CN116338914A

CN116338914A - Optical system and imaging device

Info

Publication number: CN116338914A
Application number: CN202211445048.4A
Authority: CN
Inventors: 坂井隆彦
Original assignee: Tamron Co Ltd
Current assignee: Tamron Co Ltd
Priority date: 2021-12-22
Filing date: 2022-11-18
Publication date: 2023-06-27
Also published as: JP2023092730A

Abstract

The object is to provide a zoom lens and an imaging device which are miniaturized and light-weighted and have high imaging performance in the whole zoom field. The solution is that a zoom lens is composed of a 1 st lens group (G1) with negative focal power, a 2 nd lens group (G2) with positive focal power, a 3 rd lens group (G3) with negative focal power, a 4 th lens group (G4) with positive focal power, a 5 th lens group (G5) with negative focal power and a rear group (G6) in sequence from the object side, wherein the interval between adjacent lens groups changes when zooming, and a prescribed conditional expression is satisfied. The imaging device further includes the zoom lens and an imaging element.

Description

Optical system and imaging device

Technical Field

The present invention relates to an optical system and an imaging device, and more particularly to an optical system and an imaging device suitable for imaging devices using solid-state imaging elements (such as CCDs and CMOS) such as digital cameras and digital video cameras.

Background

Conventionally, various imaging devices using a solid-state imaging element, such as video cameras, digital cameras, single-lens reflex cameras, and single-lens non-reflex cameras, have been widely used. As an imaging optical system used in these imaging devices, a zoom lens which can cover a wide imaging angle of view, has high resolution, and is small in size is required. In addition, such a zoom lens is also required to realize high-speed and high-precision autofocus.

In recent years, imaging apparatuses having not only a still image imaging function but also a moving image imaging function have been widely used. Even when auto-focusing based on the phase difference method is used in still image capturing, the contrast method is used in moving image capturing. For example, by repeating a series of operations of "vibrating (wobbling) a part of the lens group (focus lens group) at a high speed in the optical axis direction to generate an out-of-focus state and an in-focus state, detecting a signal component of a certain frequency band of a part of the image area from the output signal of the image pickup device, determining an optimal position of the focus lens group as an in-focus state, and moving the focus lens group to the optimal position", it is possible to continuously automatically focus on the subject even at the time of moving image pickup.

However, in the case of vibration, the size of an image corresponding to an object may change. This is mainly because the focal length of the entire lens system varies due to the movement of the focus lens group in the optical axis direction. When the fluctuation of the angle of view due to vibration is large, a sense of incongruity may occur in the captured image or the like. In order to reduce this uncomfortable feeling, a lens group located rearward with respect to the diaphragm is considered as a focus lens group. With the miniaturization of the non-reflection camera, miniaturization of the zoom lens itself is required, and therefore, of course, miniaturization and weight reduction of the focus lens group are required, and further miniaturization and weight reduction of the focus lens group are required in order to continuously drive the focus group at high speed at the time of moving image capturing.

In addition, in the conventional imaging sensor that receives an optical image and converts the optical image into an electrical image signal, there is a limit to efficiently take in incident light by an on-chip microlens or the like, and therefore, it is desirable to make the exit pupil larger to a certain extent or more on the lens side to secure the telecentricity of the incident light beam to the imaging sensor. However, in recent imaging sensors, with the improvement of aperture ratio and the progress of design freedom of on-chip microlenses, restrictions on the exit pupil required on the lens side are also becoming smaller. Therefore, although various inventions have been made in the past to ensure telecentricity by disposing a positive lens group behind the lens of a zoom lens, in recent years, even if a negative lens group is disposed behind the lens and the light beam is obliquely incident on the image pickup sensor, peripheral dimming (shading) due to mismatching with the pupil of an on-chip microlens or the like becomes less noticeable. In addition, software and camera systems have been advanced and improved, and even if distortion aberration is so large as to be noticeable in the past, it is now possible to correct the distortion aberration by image processing.

In such a background, for example, patent document 1 proposes a wide-angle zoom lens including 6 groups of negative, positive, and having a 5 th lens group as a focus lens group. The wide-angle zoom lens disclosed in patent document 1 is designed as an imaging optical system of a single-lens reflex camera, and thus rear Jiao Jiaochang with respect to the total optical length. Therefore, when this wide-angle zoom lens is used as an imaging optical system of a single-lens non-reflection camera, the total optical length is long, and it cannot be said that miniaturization and weight saving are sufficiently achieved. Therefore, the focusing lens group is not sufficiently miniaturized and lightweight.

Patent document 2 also proposes a wide-angle zoom lens including 6 groups of negative, positive, negative, and positive, and having a 5 th lens group as a focus lens group. The wide-angle zoom lens disclosed in patent document 2 is designed as an imaging optical system of a single-lens non-reflection camera, and therefore has a short back focal length with respect to the total optical length, and is small and lightweight. However, the zoom ratio is about 2 times smaller, and it cannot be said that miniaturization and weight saving are sufficiently achieved with respect to the zoom ratio. Therefore, when it is desired to realize a zoom lens having a large zoom ratio, not only the enlargement and the weight increase of the entire zoom lens but also the enlargement and the weight increase of the focus lens group are caused.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 4845993

Patent document 2: japanese patent No. 5699950

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to provide a zoom lens and an imaging apparatus that are compact and lightweight and have high imaging performance in the entire zoom range.

Means for solving the problems

In order to solve the above-described problems, a zoom lens according to the present invention is composed of, in order from an object side, a 1 st lens group having negative optical power, a 2 nd lens group having positive optical power, a 3 rd lens group having negative optical power, a 4 th lens group having positive optical power, a 5 th lens group having negative optical power, and a rear group having 1 or more lens groups, and is characterized in that the following conditional expression is satisfied.

(1) 6.05≤β2t/β2w≤15.00

Wherein, the liquid crystal display device comprises a liquid crystal display device,

beta 2w: lateral magnification at infinity focusing at the wide-angle end of the 2 nd lens group

Beta 2t: lateral magnification at infinity focusing at telephoto end of the 2 nd lens group

In order to solve the above-described problems, an image pickup apparatus according to the present invention includes the zoom lens and an image pickup device that converts an optical image formed by the zoom lens into an electrical signal.

Effects of the invention

According to the present invention, a zoom lens and an imaging apparatus that are miniaturized and light-weighted and have high imaging performance in the entire zoom field can be provided.

Drawings

Fig. 1 is a lens cross-sectional view of a zoom lens according to embodiment 1 of the present invention.

Fig. 2 is an aberration diagram in the wide-angle end state of the zoom lens of embodiment 1.

Fig. 3 is an aberration diagram in the intermediate focal length state of the zoom lens of embodiment 1.

Fig. 4 is an aberration diagram in the telephoto end state of the zoom lens of embodiment 1.

Fig. 5 is a lens cross-sectional view of a zoom lens according to embodiment 2 of the present invention.

Fig. 6 is an aberration diagram in the wide-angle end state of the zoom lens of embodiment 2.

Fig. 7 is an aberration diagram in an intermediate focal length state of the zoom lens of embodiment 2.

Fig. 8 is an aberration diagram in the telephoto end state of the zoom lens of embodiment 2.

Fig. 9 is a lens cross-sectional view of a zoom lens according to embodiment 3 of the present invention.

Fig. 10 is an aberration diagram in the wide-angle end state of the zoom lens of embodiment 3.

Fig. 11 is an aberration diagram in an intermediate focal length state of the zoom lens of embodiment 3.

Fig. 12 is an aberration diagram in a telephoto end state of the zoom lens of embodiment 3.

Fig. 13 is a lens cross-sectional view of a zoom lens according to embodiment 4 of the present invention.

Fig. 14 is an aberration diagram in the wide-angle end state of the zoom lens of embodiment 4.

Fig. 15 is an aberration diagram in the intermediate focal length state of the zoom lens of embodiment 4.

Fig. 16 is an aberration diagram in the telephoto end state of the zoom lens of embodiment 4.

Fig. 17 is a lens cross-sectional view of a zoom lens according to embodiment 5 of the present invention.

Fig. 18 is an aberration diagram in the wide-angle end state of the zoom lens of embodiment 5.

Fig. 19 is an aberration diagram in an intermediate focal length state of the zoom lens of embodiment 5.

Fig. 20 is an aberration diagram in a telephoto end state of the zoom lens of embodiment 5.

Detailed Description

Embodiments of a zoom lens and an imaging apparatus according to the present invention are described below. However, the zoom lens and the image pickup apparatus described below are one embodiment of the optical system and the image pickup apparatus according to the present invention, and the zoom lens and the image pickup apparatus according to the present invention are not limited to the following embodiments.

1. Zoom lens

1-1 optical constitution

The zoom lens is composed of a 1 st lens group having negative optical power, a 2 nd lens group having positive optical power, a 3 rd lens group having negative optical power, a 4 th lens group having positive optical power, a 5 th lens group having negative optical power, and a rear group having 1 or more lens groups, which are arranged in order from an object side, and the interval between adjacent lens groups on an optical axis varies upon zooming.

In this zoom lens, by having a configuration of 6 or more groups, aberration variation at the time of zooming is easily suppressed, and high imaging performance is easily obtained regardless of the imaging distance. In addition, in this zoom lens, by disposing the 1 st lens group having negative optical power on the most object side, the first negative optical power arrangement is made, so that it is easy to realize a zoom lens having a wide angle of view and a short back focus. Thus, miniaturization and weight saving are easily achieved and high imaging performance is obtained in the entire zoom field. In addition, by achieving miniaturization and weight reduction of the whole, miniaturization and weight reduction can be achieved also for the focus lens group, and rapid autofocus can be achieved.

The specific lens configuration of each lens group is not particularly limited, but, for example, the following configuration is preferably employed.

(1) 1 st lens group

The 1 st lens group has 1 or more negative lenses for having negative optical power. It is preferable that at least 1 sheet of the negative lenses included in the 1 st lens group is a concave-convex lens having a concave shape on the image side. By configuring the negative lens to include such a lens shape, it is possible to dispose a strong negative power for the 1 st lens group and prevent off-axis light rays from being strongly bent when passing through the respective surfaces configuring the 1 st lens group. Therefore, occurrence of curvature of field, distortion aberration, and the like can be reduced, and a zoom lens having excellent image plane characteristics can be obtained. In order to improve the image plane characteristics, at least 1 lens out of the lenses in the 1 st lens group preferably has an aspherical surface of 1 or more. In order to satisfactorily correct each aberration such as spherical aberration and coma, the 1 st lens group preferably has at least 1 lens with positive optical power.

(2) Lens group 2

The 2 nd lens group is not particularly limited as long as it has positive optical power, and its specific lens configuration and the like. The 2 nd lens group has 1 or more positive lenses for positive optical power. If the 2 nd lens group is constituted to include 2 positive lenses, it is easy to configure the 2 nd lens group with strong positive power required to achieve a high zoom ratio, and suppress curvature of field, distortion aberration, and obtain good imaging performance. In addition, by setting the object side to be convex, spherical aberration can be suppressed. By further including a negative lens, spherical aberration can be suppressed more effectively.

(3) 3 rd lens group

The 3 rd lens group is not particularly limited as long as it has negative optical power, and its specific lens configuration and the like. The 3 rd lens group has at least 1 negative lens for having negative optical power. In addition, in terms of correcting various aberrations, it is preferable to configure to include at least 1 positive lens.

In the zoom lens, there is no particular limitation as to whether or not there is an anti-vibration group, and for example, the 3 rd lens group may be constituted by a 3 rd group having positive optical power and a 3 rd group having negative optical power in order from the object side, the 3 rd group being movable in a direction perpendicular to the optical axis direction, and the 3 rd group being used as an anti-vibration group at the time of vibration such as hand shake. In addition, in the case where the 3b group is used as the vibration isolation group, it is also assumed that the air interval between the 3a group and the 3b group does not change upon zooming.

(4) 4 th lens group

The 4 th lens group is not particularly limited as long as it has positive optical power, and its specific lens configuration and the like. The 4 th lens group has at least 1 positive lens in order to have positive optical power. In order to ensure the optical power required for the 4 th lens group and to suppress occurrence of aberrations such as spherical aberration, it is preferable to include 2 or more positive lenses, and it is also preferable to include 1 or more negative lenses. For example, by forming the 4 th lens group from a positive lens, a negative lens, a positive lens, and a negative lens in order from the object side, various aberrations such as spherical aberration can be corrected well, and a zoom lens having high imaging performance can be realized more easily. In addition, by configuring the 4 th lens group from a plurality of lenses in this way, the optical power to be shared by the 1 st lens can be prevented from becoming excessively large, and therefore, the influence of an eccentric error or the like at the time of assembly can be reduced.

Further, at least 1 lens out of lenses in the 4 th lens group preferably has an aspherical surface of 1 or more surfaces. In particular, the lens disposed closest to the object side of the 4 th lens group preferably has an aspherical surface of 1 plane or more. In this case, the lens disposed closest to the object side of the 4 th lens group is more preferably a positive lens as described above. By disposing the aspherical surface in the 4 th lens group, each aberration, in particular, the spherical aberration can be corrected well.

(5) 5 th lens group

The 5 th lens group is not particularly limited as long as it has negative optical power, and its specific lens configuration and the like. The light flux converged by the 4 th lens group having a positive refractive power is incident to the 5 th lens group. The 5 th lens group is disposed on the image plane side in the zoom lens. This can suppress the height of the light beam entering the 5 th lens group to be low, and can suppress the variation in the height of the light beam at the time of zooming. Therefore, if the 5 th lens group is used as the focus lens group, miniaturization and weight saving of the focus lens group are easily achieved, and rapid autofocus is easily achieved. Further, since the variation in the light ray height is small, the 5 th lens group is used as the focusing lens group, whereby the variation in the angle of view can be suppressed even in the case of vibration, and live view imaging, moving image imaging, and the like can be performed well.

In addition, if the 5 th lens group is constituted by only a single lens element having negative optical power, the 5 th lens group is preferably used as a focus lens group in order to achieve a reduction in weight and size of the focus lens group and to achieve rapid auto focus. The term "single lens element" refers to an element composed of only 1 lens or one bonded lens formed by bonding a plurality of lenses.

(6) Rear group

In this zoom lens, the rear group has 1 or more lens groups. That is, the rear group may be composed of only 1 lens group, or may be composed of 2 or more lens groups. The rear group may have both positive and negative optical power as a whole. Therefore, each lens group constituting the rear group may have either positive or negative optical power. From the viewpoint of achieving downsizing and weight saving of the zoom lens, the rear group is preferably constituted by 1 or 2 lens groups.

(7) Aperture diaphragm

An aperture stop is disposed in the zoom lens. In this zoom lens, the position of the aperture stop is not particularly limited, and is preferably arranged between the image plane side of the 1 st lens group and the object plane side of the rear group, for example. In particular, it is preferable to dispose the lens group on the image plane side of the 2 nd lens group, the lens group on the object side of the 5 th lens group, and the lens group on the object side of the 4 th lens group.

1-2. Action

(1) Zooming

The zoom lens performs magnification change by changing the interval between adjacent lens groups on the optical axis during zooming. The respective lens groups may be changed in interval on the optical axis, and at the time of zooming, all the lens groups may be moved along the optical axis, or a part of the lens groups may be fixed in the optical axis direction and the other lens groups may be moved along the optical axis.

The presence or absence of movement of each lens group is not particularly limited, and the direction and amount of movement of each lens group can be appropriately set. Although the presence or absence of movement, the direction of movement, and the amount of movement of all the lens groups may be made different, for example, it is preferable to use the 4 th lens group as the movement group so that the amount of movement of the 4 th lens group at the time of zooming is equal to the amount of movement of at least any one lens group among lens groups arranged after the 5 th lens group. As lens groups arranged after the 5 th lens group, the 6 th lens group is meant in the case where the rear group is constituted by 1 lens group, and at least one lens group among the lens groups included in the rear group is meant in the case where the rear group is constituted by 2 or more lens groups. The zoom lens is composed of more than 6 groups. Therefore, if all the lens groups are moved by different amounts of movement according to the imaging distance, the driving mechanism for driving each lens group becomes complicated, and the number of components increases, resulting in an increase in the overall size. In addition, if the driving mechanism becomes complicated or the number of parts increases, manufacturing errors are also liable to occur, and thus it is difficult to obtain imaging performance conforming to the design. Accordingly, if at least one lens group among the 4 th lens group and the lens groups arranged after the 5 th lens group is moved by the same movement amount, these lens groups can be mounted on the same lens frame to move, and therefore, the driving mechanism can be simplified, and the increase in the number of components can be suppressed. Therefore, the lens is easily constituted by a plurality of groups, and the aberration variation at the time of zooming is suppressed, and the entire lens is kept small and lightweight.

(2) Focusing

In this zoom lens, it is preferable that a lens group disposed on the image plane side of the aperture stop is moved along the optical axis so as to focus on a limited-distance object from infinity. By disposing the focus lens group on the image plane side of the aperture stop in this manner, the fluctuation of the angle of view at the time of the vibration can be suppressed. In particular, it is preferable to dispose the aperture stop on the object side of the 5 th lens group and use the 5 th lens group as a focus lens group in order to suppress fluctuation of the angle of view during vibration and to reduce the size and weight of the focus lens group.

As described above, since the 5 th lens group is constituted by a single lens element, the 5 th lens group can be miniaturized and reduced in weight when the 5 th lens group is used as the focus lens group, and therefore, the drive mechanism such as the actuator for moving the focus lens group along the optical axis during focusing can be miniaturized and reduced in weight, and the entire zoom lens can be miniaturized and reduced in weight. In particular, in order to achieve more rapid autofocus and further downsizing and weight reduction of the zoom lens, it is preferable that the focus lens group be constituted of only 1 negative lens.

1-3 conditional expression

The zoom lens preferably satisfies one or more of the following conditional expressions.

1-3-1 conditional expression (1)

(1) 6.05≤β2t/β2w≤15.00

beta 2w: lateral magnification at infinity focusing at wide angle end of the 2 nd lens group

The conditional expression (1) is an expression defining a ratio of a lateral magnification at the wide angle end of the 2 nd lens group at the time of infinity focusing to a lateral magnification at the telephoto end of the 2 nd lens group at the time of infinity focusing, and is an expression defining a magnification ratio assumed by the 2 nd lens group at the time of zooming. By satisfying the conditional expression (1), a zoom lens having excellent imaging performance can be obtained while ensuring a desired predetermined zoom ratio. Further, by satisfying the conditional expression (1), the negative optical power to be disposed for the 2 nd lens group is within an appropriate range, and it is possible to suppress degradation of imaging performance due to an decentering error or the like at the time of assembly.

On the other hand, if the value of the conditional expression (1) is lower than the lower limit value, the negative power to be placed on the 2 nd lens group becomes small, and the amount of movement of the 2 nd lens group during zooming needs to be increased in order to secure a predetermined zoom ratio. Therefore, it is difficult to ensure a required zoom ratio. Alternatively, the total optical length of the zoom lens becomes long, and thus it is difficult to maintain the zoom lens compact. On the other hand, if the numerical value of conditional expression (1) exceeds the upper limit value, the negative optical power of the lens group 2 is too large, and the influence on the imaging performance due to the decentering error at the time of assembly becomes large, which is not preferable in that the ease of manufacture becomes high in order to obtain imaging performance conforming to the design.

In order to obtain the above effect, the lower limit value of the conditional expression (1) is more preferably 6.17, and still more preferably 6.50. The upper limit of the conditional expression (1) is more preferably 13.00, and still more preferably 10.00. In addition, when these preferred values are adopted, the inequality sign (+.ltoreq.) with the equal sign may be replaced with the inequality sign (<) in the conditional expression (1). The same applies to other conditional expressions, and when other conditional expressions are expressed with different signs, the different signs may be replaced with different signs with equal signs.

1-3-2 conditional (2)

In this zoom lens, when the 3 rd lens group is constituted by the 3 rd group a having positive optical power and the 3 rd group b having negative optical power in order from the object side as described above, and the 3 rd group b is used as the vibration-proof group, the following conditional expression (2) is preferably satisfied.

(2) 0.28＜f3B/f3＜1.35

f3B: focal length of group 3b

f3: focal length of 3 rd lens group

The conditional expression (2) is an expression defining a ratio of the focal length of the 3 rd group to the focal length of the 3 rd lens group. By satisfying the conditional expression (2), the optical power of the 3b group as the vibration isolation group is in an appropriate range. Therefore, when the 3b group is moved in a direction perpendicular to the optical axis at the time of vibration prevention, that is, when the 3b group is decentered, the occurrence of decentering coma and decentering astigmatism can be suppressed, and deterioration of imaging performance at the time of vibration prevention can be suppressed. Further, since the amount of movement of the 3b group during vibration isolation can be suppressed to an appropriate range, the load on the vibration isolation driving mechanism can be reduced, and the vibration isolation driving mechanism can be reduced in size and weight. Therefore, even when the zoom lens is provided with a vibration isolation function, the zoom lens can be kept compact and lightweight, and good imaging performance at the time of vibration isolation can be maintained.

On the other hand, if the value of the conditional expression (2) is equal to or less than the lower limit value, the optical density of the 3b group is too high, and decentering coma and astigmatism generated when decentering the 3b group become large, which is not preferable, and therefore, the imaging performance at the time of vibration prevention is reduced. On the other hand, if the value of conditional expression (2) is equal to or greater than the upper limit value, the negative power to be arranged for the 3 rd lens group becomes too weak, and the amount of movement of the 3 rd lens group during vibration isolation becomes large. As a result, the load of the vibration-proof driving mechanism increases, which leads to an increase in the size of the vibration-proof driving mechanism, and it is difficult to achieve miniaturization of the entire zoom lens including the lens barrel, which is not preferable.

In order to obtain the above effect, the lower limit value of the conditional expression (2) is more preferably 0.29, and still more preferably 0.30. The upper limit of the conditional expression (2) is more preferably 1.17, and still more preferably 0.90.

1-3-3 conditional (3)

In this zoom lens, when a lens group disposed on the image plane side of the aperture stop is used as a focus lens group, the following conditional expression (3) is preferably satisfied.

(3)0.25＜Dwif/Dw＜0.44

dwif: distance on optical axis between aperture stop and focus lens group at the time of infinity focusing at wide-angle end

Dw: optical full length of the zoom lens at wide angle end

The conditional expression (3) is an expression defining a positional relationship between the aperture stop and the focus lens group at the time of infinity focusing at the wide-angle end. By satisfying the conditional expression (3), fluctuation of the angle of view during vibration can be suppressed, and live view imaging, moving image imaging, and the like can be performed well. The total optical length refers to the distance on the optical axis from the most object side surface vertex of the optical system to the image plane.

On the other hand, if the value of the conditional expression (3) is equal to or less than the lower limit value, the fluctuation of the angle of view during vibration increases, and there is a case where an uncomfortable feeling is generated in the image during live view imaging or moving image imaging. On the other hand, if the numerical value of conditional expression (3) is equal to or greater than the upper limit value, the lens group disposed on the image plane side of the aperture stop is undesirably enlarged.

In order to obtain the above effect, the lower limit value of the conditional expression (3) is more preferably 0.26, and still more preferably 0.27. The upper limit of conditional expression (3) is more preferably 0.38, and still more preferably 0.29.

1-3-4 conditional expression (4) and conditional expression (5)

In the zoom lens, when the focus lens group is constituted by only 1 negative lens, the following conditional expressions (4) and (5) are preferably satisfied.

(4) nd＞1.83

(5) νd＞30

nd: refractive index of the negative lens at d-line

And νd: abbe number of the negative lens at d-line

The conditional expression (4) is an expression defining the refractive index of the negative lenses constituting the focus lens group at the d-line, and the conditional expression (5) is an expression defining the abbe number of the negative lenses constituting the focus lens group at the d-line. By configuring the focus lens group with negative lenses satisfying the conditional expression (4) and the conditional expression (5), it is possible to secure sufficient optical power for the focus lens group and suppress chromatic aberration. Therefore, the amount of movement of the focus lens group during focusing can be suppressed to be small, an increase in the number of lens pieces for chromatic aberration correction can be easily suppressed, miniaturization and weight saving of the zoom lens can be realized, and good imaging performance can be realized.

On the other hand, if the value of the conditional expression (4) is equal to or less than the lower limit value, the focal power of the focus lens group becomes weak, and when the focus lens group is constituted by the 1 negative lenses, the amount of movement during focusing needs to be increased. Therefore, the total optical length becomes long, or it is difficult to configure the focus lens group with only 1 negative lens, which is not preferable. If the value of conditional expression (5) is equal to or less than the lower limit value, the chromatic dispersion increases, and it is difficult to suppress chromatic aberration. Therefore, it is necessary to include a positive lens or the like for correcting chromatic aberration, and it is difficult to configure the focus lens group with only 1 negative lens, which is not preferable.

In order to obtain the above effect, the lower limit value of the conditional expression (4) is more preferably 1.85, and still more preferably 1.87. The lower limit value of conditional expression (5) is more preferably 32, and still more preferably 37.

2. Image pickup apparatus

Next, an imaging device according to the present invention will be described. The imaging device according to the present invention is characterized by comprising the imaging lens according to the present invention and an imaging element for converting an optical image formed by the imaging lens into an electrical signal. Further, the image pickup element is preferably provided on the image side of the optical system.

Here, the image pickup device and the like are not particularly limited, and a solid-state image pickup device and the like such as a CCD (Charge Coupled Device: charge coupled device) sensor, a CMOS (Complementary Metal Oxide Semiconductor: complementary metal oxide semiconductor) sensor and the like can also be used. The imaging device according to the present invention is suitable for imaging devices such as digital cameras and video cameras using these solid-state imaging elements. The imaging device can be applied to various imaging devices such as a single-lens reflex camera, a mirror-less single-lens camera, a digital camera, a monitoring camera, a vehicle-mounted camera, and a unmanned aerial vehicle-mounted camera. The imaging device may be a lens-replaceable imaging device or a fixed lens-type imaging device in which a lens is fixed to a housing.

Next, examples are shown and the present invention is specifically explained. However, the present invention is not limited to the following examples.

Example 1

(1) Optical structure

Fig. 1 is a lens cross-sectional view of a zoom lens according to embodiment 1 of the present invention, in which an upper portion represents a wide-angle end state (W), a middle portion represents an intermediate focal length state (M), and a lower portion represents a telephoto end state (T). This is the same in the lens cross-sectional view shown in each embodiment, and therefore, the description is omitted below.

As shown in fig. 1, the zoom lens includes, in order from an object side: a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group having negative optical power, a 4 th lens group G4 having positive optical power, a 5 th lens group G5 having negative optical power, and a 6 th lens group G6 having negative optical power. The aperture stop SP is disposed on the object side of the 3 rd lens group G3.

Specifically, the 1 st lens group G1 is configured from, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a biconvex lens.

The 2 nd lens group G2 is composed of a biconvex lens and a cemented lens formed by a biconvex lens and a biconcave lens cemented together in order from the object side.

The 3 rd lens group G3 is composed of, in order from the object side, a positive meniscus lens having a convex surface facing the object side, and a plano-concave lens having a concave surface facing the object side.

The 4 th lens group G4 is composed of, in order from the object side, a biconvex lens, and a cemented lens formed by joining 3 lenses, namely, a negative meniscus lens having a convex surface facing the object side, a biconvex lens, and a negative meniscus lens having a concave surface facing the object side.

The 5 th lens group G5 is constituted by a biconcave lens.

The 6 th lens group G6 is composed of a biconvex lens and a biconcave lens.

In this zoom lens, upon zooming from the wide-angle end to the telephoto end, the 1 st lens group G1 moves so as to draw a convex locus to the image plane side, and the 2 nd lens group G2 to the 6 th lens group G6 each move to the object side. At this time, the 4 th lens group G4 and the 6 th lens group G6 move toward the object side by the same movement amount. In this zoom lens, the 5 th lens group G5 is a focus lens group, and focusing is performed from infinity to a limited-distance object by moving the 5 th lens group G5 toward the image plane side in the optical axis direction.

(2) Numerical examples

Next, numerical embodiments of the optical system are described. The following represents surface data, aspherical surface data, various data, and variable intervals of the optical system.

In (surface data), "surface No." indicates the number of lens surfaces counted from the object side (surface number), "r" indicates the radius of curvature of the lens surfaces, "d" indicates the interval of the lens surfaces on the optical axis, "Nd" indicates the refractive index corresponding to the d-line (wavelength λ=587.6 nm), and "νd" indicates the abbe number corresponding to the d-line. In the column of "face No.", the "x" indicated by the symbol following the face number indicates that the face is aspherical, and the "SP" indicated that the face is an aperture stop SP. In addition, the mark "D o" (in this embodiment, D9 or the like) in the column of "D" indicates a variable interval at the time of zooming. In the numerical examples shown below, the units of length are all "mm", and the units of angle of view are all "°. In addition, "≡" represents infinity in each numerical example.

The (aspherical data) represents the aspherical coefficient of each aspherical surface. Here, the aspherical surface is defined by the following equation, with x being the displacement amount with respect to the plane vertex in the optical axis direction.

x＝(h2/r)/[1+{1-(1+K)×(h/r)2}1/2)]

+A4×h4+A6×h6+A8×h8+A10×h10+A12×h12

In the above formula, h represents a height with respect to the optical axis, r represents a paraxial radius of curvature, K represents a conic coefficient, and An represents An aspherical coefficient n times. In addition, "E.+ -. XX" represents an index tag, meaning ".+ -. 10.+ -. XX".

In (various data), a zoom ratio represents a ratio of a focal length at a telephoto end to a focal length at a wide-angle end of the zoom lens, and a focal length, an F value, a field angle, an image height, an optical full length, BF (back focus), respectively represent values at the wide-angle end, an intermediate focal length, and the telephoto end.

In (variable intervals), respective variable intervals at the wide-angle end, intermediate focal length, and telephoto end are indicated.

Further, the values of the conditional expressions (1) to (5) are shown in table 1 (hereinafter). These matters related to the numerical embodiments are similar to those of the numerical embodiments shown in other embodiments, and therefore, the description thereof will be omitted below.

Fig. 2, 3 and 4 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing in the wide-angle end state, the intermediate focal length state and the telephoto end state. In each longitudinal aberration diagram, spherical aberration, astigmatism, and distortion aberration are expressed in order from the left facing the diagram. In the graph showing spherical aberration, the vertical axis represents a ratio to an open F value (fno.), the horizontal axis represents defocus (mm), and spherical aberration at d-line (wavelength λ=587.56 nm) is shown. In the graph showing astigmatism, the vertical axis represents the half field angle (ω), the horizontal axis represents defocus (mm), the solid line represents the sagittal image plane (S) corresponding to the d-line, and the dotted line represents the meridional image plane (M) corresponding to the d-line. In the graph showing the distortion aberration, the vertical axis represents the half field angle (ω), and the horizontal axis represents the distortion aberration. These matters related to the respective drawings are similar to those of the longitudinal aberration diagrams shown in other embodiments, and therefore, the description thereof will be omitted below.

(face data)

Face No.	r	d	Nd	νd
					1	116.662	1.500	1.900	37.372
2	22.255	7.287
					3	125.511	1.500	1.589	61.252
4	42.479	0.150	1.515	49.963
					5*	34.738	7.483
6	-58.107	1.500	1.497	81.607
					7	36.299	0.300
8	36.657	6.331	1.750	35.332
					9	-98.710	(D9)
10	250.808	3.271	1.517	64.197
					11	-39.893	0.150
12	30.971	5.064	1.497	81.607
					13	-46.946	1.000	1.911	35.249
14	238.287	(D14)
					15SP	∞	1.000
16	70.422	2.427	1.923	20.880
					17	96925.576	2.693
18*	-32.894	1.000	1.851	40.104
					19*	∞	(D19)
20*	36.888	5.947	1.851	40.104
					21*	-33.900	0.162
22	119.269	0.900	1.905	35.036
					23	17.848	9.876	1.497	81.607
24	-15.385	1.000	2.001	25.458
					25	-21.416	(D25)
26	-8321.643	0.800	1.881	40.138
					27	31.452	(D27)
28	230.024	3.136	1.808	22.760
					29	-60.347	0.300
30	-457.051	1.200	1.835	42.721
					31	42.221	(D31)
Image plane	∞

(aspherical data)

(various data)

Zoom ratio	2.767
				Focal length	17.520	29.114	48.483
F value	4.120	4.120	4.120
				Angle of view	110.747	71.937	47.366
Image height	21.633	21.633	21.633
				Optical full length	134.456	133.533	134.456
BF	18.462	27.816	50.815

(variable spacing)

Focal length	17.520	29.114	48.483
				D9	30.694	13.079	1.000
D14	1.588	16.382	8.584
				D19	10.720	3.263	1.065
D25	2.087	2.159	2.005
				D27	4.926	4.855	5.009
D31	18.462	27.816	50.815

Example 2

(1) Optical structure

Fig. 5 is a lens cross-sectional view of a zoom lens according to embodiment 2 of the present invention. As shown in fig. 5, the zoom lens includes, in order from the object side: a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group having negative optical power, a 4 th lens group G4 having positive optical power, a 5 th lens group G5 having negative optical power, and a 6 th lens group G6 having negative optical power. The aperture stop SP is disposed on the object side of the 3 rd lens group.

The 3 rd lens group G3 is composed of a biconvex lens and a plano-concave lens having a concave surface facing the object side in order from the object side.

The 5 th lens group G5 is constituted by a biconcave lens.

The 6 th lens group G6 is composed of a biconvex lens and a biconcave lens.

(2) Numerical examples

Next, a numerical embodiment of the zoom lens is described. The following represents surface data, aspherical surface data, various data, and variable interval data of the zoom lens.

Fig. 6, 7, and 8 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(face data)

/>

(aspherical data)

Face No.

K

A4

A6

A8

A10

A12

5

0.00000

-8.49948E-06

-1.39065E-08

2.71461E-11

-2.84477E-15

-1.13437E-16

18

0.00000

-1.08768E-05

1.42275E-08

2.34536E-10

4.42543E-14

-8.81094E-15

19

0.00000

-2.18182E-05

5.84966E-08

-2.67964E-10

3.37438E-12

-2.17461E-14

20

0.00000

-3.21034E-06

1.03186E-07

3.79315E-10

-1.57233E-12

1.96337E-14

21

0.00000

3.29171E-05

2.87556E-08

1.03088E-09

-7.14554E-12

5.14222E-14

(various specifications)

(variable spacing)

Focal length	17.521	29.120	48.481
				D9	30.396	12.940	1.000
D14	1.617	14.823	8.249
				D19	10.599	3.495	1.031
D25	2.168	2.138	2.005
				D27	4.972	5.002	5.135
D31	18.324	27.660	50.655

Example 3

(1) Optical structure

Fig. 9 is a lens cross-sectional view of a zoom lens according to embodiment 3 of the present invention. As shown in fig. 9, the zoom lens includes, in order from an object side: a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group having negative optical power, a 4 th lens group G4 having positive optical power, a 5 th lens group G5 having negative optical power, and a 6 th lens group G6 having negative optical power. The aperture stop SP is disposed on the object side of the 3 rd lens group.

Specifically, the 1 st lens group G1 is configured from, in order from the object side, a negative meniscus lens having a convex surface facing the object side, and a cemented lens formed by a biconcave lens and a biconvex lens cemented.

The 2 nd lens group G2 is composed of, in order from the object side, a positive meniscus lens having a concave surface facing the object side, and a cemented lens formed by a biconvex lens and a biconcave lens cemented.

The 3 rd lens group G3 is composed of, in order from the object side, a 3 rd a group having positive optical power, and a 3 rd b group having negative optical power. Group 3a is composed of positive meniscus lenses with convex surfaces facing the object side. Group 3b is composed of a cemented lens formed by a biconcave lens and a biconvex lens.

The 5 th lens group G5 is composed of a negative meniscus lens having a convex surface facing the object side.

The 6 th lens group G6 is composed of a biconvex lens and a biconcave lens.

In this zoom lens, upon zooming from the wide-angle end to the telephoto end, the 1 st lens group G1 moves so as to draw a convex locus to the image plane side, and the 2 nd lens group G2 to the 6 th lens group G6 each move to the object side. At this time, the 4 th lens group G4 and the 6 th lens group G6 move toward the object side by the same movement amount. In this zoom lens, the 5 th lens group G5 is a focus lens group, and focusing is performed from infinity to a limited-distance object by moving the 5 th lens group G5 toward the image plane side in the optical axis direction. In this zoom lens, the 3 b-th structure is movable in a direction perpendicular to the optical axis, and functions as an anti-vibration group VC.

(2) Numerical examples

Fig. 10, 11, and 12 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(face data)

(aspherical data)

Face No.

K

A4

A6

A8

A10

A12

5

0.00000

-1.19398E-05

-1.10752E-09

-1.54010E-10

5.81099E-13

-1.08575E-15

17

0.00000

5.47310E-06

-6.69571E-09

-5.83936E-11

8.47422E-13

-2.65483E-15

20

0.00000

-7.54991E-06

2.77768E-08

-6.99811E-11

-2.17135E-14

0.00000E+00

21

0.00000

1.89851E-05

-1.51570E-08

-5.20330E-12

-1.14685E-13

0.00000E+00

(various specifications)

Zoom ratio	2.767
				Focal length	17.524	29.093	48.479
F value	4.120	4.120	4.120
				Angle of view	110.761	74.502	47.796
Image height	21.633	21.633	21.633
				Optical full length	131.927	124.228	131.927
BF	18.590	31.102	53.306

(variable spacing)

Example 4

(1) Optical structure

Fig. 13 is a lens cross-sectional view of a zoom lens according to embodiment 4 of the present invention. As shown in fig. 13, the zoom lens includes, in order from the object side: a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group having negative optical power, a 4 th lens group G4 having positive optical power, a 5 th lens group G5 having negative optical power, and a 6 th lens group G6 having negative optical power. The aperture stop SP is disposed on the object side of the 3 rd lens group.

Specifically, the 1 st lens group G1 is configured from, in order from the object side, a negative meniscus lens having a convex surface facing the object side, and a cemented lens formed by a biconcave lens and a positive meniscus lens having a convex surface facing the object side.

The 2 nd lens group G2 is composed of, in order from the object side, a positive meniscus lens having a concave surface facing the object side, and a cemented lens formed by a biconvex lens and a negative meniscus lens having a concave surface facing the object side.

The 3 rd lens group G3 is composed of, in order from the object side, a 3 rd a group having positive optical power, and a 3 rd b group having negative optical power. Group 3a is composed of positive meniscus lenses with convex surfaces facing the object side. Group 3b is composed of a cemented lens formed by a biconcave lens and a positive meniscus lens with its convex surface facing the object side.

The 6 th lens group G6 is composed of a biconvex lens and a biconcave lens.

(2) Numerical examples

Fig. 14, 15, and 16 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(face data)

(aspherical data)

Face No.

K

A4

A6

A8

A10

A12

5

0.00000

-1.29756E-05

-1.21587E-08

-1.25616E-10

4.19080E-13

-8.30275E-16

17

0.00000

9.69098E-06

2.10582E-08

-2.90183E-10

1.62250E-12

-3.55012E-15

20

0.00000

3.30964E-06

3.34192E-09

8.68898E-11

-5.60914E-13

0.00000E+00

21

0.00000

2.56252E-05

-2.23895E-08

3.72866E-12

-3.42994E-13

0.00000E+00

(various specifications)

Zoom ratio	2.766
				Focal length	17.529	29.104	48.479
F value	4.120	4.120	4.120
				Angle of view	110.806	72.896	47.493
Image height	21.633	21.633	21.633
				Optical full length	134.520	130.515	134.520
BF	18.643	29.793	52.873

(variable spacing)

Focal length	17.529	29.104	48.479
				D8	30.892	13.243	2.132
D13	1.200	9.893	4.161
				D19	9.431	3.232	1.000
D25	0.981	0.999	1.006
				D27	4.976	4.957	4.951
D31	18.643	29.793	52.873

Example 5

(1) Optical structure

Fig. 17 is a lens cross-sectional view of a zoom lens according to embodiment 5 of the present invention. As shown in fig. 17, the zoom lens includes, in order from the object side: a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group having negative optical power, a 4 th lens group G4 having positive optical power, a 5 th lens group G5 having negative optical power, a 6 th lens group G6 having positive optical power, and a 7 th lens group G7 having negative optical power. The aperture stop SP is disposed on the object side of the 3 rd lens group.

The 2 nd lens group G2 is composed of, in order from the object side, a biconvex lens, and a cemented lens formed by a biconvex lens and a negative meniscus lens with a concave surface facing the object side.

The 3 rd lens group G3 is composed of a plano-convex lens having a plane object side and a plano-concave lens having a concave surface facing the object side in order from the object side.

The 6 th lens group G6 is composed of a biconvex lens and a negative meniscus lens having a concave surface facing the object side.

The 7 th lens group G7 is constituted by a biconcave lens.

In this zoom lens, upon zooming from the wide-angle end to the telephoto end, the 1 st lens group G1 moves so as to draw a convex locus to the image plane side, the 2 nd lens group G2 to the 6 th lens group G6 each move to the object side, and the 7 th lens group G7 is fixed in the optical axis direction. At this time, the 4 th lens group G4 and the 6 th lens group G6 move toward the object side by the same movement amount. In this zoom lens, the 5 th lens group G5 is a focus lens group, and focusing is performed from infinity to a limited-distance object by moving the 5 th lens group toward the image plane side in the optical axis direction.

(2) Numerical examples

Fig. 18, 19, and 20 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(face data)

/>

(aspherical data)

Face No.

K

A4

A6

A8

A10

A12

5

0.00000

-1.08858E-05

-1.79866E-08

4.17985E-11

-2.22629E-14

-1.14401E-16

18

0.00000

-3.95092E-05

7.10557E-07

-6.04300E-09

2.28934E-11

-8.81094E-15

19

0.00000

-5.57906E-05

7.02750E-07

-6.09063E-09

2.45401E-11

-2.17461E-14

20

0.00000

-8.01562E-06

6.99384E-09

1.20370E-09

-1.38755E-11

5.88224E-14

21

0.00000

3.08260E-05

-4.40833E-08

1.05042E-09

-1.16373E-11

5.14222E-14

(various specifications)

Zoom ratio	2.767
				Focal length	17.525	29.144	48.493
F value	4.120	4.120	4.120
				Angle of view	110.717	71.408	46.937
Image height	21.633	21.633	21.633
				Optical full length	136.148	130.882	136.148
BF	19.219	19.219	19.219

(variable spacing)

Focal length	17.525	29.144	48.493
				D9	31.232	12.302	1.000
D14	1.471	12.971	12.863
				D19	11.139	5.058	1.000
D25	1.985	2.580	2.003
				D27	4.932	4.337	4.915
D31	1.000	9.244	29.979

TABLE 1

Example 1	Example 2	Example 3	Example 4	Example 5
						(1)β2t/β2w	10.00	6.50	6.50	7.01	10.00
(2)f3B/f3	-	-	0.87	0.33	-
						(3)Dwif/Dw	0.281	0.280	0.282	0.281	0.279
(4)nd	1.881	1.881	1.881	1.881	1.881
						(5)νd	40.138	40.138	40.138	40.138	40.138

Industrial applicability

Claims

1. A zoom lens comprising, in order from an object side, a 1 st lens group having negative optical power, a 2 nd lens group having positive optical power, a 3 rd lens group having negative optical power, a 4 th lens group having positive optical power, a 5 th lens group having negative optical power, and a rear group having 1 or more lens groups, wherein the intervals between adjacent lens groups change upon zooming,

the zoom lens satisfies the following conditional expression:

(1)6.05≤β2t/β2w≤15.00

Beta 2t: a lateral magnification at infinity focusing at the telephoto end of the 2 nd lens group.

2. The zoom lens according to claim 1,

in zooming, the movement amount of the 4 th lens group is equal to the movement amount of at least one lens group among the lens groups included in the rear group.

3. The zoom lens according to claim 1 or claim 2,

the 4 th lens group is composed of a positive lens, a negative lens, a positive lens, and a negative lens arranged in order from the object side.

4. A zoom lens according to claim 3,

the positive lens disposed closest to the object side in the 4 th lens group has an aspherical surface.

5. The zoom lens according to any one of claim 1 to claim 4,

the 3 rd lens group is composed of a 3 rd group a having positive optical power and a 3 rd group b having negative optical power in order from the object side,

the 3 b-th group is configured to be movable in a direction perpendicular to the optical axis,

the zoom lens satisfies the following conditions:

(2)0.28＜f3B/f3＜1.35

f3B: focal length of the 3b th group

f3: focal length of the 3 rd lens group.

6. The zoom lens according to any one of claim 1 to claim 5,

an aperture stop is provided within the zoom lens,

the aperture stop is provided with a focusing lens group which moves along an optical axis when focusing on an object with a limited distance from infinity.

7. The zoom lens according to claim 6,

the focus lens group satisfies the following conditions:

(3)0.25＜Dwif/Dw＜0.44

dwif: distance on optical axis between the aperture stop and the focus lens group at the time of infinity focusing at the wide-angle end

Dw: the optical full length of the zoom lens at the wide-angle end.

8. The zoom lens according to claim 6 or claim 7,

the focus lens group is composed of only 1 negative lens,

and satisfies the following conditions:

(4)nd＞1.83

(5)νd＞30

nd: refractive index at d-line of the negative lens constituting the focus lens group

And νd: abbe number of the negative lens constituting the focus lens group at d-line.

9. The zoom lens according to any one of claim 1 to claim 8,

the 5 th lens group is a focus lens group that moves when focusing from infinity to a limited-distance object.

10. An image pickup apparatus comprising the zoom lens according to any one of claims 1 to 9, and an image pickup device for converting an optical image formed by the zoom lens into an electrical signal.