Zoom lens and image capturing device having the same

Abstract

To provide a zoom lens which features a wide angle of view at the wide-angle end, a small minimum shooting distance and a large aperture, and yet offers high optical performance.SOLUTION: A zoom lens provided herein consists of a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a rear group including one or more lens groups and having positive composite refractive power at the wide-angle end, all arranged in order from the object side to the image side, and is configured such that a distance between each pair of adjacent lens groups changes while zooming. A lens on the most object side in the first lens group has negative refractive power. The third lens group moves while focusing. A focal length of the zoom lens at the wide-angle end, a focal length of the second lens, and a focal length of the third lens group are each set appropriately.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a zoom lens, and is particularly suitable for digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, etc.

Background Art

[0002] In recent years, for the optical system used in imaging devices, there has been a demand for being small in size, shortening the distance between an object and a lens (the shortest shooting distance) at the time of closest shooting and having a large maximum shooting magnification, and having high optical performance. In order to obtain good optical performance while reducing the size of the entire optical system, it is important to appropriately set the refractive power and configuration of each lens group, the movement conditions associated with zooming of each lens group, and the like.

[0003] Patent Document 1 discloses a zoom lens including first to fifth lens groups having negative, positive, negative, positive, and negative refractive powers, arranged in order from the object side to the image side.

[0004] Patent Document 2 discloses a zoom lens including first to fourth lens groups having negative, positive, negative, and negative refractive powers, arranged in order from the object side to the image side.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the zoom lens of Patent Document 1, focusing is performed by a third lens group, which is a focus group arranged on the object side of the aperture stop. However, since the focus sensitivity of the third lens group is low, if an attempt is made to shorten the minimum shooting distance, the zoom lens becomes large-sized, which is not preferable.

[0007] In the zoom lens of Patent Document 2, focusing is performed by a third lens group, which is a focus group arranged on the image side of the aperture stop. However, although the focus sensitivity of the third lens group is high, since the refractive power of the third lens group is strong, it is advantageous for shortening the minimum shooting distance. However, the mass of the third lens group increases, and changes in optical performance such as field curvature accompanying focusing increase, which is not preferable.

[0008] An object of the present invention is to provide a zoom lens that ensures a wide angle of view at the wide-angle end, has a short minimum shooting distance, is large-aperture, and provides high optical performance.

Means for Solving the Problems

[0009] A zoom lens according to one aspect of the present invention includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and one or more lens groups, which are arranged in order from the object side to the image side, and a rear group having a positive combined refractive power at the wide-angle end. The zoom lens is a zoom lens in which the distance between adjacent lens groups changes during zooming. The lens closest to the object side of the first lens group has a negative refractive power. During focusing, the third lens group moves. When the focal length of the zoom lens at the wide-angle end is fw, the focal length of the second lens group is f2, and the focal length of the third lens group is f3, -1.0 < fw / f3 < -0.3 -0.7 < f3 / f2 < 0.0 It is characterized by satisfying the following conditional expressions.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a zoom lens that ensures a wide angle of view at the wide-angle end, has a short minimum shooting distance, and has high optical performance while having a large aperture.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant descriptions are omitted.

[0013] In the following description, the wide-angle end and the telephoto end refer to the zoom positions when the lens group for zooming is located at both ends of the range where it can move on the optical axis due to the mechanism.

[0014] Figures 1, 3, 5, and 7 are cross-sectional views of the wide-angle end (short focal length end) and the telephoto end (long focal length end) of the zoom lenses of Examples 1 to 4, respectively. The zoom lenses of each example are optical systems used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras. Further, the zoom lenses of each example can also be used as projection optical systems for projection devices (projectors).

[0015] In each cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). The zoom lenses of each example are configured to have a plurality of lens groups. In this specification, a lens group is a collection of lenses that move integrally or remain stationary during zooming. That is, in the zoom lenses of each example, the distance between adjacent lens groups changes during zooming. Note that a lens group may be composed of a single lens or a plurality of lenses. Further, a lens group may include an aperture stop.

[0016] In each cross-sectional view, Li represents the i-th lens group (i is a natural number) counted from the object side. Further, SP is an aperture stop that determines (limits) the light beam of the open F-number (Fno). IP is the image plane. When the zoom lens of each example is used as a photographing optical system of a digital still camera or a digital video camera, the imaging surface of a solid-state imaging device (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is arranged. When the zoom lens of each example is used as a photographing optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP. The direction of the arrow indicated as "Focus" indicates the moving direction of the lens group during focusing from infinity to a short distance.

[0017] Figures 2, 4, 6, and 8 are aberration diagrams of the zoom lenses of Examples 1 to 4, respectively. In each aberration diagram, (A) is the aberration diagram at the wide-angle end, and (B) is the aberration diagram at the telephoto end.

[0018] In the spherical aberration diagram, Fno is the F-number, showing the amount of spherical aberration with respect to the d-line (wavelength 587.56 nm) and the g-line (wavelength 435.835 nm). In the astigmatism diagram, ΔS represents the amount of astigmatism in the sagittal image plane for the d-line, and ΔM represents the amount of astigmatism in the meridional image plane for the d-line. The distortion aberration diagram shows the amount of distortion aberration with respect to the d-line. The chromatic aberration diagram shows the amount of chromatic aberration for the g-line. ω is the semi-field angle (°), which is the field angle based on ray tracing values.

[0019] Next, the characteristic configurations of the zoom lenses in each embodiment will be described.

[0020] The zoom lenses of each embodiment have a plurality of lens groups as described above. The plurality of lens groups are composed of a first lens group L1 with negative refractive power (optical power = reciprocal of focal length), a second lens group L2 with positive refractive power, a third lens group L3 with negative refractive power, and a rear group LR with positive refractive power including one or more lens groups, arranged in order from the object side to the image side. By arranging the first lens group L1 with negative refractive power and the second lens group L2 with positive refractive power in order from the object side to the image side, a wide field angle can be ensured in the wide-angle range, and aberrations can be corrected well throughout the zoom range. Also, since the rear group LR includes one or more lens groups, coma aberration generated on the image side of the aperture stop SP, which changes during zooming, can be corrected well, and in particular, spherical aberration and coma aberration that are likely to occur due to the increase in the light beam in the telephoto range can be corrected well. Note that the first lens group L1 does not move (is fixed) during zooming and focusing.

[0021] The lens L11 on the most object side of the first lens group L1 has negative refractive power. Placing a lens with positive refractive power on the most object side is advantageous for correcting distortion aberration at the wide-angle end, but it is not preferable because it increases the weight of the zoom lens and the diameter of the filter attached to the object side becomes large.

[0022] During focusing, the third lens group L3 moves as the focusing group.

[0023] The zoom lenses of the respective embodiments satisfy the following conditional expressions (1) and (2).

[0024] -1.0 < fw / f3 < -0.3 (1) -0.7 < f3 / f2 < 0.0 (2) Here, fw is the focal length of the zoom lens at the wide-angle end. f2 is the focal length of the second lens group L2. f3 is the focal length of the third lens group L3.

[0025] Conditional expression (1) defines the value of the ratio of the focal length of the zoom lens at the wide-angle end to the focal length of the third lens group L3, and is a condition for achieving both shortening of the shortest shooting distance and suppression of optical performance changes due to focusing. If it is below the lower limit value of conditional expression (1), the refractive power of the third lens group L3 becomes strong, which is advantageous for shortening the shortest shooting distance, but it becomes difficult to suppress optical performance changes due to focusing, which is not preferable. If it exceeds the upper limit value of conditional expression (1), the refractive power of the third lens group L3 becomes weak, which is advantageous for suppressing optical performance changes due to focusing, but it becomes difficult to shorten the shortest shooting distance or the zoom lens becomes larger, which is not preferable.

[0026] Conditional expression (2) defines the value of the ratio of the focal length of the third lens group L3 to the focal length of the second lens group L2, and is a condition for suppressing optical performance changes due to focusing. If it is below the lower limit value of conditional expression (2), the refractive power of the third lens group L3 becomes weaker than that of the second lens group L2, which is advantageous for suppressing optical performance changes due to focusing, but it becomes difficult to shorten the shortest shooting distance or the zoom lens becomes larger, which is not preferable. If it exceeds the upper limit value of conditional expression (2), the refractive power of the third lens group L3 becomes positive, and it becomes difficult to correct spherical aberration and axial chromatic aberration generated by the axial light beam generated in the second lens group L2, which is not preferable.

[0027] As described above, by appropriately configuring each lens group and satisfying the conditional expressions (1) and (2), it is possible to realize a zoom lens that ensures a wide angle of view at the wide-angle end, has a short minimum shooting distance, has a large aperture, and provides high optical performance from infinity shooting to closest shooting.

[0028] Note that it is preferable that the numerical ranges of the conditional expressions (1) and (2) be the numerical ranges of the following conditional expressions (1a) and (2a).

[0029] -0.70 < fw / f3 < -0.32 (1a) -0.65 < f3 / f2 < -0.20 (2a) By satisfying the conditional expression (1a), it is easy to suppress the spherical aberration generated by the on-axis light beam in the wide-angle region. Further, by satisfying the conditional expression (2a), it is easy to achieve both the curvature of field and the increase in lateral chromatic aberration towards the wide-angle end generated by the off-axis light beam and the miniaturization of the zoom lens.

[0030] Also, it is preferable that the numerical ranges of the conditional expressions (1) and (2) be the numerical ranges of the following conditional expressions (1b) and (2b).

[0031] -0.5 < fw / f3 < -0.35 (1b) -0.6 < f3 / f2 < -0.5 (2b) Next, in the zoom lens of each embodiment, a preferable configuration to be satisfied will be described.

[0032] It is preferable that the first lens group L1 has three negative-power lenses arranged in order from the object side to the image side. With such a configuration, it is possible to ensure a wide angle of view in the wide-angle region and favorably correct various off-axis aberrations such as coma aberration and curvature of field, which is preferable.

[0033] It is preferable that the first lens group L1 is composed of three negative-power lenses and one positive-power lens arranged in order from the object side to the image side. With such a configuration, the degree of freedom in selecting the lens material of the negative-power lens increases, and various aberrations such as lateral chromatic aberration can be favorably corrected, which is preferable.

[0034] The lens with negative refractive power included in the first lens group L1 preferably has an aspherical surface on one side. With such a configuration, it is preferable because it becomes easy to achieve miniaturization while effectively correcting the field curvature at the wide-angle end. However, if it has two or more aspherical surfaces, although it is advantageous for correcting field curvature and distortion aberration, it becomes difficult to mold the lens and it becomes difficult to ensure optical performance, so it is not preferable.

[0035] The second lens group L2 preferably has one lens with positive refractive power. With such a configuration, while achieving weight reduction, it becomes easy for the light beam incident on the third lens group L3 to be incident parallel to the optical axis, and it is possible to suppress the variation in spherical aberration associated with focusing.

[0036] The second lens group L2 preferably consists of a single positive refractive power lens disposed on the object side of the aperture stop. With such a configuration, it is possible to converge the light beam diverged by the first lens group L1 and make the light beam incident on the third lens group L3 substantially afocal, and it is preferable because it becomes easy to suppress the variation in spherical aberration due to focusing.

[0037] The third lens group L3 preferably has one lens with negative refractive power. With such a configuration, it is preferable because it is possible to suppress the variation in field curvature and longitudinal chromatic aberration associated with focusing and achieve weight reduction of the third lens group L3.

[0038] The third lens group L3 is desirably adjacent to the aperture stop. With such a configuration, it is easy to suppress the field curvature generated by focusing.

[0039] The third lens group L3 preferably consists of a single negative refractive power lens disposed on the object side of the aperture stop. With such a configuration, it is preferable because it is possible to suppress the variation due to focusing of the spherical aberration mainly generated by the on-axis light beam. Also, it is preferable because it is possible to achieve weight reduction of the third lens group L3.

[0040] The aperture stop SP is preferably disposed between the third lens group L3 and the fourth lens group L4. With such a configuration, the exit pupil can be disposed on the object side, which is preferable because the first lens group L1 can be miniaturized. Also, since it is possible to dispose more lenses on the image side than the aperture stop SP, it is preferable because it becomes easy to suppress fluctuations due to focusing of field curvature and magnification chromatic aberration mainly generated by off-axis rays.

[0041] The final group disposed closest to the image side of the rear group LR is preferably configured to be fixed or have a short movement amount (the movement amount is shorter than a predetermined amount) during zooming. With such a configuration, it is possible to simplify the lens group that moves a long distance during zooming, which is preferable because the zoom mechanism is easy to configure. Also, by disposing a lens near the imaging surface in the telephoto range, various aberrations such as field curvature and magnification chromatic aberration generated by off-axis rays can be corrected well, which is preferable.

[0042] The rear group LR preferably has at least two aspherical surfaces. With such a configuration, it is easy to miniaturize while effectively correcting field curvature in the wide-angle range and spherical aberration in the telephoto range, which is preferable.

[0043] The rear group LR preferably has two cemented lenses each composed of a positive refractive power lens and a negative refractive power lens. With such a configuration, it is possible to well correct various aberrations such as variations in spherical aberration for each wavelength and axial chromatic aberration in the telephoto range, which is preferable.

[0044] The lens group disposed closest to the image side is preferably fixed with respect to the image plane position during zooming. With such a configuration, it is possible to reduce the generation of dust etc. when removed like an interchangeable lens, which is preferable because it becomes easy to ensure durability.

[0045] The lens disposed closest to the image side among the lens groups disposed closest to the image side is preferably a lens having a convex shape on the image side. With such a configuration, it becomes relatively easy to secure the back focus, and it is preferable because it is possible to suppress the condensation of unnecessary light (ghost) caused by the imaging element.

[0046] The lens group disposed closest to the image side preferably consists of a single positive refractive power lens. With such a configuration, it is preferable because it is possible to reduce the weight of the zoom lens, gently reduce the incident angle of off-axis light beams incident on the imaging surface, and suppress the occurrence of color separation occurring on the imaging surface.

[0047] Next, the preferable conditions that the zoom lens of each embodiment satisfies will be described. The zoom lens of each embodiment preferably satisfies one or more of the following conditional expressions (3) to (13).

[0048] 0.6 < f1 / f3 < 2.0 (3) -4.0 < f1 / fw < -1.8 (4) -0.7 < f1 / f2 < 0.0 (5) -1.0 < ft / f3 < -0.4 (6) 0.00 < MD3t / TLt < 0.55 (7) 0.5 < ES3w < 1.1 (8) 1.2 < ES3t < 2.3 (9) 0.05 < skw / TLw < 0.20 (10) -1.4 < SF3 < -0.9 (11) 40 < νd3n < 65 (12) 45 < ωw < 60 (13) Here, f1 is the focal length of the first lens group L1. ft is the focal length of the zoom lens at the telephoto end. MD3t is the distance that the third lens group L3 moves on the optical axis during focusing at the telephoto end. TLt is the overall optical length of the zoom lens at the telephoto end. ES3w is the focus sensitivity of the third lens group L3 at the wide-angle end when focused at infinity. ES3t is the focus sensitivity of the third lens group L3 at the telephoto end when focused at infinity. skw is the back focus at the wide-angle end. TLw is the overall optical length of the zoom lens at the wide-angle end. SF3 is the shape factor of the lenses constituting the third lens group L3. νd3n is the average Abbe number of the lenses with negative refractive index included in the third lens group L3. ωw[°] is the semi-field angle at the wide-angle end.

[0049] Note that the shape factor SF is the shape factor of the lens L. When the focal length of the lens L is fL, the radius of curvature of the object side surface is R1, and the radius of curvature of the image side surface is R2, it is defined by the following formula.

[0050] SF = sgn(fL)×(R2 + R1) / (R2 - R1) In the case of an aspherical shape, it means its base R (the radius of the reference quadric surface). sgn means the sign function, taking +1 when fL is a positive value and -1 when fL is a negative value.

[0051] Also, the focus sensitivity is, when focused at infinity, with the lateral magnifications of the moving group i and the lens group r arranged on the image side of the moving group i being βi and βr respectively, (1 - βi 2 )×βr 2 represented by.

[0052] Conditional expression (3) defines the value of the ratio of the focal length of the first lens group L1 to the focal length of the third lens group L3, and is a condition for achieving both ensuring a wide angle of view at the wide-angle end and suppressing changes in optical performance due to focusing. If it is below the lower limit value of conditional expression (3), the refractive power of the third lens group L3 becomes stronger than that of the first lens group L1, which is advantageous for shortening the shortest shooting distance. However, it becomes difficult to suppress changes in optical performance due to focusing, which is not preferable. If it exceeds the upper limit value of conditional expression (3), the refractive power of the third lens group L3 becomes weaker than that of the first lens group L1, which is advantageous for suppressing changes in optical performance due to focusing. However, it becomes difficult to shorten the shortest shooting distance or the zoom lens becomes larger, which is not preferable.

[0053] Conditional expression (4) defines the value of the ratio of the focal length of the first lens group L1 to the focal length of the zoom lens at the wide-angle end, and is a condition for achieving both ensuring a wide angle of view at the wide-angle end and suppressing changes in optical performance due to focusing. If it is below the lower limit value of conditional expression (4), the focal length of the first lens group L1 with respect to the focal length of the zoom lens at the wide-angle end becomes shorter. Therefore, in order to make the light beam incident on the third lens group L3 parallel to the optical axis, it is necessary to increase the refractive power of the second lens group L2. This causes spherical aberration and chromatic aberration of magnification generated in the second lens group L2, which is not preferable. If it exceeds the upper limit value of conditional expression (4), the focal length of the first lens group L1 with respect to the focal length of the zoom lens at the wide-angle end becomes longer, making it difficult to ensure a wide angle of view at the wide-angle end, which is not preferable.

[0054] Conditional expression (5) defines the value of the ratio of the focal length of the first lens group L1 to the focal length of the second lens group L2, and is a condition for achieving both miniaturization of the zoom lens and suppression of changes in optical performance due to focusing. If it is below the lower limit value of conditional expression (5), the refractive power of the second lens group L2 becomes weak, and the light beam incident on the third lens group becomes a divergent light beam with respect to the optical axis, which is advantageous for suppressing fluctuations in spherical aberration due to focusing. However, it is not preferable because miniaturization of the zoom lens becomes difficult. If it exceeds the upper limit value of conditional expression (5), the refractive power of the second lens group L2 becomes stronger than that of the first lens group L1, which is advantageous for miniaturization of the zoom lens. However, the light beam incident on the third lens group L3 becomes a convergent light beam with respect to the optical axis. Therefore, the fluctuation of spherical aberration due to focusing becomes large, which is not preferable.

[0055] Conditional expression (6) defines the value of the ratio of the focal length of the zoom lens at the telephoto end to the focal length of the third lens group L3, and is a condition for achieving both shortening of the shortest shooting distance and suppression of changes in optical performance due to focusing. If it is below the lower limit value of conditional expression (6), the refractive power of the third lens group L3 becomes strong, which is advantageous for shortening the shortest shooting distance. However, it is not preferable because it becomes difficult to suppress changes in optical performance due to focusing. If it exceeds the upper limit value of conditional expression (6), the refractive power of the third lens group L3 becomes weak, which is advantageous for suppressing changes in optical performance due to focusing. However, it is not preferable because it becomes difficult to shorten the shortest shooting distance or the zoom lens becomes enlarged.

[0056] Conditional expression (7) defines the value of the ratio of the distance that the third lens group L3 moves on the optical axis when focusing with respect to the overall optical length of the zoom lens at the telephoto end, and is a condition for achieving both miniaturization of the zoom lens and shortening of the shortest shooting distance. If it is below the lower limit value of conditional expression (7), the moving amount of the third lens group L3 becomes shorter with respect to the overall optical length of the zoom lens at the telephoto end, which is advantageous for miniaturization of the zoom lens, but the shortest shooting distance becomes difficult, so it is not preferable. If it exceeds the upper limit value of conditional expression (7), the moving amount of the third lens group L3 becomes longer with respect to the overall optical length of the zoom lens at the telephoto end, which is advantageous for shortening the shortest shooting distance, but the zoom lens becomes larger, so it is not preferable.

[0057] Conditional expression (8) defines the focus sensitivity of the third lens group L3 at the wide-angle end, and is a condition for achieving both shortening of the shortest shooting distance and suppression of changes in optical performance due to focusing. If it is below the lower limit value of conditional expression (8), the focus sensitivity of the third lens group L3 becomes low, so it becomes easy to suppress fluctuations in optical performance due to focusing, but it becomes difficult to shorten the shortest shooting distance, so it is not preferable. Also, it becomes difficult to move the focusing group at high speed, so it is not preferable. If it exceeds the upper limit value of conditional expression (8), the focus sensitivity of the third lens group L3 becomes high, so it becomes easy to shorten the shortest shooting distance at the wide-angle end, but it becomes difficult to suppress fluctuations in field curvature and distortion aberration mainly caused by off-axis rays due to focusing, so it is not preferable. Also, it becomes difficult to control the focusing group with high accuracy, so it is not preferable.

[0058] Conditional expression (9) defines the focus sensitivity of the third lens group L3 at the telephoto end, and is a condition for achieving both shortening of the shortest shooting distance and suppression of optical performance changes due to focusing. If it is below the lower limit value of conditional expression (9), the focus sensitivity of the third lens group L3 becomes low, so suppression of optical performance fluctuations due to focusing becomes easy, but shortening of the shortest shooting distance becomes difficult, which is not preferable. Also, it becomes difficult to move the focusing group at high speed, which is not preferable. If it exceeds the upper limit value of conditional expression (9), the focus sensitivity of the third lens group L3 becomes high, so shortening of the shortest shooting distance at the telephoto end becomes easy, but suppression of fluctuations in field curvature and distortion aberration mainly caused by off-axis rays due to focusing becomes difficult, which is not preferable. Also, it becomes difficult to control the focusing group with high accuracy, which is not preferable.

[0059] Conditional expression (10) defines the value of the ratio of the back focus at the wide-angle end to the overall optical length of the zoom lens at the wide-angle end, and is a condition for achieving both miniaturization of the zoom lens and ensuring the movement distance of the focusing group. If it is below the lower limit value of conditional expression (10), it becomes easy to ensure the movement distance of the third lens group L3, but it becomes difficult to appropriately arrange mechanical members in the mount part, which is not preferable. If it exceeds the upper limit value of conditional expression (10), the back focus with respect to the overall optical length becomes long, and the degree of freedom in arranging mechanical members in the mount part improves, but it becomes difficult to ensure the movement distance of the third lens group L3, which is not preferable.

[0060] The conditional expression (11) defines the shape factor of the lenses that make up the third lens group L3, and is a condition for suppressing changes in optical performance due to focusing. When the value of the conditional expression (11) is -1 and the lens has a negative refractive index, the lens has a plano-concave shape with the concave surface facing the object side. If it is below the lower limit value of the conditional expression (11), the curvature of the object-side surface of the lens becomes small, making it difficult to suppress the variation in spherical aberration generated by the on-axis light beam due to focusing, which is not preferable. Also, since the curvature becomes small, it becomes a meniscus-shaped lens, making it difficult to process and form the lens, which is not preferable. If it exceeds the upper limit value of the conditional expression (11), the curvature of the object-side surface of the lens becomes large, making it easy to suppress the variation in spherical aberration generated by the on-axis light beam on the object-side surface due to focusing. However, the lens shape becomes a biconcave shape, making it difficult to suppress the field curvature generated by the off-axis light beam due to focusing, which is not preferable.

[0061] The conditional expression (12) defines the average value of the Abbe numbers of the lenses with negative refractive power included in the third lens group L3. By optimizing the Abbe numbers of the lenses included in the third lens group L3, it becomes possible to suppress the variation in axial chromatic aberration due to focusing. If it is below the lower limit value of the conditional expression (12), it becomes easy to suppress the field curvature and distortion aberration mainly generated by off-axis light rays, but it becomes difficult to correct the lateral chromatic aberration, which is not preferable. If it exceeds the upper limit value of the conditional expression (12), the correction effect of the lateral chromatic aberration increases, but it causes deterioration of the axial chromatic aberration, and it becomes difficult to optimize the refractive power of the lens with negative refractive power, leading to an increase in the lens diameter, which is not preferable.

[0062] The conditional expression (13) defines the angle of view. If it is below the lower limit value of the conditional expression (13), it becomes difficult to widen the angle of view, which is not preferable. If it exceeds the upper limit value of the conditional expression (13), it becomes possible to take pictures with an angle of view larger than the desired angle of view, leading to an increase in the size of the zoom lens, which is not preferable.

[0063] Note that it is preferable to set the numerical ranges of the conditional expressions (3) to (13) as the numerical ranges of the following conditional expressions (3a) to (13a).

[0064] 0.7 < f1 / f3 < 1.5 (3a) -3.0 < f1 / fw < -1.9 (4a) -0.65 < f1 / f2 < -0.20 (5a) -0.85 < ft / f3 < -0.50 (6a) 0.15 < MD3t / TLt < 0.50 (7a) 0.55 < ES3w < 0.90 (8a) 1.3 < ES3t < 2.1 (9a) 0.06 < skw / TLw < 0.15 (10a) -1.20 < SF3 < -0.95 (11a) 42 < νd3n < 63 (12a) 47 < ωw < 57 (13a) Also, it is preferable that the numerical ranges of conditional expressions (3) to (13) be the numerical ranges of the following conditional expressions (3b) to (13b).

[0065] 0.8 < f1 / f3 < 1.0 (3b) -2.5 < f1 / fw < -2.0 (4b) -0.6 < f1 / f2 < -0.4 (5b) -0.75 < ft / f3 < -0.58 (6b) 0.25 < MD3t / TLt < 0.45 (7b) 0.62 < ES3w < 0.82 (8b) 1.45 < ES3t < 2.00 (9b) 0.075 < skw / TLw < 0.130 (10b) -1.10 < SF3 < -0.98 (11b) 45 < νd3n < 62 (12b) 48 < ωw < 55 (13b) Next, the zoom lenses of each example will be described in detail.

[0066] The zoom lens of Example 1 is a zoom lens with a zoom ratio of 1.7 and an aperture ratio of about 2.9. The plurality of lens groups included in the zoom lens of Example 1 consists of a first lens group L1, a second lens group L2, a third lens group L3, a fourth lens group L4, and a fifth lens group L5, which are arranged in order from the object side to the image side and have negative, positive, negative, positive, and positive refractive powers. The rear group LR is a combined group from the fourth lens group L4 to the fifth lens group L5 and is a positive rear group. In the zoom lens of Example 1, in the reference state where the object distance is infinite, the fifth lens group L5 is fixed during zooming. When focusing on a nearby object, the third lens group L3 moves toward the object side.

[0067] The zoom lens of Example 2 is a zoom lens with a zoom ratio of 1.8 and an aperture ratio of about 2.9. The plurality of lens groups included in the zoom lens of Example 2 consists of a first lens group L1, a second lens group L2, a third lens group L3, a fourth lens group L4, a fifth lens group L5, and a sixth lens group L6, which are arranged in order from the object side to the image side and have negative, positive, negative, positive, positive, and positive refractive powers. The rear group LR is a combined group from the fourth lens group L4 to the sixth lens group L6 and is a positive rear group. In the zoom lens of Example 2, in the reference state where the object distance is infinite, all the lens groups move during zooming. When focusing on a nearby object, the third lens group L3 moves toward the object side.

[0068] The zoom lens of Example 3 is a zoom lens with a zoom ratio of 1.7 and an aperture ratio of about 2.9. The plurality of lens groups included in the zoom lens of Example 3 consists of a first lens group L1, a second lens group L2, a third lens group L3, a fourth lens group L4, and a fifth lens group L5, which are arranged in order from the object side to the image side and have negative, positive, negative, positive, and positive refractive powers. The rear group LR is a combined group from the fourth lens group L4 to the fifth lens group L5 and is a positive rear group. In the zoom lens of Example 3, in the reference state where the object distance is infinite, the fifth lens group L5 is fixed during zooming. When focusing on a nearby object, the third lens group L3 moves toward the object side.

[0069] The zoom lens of Example 4 is a zoom lens with a zoom ratio of 1.7 and an aperture ratio of about 2.9. The plurality of lens groups included in the zoom lens of Example 4 are composed of a first lens group L1, a second lens group L2, a third lens group L3, and a fourth lens group L4 having negative, positive, negative, and positive refractive powers, which are arranged in order from the object side to the image side. The rear group LR is a positive rear group composed of the fourth lens group L4. In the zoom lens of Example 4, when focusing on a near object, the third lens group L3 moves toward the object side.

[0070] In addition, in the zoom lens of each example, it is also possible to adopt a configuration in which the entire or a part of any lens group is moved so as to include a component in a direction perpendicular to the optical axis as an anti-vibration group, or rotated (oscillated) in a plane direction including the optical axis to perform anti-vibration. In the zoom lens of each example, it is preferable to perform anti-vibration by moving the entire or a part of the lens group arranged on the image side of the aperture stop SP of the rear group LR so as to include a component in a direction perpendicular to the optical axis. There is no particular limitation on the number of lenses and the shape of the anti-vibration group. Further, the anti-vibration group preferably has a negative refractive power. Further, the anti-vibration group is preferably a cemented lens composed of one lens with a negative refractive power and one lens with a positive refractive power.

[0071] Also, the zoom lens of each example preferably does not include a diffractive optical element. Although providing a diffractive optical element is advantageous from the viewpoint of chromatic aberration correction, it is not preferable because diffractive flare occurs in the diffractive optical element.

[0072] Numerical Examples 1 to 4 corresponding to Examples 1 to 4 are shown below.

[0073] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axis distance (distance on the optical axis) between the m-th surface and the (m + 1)-th surface. Here, m is the surface number counted from the light incident side. Also, nd represents the refractive index of each optical member with respect to the d-line, and νd represents the Abbe number of the optical member. Note that the Abbe number νd of a certain material, when the refractive indices at the d-line (587.56 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines are Nd, NF, and NC, νd=(Nd - 1) / (NF - NC) is represented by

[0074] Note that in each numerical example, d, focal length (mm), F-number, and half field angle [°] are all values when the zoom lens of each example is focused on an infinite object. "Back focus" is the distance on the optical axis from the final lens surface (the lens surface closest to the image side) to the paraxial image plane, expressed in terms of the air equivalent length. "Overall lens length" is the length obtained by adding the back focus to the distance on the optical axis from the frontmost lens surface (the lens surface closest to the object side) to the final surface of the zoom lens. "Lens group" shall include not only cases composed of multiple lenses but also cases composed of a single lens.

[0075] Also, when the optical surface is an aspherical surface, an asterisk (*) is attached to the right side of the surface number. The aspherical shape is expressed as follows when X is the displacement amount from the vertex of the surface in the optical axis direction, H is the height from the optical axis in the 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:

[0076] [Number]

[0077] is represented by. Note that "e±XX" in each aspherical coefficient means "×10± XX ".

[0078] [Numerical Example 1] Unit: mm Surface data Surface numbers r d nd νd 1 88.348 1.40 1.95375 32.3 2 23.448 0.05 1.53344 52.7 3* 20.527 6.84 4 79.576 1.20 1.48749 70.2 5 23.135 8.51 6 -45.566 1.10 1.49700 81.7 7 54.458 0.12 8 41.235 6.10 1.90043 37.4 9 -79.023 (variable) 10 48.326 2.05 1.77250 49.6 11 167.459 (variable) 12 -27.423 0.85 1.60311 60.6 13 ∞ (variable) 14 (aperture) ∞ 0.84 15 65.416 5.06 1.49700 81.7 16 -27.205 0.15 17 41.064 7.35 1.49700 81.7 18 -19.198 0.95 1.83481 42.7 19 -81.206 5.25 20 -64.814 2.07 1.90366 31.3 21 -28.769 0.90 1.61340 44.3 22 108.154 1.82 23 31.407 7.09 1.49700 81.7 24 -31.407 0.25 25 30.238 7.77 1.53775 74.7 26 -22.679 1.00 1.83481 42.7 27 29.093 3.93 28* -69.646 1.70 1.58283 59.5 29* -1000.000 (Variable) 30 -104.423 6.93 1.48749 70.2 31 -28.354 10.24 Image plane ∞ Aspherical data The third surface K = 0.00000e+00 A 4=-1.09451e-05 A 6= 4.50666e-10 A 8=-1.50489e-10 A10= 4.73240e-13 A12=-9.51176e-16 The 28th surface K = 0.00000e+00 A 4=-9.63028e-05 A 6= 7.20183e-08 A 8= 1.66700e-09 A10=-1.33893e-11 A12= 3.80428e-14 The 29th surface K = 0.00000e+00 A 4=-4.66095e-05 A 6= 1.56445e-07 A 8= 1.63379e-09 A10=-1.04456e-11 A12= 2.08882e-14 Various data Zoom ratio 1.65 Wide angle, middle, telephoto Focal length 16.48 20.00 27.17 F-number 2.88 2.88 2.88 Half field angle [°] 47.52 43.53 37.44 Image height 18.00 19.00 20.80 Overall lens length 130.34 124.44 119.83 BF 10.24 10.24 10.24 d 9 23.28 13.64 1.33 d11 6.26 7.23 8.47 d13 4.76 3.79 2.54 d29 4.52 8.26 15.96 Zoom lens group data Group start surface Focal length 1 1 -38.49 2 10 87.28 3 12 -45.47 4 14 23.93 5 30 77.53 [Numerical Example 2] Unit: mm Surface data Surface number r d nd νd 1 61.904 1.40 1.95375 32.3 2 20.247 0.05 1.51640 52.2 3* 18.373 5.67 4 44.033 1.20 1.71828 55.3 5 25.653 6.21 6 -106.598 1.00 1.49700 81.7 7 32.583 0.15 8 29.498 5.11 2.02677 28.4 9 288.201 (Variable) 10 -18.019 1.20 1.51588 64.6 11 -30.092 (Variable) 12 (Aperture) ∞ 1.80 13 117.663 5.12 1.49700 81.7 14 -23.189 0.15 15 36.389 7.48 1.53775 74.7 16 -18.380 1.30 1.91082 35.2 17 -66.282 4.31 18 -61.062 2.40 1.84666 23.9 19 -25.843 1.00 1.61340 44.3 20 110.697 4.38 21 42.465 6.11 1.49700 81.7 22 -27.481 0.15 23 23.479 7.82 1.53775 74.7 24 -24.794 1.00 1.83481 42.7 25 21.148 4.28 26* -55.112 1.70 1.58313 59.4 27* -378.334 (variable) 28 -762.923 8.13 1.48749 70.2 29 -30.263 10.79 Image plane ∞ Aspherical data The third surface K = 0.00000e+00 A 4=-9.89514e-06 A 6= 5.32321e-08 A 8=-1.00711e-09 A10= 7.77335e-12 A12=-3.77833e-14 A14= 9.76335e-17 A16=-1.12886e-19 The 26th surface K = 0.00000e+00 A 4=-3.77487e-05 A 6= 4.15778e-08 A 8=-2.33823e-09 A10= 4.73379e-12 A12= 3.16760e-14 The 27th surface K = 0.00000e+00 A 4= 5.51540e-06 A 6= 9.32432e-09 A 8=-6.53949e-10 A10= 1.29016e-12 A12= 1.57567e-14 Various data Zoom ratio 1.64 Wide angle Middle Telephoto Focal length 16.48 23.24 27.08 F-number 2.90 2.90 2.90 Half drawing angle [°] 47.52 39.27 37.53 Image height 18.00 19.00 20.80 Overall lens length 121.45 116.36 115.52 BF 10.79 10.79 10.79 d 9 25.15 13.50 8.50 d11 3.90 2.69 2.66 d27 2.49 10.26 14.44 Zoom lens group data Group Starting surface Focal length 1 1 -33.05 2 10 -90.10 3 12 22.59 4 28 64.41 [Numerical Example 3] Unit mm Surface data Surface number r d nd νd 1 95.821 1.40 1.95375 32.3 2 24.913 0.05 1.53344 52.7 3* 20.931 6.56 4 72.105 1.20 1.48749 70.2 5 21.713 8.96 6 -48.789 1.10 1.49700 81.7 7 41.515 0.44 8 37.589 6.19 1.90043 37.4 9 -93.472 (Variable) 10 56.409 2.01 1.90043 37.4 11 762.938 (Variable) 12 -29.371 0.85 1.80400 46.5 13 -1412.490 (Variable) 14 (Aperture) ∞ 0.32 15 46.742 5.41 1.49700 81.7 16 -27.837 0.15 17 65.203 6.69 1.49700 81.7 18 -18.965 0.95 1.83481 42.7 19 -69.379 (variable) 20 -74.743 1.89 1.90366 31.3 21 -33.041 0.90 1.61340 44.3 22 151.062 1.42 23 40.382 1.82 1.49700 81.7 24 67.668 0.25 25 32.853 6.24 1.49700 81.7 26 -39.046 0.25 27 27.936 7.63 1.49700 81.7 28 -24.955 1.00 1.83481 42.7 29 28.187 4.54 30* -48.034 1.70 1.58313 59.4 31* -500.000 (variable) 32 -276.116 8.07 1.48749 70.2 33 -28.078 (variable) Image plane ∞ Aspherical data The 3rd surface K = 0.00000e+00 A 4=-1.51906e-05 A 6= 1.91375e-08 A 8=-2.94966e-10 A10= 8.97817e-13 A12=-1.34384e-15 The 30th surface K = 0.00000e+00 A 4=-1.45126e-04 A 6= 7.06611e-07 A 8=-2.79426e-09 A10= 7.89144e-12 A12= 1.23197e-15 Page 31 K = 0.00000e+00 A 4=-8.48617e-05 A 6= 6.91573e-07 A 8=-1.40031e-09 A10=-1.74538e-12 A12= 1.19952e-14 Various data Zoom ratio 1.76 Wide angle, medium, telephoto Focal length 15.45 20.00 27.17 F-number 2.88 2.88 2.94 Half field angle [°] 49.36 43.53 37.44 Image height 18.00 19.00 20.80 Overall lens length 131.80 125.47 122.18 BF 10.54 10.14 14.33 d 9 24.92 12.85 1.23 d11 5.11 5.74 7.42 d13 4.69 4.06 2.38 d19 6.56 7.42 5.94 d31 2.00 7.27 12.88 d33 10.54 10.14 14.33 Zoom lens group data Group, starting surface, focal length 1 1 -35.33 2 10 67.56 3 12 -37.32 4 14 32.96 5 20 269.82 6 32 63.44 [Numerical Example 4] Unit: mm Surface data Surface number, r, d, nd, νd 1 78.872 1.40 1.95375 32.3 2 22.896 0.05 1.53344 52.7 3* 20.227 8.31 4 200.411 1.20 1.48749 70.2 5 25.464 7.66 6 -48.603 1.10 1.49700 81.7 7 62.393 0.02 8 44.316 5.86 1.90043 37.4 9 -78.174 (variable) 10 53.173 2.09 1.77250 49.6 11 -1177.147 (variable) 12 -28.835 0.85 1.80400 46.5 13 -920.496 (variable) 14 (aperture) ∞ 0.75 15 59.409 5.27 1.49700 81.7 16 -26.572 0.15 17 33.819 7.29 1.49700 81.7 18 -21.030 0.95 1.83481 42.7 19 -72.587 6.04 20 -79.145 1.95 1.90366 31.3 21 -32.917 0.90 1.61340 44.3 22 151.791 3.84 23 28.144 7.92 1.49700 81.7 24 -28.144 0.25 25 -91.165 7.06 1.53775 74.7 26 -15.265 1.00 1.87070 40.7 27 200.381 1.99 28* -151.005 1.70 1.58283 59.5 29* -346.238 (variable) Image plane ∞ Aspherical Data The 3rd surface K = 0.00000e+00 A 4=-1.15752e-05 A 6= 1.10546e-08 A 8=-2.01990e-10 A10= 6.49607e-13 A12=-1.25742e-15 The 28th surface K = 0.00000e+00 A 4=-1.36676e-04 A 6= 5.94812e-07 A 8=-6.80753e-09 A10= 5.82397e-11 A12=-1.54761e-13 The 29th surface K = 0.00000e+00 A 4=-9.09558e-05 A 6= 4.51269e-07 A 8=-2.97982e-09 A10= 2.43608e-11 A12=-6.50628e-14 Various data Zoom ratio 1.65 Wide angle, middle, telephoto Focal length 16.48 20.00 27.17 F-number 2.88 2.88 2.88 Half field angle [°] 47.52 43.53 37.44 Image height 18.00 19.00 20.80 Overall lens length 126.87 120.19 113.25 BF 16.22 19.53 26.45 d 9 24.22 14.13 1.36 d11 6.27 7.20 7.24 d13 4.57 3.74 2.59 d29 16.22 19.53 26.45 Zoom lens group data Group, starting surface, focal length 1 1 -36.28 2 10 65.91 3 12 -37.04 4 14 23.09 The various values in each numerical example are summarized in Table 1 below.

[0079]

Table 1

[0080] [Imaging device] Next, an embodiment of a digital still camera (imaging device) using the zoom lens of the present invention as an imaging optical system will be described with reference to FIG. 9. In FIG. 9, 10 is a camera body, and 11 is a photographing optical system constituted by any one of the zoom lens optical systems described in Examples 1 to 4. 12 is a solid-state imaging device (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built in the camera body and receives and photoelectrically converts the optical image formed by the photographing optical system 11. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror.

[0081] By applying the zoom lens of the present invention to an imaging device such as a digital still camera in this way, an imaging device with a small lens can be obtained.

[0082] The disclosure of this embodiment includes the following configurations. (Configuration 1) A zoom lens including, 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, a third lens group having a negative refractive power, and one or more lens groups, and a rear group having a positive combined refractive power at the wide-angle end, and the distance between adjacent lens groups changes during zooming, The lens closest to the object side of the first lens group has a negative refractive power, During focusing, the third lens group moves, When the focal length of the zoom lens at the wide-angle end is fw, the focal length of the second lens group is f2, and the focal length of the third lens group is f3, -1.0 < fw / f3 < -0.3 -0.7 < f3 / f2 < 0.0 A zoom lens characterized by satisfying the following conditional expression. (Configuration 2) When the focal length of the first lens group is f1, 0.6 < f1 / f3 < 2.0 The zoom lens according to Configuration 1, characterized by satisfying the following conditional expression. (Configuration 3) When the focal length of the first lens group is f1, -4.0 < f1 / fw < -1.8 The zoom lens according to Configuration 1 or 2, characterized by satisfying the following conditional expression. (Configuration 4) When the focal length of the first lens group is f1, -0.7 < f1 / f2 < 0.0 The zoom lens according to any one of Configurations 1 to 3, characterized by satisfying the following conditional expression. (Configuration 5) When the focal length of the zoom lens at the telephoto end is ft, -1.0 < ft / f3 < -0.4 The zoom lens according to any one of Configurations 1 to 4, characterized by satisfying the following conditional expression. (Configuration 6) When the distance that the third lens group moves on the optical axis during focusing at the telephoto end is MD3t, and the overall optical length of the zoom lens at the telephoto end is TLt, 0.00 < MD3t / TLt < 0.55 The zoom lens according to any one of Configurations 1 to 5, characterized by satisfying the following conditional expression. (Configuration 7) When the focus sensitivity of the third lens group at the wide-angle end is ES3w, 0.5 < ES3w < 1.1 The zoom lens according to any one of Configurations 1 to 6, characterized by satisfying the following conditional expression. (Configuration 8) When the focus sensitivity of the third lens group at the telephoto end is ES3t, 1.2 < ES3t < 2.3 The zoom lens according to any one of Configurations 1 to 7, characterized by satisfying the conditional expression. (Configuration 9) When the back focus at the wide-angle end is skw and the overall optical length of the zoom lens at the wide-angle end is TLw, 0.05 < skw / TLw < 0.20 The zoom lens according to any one of Configurations 1 to 8, characterized by satisfying the conditional expression. (Configuration 10) When the shape factor of the lens constituting the third lens group is SF3, -1.4 < SF3 < -0.9 The zoom lens according to any one of Configurations 1 to 9, characterized by satisfying the conditional expression. (Configuration 11) When the average Abbe number of the negative refractive index lenses included in the third lens group is νd3n, 40 < νd3n < 65 The zoom lens according to any one of Configurations 1 to 10, characterized by satisfying the conditional expression. (Configuration 12) When the half field angle of the zoom lens at the wide-angle end is ωw [°], 45 < ωw < 60 The zoom lens according to any one of Configurations 1 to 11, characterized by satisfying the conditional expression. (Configuration 13) The first lens group has three negative refractive power lenses arranged in sequence from the object side to the image side, and the zoom lens according to any one of Configurations 1 to 12, characterized by this. (Configuration 14) The first lens group consists of three negative refractive power lenses and one positive refractive power lens arranged in sequence from the object side to the image side, and the zoom lens according to any one of Configurations 1 to 13, characterized by this. (Configuration 15) The third lens group is composed of a single negative lens disposed on the object side of the aperture stop, and is the zoom lens according to any one of Configurations 1 to 14. (Configuration 16) It further has an aperture stop that determines the light beam of the open F number. The rear group includes a fourth lens group disposed on the image side of the third lens group. The aperture stop is disposed between the third lens group and the fourth lens group, and is the zoom lens according to any one of Configurations 1 to 15. (Configuration 17) The rear group has two cemented lenses composed of a lens with a positive refractive power and a lens with a negative refractive power, and is the zoom lens according to any one of Configurations 1 to 16. (Configuration 18) The lens group disposed closest to the image side is fixed during zooming, and is the zoom lens according to any one of Configurations 1 to 17. (Configuration 19) The lens disposed closest to the image side of the lens group disposed closest to the image side is a lens with a convex shape on the image side, and is the zoom lens according to any one of Configurations 1 to 18. (Configuration 20) The lens group disposed closest to the image side is composed of a single lens with a positive refractive power, and is the zoom lens according to any one of Configurations 1 to 19. (Configuration 21) The zoom lens according to any one of Configurations 1 to 20, which is composed of the first lens group, the second lens group, the third lens group, a fourth lens group with a positive refractive power, and a fifth lens group with a positive refractive power, arranged in order from the object side to the image side. (Configuration 22) The zoom lens according to any one of Configurations 1 to 20, which is composed of the first lens group, the second lens group, the third lens group, a fourth lens group with a positive refractive power, a fifth lens group with a positive refractive power, and a sixth lens group with a positive refractive power, arranged in order from the object side to the image side. (Configuration 23) The zoom lens according to any one of Configurations 1 to 20, comprising, in order from the object side to the image side, the first lens group, the second lens group, the third lens group, and the fourth lens group having a positive refractive power. (Configuration 24) An imaging device, comprising: the zoom lens according to any one of Configurations 1 to 23; and an imaging element that receives an image formed by the zoom lens.

[0083] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

Explanation of Reference Numerals

[0084] L1 First lens group L2 Second lens group L3 Third lens group LR Rear group

Claims

1. A zoom lens including, 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, a third lens group having a negative refractive power, and one or more lens groups, and a rear group having a positive combined refractive power at the wide-angle end, wherein the distance between adjacent lens groups changes during zooming, The lens closest to the object side in the first lens group has a negative refractive power, During focusing, the third lens group moves, When the focal length of the zoom lens at the wide-angle end is fw, the focal length of the second lens group is f2, and the focal length of the third lens group is f3, -1.0 < fw / f3 < -0.3 -0.7 < f3 / f2 < 0.0 A zoom lens characterized by satisfying the conditional expressions.

2. When the focal length of the first lens group is f1, 0.6 < f1 / f3 < 2.0 The zoom lens according to claim 1, characterized by satisfying the conditional expressions.

3. When the focal length of the first lens group is f1, -4.0 < f1 / fw < -1.8 The zoom lens according to claim 1 or 2, characterized by satisfying the conditional expressions.

4. When the focal length of the first lens group is f1, -0.7 < f1 / f2 < 0.0 The zoom lens according to claim 1 or 2, characterized by satisfying the conditional expressions.

5. When the focal length of the zoom lens at the telephoto end is ft, -1.0 < ft / f3 < -0.4 The zoom lens according to claim 1 or 2, characterized by satisfying the conditional expressions.

6. When the distance that the third lens group moves on the optical axis during focusing at the telephoto end is MD3t and the overall optical length of the zoom lens at the telephoto end is TLt, 0.00 < MD3t / TLt < 0.55 The zoom lens according to claim 1 or 2, characterized in that it satisfies the conditional expression.

7. When the focus sensitivity of the third lens group at the wide-angle end is ES3w, 0.5 < ES3w < 1.1 The zoom lens according to claim 1 or 2, characterized in that it satisfies the conditional expression.

8. When the focus sensitivity of the third lens group at the telephoto end is ES3t, 1.2 < ES3t < 2.3 The zoom lens according to claim 1 or 2, characterized in that it satisfies the conditional expression.

9. When the back focus at the wide-angle end is skw and the overall optical length of the zoom lens at the wide-angle end is TLw, 0.05 < skw / TLw < 0.20 The zoom lens according to claim 1 or 2, characterized in that it satisfies the conditional expression.

10. When the shape factor of the lens constituting the third lens group is SF3, -1.4 < SF3 < -0.9 The zoom lens according to claim 1 or 2, characterized in that it satisfies the conditional expression.

11. When the average Abbe number of the lenses with negative refractive index included in the third lens group is νd3n, 40 < νd3n < 65 The zoom lens according to claim 1 or 2, characterized in that it satisfies the conditional expression.

12. When the half field angle of the zoom lens at the wide-angle end is ωw [°], 45 < ωw < 60 The zoom lens according to claim 1 or 2, characterized by satisfying the following conditional expression.

13. The zoom lens according to claim 1 or 2, characterized in that the first lens group has three consecutive lenses with negative refractive power, arranged in order from the object side to the image side.

14. The zoom lens according to claim 1 or 2, characterized in that the first lens group consists of three lenses with negative refractive power and one lens with positive refractive power, arranged in order from the object side to the image side.

15. The zoom lens according to claim 1 or 2, characterized in that the third lens group consists of a single lens with negative refractive power, arranged on the object side of the aperture stop.

16. Further having an aperture stop for determining the light beam of the open F-number, The rear group includes a fourth lens group arranged on the image side of the third lens group, The zoom lens according to claim 1 or 2, characterized in that the aperture stop is arranged between the third lens group and the fourth lens group.

17. The zoom lens according to claim 1 or 2, characterized in that the rear group has two cemented lenses consisting of a lens with positive refractive power and a lens with negative refractive power.

18. The zoom lens according to claim 1 or 2, characterized in that the lens group arranged closest to the image side is fixed during zooming.

19. The zoom lens according to claim 1 or 2, characterized in that the lens arranged closest to the image side of the lens group arranged closest to the image side is a lens with a convex shape on the image side.

20. The zoom lens according to claim 1 or 2, characterized in that the lens group arranged closest to the image side consists of a single lens with positive refractive power.

21. The zoom lens according to claim 1 or 2, comprising, in order from the object side to the image side, the first lens group, the second lens group, the third lens group, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power.

22. The zoom lens according to claim 1 or 2, comprising, in order from the object side to the image side, the first lens group, the second lens group, the third lens group, a fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, and a sixth lens group having a positive refractive power.

23. The zoom lens according to claim 1 or 2, comprising, in order from the object side to the image side, the first lens group, the second lens group, the third lens group, and a fourth lens group having a positive refractive power.

24. An imaging device, comprising the zoom lens according to claim 1 or 2, and an imaging element that receives an image formed by the zoom lens.

Images