.0565 2.5819 1.92119 23.96
30 -69.0243 0.9000 1.74320 49.34
31 41.8040 (d31)
32 56.5596 7.1467 1.51680 64.20
33 -40.2114 (d33)
34ASPH -24.1695 1.3000 1.85108 40.12
35ASPH -100.4819 (d35)
36 ∞ 2.5000 1.51680 64.20
37∞1.0000

[Aspheric data]
No. K A4 A6 A8 A10 A12
28 0 1.04508E-05 8.29492E-09 1.06901E-11 4.14662E-14 9.30080E-17
34 0 1.84389E-07 1.05065E-07 -4.20367E-10 9.60849E-13 -8.55606E-16
35 0 -8.76883E-06 7.89457E-08 -3.12890E-10 6.29699E-13 -5.16796E-16

[Magnification data (focused at infinity)]
Wide Angle Mid-Telephoto
Focal length 51.5000 99.9998 194.0000
Fno 2.9100 2.9100 2.9100
ω 23.8494 12.1803 6.1470
d 5 2.0000 34.2578 71.7384
d13 8.0382 3.8129 6.4407
d16 49.6170 24.9735 5.3676
d28 5.8719 8.1244 3.5000
d31 28.4733 26.2208 30.8452
d33 7.5167 8.7313 6.5207
d35 12.4984 17.9411 17.3671

[Magnification data (when focusing at finite distance)]
Shooting distance 1000 1000 1300
d13 17.8853 9.7720 8.3083
d16 39.7698 19.0144 3.5000
d28 9.7132 16.4756 20.2886
d31 24.6320 17.8696 14.0566

(1) Optical Configuration Fig. 15 is a cross-sectional view of a zoom lens according to a third embodiment of the present invention at the wide-angle end when focusing at infinity. The zoom lens includes multiple lens groups G1 to G7, and zooms from the wide-angle end to the telephoto end by changing the spacing between adjacent lens groups. The zoom lens includes an object-side negative group GF having negative refractive power overall on the object side, and an image-side positive group GB having positive refractive power overall on the image side, separated by the largest variable spacing at the wide-angle end during zooming.

The object-side negative group GF has a focus group Fa with negative refractive power, and the focus group Fa has a lens La, which is a negative meniscus lens with a diverging surface on the object side, closest to the object side, and a lens Lb, which is a positive lens, on the image side of the lens La, and is composed of these two lenses.

More specifically, the object-side negative group GF includes, in order from the object side, a lens group G1 (first lens group) most adjacent to the object that has positive refractive power, a lens group G2 (second lens group) that has negative refractive power, and a focus group Fa (third lens group G3).

An aperture stop S is disposed on the most object side of the image side positive group GB. The image side positive group GB includes an image side focus group having positive refractive power, and three lens groups having positive refractive power.
More specifically, the image side positive group GB includes, in order from the object side, four lens groups: a positive lens group G4 (fourth lens group) including the aperture stop S, an image side focus group G5 (fifth lens group), a lens group G6 (sixth lens group) having positive refractive power and consisting of only one positive lens, and a most image side lens group G7 (seventh lens group) having negative refractive power and consisting of a negative meniscus lens having a diverging surface on the object side. Note that the specific lens configuration of each lens group is as shown in the figure, and description thereof will be omitted here.

When zooming from the wide-angle end to the telephoto end, of the three lens groups G1 to G3 that make up the object-side negative group GF, the lens group G1 closest to the object moves toward the object side, and the remaining two lens groups G2 and G3, including the focus group Fa, move toward the image side. All of the lens groups G4 to G7 that make up the image-side positive group GB move toward the object side. At that time, the two positive lens groups G4 and G6 that sandwich the image-side focus group G5 are fixed to the same ring frame and mechanically linked, and move toward the object side along the same trajectory.

In addition, when focusing from infinity to a close-distance object, the focus group Fa and the image-side focus group G5 move toward the image side along the optical axis.

(2) Numerical Examples Numerical examples to which specific numerical values of the zoom lens are applied are shown below. Values corresponding to the conditional expressions are shown in Table 1 below. Figs. 16 to 18 respectively show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal position, and telephoto end when focused on infinity, and Figs. 19 to 21 respectively show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal position, and telephoto end when focused on infinity.

[Face data]
No. RD Nd ABV
1 174.9946 2.0000 1.80610 33.27
2 102.4447 9.8586 1.43700 95.10
3 -357.7691 0.2000
4 87.8166 6.6440 1.49700 81.61
5 383.9713 (d5)
6 290.8586 1.0000 2.00100 29.13
7 42.9464 3.1046
8 1514.6773 1.0000 1.75500 52.32
9 92.7843 0.2000
10 71.1101 5.4634 1.80000 29.84
11 -54.7031 0.8398
12 -50.5513 1.0000 1.65100 56.24
13 107.2152 (d13)
14 -43.5282 1.2000 1.49700 81.61
15 1774.9054 0.2000
16 109.7267 2.9186 1.84666 23.78
17 -1234.2168 (d17)
18STOP∞0.8000
19 48.6686 4.4632 1.71700 47.93
20 195.6443 0.4282
21 30.5507 7.4967 1.43700 95.10
22 -194.2167 1.0000 1.85025 30.05
23 27.2948 4.6081 1.62004 36.26
24 67.2775 0.2000
25ASPH 32.0034 5.8198 1.80610 40.73
26ASPH -248.2766 0.2000
27 51.1416 1.0000 1.83400 37.21
28 19.1238 4.8049 1.49710 81.56
29ASPH 73.0869 (d29)
30 466.9736 2.2685 1.92286 20.88
31 -88.3142 0.9000 1.77250 49.60
32 38.3605 (d32)
33 208.8169 4.7070 1.49700 81.61
34 -39.8811 (d34)
35ASPH -20.6684 1.3000 1.77377 47.17
36ASPH -40.5912 (d36)
37 ∞ 2.5000 1.51680 64.20
38∞1.0000

[Aspheric data]
No. K A4 A6 A8 A10 A12
25 0 -1.97210E-06 1.53875E-09 -5.36682E-13 1.14007E-14 0.00000E+00
26 0 6.11842E-07 3.83941E-09 -2.95846E-12 1.47430E-15 0.00000E+00
29 0 1.49954E-05 1.32332E-08 2.37621E-11 8.72191E-15 8.46004E-16
35 0 5.84605E-06 1.17250E-07 -4.29479E-10 8.18571E-13 -1.01409E-16
36 0 -4.37657E-06 8.03907E-08 -3.43893E-10 6.46644E-13 -4.15174E-16

[Magnification data (focused at infinity)]
Wide Angle Mid-Telephoto
Focal length 51.4970 100.0108 194.0138
Fno 2.9100 2.9100 2.9100
ω 23.1142 11.7116 6.0997
d 5 2.0000 39.4666 73.9566
d13 6.0050 8.9963 5.6465
d17 41.7244 16.0178 1.5000
d29 2.0018 7.9845 2.8916
d32 21.5710 15.5884 20.6813
d34 18.0716 15.3957 12.3015
d36 14.5012 17.1775 20.2711

[Magnification data (when focusing at finite distance)]
Shooting distance 1000 1000 1000
d13 8.5162 9.3512 5.7054
d17 39.2132 15.6629 1.4411
d29 3.6270 13.2804 20.5794
d32 19.9459 10.2924 2.9935

[Table 1]
Conditional Expression Example 1 Example 2 Example 3
|ff/fw| 1.338 1.324 1.212

[summary]
A zoom lens according to a first aspect of the present invention is a zoom lens that includes a plurality of lens groups and zooms from a wide-angle end to a telephoto end by changing an interval between adjacent lens groups,
an object-side negative lens group having negative refractive power as a whole on the object side, and an image-side positive lens group having positive refractive power as a whole on the image side, the object-side negative lens group being separated by the largest variable distance at the wide-angle end among the variable distances during zooming;
each of the object-side negative group and the image-side positive group includes one or more lens groups;
each of the object-side negative lens unit and the image-side positive lens unit includes at least one focus lens unit;
When focusing from infinity to a close object, the focus group is moved along the optical axis;
The focus unit Fa included in the object-side negative unit has negative refractive power and moves toward the image side during focusing from an object at infinity to a close object.

The zoom lens according to the second aspect of the present invention is preferably the first aspect, and further preferably includes a lens La having negative refractive power closest to the object.

A zoom lens according to a third aspect of the present invention is a zoom lens according to the first or second aspect,
It is preferable that the lens La has a diverging surface on the object side.

A zoom lens according to a fourth aspect of the present invention is any one of the first to third aspects,
It is preferable to provide a lens Lb having a positive refractive power closest to the image side.

A zoom lens according to a fifth aspect of the present invention is any one of the first to fourth aspects,
It is preferable that the focus group Fa is composed of two or less lenses.

A zoom lens according to a sixth aspect of the present invention is any one of the first to fifth aspects,
It is preferable that the lens group disposed closest to the object side has positive refractive power.

A zoom lens according to a seventh aspect of the present invention is any one of the first to sixth aspects,
It is preferable that the lens group disposed closest to the object side is composed of three lenses or less.

A zoom lens according to an eighth aspect of the present invention is any one of the first to seventh aspects,
During zooming from the wide-angle end to the telephoto end, it is preferable that the lens unit disposed closest to the object side moves toward the object side.

A zoom lens according to a ninth aspect of the present invention is any one of the first to eighth aspects,
the image side positive group includes at least three lens groups,
It is preferable that at least one lens group sandwiched between two lens groups move along the optical axis on the same locus during zooming.

A zoom lens according to a tenth aspect of the present invention is any one of the first to ninth aspects,
It is preferable that the number of focus groups disposed in the object-side negative group and the image-side positive group each is one.

In the zoom lens according to the eleventh aspect of the present invention, in any one of the first to tenth aspects, it is preferable that the following conditional expression be satisfied:
0.5 < |ff/fw| < 2.0
however,
ff: focal length of the object-side negative lens group at the wide-angle end when focusing on infinity, fw: focal length of the zoom lens at the wide-angle end when focusing on infinity

The twelfth aspect of the present invention is an imaging device comprising a zoom lens according to any one of the first to eleventh aspects, and an imaging element on the image side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal.

The present invention makes it possible to provide a zoom lens and imaging device that is compact and has high optical performance across the entire focus range while achieving a high zoom ratio.

1: Imaging device 2: Imaging device body 3: Lens barrel 21: Imaging element 31: Aperture stop Fa: Focus group Fa
La: Lens La
S: Aperture stop IMG: Image plane

Claims (12)

A zoom lens that includes a plurality of lens groups and zooms from a wide-angle end to a telephoto end by changing the spacing between adjacent lens groups,
an object-side negative lens group having a negative refractive power as a whole on the object side, and an image-side positive lens group having a positive refractive power as a whole on the image side, the object-side negative lens group being separated by the largest variable distance at the wide-angle end among the variable distances during zooming;
each of the object-side negative group and the image-side positive group includes one or more lens groups;
each of the object-side negative lens unit and the image-side positive lens unit includes at least one focus lens unit;
When focusing from infinity to a close object, the focus group is moved along the optical axis;
a focus unit Fa included in the object-side negative unit has negative refractive power and moves toward the image side during focusing from an object at infinity to an object at a close distance. The zoom lens of claim 1, wherein the focus group Fa includes a lens La having negative refractive power closest to the object side. The zoom lens according to claim 2, wherein the lens La has a diverging surface on the object side. The zoom lens of claim 1, wherein the focus group Fa includes a lens Lb having positive refractive power closest to the image side. The zoom lens of claim 1, wherein the focus group Fa is composed of two or less lenses. The zoom lens of claim 1, in which the lens group located closest to the object has positive refractive power. The zoom lens according to claim 1, wherein the lens group arranged closest to the object side is composed of three or less lenses. The zoom lens according to claim 1, in which the lens group arranged closest to the object moves toward the object when zooming from the wide-angle end to the telephoto end. the image side positive group includes at least three lens groups,
2. The zoom lens according to claim 1, wherein at least one lens group is sandwiched between two lens groups that move along the optical axis on the same locus during zooming. The zoom lens according to claim 1, wherein the object-side negative group and the image-side positive group each include one focus group. 2. The zoom lens according to claim 1, which satisfies the following condition:
0.5 < |ff/fw| < 2.0
however,
ff: focal length of the object-side negative lens group at the wide-angle end when focusing on infinity, fw: focal length of the zoom lens at the wide-angle end when focusing on infinity An imaging device comprising the zoom lens according to any one of claims 1 to 11 and an imaging element on the image side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal.

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