Zoom lens and imaging device having the same

Abstract

To provide a zoom lens which has a light-weight focusing group and exhibits little variation in optical performance while focusing.SOLUTION: A zoom lens L0 is provided, comprising a first lens group L1 having negative refractive power, a second lens group L2 having positive refractive power, and a rear group LR comprising one or more lens groups. The zoom lens L0 has an aperture stop SP. The rear group LR comprises a focusing group LF with negative refractive power configured to move toward the image side while shifting focus from infinity to a short distance, and at least one lens group located on the image side of the focusing group. The first lens group L1 has three or more negative lenses. The focusing group LF consists of a cemented lens or a single lens. The zoom lens L0 satisfies given conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a zoom lens and the like, which is suitable for imaging devices such as digital video cameras, digital still cameras, broadcast cameras, and cameras for silver halide film. [Background technology]

[0002] In a wide-angle zoom lens, there is a demand for a compact optical system and a lightweight focus group for high-speed focusing.

[0003] Patent Document 1 discloses a zoom lens that is configured with one negative lens element in order to reduce the weight of the focus group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-157168 Summary of the Invention [Problem to be solved by the invention]

[0005] The zoom lens described in Patent Document 1 is configured to generate large negative distortion in order to make the zoom lens compact. However, with the configuration of the focus group of the zoom lens disclosed in Patent Document 1, it is expected that astigmatism and curvature of field will fluctuate significantly during focusing.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a zoom lens in which the focus group is lightweight and the fluctuation in optical performance during focusing is small. [Means for solving the problem]

[0007] A zoom lens of the present invention has, arranged in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a rear group including one or more lens groups, wherein the first lens group moves during zooming, changing the spacing between adjacent lens groups; the zoom lens has an aperture stop; the rear group has a focus group with negative refractive power that moves toward the image side during focusing from infinity to a close distance, and at least one lens group provided on the image side of the focus group, the first lens group has three or more negative lenses, the focus group is composed of a cemented lens or a single lens, the refractive index of the negative lens included in the focus group is 1.75 or more; Let Lfw be the distance from the aperture stop to the vertex of the surface of the focus group closest to the object at the wide-angle end, Ls be the distance from the aperture stop to the image plane at the wide-angle end, Ra be the radius of curvature of the lens surface of the focus group closest to the object side, Rb be the radius of curvature of the lens surface of the focus group closest to the image side, y be the maximum real image height at the wide-angle end, and y0 be the ideal image height of the maximum angle of view of the zoom lens at the wide-angle end. 0.3 <Lfw / Ls<0.5 0.8<(Rb+Ra) / (Rb-Ra)<2.2 -20<100×(y-y0) / y0<-8 The present invention is characterized in that the following conditional expression is satisfied: [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a zoom lens in which the focus group is lightweight and the fluctuation in optical performance during focusing is small. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of a zoom lens according to a first embodiment. [Figure 2] 3A to 3C are aberration diagrams of the zoom lens of Example 1. [Figure 3] FIG. 10 is a cross-sectional view of a zoom lens according to a second embodiment. [Figure 4] 10A to 10C are aberration diagrams of the zoom lens of Example 2. [Figure 5] FIG. 10 is a cross-sectional view of a zoom lens according to a third embodiment. [Figure 6] 10A to 10C are aberration diagrams of the zoom lens of Example 3. [Figure 7] FIG. 10 is a cross-sectional view of a zoom lens according to a fourth embodiment. [Figure 8] 10A to 10C are aberration diagrams of the zoom lens of Example 4. [Figure 9] FIG. 10 is a cross-sectional view of a zoom lens according to a fifth embodiment. [Figure 10] 10A to 10C are aberration diagrams of the zoom lens of Example 5. [Figure 11] FIG. 10 is a cross-sectional view of a zoom lens according to a sixth embodiment. [Figure 12] 10A to 10C are aberration diagrams of the zoom lens of Example 6. [Figure 13] FIG. 1 is a schematic diagram showing an imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a zoom lens and an image pickup apparatus having the same according to the present invention will be described with reference to the accompanying drawings.

[0011] 1, 3, 5, 7, 9, and 11 are cross-sectional views of the zoom lens L0 of Examples 1 to 6, respectively. The zoom lens L0 of each Example is a zoom lens used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, cameras using silver halide film, surveillance cameras, and vehicle-mounted cameras.

[0012] In each lens cross-sectional view, the left side is the object side and the right side is the image side. The zoom lens L0 of each embodiment may also be used as a projection lens for a projector, etc. In this case, the left side is the screen side and the right side is the projected image side.

[0013] The zoom lens L0 of each embodiment has, arranged in order from the object side to the image side, a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, and a rear lens unit LR including one or more lens units. The rear lens unit LR also has a focus lens unit LF that moves during focusing, and has at least one lens unit on the image side of the focus lens unit LF.

[0014] In each cross-sectional view, Li represents the i-th lens group counting from the object side (i is a natural number). In this specification, a lens group refers to a group of lenses that move or remain stationary as a unit during zooming. In other words, the distance between adjacent lens groups changes during zooming. Each lens group may consist of a single lens or multiple lenses. Each lens group may also include an aperture stop.

[0015] The arrows shown in each lens cross section indicate the movement locus during zooming from the wide-angle end to the telephoto end, and the movement locus during focusing from infinity to a close distance.

[0016] In each lens cross-sectional view, SP denotes an aperture stop. IP denotes an image plane, where the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed when the zoom lens of each embodiment is used in a digital still camera or digital video camera. When the zoom lens of each embodiment is used as a photographic zoom lens for a silver halide film camera, a photosensitive surface equivalent to the film surface is placed on the image plane IP.

[0017] 2, 4, 6, 8, 10, and 12 are aberration diagrams of the zoom lenses of Examples 1 to 6, respectively. In each aberration diagram, (A) is an aberration diagram at the wide-angle end, and (B) is an aberration diagram at the telephoto end. Both (A) and (B) show the cases where the object distance is infinity and the case where the object distance is very close.

[0018] In the spherical aberration diagram, Fno is the F-number, and shows the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm). In the astigmatism diagram, S shows the amount of aberration on the sagittal image plane, and M shows the amount of aberration on the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration of magnification for the g-line is shown. ω is the half angle of view (°).

[0019] Next, the characteristic configuration of the zoom lens of each embodiment will be described.

[0020] In the zoom lenses of each embodiment, the refractive power of the first lens unit L1 is made negative, thereby moving the entrance pupil closer to the object and reducing the diameter of the front lens (the lens closest to the object). Furthermore, the refractive power of the second lens unit L2 is made positive, thereby converging the on-axis marginal rays diverged by the first lens unit L1 and reducing the diameters of the second lens unit L2 and subsequent lens units. Furthermore, by locating the focus unit LF, which moves during focusing, at a position of the rear unit LR that is not closest to the image, it is possible to relatively reduce the intensity of off-axial rays incident on the focus unit LF. This allows the diameter of the focus unit LF to be reduced.

[0021] Furthermore, by providing three or more negative lenses in the first lens unit L1, the curvature of field and astigmatism that occur particularly at the wide-angle end are effectively reduced.

[0022] Furthermore, the focus group LF is made lighter by being constructed from a cemented lens or a single lens.

[0023] In addition, the following conditional expressions are satisfied: where Lfw is the distance from the aperture stop SP to the vertex of the lens surface in the focus group LF closest to the object at the wide-angle end; Ls is the distance from the aperture stop SP to the image plane IP at the wide-angle end; Ra is the radius of curvature of the lens surface in the focus group LF closest to the object; and Rb is the radius of curvature of the lens surface in the focus group LF closest to the image. 0.3 <Lfw / Ls<0.5 (1) 0.8<(Rb+Ra) / (Rb-Ra)<2.2 (2)

[0024] Conditional formula (1) is a conditional formula regarding the arrangement of the focus group LF at the wide-angle end. If the upper limit is exceeded, the focus group LF becomes farther away from the aperture stop SP. In this case, the off-axial rays incident on the focus group LF cannot be made sufficiently low, and the diameter of the focus group LF tends to become large. Also, if the lower limit is not met, the focus group LF will be arranged at a position high above the axial marginal rays, which is undesirable because it tends to increase the fluctuation in spherical aberration associated with focusing.

[0025] Moreover, conditional expression (2) is a conditional expression relating to the shape factor of the focus unit LF. By making the focus unit LF concentric with the aperture stop SP, it is possible to reduce fluctuations in astigmatism and field curvature during focusing.

[0026] The variation ΔIII of the astigmatism coefficient when the object moves is given by the following equation: ΔIII=-δ(V+IIs)+δ 2 Is

[0027] Here, δ is a parameter of object movement, V is a distortion aberration coefficient, IIs is a coma aberration coefficient of the pupil, and Is is a spherical aberration coefficient of the pupil.

[0028] Here, it can be seen that if large negative distortion is generated in order to reduce the size of a zoom lens, the distortion coefficient V increases, resulting in larger fluctuations in ΔIII (the astigmatism coefficient when an object moves). Here, if the shape of the focus group has a concave shape with a strong curvature on the image side, off-axial light rays will enter the image side surface of the focus group at an angle, resulting in larger fluctuations in astigmatism and field curvature when the focus group moves. In other words, the effects of large negative distortion and the effects of the focus group shape occur simultaneously, resulting in significant fluctuations in astigmatism due to focusing.

[0029] Therefore, in order to suppress fluctuations in astigmatism and field curvature during focusing, the focus group is configured to be concentric with the aperture so that conditional expression (2) is satisfied. This allows off-axial rays to be incident gently (close to perpendicularly) on the surface of the focus group, thereby suppressing fluctuations in imaging performance associated with focusing. If the upper limit is exceeded, the lens surface closest to the image side of the focus group LF will have a concave shape with too strong a curvature toward the object side, causing marginal rays of the axial light beam to enter at an angle and increasing fluctuations in spherical aberration, which is undesirable. If the lower limit is exceeded, the lens surface closest to the image side of the focus group LF will have a concave shape with too strong a curvature toward the image side, causing large fluctuations in astigmatism and field curvature, which is also undesirable.

[0030] With the above configuration, it is possible to obtain a zoom lens L0 in which the focus group LF is lightweight and in which fluctuations in optical performance during focusing are small.

[0031] It is preferable that at least one of the upper limit and lower limit of the numerical range of either conditional expression (1) or (2) satisfies the range of the following conditional expression (1a) or (2a). 0.32 <Lfw / Ls<0.47 (1a) 0.9<(Rb+Ra) / (Rb-Ra)<2.0 (2a)

[0032] It is even more preferable that at least one of the upper limit value or the lower limit value of the numerical range of either conditional expression (1) or (2) is set to the range of the following conditional expression (1b). 0.33 <Lfw / Ls<0.45 (1b) 1.0<(Rb+Ra) / (Rb-Ra)<1.9 (2b)

[0033] Next, a preferred configuration of the zoom lens L0 in each embodiment will be described.

[0034] The focus group LF may be made up of a cemented lens, but it is more preferable that it be made up of a single lens, which allows the focus group LF to be made even lighter.

[0035] It is also preferable that the focus unit LF move toward the object side during zooming from the wide-angle end to the telephoto end, which allows the focus unit LF to be positioned at a lower position for off-axial rays at the telephoto end, making it easier to further reduce the diameter of the focus unit LF.

[0036] It is also preferable to provide a lens group with positive refractive power closest to the image side of the rear group LR. This increases the focus (position) sensitivity of the focus group LF. This makes it possible to reduce the amount of movement of the focus group LF during focusing from infinity to close range. As a result, the diameter of the focus group LF can be reduced.

[0037] It is also preferable that the zoom lens L0 comprises a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a focus group LF, a fourth lens group L4 with positive refractive power, and a fifth lens group L5 with positive refractive power, thereby ensuring an appropriate back focus due to the positive refractive powers of the fourth lens group L4 and the fifth lens group L5.

[0038] Alternatively, the zoom lens L0 may be configured with a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, a focus unit LF, a fourth lens unit L4 with negative refractive power, and a fifth lens unit L5 with positive refractive power, which makes it possible to cancel chromatic aberration of magnification between the fourth lens unit L4 and the fifth lens unit L5, thereby achieving even higher performance.

[0039] Furthermore, by configuring the focus group LF, the fourth lens group L4, and the fifth lens group L5 each with a single lens, the weight of the zoom lens L0 can be further reduced.

[0040] Furthermore, when the focus group LF, the fourth lens group L4, and the positive fifth lens group L5 are each composed of a single lens, it is advisable to make the image-side lens surface of each lens convex, which allows off-axis light rays to be incident gently (close to perpendicularly) on the surface, thereby suppressing fluctuations in astigmatism and field curvature during focusing.

[0041] Furthermore, it is preferable that the refractive index of the negative lens in the focus unit LF is 1.75 or more. This allows the curvature of the focus unit LF to be gentler, and the volume of the focus unit LF to be reduced. This allows the weight of the focus unit LF to be reduced.

[0042] Next, the conditional expressions that are preferably satisfied in the zoom lens L0 of each embodiment will be described.

[0043] It is preferable that the zoom lens L0 of each embodiment satisfies one or more of the following conditional expressions. -3.5<(1-βf 2 )×βr 2 <-1.3 (3) 0.6 <skw / fw<1.4 (4) 28<νdn<45 (5) 0.020 <Dt / ft<0.12 (6) -20<100×(y-y0) / y0<-8 (7) -3.5 <fna / fw<-1.0 (8) 1.4 <fs / fw<3.0 (9) 0.8 <Lft / Lfw<1.4 (10) 1.2 <ft / fw<2.1 (11)

[0044] Here, βf is the lateral magnification of the focus group LF at the telephoto end. βr is the combined lateral magnification of all lens groups located closer to the image side than the focus group LF at the telephoto end. skw is the back focal length at the wide-angle end. fw is the focal length of the entire zoom lens system L0 at the wide-angle end. νdn is the Abbe number of the negative lens included in the focus group LF. Dt is the amount of movement of the focus group LF associated with focusing from infinity to close range at the telephoto end. Here, Dt takes a positive value when the focus group LF moves from the object side to the image side. ft is the focal length of the entire zoom lens system L0 at the telephoto end. y is the maximum real image height at the wide-angle end. y0 is the ideal image height at the angle of view (maximum angle of view) corresponding to the maximum real image height y at the wide-angle end. fna is the focal length of the focus group LF. fs is the combined focal length of all lenses from the aperture stop SP to the focus group LF at the wide-angle end. Lft is the distance from the aperture stop SP to the vertex of the object-side lens surface of the focus unit LF at the telephoto end.

[0045] Conditional expression (3) represents the focus (position) sensitivity of the focus group LF at the telephoto end. If the lower limit is not met, the absolute value of the ratio between the angle of incidence of an on-axis ray onto the focus group LF and the angle of emergence onto the lens group arranged on the image side of the focus group LF becomes too large, resulting in excessive fluctuations in spherical aberration when the focus group LF moves during focusing. If the upper limit is met, the focus sensitivity becomes too low, the amount of movement from infinity to close range becomes large, and the focus group LF may be positioned at a high position for off-axial rays, resulting in a large focus group LF.

[0046] Condition (4) expresses the ratio of the back focal length at the wide-angle end to the focal length of the entire system at the wide-angle end. If the lower limit is not met, the back focal length at the wide-angle end becomes too short. As a result, ghosting is more likely to occur due to reflected light between the low-pass filter or IR-cut filter located on the object side of the image plane IP and the lens closest to the image in the zoom lens L0. If the upper limit is exceeded, the zoom lens will undesirably become too large.

[0047] Conditional expression (5) represents the Abbe number of the negative lens in the focus group LF. Exceeding the upper limit is not desirable because it becomes difficult for the negative lens in the focus group LF to sufficiently cancel out the lateral chromatic aberration that occurs in the rear group LR when focusing at infinity. If the lower limit is not satisfied, lateral chromatic aberration tends to become large, particularly on the close-up side. Note that when the focus group LF includes multiple negative lenses, conditional expression (5) only needs to be satisfied by at least one negative lens, but it is preferable that all negative lenses satisfy it.

[0048] Conditional expression (6) represents the ratio of the amount of movement of the focus group LF at the telephoto end accompanying focusing from infinity to close range to the focal length of the entire system at the telephoto end. If the lower limit is not met, the refractive power of the focus group LF must be increased to enable focusing at sufficiently close ranges. As a result, fluctuations in spherical aberration, field curvature, and astigmatism accompanying focusing tend to become large. If the upper limit is exceeded, the amount of movement of the focus group LF becomes too large, and the focus group LF may be positioned at a high position on the close range side for off-axial rays, resulting in a large focus group LF.

[0049] Conditional expression (7) expresses the distortion rate at the wide-angle end. The ideal image height y0 is calculated by f × tan θ, where f is the focal length of the entire system at the wide-angle end, and θ is the angle (half angle of view) between the optical axis and the ray of light incident from the object side corresponding to the maximum real image height y and the entire system's closest point. The real image height y can be determined by the maximum radius of the image circle of the zoom lens L0. If the upper limit is exceeded, the refractive power of the first lens unit L1 must be reduced to reduce the absolute value of the distortion rate. This increases the distance from the lens surface closest to the object to the image plane IP, making the zoom lens L0 more bulky. If the lower limit is exceeded, the absolute value of the distortion rate becomes too large, significantly compressing the peripheral areas of the image, making it difficult to obtain images of sufficiently high image quality.

[0050] Conditional expression (8) represents the ratio of the focal length of the focus unit LF to the focal length of the entire system at the wide-angle end. If the lower limit is not met, the absolute value of the focal length of the focus unit LF becomes too long, resulting in a large amount of movement during focusing. As a result, the focus unit LF may be positioned at a high position for off-axial light rays, resulting in an increase in size of the focus unit LF. If the upper limit is met, the absolute value of the focal length of the focus unit LF becomes too short, resulting in excessive fluctuations in spherical aberration, field curvature, and astigmatism during focusing.

[0051] Conditional expression (9) represents the ratio of the composite focal length of each lens from the aperture stop SP to the focus group LF to the focal length of the entire system at the wide-angle end. If the lower limit is exceeded, the composite focal length of the lens groups from the aperture stop SP to the focus group LF becomes too short, resulting in excessive spherical aberration. If the upper limit is exceeded, the composite focal length of the lens groups from the aperture stop SP to the focus group LF becomes too long, causing the height of off-axial rays incident on the focus group LF to increase, resulting in an increase in the size of the focus group LF.

[0052] Conditional expression (10) represents the ratio of the distance from the aperture stop SP to the vertex of the lens surface of the focus group LF closest to the object at the telephoto end to the distance from the aperture stop SP to the vertex of the lens surface of the focus group LF closest to the object at the wide-angle end. If the ratio is below the lower limit, the distance from the aperture stop SP to the vertex of the lens surface of the focus group LF closest to the object at the wide-angle end becomes too long, resulting in off-axial rays entering the focus group LF at the wide-angle end becoming higher and larger. If the ratio is above the upper limit, the distance from the aperture stop SP to the vertex of the lens surface of the focus group LF closest to the object at the telephoto end becoming too long, resulting in off-axial rays entering the focus group LF at the telephoto end becoming higher and larger.

[0053] Condition (11) defines the zoom ratio. If the upper limit is exceeded, the amount of movement of each lens group tends to increase, and the zoom lens L0 tends to become larger in size in order to secure space for the movement. If the lower limit is not reached, the zoom ratio becomes too small, making it difficult for the zoom lens to function satisfactorily.

[0054] It is more preferable to set at least one of the upper and lower limits of the conditional expressions (3) to (11) to the following numerical ranges. -3.3<(1-βf 2 )×βr 2 <-1.4 (3a) 0.7 <skw / fw<1.3 (4a) 30<νdn<42 (5a) 0.030 <Dt / ft<0.11 (6a) -19<100×(y-y0) / y0<-10 (7a) -3.1 <fna / fw<-1.1 (8a) 1.6 <fs / fw<2.7 (9a) 0.9 <Lft / Lfw<1.3 (10a) 1.3 <ft / fw<2.0 (11a)

[0055] It is more preferable to set at least one of the upper and lower limits of the conditional expressions (3) to (11) to the following numerical ranges. -3.2<(1-βf 2 )×βr 2 <-1.5 (3b) 0.8 <skw / fw<1.2 (4b) 34<νdn<40 (5b) 0.035 <Dt / ft<0.10 (6b) -18<100×(y-y0) / y0<-14 (7b) -2.8 <fna / fw<-1.2 (8b) 1.7 <fs / fw<2.4 (9b) 1.0 <Lft / Lfw<1.2 (10b) 1.4 <ft / fw<1.9 (11b)

[0056] Next, the configuration of the zoom lens L0 in each embodiment will be described in detail.

[0057] [Example 1] The zoom lens L0 of Example 1 is composed of, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with negative refractive power, a fourth lens group L4 with positive refractive power, and a fifth lens group L5 with positive refractive power. By alternating the lens groups with negative refractive power and positive refractive power, lateral color and axial chromatic aberration are appropriately corrected. Furthermore, by making the fifth lens group L5 positive, a wide angle of view is achieved while ensuring a sufficient back focus, and ghosting caused by unwanted light reflected between the image plane IP (or a low-pass filter or IR cut filter that may be arranged on the object side thereof) and the fifth lens group L5 can be suppressed. Furthermore, the third lens group L3 is configured to move during focusing, and the object side of the third lens group L3 has a concentric shape, with a concave surface relative to the aperture stop SP. As a result, even when the third lens unit L3 moves during focusing, fluctuations in field curvature and astigmatism are suppressed, enabling high performance across the entire image field. Furthermore, by configuring the third lens unit L3 with two lenses, a positive lens and a negative lens, it is possible to suppress fluctuations in lateral chromatic aberration and axial chromatic aberration even when the third lens unit L3 moves in the optical axis direction.

[0058] In addition, the first lens group is designed to move monotonically toward the image side during zooming from the wide-angle end to the telephoto end, which increases the absolute value of the focal length of the first lens group (weakens the refractive power) and improves the performance of the zoom lens L0.

[0059] [Example 2] In Example 2, the third lens unit L3, which is the focusing unit, is configured with one negative lens, unlike Example 1. This makes it possible to reduce the size of the third lens unit L3, which moves during focusing.

[0060] [Example 3] The zoom lens L0 of Example 3 is composed of, arranged in order from the object side to the image side, a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, a third lens unit L3 with negative refractive power, a fourth lens unit L4 with negative refractive power, and a fifth lens unit L5 with positive refractive power. By making the fourth lens unit L4 have negative refractive power, chromatic aberration of magnification that occurs in the fifth lens unit L5 with positive refractive power can be effectively corrected. In addition, by locating a positive lens closest to the object side, negative distortion that occurs in the first lens unit L1 is reduced, and by suppressing distortion, compression at the periphery of the image is suppressed, thereby improving resolution.

[0061] In addition, by cementing the fourth and fifth lenses together, the intensity of unwanted light reflected between the fourth and fifth lenses is reduced, suppressing ghosting.

[0062] Furthermore, by moving the fifth lens unit L5 toward the object side from the wide-angle end to the telephoto end, the fifth lens unit L5 can be positioned at a position where the height of off-axial rays is low at the telephoto end, thereby reducing the diameter.

[0063] [Example 4] The zoom lens L0 of Example 4 is composed of a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, a third lens unit L3 with positive refractive power, a fourth lens unit L4 with negative refractive power, a fifth lens unit L5 with positive refractive power, and a sixth lens unit L6 with positive refractive power. By dividing the positive refractive power lens unit before and after the aperture stop SP into two lens units that move independently during zooming, spherical aberration and coma are effectively corrected over a wide zoom range.

[0064] [Example 5] The zoom lens L0 of Example 5 is composed of, arranged in order from the object side to the image side, a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, a third lens unit L3 with negative refractive power, a fourth lens unit L4 with positive refractive power, and a fifth lens unit L5 with negative refractive power. By making the fourth lens unit L4 positive and the fifth lens unit L5 negative refractive power, the position of the combined front principal point of the fourth lens unit L4 and the fifth lens unit L5 can be moved toward the object side, shortening the back focal length and enabling the zoom lens L0 to be made more compact.

[0065] [Example 6] The zoom lens L0 of Example 5 is composed of, arranged in order from the object side to the image side, a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, a third lens unit L3 with negative refractive power, and a fourth lens unit L4 with positive refractive power. By providing one positive lens and one negative lens in the fourth lens unit L4, lateral chromatic aberration is effectively corrected over a wide zoom range.

[0066] The zoom lens L0 of each of the above-described embodiments may be used in an imaging device having an image processing function for correcting aberrations (distortion aberration and chromatic aberration of magnification).

[0067] Numerical Examples 1 to 6 corresponding to Examples 1 to 6, respectively, are shown below.

[0068] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial spacing (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. Furthermore, nd represents the refractive index of each optical element at the d-line, and vd represents the Abbe number of the optical element. The Abbe number vd of a certain material is given by Nd, NF, NC, and Ng, respectively, when the refractive indices at the Fraunhofer d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm) are Nd, NF, NC, and Ng, respectively. νd=(Nd-1) / (NF-NC) It is expressed as:

[0069] If the optical surface is aspherical, an asterisk (*) is added to the right of the surface number. The aspherical shape is expressed as follows: X is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10, A12, ... are the aspherical coefficients of each order. x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h 8+A10×h 10 In addition, "e±XX" in each aspherical coefficient is "×10± XX " means.

[0070] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 45.932 1.80 2.00100 29.1 36.70 2 19.277 7.27 29.17 3 81.393 1.40 1.84943 42.6 27.28 4 20.862 6.78 24.31 5 -32.534 1.30 1.49700 81.5 24.21 6 39.245 0.34 25.06 7 36.818 6.92 1.78582 36.7 25.39 8 -45.455 (variable) 25.35 9 46.667 1.80 1.60738 56.8 11.23 10 ∞ 3.00 10.63 11 (Aperture) ∞ 3.00 10.34 12 88.981 1.00 1.80400 46.5 10.34 13 19.604 2.53 1.71300 53.9 10.25 14 -123.595 2.00 10.21 15 16.661 2.78 1.51633 64.1 10.41 16 47.619 4.87 10.69 17 34.510 1.00 1.90043 37.4 12.26 18 11.580 5.34 1.49700 81.5 12.24 19 -36.852 (variable) 13.26 20 -26.584 3.17 1.77250 49.6 14.02 21 -13.000 1.10 1.85107 36.9 14.79 22 -225.385 (variable) 16.29 23* -50.000 3.00 1.53110 55.9 21.52 24* -34.796 (variable) 23.70 25 -157.498 4.50 1.79008 48.6 36.60 26 -45.000 13.50 37.47 Image plane ∞ Aspheric data Page 23 K = 0.00000e+000 A 4=-7.50939e-005 A 6= 6.59902e-007 A 8=-4.44635e-009 A10= 1.37303e-011 Page 24 K = 0.00000e+000 A 4=-3.09530e-005 A 6= 4.44991e-007 A 8=-1.75524e-009 A10= 4.51720e-012 Various data Zoom ratio 1.89 Wide-angle Mid-range Telephoto Focal length 15.45 20.34 29.15 F-number 4.60 5.25 6.32 Half angle of view (°) 49.36 44.61 36.19 Image height 18.00 20.06 21.33 Lens length 115.26 109.84 107.01 BF 13.50 13.50 13.50 d 8 25.18 13.47 1.21 d19 2.67 3.30 5.13 d22 7.82 7.19 5.36 d24 1.20 7.49 16.92 Entrance pupil position 17.00 15.69 13.74 Exit pupil position -64.71 -86.93 -130.67 Front principal point position 29.40 31.91 37.00 Back principal point position -1.95 -6.84 -15.65 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -25.31 25.82 -0.46 -26.81 2 9 24.31 27.31 9.72 -14.84 3 20 -31.88 4.27 0.06 -2.33 4 23 201.66 3.00 6.03 4.20 5 25 78.36 4.50 3.46 0.99 Single lens data Lens starting surface focal length 1 1 -34.34 2 3 -33.38 3 5 -35.58 4 7 26.88 5 9 76.83 6 12 -31.48 7 13 23.91 8 15 48.16 9 17 -19.76 10 18 18.40 11 20 29.90 12 21 -16.25 13 23 201.66 14 25 78.36

[0071] [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 39.485 1.80 2.00100 29.1 35.98 2 19.277 6.35 29.06 3 81.393 1.40 1.90043 37.4 27.89 4 21.695 6.53 24.75 5 -37.674 1.30 1.49700 81.5 24.58 6 45.445 1.55 24.80 7 48.066 6.33 1.80610 33.3 25.36 8 -58.121 (variable) 25.19 9 75.709 2.91 1.63930 44.9 12.62 10 -99.071 5.00 11.75 11 (Aperture) ∞ 3.00 10.25 12 90.807 1.00 1.80400 46.5 10.20 13 21.203 2.41 1.71300 53.9 10.11 14 -125.965 2.00 10.05 15 14.434 3.39 1.48749 70.2 10.46 16 47.619 3.38 10.70 17 40.616 1.00 1.90043 37.4 11.54 18 10.473 5.52 1.49700 81.5 11.52 19 -36.785 (variable) 12.72 20 -24.105 1.10 1.80100 35.0 14.79 21 -332.736 (variable) 15.94 22* -50.000 3.00 1.53110 55.9 21.21 23* -33.834 (variable) 23.27 24 -186.603 4.91 1.80400 46.5 37.46 25 -45.000 13.50 38.41 Image plane ∞ Aspheric data Page 22 K = 0.00000e+000 A 4=-3.17244e-005 A 6= 2.39294e-007 A 8=-2.65521e-009 A10= 1.39956e-011 Page 23 K = 0.00000e+000 A 4= 7.78280e-006 A 6= 1.77889e-007 A 8=-9.23774e-010 A10= 4.78158e-012 Various data Zoom ratio 1.89 Wide-angle Mid-range Telephoto Focal length 15.45 20.53 29.15 F-number 4.60 5.27 6.36 Half angle of view (°) 49.88 45.31 36.58 Image height 18.34 20.75 21.63 Lens total length 115.28 109.06 106.60 BF 13.50 13.50 13.50 d 8 24.84 12.64 1.20 d19 2.86 4.14 6.51 d21 9.00 7.72 5.35 d23 1.20 7.19 16.16 Entrance pupil position 17.59 16.29 14.57 Exit pupil position -64.63 -84.63 -125.12 Front principal point position 29.98 32.52 37.59 Back principal point position -1.95 -7.03 -15.65 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -24.39 25.25 0.53 -24.54 2 9 24.70 29.61 10.23 -15.77 3 20 -32.50 1.10 -0.05 -0.66 4 22 185.12 3.00 5.69 3.85 5 24 72.63 4.91 3.53 0.85 Single lens data Lens starting surface focal length 1 1 -39.38 2 3 -33.22 3 5 -41.23 4 7 33.53 5 9 67.57 6 12 -34.63 7 13 25.63 8 15 41.11 9 17 -15.92 10 18 17.06 11 20 -32.50 12 22 185.12 13 24 72.63

[0072] [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 52.248 2.62 1.51633 64.1 28.75 2 140.000 0.15 26.67 3 26.292 0.80 1.90043 37.4 20.18 4 10.697 3.20 15.85 5 60.521 0.80 1.95375 32.3 15.54 6 10.056 3.71 13.19 7 -25.717 0.80 1.49700 81.5 13.14 8 14.607 4.06 1.90366 31.3 13.41 9 -55.225 (variable) 13.10 10 -101.139 2.20 1.48749 70.2 7.88 11 -21.879 2.89 8.23 12 (Aperture) ∞ 1.75 8.52 13 13.538 5.13 1.48749 70.2 8.74 14 -10.601 1.00 1.77250 49.6 8.16 15 -22.350 3.58 8.16 16 20.040 0.70 1.90043 37.4 9.69 17 8.853 4.71 1.49700 81.5 9.63 18 -21.100 (variable) 10.46 19 -19.295 0.70 1.91082 35.3 10.75 20 -100.891 (variable) 11.26 21* -24.999 1.50 1.53110 55.9 14.14 22* -26.775 (variable) 15.39 23 -182.094 4.42 1.60311 60.6 18.76 24 -22.000 (variable) 20.18 Image plane ∞ Aspheric data Page 21 K = 0.00000e+000 A 4=-1.91538e-004 A 6= 5.07567e-006 A 8=-8.17417e-008 A10= 5.32571e-010 Page 22 K = 0.00000e+000 A 4=-6.30674e-005 A 6= 4.22634e-006 A 8=-5.18522e-008 A10= 2.90202e-010 Various data Zoom ratio 1.47 Wide-angle Mid-range Telephoto Focal length 9.97 12.66 14.64 F-number 3.50 3.94 4.23 Half angle of view (°) 49.63 44.83 41.54 Image height 11.72 12.58 12.97 Lens length 72.73 71.60 71.78 BF 10.06 12.25 14.31 d 9 10.09 4.76 1.89 d18 1.44 2.18 2.76 d20 5.42 4.68 4.11 d22 0.99 3.00 4.00 d24 10.06 12.25 14.31 Entrance pupil position 11.15 10.50 10.06 Exit pupil position -51.09 -59.37 -63.10 Front principal point position 19.49 20.92 21.93 Back principal point position 0.09 -0.40 -0.33 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -12.21 16.14 2.87 -11.14 2 10 15.46 21.97 9.98 -10.48 3 19 -26.30 0.70 -0.09 -0.45 4 21 -1004.27 1.50 -19.52 -20.90 5 23 41.06 4.42 3.10 0.37 Single lens data Lens starting surface focal length 1 1 159.82 2 3 -20.53 3 5 -12.74 4 7 -18.62 5 8 13.15 6 10 56.75 7 13 13.11 8 14 -27.11 9 16 -18.15 10 17 13.24 11 19 -26.30 12 21 -1004.27 13 23 41.06

[0073] [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 40.925 1.80 2.05090 26.9 33.27 2 21.334 4.87 27.89 3 79.995 1.40 1.95375 32.3 26.78 4 24.034 4.47 23.95 5 -91.221 1.30 1.49700 81.5 23.68 6 31.289 2.00 22.62 7 59.784 3.91 1.82097 22.5 22.63 8 -85.008 (variable) 22.27 9 100.000 1.00 1.63980 34.5 9.42 10 20.000 2.47 1.88645 38.8 9.51 11 -90.366 3.00 9.49 12 (Aperture) ∞ (Variable) 9.12 13 15.735 3.66 1.52647 69.8 11.78 14 -17.484 0.59 11.90 15 -16.171 1.00 1.90043 37.4 11.76 16 44.055 5.10 1.49700 81.5 12.35 17 -13.352 (variable) 13.43 18 -14.286 1.10 1.87587 39.9 13.46 19 -74.875 (variable) 14.64 20 5903.921 2.85 1.49700 81.5 19.07 21* -33.757 (variable) 20.14 22 -98.558 3.58 1.80400 46.5 26.77 23 -45.000 (variable) 28.10 Image plane ∞ Aspheric data Page 21 K = 0.00000e+000 A 4= 6.79219e-005 A 6= 1.06797e-007 A 8= 1.34694e-009 A10=-5.68552e-012 Various data Zoom ratio 1.82 Wide-angle Mid-range Telephoto Focal length 16.00 20.22 29.17 F-number 4.60 4.97 5.66 Half angle of view (°) 48.58 45.05 36.57 Image height 18.14 20.26 21.64 Lens length 99.94 95.51 91.54 BF 13.04 19.20 30.42 d 8 22.55 12.93 1.20 d12 4.71 4.81 4.91 d17 2.26 2.44 3.69 d19 5.43 4.78 3.15 d21 7.84 7.24 4.07 d23 13.04 19.20 30.42 Entrance pupil position 17.09 15.78 13.40 Exit pupil position -53.81 -50.02 -38.59 Front principal point position 29.26 30.09 30.24 Back principal point position -2.96 -1.02 1.25 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -22.38 19.75 2.35 -15.16 2 9 35.44 6.47 0.93 -4.01 3 13 27.72 10.35 4.14 -3.77 4 18 -20.33 1.10 -0.14 -0.73 5 20 67.55 2.85 1.89 -0.01 6 22 100.02 3.58 3.55 1.62 Single lens data Lens starting surface focal length 1 1 -44.50 2 3 -36.47 3 5 -46.71 4 7 43.28 5 9 -39.27 6 10 18.67 7 13 16.35 8 15 -13.03 9 16 21.24 10 18 -20.33 11 20 67.55 12 22 100.02

[0074] [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 50.254 1.80 2.05090 26.9 36.85 2 19.398 6.82 29.33 3 135.195 1.40 1.95375 32.3 28.56 4 30.089 5.41 26.58 5 -47.967 1.30 1.49700 81.5 26.52 6 37.077 0.19 27.13 7 35.891 7.61 1.82283 30.8 27.32 8 -62.958 (variable) 27.08 9 100.000 1.00 1.53458 47.9 10.67 10 20.000 2.47 1.84733 42.8 10.74 11 -7293.532 3.20 10.64 12 (Aperture) ∞ 6.70 10.31 13 20.310 3.45 1.56657 68.8 11.12 14 -23.439 0.77 11.40 15 -17.148 1.00 1.90043 37.4 11.36 16 58.384 4.41 1.49700 81.5 12.04 17 -15.093 (variable) 13.17 18 -22.042 1.10 1.85000 35.0 14.06 19 -73.968 (variable) 14.82 20* 123.352 4.61 1.51380 54.6 21.29 21* -32.035 (variable) 22.35 22 -43.536 1.50 1.88449 39.0 23.28 23 -87.118 (variable) 24.42 Image plane ∞ Aspheric data Page 20 K = 0.00000e+000 A 4= 7.78121e-006 A 6=-1.41841e-007 A 8= 1.32693e-009 A10=-7.58503e-012 Page 21 K = 0.00000e+000 A 4= 4.93770e-005 A 6=-4.36212e-008 A 8= 1.50692e-009 A10=-6.87281e-012 Various data Zoom ratio 1.88 Wide-angle Mid-range Telephoto Focal length 15.53 20.47 29.15 F-number 4.60 5.01 5.59 Half angle of view (°) 49.20 43.44 35.66 Image height 18.00 19.38 20.92 Lens total length 120.00 109.11 99.49 BF 15.70 23.59 24.20 d 8 32.68 17.17 1.20 d17 4.32 4.50 5.63 d19 10.14 6.17 3.93 d21 2.40 2.92 9.77 d23 15.70 23.59 24.20 Entrance pupil position 17.77 16.10 13.44 Exit pupil position -40.00 -33.43 -33.85 Front principal point position 28.97 29.22 27.95 Back principal point position 0.16 3.13 -4.95 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -26.49 24.53 -0.82 -23.99 2 9 25.34 23.00 10.82 -11.53 3 18 -37.30 1.10 -0.25 -0.86 4 20 50.00 4.61 2.44 -0.63 5 22 -100.01 1.50 -0.81 -1.62 Single lens data Lens starting surface focal length 1 1 -30.99 2 3 -40.84 3 5 -41.86 4 7 28.78 5 9 -46.97 6 10 23.54 7 13 19.77 8 15 -14.63 9 16 24.62 10 18 -37.30 11 20 50.00 12 22 -100.01

[0075] [Numerical Example 6] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 46.382 1.80 2.05090 26.9 36.85 2 19.375 6.91 29.33 3 148.313 1.40 1.95375 32.3 28.56 4 28.489 5.81 26.58 5 -43.395 1.30 1.49700 81.5 26.52 6 35.729 0.20 27.13 7 35.165 8.11 1.79522 32.0 27.32 8 -51.640 (variable) 27.08 9 100.000 1.00 1.51753 52.4 10.67 10 20.000 2.47 1.82588 45.0 10.74 11 -7234.968 3.06 10.64 12 (Aperture) ∞ 7.94 10.31 13 20.503 3.02 1.56724 64.1 11.12 14 -21.985 0.74 11.40 15 -16.908 1.00 1.90043 37.4 11.36 16 58.603 4.42 1.49700 81.5 12.04 17 -15.011 (variable) 13.17 18 -23.876 1.10 1.85000 35.0 14.06 19 -82.849 (variable) 14.82 20* 112.899 3.87 1.49967 65.6 21.29 21* -32.833 2.02 22.35 22 -40.113 1.50 1.75377 52.3 23.28 23 -87.118 (variable) 24.42 Image plane ∞ Aspheric data Page 20 K = 0.00000e+000 A 4= 8.69555e-006 A 6=-1.43147e-007 A 8= 1.23812e-009 A10=-8.16964e-012 Page 21 K = 0.00000e+000 A 4= 4.80363e-005 A 6=-4.52567e-008 A 8= 1.32395e-009 A10=-7.40260e-012 Various data Zoom ratio 1.87 Wide-angle Mid-range Telephoto Focal length 15.60 19.00 29.15 F-number 4.54 4.86 5.73 Half angle of view (°) 49.09 44.98 35.72 Image height 18.00 18.99 20.96 Lens total length 120.00 112.82 104.38 BF 18.33 24.39 34.47 d 8 30.79 19.62 1.20 d17 2.82 2.53 3.93 d19 10.38 8.60 7.10 d23 18.33 24.39 34.47 Entrance pupil position 17.79 16.60 13.71 Exit pupil position -40.00 -36.67 -35.07 Front principal point position 29.21 29.69 30.64 Back principal point position 2.73 5.39 5.32 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -27.61 25.54 -1.42 -26.70 2 9 25.57 23.66 12.00 -11.67 3 18 -39.80 1.10 -0.24 -0.84 4 20 101.68 7.39 0.11 -5.31 Single lens data Lens starting surface focal length 1 1 -32.78 2 3 -37.19 3 5 -39.21 4 7 27.44 5 9 -48.51 6 10 24.15 7 13 19.20 8 15 -14.48 9 16 24.53 10 18 -39.80 11 20 51.36 12 22 -100.00

[0076] The table below shows the various values ​​for each example.

[0077] [Table 1]

[0078] [Imaging device] Next, an embodiment of a digital still camera (image capture device) using the zoom lens of the present invention will be described with reference to Fig. 13. In Fig. 13, 10 is a camera body, and 11 is a lens device including any of the zoom lenses L0 described in Examples 1 to 6.

[0079] Reference numeral 12 denotes a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the camera body and receives and photoelectrically converts the optical image formed by the lens device 11. The camera body 10 may be a so-called single-lens reflex camera that has a quick-turn mirror, or a so-called mirrorless camera that does not have a quick-turn mirror.

[0080] In this way, by applying the zoom lens L0 of the present invention to an imaging device such as a digital still camera, quick focusing is possible and high-quality images with little fluctuation in image quality at each focus position can be obtained.

[0081] Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0082] L0 zoom lens L1 First lens group L2 Second lens group LF Focus Group LR rear group SP aperture stop

Claims

1. A zoom lens having, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a rear group including one or more lens groups, wherein the first lens group moves during zooming, changing the spacing between adjacent lens groups; the zoom lens has an aperture stop; the rear group has a focus group with negative refractive power that moves toward the image side during focusing from infinity to a close distance, and at least one lens group provided on the image side of the focus group, the first lens group has three or more negative lenses, the focus group is composed of a cemented lens or a single lens, the refractive index of the negative lens included in the focus group is 1.75 or more; Let Lfw be the distance from the aperture stop to the vertex of the surface of the focus group closest to the object side at the wide-angle end, Ls be the distance from the aperture stop to the image plane at the wide-angle end, Ra be the radius of curvature of the lens surface of the focus group closest to the object side, Rb be the radius of curvature of the lens surface of the focus group closest to the image side, y be the maximum real image height at the wide-angle end, and y0 be the ideal image height of the maximum angle of view of the zoom lens at the wide-angle end. 0.3<Lfw / Ls<0.5 0.8<(Rb+Ra) / (Rb-Ra)<2.2 -20<100×(y-y0) / y0<-8 A zoom lens characterized by satisfying the following conditional expressions:

2. 2. The zoom lens according to claim 1, wherein the focus group is composed of a single lens.

3. When the lateral magnification of the focus group at the telephoto end is βf and the combined lateral magnification of all lens groups arranged on the image side of the focus group at the telephoto end is βr, -3.5<(1-β&) ２ )×βr ２ <-1.3 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. A zoom lens having, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a rear group including one or more lens groups, wherein the first lens group moves during zooming, changing the spacing between adjacent lens groups; the zoom lens has an aperture stop; the rear group has a focus group with negative refractive power that moves toward the image side during focusing from infinity to a close distance, and at least one lens group provided on the image side of the focus group, the first lens group has three or more negative lenses, the focus group is composed of a cemented lens or a single lens, Let Lfw be the distance from the aperture stop to the vertex of the surface of the focus group closest to the object at the wide-angle end, Ls be the distance from the aperture stop to the image plane at the wide-angle end, Ra be the radius of curvature of the lens surface of the focus group closest to the object side, Rb be the radius of curvature of the lens surface of the focus group closest to the image side, βf be the lateral magnification of the focus group at the telephoto end, and βr be the combined lateral magnification of all lens groups arranged closer to the image than the focus group at the telephoto end. 0.3<Lfw / Ls<0.5 0.8<(Rb+Ra) / (Rb-Ra)<2.2 -3.5<(1-β&) ２ )×βr ２ <-1.3 A zoom lens characterized by satisfying the following conditional expressions:

5. When the back focus at the wide-angle end is skw and the focal length of the zoom lens at the wide-angle end is fw, 0.6<skw / fw<1.4 5. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. A zoom lens having, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a rear group including one or more lens groups, wherein the first lens group moves during zooming, changing the spacing between adjacent lens groups; the zoom lens has an aperture stop; the rear group has a focus group with negative refractive power that moves toward the image side during focusing from infinity to a close distance, and at least one lens group provided on the image side of the focus group, the first lens group has three or more negative lenses, the focus group is composed of a cemented lens or a single lens, the refractive index of the negative lens included in the focus group is 1.75 or more; Let Lfw be the distance from the aperture stop to the vertex of the surface of the focus group closest to the object side at the wide-angle end, Ls be the distance from the aperture stop to the image plane at the wide-angle end, Ra be the radius of curvature of the lens surface of the focus group closest to the object side, Rb be the radius of curvature of the lens surface of the focus group closest to the image side, skw be the back focus at the wide-angle end, and fw be the focal length of the zoom lens at the wide-angle end. 0.3<Lfw / Ls<0.5 0.8<(Rb+Ra) / (Rb-Ra)<2.2 0.6<skw / fw<1.4 A zoom lens characterized by satisfying the following conditional expressions:

7. When the Abbe number of the negative lens included in the focus group is νdn, 28<νdn<45 7. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. A zoom lens having, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a rear group including one or more lens groups, wherein the first lens group moves during zooming, changing the spacing between adjacent lens groups; the zoom lens has an aperture stop; the rear group has a focus group with negative refractive power that moves toward the image side during focusing from infinity to a close distance, and at least one lens group provided on the image side of the focus group, the first lens group has three or more negative lenses, the focus group is composed of a cemented lens or a single lens, the refractive index of the negative lens included in the focus group is 1.75 or more; Let Lfw be the distance from the aperture stop to the vertex of the surface of the focus group closest to the object at the wide-angle end, Ls be the distance from the aperture stop to the image plane at the wide-angle end, Ra be the radius of curvature of the lens surface of the focus group closest to the object, Rb be the radius of curvature of the lens surface of the focus group closest to the image, and νdn be the Abbe number of a negative lens included in the focus group. 0.3<Lfw / Ls<0.5 0.8<(Rb+Ra) / (Rb-Ra)<2.2 28<νdn<45 A zoom lens characterized by satisfying the following conditional expressions:

9. When the amount of movement of the focus group at the telephoto end accompanying focusing from infinity to a close distance is Dt and the focal length of the zoom lens at the telephoto end is ft, 0.020<Dt / ft<0.12 9. The zoom lens according to claim 1, wherein the following condition is satisfied:

10. When the focal length of the focus group is fna and the focal length of the zoom lens at the wide-angle end is fw, -3.5<fna / fw<-1.0 10. The zoom lens according to claim 1, wherein the following condition is satisfied:

11. When the composite focal length of all lenses from the aperture stop to the focus group at the wide-angle end is fs and the focal length of the zoom lens at the wide-angle end is fw, 1.4<fs / fw<3.0 11. The zoom lens according to claim 1, wherein the following condition is satisfied:

12. A zoom lens having, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a rear group including one or more lens groups, wherein the first lens group moves during zooming, changing the spacing between adjacent lens groups; the zoom lens has an aperture stop; the rear group has a focus group with negative refractive power that moves toward the image side during focusing from infinity to a close distance, and at least one lens group provided on the image side of the focus group, the first lens group has three or more negative lenses, the focus group is composed of a cemented lens or a single lens, the refractive index of the negative lens included in the focus group is 1.75 or more; Let Lfw be the distance from the aperture stop to the vertex of the surface of the focus group closest to the object at the wide-angle end, Ls be the distance from the aperture stop to the image plane at the wide-angle end, Ra be the radius of curvature of the lens surface of the focus group closest to the object side, Rb be the radius of curvature of the lens surface of the focus group closest to the image side, fs be the composite focal length of all lenses from the aperture stop to the focus group at the wide-angle end, and fw be the focal length of the zoom lens at the wide-angle end. 0.3<Lfw / Ls<0.5 0.8<(Rb+Ra) / (Rb-Ra)<2.2 1.4<fs / fw<3.0 A zoom lens characterized by satisfying the following conditional expressions:

13. When the distance from the aperture stop at the telephoto end to the vertex of the object-side lens surface of the focus group is Lft, 0.8<Lft / Lfw<1.4 13. The zoom lens according to claim 1, wherein the following condition is satisfied:

14. When the focal length of the zoom lens at the telephoto end is ft and the focal length of the zoom lens at the wide-angle end is fw, 1.2<ft / fw<2.1 14. The zoom lens according to claim 1, wherein the following condition is satisfied:

15. 15. The zoom lens according to claim 1, wherein the focus group moves toward the object side during zooming from the wide-angle end to the telephoto end.

16. 16. The zoom lens according to claim 1, wherein a lens group having a positive refractive power is disposed closest to the image side of the rear group.

17. 17. An imaging device comprising: the zoom lens according to claim 1; and an imaging element that receives an image formed by the zoom lens.

Images