Zoom lens and imaging device

Abstract

To provide a compact zoom lens with high magnification and excellent optical characteristics. [Solution] A zoom lens (L0) is provided, consisting of a first lens group (L1) with positive refractive power, a second lens group (L2) with negative refractive power, a third lens group (L3) with positive refractive power, and a rear group containing multiple lens groups, arranged in order from the object side to the image side, wherein the distance between adjacent lens groups changes during zooming, and the third lens group has a cemented lens, the focal length f1 of the first lens group, the focal length ft of the zoom lens at the telephoto end, the amount of movement mr of the lens group LR, which is positioned closest to the image in the rear group, during zooming from the wide-angle end to the telephoto end, the distance bfw on the optical axis from the closest surface of the lens group LR at the wide-angle end to the image plane, and the amount of movement m3 of the third lens group during zooming from the wide-angle end to the telephoto end, all satisfy a predetermined conditional equation.

Description

Technical Field

[0001] The present invention relates to a zoom lens suitable for a digital camera, a video camera, a surveillance camera, etc., and an imaging device including the same.

Background Art

[0002] Patent Documents 1 to 3 disclose a zoom lens including a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a plurality of lens groups, which are arranged in order from the object side to the image side.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the zoom lenses disclosed in Patent Documents 1 to 3, in order to achieve a high magnification, it is effective to increase the movement amount of the lens groups constituting the zoom lens or to increase the power of the lens groups. However, when the movement amount of the lens groups is increased, the mechanical mechanism becomes complicated and the zoom lens becomes large-sized. Further, when the power of the lens groups is increased, the aberration variation during zooming becomes large and it becomes difficult to improve the performance.

[0005] Therefore, an object of the present invention is to provide a zoom lens and an imaging device that are small-sized, have a high magnification, and have high optical characteristics.

Means for Solving the Problems

[0006] A zoom lens as one aspect of the present invention comprises a rear group having multiple lens groups arranged sequentially from the object side to the image side, including a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, wherein the spacing between adjacent lens groups changes during zooming, and during image shake correction, either the entire third lens group, a part of the third lens group, the entire fourth lens group, or a part of the fourth lens group moves in a direction that includes a component perpendicular to the optical axis, and the focal point of the first lens group When the distance is f1, the focal length of the zoom lens at the telephoto end is ft, the amount of movement of the rear lens group LR, which is positioned closest to the image, during zooming from the wide-angle end to the telephoto end is mr, the distance on the optical axis from the closest surface of lens group LR to the image plane at the wide-angle end is bfw, the amount of movement of the third lens group during zooming from the wide-angle end to the telephoto end is m3, and the sign of the amount of movement of the lens group is positive when moving from the object side to the image side, and negative when moving from the image side to the object side, the device is characterized by satisfying a predetermined conditional equation.

[0007] Other objects and features of the present invention are described in the following examples. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a zoom lens and imaging device that are compact, have high magnification, and possess excellent optical characteristics. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of the zoom lens in Example 1. [Figure 2] This is an aberration diagram of the zoom lens at the wide-angle end, intermediate zoom position, and telephoto end in Example 1. [Figure 3] This is a cross-sectional view of the zoom lens in Example 2. [Figure 4] This is an aberration diagram of the zoom lens at the wide-angle end, intermediate zoom position, and telephoto end in Example 2. [Figure 5] This is a cross-sectional view of the zoom lens in Example 3. [Figure 6] This is an aberration diagram of the zoom lens at the wide-angle end, intermediate zoom position, and telephoto end in Example 3. [Figure 7] This is a cross-sectional view of the zoom lens in Example 4. [Figure 8] This is an aberration diagram of the zoom lens at the wide-angle end, intermediate zoom position, and telephoto end in Example 4. [Figure 9] This is a cross-sectional view of the zoom lens in Example 5. [Figure 10] This is an aberration diagram of the zoom lens at the wide-angle end, intermediate zoom position, and telephoto end in Example 5. [Figure 11] This is a schematic diagram of an imaging device equipped with a zoom lens for each embodiment. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] Figures 1, 3, 5, 7, and 9 are cross-sectional views of the zoom lens (optical system) L0 of each of the embodiments 1 to 5 when focused at infinity. The zoom lens L0 of each embodiment is an optical system used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras.

[0012] In each cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). The zoom lens L0 in each embodiment is composed of multiple lens groups. In each cross-sectional view, i indicates the order of the lens groups from the object side, and Li is the i-th lens group. In each embodiment, a lens group is a collection of lenses that move or remain stationary as a whole during zooming. That is, in the zoom lens L0 of each embodiment, the distance between adjacent lens groups changes when zooming from the wide-angle end to the telephoto end. A lens group may consist of one lens or multiple lenses. A lens group may also include an aperture diaphragm.

[0013] SP is an aperture stop. In each embodiment, the aperture stop SP is included in the third lens group L3, but is not limited thereto. IP is an image plane. When the zoom lens L0 of each embodiment is used as an imaging optical system of a digital still camera or a digital video camera, the imaging surface of an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is disposed. When the zoom lens L0 of each embodiment is used as an imaging optical system of a camera for silver halide film, a photosensitive surface corresponding to the film surface is placed on the image plane IP. In each cross-sectional view, the solid arrows schematically show the movement trajectories of the respective lens groups at infinity focus during zooming from the wide-angle end to the telephoto end. In each embodiment, the wide-angle end and the telephoto end refer to the zoom positions when the respective lens groups of the zoom lens L0 are located at both ends within the range where they can move on the optical axis OA due to mechanical reasons.

[0014] Figures 2, 4, 6, 8, and 10 are aberration diagrams of the zoom lenses L0 of Embodiments 1 to 5, respectively. In each aberration diagram, (A) is the aberration diagram of the zoom lens L0 at the wide-angle end, (B) is the aberration diagram of the zoom lens L0 at an intermediate zoom position, and (C) is the aberration diagram of the zoom lens L0 at the telephoto end. In the spherical aberration diagram, Fno is the F-number, and it shows the amount of spherical aberration with respect to the d-line (wavelength 587.6 nm) and the g-line (wavelength 435.8 nm). In the astigmatism diagram, ΔS shows the amount of astigmatism on the sagittal image plane, and ΔM shows the amount of astigmatism on the meridional image plane. In the distortion diagram, it shows the amount of distortion with respect to the d-line. In the chromatic aberration diagram, it shows the amount of chromatic aberration with respect to the g-line. ω is the imaging semi-angle (degrees).

[0015] Conventionally, a zoom lens including a first lens group L1 having a positive refractive power, a second lens group L2 having a negative refractive power, a third lens group L3 having a positive refractive power, and a plurality of lens groups arranged in order from the object side to the image side is known. In such a zoom lens, increasing the power of the first lens group L1 facilitates magnification, but aberration variation during zooming and longitudinal chromatic aberration at the telephoto end become large, making it difficult to achieve high performance. Also, increasing the movement amount of the first lens group L1 facilitates magnification, but the mechanical mechanism becomes complex and the size increases. Therefore, in order to achieve both high magnification and miniaturization of the zoom lens and realize high optical performance, it is important to appropriately set the power of the first lens group L1. Also, it is effective to appropriately set the configuration and movement amount of the subsequent lens groups so as to cancel various aberrations generated in the first lens group L1.

[0016] The zoom lens L0 of each embodiment has a first lens group L1 having a positive refractive power, a second lens group L2, a third lens group L3 having a positive refractive power, and a rear group including a plurality of lens groups arranged in order from the object side to the image side. By arranging a plurality of lens groups on the image side of the third lens group L3 and changing the interval between adjacent lens groups during zooming, it becomes easy to suppress aberration variation during zooming and achieve high performance. In each embodiment, the lens group refers to a lens or a lens group having at least one lens having power and changing the air interval between each other during zooming.

[0017] The zoom lens L0 of each embodiment satisfies the following conditional expressions (1), (2), and (3).

[0018] 0.20 < f1 / ft < 0.40 ···(1) -4.0 < mr / bfw < -1.5 ···(2) -7.0 < m3 / bfw < -2.5 ···(3) Here, f1 is the focal length of the first lens L1, and ft is the total focal length of the zoom lens L0 at the telephoto end. mr is the amount of movement of the lens group LR, which is positioned closest to the image in the rear group, when zooming from the wide-angle end to the telephoto end, with the amount of movement from the object side to the image side being considered positive. bfw is the distance along the optical axis from the closest surface of the lens group LR, which is positioned closest to the image in the rear group, to the image plane IP at the wide-angle end (distance along the optical axis OA). m3 is the amount of movement of the third lens group L3 when zooming from the wide-angle end to the telephoto end, with the amount of movement from the object side to the image side being considered positive.

[0019] Conditional equation (1) defines the ratio of the focal length f1 of the first lens group L1 to the total focal length ft of the zoom lens L0 at the telephoto end. Exceeding the upper limit of conditional equation (1) is undesirable because it increases the focal length f1 of the first lens group L1 and makes the zoom lens L0 larger. On the other hand, falling below the lower limit of conditional equation (1) is undesirable because it decreases the focal length f1 of the first lens group L1, increases the aberration fluctuations occurring in the first lens group L1, and makes it difficult to achieve high image quality.

[0020] Conditional equation (2) defines the relationship between the amount of movement of lens group LR and the back focus. By changing the distance from lens group LR to the image plane IP during zooming, the ray height can be changed. Therefore, by appropriately setting the relationship between the amount of movement of lens group LR, which is positioned closest to the image, during zooming and the back focus at the wide-angle end, it becomes easier to suppress aberration fluctuations that occur in the first lens group L1. If the value falls below the lower limit of conditional equation (2), the amount of movement of lens group LR becomes small, that is, the absolute value of the amount of movement toward the object becomes large, and the change in the ray height passing through lens group LR becomes too large, resulting in excessive aberration correction during zooming, which is undesirable. On the other hand, if the value exceeds the upper limit of conditional equation (2), the amount of movement of lens group LR becomes large, that is, the absolute value of the amount of movement toward the object becomes small, or the absolute value of the amount of movement toward the image becomes large, so the distance from lens group LR to the image plane IP becomes shorter at the telephoto end. As a result, the lens diameter of lens group LR becomes larger, making miniaturization difficult, which is undesirable.

[0021] Conditional equation (3) defines the relationship between the amount of movement of the third lens group L3 and the back focus. If the value falls below the lower limit of conditional equation (3), the amount of movement of the third lens group L3 becomes small, meaning the absolute value of the amount of movement of the third lens group L3 toward the object becomes large, which is undesirable because it complicates the mechanical mechanism and leads to a larger size. On the other hand, if the value exceeds the upper limit of conditional equation (3), the amount of movement of the third lens group L3 becomes large, meaning the absolute value of the amount of movement toward the object becomes small, which is undesirable because it makes high magnification difficult.

[0022] In each embodiment, it is preferable that the numerical ranges of conditional expressions (1) to (3) be the numerical ranges of the following conditional expressions (1A) to (3A), respectively.

[0023] 0.24 <f1 / ft<0.38 ···(1A) -3.5 <mr / bfw<-1.6 ···(2A) -6.0 <m3 / bfw<-2.7 ···(3A) Furthermore, in each embodiment, it is more preferable to set the numerical ranges of conditional expressions (1) to (3) to the numerical ranges of the following conditional expressions (1B) to (3B), respectively.

[0024] 0.26 <f1 / ft<0.36 ···(1B) -2.9 <mr / bfw<-1.7 ···(2B) -5.7 <m3 / bfw<-2.9 ···(3B) Next, preferred configurations for the zoom lens L0 in each embodiment will be described. In the zoom lens L0 of each embodiment, it is preferable to place the aperture diaphragm SP in the third lens group L3. This makes it easier to suppress the front element diameter. Furthermore, it is preferable that the first lens group L1 has one negative lens and three positive lenses arranged in order from the object side to the image side. This makes it easier to increase the refractive power of the first lens group L1 while suppressing aberrations occurring in the first lens group L1. In the zoom lens L0 of each embodiment, it is preferable to configure the lens group LR with a single lens. This makes it easier to reduce the weight of the lens group LR and simplifies the mechanical mechanism, which is advantageous for miniaturization.

[0025] The zoom lens L0 of each embodiment preferably satisfies at least one of the following conditional expressions (4) to (10).

[0026] 0.3 <fr / f1<2.8 ···(4) -9.0 <f1 / f2<-3.5 ···(5) -1.2 <m1 / f1<-0.4 ···(6) 3.0 < β2t / β2w < 12.0 ···(7) 2.0 <dpw / fw<7.0 ···(8) 0.4 <Lt / ft<1.2 ···(9) 15.0 <VdLR<50.0 ···(10) Here, fr is the focal length of lens group LR, and f2 is the focal length of the second lens group L2. m1 is the amount of movement of the first lens group L1 when zooming from the wide-angle end to the telephoto end, with the amount of movement from the object side to the image side being considered positive. β2t is the lateral magnification of the second lens group L2 at the telephoto end, and β2w is the lateral magnification of the second lens group L2 at the wide-angle end. dpw is the distance along the optical axis from the aperture diaphragm SP to the image plane IP at the wide-angle end. fw is the total focal length of the zoom lens L0 at the wide-angle end. Lt is the distance along the optical axis from the object-side surface of the zoom lens L0 to the image plane IP at the telephoto end. VdLR is the Abbe number of the lenses constituting lens group LR.

[0027] Conditional equation (4) specifies the ratio of the focal length fr of lens group LR to the focal length f1 of the first lens group L1. By having lens group LR have positive refractive power and a symmetrical power arrangement with respect to the aperture diaphragm SP, aberration correction becomes easier. Furthermore, by setting the focal length fr of lens group LR to have an appropriate relationship with the focal length f1 of the first lens group L1, it becomes easier to reduce various aberrations, especially chromatic aberration and distortion. If the upper limit of conditional equation (4) is exceeded, the focal length fr of lens group LR becomes large, the aberration correction effect becomes insufficient, and it becomes difficult to reduce various aberrations, especially chromatic aberration and distortion. On the other hand, if it falls below the lower limit of conditional equation (4), the focal length fr of lens group LR becomes small, the exit pupil position at the telephoto end becomes farther from the image plane, and the lens diameter of lens group LR becomes larger, resulting in a larger zoom lens L0, which is undesirable. Furthermore, it is preferable that the LR lens group moves in a convex trajectory toward the object when zooming from the wide-angle end to the telephoto end (moving toward the object first, then toward the image). This makes it easier to maximize the aberration correction effect of the LR lens group. Here, a convex trajectory toward the object means that, with the paraxial image plane position as a reference, when zooming from the wide-angle end to the telephoto end, the trajectory moves toward the object from the wide-angle end to the intermediate zoom position, and then moves toward the image position from the intermediate zoom position to the telephoto end.

[0028] Conditional equation (5) defines the ratio of the focal length f1 of the first lens group L1 to the focal length f2 of the second lens group L2. By appropriately adjusting these relationships, it becomes easier to suppress the front element diameter and shorten the overall length. If the upper limit of conditional equation (5) is exceeded, the focal length f1 of the first lens group L1 becomes small, and the absolute value of the focal length f2 of the second lens group L2 becomes large. As a result, the entrance pupil position at the wide-angle end becomes too far from the object-side plane, leading to a larger front element diameter, which is undesirable. On the other hand, if the lower limit of conditional equation (5) is exceeded, the focal length f1 of the first lens group L1 becomes large, and the absolute value of the focal length f2 of the second lens group L2 becomes small. As a result, the amount of movement of the first lens group L1 required for zooming becomes large, which is undesirable.

[0029] Conditional equation (6) defines the relationship between the amount of movement m1 of the first lens group L1 and the focal length f1. By appropriately setting these relationships, high magnification and miniaturization become easier. Exceeding the upper limit of conditional equation (6) is undesirable because it either reduces the focal length f1 of the first lens group L1 or increases the absolute value of the amount of movement m1, resulting in increased size. On the other hand, falling below the lower limit of conditional equation (6) is undesirable because it either increases the focal length f2 of the second lens group L2 or decreases the absolute value of the amount of movement m1 of the first lens group L1, making high magnification difficult.

[0030] Conditional equation (7) defines the relationship between the lateral magnification at the wide-angle end and the telephoto end of the second lens group L2. By appropriately setting these relationships, high magnification and high performance can be easily achieved. If the upper limit of conditional equation (7) is exceeded, the absolute value of the lateral magnification at the telephoto end becomes large, or the absolute value of the lateral magnification at the wide-angle end becomes small, resulting in excessively large changes in lateral magnification. Consequently, it becomes difficult to correct various aberrations, and in particular, it becomes difficult to suppress fluctuations in spherical aberration and astigmatism, which is undesirable. On the other hand, if the lower limit of conditional equation (7) is exceeded, the absolute value of the lateral magnification at the telephoto end becomes small, or the absolute value of the lateral magnification at the wide-angle end becomes small, resulting in excessively small changes in lateral magnification. Consequently, it becomes difficult to achieve high magnification, which is undesirable.

[0031] Conditional equation (8) defines the relationship between the position of the aperture SP and the image plane IP at the wide-angle end. At the wide-angle end, the off-axis ray angle is large, so appropriately setting the position of the aperture SP is important for suppressing the front and rear element diameters. Exceeding the upper limit of conditional equation (8) is undesirable because it increases the distance from the aperture SP to the image plane IP, resulting in a larger rear element diameter and a larger zoom lens L0. On the other hand, falling below the lower limit of conditional equation (8) is undesirable because it decreases the distance from the aperture SP to the image plane IP, resulting in a larger front element diameter and a larger zoom lens L0.

[0032] Conditional expression (9) defines the ratio of the overall length to the focal length of the zoom lens L0 at the telephoto end. By appropriately setting the ratio of the overall length to the focal length of the zoom lens L0, it becomes easy to achieve both shortening of the overall length and improvement in image quality. If it exceeds the upper limit of conditional expression (9), the overall length of the zoom lens L0 becomes long and it becomes large, which is not preferable. On the other hand, if it is below the lower limit of conditional expression (9), the overall length of the zoom lens L0 becomes short and aberration correction becomes difficult, and particularly correction of spherical aberration, chromatic aberration of magnification, and coma aberration at the telephoto end becomes difficult, which is not preferable.

[0033] Conditional expression (10) defines the Abbe number of the lenses constituting the lens group LR. If the Abbe number becomes large exceeding the upper limit of conditional expression (10), the chromatic aberration of magnification generated in the lens group LR becomes small, and it becomes difficult to cancel the chromatic aberration of magnification generated in the first lens group L1, making it difficult to improve image quality, which is not preferable. On the other hand, if the Abbe number becomes small being below the lower limit of conditional expression (10), the color shift sensitivity when eccentric becomes large, and the required accuracy during assembly becomes too high, which is not preferable.

[0034] In each embodiment, it is preferable that the numerical ranges of conditional expressions (4) to (10) are respectively the numerical ranges of the following conditional expressions (4A) to (10A).

[0035] 0.5 < fr / f1 < 1.9 ···(4A) -8.0 < f1 / f2 < -4.5 ···(5A) -1.0 < m1 / f1 < -0.5 ···(6A) 4.2 < β2t / β2w < 9.0 ···(7A) 2.5 < dpw / fw < 5.5 ···(8A) 0.5 < Lt / ft < 0.9 ···(9A) 20.0 < VdLR < 46.0 ···(10A) Also, in each embodiment, it is more preferable that the numerical ranges of conditional expressions (4) to (10) are respectively the numerical ranges of the following conditional expressions (4B) to (10B).

[0036] 0.6 < fr / f1 < 1.5 ···(4B) -6.8 <f1 / f2<-5.3 ···(5B) -0.9 <m1 / f1<-0.6 ···(6B) 4.6 < β2t / β2w < 8.5 ···(7B) 3.0 <dpw / fw<4.7 ···(8B) 0.55 <Lt / ft<0.85 ···(9B) 25.0 <VdLR<41.0 ···(10B) Next, we will describe the zoom lens L0 of each embodiment in detail.

[0037] As shown in Figures 1, 3, and 7, the zoom lens L0 of Examples 1, 2, and 4 has a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, and a third lens group L3 with positive refractive power, arranged in order from the object side to the image side. The zoom lens L0 of Example 1 also has a fourth lens group L4 with positive refractive power, a fifth lens group L5 with negative refractive power, a sixth lens group L6 with negative refractive power, and a seventh lens group L7 with positive refractive power. The fourth lens group L4, fifth lens group L5, sixth lens group L6, and seventh lens group L7 correspond to multiple lens groups positioned closer to the image side than the third lens group L3. The seventh lens group L7 also corresponds to lens group LR. When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. By changing the distance between the third lens group L3 and the fourth lens group L4, variations in astigmatism can be suppressed in particular. By changing the distance between the fourth lens group L4 and the fifth lens group L5, variations in coma aberration can be suppressed in particular. By changing the distance between the fifth lens group L5 and the sixth lens group L6, variations in distortion can be suppressed in particular. By changing the distance between the sixth lens group L6 and the seventh lens group L7, variations in chromatic aberration can be suppressed in particular. By changing the distance between multiple lens groups, the correction of various aberrations across the entire zoom range is improved.

[0038] As shown in Figure 3, the zoom lens L0 of Example 3 has a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, and a third lens group L3 with positive refractive power, arranged in order from the object side to the image side. The zoom lens L0 of Example 3 also has a fourth lens group L4 with negative refractive power, a fifth lens group L5 with positive refractive power, a sixth lens group L6 with negative refractive power, a seventh lens group L7 with negative refractive power, and an eighth lens group L8 with positive refractive power. In the zoom lens L0 of Example 3, the eighth lens group 8 corresponds to lens group LR. When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. By changing the spacing between the third lens group L3 and the fourth lens group L4, variations in astigmatism can be suppressed in particular. By changing the spacing between the fourth lens group L4 and the fifth lens group L5, variations in spherical aberration can be suppressed in particular. By changing the distance between the fifth lens group L5 and the sixth lens group L6, variations in coma aberration can be suppressed in particular. By changing the distance between the sixth lens group L6 and the seventh lens group L7, variations in distortion aberration can be suppressed in particular. By changing the distance between the seventh lens group L7 and the eighth lens group L8, variations in chromatic aberration can be suppressed in particular. By changing the distance between multiple lens groups, correction of various aberrations is improved throughout the entire zoom range. The third lens group L3 and the fifth lens group L5 move along the same trajectory when zooming from the wide-angle end to the telephoto end. This allows for simplification of the mechanical mechanism.

[0039] As shown in Figure 9, the zoom lens L0 of Example 5 has a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, and a third lens group L3 with positive refractive power, arranged in order from the object side to the image side. The zoom lens L0 of Example 5 also has a fourth lens group L4 with negative refractive power, a fifth lens group L5 with negative refractive power, and a sixth lens group L6 with positive refractive power. In the zoom lens L0 of Example 5, the sixth lens group L6 corresponds to lens group LR. When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. By changing the spacing between the third lens group L3 and the fourth lens group L4, fluctuations in coma aberration can be suppressed in particular. By changing the spacing between the fourth lens group L4 and the fifth lens group L5, fluctuations in distortion aberration can be suppressed in particular. By changing the spacing between the fifth lens group L5 and the sixth lens group L6, variations in chromatic aberration, particularly lateral aberration, can be suppressed. By changing the spacing between multiple lens groups, various aberrations can be corrected effectively across the entire zoom range.

[0040] In this way, by arranging multiple lens groups on the image side of the third lens group L3 and changing the spacing between the multiple lens groups, aberrations can be corrected effectively across the entire zoom range. In particular, by arranging at least three lens groups on the image side of the third lens group L3, aberrations can be corrected effectively. Note that the configuration of the multiple lens groups is not limited to the configuration of each embodiment. For example, the mechanical mechanism can be simplified by moving the fourth lens group L4 and the fifth lens group L5 of Embodiment 1 as a single unit. Furthermore, by dividing the third lens group L3 of Embodiment 1 and changing the spacing between each lens group, fluctuations in spherical aberration can be further reduced, resulting in higher image quality.

[0041] In the zoom lens L0 of Examples 1 to 5, image shake correction may be reduced by moving a portion of the zoom lens L0 in a direction that includes a component perpendicular to the optical axis OA. In particular, by making the portion moved during image shake correction the entirety or part of the third lens group L3 or the fourth lens group L4, which have a relatively small diameter, the actuator for driving can be made smaller, and the lens device including the zoom lens L0 can be miniaturized.

[0042] The following shows numerical examples 1 to 5 corresponding to each example. In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (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 element with respect to the d line, and νd represents the Abbe number of the optical element. Note that the Abbe number νd of a certain material is given by Nd, NF, and NC when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm), respectively. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0043] In each numerical example, d, focal length (mm), F-number, and half-angle of view (degrees) are all values ​​when the optical system of each example is focused on an object at infinity. BF (back focus) is the distance along the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed in terms of air-equivalent length. The total length of the lens is the distance along the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final surface of the zoom lens, plus the back focus. The lens group includes not only cases where it is composed of multiple lenses, but also cases where it is composed of a single lens. Also, if the optical surface is aspherical, the sign * is added to the right of the surface number. The aspherical shape is given by the following formula, where X is the displacement from the vertex of the surface in the direction of the optical axis, H is the height from the optical axis in the direction perpendicular to the optical axis, R is the radius of paraxial curvature, K is the cone constant, and A2, A4, A6, A8, A10, and A12 are aspherical coefficients, respectively.

[0044]

number

[0045] In each aspherical coefficient, "ex" is "10 -x This means "[...]." In addition to specifications such as focal length and F-number, the angle of view is the half-angle of view (degrees) of the entire system, the image height is the maximum image height that determines the half-angle of view, and the total lens length is the distance from the first lens surface to the image plane. The half-angle of view is the paraxial calculated value calculated from the focal length and increased height. The back focus BF indicates the length from the final lens surface to the image plane. In addition, the data for each lens group indicates the focal length of each lens group.

[0046] Furthermore, the portion where the spacing d between each optical surface is (variable) changes during zooming, and the surface spacing according to the focal length is shown in a separate table. In addition, Table 1 shows the calculation results of each conditional formula based on the lens data of numerical examples 1 to 5.

[0047] (Numerical Example 1) Surface data Face number rd nd νd 1 255.425 1.60 1.87070 40.7 2 85.494 7.53 1.43875 94.7 3 -1859.867 0.15 4 115.473 4.70 1.49700 81.5 5 757.187 0.15 6 81.241 6.72 1.53775 74.7 7 1516.193 (variable) 8* 2688.270 1.00 1.88300 40.8 9 21.226 7.81 10 -39.142 0.80 1.72916 54.7 11 81.078 0.39 12 51.907 4.85 1.85478 24.8 13 -48.997 2.20 14 -23.647 1.00 1.59282 68.6 15 -60.312 (variable) 16 (aperture) ∞ 0.50 17 35.307 6.08 1.65412 39.7 18 -52.038 1.50 1.59522 67.7 19 -238.158 1.98 20 44.197 4.56 1.48749 70.2 21 -61.611 1.30 1.95375 32.3 22 81.466 2.78 23 1589.792 1.20 2.05090 26.9 24 31.846 4.93 1.48749 70.2 25 -84.723 0.15 26 42.427 4.90 1.67270 32.1 27 -57.733 2.57 28 -37.849 2.57 1.85478 24.8 29 -23.648 1.20 1.80400 46.6 30 395.421 (variable) 31 35.831 8.43 1.49700 81.5 32 -33.018 1.20 2.05090 26.9 33 -92.495 0.15 34* 95.764 7.09 1.58313 59.4 35* -30.813 (variable) 36 94.522 3.12 1.85478 24.8 37 -145.150 1.00 1.80400 46.5 38 29.187 (Variable) 39* -35.535 1.20 1.58313 59.4 40* -390.712 (variable) 41 182.834 2.61 1.72047 34.7 42 -309.086 (variable) Image plane ∞ Aspherical data Side 8 K = 0.00000e+000 A 4= 5.11258e-006 A 6= 2.33796e-010 A 8=-1.55382e-011 A10= 4.35749e-014 Page 34 K = 0.00000e+000 A 4=-1.35080e-005 A 6=-6.25836e-009 Page 35 K = 0.00000e+000 A 4= 4.06644e-006 A 6=-9.27789e-009 A 8= 3.24854e-012 Page 39 K = 0.00000e+000 A 4=-1.62256e-005 A 6= 6.95891e-008 Page 40 K = 0.00000e+000 A 4=-1.69549e-005 A 6= 8.34948e-008 A 8=-1.23021e-010 A10= 1.79021e-013 Various data Zoom ratio 15.68 Wide-angle, Medium, Telephoto Focal length 24.74 76.74 387.90 F-numbers: 3.60, 5.30, 6.50 Half-angle 39.51 15.75 3.19 Image height 20.40 21.64 21.64 Lens length: 194.51 x 241.18 x 287.86 BF 13.32 48.47 46.46 d 7 0.80 32.19 75.34 d15 41.25 24.57 1.49 d30 8.70 1.35 1.50 d35 2.75 1.32 3.40 d38 26.36 26.53 26.10 d40 1.39 6.82 33.63 d42 13.32 48.47 46.46 Zoom lens group data Group starting plane focal length 1 1 117.12 2 8 -19.07 3 16 69.43 4 31 32.56 5 36 -56.83 6 39 -67.12 7 41 159.81 (Numerical Example 2) Surface data Face number rd nd νd 1 199.405 1.60 1.90043 37.4 2 75.771 7.61 1.43875 94.7 3 2140.436 0.15 4 115.473 4.66 1.49700 81.5 5 1098.547 0.15 6 69.666 7.10 1.59522 67.7 7 846.408 (variable) 8* 551.105 1.00 1.88300 40.8 9 20.523 6.99 10 -39.928 0.80 1.77250 49.6 11 72.405 0.40 12 46.081 4.80 1.85478 24.8 13 -43.915 1.53 14 -24.602 1.00 1.59282 68.6 15 -125.843 (variable) 16 (aperture) ∞ 0.50 17 30.968 4.13 1.65412 39.7 18 -217.058 1.50 1.59522 67.7 19 -448.901 3.35 20 56.088 3.24 1.48749 70.2 21 -67.751 1.30 1.95375 32.3 22 141.265 2.14 23 226.016 1.20 2.05090 26.9 24 32.840 3.60 1.48749 70.2 25 -123.382 0.15 26 40.663 3.54 1.67270 32.1 27 -78.743 2.82 28 -32.963 1.50 1.72825 28.5 29 -25.296 1.20 1.80400 46.6 30 -351.179 (variable) 31 29.318 7.97 1.49700 81.5 32 -35.576 1.20 2.05090 26.9 33 -80.849 0.15 34* 97.098 5.81 1.58313 59.4 35* -31.216 (variable) 36 74.951 2.88 1.85478 24.8 37 -213.306 1.00 1.80400 46.5 38 23.473 (Variable) 39* -27.665 1.20 1.58313 59.4 40* -341.237 (variable) 41 104.931 3.23 1.72047 34.7 42 -326.245 (variable) Image plane ∞ Aspherical data Side 8 K = 0.00000e+000 A 4= 3.30413e-006 A 6=-2.34829e-010 A 8=-7.25877e-012 A10= 3.62542e-014 Page 34 K = 0.00000e+000 A 4=-2.52752e-005 A 6=-1.72796e-008 Page 35 K = 0.00000e+000 A 4= 1.03432e-006 A 6=-1.72341e-008 A 8=-2.03279e-012 Page 39 K = 0.00000e+000 A 4=-8.73928e-006 A 6= 3.74509e-008 Page 40 K = 0.00000e+000 A 4=-1.11329e-005 A 6= 5.14822e-008 A 8=-1.29169e-010 A10= 2.27948e-013 Various data Zoom ratio 11.73 Wide-angle, Medium, Telephoto Focal length 24.72 69.39 289.87 F-numbers: 3.60, 5.30, 5.88 Half-angle 39.53 17.32 4.27 Image height 20.40 21.64 21.64 Lens length: 168.78 mm, 202.25 mm, 235.73 mm BF 13.34 39.12 36.81 d 7 0.80 26.27 60.83 d15 33.80 18.89 1.50 d30 7.45 2.46 1.50 d35 1.70 1.20 1.20 d38 18.58 18.88 19.79 d40 1.72 4.03 22.71 d42 13.34 39.12 36.81 Zoom lens group data Group starting plane focal length 1 1 100.42 2 8 -17.92 3 16 57.20 4 31 28.10 5 36 -45.90 6 39 -51.70 7 41 110.55 (Numerical Example 3) Surface data Face number rd nd νd 1 225.740 1.60 1.83400 37.2 2 108.865 6.89 1.43875 94.7 3 -1600.000 0.15 4 134.358 5.00 1.43875 94.7 5 2064.513 0.15 6 80.623 6.63 1.43875 94.7 7 448.566 (variable) 8* 397.426 1.00 1.88300 40.8 9 20.687 7.82 10 -37.394 0.80 1.72916 54.7 11 118.335 0.31 12 60.610 5.48 1.76182 26.5 13 -33.730 1.26 14 -23.918 1.00 1.53775 74.7 15 -161.887 (variable) 16 34.423 3.74 1.85478 24.8 17 160.877 2.50 18 (aperture) ∞ 0.00 19 41.440 1.20 1.92286 20.9 20 21.729 5.67 1.48749 70.2 21 341.505 0.15 22 35.787 5.42 1.49700 81.5 23 -54.438 1.00 2.00100 29.1 24 -132.964 (variable) 25 -839.627 1.00 1.95375 32.3 26 58.544 1.77 27 -88.361 1.00 1.76200 40.1 28 24.743 4.00 1.85478 24.8 29 371.204 (variable) 30 26.029 7.41 1.48749 70.2 31 -26.003 1.00 1.95375 32.3 32 -211.831 2.00 33* 36.433 7.20 1.58313 59.4 34* -31.674 (variable) 35 69.957 2.71 1.80810 22.8 36 -273.805 1.00 1.80400 46.5 37 24.333 (Variable) 38* -32.780 1.20 1.58313 59.4 39* -278.467 (variable) 40 348.028 2.86 1.72047 34.7 41 -138.495 (variable) Image plane ∞ Aspherical data Side 8 K = 0.00000e+000 A 4= 3.75838e-006 A 6= 1.01163e-009 A 8=-2.25190e-011 A10= 6.72743e-014 Page 33 K = 0.00000e+000 A 4=-2.30192e-005 A 6=-1.02293e-008 Page 34 K = 0.00000e+000 A 4= 7.93294e-006 A 6=-2.74475e-008 A 8= 2.05118e-011 Page 38 K = 0.00000e+000 A 4=-3.40508e-005 A 6= 1.11351e-007 Page 39 K = 0.00000e+000 A 4=-3.59306e-005 A 6= 1.49211e-007 A 8=-2.96761e-010 A10= 4.90321e-013 Various data Zoom ratio 15.67 Wide-angle, Medium, Telephoto Focal length 24.76 83.42 387.85 F-numbers: 3.60, 5.10, 6.50 Half-angle 39.49 14.54 3.19 Image height 20.40 21.64 21.64 Lens length: 171.65 x 227.55 x 283.44 BF 12.35 51.91 46.44 d 7 0.80 35.74 79.26 d15 36.55 17.95 0.79 d24 1.00 2.89 5.44 d29 5.94 4.04 1.50 d34 1.19 1.58 1.73 d37 21.84 13.95 21.35 d39 1.05 8.54 36.00 d41 12.35 51.91 46.44 Zoom lens group data Group starting plane focal length 1 1 127.84 2 8 -19.14 3 16 32.42 4 25 -40.11 5 30 28.16 6 35 -48.33 7 38 -63.83 8 40 137.85 (Numerical Example 4) Surface data Face number rd nd νd 1 220.056 1.60 1.88300 40.8 2 93.279 8.03 1.43875 94.7 3 -1293.245 0.15 4 97.100 5.97 1.49700 81.5 5 459.954 0.15 6 117.399 5.37 1.49700 81.5 7 1179.051 (variable) 8* 287.064 1.00 1.88300 40.8 9 25.736 7.94 10 -53.742 0.80 1.72916 54.7 11 82.289 0.15 12 47.361 5.44 1.85478 24.8 13 -68.849 3.86 14 -25.876 1.00 1.59282 68.6 15 -165.250 (variable) 16 (aperture) ∞ 0.50 17 31.300 5.94 1.65412 39.7 18 -78.341 1.50 1.53775 74.7 19 184.715 0.64 20 40.252 4.37 1.48749 70.2 21 -87.206 1.30 1.95375 32.3 22 81.666 2.63 23 349.412 1.20 2.05090 26.9 24 27.148 5.60 1.48749 70.2 25 -69.169 0.15 26 35.657 5.32 1.67270 32.1 27 -53.436 2.40 28 -37.138 2.92 1.85478 24.8 29 -21.053 1.20 1.80400 46.6 30 91.373 (Variable) 31 27.579 8.08 1.49700 81.5 32 -31.348 1.20 2.05090 26.9 33 -116.343 0.15 34* 70.266 6.46 1.58313 59.4 35* -29.189 (variable) 36 70.017 2.72 1.85478 24.8 37 -298.217 1.00 1.80400 46.5 38 22.447 (Variable) 39* -28.961 1.20 1.49700 81.5 40 * 170.942 (variable) 41 85.814 3.17 1.72047 29.0 42 -2568.107 (variable) Image plane ∞ Aspherical data Side 8 K = 0.00000e+000 A 4= 1.78579e-006 A 6= 1.38483e-009 A 8=-3.45739e-012 A10= 1.70654e-014 Page 34 K = 0.00000e+000 A 4=-2.29409e-005 A 6=-1.68589e-008 Page 35 K = 0.00000e+000 A 4= 2.22442e-006 A 6=-1.75687e-008 A 8=-2.35901e-012 Page 39 K = 0.00000e+000 A 4=-1.54091e-006 A 6= 2.39947e-008 Page 40 K = 0.00000e+000 A 4=-6.09353e-006 A 6= 3.17194e-008 A 8=-1.07433e-010 A10= 2.14422e-013 Various data Zoom ratio 16.83 Wide-angle, Medium, Telephoto Focal length 28.81 94.89 484.70 F-numbers: 3.60, 5.30, 7.20 Half-angle 35.30 12.84 2.56 Image height 20.40 21.64 21.64 Lens length: 194.00 x 240.17 x 286.34 BF 13.85 43.81 39.37 d 7 0.80 42.00 89.13 d15 46.22 22.88 1.50 d30 3.17 1.31 1.50 d35 1.19 4.12 1.20 d38 25.44 19.33 26.49 d40 2.23 5.61 26.05 d42 13.85 43.81 39.37 Zoom lens group data Group starting plane focal length 1 1 134.78 2 8 -21.22 3 16 70.23 4 31 29.22 5 36 -44.34 6 39 -49.73 7 41 115.31 (Numerical Example 5) Surface data Face number rd nd νd 1 223.853 1.60 1.88300 40.8 2 113.461 8.76 1.43875 94.7 3 -7333.776 0.15 4 115.066 7.20 1.43875 94.7 5 647.350 0.15 6 159.127 4.98 1.49700 81.5 7 765.639 (variable) 8 91.064 1.80 1.80311 46.7 9 26.688 9.72 10 -83.582 1.40 1.72788 54.9 11 76.171 0.15 12 45.585 5.11 1.84666 23.8 13 -571.011 8.84 14 -36.426 1.40 1.59282 68.6 15 -209.675 (variable) 16 (aperture) ∞ 0.50 17 33.903 5.16 1.65412 39.7 18 -96.183 1.50 1.53775 74.7 19 108.454 3.24 20 41.851 3.65 1.48749 70.2 21 -137.968 1.30 1.95375 32.3 22 80.578 2.63 23 282.536 1.20 2.05090 26.9 24 27.481 5.52 1.48749 70.2 25 -59.637 0.15 26 34.183 5.19 1.67270 32.1 27 -55.307 2.44 28 -36.723 5.58 1.85478 24.8 29 -23.880 1.20 1.80400 46.6 30 140.439 1.82 31 32.792 6.67 1.49700 81.5 32 -36.536 1.20 2.05090 26.9 33 -107.126 0.15 34* 1059.034 5.43 1.58313 59.4 35* -27.868 (variable) 36 65.301 2.63 1.85478 24.8 37 -432.146 1.00 1.80400 46.5 38 21.709 (Variable) 39* -28.832 1.20 1.49700 81.5 40 * 245.015 (variable) 41 74.912 3.12 1.72047 40.0 42 586.438 (variable) Image plane ∞ Aspherical data Page 34 K = 0.00000e+000 A 4=-2.02740e-005 A 6=-8.62308e-009 Page 35 K = 0.00000e+000 A 4=-1.55557e-006 A 6=-4.58763e-009 A 8=-7.70161e-012 Page 39 K = 0.00000e+000 A 4= 8.69486e-006 A 6=-6.30755e-009 Page 40 K = 0.00000e+000 A 4= 3.44567e-006 A 6=-1.80194e-008 A 8= 2.95620e-011 A10=-7.04293e-014 Various data Zoom ratio 17.61 Wide-angle, Medium, Telephoto Focal length 33.05 140.67 581.87 F-numbers: 4.10, 5.90, 7.20 Half-angle 31.69 8.74 2.13 Image height 20.40 21.64 21.64 Lens length: 218.72 x 276.34 x 333.97 BF 14.32 39.28 46.78 d 7 0.80 69.66 117.45 d15 56.37 17.64 1.52 d35 1.20 7.70 1.36 d38 30.79 19.31 24.32 d40 1.50 9.01 28.80 d42 14.32 39.28 46.78 Zoom lens group data Group starting plane focal length 1 1 176.42 2 8 -26.51 3 16 37.19 4 36 -43.72 5 39 -51.83 6 41 118.90

[0048] [Table 1]

[0049] Next, with reference to Figure 11, embodiments of a digital still camera (imaging device 10) using the zoom lens L0 of each embodiment as the imaging optical system will be described. Figure 11 is a schematic diagram of the imaging device 10 equipped with the zoom lens L0 of each embodiment.

[0050] In Figure 11, 13 is the camera body, and 11 is the imaging optical system composed of a zoom lens L0 from any of Examples 1 to 5. 12 is an image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor, which is built into the camera body 13 and receives the optical image formed by the imaging optical system 11 and converts it into photoelectric energy. The camera body 13 may be a so-called single-lens reflex camera with a quick-turn mirror, or a so-called mirrorless camera without a quick-turn mirror.

[0051] By applying the zoom lens of the present invention to an imaging device 10 such as a digital still camera, an imaging device with high optical performance can be obtained. The zoom lenses of each embodiment can also be similarly applied to video cameras.

[0052] According to each embodiment, it is possible to provide a zoom lens and imaging device that are compact, have high magnification, and possess excellent optical characteristics.

[0053] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its essence. [Explanation of Symbols]

[0054] L0 Zoom Lens L1 First lens group L2 Second lens group L3 Third lens group LR lens group

Claims

1. A zoom lens comprising a rear group having multiple lens groups arranged sequentially from the object side to the image side, including a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, wherein the spacing between adjacent lens groups changes during zooming. During image shake correction, either the entire third lens group, a part of the third lens group, the entire fourth lens group, or a part of the fourth lens group moves in a direction that includes a component perpendicular to the optical axis. When the focal length of the first lens group is f1, the focal length of the zoom lens at the telephoto end is ft, the amount of movement of the lens group LR, which is positioned closest to the image in the rear group, during zooming from the wide-angle end to the telephoto end is mr, the distance on the optical axis from the closest surface of the lens group LR to the image plane at the wide-angle end is bfw, the amount of movement of the third lens group during zooming from the wide-angle end to the telephoto end is m3, and the sign of the amount of movement of the lens group is positive when it moves from the object side to the image side, and negative when it moves from the image side to the object side, 0.20<f1 / ft<0.40 -4.0<mr / bfw<-1.5 -7.0<m3 / bfw<-2.5 A zoom lens characterized by satisfying the following conditional equation.

2. The zoom lens according to claim 1, characterized in that the rear group has at least three lens groups.

3. The zoom lens according to claim 1 or 2, characterized in that the first lens group has one negative lens and three positive lenses.

4. The zoom lens according to any one of claims 1 to 3, characterized in that the lens group LR moves toward the object side and then toward the image side when zooming from the wide-angle end to the telephoto end.

5. When the focal length of the lens group LR is denoted as fr, 0.3<fr / f1<2.8 A zoom lens according to any one of claims 1 to 4, characterized in that it satisfies the following conditional expression.

6. When the focal length of the second lens group is f2, -9.0<f1 / f2<-3.5 A zoom lens according to any one of claims 1 to 5, characterized in that it satisfies the following conditional expression.

7. When the amount of movement of the first lens group when zooming from the wide-angle end to the telephoto end is m1, -1.2<m1 / f1<-0.4 A zoom lens according to any one of claims 1 to 6, characterized in that it satisfies the following conditional expression.

8. When the lateral magnification of the second lens group at the telephoto end is β2t and the lateral magnification of the second lens group at the wide-angle end is β2w, 3.0<β2t / β2w<12.0 A zoom lens according to any one of claims 1 to 7, characterized in that it satisfies the following conditional expression.

9. It further has an aperture diaphragm, When dpw is the distance along the optical axis from the aperture diaphragm to the image plane at the wide-angle end, and fw is the focal length of the zoom lens at the wide-angle end, 2.0<dpw / fw<7.0 A zoom lens according to any one of claims 1 to 8, characterized in that it satisfies the following conditional expression.

10. When Lt is the distance along the optical axis from the object-side surface of the zoom lens to the image plane at the telephoto end, 0.4<Lt / ft<1.2 A zoom lens according to any one of claims 1 to 9, characterized in that it satisfies the following conditional expression.

11. The zoom lens according to any one of claims 1 to 10, characterized in that the lens group LR is composed of single lenses.

12. When the Abbe number of the single lens is VdLR, 15.0<VdLR<50.0 The zoom lens according to claim 11, characterized in that it satisfies the following condition.

13. An imaging device characterized by having a zoom lens according to any one of claims 1 to 12, and an image sensor that receives an image formed by the zoom lens.

Images